WO2014156195A1 - Binder composition for secondary battery electrodes, method for producing same, slurry composition for secondary battery electrodes, electrode for secondary batteries, and secondary battery - Google Patents

Binder composition for secondary battery electrodes, method for producing same, slurry composition for secondary battery electrodes, electrode for secondary batteries, and secondary battery Download PDF

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Publication number
WO2014156195A1
WO2014156195A1 PCT/JP2014/001852 JP2014001852W WO2014156195A1 WO 2014156195 A1 WO2014156195 A1 WO 2014156195A1 JP 2014001852 W JP2014001852 W JP 2014001852W WO 2014156195 A1 WO2014156195 A1 WO 2014156195A1
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Prior art keywords
secondary battery
monomer
binder composition
mass
parts
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PCT/JP2014/001852
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French (fr)
Japanese (ja)
Inventor
鍵 王
豊 丸橋
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日本ゼオン株式会社
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Priority to CN201480016769.0A priority Critical patent/CN105074977B/en
Priority to JP2015508095A priority patent/JP6206484B2/en
Publication of WO2014156195A1 publication Critical patent/WO2014156195A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a binder composition for a secondary battery electrode and a manufacturing method thereof, a slurry composition for a secondary battery electrode, an electrode for a secondary battery, and a secondary battery.
  • Secondary batteries especially lithium ion secondary batteries, are small and light, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications.
  • the battery members such as the electrodes (positive electrode and negative electrode) of the secondary battery are obtained by binding the components contained in these battery members or the components and a substrate (for example, a current collector) with a binder.
  • a substrate for example, a current collector
  • a binder for example, a current collector
  • an electrode of a secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector.
  • the electrode mixture layer is formed by, for example, applying an electrode slurry composition in which an electrode active material and a binder composition are dispersed in a dispersion medium on a current collector, and drying the electrode active material and the like with a binder. It is formed by binding.
  • attempts have been made to improve the binder composition and slurry composition used for forming these battery members in order to achieve further performance improvement of the secondary battery.
  • Patent Documents 1 to 3 it has been proposed to use a binder composition containing a specific copolymer for the production of a secondary battery electrode (see, for example, Patent Documents 1 to 3).
  • the binder composition described in Patent Document 1 it contains a copolymer having specific properties obtained by emulsion polymerization of styrene, an ethylenically unsaturated carboxylic acid ester, an ethylenically unsaturated carboxylic acid, and an internal crosslinking agent. Therefore, the active material and the active material and the current collector can be satisfactorily bound in an aqueous dispersion, and by using such a binder composition, a lithium ion secondary battery excellent in charge / discharge high temperature cycle characteristics Can be provided.
  • the binder composition described in Patent Document 2 contains a copolymer of an acrylate ester or a methacrylic ester and an ⁇ , ⁇ -unsaturated nitrile compound.
  • An excellent positive electrode can be provided.
  • a predetermined ⁇ , ⁇ -ethylenically unsaturated nitrile compound such as acrylonitrile is polymerized, and then a predetermined ethylenically unsaturated carboxylic acid such as 2-ethylhexyl acrylate is used. Since a copolymer (multistage polymer) obtained by adding and polymerizing an ester or the like is contained, a positive electrode excellent in binding power and flexibility can be provided.
  • JP 2011-243464 A International Publication No. 2006/038652 Japanese Patent No. 4736804
  • the present invention can provide a secondary battery that has excellent high-temperature storage characteristics and high-temperature cycle characteristics, in which generation of gas due to residual monomers is suppressed, and is excellent in stability over time.
  • An object is to provide a binder composition.
  • an object of this invention is to provide the slurry composition for secondary battery electrodes using the said binder composition.
  • an object of this invention is to provide the electrode for secondary batteries using the said slurry composition for secondary battery electrodes.
  • Another object of the present invention is to provide a secondary battery using the secondary battery electrode, which has excellent high-temperature storage characteristics and high-temperature cycle characteristics and reduced gas generation.
  • a polymer is prepared once, and then a polymerization initiator such as persulfate is further added to further advance the polymerization reaction (that is, the residual monomer is polymerized). It is also conceivable to reduce the amount of residual monomer containing a (meth) acrylic acid ester monomer at or above.
  • a polymerization initiator was further added and the polymerization reaction proceeded, a large amount of the residue of the polymerization initiator such as persulfate was present in the binder composition or the secondary. It became clear that the electrical characteristics of the secondary battery might be deteriorated due to inclusion in the battery.
  • the present inventors conducted further intensive studies for the purpose of solving the above problems. And the present inventors polymerize the residual monomer by reducing the amount of residual monomer without using a large amount of peroxide by performing redox polymerization using a reductone compound after preparing a polymer once. I was inspired by that. Furthermore, the inventors of the present invention also provide a secondary battery electrode binder composition containing a particulate polymer prepared using a (meth) acrylate monomer, and a (meth) acrylate ester having a boiling point of 145 ° C. or higher.
  • the present invention aims to advantageously solve the above problems, and the binder composition for a secondary battery electrode of the present invention comprises at least one of a particulate polymer, a reductone compound and an oxidant thereof.
  • the water-containing particulate polymer is obtained by polymerizing a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, and the (meth) acrylic acid having a boiling point of 145 ° C. or higher.
  • the content ratio of the ester monomer is 1 ⁇ 10 ⁇ 6 parts by mass to 1500 ⁇ 10 ⁇ 6 parts by mass with respect to 100 parts by mass of the particulate polymer.
  • the binder composition for secondary battery electrodes is formed by using a reductone compound and limiting the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher to a predetermined range.
  • the secondary battery obtained by using such a binder composition for a secondary battery electrode it is possible to suppress the generation of gas due to the residual monomer.
  • the said binder composition for secondary battery electrodes is used, the secondary battery which has a favorable high temperature storage characteristic and a high temperature cycling characteristic can be provided.
  • At least one of the reductone compound and its oxidant is selected from (iso) ascorbic acid and its salt, and their oxidant. It is preferable that This is because (iso) ascorbic acid and salts thereof, and oxidants thereof have little influence on battery characteristics and lead to improvement of slurry stability.
  • the content ratio of at least one of the reductone compound and its oxidant is 0.05 parts by mass or more and 5 parts by mass per 100 parts by mass of the particulate polymer.
  • the following is preferable.
  • the content of at least one of a reductone compound and its oxidant while sufficiently reducing the amount of residual monomer such as a (meth) acrylate monomer having a boiling point of 145 ° C. or higher in the binder composition for secondary battery electrodes As a result, the electrical characteristics of the secondary battery produced using the binder composition for secondary battery electrodes deteriorated, and at least one of the reductone compound and its oxidant remaining in the binder composition was decomposed. This is because the generation of gas in the secondary battery can be suppressed.
  • the monomer mixture preferably further contains a crosslinkable monomer.
  • the degree of swelling of the electrode formed using the binder composition for a secondary battery electrode with respect to the electrolyte solution is set to an appropriate level, and the high-temperature storage characteristics and high temperature of a lithium ion secondary battery produced using such a binder composition This is because the cycle characteristics can be improved.
  • the monomer mixture further contains 5 to 35% by mass of a (meth) acrylonitrile monomer. This is because the peel strength of the electrode mixture layer formed using the binder composition for secondary battery electrodes can be improved, and the degree of swelling with respect to the electrolytic solution can be made moderate.
  • the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is preferably 2-ethylhexyl acrylate. Since a polymer obtained using 2-ethylhexyl acrylate has high electrochemical stability and flexibility, current collection of an electrode mixture layer obtained using a binder composition for a secondary battery electrode blended with such a polymer. This is because the adhesion strength to the body can be improved, and as a result, the battery characteristics of the secondary battery having such an electrode mixture layer can be improved.
  • the manufacturing method of the binder composition for secondary battery electrodes of this invention is (meth) acrylic acid ester single-piece
  • a step (2) of 1 ⁇ 10 ⁇ 6 parts by mass to 1500 ⁇ 10 ⁇ 6 parts by mass with respect to 100 parts by mass of the combined product a step (2) of 1 ⁇ 10 ⁇ 6 parts by mass to 1500 ⁇ 10 ⁇ 6 parts by mass with respect to 100 parts by mass of the combined product .
  • the slurry composition for secondary battery electrodes of this invention is the binder composition and electrode for any of the above-mentioned secondary battery electrodes. It is characterized by containing an active material.
  • Such a slurry composition for a secondary battery electrode is excellent in stability over time, and when such a slurry composition for a secondary battery electrode is used, generation of gas due to residual monomers is suppressed, and good high-temperature storage characteristics and A secondary battery having high-temperature cycle characteristics can be provided.
  • the electrode for secondary batteries of this invention apply
  • the secondary battery of this invention is equipped with a positive electrode, a negative electrode, electrolyte solution, and a separator, and at least one of the said positive electrode and the said negative electrode is The electrode for a secondary battery described above.
  • Such a secondary battery has excellent high-temperature storage characteristics and high-temperature cycle characteristics, and gas generation is suppressed.
  • ADVANTAGE OF THE INVENTION According to this invention, generation
  • a binder composition can be provided.
  • the slurry composition for secondary battery electrodes using the said binder composition can be provided.
  • the electrode for secondary batteries using the said slurry composition for secondary battery electrodes can be provided.
  • the binder composition for secondary battery electrodes of the present invention is used when forming an electrode of a secondary battery.
  • the slurry composition for secondary battery electrodes of this invention is prepared including the binder composition for secondary battery electrodes of this invention, and an electrode active material.
  • the manufacturing method of the binder composition for secondary battery electrodes of this invention can be used when manufacturing the binder composition for secondary battery electrodes of this invention.
  • the secondary battery electrode of the present invention can be produced using the slurry composition for the secondary battery electrode of the present invention, and the lithium ion secondary battery of the present invention is the secondary battery electrode of the present invention. It is characterized by using.
  • the binder composition for secondary battery electrodes of the present invention is an aqueous binder composition using water as a dispersion medium, and includes at least one of a particulate polymer, a reductone compound, and an oxidant thereof.
  • the particulate polymer is a particulate polymer produced by polymerizing a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher.
  • the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is 1 ⁇ 10 ⁇ 6 mass relative to 100 mass parts of the particulate polymer.
  • the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher contained in the binder composition of the present invention is a polymerization of a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher.
  • “(meth) acryl” refers to acryl and / or methacryl.
  • the component contained in the electrode mixture layer (for example, the electrode active material) is produced from the electrode in the manufactured electrode. It is a component that can be held so as not to be detached.
  • a particulate polymer to be blended in the binder composition a particulate polymer produced by polymerizing a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher described below is used. be able to.
  • a particulate polymer is produced
  • the binder composition of the present invention is used for forming a positive electrode (secondary battery positive electrode binder composition)
  • the particulate polymer is an ⁇ , ⁇ -unsaturated nitrile monomer such as a (meth) acrylonitrile monomer.
  • (meth) acrylonitrile refers to acrylonitrile and / or methacrylonitrile.
  • the monomer mixture used when polymerizing the particulate polymer contains a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher.
  • the electrochemical stability and flexibility of the particulate polymer obtained by polymerizing the monomer mixture can be enhanced.
  • the adhesive strength of the electrode compound layer using a binder composition can be raised and the peel strength of an electrode can be improved, the battery characteristic of a secondary battery can be improved.
  • examples of the (meth) acrylic acid ester monomer include compounds represented by the formula (I): CH 2 ⁇ CR 1 —COOR 2 .
  • R 1 represents a hydrogen atom or a methyl group
  • R 2 represents an alkyl group, a cycloalkyl group, or a functional group in which a part thereof is substituted.
  • Examples of (meth) acrylate monomers having a boiling point of 145 ° C. or higher include n-butyl acrylate (BA), n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate.
  • acrylates such as 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, hexyl acrylate, nonyl acrylate, lauryl acrylate, stearyl acrylate, and benzyl acrylate; n-butyl methacrylate, methacrylic acid Isobutyl, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stear methacrylate Le, and the like methacrylates such as benzyl methacrylate.
  • These monomers may be used individually by 1 type, and may be used in combination of 2 or more types.
  • acrylate is preferable, 2-ethylhexyl acrylate and n-butyl acrylate are preferable in terms of improving the peel strength of the secondary battery electrode, and 2-ethylhexyl acrylate is particularly preferable.
  • 2-ethylhexyl acrylate has a long side chain and reduces Tg of a polymer having monomer units derived from 2-ethylhexyl acrylate to improve flexibility and to improve electrochemical stability
  • a polymer Improved the adhesion strength of the electrode mixture layer obtained by using the binder composition for secondary battery electrodes blended with the current collector, and thus the battery characteristics of the secondary battery using the electrode having the electrode mixture layer It is because it can improve.
  • the boiling point of the (meth) acrylic acid ester monomer can be measured according to JIS K2254.
  • the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is preferably 10% by mass or more, more preferably 15% by mass in the monomer mixture. % Or more, still more preferably 30% by mass or more, particularly preferably 50% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less.
  • the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher in the monomer mixture 10% by mass or higher, flexibility is provided to the negative electrode mixture layer formed using the binder composition. be able to.
  • the peel strength of the negative electrode mixture layer formed using the binder composition can be improved by setting the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher to 70% by mass or less. .
  • the content rate of the (meth) acrylic acid ester monomer with a boiling point of 145 degreeC or more mentioned above in a monomer mixture Preferably it is 60 mass% or more, More preferably 65% by weight or more, still more preferably 70% by weight or more, particularly preferably 75% by weight or more, and preferably 95% by weight or less, more preferably 90% by weight or less, still more preferably 85% by weight or less, particularly preferably Is 83 mass% or less.
  • the polymer is prevented from excessive swelling with respect to the electrolyte solution, and the binder
  • the peel strength of the positive electrode mixture layer formed using the composition can be improved, and the flexibility of the positive electrode mixture layer can be improved to make the positive electrode having the positive electrode mixture layer difficult to break.
  • the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher to 95% by mass or less the polymer is appropriately swollen with respect to the electrolytic solution, and the binder composition is used. An increase in electrical resistance of a secondary battery including the positive electrode formed in this manner can be suppressed, and the mechanical strength of the particulate polymer can be maintained and adhesion can be maintained.
  • the boiling point of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is preferably 150 ° C. or higher and 250 ° C. or lower.
  • High-boiling point (meth) acrylate monomer units generally have long side chains, and polymers comprising such monomer units are rich in flexibility and have good binding properties. This is because the battery characteristics of a secondary battery produced using a binder composition containing such a polymer can be improved.
  • Crosslinking monomer When using a binder composition for formation of a negative electrode, it is preferable that the monomer mixture used when superposing
  • the crosslinkable monomer is a monomer having the following crosslinkable group.
  • the crosslinkable group a heat crosslinkable group that usually causes a crosslinking reaction by heat is used.
  • the crosslinkable group include an epoxy group, an N-methylolamide group, an oxazoline group, and an allyl group.
  • the crosslinkable group and the crosslinking density can be easily adjusted.
  • a methylolamide group, an epoxy group, and an allyl group are preferred.
  • the higher the crosslinking density the lower the degree of swelling of the particulate polymer with respect to the electrolytic solution. Therefore, the degree of swelling of the particulate polymer can be controlled by adjusting the crosslinking density.
  • the kind of crosslinkable group may be one kind, and may be two or more kinds.
  • a crosslinkable monomer shall not be contained in the (meth) acrylic acid ester monomer mentioned above.
  • the monomer containing an epoxy group include a monomer containing a carbon-carbon double bond and an epoxy group, a monomer containing a halogen atom and an epoxy group, and the like.
  • Examples of the monomer containing a carbon-carbon double bond and an epoxy group include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl ether; butadiene monoepoxide, Diene or polyene monoepoxides such as chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene; Alkenyl epoxides such as epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-he
  • Examples of the monomer having a halogen atom and an epoxy group include epihalohydrin such as epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin, ⁇ -methylepichlorohydrin; p-chlorostyrene oxide; dibromo Phenyl glycidyl ether; and the like.
  • Examples of the monomer containing an N-methylolamide group include (meth) acrylamides having a methylol group such as N-methylol (meth) acrylamide.
  • Examples of the monomer containing an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl- Examples include 2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like.
  • Examples of the monomer containing an allyl group include allyl acrylate and allyl methacrylate.
  • crosslinkable monomer allyl acrylate or allyl methacrylate is preferable from the viewpoint of improvement in crosslink density and high copolymerizability.
  • the content of the crosslinkable monomer is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, particularly preferably 1% by mass or more, preferably 5% by mass in the monomer mixture. Hereinafter, it is more preferably 3% by mass or less, particularly preferably 2% by mass or less.
  • the degree of swelling in the electrolytic solution is set to an appropriate level, and the binder composition obtained using such a monomer mixture is used. This is because the high-temperature storage characteristics and high-temperature cycle characteristics of the secondary battery can be improved. Moreover, it is because the softness
  • Aromatic vinyl monomer When the binder composition is used for forming the negative electrode, the monomer mixture used for polymerizing the particulate polymer is styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, It is preferable to further contain a styrene monomer such as vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, ⁇ -methyl styrene, divinyl benzene and the like. Of these, styrene is preferably used as the aromatic vinyl monomer.
  • these may be used individually by 1 type and may be used in combination of 2 or more types.
  • an aromatic vinyl monomer such as a styrene monomer
  • the Tg of the polymer having monomer units derived from the aromatic vinyl monomer is increased, and the polymer strength of the particulate polymer is increased, As a result, the peel strength of the negative electrode mixture layer can be improved.
  • an aromatic vinyl monomer such as a styrene monomer
  • the ⁇ electron of the aromatic ring introduced into the particulate polymer contained in the binder composition and the aromatic of the carbon-based negative electrode active material. This is because the dispersibility of the conductive material can be improved by the interaction with the ⁇ electrons of the group ring.
  • the blending amount of the aromatic vinyl monomer such as the styrene monomer is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 80% by mass in the monomer mixture.
  • it is more preferably 70% by mass or less, particularly preferably 60% by mass or less.
  • the monomer mixture used when polymerizing the particulate polymer preferably further contains a monomer containing an acidic group (hereinafter sometimes referred to as “acidic group-containing monomer”).
  • a monomer unit containing an acidic group (hereinafter sometimes referred to as an “acidic group-containing monomer unit”) is particulate. It can be introduced into the polymer.
  • the acidic group include a carboxylic acid group (—COOH), a sulfonic acid group (—SO 3 H), and a phosphoric acid group (—PO 3 H 2 ).
  • the acidic group-containing monomer may have one acidic group or two or more acidic groups.
  • the number of acidic groups which the monomer containing an acidic group has may be one, and two or more may be sufficient as it.
  • the monomer containing a carboxylic acid group a monomer having a carboxylic acid group and a polymerizable group is usually used.
  • the monomer containing a carboxylic acid group include an unsaturated carboxylic acid monomer.
  • the unsaturated carboxylic acid monomer is a monomer having a carbon-carbon unsaturated bond and having a carboxylic acid group.
  • Examples of the unsaturated carboxylic acid monomer include unsaturated monocarboxylic acid and derivatives thereof; unsaturated dicarboxylic acid and acid anhydrides and derivatives thereof; and the like.
  • unsaturated monocarboxylic acids include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid.
  • unsaturated monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, ⁇ -acetoxyacrylic acid, ⁇ -trans-aryloxyacrylic acid, ⁇ -chloro- ⁇ -E-methoxyacrylic acid, and ⁇ -Derivatives of ethylenically unsaturated monocarboxylic acids, such as diaminoacrylic acid.
  • unsaturated dicarboxylic acids include ethylenically unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid.
  • unsaturated dicarboxylic acid anhydrides include ethylenically unsaturated dicarboxylic acid anhydrides such as maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
  • Examples of derivatives of unsaturated dicarboxylic acids include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, methylallyl maleate; and diphenyl maleate, nonyl maleate, maleate Examples thereof include maleate esters such as decyl acid, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate.
  • Examples of monomers having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methyl. Examples thereof include propanesulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid. In the present specification, “(meth) allyl” means allyl and / or methallyl.
  • Monomers having a phosphoric acid group include phosphoric acid-2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, ethyl phosphate- (meth) acryloyloxyethyl phosphate, ethylene phosphate And methacrylate.
  • acrylic acid, methacrylic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and ethylene methacrylate phosphate are preferable.
  • unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and ethylenically unsaturated dicarboxylic acids such as itaconic acid are preferred. This is because the storage stability of the binder composition can be improved by further increasing the dispersibility of the particulate polymer in water.
  • the compounding amount of the acidic group-containing monomer is preferably 0.5% by mass or more, more preferably 1% by mass or more, particularly preferably 1.5% by mass or more, preferably 8% by mass in the monomer mixture. % Or less, more preferably 5% by mass or less, and particularly preferably 4% by mass or less.
  • the monomer mixture used for polymerizing the particulate polymer in the present invention is not limited to those described above unless the present invention is significantly impaired. May contain body.
  • These arbitrary monomers are monomers copolymerizable with the above-mentioned monomers.
  • Examples of monomers copolymerizable with the above-mentioned monomers include amide monomers such as acrylamide; olefins such as ethylene and propylene; diene monomers such as butadiene and isoprene; vinyl chloride; Monomers containing halogen atoms such as vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; methyl vinyl ketone and ethyl vinyl Vinyl ketones such as ketone, butyl vinyl ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; heterocyclic compounds containing a heterocyclic ring such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole; methyl (meth) acrylate, ethyl (meth) acrylate, propy
  • an ⁇ , ⁇ -unsaturated nitrile monomer and an acidic group-containing monomer can be suitably blended in the monomer mixture used for the polymerization of the particulate polymer.
  • the body is described in detail.
  • the monomer mixture used for polymerizing the particulate polymer further contains an ⁇ , ⁇ -unsaturated nitrile monomer such as a (meth) acrylonitrile monomer. It is preferable. This is because the use of an ⁇ , ⁇ -unsaturated nitrile monomer such as a (meth) acrylonitrile monomer can increase the binding strength of the binder composition and can significantly improve the strength of the positive electrode.
  • Examples of the ⁇ , ⁇ -unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, ⁇ -chloroacrylonitrile, ⁇ -ethylacrylonitrile and the like. Among these, acrylonitrile and methacrylonitrile are preferable and acrylonitrile is particularly preferable from the viewpoint of improving mechanical strength and binding properties. In addition, these may be used individually by 1 type and may be used in combination of 2 or more types.
  • the blending amount of the ⁇ , ⁇ -unsaturated nitrile monomer such as (meth) acrylonitrile monomer is preferably 1 to 50% by mass, more preferably 5 to 35% by mass in the monomer mixture. is there.
  • the content of an ⁇ , ⁇ -unsaturated nitrile monomer such as a (meth) acrylonitrile monomer is less than 1% by mass, the Tg of the particulate polymer is lowered, and the binder composition containing such a particulate polymer There is a possibility that the peel strength of the positive electrode mixture layer formed using the product may be lowered. Furthermore, in this case, the particulate polymer is likely to swell excessively with respect to the electrolytic solution, which may cause a decrease in peel strength.
  • a secondary material produced using such a binder composition with an appropriate value for the degree of swelling of the particulate polymer with respect to the electrolyte while improving the peel strength of the positive electrode produced using the binder composition containing the particulate polymer An increase in the internal resistance of the battery can be suppressed.
  • polymerizing a particulate polymer further contains an acidic group containing monomer.
  • the acidic group-containing monomer those described above in the section of “Monomer used for polymerization of particulate polymer in binder composition for negative electrode” can be used.
  • the blending amount in the monomer mixture is the same.
  • the monomer mixture used when polymerizing the particulate polymer in the present invention is not limited to those described above unless the present invention is significantly impaired. May contain body.
  • These arbitrary monomers are monomers copolymerizable with the above-mentioned monomers. Examples of monomers copolymerizable with the above-described monomers include styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl.
  • Styrene monomers such as styrene, ⁇ -methylstyrene and divinylbenzene; Amide monomers such as acrylamide; Olefins such as ethylene and propylene; Diene monomers such as butadiene and isoprene; Vinyl chloride and vinylidene chloride Halogen atom-containing monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, etc .; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl vinyl ketone, Butyl vinyl keto , Vinyl ketones such as hexyl vinyl ketone and isopropenyl vinyl ketone; heterocycle-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (
  • the particulate polymer has a crosslinked structure.
  • the cross-linked structure can be formed by introducing the cross-linked monomer into the particulate polymer.
  • the particulate polymer may have a crosslinked structure.
  • a method for introducing a cross-linked structure for example, a method of incorporating a cross-linkable group by polymerizing a polymer from a monomer composition containing the above cross-linkable monomer, a combination of a polymer and a cross-linking agent And the method used.
  • the polymer can be crosslinked by irradiation with heat or energy rays.
  • the degree of crosslinking can be adjusted by the intensity of heating or irradiation with energy rays. Since the degree of swelling decreases as the degree of crosslinking increases, the degree of swelling of the particulate polymer can be controlled by adjusting the degree of crosslinking.
  • the weight average molecular weight of the particulate polymer is preferably 10,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, more preferably 500,000 or less.
  • the weight average molecular weight of the particulate polymer can be determined as a value in terms of polystyrene using tetrahydrofuran as a developing solvent by gel permeation chromatography (GPC).
  • the glass transition temperature (Tg) of the particulate polymer is preferably ⁇ 50 ° C. or higher, more preferably ⁇ 45 ° C.
  • the glass transition temperature of the particulate polymer is in the above range, a secondary battery electrode having excellent strength and flexibility can be obtained, and a secondary battery having high output characteristics can be obtained.
  • the glass transition temperature of the particulate polymer can be adjusted by combining various monomers.
  • the particulate polymer is insoluble in water. Therefore, the particulate polymer is usually in the form of particles in the binder composition and the slurry composition for secondary battery electrodes containing the binder composition, and is included in the secondary battery electrode while maintaining the particle shape. It is.
  • the particulate polymer being “water-insoluble” means that when 0.5 g of the compound is dissolved in 100 g of water at 25 ° C., the insoluble content becomes 90% by mass or more.
  • the volume average particle diameter of the particulate polymer is usually 0.001 ⁇ m or more, preferably 0.01 ⁇ m or more, more preferably 0.05 ⁇ m or more, and usually 100 ⁇ m or less, preferably 10 ⁇ m or less, more preferably 1 ⁇ m or less. is there.
  • the binder composition can exhibit an excellent binding force even when used in a small amount.
  • the volume average particle diameter is measured using a light scattering particle diameter measuring instrument.
  • the shape of the particles may be either spherical or irregular.
  • a particulate polymer may be used individually by 1 type, and may be used in combination of 2 or more types.
  • the proportion of the particulate polymer in the solid content of the binder composition is usually 50% by mass or more, and preferably 70% by mass or more.
  • the “reductone compound” contained in the binder composition for a secondary battery electrode of the present invention refers to a compound having a R 3 C (OH) ⁇ C (OH) C ( ⁇ O) R 4 structure and a salt thereof. .
  • R 3 and R 4 may each be an independent organic group, or may together form a ring structure.
  • Examples of the compound having the R 3 C (OH) ⁇ C (OH) C ( ⁇ O) R 4 structure include glucic acid and its derivatives, reductic acid and its derivatives, ascorbic acid and its isomers, derivatives and the like. It is done.
  • the reductone compound is included in the form of an oxidant (deprotonated reductone; a compound having a R 3 C ( ⁇ O) C ( ⁇ O) C ( ⁇ O) R 4 structure and a salt thereof). Also good. Among these, at least one selected from ascorbic acid and its isomers, derivatives, salts thereof, and oxidants thereof is preferable because of low cost, toxicity, and environmental burden and high human safety.
  • Ascorbic acid (vitamin C) and its isomers and derivatives include, for example, D- or L-ascorbic acid and its sugar derivatives (for example, ⁇ -lactoascorbic acid, glucoascorbic acid, fucoscorbic acid, glucoheptascorbic acid, Maltoascorbic acid), isoascorbic acid (or L-erythroascorbic acid), also called erythorbic acid, enediol type ascorbic acid, enaminol type ascorbic acid, thioenolic type ascorbic acid, and ascorbyl palmitate.
  • D- or L-ascorbic acid and its sugar derivatives for example, ⁇ -lactoascorbic acid, glucoascorbic acid, fucoscorbic acid, glucoheptascorbic acid, Maltoascorbic acid
  • isoascorbic acid (or L-erythroascorbic acid) also called erythorbic acid,
  • ascorbic acid (vitamin C) and isomers and derivatives thereof include salts of the above-described compounds (for example, alkali metal salts, ammonium salts or salts known in the art), such as sodium ascorbic acid.
  • salts of the above-described compounds for example, alkali metal salts, ammonium salts or salts known in the art
  • sodium ascorbic acid such as sodium ascorbic acid.
  • potassium salt of ascorbic acid L-ascorbyl magnesium phosphate may be mentioned.
  • at least one of reductone compound and its oxidant is at least 1 sort (s) selected from (iso) ascorbic acid and its salt, and those oxidants.
  • the salt of (iso) ascorbic acid is preferably an alkali metal salt, more preferably a sodium salt. A mixture of these reductone compounds can be used as necessary.
  • the binder composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, particularly preferably at least one of the reductone compound and its oxidant with respect to 100 parts by mass of the particulate polymer. 0.3 parts by mass or more, preferably 5 parts by mass or less, more preferably 2 parts by mass or less, particularly preferably 1 part by mass or less.
  • residual monomers such as (meth) acrylic acid ester monomers having a boiling point of 145 ° C. or more are sufficiently reduced. can do.
  • the content of at least one of the reductone compound and its oxidant is 5 parts by mass or less with respect to 100 parts by mass of the particulate polymer.
  • the amount of gas generated by decomposition of the remaining reductone compound can be reduced by preventing at least one of the compound and its oxidant from remaining in large amounts, and the initial capacity of the secondary battery can be improved. be able to.
  • the binder composition may contain known arbitrary components that can be blended in the binder composition in addition to the components described above. Moreover, residues, such as a polymerization initiator used for superposition
  • the binder composition has a solid content of usually 10% by mass or more, preferably 20% by mass or more, usually 70% by mass or less, preferably 60% by mass or less.
  • content of the (meth) acrylic acid ester monomer with a boiling point of 145 degreeC or more in the binder composition containing the particulate polymer polymerized using the monomer mixture mentioned above is particulate polymer 100 mass. 1500 ⁇ 10 ⁇ 6 parts by mass or less, preferably 1000 ⁇ 10 ⁇ 6 parts by mass or less, more preferably 500 ⁇ 10 ⁇ 6 parts by mass or less, and 300 ⁇ 10 ⁇ 6 parts by mass. It is particularly preferred that the amount is not more than parts.
  • the binder composition has a boiling point of 145 ° C.
  • the (meth) acrylate monomer is often contained in an amount of 1 ⁇ 10 ⁇ 6 parts by mass or more with respect to 100 parts by mass of the particulate polymer.
  • binder is made into the binder composition by making the content rate of the (meth) acrylic acid ester monomer of boiling point 145 degreeC or more in a binder composition into 1500x10-6 mass parts or less with respect to 100 mass parts of particulate polymers.
  • the amount of gas generated in the secondary battery formed using the composition can be reduced, the high-temperature storage characteristics and the high-temperature cycle characteristics can be improved, and the excellent temporal stability of the binder composition can be obtained.
  • a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is polymerized in water until the polymerization conversion becomes 90% by mass or more.
  • Step (1) to obtain a mixture containing a monomer and an unreacted monomer, and after step (1), a reductone compound and a peroxide are added to the mixture to polymerize the unreacted monomer,
  • step (2) of setting the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C.
  • the method for producing the binder composition of the present invention comprises at least two steps: a step of polymerizing the majority of the monomer mixture and a step of further polymerizing the remaining unreacted residual monomer to reduce the amount of residual monomer. And a step of polymerizing the particulate polymer by polymerization.
  • the monomer mixture is preferably emulsified in advance and then added to the reactor for polymerization.
  • step (1) a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher that can be used for the production of the particulate polymer described above is polymerized in water.
  • the polymerization in the step (1) may be performed in one stage or may be performed in multiple stages.
  • the polymerization conversion rate can be controlled by adjusting the reaction temperature, reaction time, and the like.
  • the polymerization conversion rate in the step (1) is 90% by mass or more, preferably 95% by mass or more is to obtain a particulate polymer having desired properties.
  • the polymerization conversion rate in the step (1) is 90% by mass or more, preferably 95% by mass or more, so that it can be newly generated by redox polymerization in the step (2). It is possible to reduce the amount of the particulate polymer having a property different from that of the particulate polymer.
  • any method such as a suspension polymerization method or an emulsion polymerization method may be used.
  • any of ions, radicals, and living radicals may be used as the reactive species.
  • it is easy to obtain a high molecular weight polymer, and since the polymer is obtained in the form of particles dispersed in water, there is no need for redispersion treatment, and for producing a secondary battery electrode as it is.
  • an emulsion polymerization method is particularly preferable.
  • the emulsion polymerization method can be carried out according to a conventional method (see, for example, “Experimental Chemistry Course” Vol. 28 (Publisher: Maruzen Co., Ltd., edited by The Chemical Society of Japan)).
  • a sealed container equipped with a stirrer and a heating device
  • water an additive such as a dispersant, an emulsifier, a crosslinking agent, a polymerization initiator, and the monomer mixture described above are added so as to have a predetermined composition.
  • a method may be used in which the composition in the container is stirred to emulsify the monomer or the like in water, and the temperature is increased while stirring to initiate polymerization. Or after emulsifying the said composition, it can put into an airtight container, and the method of starting reaction similarly can be used.
  • Examples of the emulsifier used when carrying out the emulsion polymerization in the step (1) include nonionic emulsifiers such as polyoxyethylene alkylene ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester and the like.
  • Anionic emulsifiers such as fatty acids such as myristic acid, palmitic acid, oleic acid, linolenic acid and salts thereof, alkylallyl sulfonates, higher alcohol sulfates, alkyl sulfosuccinic acids; ammonium chlorides such as trimethylammonium chloride and dialkylammonium chloride And cationic emulsifiers such as benzylammonium salts and quaternary ammonium salts; sulfoesters of ⁇ , ⁇ -unsaturated carboxylic acids, ⁇ , ⁇ -unsaturated carbo Sulphate esters of acids, such as copolymerizable emulsifiers containing a double bond such as sulfoalkyl aryl ether.
  • fatty acids such as myristic acid, palmitic acid, oleic acid, linolenic acid and salts thereof, alkylallyl s
  • emulsifiers can be used alone or in combination of two or more.
  • the amount of the emulsifier used is 0.1 to 10% by mass relative to the monomer mixture. If it is less than 0.1% by mass, aggregates are produced during polymerization. On the other hand, if it exceeds 10% by mass, the average particle size of the obtained particulate polymer becomes small.
  • step (1) water-soluble initiators such as potassium persulfate, ammonium persulfate, and hydrogen peroxide as radical polymerization initiators; benzoyl peroxide, di-t-butyl peroxide, 2,2-azobis-2,4 Oil-soluble initiators such as dimethylvaleronitrile;
  • the addition amount of the polymerization initiator varies depending on each initiator, but in the case of a water-soluble initiator, it is 0.1% by mass or more and 5% by mass or less, and in the case of an oil-soluble initiator, 0.1% by mass or more and 3% by mass % Or less.
  • the reaction temperature in step (1) is usually 0 ° C. or higher, preferably 40 ° C. or higher, usually 150 ° C.
  • the polymerization time is usually 1 hour or more and 20 hours or less. If the polymerization temperature is too low, the reaction rate is too slow and the efficiency is poor, and if the polymerization temperature is too high, the aqueous medium tends to evaporate, making the polymerization difficult.
  • the reaction pressure may be normal pressure. Although the reaction can be carried out in air, it is preferably in the presence of an inert gas such as nitrogen or argon.
  • the dispersant those used in ordinary synthesis may be used.
  • the dispersant include benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecylsulfate; sodium dioctylsulfosuccinate and sodium dihexylsulfosuccinate Sulfosuccinates such as; fatty acid salts such as sodium laurate; ethoxy sulfate salts such as polyoxyethylene lauryl ether sulfate sodium salt, polyoxyethylene nonylphenyl ether sulfate sodium salt; alkane sulfonates; alkyl ether phosphates Sodium salt; polyoxyethylene nonylphenyl ether, polyoxyethylene sorbitan lauryl ester, polyoxyethylene- Nonionic
  • benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecylsulfate can be preferably used. More preferably, benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate can be used from the viewpoint of excellent oxidation resistance. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. The amount of the dispersant is usually 0.01 parts by mass to 10 parts by mass with respect to 100 parts by mass of the total amount of the monomer mixture.
  • seed polymerization may be performed using seed particles.
  • step (2) Here, in the step (1) described above, it is difficult to set the polymerization conversion rate to 100% by mass, and an unreacted monomer containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher remains. To do. Therefore, in the step (2), an unreacted monomer (residual monomer) remaining after the step (1) is polymerized using a redox initiator that uses a reductone compound and a peroxide in combination, and a binder composition is obtained. Reduce the amount of residual monomer in it.
  • step (2) a reductone compound and a peroxide are added to the polymerization system containing a mixture of a polymer and an unreacted monomer obtained through step (1).
  • the redox polymerization is carried out until the content of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is 1 ⁇ 10 ⁇ 6 parts by mass to 1500 ⁇ 10 ⁇ 6 parts by mass with respect to 100 parts by mass of the polymer.
  • the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher should be adjusted by changing the amount of the reductone compound and peroxide used in step (2) and the redox polymerization conditions. Can do.
  • the reaction temperature of the step (2) is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, preferably 80 ° C. or lower, more preferably 60 ° C. or lower. If the polymerization temperature is too low, the reaction rate is too slow, so the efficiency is poor, and if the polymerization temperature is too high, the decomposition rate of the redox initiator (reductone compounds and peroxides) is too high, making the polymerization difficult. is there. By performing redox polymerization, the polymerization reaction of the residual monomer can be performed even under such a mild temperature condition.
  • the polymerization time in step (2) is preferably 1 hour or more and 6 hours or less.
  • the temperature of the polymerization system is set to a temperature higher than the polymerization temperature at the time of redox polymerization (for example, more than 80 ° C ), It is preferable to remove or decompose the peroxide.
  • the pressure of the reaction in the step (2) may be a normal pressure.
  • the reaction can be carried out in air, it is preferably in the presence of an inert gas such as nitrogen or argon.
  • the amount of the reductone compound is appropriately changed according to the kind of the peroxide, but is preferably 0.05% by mass or more, preferably with respect to the amount of the monomer mixture used in the step (1). 0.1 mass% or more, usually 5 mass% or less, preferably 1 mass% or less.
  • the amount of the reductone compound used is too small, redox polymerization does not proceed sufficiently, and the residual monomer reducing effect may be insufficient.
  • the reductone compounds may be added all at once or dividedly, but in terms of improving the residual monomer reduction efficiency, divided addition is preferred.
  • the blending amount of the polymerization initiator is reduced as compared with the case where other polymerization methods are employed to reduce the residual monomer, and polymerization is started in the binder composition. It is possible to prevent the residue of the agent from remaining in large quantities.
  • the reductone compounds used in the step (2) can include the reductone compounds exemplified in the section of the binder composition, and as mentioned above, ascorbic acid, its isomers and derivatives, and salts thereof. Is preferred.
  • the peroxide include water-soluble peroxides exemplified below. Since the binder composition of this invention is a binder composition used for manufacture of a secondary battery, it is preferable to use the peroxide which does not contain a transition metal element. In addition, that the peroxide is “water-soluble” means that it has a water solubility of 5% by mass or more in water at 25 ° C.
  • peroxide that can be used in the present invention, hydrogen peroxide, peroxy acid salt, peroxodisulfuric acid and its salt, peroxy ester salt, peroxide ammonium or alkali metal salt, perborate, persulfate And tert-butyl hydroperoxide (t-BuOOH), benzoyl peroxide.
  • tert-butyl hydroperoxide, hydrogen peroxide, and peracetic acid are preferable, and tert-butyl hydroperoxide is particularly preferable. This is because radical species generated from peroxides that are water-soluble and have a low molecular weight have high molecular mobility and can reduce residual monomers effectively because of their low molecular weight.
  • the amount of peroxide used is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, preferably 5% by mass or less, based on the amount of the monomer mixture used in step (1). More preferably, it is 1 mass% or less.
  • the slurry composition for secondary battery electrodes of the present invention is characterized by containing the above-mentioned binder composition and electrode active material (positive electrode active material or negative electrode active material).
  • electrode active material positive electrode active material or negative electrode active material.
  • the slurry composition for secondary battery electrodes of the present invention may contain a conductive material, a viscosity modifier, a surfactant, a dispersant and the like in addition to the binder composition and the electrode active material.
  • the ratio of the binder composition contained in the slurry composition of the present invention can be adjusted as appropriate so that the performance of the obtained battery is satisfactorily exhibited.
  • the ratio of the solid content of the binder composition to 100 parts by mass of the electrode active material is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and usually 50 parts by mass.
  • Part or less preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and particularly preferably 3 parts by weight or less.
  • a negative electrode active material When using a slurry composition for formation of a negative electrode, a negative electrode active material is used as an electrode active material.
  • the negative electrode active material is an electrode active material used in the negative electrode, and is a material that transfers electrons in the negative electrode of the secondary battery.
  • a material that can occlude and release lithium is usually used as the negative electrode active material. Examples of the material that can occlude and release lithium include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material obtained by combining these materials.
  • the carbon-based negative electrode active material refers to an active material having carbon as a main skeleton into which lithium can be inserted (also referred to as “dope”).
  • Examples of the carbon-based negative electrode active material include a carbonaceous material and a graphite material. Is mentioned.
  • the carbonaceous material is a material having a low degree of graphitization (ie, low crystallinity) obtained by carbonizing a carbon precursor by heat treatment at 2000 ° C. or lower.
  • the minimum of the heat processing temperature at the time of carbonizing is not specifically limited, For example, it can be 500 degreeC or more.
  • Examples of the carbonaceous material include graphitizable carbon that easily changes the carbon structure depending on the heat treatment temperature, and non-graphitizable carbon having a structure close to an amorphous structure typified by glassy carbon.
  • the graphitizable carbon for example, a carbon material using tar pitch obtained from petroleum or coal as a raw material can be mentioned. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch carbon fibers, pyrolytic vapor grown carbon fibers, and the like.
  • examples of the non-graphitizable carbon include a phenol resin fired body, polyacrylonitrile-based carbon fiber, pseudo-isotropic carbon, furfuryl alcohol resin fired body (PFA), and hard carbon.
  • the graphite material is a material having high crystallinity close to that of graphite obtained by heat-treating graphitizable carbon at 2000 ° C. or higher.
  • the upper limit of heat processing temperature is not specifically limited, For example, it can be 5000 degrees C or less.
  • the graphite material include natural graphite and artificial graphite.
  • the artificial graphite for example, artificial graphite obtained by heat-treating carbon containing graphitizable carbon mainly at 2800 ° C. or higher, graphitized MCMB heat-treated at 2000 ° C. or higher, and mesophase pitch-based carbon fiber at 2000 ° C. Examples thereof include graphitized mesophase pitch-based carbon fibers that have been heat-treated.
  • the metal-based negative electrode active material is an active material containing a metal, and usually contains an element capable of inserting lithium in the structure, and the theoretical electric capacity per unit mass when lithium is inserted is 500 mAh / g or more.
  • the metal active material include lithium metal and a single metal capable of forming a lithium alloy (for example, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn). , Sr, Zn, Ti, etc.) and alloys thereof, and oxides, sulfides, nitrides, silicides, carbides, phosphides, and the like thereof.
  • active materials containing silicon are preferable. This is because the capacity of the lithium ion secondary battery can be increased by using the silicon-based negative electrode active material.
  • silicon-based negative electrode active materials examples include silicon (Si), alloys of silicon and cobalt, nickel, iron, etc., SiO, SiOx, mixtures of Si-containing materials and carbon materials, and Si-containing materials coated with conductive carbon.
  • Si silicon
  • alloys of silicon and cobalt nickel, iron, etc.
  • SiO, SiOx mixtures of Si-containing materials and carbon materials
  • Si-containing materials coated with conductive carbon examples include silicon (Si), alloys of silicon and cobalt, nickel, iron, etc., SiO, SiOx, mixtures of Si-containing materials and carbon materials, and Si-containing materials coated with conductive carbon.
  • Si-containing materials coated with conductive carbon.
  • a composite of a Si-containing material and conductive carbon formed into a composite can be used.
  • SiOx is a compound containing at least one of SiO and SiO 2 and Si, and x is usually 0.01 or more and less than 2.
  • SiOx can be formed using the disproportionation reaction of a silicon monoxide (SiO), for example.
  • SiOx can be prepared by heat-treating SiO, optionally in the presence of a polymer such as polyvinyl alcohol, to produce silicon and silicon dioxide. The heat treatment can be performed at a temperature of 900 ° C. or higher, preferably 1000 ° C. or higher, in an atmosphere containing an organic gas and / or steam after grinding and mixing SiO and optionally a polymer.
  • Si-containing material such as silicon and SiOx
  • carbon material such as carbonaceous material and graphite material
  • a polymer such as polyvinyl alcohol. Things.
  • carbonaceous material and a graphite material the material which can be used as a carbon-type negative electrode active material can be used.
  • a composite of Si-containing material and conductive carbon for example, a pulverized mixture of SiO, a polymer such as polyvinyl alcohol, and optionally a carbon material is heat-treated in an atmosphere containing, for example, an organic gas and / or steam.
  • a known method such as a method of coating the surface of SiO particles with an organic gas or the like by chemical vapor deposition, or a composite particle (granulation) of SiO particles and graphite or artificial graphite by a mechanochemical method. Can be used.
  • the negative electrode active material when a carbon-based negative electrode active material or a metal-based negative electrode active material is used as the negative electrode active material, these negative electrode active materials expand and contract as the lithium ion secondary battery is charged and discharged. Therefore, when these negative electrode active materials are used, normally, the negative electrode gradually expands due to repeated expansion and contraction of the negative electrode active material, the secondary battery is deformed, and electrical characteristics such as cycle characteristics are obtained. May be reduced.
  • the negative electrode bulge caused by expansion and contraction of the negative electrode active material is suppressed by the cross-linked structure formed due to the cross-linkable monomer described above. Electrical characteristics such as cycle characteristics can be improved.
  • capacitance of a lithium ion secondary battery can be increased if the said silicon-type negative electrode active material is used, generally a silicon-type negative electrode active material expand
  • the negative electrode active material when a mixture of a carbon-based negative electrode active material and a silicon-based negative electrode active material is used as the negative electrode active material, from the viewpoint of sufficiently increasing the capacity of the lithium ion secondary battery while sufficiently suppressing the occurrence of swelling of the negative electrode. It is preferable to use artificial graphite as the carbon-based negative electrode active material, and as the silicon-based negative electrode active material, Si, SiOx, a mixture of a Si-containing material and a carbon material, and a composite of a Si-containing material and conductive carbon.
  • a composite of a Si-containing material and conductive carbon as the silicon-based negative electrode active material, and a composite in which SiOx is dispersed in a conductive carbon matrix. It is particularly preferable to use (Si—SiOx—C composite). While these negative electrode active materials can occlude and release a relatively large amount of lithium, the volume change when lithium is occluded and released is relatively small. Therefore, if these negative electrode active materials are used, a lithium ion secondary using a negative electrode for a lithium ion secondary battery formed using the slurry composition while suppressing an increase in volume change of the negative electrode active material during charge / discharge. The capacity of the battery can be sufficiently increased.
  • the particle size and specific surface area of the negative electrode active material are not particularly limited, and can be the same as those of conventionally used negative electrode active materials.
  • the content ratio of the negative electrode active material in the slurry composition of the present invention is preferably 90% by mass or more, more preferably 95% by mass or more, preferably 99.9% by mass or less, more preferably 99% by mass or less. .
  • the capacity of the secondary battery of the present invention can be increased, and the flexibility of the negative electrode and the binding property between the current collector and the negative electrode mixture layer are improved. Can be made.
  • a positive electrode active material is used as the electrode active material.
  • the positive electrode active material is an electrode active material used in the positive electrode, and is a material that transfers electrons in the positive electrode of the secondary battery.
  • the secondary battery of the present invention is a lithium ion secondary battery
  • a material capable of inserting and extracting lithium ions is usually used as the positive electrode active material.
  • Such positive electrode active materials are roughly classified into those made of inorganic compounds and those made of organic compounds.
  • Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, transition metal sulfides, lithium-containing composite metal oxides of lithium and transition metals, and the like.
  • Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.
  • Examples of the transition metal oxide include MnO, MnO 2 , V 2 O 5 , V 6 O 13 , TiO 2 , Cu 2 V 2 O 3 , amorphous V 2 O—P 2 O 5 , MoO 3 , V 2 O 5 , V 6 O 13 and the like are mentioned, and among them, MnO, V 2 O 5 , V 6 O 13 and TiO 2 are preferable from the viewpoint of cycle stability and capacity of the secondary battery.
  • transition metal sulfide examples include TiS 2 , TiS 3 , amorphous MoS 2 , and FeS.
  • lithium-containing composite metal oxide examples include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.
  • lithium-containing composite metal oxide having a layered structure examples include lithium-containing cobalt oxide (LiCoO 2 ), lithium-containing nickel oxide (LiNiO 2 ), Co—Ni—Mn lithium composite oxide, Ni—Mn— Examples thereof include a lithium composite oxide of Al, a lithium composite oxide of Ni—Co—Al, and a solid solution of LiMaO 2 and Li 2 MbO 3 . Examples of the solid solution of LiMaO 2 and Li 2 MbO 3 include xLiMaO 2. (1-x) Li 2 MbO 3 .
  • x represents a number satisfying 0 ⁇ x ⁇ 1
  • Ma represents one or more transition metals having an average oxidation state of 3+
  • Mb represents one or more transition metals having an average oxidation state of 4+.
  • LiCoO 2 is preferably used from the viewpoint of improving the cycle characteristics of the secondary battery
  • LiMaO is used from the viewpoint of improving the energy density of the secondary battery.
  • a solid solution of 2 and Li 2 MbO 3 is preferred.
  • xLiMaO 2 ⁇ (1-x) Li 2 MbO 3 (x represents a number satisfying 0 ⁇ x ⁇ 1, Ma is Ni, Co, Mn Mb represents one or more selected from the group consisting of Mn, Zr and Ti).
  • xLiMaO 2 ⁇ (1-x) Li 2 MnO 3 (x represents a number satisfying 0 ⁇ x ⁇ 1, and Ma is one or more selected from the group consisting of Ni, Co, Mn, Fe, and Ti. Is preferred).
  • An example of such a solid solution is Li [Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ] O 2 .
  • Examples of the lithium-containing composite metal oxide having a spinel structure include compounds in which a part of Mn of lithium manganate (LiMn 2 O 4 ) is substituted with another transition metal.
  • LiMn 2 O 4 lithium manganate
  • a specific example is Li s [Mn 2 ⁇ t Md t ] O 4 .
  • Md represents one or more transition metals having an average oxidation state of 4+.
  • Specific examples of Md include Ni, Co, Fe, Cu, and Cr.
  • T represents a number satisfying 0 ⁇ t ⁇ 1, and s represents a number satisfying 0 ⁇ s ⁇ 1.
  • a lithium-excess spinel compound represented by Li 1 + x Mn 2 ⁇ x O 4 (0 ⁇ X ⁇ 2) can also be used.
  • s represents a number satisfying 0 ⁇ s ⁇ 1
  • t represents a number satisfying 0 ⁇ t ⁇ 1
  • z represents a number satisfying 0 ⁇ z ⁇ 0.1.
  • LiNi 0.5 Mn 1.5 O 4 in which Mn of lithium manganate is substituted with Ni is also preferable.
  • LiNi 0.5 Mn 1.5 O 4 and the like can replace all of Mn 3+ considered to be a factor of structural deterioration.
  • LiNi 0.5 Mn 1.5 O 4 and the like undergo an electrochemical reaction from Ni 2+ to Ni 4+ , a secondary battery having a high operating voltage and a high capacity can be realized.
  • Examples of the lithium-containing composite metal oxide having an olivine type structure include an olivine type lithium phosphate compound represented by Li y McPO 4 .
  • Mc represents one or more transition metals having an average oxidation state of 3+, and examples thereof include Mn, Fe, and Co.
  • Y represents a number satisfying 0 ⁇ y ⁇ 2.
  • Mn or Co may be partially substituted with another metal.
  • the metal that can be substituted include Fe, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B, and Mo.
  • examples of the positive electrode active material made of an inorganic compound include a positive electrode active material having a polyanion structure such as Li 2 MeSiO 4 , LiFeF 3 having a perovskite structure, and Li 2 Cu 2 O 4 having an orthorhombic structure. Can be mentioned.
  • Me represents Fe or Mn.
  • examples of the positive electrode active material made of an organic compound include conductive polymers such as polyacetylene and poly-p-phenylene.
  • a composite material covered with a carbon material may be produced by reducing and firing an iron-based oxide in the presence of a carbon source material, and this composite material may be used as a positive electrode active material.
  • Iron-based oxides tend to have poor electrical conductivity, but can be used as a high-performance positive electrode active material by using a composite material as described above.
  • the positive electrode active material is preferably a lithium-containing composite metal oxide because it has a high energy density.
  • Many lithium-containing composite metal oxides have a hydrophilic group as a surface functional group. Therefore, by using the lithium-containing composite metal oxide, a slurry composition having high dispersion stability can be obtained, and the binding between the positive electrode active materials in the electrode can be kept strong.
  • the surface state of the positive electrode active material can be determined by measuring the contact angle between the positive electrode active material and the solvent. For example, it can be confirmed by pressure-molding only the positive electrode active material to produce pellets and determining the contact angle of the pellets with a polar solvent (for example, N-methylpyrrolidone). A lower contact angle indicates that the positive electrode active material is more hydrophilic.
  • examples of the positive electrode active material include nickel hydroxide particles.
  • the nickel hydroxide particles may be dissolved in cobalt, zinc, cadmium, or the like, or may be coated with a cobalt compound whose surface is subjected to an alkali heat treatment.
  • the positive electrode active material may be partially element-substituted.
  • an inorganic compound and an organic compound may be used in combination.
  • one type of positive electrode active material may be used alone, or two or more types may be used in combination at any ratio.
  • the particle size of the positive electrode active material particles is usually selected as appropriate in consideration of other constituent requirements of the secondary battery.
  • the 50% volume cumulative diameter of the positive electrode active material particles is usually 0.1 ⁇ m or more, preferably 0.4 ⁇ m or more, more preferably 1 ⁇ m or more, from the viewpoint of improving battery characteristics such as load characteristics and cycle characteristics. It is 50 ⁇ m or less, preferably 30 ⁇ m or less, more preferably 20 ⁇ m or less. When the 50% volume cumulative diameter is within this range, a secondary battery having excellent output characteristics and a large charge / discharge capacity can be obtained. Moreover, the handling at the time of manufacturing the slurry composition for manufacturing a positive electrode compound material layer and manufacturing a positive electrode is easy.
  • the 50% volume cumulative diameter can be determined by measuring the particle size distribution by laser diffraction.
  • lithium-containing nickel oxide (LiNiO 2 ), lithium-containing cobalt oxide (LiCoO). 2 ), Co—Ni—Mn lithium composite oxide (Li (Co 2 Mn Ni) O 2 ), Li [Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ] O 2 , LiNi 0.5 Mn 1.5 O 4 and the like are preferable.
  • Co-Ni-Mn lithium composite oxide (Li (Co Mn Ni) O 2 ) and lithium-containing cobalt oxide (LiCoO 2 ) are preferable.
  • the content ratio of the positive electrode active material in the slurry composition of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less. is there. By setting the content ratio of the positive electrode active material in the slurry composition within the above range, a good slurry composition and positive electrode can be produced.
  • the said slurry composition contains a electrically conductive material.
  • the conductive material include particles made of carbon allotrope having conductivity.
  • the conductive material include conductive carbon such as acetylene black, ketjen black, carbon black, graphite, vapor grown carbon fiber, and carbon nanotube. Further, for example, carbon powder such as graphite, fibers and foils of various metals, and the like are also included.
  • a conductive material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
  • acetylene black is used as the conductive material from the viewpoint of improving the electrical contact between the positive electrode active materials and improving the electrical characteristics of the secondary battery using the positive electrode formed using the slurry composition. It is preferable.
  • the 50% volume cumulative diameter of the conductive material is preferably smaller than the 50% volume cumulative diameter of the positive electrode active material.
  • the specific range of the 50% volume cumulative diameter of the conductive material is usually 0.001 ⁇ m or more, preferably 0.05 ⁇ m or more, more preferably 0.01 ⁇ m or more, and usually 10 ⁇ m or less, preferably 5 ⁇ m or less, more preferably 1 ⁇ m. It is as follows. When the 50% volume cumulative diameter of the conductive material is within this range, high conductivity can be obtained with a smaller amount of use.
  • the amount of the conductive material is usually 0.01 parts by mass or more, preferably 1 part by mass or more, and usually 20 parts by mass or less, preferably 10 parts by mass or less with respect to 100 parts by mass of the positive electrode active material.
  • the amount of the conductive material When the amount of the conductive material is within this range, the capacity of the secondary battery can be increased and high load characteristics can be exhibited. If the amount of the conductive material is too small, the conductive path formed by electrical contact between the positive electrode active materials becomes insufficient, and the output of the secondary battery may be reduced. On the other hand, when the blending amount of the conductive material is too large, the stability of the slurry composition is lowered and the density of the positive electrode mixture layer in the positive electrode is lowered, so that the capacity of the lithium ion secondary battery cannot be sufficiently increased. .
  • the viscosity modifier is for adjusting the viscosity of the slurry composition and facilitating the application of the slurry composition on the current collector.
  • a water-soluble polymer can be used as the viscosity modifier.
  • examples of the viscosity modifier include cellulose polymers such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose, and ammonium salts and alkali metal salts of these cellulose polymers; modified or unmodified poly (meth) acrylic Acids and ammonium and alkali metal salts of these poly (meth) acrylic acids; modified or unmodified polyvinyl alcohol, copolymers of acrylic acid or acrylates with vinyl alcohol, maleic anhydride, maleic acid or Polyvinyl alcohols such as copolymers of fumaric acid and vinyl alcohol; polyethylene glycol, polyvinyl pyrrolidone, modified polyacrylic acid, oxidized starch, phosphate starch, casein, various modified starches, acrylonitrile Butadiene copolymer hydrides can be used.
  • any polymer that is water-soluble and has a thiol group at the terminal water-soluble polymer having a thiol group at the terminal
  • the compounding quantity of a viscosity modifier is 0.1 mass part or more normally per 100 mass parts of electrode active materials, Preferably, it is 0.3 mass part or more, Usually 2 mass parts or less, Preferably it is 1 mass part or less.
  • the blending amount of the viscosity modifier is within the above range, a slurry composition having a good viscosity can be obtained. Therefore, the slurry composition can be satisfactorily applied onto the current collector during electrode formation, and as a result, the product life of the obtained electrode can be extended.
  • the slurry composition of the present invention may further contain a surfactant.
  • the surfactant is effective for preventing the repelling that occurs when applying the slurry composition to the current collector and improving the smoothness of the electrode.
  • examples of the surfactant include alkyl surfactants, silicon surfactants, fluorine surfactants, metal surfactants, and the like.
  • the compounding amount of the surfactant is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the electrode active material. When the surfactant is in the above range, productivity and smoothness during electrode production are improved, and the battery characteristics of the secondary battery are excellent.
  • the slurry composition of the present invention may further contain a dispersant.
  • the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound.
  • a specific dispersing agent is selected according to the electrode active material and conductive material to be used. By using the dispersant, the stability of the slurry composition is improved and a smooth electrode is obtained, so that the battery capacity of the secondary battery can be increased.
  • the amount of the dispersing agent is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and usually 10 parts by mass with respect to 100 parts by mass of the electrode active material. Part or less, preferably 5 parts by weight or less, more preferably 2 parts by weight or less.
  • the slurry composition of the present invention may contain components such as a reinforcing material, an antioxidant, and an electrolytic solution additive having a function of suppressing decomposition of the electrolytic solution.
  • components such as a reinforcing material, an antioxidant, and an electrolytic solution additive having a function of suppressing decomposition of the electrolytic solution.
  • known ones can be used. For example, those described in International Publication No. 2012/115096, International Publication No. 2012/036260, and Japanese Patent Application Laid-Open No. 2012-204303 can be used. it can.
  • the slurry composition of the present invention can be prepared by dispersing each of the above components in an aqueous medium as a dispersion medium. Specifically, the above components and the aqueous medium are mixed using a mixer such as a ball mill, a sand mill, a bead mill, a pigment disperser, a grinder, an ultrasonic disperser, a homogenizer, a planetary mixer, or a fill mix. Thus, a slurry composition can be prepared.
  • a slurry composition can be prepared.
  • water is usually used, but an aqueous solution of an arbitrary compound or a mixed solution of a small amount of an organic medium and water may be used.
  • the solid content concentration of the slurry composition can be set to a concentration at which each component can be uniformly dispersed, for example, 10 to 80% by mass. Further, the mixing of each of the above components and the aqueous medium can be usually carried out in the range of room temperature to 80 ° C. for 10 minutes to several hours.
  • the viscosity of the slurry composition is preferably 10 mPa ⁇ s or more, more preferably 100 mPa ⁇ s or more, preferably 100,000 mPa ⁇ s or less, more preferably from the viewpoint of the temporal stability and coating properties of the slurry composition. Is 50,000 mPa ⁇ s or less.
  • the viscosity is a value measured using a B-type viscometer at 25 ° C. and a rotation speed of 60 rpm.
  • the pH of the said slurry composition is 7 or more normally, Preferably it is 8 or more, Usually, 12 or less, Preferably it is 11.5 or less.
  • a method of adjusting the pH of the slurry composition for example, a method of adjusting the pH of the slurry composition by washing the positive electrode active material before preparing the slurry composition, bubbling carbon dioxide gas to the prepared slurry composition Examples thereof include a method for adjusting pH and a method for adjusting using a pH adjusting agent.
  • a pH adjuster is a water-soluble substance which shows acidity. Either a strong acid or a weak acid may be used.
  • water-soluble substances that exhibit weak acidity include organic compounds having an acid group such as a carboxylic acid group, a phosphoric acid group, and a sulfonic acid group.
  • an organic compound having a carboxylic acid group is particularly preferably used.
  • Specific examples of the compound having a carboxylic acid group include succinic acid, phthalic acid, maleic acid, succinic anhydride, phthalic anhydride, maleic anhydride and the like. These compounds can be made into acid anhydrides having little influence in the secondary battery by drying.
  • water-soluble substances that exhibit strong acidity include hydrochloric acid, nitric acid, sulfuric acid, and acetic acid.
  • pH adjusting agents described above it is preferable that they are decomposed or volatilized in the drying step of the slurry composition. In this case, no pH adjuster remains in the obtained positive electrode.
  • examples of such a pH adjuster include acetic acid and hydrochloric acid.
  • a pH adjuster may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
  • the pH of the slurry composition may be adjusted at any time as long as it is during the production process of the slurry composition. Especially, after adjusting a slurry composition to desired solid content concentration, it is preferable to adjust pH with a pH adjuster. By adjusting the pH after adjusting the slurry composition to a predetermined solid content concentration, it is possible to easily adjust the pH while preventing dissolution of the positive electrode active material.
  • the slurry composition of the present invention is prepared by preparing the binder composition of the present invention and then mixing the binder composition and the electrode active material, or dispersing them in an aqueous medium as a dispersion medium. Also good.
  • the secondary battery electrode of the present invention is obtained by applying the slurry composition for a secondary battery electrode obtained as described above on a current collector, and applying the slurry for the secondary battery electrode on the current collector. It is obtained by drying the composition.
  • the electrode for a secondary battery of the present invention includes a current collector and an electrode mixture layer formed on the current collector.
  • the electrode mixture layer includes at least an electrode active material and a particulate weight. The merger is included.
  • each component such as an electrode active material contained in the electrode mixture layer is contained in the slurry composition of the present invention, and a suitable abundance ratio of these components is determined according to the present invention. It is the same as the preferred abundance ratio of each component in the slurry composition.
  • a method for applying the slurry composition for a secondary battery electrode on the current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, or the like can be used. At this time, the slurry composition may be applied to only one side of the current collector or may be applied to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the thickness of the electrode mixture layer obtained by drying.
  • the current collector to which the slurry composition is applied is not particularly limited as long as it is a material having electrical conductivity and electrochemical durability.
  • the current collector is preferably made of metal, such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum.
  • a copper foil is particularly preferable as the current collector used for the negative electrode
  • aluminum is particularly preferable as the current collector used for the positive electrode.
  • One type of current collector material may be used alone, or two or more types may be used in combination at any ratio.
  • the shape of the current collector is not particularly limited, but a sheet shape having a thickness of about 0.001 mm to 0.5 mm is preferable.
  • the current collector is used after roughening the surface in advance in order to increase the adhesive strength of the electrode mixture layer.
  • the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method.
  • a mechanical polishing method usually, a polishing cloth with a fixed abrasive particle, a grindstone, an emery buff, a wire brush provided with a steel wire or the like is used.
  • a method for drying the slurry composition on the current collector is not particularly limited, and a known method can be used. For example, drying with warm air, hot air, low-humidity air, vacuum drying, irradiation with infrared rays, electron beams, or the like. A drying method is mentioned. Thus, by drying the slurry composition on the current collector, an electrode mixture layer is formed on the current collector, and a lithium ion secondary battery electrode including the current collector and the electrode mixture layer is obtained. be able to.
  • the electrode mixture layer may be subjected to pressure treatment using a die press or a roll press.
  • the pressure treatment can improve the adhesion between the electrode mixture layer and the current collector and reduce the porosity of the electrode.
  • the porosity is preferably 5% or more, more preferably 7% or more, preferably 15% or less, more preferably 13% or less.
  • the thickness of the electrode mixture layer is usually 5 ⁇ m or more, preferably 10 ⁇ m or more, and usually 300 ⁇ m or less, preferably 250 ⁇ m or less. When the thickness of the electrode mixture layer is in the above range, both load characteristics and energy density are high.
  • the water content in the electrode mixture layer is preferably 1000 ppm or less, and more preferably 500 ppm or less. By setting the water content of the electrode mixture layer within the above range, a secondary battery electrode having excellent durability can be realized. The amount of water can be measured by a known method such as the Karl Fischer method.
  • the powder molding method refers to preparing a slurry composition for producing an electrode for a secondary battery, preparing composite particles including an electrode active material from the slurry composition, and placing the composite particles on a current collector. It is a manufacturing method which supplies the electrode for secondary batteries by forming an electrode compound-material layer by supplying and roll-pressing as needed and shaping
  • the secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolytic solution, and a separator, and uses the secondary battery electrode of the present invention as at least one of the positive electrode and the negative electrode.
  • the secondary battery of the present invention is excellent in high temperature storage characteristics and high temperature cycle characteristics, and gas generation is suppressed.
  • the secondary battery of the present invention may be any of a lithium ion secondary battery, a nickel hydride secondary battery, and the like. Among these, lithium ion secondary batteries are preferable because performance improvement effects such as improvement of cycle characteristics and output characteristics are particularly remarkable.
  • the secondary battery of the present invention is a lithium ion secondary battery will be described.
  • At least one of the positive electrode and the negative electrode may be the electrode for the secondary battery of the present invention. That is, a known electrode may be used as either the positive electrode or the negative electrode.
  • Examples of known positive electrodes include those usually comprising a current collector and a positive electrode mixture layer formed on the surface of the current collector.
  • the positive electrode mixture layer comprises a positive electrode active material, a conductive material and a binder.
  • the positive electrode active material, and the conductive material those described above in the sections of “secondary battery electrode” and “secondary battery electrode slurry composition” can be used.
  • the binder any known binder can be used as long as the present invention is not significantly impaired.
  • the positive electrode mixture layer may contain components other than the positive electrode active material, the conductive material, and the binder as necessary, for example, the components listed as “other components” in the section of “Slurry composition for secondary battery electrode”. It may be included. One of these may be used alone, or two or more of these may be used in combination at any ratio.
  • the negative electrode there is usually one having a current collector and a negative electrode mixture layer formed on the surface of the current collector, and the negative electrode mixture layer contains a negative electrode active material and a binder.
  • the current collector and the negative electrode active material those described above in the sections of “secondary battery electrode” and “secondary battery electrode slurry composition” can be used.
  • the binder any known binder can be used as long as the present invention is not significantly impaired. Examples of such binders include polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, and polyacrylonitrile derivatives.
  • a soft polymer such as an acrylic soft polymer, a diene soft polymer, an olefin soft polymer, or a vinyl soft polymer may be used. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.
  • the negative electrode mixture layer contains components other than the negative electrode active material and the binder, for example, the components listed as “other components” in the section of “slurry composition for secondary battery electrode” as necessary. May be. One of these may be used alone, or two or more of these may be used in combination at any ratio.
  • the total thickness of these electrodes is usually 5 ⁇ m or more, preferably 10 ⁇ m or more, and usually 300 ⁇ m or less, preferably 250 ⁇ m or less. When the thickness of the electrode is in the above range, both load characteristics and energy density can be improved.
  • Electrodes prepare the slurry composition for electrodes containing an electrode active material, a binder, and water similarly to the electrode for secondary batteries of this invention, for example,
  • the layer of the slurry composition is used as a collector. It may be formed and the layer dried.
  • Electrode As an electrolytic solution for a lithium ion secondary battery, for example, a nonaqueous electrolytic solution in which a supporting electrolyte is dissolved in a nonaqueous solvent is used.
  • a lithium salt is usually used.
  • the lithium salt include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi, and the like.
  • LiPF 6 , LiClO 4 , and CF 3 SO 3 Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferable.
  • One of these may be used alone, or two or more of these may be used in combination at any ratio. Since the lithium ion conductivity increases as the supporting electrolyte having a higher degree of dissociation is used, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.
  • the concentration of the supporting electrolyte in the electrolytic solution is usually 1% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less. Depending on the type of supporting electrolyte, it may be used usually at a concentration of 0.5 mol / L to 2.5 mol / L. If the concentration of the supporting electrolyte is too low or too high, the ionic conductivity may decrease.
  • the non-aqueous solvent is not particularly limited as long as it can dissolve the supporting electrolyte.
  • non-aqueous solvents include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (MEC); and esters such as ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; Among these, carbonates are preferable because they have a high dielectric constant and a wide stable potential region.
  • a non-aqueous solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
  • an additive in electrolyte solution examples include carbonate compounds such as vinylene carbonate (VC).
  • An additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.
  • an electrolytic solution other than the above for example, a polymer electrolyte such as polyethylene oxide or polyacrylonitrile; a gel polymer electrolyte obtained by impregnating the polymer electrolyte with an electrolytic solution; an inorganic solid electrolyte such as LiI or Li 3 N; Also good.
  • a polyolefin resin such as polyethylene or polypropylene, or a microporous film or nonwoven fabric containing an aromatic polyamide resin; a porous resin coat containing an inorganic ceramic powder;
  • microporous membranes made of polyolefin resins (polyethylene, polypropylene, polybutene, polyvinyl chloride), and resins such as mixtures or copolymers thereof; polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, Examples thereof include a microporous film made of a resin such as polyimide, polyimide amide, polyaramid, polycycloolefin, nylon, and polytetrafluoroethylene; a polyolefin fiber woven or non-woven fabric thereof; an aggregate of insulating substance particles, and the like.
  • a microporous film made of a polyolefin-based resin is preferable
  • the thickness of the separator is usually 0.5 ⁇ m or more, preferably 1 ⁇ m or more, and usually 40 ⁇ m or less, preferably 30 ⁇ m or less, more preferably 10 ⁇ m or less. Within this range, the resistance due to the separator in the secondary battery is reduced, and the workability when manufacturing the secondary battery is excellent.
  • a positive electrode and a negative electrode are overlapped via a separator, and this is wound into a battery container according to the shape of the battery.
  • the method of injecting and sealing is mentioned.
  • an expanded metal; an overcurrent prevention element such as a fuse or a PTC element; a lead plate or the like may be inserted to prevent an increase in pressure inside the battery or overcharge / discharge.
  • the shape of the secondary battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.
  • the manufactured laminated cell type lithium ion secondary battery was charged to 4.3 V by a constant current method of 0.1 C in a 25 ° C. environment, and then stored at 80 ° C. for 50 hours.
  • the cell of the laminated cell type lithium ion secondary battery was sandwiched between glass plates, and the thickness of the cell was measured with a micro gauge.
  • the thickness of the cell before storage at 80 ° C. is a
  • the thickness of the cell after storage at 80 ° C. for 50 hours is b
  • the thickness ratio (b / a) before and after storage at 80 ° C. is determined. did. It shows that the smaller the calculated ratio (b / a), the smaller the gas generation amount and the better the gas generation suppression effect.
  • Ratio (b / a) is 1.00 times or more and 1.05 times or less
  • B: Ratio (b / a) is more than 1.05 times and 1.10 times or less
  • D: Ratio (b / a) is more than 1.15 times and less than 1.20 times
  • the manufactured laminated cell type lithium ion secondary battery was charged to 4.3 V by a constant current method of 0.1 C in a 25 ° C. environment, and then stored at 80 ° C. for 100 hours.
  • the open circuit voltage (Open circuit voltage, hereinafter referred to as “OCV”) before the start of storage at 80 ° C. and the OCV of the cell after storage for 100 hours at 80 ° C. were measured.
  • the OCV ratio after storage for 100 hours is defined as the OCV maintenance rate, and is determined according to the following criteria. It shows that it is excellent in a high temperature storage characteristic, ie, a lifetime characteristic, so that an OCV maintenance factor is large.
  • OCV maintenance rate is 99.0% or more
  • B OCV maintenance rate is 98.8% or more and less than 99.0%
  • C OCV maintenance rate is 98.6% or more and less than 98.8%
  • D OCV maintenance rate is 98 0.4% or more and less than 98.6%
  • E OCV maintenance rate is 98.2% or more and less than 98.4%
  • F OCV maintenance rate is 98.0% or more and less than 98.2%
  • Capacity maintenance rate is 90% or more
  • ⁇ Peel strength (adhesiveness between negative electrode mixture layer and current collector)>
  • the produced negative electrode for a secondary battery was cut into a rectangular shape having a length of 100 mm and a width of 10 mm to obtain a test piece.
  • a stress was measured when one end of the current collector was pulled in a vertical direction at a pulling speed of 50 mm / min and peeled off (the cellophane tape was fixed to the test stand). The measurement was performed three times, the average value was obtained and this was taken as the peel peel strength, and evaluated according to the following criteria. It shows that it is excellent in the adhesiveness of a negative mix layer and a collector, so that the value of peeling peel strength is large.
  • Peel peel strength is 30 N / m or more
  • B Peel peel strength is 25 N / m or more and less than 30 N / m
  • C Peel peel strength is 20 N / m or more and less than 25 N / m
  • D Peel peel strength is less than 20 N / m
  • the amount of (meth) acrylic acid ester monomer (residual monomer) in the binder composition was measured by gas chromatography. Specifically, first, a sample for measurement was prepared by diluting with acetone so that the solid content concentration of the particulate polymer in the binder composition was 1% by mass and filtering using 5C filter paper. And about the prepared sample, the gas chromatography was implemented on condition of the following.
  • Apparatus Agilent 6850A (manufactured by Agilent Technologies) Column: HP-1 Average linear velocity: 15 cm / s Injection volume: 1ml Inlet temperature: 250 ° C Split ratio: 20: 1 Detector: Flame ionization detector (FID) Detector temperature: 280 ° C Oven: Hold at 40 ° C for 3 minutes, then heat at 10 ° C / minute and hold at 280 ° C for 5 minutes
  • volume average particle size of the particulate polymer was measured using a light scattering particle size measuring device (Coulter LS230, manufactured by Coulter Inc.).
  • the binder composition for secondary battery electrodes of the present invention was used for forming a negative electrode, the case where it was used for forming a positive electrode was evaluated.
  • the binder composition of the present invention was used for forming a negative electrode.
  • styrene as an aromatic vinyl monomer
  • acidic An emulsion was prepared by adding 8.0 parts of itaconic acid (IA) as a group-containing monomer and 4.8 parts of sodium lauryl sulfate and 192 parts of ion-exchanged water as a dispersant. This emulsion was sequentially added from polymerization vessel B to polymerization vessel A over about 180 minutes. Thereafter, the mixture was stirred for about 120 minutes, and when the polymerization conversion rate (monomer consumption amount) reached 93%, it was cooled to 40 ° C.
  • IA itaconic acid
  • the obtained particulate polymer had a glass transition temperature of ⁇ 6.2 ° C. and a volume average particle size of 0.167 ⁇ m.
  • the content of the (meth) acrylic acid ester monomer unit having a boiling point of 145 ° C. or higher in the particulate polymer is 50%, the content of the acidic group-containing monomer unit is 2%, and the aromatic vinyl monomer unit. was 47%, and the crosslinkable monomer unit content was 1%.
  • the content of the (meth) acrylic acid ester monomer (2-EHA) having a boiling point of 145 ° C. or higher with respect to 100 parts by mass of the particulate polymer was 208 ⁇ 10 ⁇ 6 parts by mass.
  • This negative electrode slurry composition was applied to one side of a 10 ⁇ m thick copper foil, dried at 110 ° C. for 3 hours, and then roll pressed to obtain a negative electrode having a negative electrode mixture layer having a thickness of 60 ⁇ m. About the obtained negative electrode, peel strength was measured. The results are shown in Table 1.
  • Co-Ni-Mn lithium composite oxide based active material product name: Cellseed NMC613, manufactured by Nippon Chemical Industry Co., Ltd .; hereinafter sometimes referred to as “NMC”
  • NMC Cellseed NMC613, manufactured by Nippon Chemical Industry Co., Ltd .
  • CMC sodium salt
  • BM-610B binder solid content concentration 40%
  • the obtained positive electrode slurry composition was applied to an aluminum foil having a thickness of 18 ⁇ m, dried at 120 ° C. for 3 hours, and then roll-pressed to obtain a positive electrode having a positive electrode mixture layer having a thickness of 50 ⁇ m.
  • a battery container was prepared using a laminate film made of an aluminum sheet and a polypropylene resin covering both surfaces thereof. Subsequently, the mixture layer was removed from the end portions of the positive electrode and the negative electrode obtained above to form a portion where the copper foil or the aluminum foil was exposed. A Ni tab was welded to the portion where the aluminum foil of the positive electrode was exposed, and a Cu tab was welded to the portion where the copper foil of the negative electrode was exposed. The obtained tabbed positive electrode and tabbed negative electrode were stacked with a separator made of a polyethylene microporous film interposed therebetween.
  • the direction of the surface of the electrode was such that the surface on the positive electrode mixture layer side and the surface of the negative electrode mixture layer side face each other.
  • the stacked electrode and separator were wound and stored in the battery container.
  • the electrolytic solution a solution prepared by dissolving LiPF 6 to a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 2 at 25 ° C. was used. .
  • the laminate film was sealed to produce a laminate cell type lithium ion secondary battery which is the lithium ion secondary battery of the present invention.
  • the amount of gas generation, high temperature storage characteristics, and high temperature cycle characteristics of the obtained laminated cell type lithium ion secondary battery were evaluated. The results are shown in Table 1.
  • Example 2 Table 1 shows the blending amount of 2-ethylhexyl acrylate, which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, blending amount of styrene, which is an aromatic vinyl monomer, and the polymerization conversion rate in step (1).
  • a binder composition was prepared in the same manner as in Example 1 except that the composition was changed as shown in FIG. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition
  • the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition.
  • the peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • Example 3 Example 1 except that the blending amount of styrene as an aromatic vinyl monomer and the polymerization conversion rate in the step (1) were changed as shown in Table 1 and allyl methacrylate as a crosslinkable monomer was not blended.
  • a binder composition was prepared, and stability over time was evaluated.
  • polymerization can A and B was made to be the same as that of Example 1.
  • the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the amount of gas generation, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • Example 4 Table 1 shows the blending amount of 2-ethylhexyl acrylate, which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, blending amount of styrene, which is an aromatic vinyl monomer, and the polymerization conversion rate in step (1).
  • the binder composition was prepared in the same manner as in Example 1 except that 20 parts of butadiene was added as another monomer, and the stability over time was evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition
  • the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition.
  • the peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • Table 1 shows the blending amount of 2-ethylhexyl acrylate, which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or more, blending amount of styrene, which is an aromatic vinyl monomer, and polymerization conversion rate in polymerization step 1. Except for changing as shown, a binder composition was prepared in the same manner as in Example 1, and stability over time was evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition
  • the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition.
  • the peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • Example 6 A binder composition was prepared in the same manner as in Example 1 except that butyl acrylate was used in place of 2-ethylhexyl acrylate as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher. evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition
  • Example 7 to 10 A binder composition was prepared in the same manner as in Example 1 except that sodium ascorbate, which is a reductone compound, was changed to the reductone compound shown in Table 1, and the stability over time was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the lithium ion secondary battery. The results are shown in Table 1.
  • Example 1 except that the blending ratio of sodium ascorbate as a reductone compound was changed as shown in Table 1, and the blending ratio of tert-butyl hydroperoxide as a peroxide was changed as shown in Table 1.
  • a binder composition was prepared, and stability over time was evaluated.
  • the laminated cell battery type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • Example 15 A binder composition was prepared in the same manner as in Example 1 except that the peroxide tert-butyl hydroperoxide was changed to benzoyl peroxide (BPO), and the stability over time was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • Example 1 Binder composition in the same manner as in Example 1 except that sodium ascorbate which is a reductone compound is not blended and the reaction is performed at 40 ° C. for 2 hours and then at 80 ° C. for 2 hours in Step (2). Were prepared and the stability over time was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • Example 2 A binder composition was prepared in the same manner as in Example 1 except that ethyl acrylate (EA) having a boiling point of 100 ° C. was used instead of 2-ethylhexyl acrylate which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher. Prepared and evaluated for stability over time. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • the mixture was stirred for about 120 minutes, and when the polymerization conversion rate (monomer consumption) reached 93%, distillation was performed under reduced pressure over 8 hours using an evaporator at 80 ° C. and 100 hPa (0.1 atm). It was. Thereafter, the mixture was cooled, a 5% aqueous sodium hydroxide solution was added to adjust the pH to 8, and an aqueous dispersion (binder composition) containing a desired particulate polymer was obtained. The obtained binder composition was evaluated for stability over time. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the lithium ion secondary battery. The results are shown in Table 1.
  • Example 4 A binder composition was prepared in the same manner as in Example 1 except that succinic acid was added instead of sodium ascorbate, which is a reductone compound, and stability over time was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • Example 5 A binder composition was prepared in the same manner as in Example 1 except that the step (2) was carried out at a polymerization conversion rate of 81% in the step (1), and the temporal stability was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • step (2) was not performed.
  • step (1) the polymerization conversion rate in step (1) reached 93%
  • the mixture was cooled to 40 ° C., 0.3% by mass of ammonium persulfate (APS), which is a peroxide, was added, and the mixture was further reacted for 4 hours.
  • APS ammonium persulfate
  • 5% sodium hydroxide aqueous solution was added with respect to this aqueous dispersion, and it adjusted to pH8, and obtained the aqueous dispersion (binder composition) containing a desired particulate polymer.
  • the obtained binder composition was evaluated for stability over time.
  • the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition.
  • the peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
  • the binder compositions of Examples 1 to 15 have good stability over time, and the negative electrode produced using such a binder composition has good peel strength. It can be seen that the secondary battery manufactured in this manner has a reduced gas generation amount and good high-temperature storage characteristics and high-temperature cycle characteristics.
  • Comparative Example 1 in which sodium ascorbate, which is a reductone compound, was not blended the residual amount of 2-ethylhexyl acrylate monomer in the obtained binder composition was large, and the temporal stability of the binder composition was low.
  • the stability of the binder composition is good, Although the peel strength of the negative electrode produced using the obtained binder is good and the amount of gas generated in the secondary battery is small, it can be seen that the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate. This is considered to be because the flexibility of the particulate polymer in the binder composition was lowered, and the binding property was lowered as the binder composition, which adversely affected the battery characteristics.
  • Example 1 and 3 it can be seen that the high-temperature storage characteristics and the high-temperature cycle characteristics of the secondary battery can be improved by using a crosslinkable monomer when forming the particulate polymer.
  • the peel strength of the negative electrode can be improved by adjusting the blending amount of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or more when forming the particulate polymer. I understand that.
  • Example 1 and Examples 7 to 10 it can be seen that all characteristics can be arranged in a high dimension by using ascorbic acid and its isomers, derivatives, and salts as reductone compounds.
  • Example 9 using ascorbyl palmitate, the gas generation amount, high-temperature storage characteristics, high-temperature cycle characteristics, and stability over time of the binder composition were inferior to Examples 1, 7, 8, and 10, but this This is because the molecular weight of ascorbyl palmitate is relatively large, and if it is added in the same amount as other ascorbic acid-based reductone compounds, the amount in terms of moles is reduced and the residual monomer reduction effect cannot be fully exhibited. It is thought that.
  • the amount of reductone compound and peroxide by adjusting the amount of reductone compound and peroxide, the amount of residual monomers can be sufficiently reduced, the amount of gas generated can be reduced, and high temperature storage characteristics and high temperature cycles can be achieved. It can be seen that the characteristics can be further improved.
  • the amount of sodium ascorbate, which is a reductone compound is relatively large, and it is considered that ascorbic acid remaining in the binder composition increases the gas generation amount.
  • the binder composition of the present invention was used for forming a positive electrode.
  • acrylonitrile as an ⁇ , ⁇ -unsaturated nitrile monomer 74.4 parts
  • 4.8 parts of sodium lauryl sulfate and 192 parts of ion-exchanged water as dispersants were added and stirred to prepare an emulsion.
  • This emulsion was sequentially added from polymerization vessel B to polymerization vessel A over about 180 minutes. Thereafter, the mixture was stirred for about 120 minutes, and when the polymerization conversion rate (monomer consumption amount) reached 95%, it was cooled to 40 ° C.
  • the obtained particulate polymer had a glass transition temperature of ⁇ 38.0 ° C. and a volume average particle size of 0.11 ⁇ m.
  • the content ratio of (meth) acrylic acid ester monomer units having a boiling point of 145 ° C. or higher is 78%
  • the content ratio of acidic group-containing monomer units is 2%
  • ⁇ , ⁇ -unsaturated nitrile was 20%.
  • the content of the (meth) acrylic acid ester monomer (2-EHA) having a boiling point of 145 ° C. or higher with respect to 100 parts by mass of the particulate polymer was 208 ⁇ 10 ⁇ 6 parts by mass.
  • Co-Ni-Mn lithium composite oxide based active material product name: Cellseed NMC613, manufactured by Nippon Chemical Industry Co., Ltd .; hereinafter sometimes referred to as “NMC”
  • NMC Cellseed NMC613, manufactured by Nippon Chemical Industry Co., Ltd .
  • CMC sodium salt
  • aqueous solution of carboxymethyl cellulose as a viscosity modifier
  • the positive electrode slurry composition was applied to an aluminum foil having a thickness of 18 ⁇ m, dried at 120 ° C. for 3 hours, and then roll pressed to obtain a positive electrode having a positive electrode mixture layer having a thickness of 50 ⁇ m.
  • slurry composition for negative electrode and negative electrode > 98 parts of graphite having a volume average particle diameter of 20 ⁇ m and a specific surface area of 4.2 m 2 / g as a negative electrode active material, and negative electrode binder BM-400B (40 of styrene-butadiene copolymer manufactured by Nippon Zeon Co., Ltd.) as a binder. (Mass% aqueous dispersion) is mixed with 1.0 part in solid content and 0.8 part in CMC with solid content. Further, water is added and mixed with a planetary mixer to obtain a slurry composition for negative electrode. Prepared. This negative electrode slurry composition was applied to one side of a 10 ⁇ m thick copper foil, dried at 110 ° C. for 3 hours, and then roll pressed to obtain a negative electrode having a negative electrode mixture layer having a thickness of 60 ⁇ m.
  • BM-400B 40 of styrene-butadiene copolymer manufactured by Nippon Zeon Co
  • a battery container was prepared using a laminate film made of an aluminum sheet and a polypropylene resin covering both surfaces thereof. Subsequently, the mixture layer was removed from the end portions of the positive electrode and the negative electrode obtained above to form a portion where the copper foil or the aluminum foil was exposed. A Ni tab was welded to the portion where the aluminum foil of the positive electrode was exposed, and a Cu tab was welded to the portion where the copper foil of the negative electrode was exposed. The obtained tabbed positive electrode and tabbed negative electrode were stacked with a separator made of a polyethylene microporous film interposed therebetween.
  • the direction of the surface of the electrode was such that the surface on the positive electrode mixture layer side and the surface of the negative electrode mixture layer side face each other.
  • the stacked electrode and separator were wound and stored in the battery container.
  • the electrolytic solution a solution prepared by dissolving LiPF 6 to a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 2 at 25 ° C. was used. .
  • the laminate film was sealed to produce a laminate cell type lithium ion secondary battery which is the lithium ion secondary battery of the present invention.
  • the amount of gas generation and high-temperature storage characteristics of the obtained laminated cell type lithium ion secondary battery were evaluated. The results are shown in Table 2.
  • the positive electrode obtained above was cut into a circle having a diameter of 13 mm.
  • the negative electrode obtained above was cut into a circle having a diameter of 14 mm.
  • a single-layer polypropylene separator (porosity 55%) produced by a dry method having a thickness of 25 ⁇ m was cut into a circle having a diameter of 18 mm. These were housed in a stainless steel coin-type outer container (diameter 20 mm, height 1.8 mm, stainless steel thickness 0.25 mm) provided with polypropylene packing.
  • the arrangement of the circular electrodes and separators in the outer container was as follows. The circular positive electrode was disposed so that the aluminum foil was in contact with the bottom surface of the outer container.
  • the circular separator was disposed so as to be interposed between the circular positive electrode and the circular negative electrode.
  • a full coin cell type lithium ion battery which is a lithium ion secondary battery of the present invention having a diameter of 20 mm and a thickness of about 3.2 mm, is sealed by covering with a stainless steel cap having a thickness of 0.2 mm and sealing the outer container.
  • a secondary battery (coin cell CR2032) was produced. The high-temperature cycle characteristics of the obtained full coin cell type lithium ion secondary battery were evaluated. The results are shown in Table 2.
  • Example 17 to 18 The blending amount of 2-ethylhexyl acrylate which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher and the blending amount of acrylonitrile which is an ⁇ , ⁇ -unsaturated nitrile monomer were changed as shown in Table 2, respectively. Except for this, a binder composition was prepared in the same manner as in Example 16, and the stability over time was evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition
  • Example 16 volume average particle diameter of the obtained particulate polymer was 0.11 ⁇ m as in Example 16. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • Example 19 A binder composition was prepared in the same manner as in Example 16 except that n-butyl acrylate (boiling point 148 ° C.) was used as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, and the stability over time was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • Example 20 to 23 A binder composition was prepared in the same manner as in Example 16 except that sodium ascorbate, which is a reductone compound, was changed to a reductone compound shown in Table 2, and the temporal stability was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • Example 1 except that the blending ratio of sodium ascorbate as a reductone compound was changed as shown in Table 2, and the blending ratio of tert-butyl hydroperoxide as a peroxide was changed as shown in Table 2.
  • a binder composition was prepared in the same manner as in No. 16, and the stability over time was evaluated. Further, using the prepared binder composition, a laminated cell battery type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and high temperature storage characteristics were respectively obtained. In addition, the high-temperature cycle characteristics were evaluated. The results are shown in Table 2.
  • Example 28 A binder composition was prepared in the same manner as in Example 16 except that the peroxide tert-butyl hydroperoxide was changed to benzoyl peroxide (BPO), and the stability over time was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • Example 7 Binder composition in the same manner as in Example 16 except that sodium ascorbate which is a reductone compound is not blended, and the reaction is performed at 40 ° C. for 2 hours and then at 80 ° C. for 2 hours in Step (2). Were prepared and the stability over time was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • a binder composition was prepared in the same manner as in Example 16 except that ethyl acrylate (EA) having a boiling point of 100 ° C. was used in place of 2-ethylhexyl acrylate which is a (meth) acrylic acid ester monomer, and was stable over time. Sex was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • acrylonitrile as an ⁇ , ⁇ -unsaturated nitrile monomer 74.4 parts
  • 4.8 parts of sodium lauryl sulfate and 192 parts of ion-exchanged water as dispersants were added and stirred to prepare an emulsion.
  • This emulsion was sequentially added from polymerization vessel B to polymerization vessel A over about 180 minutes. Thereafter, the mixture was stirred for about 120 minutes, and when the polymerization conversion rate (monomer consumption) reached 95%, distillation was performed under reduced pressure over 8 hours using an evaporator at 80 ° C. and 100 hPa (0.1 atm). .
  • binder composition aqueous dispersion (binder composition) containing a desired particulate polymer was obtained.
  • the obtained binder composition was evaluated for stability over time. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • Example 10 A binder composition was prepared in the same manner as in Example 16 except that succinic acid was added instead of sodium ascorbate, which is a reductone compound, and stability over time was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • Example 11 A binder composition was prepared in the same manner as in Example 16 except that the step (2) was carried out at a polymerization conversion rate of 80% in the step (1), and the temporal stability was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
  • step (2) was not performed.
  • step (2) was not performed.
  • the polymerization conversion rate in step (1) reached 95%
  • the mixture was cooled to 40 ° C., 0.3% by mass of ammonium persulfate (APS) as a peroxide was added, and the reaction was further continued for 4 hours.
  • APS ammonium persulfate
  • 5% sodium hydroxide aqueous solution was added with respect to this aqueous dispersion, and it adjusted to pH8, and obtained the aqueous dispersion (binder composition) containing a desired particulate polymer.
  • the obtained binder composition was evaluated for stability over time.
  • the binder compositions of Examples 16 to 28 have good temporal stability, and the secondary battery produced using such a binder composition has a reduced amount of gas generation, high temperature storage characteristics and It can be seen that the high-temperature cycle characteristics are good.
  • Comparative Example 7 in which sodium ascorbate as a reductone compound was not blended, the residual amount of 2-ethylhexyl acrylate monomer in the obtained binder composition was large, and the stability of the binder composition with time was low. And it turns out that the gas generation amount of the secondary battery manufactured using this binder composition increases, and a high temperature storage characteristic and a high temperature cycling characteristic deteriorate remarkably.
  • the stability of the binder composition is good, Although the amount of gas generated in the secondary battery produced using the obtained binder is small, it can be seen that the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate. This is considered to be because the flexibility of the particulate polymer in the binder composition was lowered, and the binding property was lowered as the binder composition, which adversely affected the battery characteristics.
  • the compounding amounts of the redox initiator sodium ascorbate and Tert-butyl hydroperoxide
  • the unconverted monomer cannot be sufficiently polymerized in the redox polymerization, and the result It is considered that the residual monomer amount increases and the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate.
  • the temporal stability of the binder composition was good. The gas generation of the secondary battery is not a little, but the residual monomer amount in the binder composition cannot be sufficiently reduced, and the battery characteristics deteriorate.
  • ADVANTAGE OF THE INVENTION generation
  • a binder composition can be provided.
  • the slurry composition for secondary battery electrodes using the said binder composition can be provided.
  • the electrode for secondary batteries using the said slurry composition for secondary battery electrodes can be provided.

Abstract

The purpose of the present invention is to provide a binder composition for secondary battery electrodes, which has excellent long-term stability and is capable of providing a secondary battery that is suppressed in gas generation caused by residual monomers and has good high-temperature storage characteristics and high-temperature cycle characteristics. A binder composition according to the present invention contains a particulate polymer, water and a reductone compound and/or an oxidized form of a reductone compound. The particulate polymer is obtained by polymerizing a monomer mixture that contains a (meth)acrylic acid ester monomer having a boiling point of 145°C or more, and the content ratio of the (meth)acrylic acid ester monomer having a boiling point of 145°C or more is from 1 × 10-6 parts by mass to 1,500 × 10-6 parts by mass (inclusive) relative to 100 parts by mass of the particulate polymer.

Description

二次電池電極用バインダー組成物及びその製造方法、二次電池電極用スラリー組成物、二次電池用電極、並びに、二次電池Binder composition for secondary battery electrode and method for producing the same, slurry composition for secondary battery electrode, electrode for secondary battery, and secondary battery
　本発明は、二次電池電極用バインダー組成物及びその製造方法、二次電池電極用スラリー組成物、二次電池用電極、並びに、二次電池に関するものである。 The present invention relates to a binder composition for a secondary battery electrode and a manufacturing method thereof, a slurry composition for a secondary battery electrode, an electrode for a secondary battery, and a secondary battery.
　二次電池、なかでもリチウムイオン二次電池は、小型で軽量、且つエネルギー密度が高く、さらに繰り返し充放電が可能という特性があり、幅広い用途に使用されている。 Secondary batteries, especially lithium ion secondary batteries, are small and light, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications.
　ここで、二次電池の電極（正極及び負極）などの電池部材は、これらの電池部材に含まれる成分同士、又は、該成分と基材（例えば、集電体）とをバインダーで結着して形成されている。具体的には、例えば二次電池の電極は、通常、集電体と、集電体上に形成された電極合材層とを備えている。そして、電極合材層は、例えば、電極活物質およびバインダー組成物などを分散媒に分散させてなる電極用スラリー組成物を集電体上に塗布し、乾燥させて電極活物質などをバインダーで結着することにより形成されている。
　そこで、近年では、二次電池の更なる性能向上を達成すべく、これら電池部材の形成に用いられるバインダー組成物やスラリー組成物の改良が試みられている。 Here, the battery members such as the electrodes (positive electrode and negative electrode) of the secondary battery are obtained by binding the components contained in these battery members or the components and a substrate (for example, a current collector) with a binder. Is formed. Specifically, for example, an electrode of a secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector. The electrode mixture layer is formed by, for example, applying an electrode slurry composition in which an electrode active material and a binder composition are dispersed in a dispersion medium on a current collector, and drying the electrode active material and the like with a binder. It is formed by binding.
Thus, in recent years, attempts have been made to improve the binder composition and slurry composition used for forming these battery members in order to achieve further performance improvement of the secondary battery.
　具体的には、特定の共重合体を含有するバインダー組成物を二次電池用電極の製造に用いることが提案されてきた（例えば、特許文献１～３参照）。特許文献１に記載のバインダー組成物によれば、スチレン、エチレン性不飽和カルボン酸エステル、エチレン性不飽和カルボン酸、及び内部架橋剤を乳化重合して得られる特定性状の共重合体を含有しているので、水分散系で活物質同士及び活物質と集電体とを良好に結着させることができ、かかるバインダー組成物を用いることで、充放電高温サイクル特性に優れるリチウムイオン二次電池を提供することができる。 Specifically, it has been proposed to use a binder composition containing a specific copolymer for the production of a secondary battery electrode (see, for example, Patent Documents 1 to 3). According to the binder composition described in Patent Document 1, it contains a copolymer having specific properties obtained by emulsion polymerization of styrene, an ethylenically unsaturated carboxylic acid ester, an ethylenically unsaturated carboxylic acid, and an internal crosslinking agent. Therefore, the active material and the active material and the current collector can be satisfactorily bound in an aqueous dispersion, and by using such a binder composition, a lithium ion secondary battery excellent in charge / discharge high temperature cycle characteristics Can be provided.
　また、特許文献２に記載のバインダー組成物によれば、アクリル酸エステル又はメタクリル酸エステルと、α,β－不飽和ニトリル化合物との共重合体を含有しているので、結着力および柔軟性に優れる正極を提供することができる。そして、特許文献３に記載のバインダー組成物によれば、アクリロニトリルなどの所定のα，β－エチレン性不飽和ニトリル化合物等を重合した後に、２－エチルヘキシルアクリレートなどの所定のエチレン性不飽和カルボン酸エステル等を添加および重合して得た共重合体（多段重合体）を含有しているので、結着力および柔軟性に優れる正極を提供することができる。 In addition, the binder composition described in Patent Document 2 contains a copolymer of an acrylate ester or a methacrylic ester and an α, β-unsaturated nitrile compound. An excellent positive electrode can be provided. According to the binder composition described in Patent Document 3, a predetermined α, β-ethylenically unsaturated nitrile compound such as acrylonitrile is polymerized, and then a predetermined ethylenically unsaturated carboxylic acid such as 2-ethylhexyl acrylate is used. Since a copolymer (multistage polymer) obtained by adding and polymerizing an ester or the like is contained, a positive electrode excellent in binding power and flexibility can be provided.
特開２０１１－２４３４６４号公報JP 2011-243464 A 国際公開第２００６／０３８６５２号International Publication No. 2006/038652 特許第４７３６８０４号公報Japanese Patent No. 4736804
　しかし、特許文献１～３に記載のバインダー組成物では、共重合体を生成する際に重合されなかった未反応単量体がバインダー組成物中に残留していた。この残留したモノマーは、かかるバインダー組成物を用いて二次電池を製造した際に、二次電池中に混入する。そして、二次電池に混入した残留モノマーは、二次電池が高充電状態や高温状態で保存された場合に、分解され、ガスを発生する。そのため、上記従来のバインダー組成物を用いた二次電池では、ガスの発生による膨れが生じ、高温保存特性や、高温サイクル特性などが低下する虞があった。 However, in the binder compositions described in Patent Documents 1 to 3, unreacted monomers that were not polymerized when forming the copolymer remained in the binder composition. The remaining monomer is mixed in the secondary battery when the secondary battery is manufactured using the binder composition. The residual monomer mixed in the secondary battery is decomposed to generate gas when the secondary battery is stored in a high charge state or a high temperature state. For this reason, in the secondary battery using the conventional binder composition, there is a possibility that the swelling due to the generation of gas occurs and the high-temperature storage characteristics, the high-temperature cycle characteristics, and the like are deteriorated.
　さらに、近年、二次電池用の電極の製造において、環境負荷低減などの観点から、溶媒として水系媒体を用いた水系スラリー組成物への関心が高まっているが、特に水系のバインダー組成物には、組成物中に残留モノマーが存在すると、長期保存する際に残留モノマーに起因して沈殿物が発生するため、経時安定性が低いという問題もあった。 Furthermore, in recent years, in the production of electrodes for secondary batteries, from the viewpoint of reducing environmental impact, interest in aqueous slurry compositions using an aqueous medium as a solvent has increased, but in particular for aqueous binder compositions. When the residual monomer is present in the composition, a precipitate is generated due to the residual monomer during long-term storage, which causes a problem that stability with time is low.
　そこで、本発明は、残留モノマーに起因したガスの発生が抑制され、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することができる、経時安定性に優れた二次電池電極用バインダー組成物を提供することを目的とする。また、本発明は、当該バインダー組成物を用いた二次電池電極用スラリー組成物を提供することを目的とする。更に、本発明は、当該二次電池電極用スラリー組成物を用いた二次電池用電極を提供することを目的とする。
　また、本発明は、当該二次電池用電極を用いた、高温保存特性及び高温サイクル特性に優れると共に、ガス発生が低減された二次電池を提供することを目的とする。 Therefore, the present invention can provide a secondary battery that has excellent high-temperature storage characteristics and high-temperature cycle characteristics, in which generation of gas due to residual monomers is suppressed, and is excellent in stability over time. An object is to provide a binder composition. Moreover, an object of this invention is to provide the slurry composition for secondary battery electrodes using the said binder composition. Furthermore, an object of this invention is to provide the electrode for secondary batteries using the said slurry composition for secondary battery electrodes.
Another object of the present invention is to provide a secondary battery using the secondary battery electrode, which has excellent high-temperature storage characteristics and high-temperature cycle characteristics and reduced gas generation.
　ここで、上述した残留モノマーの問題に対し、重合体の調製後にバインダー組成物を減圧下で加熱すること等によりバインダー組成物から残留モノマーを除去することが考えられる。しかし、本発明者らが鋭意研究を重ねたところ、特に（メタ）アクリル酸エステル単量体を用いて調製した重合体を含むバインダー組成物では、柔軟性および密着強度に優れる電極を得て二次電池の電気的特性などを向上させることができる一方で、沸点１４５℃以上の（メタ）アクリル酸エステル単量体が残留した場合には、減圧や加熱を用いても当該残留した沸点１４５℃以上の（メタ）アクリル酸エステル単量体を十分に除去することができないことが明らかとなった。
　また、上述した残留モノマーの問題に対し、重合体を一度調製した後に過硫酸塩などの重合開始剤を更に添加して重合反応を更に進める（即ち、残留モノマーを重合させる）ことで、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む残留モノマーの量を低減することも考えられる。しかし、本発明者らが鋭意研究を重ねたところ、重合開始剤を更に添加して重合反応を進めた場合には、過硫酸塩などの重合開始剤の残渣が大量にバインダー組成物や二次電池中に含まれることとなり、二次電池の電気的特性が低下する虞があることが明らかとなった。 Here, with respect to the problem of the residual monomer described above, it is conceivable to remove the residual monomer from the binder composition by heating the binder composition under reduced pressure after the preparation of the polymer. However, as a result of extensive research by the present inventors, in particular, a binder composition containing a polymer prepared using a (meth) acrylic acid ester monomer is used to obtain an electrode excellent in flexibility and adhesion strength. While the electrical characteristics of the secondary battery can be improved, when a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher remains, the residual boiling point of 145 ° C. is maintained even if reduced pressure or heating is used. It was revealed that the above (meth) acrylic acid ester monomer could not be removed sufficiently.
Further, in order to solve the above-mentioned problem of residual monomer, a polymer is prepared once, and then a polymerization initiator such as persulfate is further added to further advance the polymerization reaction (that is, the residual monomer is polymerized). It is also conceivable to reduce the amount of residual monomer containing a (meth) acrylic acid ester monomer at or above. However, as a result of extensive research conducted by the present inventors, when a polymerization initiator was further added and the polymerization reaction proceeded, a large amount of the residue of the polymerization initiator such as persulfate was present in the binder composition or the secondary. It became clear that the electrical characteristics of the secondary battery might be deteriorated due to inclusion in the battery.
　そこで、本発明者らは、上記課題を解決することを目的として更に鋭意検討を重ねた。そして、本発明者らは、重合体を一度調製した後にレダクトン類化合物を用いてレドックス重合を行うことにより、残留モノマーを重合させ、大量の過酸化物を使用することなく残留モノマー量を低減することに着想した。更に本発明者らは、（メタ）アクリル酸エステル単量体を用いて調製した粒子状の重合体を含む二次電池電極用バインダー組成物において、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を粒子状重合体１００質量部に対して特定の範囲まで低減させることにより、ガスの発生が抑制され、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することが可能な、経時安定性に優れた二次電池電極用バインダー組成物を提供することができることを見出し、本発明を完成させた。 Therefore, the present inventors conducted further intensive studies for the purpose of solving the above problems. And the present inventors polymerize the residual monomer by reducing the amount of residual monomer without using a large amount of peroxide by performing redox polymerization using a reductone compound after preparing a polymer once. I was inspired by that. Furthermore, the inventors of the present invention also provide a secondary battery electrode binder composition containing a particulate polymer prepared using a (meth) acrylate monomer, and a (meth) acrylate ester having a boiling point of 145 ° C. or higher. To provide a secondary battery in which the generation of gas is suppressed by reducing the content ratio of the monomer to a specific range with respect to 100 parts by mass of the particulate polymer, and the battery has good high-temperature storage characteristics and high-temperature cycle characteristics. It was found that a binder composition for secondary battery electrodes excellent in stability over time could be provided, and the present invention was completed.
　即ち、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池電極用バインダー組成物は、粒子状重合体、レダクトン類化合物およびその酸化体の少なくとも一方、及び水を含み、前記粒子状重合体は、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を重合してなり、前記沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合は、前記粒子状重合体１００質量部に対して１×１０-6質量部以上１５００×１０-6質量部以下であることを特徴とする。このように、二次電池電極用バインダー組成物において、レダクトン類化合物を使用し、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を所定範囲に制限することで、バインダー組成物の経時安定性を向上させることができると共に、かかる二次電池電極用バインダー組成物を用いて得られる二次電池において残留モノマーに起因したガスが発生するのを抑制することができる。そして、当該二次電池電極用バインダー組成物を用いれば、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することができる。 That is, the present invention aims to advantageously solve the above problems, and the binder composition for a secondary battery electrode of the present invention comprises at least one of a particulate polymer, a reductone compound and an oxidant thereof. And the water-containing particulate polymer is obtained by polymerizing a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, and the (meth) acrylic acid having a boiling point of 145 ° C. or higher. The content ratio of the ester monomer is 1 × 10 −6 parts by mass to 1500 × 10 −6 parts by mass with respect to 100 parts by mass of the particulate polymer. Thus, in the binder composition for secondary battery electrodes, the binder composition is formed by using a reductone compound and limiting the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher to a predetermined range. In the secondary battery obtained by using such a binder composition for a secondary battery electrode, it is possible to suppress the generation of gas due to the residual monomer. And if the said binder composition for secondary battery electrodes is used, the secondary battery which has a favorable high temperature storage characteristic and a high temperature cycling characteristic can be provided.
　また、本発明の二次電池電極用バインダー組成物において、前記レダクトン類化合物およびその酸化体の少なくとも一方が、（イソ）アスコルビン酸及びその塩、並びに、それらの酸化体から選択される少なくとも１種であることが好ましい。（イソ）アスコルビン酸及びその塩、並びに、それらの酸化体は、電池特性に影響が少なく、スラリー安定性の向上にも繋がるからである。 In the binder composition for a secondary battery electrode of the present invention, at least one of the reductone compound and its oxidant is selected from (iso) ascorbic acid and its salt, and their oxidant. It is preferable that This is because (iso) ascorbic acid and salts thereof, and oxidants thereof have little influence on battery characteristics and lead to improvement of slurry stability.
　更に、本発明の二次電池電極用バインダー組成物において、前記レダクトン類化合物およびその酸化体の少なくとも一方の含有割合が、前記粒子状重合体１００質量部あたり、０．０５質量部以上５質量部以下であることが好ましい。二次電池電極用バインダー組成物中の沸点１４５℃以上の（メタ）アクリル酸エステル単量体などの残留モノマーの量を十分に低減しつつ、レダクトン類化合物およびその酸化体の少なくとも一方の含有量が多くなって二次電池電極用バインダー組成物を用いて作製した二次電池の電気的特性が低下し、またバインダー組成物中に残留したレダクトン類化合物およびその酸化体の少なくとも一方が分解されて二次電池においてガスが発生することを抑制することができるからである。 Furthermore, in the binder composition for a secondary battery electrode of the present invention, the content ratio of at least one of the reductone compound and its oxidant is 0.05 parts by mass or more and 5 parts by mass per 100 parts by mass of the particulate polymer. The following is preferable. The content of at least one of a reductone compound and its oxidant while sufficiently reducing the amount of residual monomer such as a (meth) acrylate monomer having a boiling point of 145 ° C. or higher in the binder composition for secondary battery electrodes As a result, the electrical characteristics of the secondary battery produced using the binder composition for secondary battery electrodes deteriorated, and at least one of the reductone compound and its oxidant remaining in the binder composition was decomposed. This is because the generation of gas in the secondary battery can be suppressed.
　ここで、本発明の二次電池電極用バインダー組成物において、前記単量体混合物は、さらに架橋性単量体を含むことが好ましい。二次電池電極用バインダー組成物を用いて形成される電極の電解液に対する膨潤度を適当な大きさにすると共に、かかるバインダー組成物を用いて製造したリチウムイオン二次電池の高温保存特性及び高温サイクル特性を向上させることができるからである。 Here, in the binder composition for a secondary battery electrode of the present invention, the monomer mixture preferably further contains a crosslinkable monomer. The degree of swelling of the electrode formed using the binder composition for a secondary battery electrode with respect to the electrolyte solution is set to an appropriate level, and the high-temperature storage characteristics and high temperature of a lithium ion secondary battery produced using such a binder composition This is because the cycle characteristics can be improved.
　また、本発明の二次電池電極用バインダー組成物において、前記単量体混合物は、さらに（メタ）アクリロニトリル単量体を５～３５質量％含むことが好ましい。二次電池電極用バインダー組成物を用いて形成される電極合材層のピール強度を向上させると共に、電解液に対する膨潤度を適度な大きさにすることができるからである。 In the binder composition for a secondary battery electrode of the present invention, it is preferable that the monomer mixture further contains 5 to 35% by mass of a (meth) acrylonitrile monomer. This is because the peel strength of the electrode mixture layer formed using the binder composition for secondary battery electrodes can be improved, and the degree of swelling with respect to the electrolytic solution can be made moderate.
　くわえて、本発明の二次電池電極用バインダー組成物において、前記沸点が１４５℃以上の（メタ）アクリル酸エステル単量体が、２－エチルヘキシルアクリレートであることが好ましい。２－エチルヘキシルアクリレートを用いて得られる重合体は電気化学的安定性及び柔軟性が高いため、かかる重合体を配合した二次電池電極用バインダー組成物を用いて得た電極合材層の集電体に対する密着強度を向上し、ひいては、かかる電極合材層を有する二次電池の電池特性を向上させることができるからである。 In addition, in the binder composition for secondary battery electrodes of the present invention, the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is preferably 2-ethylhexyl acrylate. Since a polymer obtained using 2-ethylhexyl acrylate has high electrochemical stability and flexibility, current collection of an electrode mixture layer obtained using a binder composition for a secondary battery electrode blended with such a polymer. This is because the adhesion strength to the body can be improved, and as a result, the battery characteristics of the secondary battery having such an electrode mixture layer can be improved.
　また、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池電極用バインダー組成物の製造方法は、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を重合転化率が９０質量％以上となるまで水中で重合し、重合体と未反応の単量体とを含む混合物を得る工程（１）と、前記工程（１）の後、前記混合物にレダクトン類化合物および過酸化物を添加して前記未反応の単量体を重合し、前記沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を、重合体１００質量部に対して１×１０-6質量部以上１５００×１０-6質量部以下にする工程（２）とを含む、ことを特徴とする。このように、二段階の重合工程により二次電池電極用バインダー組成物を製造するにあたり、最初の段階の重合転化率が９０質量％以上となった後に、重合系中にレダクトン類化合物および過酸化物を添加し、レドックス重合反応を用いて残留モノマーを重合させれば、重合体の物性に影響を与えることなく、上述した二次電池電極用バインダー組成物を容易に製造することができる。 Moreover, this invention aims at solving the said subject advantageously, The manufacturing method of the binder composition for secondary battery electrodes of this invention is (meth) acrylic acid ester single-piece | unit with a boiling point of 145 degreeC or more. A step (1) of polymerizing a monomer mixture containing a monomer in water until the polymerization conversion rate is 90% by mass or more to obtain a mixture containing the polymer and an unreacted monomer, and the step (1) ), A reductone compound and a peroxide are added to the mixture to polymerize the unreacted monomer, and the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is increased. And a step (2) of 1 × 10 −6 parts by mass to 1500 × 10 −6 parts by mass with respect to 100 parts by mass of the combined product . Thus, in producing a binder composition for a secondary battery electrode by a two-stage polymerization process, after the polymerization conversion rate in the first stage is 90% by mass or more, a reductone compound and a peroxide are introduced into the polymerization system. If a residual monomer is polymerized using a redox polymerization reaction, the above-mentioned binder composition for a secondary battery electrode can be easily produced without affecting the physical properties of the polymer.
　更に、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池電極用スラリー組成物は、上述の何れかの二次電池電極用バインダー組成物及び電極活物質を含むことを特徴とする。このような二次電池電極用スラリー組成物は、経時安定性に優れ、かかる二次電池電極用スラリー組成物を用いれば、残留モノマーに起因したガスの発生が抑制され、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することができる。 Furthermore, this invention aims at solving the said subject advantageously, The slurry composition for secondary battery electrodes of this invention is the binder composition and electrode for any of the above-mentioned secondary battery electrodes. It is characterized by containing an active material. Such a slurry composition for a secondary battery electrode is excellent in stability over time, and when such a slurry composition for a secondary battery electrode is used, generation of gas due to residual monomers is suppressed, and good high-temperature storage characteristics and A secondary battery having high-temperature cycle characteristics can be provided.
　そして、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池用電極は、集電体上に、上述の二次電池電極用スラリー組成物を塗布し、前記集電体上に塗布された二次電池電極用スラリー組成物を乾燥して得られることを特徴とする。このような二次電池用電極を用いれば、残留モノマーに起因したガスの発生が抑制され、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することができる。 And this invention aims at solving the said subject advantageously, The electrode for secondary batteries of this invention apply | coats the above-mentioned slurry composition for secondary battery electrodes on a collector. And it is obtained by drying the slurry composition for secondary battery electrodes apply | coated on the said electrical power collector. By using such a secondary battery electrode, it is possible to provide a secondary battery having excellent high-temperature storage characteristics and high-temperature cycle characteristics by suppressing generation of gas due to residual monomers.
　そして、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池は、正極、負極、電解液及びセパレータを備え、前記正極および前記負極の少なくとも一方が、上述の二次電池用電極であることを特徴とする。このような二次電池は、高温保存特性及び高温サイクル特性に優れると共に、ガス発生が抑制されている。 And this invention aims at solving the said subject advantageously, The secondary battery of this invention is equipped with a positive electrode, a negative electrode, electrolyte solution, and a separator, and at least one of the said positive electrode and the said negative electrode is The electrode for a secondary battery described above. Such a secondary battery has excellent high-temperature storage characteristics and high-temperature cycle characteristics, and gas generation is suppressed.
　本発明によれば、残留モノマーに起因したガスの発生が抑制され、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することができる、経時安定性に優れた二次電池電極用バインダー組成物を提供することができる。また、本発明によれば、当該バインダー組成物を用いた二次電池電極用スラリー組成物を提供することができる。更に、本発明によれば、当該二次電池電極用スラリー組成物を用いた二次電池用電極を提供することができる。
　また、本発明によれば、当該二次電池用電極を用いた、高温保存特性及び高温サイクル特性に優れると共に、ガス発生が低減された二次電池を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the gas resulting from a residual monomer is suppressed, and the secondary battery electrode which was excellent in temporal stability which can provide the secondary battery which has a favorable high temperature storage characteristic and a high temperature cycling characteristic can be provided. A binder composition can be provided. Moreover, according to this invention, the slurry composition for secondary battery electrodes using the said binder composition can be provided. Furthermore, according to this invention, the electrode for secondary batteries using the said slurry composition for secondary battery electrodes can be provided.
In addition, according to the present invention, it is possible to provide a secondary battery using the secondary battery electrode that has excellent high-temperature storage characteristics and high-temperature cycle characteristics and reduced gas generation.
　以下、本発明の実施形態について詳細に説明する。
　ここで、本発明の二次電池電極用バインダー組成物は、二次電池の電極を形成する際に用いられる。そして、本発明の二次電池電極用スラリー組成物は、本発明の二次電池電極用バインダー組成物及び電極活物質を含んで調製される。また、本発明の二次電池電極用バインダー組成物の製造方法は、本発明の二次電池電極用バインダー組成物を製造する際に用いることができる。
　さらに、本発明の二次電池用電極は、本発明の二次電池電極用スラリー組成物を用いて製造することができ、本発明のリチウムイオン二次電池は、本発明の二次電池用電極を用いたことを特徴とする。 Hereinafter, embodiments of the present invention will be described in detail.
Here, the binder composition for secondary battery electrodes of the present invention is used when forming an electrode of a secondary battery. And the slurry composition for secondary battery electrodes of this invention is prepared including the binder composition for secondary battery electrodes of this invention, and an electrode active material. Moreover, the manufacturing method of the binder composition for secondary battery electrodes of this invention can be used when manufacturing the binder composition for secondary battery electrodes of this invention.
Further, the secondary battery electrode of the present invention can be produced using the slurry composition for the secondary battery electrode of the present invention, and the lithium ion secondary battery of the present invention is the secondary battery electrode of the present invention. It is characterized by using.
（二次電池電極用バインダー組成物）
　本発明の二次電池電極用バインダー組成物は、水を分散媒とした水系バインダー組成物であり、粒子状重合体及びレダクトン類化合物およびその酸化体の少なくとも一方を含む。ここで、粒子状重合体は沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を重合して生成された粒子状重合体である。さらに、本発明の二次電池電極用バインダー組成物は、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合が、粒子状重合体１００質量部に対して１×１０-6質量部以上１５００×１０-6質量部以下であることを特徴とする。ここで、本発明のバインダー組成物に含まれる沸点１４５℃以上の（メタ）アクリル酸エステル単量体は、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を重合させて粒子状重合体を生成させた後に、重合していない、単量体のままの状態（いわゆる、遊離状態）で残った（メタ）アクリル酸エステル単量体である。
　なお、本発明において、「（メタ）アクリル」とは、アクリル及び／又はメタクリルを指す。 (Binder composition for secondary battery electrode)
The binder composition for secondary battery electrodes of the present invention is an aqueous binder composition using water as a dispersion medium, and includes at least one of a particulate polymer, a reductone compound, and an oxidant thereof. Here, the particulate polymer is a particulate polymer produced by polymerizing a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher. Furthermore, in the binder composition for secondary battery electrodes of the present invention, the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is 1 × 10 −6 mass relative to 100 mass parts of the particulate polymer. Or more and 1500 × 10 −6 parts by mass or less. Here, the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher contained in the binder composition of the present invention is a polymerization of a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher. (Meth) acrylic acid ester monomer that is not polymerized and remains in a monomer-like state (so-called free state) after the formation of the particulate polymer.
In the present invention, “(meth) acryl” refers to acryl and / or methacryl.
［粒子状重合体］
　粒子状重合体は、本発明の二次電池電極用バインダー組成物を用いて電極を形成した際に、製造した電極において、電極合材層に含まれる成分（例えば、電極活物質）が電極から脱離しないように保持しうる成分である。
　バインダー組成物に配合する粒子状重合体としては、以下に説明する沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を重合して生成される粒子状重合体を用いることができる。
　なお、本発明のバインダー組成物を負極の形成に用いる場合（二次電池負極用バインダー組成物）、粒子状重合体は、架橋性単量体を更に含む単量体混合物を重合して生成されることが好ましく、スチレンなどの芳香族ビニル単量体や、酸性基を含有する単量体を更に含む単量体混合物を重合して生成されることが更に好ましい。
　また、本発明のバインダー組成物を正極の形成に用いる場合（二次電池正極用バインダー組成物）、粒子状重合体は、（メタ）アクリロニトリル単量体などのα,β－不飽和ニトリル単量体を更に含む単量体混合物を重合して生成されることが好ましく、酸性基を含有する単量体を更に含む単量体混合物を重合して生成されることが更に好ましい。なお、本発明において、「（メタ）アクリロニトリル」とは、アクリロニトリル及び／又はメタクリロニトリルを指す。
　以下、本発明における粒子状重合体を生成するための単量体混合物に配合されうる各単量体について詳述する。 [Particulate polymer]
When the particulate polymer is formed using the binder composition for a secondary battery electrode of the present invention, the component contained in the electrode mixture layer (for example, the electrode active material) is produced from the electrode in the manufactured electrode. It is a component that can be held so as not to be detached.
As the particulate polymer to be blended in the binder composition, a particulate polymer produced by polymerizing a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher described below is used. be able to.
In addition, when using the binder composition of this invention for formation of a negative electrode (binder composition for secondary battery negative electrodes), a particulate polymer is produced | generated by superposing | polymerizing the monomer mixture which further contains a crosslinkable monomer. It is more preferable that it is produced by polymerizing a monomer mixture further containing an aromatic vinyl monomer such as styrene or a monomer containing an acidic group.
In addition, when the binder composition of the present invention is used for forming a positive electrode (secondary battery positive electrode binder composition), the particulate polymer is an α, β-unsaturated nitrile monomer such as a (meth) acrylonitrile monomer. It is preferably produced by polymerizing a monomer mixture further containing a polymer, and more preferably produced by polymerizing a monomer mixture further containing a monomer containing an acidic group. In the present invention, “(meth) acrylonitrile” refers to acrylonitrile and / or methacrylonitrile.
Hereinafter, each monomer which can be mix | blended with the monomer mixture for producing | generating the particulate polymer in this invention is explained in full detail.
＜沸点１４５℃以上の（メタ）アクリル酸エステル単量体＞
　粒子状重合体を重合する際に使用する単量体混合物は、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含有する。沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含有することで、単量体混合物を重合して得られる粒子状重合体の電気化学的安定性及び柔軟性を高めることができる。そして、バインダー組成物を用いた電極合材層の密着強度を高めて電極のピール強度を向上させることができると共に、二次電池の電池特性を向上させることができる。
　ここで、（メタ）アクリル酸エステル単量体としては、例えば、式（Ｉ）：ＣＨ2＝ＣＲ1－ＣＯＯＲ2で表される化合物が挙げられる。式（Ｉ）において、Ｒ1は水素原子またはメチル基を表し、Ｒ2はアルキル基またはシクロアルキル基、或いは、それらの一部を置換した官能基を表す。
　そして、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の例を挙げると、ｎ－ブチルアクリレート（ＢＡ）、アクリル酸ｎ－アミル、アクリル酸イソアミル、アクリル酸ｎ－ヘキシル、２－エチルヘキシルアクリレート（２ＥＨＡ）、アクリル酸－２－メトキシエチル、アクリル酸－２－エトキシエチル、アクリル酸ヘキシル、アクリル酸ノニル、アクリル酸ラウリル、アクリル酸ステアリル、ベンジルアクリレートなどのアクリレート；メタクリル酸ｎ－ブチル、メタクリル酸イソブチル、メタクリル酸ｎ－アミル、メタクリル酸イソアミル、メタクリル酸ｎ－ヘキシル、メタクリル酸２－エチルヘキシル、メタクリル酸オクチル、メタクリル酸イソデシル、メタクリル酸ラウリル、メタクリル酸トリデシル、メタクリル酸ステアリル、ベンジルメタクリレートなどのメタアクリレート等が挙げられる。これらの単量体は、１種類を単独で用いてもよく、２種類以上を組み合わせて用いてもよい。これらの中でも、アクリレートが好ましく、２－エチルヘキシルアクリレート及びｎ－ブチルアクリレートが、二次電池用電極のピール強度を向上できる点で好ましく、さらに、２－エチルヘキシルアクリレートが特に好ましい。２－エチルヘキシルアクリレートは側鎖が長く、２－エチルヘキシルアクリレート由来の単量体単位を有する重合体のＴｇを低減させて柔軟性を向上させると共に、電気化学的安定性を向上させるため、かかる重合体を配合した二次電池電極用バインダー組成物を用いて得た電極合材層の集電体に対する密着強度を向上し、ひいては、かかる電極合材層を有する電極を用いた二次電池の電池特性を向上できるからである。
　ここで、（メタ）アクリル酸エステル単量体の沸点は、ＪＩＳ　Ｋ２２５４に従って測定することができる。 <A (meth)acrylic acid ester monomer having a boiling point of 145° C. or higher>
The monomer mixture used when polymerizing the particulate polymer contains a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher. By containing the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, the electrochemical stability and flexibility of the particulate polymer obtained by polymerizing the monomer mixture can be enhanced. And while the adhesive strength of the electrode compound layer using a binder composition can be raised and the peel strength of an electrode can be improved, the battery characteristic of a secondary battery can be improved.
Here, examples of the (meth) acrylic acid ester monomer include compounds represented by the formula (I): CH 2 ═CR 1 —COOR 2 . In the formula (I), R 1 represents a hydrogen atom or a methyl group, and R 2 represents an alkyl group, a cycloalkyl group, or a functional group in which a part thereof is substituted.
Examples of (meth) acrylate monomers having a boiling point of 145 ° C. or higher include n-butyl acrylate (BA), n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate. (2EHA), acrylates such as 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, hexyl acrylate, nonyl acrylate, lauryl acrylate, stearyl acrylate, and benzyl acrylate; n-butyl methacrylate, methacrylic acid Isobutyl, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, isodecyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stear methacrylate Le, and the like methacrylates such as benzyl methacrylate. These monomers may be used individually by 1 type, and may be used in combination of 2 or more types. Among these, acrylate is preferable, 2-ethylhexyl acrylate and n-butyl acrylate are preferable in terms of improving the peel strength of the secondary battery electrode, and 2-ethylhexyl acrylate is particularly preferable. Since 2-ethylhexyl acrylate has a long side chain and reduces Tg of a polymer having monomer units derived from 2-ethylhexyl acrylate to improve flexibility and to improve electrochemical stability, such a polymer Improved the adhesion strength of the electrode mixture layer obtained by using the binder composition for secondary battery electrodes blended with the current collector, and thus the battery characteristics of the secondary battery using the electrode having the electrode mixture layer It is because it can improve.
Here, the boiling point of the (meth) acrylic acid ester monomer can be measured according to JIS K2254.
　バインダー組成物を負極の形成に用いる場合、上述した沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合は、単量体混合物中、好ましくは１０質量％以上、より好ましくは１５質量％以上、更により好ましくは３０質量％以上、特に好ましくは５０質量％以上、及び、好ましくは７０質量％以下、より好ましくは６０質量％以下である。単量体混合物中の沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を１０質量％以上とすることで、バインダー組成物を用いて形成した負極合材層に柔軟性を与えることができる。さらに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を７０質量％以下とすることで、バインダー組成物を用いて形成した負極合材層のピール強度を向上させることができる。 When the binder composition is used for forming the negative electrode, the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is preferably 10% by mass or more, more preferably 15% by mass in the monomer mixture. % Or more, still more preferably 30% by mass or more, particularly preferably 50% by mass or more, and preferably 70% by mass or less, more preferably 60% by mass or less. By making the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher in the monomer mixture 10% by mass or higher, flexibility is provided to the negative electrode mixture layer formed using the binder composition. be able to. Furthermore, the peel strength of the negative electrode mixture layer formed using the binder composition can be improved by setting the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher to 70% by mass or less. .
　また、バインダー組成物を正極の形成に用いる場合、上述した沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合は、単量体混合物中、好ましくは６０質量％以上、より好ましくは６５質量％以上、更により好ましくは７０質量％以上、特に好ましくは７５質量％以上、及び、好ましくは９５質量％以下、より好ましくは９０質量％以下、更により好ましくは８５質量％以下、特に好ましくは８３質量％以下である。単量体混合物中の沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を６０質量％以上とすることで、電解液に対して重合体が過剰に膨潤しないようにして、バインダー組成物を用いて形成した正極合材層のピール強度を向上させることができると共に、正極合材層の柔軟性を向上させて、当該正極合材層を有する正極を割れにくくすることができる。さらに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を９５質量％以下とすることで、電解液に対して重合体が適度に膨潤するようにして、バインダー組成物を用いて形成した正極を備える二次電池の電気抵抗の上昇を抑制することができると共に、粒子状重合体の機械強度を維持して密着性を維持することができる。 Moreover, when using a binder composition for formation of a positive electrode, the content rate of the (meth) acrylic acid ester monomer with a boiling point of 145 degreeC or more mentioned above in a monomer mixture, Preferably it is 60 mass% or more, More preferably 65% by weight or more, still more preferably 70% by weight or more, particularly preferably 75% by weight or more, and preferably 95% by weight or less, more preferably 90% by weight or less, still more preferably 85% by weight or less, particularly preferably Is 83 mass% or less. By setting the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher in the monomer mixture to 60 mass% or higher, the polymer is prevented from excessive swelling with respect to the electrolyte solution, and the binder The peel strength of the positive electrode mixture layer formed using the composition can be improved, and the flexibility of the positive electrode mixture layer can be improved to make the positive electrode having the positive electrode mixture layer difficult to break. Furthermore, by setting the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher to 95% by mass or less, the polymer is appropriately swollen with respect to the electrolytic solution, and the binder composition is used. An increase in electrical resistance of a secondary battery including the positive electrode formed in this manner can be suppressed, and the mechanical strength of the particulate polymer can be maintained and adhesion can be maintained.
　さらに、上述の沸点１４５℃以上の（メタ）アクリル酸エステル単量体の沸点は、１５０℃以上、２５０℃以下であることが好ましい。高沸点の（メタ）アクリル酸エステル単量体単位には、概して側鎖が長く、かかる単量体単位を含んでなる重合体は、柔軟性に富み、また、結着性が良好であるため、かかる重合体を含むバインダー組成物を用いて製造した二次電池の電池特性を向上させることができるからである。 Furthermore, the boiling point of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is preferably 150 ° C. or higher and 250 ° C. or lower. High-boiling point (meth) acrylate monomer units generally have long side chains, and polymers comprising such monomer units are rich in flexibility and have good binding properties. This is because the battery characteristics of a secondary battery produced using a binder composition containing such a polymer can be improved.
＜負極用バインダー組成物中の粒子状重合体の重合に用いる単量体＞
　以下、バインダー組成物を負極の形成に用いる場合に、粒子状重合体の重合に使用する単量体混合物に好適に配合されうる、架橋性単量体、芳香族ビニル単量体、および酸性基を含有する単量体について詳述する。 <Monomer used for polymerization of particulate polymer in binder composition for negative electrode>
Hereinafter, when the binder composition is used for forming a negative electrode, a crosslinkable monomer, an aromatic vinyl monomer, and an acidic group that can be suitably blended in the monomer mixture used for polymerization of the particulate polymer. The monomer containing is described in detail.
＜＜架橋性単量体＞＞
　バインダー組成物を負極の形成に用いる場合、粒子状重合体を重合する際に使用する単量体混合物は、架橋性単量体を更に含むことが好ましい。かかる粒子状重合体を含むバインダー組成物を用いて製造したリチウムイオン二次電池の高温保存特性や高温サイクル特性を向上させることができるからである。 << Crosslinking monomer >>
When using a binder composition for formation of a negative electrode, it is preferable that the monomer mixture used when superposing | polymerizing a particulate polymer further contains a crosslinkable monomer. This is because the high-temperature storage characteristics and high-temperature cycle characteristics of a lithium ion secondary battery produced using a binder composition containing such a particulate polymer can be improved.
　架橋性単量体は、以下の架橋性基を有する単量体である。
　架橋性基としては、通常は熱により架橋反応を生じる熱架橋性基を用いる。架橋性基の例を挙げると、エポキシ基、Ｎ－メチロールアミド基、オキサゾリン基、アリル基などが挙げられ、なかでも架橋および架橋密度の調節が容易であるので、架橋性基としては、Ｎ－メチロールアミド基、エポキシ基、アリル基が好ましい。架橋密度が高いほど、粒子状重合体の電解液に対する膨潤度が低くなるため、架橋密度を調節することにより、粒子状重合体の膨潤度を制御することが可能である。なお、架橋性基の種類は、１種類であってもよく、２種類以上であってもよい。
　架橋性単量体は、前述した（メタ）アクリル酸エステル単量体には含まれないものとする。
　エポキシ基を含有する単量体としては、例えば、炭素－炭素二重結合およびエポキシ基を含有する単量体、ハロゲン原子およびエポキシ基を含有する単量体、などが挙げられる。
　炭素－炭素二重結合およびエポキシ基を含有する単量体としては、例えば、ビニルグリシジルエーテル、アリルグリシジルエーテル、ブテニルグリシジルエーテル、ｏ－アリルフェニルグリシジルエーテル等の不飽和グリシジルエーテル；ブタジエンモノエポキシド、クロロプレンモノエポキシド、４，５－エポキシ－２－ペンテン、３，４－エポキシ－１－ビニルシクロヘキセン、１，２－エポキシ－５，９－シクロドデカジエン等のジエンまたはポリエンのモノエポキシド；３，４－エポキシ－１－ブテン、１，２－エポキシ－５－ヘキセン、１，２－エポキシ－９－デセン等のアルケニルエポキシド；グリシジルアクリレート、グリシジルメタクリレート、グリシジルクロトネート、グリシジル－４－ヘプテノエート、グリシジルソルベート、グリシジルリノレート、グリシジル－４－メチル－３－ペンテノエート、３－シクロヘキセンカルボン酸のグリシジルエステル、４－メチル－３－シクロヘキセンカルボン酸のグリシジルエステル等の不飽和カルボン酸のグリシジルエステル類；などが挙げられる。
　ハロゲン原子およびエポキシ基を有する単量体としては、例えば、エピクロロヒドリン、エピブロモヒドリン、エピヨードヒドリン、エピフルオロヒドリン、β－メチルエピクロルヒドリン等のエピハロヒドリン；ｐ－クロロスチレンオキシド；ジブロモフェニルグリシジルエーテル；などが挙げられる。
　Ｎ－メチロールアミド基を含有する単量体としては、例えば、Ｎ－メチロール（メタ）アクリルアミド等のメチロール基を有する（メタ）アクリルアミド類などが挙げられる。
　オキサゾリン基を含有する単量体としては、例えば、２－ビニル－２－オキサゾリン、２－ビニル－４－メチル－２－オキサゾリン、２－ビニル－５－メチル－２－オキサゾリン、２－イソプロペニル－２－オキサゾリン、２－イソプロペニル－４－メチル－２－オキサゾリン、２－イソプロペニル－５－メチル－２－オキサゾリン、２－イソプロペニル－５－エチル－２－オキサゾリン等が挙げられる。
　アリル基を含有する単量体としては、例えば、アリルアクリレート、アリルメタクリレートなどが挙げられる。 The crosslinkable monomer is a monomer having the following crosslinkable group.
As the crosslinkable group, a heat crosslinkable group that usually causes a crosslinking reaction by heat is used. Examples of the crosslinkable group include an epoxy group, an N-methylolamide group, an oxazoline group, and an allyl group. Among them, the crosslinkable group and the crosslinking density can be easily adjusted. A methylolamide group, an epoxy group, and an allyl group are preferred. The higher the crosslinking density, the lower the degree of swelling of the particulate polymer with respect to the electrolytic solution. Therefore, the degree of swelling of the particulate polymer can be controlled by adjusting the crosslinking density. In addition, the kind of crosslinkable group may be one kind, and may be two or more kinds.
A crosslinkable monomer shall not be contained in the (meth) acrylic acid ester monomer mentioned above.
Examples of the monomer containing an epoxy group include a monomer containing a carbon-carbon double bond and an epoxy group, a monomer containing a halogen atom and an epoxy group, and the like.
Examples of the monomer containing a carbon-carbon double bond and an epoxy group include unsaturated glycidyl ethers such as vinyl glycidyl ether, allyl glycidyl ether, butenyl glycidyl ether, o-allylphenyl glycidyl ether; butadiene monoepoxide, Diene or polyene monoepoxides such as chloroprene monoepoxide, 4,5-epoxy-2-pentene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5,9-cyclododecadiene; Alkenyl epoxides such as epoxy-1-butene, 1,2-epoxy-5-hexene, 1,2-epoxy-9-decene; glycidyl acrylate, glycidyl methacrylate, glycidyl crotonate, glycidyl-4-heptenoate, glycidyl sol Glycidyl esters of unsaturated carboxylic acids such as glycidyl ester, glycidyl linoleate, glycidyl-4-methyl-3-pentenoate, glycidyl ester of 3-cyclohexene carboxylic acid, glycidyl ester of 4-methyl-3-cyclohexene carboxylic acid, etc. Is mentioned.
Examples of the monomer having a halogen atom and an epoxy group include epihalohydrin such as epichlorohydrin, epibromohydrin, epiiodohydrin, epifluorohydrin, β-methylepichlorohydrin; p-chlorostyrene oxide; dibromo Phenyl glycidyl ether; and the like.
Examples of the monomer containing an N-methylolamide group include (meth) acrylamides having a methylol group such as N-methylol (meth) acrylamide.
Examples of the monomer containing an oxazoline group include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, 2-vinyl-5-methyl-2-oxazoline, 2-isopropenyl- Examples include 2-oxazoline, 2-isopropenyl-4-methyl-2-oxazoline, 2-isopropenyl-5-methyl-2-oxazoline, 2-isopropenyl-5-ethyl-2-oxazoline and the like.
Examples of the monomer containing an allyl group include allyl acrylate and allyl methacrylate.
　これらの中でも、架橋性単量体としては、架橋密度の向上及び高い共重合性の観点から、アリルアクリレート又はアリルメタクリレートが好ましい。 Among these, as the crosslinkable monomer, allyl acrylate or allyl methacrylate is preferable from the viewpoint of improvement in crosslink density and high copolymerizability.
　架橋性単量体の含有割合は、単量体混合物中、好ましくは０．５質量％以上、より好ましくは０．８質量％以上、特に好ましくは１質量％以上であり、好ましくは５質量％以下、より好ましくは３質量％以下、特に好ましくは２質量％以下である。架橋性単量体の配合量を０．５質量％以上とすることで、電解液への膨潤度を適当な大きさとすると共に、かかる単量体混合物を用いて得たバインダー組成物により製造した二次電池の高温保存特性及び高温サイクル特性を向上させることができるからである。また、架橋性単量体の配合量を５質量％以下とすることで、負極合材層の柔軟性を維持することができるからである。 The content of the crosslinkable monomer is preferably 0.5% by mass or more, more preferably 0.8% by mass or more, particularly preferably 1% by mass or more, preferably 5% by mass in the monomer mixture. Hereinafter, it is more preferably 3% by mass or less, particularly preferably 2% by mass or less. By making the blending amount of the crosslinkable monomer 0.5% by mass or more, the degree of swelling in the electrolytic solution is set to an appropriate level, and the binder composition obtained using such a monomer mixture is used. This is because the high-temperature storage characteristics and high-temperature cycle characteristics of the secondary battery can be improved. Moreover, it is because the softness | flexibility of a negative mix layer can be maintained because the compounding quantity of a crosslinkable monomer shall be 5 mass% or less.
＜＜芳香族ビニル単量体＞＞
　バインダー組成物を負極の形成に用いる場合、粒子状重合体を重合する際に使用する単量体混合物は、スチレン、クロロスチレン、ビニルトルエン、ｔ－ブチルスチレン、ビニル安息香酸、ビニル安息香酸メチル、ビニルナフタレン、クロロメチルスチレン、ヒドロキシメチルスチレン、α－メチルスチレン、ジビニルベンゼン等のスチレン系単量体を更に含むことが好ましい。中でも、芳香族ビニル単量体として、スチレンを使用することが好ましい。なお、これらは１種類を単独で用いてもよく、２種類以上を組み合わせて用いてもよい。
　スチレン系単量体のような芳香族ビニル単量体の使用により、芳香族ビニル単量体由来の単量体単位を有する重合体のＴｇを高め、粒子状重合体のポリマー強度を強くし、ひいては負極合材層のピール強度を向上させることができるからである。さらに、スチレン系単量体のような芳香族ビニル単量体の使用により、バインダー組成物に含有される粒子状重合体に導入された芳香族環のπ電子と、炭素系負極活物質の芳香族環のπ電子との相互作用により、導電材の分散性を向上させることができるからである。
　ここで、スチレン系単量体のような芳香族ビニル単量体の配合量は、単量体混合物中、好ましくは２０質量％以上、より好ましくは３０質量％以上であり、好ましくは８０質量％以下、より好ましくは７０質量％以下、特に好ましくは６０質量％以下である。芳香族ビニル単量体の配合量を２０質量％以上とすることで、上述したような負極合材層のピール強度の向上や、導電材の分散性の向上といった効果を得ることができ、配合量を８０質量％以下とすることで、負極合材層の柔軟性を維持することができるからである。 << Aromatic vinyl monomer >>
When the binder composition is used for forming the negative electrode, the monomer mixture used for polymerizing the particulate polymer is styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, It is preferable to further contain a styrene monomer such as vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene, divinyl benzene and the like. Of these, styrene is preferably used as the aromatic vinyl monomer. In addition, these may be used individually by 1 type and may be used in combination of 2 or more types.
By using an aromatic vinyl monomer such as a styrene monomer, the Tg of the polymer having monomer units derived from the aromatic vinyl monomer is increased, and the polymer strength of the particulate polymer is increased, As a result, the peel strength of the negative electrode mixture layer can be improved. Further, by using an aromatic vinyl monomer such as a styrene monomer, the π electron of the aromatic ring introduced into the particulate polymer contained in the binder composition and the aromatic of the carbon-based negative electrode active material. This is because the dispersibility of the conductive material can be improved by the interaction with the π electrons of the group ring.
Here, the blending amount of the aromatic vinyl monomer such as the styrene monomer is preferably 20% by mass or more, more preferably 30% by mass or more, and preferably 80% by mass in the monomer mixture. Hereinafter, it is more preferably 70% by mass or less, particularly preferably 60% by mass or less. By setting the blending amount of the aromatic vinyl monomer to 20% by mass or more, it is possible to obtain the effects of improving the peel strength of the negative electrode mixture layer as described above and improving the dispersibility of the conductive material. This is because the flexibility of the negative electrode mixture layer can be maintained by adjusting the amount to 80% by mass or less.
＜＜酸性基含有単量体＞＞
　粒子状重合体を重合する際に使用する単量体混合物は、酸性基を含有する単量体（以下、「酸性基含有単量体」と称することがある）を更に含むことが好ましい。酸性基を含有する単量体を含む単量体混合物を重合することで、酸性基を含有する単量体単位（以下、「酸性基含有単量体単位」と称することがある）を粒子状重合体に導入することができる。酸性基としては、例えば、カルボン酸基（－ＣＯＯＨ）、スルホン酸基（－ＳＯ3Ｈ）、リン酸基（－ＰＯ3Ｈ2）などが挙げられる。ただし、酸性基含有単量体が有する酸性基は、１種類でもよく、２種類以上でもよい。また、酸性基を含有する単量体が有する酸性基の数は、１つでもよく、２つ以上でもよい。 << Acid group-containing monomer >>
The monomer mixture used when polymerizing the particulate polymer preferably further contains a monomer containing an acidic group (hereinafter sometimes referred to as “acidic group-containing monomer”). By polymerizing a monomer mixture containing a monomer containing an acidic group, a monomer unit containing an acidic group (hereinafter sometimes referred to as an “acidic group-containing monomer unit”) is particulate. It can be introduced into the polymer. Examples of the acidic group include a carboxylic acid group (—COOH), a sulfonic acid group (—SO 3 H), and a phosphoric acid group (—PO 3 H 2 ). However, the acidic group-containing monomer may have one acidic group or two or more acidic groups. Moreover, the number of acidic groups which the monomer containing an acidic group has may be one, and two or more may be sufficient as it.
　カルボン酸基を含有する単量体としては、通常、カルボン酸基及び重合可能な基を有する単量体を用いる。カルボン酸基を含有する単量体の例としては、不飽和カルボン酸単量体を挙げることができる。不飽和カルボン酸単量体は、炭素－炭素不飽和結合を有し、且つ、カルボン酸基を有する単量体である。
　不飽和カルボン酸単量体の例としては、不飽和モノカルボン酸及びその誘導体；不飽和ジカルボン酸及びその酸無水物並びにそれらの誘導体；などが挙げられる。
　不飽和モノカルボン酸の例としては、アクリル酸、メタクリル酸、及びクロトン酸等の、エチレン性不飽和モノカルボン酸が挙げられる。
　不飽和モノカルボン酸の誘導体の例としては、２－エチルアクリル酸、イソクロトン酸、α－アセトキシアクリル酸、β－ｔｒａｎｓ－アリールオキシアクリル酸、α－クロロ－β－Ｅ－メトキシアクリル酸、及びβ－ジアミノアクリル酸等の、エチレン性不飽和モノカルボン酸の誘導体が挙げられる。
　不飽和ジカルボン酸の例としては、マレイン酸、フマル酸、及びイタコン酸等の、エチレン性不飽和ジカルボン酸が挙げられる。
　不飽和ジカルボン酸の酸無水物の例としては、無水マレイン酸、アクリル酸無水物、メチル無水マレイン酸、及びジメチル無水マレイン酸等の、エチレン性不飽和ジカルボン酸の無水物が挙げられる。
　不飽和ジカルボン酸の誘導体の例としては、メチルマレイン酸、ジメチルマレイン酸、フェニルマレイン酸、クロロマレイン酸、ジクロロマレイン酸、フルオロマレイン酸等のマレイン酸メチルアリル；並びにマレイン酸ジフェニル、マレイン酸ノニル、マレイン酸デシル、マレイン酸ドデシル、マレイン酸オクタデシル、マレイン酸フルオロアルキル等のマレイン酸エステルが挙げられる。 As the monomer containing a carboxylic acid group, a monomer having a carboxylic acid group and a polymerizable group is usually used. Examples of the monomer containing a carboxylic acid group include an unsaturated carboxylic acid monomer. The unsaturated carboxylic acid monomer is a monomer having a carbon-carbon unsaturated bond and having a carboxylic acid group.
Examples of the unsaturated carboxylic acid monomer include unsaturated monocarboxylic acid and derivatives thereof; unsaturated dicarboxylic acid and acid anhydrides and derivatives thereof; and the like.
Examples of unsaturated monocarboxylic acids include ethylenically unsaturated monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid.
Examples of unsaturated monocarboxylic acid derivatives include 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, α-chloro-β-E-methoxyacrylic acid, and β -Derivatives of ethylenically unsaturated monocarboxylic acids, such as diaminoacrylic acid.
Examples of unsaturated dicarboxylic acids include ethylenically unsaturated dicarboxylic acids such as maleic acid, fumaric acid, and itaconic acid.
Examples of unsaturated dicarboxylic acid anhydrides include ethylenically unsaturated dicarboxylic acid anhydrides such as maleic anhydride, acrylic anhydride, methyl maleic anhydride, and dimethyl maleic anhydride.
Examples of derivatives of unsaturated dicarboxylic acids include methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, methylallyl maleate; and diphenyl maleate, nonyl maleate, maleate Examples thereof include maleate esters such as decyl acid, dodecyl maleate, octadecyl maleate, and fluoroalkyl maleate.
　スルホン酸基を有する単量体としては、ビニルスルホン酸、メチルビニルスルホン酸、（メタ）アリルスルホン酸、スチレンスルホン酸、（メタ）アクリル酸－２－スルホン酸エチル、２－アクリルアミド－２－メチルプロパンスルホン酸、３－アリロキシ－２－ヒドロキシプロパンスルホン酸などが挙げられる。
　なお、本明細書において、「（メタ）アリル」とは、アリルおよび／またはメタアリルを意味する。 Examples of monomers having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, styrene sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methyl. Examples thereof include propanesulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid.
In the present specification, “(meth) allyl” means allyl and / or methallyl.
　リン酸基を有する単量体としては、リン酸－２－（メタ）アクリロイルオキシエチル、リン酸メチル－２－（メタ）アクリロイルオキシエチル、リン酸エチル－（メタ）アクリロイルオキシエチル、リン酸エチレンメタクリレートなどが挙げられる。 Monomers having a phosphoric acid group include phosphoric acid-2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, ethyl phosphate- (meth) acryloyloxyethyl phosphate, ethylene phosphate And methacrylate.
　これらの中でも、酸性基含有単量体としては、アクリル酸、メタクリル酸、イタコン酸、２－アクリルアミド－２－メチルプロパンスルホン酸（ＡＭＰＳ）、リン酸エチレンメタクリレートが好ましい。さらには、バインダー組成物の保存安定性を向上させる観点から、アクリル酸、メタクリル酸等の不飽和モノカルボン酸や、イタコン酸等のエチレン性不飽和ジカルボン酸が好ましい。粒子状重合体の水に対する分散性をより高めることにより、バインダー組成物の保存安定性を向上させることができるからである。 Among these, as the acid group-containing monomer, acrylic acid, methacrylic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), and ethylene methacrylate phosphate are preferable. Furthermore, from the viewpoint of improving the storage stability of the binder composition, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, and ethylenically unsaturated dicarboxylic acids such as itaconic acid are preferred. This is because the storage stability of the binder composition can be improved by further increasing the dispersibility of the particulate polymer in water.
　酸性基含有単量体の配合量は、単量体混合物中、好ましくは０．５質量％以上、より好ましくは１質量％以上、特に好ましくは１．５質量％以上であり、好ましくは８質量％以下、より好ましくは５質量％以下、特に好ましくは４質量％以下である。酸性基含有単量体の比率を０．５質量％以上とすることにより、バインダー組成物の製造安定性及び保存安定性を向上させることができる。一方、酸性基含有単量体の比率を８質量％以下とすることにより、バインダー組成物の結着性を維持すると共に、かかるバインダー組成物を用いて構成した二次電池のサイクル特性を改善することができる。 The compounding amount of the acidic group-containing monomer is preferably 0.5% by mass or more, more preferably 1% by mass or more, particularly preferably 1.5% by mass or more, preferably 8% by mass in the monomer mixture. % Or less, more preferably 5% by mass or less, and particularly preferably 4% by mass or less. By setting the ratio of the acidic group-containing monomer to 0.5% by mass or more, the production stability and storage stability of the binder composition can be improved. On the other hand, by setting the ratio of the acidic group-containing monomer to 8% by mass or less, the binding property of the binder composition is maintained, and the cycle characteristics of a secondary battery configured using such a binder composition are improved. be able to.
＜＜その他の単量体＞＞
　さらに、バインダー組成物を負極の形成に用いる場合、本発明における粒子状重合体を重合する際に使用する単量体混合物は、本発明を著しく損なわない限り、上述したもの以外に任意の単量体を含んでいてもよい。これらの任意の単量体は、上述した単量体と共重合可能な単量体である。上述した単量体と共重合可能な単量体の例を挙げると、アクリルアミドなどのアミド系単量体；エチレン、プロピレン等のオレフィン類；ブタジエン、イソプレン等のジエン系単量体；塩化ビニル、塩化ビニリデン等のハロゲン原子含有単量体；酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、安息香酸ビニル等のビニルエステル類；メチルビニルエーテル、エチルビニルエーテル、ブチルビエルエーテル等のビニルエーテル類；メチルビニルケトン、エチルビニルケトン、ブチルビニルケトン、ヘキシルビニルケトン、イソプロペニルビニルケトン等のビニルケトン類；Ｎ－ビニルピロリドン、ビニルピリジン、ビニルイミダゾール等の複素環含有ビニル化合物；メチル（メタ）アクリレート、エチル（メタ）アクリレート、プロピル（メタ）アクリレートなどの沸点１４５℃未満の（メタ）アクリル酸エステル単量体；後述するα，β－不飽和ニトリル単量体などが挙げられる。これらは、１種類を単独で用いてもよく、２種類以上を組み合わせて用いてもよい。 << Other monomers >>
Further, when the binder composition is used for forming a negative electrode, the monomer mixture used for polymerizing the particulate polymer in the present invention is not limited to those described above unless the present invention is significantly impaired. May contain body. These arbitrary monomers are monomers copolymerizable with the above-mentioned monomers. Examples of monomers copolymerizable with the above-mentioned monomers include amide monomers such as acrylamide; olefins such as ethylene and propylene; diene monomers such as butadiene and isoprene; vinyl chloride; Monomers containing halogen atoms such as vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether and butyl vinyl ether; methyl vinyl ketone and ethyl vinyl Vinyl ketones such as ketone, butyl vinyl ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; heterocyclic compounds containing a heterocyclic ring such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (Me ) Boiling point 145 below ° C. (meth) acrylic acid ester monomers such as acrylate; alpha described later, and the like β- unsaturated nitrile monomer. These may be used alone or in combination of two or more.
＜正極用バインダー組成物中の粒子状重合体の重合に用いる単量体＞
　以下、バインダー組成物を正極の形成に用いる場合に、粒子状重合体の重合に使用する単量体混合物に好適に配合されうる、α,β－不飽和ニトリル単量体および酸性基含有単量体について詳述する。 <Monomer used for polymerization of particulate polymer in binder composition for positive electrode>
Hereinafter, when the binder composition is used for forming a positive electrode, an α, β-unsaturated nitrile monomer and an acidic group-containing monomer can be suitably blended in the monomer mixture used for the polymerization of the particulate polymer. The body is described in detail.
＜α,β－不飽和ニトリル単量体＞
　バインダー組成物を正極の形成に用いる場合、粒子状重合体を重合する際に使用する単量体混合物は、（メタ）アクリロニトリル単量体などのα,β－不飽和ニトリル単量体を更に含むことが好ましい。（メタ）アクリロニトリル単量体などのα,β－不飽和ニトリル単量体の使用により、バインダー組成物の結着力を高めて正極の強度を顕著に向上させることができるからである。
　α，β－不飽和ニトリル単量体としては、アクリロニトリル、メタクリロニトリル、α－クロロアクリロニトリル、α－エチルアクリロニトリルなどが挙げられる。これらの中でも、機械的強度および結着性向上の観点からは、アクリロニトリルおよびメタクリロニトリルが好ましく、アクリロニトリルが特に好ましい。なお、これらは１種類を単独で用いてもよく、２種類以上を組み合わせて用いてもよい。
　ここで、（メタ）アクリロニトリル単量体などのα,β－不飽和ニトリル単量体の配合量は、単量体混合物中、好ましくは１～５０質量％、より好ましくは５～３５質量％である。（メタ）アクリロニトリル単量体などのα,β－不飽和ニトリル単量体の含有量が１質量％未満の場合、粒子状重合体のＴｇが低くなり、かかる粒子状重合体を含有するバインダー組成物を用いて形成した正極合材層のピール強度が低下する虞がある。さらにこの場合、粒子状重合体が電解液に対して過剰に膨潤し易くなり、このことによってもピール強度が低下する虞がある。他方、（メタ）アクリロニトリル単量体などのα,β－不飽和ニトリル単量体の含有量が５０質量％超の場合、粒子状重合体のＴｇが高くなり、かかる粒子状重合体を含有するバインダー組成物を用いて形成した正極合材層の柔軟性が低下する虞がある。さらにこの場合、粒子状重合体が電解液に対してより膨潤しにくくなり、かかる正極合材層を用いて製造した電極の抵抗が上昇する虞がある。すなわち、アクリロニトリル単量体の単量体混合物中の含有量を、好ましくは１～５０質量％、より好ましくは５～３５質量％とすることで、かかる単量体混合物を重合して得た粒子状重合体を含有するバインダー組成物を用いて製造した正極のピール強度を向上させると共に、粒子状重合体の電解液に対する膨潤度を適切な値として、かかるバインダー組成物を用いて製造した二次電池の内部抵抗の増加を抑制することができる。 <Α, β-unsaturated nitrile monomer>
When the binder composition is used for forming the positive electrode, the monomer mixture used for polymerizing the particulate polymer further contains an α, β-unsaturated nitrile monomer such as a (meth) acrylonitrile monomer. It is preferable. This is because the use of an α, β-unsaturated nitrile monomer such as a (meth) acrylonitrile monomer can increase the binding strength of the binder composition and can significantly improve the strength of the positive electrode.
Examples of the α, β-unsaturated nitrile monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile and the like. Among these, acrylonitrile and methacrylonitrile are preferable and acrylonitrile is particularly preferable from the viewpoint of improving mechanical strength and binding properties. In addition, these may be used individually by 1 type and may be used in combination of 2 or more types.
Here, the blending amount of the α, β-unsaturated nitrile monomer such as (meth) acrylonitrile monomer is preferably 1 to 50% by mass, more preferably 5 to 35% by mass in the monomer mixture. is there. When the content of an α, β-unsaturated nitrile monomer such as a (meth) acrylonitrile monomer is less than 1% by mass, the Tg of the particulate polymer is lowered, and the binder composition containing such a particulate polymer There is a possibility that the peel strength of the positive electrode mixture layer formed using the product may be lowered. Furthermore, in this case, the particulate polymer is likely to swell excessively with respect to the electrolytic solution, which may cause a decrease in peel strength. On the other hand, when the content of α, β-unsaturated nitrile monomer such as (meth) acrylonitrile monomer is more than 50% by mass, Tg of the particulate polymer becomes high, and the particulate polymer is contained. There is a possibility that the flexibility of the positive electrode mixture layer formed using the binder composition is lowered. Furthermore, in this case, the particulate polymer is less likely to swell with respect to the electrolytic solution, and the resistance of the electrode manufactured using such a positive electrode mixture layer may increase. That is, particles obtained by polymerizing the monomer mixture by setting the content of the acrylonitrile monomer in the monomer mixture to preferably 1 to 50% by mass, more preferably 5 to 35% by mass. A secondary material produced using such a binder composition with an appropriate value for the degree of swelling of the particulate polymer with respect to the electrolyte while improving the peel strength of the positive electrode produced using the binder composition containing the particulate polymer An increase in the internal resistance of the battery can be suppressed.
＜＜酸性基含有単量体＞＞
　バインダー組成物を正極の形成に用いる場合、粒子状重合体を重合する際に使用する単量体混合物は、酸性基含有単量体を更に含むことが好ましい。ここで、酸性基含有単量体は、「負極用バインダー組成物中の粒子状重合体の重合に用いる単量体」の項で上述したものを用いることができ、好適な例および好適な単量体混合物中の配合量も同様である。 << Acid group-containing monomer >>
When using a binder composition for formation of a positive electrode, it is preferable that the monomer mixture used when superposing | polymerizing a particulate polymer further contains an acidic group containing monomer. Here, as the acidic group-containing monomer, those described above in the section of “Monomer used for polymerization of particulate polymer in binder composition for negative electrode” can be used. The blending amount in the monomer mixture is the same.
＜＜その他の単量体＞＞
　さらに、バインダー組成物を正極の形成に用いる場合、本発明における粒子状重合体を重合する際に使用する単量体混合物は、本発明を著しく損なわない限り、上述したもの以外に任意の単量体を含んでいてもよい。これらの任意の単量体は、上述した単量体と共重合可能な単量体である。上述した単量体と共重合可能な単量体の例を挙げると、スチレン、クロロスチレン、ビニルトルエン、ｔ－ブチルスチレン、ビニル安息香酸、ビニル安息香酸メチル、ビニルナフタレン、クロロメチルスチレン、ヒドロキシメチルスチレン、α－メチルスチレン、ジビニルベンゼン等のスチレン系単量体；アクリルアミドなどのアミド系単量体；エチレン、プロピレン等のオレフィン類；ブタジエン、イソプレン等のジエン系単量体；塩化ビニル、塩化ビニリデン等のハロゲン原子含有単量体；酢酸ビニル、プロピオン酸ビニル、酪酸ビニル、安息香酸ビニル等のビニルエステル類；メチルビニルエーテル、エチルビニルエーテル、ブチルビエルエーテル等のビニルエーテル類；メチルビニルケトン、エチルビニルケトン、ブチルビニルケトン、ヘキシルビニルケトン、イソプロペニルビニルケトン等のビニルケトン類；Ｎ－ビニルピロリドン、ビニルピリジン、ビニルイミダゾール等の複素環含有ビニル化合物；メチル（メタ）アクリレート、エチル（メタ）アクリレート、プロピル（メタ）アクリレートなどの沸点１４５℃未満の（メタ）アクリル酸エステル単量体；上述した架橋性単量体などが挙げられる。これらは、１種類を単独で用いてもよく、２種類以上を組み合わせて用いてもよい。 << Other monomers >>
Further, when the binder composition is used for forming the positive electrode, the monomer mixture used when polymerizing the particulate polymer in the present invention is not limited to those described above unless the present invention is significantly impaired. May contain body. These arbitrary monomers are monomers copolymerizable with the above-mentioned monomers. Examples of monomers copolymerizable with the above-described monomers include styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl. Styrene monomers such as styrene, α-methylstyrene and divinylbenzene; Amide monomers such as acrylamide; Olefins such as ethylene and propylene; Diene monomers such as butadiene and isoprene; Vinyl chloride and vinylidene chloride Halogen atom-containing monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, etc .; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl vinyl ketone, Butyl vinyl keto , Vinyl ketones such as hexyl vinyl ketone and isopropenyl vinyl ketone; heterocycle-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole; methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, etc. (Meth) acrylic acid ester monomers having a boiling point of less than 145 ° C .; crosslinkable monomers described above. These may be used alone or in combination of two or more.
＜粒子状重合体の構造＞
　バインダー組成物を負極の形成に用いる場合、粒子状重合体は、架橋構造を有していることが好ましい。架橋構造は、上述したように、架橋性単量体により粒子状重合体中に導入することにより形成することができる。
　そして、バインダー組成物を正極の形成に用いる場合も、粒子状重合体は、架橋構造を有していてもよい。架橋構造を導入する方法としては、例えば、重合体を、上述の架橋性単量体を含む単量体組成物から重合することで架橋性基を含有させる方法、重合体と架橋剤とを組み合わせて用いる方法が挙げられる。この場合、加熱又はエネルギー線を照射することにより、重合体を架橋させることができる。架橋度は、加熱又はエネルギー線の照射の強度により調節しうる。架橋度が高いほど膨潤度が小さくなるので、架橋度を調整することにより、粒子状重合体の膨潤度を制御することが可能である。 <Structure of particulate polymer>
When using a binder composition for formation of a negative electrode, it is preferable that the particulate polymer has a crosslinked structure. As described above, the cross-linked structure can be formed by introducing the cross-linked monomer into the particulate polymer.
And also when using a binder composition for formation of a positive electrode, the particulate polymer may have a crosslinked structure. As a method for introducing a cross-linked structure, for example, a method of incorporating a cross-linkable group by polymerizing a polymer from a monomer composition containing the above cross-linkable monomer, a combination of a polymer and a cross-linking agent And the method used. In this case, the polymer can be crosslinked by irradiation with heat or energy rays. The degree of crosslinking can be adjusted by the intensity of heating or irradiation with energy rays. Since the degree of swelling decreases as the degree of crosslinking increases, the degree of swelling of the particulate polymer can be controlled by adjusting the degree of crosslinking.
　さらに、粒子状重合体の重量平均分子量は、好ましくは１００００以上、より好ましくは２００００以上であり、好ましくは１００００００以下、より好ましくは５０００００以下である。粒子状重合体の重量平均分子量が上記範囲にあることにより、二次電池用電極の強度及び電極活物質の分散性を良好にし易い。粒子状重合体の重量平均分子量は、ゲルパーミエーションクロマトグラフィー（ＧＰＣ）によって、テトラヒドロフランを展開溶媒としたポリスチレン換算の値として求めうる。
　また、粒子状重合体のガラス転移温度（Ｔｇ）は、好ましくは－５０℃以上、より好ましくは－４５℃以上、特に好ましくは－４０℃以上であり、好ましくは２５℃以下、より好ましくは１５℃以下、特に好ましくは５℃以下である。粒子状重合体のガラス転移温度が上記範囲にあることにより、優れた強度と柔軟性を有する二次電池用電極を得ることができ、出力特性の高い二次電池を得ることができる。なお、粒子状重合体のガラス転移温度は、様々な単量体を組み合わせることによって調整可能である。 Furthermore, the weight average molecular weight of the particulate polymer is preferably 10,000 or more, more preferably 20,000 or more, preferably 1,000,000 or less, more preferably 500,000 or less. When the weight average molecular weight of the particulate polymer is in the above range, the strength of the secondary battery electrode and the dispersibility of the electrode active material are easily improved. The weight average molecular weight of the particulate polymer can be determined as a value in terms of polystyrene using tetrahydrofuran as a developing solvent by gel permeation chromatography (GPC).
The glass transition temperature (Tg) of the particulate polymer is preferably −50 ° C. or higher, more preferably −45 ° C. or higher, particularly preferably −40 ° C. or higher, preferably 25 ° C. or lower, more preferably 15 C. or lower, particularly preferably 5 C or lower. When the glass transition temperature of the particulate polymer is in the above range, a secondary battery electrode having excellent strength and flexibility can be obtained, and a secondary battery having high output characteristics can be obtained. The glass transition temperature of the particulate polymer can be adjusted by combining various monomers.
　通常、粒子状重合体は、非水溶性である。したがって、通常、粒子状重合体は、バインダー組成物及び当該バインダー組成物を含む二次電池電極用スラリー組成物において粒子状となっており、その粒子形状を維持したまま二次電池用電極に含まれる。ここで、粒子状重合体が「非水溶性」であるとは、２５℃において、その化合物０．５ｇを１００ｇの水に溶解した際に、不溶分が９０質量％以上となることをいう。
　粒子状重合体の体積平均粒子径は、通常は０．００１μｍ以上、好ましくは０．０１μｍ以上、より好ましくは０．０５μｍ以上であり、通常１００μｍ以下、好ましくは１０μｍ以下、より好ましくは１μｍ以下である。バインダー組成物に含有される粒子状重合体の体積平均粒子径がこの範囲であることにより、かかるバインダー組成物は、少量の使用でも優れた結着力を発現しうる。ここで、体積平均粒子径は、光散乱粒子径測定器を用いて測定したものである。粒子の形状は、球形及び異形のどちらでもかまわない。
　また、粒子状重合体は、１種類を単独で用いてもよく、２種類以上を組み合わせて用いてもよい。
　バインダー組成物の固形分における、粒子状重合体の割合は、通常５０質量％以上であり、好ましくは７０質量％以上である。 Usually, the particulate polymer is insoluble in water. Therefore, the particulate polymer is usually in the form of particles in the binder composition and the slurry composition for secondary battery electrodes containing the binder composition, and is included in the secondary battery electrode while maintaining the particle shape. It is. Here, the particulate polymer being “water-insoluble” means that when 0.5 g of the compound is dissolved in 100 g of water at 25 ° C., the insoluble content becomes 90% by mass or more.
The volume average particle diameter of the particulate polymer is usually 0.001 μm or more, preferably 0.01 μm or more, more preferably 0.05 μm or more, and usually 100 μm or less, preferably 10 μm or less, more preferably 1 μm or less. is there. When the volume average particle diameter of the particulate polymer contained in the binder composition is within this range, the binder composition can exhibit an excellent binding force even when used in a small amount. Here, the volume average particle diameter is measured using a light scattering particle diameter measuring instrument. The shape of the particles may be either spherical or irregular.
Moreover, a particulate polymer may be used individually by 1 type, and may be used in combination of 2 or more types.
The proportion of the particulate polymer in the solid content of the binder composition is usually 50% by mass or more, and preferably 70% by mass or more.
［レダクトン類化合物］
　本発明の二次電池電極用バインダー組成物に含有される「レダクトン類化合物」とは、Ｒ3Ｃ(ＯＨ)=Ｃ(ＯＨ)Ｃ(=Ｏ)Ｒ4構造を有する化合物及びその塩を指す。ただし、Ｒ3及びＲ4は、それぞれ独立の任意の有機基であってもよいし、共に環構造を形成していても良い。Ｒ3Ｃ(ＯＨ)=Ｃ(ＯＨ)Ｃ(=Ｏ)Ｒ4構造を有する化合物としては、例えば、グルシン酸とその誘導体、レダクチン酸とその誘導体、アスコルビン酸とその異性体、誘導体等が挙げられる。また、前記レダクトン類化合物は、酸化体（脱プロトン化レダクトン；Ｒ3Ｃ(=Ｏ)Ｃ(=Ｏ)Ｃ(=Ｏ)Ｒ4構造を有する化合物及びその塩）の形態で含まれていてもよい。これらの中でも、コスト、毒性及び環境負荷が低く、さらに人体安全性が高いため、アスコルビン酸とその異性体、誘導体及びそれらの塩並びにそれらの酸化体から選択される少なくとも１種が好ましい。 [Reductone compounds]
The “reductone compound” contained in the binder composition for a secondary battery electrode of the present invention refers to a compound having a R 3 C (OH) ═C (OH) C (═O) R 4 structure and a salt thereof. . However, R 3 and R 4 may each be an independent organic group, or may together form a ring structure. Examples of the compound having the R 3 C (OH) ═C (OH) C (═O) R 4 structure include glucic acid and its derivatives, reductic acid and its derivatives, ascorbic acid and its isomers, derivatives and the like. It is done. The reductone compound is included in the form of an oxidant (deprotonated reductone; a compound having a R 3 C (═O) C (═O) C (═O) R 4 structure and a salt thereof). Also good. Among these, at least one selected from ascorbic acid and its isomers, derivatives, salts thereof, and oxidants thereof is preferable because of low cost, toxicity, and environmental burden and high human safety.
　アスコルビン酸（ビタミンＣ）とその異性体、誘導体としては、例えば、Ｄ－またはＬ－アスコルビン酸とその糖誘導体（例えばγ－ラクトアスコルビン酸、グルコアスコルビン酸、フコアスコルビン酸、グルコヘプトアスコルビン酸、マルトアスコルビン酸）、エリソルビン酸とも称されるイソアスコルビン酸（またはＬ－エリスロアスコルビン酸）、エンジオール型アスコルビン酸、エナミノール型アスコルビン酸、チオエノ－ル型アスコルビン酸、及び、パルチミン酸アスコルビルが挙げられる。また、アスコルビン酸（ビタミンＣ）とその異性体、誘導体の塩としては、上述した化合物の塩（例えばアルカリ金属塩、アンモニウム塩または当技術分野において知られている塩）、例えば、アスコルビン酸のナトリウム塩、アスコルビン酸のカリウム塩の他、リン酸Ｌ－アスコルビルマグネシウムが挙げられる。
　なかでも、レダクトン類化合物およびその酸化体の少なくとも一方が、（イソ）アスコルビン酸及びその塩、並びに、それらの酸化体から選択される少なくとも１種であることが好ましい。（イソ）アスコルビン酸の塩としては、アルカリ金属塩が好ましく、ナトリウム塩がより好ましい。必要に応じてこれらのレダクトン類化合物の混合物を用いることができる。 Ascorbic acid (vitamin C) and its isomers and derivatives include, for example, D- or L-ascorbic acid and its sugar derivatives (for example, γ-lactoascorbic acid, glucoascorbic acid, fucoscorbic acid, glucoheptascorbic acid, Maltoascorbic acid), isoascorbic acid (or L-erythroascorbic acid), also called erythorbic acid, enediol type ascorbic acid, enaminol type ascorbic acid, thioenolic type ascorbic acid, and ascorbyl palmitate. In addition, ascorbic acid (vitamin C) and isomers and derivatives thereof include salts of the above-described compounds (for example, alkali metal salts, ammonium salts or salts known in the art), such as sodium ascorbic acid. In addition to the salt and potassium salt of ascorbic acid, L-ascorbyl magnesium phosphate may be mentioned.
Especially, it is preferable that at least one of reductone compound and its oxidant is at least 1 sort (s) selected from (iso) ascorbic acid and its salt, and those oxidants. The salt of (iso) ascorbic acid is preferably an alkali metal salt, more preferably a sodium salt. A mixture of these reductone compounds can be used as necessary.
　バインダー組成物は、レダクトン類化合物およびその酸化体の少なくとも一方を、粒子状重合体１００質量部に対して好ましくは０．０５質量部以上、より好ましくは、０．１質量部以上、特に好ましくは０．３質量部以上、好ましくは５質量部以下、より好ましくは２質量部以下、特に好ましくは１質量部以下含有する。レダクトン類化合物の含有量を粒子状重合体１００質量部に対して０．０５質量部以上とすることで、沸点１４５℃以上の（メタ）アクリル酸エステル単量体などの残留モノマーを十分に低減することができる。さらに、レダクトン類化合物およびその酸化体の少なくとも一方の含有量を粒子状重合体１００質量部に対して５質量部以下とすることで、バインダー組成物を用いて製造した二次電池において、レダクトン類化合物およびその酸化体の少なくとも一方が多量に残留することを防いで、残留したレダクトン類化合物が分解されて発生するガスの量を低減することができ、さらに、二次電池の初期容量を向上させることができる。 The binder composition is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, particularly preferably at least one of the reductone compound and its oxidant with respect to 100 parts by mass of the particulate polymer. 0.3 parts by mass or more, preferably 5 parts by mass or less, more preferably 2 parts by mass or less, particularly preferably 1 part by mass or less. By making the content of the reductone compound 0.05 parts by mass or more with respect to 100 parts by mass of the particulate polymer, residual monomers such as (meth) acrylic acid ester monomers having a boiling point of 145 ° C. or more are sufficiently reduced. can do. Furthermore, in the secondary battery manufactured using the binder composition, the content of at least one of the reductone compound and its oxidant is 5 parts by mass or less with respect to 100 parts by mass of the particulate polymer. The amount of gas generated by decomposition of the remaining reductone compound can be reduced by preventing at least one of the compound and its oxidant from remaining in large amounts, and the initial capacity of the secondary battery can be improved. be able to.
［その他の成分］
　バインダー組成物は、上述した成分に加え、バインダー組成物に配合し得る既知の任意成分を含有していても良い。また、粒子状重合体の重合に使用した重合開始剤などの残渣を含んでいてもよい。 [Other ingredients]
The binder composition may contain known arbitrary components that can be blended in the binder composition in addition to the components described above. Moreover, residues, such as a polymerization initiator used for superposition | polymerization of a particulate polymer, may be included.
　さらに、バインダー組成物は、固形分濃度が通常１０質量％以上、好ましくは２０質量％以上、通常７０質量％以下、好ましくは６０質量％以下である。 Furthermore, the binder composition has a solid content of usually 10% by mass or more, preferably 20% by mass or more, usually 70% by mass or less, preferably 60% by mass or less.
　なお、上述した単量体混合物を用いて重合した粒子状重合体を含むバインダー組成物中の、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有量は、粒子状重合体１００質量部に対して１５００×１０-6質量部以下であり、１０００×１０-6質量部以下であることが好ましく、５００×１０-6質量部以下であることがさらに好ましく、３００×１０-6質量部以下であることが特に好ましい。残留モノマーに起因したガスの発生及び経時安定性の低下を抑制し、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供する観点からは、バインダー組成物は、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含有しないことが好ましいが、（メタ）アクリル酸エステル単量体の含有割合を０質量部とすることは、工業的には困難であるので、沸点１４５℃以上の（メタ）アクリル酸エステル単量体は、粒子状重合体１００質量部に対して１×１０-6質量部以上含有されることが多い。また、バインダー組成物中における沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を、粒子状重合体１００質量部に対して１５００×１０-6質量部以下とすることで、バインダー組成物を用いて形成した二次電池のガス発生量を低減させ、高温保存特性及び高温サイクル特性を優れたものとすると共に、バインダー組成物の優れた経時安定性を得ることができる。 In addition, content of the (meth) acrylic acid ester monomer with a boiling point of 145 degreeC or more in the binder composition containing the particulate polymer polymerized using the monomer mixture mentioned above is particulate polymer 100 mass. 1500 × 10 −6 parts by mass or less, preferably 1000 × 10 −6 parts by mass or less, more preferably 500 × 10 −6 parts by mass or less, and 300 × 10 −6 parts by mass. It is particularly preferred that the amount is not more than parts. The binder composition has a boiling point of 145 ° C. or more from the viewpoint of suppressing generation of gas due to residual monomer and deterioration of stability over time, and providing a secondary battery having good high-temperature storage characteristics and high-temperature cycle characteristics. Although it is preferable not to contain a meth) acrylic acid ester monomer, it is industrially difficult to set the content ratio of the (meth) acrylic acid ester monomer to 0 part by mass. The (meth) acrylate monomer is often contained in an amount of 1 × 10 −6 parts by mass or more with respect to 100 parts by mass of the particulate polymer. Moreover, binder is made into the binder composition by making the content rate of the (meth) acrylic acid ester monomer of boiling point 145 degreeC or more in a binder composition into 1500x10-6 mass parts or less with respect to 100 mass parts of particulate polymers. The amount of gas generated in the secondary battery formed using the composition can be reduced, the high-temperature storage characteristics and the high-temperature cycle characteristics can be improved, and the excellent temporal stability of the binder composition can be obtained.
（バインダー組成物の製造方法）
　本発明のバインダー組成物の製造方法は、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を重合転化率が９０質量％以上となるまで水中で重合し、重合体と未反応の単量体とを含む混合物を得る工程（１）と、工程（１）の後、混合物にレダクトン類化合物および過酸化物を添加して未反応の単量体を重合し、前記沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を、重合体１００質量部に対して１×１０-6質量部以上１５００×１０-6質量部以下にする工程（２）を含む。すなわち、本発明のバインダー組成物の製造方法は、単量体混合物の大部分を重合させる工程と、残留した未反応の残留モノマーを更に重合させて残留モノマー量を減少させる工程との少なくとも２段階の重合により粒子状重合体を重合する工程を含む。さらに、本発明のバインダー組成物の製造方法では、工程（１）において、単量体混合物を予めエマルジョン化した後、反応器に添加して重合することが好ましい。 (Manufacturing method of binder composition)
In the method for producing the binder composition of the present invention, a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is polymerized in water until the polymerization conversion becomes 90% by mass or more. Step (1) to obtain a mixture containing a monomer and an unreacted monomer, and after step (1), a reductone compound and a peroxide are added to the mixture to polymerize the unreacted monomer, The step (2) of setting the content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher to 1 × 10 −6 parts by mass to 1500 × 10 −6 parts by mass with respect to 100 parts by mass of the polymer. Including. That is, the method for producing the binder composition of the present invention comprises at least two steps: a step of polymerizing the majority of the monomer mixture and a step of further polymerizing the remaining unreacted residual monomer to reduce the amount of residual monomer. And a step of polymerizing the particulate polymer by polymerization. Furthermore, in the method for producing the binder composition of the present invention, in step (1), the monomer mixture is preferably emulsified in advance and then added to the reactor for polymerization.
［単量体混合物の重合工程（１）］
　工程（１）では、上述した粒子状重合体の製造に使用し得る、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を水中で重合する。そして、工程（１）では、重合転化率（＝（得られた重合体量／単量体混合物の量）×１００％）が９０質量％以上、好ましくは９５質量％以上になるまで単量体混合物を重合する。ここで、工程（１）における重合は、１段階で行っても良いし、多段階に分けて行っても良い。
　なお、重合転化率は、反応温度や反応時間等を調整することにより制御することができる。そして、工程（１）の重合転化率を９０質量％以上、好ましくは９５質量％以上としたのは、所望の性状を有する粒子状重合体を得るためである。このように、工程（１）における重合転化率を９０質量％以上、好ましくは９５質量％以上とすることで、工程（２）においてレドックス重合で新たに生成されうる、既に工程（１）で生成されている粒子状重合体とは性状の異なる粒子状重合体の量を低減することができる。 [Monomer mixture polymerization step (1)]
In the step (1), a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher that can be used for the production of the particulate polymer described above is polymerized in water. In step (1), the polymerization conversion rate (= (amount of polymer obtained / amount of monomer mixture) × 100%) is 90% by mass or more, preferably 95% by mass or more. Polymerize the mixture. Here, the polymerization in the step (1) may be performed in one stage or may be performed in multiple stages.
The polymerization conversion rate can be controlled by adjusting the reaction temperature, reaction time, and the like. The reason why the polymerization conversion rate in the step (1) is 90% by mass or more, preferably 95% by mass or more is to obtain a particulate polymer having desired properties. As described above, the polymerization conversion rate in the step (1) is 90% by mass or more, preferably 95% by mass or more, so that it can be newly generated by redox polymerization in the step (2). It is possible to reduce the amount of the particulate polymer having a property different from that of the particulate polymer.
　工程（１）における重合方法としては、例えば懸濁重合法、乳化重合法等のいずれの方法を用いてもよい。また、反応種としては、イオン、ラジカル、及びリビングラジカルのうちのいずれを用いてもよい。なかでも、高分子量の重合体が得やすいこと、並びに、重合体が水に分散した粒子の状態で得られるので再分散化の処理が不要であり、そのまま二次電池用電極を製造するためのスラリー組成物に供することができることなど、製造効率の観点から、乳化重合法が特に好ましい。また、重合は、セミバッチ方式で実施することが好ましい。セミバッチ方式を採用し、乳化重合法で重合を行えば、生成される粒子状重合体の分散性が良く、粒子状重合体の粒径分布が狭く、高速で高重合度のポリマーが得られるからである。
　なお、乳化重合法は、常法に従って実施し得る（例えば、「実験化学講座」第２８巻（発行元：丸善（株）、日本化学会編）参照）。すなわち、攪拌機及び加熱装置付きの密閉容器に、水と、分散剤、乳化剤、架橋剤などの添加剤と、重合開始剤と、上述した単量体混合物とを所定の組成になるように加え、容器中の組成物を攪拌して単量体等を水に乳化させ、攪拌しながら温度を上昇させて重合を開始する方法を用いうる。あるいは、上記組成物を乳化させた後に密閉容器に入れ、同様に反応を開始させる方法を用いうる。 As a polymerization method in the step (1), any method such as a suspension polymerization method or an emulsion polymerization method may be used. Moreover, any of ions, radicals, and living radicals may be used as the reactive species. Among them, it is easy to obtain a high molecular weight polymer, and since the polymer is obtained in the form of particles dispersed in water, there is no need for redispersion treatment, and for producing a secondary battery electrode as it is. From the viewpoint of production efficiency, such as being able to be used in a slurry composition, an emulsion polymerization method is particularly preferable. Moreover, it is preferable to implement superposition | polymerization by a semibatch system. If the semi-batch method is used and polymerization is carried out by the emulsion polymerization method, the dispersibility of the produced particulate polymer is good, the particle size distribution of the particulate polymer is narrow, and a polymer with a high degree of polymerization can be obtained at high speed. It is.
The emulsion polymerization method can be carried out according to a conventional method (see, for example, “Experimental Chemistry Course” Vol. 28 (Publisher: Maruzen Co., Ltd., edited by The Chemical Society of Japan)). That is, in a sealed container equipped with a stirrer and a heating device, water, an additive such as a dispersant, an emulsifier, a crosslinking agent, a polymerization initiator, and the monomer mixture described above are added so as to have a predetermined composition. A method may be used in which the composition in the container is stirred to emulsify the monomer or the like in water, and the temperature is increased while stirring to initiate polymerization. Or after emulsifying the said composition, it can put into an airtight container, and the method of starting reaction similarly can be used.
　工程（１）において乳化重合を実施する場合に使用する乳化剤としては、例えば、ポリオキシエチレンアルキレンエーテル、ポリオキシエチレンアルキルフェノールエーテル、ポリオキシエチレンアルキルエステル、ポリオキシエチレンソルビタンアルキルエステル等の非イオン性乳化剤；ミリスチミン酸、パルミチン酸、オレイン酸、リノレン酸の如き脂肪酸及びその塩、アルキルアリルスルホン酸塩、高級アルコール硫酸エステル、アルキルスルホコハク酸等のアニオン系乳化剤；トリメチルアンモニウムクロライド、ジアルキルアンモニウムクロライドの如きアンモニウムクロライドや、ベンジルアンモニウム塩等及び第４級アンモニウム塩等のカチオン系乳化剤；α，β－不飽和カルボン酸のスルホエステル、α，β－不飽和カルボン酸のサルフェートエステル、スルホアルキルアリールエーテル等の二重結合を含む共重合性乳化剤などを挙げることができる。これらの乳化剤は１種で又は２種以上を組み合わせて用いることができる。水相液として、水に乳化剤を溶解した液を用いる場合、乳化剤の使用量は、単量体混合物に対して０．１～１０質量％である。０．１質量％未満では、重合時に凝集物が生じる。逆に１０質量％超では、得られる粒子状重合体の平均粒子径が小さくなる。 Examples of the emulsifier used when carrying out the emulsion polymerization in the step (1) include nonionic emulsifiers such as polyoxyethylene alkylene ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester and the like. Anionic emulsifiers such as fatty acids such as myristic acid, palmitic acid, oleic acid, linolenic acid and salts thereof, alkylallyl sulfonates, higher alcohol sulfates, alkyl sulfosuccinic acids; ammonium chlorides such as trimethylammonium chloride and dialkylammonium chloride And cationic emulsifiers such as benzylammonium salts and quaternary ammonium salts; sulfoesters of α, β-unsaturated carboxylic acids, α, β-unsaturated carbo Sulphate esters of acids, such as copolymerizable emulsifiers containing a double bond such as sulfoalkyl aryl ether. These emulsifiers can be used alone or in combination of two or more. When using a solution in which an emulsifier is dissolved in water as the aqueous phase liquid, the amount of the emulsifier used is 0.1 to 10% by mass relative to the monomer mixture. If it is less than 0.1% by mass, aggregates are produced during polymerization. On the other hand, if it exceeds 10% by mass, the average particle size of the obtained particulate polymer becomes small.
　工程（１）において、ラジカル重合開始剤として、過硫酸カリウム、過硫酸アンモニウム、過酸化水素などの水溶性開始剤；過酸化ベンゾイル、ジ－ｔ－ブチルペルオキサイド、２，２－アゾビス－２，４－ジメチルバレロニトリルなどの油溶性開始剤；などを使用することができる。重合開始剤の添加量は、各開始剤によって異なるが、水溶性開始剤の場合は、０．１質量％以上５質量％以下、油溶性開始剤の場合は、０．１質量％以上３質量％以下である。
　さらに、工程（１）の反応温度は、通常０℃以上、好ましくは４０℃以上、通常１５０℃以下、好ましくは９５℃以下である。また、重合時間は通常１時間以上、２０時間以下である。重合温度が低すぎると反応速度が遅すぎ効率が悪く、重合温度が高すぎると水性媒体が蒸発しやすいため重合が困難になる。反応の圧力は常圧でもよい。反応は空気中でも可能であるが、窒素、アルゴン等の不活性ガスの存在下が好ましい。 In step (1), water-soluble initiators such as potassium persulfate, ammonium persulfate, and hydrogen peroxide as radical polymerization initiators; benzoyl peroxide, di-t-butyl peroxide, 2,2-azobis-2,4 Oil-soluble initiators such as dimethylvaleronitrile; The addition amount of the polymerization initiator varies depending on each initiator, but in the case of a water-soluble initiator, it is 0.1% by mass or more and 5% by mass or less, and in the case of an oil-soluble initiator, 0.1% by mass or more and 3% by mass % Or less.
Furthermore, the reaction temperature in step (1) is usually 0 ° C. or higher, preferably 40 ° C. or higher, usually 150 ° C. or lower, preferably 95 ° C. or lower. The polymerization time is usually 1 hour or more and 20 hours or less. If the polymerization temperature is too low, the reaction rate is too slow and the efficiency is poor, and if the polymerization temperature is too high, the aqueous medium tends to evaporate, making the polymerization difficult. The reaction pressure may be normal pressure. Although the reaction can be carried out in air, it is preferably in the presence of an inert gas such as nitrogen or argon.
　分散剤としては、通常の合成で使用されるものを用いてもよい。分散剤の具体例としては、ドデシルベンゼンスルホン酸ナトリウム、ドデシルフェニルエーテルスルホン酸ナトリウムなどのベンゼンスルホン酸塩；ラウリル硫酸ナトリウム、テトラドデシル硫酸ナトリウムなどのアルキル硫酸塩；ジオクチルスルホコハク酸ナトリウム、ジヘキシルスルホコハク酸ナトリウムなどのスルホコハク酸塩；ラウリン酸ナトリウムなどの脂肪酸塩；ポリオキシエチレンラウリルエーテルサルフェートナトリウム塩、ポリオキシエチレンノニルフェニルエ－テルサルフェートナトリウム塩などのエトキシサルフェート塩；アルカンスルホン酸塩；アルキルエーテルリン酸エステルナトリウム塩；ポリオキシエチレンノニルフェニルエーテル、ポリオキシエチレンソルビタンラウリルエステル、ポリオキシエチレン－ポリオキシプロピレンブロック共重合体などの非イオン性乳化剤；ゼラチン、無水マレイン酸－スチレン共重合体、ポリビニルピロリドン、ポリアクリル酸ナトリウム、重合度７００以上かつケン化度７５％以上のポリビニルアルコールなどの水溶性高分子；などが挙げられる。これらの中でも好ましくは、ドデシルベンゼンスルホン酸ナトリウム、ドデシルフェニルエーテルスルホン酸ナトリウムなどのベンゼンスルホン酸塩；ラウリル硫酸ナトリウム、テトラドデシル硫酸ナトリウムなどのアルキル硫酸塩を用いることができる。更に好ましくは、耐酸化性に優れるという点から、ドデシルベンゼンスルホン酸ナトリウム、ドデシルフェニルエーテルスルホン酸ナトリウムなどのベンゼンスルホン酸塩を用いることができる。なお、これらは１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。分散剤の量は、単量体混合物の総量１００質量部に対して、通常０．０１質量部～１０質量部である。 As the dispersant, those used in ordinary synthesis may be used. Specific examples of the dispersant include benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecylsulfate; sodium dioctylsulfosuccinate and sodium dihexylsulfosuccinate Sulfosuccinates such as; fatty acid salts such as sodium laurate; ethoxy sulfate salts such as polyoxyethylene lauryl ether sulfate sodium salt, polyoxyethylene nonylphenyl ether sulfate sodium salt; alkane sulfonates; alkyl ether phosphates Sodium salt; polyoxyethylene nonylphenyl ether, polyoxyethylene sorbitan lauryl ester, polyoxyethylene- Nonionic emulsifiers such as reoxypropylene block copolymers; gelatin, maleic anhydride-styrene copolymers, polyvinyl pyrrolidone, sodium polyacrylate, water-soluble water such as polyvinyl alcohol having a polymerization degree of 700 or more and a saponification degree of 75% or more Functional polymers; and the like. Among these, benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate; alkyl sulfates such as sodium lauryl sulfate and sodium tetradodecylsulfate can be preferably used. More preferably, benzenesulfonates such as sodium dodecylbenzenesulfonate and sodium dodecylphenylethersulfonate can be used from the viewpoint of excellent oxidation resistance. In addition, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. The amount of the dispersant is usually 0.01 parts by mass to 10 parts by mass with respect to 100 parts by mass of the total amount of the monomer mixture.
　さらに、工程（１）における重合に際しては、シード粒子を採用してシード重合を行ってもよい。 Furthermore, in the polymerization in the step (1), seed polymerization may be performed using seed particles.
［重合工程（２）］
　ここで、上述した工程（１）では、重合転化率を１００質量％とすることは困難であり、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む未反応の単量体が残留する。
　そこで、工程（２）では、レダクトン類化合物および過酸化物を併用するレドックス系開始剤を用いて工程（１）の後に残った未反応の単量体（残留モノマー）を重合させ、バインダー組成物中の残留モノマー量を低減させる。具体的には、工程（２）では、工程（１）を経て得られた、重合体と未反応の単量体との混合物を含む重合系に対し、レダクトン類化合物および過酸化物を添加して、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合が重合体１００質量部に対して１×１０-6質量部以上１５００×１０-6質量部以下になるまでレドックス重合を行う。
　なお、沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合は、工程（２）で使用するレダクトン類化合物および過酸化物の量や、レドックス重合条件を変更することにより調整することができる。 [Polymerization step (2)]
Here, in the step (1) described above, it is difficult to set the polymerization conversion rate to 100% by mass, and an unreacted monomer containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher remains. To do.
Therefore, in the step (2), an unreacted monomer (residual monomer) remaining after the step (1) is polymerized using a redox initiator that uses a reductone compound and a peroxide in combination, and a binder composition is obtained. Reduce the amount of residual monomer in it. Specifically, in step (2), a reductone compound and a peroxide are added to the polymerization system containing a mixture of a polymer and an unreacted monomer obtained through step (1). The redox polymerization is carried out until the content of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is 1 × 10 −6 parts by mass to 1500 × 10 −6 parts by mass with respect to 100 parts by mass of the polymer. Do.
The content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher should be adjusted by changing the amount of the reductone compound and peroxide used in step (2) and the redox polymerization conditions. Can do.
　ここで、工程（２）の反応温度は、好ましくは０℃以上、より好ましくは１０℃以上、好ましくは８０℃以下、より好ましくは６０℃以下である。重合温度が低すぎると反応速度が遅すぎるため、効率が悪く、重合温度が高すぎるとレドックス系開始剤（レダクトン類化合物及び過酸化物）の分解速度が速すぎるため重合が困難になる場合がある。レドックス重合を行うことで、このような穏やかな温度条件でも残留モノマーの重合反応を行うことができる。また、工程（２）における重合時間は好ましくは１時間以上、６時間以下である。
　なお、工程（２）では、上述の反応温度で、好ましくは１時間以上、６時間以下レドックス重合を実施した後に、重合系の温度をレドックス重合時の重合温度より高い温度（例えば、８０℃超）として、過酸化物を除去又は分解させることが好ましい。これにより、得られたバインダー組成物中において、過酸化物の含有量が低減され、かかるバインダー組成物を用いて二次電池を製造した場合に、二次電池の電池性能や安全性を向上させることができる。
　また、工程（２）における反応の圧力は常圧でもよい。反応は空気中でも可能であるが、窒素、アルゴン等の不活性ガスの存在下が好ましい。レダクトン類化合物の使用量は過酸化物の種類に応じて適宜変更するが、好ましくは、工程（１）で使用した単量体混合物の量に対して、通常０．０５質量％以上、好ましくは０．１質量％以上、通常５質量％以下、好ましくは１質量％以下である。なお、残留モノマーの含有率によってレダクトン類化合物の使用量を調整してもよい。レダクトン類化合物の使用量が多すぎると、バインダー組成物中で大量に残留するため、当該バインダー組成物を用いた二次電池のガス発生量が増加して、初期容量に影響する。レダクトン類化合物の使用量が少なすぎると、レドックス重合が十分に進行せず、残留モノマーの低減効果が不十分となる虞がある。レダクトン類化合物は一括添加しても分割添加してもよいが、残留モノマー低減効率を向上するという観点では、分割添加が好ましい。
　なお、工程（２）でレドックス重合を実施することにより、他の重合方法を採用して残留モノマーの低減を図った場合よりも重合開始剤の配合量を低減し、バインダー組成物中に重合開始剤の残渣が大量に残留するのを防止することができる。 Here, the reaction temperature of the step (2) is preferably 0 ° C. or higher, more preferably 10 ° C. or higher, preferably 80 ° C. or lower, more preferably 60 ° C. or lower. If the polymerization temperature is too low, the reaction rate is too slow, so the efficiency is poor, and if the polymerization temperature is too high, the decomposition rate of the redox initiator (reductone compounds and peroxides) is too high, making the polymerization difficult. is there. By performing redox polymerization, the polymerization reaction of the residual monomer can be performed even under such a mild temperature condition. The polymerization time in step (2) is preferably 1 hour or more and 6 hours or less.
In the step (2), after the redox polymerization is carried out at the above reaction temperature, preferably 1 hour or more and 6 hours or less, the temperature of the polymerization system is set to a temperature higher than the polymerization temperature at the time of redox polymerization (for example, more than 80 ° C ), It is preferable to remove or decompose the peroxide. Thereby, in the obtained binder composition, the content of peroxide is reduced, and when a secondary battery is produced using such a binder composition, the battery performance and safety of the secondary battery are improved. be able to.
Further, the pressure of the reaction in the step (2) may be a normal pressure. Although the reaction can be carried out in air, it is preferably in the presence of an inert gas such as nitrogen or argon. The amount of the reductone compound is appropriately changed according to the kind of the peroxide, but is preferably 0.05% by mass or more, preferably with respect to the amount of the monomer mixture used in the step (1). 0.1 mass% or more, usually 5 mass% or less, preferably 1 mass% or less. In addition, you may adjust the usage-amount of reductone compounds by the content rate of a residual monomer. If the amount of the reductone compound used is too large, it remains in a large amount in the binder composition, so that the amount of gas generated in the secondary battery using the binder composition increases, which affects the initial capacity. If the amount of the reductone compound used is too small, redox polymerization does not proceed sufficiently, and the residual monomer reducing effect may be insufficient. The reductone compounds may be added all at once or dividedly, but in terms of improving the residual monomer reduction efficiency, divided addition is preferred.
In addition, by carrying out redox polymerization in step (2), the blending amount of the polymerization initiator is reduced as compared with the case where other polymerization methods are employed to reduce the residual monomer, and polymerization is started in the binder composition. It is possible to prevent the residue of the agent from remaining in large quantities.
　ここで、工程（２）で使用するレダクトン類化合物としては、バインダー組成物の項において例示したレダクトン類化合物を挙げることができ、上述したようにアスコルビン酸、及びその異性体や誘導体並びにそれらの塩が好ましい。また、過酸化物としては、以下に例示するような水溶性過酸化物が挙げられる。本発明のバインダー組成物は、二次電池の製造に使用するバインダー組成物であるため、遷移金属元素を含有しない過酸化物を使用することが好ましい。また、過酸化物が「水溶性」であるとは、２５℃において水中に、５質量％以上の水溶性を有することを言う。 Here, the reductone compounds used in the step (2) can include the reductone compounds exemplified in the section of the binder composition, and as mentioned above, ascorbic acid, its isomers and derivatives, and salts thereof. Is preferred. Examples of the peroxide include water-soluble peroxides exemplified below. Since the binder composition of this invention is a binder composition used for manufacture of a secondary battery, it is preferable to use the peroxide which does not contain a transition metal element. In addition, that the peroxide is “water-soluble” means that it has a water solubility of 5% by mass or more in water at 25 ° C.
　すなわち、本発明において使用可能な過酸化物としては、過酸化水素、ペルオキシ酸塩、ペルオクソ二硫酸およびその塩、ペルオキシエステル塩、ペルオキサイドのアンモニウムまたはアルカリ金属塩、過ホウ酸塩、過硫酸塩及びｔｅｒｔ－ブチルヒドロペルオキシド（ｔ－ＢｕＯＯＨ）、過酸化ベンゾイルが挙げられる。なかでも、ｔｅｒｔ－ブチルヒドロペルオキシド、過酸化水素、及び過酢酸が好ましく、ｔｅｒｔ－ブチルヒドロペルオキシドが特に好ましい。水溶性であり、且つ分子量の小さい過酸化物から生成されたラジカル種は、分子量が小さいため水中での移動性が高く、残留モノマーを効果的に低減することができるからである。 That is, as the peroxide that can be used in the present invention, hydrogen peroxide, peroxy acid salt, peroxodisulfuric acid and its salt, peroxy ester salt, peroxide ammonium or alkali metal salt, perborate, persulfate And tert-butyl hydroperoxide (t-BuOOH), benzoyl peroxide. Of these, tert-butyl hydroperoxide, hydrogen peroxide, and peracetic acid are preferable, and tert-butyl hydroperoxide is particularly preferable. This is because radical species generated from peroxides that are water-soluble and have a low molecular weight have high molecular mobility and can reduce residual monomers effectively because of their low molecular weight.
　過酸化物の使用量は、工程（１）で使用した単量体混合物の量に対して、好ましくは０．０５質量％以上、より好ましくは０．１質量％以上、好ましくは５質量％以下、より好ましくは１質量％以下である。なお、残留モノマーの含有率によってレダクトン類化合物の使用量を調整してもよい。過酸化物の使用量を所定範囲とすることで、バインダー組成物において十分な残留モノマー低減効果を達成することができる。さらに、かかるバインダー組成物を用いて二次電池を製造した場合に、二次電池中に残留する過酸化物の量を低減して、二次電池におけるガス発生を抑制して電池性能への悪影響を低減することができる。
　なお、上述した工程（１）及び工程（２）の間に、例えば、蒸留工程などの追加工程を実施することも可能である。 The amount of peroxide used is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, preferably 5% by mass or less, based on the amount of the monomer mixture used in step (1). More preferably, it is 1 mass% or less. In addition, you may adjust the usage-amount of reductone compounds by the content rate of a residual monomer. By making the usage-amount of a peroxide into a predetermined range, sufficient residual monomer reduction effect can be achieved in a binder composition. Further, when a secondary battery is manufactured using such a binder composition, the amount of peroxide remaining in the secondary battery is reduced, and gas generation in the secondary battery is suppressed, thereby adversely affecting the battery performance. Can be reduced.
In addition, it is also possible to implement additional processes, such as a distillation process, between the process (1) and process (2) mentioned above.
（二次電池電極用スラリー組成物）
　本発明の二次電池電極用スラリー組成物は、上述のバインダー組成物及び電極活物質（正極活物質又は負極活物質）を含むことを特徴とする。このような二次電池電極用スラリー組成物を用いれば、得られる二次電池において残留モノマーに起因したガスの発生が抑制され、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することができる。
　なお、本発明の二次電池電極用スラリー組成物は、バインダー組成物及び電極活物質に加え、導電材、粘度調整剤、界面活性剤、分散剤などを含んでいても良い。 (Slurry composition for secondary battery electrode)
The slurry composition for secondary battery electrodes of the present invention is characterized by containing the above-mentioned binder composition and electrode active material (positive electrode active material or negative electrode active material). By using such a slurry composition for secondary battery electrodes, generation of gas due to residual monomer in the obtained secondary battery is suppressed, and a secondary battery having good high-temperature storage characteristics and high-temperature cycle characteristics is provided. be able to.
In addition, the slurry composition for secondary battery electrodes of the present invention may contain a conductive material, a viscosity modifier, a surfactant, a dispersant and the like in addition to the binder composition and the electrode active material.
[バインダー組成物]
　本発明のスラリー組成物が含有するバインダー組成物の割合は、得られる電池の性能が良好に発現されるよう適宜調整することができる。例えば、電極活物質１００質量部に対するバインダー組成物固形分の割合として、通常０．１質量部以上、好ましくは０．５質量部以上、より好ましくは０．８質量部以上であり、通常５０質量部以下、好ましくは２０質量部以下、より好ましくは１０質量部以下、特に好ましくは３質量部以下とすることができる。バインダー組成物の量をこの範囲にすることにより、密着性を充分に確保でき、二次電池の容量を高くでき、且つ、二次電池用電極の内部抵抗を低くすることができる。 [Binder composition]
The ratio of the binder composition contained in the slurry composition of the present invention can be adjusted as appropriate so that the performance of the obtained battery is satisfactorily exhibited. For example, the ratio of the solid content of the binder composition to 100 parts by mass of the electrode active material is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and usually 50 parts by mass. Part or less, preferably 20 parts by weight or less, more preferably 10 parts by weight or less, and particularly preferably 3 parts by weight or less. By setting the amount of the binder composition within this range, sufficient adhesion can be secured, the capacity of the secondary battery can be increased, and the internal resistance of the secondary battery electrode can be decreased.
［負極活物質］
　スラリー組成物を負極の形成に用いる場合、電極活物質として負極活物質を用いる。負極活物質は、負極において用いられる電極活物質であり、二次電池の負極において電子の受け渡しをする物質である。例えば、本発明の二次電池がリチウムイオン二次電池である場合、負極活物質としては、通常、リチウムを吸蔵および放出し得る物質が用いられる。リチウムを吸蔵および放出し得る物質としては、例えば、炭素系負極活物質、金属系負極活物質、およびこれらを組み合わせた負極活物質などが挙げられる。 [Negative electrode active material]
When using a slurry composition for formation of a negative electrode, a negative electrode active material is used as an electrode active material. The negative electrode active material is an electrode active material used in the negative electrode, and is a material that transfers electrons in the negative electrode of the secondary battery. For example, when the secondary battery of the present invention is a lithium ion secondary battery, a material that can occlude and release lithium is usually used as the negative electrode active material. Examples of the material that can occlude and release lithium include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material obtained by combining these materials.
　炭素系負極活物質とは、リチウムを挿入（「ドープ」ともいう。）可能な、炭素を主骨格とする活物質をいい、炭素系負極活物質としては、例えば炭素質材料と黒鉛質材料とが挙げられる。
　炭素質材料は、炭素前駆体を２０００℃以下で熱処理して炭素化させることによって得られる、黒鉛化度の低い（即ち、結晶性の低い）材料である。なお、炭素化させる際の熱処理温度の下限は特に限定されないが、例えば５００℃以上とすることができる。
　そして、炭素質材料としては、例えば、熱処理温度によって炭素の構造を容易に変える易黒鉛性炭素や、ガラス状炭素に代表される非晶質構造に近い構造を持つ難黒鉛性炭素などが挙げられる。
　ここで、易黒鉛性炭素としては、例えば、石油または石炭から得られるタールピッチを原料とした炭素材料が挙げられる。具体例を挙げると、コークス、メソカーボンマイクロビーズ（ＭＣＭＢ）、メソフェーズピッチ系炭素繊維、熱分解気相成長炭素繊維などが挙げられる。
　また、難黒鉛性炭素としては、例えば、フェノール樹脂焼成体、ポリアクリロニトリル系炭素繊維、擬等方性炭素、フルフリルアルコール樹脂焼成体（ＰＦＡ）、ハードカーボンなどが挙げられる。 The carbon-based negative electrode active material refers to an active material having carbon as a main skeleton into which lithium can be inserted (also referred to as “dope”). Examples of the carbon-based negative electrode active material include a carbonaceous material and a graphite material. Is mentioned.
The carbonaceous material is a material having a low degree of graphitization (ie, low crystallinity) obtained by carbonizing a carbon precursor by heat treatment at 2000 ° C. or lower. In addition, although the minimum of the heat processing temperature at the time of carbonizing is not specifically limited, For example, it can be 500 degreeC or more.
Examples of the carbonaceous material include graphitizable carbon that easily changes the carbon structure depending on the heat treatment temperature, and non-graphitizable carbon having a structure close to an amorphous structure typified by glassy carbon. .
Here, as the graphitizable carbon, for example, a carbon material using tar pitch obtained from petroleum or coal as a raw material can be mentioned. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch carbon fibers, pyrolytic vapor grown carbon fibers, and the like.
In addition, examples of the non-graphitizable carbon include a phenol resin fired body, polyacrylonitrile-based carbon fiber, pseudo-isotropic carbon, furfuryl alcohol resin fired body (PFA), and hard carbon.
　黒鉛質材料は、易黒鉛性炭素を２０００℃以上で熱処理することによって得られる、黒鉛に近い高い結晶性を有する材料である。なお、熱処理温度の上限は、特に限定されないが、例えば５０００℃以下とすることができる。
　そして、黒鉛質材料としては、例えば、天然黒鉛、人造黒鉛などが挙げられる。
　ここで、人造黒鉛としては、例えば、易黒鉛性炭素を含んだ炭素を主に２８００℃以上で熱処理した人造黒鉛、ＭＣＭＢを２０００℃以上で熱処理した黒鉛化ＭＣＭＢ、メソフェーズピッチ系炭素繊維を２０００℃以上で熱処理した黒鉛化メソフェーズピッチ系炭素繊維などが挙げられる。 The graphite material is a material having high crystallinity close to that of graphite obtained by heat-treating graphitizable carbon at 2000 ° C. or higher. In addition, although the upper limit of heat processing temperature is not specifically limited, For example, it can be 5000 degrees C or less.
Examples of the graphite material include natural graphite and artificial graphite.
Here, as the artificial graphite, for example, artificial graphite obtained by heat-treating carbon containing graphitizable carbon mainly at 2800 ° C. or higher, graphitized MCMB heat-treated at 2000 ° C. or higher, and mesophase pitch-based carbon fiber at 2000 ° C. Examples thereof include graphitized mesophase pitch-based carbon fibers that have been heat-treated.
　金属系負極活物質とは、金属を含む活物質であり、通常は、リチウムの挿入が可能な元素を構造に含み、リチウムが挿入された場合の単位質量当たりの理論電気容量が５００ｍＡｈ／ｇ以上である活物質をいう。金属系活物質としては、例えば、リチウム金属、リチウム合金を形成し得る単体金属（例えば、Ａｇ、Ａｌ、Ｂａ、Ｂｉ、Ｃｕ、Ｇａ、Ｇｅ、Ｉｎ、Ｎｉ、Ｐ、Ｐｂ、Ｓｂ、Ｓｉ、Ｓｎ、Ｓｒ、Ｚｎ、Ｔｉなど）およびその合金、並びに、それらの酸化物、硫化物、窒化物、ケイ化物、炭化物、燐化物などが用いられる。 The metal-based negative electrode active material is an active material containing a metal, and usually contains an element capable of inserting lithium in the structure, and the theoretical electric capacity per unit mass when lithium is inserted is 500 mAh / g or more. Is an active material. Examples of the metal active material include lithium metal and a single metal capable of forming a lithium alloy (for example, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn). , Sr, Zn, Ti, etc.) and alloys thereof, and oxides, sulfides, nitrides, silicides, carbides, phosphides, and the like thereof.
　そして、金属系負極活物質の中でも、ケイ素を含む活物質（シリコン系負極活物質）が好ましい。シリコン系負極活物質を用いることにより、リチウムイオン二次電池を高容量化することができるからである。 Of the metal-based negative electrode active materials, active materials containing silicon (silicon-based negative electrode active materials) are preferable. This is because the capacity of the lithium ion secondary battery can be increased by using the silicon-based negative electrode active material.
　シリコン系負極活物質としては、例えば、ケイ素（Ｓｉ）、ケイ素とコバルト、ニッケル、鉄などとの合金、ＳｉＯ、ＳｉＯｘ、Ｓｉ含有材料と炭素材料との混合物、Ｓｉ含有材料を導電性カーボンで被覆または複合化してなるＳｉ含有材料と導電性カーボンとの複合化物などが挙げられる。 Examples of silicon-based negative electrode active materials include silicon (Si), alloys of silicon and cobalt, nickel, iron, etc., SiO, SiOx, mixtures of Si-containing materials and carbon materials, and Si-containing materials coated with conductive carbon. Alternatively, a composite of a Si-containing material and conductive carbon formed into a composite can be used.
　ここで、ＳｉＯｘは、ＳｉＯおよびＳｉＯ2の少なくとも一方と、Ｓｉとを含有する化合物であり、ｘは、通常、０．０１以上２未満である。そして、ＳｉＯｘは、例えば、一酸化ケイ素（ＳｉＯ）の不均化反応を利用して形成することができる。具体的には、ＳｉＯｘは、ＳｉＯを、任意にポリビニルアルコールなどのポリマーの存在下で熱処理し、ケイ素と二酸化ケイ素とを生成させることにより、調製することができる。なお、熱処理は、ＳｉＯと、任意にポリマーとを粉砕混合した後、有機物ガス及び／又は蒸気を含む雰囲気下、９００℃以上、好ましくは１０００℃以上の温度で行うことができる。 Here, SiOx is a compound containing at least one of SiO and SiO 2 and Si, and x is usually 0.01 or more and less than 2. And SiOx can be formed using the disproportionation reaction of a silicon monoxide (SiO), for example. Specifically, SiOx can be prepared by heat-treating SiO, optionally in the presence of a polymer such as polyvinyl alcohol, to produce silicon and silicon dioxide. The heat treatment can be performed at a temperature of 900 ° C. or higher, preferably 1000 ° C. or higher, in an atmosphere containing an organic gas and / or steam after grinding and mixing SiO and optionally a polymer.
　Ｓｉ含有材料と炭素材料との混合物としては、ケイ素やＳｉＯｘなどのＳｉ含有材料と、炭素質材料や黒鉛質材料などの炭素材料とを、任意にポリビニルアルコールなどのポリマーの存在下で粉砕混合したものが挙げられる。なお、炭素質材料や黒鉛質材料としては、炭素系負極活物質として使用し得る材料を用いることができる。 As a mixture of Si-containing material and carbon material, Si-containing material such as silicon and SiOx and carbon material such as carbonaceous material and graphite material were optionally pulverized and mixed in the presence of a polymer such as polyvinyl alcohol. Things. In addition, as a carbonaceous material and a graphite material, the material which can be used as a carbon-type negative electrode active material can be used.
　Ｓｉ含有材料と導電性カーボンとの複合化物としては、例えば、ＳｉＯと、ポリビニルアルコールなどのポリマーと、任意に炭素材料との粉砕混合物を、例えば有機物ガス及び／又は蒸気を含む雰囲気下で熱処理してなる化合物を挙げることができる。また、ＳｉＯの粒子に対して、有機物ガスなどを化学的蒸着法によって表面をコーティングする方法、ＳｉＯの粒子と黒鉛または人造黒鉛をメカノケミカル法によって複合粒子化（造粒化）するなど公知の方法を用いることができる。 As a composite of Si-containing material and conductive carbon, for example, a pulverized mixture of SiO, a polymer such as polyvinyl alcohol, and optionally a carbon material is heat-treated in an atmosphere containing, for example, an organic gas and / or steam. Can be mentioned. Also, a known method such as a method of coating the surface of SiO particles with an organic gas or the like by chemical vapor deposition, or a composite particle (granulation) of SiO particles and graphite or artificial graphite by a mechanochemical method. Can be used.
　ここで、炭素系負極活物質や金属系負極活物質を負極活物質として用いた場合、これらの負極活物質はリチウムイオン二次電池の充放電に伴って膨張および収縮する。そのため、これらの負極活物質を使用した場合には、通常、負極活物質の膨張および収縮の繰り返しに起因して、負極が次第に膨らみ、二次電池が変形してサイクル特性などの電気的特性が低下する可能性がある。しかし、本発明のバインダー組成物を用いて形成した負極では、上述した架橋性単量体に起因して形成される架橋構造により、負極活物質の膨張および収縮に起因した負極の膨らみを抑制し、サイクル特性などの電気的特性を向上することができる。 Here, when a carbon-based negative electrode active material or a metal-based negative electrode active material is used as the negative electrode active material, these negative electrode active materials expand and contract as the lithium ion secondary battery is charged and discharged. Therefore, when these negative electrode active materials are used, normally, the negative electrode gradually expands due to repeated expansion and contraction of the negative electrode active material, the secondary battery is deformed, and electrical characteristics such as cycle characteristics are obtained. May be reduced. However, in the negative electrode formed using the binder composition of the present invention, the negative electrode bulge caused by expansion and contraction of the negative electrode active material is suppressed by the cross-linked structure formed due to the cross-linkable monomer described above. Electrical characteristics such as cycle characteristics can be improved.
　なお、上記シリコン系負極活物質を用いれば、リチウムイオン二次電池を高容量化することはできるものの、一般に、シリコン系負極活物質は充放電に伴って大きく（例えば５倍程度に）膨張および収縮する。そこで、負極の膨れの発生を十分に抑制しつつリチウムイオン二次電池を高容量化する観点からは、炭素系負極活物質とシリコン系負極活物質との混合物を負極活物質として用いることが好ましい。 In addition, although the capacity | capacitance of a lithium ion secondary battery can be increased if the said silicon-type negative electrode active material is used, generally a silicon-type negative electrode active material expand | swells greatly (for example, about 5 times) with charging / discharging. Shrink. Therefore, from the viewpoint of increasing the capacity of the lithium ion secondary battery while sufficiently suppressing the occurrence of swelling of the negative electrode, it is preferable to use a mixture of a carbon-based negative electrode active material and a silicon-based negative electrode active material as the negative electrode active material. .
　ここで、炭素系負極活物質とシリコン系負極活物質との混合物を負極活物質として用いる場合、負極の膨れの発生を十分に抑制しつつリチウムイオン二次電池を十分に高容量化する観点からは、炭素系負極活物質として人造黒鉛を使用することが好ましく、シリコン系負極活物質としてＳｉ、ＳｉＯｘ、Ｓｉ含有材料と炭素材料との混合物およびＳｉ含有材料と導電性カーボンとの複合化物からなる群より選択される一種以上を用いることが好ましく、シリコン系負極活物質としてＳｉ含有材料と導電性カーボンとの複合化物を用いることが更に好ましく、導電性カーボンのマトリックス中にＳｉＯｘが分散した複合化物（Ｓｉ－ＳｉＯｘ－Ｃ複合体）を用いることが特に好ましい。これらの負極活物質は、比較的大量のリチウムを吸蔵および放出し得る一方で、リチウムを吸蔵および放出した際の体積変化が比較的小さい。従って、これらの負極活物質を用いれば、充放電時の負極活物質の体積変化の増大を抑制しつつ、スラリー組成物を用いて形成したリチウムイオン二次電池用負極を用いたリチウムイオン二次電池を十分に高容量化することができる。 Here, when a mixture of a carbon-based negative electrode active material and a silicon-based negative electrode active material is used as the negative electrode active material, from the viewpoint of sufficiently increasing the capacity of the lithium ion secondary battery while sufficiently suppressing the occurrence of swelling of the negative electrode. It is preferable to use artificial graphite as the carbon-based negative electrode active material, and as the silicon-based negative electrode active material, Si, SiOx, a mixture of a Si-containing material and a carbon material, and a composite of a Si-containing material and conductive carbon. It is preferable to use one or more selected from the group, and it is more preferable to use a composite of a Si-containing material and conductive carbon as the silicon-based negative electrode active material, and a composite in which SiOx is dispersed in a conductive carbon matrix. It is particularly preferable to use (Si—SiOx—C composite). While these negative electrode active materials can occlude and release a relatively large amount of lithium, the volume change when lithium is occluded and released is relatively small. Therefore, if these negative electrode active materials are used, a lithium ion secondary using a negative electrode for a lithium ion secondary battery formed using the slurry composition while suppressing an increase in volume change of the negative electrode active material during charge / discharge. The capacity of the battery can be sufficiently increased.
　ここで、負極活物質の粒径や比表面積は、特に限定されることなく、従来使用されている負極活物質と同様とすることができる。 Here, the particle size and specific surface area of the negative electrode active material are not particularly limited, and can be the same as those of conventionally used negative electrode active materials.
　本発明のスラリー組成物における負極活物質の含有割合は、好ましくは９０質量％以上、より好ましくは９５質量％以上であり、好ましくは９９．９質量％以下、より好ましくは９９質量％以下である。負極活物質の含有量を上記範囲とすることにより、本発明の二次電池の容量を大きくでき、また、負極の柔軟性、及び、集電体と負極合材層との結着性を向上させることができる。 The content ratio of the negative electrode active material in the slurry composition of the present invention is preferably 90% by mass or more, more preferably 95% by mass or more, preferably 99.9% by mass or less, more preferably 99% by mass or less. . By setting the content of the negative electrode active material in the above range, the capacity of the secondary battery of the present invention can be increased, and the flexibility of the negative electrode and the binding property between the current collector and the negative electrode mixture layer are improved. Can be made.
［正極活物質］
　スラリー組成物を正極の形成に用いる場合、電極活物質として正極活物質を用いる。正極活物質は、正極において用いられる電極活物質であり、二次電池の正極において電子の受け渡しをする物質である。例えば、本発明の二次電池がリチウムイオン二次電池である場合、正極活物質としては、通常、リチウムイオンの挿入及び脱離が可能な物質が用いられる。このような正極活物質は、無機化合物からなるものと有機化合物からなるものとに大別される。 [Positive electrode active material]
When the slurry composition is used for forming a positive electrode, a positive electrode active material is used as the electrode active material. The positive electrode active material is an electrode active material used in the positive electrode, and is a material that transfers electrons in the positive electrode of the secondary battery. For example, when the secondary battery of the present invention is a lithium ion secondary battery, a material capable of inserting and extracting lithium ions is usually used as the positive electrode active material. Such positive electrode active materials are roughly classified into those made of inorganic compounds and those made of organic compounds.
　無機化合物からなる正極活物質としては、例えば、遷移金属酸化物、遷移金属硫化物、リチウムと遷移金属とのリチウム含有複合金属酸化物などが挙げられる。上記の遷移金属としては、例えば、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｍｏ等が挙げられる。遷移金属酸化物としては、例えば、ＭｎＯ、ＭｎＯ2、Ｖ2Ｏ5、Ｖ6Ｏ13、ＴｉＯ2、Ｃｕ2Ｖ2Ｏ3、非晶質Ｖ2Ｏ－Ｐ2Ｏ5、ＭｏＯ3、Ｖ2Ｏ5、Ｖ6Ｏ13等が挙げられ、なかでも、二次電池のサイクル安定性と容量からＭｎＯ、Ｖ2Ｏ5、Ｖ6Ｏ13、ＴｉＯ2が好ましい。遷移金属硫化物としては、例えば、ＴｉＳ2、ＴｉＳ3、非晶質ＭｏＳ2、ＦｅＳ等が挙げられる。リチウム含有複合金属酸化物としては、例えば、層状構造を有するリチウム含有複合金属酸化物、スピネル構造を有するリチウム含有複合金属酸化物、オリビン型構造を有するリチウム含有複合金属酸化物などが挙げられる。層状構造を有するリチウム含有複合金属酸化物としては、例えば、リチウム含有コバルト酸化物（ＬｉＣｏＯ2）、リチウム含有ニッケル酸化物（ＬｉＮｉＯ2）、Ｃｏ－Ｎｉ－Ｍｎのリチウム複合酸化物、Ｎｉ－Ｍｎ－Ａｌのリチウム複合酸化物、Ｎｉ－Ｃｏ－Ａｌのリチウム複合酸化物、ＬｉＭａＯ2とＬｉ2ＭｂＯ3との固溶体、などが挙げられる。また、ＬｉＭａＯ2とＬｉ2ＭｂＯ3との固溶体としては、例えば、ｘＬｉＭａＯ2・（１－ｘ）Ｌｉ2ＭｂＯ3などが挙げられる。ここで、ｘは０＜ｘ＜１を満たす数を表し、Ｍａは平均酸化状態が３＋である１種類以上の遷移金属を表し、Ｍｂは平均酸化状態が４＋である１種類以上の遷移金属を表す。
　なお、本明細書において、「平均酸化状態」とは、前記「１種類以上の遷移金属」の平均の酸化状態を示し、遷移金属のモル量と原子価とから算出される。例えば、「１種類以上の遷移金属」が、５０ｍｏｌ％のＮｉ2+と５０ｍｏｌ％のＭｎ4+から構成される場合には、「１種類以上の遷移金属」の平均酸化状態は、（０．５）×（２＋）＋（０．５）×（４＋）＝３＋となる。 Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, transition metal sulfides, lithium-containing composite metal oxides of lithium and transition metals, and the like. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo. Examples of the transition metal oxide include MnO, MnO 2 , V 2 O 5 , V 6 O 13 , TiO 2 , Cu 2 V 2 O 3 , amorphous V 2 O—P 2 O 5 , MoO 3 , V 2 O 5 , V 6 O 13 and the like are mentioned, and among them, MnO, V 2 O 5 , V 6 O 13 and TiO 2 are preferable from the viewpoint of cycle stability and capacity of the secondary battery. Examples of the transition metal sulfide include TiS 2 , TiS 3 , amorphous MoS 2 , and FeS. Examples of the lithium-containing composite metal oxide include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure. Examples of the lithium-containing composite metal oxide having a layered structure include lithium-containing cobalt oxide (LiCoO 2 ), lithium-containing nickel oxide (LiNiO 2 ), Co—Ni—Mn lithium composite oxide, Ni—Mn— Examples thereof include a lithium composite oxide of Al, a lithium composite oxide of Ni—Co—Al, and a solid solution of LiMaO 2 and Li 2 MbO 3 . Examples of the solid solution of LiMaO 2 and Li 2 MbO 3 include xLiMaO 2. (1-x) Li 2 MbO 3 . Here, x represents a number satisfying 0 <x <1, Ma represents one or more transition metals having an average oxidation state of 3+, and Mb represents one or more transition metals having an average oxidation state of 4+. To express.
In this specification, the “average oxidation state” indicates an average oxidation state of the “one or more transition metals”, and is calculated from the molar amount and valence of the transition metal. For example, when “one or more transition metals” is composed of 50 mol% Ni 2+ and 50 mol% Mn 4+ , the average oxidation state of “one or more transition metals” is (0. 5) × (2 +) + (0.5) × (4 +) = 3+
　層状構造を有するリチウム含有複合金属酸化物の中でも、二次電池のサイクル特性を向上させるという観点からは、ＬｉＣｏＯ2を用いることが好ましく、二次電池のエネルギー密度を向上させるという観点からは、ＬｉＭａＯ2とＬｉ2ＭｂＯ3との固溶体が好ましい。また、ＬｉＭａＯ2とＬｉ2ＭｂＯ3との固溶体としては、特に、ｘＬｉＭａＯ2・（１－ｘ）Ｌｉ2ＭｂＯ3（ｘは０＜ｘ＜１を満たす数を表し、ＭａはＮｉ、Ｃｏ、Ｍｎ、Ｆｅ及びＴｉからなる群より選ばれる１種類以上を表し、ＭｂはＭｎ、Ｚｒ及びＴｉからなる群より選ばれる１種類以上を表す。）が好ましい。なかでも、特にｘＬｉＭａＯ2・（１－ｘ）Ｌｉ2ＭｎＯ3（ｘは０＜ｘ＜１を満たす数を表し、ＭａはＮｉ、Ｃｏ、Ｍｎ、Ｆｅ及びＴｉからなる群より選ばれる１種類以上を表す。）が好ましい。そのような固溶体には、例えば、Ｌｉ［Ｎｉ0.17Ｌｉ0.2Ｃｏ0.07Ｍｎ0.56］Ｏ2がある。 Among the lithium-containing composite metal oxides having a layered structure, LiCoO 2 is preferably used from the viewpoint of improving the cycle characteristics of the secondary battery, and LiMaO is used from the viewpoint of improving the energy density of the secondary battery. A solid solution of 2 and Li 2 MbO 3 is preferred. Further, as a solid solution of LiMaO 2 and Li 2 MbO 3 , in particular, xLiMaO 2 · (1-x) Li 2 MbO 3 (x represents a number satisfying 0 <x <1, Ma is Ni, Co, Mn Mb represents one or more selected from the group consisting of Mn, Zr and Ti). In particular, xLiMaO 2 · (1-x) Li 2 MnO 3 (x represents a number satisfying 0 <x <1, and Ma is one or more selected from the group consisting of Ni, Co, Mn, Fe, and Ti. Is preferred). An example of such a solid solution is Li [Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ] O 2 .
　スピネル構造を有するリチウム含有複合金属酸化物としては、例えば、マンガン酸リチウム（ＬｉＭｎ2Ｏ4）のＭｎの一部を他の遷移金属で置換した化合物が挙げられる。具体例としては、Ｌｉs［Ｍｎ2-tＭｄt］Ｏ4が挙げられる。ここで、Ｍｄは平均酸化状態が４＋である１種類以上の遷移金属を表す。Ｍｄの具体例としては、Ｎｉ、Ｃｏ、Ｆｅ、Ｃｕ、Ｃｒ等が挙げられる。また、ｔは０＜ｔ＜１を満たす数を表し、ｓは０≦ｓ≦１を満たす数を表す。なお、正極活物質としては、Ｌｉ1+xＭｎ2-xＯ4（０＜Ｘ＜２）で表されるリチウム過剰のスピネル化合物なども用いることができる。 Examples of the lithium-containing composite metal oxide having a spinel structure include compounds in which a part of Mn of lithium manganate (LiMn 2 O 4 ) is substituted with another transition metal. A specific example is Li s [Mn 2−t Md t ] O 4 . Here, Md represents one or more transition metals having an average oxidation state of 4+. Specific examples of Md include Ni, Co, Fe, Cu, and Cr. T represents a number satisfying 0 <t <1, and s represents a number satisfying 0 ≦ s ≦ 1. As the positive electrode active material, a lithium-excess spinel compound represented by Li 1 + x Mn 2−x O 4 (0 <X <2) can also be used.
　なかでも、マンガン酸リチウムのＭｎをＦｅで置換したＬｉsＦｅtＭｎ2-tＯ4-zは、コストが安価であることから好ましい。ここで、ｓは０≦ｓ≦１を満たす数を表し、ｔは０＜ｔ＜１を満たす数を表し、ｚは０≦ｚ≦０．１を満たす数を表す。また、例えばマンガン酸リチウムのＭｎをＮｉで置換したＬｉＮｉ0.5Ｍｎ1.5Ｏ4なども、好ましい。ＬｉＮｉ0.5Ｍｎ1.5Ｏ4などは、構造劣化の因子と考えられているＭｎ3+を全て置換することができる。さらに、ＬｉＮｉ0.5Ｍｎ1.5Ｏ4などは、Ｎｉ2+からＮｉ4+への電気化学反応をすることから、高い作動電圧で、かつ、高い容量を有する二次電池を実現できる。 Among them, Li s Fe t Mn 2- t O 4-z where the Mn of the lithium manganate obtained by substituting Fe is preferred because the cost is inexpensive. Here, s represents a number satisfying 0 ≦ s ≦ 1, t represents a number satisfying 0 <t <1, and z represents a number satisfying 0 ≦ z ≦ 0.1. Further, for example, LiNi 0.5 Mn 1.5 O 4 in which Mn of lithium manganate is substituted with Ni is also preferable. LiNi 0.5 Mn 1.5 O 4 and the like can replace all of Mn 3+ considered to be a factor of structural deterioration. Furthermore, since LiNi 0.5 Mn 1.5 O 4 and the like undergo an electrochemical reaction from Ni 2+ to Ni 4+ , a secondary battery having a high operating voltage and a high capacity can be realized.
　オリビン型構造を有するリチウム含有複合金属酸化物としては、例えば、ＬｉyＭｃＰＯ4で表されるオリビン型リン酸リチウム化合物が挙げられる。ここで、Ｍｃは平均酸化状態が３＋である１種類以上の遷移金属を表し、例えばＭｎ、Ｆｅ、及びＣｏ等が挙げられる。また、ｙは０≦ｙ≦２を満たす数を表す。さらに、ＬｉyＭｃＰＯ4で表されるオリビン型リン酸リチウム化合物は、ＭｎまたはＣｏは他の金属で一部置換されていてもよい。置換しうる金属としては、例えば、Ｆｅ、Ｃｕ、Ｍｇ、Ｚｎ、Ｖ、Ｃａ、Ｓｒ、Ｂａ、Ｔｉ、Ａｌ、Ｓｉ、Ｂ及びＭｏなどが挙げられる。 Examples of the lithium-containing composite metal oxide having an olivine type structure include an olivine type lithium phosphate compound represented by Li y McPO 4 . Here, Mc represents one or more transition metals having an average oxidation state of 3+, and examples thereof include Mn, Fe, and Co. Y represents a number satisfying 0 ≦ y ≦ 2. Furthermore, in the olivine-type lithium phosphate compound represented by Li y McPO 4 , Mn or Co may be partially substituted with another metal. Examples of the metal that can be substituted include Fe, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, Si, B, and Mo.
　さらに、無機化合物からなる正極活物質としては、例えば、Ｌｉ2ＭｅＳｉＯ4等のポリアニオン構造を有する正極活物質、ペロブスカイト構造を有するＬｉＦｅＦ3、斜方昌構造を有するＬｉ2Ｃｕ2Ｏ4など、が挙げられる。ここでＭｅは、Ｆｅ又はＭｎを表す。有機化合物からなる正極活物質としては、例えば、ポリアセチレン、ポリ－ｐ－フェニレンなどの導電性高分子が挙げられる。 Furthermore, examples of the positive electrode active material made of an inorganic compound include a positive electrode active material having a polyanion structure such as Li 2 MeSiO 4 , LiFeF 3 having a perovskite structure, and Li 2 Cu 2 O 4 having an orthorhombic structure. Can be mentioned. Here, Me represents Fe or Mn. Examples of the positive electrode active material made of an organic compound include conductive polymers such as polyacetylene and poly-p-phenylene.
　また、例えば、鉄系酸化物を炭素源物質の存在下において還元焼成することで、炭素材料で覆われた複合材料を作製し、この複合材料を正極活物質として用いてもよい。鉄系酸化物は電気伝導性に乏しい傾向があるが、前記のような複合材料にすることにより、高性能な正極活物質として使用できる。 Also, for example, a composite material covered with a carbon material may be produced by reducing and firing an iron-based oxide in the presence of a carbon source material, and this composite material may be used as a positive electrode active material. Iron-based oxides tend to have poor electrical conductivity, but can be used as a high-performance positive electrode active material by using a composite material as described above.
　上述した中でも、正極活物質は、高いエネルギー密度を有することから、リチウム含有複合金属酸化物が好ましい。リチウム含有複合金属酸化物は、表面官能基として親水性基を有するものが多い。そのため、リチウム含有複合金属酸化物を用いることで、分散安定性の高いスラリー組成物を得ることができ、また、電極内での正極活物質間の結着も強固に保つことができる。
　ここで、正極活物質の表面状態は、正極活物質と溶媒との接触角を測ることにより求めることができる。例えば、正極活物質のみを加圧成型してペレットを作製し、極性溶媒（例えば、Ｎ－メチルピロリドン）に対する前記ペレットの接触角を求めることで、確認できる。接触角が低いほど、その正極活物質は親水性であることを示す。 Among the above, the positive electrode active material is preferably a lithium-containing composite metal oxide because it has a high energy density. Many lithium-containing composite metal oxides have a hydrophilic group as a surface functional group. Therefore, by using the lithium-containing composite metal oxide, a slurry composition having high dispersion stability can be obtained, and the binding between the positive electrode active materials in the electrode can be kept strong.
Here, the surface state of the positive electrode active material can be determined by measuring the contact angle between the positive electrode active material and the solvent. For example, it can be confirmed by pressure-molding only the positive electrode active material to produce pellets and determining the contact angle of the pellets with a polar solvent (for example, N-methylpyrrolidone). A lower contact angle indicates that the positive electrode active material is more hydrophilic.
　また、本発明の二次電池がニッケル水素二次電池である場合、正極活物質としては、例えば、水酸化ニッケル粒子が挙げられる。水酸化ニッケル粒子は、コバルト、亜鉛、カドミウム等を固溶していてもよく、あるいは表面がアルカリ熱処理されたコバルト化合物で被覆されていてもよい。 Further, when the secondary battery of the present invention is a nickel hydride secondary battery, examples of the positive electrode active material include nickel hydroxide particles. The nickel hydroxide particles may be dissolved in cobalt, zinc, cadmium, or the like, or may be coated with a cobalt compound whose surface is subjected to an alkali heat treatment.
　正極活物質は、部分的に元素置換したものであってもよい。また、正極活物質としては、無機化合物と有機化合物とを組み合わせて用いてもよい。さらに、正極活物質は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。 The positive electrode active material may be partially element-substituted. As the positive electrode active material, an inorganic compound and an organic compound may be used in combination. Furthermore, one type of positive electrode active material may be used alone, or two or more types may be used in combination at any ratio.
　正極活物質の粒子の粒子径は、通常、二次電池の他の構成要件との兼ね合いで適宜選択される。正極活物質の粒子の５０％体積累積径は、負荷特性及びサイクル特性などの電池特性の向上の観点から、通常０．１μｍ以上、好ましくは０．４μｍ以上、更に好ましくは１μｍ以上であり、通常５０μｍ以下、好ましくは３０μｍ以下、より好ましくは２０μｍ以下である。５０％体積累積径がこの範囲であると、出力特性に優れ、充放電容量が大きい二次電池を得ることができる。また、正極合材層を製造するためのスラリー組成物を製造する際及び正極を製造する際の取扱いが容易である。５０％体積累積径は、レーザー回折で粒度分布を測定することにより求めることができる。 The particle size of the positive electrode active material particles is usually selected as appropriate in consideration of other constituent requirements of the secondary battery. The 50% volume cumulative diameter of the positive electrode active material particles is usually 0.1 μm or more, preferably 0.4 μm or more, more preferably 1 μm or more, from the viewpoint of improving battery characteristics such as load characteristics and cycle characteristics. It is 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less. When the 50% volume cumulative diameter is within this range, a secondary battery having excellent output characteristics and a large charge / discharge capacity can be obtained. Moreover, the handling at the time of manufacturing the slurry composition for manufacturing a positive electrode compound material layer and manufacturing a positive electrode is easy. The 50% volume cumulative diameter can be determined by measuring the particle size distribution by laser diffraction.
　上述した中でも、スラリー組成物を用いて形成した正極を使用した二次電池の高容量化の観点からは、正極活物質として、リチウム含有ニッケル酸化物（ＬｉＮｉＯ2）、リチウム含有コバルト酸化物（ＬｉＣｏＯ2）、Ｃｏ－Ｎｉ－Ｍｎのリチウム複合酸化物（Ｌｉ（Ｃｏ Ｍｎ Ｎｉ）Ｏ2）、Ｌｉ［Ｎｉ0.17Ｌｉ0.2Ｃｏ0.07Ｍｎ0.56］Ｏ2、ＬｉＮｉ0.5Ｍｎ1.5Ｏ4などが好ましく、なかでも、Ｃｏ－Ｎｉ－Ｍｎのリチウム複合酸化物（Ｌｉ（Ｃｏ Ｍｎ Ｎｉ）Ｏ2）及びリチウム含有コバルト酸化物（ＬｉＣｏＯ2）が好ましい。 Among the above, from the viewpoint of increasing the capacity of the secondary battery using the positive electrode formed using the slurry composition, as the positive electrode active material, lithium-containing nickel oxide (LiNiO 2 ), lithium-containing cobalt oxide (LiCoO). 2 ), Co—Ni—Mn lithium composite oxide (Li (Co 2 Mn Ni) O 2 ), Li [Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ] O 2 , LiNi 0.5 Mn 1.5 O 4 and the like are preferable. Co-Ni-Mn lithium composite oxide (Li (Co Mn Ni) O 2 ) and lithium-containing cobalt oxide (LiCoO 2 ) are preferable.
　本発明のスラリー組成物における正極活物質の含有割合は、好ましくは５０質量％以上、より好ましくは６０質量％以上、また、好ましくは９５質量％以下、より好ましくは９０質量％以下となる範囲である。スラリー組成物における正極活物質の含有割合を上記範囲とすることにより、良好なスラリー組成物及び正極を作製することができる。 The content ratio of the positive electrode active material in the slurry composition of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, and preferably 95% by mass or less, more preferably 90% by mass or less. is there. By setting the content ratio of the positive electrode active material in the slurry composition within the above range, a good slurry composition and positive electrode can be produced.
［導電材］
　スラリー組成物を正極の形成に用いる場合、当該スラリー組成物は導電材を含むことが好ましい。導電材としては、例えば、導電性を有する、炭素の同素体からなる粒子が挙げられる。導電材を用いることにより、正極活物質同士の電気的接触を向上させることができ、特にリチウムイオン二次電池に用いる場合に放電負荷特性を改善することができる。
　導電材の具体例を挙げると、アセチレンブラック、ケッチェンブラック、カーボンブラック、グラファイト、気相成長カーボン繊維、カーボンナノチューブ等の導電性カーボンが挙げられる。また、例えば、黒鉛等の炭素粉末、各種金属のファイバー及び箔なども挙げられる。ここで、導電材は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。これらの中でも、正極活物質同士の電気的接触を向上させ、スラリー組成物を用いて形成した正極を使用した二次電池の電気的特性を向上させる観点からは、導電材として、アセチレンブラックを用いることが好ましい。 [Conductive material]
When using a slurry composition for formation of a positive electrode, it is preferable that the said slurry composition contains a electrically conductive material. Examples of the conductive material include particles made of carbon allotrope having conductivity. By using a conductive material, electrical contact between the positive electrode active materials can be improved, and discharge load characteristics can be improved particularly when used in a lithium ion secondary battery.
Specific examples of the conductive material include conductive carbon such as acetylene black, ketjen black, carbon black, graphite, vapor grown carbon fiber, and carbon nanotube. Further, for example, carbon powder such as graphite, fibers and foils of various metals, and the like are also included. Here, a conductive material may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. Among these, acetylene black is used as the conductive material from the viewpoint of improving the electrical contact between the positive electrode active materials and improving the electrical characteristics of the secondary battery using the positive electrode formed using the slurry composition. It is preferable.
　導電材の５０％体積累積径は、正極活物質の５０％体積累積径よりも小さいことが好ましい。導電材の５０％体積累積径の具体的範囲は、通常０．００１μｍ以上、好ましくは０．０５μｍ以上、より好ましくは０．０１μｍ以上であり、通常１０μｍ以下、好ましくは５μｍ以下、より好ましくは１μｍ以下である。導電材の５０％体積累積径がこの範囲にあると、より少ない使用量で高い導電性が得られる。
　導電材の量は、正極活物質１００質量部に対して、通常０．０１質量部以上、好ましくは１質量部以上であり、通常２０質量部以下、好ましくは１０質量部以下である。導電材の量がこの範囲にあることにより、二次電池の容量を高くでき、また、高い負荷特性を示すことができる。導電材の配合量が少なすぎると、正極活物質同士の電気的接触により形成される導電パスが不十分となり、二次電池の出力が低下する虞がある。一方、導電材の配合量が多すぎると、スラリー組成物の安定性が低下すると共に正極中の正極合材層の密度が低下し、リチウムイオン二次電池を十分に高容量化することができない。 The 50% volume cumulative diameter of the conductive material is preferably smaller than the 50% volume cumulative diameter of the positive electrode active material. The specific range of the 50% volume cumulative diameter of the conductive material is usually 0.001 μm or more, preferably 0.05 μm or more, more preferably 0.01 μm or more, and usually 10 μm or less, preferably 5 μm or less, more preferably 1 μm. It is as follows. When the 50% volume cumulative diameter of the conductive material is within this range, high conductivity can be obtained with a smaller amount of use.
The amount of the conductive material is usually 0.01 parts by mass or more, preferably 1 part by mass or more, and usually 20 parts by mass or less, preferably 10 parts by mass or less with respect to 100 parts by mass of the positive electrode active material. When the amount of the conductive material is within this range, the capacity of the secondary battery can be increased and high load characteristics can be exhibited. If the amount of the conductive material is too small, the conductive path formed by electrical contact between the positive electrode active materials becomes insufficient, and the output of the secondary battery may be reduced. On the other hand, when the blending amount of the conductive material is too large, the stability of the slurry composition is lowered and the density of the positive electrode mixture layer in the positive electrode is lowered, so that the capacity of the lithium ion secondary battery cannot be sufficiently increased. .
［粘度調整剤］
　粘度調整剤は、スラリー組成物の粘度を調整し、集電体上へのスラリー組成物の塗布を容易にするためのものである。そして、粘度調整剤としては、例えば水溶性高分子を用いることができる。具体的には、粘度調整剤としては、カルボキシメチルセルロース、メチルセルロース、ヒドロキシプロピルセルロースなどのセルロース系ポリマー、並びに、これらのセルロース系ポリマーのアンモニウム塩およびアルカリ金属塩；変性または未変性のポリ（メタ）アクリル酸、並びに、これらのポリ（メタ）アクリル酸のアンモニウム塩およびアルカリ金属塩；変性または未変性のポリビニルアルコール、アクリル酸またはアクリル酸塩とビニルアルコールとの共重合体、無水マレイン酸、マレイン酸またはフマル酸とビニルアルコールとの共重合体などのポリビニルアルコール類；ポリエチレングリコール、ポリビニルピロリドン、変性ポリアクリル酸、酸化スターチ、リン酸スターチ、カゼイン、各種変性デンプン、アクリロニトリル－ブタジエン共重合体水素化物などを用いることができる。さらに、粘度調整剤として、水溶性で、末端にチオール基を有する任意の高分子（末端にチオール基を有する水溶性高分子）を用いることができる。 [Viscosity modifier]
The viscosity modifier is for adjusting the viscosity of the slurry composition and facilitating the application of the slurry composition on the current collector. For example, a water-soluble polymer can be used as the viscosity modifier. Specifically, examples of the viscosity modifier include cellulose polymers such as carboxymethyl cellulose, methyl cellulose, and hydroxypropyl cellulose, and ammonium salts and alkali metal salts of these cellulose polymers; modified or unmodified poly (meth) acrylic Acids and ammonium and alkali metal salts of these poly (meth) acrylic acids; modified or unmodified polyvinyl alcohol, copolymers of acrylic acid or acrylates with vinyl alcohol, maleic anhydride, maleic acid or Polyvinyl alcohols such as copolymers of fumaric acid and vinyl alcohol; polyethylene glycol, polyvinyl pyrrolidone, modified polyacrylic acid, oxidized starch, phosphate starch, casein, various modified starches, acrylonitrile Butadiene copolymer hydrides can be used. Furthermore, any polymer that is water-soluble and has a thiol group at the terminal (water-soluble polymer having a thiol group at the terminal) can be used as the viscosity modifier.
　なお、粘度調整剤の配合量は、電極活物質１００質量部当たり、通常０．１質量部以上、好ましくは、０．３質量部以上、通常２質量部以下、好ましくは１質量部以下である。粘度調整剤の配合量を上記範囲内とすれば、良好な粘性を有するスラリー組成物を得ることができる。従って、電極形成時に集電体上へスラリー組成物を良好に塗布することができ、その結果、得られる電極の製品寿命を長寿命化することができる。 In addition, the compounding quantity of a viscosity modifier is 0.1 mass part or more normally per 100 mass parts of electrode active materials, Preferably, it is 0.3 mass part or more, Usually 2 mass parts or less, Preferably it is 1 mass part or less. . When the blending amount of the viscosity modifier is within the above range, a slurry composition having a good viscosity can be obtained. Therefore, the slurry composition can be satisfactorily applied onto the current collector during electrode formation, and as a result, the product life of the obtained electrode can be extended.
［界面活性剤］
　本発明のスラリー組成物は、更に界面活性剤を含有してもよい。界面活性剤は、スラリー組成物を集電体に塗工する時に発生するはじきを防止し、電極の平滑性を向上させるために有効である。界面活性剤としては、例えば、アルキル系界面活性剤、シリコン系界面活性剤、フッ素系界面活性剤、金属系界面活性剤などが挙げられる。界面活性剤の配合量は、電極活物質１００質量部に対して、好ましくは０．０１質量部～１０質量部である。界面活性剤が上記範囲であることにより電極作製時の生産性、平滑性が良好になり、二次電池の電池特性が優れたものになる。 [Surfactant]
The slurry composition of the present invention may further contain a surfactant. The surfactant is effective for preventing the repelling that occurs when applying the slurry composition to the current collector and improving the smoothness of the electrode. Examples of the surfactant include alkyl surfactants, silicon surfactants, fluorine surfactants, metal surfactants, and the like. The compounding amount of the surfactant is preferably 0.01 to 10 parts by mass with respect to 100 parts by mass of the electrode active material. When the surfactant is in the above range, productivity and smoothness during electrode production are improved, and the battery characteristics of the secondary battery are excellent.
［分散剤］
　本発明のスラリー組成物は、更に分散剤を含有してもよい。分散剤としては、例えば、アニオン性化合物、カチオン性化合物、非イオン性化合物、高分子化合物などが例示される。具体的な分散剤は、用いる電極活物質及び導電材に応じて選択される。分散剤を用いることにより、スラリー組成物の安定性が向上し、平滑な電極が得られるので、二次電池の電池容量を高めることができる。
　分散剤の配合量は、電極活物質１００質量部に対して、通常は０．１質量部以上、好ましくは０．５質量部以上、より好ましくは０．８質量部以上であり、通常１０質量部以下、好ましくは５質量部以下、より好ましくは２質量部以下である。 [Dispersant]
The slurry composition of the present invention may further contain a dispersant. Examples of the dispersant include an anionic compound, a cationic compound, a nonionic compound, and a polymer compound. A specific dispersing agent is selected according to the electrode active material and conductive material to be used. By using the dispersant, the stability of the slurry composition is improved and a smooth electrode is obtained, so that the battery capacity of the secondary battery can be increased.
The amount of the dispersing agent is usually 0.1 parts by mass or more, preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, and usually 10 parts by mass with respect to 100 parts by mass of the electrode active material. Part or less, preferably 5 parts by weight or less, more preferably 2 parts by weight or less.
［その他の成分］
　本発明のスラリー組成物は、上記成分の他に、例えば、補強材、酸化防止剤、電解液の分解を抑制する機能を有する電解液添加剤などの成分を含有していてもよい。これらの他の成分は、公知のものを使用することができ、例えば国際公開第２０１２／１１５０９６号、国際公開第２０１２／０３６２６０号、特開２０１２－２０４３０３号公報に記載のものを使用することができる。 [Other ingredients]
In addition to the above components, the slurry composition of the present invention may contain components such as a reinforcing material, an antioxidant, and an electrolytic solution additive having a function of suppressing decomposition of the electrolytic solution. As these other components, known ones can be used. For example, those described in International Publication No. 2012/115096, International Publication No. 2012/036260, and Japanese Patent Application Laid-Open No. 2012-204303 can be used. it can.
（スラリー組成物の調製）
　本発明のスラリー組成物は、上記各成分を分散媒としての水系媒体中に分散させることにより調製することができる。具体的には、ボールミル、サンドミル、ビーズミル、顔料分散機、らい潰機、超音波分散機、ホモジナイザー、プラネタリーミキサー、フィルミックスなどの混合機を用いて上記各成分と水系媒体とを混合することにより、スラリー組成物を調製することができる。
　なお、水系媒体としては、通常は水を用いるが、任意の化合物の水溶液や、少量の有機媒体と水との混合溶液などを用いてもよい。また、スラリー組成物の固形分濃度は、各成分を均一に分散させることができる濃度、例えば、１０～８０質量％とすることができる。更に、上記各成分と水系媒体との混合は、通常、室温～８０℃の範囲で、１０分～数時間行うことができる。 (Preparation of slurry composition)
The slurry composition of the present invention can be prepared by dispersing each of the above components in an aqueous medium as a dispersion medium. Specifically, the above components and the aqueous medium are mixed using a mixer such as a ball mill, a sand mill, a bead mill, a pigment disperser, a grinder, an ultrasonic disperser, a homogenizer, a planetary mixer, or a fill mix. Thus, a slurry composition can be prepared.
As the aqueous medium, water is usually used, but an aqueous solution of an arbitrary compound or a mixed solution of a small amount of an organic medium and water may be used. The solid content concentration of the slurry composition can be set to a concentration at which each component can be uniformly dispersed, for example, 10 to 80% by mass. Further, the mixing of each of the above components and the aqueous medium can be usually carried out in the range of room temperature to 80 ° C. for 10 minutes to several hours.
　スラリー組成物の粘度は、スラリー組成物の経時安定性及び塗工性の観点から、好ましくは１０ｍＰａ・ｓ以上、より好ましくは１００ｍＰａ・ｓ以上であり、好ましくは１００，０００ｍＰａ・ｓ以下、より好ましくは５０，０００ｍＰａ・ｓ以下である。前記粘度は、Ｂ型粘度計を用いて２５℃、回転数６０ｒｐｍで測定した時の値である。 The viscosity of the slurry composition is preferably 10 mPa · s or more, more preferably 100 mPa · s or more, preferably 100,000 mPa · s or less, more preferably from the viewpoint of the temporal stability and coating properties of the slurry composition. Is 50,000 mPa · s or less. The viscosity is a value measured using a B-type viscometer at 25 ° C. and a rotation speed of 60 rpm.
　そして、スラリー組成物を正極の形成に用いる場合、当該スラリー組成物のｐＨは、通常７以上、好ましくは８以上であり、通常１２以下、好ましくは１１．５以下である。スラリー組成物のｐＨを上記範囲とすることにより、スラリー組成物の安定性を高めることができ、また、集電体の腐食抑制効果を奏することができる。
　スラリー組成物のｐＨを調整する方法としては、例えば、スラリー組成物の調製前に正極活物質を洗浄してスラリー組成物のｐＨを調整する方法、作製したスラリー組成物に炭酸ガスをバブリングしてｐＨを調整する方法、ｐＨ調整剤を使って調整する方法などが挙げられる。なかでも、ｐＨ調整剤を用いることが好ましい。ｐＨ調整剤の種類は特に限定されないが、酸性を示す水溶性物質であることが好ましい。強酸及び弱酸のいずれを使用してもよい。弱酸性を示す水溶性物質の例としては、カルボン酸基、リン酸基、スルホン酸基など酸基を有する有機化合物が挙げられる。これらの中でも、特にカルボン酸基を有する有機化合物が好ましく用いられる。カルボン酸基を有する化合物の具体例としては、コハク酸、フタル酸、マレイン酸、無水コハク酸、無水フタル酸、無水マレイン酸などが挙げられる。こられの化合物は、乾燥することにより二次電池内において影響が少ない酸無水物にすることができる。また、強酸性を示す水溶性物質の例としては、塩酸、硝酸、硫酸、酢酸などが挙げられる。 And when using a slurry composition for formation of a positive electrode, the pH of the said slurry composition is 7 or more normally, Preferably it is 8 or more, Usually, 12 or less, Preferably it is 11.5 or less. By adjusting the pH of the slurry composition to the above range, the stability of the slurry composition can be increased, and the current collector can be prevented from being corroded.
As a method of adjusting the pH of the slurry composition, for example, a method of adjusting the pH of the slurry composition by washing the positive electrode active material before preparing the slurry composition, bubbling carbon dioxide gas to the prepared slurry composition Examples thereof include a method for adjusting pH and a method for adjusting using a pH adjusting agent. Especially, it is preferable to use a pH adjuster. Although the kind of pH adjuster is not specifically limited, It is preferable that it is a water-soluble substance which shows acidity. Either a strong acid or a weak acid may be used. Examples of water-soluble substances that exhibit weak acidity include organic compounds having an acid group such as a carboxylic acid group, a phosphoric acid group, and a sulfonic acid group. Among these, an organic compound having a carboxylic acid group is particularly preferably used. Specific examples of the compound having a carboxylic acid group include succinic acid, phthalic acid, maleic acid, succinic anhydride, phthalic anhydride, maleic anhydride and the like. These compounds can be made into acid anhydrides having little influence in the secondary battery by drying. Examples of water-soluble substances that exhibit strong acidity include hydrochloric acid, nitric acid, sulfuric acid, and acetic acid.
　上述のｐＨ調整剤の中でも、スラリー組成物の乾燥工程において分解または揮発するものであることが好ましい。この場合、得られた正極にｐＨ調整剤が残留しない。このようなｐＨ調整剤としては、例えば、酢酸、塩酸などが挙げられる。また、ｐＨ調整剤は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。 Among the pH adjusting agents described above, it is preferable that they are decomposed or volatilized in the drying step of the slurry composition. In this case, no pH adjuster remains in the obtained positive electrode. Examples of such a pH adjuster include acetic acid and hydrochloric acid. Moreover, a pH adjuster may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.
　また、スラリー組成物のｐＨの調整は、スラリー組成物の製造工程中であれば、何時行っても構わない。なかでも、スラリー組成物を所望の固形分濃度まで調整した後に、ｐＨ調整剤によりｐＨを調整することが好ましい。スラリー組成物を所定の固形分濃度まで調整した後にｐＨの調整を行うことにより、正極活物質の溶解を防止しながらｐＨの調整を容易に行うことができる。 Further, the pH of the slurry composition may be adjusted at any time as long as it is during the production process of the slurry composition. Especially, after adjusting a slurry composition to desired solid content concentration, it is preferable to adjust pH with a pH adjuster. By adjusting the pH after adjusting the slurry composition to a predetermined solid content concentration, it is possible to easily adjust the pH while preventing dissolution of the positive electrode active material.
　なお、本発明のスラリー組成物は、本発明のバインダー組成物を調製した後、該バインダー組成物と電極活物質と混合し、或いは、分散媒としての水系媒体中に分散させることにより調製してもよい。 The slurry composition of the present invention is prepared by preparing the binder composition of the present invention and then mixing the binder composition and the electrode active material, or dispersing them in an aqueous medium as a dispersion medium. Also good.
（二次電池用電極）
　本発明の二次電池用電極は、集電体上に、上述のようにして得られた二次電池電極用スラリー組成物を塗布し、集電体上に塗布された二次電池電極用スラリー組成物を乾燥して得られることを特徴とする。
　そして、本発明の二次電池用電極は、集電体と、集電体上に形成された電極合材層とを備え、電極合材層には、少なくとも、電極活物質と、粒子状重合体とが含まれている。なお、電極合材層中に含まれている電極活物質などの各成分は、本発明のスラリー組成物中に含まれていたものであり、それら各成分の好適な存在比は、本発明のスラリー組成物中の各成分の好適な存在比と同じである。 (Electrode for secondary battery)
The secondary battery electrode of the present invention is obtained by applying the slurry composition for a secondary battery electrode obtained as described above on a current collector, and applying the slurry for the secondary battery electrode on the current collector. It is obtained by drying the composition.
The electrode for a secondary battery of the present invention includes a current collector and an electrode mixture layer formed on the current collector. The electrode mixture layer includes at least an electrode active material and a particulate weight. The merger is included. In addition, each component such as an electrode active material contained in the electrode mixture layer is contained in the slurry composition of the present invention, and a suitable abundance ratio of these components is determined according to the present invention. It is the same as the preferred abundance ratio of each component in the slurry composition.
［塗布工程］
　上記二次電池電極用スラリー組成物を集電体上に塗布する方法としては、特に限定されず公知の方法を用いることができる。具体的には、塗布方法としては、ドクターブレード法、ディップ法、リバースロール法、ダイレクトロール法、グラビア法、エクストルージョン法、ハケ塗り法などを用いることができる。この際、スラリー組成物を集電体の片面だけに塗布してもよいし、両面に塗布してもよい。塗布後乾燥前の集電体上のスラリー膜の厚みは、乾燥して得られる電極合材層の厚みに応じて適宜に設定しうる。 [Coating process]
A method for applying the slurry composition for a secondary battery electrode on the current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method, or the like can be used. At this time, the slurry composition may be applied to only one side of the current collector or may be applied to both sides. The thickness of the slurry film on the current collector after application and before drying can be appropriately set according to the thickness of the electrode mixture layer obtained by drying.
　ここで、スラリー組成物を塗布する集電体は、電気導電性を有し且つ電気化学的に耐久性のある材料であれば特に制限されない。耐熱性を有するとの観点から、集電体の材料としては金属が好ましく、例えば、鉄、銅、アルミニウム、ニッケル、ステンレス鋼、チタン、タンタル、金、白金などが好ましい。なかでも、中でも、負極に用いる集電体としては銅箔が特に好ましく、正極に用いる集電体としてはアルミニウムが特に好ましい。集電体の材料は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。
　また、集電体の形状は特に制限されないが、厚さ０．００１ｍｍ～０．５ｍｍ程度のシート状のものが好ましい。さらに、集電体は、電極合材層の接着強度を高めるため、表面に予め粗面化処理して使用することが好ましい。粗面化方法としては、例えば、機械的研磨法、電解研磨法、化学研磨法などが挙げられる。機械的研磨法においては、通常、研磨剤粒子を固着した研磨布紙、砥石、エメリーバフ、鋼線などを備えたワイヤーブラシ等が使用される。また、電極合材層の接着強度や導電性を高めるために、集電体の表面に中間層を形成してもよい。 Here, the current collector to which the slurry composition is applied is not particularly limited as long as it is a material having electrical conductivity and electrochemical durability. From the viewpoint of heat resistance, the current collector is preferably made of metal, such as iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, or platinum. Among these, a copper foil is particularly preferable as the current collector used for the negative electrode, and aluminum is particularly preferable as the current collector used for the positive electrode. One type of current collector material may be used alone, or two or more types may be used in combination at any ratio.
The shape of the current collector is not particularly limited, but a sheet shape having a thickness of about 0.001 mm to 0.5 mm is preferable. Furthermore, it is preferable that the current collector is used after roughening the surface in advance in order to increase the adhesive strength of the electrode mixture layer. Examples of the roughening method include a mechanical polishing method, an electrolytic polishing method, and a chemical polishing method. In the mechanical polishing method, usually, a polishing cloth with a fixed abrasive particle, a grindstone, an emery buff, a wire brush provided with a steel wire or the like is used. Moreover, in order to improve the adhesive strength and electroconductivity of an electrode compound-material layer, you may form an intermediate | middle layer in the surface of an electrical power collector.
［乾燥工程］
　集電体上のスラリー組成物を乾燥する方法としては、特に限定されず公知の方法を用いることができ、例えば温風、熱風、低湿風による乾燥、真空乾燥、赤外線や電子線などの照射による乾燥法が挙げられる。このように集電体上のスラリー組成物を乾燥することで、集電体上に電極合材層を形成し、集電体と電極合材層とを備えるリチウムイオン二次電池用電極を得ることができる。 [Drying process]
A method for drying the slurry composition on the current collector is not particularly limited, and a known method can be used. For example, drying with warm air, hot air, low-humidity air, vacuum drying, irradiation with infrared rays, electron beams, or the like. A drying method is mentioned. Thus, by drying the slurry composition on the current collector, an electrode mixture layer is formed on the current collector, and a lithium ion secondary battery electrode including the current collector and the electrode mixture layer is obtained. be able to.
　なお、乾燥工程の後、金型プレスまたはロールプレスなどを用い、電極合材層に加圧処理を施してもよい。加圧処理により電極合材層と集電体との密着性を向上させると共に、電極の空隙率を低くすることができる。空隙率は、好ましくは５％以上、より好ましくは７％以上であり、好ましくは１５％以下、より好ましくは１３％以下である。空隙率を前記範囲の下限値以上とすることにより、高い体積容量が得易くなり、電極合材層を集電体から剥がれ難くすることができる。また、上限値以下とすることにより、高い充電効率及び放電効率が得られる。 In addition, after the drying step, the electrode mixture layer may be subjected to pressure treatment using a die press or a roll press. The pressure treatment can improve the adhesion between the electrode mixture layer and the current collector and reduce the porosity of the electrode. The porosity is preferably 5% or more, more preferably 7% or more, preferably 15% or less, more preferably 13% or less. By setting the porosity to be equal to or higher than the lower limit of the above range, a high volume capacity can be easily obtained, and the electrode mixture layer can be made difficult to peel from the current collector. Moreover, high charging efficiency and discharge efficiency are obtained by setting it as an upper limit or less.
　電極合材層の厚みは、通常５μｍ以上、好ましくは１０μｍ以上であり、通常３００μｍ以下、好ましくは２５０μｍ以下である。電極合材層の厚みが前記範囲にあることにより、負荷特性及びエネルギー密度共に高い特性を示す。
　また、電極合材層における水分量は、１０００ｐｐｍ以下であることが好ましく、５００ｐｐｍ以下であることがより好ましい。電極合材層の水分量を上記範囲内とすることにより、耐久性に優れる二次電池用電極を実現できる。水分量は、カールフィッシャー法等の既知の方法により測定しうる。 The thickness of the electrode mixture layer is usually 5 μm or more, preferably 10 μm or more, and usually 300 μm or less, preferably 250 μm or less. When the thickness of the electrode mixture layer is in the above range, both load characteristics and energy density are high.
The water content in the electrode mixture layer is preferably 1000 ppm or less, and more preferably 500 ppm or less. By setting the water content of the electrode mixture layer within the above range, a secondary battery electrode having excellent durability can be realized. The amount of water can be measured by a known method such as the Karl Fischer method.
　また、本発明の電極の別の製造方法の例としては、粉体成型法が挙げられる。粉体成型法とは、二次電池用電極を製造するためのスラリー組成物を用意し、そのスラリー組成物から電極活物質などを含む複合粒子を調製し、その複合粒子を集電体上に供給し、所望により更にロールプレスして成形することにより電極合材層を形成して、二次電池用電極を得る製造方法である。この際、スラリー組成物としては、上述したものと同様のスラリー組成物を用いてもよい。 Further, as another example of the method for producing the electrode of the present invention, a powder molding method can be mentioned. The powder molding method refers to preparing a slurry composition for producing an electrode for a secondary battery, preparing composite particles including an electrode active material from the slurry composition, and placing the composite particles on a current collector. It is a manufacturing method which supplies the electrode for secondary batteries by forming an electrode compound-material layer by supplying and roll-pressing as needed and shaping | molding. At this time, as the slurry composition, the same slurry composition as described above may be used.
（二次電池）
　本発明の二次電池は、正極と、負極と、電解液と、セパレータとを備え、正極および負極の少なくとも一方として、本発明の二次電池用電極を用いたものである。本発明の二次電池は、高温保存特性及び高温サイクル特性に優れると共に、ガス発生が抑制されている。 (Secondary battery)
The secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolytic solution, and a separator, and uses the secondary battery electrode of the present invention as at least one of the positive electrode and the negative electrode. The secondary battery of the present invention is excellent in high temperature storage characteristics and high temperature cycle characteristics, and gas generation is suppressed.
　本発明の二次電池は、リチウムイオン二次電池、ニッケル水素二次電池等のいずれであってもよい。なかでも、サイクル特性の向上、出力特性の向上などの性能向上効果が特に顕著であることから、リチウムイオン二次電池が好ましい。以下、本発明の二次電池がリチウムイオン二次電池である場合について、説明する。 The secondary battery of the present invention may be any of a lithium ion secondary battery, a nickel hydride secondary battery, and the like. Among these, lithium ion secondary batteries are preferable because performance improvement effects such as improvement of cycle characteristics and output characteristics are particularly remarkable. Hereinafter, the case where the secondary battery of the present invention is a lithium ion secondary battery will be described.
［正極および負極］
　本発明の二次電池は、上述のように、正極および負極の少なくとも一方が、本発明の二次電池用電極であればよい。すなわち、正極および負極の何れか一方として、既知の電極を用いてもよい。 [Positive electrode and negative electrode]
As described above, in the secondary battery of the present invention, at least one of the positive electrode and the negative electrode may be the electrode for the secondary battery of the present invention. That is, a known electrode may be used as either the positive electrode or the negative electrode.
　既知の正極としては、通常、集電体と、集電体の表面に形成された正極合材層とを備えるものが挙げられ、当該正極合材層は、正極活物質、導電材およびバインダーを含む。集電体、正極活物質および導電材としては、「二次電池用電極」、「二次電池電極用スラリー組成物」の項で上述したものを用いることができる。そしてバインダーとしては、本発明を著しく損なわない限り、既知のあらゆるバインダーを使用することができる。また、正極合材層には、必要に応じて、正極活物質、導電材、バインダー以外の成分、例えば「二次電池電極用スラリー組成物」の項で「その他の成分」として挙げた成分が含まれていてもよい。これらは１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。 Examples of known positive electrodes include those usually comprising a current collector and a positive electrode mixture layer formed on the surface of the current collector. The positive electrode mixture layer comprises a positive electrode active material, a conductive material and a binder. Including. As the current collector, the positive electrode active material, and the conductive material, those described above in the sections of “secondary battery electrode” and “secondary battery electrode slurry composition” can be used. As the binder, any known binder can be used as long as the present invention is not significantly impaired. In addition, the positive electrode mixture layer may contain components other than the positive electrode active material, the conductive material, and the binder as necessary, for example, the components listed as “other components” in the section of “Slurry composition for secondary battery electrode”. It may be included. One of these may be used alone, or two or more of these may be used in combination at any ratio.
　既知の負極としては、通常、集電体と、集電体の表面に形成された負極合材層とを備えるものが挙げられ、当該負極合材層は、負極活物質およびバインダーを含む。集電体、負極活物質としては、「二次電池用電極」、「二次電池電極用スラリー組成物」の項で上述したものを用いることができる。そしてバインダーとしては、本発明を著しく損なわない限り、既知のあらゆるバインダーを使用することができる。そのようなバインダーとしては、例えば、ポリエチレン、ポリテトラフルオロエチレン（ＰＴＦＥ）、ポリフッ化ビニリデン（ＰＶＤＦ）、テトラフルオロエチレン－ヘキサフルオロプロピレン共重合体（ＦＥＰ）、ポリアクリル酸誘導体、ポリアクリロニトリル誘導体等の重合体；アクリル系軟質重合体、ジエン系軟質重合体、オレフィン系軟質重合体、ビニル系軟質重合体等の軟質重合体などを用いてもよい。また、これらは、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。また、負極合材層には、必要に応じて、負極活物質及びバインダー以外の成分、例えば「二次電池電極用スラリー組成物」の項で「その他の成分」として挙げた成分が含まれていてもよい。これらは１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。 As the known negative electrode, there is usually one having a current collector and a negative electrode mixture layer formed on the surface of the current collector, and the negative electrode mixture layer contains a negative electrode active material and a binder. As the current collector and the negative electrode active material, those described above in the sections of “secondary battery electrode” and “secondary battery electrode slurry composition” can be used. As the binder, any known binder can be used as long as the present invention is not significantly impaired. Examples of such binders include polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, and polyacrylonitrile derivatives. Polymer: A soft polymer such as an acrylic soft polymer, a diene soft polymer, an olefin soft polymer, or a vinyl soft polymer may be used. Moreover, these may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. In addition, the negative electrode mixture layer contains components other than the negative electrode active material and the binder, for example, the components listed as “other components” in the section of “slurry composition for secondary battery electrode” as necessary. May be. One of these may be used alone, or two or more of these may be used in combination at any ratio.
　これらの電極の厚みは、集電体と電極合材層との合計で、通常５μｍ以上、好ましくは１０μｍ以上であり、通常３００μｍ以下、好ましくは２５０μｍ以下である。電極の厚みが上記範囲にあることにより、負荷特性及びエネルギー密度の両方を良好にできる。 The total thickness of these electrodes is usually 5 μm or more, preferably 10 μm or more, and usually 300 μm or less, preferably 250 μm or less. When the thickness of the electrode is in the above range, both load characteristics and energy density can be improved.
　そしてこれらの電極は、例えば、本発明の二次電池用電極と同様に、電極活物質、バインダー及び水を含む電極用のスラリー組成物を用意し、そのスラリー組成物の層を集電体に形成し、その層を乾燥させて製造してもよい。 And these electrodes prepare the slurry composition for electrodes containing an electrode active material, a binder, and water similarly to the electrode for secondary batteries of this invention, for example, The layer of the slurry composition is used as a collector. It may be formed and the layer dried.
［電解液］
　リチウムイオン二次電池用の電解液としては、例えば、非水溶媒に支持電解質を溶解した非水電解液が用いられる。支持電解質としては、通常、リチウム塩が用いられる。リチウム塩としては、例えば、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＢＦ4、ＬｉＳｂＦ6、ＬｉＡｌＣｌ4、ＬｉＣｌＯ4、ＣＦ3ＳＯ3Ｌｉ、Ｃ4Ｆ9ＳＯ3Ｌｉ、ＣＦ3ＣＯＯＬｉ、（ＣＦ3ＣＯ）2ＮＬｉ、（ＣＦ3ＳＯ2）2ＮＬｉ、（Ｃ2Ｆ5ＳＯ2）ＮＬｉなどが挙げられる。なかでも、溶媒に溶けやすく高い解離度を示すＬｉＰＦ6、ＬｉＣｌＯ4、ＣＦ3ＳＯ3Ｌｉが好ましい。これらは１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。解離度の高い支持電解質を用いるほど、リチウムイオン伝導度が高くなるので、支持電解質の種類によりリチウムイオン伝導度を調節することができる。 [Electrolyte]
As an electrolytic solution for a lithium ion secondary battery, for example, a nonaqueous electrolytic solution in which a supporting electrolyte is dissolved in a nonaqueous solvent is used. As the supporting electrolyte, a lithium salt is usually used. Examples of the lithium salt include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi, and the like. Of these, LiPF 6 , LiClO 4 , and CF 3 SO 3 Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferable. One of these may be used alone, or two or more of these may be used in combination at any ratio. Since the lithium ion conductivity increases as the supporting electrolyte having a higher degree of dissociation is used, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.
　電解液における支持電解質の濃度は、通常１質量％以上、好ましくは５質量％以上であり、また、通常３０質量％以下、好ましくは２０質量％以下である。また、支持電解質の種類に応じて、通常０．５モル／Ｌ～２．５モル／Ｌの濃度で用いてもよい。支持電解質の濃度が低すぎても高すぎても、イオン伝導度が低下する可能性がある。 The concentration of the supporting electrolyte in the electrolytic solution is usually 1% by mass or more, preferably 5% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less. Depending on the type of supporting electrolyte, it may be used usually at a concentration of 0.5 mol / L to 2.5 mol / L. If the concentration of the supporting electrolyte is too low or too high, the ionic conductivity may decrease.
　非水溶媒としては、支持電解質を溶解できるものであれば特に限定されない。非水溶媒の例を挙げると、ジメチルカーボネート（ＤＭＣ）、エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、メチルエチルカーボネート（ＭＥＣ）などのカーボネート類；γ－ブチロラクトン、ギ酸メチルなどのエステル類；１，２－ジメトキシエタン、テトラヒドロフランなどのエーテル類；スルホラン、ジメチルスルホキシドなどの含硫黄化合物類；などが挙げられる。なかでも、誘電率が高く、安定な電位領域が広いので、カーボネート類が好ましい。非水溶媒は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。非水溶媒の粘度が低いほど、リチウムイオン伝導度が高くなるので、溶媒の種類によりリチウムイオン伝導度を調節することができる。 The non-aqueous solvent is not particularly limited as long as it can dissolve the supporting electrolyte. Examples of non-aqueous solvents include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (MEC); and esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; Among these, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. A non-aqueous solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. The lower the viscosity of the non-aqueous solvent, the higher the lithium ion conductivity. Therefore, the lithium ion conductivity can be adjusted depending on the type of solvent.
　また、電解液には添加剤を含有させてもよい。添加剤としては、例えば、ビニレンカーボネート（ＶＣ）などのカーボネート系の化合物が挙げられる。添加剤は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。また、上記以外の電解液として、例えば、ポリエチレンオキシド、ポリアクリロニトリルなどのポリマー電解質；前記ポリマー電解質に電解液を含浸したゲル状ポリマー電解質；ＬｉＩ、Ｌｉ3Ｎなどの無機固体電解質；などを用いてもよい。 Moreover, you may contain an additive in electrolyte solution. Examples of the additive include carbonate compounds such as vinylene carbonate (VC). An additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. Further, as an electrolytic solution other than the above, for example, a polymer electrolyte such as polyethylene oxide or polyacrylonitrile; a gel polymer electrolyte obtained by impregnating the polymer electrolyte with an electrolytic solution; an inorganic solid electrolyte such as LiI or Li 3 N; Also good.
［セパレータ］
　セパレータとしては、例えば、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂や、芳香族ポリアミド樹脂を含んでなる微孔膜または不織布；無機セラミック粉末を含む多孔質の樹脂コート；などを用いてもよい。具体例を挙げると、ポリオレフィン系（ポリエチレン、ポリプロピレン、ポリブテン、ポリ塩化ビニル）、及びこれらの混合物あるいは共重合体等の樹脂からなる微多孔膜；ポリエチレンテレフタレート、ポリシクロオレフィン、ポリエーテルスルフォン、ポリアミド、ポリイミド、ポリイミドアミド、ポリアラミド、ポリシクロオレフィン、ナイロン、ポリテトラフルオロエチレン等の樹脂からなる微多孔膜；ポリオレフィン系の繊維を織ったもの又はその不織布；絶縁性物質粒子の集合体等が挙げられる。これらの中でも、セパレータ全体の膜厚を薄くし二次電池内の活物質比率を上げて体積あたりの容量を上げることができるため、ポリオレフィン系の樹脂からなる微多孔膜が好ましい。 [Separator]
As the separator, for example, a polyolefin resin such as polyethylene or polypropylene, or a microporous film or nonwoven fabric containing an aromatic polyamide resin; a porous resin coat containing an inorganic ceramic powder; Specific examples include microporous membranes made of polyolefin resins (polyethylene, polypropylene, polybutene, polyvinyl chloride), and resins such as mixtures or copolymers thereof; polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, Examples thereof include a microporous film made of a resin such as polyimide, polyimide amide, polyaramid, polycycloolefin, nylon, and polytetrafluoroethylene; a polyolefin fiber woven or non-woven fabric thereof; an aggregate of insulating substance particles, and the like. Among these, a microporous film made of a polyolefin-based resin is preferable because the thickness of the entire separator can be reduced and the active material ratio in the secondary battery can be increased to increase the capacity per volume.
　セパレータの厚さは、通常０．５μｍ以上、好ましくは１μｍ以上であり、通常４０μｍ以下、好ましくは３０μｍ以下、より好ましくは１０μｍ以下である。この範囲であると、二次電池内でのセパレータによる抵抗が小さくなり、また二次電池を製造する時の作業性に優れる。 The thickness of the separator is usually 0.5 μm or more, preferably 1 μm or more, and usually 40 μm or less, preferably 30 μm or less, more preferably 10 μm or less. Within this range, the resistance due to the separator in the secondary battery is reduced, and the workability when manufacturing the secondary battery is excellent.
［二次電池の製造方法］
　二次電池の具体的な製造方法としては、例えば、正極と負極とをセパレータを介して重ね合わせ、これを電池形状に応じて巻く、折るなどして電池容器に入れ、電池容器に電解液を注入して封口する方法が挙げられる。さらに、必要に応じてエキスパンドメタル；ヒューズ、ＰＴＣ素子などの過電流防止素子；リード板などを入れ、電池内部の圧力上昇、過充放電を防止してもよい。二次電池の形状は、コイン型、ボタン型、シート型、円筒型、角形、扁平型など、何れであってもよい。 [Method for producing secondary battery]
As a specific method for producing a secondary battery, for example, a positive electrode and a negative electrode are overlapped via a separator, and this is wound into a battery container according to the shape of the battery. The method of injecting and sealing is mentioned. Further, if necessary, an expanded metal; an overcurrent prevention element such as a fuse or a PTC element; a lead plate or the like may be inserted to prevent an increase in pressure inside the battery or overcharge / discharge. The shape of the secondary battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.
　以下、本発明について実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。なお、以下の説明において、量を表す「％」及び「部」は、特に断らない限り、質量基準である。
　実施例および比較例において、バインダー組成物の経時安定性、並びに、二次電池におけるガス発生量、高温保存特性、高温サイクル特性、及びピール強度は、それぞれ以下の方法を使用して評価した。さらに、残留モノマー量、体積平均粒子径は以下の方法により測定した。 EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following description, “%” and “part” representing amounts are based on mass unless otherwise specified.
In the examples and comparative examples, the temporal stability of the binder composition, the amount of gas generated in the secondary battery, the high-temperature storage characteristics, the high-temperature cycle characteristics, and the peel strength were evaluated using the following methods, respectively. Furthermore, the residual monomer amount and the volume average particle diameter were measured by the following methods.
＜バインダー組成物の経時安定性＞
　調製したバインダー組成物を４０℃で３ヶ月保存した後、２００メッシュのスクリーンを通過させた。そして、スクリーンを通過せずにスクリーン上に残る残渣の固形分の質量を測定し、かかる質量がバインダー組成物の全固形分量に対して占める比率を算出し、以下の基準にて評価した。値が小さいほど、バインダー組成物が経時安定性に富むことを意味する。
　Ａ：残渣の比率が１００質量ｐｐｍ未満
　Ｂ：残渣の比率が１００質量ｐｐｍ以上５００質量ｐｐｍ未満
　Ｃ：残渣の比率が５００質量ｐｐｍ以上 <Stability of binder composition over time>
The prepared binder composition was stored at 40 ° C. for 3 months, and then passed through a 200 mesh screen. And the mass of the solid content of the residue remaining on the screen without passing through the screen was measured, and the ratio of the mass to the total solid content of the binder composition was calculated and evaluated according to the following criteria. A smaller value means that the binder composition is more stable over time.
A: Residue ratio is less than 100 mass ppm B: Residue ratio is 100 mass ppm or more and less than 500 mass ppm C: Residue ratio is 500 mass ppm or more
＜ガス発生量＞
　作製したラミネートセル型のリチウムイオン二次電池について、２５℃環境下で、０．１Ｃの定電流法によって４．３Ｖまで充電した後、８０℃で５０時間保存した。ラミネートセル型リチウムイオンニ次電池のセルをガラス板にて挟み、マイクロゲージにてセルの厚さを計測した。８０℃保存前のセルの厚さをａ、８０℃で５０時間保存後のセルの厚さをｂとし、８０℃保存前後の厚さの比（ｂ／ａ）を求め、以下の基準により判定した。算出した比（ｂ／ａ）が小さいほど、ガス発生量が少なく、ガス発生抑制効果に優れることを示す。
　Ａ：比（ｂ／ａ）が１．００倍以上１．０５倍以下
　Ｂ：比（ｂ／ａ）が１．０５倍超１．１０倍以下
　Ｃ：比（ｂ／ａ）が１．１０倍超１．１５倍以下
　Ｄ：比（ｂ／ａ）が１．１５倍超１．２０倍以下
　Ｅ：比（ｂ／ａ）が１．２０倍超 <Gas generation>
The manufactured laminated cell type lithium ion secondary battery was charged to 4.3 V by a constant current method of 0.1 C in a 25 ° C. environment, and then stored at 80 ° C. for 50 hours. The cell of the laminated cell type lithium ion secondary battery was sandwiched between glass plates, and the thickness of the cell was measured with a micro gauge. The thickness of the cell before storage at 80 ° C. is a, the thickness of the cell after storage at 80 ° C. for 50 hours is b, and the thickness ratio (b / a) before and after storage at 80 ° C. is determined. did. It shows that the smaller the calculated ratio (b / a), the smaller the gas generation amount and the better the gas generation suppression effect.
A: Ratio (b / a) is 1.00 times or more and 1.05 times or less B: Ratio (b / a) is more than 1.05 times and 1.10 times or less C: Ratio (b / a) is 1.10 times More than twice 1.15 times or less D: Ratio (b / a) is more than 1.15 times and less than 1.20 times E: Ratio (b / a) is more than 1.20 times
＜高温保存特性＞
　作製したラミネートセル型のリチウムイオン二次電池について、２５℃環境下で、０．１Ｃの定電流法によって４．３Ｖまで充電した後、８０℃で１００時間保存した。８０℃保存開始前の開路電圧（Ｏｐｅｎ　ｃｉｒｃｕｉｔ　ｖｏｌｔａｇｅ，以下、「ＯＣＶ」と表記する。）と８０℃で１００時間保存後のセルのＯＣＶを測定し、８０℃保存開始前のＯＣＶに対する８０℃で１００時間保存後のＯＣＶの比をＯＣＶ維持率とし、以下の基準により判定する。ＯＣＶ維持率が大きいほど、高温保存特性に優れる、すなわち寿命特性に優れることを示す。
　Ａ：ＯＣＶ維持率が９９．０％以上
　Ｂ：ＯＣＶ維持率が９８．８％以上９９．０％未満
　Ｃ：ＯＣＶ維持率が９８．６％以上９８．８％未満
　Ｄ：ＯＣＶ維持率が９８．４％以上９８．６％未満
　Ｅ：ＯＣＶ維持率が９８．２％以上９８．４％未満
　Ｆ：ＯＣＶ維持率が９８．０％以上９８．２％未満
　Ｇ：ＯＣＶ維持率が９８．０％未満 <High temperature storage characteristics>
The manufactured laminated cell type lithium ion secondary battery was charged to 4.3 V by a constant current method of 0.1 C in a 25 ° C. environment, and then stored at 80 ° C. for 100 hours. The open circuit voltage (Open circuit voltage, hereinafter referred to as “OCV”) before the start of storage at 80 ° C. and the OCV of the cell after storage for 100 hours at 80 ° C. were measured. The OCV ratio after storage for 100 hours is defined as the OCV maintenance rate, and is determined according to the following criteria. It shows that it is excellent in a high temperature storage characteristic, ie, a lifetime characteristic, so that an OCV maintenance factor is large.
A: OCV maintenance rate is 99.0% or more B: OCV maintenance rate is 98.8% or more and less than 99.0% C: OCV maintenance rate is 98.6% or more and less than 98.8% D: OCV maintenance rate is 98 0.4% or more and less than 98.6% E: OCV maintenance rate is 98.2% or more and less than 98.4% F: OCV maintenance rate is 98.0% or more and less than 98.2% G: OCV maintenance rate is 98.0 %Less than
＜高温サイクル特性＞
　作製したラミネートセル型のリチウムイオン二次電池またはフルコインセル型のリチウムイオン二次電池について、それぞれ６０℃環境下で、０．２Ｃの定電流で４．３Ｖまで充電し、０．２Ｃの定電流で３．０Ｖまで放電する充放電サイクルを行った。充放電サイクルは１００サイクルまで行い、初期放電容量（１サイクル目の放電容量）に対する１００サイクル目の放電容量の比を容量維持率とし、下記の基準で判定した。容量維持率が大きいほど繰り返し充放電による容量減が少なく、高温サイクル特性に優れていることを示す。
　Ａ：容量維持率が９０％以上
　Ｂ：容量維持率が８５％以上９０％未満
　Ｃ：容量維持率が８０％以上８５％未満
　Ｄ：容量維持率が７５％以上８０％未満
　Ｅ：容量維持率が７０％以上７５％未満
　Ｆ：容量維持率が７０％未満 <High temperature cycle characteristics>
The produced laminate cell type lithium ion secondary battery or full coin cell type lithium ion secondary battery was charged to 4.3 V at a constant current of 0.2 C in an environment of 60 ° C., and a constant current of 0.2 C. The charge / discharge cycle which discharges to 3.0V was performed. The charge / discharge cycle was performed up to 100 cycles, and the ratio of the discharge capacity at the 100th cycle to the initial discharge capacity (the discharge capacity at the first cycle) was defined as the capacity maintenance rate, and the determination was made according to the following criteria. The larger the capacity retention rate, the smaller the capacity loss due to repeated charge and discharge, and the better the high-temperature cycle characteristics.
A: Capacity maintenance rate is 90% or more B: Capacity maintenance rate is 85% or more and less than 90% C: Capacity maintenance rate is 80% or more and less than 85% D: Capacity maintenance rate is 75% or more and less than 80% E: Capacity maintenance rate 70% or more and less than 75% F: Capacity maintenance rate is less than 70%
＜ピール強度（負極合材層と集電体との密着性）＞
　作製した二次電池用負極を長さ１００ｍｍ、幅１０ｍｍの長方形状に切り出して試験片とし、負極合材層を有する面を下にし、負極合材層表面にセロハンテープ（ＪＩＳ　Ｚ１５２２に規定されるもの）を貼り付け、集電体の一端を垂直方向に引張り速度５０ｍｍ／分で引っ張って剥がしたときの応力を測定した（なお、セロハンテープは試験台に固定されている）。測定を３回行い、その平均値を求めてこれを剥離ピール強度とし、以下の基準により評価した。剥離ピール強度の値が大きいほど、負極合材層と集電体との密着性に優れることを示す。
　Ａ：剥離ピール強度が３０Ｎ／ｍ以上
　Ｂ：剥離ピール強度が２５Ｎ／ｍ以上３０Ｎ／ｍ未満
　Ｃ：剥離ピール強度が２０Ｎ／ｍ以上２５Ｎ／ｍ未満
　Ｄ：剥離ピール強度が２０Ｎ／ｍ未満 <Peel strength (adhesiveness between negative electrode mixture layer and current collector)>
The produced negative electrode for a secondary battery was cut into a rectangular shape having a length of 100 mm and a width of 10 mm to obtain a test piece. And a stress was measured when one end of the current collector was pulled in a vertical direction at a pulling speed of 50 mm / min and peeled off (the cellophane tape was fixed to the test stand). The measurement was performed three times, the average value was obtained and this was taken as the peel peel strength, and evaluated according to the following criteria. It shows that it is excellent in the adhesiveness of a negative mix layer and a collector, so that the value of peeling peel strength is large.
A: Peel peel strength is 30 N / m or more B: Peel peel strength is 25 N / m or more and less than 30 N / m C: Peel peel strength is 20 N / m or more and less than 25 N / m D: Peel peel strength is less than 20 N / m
＜（メタ）アクリル酸エステル単量体量の測定＞
　バインダー組成物中の（メタ）アクリル酸エステル単量体（残留モノマー）量は、ガスクロマトグラフィーにて測定した。具体的には、まず、バインダー組成物中の粒子状重合体の固形分濃度が１質量％になるよう、アセトンで希釈し、５Ｃろ紙を用いて濾過して測定用サンプルを準備した。そして、準備したサンプルについて、以下の条件でガスクロマトグラフィーを実施した。
　装置：Ａｇｉｌｅｎｔ ６８５０Ａ（アジレント・テクノロジー株式会社製）
　カラム：ＨＰ－１
　平均線速度：１５ｃｍ／ｓ
　注入量：１ｍｌ
　注入口温度：２５０℃
　スプリット比： ２０:１
　検出器：水素炎イオン化型検出器（ＦＩＤ：Flame Ionization Detector）
　検出器温度：２８０℃
　オーブン：４０℃で３分保持した後、１０℃／分で加熱し、２８０℃で５分間保持 <Measurement of (meth) acrylic acid ester monomer amount>
The amount of (meth) acrylic acid ester monomer (residual monomer) in the binder composition was measured by gas chromatography. Specifically, first, a sample for measurement was prepared by diluting with acetone so that the solid content concentration of the particulate polymer in the binder composition was 1% by mass and filtering using 5C filter paper. And about the prepared sample, the gas chromatography was implemented on condition of the following.
Apparatus: Agilent 6850A (manufactured by Agilent Technologies)
Column: HP-1
Average linear velocity: 15 cm / s
Injection volume: 1ml
Inlet temperature: 250 ° C
Split ratio: 20: 1
Detector: Flame ionization detector (FID)
Detector temperature: 280 ° C
Oven: Hold at 40 ° C for 3 minutes, then heat at 10 ° C / minute and hold at 280 ° C for 5 minutes
＜体積平均粒子径＞
　粒子状重合体の体積平均粒子径は、光散乱粒子径測定器（コールター社製、コールターＬＳ２３０）を用いて測定した。 <Volume average particle diameter>
The volume average particle size of the particulate polymer was measured using a light scattering particle size measuring device (Coulter LS230, manufactured by Coulter Inc.).
　以下、本発明の二次電池電極用バインダー組成物を負極の形成に使用した場合、正極の形成に使用した場合についてそれぞれ評価を行った。
　まず、本発明のバインダー組成物を負極の形成に使用した。 Hereinafter, when the binder composition for secondary battery electrodes of the present invention was used for forming a negative electrode, the case where it was used for forming a positive electrode was evaluated.
First, the binder composition of the present invention was used for forming a negative electrode.
（実施例１）
＜バインダー組成物の製造＞
［重合工程１］
　攪拌機付き重合缶Ａに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体として２－エチルヘキシルアクリレート（２－ＥＨＡ）２０部、芳香族ビニル単量体としてスチレン３７．６部、分散剤としてラウリル硫酸ナトリウム（ＬＡＳ）１．２部、イオン交換水３２０部を加えた。この重合缶Ａに、さらに重合開始剤として過硫酸アンモニウム（ＡＰＳ）１．０部及びイオン交換水４０部を加え、７０℃に加温し、９０分攪拌した。
　また、別の重合缶Ｂに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体として２－エチルヘキシルアクリレート（沸点２１５℃）１８０部、芳香族ビニル単量体としてスチレン１５０．４部、酸性基含有単量体としてイタコン酸（ＩＡ）８．０部、分散剤としてラウリル硫酸ナトリウム４．８部及びイオン交換水１９２部を加えて攪拌して、エマルジョンを作製した。このエマルジョンを、約１８０分かけて重合缶Ｂから重合缶Ａに逐次添加した。その後、約１２０分攪拌して、重合転化率（モノマー消費量）が９３％になったところで、４０℃に冷却した。 (Example 1)
<Manufacture of binder composition>
[Polymerization step 1]
In a polymerization vessel A with a stirrer, 20 parts of 2-ethylhexyl acrylate (2-EHA) as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, 37.6 parts of styrene as an aromatic vinyl monomer, as a dispersant 1.2 parts of sodium lauryl sulfate (LAS) and 320 parts of ion exchange water were added. To this polymerization can A, 1.0 part of ammonium persulfate (APS) and 40 parts of ion-exchanged water were further added as a polymerization initiator, and the mixture was heated to 70 ° C. and stirred for 90 minutes.
In another polymerization vessel B, 180 parts of 2-ethylhexyl acrylate (boiling point 215 ° C.) as a (meth) acrylate monomer having a boiling point of 145 ° C. or higher, 150.4 parts of styrene as an aromatic vinyl monomer, acidic An emulsion was prepared by adding 8.0 parts of itaconic acid (IA) as a group-containing monomer and 4.8 parts of sodium lauryl sulfate and 192 parts of ion-exchanged water as a dispersant. This emulsion was sequentially added from polymerization vessel B to polymerization vessel A over about 180 minutes. Thereafter, the mixture was stirred for about 120 minutes, and when the polymerization conversion rate (monomer consumption amount) reached 93%, it was cooled to 40 ° C.
［重合工程２］
　工程１で得られた粒子状重合体を含有する水分散液に対して、レダクトン類化合物としてアスコルビン酸ナトリウム１．２部と、過酸化物としてｔｅｒｔ－ブチルヒドロペルオキシド (ｔ-ＢｕＯＯＨ)１．２部とを添加して、更に４０℃で４時間反応させた。その後、かかる水分散液に対して５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整し、所望の粒子状重合体を含む水分散液（バインダー組成物）を得た。得られたバインダー組成物について、経時安定性を評価した。結果を表１に示す。 [Polymerization step 2]
For the aqueous dispersion containing the particulate polymer obtained in Step 1, 1.2 parts of sodium ascorbate as the reductone compound and tert-butyl hydroperoxide (t-BuOOH) 1.2 as the peroxide The mixture was further reacted at 40 ° C. for 4 hours. Then, 5% sodium hydroxide aqueous solution was added with respect to this aqueous dispersion, and it adjusted to pH8, and obtained the aqueous dispersion (binder composition) containing a desired particulate polymer. The obtained binder composition was evaluated for stability over time. The results are shown in Table 1.
　得られた粒子状重合体の、ガラス転移温度は－６．２℃、体積平均粒子径は０．１６７μｍであった。粒子状重合体中の、沸点１４５℃以上の（メタ）アクリル酸エステル単量体単位の含有割合は５０％、酸性基含有単量体単位の含有割合は２％、芳香族ビニル単量体単位の含有割合は４７％、架橋性単量体単位の含有割合は１％であった。粒子状重合体１００質量部に対する沸点１４５℃以上の（メタ）アクリル酸エステル単量体（２－ＥＨＡ）の含有割合は２０８×１０-6質量部だった。 The obtained particulate polymer had a glass transition temperature of −6.2 ° C. and a volume average particle size of 0.167 μm. The content of the (meth) acrylic acid ester monomer unit having a boiling point of 145 ° C. or higher in the particulate polymer is 50%, the content of the acidic group-containing monomer unit is 2%, and the aromatic vinyl monomer unit. Was 47%, and the crosslinkable monomer unit content was 1%. The content of the (meth) acrylic acid ester monomer (2-EHA) having a boiling point of 145 ° C. or higher with respect to 100 parts by mass of the particulate polymer was 208 × 10 −6 parts by mass.
＜負極用スラリー組成物の調製及び負極の製造＞
　負極活物質として体積平均粒子径２０μｍ、比表面積４．２ｍ2／ｇのグラファイト９８部と、結着剤として上述のバインダー組成物を固形分相当量で１．２部と、ＣＭＣを固形分相当量で０．８部とを混合し、更に水を加えてプラネタリーミキサーで混合して負極用スラリー組成物を調製した。
　この負極用スラリー組成物を厚さ１０μｍの銅箔の片面に塗布し、１１０℃で３時間乾燥した後、ロールプレスして厚さ６０μｍの負極合材層を有する負極を得た。
　得られた負極について、ピール強度を測定した。結果を表１に示す。 <Preparation of slurry composition for negative electrode and production of negative electrode>
98 parts of graphite having a volume average particle diameter of 20 μm and a specific surface area of 4.2 m 2 / g as a negative electrode active material, 1.2 parts of the above binder composition as a binder corresponding to a solid content, and CMC corresponding to a solid content 0.8 part was mixed in an amount, water was further added, and the mixture was mixed with a planetary mixer to prepare a negative electrode slurry composition.
This negative electrode slurry composition was applied to one side of a 10 μm thick copper foil, dried at 110 ° C. for 3 hours, and then roll pressed to obtain a negative electrode having a negative electrode mixture layer having a thickness of 60 μm.
About the obtained negative electrode, peel strength was measured. The results are shown in Table 1.
＜正極用スラリー組成物の調製及び正極の製造＞
　正極活物質としてＣｏ－Ｎｉ－Ｍｎのリチウム複合酸化物系の活物質（製品名：セルシードＮＭＣ６１３、日本化学工業社製。以下、「ＮＭＣ」と記載することがある。）１００部、導電材としてアセチレンブラック２部、及び粘度調整剤としてカルボキシメチルセルロースのナトリウム塩（ＣＭＣ）水溶液を固形分相当量で０．８部となる量を加え、６０分混合した。更に水を加えて希釈した後に、ＢＭ-６１０Ｂバインダー（固形分濃度４０％）を粒子状重合体として１．０部となるように添加し、１０分混合した。これを脱泡処理して艶のある流動性の良い正極用スラリー組成物を得た。
　得られた正極用スラリー組成物を厚さ１８μｍのアルミニウム箔に塗布し、１２０℃で３時間乾燥した後、ロールプレスして厚さ５０μｍの正極合材層を有する正極を得た。 <Preparation of slurry composition for positive electrode and production of positive electrode>
Co-Ni-Mn lithium composite oxide based active material (product name: Cellseed NMC613, manufactured by Nippon Chemical Industry Co., Ltd .; hereinafter sometimes referred to as “NMC”) as a positive electrode active material, as a conductive material 2 parts of acetylene black and a sodium salt (CMC) aqueous solution of carboxymethyl cellulose as a viscosity modifier were added in an amount corresponding to 0.8 part in solid content, and mixed for 60 minutes. After further diluting by adding water, BM-610B binder (solid content concentration 40%) was added as a particulate polymer to 1.0 part and mixed for 10 minutes. This was defoamed to obtain a slurry composition for a positive electrode having gloss and good fluidity.
The obtained positive electrode slurry composition was applied to an aluminum foil having a thickness of 18 μm, dried at 120 ° C. for 3 hours, and then roll-pressed to obtain a positive electrode having a positive electrode mixture layer having a thickness of 50 μm.
＜ラミネートセル型リチウムイオン二次電池の作製＞
　アルミニウムシートと、その両面を被覆するポリプロピレン樹脂とからなるラミネートフィルムを用いて電池容器を作成した。次いで、上記で得た正極および負極それぞれの端部から合材層を除去し、銅箔又はアルミニウム箔が露出した箇所を形成した。正極のアルミニウム箔が露出した箇所にはＮｉタブを、負極の銅箔が露出した箇所にはＣｕタブを溶接した。得られたタブ付きの正極及びタブ付きの負極を、ポリエチレン製の微多孔膜からなるセパレータを挟んで重ねた。電極の面の向きは、正極の合材層側の面と負極の合材層側の面とが対向する向きとした。重ねた電極及びセパレータを、捲回して上記の電池容器に収納した。続いてここに、電解液（ＥＣ／ＤＥＣ＝１／２、１Ｍ ＬｉＰＦ6）を注入した。電解液としては、エチレンカーボネートとジエチルカーボネートを２５℃の下、体積比１：２で混合した混合溶媒に、ＬｉＰＦ6を１モル／Ｌの濃度になるように溶解させて調製したものを用いた。
　次いで、ラミネートフィルムを封止させて本発明のリチウムイオン二次電池であるラミネートセル型リチウムイオン二次電池を作製した。得られたラミネートセル型リチウムイオン二次電池のガス発生量、高温保存特性及び高温サイクル特性を評価した。結果を表１に示す。 <Production of laminated cell type lithium ion secondary battery>
A battery container was prepared using a laminate film made of an aluminum sheet and a polypropylene resin covering both surfaces thereof. Subsequently, the mixture layer was removed from the end portions of the positive electrode and the negative electrode obtained above to form a portion where the copper foil or the aluminum foil was exposed. A Ni tab was welded to the portion where the aluminum foil of the positive electrode was exposed, and a Cu tab was welded to the portion where the copper foil of the negative electrode was exposed. The obtained tabbed positive electrode and tabbed negative electrode were stacked with a separator made of a polyethylene microporous film interposed therebetween. The direction of the surface of the electrode was such that the surface on the positive electrode mixture layer side and the surface of the negative electrode mixture layer side face each other. The stacked electrode and separator were wound and stored in the battery container. Subsequently, an electrolytic solution (EC / DEC = 1/2, 1M LiPF 6 ) was injected therein. As the electrolytic solution, a solution prepared by dissolving LiPF 6 to a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 2 at 25 ° C. was used. .
Next, the laminate film was sealed to produce a laminate cell type lithium ion secondary battery which is the lithium ion secondary battery of the present invention. The amount of gas generation, high temperature storage characteristics, and high temperature cycle characteristics of the obtained laminated cell type lithium ion secondary battery were evaluated. The results are shown in Table 1.
（実施例２）
　沸点１４５℃以上の（メタ）アクリル酸エステル単量体である２－エチルヘキシルアクリレートの配合量、芳香族ビニル単量体であるスチレンの配合量、及び工程（１）における重合転化率をそれぞれ表１に示す通りに変更した以外は実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。なお、各成分の配合量を変更した場合であっても、重合缶Ａ及びＢに含まれる各成分の配合量間の比率は実施例１と同様にした。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Example 2)
Table 1 shows the blending amount of 2-ethylhexyl acrylate, which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, blending amount of styrene, which is an aromatic vinyl monomer, and the polymerization conversion rate in step (1). A binder composition was prepared in the same manner as in Example 1 except that the composition was changed as shown in FIG. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition | polymerization can A and B was made to be the same as that of Example 1. FIG. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（実施例３）
　芳香族ビニル単量体であるスチレンの配合量及び工程（１）における重合転化率を表１に示す通りに変更し、架橋性単量体であるアリルメタクリレートを配合しなかった以外は実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。なお、各成分の配合量を変更した場合であっても、重合缶Ａ及びＢに含まれる各成分の配合量間の比率は実施例１と同様にした。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表１に示す。 (Example 3)
Example 1 except that the blending amount of styrene as an aromatic vinyl monomer and the polymerization conversion rate in the step (1) were changed as shown in Table 1 and allyl methacrylate as a crosslinkable monomer was not blended. In the same manner as above, a binder composition was prepared, and stability over time was evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition | polymerization can A and B was made to be the same as that of Example 1. FIG. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the amount of gas generation, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（実施例４）
　沸点１４５℃以上の（メタ）アクリル酸エステル単量体である２－エチルヘキシルアクリレートの配合量、芳香族ビニル単量体であるスチレンの配合量、及び工程（１）における重合転化率をそれぞれ表１に示す通りに変更し、さらに、その他の単量体としてブタジエンを２０部配合した以外は実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。なお、各成分の配合量を変更した場合であっても、重合缶Ａ及びＢに含まれる各成分の配合量間の比率は実施例１と同様にした。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 Example 4
Table 1 shows the blending amount of 2-ethylhexyl acrylate, which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, blending amount of styrene, which is an aromatic vinyl monomer, and the polymerization conversion rate in step (1). The binder composition was prepared in the same manner as in Example 1 except that 20 parts of butadiene was added as another monomer, and the stability over time was evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition | polymerization can A and B was made to be the same as that of Example 1. FIG. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（実施例５）
　沸点１４５℃以上の（メタ）アクリル酸エステル単量体である２－エチルヘキシルアクリレートの配合量、芳香族ビニル単量体であるスチレンの配合量、及び重合工程１における重合転化率をそれぞれ表１に示す通りに変更した以外は実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。なお、各成分の配合量を変更した場合であっても、重合缶Ａ及びＢに含まれる各成分の配合量間の比率は実施例１と同様にした。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Example 5)
Table 1 shows the blending amount of 2-ethylhexyl acrylate, which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or more, blending amount of styrene, which is an aromatic vinyl monomer, and polymerization conversion rate in polymerization step 1. Except for changing as shown, a binder composition was prepared in the same manner as in Example 1, and stability over time was evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition | polymerization can A and B was made to be the same as that of Example 1. FIG. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（実施例６）
　沸点１４５℃以上の（メタ）アクリル酸エステル単量体として、２－エチルヘキシルアクリレートに代えて、ブチルアクリレートを使用した以外は、実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。なお、各成分の配合量を変更した場合であっても、重合缶Ａ及びＢに含まれる各成分の配合量間の比率は実施例１と同様にした。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Example 6)
A binder composition was prepared in the same manner as in Example 1 except that butyl acrylate was used in place of 2-ethylhexyl acrylate as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher. evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition | polymerization can A and B was made to be the same as that of Example 1. FIG. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（実施例７～１０）
　レダクトン類化合物であるアスコルビン酸ナトリウムを、表１に示すレダクトン類化合物にそれぞれ変更した以外は実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Examples 7 to 10)
A binder composition was prepared in the same manner as in Example 1 except that sodium ascorbate, which is a reductone compound, was changed to the reductone compound shown in Table 1, and the stability over time was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the lithium ion secondary battery. The results are shown in Table 1.
（実施例１１～１４）
　レダクトン類化合物であるアスコルビン酸ナトリウムの配合割合をそれぞれ表１に示す通りに変更し、また、過酸化物であるｔｅｒｔ－ブチルヒドロペルオキシドの配合割合を表１に示す通りに変更した以外は実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル電池型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Examples 11 to 14)
Example 1 except that the blending ratio of sodium ascorbate as a reductone compound was changed as shown in Table 1, and the blending ratio of tert-butyl hydroperoxide as a peroxide was changed as shown in Table 1. In the same manner as in No. 1, a binder composition was prepared, and stability over time was evaluated. Moreover, the laminated cell battery type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（実施例１５）
　過酸化物であるｔｅｒｔ－ブチルヒドロペルオキシドを過酸化ベンゾイル（ＢＰＯ）に変更した以外は実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Example 15)
A binder composition was prepared in the same manner as in Example 1 except that the peroxide tert-butyl hydroperoxide was changed to benzoyl peroxide (BPO), and the stability over time was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（比較例１）
　レダクトン類化合物であるアスコルビン酸ナトリウムを配合せず、工程（２）において、４０℃で２時間反応させた後、８０℃で２時間反応させた以外は、実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Comparative Example 1)
Binder composition in the same manner as in Example 1 except that sodium ascorbate which is a reductone compound is not blended and the reaction is performed at 40 ° C. for 2 hours and then at 80 ° C. for 2 hours in Step (2). Were prepared and the stability over time was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（比較例２）
　沸点１４５℃以上の（メタ）アクリル酸エステル単量体である２－エチルヘキシルアクリレートに代えて、沸点が１００℃のエチルアクリレート（ＥＡ）を使用した以外は実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Comparative Example 2)
A binder composition was prepared in the same manner as in Example 1 except that ethyl acrylate (EA) having a boiling point of 100 ° C. was used instead of 2-ethylhexyl acrylate which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher. Prepared and evaluated for stability over time. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（比較例３）
＜バインダー組成物の製造＞
　攪拌機付き重合缶Ａに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体として２－エチルヘキシルアクリレート（２－ＥＨＡ）２０部、芳香族ビニル単量体としてスチレン３７．６部、分散剤としてラウリル硫酸ナトリウム（ＬＡＳ）１．２部、イオン交換水３２０部を加えた。この重合缶Ａに、さらに重合開始剤として過硫酸アンモニウム（ＡＰＳ）１．０部及びイオン交換水４０部を加え、７０℃に加温し、９０分攪拌した。
　また、別の重合缶Ｂに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体として２－エチルヘキシルアクリレート（沸点２１５℃）１８０部、芳香族ビニル単量体としてスチレン１５０．４部、酸性基含有単量体としてイタコン酸（ＩＡ）８．０部、分散剤としてラウリル硫酸ナトリウム４．８部及びイオン交換水１９２部を加えて攪拌して、エマルジョンを作製した。このエマルジョンを、約１８０分かけて重合缶Ｂから重合缶Ａに逐次添加した。
　その後、約１２０分攪拌して、重合転化率（モノマー消費量）が９３％になったところで、エバポレータを用い、８０℃、１００ｈＰａ（０．１気圧）の条件で８時間かけて減圧蒸留を行った。その後冷却し、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整し、所望の粒子状重合体を含む水分散液（バインダー組成物）を得た。得られたバインダー組成物について、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Comparative Example 3)
<Manufacture of binder composition>
In a polymerization vessel A with a stirrer, 20 parts of 2-ethylhexyl acrylate (2-EHA) as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, 37.6 parts of styrene as an aromatic vinyl monomer, as a dispersant 1.2 parts of sodium lauryl sulfate (LAS) and 320 parts of ion exchange water were added. To this polymerization can A, 1.0 part of ammonium persulfate (APS) and 40 parts of ion-exchanged water were further added as a polymerization initiator, and the mixture was heated to 70 ° C. and stirred for 90 minutes.
In another polymerization vessel B, 180 parts of 2-ethylhexyl acrylate (boiling point 215 ° C.) as a (meth) acrylate monomer having a boiling point of 145 ° C. or higher, 150.4 parts of styrene as an aromatic vinyl monomer, acidic An emulsion was prepared by adding 8.0 parts of itaconic acid (IA) as a group-containing monomer and 4.8 parts of sodium lauryl sulfate and 192 parts of ion-exchanged water as a dispersant. This emulsion was sequentially added from polymerization vessel B to polymerization vessel A over about 180 minutes.
Thereafter, the mixture was stirred for about 120 minutes, and when the polymerization conversion rate (monomer consumption) reached 93%, distillation was performed under reduced pressure over 8 hours using an evaporator at 80 ° C. and 100 hPa (0.1 atm). It was. Thereafter, the mixture was cooled, a 5% aqueous sodium hydroxide solution was added to adjust the pH to 8, and an aqueous dispersion (binder composition) containing a desired particulate polymer was obtained. The obtained binder composition was evaluated for stability over time. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the lithium ion secondary battery. The results are shown in Table 1.
（比較例４）
　レダクトン類化合物であるアスコルビン酸ナトリウムに代えてコハク酸を配合した以外は、実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Comparative Example 4)
A binder composition was prepared in the same manner as in Example 1 except that succinic acid was added instead of sodium ascorbate, which is a reductone compound, and stability over time was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（比較例５）
　工程（２）の実施タイミングを、工程（１）における重合転化率が８１％のときとした以外は、実施例１と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Comparative Example 5)
A binder composition was prepared in the same manner as in Example 1 except that the step (2) was carried out at a polymerization conversion rate of 81% in the step (1), and the temporal stability was evaluated. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
（比較例６）
　比較例６では、工程（２）を実施しなかった。工程（１）の重合転化率が９３％となったところで４０℃に冷却して、過酸化物である過硫酸アンモニウム（ＡＰＳ）０．３質量％を添加して更に４時間反応させた。その後、かかる水分散液に対して５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整し、所望の粒子状重合体を含む水分散液（バインダー組成物）を得た。得られたバインダー組成物について、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１と同様にして負極及びかかる負極を有するラミネートセル型リチウムイオン二次電池を製造した。負極についてはピール強度を評価し、ラミネートセル型リチウムイオン二次電池については、ガス発生量、高温保存特性、及び高温サイクル特性を評価した。結果を表１に示す。 (Comparative Example 6)
In Comparative Example 6, step (2) was not performed. When the polymerization conversion rate in step (1) reached 93%, the mixture was cooled to 40 ° C., 0.3% by mass of ammonium persulfate (APS), which is a peroxide, was added, and the mixture was further reacted for 4 hours. Then, 5% sodium hydroxide aqueous solution was added with respect to this aqueous dispersion, and it adjusted to pH8, and obtained the aqueous dispersion (binder composition) containing a desired particulate polymer. The obtained binder composition was evaluated for stability over time. Moreover, the laminated cell type lithium ion secondary battery which has a negative electrode and this negative electrode was manufactured like Example 1 using the prepared binder composition. The peel strength was evaluated for the negative electrode, and the gas generation amount, high-temperature storage characteristics, and high-temperature cycle characteristics were evaluated for the laminated cell type lithium ion secondary battery. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１より、実施例１～１５のバインダー組成物は、経時安定性が良好であり、かかるバインダー組成物を用いて製造した負極は、ピール強度が良好であり、さらに、かかるバインダー組成物を用いて製造した二次電池は、ガス発生量が低減され、高温保存特性及び高温サイクル特性が良好であることが分かる。一方、レダクトン類化合物であるアスコルビン酸ナトリウムを配合しなかった比較例１では、得られたバインダー組成物中における２－エチルヘキシルアクリレート単量体の残留量が多く、バインダー組成物の経時安定性が低く、且つ、かかるバインダー組成物を用いて製造した負極のピール強度に劣り、二次電池のガス発生量が増加し、高温保存特性及び高温サイクル特性が著しく悪化することが分かる。また、比較例３では、レドックス系における重合を実施しておらず、得られたバインダー組成物中における２－エチルヘキシルアクリレート単量体の残留量が多く、バインダー組成物の経時安定性が低く、且つ、かかるバインダー組成物を用いて製造した負極のピール強度に劣り、二次電池のガス発生量が増加し、高温保存特性及び高温サイクル特性が悪化することが分かる。このことから、バインダー組成物を生成するにあたって、沸点１４５℃以上の残留モノマー（２－エチルヘキシルアクリレート単量体）が残留した場合には、減圧や加熱を用いても当該残留した沸点１４５℃以上の残留モノマーを十分に除去することができないが、レドックス重合を行うことにより、残留モノマーを重合させて、残留モノマー量を低減することができることが分かる。 From Table 1, the binder compositions of Examples 1 to 15 have good stability over time, and the negative electrode produced using such a binder composition has good peel strength. It can be seen that the secondary battery manufactured in this manner has a reduced gas generation amount and good high-temperature storage characteristics and high-temperature cycle characteristics. On the other hand, in Comparative Example 1 in which sodium ascorbate, which is a reductone compound, was not blended, the residual amount of 2-ethylhexyl acrylate monomer in the obtained binder composition was large, and the temporal stability of the binder composition was low. And it turns out that it is inferior to the peel strength of the negative electrode manufactured using this binder composition, the gas generation amount of a secondary battery increases, and a high temperature storage characteristic and a high temperature cycling characteristic deteriorate remarkably. In Comparative Example 3, polymerization in a redox system was not performed, the residual amount of 2-ethylhexyl acrylate monomer in the obtained binder composition was large, and the temporal stability of the binder composition was low. It can be seen that the negative electrode produced using such a binder composition is inferior in peel strength, increases the gas generation amount of the secondary battery, and deteriorates the high-temperature storage characteristics and the high-temperature cycle characteristics. Therefore, when a residual monomer (2-ethylhexyl acrylate monomer) having a boiling point of 145 ° C. or higher remains in the production of the binder composition, the residual boiling point of 145 ° C. or higher is maintained even if reduced pressure or heating is used. It can be seen that the residual monomer cannot be removed sufficiently, but the residual monomer amount can be reduced by performing redox polymerization to polymerize the residual monomer.
　また、レダクトン類化合物であるアスコルビン酸ナトリウムに代えてコハク酸を配合した比較例４でも、同様に得られたバインダー組成物中における２－エチルヘキシルアクリレート単量体の残留量が多く、バインダー組成物の経時安定性が低く、且つ、かかるバインダー組成物を用いて製造した負極のピール強度に劣り、二次電池のガス発生量が増加し、高温保存特性及び高温サイクル特性が著しく悪化することが分かる。また、（メタ）アクリル酸エステル単量体である２－エチルヘキシルアクリレートに代えて、沸点が１００℃のエチルアクリレート（ＥＡ）を使用した比較例２では、バインダー組成物の安定性は良好であり、得られたバインダーを用いて製造した負極のピール強度も良好であり、二次電池のガス発生量も少ないものの、高温保存特性及び高温サイクル特性が悪化することが分かる。これは、バインダー組成物中の粒子状重合体の柔軟性が低下し、バインダー組成物として結着性が低下したため、電池特性に悪影響を及ぼしたことに起因すると考えられる。また、工程（２）の実施タイミングを、工程（１）における重合転化率が８１％のときとした比較例５では、２－エチルヘキシルアクリレート単量体の残留量が多く、得られたバインダー組成物の経時安定性が悪化し、かかるバインダー組成物を用いて製造した二次電池のガス発生量が増加し、高温保存特性及び高温サイクル特性が悪化することが分かる。その理由は、以下のように推測される。すなわち、工程（２）において過酸化物を添加する際に未転化の単量体の比率が比較的高くなると、レドックス系で重合すべき単量体の割合が多くなる。その一方で、レドックス開始剤（アスコルビン酸ナトリウム及びＴｅｒｔ－ブチルヒドロペルオキシド）の配合量は実施例と同様であるため、レドックス重合において未転化の単量体を十分に重合させることができなくなり、結果的に残留モノマー量が増加し、高温保存特性及び高温サイクル特性を劣化させると考えられる。また、レドックス重合系による工程（２）を実施せずに、過酸化物として過硫酸アンモニウム（ＡＰＳ）を用いて残留モノマーを低減させた比較例６では、大量の過酸化物がバインダー組成物中に残留する結果、バインダー組成物の経時安定性及び電池特性が悪化する。 Further, in Comparative Example 4 in which succinic acid was blended instead of sodium ascorbate which is a reductone compound, the residual amount of 2-ethylhexyl acrylate monomer in the binder composition obtained in the same manner was large, and the binder composition It can be seen that the stability over time is low, the peel strength of the negative electrode produced using such a binder composition is inferior, the gas generation amount of the secondary battery is increased, and the high temperature storage characteristics and the high temperature cycle characteristics are remarkably deteriorated. Further, in Comparative Example 2 using ethyl acrylate (EA) having a boiling point of 100 ° C. instead of 2-ethylhexyl acrylate which is a (meth) acrylic acid ester monomer, the stability of the binder composition is good, Although the peel strength of the negative electrode produced using the obtained binder is good and the amount of gas generated in the secondary battery is small, it can be seen that the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate. This is considered to be because the flexibility of the particulate polymer in the binder composition was lowered, and the binding property was lowered as the binder composition, which adversely affected the battery characteristics. Further, in Comparative Example 5 in which the step (2) was carried out at a polymerization conversion rate of 81% in step (1), the residual amount of 2-ethylhexyl acrylate monomer was large, and the resulting binder composition It can be seen that the aging stability of the secondary battery deteriorates, the amount of gas generated in the secondary battery produced using such a binder composition increases, and the high-temperature storage characteristics and high-temperature cycle characteristics deteriorate. The reason is presumed as follows. That is, when the ratio of the unconverted monomer is relatively high when the peroxide is added in the step (2), the ratio of the monomer to be polymerized in the redox system increases. On the other hand, since the compounding amounts of the redox initiator (sodium ascorbate and Tert-butyl hydroperoxide) are the same as in the examples, the unconverted monomer cannot be sufficiently polymerized in the redox polymerization, and the result It is considered that the residual monomer amount increases and the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate. Further, in Comparative Example 6 in which the residual monomer was reduced using ammonium persulfate (APS) as a peroxide without performing the step (2) by the redox polymerization system, a large amount of peroxide was contained in the binder composition. As a result, the stability over time and battery characteristics of the binder composition deteriorate.
　特に、実施例１及び３では、粒子状重合体の形成時に架橋性単量体を用いることで、二次電池の高温保存特性及び高温サイクル特性を向上させることができることが分かる。また、実施例１、４、及び５より、粒子状重合体の形成時に沸点１４５度以上の（メタ）アクリル酸エステル単量体の配合量を調整することで、負極のピール強度を向上させ得ることがわかる。また、実施例１及び実施例７～１０より、アスコルビン酸とその異性体、誘導体、並びにその塩をレダクトン類化合物として用いることで、全ての特性を高い次元で並立しうることがわかる。なお、パルミチン酸アスコルビルを使用した実施例９では、実施例１、７、８、及び１０よりもガス発生量、高温保存特性、高温サイクル特性、及びバインダー組成物の経時安定性に劣るが、これは、パルミチン酸アスコルビルの分子量が比較的大きく、他のアスコルビン酸系のレダクトン類化合物と同様な添加量では、モル数換算の配合量が少なくなり、残留モノマー低減効果が十分に発揮できないことに起因すると考えられる。 In particular, in Examples 1 and 3, it can be seen that the high-temperature storage characteristics and the high-temperature cycle characteristics of the secondary battery can be improved by using a crosslinkable monomer when forming the particulate polymer. Moreover, from Examples 1, 4, and 5, the peel strength of the negative electrode can be improved by adjusting the blending amount of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or more when forming the particulate polymer. I understand that. Further, from Example 1 and Examples 7 to 10, it can be seen that all characteristics can be arranged in a high dimension by using ascorbic acid and its isomers, derivatives, and salts as reductone compounds. In Example 9 using ascorbyl palmitate, the gas generation amount, high-temperature storage characteristics, high-temperature cycle characteristics, and stability over time of the binder composition were inferior to Examples 1, 7, 8, and 10, but this This is because the molecular weight of ascorbyl palmitate is relatively large, and if it is added in the same amount as other ascorbic acid-based reductone compounds, the amount in terms of moles is reduced and the residual monomer reduction effect cannot be fully exhibited. It is thought that.
　特に、実施例１及び１１～１４より、レダクトン類化合物及び過酸化物の配合量を調整することで、残留モノマー量を十分に低減して、ガス発生量を減少させ、高温保存特性及び高温サイクル特性を更に良好にし得ることがわかる。特に、実施例１１及び１３では、レダクトン類化合物であるアスコルビン酸ナトリウムの量が比較的多く、バインダー組成物中に残留したアスコルビン酸がガス発生量を増加させていると考えられる。 In particular, from Examples 1 and 11 to 14, by adjusting the amount of reductone compound and peroxide, the amount of residual monomers can be sufficiently reduced, the amount of gas generated can be reduced, and high temperature storage characteristics and high temperature cycles can be achieved. It can be seen that the characteristics can be further improved. In particular, in Examples 11 and 13, the amount of sodium ascorbate, which is a reductone compound, is relatively large, and it is considered that ascorbic acid remaining in the binder composition increases the gas generation amount.
　次に本発明のバインダー組成物を正極の形成に使用した。 Next, the binder composition of the present invention was used for forming a positive electrode.
（実施例１６）
＜バインダー組成物の製造＞
［重合工程１］
　重合缶Ａに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体として２－エチルヘキシルアクリレート（２－ＥＨＡ）４３部、α,β－不飽和ニトリル単量体としてアクリロニトリル（ＡＮ）５部、分散剤としてラウリル硫酸ナトリウム（ＬＡＳ）１．２部、イオン交換水３２０部を加えた。この重合缶Ａに、さらに重合開始剤として過硫酸アンモニウム（ＡＰＳ）１．０部及びイオン交換水４０部を加え、７０℃に加温し、９０分攪拌した。
　また、別の重合缶Ｂに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体として２－エチルヘキシルアクリレート（沸点２１５℃）２６８．６部、α,β－不飽和ニトリル単量体としてアクリロニトリル７４．４部、酸性基含有単量体としてイタコン酸（ＩＡ）８．０部、分散剤としてラウリル硫酸ナトリウム４．８部及びイオン交換水１９２部を加えて攪拌して、エマルジョンを作製した。このエマルジョンを、約１８０分かけて重合缶Ｂから重合缶Ａに逐次添加した。その後、約１２０分攪拌して、重合転化率（モノマー消費量）が９５％になったところで、４０℃に冷却した。 (Example 16)
<Manufacture of binder composition>
[Polymerization step 1]
In polymerization can A, 43 parts of 2-ethylhexyl acrylate (2-EHA) as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, 5 parts of acrylonitrile (AN) as an α, β-unsaturated nitrile monomer, As a dispersant, 1.2 parts of sodium lauryl sulfate (LAS) and 320 parts of ion-exchanged water were added. To this polymerization can A, 1.0 part of ammonium persulfate (APS) and 40 parts of ion-exchanged water were further added as a polymerization initiator, and the mixture was heated to 70 ° C. and stirred for 90 minutes.
Further, in another polymerization vessel B, 268.6 parts of 2-ethylhexyl acrylate (boiling point 215 ° C.) as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, and acrylonitrile as an α, β-unsaturated nitrile monomer 74.4 parts, 8.0 parts of itaconic acid (IA) as an acidic group-containing monomer, 4.8 parts of sodium lauryl sulfate and 192 parts of ion-exchanged water as dispersants were added and stirred to prepare an emulsion. This emulsion was sequentially added from polymerization vessel B to polymerization vessel A over about 180 minutes. Thereafter, the mixture was stirred for about 120 minutes, and when the polymerization conversion rate (monomer consumption amount) reached 95%, it was cooled to 40 ° C.
［重合工程２］
　工程１で得られた粒子状重合体を含有する水分散液に対して、レダクトン類化合物としてアスコルビン酸ナトリウム１．２部と、過酸化物としてｔｅｒｔ－ブチルヒドロペルオキシド (ｔ-ＢｕＯＯＨ)１．２部とを添加して、更に４０℃で４時間反応させた。その後、かかる水分散液に対して５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整し、所望の粒子状重合体を含む水分散液（バインダー組成物）を得た。得られたバインダー組成物について、経時安定性を評価した。結果を表２に示す。 [Polymerization step 2]
For the aqueous dispersion containing the particulate polymer obtained in Step 1, 1.2 parts of sodium ascorbate as the reductone compound and tert-butyl hydroperoxide (t-BuOOH) 1.2 as the peroxide The mixture was further reacted at 40 ° C. for 4 hours. Then, 5% sodium hydroxide aqueous solution was added with respect to this aqueous dispersion, and it adjusted to pH8, and obtained the aqueous dispersion (binder composition) containing a desired particulate polymer. The obtained binder composition was evaluated for stability over time. The results are shown in Table 2.
　得られた粒子状重合体の、ガラス転移温度は－３８．０℃、体積平均粒子径は０．１１μｍであった。粒子状重合体中の、沸点１４５℃以上の（メタ）アクリル酸エステル単量体単位の含有割合は７８％、酸性基含有単量体単位の含有割合は２％、α,β－不飽和ニトリル単量体単位の含有割合は２０％であった。粒子状重合体１００質量部に対する沸点１４５℃以上の（メタ）アクリル酸エステル単量体（２－ＥＨＡ）の含有割合は２０８×１０-6質量部だった。 The obtained particulate polymer had a glass transition temperature of −38.0 ° C. and a volume average particle size of 0.11 μm. In the particulate polymer, the content ratio of (meth) acrylic acid ester monomer units having a boiling point of 145 ° C. or higher is 78%, the content ratio of acidic group-containing monomer units is 2%, and α, β-unsaturated nitrile. The content ratio of the monomer unit was 20%. The content of the (meth) acrylic acid ester monomer (2-EHA) having a boiling point of 145 ° C. or higher with respect to 100 parts by mass of the particulate polymer was 208 × 10 −6 parts by mass.
＜正極用スラリー組成物の調製＞
　正極活物質としてＣｏ－Ｎｉ－Ｍｎのリチウム複合酸化物系の活物質（製品名：セルシードＮＭＣ６１３、日本化学工業社製。以下、「ＮＭＣ」と記載することがある。）１００部、導電材としてアセチレンブラック２部、及び粘度調整剤としてカルボキシメチルセルロースのナトリウム塩（ＣＭＣ）水溶液を固形分相当量で０．８部となる量を加え、６０分混合した。更に水を加えて希釈した後に、前記のバインダー組成物（固形分濃度４０％）を粒子状重合体として１．０部となるように添加し、１０分混合した。これを脱泡処理して艶のある流動性の良い正極用スラリー組成物を得た。 <Preparation of slurry composition for positive electrode>
Co-Ni-Mn lithium composite oxide based active material (product name: Cellseed NMC613, manufactured by Nippon Chemical Industry Co., Ltd .; hereinafter sometimes referred to as “NMC”) as a positive electrode active material, as a conductive material 2 parts of acetylene black and a sodium salt (CMC) aqueous solution of carboxymethyl cellulose as a viscosity modifier were added in an amount corresponding to 0.8 part in solid content, and mixed for 60 minutes. After further diluting by adding water, the binder composition (solid content concentration 40%) was added as a particulate polymer to 1.0 part and mixed for 10 minutes. This was defoamed to obtain a slurry composition for a positive electrode having gloss and good fluidity.
＜正極の製造＞
　上記正極用スラリー組成物を厚さ１８μｍのアルミニウム箔に塗布し、１２０℃で３時間乾燥した後、ロールプレスして厚さ５０μｍの正極合材層を有する正極を得た。 <Manufacture of positive electrode>
The positive electrode slurry composition was applied to an aluminum foil having a thickness of 18 μm, dried at 120 ° C. for 3 hours, and then roll pressed to obtain a positive electrode having a positive electrode mixture layer having a thickness of 50 μm.
＜負極用スラリー組成物および負極の製造＞
　負極活物質として体積平均粒子径２０μｍ、比表面積４．２ｍ2／ｇのグラファイト９８部と、結着剤として日本ゼオン（株）製の負極用バインダーＢＭ－４００Ｂ（スチレン－ブタジエン共重合体の４０質量％水性分散液）を固形分相当で１．０部と、ＣＭＣを固形分相当で０．８部とを混合し、更に水を加えてプラネタリーミキサーで混合して負極用スラリー組成物を調製した。この負極用スラリー組成物を厚さ１０μｍの銅箔の片面に塗布し、１１０℃で３時間乾燥した後、ロールプレスして厚さ６０μｍの負極合材層を有する負極を得た。 <Production of slurry composition for negative electrode and negative electrode>
98 parts of graphite having a volume average particle diameter of 20 μm and a specific surface area of 4.2 m 2 / g as a negative electrode active material, and negative electrode binder BM-400B (40 of styrene-butadiene copolymer manufactured by Nippon Zeon Co., Ltd.) as a binder. (Mass% aqueous dispersion) is mixed with 1.0 part in solid content and 0.8 part in CMC with solid content. Further, water is added and mixed with a planetary mixer to obtain a slurry composition for negative electrode. Prepared. This negative electrode slurry composition was applied to one side of a 10 μm thick copper foil, dried at 110 ° C. for 3 hours, and then roll pressed to obtain a negative electrode having a negative electrode mixture layer having a thickness of 60 μm.
＜ラミネートセル型リチウムイオン二次電池の作製＞
　アルミニウムシートと、その両面を被覆するポリプロピレン樹脂とからなるラミネートフィルムを用いて電池容器を作成した。次いで、上記で得た正極および負極それぞれの端部から合材層を除去し、銅箔又はアルミニウム箔が露出した箇所を形成した。正極のアルミニウム箔が露出した箇所にはＮｉタブを、負極の銅箔が露出した箇所にはＣｕタブを溶接した。得られたタブ付きの正極及びタブ付きの負極を、ポリエチレン製の微多孔膜からなるセパレータを挟んで重ねた。電極の面の向きは、正極の合材層側の面と負極の合材層側の面とが対向する向きとした。重ねた電極及びセパレータを、捲回して上記の電池容器に収納した。続いてここに、電解液（ＥＣ／ＤＥＣ＝１／２、１Ｍ ＬｉＰＦ6）を注入した。電解液としては、エチレンカーボネートとジエチルカーボネートを２５℃の下、体積比１：２で混合した混合溶媒に、ＬｉＰＦ6を１モル／Ｌの濃度になるように溶解させて調製したものを用いた。
　次いで、ラミネートフィルムを封止させて本発明のリチウムイオン二次電池であるラミネートセル型リチウムイオン二次電池を作製した。得られたラミネートセル型リチウムイオン二次電池のガス発生量、及び高温保存特性を評価した。結果を表２に示す。 <Production of laminated cell type lithium ion secondary battery>
A battery container was prepared using a laminate film made of an aluminum sheet and a polypropylene resin covering both surfaces thereof. Subsequently, the mixture layer was removed from the end portions of the positive electrode and the negative electrode obtained above to form a portion where the copper foil or the aluminum foil was exposed. A Ni tab was welded to the portion where the aluminum foil of the positive electrode was exposed, and a Cu tab was welded to the portion where the copper foil of the negative electrode was exposed. The obtained tabbed positive electrode and tabbed negative electrode were stacked with a separator made of a polyethylene microporous film interposed therebetween. The direction of the surface of the electrode was such that the surface on the positive electrode mixture layer side and the surface of the negative electrode mixture layer side face each other. The stacked electrode and separator were wound and stored in the battery container. Subsequently, an electrolytic solution (EC / DEC = 1/2, 1M LiPF 6 ) was injected therein. As the electrolytic solution, a solution prepared by dissolving LiPF 6 to a concentration of 1 mol / L in a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 2 at 25 ° C. was used. .
Next, the laminate film was sealed to produce a laminate cell type lithium ion secondary battery which is the lithium ion secondary battery of the present invention. The amount of gas generation and high-temperature storage characteristics of the obtained laminated cell type lithium ion secondary battery were evaluated. The results are shown in Table 2.
＜フルコインセル型リチウムイオン二次電池の作製＞
　上記で得られた正極を直径１３ｍｍの円形に切り抜いた。上記で得られた負極を直径１４ｍｍの円形に切り抜いた。厚さ２５μｍの乾式法により製造された単層のポリプロピレン製セパレータ（気孔率５５％）を直径１８ｍｍの円形に切り抜いた。これらを、ポリプロピレン製パッキンを設置したステンレス鋼製のコイン型外装容器（直径２０ｍｍ、高さ１．８ｍｍ、ステンレス鋼厚さ０．２５ｍｍ）中に収納した。外装容器内の円形の電極及びセパレータの配置は、下記の通りとした。円形の正極は、そのアルミニウム箔が外装容器底面に接触するよう配置した。円形のセパレータは、円形の正極と円形の負極との間に介在するよう配置した。円形の負極は、その負極合材層側の面が、円形のセパレータを介して円形の正極の正極合材層側の面に対向するよう配置した。更に負極の上にエキスパンドメタルを載置し、この容器中に電解液（ＥＣ／ＤＥＣ＝１／２、１Ｍ ＬｉＰＦ6）を空気が残らないように注入し、ポリプロピレン製パッキンを介して外装容器に厚さ０．２ｍｍのステンレス鋼のキャップをかぶせて固定し、外装容器を封止して、直径２０ｍｍ、厚さ約３．２ｍｍの本発明のリチウムイオン二次電池であるフルコインセル型リチウムイオン二次電池（コインセルＣＲ２０３２）を作製した。得られたフルコインセル型リチウムイオン二次電池について高温サイクル特性を評価した。結果を表２に示す。 <Production of full coin cell type lithium ion secondary battery>
The positive electrode obtained above was cut into a circle having a diameter of 13 mm. The negative electrode obtained above was cut into a circle having a diameter of 14 mm. A single-layer polypropylene separator (porosity 55%) produced by a dry method having a thickness of 25 μm was cut into a circle having a diameter of 18 mm. These were housed in a stainless steel coin-type outer container (diameter 20 mm, height 1.8 mm, stainless steel thickness 0.25 mm) provided with polypropylene packing. The arrangement of the circular electrodes and separators in the outer container was as follows. The circular positive electrode was disposed so that the aluminum foil was in contact with the bottom surface of the outer container. The circular separator was disposed so as to be interposed between the circular positive electrode and the circular negative electrode. The circular negative electrode was disposed such that the surface on the negative electrode mixture layer side faced the surface on the positive electrode mixture layer side of the circular positive electrode through a circular separator. Further, an expanded metal is placed on the negative electrode, and an electrolytic solution (EC / DEC = 1/2, 1M LiPF 6 ) is injected into the container so that no air remains, and is put into an outer container through a polypropylene packing. A full coin cell type lithium ion battery, which is a lithium ion secondary battery of the present invention having a diameter of 20 mm and a thickness of about 3.2 mm, is sealed by covering with a stainless steel cap having a thickness of 0.2 mm and sealing the outer container. A secondary battery (coin cell CR2032) was produced. The high-temperature cycle characteristics of the obtained full coin cell type lithium ion secondary battery were evaluated. The results are shown in Table 2.
（実施例１７～１８）
　沸点１４５℃以上の（メタ）アクリル酸エステル単量体である２－エチルヘキシルアクリレートの配合量及びα,β－不飽和ニトリル単量体であるアクリロニトリルの配合量をそれぞれ表２に示す通りに変更した以外は実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。なお、各成分の配合量を変更した場合であっても、重合缶Ａ及びＢに含まれる各成分の配合量間の比率は実施例１６と同様にした。そして、得られた粒子状重合体の体積平均粒子径は、実施例１６と同様に０．１１μｍであった。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Examples 17 to 18)
The blending amount of 2-ethylhexyl acrylate which is a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher and the blending amount of acrylonitrile which is an α, β-unsaturated nitrile monomer were changed as shown in Table 2, respectively. Except for this, a binder composition was prepared in the same manner as in Example 16, and the stability over time was evaluated. In addition, even if it was a case where the compounding quantity of each component was changed, the ratio between the compounding quantities of each component contained in superposition | polymerization can A and B was made to be the same as that of Example 16. And the volume average particle diameter of the obtained particulate polymer was 0.11 μm as in Example 16. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（実施例１９）
　沸点１４５℃以上の（メタ）アクリル酸エステル単量体としてｎ－ブチルアクリレート（沸点１４８℃）を使用した以外は実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Example 19)
A binder composition was prepared in the same manner as in Example 16 except that n-butyl acrylate (boiling point 148 ° C.) was used as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, and the stability over time was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（実施例２０～２３）
　レダクトン類化合物であるアスコルビン酸ナトリウムを、表２に示すレダクトン類化合物にそれぞれ変更した以外は実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Examples 20 to 23)
A binder composition was prepared in the same manner as in Example 16 except that sodium ascorbate, which is a reductone compound, was changed to a reductone compound shown in Table 2, and the temporal stability was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（実施例２４～２７）
　レダクトン類化合物であるアスコルビン酸ナトリウムの配合割合をそれぞれ表２に示す通りに変更し、また、過酸化物であるｔｅｒｔ－ブチルヒドロペルオキシドの配合割合を表２に示す通りに変更した以外は実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル電池型リチウムイオン二次及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Examples 24 to 27)
Example 1 except that the blending ratio of sodium ascorbate as a reductone compound was changed as shown in Table 2, and the blending ratio of tert-butyl hydroperoxide as a peroxide was changed as shown in Table 2. A binder composition was prepared in the same manner as in No. 16, and the stability over time was evaluated. Further, using the prepared binder composition, a laminated cell battery type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and high temperature storage characteristics were respectively obtained. In addition, the high-temperature cycle characteristics were evaluated. The results are shown in Table 2.
（実施例２８）
　過酸化物であるｔｅｒｔ－ブチルヒドロペルオキシドを過酸化ベンゾイル（ＢＰＯ）に変更した以外は実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Example 28)
A binder composition was prepared in the same manner as in Example 16 except that the peroxide tert-butyl hydroperoxide was changed to benzoyl peroxide (BPO), and the stability over time was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（比較例７）
　レダクトン類化合物であるアスコルビン酸ナトリウムを配合せず、工程（２）において、４０℃で２時間反応させた後、８０℃で２時間反応させた以外は、実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Comparative Example 7)
Binder composition in the same manner as in Example 16 except that sodium ascorbate which is a reductone compound is not blended, and the reaction is performed at 40 ° C. for 2 hours and then at 80 ° C. for 2 hours in Step (2). Were prepared and the stability over time was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（比較例８）
　（メタ）アクリル酸エステル単量体である２－エチルヘキシルアクリレートに代えて、沸点が１００℃のエチルアクリレート（ＥＡ）を使用した以外は実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Comparative Example 8)
A binder composition was prepared in the same manner as in Example 16 except that ethyl acrylate (EA) having a boiling point of 100 ° C. was used in place of 2-ethylhexyl acrylate which is a (meth) acrylic acid ester monomer, and was stable over time. Sex was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（比較例９）
＜バインダー組成物の製造＞
　重合缶Ａに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体として２－エチルヘキシルアクリレート（２－ＥＨＡ）４３部、α,β－不飽和ニトリル単量体としてアクリロニトリル（ＡＮ）５部、分散剤としてラウリル硫酸ナトリウム（ＬＡＳ）１．２部、イオン交換水３２０部を加えた。この重合缶Ａに、さらに重合開始剤として過硫酸アンモニウム（ＡＰＳ）１．０部及びイオン交換水４０部を加え、７０℃に加温し、９０分攪拌した。
　また、別の重合缶Ｂに、沸点１４５℃以上の（メタ）アクリル酸エステル単量体として２－エチルヘキシルアクリレート（沸点２１５℃）２６８．６部、α,β－不飽和ニトリル単量体としてアクリロニトリル７４．４部、酸性基含有単量体としてイタコン酸（ＩＡ）８．０部、分散剤としてラウリル硫酸ナトリウム４．８部及びイオン交換水１９２部を加えて攪拌して、エマルジョンを作製した。このエマルジョンを、約１８０分かけて重合缶Ｂから重合缶Ａに逐次添加した。その後、約１２０分攪拌し、重合転化率（モノマー消費量）が９５％になったところで、エバポレータを用い、８０℃、１００ｈＰａ（０．１気圧）の条件で８時間かけて減圧蒸留を行った。その後冷却し、５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整し、所望の粒子状重合体を含む水分散液（バインダー組成物）を得た。得られたバインダー組成物について、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Comparative Example 9)
<Manufacture of binder composition>
In polymerization can A, 43 parts of 2-ethylhexyl acrylate (2-EHA) as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, 5 parts of acrylonitrile (AN) as an α, β-unsaturated nitrile monomer, As a dispersant, 1.2 parts of sodium lauryl sulfate (LAS) and 320 parts of ion-exchanged water were added. To this polymerization can A, 1.0 part of ammonium persulfate (APS) and 40 parts of ion-exchanged water were further added as a polymerization initiator, and the mixture was heated to 70 ° C. and stirred for 90 minutes.
Further, in another polymerization vessel B, 268.6 parts of 2-ethylhexyl acrylate (boiling point 215 ° C.) as a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher, and acrylonitrile as an α, β-unsaturated nitrile monomer 74.4 parts, 8.0 parts of itaconic acid (IA) as an acidic group-containing monomer, 4.8 parts of sodium lauryl sulfate and 192 parts of ion-exchanged water as dispersants were added and stirred to prepare an emulsion. This emulsion was sequentially added from polymerization vessel B to polymerization vessel A over about 180 minutes. Thereafter, the mixture was stirred for about 120 minutes, and when the polymerization conversion rate (monomer consumption) reached 95%, distillation was performed under reduced pressure over 8 hours using an evaporator at 80 ° C. and 100 hPa (0.1 atm). . Thereafter, the mixture was cooled, a 5% aqueous sodium hydroxide solution was added to adjust the pH to 8, and an aqueous dispersion (binder composition) containing a desired particulate polymer was obtained. The obtained binder composition was evaluated for stability over time. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（比較例１０）
　レダクトン類化合物であるアスコルビン酸ナトリウムに代えてコハク酸を配合した以外は、実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Comparative Example 10)
A binder composition was prepared in the same manner as in Example 16 except that succinic acid was added instead of sodium ascorbate, which is a reductone compound, and stability over time was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（比較例１１）
　工程（２）の実施タイミングを、工程（１）における重合転化率が８０％のときとした以外は、実施例１６と同様にしてバインダー組成物を調製し、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Comparative Example 11)
A binder composition was prepared in the same manner as in Example 16 except that the step (2) was carried out at a polymerization conversion rate of 80% in the step (1), and the temporal stability was evaluated. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
（比較例１２）
　比較例１２では、工程（２）を実施しなかった。工程（１）の重合転化率が９５％となったところで４０℃に冷却して、過酸化物である過硫酸アンモニウム（ＡＰＳ）０．３質量％を添加して更に４時間反応させた。その後、かかる水分散液に対して５％水酸化ナトリウム水溶液を添加して、ｐＨ８に調整し、所望の粒子状重合体を含む水分散液（バインダー組成物）を得た。得られたバインダー組成物について、経時安定性を評価した。また、調製したバインダー組成物を用いて、実施例１６と同様にしてラミネートセル型リチウムイオン二次電池及びフルコインセル型リチウムイオン二次電池を製造して、それぞれ、ガス発生量、及び高温保存特性、並びに高温サイクル特性を評価した。結果を表２に示す。 (Comparative Example 12)
In Comparative Example 12, step (2) was not performed. When the polymerization conversion rate in step (1) reached 95%, the mixture was cooled to 40 ° C., 0.3% by mass of ammonium persulfate (APS) as a peroxide was added, and the reaction was further continued for 4 hours. Then, 5% sodium hydroxide aqueous solution was added with respect to this aqueous dispersion, and it adjusted to pH8, and obtained the aqueous dispersion (binder composition) containing a desired particulate polymer. The obtained binder composition was evaluated for stability over time. Further, using the prepared binder composition, a laminated cell type lithium ion secondary battery and a full coin cell type lithium ion secondary battery were produced in the same manner as in Example 16, and the gas generation amount and the high temperature storage characteristics were respectively obtained. As well as high temperature cycle characteristics. The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表２より、実施例１６～２８のバインダー組成物は、経時安定性が良好であり、且つ、かかるバインダー組成物を用いて製造した二次電池は、ガス発生量が低減され、高温保存特性及び高温サイクル特性が良好であることが分かる。一方、レダクトン類化合物であるアスコルビン酸ナトリウムを配合しなかった比較例７では、得られたバインダー組成物中における２－エチルヘキシルアクリレート単量体の残留量が多く、バインダー組成物の経時安定性が低く、且つ、かかるバインダー組成物を用いて製造した二次電池のガス発生量が増加し、高温保存特性及び高温サイクル特性が著しく悪化することが分かる。また、比較例９では、レドックス系における重合を実施しておらず、得られたバインダー組成物中における２－エチルヘキシルアクリレート単量体の残留量が多く、バインダー組成物の経時安定性が低く、且つ、かかるバインダー組成物を用いて製造した二次電池のガス発生量が増加し、高温保存特性及び高温サイクル特性が悪化することが分かる。このことから、バインダー組成物を生成するにあたって、沸点１４５℃以上の残留モノマー（２－エチルヘキシルアクリレート単量体）が残留した場合には、減圧や加熱を用いても当該残留した沸点１４５℃以上の残留モノマーを十分に除去することができないが、レドックス重合を行うことにより、残留モノマーを重合させて、残留モノマー量を低減することができることが分かる。 From Table 2, the binder compositions of Examples 16 to 28 have good temporal stability, and the secondary battery produced using such a binder composition has a reduced amount of gas generation, high temperature storage characteristics and It can be seen that the high-temperature cycle characteristics are good. On the other hand, in Comparative Example 7 in which sodium ascorbate as a reductone compound was not blended, the residual amount of 2-ethylhexyl acrylate monomer in the obtained binder composition was large, and the stability of the binder composition with time was low. And it turns out that the gas generation amount of the secondary battery manufactured using this binder composition increases, and a high temperature storage characteristic and a high temperature cycling characteristic deteriorate remarkably. In Comparative Example 9, polymerization in a redox system was not performed, the residual amount of 2-ethylhexyl acrylate monomer in the obtained binder composition was large, the stability of the binder composition with time was low, and It can be seen that the amount of gas generated in the secondary battery produced using such a binder composition increases, and the high-temperature storage characteristics and high-temperature cycle characteristics deteriorate. Therefore, when a residual monomer (2-ethylhexyl acrylate monomer) having a boiling point of 145 ° C. or higher remains in the production of the binder composition, the residual boiling point of 145 ° C. or higher is maintained even if reduced pressure or heating is used. It can be seen that the residual monomer cannot be removed sufficiently, but the residual monomer amount can be reduced by performing redox polymerization to polymerize the residual monomer.
　また、レダクトン類化合物であるアスコルビン酸ナトリウムに代えてコハク酸を配合した比較例１０でも、同様に得られたバインダー組成物中における２－エチルヘキシルアクリレート単量体の残留量が多く、バインダー組成物の経時安定性が低く、且つ、かかるバインダー組成物を用いて製造した二次電池のガス発生量が増加し、高温保存特性及び高温サイクル特性が著しく悪化することが分かる。また、（メタ）アクリル酸エステル単量体である２－エチルヘキシルアクリレートに代えて、沸点が１００℃のエチルアクリレート（ＥＡ）を使用した比較例８では、バインダー組成物の安定性は良好であり、得られたバインダーを用いて製造した二次電池のガス発生量も少ないものの、高温保存特性及び高温サイクル特性が悪化することが分かる。これは、バインダー組成物中の粒子状重合体の柔軟性が低下し、バインダー組成物として結着性が低下したため、電池特性に悪影響を及ぼしたことに起因すると考えられる。また、工程（２）の実施タイミングを、工程（１）における重合転化率が８０％のときとした比較例１１では、２－エチルヘキシルアクリレート単量体の残留量が多く、得られたバインダー組成物を用いて製造した二次電池のガス発生量が増加し、高温保存特性及び高温サイクル特性が悪化することが分かる。その理由は、以下のように推測される。すなわち、工程（２）において過酸化物を添加する際に未転化の単量体の比率が比較的高くなると、レドックス系で重合すべき単量体の割合が多くなる。その一方で、レドックス開始剤（アスコルビン酸ナトリウム及びＴｅｒｔ－ブチルヒドロペルオキシド）の配合量は実施例と同様であるため、レドックス重合において未転化の単量体を十分に重合させることができなくなり、結果的に残留モノマー量が増加し、高温保存特性及び高温サイクル特性を劣化させると考えられる。また、レドックス重合系による工程（２）を実施せずに、過酸化物として過硫酸アンモニウム（ＡＰＳ）を用いて残留モノマーを低減させた比較例１２では、バインダー組成物の経時安定性は良好であり、二次電池のガス発生も少なくないが、バインダー組成物中における残留モノマー量を十分に低減させることができず、電池特性は悪化する。 Further, in Comparative Example 10 in which succinic acid was blended instead of sodium ascorbate which is a reductone compound, the residual amount of 2-ethylhexyl acrylate monomer in the binder composition obtained in the same manner was large, and the binder composition It can be seen that the stability over time is low and the amount of gas generated in the secondary battery produced using such a binder composition increases, and the high-temperature storage characteristics and the high-temperature cycle characteristics are remarkably deteriorated. In addition, in Comparative Example 8 using ethyl acrylate (EA) having a boiling point of 100 ° C. instead of 2-ethylhexyl acrylate which is a (meth) acrylic acid ester monomer, the stability of the binder composition is good, Although the amount of gas generated in the secondary battery produced using the obtained binder is small, it can be seen that the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate. This is considered to be because the flexibility of the particulate polymer in the binder composition was lowered, and the binding property was lowered as the binder composition, which adversely affected the battery characteristics. Further, in Comparative Example 11 in which the step (2) was carried out at a polymerization conversion rate of 80% in step (1), the residual amount of 2-ethylhexyl acrylate monomer was large, and the resulting binder composition It can be seen that the amount of gas generated in the secondary battery manufactured using the battery increases, and the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate. The reason is presumed as follows. That is, when the ratio of the unconverted monomer is relatively high when the peroxide is added in the step (2), the ratio of the monomer to be polymerized in the redox system increases. On the other hand, since the compounding amounts of the redox initiator (sodium ascorbate and Tert-butyl hydroperoxide) are the same as in the examples, the unconverted monomer cannot be sufficiently polymerized in the redox polymerization, and the result It is considered that the residual monomer amount increases and the high-temperature storage characteristics and the high-temperature cycle characteristics deteriorate. Further, in Comparative Example 12 in which the residual monomer was reduced using ammonium persulfate (APS) as a peroxide without carrying out the step (2) by the redox polymerization system, the temporal stability of the binder composition was good. The gas generation of the secondary battery is not a little, but the residual monomer amount in the binder composition cannot be sufficiently reduced, and the battery characteristics deteriorate.
　特に、実施例１６及び２４～２７より、レダクトン類化合物及び過酸化物の配合量を調整することで、残留モノマー量を十分に低減して、ガス発生量を減少させ、高温保存特性及び高温サイクル特性を更に良好にし得ることがわかる。 In particular, from Examples 16 and 24 to 27, by adjusting the blending amount of the reductone compound and the peroxide, the residual monomer amount is sufficiently reduced, the gas generation amount is reduced, and the high temperature storage characteristics and the high temperature cycle are reduced. It can be seen that the characteristics can be further improved.
　本発明によれば、残留モノマーに起因したガスの発生が抑制され、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することができる、経時安定性に優れた二次電池電極用バインダー組成物を提供することができる。また、本発明によれば、当該バインダー組成物を用いた二次電池電極用スラリー組成物を提供することができる。更に、本発明によれば、当該二次電池電極用スラリー組成物を用いた二次電池用電極を提供することができる。
　また、本発明によれば、当該二次電池用電極を用いた、残留モノマーに起因したガスの発生が抑制され、良好な高温保存特性及び高温サイクル特性を有する二次電池を提供することができる。 ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of the gas resulting from a residual monomer is suppressed, and the secondary battery electrode which was excellent in temporal stability which can provide the secondary battery which has a favorable high temperature storage characteristic and a high temperature cycling characteristic can be provided. A binder composition can be provided. Moreover, according to this invention, the slurry composition for secondary battery electrodes using the said binder composition can be provided. Furthermore, according to this invention, the electrode for secondary batteries using the said slurry composition for secondary battery electrodes can be provided.
In addition, according to the present invention, it is possible to provide a secondary battery using the secondary battery electrode, in which the generation of gas due to residual monomer is suppressed, and which has good high-temperature storage characteristics and high-temperature cycle characteristics. .

Claims (10)

  1. 　粒子状重合体、レダクトン類化合物およびその酸化体の少なくとも一方、及び水を含み、
    　前記粒子状重合体は、沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を重合してなり、
    　前記沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合は、前記粒子状重合体１００質量部に対して１×１０-6質量部以上１５００×１０-6質量部以下である、二次電池電極用バインダー組成物。     Including at least one of a particulate polymer, a reductone compound and an oxidant thereof, and water,
    The particulate polymer is formed by polymerizing a monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher.
    The content ratio of the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is 1 × 10 −6 parts by mass to 1500 × 10 −6 parts by mass with respect to 100 parts by mass of the particulate polymer. A binder composition for secondary battery electrodes.
  2. 　前記レダクトン類化合物およびその酸化体の少なくとも一方が、（イソ）アスコルビン酸及びその塩、並びに、それらの酸化体から選択される少なくとも１種である、請求項１に記載の二次電池電極用バインダー組成物。 2. The binder for a secondary battery electrode according to claim 1, wherein at least one of the reductone compound and its oxidant is at least one selected from (iso) ascorbic acid and its salt and their oxidant. Composition.
  3. 　前記レダクトン類化合物およびその酸化体の少なくとも一方の含有割合が、前記粒子状重合体１００質量部あたり、０．０５質量部以上５質量部以下である、請求項１又は２に記載の二次電池電極用バインダー組成物。 The secondary battery according to claim 1 or 2, wherein a content ratio of at least one of the reductone compound and its oxidant is 0.05 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the particulate polymer. Electrode binder composition.
  4. 　前記単量体混合物は、さらに架橋性単量体を含む、請求項１～３のいずれか一項に記載の二次電池電極用バインダー組成物。 The binder composition for a secondary battery electrode according to any one of claims 1 to 3, wherein the monomer mixture further contains a crosslinkable monomer.
  5. 　前記単量体混合物は、さらに（メタ）アクリロニトリル単量体を５～３５質量％含む、請求項１～３のいずれか一項に記載の二次電池電極用バインダー組成物。 The binder composition for a secondary battery electrode according to any one of claims 1 to 3, wherein the monomer mixture further contains 5 to 35 mass% of a (meth) acrylonitrile monomer.
  6. 　前記沸点が１４５℃以上の（メタ）アクリル酸エステル単量体が、２－エチルヘキシルアクリレートである、請求項１～５のいずれか一項に記載の二次電池電極用バインダー組成物。 The binder composition for a secondary battery electrode according to any one of claims 1 to 5, wherein the (meth) acrylic acid ester monomer having a boiling point of 145 ° C or higher is 2-ethylhexyl acrylate.
  7. 　沸点１４５℃以上の（メタ）アクリル酸エステル単量体を含む単量体混合物を重合転化率が９０質量％以上となるまで水中で重合し、重合体と未反応の単量体とを含む混合物を得る工程（１）と、
    　前記工程（１）の後、前記混合物にレダクトン類化合物および過酸化物を添加して前記未反応の単量体を重合し、前記沸点１４５℃以上の（メタ）アクリル酸エステル単量体の含有割合を、重合体１００質量部に対して１×１０-6質量部以上１５００×１０-6質量部以下にする工程（２）とを含む、
    　請求項１～６のいずれか一項に記載の二次電池電極用バインダー組成物の製造方法。     A monomer mixture containing a (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is polymerized in water until the polymerization conversion becomes 90% by mass or more, and a mixture containing a polymer and an unreacted monomer (1) to obtain
    After the step (1), a reductone compound and a peroxide are added to the mixture to polymerize the unreacted monomer, and the (meth) acrylic acid ester monomer having a boiling point of 145 ° C. or higher is contained. Including a step (2) in which the ratio is 1 × 10 −6 parts by mass to 1500 × 10 −6 parts by mass with respect to 100 parts by mass of the polymer,
    The method for producing a binder composition for a secondary battery electrode according to any one of claims 1 to 6.
  8. 　請求項１～６のいずれか一項に記載の二次電池電極用バインダー組成物及び電極活物質を含む、二次電池電極用スラリー組成物。 A slurry composition for a secondary battery electrode, comprising the binder composition for a secondary battery electrode according to any one of claims 1 to 6 and an electrode active material.
  9. 　集電体上に、請求項８に記載の二次電池電極用スラリー組成物を塗布し、前記集電体上に塗布された二次電池電極用スラリー組成物を乾燥して得られる、二次電池用電極。 A secondary battery electrode slurry composition according to claim 8 is applied on a current collector, and the secondary battery electrode slurry composition applied on the current collector is dried to obtain a secondary battery electrode. Battery electrode.
  10. 　正極、負極、電解液及びセパレータを備え、前記正極および前記負極の少なくとも一方が、請求項９に記載の二次電池用電極である、二次電池。 A secondary battery comprising a positive electrode, a negative electrode, an electrolytic solution, and a separator, wherein at least one of the positive electrode and the negative electrode is the electrode for a secondary battery according to claim 9.
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WO2019181871A1 (en) * 2018-03-23 2019-09-26 日本ゼオン株式会社 Secondary battery binder composition, secondary battery electrode conductive paste, secondary battery electrode slurry composition, method for producing secondary battery electrode slurry composition, secondary battery electrode, and secondary battery
JP7415915B2 (en) 2018-03-23 2024-01-17 日本ゼオン株式会社 Binder composition for secondary batteries, conductive material paste for secondary battery electrodes, slurry composition for secondary battery electrodes, method for producing slurry composition for secondary battery electrodes, electrode for secondary batteries, and secondary battery
CN115710149A (en) * 2022-11-30 2023-02-24 西安近代化学研究所 DAP-4-based composite explosive particles and preparation method thereof
CN115710149B (en) * 2022-11-30 2024-02-20 西安近代化学研究所 DAP-4-based composite explosive particle and preparation method thereof

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