WO2023120066A1 - Electrode binder copolymer for non-aqueous secondary battery, electrode binder resin composition for non-aqueous secondary battery, and non-aqueous secondary battery electrode - Google Patents

Electrode binder copolymer for non-aqueous secondary battery, electrode binder resin composition for non-aqueous secondary battery, and non-aqueous secondary battery electrode Download PDF

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Publication number
WO2023120066A1
WO2023120066A1 PCT/JP2022/044108 JP2022044108W WO2023120066A1 WO 2023120066 A1 WO2023120066 A1 WO 2023120066A1 JP 2022044108 W JP2022044108 W JP 2022044108W WO 2023120066 A1 WO2023120066 A1 WO 2023120066A1
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electrode
mass
aqueous secondary
secondary battery
monomer
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PCT/JP2022/044108
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French (fr)
Japanese (ja)
Inventor
亮介 池端
勇汰 川原
秀雄 堀越
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株式会社レゾナック
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Publication of WO2023120066A1 publication Critical patent/WO2023120066A1/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • 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
    • H01M4/64—Carriers or collectors
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • 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

Definitions

  • the present invention relates to an electrode binder copolymer for non-aqueous secondary batteries, an electrode binder resin composition for non-aqueous secondary batteries, and a non-aqueous secondary battery electrode.
  • a non-aqueous secondary battery has a configuration including a positive electrode using a metal oxide as an active material, a negative electrode using a carbon material such as graphite as an active material, and an electrolyte, and ions move between the positive electrode and the negative electrode. It is a secondary battery in which charging and discharging of the battery are performed by.
  • Non-aqueous secondary batteries are used as power sources for notebook computers, mobile phones, power tools, and electronic/communication devices in terms of miniaturization and weight reduction. Recently, it is also used for electric vehicles and hybrid vehicles from the viewpoint of environmental vehicle application. Under these circumstances, there is a strong demand for non-aqueous secondary batteries to have higher output, higher capacity, longer life, and the like.
  • the binder used for the positive electrode and negative electrode has the role of binding the active materials together and the active material and the current collector.
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • the present invention provides an electrode binder copolymer and an electrode binder resin composition that can provide an electrode having an electrode active material layer with high peel strength against a current collector and provide a non-aqueous secondary battery with good charge-discharge cycle characteristics.
  • the purpose is to provide goods.
  • Another object of the present invention is to provide a non-aqueous secondary battery electrode that has an electrode active material layer with high peel strength against a current collector and that provides a non-aqueous secondary battery with good charge-discharge cycle characteristics. do.
  • a structural unit derived from the monomer (a1) is a (meth)acrylic acid alkyl ester having one ethylenically unsaturated bond contained in the molecule, and a hydrocarbon having one ethylenically unsaturated bond contained in the molecule.
  • the monomer (a2) is a compound having one ethylenically unsaturated bond and an anionic functional group
  • the internal cross-linking agent (a3) is a compound having two or more ethylenically unsaturated bonds in one molecule
  • the monomer (a4) is a compound represented by the following formula (1), Containing 50% by mass or more and 98% by mass or less of structural units derived from the monomer (a1), Containing 1.0% by mass or more and 15% by mass or less of structural units derived from the monomer (a2), Containing 0.020% by mass or more and 10% by mass or less of structural units derived from the internal cross-linking agent (a3),
  • An electrode binder copolymer for a non-aqueous secondary battery comprising 0.010% by mass or more and 20% by mass or less of a structural unit derived from the monomer (a4).
  • R 1 is an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.
  • a current collector made of a metal foil
  • a non-aqueous secondary battery electrode comprising an electrode active material layer formed on the current collector, A non-aqueous secondary battery electrode, wherein the electrode active material layer comprises the electrode binder copolymer for a non-aqueous secondary battery according to any one of [1] to [7], and an electrode active material.
  • a non-aqueous secondary battery comprising a positive electrode and a negative electrode, A non-aqueous secondary battery in which at least one of the positive electrode and the negative electrode contains the electrode binder copolymer for a non-aqueous secondary battery according to any one of [1] to [7].
  • an electrode having an electrode active material layer with high peel strength against a current collector can be obtained, and an electrode binder for a non-aqueous secondary battery that can obtain a non-aqueous secondary battery with good charge-discharge cycle characteristics can be obtained.
  • a polymer and an electrode binder resin composition for a non-aqueous secondary battery can be provided.
  • it is possible to provide a non-aqueous secondary battery electrode that has an electrode active material layer with high peel strength against a current collector and that provides a non-aqueous secondary battery with good charge-discharge cycle characteristics. can.
  • (Meth)acrylic is a generic term for acrylic and methacrylic
  • (meth)acrylate is a generic term for acrylate and methacrylate.
  • Non-volatile matter is the component remaining after weighing 1 g of the composition in an aluminum dish with a diameter of 5 cm and drying it at 105°C for 1 hour while circulating air in a dryer at 1 atmosphere (1013 hPa).
  • Forms of the composition include, but are not limited to, solutions, dispersions, and slurries.
  • Non-volatile content concentration is the mass ratio (mass%) of the non-volatile content after drying under the above conditions with respect to the mass (1 g) of the composition before drying.
  • Ethylenically unsaturated bond refers to an ethylenically unsaturated bond having radical polymerizability unless otherwise specified.
  • a structural unit derived from a compound having an ethylenically unsaturated bond is the chemical structure of the portion other than the ethylenically unsaturated bond of the compound and the structure of the polymer. It is assumed that the chemical structure of the portion other than the portion forming the main chain of the unit is the same.
  • a structural unit derived from acrylic acid has a COOH structure in a portion other than the main chain as a polymer.
  • an anionic functional group such as a carboxy group may also form a salt.
  • COONH 4 is also a carboxy group.
  • the electrode binder copolymer (A) for non-aqueous secondary batteries according to the present embodiment (hereinafter sometimes referred to as copolymer (A)) is a binder that can be used for electrodes for non-aqueous secondary batteries. It is a copolymer.
  • the electrode binder copolymer for non-aqueous secondary batteries (A) includes a structural unit derived from the monomer (a1) described later, a structural unit derived from the monomer (a2) described later, and an internal crosslinked polymer described later. It contains a structural unit derived from the agent (a3) and a structural unit derived from the monomer (a4) described below.
  • the copolymer (A) may contain structural units derived from other monomers (a5).
  • the monomer (a1) is a (meth)acrylic acid alkyl ester having one ethylenically unsaturated bond contained in the molecule, and a hydrocarbon compound having one ethylenically unsaturated bond contained in the molecule. At least one selected from the group consisting of In the present embodiment, the hydrocarbon compound is a hydrocarbon compound that does not have other functional groups such as anionic functional groups and hydroxy groups other than ethylenically unsaturated bonds.
  • the (meth)acrylic acid alkyl ester has a hydrocarbon structure except for the (meth)acryloyloxy group.
  • the monomer (a1) preferably contains both the (meth)acrylic acid alkyl ester and the hydrocarbon compound. From the viewpoint of adhesion between the electrode active material and the copolymer (A), the monomer (a1) preferably contains an aromatic compound having an ethylenically unsaturated bond.
  • the monomer (a1) may contain only one compound, or may contain two or more compounds.
  • Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate. , tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate and the like. .
  • At least one compound selected from the group consisting of methyl (meth)acrylate and 2-ethylhexyl (meth)acrylate is preferred.
  • Hydrocarbon compounds containing one ethylenically unsaturated bond in the molecule include, for example, aromatic compounds having an ethylenically unsaturated bond.
  • aromatic compounds having an ethylenically unsaturated bond include vinyl aromatic compounds such as styrene compounds, vinylnaphthalene compounds and vinylbiphenyl compounds.
  • the styrene-based compound the group consisting of styrene, t-butylstyrene, ⁇ -methylstyrene, p-methylstyrene, and 1,1-diphenylethylene from the viewpoint of improving the adhesion of the copolymer (A) to the electrode active material.
  • At least one compound selected from is preferred, styrene and ⁇ -methylstyrene are more preferred, and styrene is even more preferred.
  • hydrocarbon compounds having one ethylenically unsaturated bond in the molecule include aliphatic hydrocarbon compounds having an ethylenically unsaturated bond.
  • Monomer (a2) is a compound having one ethylenically unsaturated bond and an anionic functional group.
  • the monomer (a2) is a compound that has an ethylenically unsaturated bond and does not have multiple independent ethylenically unsaturated bonds.
  • the monomer (a2) may be only one type of compound, or may contain two or more types of compounds.
  • Examples of the anionic functional group possessed by the monomer (a2) include a carboxy group, a sulfo group and a phosphate group.
  • the monomer (a2) is preferably a compound having at least one of a carboxy group and a sulfo group, more preferably a compound having a carboxy group.
  • Examples of the monomer (a2) include compounds having an ethylenically unsaturated bond and a carboxy group. Examples thereof include unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and half esters of unsaturated dicarboxylic acids.
  • the monomer (a2) contains at least one of (meth)acrylic acid and itaconic acid. preferably included.
  • At least part of the structural units derived from the monomer (a2) contained in the copolymer (A) may form a salt with a basic substance.
  • a carboxyl group and a basic substance may form a salt.
  • a salt may be formed by polymerizing a monomer (a2), at least a part of which is a carboxylate, as a starting material.
  • At least part of the structural units derived from the monomer (a2) contained in the copolymer (A) may be converted into a salt by adding a basic substance after the synthesis of the copolymer (A).
  • the salt-forming monomer (a2) include sodium (meth)acrylate and sodium p-styrenesulfonate.
  • the monomer (a2) preferably contains at least one of a sulfonic acid having an ethylenically unsaturated bond and a salt thereof, more preferably a sulfonate having an ethylenically unsaturated bond.
  • the sulfonic acid preferably contains an aromatic vinyl compound having a sulfo group, and more preferably contains p-styrenesulfonic acid.
  • the sulfonate preferably contains a salt of an aromatic vinyl compound having a sulfo group, and more preferably contains a p-styrenesulfonate. From the viewpoint of improving the stability of polymerization, sodium p-styrenesulfonate ( (Also called sodium p-styrenesulfonate).
  • compounds having an ethylenically unsaturated bond and a phosphate group include 2-methacryloyloxyethyl acid phosphate, acid phosphooxypolyoxyethylene glycol monomethacrylate, acid phosphooxypolyoxypropylene glycol monomethacrylate, 3-chloro-2 -acid phosphooxypropyl methacrylate, methacryloyloxyethyl acid phosphate/monoethanolamine salt, and the like.
  • the internal cross-linking agent (a3) is a compound having two or more ethylenically unsaturated bonds in one molecule.
  • the internal cross-linking agent (a3) is a compound capable of forming a crosslinked structure in radical polymerization of monomers including the monomer (a1), the monomer (a2), and the monomer (a3). .
  • compounds having two or more ethylenically unsaturated bonds in one molecule include divinylbenzene, 1,6-hexanediol diacrylate, and 2-hydroxy-3-acryloyloxypropyl methacrylate.
  • divinylbenzene is preferable from the viewpoint of improving the adhesion of the copolymer (A) to the electrode active material.
  • Monomer (a4) is a compound represented by the following formula (1).
  • a compound that corresponds to the monomer (a4) and can also correspond to other monomers such as the monomer (a1) and the monomer (a2) is the monomer (a4) shall fall under
  • R 1 is an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and a cyclic alkyl group having 3 to 20 carbon atoms, Alternatively, it is preferably an aryl group having 6 to 20 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms.
  • These hydrocarbon groups may or may not have a substituent such as a carboxy group.
  • alkyl groups having 1 to 12 carbon atoms examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n- A hexyl group and the like can be mentioned.
  • Examples of the cyclic alkyl group having 3 to 20 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc. which may have a substituent.
  • substituents include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group and n-hexyl group. groups.
  • the aryl group having 6 to 20 carbon atoms is preferably an aryl group having 6 to 14 carbon atoms which may have one or more substituents.
  • the aryl group having 6 to 14 carbon atoms includes phenyl group, naphthyl group, anthryl group, phenanthryl group and the like.
  • substituents that such an aryl group having 6 to 14 carbon atoms may have include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert- Alkyl groups such as a butyl group, n-pentyl group and n-hexyl group; aryl groups such as a phenyl group; and aralkyl groups such as a benzyl group.
  • N-substituted maleimide A compound having a structure represented by formula (1) used in this embodiment is also called an N-substituted maleimide.
  • N-substituted maleimides include N- -alkylmaleimide; N-cycloalkylmaleimide such as N-cyclohexylmaleimide, N-cyclopentylmaleimide, N-norbornylmaleimide, N-cyclohexylmethylmaleimide, N-cyclopentylmethylmaleimide; N-phenylmaleimide, N-chlorophenylmaleimide, N-arylmaleimides such as N-methylphenylmaleimide, N-naphthylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide and N-tribromophenylmaleimide; be done.
  • R 1 may be of one type or plural types.
  • the structural unit derived from the monomer (a4) constitutes a part of the copolymer (A) that contributes to improving cycle characteristics.
  • the copolymer (A) contains a structural unit derived from the monomer (a4), the cycle characteristics (cycle capacity retention rate) of a non-aqueous secondary battery using the copolymer (A) as an electrode binder
  • the structural unit derived from the monomer (a4) has the characteristics of high polarity and strong intermolecular force due to the cyclic imide structure. This makes it possible to suppress infiltration of the electrolytic solution between the molecular chains of the copolymer, thereby suppressing deterioration of the electrode structure in the electrolytic solution. That is, it is considered that the copolymer (A) exhibits good electrolyte resistance when used as an electrode binder.
  • This action mechanism is presumed to result in an improvement in the cycle characteristics (cycle capacity retention rate) of a non-aqueous secondary battery using the copolymer (A) as an electrode binder.
  • Other monomers (a5) are monomers (a1), monomers (a2), internal cross-linking agents (a3), monomers (a4) and ("monomers (a1) to (a4) ), and is a compound that can be copolymerized with the monomers (a1) to (a4).
  • Other monomers (a5) include, for example, compounds having a glycidyl group and an ethylenically unsaturated bond, compounds having a hydroxy group and an ethylenically unsaturated bond, and the like.
  • Specific examples of compounds having a glycidyl group and an ethylenically unsaturated bond include glycidyl (meth)acrylate and the like.
  • Specific examples of compounds having a hydroxy group and an ethylenically unsaturated bond include 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate. From the viewpoint of the adhesion of the copolymer (A) to the electrode active material, 2-hydroxyethyl (meth)acrylate is preferred.
  • R 1 is preferably an alkyl group, and p is preferably an integer of 10-40. More preferably, R 1 has 10 to 40 carbon atoms, and more preferably, R 1 is a linear unsubstituted alkyl group having 10 to 40 carbon atoms. Examples of the compound represented by formula (2) include Adekariasoap SR10 (manufactured by ADEKA).
  • R 2 is preferably an alkyl group, and q is preferably an integer of 10-12. More preferably, R 2 has 10 to 40 carbon atoms, and more preferably, R 2 is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
  • Examples of the compound represented by formula (5) include Aqualon KH10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).
  • R3 is preferably an alkyl group and M1 is preferably NH4 or Na. More preferably, R 3 has 10 to 40 carbon atoms, and more preferably, R 3 is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
  • R4 is preferably an alkyl group and M2 is preferably NH4 or Na. More preferably, R 4 has 10 to 40 carbon atoms, and even more preferably, R 4 is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
  • the electrode binder resin composition for non-aqueous secondary batteries of the present embodiment preferably further contains an external cross-linking agent (b) in addition to the electrode binder copolymer for non-aqueous secondary batteries.
  • the external cross-linking agent (b) is a compound having no ethylenically unsaturated bond, preferably a silane coupling agent. This is because the cycle characteristics of a non-aqueous secondary battery using the copolymer (A) as an electrode binder are further improved.
  • silane coupling agent having no ethylenically unsaturated bond a silane coupling agent containing an epoxy group, a silane coupling agent containing an amino group, or the like can be used.
  • Silane coupling agents containing epoxy groups and having no ethylenically unsaturated bonds include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane. , etc. can be used.
  • Silane coupling agents containing an amino group and having no ethylenically unsaturated bond include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane and N-2-(aminoethyl)-3-aminopropyl. Trimethoxysilane, 3-aminopropyltrimethoxysilane, and the like can be used. These may be used individually by 1 type, and may be used in combination of 2 or more type.
  • the content of the structural unit derived from the monomer (a1) in the copolymer (A) is 50% by mass or more, preferably 70% by mass or more, and preferably 85% by mass or more. more preferred. This is because the peel strength of the electrode active material layer is improved and because the polymerization stability is improved when synthesizing the copolymer (A) by emulsion polymerization.
  • the content of the structural unit derived from the monomer (a1) in the copolymer (A) is 98% by mass or less, preferably 97% by mass or less, and preferably 96% by mass or less. more preferred. This is to ensure the content of structural units derived from the monomers (a2) to (a4).
  • the content of the structural unit derived from the monomer (a2) in the copolymer (A) is 1.0% by mass or more, preferably 2.0% by mass or more, and 3.0% by mass. % or more is more preferable. This is because the mechanical stability of the copolymer (A) is improved. It is also because the polymerization stability is improved when the copolymer (A) is synthesized by emulsion polymerization.
  • the content of structural units derived from the monomer (a2) in the copolymer (A) is 15% by mass or less, preferably 10% by mass or less, and 7.0% by mass or less. is more preferable. This is because the binding property of the electrode active material layer containing the copolymer (A) to the current collector and the binding property between the electrode active materials are improved.
  • the content of the structural unit derived from the internal cross-linking agent (a3) in the copolymer (A) is 0.020% by mass or more, preferably 0.040% by mass or more, and 0.06% by mass. % or more is more preferable. This is because the cycle characteristics of the electrode containing the copolymer (A) are improved.
  • the content of structural units derived from the internal cross-linking agent (a3) in the copolymer (A) is 10% by mass or less, preferably 5.0% by mass or less, and 3.0% by mass or less. It is more preferable that the content is 2.0% by mass or less. This is because an electrode exhibiting good flexibility can be produced from the copolymer (A).
  • the content of the structural unit derived from the monomer (a4) in the copolymer (A) is 0.010% by mass or more, preferably 0.10% by mass or more, and 1.0% by mass. % or more is more preferable. This is because the cycle characteristics of a non-aqueous secondary battery using the copolymer (A) as an electrode binder are improved while the copolymer (A) exhibits good cycle characteristics.
  • the content of the structural unit derived from the monomer (a4) in the copolymer (A) is 20% by mass or less, preferably 15% by mass or less, and preferably 10% by mass or less. More preferably, it is 7.0% by mass or less, and particularly preferably 5.0% by mass or less. This is because an electrode exhibiting good flexibility can be obtained by including the copolymer (A) having such a structure as an electrode binder.
  • the content of the structural unit derived from the other monomer (a5) in the copolymer (A) is not particularly limited as long as the object of the present invention can be achieved.
  • the content of the structural unit derived from such other monomer (a5) in the copolymer (A) is preferably 0.01% by mass or more and 10% by mass or less, and 5.0 It is more preferably 3.0% by mass or less, more preferably 3.0% by mass or less.
  • the amount of the external cross-linking agent (b) used is preferably 0.30 to 9.0 parts by mass, more preferably 0.3 to 7 parts by mass, based on 100 parts by mass of the copolymer (A). more preferably 0.4 to 5.0 parts by mass.
  • the Tg of the copolymer (A) is measured using an EXSTAR DSC/SS7020 manufactured by Hitachi High-Tech Science Co., Ltd. at a temperature increase rate of 10 ° C./min under a nitrogen gas atmosphere. is the peak top temperature.
  • the glass transition point Tg of the copolymer (A) is preferably -30°C or higher, more preferably -10°C or higher, and even more preferably 0°C or higher. This is because the cycle characteristics of a non-aqueous secondary battery using the copolymer (A) as an electrode binder are improved.
  • the glass transition point Tg of the copolymer (A) is preferably 100°C or lower, more preferably 50°C or lower, and even more preferably 30°C or lower. This is because the adhesion of the electrode active material layer containing the copolymer (A) as an electrode binder to the collector foil is improved.
  • the electrode binder copolymer (A) for non-aqueous secondary batteries is obtained by copolymerizing the monomers (a1) to (a4) and optionally another monomer (a5).
  • the monomer (a) when collectively referring to the monomers for the copolymer (A), it is referred to as the monomer (a). That is, the monomer (a) includes monomers (a1) to (a4), and optionally another monomer (a5).
  • the polymerization method includes, for example, emulsion polymerization of the monomer (a) in the aqueous medium (c).
  • components used in the synthesis of the copolymer (A) by emulsion polymerization include, for example, a non-polymerizable surfactant (d), a basic substance (e), a polymerization initiator (e), a chain A transfer agent (g) and the like can be mentioned.
  • Aqueous medium (c) is water, a hydrophilic solvent, or a mixture thereof.
  • Hydrophilic solvents include methanol, ethanol, isopropyl alcohol, N-methylpyrrolidone, and the like.
  • the aqueous medium (c) is preferably water.
  • water to which a hydrophilic solvent is added may be used as long as the polymerization stability is not impaired.
  • Non-polymerizable surfactant (d) A non-polymerizable surfactant (d) may be used in the emulsion polymerization of the monomer (a).
  • the surfactant (d) can improve the dispersion stability of the dispersion (emulsion) during and/or after polymerization.
  • As the surfactant (d) it is preferable to use an anionic surfactant or a nonionic surfactant.
  • anionic surfactants include alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, and fatty acid salts.
  • nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.
  • the above surfactants may be used singly or in combination of two or more.
  • the pH of the dispersion at 23°C is preferably from 1.5 to 10, more preferably from 6.0 to 9.0, even more preferably from 5.0 to 9.0. This is for suppressing sedimentation of the active material in the electrode slurry, which will be described later.
  • Basic substances (e) include ammonia, triethylamine, sodium hydroxide, lithium hydroxide, and the like. These basic substances (e) may be used singly or in combination of two or more.
  • radical polymerization initiator (f) used in emulsion polymerization is not particularly limited, and known initiators can be used.
  • radical polymerization initiators include persulfates such as ammonium persulfate and potassium persulfate; hydrogen peroxide; azo compounds; organic peroxides such as t-butyl hydroperoxide, tert-butyl peroxybenzoate and cumene hydroperoxide oxides. Among them, persulfates and organic peroxides are preferred.
  • a radical polymerization initiator and a reducing agent such as sodium bisulfite, Rongalit, or ascorbic acid may be used in combination during emulsion polymerization to perform redox polymerization.
  • the amount of the radical polymerization initiator to be added is preferably 0.10 parts by mass or more, more preferably 0.80 parts by mass or more, relative to 100 parts by mass of the monomer (a). This is because the conversion of the monomer (a) to the copolymer (A) during polymerization can be increased.
  • the amount of the radical polymerization initiator to be added is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less per 100 parts by mass of the monomer (a). This is because the molecular weight of the copolymer (A) can be increased, and the swelling rate of the electrode active material layer with respect to the electrolytic solution can be decreased.
  • Chain transfer agent (g) A chain transfer agent (g) is used to adjust the molecular weight of the copolymer (A) in emulsion polymerization.
  • Chain transfer agents (g) include n-dodecylmercaptan, tert-dodecylmercaptan, n-butylmercaptan, 2-ethylhexylthioglycolate, 2-mercaptoethanol, ⁇ -mercaptopropionic acid, methyl alcohol, n-propyl alcohol, isopropyl alcohol, t-butyl alcohol, benzyl alcohol and the like.
  • the emulsion polymerization method includes, for example, a method of performing emulsion polymerization while continuously supplying each component used in the emulsion polymerization.
  • the emulsion polymerization temperature is not particularly limited, but is, for example, 30 to 90°C, preferably 50 to 85°C, more preferably 55 to 80°C.
  • Emulsion polymerization is preferably carried out while stirring. Moreover, it is preferable to continuously supply the monomer (a) and the radical polymerization initiator so as to be uniform in the reaction vessel.
  • the external cross-linking agent (b) is preferably added after the emulsion polymerization is completed. Addition is preferably carried out while stirring.
  • the electrode binder resin composition for non-aqueous secondary batteries of the present embodiment (hereinafter also referred to as a binder composition) is a binder resin composition that can be used for electrodes for non-aqueous secondary batteries.
  • the binder composition contains an electrode binder copolymer for non-aqueous secondary batteries (A) and an aqueous medium (c).
  • the electrode binder copolymer for non-aqueous secondary batteries (A) is preferably dispersed in the aqueous medium (c).
  • the binder composition may contain, for example, the above components used in the synthesis of the copolymer (A).
  • the binder composition may be a dispersion obtained by the method for synthesizing the electrode binder copolymer (A) for a non-aqueous secondary battery described above, and the copolymer (A) obtained by a method other than emulsion polymerization may be dispersed in an aqueous solution.
  • a dispersion obtained by dispersing in the medium (c) may be used, or a dispersion obtained by another method may be used.
  • the electrode binder resin composition for non-aqueous secondary batteries of the present embodiment contains an electrode binder and an aqueous medium (c).
  • the electrode binder contains the electrode binder copolymer (A) for non-aqueous secondary batteries described above, and is preferably the electrode binder copolymer (A) for non-aqueous secondary batteries described above.
  • the electrode binder resin composition for non-aqueous secondary batteries of the present embodiment is preferably used for a negative electrode from the viewpoint of exhibiting the effects of the present invention.
  • Aqueous medium (c) is water, a hydrophilic solvent, or a mixture thereof.
  • hydrophilic solvent are as described in the explanation of the aqueous medium (c) in the synthesis of the electrode binder copolymer (A) for non-aqueous secondary batteries.
  • the aqueous medium (c) may be the same as or different from the aqueous medium (c) used to synthesize the copolymer (A).
  • the aqueous medium (c) may be the aqueous medium (c) used in the synthesis of the copolymer (A) as it is, or may have a structure in which an aqueous solvent is added to the aqueous medium (c).
  • the aqueous medium (c) may be replaced with a new aqueous solvent after the synthesis of.
  • the aqueous solvent to be added or replaced may have the same composition as the solvent used for synthesizing the copolymer (A), or may have a different composition.
  • the non-volatile content of the binder composition is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. This is to increase the amount of active ingredient contained in the binder composition.
  • the non-volatile content of the binder composition can be adjusted by adjusting the amount of the aqueous medium (c).
  • the non-volatile content of the binder composition may be 60% by mass or less.
  • the viscosity of the binder composition is preferably 3000 mPa ⁇ s or less, more preferably 1000 mPa ⁇ s or less, and even more preferably 200 mPa ⁇ s or less. This is for the purpose of reducing the loss of the binder during preparation of the electrode slurry, which will be described later, and shortening the degassing process of the slurry.
  • the viscosity of the binder composition was measured using a Brookfield viscometer at a liquid temperature of 23°C and a rotation speed of 60 rpm. 1, No. 2, No. 3 or No. It is a value measured using a No. 4 rotor.
  • the viscosity of the binder composition is greatly affected by the non-volatile content of the binder composition.
  • An electrode slurry contains a copolymer (A), an electrode active material, and an aqueous medium.
  • the electrode slurry preferably has a structure in which the copolymer (A) and the electrode active material are dispersed in an aqueous medium.
  • the electrode slurry may contain, in addition to these components, a thickener, a conductive aid, the above components used in synthesizing the copolymer (A), and the like.
  • the electrode slurry of the present embodiment is preferably negative electrode slurry from the viewpoint of achieving the effects of the present invention.
  • the content of the copolymer (A) is preferably 0.50 parts by mass or more, more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the electrode active material. This is because the effects of the copolymer (A) can be fully exhibited.
  • the content of the copolymer (A) is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and 3.0 parts by mass with respect to 100 parts by mass of the electrode active material. Part or less is more preferable. This is for increasing the content of the electrode active material in the electrode active material layer produced using the electrode slurry.
  • the electrode active material is a material capable of intercalating/deintercalating ions such as lithium ions that serve as charge carriers.
  • the charge carrier ions are preferably alkali metal ions, more preferably lithium ions, sodium ions, potassium ions, and even more preferably lithium ions.
  • the electrode active material that is, the negative electrode active material, preferably contains at least one of a carbon material, a material containing silicon, and a material containing titanium.
  • a carbon material used as the electrode active material include coke such as petroleum coke, pitch coke, and coal coke, carbonized organic polymers, and graphite such as artificial graphite and natural graphite.
  • Materials containing silicon include, for example, simple silicon and silicon compounds such as silicon oxide.
  • Materials containing titanium include, for example, lithium titanate. These materials may be used alone, or may be used as a mixture or composite.
  • the negative electrode active material preferably contains at least one of a carbon material and a material containing silicon, and more preferably contains a carbon material. This is because the binder copolymer (A) of the present invention is very effective in improving the binding properties between the electrode active material and between the electrode active material and the current collector.
  • the electrode active material is a material with a higher standard electrode potential than the negative electrode active material.
  • the positive electrode active material include nickel-containing lithium composite oxides such as Ni--Co--Mn-based lithium composite oxides, Ni--Mn--Al-based lithium composite oxides, and Ni--Co--Al-based lithium composite oxides.
  • the positive electrode active material one of these substances may be used, or two or more of them may be used in combination.
  • thickening agents include celluloses such as carboxymethyl cellulose (CMC), hydroxyethyl cellulose and hydroxypropyl cellulose, ammonium salts of celluloses, alkali metal salts of celluloses, polyvinyl alcohol and polyvinylpyrrolidone.
  • the thickener preferably contains at least one of carboxymethylcellulose, an ammonium salt of carboxymethylcellulose, and an alkali metal salt of carboxymethylcellulose. This is because the electrode active material is easily dispersed in the electrode slurry.
  • the content of the thickener in the electrode slurry is preferably 0.50 parts by mass or more, more preferably 0.80 parts by mass or more, relative to 100 parts by mass of the electrode active material. This is to improve the binding properties between the electrode active materials and between the electrode active materials and the current collector in the electrode active material layer produced using the electrode slurry.
  • the content of the thickening agent in the electrode slurry is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, and 1.5 parts by mass with respect to 100 parts by mass of the electrode active material. More preferably: This is because the coatability of the electrode slurry is improved.
  • Aqueous media are water, hydrophilic solvents, or mixtures thereof. Examples of the hydrophilic solvent are as described in the explanation of the aqueous medium (c) in the synthesis of the electrode binder copolymer (A) for non-aqueous secondary batteries.
  • the aqueous medium contained in the electrode slurry may be the same as the aqueous medium (c) contained in the electrode binder resin composition for non-aqueous secondary batteries, or the aqueous medium (c) used for synthesizing the copolymer (A). , can be different.
  • Carbon black, carbon fiber, or the like is preferably used as the conductive aid.
  • carbon black include furnace black, acetylene black, Denka Black (registered trademark) (manufactured by Denka Co., Ltd.), Ketjen Black (registered trademark) (manufactured by Ketjen Black International Co., Ltd.), and the like.
  • carbon fibers include carbon nanotubes, carbon nanofibers, etc.
  • Preferred examples of carbon nanotubes include VGCF (registered trademark, manufactured by Showa Denko KK), which is a vapor-grown carbon fiber.
  • the non-volatile content of the electrode slurry is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. This is because the concentration of the active ingredient in the electrode slurry is increased, and a sufficient amount of electrode active material layer can be formed with a small amount of electrode slurry.
  • the non-volatile concentration of the electrode slurry can be adjusted by adjusting the amount of the aqueous medium in the electrode slurry.
  • the viscosity of the electrode slurry is preferably 20000 mPa ⁇ s or less, more preferably 10000 mPa ⁇ s or less, and even more preferably 5000 mPa ⁇ s or less. This is because the coatability of the electrode slurry to the current collector is improved, and the productivity of the electrode is improved.
  • the viscosity of the electrode slurry is greatly affected by the non-volatile concentration of the electrode slurry and the type and amount of the thickener.
  • the pH of the electrode slurry at 23°C is preferably 2.0 to 10, more preferably 4.0 to 9.0, still more preferably 6.0 to 9.0. This is for improving the durability of the battery produced using the electrode slurry.
  • a binder composition As a method for preparing the electrode slurry in the present embodiment, a binder composition, an electrode active material, optionally a thickener, optionally an aqueous medium, optionally a conductive aid, and optionally Mix with other ingredients as appropriate.
  • the order of the components to be added is not particularly limited, and may be determined as appropriate.
  • Examples of the mixing method include a method using a mixing device such as a stirring type, a rotating type, and a shaking type.
  • a non-aqueous secondary battery electrode (hereinafter also referred to as "electrode") according to the present embodiment includes a current collector and an electrode active material layer formed on the current collector. Examples of the shape of the electrode include a laminate and a wound body, but are not particularly limited. Moreover, the formation range of the electrode active material layer on the current collector is not particularly limited, and the electrode active material layer may be formed on the entire surface of the current collector or may be formed on a part of the surface of the current collector. When the current collector is in the form of a plate, foil, or the like, the electrode active material layer may be formed on both sides, or may be formed on only one side.
  • the non-aqueous secondary battery electrode of the present embodiment is preferably a non-aqueous secondary battery negative electrode from the viewpoint of exhibiting the effects of the present invention.
  • the current collector is preferably a metal sheet (metal foil) having a thickness of 0.001 mm or more and 0.5 mm or less, and examples of metals include iron, copper, aluminum, nickel, and stainless steel.
  • the current collector is preferably copper foil.
  • the electrode active material layer contains a binder copolymer (A) and an electrode active material.
  • the electrode active material layer may contain other components contained in the above binder composition, and may contain other components contained in the above electrode slurry.
  • the electrode can be produced, for example, by coating an electrode slurry on a current collector, drying it to form an electrode active material layer, and then cutting it into a suitable size.
  • the method for applying the electrode slurry onto the current collector is not particularly limited, but examples include a reverse roll method, a direct roll method, a doctor blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, and a dipping method. method, squeeze method, and the like.
  • the electrode slurry may be applied to only one side of the current collector, or may be applied to both sides.
  • the electrode slurry When the electrode slurry is applied to both surfaces of the current collector, it may be applied to each surface one by one, or may be applied to both surfaces at the same time.
  • the electrode slurry may be applied to the current collector continuously or intermittently.
  • the amount of the electrode slurry to be applied can be appropriately determined according to the design capacity of the battery, the composition of the electrode slurry, and the like.
  • the coating amount of the electrode slurry is preferably 13 mg/cm 2 or less (coating amount per one side when coating on both sides), although it depends on the properties of the electrode slurry. This is because the generation of cracks on the electrode surface can be suppressed in the step of drying the electrode slurry.
  • an electrode active material layer is formed on the current collector.
  • the method for drying the electrode slurry is not particularly limited, but for example, hot air, reduced pressure or vacuum environment, (far) infrared rays, and low temperature air can be used alone or in combination.
  • the drying temperature and drying time of the electrode slurry can be appropriately adjusted depending on the concentration of non-volatile matter in the electrode slurry, the amount of coating applied to the current collector, and the like.
  • the drying temperature is preferably 40° C. or higher and 350° C. or lower, and more preferably 60° C. or higher and 100° C. or lower from the viewpoint of productivity.
  • the drying time is preferably 1 minute or more and 30 minutes or less.
  • An electrode sheet in which an electrode active material layer is formed on a current collector may be cut into a size and shape suitable for an electrode.
  • the method for cutting the electrode sheet is not particularly limited, and for example, a slit, laser, wire cut, cutter, Thomson, or the like can be used.
  • the electrode sheet Before or after cutting the electrode sheet, the electrode sheet may be pressed if necessary. As a result, the electrode active material can be more strongly bound to the current collector, and the thickness of the electrode can be reduced, thereby making it possible to reduce the size of the non-aqueous battery.
  • a pressing method a general method can be used, and it is particularly preferable to use a die pressing method or a roll pressing method.
  • the press pressure is not particularly limited, but is preferably 0.5 t/cm 2 or more and 5 t/cm 2 or less.
  • the line pressure is not particularly limited, but is preferably 0.5 t/cm or more and 5 t/cm or less. This is for suppressing a decrease in the capacity of the electrode active material to insert and desorb charge carriers such as lithium ions while obtaining the above effects of pressing.
  • Non-aqueous secondary battery> A lithium ion secondary battery will be described as a preferred example of the non-aqueous secondary battery according to this embodiment, but the configuration of the battery is not limited to that described here.
  • a positive electrode, a negative electrode, an electrolytic solution, and, if necessary, parts such as a separator are housed in an outer package, and one of the positive electrode and the negative electrode Alternatively, the electrode produced by the above method is used for both.
  • at least one of the positive electrode and the negative electrode contains the copolymer (A) in the electrode binder, and at least the negative electrode preferably contains the copolymer (A).
  • Electrolyte As the electrolytic solution, a non-aqueous liquid having ionic conductivity is used.
  • the electrolytic solution include a solution in which an electrolyte is dissolved in an organic solvent, an ionic liquid, and the like, and the former is preferred. This is because a non-aqueous battery with low manufacturing cost and low internal resistance can be obtained.
  • an alkali metal salt can be used, which can be appropriately selected according to the type of the electrode active material and the like.
  • electrolytes include LiClO 4 , LiBF 6 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiB 10 Cl 10 , LiAlCl 4 , LiCl, LiBr, LiB(C 2 H 5 ). 4 , CF 3 SO 3 Li, CH 3 SO 3 Li, LiCF 3 SO 3 , LiC 4 F 9 SO 3 , Li(CF 3 SO 2 ) 2 N, lithium aliphatic carboxylate, and the like.
  • Other alkali metal salts can also be used as the electrolyte.
  • the organic solvent that dissolves the electrolyte is not particularly limited, but examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), methylethyl carbonate (MEC), dimethyl carbonate (DMC), fluoroethylene carbonate.
  • carbonic ester compounds such as (FEC) and vinylene carbonate (VC); nitrile compounds such as acetonitrile; and carboxylic acid esters such as ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and propyl propionate.
  • These organic solvents may be used singly or in combination of two or more. Among them, it is preferable to use a combination of linear carbonate solvents.
  • linear carbonate-based solvents include diethyl carbonate, dimethyl carbonate, and ethylmethyl carbonate.
  • the exterior body for example, a laminated material of an aluminum foil and a resin film can be appropriately used, but it is not limited to this.
  • the shape of the battery may be coin-shaped, button-shaped, sheet-shaped, cylindrical, square, flat, or any other shape.
  • a negative electrode of a lithium ion secondary battery and a lithium ion secondary battery were produced as an example of the configuration of the present invention, and a negative electrode of a lithium ion secondary battery and a lithium ion secondary battery according to comparative examples were prepared. A comparison is made to confirm the effect of the present invention. In addition, this invention is not limited by these.
  • the water used in the following examples and comparative examples is ion-exchanged water unless otherwise specified.
  • Example 2 The amount of N-phenylmaleimide was increased from 9 parts by mass to 18 parts by mass, the amount of styrene was decreased from 187 parts by mass to 182 parts by mass, and the amount of 2-ethylhexyl acrylate was decreased from 165 parts by mass to 161 parts by mass.
  • Aqueous emulsion (EM-2) of copolymer (A) was obtained in the same manner as in Example 1 except for this.
  • Example 3 An aqueous emulsion (EM-3) of copolymer (A) was obtained in the same manner as in Example 1.
  • Comparative Example 1 In Comparative Example 1, no N-phenylmaleimide was used, the amount of styrene was increased from 187 parts by mass to 192 parts by mass, and the amount of 2-ethylhexyl acrylate was increased from 165 parts by mass to 169 parts by mass. Aqueous emulsion (cEM-1) of copolymer (A) was obtained in the same manner as in Example 1 except for this.
  • Comparative Example 2 An aqueous emulsion (cEM-2) of copolymer (A) was obtained in the same manner as in Comparative Example 1.
  • Table 2 shows details of the polymerizable surfactants Adekari Soap SR10 and Aqualon KH10 used as other monomers (a5).
  • Example 3 the resulting aqueous emulsion of copolymer (A) was cooled to room temperature. 16 parts by weight of 25% by weight aqueous ammonia (4.0 parts by weight of ammonia and 12.0 parts by weight of water) and 59 parts by weight of water were added for neutralization.
  • a binder composition (P-3) and a binder composition (cP-2) containing the copolymer (A) were obtained without adding 3-glydoxypropyltrimethoxysilane to the separable flask.
  • Table 1 shows the amounts of the components used in the synthesis of the copolymer (A) and the preparation of the binder composition.
  • the amount of water is the total amount of water used in the synthesis step and the preparation step, and the water contained in the acrylic acid aqueous solution and ammonia water is also included in the calculation. Further, in Table 1, the added amounts of acrylic acid and ammonia are the amounts of only the solutes contained in the acrylic acid aqueous solution and ammonia water.
  • Non-volatile content 1 g of the binder composition was weighed into an aluminum dish with a diameter of 5 cm, dried at 105° C. for 1 hour while air was circulated in a dryer at 1 atmosphere (1013 hPa), and then the mass of the remaining component was measured. The mass ratio (% by mass) of the components remaining after drying with respect to the mass (1 g) of the binder composition before drying was calculated as the non-volatile concentration.
  • a negative electrode and a lithium ion secondary battery were produced using the binder composition produced in each example and comparative example, and evaluated.
  • [5-1. Production of battery] [5-1-1. Production of positive electrode] 94 parts by mass of LiNi 0.6 Mn 0.2 Co 0.2 O 2 as a positive electrode active material, 3 parts by mass of acetylene black as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder. 50 parts by mass of methylpyrrolidone was added and further mixed to prepare a positive electrode slurry.
  • the positive electrode slurry was applied to both sides of a 15 ⁇ m thick aluminum foil (positive electrode current collector) by a direct roll method.
  • the amount of the positive electrode slurry applied to the positive electrode current collector was adjusted so that the thickness of the positive electrode current collector after the roll press treatment described later was 125 ⁇ m per side.
  • the positive electrode slurry applied on the positive electrode current collector was dried at 120° C. for 5 minutes and pressed with a roll press (manufactured by Thank Metal Co., press load 5 t, roll width 7 cm) to form a positive electrode active material layer.
  • a positive electrode sheet was obtained.
  • the obtained positive electrode sheet was cut into a size of 50 mm ⁇ 40 mm, and a conductive tab was attached to prepare a positive electrode.
  • the negative electrode slurry was applied to both sides of a 10 ⁇ m thick copper foil (negative electrode current collector) by a direct roll method.
  • the amount of the negative electrode slurry applied to the negative electrode current collector was adjusted so that the thickness of the negative electrode current collector after the roll press treatment described later was 170 ⁇ m per side.
  • the negative electrode slurry applied on the negative electrode current collector is dried at 90° C. for 10 minutes and pressed by a roll press (manufactured by Thank Metal Co., press load 8 t, roll width 7 cm) to form a negative electrode active material layer on the current collector.
  • a negative electrode sheet on which was formed was obtained.
  • the obtained negative electrode sheet was cut into a size of 52 mm ⁇ 42 mm, and a conductive tab was attached thereto to prepare a negative electrode.
  • a separator made of a polyolefin porous film (made of polyethylene, 25 ⁇ m) is interposed between the positive electrode and the negative electrode, and an aluminum laminate exterior body (battery pack) is formed so that the positive electrode active material layer and the negative electrode active material layer face each other. ).
  • An electrolytic solution was poured into this outer package, vacuum impregnation was performed, and the package was packed with a vacuum heat sealer to produce a lithium ion secondary battery for evaluation.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • the negative electrode active material layer was peeled off from one end of the test piece by 20 mm in the length direction, and the test piece on the copper foil side was folded back 180°, and this part ( The copper foil side of the portion of the test piece from which the negative electrode active material layer was removed) was gripped with a chuck on the upper side of the tester. Furthermore, one end of the SUS plate from which the negative electrode active material layer was peeled off was gripped with a lower chuck. In this state, the copper foil was peeled off from the test piece at a speed of 100 ⁇ 10 mm/min to obtain a peel length (mm)-peeling force (mN) graph.
  • the average value (mN) of the peel force at a peel length of 10 to 45 mm was calculated, and the value obtained by dividing the average value of the peel force by the width of the test piece of 25 mm was the peel strength of the negative electrode active material layer (mN/ mm).
  • the peel strength of the negative electrode active material layer was the peel strength of the negative electrode active material layer (mN/ mm).
  • DCR Battery internal resistance
  • the internal resistance (DCR( ⁇ )) of the battery was measured under the condition of 25° C. by the following procedure. The battery was charged at a constant current of 0.2 C from the rest potential to 3.6 V to bring the charged state to 50% of the initial capacity (50% SOC). Thereafter, discharge was performed for 60 seconds at current values of 0.2C, 0.5C, 1C and 2C. DCR ( ⁇ ) at SOC 50% was determined from the relationship between these four current values (values for 1 second) and voltage.
  • the time integrated value of the current in steps (i) and (ii) is the charge capacity
  • the time integrated value of the current in step (iv) is the discharge capacity.
  • a discharge capacity at the 1st cycle and a discharge capacity at the 100th cycle were measured. 100 ⁇ (discharge capacity at 100th cycle)/(discharge capacity at 1st cycle) [%] was calculated as the cycle capacity retention rate of the battery at high temperature.
  • the external cross-linking agent (b) in comparison with Comparative Example 2 in which the external cross-linking agent (b) was not used and Comparative Example 1 in which 3-glydoxypropyltrimethoxysilane was used as the external cross-linking agent (b), the external cross-linking agent (b) , the "discharge capacity retention rate after 100 cycles" of the produced battery increased from 75% to 77% (improved by about 2%).
  • Example 3 in which the external cross-linking agent (b) was not used and Example 1 in which the same external cross-linking agent (b) as in Comparative Example 1 was used in the same amount
  • Example 1 in which the same external cross-linking agent (b) as in Comparative Example 1 was used in the same amount
  • the “discharge capacity retention rate after 100 cycles" of the produced battery increased from 82% to 88% (improved by about 6%).
  • the improvement effect from Example 3 to Example 1 increased by a factor of 3 compared to the improvement effect from Comparative Example 2 to Comparative Example 1 (6% 2%).
  • the copolymer (A) containing a structural unit derived from the monomer (a4) having the structure represented by formula (1) was accelerated 3 times.
  • the cause of the acceleration effect was still unknown at the time of filing, but it is due to the interaction between the structure represented by the formula (1) contained in the copolymer (A) and the external cross-linking agent (b). I presume there is.

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Abstract

Provided is an electrode binder copolymer for a non-aqueous secondary battery, yielding: an electrode including an electrode active material layer that has high peeling strength with respect to a current collector; and a non-aqueous secondary battery that has favorable charge-discharge cycle properties. This electrode binder copolymer for a non-aqueous secondary battery contains structural units derived from monomers (a1 to a4). The monomer (a1) is a (meth)acrylic acid alkyl ester or hydrocarbon compound that has a single ethylenically unsaturated bond. The monomer (a4) is at least one species selected from the group consisting of compounds indicated by formula (1). The structural units derived from the monomers (a1 and a4) are contained at 50 to 98 mass% and 0.010 to 20 mass%. (In formula (1), R1 is a C1-12 alkyl group, a C3-20 cyclic alkyl group, or a C6-20 aryl group).

Description

非水系二次電池用電極バインダー共重合体、非水系二次電池用電極バインダー樹脂組成物、及び非水系二次電池電極Electrode binder copolymer for non-aqueous secondary battery, electrode binder resin composition for non-aqueous secondary battery, and non-aqueous secondary battery electrode
　本発明は、非水系二次電池用電極バインダー共重合体、非水系二次電池用電極バインダー樹脂組成物、及び非水系二次電池電極に関する。
　本願は、２０２１年１２月２３日に、日本に出願された特願２０２１－２０９９９０号に基づき優先権を主張し、その内容をここに援用する。 TECHNICAL FIELD The present invention relates to an electrode binder copolymer for non-aqueous secondary batteries, an electrode binder resin composition for non-aqueous secondary batteries, and a non-aqueous secondary battery electrode.
This application claims priority based on Japanese Patent Application No. 2021-209990 filed in Japan on December 23, 2021, the content of which is incorporated herein.
　非水系二次電池は、金属酸化物などを活物質とした正極、黒鉛等の炭素材料を活物質とした負極、および電解液を含む構成を有し、イオンが正極と負極間を移動することにより電池の充放電が行われる二次電池である。 A non-aqueous secondary battery has a configuration including a positive electrode using a metal oxide as an active material, a negative electrode using a carbon material such as graphite as an active material, and an electrolyte, and ions move between the positive electrode and the negative electrode. It is a secondary battery in which charging and discharging of the battery are performed by.
　非水系二次電池としてリチウムイオン二次電池が代表例として挙げられる。非水系二次電池は、小型化、軽量化の面からノート型パソコン、携帯電話、電動工具、電子・通信機器の電源として使用されている。また、最近では環境車両適用の観点から電気自動車やハイブリッド自動車用にも使用されている。その中で、非水系二次電池の高出力化、高容量化、長寿命化等が強く求められてきている。 A typical example of a non-aqueous secondary battery is a lithium-ion secondary battery. Non-aqueous secondary batteries are used as power sources for notebook computers, mobile phones, power tools, and electronic/communication devices in terms of miniaturization and weight reduction. Recently, it is also used for electric vehicles and hybrid vehicles from the viewpoint of environmental vehicle application. Under these circumstances, there is a strong demand for non-aqueous secondary batteries to have higher output, higher capacity, longer life, and the like.
　正極および負極に使用されるバインダーには、活物質同士および活物質と集電体を結着させる役割がある。非水系二次電池の容量向上、作業環境保全のため、水分散系バインダーの開発が進められている。たとえば、増粘剤としてカルボキシメチルセルロース（ＣＭＣ）を併用したスチレン－ブタジエンゴム（ＳＢＲ）系の水分散体が知られている。 The binder used for the positive electrode and negative electrode has the role of binding the active materials together and the active material and the current collector. In order to improve the capacity of non-aqueous secondary batteries and protect the working environment, the development of water-dispersed binders is underway. For example, a styrene-butadiene rubber (SBR)-based aqueous dispersion using carboxymethyl cellulose (CMC) as a thickener is known.
　特許文献１～５では、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および内部架橋剤を含有するエチレン性不飽和単量体を、界面活性剤の存在下、乳化重合して得られる非水系二次電池電極用バインダーが提案されている。 In Patent Documents 1 to 5, an ethylenically unsaturated monomer containing styrene, an ethylenically unsaturated carboxylic acid ester, an ethylenically unsaturated carboxylic acid and an internal cross-linking agent is emulsion-polymerized in the presence of a surfactant. The resulting binder for non-aqueous secondary battery electrodes has been proposed.
特許第５２１１７９４号公報Japanese Patent No. 5211794 特許第５７０１５１９号公報Japanese Patent No. 5701519 特許第５９９１３２１号公報Japanese Patent No. 5991321 特開２０１７－１７４８０４号公報JP 2017-174804 A 中国特許出願公開第１０４８８２６１２号明細書Chinese Patent Application Publication No. 104882612
　しかしながら、特許文献１～５に記載のバインダーを用いた場合では、充放電サイクル特性向上の余地があった。 However, when the binders described in Patent Documents 1 to 5 are used, there is room for improvement in charge-discharge cycle characteristics.
　本発明は、集電体に対する剥離強度が高い電極活物質層を有する電極が得られ、さらに充放電サイクル特性が良好な非水系二次電池が得られる電極バインダー共重合体、及び電極バインダー樹脂組成物を提供することを目的とする。また、本発明は、集電体に対する剥離強度が高い電極活物質層を有し、充放電サイクル特性が良好な非水系二次電池が得られる非水系二次電池電極を提供することを目的とする。 The present invention provides an electrode binder copolymer and an electrode binder resin composition that can provide an electrode having an electrode active material layer with high peel strength against a current collector and provide a non-aqueous secondary battery with good charge-discharge cycle characteristics. The purpose is to provide goods. Another object of the present invention is to provide a non-aqueous secondary battery electrode that has an electrode active material layer with high peel strength against a current collector and that provides a non-aqueous secondary battery with good charge-discharge cycle characteristics. do.
　すなわち、本発明の構成は以下の［１］～［１３］の通りである。
［１］　単量体（ａ１）に由来する構造単位と、単量体（ａ２）に由来する構造単位と、内部架橋剤（ａ３）に由来する構造単位と、単量体（ａ４）に由来する構造単位と、を含む非水系二次電池用電極バインダー共重合体であって、
　前記単量体（ａ１）が、分子内に含まれるエチレン性不飽和結合が１個である（メタ）アクリル酸アルキルエステル、及び分子内に含まれるエチレン性不飽和結合が１個である炭化水素化合物からなる群より選ばれる少なくとも１種類であり、
　前記単量体（ａ２）が、１個のエチレン性不飽和結合及びアニオン性官能基を有する化合物であり、
　前記内部架橋剤（ａ３）が、１分子中に２つ以上のエチレン性不飽和結合を有する化合物であり、
　前記単量体（ａ４）が、下記の式（１）で示される化合物であり、
　前記単量体（ａ１）に由来する構造単位を５０質量％以上９８質量％以下含み、
　前記単量体（ａ２）に由来する構造単位を１．０質量％以上１５質量％以下含み、
　前記内部架橋剤（ａ３）に由来する構造単位を０．０２０質量％以上１０質量％以下含み、
　前記単量体（ａ４）に由来する構造単位を０．０１０質量％以上２０質量％以下含むことを特徴とする非水系二次電池用電極バインダー共重合体。
Figure JPOXMLDOC01-appb-C000002
 （式（１）中、Ｒ１は炭素数１～１２のアルキル基、炭素数３～２０の環状アルキル基、または炭素数６～２０のアリール基である。）
［２］　前記単量体（ａ１）に由来する構造単位を７０質量％以上９７質量％以下含む［１］に記載の非水系二次電池用電極バインダー共重合体。
［３］　前記単量体（ａ２）のアニオン性官能基が、カルボキシ基、及びスルホ基のうち少なくともいずれかである［１］又は［２］に記載の非水系二次電池用電極バインダー共重合体。
［４］　前記単量体（ａ２）に由来する構造単位を２．０質量％以上１０質量％以下含む［１］～［３］のいずれかに記載の非水系二次電池用電極バインダー共重合体。
［５］　前記式（１）中、Ｒ１は炭素数６～２０のアリール基である［１］～［４］のいずれかに記載の非水系二次電池用電極バインダー共重合体。
［６］　前記式（１）で示される化合物が、Ｎ－フェニルマレイミドである、［１］～［５］のいずれかに記載の非水系二次電池用電極バインダー共重合体。
［７］　前記単量体（ａ４）に由来する構造単位の含有率は、０．１０質量％以上１５質量％以下である［１］～［６］のいずれかに記載の非水系二次電池用電極バインダー共重合体。
［８］　［１］～［７］のいずれかに記載の非水系二次電池用電極バインダー共重合体と、
　水性媒体（ｃ）と、を含む、非水系二次電池用電極バインダー樹脂組成物。
［９］　［１］～［７］のいずれかに記載の非水系二次電池用電極バインダー共重合体と、
　電極活物質と、
　水性媒体と、を含む、非水系二次電池用電極スラリー。
［１０］　金属箔からなる集電体と、
　前記集電体上に形成された電極活物質層と、を含む非水系二次電池電極であって、
　前記電極活物質層が、［１］～［７］のいずれかに記載の非水系二次電池用電極バインダー共重合体と、電極活物質と、を含む非水系二次電池電極。
［１１］　正極と、負極と、を含む非水系二次電池であって、
　前記正極及び前記の負極の少なくとも一方が、［１］～［７］のいずれかに記載の非水系二次電池用電極バインダー共重合体を含む非水系二次電池。 That is, the configuration of the present invention is as follows [1] to [13].
[1] A structural unit derived from the monomer (a1), a structural unit derived from the monomer (a2), a structural unit derived from the internal cross-linking agent (a3), and a structural unit derived from the monomer (a4) An electrode binder copolymer for a non-aqueous secondary battery comprising a structural unit to
The monomer (a1) is a (meth)acrylic acid alkyl ester having one ethylenically unsaturated bond contained in the molecule, and a hydrocarbon having one ethylenically unsaturated bond contained in the molecule. At least one selected from the group consisting of compounds,
The monomer (a2) is a compound having one ethylenically unsaturated bond and an anionic functional group,
The internal cross-linking agent (a3) is a compound having two or more ethylenically unsaturated bonds in one molecule,
The monomer (a4) is a compound represented by the following formula (1),
Containing 50% by mass or more and 98% by mass or less of structural units derived from the monomer (a1),
Containing 1.0% by mass or more and 15% by mass or less of structural units derived from the monomer (a2),
Containing 0.020% by mass or more and 10% by mass or less of structural units derived from the internal cross-linking agent (a3),
An electrode binder copolymer for a non-aqueous secondary battery, comprising 0.010% by mass or more and 20% by mass or less of a structural unit derived from the monomer (a4).
Figure JPOXMLDOC01-appb-C000002
 (In formula (1), R 1 is an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.)
[2] The electrode binder copolymer for non-aqueous secondary batteries according to [1], containing 70% by mass or more and 97% by mass or less of structural units derived from the monomer (a1).
[3] The electrode binder copolymer for non-aqueous secondary batteries according to [1] or [2], wherein the anionic functional group of the monomer (a2) is at least one of a carboxy group and a sulfo group. Combined.
[4] The electrode binder copolymer for non-aqueous secondary batteries according to any one of [1] to [3], which contains 2.0% by mass or more and 10% by mass or less of structural units derived from the monomer (a2). Combined.
[5] The electrode binder copolymer for non-aqueous secondary batteries according to any one of [1] to [4], wherein R 1 in formula (1) is an aryl group having 6 to 20 carbon atoms.
[6] The electrode binder copolymer for non-aqueous secondary batteries according to any one of [1] to [5], wherein the compound represented by formula (1) is N-phenylmaleimide.
[7] The non-aqueous secondary battery according to any one of [1] to [6], wherein the content of structural units derived from the monomer (a4) is 0.10% by mass or more and 15% by mass or less. Electrode binder copolymer.
[8] The electrode binder copolymer for non-aqueous secondary batteries according to any one of [1] to [7];
An electrode binder resin composition for a non-aqueous secondary battery, comprising an aqueous medium (c).
[9] The electrode binder copolymer for non-aqueous secondary batteries according to any one of [1] to [7];
an electrode active material;
An electrode slurry for a non-aqueous secondary battery, comprising an aqueous medium.
[10] a current collector made of a metal foil;
A non-aqueous secondary battery electrode comprising an electrode active material layer formed on the current collector,
A non-aqueous secondary battery electrode, wherein the electrode active material layer comprises the electrode binder copolymer for a non-aqueous secondary battery according to any one of [1] to [7], and an electrode active material.
[11] A non-aqueous secondary battery comprising a positive electrode and a negative electrode,
A non-aqueous secondary battery in which at least one of the positive electrode and the negative electrode contains the electrode binder copolymer for a non-aqueous secondary battery according to any one of [1] to [7].
　本発明によれば、集電体に対する剥離強度が高い電極活物質層を有する電極が得られ、さらに充放電サイクル特性が良好な非水系二次電池が得られる非水系二次電池用電極バインダー共重合体、及び非水系二次電池用電極バインダー樹脂組成物を提供することができる。また、本発明によれば、集電体に対する剥離強度が高い電極活物質層を有するし、充放電サイクル特性が良好な非水系二次電池が得られる非水系二次電池電極を提供することができる。 ADVANTAGE OF THE INVENTION According to the present invention, an electrode having an electrode active material layer with high peel strength against a current collector can be obtained, and an electrode binder for a non-aqueous secondary battery that can obtain a non-aqueous secondary battery with good charge-discharge cycle characteristics can be obtained. A polymer and an electrode binder resin composition for a non-aqueous secondary battery can be provided. Further, according to the present invention, it is possible to provide a non-aqueous secondary battery electrode that has an electrode active material layer with high peel strength against a current collector and that provides a non-aqueous secondary battery with good charge-discharge cycle characteristics. can.
　「（メタ）アクリル」とは、アクリル及びメタクリルの総称であり、「（メタ）アクリレート」とは、アクリレート及びメタクリレートの総称である。 "(Meth)acrylic" is a generic term for acrylic and methacrylic, and "(meth)acrylate" is a generic term for acrylate and methacrylate.
　「不揮発分」は、直径５ｃｍのアルミ皿に組成物を１ｇ秤量し、１気圧（１０１３ｈＰａ）で、乾燥器内で空気を循環させながら１０５℃で１時間乾燥させ後に残った成分である。組成物の形態は、溶液、分散液、スラリーが挙げられるが、これらに限られない。 "Non-volatile matter" is the component remaining after weighing 1 g of the composition in an aluminum dish with a diameter of 5 cm and drying it at 105°C for 1 hour while circulating air in a dryer at 1 atmosphere (1013 hPa). Forms of the composition include, but are not limited to, solutions, dispersions, and slurries.
　「不揮発分濃度」とは、乾燥前の組成物の質量（１ｇ）に対する、上記条件下で乾燥後の不揮発分の質量割合（質量％）である。 "Non-volatile content concentration" is the mass ratio (mass%) of the non-volatile content after drying under the above conditions with respect to the mass (1 g) of the composition before drying.
　「エチレン性不飽和結合」とは、特に断りがない限り、ラジカル重合性を有するエチレン性不飽和結合を指す。 "Ethylenically unsaturated bond" refers to an ethylenically unsaturated bond having radical polymerizability unless otherwise specified.
　エチレン性不飽和結合を有する化合物の重合体において、あるエチレン性不飽和結合を有する化合物に由来する構造単位は、その化合物のエチレン性不飽和結合以外の部分の化学構造と、重合体におけるその構造単位の主鎖を形成する部分以外の部分の化学構造とが同じであるとする。例えば、アクリル酸に由来する構造単位は、重合体として主鎖以外の部分にＣＯＯＨの構造を有している。 In a polymer of a compound having an ethylenically unsaturated bond, a structural unit derived from a compound having an ethylenically unsaturated bond is the chemical structure of the portion other than the ethylenically unsaturated bond of the compound and the structure of the polymer. It is assumed that the chemical structure of the portion other than the portion forming the main chain of the unit is the same. For example, a structural unit derived from acrylic acid has a COOH structure in a portion other than the main chain as a polymer.
　また、重合後に主鎖以外の部分を化学反応させる等、単量体の化学構造と重合体の化学構造とで対応しない場合は、重合後の化学構造を基準とする。また、カルボキシ基等のアニオン性官能基は、塩を形成してもよい。例えば、ＣＯＯＮＨ４もカルボキシ基とする。 In addition, when the chemical structure of the monomer and the chemical structure of the polymer do not correspond to each other, such as when the portion other than the main chain is chemically reacted after polymerization, the chemical structure after polymerization is used as a reference. An anionic functional group such as a carboxy group may also form a salt. For example, COONH 4 is also a carboxy group.
＜１．非水系二次電池用電極バインダー共重合体（Ａ）＞
　本実施形態にかかる非水系二次電池用電極バインダー共重合体（Ａ）（以下、共重合体（Ａ）とすることもある）は、非水系二次電池用電極に用いることが可能なバインダー共重合体である。非水系二次電池用電極バインダー共重合体（Ａ）は、後述する単量体（ａ１）に由来する構造単位と、後述する単量体（ａ２）に由来する構造単位と、後述する内部架橋剤（ａ３）に由来する構造単位と、後述する単量体（ａ４）に由来する構造単位と、を含む。共重合体（Ａ）は、その他の単量体（ａ５）に由来する構造単位を含んでもよい。 <1. Electrode binder copolymer for non-aqueous secondary battery (A)>
The electrode binder copolymer (A) for non-aqueous secondary batteries according to the present embodiment (hereinafter sometimes referred to as copolymer (A)) is a binder that can be used for electrodes for non-aqueous secondary batteries. It is a copolymer. The electrode binder copolymer for non-aqueous secondary batteries (A) includes a structural unit derived from the monomer (a1) described later, a structural unit derived from the monomer (a2) described later, and an internal crosslinked polymer described later. It contains a structural unit derived from the agent (a3) and a structural unit derived from the monomer (a4) described below. The copolymer (A) may contain structural units derived from other monomers (a5).
〔１－１．単量体（ａ１）〕
　単量体（ａ１）は、分子内に含まれるエチレン性不飽和結合が１個である（メタ）アクリル酸アルキルエステル、及び分子内に含まれるエチレン性不飽和結合が１個である炭化水素化合物からなる群より選ばれる少なくとも１種類を含む。本実施形態において、炭化水素化合物は、エチレン性不飽和結合以外の、アニオン性官能基、ヒドロキシ基等の他の官能基を有さない炭化水素化合物である。
　（メタ）アクリル酸アルキルエステルは、（メタ）アクリロイルオキシ基以外の部分が炭化水素構造である。単量体（ａ１）は、上記（メタ）アクリル酸アルキルエステル、及び上記炭化水素化合物の両方を含むことが好ましい。単量体（ａ１）は、電極活物質と共重合体（Ａ）との密着性の観点から、エチレン性不飽和結合を有する芳香族化合物を含むことが好ましい。単量体（ａ１）は、１種類の化合物のみを含んでもよく、２種類以上の化合物を含んでもよい。 [1-1. monomer (a1)]
The monomer (a1) is a (meth)acrylic acid alkyl ester having one ethylenically unsaturated bond contained in the molecule, and a hydrocarbon compound having one ethylenically unsaturated bond contained in the molecule. At least one selected from the group consisting of In the present embodiment, the hydrocarbon compound is a hydrocarbon compound that does not have other functional groups such as anionic functional groups and hydroxy groups other than ethylenically unsaturated bonds.
The (meth)acrylic acid alkyl ester has a hydrocarbon structure except for the (meth)acryloyloxy group. The monomer (a1) preferably contains both the (meth)acrylic acid alkyl ester and the hydrocarbon compound. From the viewpoint of adhesion between the electrode active material and the copolymer (A), the monomer (a1) preferably contains an aromatic compound having an ethylenically unsaturated bond. The monomer (a1) may contain only one compound, or may contain two or more compounds.
　（メタ）アクリル酸アルキルエステルとしては、例えば、（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸ｎ－プロピル、（メタ）アクリル酸イソプロピル、（メタ）アクリル酸ｎ－ブチル、（メタ）アクリル酸ｔｅｒｔ－ブチル、（メタ）アクリル酸シクロヘキシル、（メタ）アクリル酸２－エチルヘキシル、（メタ）アクリル酸イソボルニル、（メタ）アクリル酸ラウリル、（メタ）アクリル酸ステアリル等が挙げられる。これらの中でも、（メタ）アクリル酸メチル及び（メタ）アクリル酸２－エチルヘキシルからなる群から選ばれる少なくとも１種の化合物が好ましい。
　分子内に含まれるエチレン性不飽和結合が１個である炭化水素化合物としては、たとえば、エチレン性不飽和結合を有する芳香族化合物が挙げられる。但し、後述の単量体（ａ４）に該当する化合物は除く。エチレン性不飽和結合を有する芳香族化合物としては、例えば、スチレン系化合物、ビニルナフタレン系化合物、ビニルビフェ二ル系化合物等のビニル芳香族化合物が挙げられる。スチレン系化合物としては、共重合体（Ａ）の電極活物質に対する密着性向上の観点からスチレン、ｔ－ブチルスチレン、α－メチルスチレン、ｐ－メチルスチレン、及び１，１－ジフェニルエチレンからなる群から選ばれる少なくとも１種の化合物が好ましく、スチレン、α－メチルスチレンがより好ましく、スチレンが更に好ましい。
　分子内に含まれるエチレン性不飽和結合が１個である炭化水素化合物としては、エチレン性不飽和結合を有する脂肪族炭化水素化合物等も挙げられる。 Examples of (meth)acrylic acid alkyl esters include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl (meth)acrylate. , tert-butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate and the like. . Among these, at least one compound selected from the group consisting of methyl (meth)acrylate and 2-ethylhexyl (meth)acrylate is preferred.
Hydrocarbon compounds containing one ethylenically unsaturated bond in the molecule include, for example, aromatic compounds having an ethylenically unsaturated bond. However, compounds corresponding to the below-described monomer (a4) are excluded. Examples of aromatic compounds having an ethylenically unsaturated bond include vinyl aromatic compounds such as styrene compounds, vinylnaphthalene compounds and vinylbiphenyl compounds. As the styrene-based compound, the group consisting of styrene, t-butylstyrene, α-methylstyrene, p-methylstyrene, and 1,1-diphenylethylene from the viewpoint of improving the adhesion of the copolymer (A) to the electrode active material. At least one compound selected from is preferred, styrene and α-methylstyrene are more preferred, and styrene is even more preferred.
Examples of hydrocarbon compounds having one ethylenically unsaturated bond in the molecule include aliphatic hydrocarbon compounds having an ethylenically unsaturated bond.
〔１－２．単量体（ａ２）〕
　単量体（ａ２）は、１個のエチレン性不飽和結合およびアニオン性官能基を有する化合物である。本実施形態において、単量体（ａ２）は、エチレン性不飽和結合を有し、独立した複数のエチレン性不飽和結合を有しない化合物である。
　単量体（ａ２）は、１種類の化合物のみであってもよく、２種類以上の化合物を含んでいてもよい。 [1-2. monomer (a2)]
Monomer (a2) is a compound having one ethylenically unsaturated bond and an anionic functional group. In the present embodiment, the monomer (a2) is a compound that has an ethylenically unsaturated bond and does not have multiple independent ethylenically unsaturated bonds.
The monomer (a2) may be only one type of compound, or may contain two or more types of compounds.
　単量体（ａ２）の有するアニオン性官能基としては、例えば、カルボキシ基、スルホ基、及びリン酸基等が挙げられる。単量体（ａ２）は、カルボキシ基、及びスルホ基のうち少なくともいずれかを有する化合物であることが好ましく、カルボキシ基を有する化合物であることがより好ましい。
　単量体（ａ２）としては、エチレン性不飽和結合およびカルボキシ基を有する化合物が挙げられる。例えば、（メタ）アクリル酸、クロトン酸等の不飽和モノカルボン酸、マレイン酸、フマル酸、イタコン酸等の不飽和ジカルボン酸、不飽和ジカルボン酸のハーフエステル等が挙げられる。これらの中でも、共重合体（Ａ）を含む電極活物質層の、集電体に対する密着性向上の観点で、単量体（ａ２）は（メタ）アクリル酸、イタコン酸のうち少なくとも１つを含むことが好ましい。 Examples of the anionic functional group possessed by the monomer (a2) include a carboxy group, a sulfo group and a phosphate group. The monomer (a2) is preferably a compound having at least one of a carboxy group and a sulfo group, more preferably a compound having a carboxy group.
Examples of the monomer (a2) include compounds having an ethylenically unsaturated bond and a carboxy group. Examples thereof include unsaturated monocarboxylic acids such as (meth)acrylic acid and crotonic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and half esters of unsaturated dicarboxylic acids. Among these, from the viewpoint of improving the adhesion of the electrode active material layer containing the copolymer (A) to the current collector, the monomer (a2) contains at least one of (meth)acrylic acid and itaconic acid. preferably included.
　共重合体（Ａ）に含まれる、単量体（ａ２）に由来する構造単位の少なくとも一部が、塩基性物質との塩を形成していてもよい。例えば、カルボキシ基と塩基性物質との塩を形成していてもよい。少なくとも一部の成分をカルボン酸塩とした単量体（ａ２）を原料として用いて重合することで塩を形成させてもよい。また、共重合体（Ａ）の合成後に塩基性物質を添加することで、共重合体（Ａ）に含まれる単量体（ａ２）由来の構造単位の少なくとも一部を塩としてもよい。ここで、塩を形成している単量体（ａ２）としては、（メタ）アクリル酸ナトリウム、パラスチレンスルホン酸ナトリウム等が挙げられる。 At least part of the structural units derived from the monomer (a2) contained in the copolymer (A) may form a salt with a basic substance. For example, a carboxyl group and a basic substance may form a salt. A salt may be formed by polymerizing a monomer (a2), at least a part of which is a carboxylate, as a starting material. At least part of the structural units derived from the monomer (a2) contained in the copolymer (A) may be converted into a salt by adding a basic substance after the synthesis of the copolymer (A). Examples of the salt-forming monomer (a2) include sodium (meth)acrylate and sodium p-styrenesulfonate.
　単量体（ａ２）は、エチレン性不飽和結合を有するスルホン酸及びその塩のうち少なくともいずれかを含むことが好ましく、エチレン性不飽和結合を有するスルホン酸塩を含むことがより好ましい。スルホン酸としては、スルホ基を有する芳香族ビニル化合物を含むことが好ましく、パラスチレンスルホン酸を含むことがより好ましい。スルホン酸塩としては、スルホ基を有する芳香族ビニル化合物の塩を含むことが好ましく、パラスチレンスルホン酸塩を含むことがより好ましく、重合の安定性の向上の観点から、パラスチレンスルホン酸ナトリウム（p-スチレンスルホン酸ナトリウムともいう）を含むことがさらに好ましい。 The monomer (a2) preferably contains at least one of a sulfonic acid having an ethylenically unsaturated bond and a salt thereof, more preferably a sulfonate having an ethylenically unsaturated bond. The sulfonic acid preferably contains an aromatic vinyl compound having a sulfo group, and more preferably contains p-styrenesulfonic acid. The sulfonate preferably contains a salt of an aromatic vinyl compound having a sulfo group, and more preferably contains a p-styrenesulfonate. From the viewpoint of improving the stability of polymerization, sodium p-styrenesulfonate ( (Also called sodium p-styrenesulfonate).
　エチレン性不飽和結合及びリン酸基を有する化合物の具体例は、２－メタクロイロキシエチルアシッドホスフェート、アシッドホスホオキシポリオキシエチレングリコールモノメタクリレート、アシッドホスホオキシポリオキシプロピレングリコールモノメタクリレート、３－クロロ２－アシッドホスホオキシプロピルメタクリレート、メタクロイルオキシエチルアシッドホスフェート・モノエタノールアミン塩等が挙げられる。 Specific examples of compounds having an ethylenically unsaturated bond and a phosphate group include 2-methacryloyloxyethyl acid phosphate, acid phosphooxypolyoxyethylene glycol monomethacrylate, acid phosphooxypolyoxypropylene glycol monomethacrylate, 3-chloro-2 -acid phosphooxypropyl methacrylate, methacryloyloxyethyl acid phosphate/monoethanolamine salt, and the like.
〔１－３．内部架橋剤（ａ３）〕
　内部架橋剤（ａ３）は、１分子中に２つ以上のエチレン性不飽和結合を有する化合物である。内部架橋剤（ａ３）は、前記単量体（ａ１）、前記単量体（ａ２）、及び前記単量体（ａ３）を含む単量体のラジカル重合において架橋構造を形成可能な化合物である。 [1-3. Internal cross-linking agent (a3)]
The internal cross-linking agent (a3) is a compound having two or more ethylenically unsaturated bonds in one molecule. The internal cross-linking agent (a3) is a compound capable of forming a crosslinked structure in radical polymerization of monomers including the monomer (a1), the monomer (a2), and the monomer (a3). .
　１分子中に２つ以上のエチレン性不飽和結合を有する化合物の具体例は、ジビニルベンゼン、１，６－ヘキサンジオールジアクリレート、２－ヒドロキシ－３－アクリロイロキシプロピルメタクリレートが挙げられる。これらの中でも、共重合体（Ａ）の電極活物質に対する密着性向上の観点で、ジビニルベンゼンが好ましい。 Specific examples of compounds having two or more ethylenically unsaturated bonds in one molecule include divinylbenzene, 1,6-hexanediol diacrylate, and 2-hydroxy-3-acryloyloxypropyl methacrylate. Among these, divinylbenzene is preferable from the viewpoint of improving the adhesion of the copolymer (A) to the electrode active material.
〔１－４．単量体（ａ４）〕
　単量体（ａ４）は、以下の式（１）に示される化合物である。なお、本実施形態において単量体（ａ４）に該当し、単量体（ａ１）、単量体（ａ２）等、他の単量体にも該当しうる化合物は、単量体（ａ４）に該当するものとする。 [1-4. monomer (a4)]
Monomer (a4) is a compound represented by the following formula (1). In this embodiment, a compound that corresponds to the monomer (a4) and can also correspond to other monomers such as the monomer (a1) and the monomer (a2) is the monomer (a4) shall fall under
Figure JPOXMLDOC01-appb-C000003
Figure JPOXMLDOC01-appb-C000003
　式（１）中、Ｒ１は炭素数１～１２のアルキル基、炭素数３～２０の環状アルキル基、または炭素数６～２０のアリール基であり、炭素数３～２０の環状アルキル基、または炭素数６～２０のアリール基であることが好ましく、炭素数６～２０のアリール基であることがさらに好ましい。これらの炭化水素基は、カルボキシ基等の置換基を有していてもよいし、有さなくてもよい。 In formula (1), R 1 is an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms, and a cyclic alkyl group having 3 to 20 carbon atoms, Alternatively, it is preferably an aryl group having 6 to 20 carbon atoms, more preferably an aryl group having 6 to 20 carbon atoms. These hydrocarbon groups may or may not have a substituent such as a carboxy group.
　炭素数１～１２のアルキル基としては、メチル基、エチル基、ｎ－プロピル基、イソプロピル基、ｎ－ブチル基、イソブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ｎ－ペンチル基、ｎ－ヘキシル基などが挙げられる。 Examples of alkyl groups having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, n- A hexyl group and the like can be mentioned.
　炭素数３～２０の環状アルキル基としては、置換基を有してもよいシクロプロピル基、シクロブチル基、シクロペンチル基、シクロヘキシル基などが挙げられる。かかる置換基としては、メチル基、エチル基、ｎ－プロピル基、イソプロピル基、ｎ－ブチル基、イソブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ｎ－ペンチル基、ｎ－ヘキシル基などのアルキル基が挙げられる。 Examples of the cyclic alkyl group having 3 to 20 carbon atoms include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, etc. which may have a substituent. Such substituents include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group and n-hexyl group. groups.
　炭素数６～２０のアリール基としては、１つ以上の置換基を有していてもよい炭素数６～１４のアリール基が好ましい。炭素数６～１４のアリール基としては、フェニル基、ナフチル基、アントリル基、フェナントリル基などが挙げられる。かかる炭素数６～１４のアリール基が有していてもよい置換基としては、メチル基、エチル基、ｎ－プロピル基、イソプロピル基、ｎ－ブチル基、イソブチル基、ｓｅｃ－ブチル基、ｔｅｒｔ－ブチル基、ｎ－ペンチル基、ｎ－ヘキシル基などのアルキル基；フェニル基などのアリール基；ベンジル基などのアラルキル基が挙げられる。 The aryl group having 6 to 20 carbon atoms is preferably an aryl group having 6 to 14 carbon atoms which may have one or more substituents. The aryl group having 6 to 14 carbon atoms includes phenyl group, naphthyl group, anthryl group, phenanthryl group and the like. Examples of substituents that such an aryl group having 6 to 14 carbon atoms may have include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert- Alkyl groups such as a butyl group, n-pentyl group and n-hexyl group; aryl groups such as a phenyl group; and aralkyl groups such as a benzyl group.
　本実施形態で用いられる式（１）に示される構造を有する化合物はＮ－置換型マレイミドとも呼ばれる。Ｎ－置換型マレイミドの具体例としては、Ｎ－メチルマレイミド、Ｎ－エチルマレイミド、Ｎ－プロピルマレイミド、Ｎ－イソプロピルマレイミド、Ｎ－ブチルマレイミド、Ｎ－イソブチルマレイミド、Ｎ－ｔ－ブチルマレイミドなどのＮ－アルキルマレイミド；Ｎ－シクロヘキシルマレイミド、Ｎ－シクロペンチルマレイミド、Ｎ－ノルボルニルマレイミド、Ｎ－シクロヘキシルメチルマレイミド、Ｎ－シクロペンチルメチルマレイミドなどのＮ－シクロアルキルマレイミド；Ｎ－フェニルマレイミド、Ｎ－クロロフェニルマレイミド、Ｎ－メチルフェニルマレイミド、Ｎ－ナフチルマレイミド、Ｎ－ヒドロキシフェニルマレイミド、Ｎ－メトキシフェニルマレイミド、Ｎ－カルボキシフェニルマレイミド、Ｎ－ニトロフェニルマレイミド、Ｎ－トリブロモフェニルマレイミドなどのＮ－アリールマレイミドなどが挙げられる。これらのうち、サイクル特性をより向上させる観点から、Ｎ－シクロアルキルマレイミド、Ｎ－アリールマレイミドが好ましく、Ｎ－アリールマレイミドがより好ましく、Ｎ－フェニルマレイミドが特に好ましい。 A compound having a structure represented by formula (1) used in this embodiment is also called an N-substituted maleimide. Specific examples of N-substituted maleimides include N- -alkylmaleimide; N-cycloalkylmaleimide such as N-cyclohexylmaleimide, N-cyclopentylmaleimide, N-norbornylmaleimide, N-cyclohexylmethylmaleimide, N-cyclopentylmethylmaleimide; N-phenylmaleimide, N-chlorophenylmaleimide, N-arylmaleimides such as N-methylphenylmaleimide, N-naphthylmaleimide, N-hydroxyphenylmaleimide, N-methoxyphenylmaleimide, N-carboxyphenylmaleimide, N-nitrophenylmaleimide and N-tribromophenylmaleimide; be done. Among these, N-cycloalkylmaleimide and N-arylmaleimide are preferred, N-arylmaleimide is more preferred, and N-phenylmaleimide is particularly preferred, from the viewpoint of further improving cycle characteristics.
　単量体（ａ４）として、これらの化合物は１種であっても、複数種で用いてもよい。すなわちＲ１は１種であっても、複数種であってもよい。 One or more of these compounds may be used as the monomer (a4). That is, R 1 may be of one type or plural types.
　単量体（ａ４）に由来する構造単位は、共重合体（Ａ）においてサイクル特性向上に寄与する部分を構成する。 The structural unit derived from the monomer (a4) constitutes a part of the copolymer (A) that contributes to improving cycle characteristics.
　共重合体（Ａ）が、単量体（ａ４）に由来する構造単位を含むことで、共重合体（Ａ）を電極バインダーとして用いた非水系二次電池のサイクル特性（サイクル容量維持率）が向上する理由は必ずしも定かではないが、本発明者らは以下の作用機構を推察する。単量体（ａ４）に由来する構造単位は、環状イミド構造を有することで極性が高く、分子間力が強いという特性がある。このことにより、共重合体の分子鎖間への電解液の浸潤を抑制することができ、電解液中での電極構造劣化を抑制する。すなわち、共重合体（Ａ）は電極バインダーとして用いた場合に良好な耐電解液性を示すことが考えられる。この作用機構により、結果として共重合体（Ａ）を電極バインダーとして用いた非水系二次電池のサイクル特性（サイクル容量維持率）が向上すると推察される。 Since the copolymer (A) contains a structural unit derived from the monomer (a4), the cycle characteristics (cycle capacity retention rate) of a non-aqueous secondary battery using the copolymer (A) as an electrode binder Although the reason for the improvement is not necessarily clear, the present inventors presume the following mechanism of action. The structural unit derived from the monomer (a4) has the characteristics of high polarity and strong intermolecular force due to the cyclic imide structure. This makes it possible to suppress infiltration of the electrolytic solution between the molecular chains of the copolymer, thereby suppressing deterioration of the electrode structure in the electrolytic solution. That is, it is considered that the copolymer (A) exhibits good electrolyte resistance when used as an electrode binder. This action mechanism is presumed to result in an improvement in the cycle characteristics (cycle capacity retention rate) of a non-aqueous secondary battery using the copolymer (A) as an electrode binder.
〔１－５．その他の単量体（ａ５）〕
　その他の単量体（ａ５）は、単量体（ａ１）と単量体（ａ２）と内部架橋剤（ａ３）と単量体（ａ４）と（「単量体（ａ１）～（ａ４）」ともいうことがある。）のいずれにも該当しない化合物で、かつ単量体（ａ１）～（ａ４）と共重合可能な化合物である。その他の単量体（ａ５）としては、例えば、グリシジル基及びエチレン性不飽和結合を有する化合物、ヒドロキシ基及びエチレン性不飽和結合を有する化合物等が挙げられる。 [1-5. Other monomer (a5)]
Other monomers (a5) are monomers (a1), monomers (a2), internal cross-linking agents (a3), monomers (a4) and ("monomers (a1) to (a4) ), and is a compound that can be copolymerized with the monomers (a1) to (a4). Other monomers (a5) include, for example, compounds having a glycidyl group and an ethylenically unsaturated bond, compounds having a hydroxy group and an ethylenically unsaturated bond, and the like.
　グリシジル基及びエチレン性不飽和結合を有する化合物の具体例は、グリシジル（メタ）アクリレート等が挙げられる。 Specific examples of compounds having a glycidyl group and an ethylenically unsaturated bond include glycidyl (meth)acrylate and the like.
　ヒドロキシ基及びエチレン性不飽和結合を有する化合物の具体例は、（メタ）アクリル酸２－ヒドロキシエチル、（メタ）アクリル酸４－ヒドロキシブチル等が挙げられる。共重合体（Ａ）の電極活物質に対する密着性の観点から、（メタ）アクリル酸２－ヒドロキシエチルが好ましい。 Specific examples of compounds having a hydroxy group and an ethylenically unsaturated bond include 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate. From the viewpoint of the adhesion of the copolymer (A) to the electrode active material, 2-hydroxyethyl (meth)acrylate is preferred.
　その他の単量体（ａ５）としては、エチレン性不飽和結合を有し、かつ界面活性剤としての機能を有する化合物（重合性界面活性剤ともいう）である。このような単量体の例としては、以下の化学式（２）～（５）で表される化合物等が挙げられる。 The other monomer (a5) is a compound that has an ethylenically unsaturated bond and functions as a surfactant (also called a polymerizable surfactant). Examples of such monomers include compounds represented by the following chemical formulas (2) to (5).
Figure JPOXMLDOC01-appb-C000004
Figure JPOXMLDOC01-appb-C000004
　式（２）中、Ｒ１はアルキル基であることが好ましく、ｐは１０～４０の整数であることが好ましい。Ｒ１の炭素数は１０～４０であることがより好ましく、Ｒ１は炭素数１０～４０の直鎖無置換アルキル基であることがさらに好ましい。式（２）で表される化合物としては、アデカリアソープＳＲ１０（ＡＤＥＫＡ社製）が挙げられる。 In formula (2), R 1 is preferably an alkyl group, and p is preferably an integer of 10-40. More preferably, R 1 has 10 to 40 carbon atoms, and more preferably, R 1 is a linear unsubstituted alkyl group having 10 to 40 carbon atoms. Examples of the compound represented by formula (2) include Adekariasoap SR10 (manufactured by ADEKA).
Figure JPOXMLDOC01-appb-C000005
Figure JPOXMLDOC01-appb-C000005
　式（３）中、Ｒ２はアルキル基であることが好ましく、ｑは１０～１２の整数であることが好ましい。Ｒ２の炭素数は１０～４０であることがより好ましく、Ｒ２は炭素数１０～４０の直鎖無置換アルキル基であることがさらに好ましい。式（５）で表される化合物としては、アクアロンＫＨ１０（第一工業製薬株式会社製）が挙げられる。 In formula (3), R 2 is preferably an alkyl group, and q is preferably an integer of 10-12. More preferably, R 2 has 10 to 40 carbon atoms, and more preferably, R 2 is a linear unsubstituted alkyl group having 10 to 40 carbon atoms. Examples of the compound represented by formula (5) include Aqualon KH10 (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.).
Figure JPOXMLDOC01-appb-C000006
Figure JPOXMLDOC01-appb-C000006
　式（４）中、Ｒ３はアルキル基であることが好ましく、Ｍ１はＮＨ４またはＮａであることが好ましい。Ｒ３の炭素数は１０～４０であることがより好ましく、Ｒ３は炭素数１０～４０の直鎖無置換アルキル基であることがさらに好ましい。 In formula (4), R3 is preferably an alkyl group and M1 is preferably NH4 or Na. More preferably, R 3 has 10 to 40 carbon atoms, and more preferably, R 3 is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
Figure JPOXMLDOC01-appb-C000007
Figure JPOXMLDOC01-appb-C000007
　式（５）中、Ｒ４はアルキル基であることが好ましく、Ｍ２はＮＨ４またはＮａであることが好ましい。Ｒ４の炭素数は１０～４０であることがより好ましく、Ｒ４は炭素数１０～４０の直鎖無置換アルキル基であることがさらに好ましい。 In formula (5), R4 is preferably an alkyl group and M2 is preferably NH4 or Na. More preferably, R 4 has 10 to 40 carbon atoms, and even more preferably, R 4 is a linear unsubstituted alkyl group having 10 to 40 carbon atoms.
〔１－６．外部架橋剤（ｂ）〕
　本実施形態の非水系二次電池用電極バインダー樹脂組成物は、非水系二次電池用電極バインダー共重合体に加えて、さらに、外部架橋剤（ｂ）を含むことが好ましい。
　外部架橋剤（ｂ）は、エチレン性不飽和結合を有さない化合物であり、シランカップリング剤が好ましい。共重合体（Ａ）を電極バインダーとして用いた非水系二次電池のサイクル特性がより向上するためである。 [1-6. External cross-linking agent (b)]
The electrode binder resin composition for non-aqueous secondary batteries of the present embodiment preferably further contains an external cross-linking agent (b) in addition to the electrode binder copolymer for non-aqueous secondary batteries.
The external cross-linking agent (b) is a compound having no ethylenically unsaturated bond, preferably a silane coupling agent. This is because the cycle characteristics of a non-aqueous secondary battery using the copolymer (A) as an electrode binder are further improved.
　エチレン性不飽和結合を有さないシランカップリング剤としては、エポキシ基を含有するシランカップリング剤、またはアミノ基を含有するシランカップリング剤等を使用する事ができる。エポキシ基を含有しエチレン性不飽和結合を有さないシランカップリング剤としては３－グリシドキシプロピルトリメトキシシラン、３－グリシドキシプロピルメチルジエトキシシラン、３－グリシドキシプロピルトリエトキシシラン、等を使用する事ができる。
　アミノ基を含有しエチレン性不飽和結合を有さないシランカップリング剤としてはＮ－２－（アミノエチル）－３－アミノプロピルメチルジメトキシシラン、Ｎ－２－（アミノエチル）－３－アミノプロピルトリメトキシシラン、３－アミノプロピルトリメトキシシランなどを使用することができる。これらは１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 As the silane coupling agent having no ethylenically unsaturated bond, a silane coupling agent containing an epoxy group, a silane coupling agent containing an amino group, or the like can be used. Silane coupling agents containing epoxy groups and having no ethylenically unsaturated bonds include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 3-glycidoxypropyltriethoxysilane. , etc. can be used.
Silane coupling agents containing an amino group and having no ethylenically unsaturated bond include N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane and N-2-(aminoethyl)-3-aminopropyl. Trimethoxysilane, 3-aminopropyltrimethoxysilane, and the like can be used. These may be used individually by 1 type, and may be used in combination of 2 or more type.
〔１－７．共重合体（Ａ）の各構造単位の含有率〕
　単量体（ａ１）に由来する構造単位の、共重合体（Ａ）中の含有率は、５０質量％以上であり、７０質量％以上であることが好ましく、８５質量％以上であることがより好ましい。電極活物質層の剥離強度が向上するため、及び乳化重合により共重合体（Ａ）を合成する際に、重合安定性が向上するためである。 [1-7. Content of each structural unit in copolymer (A)]
The content of the structural unit derived from the monomer (a1) in the copolymer (A) is 50% by mass or more, preferably 70% by mass or more, and preferably 85% by mass or more. more preferred. This is because the peel strength of the electrode active material layer is improved and because the polymerization stability is improved when synthesizing the copolymer (A) by emulsion polymerization.
　単量体（ａ１）に由来する構造単位の、共重合体（Ａ）中の含有率は、９８質量％以下であり、９７質量％以下であることが好ましく、９６質量％以下であることがより好ましい。単量体（ａ２）～（ａ４）に由来する構造単位の含有率を確保するためである。 The content of the structural unit derived from the monomer (a1) in the copolymer (A) is 98% by mass or less, preferably 97% by mass or less, and preferably 96% by mass or less. more preferred. This is to ensure the content of structural units derived from the monomers (a2) to (a4).
　単量体（ａ２）に由来する構造単位の、共重合体（Ａ）中の含有率は、１．０質量％以上であり、２．０質量％以上であることが好ましく、３．０質量％以上であることがより好ましい。共重合体（Ａ）の機械的安定性が向上するためである。また、乳化重合により共重合体（Ａ）を合成する際に、重合安定性が向上するためである。 The content of the structural unit derived from the monomer (a2) in the copolymer (A) is 1.0% by mass or more, preferably 2.0% by mass or more, and 3.0% by mass. % or more is more preferable. This is because the mechanical stability of the copolymer (A) is improved. It is also because the polymerization stability is improved when the copolymer (A) is synthesized by emulsion polymerization.
　単量体（ａ２）に由来する構造単位の、共重合体（Ａ）中の含有率は、１５質量％以下であり、１０質量％以下であることが好ましく、７．０質量％以下であることがより好ましい。共重合体（Ａ）を含む電極活物質層の集電体に対する結着性及び電極活物質間での結着性が向上するためである。 The content of structural units derived from the monomer (a2) in the copolymer (A) is 15% by mass or less, preferably 10% by mass or less, and 7.0% by mass or less. is more preferable. This is because the binding property of the electrode active material layer containing the copolymer (A) to the current collector and the binding property between the electrode active materials are improved.
　内部架橋剤（ａ３）に由来する構造単位の、共重合体（Ａ）中の含有率は、０．０２０質量％以上であり、０．０４０質量％以上であることが好ましく、０．０６質量％以上であることがより好ましい。共重合体（Ａ）を含む電極のサイクル特性が向上するためである。 The content of the structural unit derived from the internal cross-linking agent (a3) in the copolymer (A) is 0.020% by mass or more, preferably 0.040% by mass or more, and 0.06% by mass. % or more is more preferable. This is because the cycle characteristics of the electrode containing the copolymer (A) are improved.
　内部架橋剤（ａ３）に由来する構造単位の、共重合体（Ａ）中の含有率は、１０質量％以下であり、５．０質量％以下であることが好ましく、３．０質量％以下であることがより好ましく、２．０質量％以下であることが特に好ましい。共重合体（Ａ）により良好な可撓性を示す電極を作製することができるためである。 The content of structural units derived from the internal cross-linking agent (a3) in the copolymer (A) is 10% by mass or less, preferably 5.0% by mass or less, and 3.0% by mass or less. It is more preferable that the content is 2.0% by mass or less. This is because an electrode exhibiting good flexibility can be produced from the copolymer (A).
　単量体（ａ４）に由来する構造単位の、共重合体（Ａ）中の含有率は、０．０１０質量％以上であり、０．１０質量％以上であることが好ましく、１．０質量％以上であることがより好ましい。共重合体（Ａ）が良好なサイクル特性を示しつつ、共重合体（Ａ）を電極バインダーとして用いた非水系二次電池のサイクル特性が向上するためである。 The content of the structural unit derived from the monomer (a4) in the copolymer (A) is 0.010% by mass or more, preferably 0.10% by mass or more, and 1.0% by mass. % or more is more preferable. This is because the cycle characteristics of a non-aqueous secondary battery using the copolymer (A) as an electrode binder are improved while the copolymer (A) exhibits good cycle characteristics.
　単量体（ａ４）に由来する構造単位の、共重合体（Ａ）中の含有率は、２０質量％以下であり、１５質量％以下であることが好ましく、１０質量％以下であることがより好ましく、７．０質量％以下であることがさらに好ましく、５．０質量％以下であることが特に好ましい。このような構成の共重合体（Ａ）を電極バインダーとして含むことで、良好な可撓性を示す電極が得られるためである。 The content of the structural unit derived from the monomer (a4) in the copolymer (A) is 20% by mass or less, preferably 15% by mass or less, and preferably 10% by mass or less. More preferably, it is 7.0% by mass or less, and particularly preferably 5.0% by mass or less. This is because an electrode exhibiting good flexibility can be obtained by including the copolymer (A) having such a structure as an electrode binder.
　他の単量体（ａ５）に由来する構造単位の、共重合体（Ａ）中の含有率は、本発明の目的が達成できる範囲であれば特に限定されない。このような他の単量体（ａ５）に由来する構造単位の、共重合体（Ａ）中の含有率としては、０．０１質量％以上１０質量％以下であることが好ましく、５．０質量％以下であることがより好ましく、３．０質量％以下であることがさらに好ましい。 The content of the structural unit derived from the other monomer (a5) in the copolymer (A) is not particularly limited as long as the object of the present invention can be achieved. The content of the structural unit derived from such other monomer (a5) in the copolymer (A) is preferably 0.01% by mass or more and 10% by mass or less, and 5.0 It is more preferably 3.0% by mass or less, more preferably 3.0% by mass or less.
　外部架橋剤（ｂ）の使用量としては、共重合体（Ａ）を１００質量部としたときに、０．３０～９．０質量部であることが好ましく、０．３～７質量部であることがより好ましく、０．４～５．０質量部であることがさらに好ましい。シランカップリング剤などの外部架橋剤（ｂ）の使用量を０．３質量部以上とすることにより、電解液に対する硬化皮膜の耐膨潤性を良好にしやすくでき、９．０質量部以下とすることにより、エマルジョンの経時の安定性の低下を防止できる。 The amount of the external cross-linking agent (b) used is preferably 0.30 to 9.0 parts by mass, more preferably 0.3 to 7 parts by mass, based on 100 parts by mass of the copolymer (A). more preferably 0.4 to 5.0 parts by mass. By setting the amount of the external cross-linking agent (b) such as a silane coupling agent to 0.3 parts by mass or more, the swelling resistance of the cured film to the electrolytic solution can be easily improved, and the amount is set to 9.0 parts by mass or less. Thereby, deterioration of the stability of the emulsion over time can be prevented.
〔１－８．共重合体（Ａ）のガラス転移点〕
　共重合体（Ａ）のＴｇは、日立ハイテクサイエンス社製　ＥＸＳＴＡＲ　ＤＳＣ／ＳＳ７０２０を用いて昇温速度１０℃／分、窒素ガス雰囲気下でＤＳＣ測定を行い、ＤＳＣの温度微分として得られるＤＤＳＣチャートのピークトップ温度である。 [1-8. Glass transition point of copolymer (A)]
The Tg of the copolymer (A) is measured using an EXSTAR DSC/SS7020 manufactured by Hitachi High-Tech Science Co., Ltd. at a temperature increase rate of 10 ° C./min under a nitrogen gas atmosphere. is the peak top temperature.
　共重合体（Ａ）のガラス転移点Ｔｇは、－３０℃以上であることが好ましく、－１０℃以上であることがより好ましく、０℃以上であることがさらに好ましい。共重合体（Ａ）を電極バインダーとして用いた非水系二次電池のサイクル特性が向上するためである。 The glass transition point Tg of the copolymer (A) is preferably -30°C or higher, more preferably -10°C or higher, and even more preferably 0°C or higher. This is because the cycle characteristics of a non-aqueous secondary battery using the copolymer (A) as an electrode binder are improved.
　共重合体（Ａ）のガラス転移点Ｔｇは、１００℃以下であることが好ましく、５０℃以下であることがより好ましく、３０℃以下であることがさらに好ましい。共重合体（Ａ）を電極バインダーとして含む電極活物質層の集電箔に対する密着性が向上するためである。 The glass transition point Tg of the copolymer (A) is preferably 100°C or lower, more preferably 50°C or lower, and even more preferably 30°C or lower. This is because the adhesion of the electrode active material layer containing the copolymer (A) as an electrode binder to the collector foil is improved.
＜２．非水系二次電池用電極バインダー共重合体の合成方法＞
　非水系二次電池用電極バインダー共重合体（Ａ）は、単量体（ａ１）～（ａ４）、及び必要に応じて他の単量体（ａ５）を共重合することで得られる。ここで、共重合体（Ａ）のための単量体を総称する場合は、単量体（ａ）とする。すなわち、単量体（ａ）には、単量体（ａ１）～（ａ４）、必要に応じて他の単量体（ａ５）が含まれる。重合方法としては、例えば、水性媒体（ｃ）中での単量体（ａ）の乳化重合が挙げられる。乳化重合による共重合体（Ａ）の合成において用いられるその他の成分としては、例えば、重合性を有さない界面活性剤（ｄ）、塩基性物質（ｅ）、重合開始剤（ｅ）、連鎖移動剤（ｇ）等が挙げられる。 <2. Method for Synthesizing Electrode Binder Copolymer for Nonaqueous Secondary Battery>
The electrode binder copolymer (A) for non-aqueous secondary batteries is obtained by copolymerizing the monomers (a1) to (a4) and optionally another monomer (a5). Here, when collectively referring to the monomers for the copolymer (A), it is referred to as the monomer (a). That is, the monomer (a) includes monomers (a1) to (a4), and optionally another monomer (a5). The polymerization method includes, for example, emulsion polymerization of the monomer (a) in the aqueous medium (c). Other components used in the synthesis of the copolymer (A) by emulsion polymerization include, for example, a non-polymerizable surfactant (d), a basic substance (e), a polymerization initiator (e), a chain A transfer agent (g) and the like can be mentioned.
〔２－１．水性媒体（ｃ）〕
　水性媒体（ｃ）は、水、親水性の溶媒、またはこれらの混合物である。親水性の溶媒としては、メタノール、エタノール、イソプロピルアルコール、およびＮ‐メチルピロリドン等が挙げられる。重合安定性の観点から、水性媒体（ｃ）は水であることが好ましい。なお、重合安定性を損なわない限り、水性媒体（ｃ）として、水に親水性の溶媒を添加したものを用いてもよい。 [2-1. aqueous medium (c)]
Aqueous medium (c) is water, a hydrophilic solvent, or a mixture thereof. Hydrophilic solvents include methanol, ethanol, isopropyl alcohol, N-methylpyrrolidone, and the like. From the viewpoint of polymerization stability, the aqueous medium (c) is preferably water. As the aqueous medium (c), water to which a hydrophilic solvent is added may be used as long as the polymerization stability is not impaired.
〔２－２．重合性を有さない界面活性剤（ｄ）〕
　単量体（ａ）の乳化重合において、重合性を有さない界面活性剤（ｄ）を用いてもよい。界面活性剤（ｄ）は、重合中及び／または重合後の分散液（エマルジョン）の分散安定性を向上させることができる。界面活性剤（ｄ）としては、アニオン性界面活性剤、ノニオン性界面活性剤を用いることが好ましい。 [2-2. Non-polymerizable surfactant (d)]
A non-polymerizable surfactant (d) may be used in the emulsion polymerization of the monomer (a). The surfactant (d) can improve the dispersion stability of the dispersion (emulsion) during and/or after polymerization. As the surfactant (d), it is preferable to use an anionic surfactant or a nonionic surfactant.
　アニオン性界面活性剤としては、例えば、アルキルベンゼンスルホン酸塩、アルキル硫酸エステル塩、ポリオキシエチレンアルキルエーテル硫酸エステル塩、脂肪酸塩が挙げられる。 Examples of anionic surfactants include alkylbenzene sulfonates, alkyl sulfates, polyoxyethylene alkyl ether sulfates, and fatty acid salts.
　ノニオン性界面活性剤としては、ポリオキシエチレンアルキルエーテル、ポリオキシエチレンアルキルフェニルエーテル、ポリオキシエチレン多環フェニルエーテル、ポリオキシアルキレンアルキルエーテル、ソルビタン脂肪酸エステル、ポリオキシエチレンソルビタン脂肪酸エステルが挙げられる。 Examples of nonionic surfactants include polyoxyethylene alkyl ethers, polyoxyethylene alkylphenyl ethers, polyoxyethylene polycyclic phenyl ethers, polyoxyalkylene alkyl ethers, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters.
　上記の界面活性剤は、１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 The above surfactants may be used singly or in combination of two or more.
〔２－３．塩基性物質（ｅ）〕
　単量体（ａ）を水性媒体（ｃ）中で乳化重合する場合は、塩基性物質（ｅ）を加えてもよい。塩基性物質（ｅ）を加えることで、単量体（ａ）及び／または共重合体（Ａ）に含まれる酸性成分を中和し、ｐＨを調整することができる。ｐＨを調整することで、乳化重合中及び／または乳化重合後の分散液の機械的安定性、化学的安定性を向上させることができる。 [2-3. basic substance (e)]
When the monomer (a) is emulsion polymerized in the aqueous medium (c), a basic substance (e) may be added. By adding the basic substance (e), the acidic component contained in the monomer (a) and/or copolymer (A) can be neutralized to adjust the pH. By adjusting the pH, it is possible to improve the mechanical stability and chemical stability of the dispersion during and/or after emulsion polymerization.
　分散液の２３℃でのｐＨは、１．５～１０であることが好ましく、６．０～９．０であることがより好ましく、５．０～９．０であることがさらに好ましい。後述の電極スラリー中の活物質の沈降を抑制するためである。 The pH of the dispersion at 23°C is preferably from 1.5 to 10, more preferably from 6.0 to 9.0, even more preferably from 5.0 to 9.0. This is for suppressing sedimentation of the active material in the electrode slurry, which will be described later.
　塩基性物質（ｅ）としては、アンモニア、トリエチルアミン、水酸化ナトリウム、水酸化リチウム等が挙げられる。これらの塩基性物質（ｅ）は、１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。 Basic substances (e) include ammonia, triethylamine, sodium hydroxide, lithium hydroxide, and the like. These basic substances (e) may be used singly or in combination of two or more.
〔２－４．ラジカル重合開始剤（ｆ）〕
　乳化重合の際に用いられるラジカル重合開始剤（ｆ）としては、特に限定されるものではなく、公知のものを用いることができる。ラジカル重合開始剤としては、例えば、過硫酸アンモニウム、過硫酸カリウムなどの過硫酸塩；過酸化水素；アゾ化合物；ｔ－ブチルハイドロパーオキサイド、ｔｅｒｔ－ブチルパーオキシベンゾエート、クメンハイドロパーオキサイドなどの有機過酸化物が挙げられる。中でも、過硫酸塩および有機過酸化物が好ましい。本実施形態においては、乳化重合の際にラジカル重合開始剤と、重亜硫酸ナトリウム、ロンガリット、アスコルビン酸等の還元剤とを併用して、レドックス重合してもよい。 [2-4. Radical polymerization initiator (f)]
The radical polymerization initiator (f) used in emulsion polymerization is not particularly limited, and known initiators can be used. Examples of radical polymerization initiators include persulfates such as ammonium persulfate and potassium persulfate; hydrogen peroxide; azo compounds; organic peroxides such as t-butyl hydroperoxide, tert-butyl peroxybenzoate and cumene hydroperoxide oxides. Among them, persulfates and organic peroxides are preferred. In the present embodiment, a radical polymerization initiator and a reducing agent such as sodium bisulfite, Rongalit, or ascorbic acid may be used in combination during emulsion polymerization to perform redox polymerization.
　ラジカル重合開始剤の添加量は、単量体（ａ）１００質量部に対して０．１０質量部以上であることが好ましく、０．８０質量部以上であることがより好ましい。単量体（ａ）の重合時の共重合体（Ａ）への転化率を高くすることができるためである。ラジカル重合開始剤の添加量は、単量体（ａ）１００質量部に対して３．０質量部以下であることが好ましく、２．０質量部以下であることがより好ましい。共重合体（Ａ）の分子量を高くすることができ、電極活物質層の電解液に対する膨潤率を下げることができるためである。 The amount of the radical polymerization initiator to be added is preferably 0.10 parts by mass or more, more preferably 0.80 parts by mass or more, relative to 100 parts by mass of the monomer (a). This is because the conversion of the monomer (a) to the copolymer (A) during polymerization can be increased. The amount of the radical polymerization initiator to be added is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less per 100 parts by mass of the monomer (a). This is because the molecular weight of the copolymer (A) can be increased, and the swelling rate of the electrode active material layer with respect to the electrolytic solution can be decreased.
〔２－５．連鎖移動剤（ｇ）〕
　連鎖移動剤（ｇ）は、乳化重合において共重合体（Ａ）の分子量を調整するために用いられる。連鎖移動剤（ｇ）としては、ｎ－ドデシルメルカプタン、ｔｅｒｔ－ドデシルメルカプタン、ｎ－ブチルメルカプタン、２－エチルヘキシルチオグリコレート、２－メルカプトエタノール、β－メルカプトプロピオン酸、メチルアルコール、ｎ－プロピルアルコール、イソプロピルアルコール、ｔ－ブチルアルコール、ベンジルアルコール等が挙げられる。 [2-5. Chain transfer agent (g)]
A chain transfer agent (g) is used to adjust the molecular weight of the copolymer (A) in emulsion polymerization. Chain transfer agents (g) include n-dodecylmercaptan, tert-dodecylmercaptan, n-butylmercaptan, 2-ethylhexylthioglycolate, 2-mercaptoethanol, β-mercaptopropionic acid, methyl alcohol, n-propyl alcohol, isopropyl alcohol, t-butyl alcohol, benzyl alcohol and the like.
〔２－６．乳化重合法〕
　乳化重合法としては、例えば、乳化重合に使用する各成分を連続供給しながら乳化重合する方法等が挙げられる。乳化重合の温度は、特に限定はされないが、例えば、３０～９０℃であり、５０～８５℃であることが好ましく、５５～８０℃であることがさらに好ましい。乳化重合は攪拌しながら行うことが好ましい。また、単量体（ａ）及びラジカル重合開始剤は反応容器内で均一になるよう連続供給することが好ましい。 [2-6. Emulsion polymerization method]
The emulsion polymerization method includes, for example, a method of performing emulsion polymerization while continuously supplying each component used in the emulsion polymerization. The emulsion polymerization temperature is not particularly limited, but is, for example, 30 to 90°C, preferably 50 to 85°C, more preferably 55 to 80°C. Emulsion polymerization is preferably carried out while stirring. Moreover, it is preferable to continuously supply the monomer (a) and the radical polymerization initiator so as to be uniform in the reaction vessel.
　外部架橋剤（ｂ）は上記乳化重合が完了したのち添加するのが好ましい。添加は攪拌しながら行うことが好ましい。 The external cross-linking agent (b) is preferably added after the emulsion polymerization is completed. Addition is preferably carried out while stirring.
＜３．非水系二次電池用電極バインダー樹脂組成物＞
　本実施形態の非水系二次電池用電極バインダー樹脂組成物（以下、バインダー組成物とすることもある）は、非水系二次電池用電極に用いることが可能なバインダー樹脂組成物である。バインダー組成物は、非水系二次電池用電極バインダー共重合体（Ａ）と水性媒体（ｃ）とを含む。バインダー組成物は、非水系二次電池用電極バインダー共重合体（Ａ）が水性媒体（ｃ）中に分散していることが好ましい。バインダー組成物は、これらの成分の他に、例えば、共重合体（Ａ）の合成に用いた上記の成分等を含んでいてもよい。バインダー組成物は、上記の非水系二次電池用電極バインダー共重合体（Ａ）の合成方法によって得られた分散液でもよく、乳化重合以外の方法で得られた共重合体（Ａ）を水性媒体（ｃ）に分散させることにより得られる分散液でもよく、その他の方法により得られる分散液でもよい。
　本実施形態の非水系二次電池用電極バインダー樹脂組成物が、電極バインダーと水性媒体（ｃ）とを含む。電極バインダーは、上述の非水系二次電池用電極バインダー共重合体（Ａ）を含み、上述の非水系二次電池用電極バインダー共重合体（Ａ）であることが好ましい。
　本実施形態の非水系二次電池用電極バインダー樹脂組成物は、本発明の効果をより奏する観点で、負極に用いることが好ましい。 <3. Electrode binder resin composition for non-aqueous secondary battery>
The electrode binder resin composition for non-aqueous secondary batteries of the present embodiment (hereinafter also referred to as a binder composition) is a binder resin composition that can be used for electrodes for non-aqueous secondary batteries. The binder composition contains an electrode binder copolymer for non-aqueous secondary batteries (A) and an aqueous medium (c). In the binder composition, the electrode binder copolymer for non-aqueous secondary batteries (A) is preferably dispersed in the aqueous medium (c). In addition to these components, the binder composition may contain, for example, the above components used in the synthesis of the copolymer (A). The binder composition may be a dispersion obtained by the method for synthesizing the electrode binder copolymer (A) for a non-aqueous secondary battery described above, and the copolymer (A) obtained by a method other than emulsion polymerization may be dispersed in an aqueous solution. A dispersion obtained by dispersing in the medium (c) may be used, or a dispersion obtained by another method may be used.
The electrode binder resin composition for non-aqueous secondary batteries of the present embodiment contains an electrode binder and an aqueous medium (c). The electrode binder contains the electrode binder copolymer (A) for non-aqueous secondary batteries described above, and is preferably the electrode binder copolymer (A) for non-aqueous secondary batteries described above.
The electrode binder resin composition for non-aqueous secondary batteries of the present embodiment is preferably used for a negative electrode from the viewpoint of exhibiting the effects of the present invention.
〔３－１．水性媒体（ｃ）〕
　水性媒体（ｃ）は、水、親水性の溶媒、またはこれらの混合物である。親水性の溶媒の例は、非水系二次電池用電極バインダー共重合体（Ａ）の合成における水性媒体（ｃ）の説明で挙げた通りである。水性媒体（ｃ）は、共重合体（Ａ）の合成に用いた水性媒体（ｃ）と同じでもよく、異なっていてもよい。 [3-1. aqueous medium (c)]
Aqueous medium (c) is water, a hydrophilic solvent, or a mixture thereof. Examples of the hydrophilic solvent are as described in the explanation of the aqueous medium (c) in the synthesis of the electrode binder copolymer (A) for non-aqueous secondary batteries. The aqueous medium (c) may be the same as or different from the aqueous medium (c) used to synthesize the copolymer (A).
　水性媒体（ｃ）は、共重合体（Ａ）の合成に用いる水性媒体（ｃ）をそのまま用いてもよく、水性媒体（ｃ）に水性溶媒を添加した構成でもよく、共重合体（Ａ）の合成後に水性媒体（ｃ）を新たな水性溶媒に置き換えたものでもよい。ここで、添加する、あるいは置き換える水性溶媒は、共重合体（Ａ）の合成に用いた溶媒と同じ組成でもよく、異なる組成でもよい。 The aqueous medium (c) may be the aqueous medium (c) used in the synthesis of the copolymer (A) as it is, or may have a structure in which an aqueous solvent is added to the aqueous medium (c). The aqueous medium (c) may be replaced with a new aqueous solvent after the synthesis of. Here, the aqueous solvent to be added or replaced may have the same composition as the solvent used for synthesizing the copolymer (A), or may have a different composition.
〔３－２．非水系二次電池用電極バインダー樹脂組成物の不揮発分濃度および粘度〕
　バインダー組成物の不揮発分濃度は、２０質量％以上であることが好ましく、２５質量％以上であることがより好ましく、３０質量％以上であることがさらに好ましい。バインダー組成物中に含まれる有効成分の量を多くするためである。バインダー組成物の不揮発分濃度は、水性媒体（ｃ）の量により調整できる。バインダー組成物の不揮発分濃度は、６０質量％以下であってもよい。 [3-2. Non-volatile content concentration and viscosity of electrode binder resin composition for non-aqueous secondary battery]
The non-volatile content of the binder composition is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 30% by mass or more. This is to increase the amount of active ingredient contained in the binder composition. The non-volatile content of the binder composition can be adjusted by adjusting the amount of the aqueous medium (c). The non-volatile content of the binder composition may be 60% by mass or less.
　バインダー組成物の粘度は、３０００ｍＰａ・ｓ以下であることが好ましく、１０００ｍＰａ・ｓ以下であることがより好ましく、２００ｍＰａ・ｓ以下であることがさらに好ましい。後述する電極スラリー作製時のバインダーのロス削減、及びスラリーの脱泡工程の時間短縮のためである。バインダー組成物の粘度は、ブルックフィールド型粘度計を用いて、液温２３℃、回転数６０ｒｐｍ、Ｎｏ．１、Ｎｏ．２、Ｎｏ．３またはＮｏ．４のローターを用いて測定した値である。バインダー組成物の粘度は、バインダー組成物の不揮発分濃度による影響が大きい。 The viscosity of the binder composition is preferably 3000 mPa·s or less, more preferably 1000 mPa·s or less, and even more preferably 200 mPa·s or less. This is for the purpose of reducing the loss of the binder during preparation of the electrode slurry, which will be described later, and shortening the degassing process of the slurry. The viscosity of the binder composition was measured using a Brookfield viscometer at a liquid temperature of 23°C and a rotation speed of 60 rpm. 1, No. 2, No. 3 or No. It is a value measured using a No. 4 rotor. The viscosity of the binder composition is greatly affected by the non-volatile content of the binder composition.
＜４．電極スラリー＞
　次に、本実施形態の非水系二次電池用電極スラリー（以下、電極スラリーとすることもある）について詳述する。電極スラリーは、共重合体（Ａ）と、電極活物質と、水性媒体と、を含む。電極スラリーは、共重合体（Ａ）と電極活物質と、が水性媒体中に分散している構成を有することが好ましい。電極スラリーは、これらの成分の他に、増粘剤、導電助剤、共重合体（Ａ）の合成に用いた上記の成分等を含んでもよい。
　本実施形態の電極スラリーは、より本発明の効果を奏する観点で、負極スラリーであることが好ましい。 <4. Electrode slurry>
Next, the non-aqueous secondary battery electrode slurry (hereinafter also referred to as electrode slurry) of the present embodiment will be described in detail. An electrode slurry contains a copolymer (A), an electrode active material, and an aqueous medium. The electrode slurry preferably has a structure in which the copolymer (A) and the electrode active material are dispersed in an aqueous medium. The electrode slurry may contain, in addition to these components, a thickener, a conductive aid, the above components used in synthesizing the copolymer (A), and the like.
The electrode slurry of the present embodiment is preferably negative electrode slurry from the viewpoint of achieving the effects of the present invention.
〔４－１．非水系二次電池用電極バインダー共重合体（Ａ）の含有量〕
　共重合体（Ａ）の含有量は、電極活物質１００質量部に対して、０．５０質量部以上であることが好ましく、１．０質量部以上であることがより好ましい。共重合体（Ａ）による効果を十分に発現させるためである。 [4-1. Content of electrode binder copolymer (A) for non-aqueous secondary battery]
The content of the copolymer (A) is preferably 0.50 parts by mass or more, more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the electrode active material. This is because the effects of the copolymer (A) can be fully exhibited.
　共重合体（Ａ）の含有量は、電極活物質１００質量部に対して、５．０質量部以下であることが好ましく、４．０質量部以下であることがより好ましく、３．０質量部以下であることがさらに好ましい。電極スラリーを用いて作製される電極活物質層において、電極活物質の含有率を高めるためである。 The content of the copolymer (A) is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and 3.0 parts by mass with respect to 100 parts by mass of the electrode active material. Part or less is more preferable. This is for increasing the content of the electrode active material in the electrode active material layer produced using the electrode slurry.
〔４－２．電極活物質〕
　電極活物質としては、リチウムイオン等の電荷キャリアとなるイオンを挿入（Ｉｎｔｅｒｃａｒａｔｉｏｎ）／脱離（Ｄｅｉｎｔｅｒｃａｌａｔｉｏｎ）可能な材料である。電荷キャリアとなるイオンがアルカリ金属イオンであることが好ましく、リチウムイオン、ナトリウムイオン、カリウムイオンであることがより好ましく、リチウムイオンであることがさらに好ましい。 [4-2. Electrode active material]
The electrode active material is a material capable of intercalating/deintercalating ions such as lithium ions that serve as charge carriers. The charge carrier ions are preferably alkali metal ions, more preferably lithium ions, sodium ions, potassium ions, and even more preferably lithium ions.
　電極が負極である場合、電極活物質、すなわち負極活物質は、炭素材料、ケイ素を含む材料、チタンを含む材料のうち少なくともいずれかを含むことが好ましい。電極活物質として用いられる炭素材料としては、例えば、石油コークス、ピッチコークス、石炭コークス等のコークス、有機高分子の炭素化物、人造黒鉛、天然黒鉛等の黒鉛が挙げられる。ケイ素を含む材料としては、例えば、ケイ素単体、酸化ケイ素等のケイ素化合物が挙げられる。チタンを含む材料としては、例えばチタン酸リチウム等が挙げられる。これらの材料は、単独で用いてもよいが、混合あるいは複合化して用いてもよい。 When the electrode is a negative electrode, the electrode active material, that is, the negative electrode active material, preferably contains at least one of a carbon material, a material containing silicon, and a material containing titanium. Examples of the carbon material used as the electrode active material include coke such as petroleum coke, pitch coke, and coal coke, carbonized organic polymers, and graphite such as artificial graphite and natural graphite. Materials containing silicon include, for example, simple silicon and silicon compounds such as silicon oxide. Materials containing titanium include, for example, lithium titanate. These materials may be used alone, or may be used as a mixture or composite.
　負極活物質は、炭素材料、ケイ素を含む材料のうち少なくともいずれかを含むことが好ましく、炭素材料を含むことがより好ましい。本発明のバインダー共重合体（Ａ）による電極活物質間、及び電極活物質と集電体との間の結着性を向上させる効果が非常に大きいためである。 The negative electrode active material preferably contains at least one of a carbon material and a material containing silicon, and more preferably contains a carbon material. This is because the binder copolymer (A) of the present invention is very effective in improving the binding properties between the electrode active material and between the electrode active material and the current collector.
　電極が正極である場合、電極活物質、すなわち正極活物質は、負極活物質よりも標準電極電位が貴な物質を用いる。正極活物質としては、Ｎｉ－Ｃｏ－Ｍｎ系のリチウム複合酸化物、Ｎｉ－Ｍｎ－Ａｌ系のリチウム複合酸化物、Ｎｉ－Ｃｏ－Ａｌ系のリチウム複合酸化物などのニッケルを含むリチウム複合酸化物；コバルト酸リチウム（ＬｉＣｏＯ２）；スピネル型マンガン酸リチウム（ＬｉＭｎ２Ｏ４）；オリビン型燐酸鉄リチウム；ＴｉＳ２、ＭｎＯ２、ＭｏＯ３、Ｖ２Ｏ５等のカルコゲン化合物等が挙げられる。正極活物質として、これらの物質は１種で用いてもよく、あるいは２種類以上を組み合わせて用いてもよい。 When the electrode is a positive electrode, the electrode active material, that is, the positive electrode active material, is a material with a higher standard electrode potential than the negative electrode active material. Examples of the positive electrode active material include nickel-containing lithium composite oxides such as Ni--Co--Mn-based lithium composite oxides, Ni--Mn--Al-based lithium composite oxides, and Ni--Co--Al-based lithium composite oxides. lithium cobalt oxide ( LiCoO2 ); spinel type lithium manganate ( LiMn2O4 ); olivine type lithium iron phosphate; chalcogen compounds such as TiS2 , MnO2 , MoO3 , V2O5 , and the like. As the positive electrode active material, one of these substances may be used, or two or more of them may be used in combination.
〔４－３．増粘剤〕
　増粘剤としては、カルボキシメチルセルロース（ＣＭＣ）、ヒドロキシエチルセルロース、ヒドロキシプロピルセルロース等のセルロース類、セルロース類のアンモニウム塩、セルロース類のアルカリ金属塩、ポリビニルアルコ－ル、ポリビニルピロリドン等が挙げられる。増粘剤は、カルボキシメチルセルロース、カルボキシメチルセルロースのアンモニウム塩、カルボキシメチルセルロースアルカリ金属塩のうち少なくともいずれかを含むことが好ましい。電極スラリー中で電極活物質が分散しやすくなるためである。 [4-3. Thickener]
Examples of thickening agents include celluloses such as carboxymethyl cellulose (CMC), hydroxyethyl cellulose and hydroxypropyl cellulose, ammonium salts of celluloses, alkali metal salts of celluloses, polyvinyl alcohol and polyvinylpyrrolidone. The thickener preferably contains at least one of carboxymethylcellulose, an ammonium salt of carboxymethylcellulose, and an alkali metal salt of carboxymethylcellulose. This is because the electrode active material is easily dispersed in the electrode slurry.
　電極スラリーにおける増粘剤の含有量は、電極活物質１００質量部に対して０．５０質量部以上であることが好ましく、０．８０質量部以上であることがより好ましい。電極スラリーを用いて作製される電極活物質層において、電極活物質間、及び電極活物質と集電体との間の結着性を向上させるためである。 The content of the thickener in the electrode slurry is preferably 0.50 parts by mass or more, more preferably 0.80 parts by mass or more, relative to 100 parts by mass of the electrode active material. This is to improve the binding properties between the electrode active materials and between the electrode active materials and the current collector in the electrode active material layer produced using the electrode slurry.
　電極スラリーにおける増粘剤の含有量は、電極活物質１００質量部に対して３．０質量部以下であることが好ましく、２．０質量部以下であることがより好ましく、１．５質量部以下であることがさらに好ましい。電極スラリーの塗布性が向上するためである。 The content of the thickening agent in the electrode slurry is preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, and 1.5 parts by mass with respect to 100 parts by mass of the electrode active material. More preferably: This is because the coatability of the electrode slurry is improved.
〔４－４．水性媒体〕
　水性媒体は、水、親水性の溶媒、またはこれらの混合物である。親水性の溶媒の例は、非水系二次電池用電極バインダー共重合体（Ａ）の合成における水性媒体（ｃ）の説明で挙げた通りである。電極スラリーに含まれる水性媒体は、非水系二次電池用電極バインダー樹脂組成物に含まれる水性媒体（ｃ）、あるいは共重合体（Ａ）の合成に用いた水性媒体（ｃ）と同じでもよく、異なっていてもよい。 [4-4. Aqueous medium]
Aqueous media are water, hydrophilic solvents, or mixtures thereof. Examples of the hydrophilic solvent are as described in the explanation of the aqueous medium (c) in the synthesis of the electrode binder copolymer (A) for non-aqueous secondary batteries. The aqueous medium contained in the electrode slurry may be the same as the aqueous medium (c) contained in the electrode binder resin composition for non-aqueous secondary batteries, or the aqueous medium (c) used for synthesizing the copolymer (A). , can be different.
〔４－５．導電助剤〕
　導電助剤としては、カーボンブラック、炭素繊維等を用いることが好ましい。カーボンブラックとしては、ファーネスブラック、アセチレンブラック、デンカブラック（登録商標）（デンカ株式会社製）、ケッチェンブラック（登録商標）（ケッチェンブラックインターナショナル株式会社製）等が挙げられる。炭素繊維は、カーボンナノチューブ、カーボンナノファイバー等が挙げられ、カーボンナノチューブとしては、気相法炭素繊維であるＶＧＣＦ（登録商標、昭和電工株式会社製）が好ましい例として挙げられる。 [4-5. Conductive agent]
Carbon black, carbon fiber, or the like is preferably used as the conductive aid. Examples of carbon black include furnace black, acetylene black, Denka Black (registered trademark) (manufactured by Denka Co., Ltd.), Ketjen Black (registered trademark) (manufactured by Ketjen Black International Co., Ltd.), and the like. Examples of carbon fibers include carbon nanotubes, carbon nanofibers, etc. Preferred examples of carbon nanotubes include VGCF (registered trademark, manufactured by Showa Denko KK), which is a vapor-grown carbon fiber.
〔４－６．電極スラリーの性質〕
　電極スラリーの不揮発分濃度は、２０質量％以上であることが好ましく、３０質量％以上であることがより好ましく、４０質量％以上であることがさらに好ましい。電極スラリー中の有効成分の濃度が高くなり、少ない電極スラリーの量で、十分な量の電極活物質層を形成できるためである。電極スラリーの不揮発分濃度は、電極スラリー中の水性媒体の量で調整できる。 [4-6. Properties of electrode slurry]
The non-volatile content of the electrode slurry is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. This is because the concentration of the active ingredient in the electrode slurry is increased, and a sufficient amount of electrode active material layer can be formed with a small amount of electrode slurry. The non-volatile concentration of the electrode slurry can be adjusted by adjusting the amount of the aqueous medium in the electrode slurry.
　電極スラリーの粘度は、２００００ｍＰａ・ｓ以下であることが好ましく、１００００ｍＰａ・ｓ以下であることがより好ましく、５０００ｍＰａ・ｓ以下であることがさらに好ましい。電極スラリーの集電体への塗布性を向上させ、電極の生産性が向上するためである。電極スラリーの粘度は、電極スラリーの不揮発分濃度、及び増粘剤の種類及び量により大きく影響される。 The viscosity of the electrode slurry is preferably 20000 mPa·s or less, more preferably 10000 mPa·s or less, and even more preferably 5000 mPa·s or less. This is because the coatability of the electrode slurry to the current collector is improved, and the productivity of the electrode is improved. The viscosity of the electrode slurry is greatly affected by the non-volatile concentration of the electrode slurry and the type and amount of the thickener.
　２３℃における電極スラリーのｐＨは、好ましくは２．０～１０であり、より好ましくは４．０～９．０であり、さらに好ましくは６．０～９．０である。電極スラリーを用いて作製される電池の耐久性を向上させるためである。 The pH of the electrode slurry at 23°C is preferably 2.0 to 10, more preferably 4.0 to 9.0, still more preferably 6.0 to 9.0. This is for improving the durability of the battery produced using the electrode slurry.
〔４－７．電極スラリーの製造方法〕
　本実施形態において電極スラリーを調製する方法としては、バインダー組成物と、電極活物質と、必要に応じて増粘剤と、必要に応じて水性媒体と、必要に応じて導電助剤と、必要に応じてその他の成分とを混合する。添加する成分の順序は、特に限定されず、適宜決めればよい。混合方法としては、攪拌式、回転式、振とう式等の混合装置を使用する方法が挙げられる。 [4-7. Method for producing electrode slurry]
As a method for preparing the electrode slurry in the present embodiment, a binder composition, an electrode active material, optionally a thickener, optionally an aqueous medium, optionally a conductive aid, and optionally Mix with other ingredients as appropriate. The order of the components to be added is not particularly limited, and may be determined as appropriate. Examples of the mixing method include a method using a mixing device such as a stirring type, a rotating type, and a shaking type.
＜５．非水系二次電池電極＞
　本実施形態にかかる非水系二次電池電極（以下、「電極」とすることもある）は、集電体と、集電体上に形成された電極活物質層と、を備える。電極の形状としては、例えば、積層体や捲回体が挙げられるが、特に限定されない。また、集電体上への電極活物質層の形成範囲は特に限定されず、集電体の全面に形成されていてもよく、集電体の一部の面に形成されていてもよい。集電体が板、箔等の形状である場合、電極活物質層は、両面に形成されていてもよく、片面のみに形成されていてもよい。本実施形態の非水系二次電池電極は、本発明の効果をより奏する観点で、非水系二次電池負極であることが好ましい。 <5. Non-aqueous secondary battery electrode>
A non-aqueous secondary battery electrode (hereinafter also referred to as "electrode") according to the present embodiment includes a current collector and an electrode active material layer formed on the current collector. Examples of the shape of the electrode include a laminate and a wound body, but are not particularly limited. Moreover, the formation range of the electrode active material layer on the current collector is not particularly limited, and the electrode active material layer may be formed on the entire surface of the current collector or may be formed on a part of the surface of the current collector. When the current collector is in the form of a plate, foil, or the like, the electrode active material layer may be formed on both sides, or may be formed on only one side. The non-aqueous secondary battery electrode of the present embodiment is preferably a non-aqueous secondary battery negative electrode from the viewpoint of exhibiting the effects of the present invention.
〔５－１．集電体〕
　集電体は、厚さ０．００１ｍｍ以上０．５ｍｍ以下の金属シート（金属箔）であることが好ましく、金属としては、鉄、銅、アルミニウム、ニッケル、ステンレス等が挙げられる。非水系電池電極が、リチウムイオン二次電池の負極である場合、集電体は、銅箔であることが好ましい。 [5-1. current collector]
The current collector is preferably a metal sheet (metal foil) having a thickness of 0.001 mm or more and 0.5 mm or less, and examples of metals include iron, copper, aluminum, nickel, and stainless steel. When the nonaqueous battery electrode is the negative electrode of a lithium ion secondary battery, the current collector is preferably copper foil.
〔５－２．電極活物質層〕
　本実施形態にかかる電極活物質層は、バインダー共重合体（Ａ）及び電極活物質を含む。電極活物質層は、上記のバインダー組成物に含まれるその他の成分を含んでもよく、上記の電極スラリーに含まれるその他の成分を含んでもよい。 [5-2. Electrode active material layer]
The electrode active material layer according to this embodiment contains a binder copolymer (A) and an electrode active material. The electrode active material layer may contain other components contained in the above binder composition, and may contain other components contained in the above electrode slurry.
〔５－３．電極の製造方法〕
　電極の製造方法としては、例えば、電極スラリーを集電体上に塗布し、乾燥させて電極活物質層を形成した後、適当な大きさに切断することにより製造できる。 [5-3. Electrode manufacturing method]
The electrode can be produced, for example, by coating an electrode slurry on a current collector, drying it to form an electrode active material layer, and then cutting it into a suitable size.
　電極スラリーを集電体上に塗布する方法としては、特に限定されないが、例えば、リバースロール法、ダイレクトロール法、ドクターブレード法、ナイフ法、エクストルージョン法、カーテン法、グラビア法、バー法、ディップ法、スクイーズ法等が挙げられる。これらの中でも、電極スラリーの粘性等の諸物性及び乾燥性を考慮すると、ドクターブレード法、ナイフ法、またはエクストルージョン法を用いることが好ましい。表面が滑らかで、厚さのばらつきが小さな電極活物質層を得ることができるためである。 The method for applying the electrode slurry onto the current collector is not particularly limited, but examples include a reverse roll method, a direct roll method, a doctor blade method, a knife method, an extrusion method, a curtain method, a gravure method, a bar method, and a dipping method. method, squeeze method, and the like. Among these methods, it is preferable to use the doctor blade method, the knife method, or the extrusion method in consideration of various physical properties such as viscosity and drying property of the electrode slurry. This is because an electrode active material layer with a smooth surface and small variations in thickness can be obtained.
　電極スラリーは、集電体の片面にのみ塗布してもよいし、両面に塗布してもよい。電極スラリーを集電体の両面に塗布する場合は、片面ずつ逐次塗布してもよいし、両面同時に塗布してもよい。また、電極スラリーは、集電体へ連続的に塗布してもよいし、間欠的に塗布してもよい。電極スラリーの塗布量は、電池の設計容量、及び電極スラリーの組成などに応じて適宜決定できる。電極スラリーの塗布量は、電極スラリーの性質にもよるが、１３ｍｇ／ｃｍ２以下（両面に塗布する場合、片面あたりの塗布量）であることが好ましい。電極スラリーの乾燥工程において電極表面の亀裂の発生を抑制できるためである。 The electrode slurry may be applied to only one side of the current collector, or may be applied to both sides. When the electrode slurry is applied to both surfaces of the current collector, it may be applied to each surface one by one, or may be applied to both surfaces at the same time. Moreover, the electrode slurry may be applied to the current collector continuously or intermittently. The amount of the electrode slurry to be applied can be appropriately determined according to the design capacity of the battery, the composition of the electrode slurry, and the like. The coating amount of the electrode slurry is preferably 13 mg/cm 2 or less (coating amount per one side when coating on both sides), although it depends on the properties of the electrode slurry. This is because the generation of cracks on the electrode surface can be suppressed in the step of drying the electrode slurry.
　集電体上に塗布された電極スラリーを乾燥することにより、集電体上に電極活物質層が形成される。電極スラリーの乾燥方法は、特に限定されないが、例えば、熱風、減圧あるいは真空環境、（遠）赤外線、低温風を単独あるいは組み合わせて用いることができる。電極スラリーの乾燥温度及び乾燥時間は、電極スラリー中の不揮発分濃度、集電体への塗布量等によって適宜調整することができる。乾燥温度は、４０℃以上３５０℃以下であることが好ましく、生産性の観点から、６０℃以上１００℃以下であることがより好ましい。乾燥時間は１分以上３０分以下であることが好ましい。 By drying the electrode slurry applied on the current collector, an electrode active material layer is formed on the current collector. The method for drying the electrode slurry is not particularly limited, but for example, hot air, reduced pressure or vacuum environment, (far) infrared rays, and low temperature air can be used alone or in combination. The drying temperature and drying time of the electrode slurry can be appropriately adjusted depending on the concentration of non-volatile matter in the electrode slurry, the amount of coating applied to the current collector, and the like. The drying temperature is preferably 40° C. or higher and 350° C. or lower, and more preferably 60° C. or higher and 100° C. or lower from the viewpoint of productivity. The drying time is preferably 1 minute or more and 30 minutes or less.
　集電体上に電極活物質層が形成された電極シートは、電極として適当な大きさ及び形状にするために切断されてもよい。電極シートの切断方法は特に限定されないが、例えば、スリット、レーザー、ワイヤーカット、カッター、トムソン等を用いることができる。 An electrode sheet in which an electrode active material layer is formed on a current collector may be cut into a size and shape suitable for an electrode. The method for cutting the electrode sheet is not particularly limited, and for example, a slit, laser, wire cut, cutter, Thomson, or the like can be used.
　電極シートを切断する前または後に、必要に応じて電極シートをプレスしてもよい。それによって電極活物質を集電体により強固に結着させ、さらに電極を薄くすることによる非水系電池の小型化が可能になる。プレスの方法としては、一般的な方法を用いることができ、特に金型プレス法またはロールプレス法を用いることが好ましい。金型プレス法の場合、プレス圧は、特に限定されないが、０．５ｔ／ｃｍ２以上５ｔ／ｃｍ２以下とすることが好ましい。ロールプレス法の場合、線圧は、特に限定されないが、０．５ｔ／ｃｍ以上５ｔ／ｃｍ以下とすることが好ましい。プレスによる上記効果を得つつ、電極活物質へのリチウムイオン等の電荷キャリアの挿入及び脱離容量の低下を抑制するためである。 Before or after cutting the electrode sheet, the electrode sheet may be pressed if necessary. As a result, the electrode active material can be more strongly bound to the current collector, and the thickness of the electrode can be reduced, thereby making it possible to reduce the size of the non-aqueous battery. As a pressing method, a general method can be used, and it is particularly preferable to use a die pressing method or a roll pressing method. In the case of the mold press method, the press pressure is not particularly limited, but is preferably 0.5 t/cm 2 or more and 5 t/cm 2 or less. In the roll press method, the line pressure is not particularly limited, but is preferably 0.5 t/cm or more and 5 t/cm or less. This is for suppressing a decrease in the capacity of the electrode active material to insert and desorb charge carriers such as lithium ions while obtaining the above effects of pressing.
＜６．非水系二次電池＞
　本実施形態にかかる非水系二次電池の好ましい一例として、リチウムイオン二次電池について説明するが、電池の構成はここで説明したものに限られない。本実施形態にかかる非水系二次電池は、正極と、負極と、電解液と、必要に応じてセパレータ等の部品と、が外装体に収容されたものであり、正極及び負極のうちの一方または両方に上記の方法により作製された電極を用いる。本実施形態にかかる非水系二次電池において、正極及び負極の少なくとも一方が、電極バインダー中に共重合体（Ａ）を含むが、少なくとも負極が共重合体（Ａ）を含むことが好ましい。 <6. Non-aqueous secondary battery>
A lithium ion secondary battery will be described as a preferred example of the non-aqueous secondary battery according to this embodiment, but the configuration of the battery is not limited to that described here. In the non-aqueous secondary battery according to the present embodiment, a positive electrode, a negative electrode, an electrolytic solution, and, if necessary, parts such as a separator are housed in an outer package, and one of the positive electrode and the negative electrode Alternatively, the electrode produced by the above method is used for both. In the non-aqueous secondary battery according to this embodiment, at least one of the positive electrode and the negative electrode contains the copolymer (A) in the electrode binder, and at least the negative electrode preferably contains the copolymer (A).
〔６－１．電解液〕
　電解液としては、イオン伝導性を有する非水系の液体を使用する。電解液としては、電解質を有機溶媒に溶解させた溶液、イオン液体等が挙げられるが、前者が好ましい。製造コストが低く、内部抵抗の低い非水系電池が得られるためである。 [6-1. Electrolyte]
As the electrolytic solution, a non-aqueous liquid having ionic conductivity is used. Examples of the electrolytic solution include a solution in which an electrolyte is dissolved in an organic solvent, an ionic liquid, and the like, and the former is preferred. This is because a non-aqueous battery with low manufacturing cost and low internal resistance can be obtained.
　電解質としては、アルカリ金属塩を用いることができ、電極活物質の種類等に応じ適宜選択できる。電解質としては、例えば、ＬｉＣｌＯ４、ＬｉＢＦ６、ＬｉＰＦ６、ＬｉＣＦ３ＳＯ３、ＬｉＣＦ３ＣＯ２、ＬｉＡｓＦ６、ＬｉＳｂＦ６、ＬｉＢ１０Ｃｌ１０、ＬｉＡｌＣｌ４、ＬｉＣｌ、ＬｉＢｒ、ＬｉＢ（Ｃ２Ｈ５）４、ＣＦ３ＳＯ３Ｌｉ、ＣＨ３ＳＯ３Ｌｉ、ＬｉＣＦ３ＳＯ３、ＬｉＣ４Ｆ９ＳＯ３、Ｌｉ（ＣＦ３ＳＯ２）２Ｎ、脂肪族カルボン酸リチウム等が挙げられる。また、電解質として、その他のアルカリ金属塩を用いることもできる。 As the electrolyte, an alkali metal salt can be used, which can be appropriately selected according to the type of the electrode active material and the like. Examples of electrolytes include LiClO 4 , LiBF 6 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiB 10 Cl 10 , LiAlCl 4 , LiCl, LiBr, LiB(C 2 H 5 ). 4 , CF 3 SO 3 Li, CH 3 SO 3 Li, LiCF 3 SO 3 , LiC 4 F 9 SO 3 , Li(CF 3 SO 2 ) 2 N, lithium aliphatic carboxylate, and the like. Other alkali metal salts can also be used as the electrolyte.
　電解質を溶解する有機溶媒としては、特に限定されないが、例えば、エチレンカーボネート（ＥＣ）、プロピレンカーボネート（ＰＣ）、ジエチルカーボネート（ＤＥＣ）、メチルエチルカーボネート（ＭＥＣ）、ジメチルカーボネート（ＤＭＣ）、フルオロエチレンカーボネート（ＦＥＣ）、ビニレンカーボネート（ＶＣ）等の炭酸エステル化合物；アセトニトリル等のニトリル化合物；酢酸エチル、酢酸プロピル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸プロピルなどのカルボン酸エステルが挙げられる。これらの有機溶媒は、１種単独で使用してもよいし、２種以上を組み合わせて使用してもよい。中でも、直鎖カーボネート系溶媒を組合せたものを用いることが好ましい。直鎖カーボネート系溶媒としては炭酸ジエチル、炭酸ジメチル、炭酸エチルメチルが挙げられる。 The organic solvent that dissolves the electrolyte is not particularly limited, but examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), methylethyl carbonate (MEC), dimethyl carbonate (DMC), fluoroethylene carbonate. carbonic ester compounds such as (FEC) and vinylene carbonate (VC); nitrile compounds such as acetonitrile; and carboxylic acid esters such as ethyl acetate, propyl acetate, methyl propionate, ethyl propionate and propyl propionate. These organic solvents may be used singly or in combination of two or more. Among them, it is preferable to use a combination of linear carbonate solvents. Examples of linear carbonate-based solvents include diethyl carbonate, dimethyl carbonate, and ethylmethyl carbonate.
〔６－２．外装体〕
　外装体としては、例えばアルミニウム箔と樹脂フィルムとのラミネート材などを適宜使用できるが、これに限られない。電池の形状は、コイン型、ボタン型、シート型、円筒型、角型、扁平型等、いずれの形状であってもよい。 [6-2. exterior body]
As the exterior body, for example, a laminated material of an aluminum foil and a resin film can be appropriately used, but it is not limited to this. The shape of the battery may be coin-shaped, button-shaped, sheet-shaped, cylindrical, square, flat, or any other shape.
　以下の実施例では、本発明の構成の一例としてリチウムイオン二次電池の負極、及びリチウムイオン二次電池を作製し、比較例にかかるリチウムイオン二次電池の負極、及びリチウムイオン二次電池と比較して、本発明の効果を確認する。なお、本発明はこれらによって限定されるものではない。なお、以下の実施例及び比較例で用いられる水は、特に断りがなければ、イオン交換水である。 In the following examples, a negative electrode of a lithium ion secondary battery and a lithium ion secondary battery were produced as an example of the configuration of the present invention, and a negative electrode of a lithium ion secondary battery and a lithium ion secondary battery according to comparative examples were prepared. A comparison is made to confirm the effect of the present invention. In addition, this invention is not limited by these. The water used in the following examples and comparative examples is ion-exchanged water unless otherwise specified.
＜１．非水系二次電池用電極バインダー共重合体（Ａ）の合成工程＞
〔１－１．実施例１〕
　水を２７３質量部と、スチレンを１８７質量部と、メタクリル酸メチルを０．１８質量部と、アクリル酸２－エチルヘキシルを１６５質量部と、アクリル酸２－ヒドロキシエチルを７．５質量部と、イタコン酸を７．５質量部と、アクリル酸８０％水溶液を１５質量部（アクリル酸を１２質量部及び水を３．０質量部）と、ジビニルベンゼンを０．３質量部と、Ｎ－フェニルマレイミド（日本触媒）９．０質量部と、ｐ－スチレンスルホン酸ナトリウムを２．３質量部と、アデカリアソープ（登録商標）ＳＲ－１０を０．７６質量部と、アクアロン（登録商標）ＫＨ－１０を０．９質量部と、を混合して乳化した単量体乳化液を作製した。 <1. Synthesis step of electrode binder copolymer (A) for non-aqueous secondary battery>
[1-1. Example 1]
273 parts by mass of water, 187 parts by mass of styrene, 0.18 parts by mass of methyl methacrylate, 165 parts by mass of 2-ethylhexyl acrylate, 7.5 parts by mass of 2-hydroxyethyl acrylate, 7.5 parts by mass of itaconic acid, 15 parts by mass of 80% acrylic acid aqueous solution (12 parts by mass of acrylic acid and 3.0 parts by mass of water), 0.3 parts by mass of divinylbenzene, N-phenyl 9.0 parts by mass of maleimide (Nippon Shokubai), 2.3 parts by mass of sodium p-styrenesulfonate, 0.76 parts by mass of Adekari Soap (registered trademark) SR-10, and Aqualon (registered trademark) KH A monomer emulsion was prepared by mixing and emulsifying 0.9 parts by mass of -10.
　冷却管、温度計、攪拌機、滴下ロートを有する容積１Ｌのセパラブルフラスコに、水１２５質量部を入れて、７５℃に昇温した。このセパラブルフラスコに、上記の単量体乳化液と、重合開始剤として過硫酸カリウム１．０５質量部を水３０質量部に溶解した水溶液と、ロンガリット０．５５質量部を３０質量部の水に溶解した水溶液と、を８０℃で４時間かけて攪拌しながら滴下し、乳化重合した。単量体乳化液と過硫酸カリウム水溶液、ロンガリット水溶液とを滴下した後、セパラブルフラスコ内の混合液を８０℃で６０分攪拌した。 125 parts by mass of water was put into a 1 L separable flask equipped with a cooling tube, a thermometer, a stirrer, and a dropping funnel, and the temperature was raised to 75°C. In this separable flask, the above monomer emulsion, an aqueous solution obtained by dissolving 1.05 parts by mass of potassium persulfate as a polymerization initiator in 30 parts by mass of water, and 0.55 parts by mass of Rongalite in 30 parts by mass of water. was added dropwise with stirring at 80° C. over 4 hours to carry out emulsion polymerization. After dropping the monomer emulsion, the aqueous potassium persulfate solution, and the aqueous Rongalite solution, the mixture in the separable flask was stirred at 80° C. for 60 minutes.
　次に、ｔｅｒｔ－ブチルパーオキシベンゾエート（化薬アクゾ株式会社製、トリゴノックスＣ）０．６０質量部及びアスコルビン酸０．４０質量部を、１０質量部の水に溶解した水溶液を加えた。次に、ｔｅｒｔ－ブチルヒドロパーオキサイド（化薬アクゾ株式会社製、トリゴノックスＡ－Ｗ７０）１．２３質量部を２７質量部の水に溶解した水溶液と、ロンガリット１．８質量部を２７質量部の水に溶解した水溶液と、を滴下しながら６０分攪拌し、重合を行った。共重合体（Ａ）の水系エマルジョン（ＥＭ－１）が得られた。 Next, an aqueous solution of 0.60 parts by mass of tert-butyl peroxybenzoate (Trigonox C, manufactured by Kayaku Akzo Co., Ltd.) and 0.40 parts by mass of ascorbic acid dissolved in 10 parts by mass of water was added. Next, an aqueous solution obtained by dissolving 1.23 parts by mass of tert-butyl hydroperoxide (Trigonox A-W70, manufactured by Kayaku Akzo Co., Ltd.) in 27 parts by mass of water, and 1.8 parts by mass of Rongalit in 27 parts by mass. Polymerization was carried out by stirring for 60 minutes while dropping an aqueous solution dissolved in water. An aqueous emulsion (EM-1) of copolymer (A) was obtained.
〔１－２．実施例２〕
　Ｎ－フェニルマレイミドを９質量部から１８質量部に増量し、スチレンを１８７質量部から１８２質量部に減量し、アクリル酸２－エチルヘキシルを１６５質量部から１６１質量部に減量した。このこと以外は実施例１と同様な方法で共重合体（Ａ）の水系エマルジョン（ＥＭ－２）が得られた。 [1-2. Example 2]
The amount of N-phenylmaleimide was increased from 9 parts by mass to 18 parts by mass, the amount of styrene was decreased from 187 parts by mass to 182 parts by mass, and the amount of 2-ethylhexyl acrylate was decreased from 165 parts by mass to 161 parts by mass. Aqueous emulsion (EM-2) of copolymer (A) was obtained in the same manner as in Example 1 except for this.
〔１－３．実施例３〕
　実施例１と同様な方法で共重合体（Ａ）の水系エマルジョン（ＥＭ－３）が得られた。 [1-3. Example 3]
An aqueous emulsion (EM-3) of copolymer (A) was obtained in the same manner as in Example 1.
〔１－４．比較例１〕
　比較例１ではＮ－フェニルマレイミドを用いず、スチレンを１８７質量部から１９２質量部に増量し、アクリル酸２－エチルヘキシルを１６５質量部から１６９質量部に増量した。このこと以外は実施例１と同様な方法で共重合体（Ａ）の水系エマルジョン（ｃＥＭ－１）が得られた。 [1-4. Comparative Example 1]
In Comparative Example 1, no N-phenylmaleimide was used, the amount of styrene was increased from 187 parts by mass to 192 parts by mass, and the amount of 2-ethylhexyl acrylate was increased from 165 parts by mass to 169 parts by mass. Aqueous emulsion (cEM-1) of copolymer (A) was obtained in the same manner as in Example 1 except for this.
〔１－５．比較例２〕
　比較例１と同様な方法で共重合体（Ａ）の水系エマルジョン（ｃＥＭ－２）が得られた。 [1-5. Comparative Example 2]
An aqueous emulsion (cEM-2) of copolymer (A) was obtained in the same manner as in Comparative Example 1.
　その他の単量体（ａ５）として用いた重合性界面活性剤であるアデカリアソープＳＲ１０、アクアロンＫＨ１０の詳細について表２に示す。 Table 2 shows details of the polymerizable surfactants Adekari Soap SR10 and Aqualon KH10 used as other monomers (a5).
＜２．非水系二次電池用電極バインダー樹脂組成物の調製工程＞
　実施例１、２および比較例１で同様に行った。得られた共重合体（Ａ）の水系エマルジョンを室温までに冷却した。次に２５質量％のアンモニア水１６質量部、及び水５９質量部を添加して中和した。セパラブルフラスコに、外部架橋剤としてエポキシ基を含有するシランカップリング剤である３－グリドキシプロピルトリメトキシシラン（信越化学製、ＫＢＭ－４０３）２．０質量部を添加し、３０分間攪拌した。それぞれの共重合体（Ａ）を含むバインダー組成物（Ｐ－１）、バインダー組成物（Ｐ－２）、バインダー組成物（ｃＰ－１）を得た。 <2. Preparation step of electrode binder resin composition for non-aqueous secondary battery>
Examples 1 and 2 and Comparative Example 1 were carried out in the same manner. The resulting aqueous emulsion of copolymer (A) was cooled to room temperature. Next, 16 parts by mass of 25% by mass ammonia water and 59 parts by mass of water were added for neutralization. In a separable flask, 2.0 parts by mass of 3-glydoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.), which is a silane coupling agent containing an epoxy group as an external cross-linking agent, was added and stirred for 30 minutes. . A binder composition (P-1), a binder composition (P-2), and a binder composition (cP-1) containing each copolymer (A) were obtained.
　実施例３及び比較例２においては、得られた共重合体（Ａ）の水系エマルジョンを室温までに冷却した。２５質量％のアンモニア水１６質量部（アンモニアを４．０質量部及び水を１２．０質量部）、及び水５９質量部を添加して中和した。セパラブルフラスコに、３－グリドキシプロピルトリメトキシシランを加えず、共重合体（Ａ）を含むバインダー組成物（Ｐ－３）、バインダー組成物（ｃＰ－２）を得た。 In Example 3 and Comparative Example 2, the resulting aqueous emulsion of copolymer (A) was cooled to room temperature. 16 parts by weight of 25% by weight aqueous ammonia (4.0 parts by weight of ammonia and 12.0 parts by weight of water) and 59 parts by weight of water were added for neutralization. A binder composition (P-3) and a binder composition (cP-2) containing the copolymer (A) were obtained without adding 3-glydoxypropyltrimethoxysilane to the separable flask.
　共重合体（Ａ）の合成及びバインダー組成物の調製に用いた成分の使用量を表１に示す。なお、表１で、水の量は、上記合成工程及び調製工程で用いられた水の合計量であり、上記のアクリル酸水溶液及びアンモニア水に含まれている水も計算に含まれる。また、表１において、アクリル酸及びアンモニアの添加量は、上記のアクリル酸水溶液及びアンモニア水に含まれる溶質のみの量である。 Table 1 shows the amounts of the components used in the synthesis of the copolymer (A) and the preparation of the binder composition. In Table 1, the amount of water is the total amount of water used in the synthesis step and the preparation step, and the water contained in the acrylic acid aqueous solution and ammonia water is also included in the calculation. Further, in Table 1, the added amounts of acrylic acid and ammonia are the amounts of only the solutes contained in the acrylic acid aqueous solution and ammonia water.
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000008
Figure JPOXMLDOC01-appb-T000009
Figure JPOXMLDOC01-appb-T000009
＜３．バインダー組成物の評価＞
　実施例および比較例で得られたバインダー組成物、これらバインダー組成物を用いて得た電池の物性および性能評価試験は、以下の方法により行った。評価結果を表１に示す。 <3. Evaluation of Binder Composition>
The physical properties and performance evaluation tests of the binder compositions obtained in Examples and Comparative Examples and the batteries obtained using these binder compositions were conducted by the following methods. Table 1 shows the evaluation results.
〔３－１．不揮発分濃度〕
　直径５ｃｍのアルミ皿にバインダー組成物を１ｇ秤量し、１気圧（１０１３ｈＰａ）で、乾燥器内で空気を循環させながら１０５℃で１時間乾燥させ後に残った成分の質量を測定した。乾燥前のバインダー組成物の質量（１ｇ）に対する、乾燥後に残った上記成分の質量割合（質量％）を不揮発分濃度として算出した。 [3-1. Non-volatile content]
1 g of the binder composition was weighed into an aluminum dish with a diameter of 5 cm, dried at 105° C. for 1 hour while air was circulated in a dryer at 1 atmosphere (1013 hPa), and then the mass of the remaining component was measured. The mass ratio (% by mass) of the components remaining after drying with respect to the mass (1 g) of the binder composition before drying was calculated as the non-volatile concentration.
〔３－２．粘度〕
　ブルックフィールド型粘度計を用いて、液温２３℃、回転数６０ｒｐｍ、Ｎｏ．１、Ｎｏ．２、Ｎｏ．３またはＮｏ．４のローターを用いて測定した。 [3-2. viscosity〕
Using a Brookfield type viscometer, the liquid temperature was 23° C., the number of revolutions was 60 rpm, and No. 1, No. 2, No. 3 or No. 4 rotors were used.
＜４．電極バインダーの評価＞
　ポリエチレンシート上にバインダー組成物を流延し、５０℃、５時間乾燥させたのち、５０℃で１時間真空乾燥させて厚さ０．５ｍｍのフィルムを得た。このフィルムを用いて以下の評価を行った。評価結果を表１に示す。 <4. Evaluation of electrode binder>
The binder composition was cast on a polyethylene sheet, dried at 50° C. for 5 hours, and then vacuum dried at 50° C. for 1 hour to obtain a film with a thickness of 0.5 mm. Using this film, the following evaluations were carried out. Table 1 shows the evaluation results.
〔４－１．共重合体（Ａ）のガラス転移点Ｔｇ〕
　得られたフィルムを２ｍｍ×２ｍｍにカットし、アルミパンに密封して日立ハイテクサイエンス社製　ＥＸＳＴＡＲ　ＤＳＣ／ＳＳ７０２０を用いて昇温速度１０℃／分、窒素ガス雰囲気下でＤＳＣ測定を行った。ＤＳＣの温度微分として得られるＤＤＳＣチャートのピークトップ温度を測定し、この温度を共重合体（Ａ）のガラス転移点Ｔｇ（℃）とした。測定温度範囲は－４０℃～１００℃とした。 [4-1. Glass transition point Tg of copolymer (A)]
The resulting film was cut to 2 mm×2 mm, sealed in an aluminum pan, and subjected to DSC measurement using an EXSTAR DSC/SS7020 manufactured by Hitachi High-Tech Science Co., Ltd. at a heating rate of 10° C./min under a nitrogen gas atmosphere. The peak top temperature of the DDSC chart obtained as temperature differential of DSC was measured, and this temperature was defined as the glass transition point Tg (°C) of the copolymer (A). The measurement temperature range was -40°C to 100°C.
＜５．電極及び電池性能の評価＞
　各実施例及び比較例で作製したバインダー組成物を用いて、負極及びリチウムイオン二次電池を作製して、評価を行った。 <5. Evaluation of electrode and battery performance>
A negative electrode and a lithium ion secondary battery were produced using the binder composition produced in each example and comparative example, and evaluated.
〔５－１．電池の作製〕
［５－１－１．正極の作製］
　正極活物質としてＬｉＮｉ０．６Ｍｎ０．２Ｃｏ０．２Ｏ２を９４質量部、導電助剤としてアセチレンブラックを３質量部、バインダーとしてポリフッ化ビニリデン３質量部を混合したものに、Ｎ－メチルピロリドンを５０質量部加えてさらに混合して正極スラリーを作製した。 [5-1. Production of battery]
[5-1-1. Production of positive electrode]
94 parts by mass of LiNi 0.6 Mn 0.2 Co 0.2 O 2 as a positive electrode active material, 3 parts by mass of acetylene black as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder. 50 parts by mass of methylpyrrolidone was added and further mixed to prepare a positive electrode slurry.
　厚さ１５μｍのアルミニウム箔（正極集電体）の両面に、正極スラリーを、ダイレクトロール法により塗布した。正極集電体への正極スラリーの塗布量は、後述するロールプレス処理後の厚さが片面当たり１２５μｍになるように調整した。 The positive electrode slurry was applied to both sides of a 15 μm thick aluminum foil (positive electrode current collector) by a direct roll method. The amount of the positive electrode slurry applied to the positive electrode current collector was adjusted so that the thickness of the positive electrode current collector after the roll press treatment described later was 125 μm per side.
　正極集電体上に塗布された正極スラリーを、１２０℃で５分乾燥し、ロールプレスにより（サンクメタル社製、プレス荷重５ｔ、ロール幅７ｃｍ）でプレスし、正極活物質層が形成された正極シートを得た。得られた正極シートを５０ｍｍ×４０ｍｍに切り出し、導電タブをつけて正極を作製した。 The positive electrode slurry applied on the positive electrode current collector was dried at 120° C. for 5 minutes and pressed with a roll press (manufactured by Thank Metal Co., press load 5 t, roll width 7 cm) to form a positive electrode active material layer. A positive electrode sheet was obtained. The obtained positive electrode sheet was cut into a size of 50 mm×40 mm, and a conductive tab was attached to prepare a positive electrode.
［５－１－２．負極の作製］
　負極活物質として人造黒鉛（Ｇ４９、江西紫宸科技有限公司製）を１００質量部、各実施例及び比較例で作製したバインダー組成物を３．９質量部（不揮発分として１．５質量部）、およびＣＭＣ（カルボキシメチルセルロース－ナトリウム塩・日本製紙ケミカル（株）製サンローズ（登録商標）ＭＡＣ５００ＬＣ）の２質量％水溶液を６２質量部混合し、さらに水を２８質量部添加して、負極スラリーを得た。 [5-1-2. Production of negative electrode]
100 parts by mass of artificial graphite (G49, manufactured by Jiangxi Shishin Technology Co., Ltd.) as a negative electrode active material, and 3.9 parts by mass of the binder composition prepared in each example and comparative example (1.5 parts by mass as nonvolatile matter) , and 62 parts by mass of a 2% by mass aqueous solution of CMC (carboxymethyl cellulose - sodium salt, Sunrose (registered trademark) MAC500LC manufactured by Nippon Paper Chemicals Co., Ltd.), and 28 parts by mass of water are added to prepare a negative electrode slurry. Obtained.
　厚さ１０μｍの銅箔（負極集電体）の両面に、負極スラリーを、ダイレクトロール法により塗布した。負極集電体への負極スラリーの塗布量は、後述するロールプレス処理後の厚さが片面当たり１７０μｍになるように調整した。 The negative electrode slurry was applied to both sides of a 10 μm thick copper foil (negative electrode current collector) by a direct roll method. The amount of the negative electrode slurry applied to the negative electrode current collector was adjusted so that the thickness of the negative electrode current collector after the roll press treatment described later was 170 μm per side.
　負極集電体上に塗布された負極スラリーを、９０℃で１０分乾燥させ、ロールプレスにより（サンクメタル社製、プレス荷重８ｔ、ロール幅７ｃｍ）プレスし、集電体上に負極活物質層が形成された負極シートを得た。得られた負極シートを５２ｍｍ×４２ｍｍに切り出し、導電タブをつけて負極を作製した。 The negative electrode slurry applied on the negative electrode current collector is dried at 90° C. for 10 minutes and pressed by a roll press (manufactured by Thank Metal Co., press load 8 t, roll width 7 cm) to form a negative electrode active material layer on the current collector. A negative electrode sheet on which was formed was obtained. The obtained negative electrode sheet was cut into a size of 52 mm×42 mm, and a conductive tab was attached thereto to prepare a negative electrode.
［５－１－３．電池の作製］
　正極と負極との間にポリオレフィン系の多孔性フィルムからなるセパレータ（ポリエチレン製、２５μｍ）を介在させて、正極活物質層と負極活物質層とが互いに対向するようにアルミラミネート外装体（電池パック）の中に収納した。この外装体中に電解液を注液し真空含浸を行い、真空ヒートシーラーでパッキングし、評価用のリチウムイオン二次電池を作製した。電解液は、エチレンカーボネート（ＥＣ）／エチルメチルカーボネート（ＥＭＣ）／ジエチルカーボネート（ＤＥＣ）＝３０／５０／２０（体積比）の混合溶媒にＬｉＰＦ６を１．０ｍｏｌ／Ｌで溶解させた溶液９９質量部に、ビニレンカーボネート１質量部を混合して作製した。 [5-1-3. Production of battery]
A separator made of a polyolefin porous film (made of polyethylene, 25 μm) is interposed between the positive electrode and the negative electrode, and an aluminum laminate exterior body (battery pack) is formed so that the positive electrode active material layer and the negative electrode active material layer face each other. ). An electrolytic solution was poured into this outer package, vacuum impregnation was performed, and the package was packed with a vacuum heat sealer to produce a lithium ion secondary battery for evaluation. The electrolytic solution was a solution 99 in which LiPF 6 was dissolved at 1.0 mol/L in a mixed solvent of ethylene carbonate (EC)/ethyl methyl carbonate (EMC)/diethyl carbonate (DEC) = 30/50/20 (volume ratio). It was prepared by mixing 1 part by mass of vinylene carbonate with 1 part by mass of vinylene carbonate.
〔５－２．電極及び電池の評価〕
［５－２－１．負極活物質層の剥離強度（電極性能）］
　負極活物質層の集電体に対する剥離強度を以下のように測定した。上記の負極作製工程におけるプレス後の負極シートを２５ｍｍ×１００ｍｍのサイズにカットし、試験片とした。試験片上の負極活物質層と、幅５０ｍｍ、長さ２００ｍｍＳＵＳ板とを両面テープ（ＮＩＴＴＯＴＡＰＥ（登録商標）　Ｎｏ．５、日東電工（株）製）を用いて、試験片の中心とＳＵＳ板の中心とが一致するように貼り合わせた。なお、両面テープは試験片の全範囲をカバーするように貼り合わせた。 [5-2. Evaluation of electrodes and batteries]
[5-2-1. Peel strength of negative electrode active material layer (electrode performance)]
The peel strength of the negative electrode active material layer to the current collector was measured as follows. The negative electrode sheet after pressing in the negative electrode production process was cut into a size of 25 mm×100 mm to obtain a test piece. The negative electrode active material layer on the test piece and the SUS plate with a width of 50 mm and a length of 200 mm using double-sided tape (NITTOTAPE (registered trademark) No. 5, manufactured by Nitto Denko Co., Ltd.), the center of the test piece and the center of the SUS plate and pasted together so that the The double-faced tape was attached so as to cover the entire area of the test piece.
　試験片とＳＵＳ板とを貼り合わせた状態で１０分放置した後、負極活物質層を、試験片の一端から長さ方向に２０ｍｍ剥がし、銅箔側の試験片を１８０°折り返し、この部分（負極活物質層を剥がした試験片の部分の銅箔側）を試験機の上側のチャックで掴んだ。さらに、負極活物質層を剥がした側のＳＵＳ板の一端を下側チャックで掴んだ。その状態で、試験片から銅箔を１００±１０ｍｍ／ｍｉｎの速度で引き剥がし、剥離長さ（ｍｍ）－剥離力（ｍＮ）のグラフを得た。得られたグラフにおいて剥離長さ１０～４５ｍｍにおける剥離力の平均値（ｍＮ）を算出し、剥離力の平均値を試験片の幅２５ｍｍで割った数値を負極活物質層の剥離強度（ｍＮ／ｍｍ）とした。なお、いずれの実施例及び比較例においても、試験中、両面テープとＳＵＳ板の間での剥離、及び両面テープと負極活物質層との間での界面剥離は起こらなかった。 After leaving the test piece and the SUS plate bonded together for 10 minutes, the negative electrode active material layer was peeled off from one end of the test piece by 20 mm in the length direction, and the test piece on the copper foil side was folded back 180°, and this part ( The copper foil side of the portion of the test piece from which the negative electrode active material layer was removed) was gripped with a chuck on the upper side of the tester. Furthermore, one end of the SUS plate from which the negative electrode active material layer was peeled off was gripped with a lower chuck. In this state, the copper foil was peeled off from the test piece at a speed of 100±10 mm/min to obtain a peel length (mm)-peeling force (mN) graph. In the resulting graph, the average value (mN) of the peel force at a peel length of 10 to 45 mm was calculated, and the value obtained by dividing the average value of the peel force by the width of the test piece of 25 mm was the peel strength of the negative electrode active material layer (mN/ mm). In any of the examples and comparative examples, during the test, no peeling occurred between the double-sided tape and the SUS plate, and no peeling occurred at the interface between the double-sided tape and the negative electrode active material layer.
［５－２－２．電池の内部抵抗（ＤＣＲ）］
　電池の内部抵抗（ＤＣＲ（Ω））の測定は、２５℃の条件下、以下の手順で行った。レストポテンシャルから３．６Ｖまで０．２Ｃの定電流充電し、充電状態を初期容量の５０％（ＳＯＣ５０％）にした。その後、０．２Ｃ、０．５Ｃ、１Ｃおよび２Ｃの各電流値で６０秒間放電を行った。これらの４種の電流値（１秒間での値）と電圧の関係からＳＯＣ５０％でのＤＣＲ（Ω）を決定した。 [5-2-2. Battery internal resistance (DCR)]
The internal resistance (DCR(Ω)) of the battery was measured under the condition of 25° C. by the following procedure. The battery was charged at a constant current of 0.2 C from the rest potential to 3.6 V to bring the charged state to 50% of the initial capacity (50% SOC). Thereafter, discharge was performed for 60 seconds at current values of 0.2C, 0.5C, 1C and 2C. DCR (Ω) at SOC 50% was determined from the relationship between these four current values (values for 1 second) and voltage.
［５－２－３．高温下でのサイクル容量維持率（電池性能）］
　電池の、高温下でのサイクル容量維持率は、４５℃の条件下、以下の工程（ｉ）～（ｉｖ）の順で繰り返し行った。ここで、（ｉ）～（ｉｖ）の一連の操作１回分を１サイクルとする。 [5-2-3. Cycle capacity retention rate at high temperature (battery performance)]
The cycle capacity retention rate of the battery under high temperature was evaluated by repeating the following steps (i) to (iv) under the condition of 45°C. Here, one cycle is defined as a series of operations (i) to (iv).
（ｉ）電圧４．２Ｖになるまで、電流１Ｃで充電する（定電流（ＣＣ）充電）。
（ｉｉ）電圧４．２Ｖで、電流０．０５Ｃになるまで充電する（低電圧（ＣＶ）充電）。（ｉｉｉ）３０分静置する。
（ｉｖ）電圧２．７５Ｖになるまで電流１Ｃで放電する（定電流（ＣＣ）放電）。 (i) Charge at a current of 1 C until the voltage reaches 4.2 V (constant current (CC) charge).
(ii) charging at a voltage of 4.2 V to a current of 0.05 C (low voltage (CV) charging); (iii) Set aside for 30 minutes.
(iv) Discharge at a current of 1 C to a voltage of 2.75 V (constant current (CC) discharge).
　工程（ｉ）及び（ｉｉ）における、電流の時間積分値を充電容量、工程（ｉｖ）における、電流の時間積分値を放電容量とする。１サイクル目の放電容量、及び１００サイクル目の放電容量を測定した。１００×（１００サイクル目の放電容量）／（１サイクル目の放電容量）［％］を電池の高温下でのサイクル容量維持率として算出し、表１に示した。 The time integrated value of the current in steps (i) and (ii) is the charge capacity, and the time integrated value of the current in step (iv) is the discharge capacity. A discharge capacity at the 1st cycle and a discharge capacity at the 100th cycle were measured. 100×(discharge capacity at 100th cycle)/(discharge capacity at 1st cycle) [%] was calculated as the cycle capacity retention rate of the battery at high temperature.
＜６．評価結果＞
　表１の実施例１～３からわかるように、式（１）で示される構造の単量体（ａ４）に由来する構造単位を有する共重合体（Ａ）を電極バインダーとして含むことで、集電体に対する剥離強度が高い電極活物質層を有する電極が得られることがわかる。そして、この電極を用いて作製された電池は優れたサイクル特性を有することがわかる。 <6. Evaluation result>
As can be seen from Examples 1 to 3 in Table 1, by including the copolymer (A) having a structural unit derived from the monomer (a4) having the structure represented by formula (1) as an electrode binder, It can be seen that an electrode having an electrode active material layer with high peel strength against an electric body can be obtained. It is also found that the battery produced using this electrode has excellent cycle characteristics.
　一方、式（１）で示される構造の単量体（ａ４）に由来する構造単位を含まない共重合体を電極バインダーとした比較例１～２においては、作製された電池のサイクル特性が劣るものであった。 On the other hand, in Comparative Examples 1 and 2 in which the electrode binder was a copolymer containing no structural unit derived from the monomer (a4) having the structure represented by formula (1), the cycle characteristics of the produced batteries were inferior. It was something.
　また、外部架橋剤（ｂ）を使用しなかった比較例２と、外部架橋剤（ｂ）として３－グリドキシプロピルトリメトキシシランを使用した比較例１との対比において、外部架橋剤（ｂ）の使用によって、作製された電池の「１００サイクル後の放電容量維持率」は、７５％から７７％になった（約２％改善した）。 Further, in comparison with Comparative Example 2 in which the external cross-linking agent (b) was not used and Comparative Example 1 in which 3-glydoxypropyltrimethoxysilane was used as the external cross-linking agent (b), the external cross-linking agent (b) , the "discharge capacity retention rate after 100 cycles" of the produced battery increased from 75% to 77% (improved by about 2%).
　一方、外部架橋剤（ｂ）を使用しなかった実施例３と、比較例１と同じ外部架橋剤（ｂ）を同じ量で使用した実施例１との対比において、外部架橋剤（ｂ）の使用によって、作製された電池の「１００サイクル後の放電容量維持率」は、８２％から８８％になった（約６％改善した）。同じ量の外部架橋剤（ｂ）の使用にも関わらず、実施例３から実施例１への改善効果は、比較例２から比較例１への改善効果に比べて３倍増大した（６％対２％）。すなわち、式（１）で示される構造の単量体（ａ４）に由来する構造単位を含む共重合体（Ａ）を電極バインダーとして含むことで、それ自身による改善効果以外は、外部架橋剤（ｂ）の使用による改善効果を３倍に促進した。その促進効果の原因は出願時においてまだ未解明であったが、共重合体（Ａ）に含まれている式（１）で示される構造と外部架橋剤（ｂ）との相互作用による効果であると、推測する。 On the other hand, in comparison with Example 3 in which the external cross-linking agent (b) was not used and Example 1 in which the same external cross-linking agent (b) as in Comparative Example 1 was used in the same amount, By use, the "discharge capacity retention rate after 100 cycles" of the produced battery increased from 82% to 88% (improved by about 6%). Despite the use of the same amount of external cross-linking agent (b), the improvement effect from Example 3 to Example 1 increased by a factor of 3 compared to the improvement effect from Comparative Example 2 to Comparative Example 1 (6% 2%). That is, by including the copolymer (A) containing a structural unit derived from the monomer (a4) having the structure represented by formula (1) as an electrode binder, the external cross-linking agent ( The improvement effect by use of b) was accelerated 3 times. The cause of the acceleration effect was still unknown at the time of filing, but it is due to the interaction between the structure represented by the formula (1) contained in the copolymer (A) and the external cross-linking agent (b). I presume there is.

Claims (11)

  1. 　単量体（ａ１）に由来する構造単位と、単量体（ａ２）に由来する構造単位と、内部架橋剤（ａ３）に由来する構造単位と、単量体（ａ４）に由来する構造単位と、を含む非水系二次電池用電極バインダー共重合体であって、
    　前記単量体（ａ１）が、分子内に含まれるエチレン性不飽和結合が１個である（メタ）アクリル酸アルキルエステル、及び分子内に含まれるエチレン性不飽和結合が１個である炭化水素化合物からなる群より選ばれる少なくとも１種類であり、
    　前記単量体（ａ２）が、１個のエチレン性不飽和結合及びアニオン性官能基を有する化合物であり、
    　前記内部架橋剤（ａ３）が、１分子中に２つ以上のエチレン性不飽和結合を有する化合物であり、
    　前記単量体（ａ４）が、下記の式（１）で示される化合物であり、
    　前記単量体（ａ１）に由来する構造単位を５０質量％以上９８質量％以下含み、
    　前記単量体（ａ２）に由来する構造単位を１．０質量％以上１５質量％以下含み、
    　前記内部架橋剤（ａ３）に由来する構造単位を０．０２０質量％以上１０質量％以下含み、
    　前記単量体（ａ４）に由来する構造単位を０．０１０質量％以上２０質量％以下含むことを特徴とする非水系二次電池用電極バインダー共重合体。
    Figure JPOXMLDOC01-appb-C000001
     （式（１）中、Ｒ１は炭素数１～１２のアルキル基、炭素数３～２０の環状アルキル基、または炭素数６～２０のアリール基である。）     A structural unit derived from the monomer (a1), a structural unit derived from the monomer (a2), a structural unit derived from the internal cross-linking agent (a3), and a structural unit derived from the monomer (a4) And, an electrode binder copolymer for a non-aqueous secondary battery containing,
    The monomer (a1) is a (meth)acrylic acid alkyl ester having one ethylenically unsaturated bond contained in the molecule, and a hydrocarbon having one ethylenically unsaturated bond contained in the molecule. At least one selected from the group consisting of compounds,
    The monomer (a2) is a compound having one ethylenically unsaturated bond and an anionic functional group,
    The internal cross-linking agent (a3) is a compound having two or more ethylenically unsaturated bonds in one molecule,
    The monomer (a4) is a compound represented by the following formula (1),
    Containing 50% by mass or more and 98% by mass or less of structural units derived from the monomer (a1),
    Containing 1.0% by mass or more and 15% by mass or less of structural units derived from the monomer (a2),
    Containing 0.020% by mass or more and 10% by mass or less of structural units derived from the internal cross-linking agent (a3),
    An electrode binder copolymer for a non-aqueous secondary battery, comprising 0.010% by mass or more and 20% by mass or less of a structural unit derived from the monomer (a4).
    Figure JPOXMLDOC01-appb-C000001
     (In formula (1), R 1 is an alkyl group having 1 to 12 carbon atoms, a cyclic alkyl group having 3 to 20 carbon atoms, or an aryl group having 6 to 20 carbon atoms.)
  2. 　前記単量体（ａ１）に由来する構造単位を７０質量％以上９７質量％以下含む、請求項１に記載の非水系二次電池用電極バインダー共重合体。 The electrode binder copolymer for non-aqueous secondary batteries according to claim 1, comprising 70% by mass or more and 97% by mass or less of structural units derived from the monomer (a1).
  3. 　前記単量体（ａ２）のアニオン性官能基が、カルボキシ基、及びスルホ基のうち少なくともいずれかである、請求項１又は２に記載の非水系二次電池用電極バインダー共重合体。 The electrode binder copolymer for non-aqueous secondary batteries according to claim 1 or 2, wherein the anionic functional group of the monomer (a2) is at least one of a carboxy group and a sulfo group.
  4. 　前記単量体（ａ２）に由来する構造単位を２．０質量％以上１０質量％以下含む、請求項１～３のいずれか１項に記載の非水系二次電池用電極バインダー共重合体。 The electrode binder copolymer for non-aqueous secondary batteries according to any one of claims 1 to 3, containing 2.0% by mass or more and 10% by mass or less of structural units derived from the monomer (a2).
  5. 　前記式（１）中、Ｒ１は炭素数６～２０のアリール基である、請求項１～４のいずれか１項に記載の非水系二次電池用電極バインダー共重合体。 The electrode binder copolymer for non-aqueous secondary batteries according to any one of claims 1 to 4, wherein in formula (1), R 1 is an aryl group having 6 to 20 carbon atoms.
  6. 　前記式（１）で示される化合物が、Ｎ－フェニルマレイミドである、請求項１～５のいずれか１項に記載の非水系二次電池用電極バインダー共重合体。 The electrode binder copolymer for non-aqueous secondary batteries according to any one of claims 1 to 5, wherein the compound represented by formula (1) is N-phenylmaleimide.
  7. 　前記単量体（ａ４）に由来する構造単位の含有率は、０．１０質量％以上１５質量％以下である、請求項１～６のいずれか１項に記載の非水系二次電池用電極バインダー共重合体。 The electrode for a non-aqueous secondary battery according to any one of claims 1 to 6, wherein the content of structural units derived from the monomer (a4) is 0.10% by mass or more and 15% by mass or less. Binder copolymer.
  8. 　請求項１～７のいずれか１項に記載の非水系二次電池用電極バインダー共重合体と、
    　水性媒体（ｃ）と、を含む、非水系二次電池用電極バインダー樹脂組成物。     The electrode binder copolymer for non-aqueous secondary batteries according to any one of claims 1 to 7,
    An electrode binder resin composition for a non-aqueous secondary battery, comprising an aqueous medium (c).
  9. 　請求項１～７のいずれか１項に記載の非水系二次電池用電極バインダー共重合体と、
    　電極活物質と、
    　水性媒体と、を含む、非水系二次電池用電極スラリー。     The electrode binder copolymer for non-aqueous secondary batteries according to any one of claims 1 to 7,
    an electrode active material;
    An electrode slurry for a non-aqueous secondary battery, comprising an aqueous medium.
  10. 　金属箔からなる集電体と、
    　前記集電体上に形成された電極活物質層と、を含む非水系二次電池電極であって、
    　前記電極活物質層が、請求項１～７のいずれか１項に記載の非水系二次電池用電極バインダー共重合体と、電極活物質と、を含む非水系二次電池電極。     a current collector made of metal foil;
    A non-aqueous secondary battery electrode comprising an electrode active material layer formed on the current collector,
    A nonaqueous secondary battery electrode, wherein the electrode active material layer comprises the electrode binder copolymer for a nonaqueous secondary battery according to any one of claims 1 to 7, and an electrode active material.
  11. 　正極と、負極と、を含む非水系二次電池であって、
    　前記正極及び前記の負極の少なくとも一方が、請求項１～７のいずれか１項に記載の非水系二次電池用電極バインダー共重合体を含む非水系二次電池。     A non-aqueous secondary battery comprising a positive electrode and a negative electrode,
    A non-aqueous secondary battery, wherein at least one of the positive electrode and the negative electrode comprises the electrode binder copolymer for a non-aqueous secondary battery according to any one of claims 1 to 7.
PCT/JP2022/044108 2021-12-23 2022-11-30 Electrode binder copolymer for non-aqueous secondary battery, electrode binder resin composition for non-aqueous secondary battery, and non-aqueous secondary battery electrode WO2023120066A1 (en)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019157001A (en) * 2018-03-14 2019-09-19 テクノＵｍｇ株式会社 Aqueous binder
WO2021131813A1 (en) * 2019-12-27 2021-07-01 昭和電工株式会社 Copolymer for electrode binder, electrode binder resin composition, and electrode for non-aqueous secondary battery

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2019157001A (en) * 2018-03-14 2019-09-19 テクノＵｍｇ株式会社 Aqueous binder
WO2021131813A1 (en) * 2019-12-27 2021-07-01 昭和電工株式会社 Copolymer for electrode binder, electrode binder resin composition, and electrode for non-aqueous secondary battery

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