WO2019167322A1 - Binder composition, electrode mixture and non-aqueous electrolyte secondary battery - Google Patents

Binder composition, electrode mixture and non-aqueous electrolyte secondary battery Download PDF

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Publication number
WO2019167322A1
WO2019167322A1 PCT/JP2018/036676 JP2018036676W WO2019167322A1 WO 2019167322 A1 WO2019167322 A1 WO 2019167322A1 JP 2018036676 W JP2018036676 W JP 2018036676W WO 2019167322 A1 WO2019167322 A1 WO 2019167322A1
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Prior art keywords
binder composition
vinylidene fluoride
electrode mixture
electrode
group
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PCT/JP2018/036676
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French (fr)
Japanese (ja)
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壮哉 土肥
勇樹 堺
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株式会社クレハ
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Priority to KR1020207025728A priority Critical patent/KR102451851B1/en
Priority to CN201880087505.2A priority patent/CN111684631B/en
Publication of WO2019167322A1 publication Critical patent/WO2019167322A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 a binder composition used in the production of a nonaqueous electrolyte secondary battery, particularly a lithium ion secondary battery, and an electrode mixture using the same.
  • Nonaqueous electrolyte secondary batteries are also used in hybrid vehicles combining secondary batteries and engines, and electric vehicles powered by secondary batteries, from the viewpoint of global environmental problems and energy saving. Applications are expanding.
  • the electrode for a non-aqueous electrolyte secondary battery has a structure having a current collector and an electrode mixture layer formed on the current collector.
  • the electrode mixture layer is generally formed by applying an electrode mixture containing an electrode active material and a binder composition onto a current collector in a slurry state in which the electrode mixture is dispersed in an appropriate solvent, and volatilizing the solvent.
  • a vinylidene fluoride (VDF) polymer such as polyvinylidene fluoride (PVDF) is mainly used.
  • Patent Document 1 discloses a shear rate of 0 to 1000 in order to control the thickness after coating on a current collector.
  • a mixture slurry prepared such that a flow curve in the range of s ⁇ 1 ] is approximated with a specific correlation coefficient for a specific flow equation is disclosed.
  • the electrode mixture of Patent Document 1 has a problem that an irreversible thickening phenomenon may occur during storage in a slurry state.
  • an electrode mixture containing a binder composition using a VDF / CTFE copolymer has a thixotropic property (viscosity decreases with time when it is subjected to shear stress, and decreases with time when compared with other VDF polymers).
  • thixotropic property viscosity decreases with time when it is subjected to shear stress, and decreases with time when compared with other VDF polymers.
  • the present invention has been made in view of the above-mentioned problems, and its purpose is to suppress a irreversible thickening phenomenon during storage of a slurry-like electrode mixture, and to suppress its thixotropic property. Is to provide.
  • the “electrode” in this specification and the like means that an electrode mixture layer formed from an electrode mixture using the binder composition in the present embodiment is formed on a current collector. It means an electrode of a non-aqueous electrolyte secondary battery.
  • the “battery” in this specification and the like means a nonaqueous electrolyte secondary battery including an “electrode”.
  • “thixotropic property” in the present specification and the like means a property that the viscosity decreases with time when the shear stress is continued, and the viscosity increases when stationary, and OC ⁇ C. Lin “Thixotropic behavior of gel- like systems ”J. Appl. Polym. Sci. Vol.19, 199-214, 1975 can be expressed by the thixotropy coefficient ⁇ . It can be said that the thixotropy is suppressed as the thixotropy coefficient ⁇ is smaller.
  • the binder composition according to this embodiment is an electrode of a battery, and in an electrode in which an electrode mixture layer containing an electrode active material is formed on a current collector, the electrode active material is bound to the current collector. It is used to make it.
  • the binder composition contains a vinylidene fluoride polymer and a specific polymer additive. Moreover, in the binder composition which concerns on this embodiment, as long as the desired effect is not inhibited, another polymer and additive may be included.
  • the vinylidene fluoride polymer according to an aspect of the present invention is a vinylidene fluoride homopolymer in a range that does not inhibit the thickening phenomenon suppressing effect of the vinylidene fluoride copolymer, Or the vinylidene fluoride copolymer which does not contain the structural unit derived from chlorotrifluoroethylene may be included.
  • Examples of the vinylidene fluoride copolymer not containing a structural unit derived from chlorotrifluoroethylene include a VDF / APS copolymer containing a structural unit derived from mono (acryloxypropyl) succinate (APS), hexa VDF / HFP copolymer containing structural units derived from fluoropropylene (HFP), VDF / AA copolymer containing structural units derived from acrylic acid (AA), VDF / HFP / APS copolymer, etc. Can be mentioned.
  • the vinylidene fluoride polymer is a vinylidene fluoride copolymer.
  • the vinylidene fluoride copolymer according to one embodiment of the present invention preferably contains 70% by mole or more of vinylidene fluoride-derived units, more preferably 80% by mole or more, and more preferably 85% by mole or more. It is particularly preferable to contain. Although there is no restriction
  • a silane coupling agent or titanate having both a reactive group and a hydrolyzable group in combination with a vinylidene fluoride polymer such as an amino group or a mercapto group in a solvent that dissolves or swells the vinylidene fluoride polymer.
  • a modified vinylidene fluoride polymer obtained by treatment in a system coupling agent is also used.
  • the effects of the present invention can be suitably achieved by further including a structural unit derived from a monomer component having a carboxyl group.
  • the monomer component having a carboxyl group include acrylic acid, methacrylic acid, monomethyl maleate, 2-carboxyethyl acrylate, methacrylic acid (2-carboxyethyl), succinic acid mono (acryloxyethyl), and succinic acid mono ( Acryloxypropyl), mono (acryloxyethyl) phthalate, mono (methacryloxyethyl) succinate, mono (methacryloxypropyl) succinate, mono (methacryloxyethyl) phthalate, and trifluoroacrylic acid . These may be used individually by 1 type, or may use 2 or more types.
  • the carboxyl group-containing structural unit is contained in an amount of 0.01 to 3 mol%.
  • the content is preferably 0.05 to 1 mol%, and more preferably 0.08 to 0.5 mol%.
  • the functional group amount is less than 0.01 mol%, sufficient adhesion may not be obtained.
  • properties, such as a chemical resistance intrinsic to a fluororesin may be impaired.
  • the abundance of each structural unit can be determined by 1 H NMR or 19 F NMR.
  • methyl cellulose methoxylated methyl cellulose, propoxylated methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyethylene oxide, gelatin and the like can be used.
  • diisopropyl peroxydicarbonate dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, di (perfluoroacyl) peroxide Oxide, t-butyl peroxypivalate, etc.
  • diisopropyl peroxydicarbonate dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, di (perfluoroacyl) peroxide Oxide, t-butyl peroxypivalate, etc.
  • the degree of polymerization of the resulting polymer is adjusted by adding a chain transfer agent such as ethyl acetate, methyl acetate, acetone, ethanol, n-propanol, acetaldehyde, propyl aldehyde, ethyl propionate, and carbon tetrachloride. It is also possible.
  • a chain transfer agent such as ethyl acetate, methyl acetate, acetone, ethanol, n-propanol, acetaldehyde, propyl aldehyde, ethyl propionate, and carbon tetrachloride. It is also possible.
  • the binder composition, together with the vinylidene fluoride copolymer includes the following repeating units: -[CH 2 -CHR]-
  • a polymer additive comprising a polymer material having
  • R is a chain or cyclic amide group, a nitrile group, a hydroxy group, an ester-containing group, or an alkyl group having 1 to 4 carbon atoms, and at least one hydrogen atom of the alkyl group is a chain. Or a substituent substituted with a amide group, a nitrile group or a hydroxy group.
  • the “chain or cyclic amide group” has the formula: —CONR 1 R 2 or —NR 1 COR 2 (wherein R 1 and R 2 may be the same or different from each other).
  • Examples of such a chain or cyclic amide group include a 2-pyrrolidone group, an acetamido group, and an N-methylacetamido group.
  • the 2-pyrrolidone group, the acetamide group, and the N-methylacetamide group are monovalent groups in which one hydrogen atom bonded to a carbonyl carbon atom or a nitrogen atom in the corresponding compound is substituted with a bond. Represents a group.
  • the binder composition can suppress thixotropic properties while retaining the effect of suppressing the thickening phenomenon of the slurry when used as an electrode mixture.
  • polymer material examples include polyvinyl pyrrolidone, polyacrylonitrile, polyvinyl alcohol, and the like.
  • polyvinyl alcohol includes polyvinyl alcohol obtained by saponifying polyvinyl acetate and having an acetyl group remaining in a range of 30 mol% or less.
  • the method for producing the polymer material according to one embodiment of the present invention is not particularly limited, and the polymer material can be produced in the same manner as the above-described vinylidene fluoride copolymer.
  • the binder composition according to this embodiment includes a vinylidene fluoride polymer containing the vinylidene fluoride copolymer and a polymer additive.
  • the vinylidene fluoride copolymer may be used alone, or two or more types of vinylidene fluoride copolymers may be used in combination.
  • the polymer additive may be used alone or in combination of two or more polymer materials.
  • the binder composition according to this embodiment may further contain another polymer and various additives as long as the desired effect is not impaired.
  • the content of the vinylidene fluoride copolymer in the binder composition is preferably 2.5% by mass or more, more preferably 5% by mass or more, and still more preferably 10% by mass.
  • the content of the vinylidene fluoride copolymer is within this range, an irreversible thickening phenomenon during storage can be suppressed when the binder composition is used as an electrode mixture.
  • the content of the polymer additive in the binder composition is preferably 1 to 50% by mass, more preferably 2 to 2% when the total of the vinylidene fluoride polymer and the polymer additive is 100% by mass. 30% by mass, more preferably 2.5 to 10% by mass.
  • the content of the polymer additive is within this range, when the binder composition is used as an electrode mixture, the effect of suppressing an increase in thixotropic properties is further enhanced.
  • the binder composition may further contain a conventional additive as required.
  • the electrode mixture in the present embodiment is obtained by adding an electrode active material and a solvent to a binder composition.
  • An electrode can be produced by applying this electrode mixture on a current collector to form an electrode mixture layer.
  • the electrode mixture is in the form of a slurry and can be adjusted to a desired viscosity by adjusting the amount of the solvent.
  • the electrode mixture can be used as an electrode mixture for the positive electrode or an electrode mixture for the negative electrode by changing the type of the electrode active material according to the type of the current collector to be applied.
  • the electrode mixture in the present embodiment is preferably a positive electrode mixture using a positive electrode active material, that is, a positive electrode active material (positive electrode material).
  • the solvent used in the electrode mixture in the present embodiment is not particularly limited as long as the solvent can dissolve the vinylidene fluoride polymer and the polymer additive.
  • the solvent include N-methyl-2-pyrrolidone (NMP), water, dimethylformamide, N, N-dimethylacetamide, N, N-dimethylsulfoxide, hexamethylphosphoamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate. , Trimethyl phosphate, acetone, methyl ethyl ketone, and tetrahydrofuran. These solvents may be used alone or as a mixed solvent in which two or more kinds are mixed.
  • the solvent used in the electrode mixture is preferably a nitrogen-containing organic solvent such as N-methyl-2-pyrrolidone, N, N-dimethylformamide and N, N-dimethylacetamide, and N-methyl-2-pyrrolidone is preferred. More preferred.
  • the amount of the solvent is preferably 400 to 10000 parts by mass, and more preferably 600 to 8000 parts by mass. Within the range of the amount of the solvent described above, the solution viscosity is moderate and the handling property is excellent.
  • the electrode active material used in the electrode mixture in the present embodiment is an electrode active material for a negative electrode, that is, a negative electrode, when the electrode mixture according to the present embodiment is used as an electrode mixture for a negative electrode.
  • An active material may be used.
  • a positive electrode active material that is, a positive electrode active material may be used.
  • the positive electrode active material examples include a lithium-based positive electrode active material containing lithium.
  • the lithium-based positive electrode active material examples include a composite metal chalcogen compound represented by the general formula LiMY 2 such as LiCoO 2 and LiCo x Ni 1-x O 2 (0 ⁇ x ⁇ 1), or a composite metal oxide, LiMn 2 O And composite metal oxides having a spinel structure such as 4 and olivine type lithium compounds such as LiFePO 4 .
  • M is at least one of transition metals such as Co, Ni, Fe, Mn, Cr and V or Al
  • Y is a chalcogen element such as O and S.
  • the negative electrode active material conventionally known materials including carbon-based materials such as graphite can be used.
  • the electrode active material may be added directly to the binder composition together with the solvent.
  • the electrode active material may be first added to a solvent, and the mixture after stirring may be added to the binder composition. Or you may make it add an electrode active material to the binder solution obtained by mixing a binder composition and a solvent.
  • the electrode mixture in the present embodiment may further contain a conductive aid.
  • the conductive additive is added for the purpose of improving the conductivity of the electrode mixture layer when using an active material having a low electron conductivity such as LiCoO 2 .
  • the conductive assistant for example, carbon black, carbon nanotubes, carbonaceous materials such as graphite fine powder and graphite fiber, and metal fine powder or metal fiber such as nickel and aluminum can be used.
  • the electrode mixture in this embodiment may contain components other than the above-described components.
  • examples of other components include organic acids such as oxalic acid and succinic acid, and conventional additives such as a dispersant.
  • the electrode mixture according to the present embodiment is prepared by mixing the binder composition, the solvent and the electrode active material, and, if necessary, the conductive auxiliary agent and other various components in any order to form a slurry. Can be obtained.
  • a binder solution is prepared by mixing a binder composition and a solvent, an electrode active material is added to the obtained binder solution together with a conductive additive, and the mixture is stirred and mixed to prepare an electrode mixture. Can do.
  • a conductive assistant dispersion is prepared by mixing a conductive assistant and a solvent, and a binder composition, an electrode active material, and the like are added to the obtained conductive assistant dispersion, and the mixture is stirred and mixed to form an electrode.
  • a mixture may be prepared.
  • the electrode mixture may be prepared by preparing the binder solution and the conductive auxiliary agent dispersion, respectively, and stirring and mixing them with an electrode active material or the like.
  • FIG. 1 is a cross-sectional view of an electrode in the present embodiment.
  • the electrode 10 includes a current collector 11 and electrode mixture layers 12 a and 12 b, and electrode mixture layers 12 a and 12 b are formed on the current collector 11.
  • the electrode 10 becomes a positive electrode when the electrode mixture layers 12a and 12b are obtained using the electrode mixture for the positive electrode, and the electrode mixture layers 12a and 12b using the electrode mixture for the negative electrode. Is obtained as a negative electrode.
  • the current collector 11 is a base material for the electrode 10 and a terminal for taking out electricity. Examples of the material of the current collector 11 include iron, stainless steel, steel, copper, aluminum, nickel, and titanium.
  • the shape of the current collector 11 is preferably a foil or a net. When the electrode 10 is a positive electrode, the current collector 11 is preferably an aluminum foil.
  • the thickness of the current collector 11 is preferably 5 to 100 ⁇ m, and more preferably 5 to 20 ⁇ m.
  • the electrode mixture layers 12a and 12b are layers obtained by applying the electrode mixture described above to the current collector 11 and drying it.
  • a method for applying the electrode mixture a known method in the technical field can be used, and a method using a bar coater, a die coater, a comma coater, or the like can be given.
  • the drying temperature for forming the electrode mixture layers 12a and 12b is preferably 50 to 170 ° C.
  • the thickness of the electrode mixture layers 12a and 12b is preferably 10 to 1000 ⁇ m.
  • the electrode 10 has electrode mixture layers 12 a and 12 b formed on both surfaces of the current collector 11.
  • the present invention is not limited to this, and one surface of the current collector 11 is not limited thereto.
  • the electrode mixture layer may be formed only on the surface.
  • the thickness of the electrode mixture layer is usually 20 to 250 ⁇ m, preferably 20 to 150 ⁇ m.
  • the basis weight of the mixture layer is usually 20 to 700 g / m 2 , preferably 30 to 500 g / m 2 .
  • FIG. 2 is an exploded perspective view of the nonaqueous electrolyte secondary battery.
  • the battery 100 includes a positive electrode 1, a negative electrode 2, a separator 3, and a metal casing 5.
  • the battery 100 has a structure in which a power generation element in which a laminated body in which a separator 3 is disposed between a positive electrode 1 and a negative electrode 2 is spirally wound is housed in a metal casing 5.
  • the positive electrode 1 or the negative electrode 2 is the same as the electrode 10 in FIG.
  • the separator 3 a known material such as a porous film of a polymer material such as polypropylene and polyethylene can be used.
  • the battery 100 is illustrated as a cylindrical battery, but the battery 100 in the present embodiment is not limited to this, and may be a coin-shaped, rectangular, or paper-type battery.
  • a binder composition according to an embodiment of the present invention is a binder composition used for binding an electrode active material to a current collector, and the binder composition is a hook composition.
  • a vinylidene fluoride polymer and a polymer additive the vinylidene fluoride polymer includes a vinylidene fluoride copolymer including a structural unit derived from vinylidene fluoride and a structural unit derived from chlorotrifluoroethylene
  • the polymer additive includes the following repeating units: -[CH 2 -CHR]- It is a binder composition which is a polymer material having (In the above repeating unit, R is a chain or cyclic amide group, a nitrile group, a hydroxy group, an ester-containing group, or an alkyl group having 1 to 4 carbon atoms, and at least one hydrogen atom of the alkyl group is Indicates a substituent substituted with a chain or cyclic
  • R is preferably a chain or cyclic amide group, a nitrile group, or a hydroxy group.
  • the polymer additive is preferably polyvinyl pyrrolidone, polyacrylonitrile, or polyvinyl alcohol.
  • the polymer additive may be 1% by mass or more and 50% when the total of the vinylidene fluoride polymer and the polymer additive is 100% by mass. It is preferable that it is contained by mass% or less.
  • the vinylidene fluoride copolymer preferably further includes a structural unit derived from a monomer component having a carboxyl group.
  • An electrode mixture according to an embodiment of the present invention is an electrode mixture including the above-described binder composition, a solvent, and an electrode active material.
  • a nonaqueous electrolyte secondary battery according to an embodiment of the present invention is a nonaqueous electrolyte secondary battery including an electrode mixture layer formed from the above electrode mixture.
  • an electrode mixture was produced using various binder compositions according to the present invention, and a thixotropic coefficient and a gelation evaluation test of the slurry were performed using the mixture.
  • inherent viscosity in the present specification is a value measured by the following method.
  • a vinylidene fluoride copolymer solution is prepared by dissolving 80 mg of vinylidene fluoride copolymer in 20 mL of N, N-dimethylformamide.
  • the viscosity ⁇ of the solution is measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C.
  • the inherent viscosity ⁇ i is obtained by the following formula using the viscosity ⁇ .
  • ⁇ i (1 / C) ⁇ ln ( ⁇ / ⁇ 0)
  • ⁇ 0 is the viscosity of N, N-dimethylformamide as a solvent
  • C is 0.4 g / dL.
  • Example 1 As a vinylidene fluoride copolymer, vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) (weight ratio 96: 4) are polymerized, and a VDF-CTFE copolymer (inherent viscosity 2.1 dL / g) is used. did. In addition, polyvinyl pyrrolidone (PVP K15) (number average molecular weight 10,000, P0471 manufactured by Tokyo Chemical Industry Co., Ltd.) was used as a polymer additive.
  • PVDF vinylidene fluoride
  • CTFE chlorotrifluoroethylene
  • the above-mentioned vinylidene fluoride copolymer and polymer additive were mixed so that the polymer additive was 5% by mass with respect to the total mass to obtain a binder composition.
  • Lithium-cobalt composite oxide (LCO; LiCoO 2 , Cellseed C10N, manufactured by Nippon Chemical Industry Co., Ltd., average particle size 10 ⁇ m) as an electrode active material 100 parts by mass, carbon black (SP; SuperPal manufactured by Timcal Japan) (Registered trademark) Li, 2 parts by mass of an average particle diameter of 40 nm, specific surface area of 60 m 2 / g) and 2 parts by mass of the binder composition were uniformly dispersed in N-methyl-2-pyrrolidone to form a slurry.
  • An electrode mixture having a total solid content concentration of 76% by mass of the binder composition, the electrode active material, and the conductive additive with respect to the total mass was prepared.
  • the obtained electrode mixture was coated on a 15 ⁇ m-thick aluminum foil as a current collector with a bar coater and dried at 110 ° C. for 30 minutes in a nitrogen atmosphere using a thermostatic bath. Was made.
  • Example 2 As a vinylidene fluoride copolymer, VDF, CTFE and mono (acryloxypropyl) succinate (APS) (weight ratio 96: 4: 1) were polymerized to obtain a VDF-CTFE-APS copolymer (inherent viscosity 2.3 dL). / G) was used in the same manner as in Example 1 except that a binder composition was obtained.
  • the binder composition obtained above in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 74% by mass, the electrode mixture and the electrode was made.
  • the binder composition obtained above in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 78% by mass, the electrode mixture and the electrode was made.
  • Example 4 As a vinylidene fluoride copolymer, VDF, CTFE and monomethyl maleate (MMM) (weight ratio 98: 2: 0.7) were polymerized to obtain a VDF-CTFE-MMM copolymer (inherent viscosity 2.3 dL / g). A binder composition was obtained in the same manner as in Example 1 except that it was used.
  • an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 75% by mass. Was made.
  • Example 5 A binder composition was obtained in the same manner as in Example 2 except that the polymer additive was 2.5% by mass with respect to the total mass of the binder composition.
  • the binder composition obtained above in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 73% by mass, the electrode mixture and the electrode was made.
  • Example 6 A binder composition was obtained in the same manner as in Example 1 except that polyvinyl pyrrolidone (PVP K90) (number average molecular weight 360,000, manufactured by Tokyo Chemical Industry Co., Ltd., P0473) was used as the polymer additive.
  • PVP K90 polyvinyl pyrrolidone
  • an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 75% by mass. Was made.
  • Example 7 A binder composition was obtained in the same manner as in Example 1 except that polyvinyl alcohol (PVA) (manufactured by Nippon Synthetic Chemical Co., Ltd., Gohsenol GH-17) was used as a polymer additive.
  • PVA polyvinyl alcohol
  • an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 75% by mass. Was made.
  • Example 8 A binder composition was obtained in the same manner as in Example 1 except that polyacrylonitrile (PAN) (weight average molecular weight 150,000, manufactured by Sigma-Aldrich, 181315) was used as the polymer additive.
  • PAN polyacrylonitrile
  • the binder composition obtained above in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 73% by mass, the electrode mixture and the electrode was made.
  • Example 9 In the same manner as in Example 1, a binder composition was obtained.
  • NCA nickel cobalt lithium aluminum oxide
  • SP carbon black
  • an average particle diameter of 40 nm, 2 parts by mass of a specific surface area of 60 m 2 / g) and 2 parts by mass of the above binder composition were uniformly dispersed in N-methyl-2-pyrrolidone to obtain a total solid of the binder composition, the electrode active material and the conductive assistant.
  • An electrode mixture having a partial concentration of 79% by mass was produced.
  • Example 10 Except for polymerizing VDF, CTFE and APS (weight ratio 96: 4: 1) as a vinylidene fluoride copolymer and using VDF-CTFE-APS copolymer (inherent viscosity 2.3 dL / g) In the same manner as in Example 1, a binder composition was obtained.
  • the binder composition obtained above in the same manner as in Example 9 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 74% by mass, the electrode mixture and the electrode was made.
  • an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 68% by mass. Was made.
  • an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material, and the conductive additive was 70% by mass. Was made.
  • the binder composition obtained above in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 73% by mass, the electrode mixture and the electrode was made.
  • Example 5 A binder composition was obtained in the same manner as in Example 1 except that polyethylene glycol (PEG) was used instead of polyvinyl pyrrolidone (PVP K15) which is a polymer additive.
  • PEG polyethylene glycol
  • PVP K15 polyvinyl pyrrolidone
  • the binder composition obtained above in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 69% by mass, the electrode mixture and the electrode Was made.
  • Example 6 A binder composition was obtained in the same manner as in Example 1 except that polyacrylic acid (PAA) was used instead of polyvinyl pyrrolidone (PVP K15) which is a polymer additive.
  • PAA polyacrylic acid
  • PVP K15 polyvinyl pyrrolidone
  • an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 68% by mass. Was made.
  • the binder composition obtained above in the same manner as in Example 9 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 76% by mass, the electrode mixture and the electrode was made.
  • an electrode mixture and an electrode were obtained in the same manner as in Example 9, except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 78% by mass. Was made.
  • thixotropy coefficient ⁇ of electrode mixture slurry The electrode slurry was measured for 300 seconds at 25 ° C. and a shear rate of 2 s ⁇ 1 using an E-type viscometer (Toki Sangyo Co., Ltd., RE-80).
  • the thixotropy coefficient ⁇ can be obtained from the following equation using the maximum viscosity ⁇ 0 after the start of measurement and the viscosity ⁇ at the time when the change in viscosity over time has disappeared.
  • the difference between the initial shear stress ( ⁇ 0) and the equilibrium shear stress ( ⁇ ) is small, and the thixotropic coefficient ⁇ is 0 to 0.2.
  • the viscosity change accompanying shearing hardly occurred, and the thixotropic property was well suppressed.
  • the electrode mixture slurry did not gel after a certain period of time, and was applied onto an aluminum foil and dried to form a smooth electrode mixture layer.
  • Comparative Examples 1 to 8 did not contain the polymer additive made of the polymer material of the present invention, so that the viscosity change caused by shearing occurred and the thixotropy coefficient showed a high value.

Abstract

Provided is a binder composition by which the occurrence of irreversible thickening is suppressed when a slurry-like electrode mixture is stored, and by which thixotropy of the slurry-like electrode mixture is also suppressed. This binder composition contains a vinylidene fluoride copolymer and a polymer additive. The vinylidene fluoride copolymer contains structural units derived from vinylidene fluoride and structural units derived from chlorotrifluoroethylene. The polymer additive is a polymer material having the repeating unit -[CH2-CHR]-.

Description

バインダー組成物、電極合剤および非水電解質二次電池Binder composition, electrode mixture, and nonaqueous electrolyte secondary battery
　本発明は、非水電解質二次電池、特にリチウムイオン二次電池の製造に用いられるバインダー組成物、およびそれを用いた電極合剤に関する。 The present invention relates to a binder composition used in the production of a nonaqueous electrolyte secondary battery, particularly a lithium ion secondary battery, and an electrode mixture using the same.
　近年、電子技術の発展はめざましく、小型携帯機器の高機能化が進んでいる。そのため、これらに使用される電源には小型化および軽量化、すなわち高エネルギー密度化が求められている。高いエネルギー密度を有する電池として、リチウムイオン二次電池などに代表される非水電解質二次電池が、広く使用されている。 In recent years, the development of electronic technology has been remarkable, and advanced functions of small portable devices are progressing. For this reason, power sources used for these are required to be smaller and lighter, that is, to have higher energy density. As a battery having a high energy density, a non-aqueous electrolyte secondary battery represented by a lithium ion secondary battery or the like is widely used.
　また、非水電解質二次電池は、地球環境問題および省エネルギーの観点から、二次電池とエンジンとを組み合わせたハイブリッド自動車、および二次電池を電源にした電気自動車などにも利用されており、その用途が拡大している。 Nonaqueous electrolyte secondary batteries are also used in hybrid vehicles combining secondary batteries and engines, and electric vehicles powered by secondary batteries, from the viewpoint of global environmental problems and energy saving. Applications are expanding.
　非水電解質二次電池用の電極は、集電体と集電体上に形成される電極合剤層とを有する構造となっている。電極合剤層は、一般に電極活物質とバインダー組成物とを含む電極合剤が適当な溶媒中に分散されたスラリー状態で集電体上に塗布され、溶媒を揮散して形成される。バインダー（結着剤）としては、ポリフッ化ビニリデン（ＰＶＤＦ）等のフッ化ビニリデン（ＶＤＦ）系ポリマーが主に使用されている。 The electrode for a non-aqueous electrolyte secondary battery has a structure having a current collector and an electrode mixture layer formed on the current collector. The electrode mixture layer is generally formed by applying an electrode mixture containing an electrode active material and a binder composition onto a current collector in a slurry state in which the electrode mixture is dispersed in an appropriate solvent, and volatilizing the solvent. As the binder (binder), a vinylidene fluoride (VDF) polymer such as polyvinylidene fluoride (PVDF) is mainly used.
　このようなＶＤＦ系ポリマーを用いたバインダー組成物を含む電極合剤として、例えば、特許文献１には、集電体上に塗布した後の厚みを制御するために、ずり速度が０から１０００［ｓ－１］の範囲における流動曲線が、特定の流動方程式に対して特定の相関係数の条件で近似されるように調製された合剤スラリーが開示されている。 As an electrode mixture containing a binder composition using such a VDF polymer, for example, Patent Document 1 discloses a shear rate of 0 to 1000 in order to control the thickness after coating on a current collector. A mixture slurry prepared such that a flow curve in the range of s −1 ] is approximated with a specific correlation coefficient for a specific flow equation is disclosed.
日本国公開特許公報「特開２００４－９５１９８号公報」（２００４年３月２５日公開）Japanese Patent Publication “JP-A-2004-95198” (published on March 25, 2004) 日本国公開特許公報「特開平１１－１９５４１９号公報」（１９９９年７月２１日公開）Japanese Patent Publication “JP 11-195419 A” (released July 21, 1999)
　しかしながら、特許文献１の電極合剤は、スラリー状態での保管時に、不可逆的な増粘現象が発生し得るという問題がある。 However, the electrode mixture of Patent Document 1 has a problem that an irreversible thickening phenomenon may occur during storage in a slurry state.
　この問題に対し、バインダー組成物中の結着剤として、ＶＤＦに由来する構造単位とクロロトリフルオロエチレン（ＣＴＦＥ）に由来する構造単位との共重合体（ＶＤＦ／ＣＴＦＥ共重合体）を用いることにより、保管時の増粘現象を抑制することが試みられている（特許文献２）。 To solve this problem, a copolymer of a structural unit derived from VDF and a structural unit derived from chlorotrifluoroethylene (CTFE) (VDF / CTFE copolymer) is used as a binder in the binder composition. Therefore, attempts have been made to suppress the thickening phenomenon during storage (Patent Document 2).
　しかしながら、ＶＤＦ／ＣＴＦＥ共重合体を用いたバインダー組成物を含む電極合剤は、他のＶＤＦ系ポリマーに比して、チキソトロピー性（せん断応力を受け続けると粘度が時間とともに低下し、静止すると粘度が上昇する性質）が高く、電極作製時における作業効率の低下、および作製される電極合剤層の厚みの不均一化等が生じる場合があり、電池性能に影響が及び得るという問題がある。 However, an electrode mixture containing a binder composition using a VDF / CTFE copolymer has a thixotropic property (viscosity decreases with time when it is subjected to shear stress, and decreases with time when compared with other VDF polymers). There is a problem that the working efficiency at the time of electrode production and the thickness of the electrode mixture layer to be produced may be nonuniform, which may affect the battery performance.
　本発明は、上述の問題に鑑みてなされたものであり、その目的は、スラリー状電極合剤の保管時における不可逆的な増粘現象を抑制すると共に、そのチキソトロピー性をも抑制するバインダー組成物を提供することにある。 The present invention has been made in view of the above-mentioned problems, and its purpose is to suppress a irreversible thickening phenomenon during storage of a slurry-like electrode mixture, and to suppress its thixotropic property. Is to provide.
　本発明者らは上記課題を達成するために、鋭意研究を重ねた結果、ＶＤＦ／ＣＴＦＥ共重合体と、特定の添加剤とを組み合わせることにより、上記課題を解決し得ることを見出し、本発明を完成させた。本発明は以下のように記載することができる。 As a result of intensive studies to achieve the above problems, the present inventors have found that the above problems can be solved by combining a VDF / CTFE copolymer and a specific additive. Was completed. The present invention can be described as follows.
　本発明に係るバインダー組成物は、上記課題を解決するために、電極活物質を集電体に結着させるために用いられるバインダー組成物であって、上記バインダー組成物は、フッ化ビニリデン重合体とポリマー添加剤とを含み、上記フッ化ビニリデン重合体は、フッ化ビニリデンに由来する構造単位とクロロトリフルオロエチレンに由来する構造単位とを含むフッ化ビニリデン共重合体を含み、上記ポリマー添加剤は、以下の繰り返し単位：
－［ＣＨ２－ＣＨＲ］－
を有するポリマー材料であるバインダー組成物である。
（上記繰り返し単位において、Ｒは、鎖状若しくは環状アミド基、ニトリル基、ヒドロキシ基、エステル含有基、または、炭素数１～４のアルキル基であって、当該アルキル基の水素原子の少なくとも１つが鎖状若しくは環状アミド基、ニトリル基またはヒドロキシ基で置換されている置換基を示す。） The binder composition according to the present invention is a binder composition used for binding an electrode active material to a current collector in order to solve the above-described problems, and the binder composition is a vinylidene fluoride polymer. And the polymer additive, the vinylidene fluoride polymer includes a vinylidene fluoride copolymer including a structural unit derived from vinylidene fluoride and a structural unit derived from chlorotrifluoroethylene, and the polymer additive Is the following repeating unit:
-[CH 2 -CHR]-
It is a binder composition which is a polymer material having
(In the above repeating unit, R is a chain or cyclic amide group, a nitrile group, a hydroxy group, an ester-containing group, or an alkyl group having 1 to 4 carbon atoms, and at least one hydrogen atom of the alkyl group is Indicates a substituent substituted with a chain or cyclic amide group, a nitrile group or a hydroxy group.)
　本発明は、スラリー状電極合剤の保管時における不可逆的な増粘現象を抑制すると共に、そのチキソトロピー性をも抑制するバインダー組成物を提供することができるという効果を奏する。 The present invention has an effect that it is possible to provide a binder composition that suppresses the irreversible thickening phenomenon during storage of the slurry electrode mixture and also suppresses its thixotropic property.
本実施形態における非水電解質二次電池における電極の断面図である。It is sectional drawing of the electrode in the nonaqueous electrolyte secondary battery in this embodiment. 本実施形態における非水電解質二次電池の分解斜視図である。It is a disassembled perspective view of the nonaqueous electrolyte secondary battery in this embodiment.
　以下、本発明の一実施形態について詳細に説明する。ここで、本明細書等における「電極」とは、特に断りのない限り、本実施形態におけるバインダー組成物を用いた電極合剤から形成される電極合剤層が集電体上に形成されている、非水電解質二次電池の電極を意味する。また、本明細書等における「電池」とは、「電極」を備えた非水電解質二次電池を意味する。また、本明細書等における「チキソトロピー性」とは、せん断応力を受け続けると粘度が時間とともに低下し、静止すると粘度が上昇する性質を意味しており、O.C. C. Lin “Thixotropic behavior of gel-like systems” J. Appl. Polym. Sci. Vol.19, 199-214, 1975において定義されるチキソトロピー係数λでもって表すことができる。チキソトロピー係数λが小さいほど、チキソトロピー性が抑制されているといえる。 Hereinafter, an embodiment of the present invention will be described in detail. Here, unless otherwise specified, the “electrode” in this specification and the like means that an electrode mixture layer formed from an electrode mixture using the binder composition in the present embodiment is formed on a current collector. It means an electrode of a non-aqueous electrolyte secondary battery. In addition, the “battery” in this specification and the like means a nonaqueous electrolyte secondary battery including an “electrode”. In addition, “thixotropic property” in the present specification and the like means a property that the viscosity decreases with time when the shear stress is continued, and the viscosity increases when stationary, and OC 、 C. Lin “Thixotropic behavior of gel- like systems ”J. Appl. Polym. Sci. Vol.19, 199-214, 1975 can be expressed by the thixotropy coefficient λ. It can be said that the thixotropy is suppressed as the thixotropy coefficient λ is smaller.
　（バインダー組成物）
　本実施形態に係るバインダー組成物は、電池が有する電極であって、集電体上に電極活物質を含む電極合剤層が形成されてなる電極において、電極活物質を集電体に結着させるために用いられるものである。 (Binder composition)
The binder composition according to this embodiment is an electrode of a battery, and in an electrode in which an electrode mixture layer containing an electrode active material is formed on a current collector, the electrode active material is bound to the current collector. It is used to make it.
　バインダー組成物には、フッ化ビニリデン重合体と特定のポリマー添加剤とが含まれている。また、本実施形態に係るバインダー組成物においては、所望の効果を阻害しない限り、さらに別の重合体および添加剤を含んでいてもよい。 The binder composition contains a vinylidene fluoride polymer and a specific polymer additive. Moreover, in the binder composition which concerns on this embodiment, as long as the desired effect is not inhibited, another polymer and additive may be included.
　［フッ化ビニリデン重合体］
　本発明の一態様に係るフッ化ビニリデン重合体は、フッ化ビニリデンに由来する構造単位と、クロロトリフルオロエチレンに由来する構造単位と、を含むフッ化ビニリデン共重合体（コポリマー）を含む。フッ化ビニリデン由来単位に加えて、クロロトリフルオロエチレン由来単位を含むことにより、得られる共重合体を結着剤として用いる電極合剤は、スラリー状態での保管時に、不可逆的な増粘現象を抑制し、スラリーがゲル化することを防止することができる。 [Vinylidene fluoride polymer]
The vinylidene fluoride polymer according to one embodiment of the present invention includes a vinylidene fluoride copolymer (copolymer) including a structural unit derived from vinylidene fluoride and a structural unit derived from chlorotrifluoroethylene. By including chlorotrifluoroethylene-derived units in addition to vinylidene fluoride-derived units, the electrode mixture using the resulting copolymer as a binder exhibits an irreversible thickening phenomenon during storage in a slurry state. It can suppress and it can prevent that a slurry gelatinizes.
　本発明の一態様に係るフッ化ビニリデン重合体は、上記フッ化ビニリデン共重合体に加えて、フッ化ビニリデン共重合体による増粘現象抑制効果を阻害しない範囲で、フッ化ビニリデン単独重合体、または、クロロトリフルオロエチレンに由来する構造単位を含まないフッ化ビニリデン共重合体を含んでいてもよい。このようなクロロトリフルオロエチレンに由来する構造単位を含まないフッ化ビニリデン共重合体としては、コハク酸モノ（アクリロキシプロピル）（ＡＰＳ）に由来する構造単位を含むＶＤＦ／ＡＰＳ共重合体、ヘキサフルオロプロピレン（ＨＦＰ）に由来する構造単位を含むＶＤＦ／ＨＦＰ共重合体、アクリル酸（ＡＡ）に由来する構造単位を含むＶＤＦ／ＡＡ共重合体、および、ＶＤＦ／ＨＦＰ／ＡＰＳ共重合体等が挙げられる。 In addition to the above-mentioned vinylidene fluoride copolymer, the vinylidene fluoride polymer according to an aspect of the present invention is a vinylidene fluoride homopolymer in a range that does not inhibit the thickening phenomenon suppressing effect of the vinylidene fluoride copolymer, Or the vinylidene fluoride copolymer which does not contain the structural unit derived from chlorotrifluoroethylene may be included. Examples of the vinylidene fluoride copolymer not containing a structural unit derived from chlorotrifluoroethylene include a VDF / APS copolymer containing a structural unit derived from mono (acryloxypropyl) succinate (APS), hexa VDF / HFP copolymer containing structural units derived from fluoropropylene (HFP), VDF / AA copolymer containing structural units derived from acrylic acid (AA), VDF / HFP / APS copolymer, etc. Can be mentioned.
　本発明の好ましい一態様としては、フッ化ビニリデン重合体は、フッ化ビニリデン共重合体である。 In a preferred embodiment of the present invention, the vinylidene fluoride polymer is a vinylidene fluoride copolymer.
　本発明の一態様に係るフッ化ビニリデン共重合体は、フッ化ビニリデン由来単位を７０モル％以上で含有することが好ましく、８０モル％以上で含有することがより好ましく、さらには８５モル％以上で含有することが特に好ましい。上限に制限はないが、９９．５モル％以下とすることが好ましい。また、クロロトリフルオロエチレン由来単位は０．１～１０モル％であることが好ましく、０．３～５モル％であることが更に好ましく、０．５～３モル％であることが最も好ましい。ＣＴＦＥ量が上記の範囲であることにより、スラリーのゲル化を防止しながらも、電解液への膨張を抑制して電池性能が低下することを避けることができる。 The vinylidene fluoride copolymer according to one embodiment of the present invention preferably contains 70% by mole or more of vinylidene fluoride-derived units, more preferably 80% by mole or more, and more preferably 85% by mole or more. It is particularly preferable to contain. Although there is no restriction | limiting in an upper limit, it is preferable to set it as 99.5 mol% or less. Further, the chlorotrifluoroethylene-derived unit is preferably 0.1 to 10 mol%, more preferably 0.3 to 5 mol%, and most preferably 0.5 to 3 mol%. When the amount of CTFE is in the above range, it is possible to prevent the battery performance from being deteriorated by suppressing expansion into the electrolytic solution while preventing gelation of the slurry.
　上記２種類の構造単位に加えてさらに、共重合可能な他の単量体を含めた三元以上の共重合体としてもよい。このような単量体としては、例えば、エチレンおよびプロピレン等の炭化水素系単量体、フッ化ビニル、トリフルオロエチレン、テトラフルオロエチレン、ヘキサフルオロプロピレンおよびフルオロアルキルビニルエーテル等の含フッ素単量体、またはアリルグリシジルエーテルおよびクルトン酸グリシジルエステル等のエポキシ基含有ビニル単量体を共重合体成分として含んでいてもよい。更には、フッ化ビニリデン系重合体を溶解または膨潤する溶媒中で、アミノ基またはメルカプト基等のフッ化ビニリデン系重合体と反応性基と加水分解性基を併有するシラン系カップリング剤あるいはチタネート系カップリング剤中で処理してなる変性フッ化ビニリデン系重合体も用いられる。 In addition to the two types of structural units described above, a ternary or higher copolymer containing other copolymerizable monomers may be used. Examples of such monomers include hydrocarbon monomers such as ethylene and propylene, fluorine-containing monomers such as vinyl fluoride, trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, and fluoroalkyl vinyl ether, Alternatively, an epoxy group-containing vinyl monomer such as allyl glycidyl ether and cruconic acid glycidyl ester may be contained as a copolymer component. Furthermore, a silane coupling agent or titanate having both a reactive group and a hydrolyzable group in combination with a vinylidene fluoride polymer such as an amino group or a mercapto group in a solvent that dissolves or swells the vinylidene fluoride polymer. A modified vinylidene fluoride polymer obtained by treatment in a system coupling agent is also used.
　特に、カルボキシル基を有する単量体成分に由来する構造単位をさらに含むことにより、本発明の効果を好適に達成することができる。カルボキシル基を有する単量体成分としては、アクリル酸、メタクリル酸、マレイン酸モノメチル、アクリル酸２－カルボキシエチル、メタクリル酸（２－カルボキシエチル）、コハク酸モノ（アクリロキシエチル）、コハク酸モノ（アクリロキシプロピル）、フタル酸モノ（アクリロキシエチル）、コハク酸モノ（メタクリロキシエチル）、コハク酸モノ（メタクリロキシプロピル）、フタル酸モノ（メタクリロキシエチル）、およびトリフルオロアクリル酸等が挙げられる。これらは、一種単独で用いても、二種以上を用いてもよい。 In particular, the effects of the present invention can be suitably achieved by further including a structural unit derived from a monomer component having a carboxyl group. Examples of the monomer component having a carboxyl group include acrylic acid, methacrylic acid, monomethyl maleate, 2-carboxyethyl acrylate, methacrylic acid (2-carboxyethyl), succinic acid mono (acryloxyethyl), and succinic acid mono ( Acryloxypropyl), mono (acryloxyethyl) phthalate, mono (methacryloxyethyl) succinate, mono (methacryloxypropyl) succinate, mono (methacryloxyethyl) phthalate, and trifluoroacrylic acid . These may be used individually by 1 type, or may use 2 or more types.
　フッ化ビニリデン由来単位およびクロロトリフルオロエチレン由来単位に加えて、カルボキシル基を有する単量体成分に由来する構造単位をさらに含む場合は、該カルボキシル基含有構造単位を、０．０１～３モル％で含有することが好ましく、０．０５～１モル％であることがより好ましく、０．０８～０．５モル％であることが最も好ましい。官能基量が０．０１モル％より少ないと、十分な接着性が得られないことがある。また、３モル％より多いと、フッ素樹脂本来の耐薬品性等の性質が損なわれることがある。 In the case of further containing a structural unit derived from a monomer component having a carboxyl group in addition to the vinylidene fluoride-derived unit and chlorotrifluoroethylene-derived unit, the carboxyl group-containing structural unit is contained in an amount of 0.01 to 3 mol%. The content is preferably 0.05 to 1 mol%, and more preferably 0.08 to 0.5 mol%. When the functional group amount is less than 0.01 mol%, sufficient adhesion may not be obtained. Moreover, when more than 3 mol%, properties, such as a chemical resistance intrinsic to a fluororesin, may be impaired.
　なお、各構成単位の存在量は１Ｈ　ＮＭＲもしくは１９Ｆ　ＮＭＲによって求めることができる。 The abundance of each structural unit can be determined by 1 H NMR or 19 F NMR.
　本発明の一態様に係るフッ化ビニリデン共重合体は、インヘレント粘度（樹脂４ｇを１リットルのＮ，Ｎ－ジメチルホルムアミドに溶解させた溶液の３０℃における対数粘度）が、０．５～２０ｄＬ／ｇ、特に０．８～１０ｄＬ／ｇの範囲内の値を有することが好ましい。 The vinylidene fluoride copolymer according to one embodiment of the present invention has an inherent viscosity (logarithmic viscosity at 30 ° C. of a solution obtained by dissolving 4 g of resin in 1 liter of N, N-dimethylformamide) of 0.5 to 20 dL / g, in particular a value in the range of 0.8 to 10 dL / g.
　本発明の一態様に係るフッ化ビニリデン共重合体を製造する方法としては、特に限定されず、懸濁重合、乳化重合および溶液重合等の従来公知の方法を挙げることができる。これらの中でも、後処理の容易さ等の点から、共重合の方法としては、水系の懸濁重合または乳化重合であることが好ましく、水系の懸濁重合であることがより好ましい。 The method for producing the vinylidene fluoride copolymer according to one embodiment of the present invention is not particularly limited, and examples thereof include conventionally known methods such as suspension polymerization, emulsion polymerization, and solution polymerization. Among these, from the viewpoint of ease of post-treatment, the copolymerization method is preferably aqueous suspension polymerization or emulsion polymerization, and more preferably aqueous suspension polymerization.
　水を分散媒とした懸濁重合における懸濁剤としては、メチルセルロース、メトキシ化メチルセルロース、プロポキシ化メチルセルロース、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、ポリビニルアルコール、ポリエチレンオキシドおよびゼラチン等を使用することができる。 As a suspending agent in suspension polymerization using water as a dispersion medium, methyl cellulose, methoxylated methyl cellulose, propoxylated methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyethylene oxide, gelatin and the like can be used.
　また、重合開始剤としては、ジイソプロピルペルオキシジカーボネート、ジノルマルプロピルペルオキシジカーボネート、ジノルマルヘプタフルオロプロピルペルオキシジカーボネート、イソブチリルペルオキサイド、ジ（クロロフルオロアシル）ペルオキサイド、ジ（ペルフルオロアシル）ペルオキサイド、ｔ－ブチルペルオキシピバレート等が使用できる。 In addition, as polymerization initiators, diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, di (perfluoroacyl) peroxide Oxide, t-butyl peroxypivalate, etc. can be used.
　また、酢酸エチル、酢酸メチル、アセトン、エタノール、ｎ－プロパノール、アセトアルデヒド、プロピルアルデヒド、プロピオン酸エチル、および四塩化炭素等の連鎖移動剤を添加することにより、得られる重合体の重合度を調節することも可能である。 In addition, the degree of polymerization of the resulting polymer is adjusted by adding a chain transfer agent such as ethyl acetate, methyl acetate, acetone, ethanol, n-propanol, acetaldehyde, propyl aldehyde, ethyl propionate, and carbon tetrachloride. It is also possible.
　［ポリマー添加剤］
　本発明の一態様において、バインダー組成物は、フッ化ビニリデン共重合体と共に、以下の繰り返し単位：
－［ＣＨ２－ＣＨＲ］－
を有するポリマー材料からなるポリマー添加剤を含有する。 [Polymer additive]
In one embodiment of the present invention, the binder composition, together with the vinylidene fluoride copolymer, includes the following repeating units:
-[CH 2 -CHR]-
A polymer additive comprising a polymer material having
　上記繰り返し単位において、Ｒは、鎖状若しくは環状アミド基、ニトリル基、ヒドロキシ基、エステル含有基、または、炭素数１～４のアルキル基であって、当該アルキル基の水素原子の少なくとも１つが鎖状若しくは環状アミド基、ニトリル基またはヒドロキシ基で置換されている置換基を示す。 In the above repeating unit, R is a chain or cyclic amide group, a nitrile group, a hydroxy group, an ester-containing group, or an alkyl group having 1 to 4 carbon atoms, and at least one hydrogen atom of the alkyl group is a chain. Or a substituent substituted with a amide group, a nitrile group or a hydroxy group.
　本願明細書において、「鎖状または環状アミド基」は、式：－ＣＯＮＲ１Ｒ２または－ＮＲ１ＣＯＲ２（式中、Ｒ１およびＲ２は、それぞれ同じであっても異なっていてもよく、水素原子または炭素数１～６個の低級アルキル基であるか、または、Ｒ１およびＲ２が一緒になって、結合する窒素原子と共に単環式複素環を形成する）で表される鎖状アミド基および環状アミド基を意味する。このような鎖状または環状アミド基としては、例えば、２－ピロリドン基、アセトアミド基、Ｎ－メチルアセトアミド基等が挙げられる。ここで、２－ピロリドン基、アセトアミド基、Ｎ－メチルアセトアミド基とは、それぞれ対応する化合物中のカルボニル炭素原子又は窒素原子に結合する１個の水素原子が、結合手で置換された一価の基を表す。 In the present specification, the “chain or cyclic amide group” has the formula: —CONR 1 R 2 or —NR 1 COR 2 (wherein R 1 and R 2 may be the same or different from each other). , A hydrogen atom or a lower alkyl group having 1 to 6 carbon atoms, or R 1 and R 2 together form a monocyclic heterocycle with the nitrogen atom to which they are bonded) Mean amide group and cyclic amide group. Examples of such a chain or cyclic amide group include a 2-pyrrolidone group, an acetamido group, and an N-methylacetamido group. Here, the 2-pyrrolidone group, the acetamide group, and the N-methylacetamide group are monovalent groups in which one hydrogen atom bonded to a carbonyl carbon atom or a nitrogen atom in the corresponding compound is substituted with a bond. Represents a group.
　フッ化ビニリデン共重合体と共にポリマー添加剤を含むことにより、バインダー組成物は、電極合剤としたときに、スラリーの増粘現象の抑制効果を保持しつつ、チキソトロピー性を抑制することができる。 By including a polymer additive together with the vinylidene fluoride copolymer, the binder composition can suppress thixotropic properties while retaining the effect of suppressing the thickening phenomenon of the slurry when used as an electrode mixture.
　ポリマー材料は、繰り返し単位におけるＲが同一であるホモポリマーであっても、Ｒが異なるランダムまたはブロックコポリマーであってもよい。 The polymer material may be a homopolymer having the same R in the repeating unit, or may be a random or block copolymer having a different R.
　ポリマー材料としては、例えば、ポリビニルピロリドン、ポリアクリロニトリル、ポリビニルアルコール等が挙げられる。 Examples of the polymer material include polyvinyl pyrrolidone, polyacrylonitrile, polyvinyl alcohol, and the like.
　なお、本願明細書において、用語「ポリビニルアルコール」は、ポリ酢酸ビニルをケン化して得られるポリビニルアルコールであって、３０モル％以下の範囲でアセチル基が残存しているものを包含する。 In the present specification, the term “polyvinyl alcohol” includes polyvinyl alcohol obtained by saponifying polyvinyl acetate and having an acetyl group remaining in a range of 30 mol% or less.
　本発明の一態様に係るポリマー材料を製造する方法としては、特に限定されず、上述のフッ化ビニリデン共重合体と同様にして製造することができる。 The method for producing the polymer material according to one embodiment of the present invention is not particularly limited, and the polymer material can be produced in the same manner as the above-described vinylidene fluoride copolymer.
　［バインダー組成物］
　本実施形態に係るバインダー組成物は、上記フッ化ビニリデン共重合体を含むフッ化ビニリデン重合体、および、ポリマー添加剤を含む。フッ化ビニリデン共重合体は単独で用いてもよく、２種類以上のフッ化ビニリデン共重合体を併用してもよい。同様に、ポリマー添加剤は単独のポリマー材料で用いてもよく、２種類以上のポリマー材料を併用してもよい。 [Binder composition]
The binder composition according to this embodiment includes a vinylidene fluoride polymer containing the vinylidene fluoride copolymer and a polymer additive. The vinylidene fluoride copolymer may be used alone, or two or more types of vinylidene fluoride copolymers may be used in combination. Similarly, the polymer additive may be used alone or in combination of two or more polymer materials.
　本実施形態に係るバインダー組成物においては、所望の効果を阻害しない限り、さらに別の重合体、および各種添加剤を含んでいてもよい。 The binder composition according to this embodiment may further contain another polymer and various additives as long as the desired effect is not impaired.
　バインダー組成物におけるフッ化ビニリデン共重合体の含有量は、２．５質量％以上であることが好ましく、５質量％以上であることがより好ましく、１０質量％であることが更に好ましい。フッ化ビニリデン共重合体の含有量がこの範囲であることにより、バインダー組成物を電極合剤としたときに、保管時における不可逆的な増粘現象を抑制することができる。 The content of the vinylidene fluoride copolymer in the binder composition is preferably 2.5% by mass or more, more preferably 5% by mass or more, and still more preferably 10% by mass. When the content of the vinylidene fluoride copolymer is within this range, an irreversible thickening phenomenon during storage can be suppressed when the binder composition is used as an electrode mixture.
　また、バインダー組成物におけるポリマー添加剤の含有量は、フッ化ビニリデン重合体とポリマー添加剤との合計を１００質量％としたときに、好ましくは１～５０質量％であり、より好ましくは２～３０質量％であり、さらに好ましくは２．５～１０質量％である。ポリマー添加剤の含有量がこの範囲であることにより、バインダー組成物を電極合剤としたときに、チキソトロピー性の上昇を抑制する効果が一層高まる。 Further, the content of the polymer additive in the binder composition is preferably 1 to 50% by mass, more preferably 2 to 2% when the total of the vinylidene fluoride polymer and the polymer additive is 100% by mass. 30% by mass, more preferably 2.5 to 10% by mass. When the content of the polymer additive is within this range, when the binder composition is used as an electrode mixture, the effect of suppressing an increase in thixotropic properties is further enhanced.
　バインダー組成物は、必要に応じて、さらに慣用の添加剤を含んでいてもよい。 The binder composition may further contain a conventional additive as required.
　［電極合剤］
　本実施形態における電極合剤は、バインダー組成物に、電極活物質と溶媒とを含ませたものである。この電極合剤を集電体上に塗布して電極合剤層を形成することにより、電極を作製することができる。電極合剤は、スラリー状であり、溶媒の量を調節することによって、所望の粘度に調整することができる。 [Electrode mixture]
The electrode mixture in the present embodiment is obtained by adding an electrode active material and a solvent to a binder composition. An electrode can be produced by applying this electrode mixture on a current collector to form an electrode mixture layer. The electrode mixture is in the form of a slurry and can be adjusted to a desired viscosity by adjusting the amount of the solvent.
　電極合剤は、塗布対象である集電体の種類等に応じて電極活物質等の種類を変更することにより、正極用の電極合剤、または負極用の電極合剤とすることができる。本実施形態における電極合剤は、正極用の電極活物質、すなわち正極活物質（正極材料）を用いた正極用の電極合剤であることが好ましい。 The electrode mixture can be used as an electrode mixture for the positive electrode or an electrode mixture for the negative electrode by changing the type of the electrode active material according to the type of the current collector to be applied. The electrode mixture in the present embodiment is preferably a positive electrode mixture using a positive electrode active material, that is, a positive electrode active material (positive electrode material).
　（溶媒）
　本実施形態における電極合剤において用いられる溶媒としては、フッ化ビニリデン重合体およびポリマー添加剤を溶解できる溶媒であれば特に限定されるものではない。溶媒としては、例えばＮ－メチル－２－ピロリドン（ＮＭＰ）、水、ジメチルホルムアミド、Ｎ，Ｎ－ジメチルアセトアミド、Ｎ，Ｎ－ジメチルスルホキシド、ヘキサメチルホスホアミド、ジオキサン、テトラヒドロフラン、テトラメチルウレア、トリエチルホスフェート、トリメチルホスフェート、アセトン、メチルエチルケトン、およびテトラヒドロフランなどが挙げられる。これらの溶媒は、単独で用いてもよいし、二種類以上を混合した混合溶媒として用いてもよい。電極合剤において用いられる溶媒は、中でも、Ｎ－メチル－２－ピロリドン、Ｎ，Ｎ－ジメチルホルムアミドおよびＮ，Ｎ－ジメチルアセトアミドなどの含窒素系有機溶媒が好ましく、Ｎ－メチル－２－ピロリドンがより好ましい。 (solvent)
The solvent used in the electrode mixture in the present embodiment is not particularly limited as long as the solvent can dissolve the vinylidene fluoride polymer and the polymer additive. Examples of the solvent include N-methyl-2-pyrrolidone (NMP), water, dimethylformamide, N, N-dimethylacetamide, N, N-dimethylsulfoxide, hexamethylphosphoamide, dioxane, tetrahydrofuran, tetramethylurea, triethyl phosphate. , Trimethyl phosphate, acetone, methyl ethyl ketone, and tetrahydrofuran. These solvents may be used alone or as a mixed solvent in which two or more kinds are mixed. The solvent used in the electrode mixture is preferably a nitrogen-containing organic solvent such as N-methyl-2-pyrrolidone, N, N-dimethylformamide and N, N-dimethylacetamide, and N-methyl-2-pyrrolidone is preferred. More preferred.
　フッ化ビニリデン重合体およびポリマー添加剤の総量を１００質量部とすると、溶媒の量は４００～１００００質量部であることが好ましく、６００～８０００質量部であることがより好ましい。上述した溶媒の量の範囲内では適度な溶液粘度となり、ハンドリング性に優れる。 When the total amount of the vinylidene fluoride polymer and the polymer additive is 100 parts by mass, the amount of the solvent is preferably 400 to 10000 parts by mass, and more preferably 600 to 8000 parts by mass. Within the range of the amount of the solvent described above, the solution viscosity is moderate and the handling property is excellent.
　（電極活物質）
　本実施形態における電極合剤において用いられる電極活物質は、上述したように、本実施形態に係る電極合剤を負極用の電極合剤とする場合には、負極用の電極活物質、すなわち負極活物質を用いればよく、本実施形態に係る電極合剤を正極用の電極合剤とする場合には、正極用の電極活物質、すなわち正極活物質を用いればよい。 (Electrode active material)
As described above, the electrode active material used in the electrode mixture in the present embodiment is an electrode active material for a negative electrode, that is, a negative electrode, when the electrode mixture according to the present embodiment is used as an electrode mixture for a negative electrode. An active material may be used. When the electrode mixture according to this embodiment is used as a positive electrode mixture, a positive electrode active material, that is, a positive electrode active material may be used.
　正極活物質としては、例えば、リチウムを含むリチウム系正極活物質が挙げられる。リチウム系正極活物質としては例えば、ＬｉＣｏＯ２およびＬｉＣｏｘＮｉ１－ｘＯ２（０≦ｘ＜１）等の一般式ＬｉＭＹ２で表わされる複合金属カルコゲン化合物、または複合金属酸化物、ＬｉＭｎ２Ｏ４などのスピネル構造をとる複合金属酸化物およびＬｉＦｅＰＯ４などのオリビン型リチウム化合物等が挙げられる。ここでＭは、Ｃｏ、Ｎｉ、Ｆｅ、Ｍｎ、ＣｒおよびＶ等の遷移金属もしくはＡｌの少なくとも一種であり、ＹはＯおよびＳ等のカルコゲン元素である。 Examples of the positive electrode active material include a lithium-based positive electrode active material containing lithium. Examples of the lithium-based positive electrode active material include a composite metal chalcogen compound represented by the general formula LiMY 2 such as LiCoO 2 and LiCo x Ni 1-x O 2 (0 ≦ x <1), or a composite metal oxide, LiMn 2 O And composite metal oxides having a spinel structure such as 4 and olivine type lithium compounds such as LiFePO 4 . Here, M is at least one of transition metals such as Co, Ni, Fe, Mn, Cr and V or Al, and Y is a chalcogen element such as O and S.
　負極活物質としては、黒鉛などの炭素系材料をはじめとした従来公知の材料を用いることができる。 As the negative electrode active material, conventionally known materials including carbon-based materials such as graphite can be used.
　本実施形態において、電極活物質は、溶媒と共に、バインダー組成物に直接添加すればよい。あるいは、電極活物質をまず溶媒に添加して、撹拌混合したものをバインダー組成物に添加するようにしてもよい。あるいは、バインダー組成物と溶媒とを混合して得られるバインダー溶液に、電極活物質を添加するようにしてもよい。 In this embodiment, the electrode active material may be added directly to the binder composition together with the solvent. Alternatively, the electrode active material may be first added to a solvent, and the mixture after stirring may be added to the binder composition. Or you may make it add an electrode active material to the binder solution obtained by mixing a binder composition and a solvent.
　（導電助剤）
　本実施形態における電極合剤は、さらに導電助剤を含んでいてもよい。導電助剤は、ＬｉＣｏＯ２等の電子伝導性の小さい活物質を使用する場合に、電極合剤層の導電性を向上する目的で添加するものである。導電助剤としては、例えば、カーボンブラック、カーボンナノチューブ、黒鉛微粉末および黒鉛繊維等の炭素物物質、ならびにニッケルおよびアルミニウム等の金属微粉末または金属繊維を用いることができる。 (Conductive aid)
The electrode mixture in the present embodiment may further contain a conductive aid. The conductive additive is added for the purpose of improving the conductivity of the electrode mixture layer when using an active material having a low electron conductivity such as LiCoO 2 . As the conductive assistant, for example, carbon black, carbon nanotubes, carbonaceous materials such as graphite fine powder and graphite fiber, and metal fine powder or metal fiber such as nickel and aluminum can be used.
　（電極合剤の他の成分）
　本実施形態における電極合剤は、上述の成分以外の他の成分を含んでいてもよい。他の成分としては、例えば、シュウ酸やコハク酸などの有機酸、分散剤等の慣用の添加剤等を挙げることができる。 (Other components of electrode mixture)
The electrode mixture in this embodiment may contain components other than the above-described components. Examples of other components include organic acids such as oxalic acid and succinic acid, and conventional additives such as a dispersant.
　（電極合剤の調製）
　本実施形態にかかる電極合剤は、上述のバインダー組成物、溶媒および電極活物質、並びに、必要に応じて、導電助剤、および他の各種成分等を、任意の順序で混合し、スラリー化することにより得られる。 (Preparation of electrode mixture)
The electrode mixture according to the present embodiment is prepared by mixing the binder composition, the solvent and the electrode active material, and, if necessary, the conductive auxiliary agent and other various components in any order to form a slurry. Can be obtained.
　例えば、バインダー組成物と溶媒とを混合することによりバインダー溶液を調製し、得られたバインダー溶液に、電極活物質を、導電助剤等と共に添加し、撹拌混合して電極合剤を調製することができる。 For example, a binder solution is prepared by mixing a binder composition and a solvent, an electrode active material is added to the obtained binder solution together with a conductive additive, and the mixture is stirred and mixed to prepare an electrode mixture. Can do.
　また、導電助剤と溶媒とを混合することにより導電助剤分散液を調製し、得られた導電助剤分散液に、バインダー組成物、および電極活物質等を添加し、撹拌混合して電極合剤を調製してもよい。 Also, a conductive assistant dispersion is prepared by mixing a conductive assistant and a solvent, and a binder composition, an electrode active material, and the like are added to the obtained conductive assistant dispersion, and the mixture is stirred and mixed to form an electrode. A mixture may be prepared.
　また、上記バインダー溶液および上記導電助剤分散液をそれぞれ調製し、これらを電極活物質等と撹拌混合して電極合剤を調製してもよい。 Further, the electrode mixture may be prepared by preparing the binder solution and the conductive auxiliary agent dispersion, respectively, and stirring and mixing them with an electrode active material or the like.
　［非水電解質二次電池用電極］
　図１を参照して、本実施形態に係る電極に関して以下に説明する。図１は、本実施形態における電極の断面図である。図１に示すように、電極１０は、集電体１１、電極合剤層１２ａおよび１２ｂを有しており、集電体１１上に電極合剤層１２ａおよび１２ｂが形成されている。電極１０は、上述したように、正極用の電極合剤を用いて電極合剤層１２ａおよび１２ｂが得られる場合には正極となり、負極用の電極合剤を用いて電極合剤層１２ａおよび１２ｂが得られる場合には負極となる。 [Nonaqueous electrolyte secondary battery electrode]
The electrode according to this embodiment will be described below with reference to FIG. FIG. 1 is a cross-sectional view of an electrode in the present embodiment. As shown in FIG. 1, the electrode 10 includes a current collector 11 and electrode mixture layers 12 a and 12 b, and electrode mixture layers 12 a and 12 b are formed on the current collector 11. As described above, the electrode 10 becomes a positive electrode when the electrode mixture layers 12a and 12b are obtained using the electrode mixture for the positive electrode, and the electrode mixture layers 12a and 12b using the electrode mixture for the negative electrode. Is obtained as a negative electrode.
　集電体１１は、電極１０の基材であり、電気を取り出すための端子である。集電体１１の材質としては、鉄、ステンレス鋼、鋼、銅、アルミニウム、ニッケル、およびチタン等を挙げることができる。集電体１１の形状は、箔または網であることが好ましい。電極１０が正極である場合、集電体１１としては、アルミニウム箔とすることが好ましい。集電体１１の厚みは、５～１００μｍであることが好ましく、５～２０μｍがより好ましい。 The current collector 11 is a base material for the electrode 10 and a terminal for taking out electricity. Examples of the material of the current collector 11 include iron, stainless steel, steel, copper, aluminum, nickel, and titanium. The shape of the current collector 11 is preferably a foil or a net. When the electrode 10 is a positive electrode, the current collector 11 is preferably an aluminum foil. The thickness of the current collector 11 is preferably 5 to 100 μm, and more preferably 5 to 20 μm.
　電極合剤層１２ａおよび１２ｂは、上述した電極合剤を集電体１１に塗布して、乾燥させることにより得られる層である。電極合剤の塗布方法としては、当該技術分野における公知の方法を用いることができ、バーコーター、ダイコーターまたはコンマコーターなどを用いる方法を挙げることができる。電極合剤層１２ａおよび１２ｂを形成させるための乾燥温度としては、５０～１７０℃であることが好ましい。また、電極合剤層１２ａおよび１２ｂの厚みは、１０～１０００μｍであることが好ましい。なお、図１において電極１０は、集電体１１の両面に電極合剤層１２ａおよび１２ｂが形成されているが、もちろんこれに限定されるものではなく、集電体１１のいずれか一方の面にのみに、電極合剤層が形成されているものであってもよい。 The electrode mixture layers 12a and 12b are layers obtained by applying the electrode mixture described above to the current collector 11 and drying it. As a method for applying the electrode mixture, a known method in the technical field can be used, and a method using a bar coater, a die coater, a comma coater, or the like can be given. The drying temperature for forming the electrode mixture layers 12a and 12b is preferably 50 to 170 ° C. The thickness of the electrode mixture layers 12a and 12b is preferably 10 to 1000 μm. In FIG. 1, the electrode 10 has electrode mixture layers 12 a and 12 b formed on both surfaces of the current collector 11. However, the present invention is not limited to this, and one surface of the current collector 11 is not limited thereto. The electrode mixture layer may be formed only on the surface.
　電極合剤層の厚さは、通常は２０～２５０μｍであり、好ましくは２０～１５０μｍである。また、合剤層の目付量は、通常は２０～７００ｇ／ｍ２であり、好ましくは３０～５００ｇ／ｍ２である。 The thickness of the electrode mixture layer is usually 20 to 250 μm, preferably 20 to 150 μm. The basis weight of the mixture layer is usually 20 to 700 g / m 2 , preferably 30 to 500 g / m 2 .
　［非水電解質二次電池］
　図２を参照して、本実施形態に係る電池について以下に説明する。図２は、非水電解質二次電池の分解斜視図である。電池１００は、正極１、負極２、セパレータ３および金属ケーシング５を有している。具体的には、電池１００は、正極１と負極２との間にセパレータ３を配置した積層体を渦巻き状に巻き回した発電素子が、金属ケーシング５中に収容されている構造を有している。ここで、正極１または負極２は、図１における電極１０と同様のものである。セパレータ３としては、ポリプロピレンおよびポリエチレン等の高分子物質の多孔性膜などの公知の材料を用いることができる。 [Nonaqueous electrolyte secondary battery]
The battery according to this embodiment will be described below with reference to FIG. FIG. 2 is an exploded perspective view of the nonaqueous electrolyte secondary battery. The battery 100 includes a positive electrode 1, a negative electrode 2, a separator 3, and a metal casing 5. Specifically, the battery 100 has a structure in which a power generation element in which a laminated body in which a separator 3 is disposed between a positive electrode 1 and a negative electrode 2 is spirally wound is housed in a metal casing 5. Yes. Here, the positive electrode 1 or the negative electrode 2 is the same as the electrode 10 in FIG. As the separator 3, a known material such as a porous film of a polymer material such as polypropylene and polyethylene can be used.
　なお、図２において、電池１００を円筒形電池として図示しているが、本実施形態における電池１００はこれに限定されるものではなく、コイン形、角形またはペーパー形電池であってもよい。 In FIG. 2, the battery 100 is illustrated as a cylindrical battery, but the battery 100 in the present embodiment is not limited to this, and may be a coin-shaped, rectangular, or paper-type battery.
　（まとめ）
　本発明の一実施形態に係るバインダー組成物は、上記課題を解決するために、電極活物質を集電体に結着させるために用いられるバインダー組成物であって、上記バインダー組成物は、フッ化ビニリデン重合体とポリマー添加剤とを含み、上記フッ化ビニリデン重合体は、フッ化ビニリデンに由来する構造単位とクロロトリフルオロエチレンに由来する構造単位とを含むフッ化ビニリデン共重合体を含み、上記ポリマー添加剤は、以下の繰り返し単位：
－［ＣＨ２－ＣＨＲ］－
を有するポリマー材料であるバインダー組成物である。
（上記繰り返し単位において、Ｒは、鎖状若しくは環状アミド基、ニトリル基、ヒドロキシ基、エステル含有基、または、炭素数１～４のアルキル基であって、当該アルキル基の水素原子の少なくとも１つが鎖状若しくは環状アミド基、ニトリル基またはヒドロキシ基で置換されている置換基を示す。） (Summary)
In order to solve the above problems, a binder composition according to an embodiment of the present invention is a binder composition used for binding an electrode active material to a current collector, and the binder composition is a hook composition. A vinylidene fluoride polymer and a polymer additive, the vinylidene fluoride polymer includes a vinylidene fluoride copolymer including a structural unit derived from vinylidene fluoride and a structural unit derived from chlorotrifluoroethylene, The polymer additive includes the following repeating units:
-[CH 2 -CHR]-
It is a binder composition which is a polymer material having
(In the above repeating unit, R is a chain or cyclic amide group, a nitrile group, a hydroxy group, an ester-containing group, or an alkyl group having 1 to 4 carbon atoms, and at least one hydrogen atom of the alkyl group is Indicates a substituent substituted with a chain or cyclic amide group, a nitrile group or a hydroxy group.)
　また、本発明の一実施形態に係るバインダー組成物では、上記繰り返し単位において、Ｒは、鎖状若しくは環状アミド基、ニトリル基またはヒドロキシ基であることが好ましい。 In the binder composition according to an embodiment of the present invention, in the repeating unit, R is preferably a chain or cyclic amide group, a nitrile group, or a hydroxy group.
　また、本発明の一実施形態に係るバインダー組成物では、上記ポリマー添加剤は、ポリビニルピロリドン、ポリアクリロニトリルまたはポリビニルアルコールであることが好ましい。 In the binder composition according to an embodiment of the present invention, the polymer additive is preferably polyvinyl pyrrolidone, polyacrylonitrile, or polyvinyl alcohol.
　また、本発明の一実施形態に係るバインダー組成物では、上記ポリマー添加剤は、上記フッ化ビニリデン重合体と上記ポリマー添加剤との合計を１００質量％としたときに、１質量％以上かつ５０質量％以下含まれていることが好ましい。 In the binder composition according to an embodiment of the present invention, the polymer additive may be 1% by mass or more and 50% when the total of the vinylidene fluoride polymer and the polymer additive is 100% by mass. It is preferable that it is contained by mass% or less.
　また、本発明の一実施形態に係るバインダー組成物では、上記フッ化ビニリデン共重合体は、カルボキシル基を有する単量体成分に由来する構造単位をさらに含むことが好ましい。 In the binder composition according to an embodiment of the present invention, the vinylidene fluoride copolymer preferably further includes a structural unit derived from a monomer component having a carboxyl group.
　本発明の一実施形態に係る電極合剤は、上述のバインダー組成物と、溶媒と、電極活物質とを含む電極合剤である。 An electrode mixture according to an embodiment of the present invention is an electrode mixture including the above-described binder composition, a solvent, and an electrode active material.
　本発明の一実施形態に係る非水電解質二次電池は、上述の電極合剤から形成された電極合剤層を備える非水電解質二次電池である。 A nonaqueous electrolyte secondary battery according to an embodiment of the present invention is a nonaqueous electrolyte secondary battery including an electrode mixture layer formed from the above electrode mixture.
　以下に実施例を示し、本発明の実施の形態についてさらに詳しく説明する。もちろん、本発明は以下の実施例に限定されるものではなく、細部については様々な態様が可能であることはいうまでもない。さらに、本発明は上述した実施形態に限定されるものではなく、請求項に示した範囲で種々の変更が可能であり、それぞれ開示された技術的手段を適宜組み合わせて得られる実施形態についても本発明の技術的範囲に含まれる。また、本明細書中に記載された文献の全てが参考として援用される。 Examples will be shown below, and the embodiments of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail. Further, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope shown in the claims, and the present invention is also applied to the embodiments obtained by appropriately combining the disclosed technical means. It is included in the technical scope of the invention. Moreover, all the literatures described in this specification are used as reference.
　後述のように、本発明に係る種々のバインダー組成物を用いて電極合剤を製造し、それを用いてチキソトロピー係数およびスラリーのゲル化評価試験を行った。なお、本明細書における「インヘレント粘度」は、以下の方法により測定される値である。 As described later, an electrode mixture was produced using various binder compositions according to the present invention, and a thixotropic coefficient and a gelation evaluation test of the slurry were performed using the mixture. In addition, “inherent viscosity” in the present specification is a value measured by the following method.
　（インヘレント粘度ηｉ）
　インヘレント粘度ηｉを算出するために、フッ化ビニリデン共重合体８０ｍｇを２０ｍＬのＮ，Ｎ－ジメチルホルムアミドに溶解することによってフッ化ビニリデン共重合体溶液を作製する。当該溶液の粘度ηを、３０℃の恒温槽内においてウベローデ粘度計を用いて測定する。インヘレント粘度ηｉは、当該粘度ηを用いて下記式によって求められる。 (Inherent viscosity ηi)
In order to calculate the inherent viscosity ηi, a vinylidene fluoride copolymer solution is prepared by dissolving 80 mg of vinylidene fluoride copolymer in 20 mL of N, N-dimethylformamide. The viscosity η of the solution is measured using a Ubbelohde viscometer in a constant temperature bath at 30 ° C. The inherent viscosity ηi is obtained by the following formula using the viscosity η.
　　ηｉ＝（１／Ｃ）・ｌｎ（η／η０）
　上記式において、η０は溶媒であるＮ，Ｎ－ジメチルホルムアミドの粘度、Ｃは０．４ｇ／ｄＬである。 ηi = (1 / C) · ln (η / η0)
In the above formula, η0 is the viscosity of N, N-dimethylformamide as a solvent, and C is 0.4 g / dL.
　（実施例１）
　フッ化ビニリデン共重合体として、フッ化ビニリデン（ＶＤＦ）およびクロロトリフルオロエチレン（ＣＴＦＥ）（重量比９６：４）を重合し、ＶＤＦ－ＣＴＦＥ共重合体（インヘレント粘度２．１ｄＬ／ｇ）を使用した。また、ポリマー添加剤として、ポリビニルピロリドン（ＰＶＰ　Ｋ１５）（数平均分子量１０，０００、東京化成工業(株)製Ｐ０４７１）を使用した。 Example 1
As a vinylidene fluoride copolymer, vinylidene fluoride (VDF) and chlorotrifluoroethylene (CTFE) (weight ratio 96: 4) are polymerized, and a VDF-CTFE copolymer (inherent viscosity 2.1 dL / g) is used. did. In addition, polyvinyl pyrrolidone (PVP K15) (number average molecular weight 10,000, P0471 manufactured by Tokyo Chemical Industry Co., Ltd.) was used as a polymer additive.
　上記フッ化ビニリデン共重合体とポリマー添加剤とを、総質量に対しポリマー添加剤が５質量％となるように混合して、バインダー組成物を得た。 The above-mentioned vinylidene fluoride copolymer and polymer additive were mixed so that the polymer additive was 5% by mass with respect to the total mass to obtain a binder composition.
　電極活物質としてリチウム－コバルト複合酸化物（ＬＣＯ；ＬｉＣｏＯ２、セルシードＣ１０Ｎ、日本化学工業（株）製、平均粒子径１０μｍ）１００質量部、導電助剤としてカーボンブラック（ＳＰ；Ｔｉｍｃａｌ　Ｊａｐａｎ社製　ＳｕｐｅｒＰ（登録商標）Ｌｉ、平均粒子径４０ｎｍ、比表面積６０ｍ２／ｇ）２質量部、および上記バインダー組成物２質量部を、Ｎ－メチル－２－ピロリドン中に均一に分散させてスラリーとし、スラリー総質量に対する、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７６質量％の電極合剤を作製した。 Lithium-cobalt composite oxide (LCO; LiCoO 2 , Cellseed C10N, manufactured by Nippon Chemical Industry Co., Ltd., average particle size 10 μm) as an electrode active material 100 parts by mass, carbon black (SP; SuperPal manufactured by Timcal Japan) (Registered trademark) Li, 2 parts by mass of an average particle diameter of 40 nm, specific surface area of 60 m 2 / g) and 2 parts by mass of the binder composition were uniformly dispersed in N-methyl-2-pyrrolidone to form a slurry. An electrode mixture having a total solid content concentration of 76% by mass of the binder composition, the electrode active material, and the conductive additive with respect to the total mass was prepared.
　得られた電極合剤を、集電体である厚さ１５μｍのアルミ箔上にバーコーターで塗布し、これを恒温槽を用いて、窒素雰囲気下にて１１０℃で３０分間乾燥を行い、電極を作製した。 The obtained electrode mixture was coated on a 15 μm-thick aluminum foil as a current collector with a bar coater and dried at 110 ° C. for 30 minutes in a nitrogen atmosphere using a thermostatic bath. Was made.
　（実施例２）
　フッ化ビニリデン共重合体として、ＶＤＦ、ＣＴＦＥおよびコハク酸モノ（アクリロキシプロピル）（ＡＰＳ）（重量比９６：４：１）を重合し、ＶＤＦ－ＣＴＦＥ－ＡＰＳ共重合体（インヘレント粘度２．３ｄＬ／ｇ）を使用した以外は、実施例１と同様にして、バインダー組成物を得た。 (Example 2)
As a vinylidene fluoride copolymer, VDF, CTFE and mono (acryloxypropyl) succinate (APS) (weight ratio 96: 4: 1) were polymerized to obtain a VDF-CTFE-APS copolymer (inherent viscosity 2.3 dL). / G) was used in the same manner as in Example 1 except that a binder composition was obtained.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７４質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 74% by mass, the electrode mixture and the electrode Was made.
　（実施例３）
　フッ化ビニリデン共重合体として、ＶＤＦ、ＣＴＦＥおよびＡＰＳ（重量比９６：４：１）を重合し、ＶＤＦ－ＣＴＦＥ－ＡＰＳ共重合体（モル比：ＶＤＦ／ＣＴＦＥ／ＡＰＳ＝９６／４／１、インヘレント粘度２．５ｄＬ／ｇ）を使用し、バインダー組成物の総質量に対しポリマー添加剤が１０質量％となるようにした以外は、実施例１と同様にして、バインダー組成物を得た。 (Example 3)
As a vinylidene fluoride copolymer, VDF, CTFE and APS (weight ratio 96: 4: 1) were polymerized, and a VDF-CTFE-APS copolymer (molar ratio: VDF / CTFE / APS = 96/4/1), A binder composition was obtained in the same manner as in Example 1 except that the inherent viscosity was 2.5 dL / g) and the polymer additive was 10% by mass relative to the total mass of the binder composition.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７８質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 78% by mass, the electrode mixture and the electrode Was made.
　（実施例４）
　フッ化ビニリデン共重合体としてＶＤＦ、ＣＴＦＥおよびマレイン酸モノメチル（ＭＭＭ）（重量比９８：２：０．７）を重合し、ＶＤＦ－ＣＴＦＥ－ＭＭＭ共重合体（インヘレント粘度２．３ｄＬ／ｇ）を使用した以外は、実施例１と同様にして、バインダー組成物を得た。 (Example 4)
As a vinylidene fluoride copolymer, VDF, CTFE and monomethyl maleate (MMM) (weight ratio 98: 2: 0.7) were polymerized to obtain a VDF-CTFE-MMM copolymer (inherent viscosity 2.3 dL / g). A binder composition was obtained in the same manner as in Example 1 except that it was used.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７５質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 75% by mass. Was made.
　（実施例５）
　バインダー組成物の総質量に対しポリマー添加剤が２．５質量％となるようにした以外は、実施例２と同様にして、バインダー組成物を得た。 (Example 5)
A binder composition was obtained in the same manner as in Example 2 except that the polymer additive was 2.5% by mass with respect to the total mass of the binder composition.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７３質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 73% by mass, the electrode mixture and the electrode Was made.
　（実施例６）
　ポリマー添加剤として、ポリビニルピロリドン（ＰＶＰ　Ｋ９０）（数平均分子量３６０，０００、東京化成工業(株)製、Ｐ０４７３）を使用した以外は、実施例１と同様にして、バインダー組成物を得た。 (Example 6)
A binder composition was obtained in the same manner as in Example 1 except that polyvinyl pyrrolidone (PVP K90) (number average molecular weight 360,000, manufactured by Tokyo Chemical Industry Co., Ltd., P0473) was used as the polymer additive.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７５質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 75% by mass. Was made.
　（実施例７）
　ポリマー添加剤として、ポリビニルアルコール（ＰＶＡ）（日本合成化学(株)製、ゴーセノールＧＨ－１７）を使用した以外は、実施例１と同様にして、バインダー組成物を得た。 (Example 7)
A binder composition was obtained in the same manner as in Example 1 except that polyvinyl alcohol (PVA) (manufactured by Nippon Synthetic Chemical Co., Ltd., Gohsenol GH-17) was used as a polymer additive.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７５質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 75% by mass. Was made.
　（実施例８）
　ポリマー添加剤として、ポリアクリルニトリル（ＰＡＮ）（重量平均分子量１５０，０００、シグマ・アルドリッチ社製、１８１３１５）を使用した以外は、実施例１と同様にして、バインダー組成物を得た。 (Example 8)
A binder composition was obtained in the same manner as in Example 1 except that polyacrylonitrile (PAN) (weight average molecular weight 150,000, manufactured by Sigma-Aldrich, 181315) was used as the polymer additive.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７３質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 73% by mass, the electrode mixture and the electrode Was made.
　（実施例９）
　実施例１と同様にして、バインダー組成物を得た。 Example 9
In the same manner as in Example 1, a binder composition was obtained.
　電極活物質としてニッケルコバルトアルミニウム酸リチウム（ＮＣＡ、平均粒径Ｄ５０１４．７μｍ）１００質量部、導電助剤としてカーボンブラック（ＳＰ；Ｔｉｍｃａｌ　Ｊａｐａｎ社製　ＳｕｐｅｒＰ（登録商標） Ｌｉ、平均粒子径４０ｎｍ、比表面積６０ｍ２／ｇ）２質量部、および上記バインダー組成物２質量部を、Ｎ－メチル－２－ピロリドン中に均一に分散させて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７９質量％の電極合剤を作製した。 100 parts by mass of nickel cobalt lithium aluminum oxide (NCA, average particle diameter D 50 14.7 μm) as an electrode active material, and carbon black (SP; SuperP (registered trademark) Li manufactured by Timcal Japan), an average particle diameter of 40 nm, 2 parts by mass of a specific surface area of 60 m 2 / g) and 2 parts by mass of the above binder composition were uniformly dispersed in N-methyl-2-pyrrolidone to obtain a total solid of the binder composition, the electrode active material and the conductive assistant. An electrode mixture having a partial concentration of 79% by mass was produced.
　得られた電極合剤を用いて、実施例１と同様にして、電極を作製した。 Using the obtained electrode mixture, an electrode was prepared in the same manner as in Example 1.
　（実施例１０）
　フッ化ビニリデン共重合体として、ＶＤＦ、ＣＴＦＥおよびＡＰＳ（重量比９６：４：１）を重合し、ＶＤＦ－ＣＴＦＥ－ＡＰＳ共重合体（インヘレント粘度２．３ｄＬ／ｇ）を使用した以外は、実施例１と同様にして、バインダー組成物を得た。 (Example 10)
Except for polymerizing VDF, CTFE and APS (weight ratio 96: 4: 1) as a vinylidene fluoride copolymer and using VDF-CTFE-APS copolymer (inherent viscosity 2.3 dL / g) In the same manner as in Example 1, a binder composition was obtained.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７４質量％である以外は、実施例９と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 9 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 74% by mass, the electrode mixture and the electrode Was made.
　（比較例１）
　実施例１で用いたフッ化ビニリデン共重合体のみからなるバインダー組成物を得た。 (Comparative Example 1)
A binder composition consisting only of the vinylidene fluoride copolymer used in Example 1 was obtained.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が６８質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 68% by mass. Was made.
　（比較例２）
　実施例２で用いたフッ化ビニリデン共重合体のみからなるバインダー組成物を得た。 (Comparative Example 2)
A binder composition consisting only of the vinylidene fluoride copolymer used in Example 2 was obtained.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７０質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material, and the conductive additive was 70% by mass. Was made.
　（比較例３）
　実施例３で用いたフッ化ビニリデン共重合体のみからなるバインダー組成物を得た。 (Comparative Example 3)
A binder composition consisting only of the vinylidene fluoride copolymer used in Example 3 was obtained.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７２質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 72% by mass, the electrode mixture and the electrode Was made.
　（比較例４）
　実施例４で用いたフッ化ビニリデン共重合体のみからなるバインダー組成物を得た。 (Comparative Example 4)
A binder composition consisting only of the vinylidene fluoride copolymer used in Example 4 was obtained.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７３質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 73% by mass, the electrode mixture and the electrode Was made.
　（比較例５）
　ポリマー添加剤であるポリビニルピロリドン（ＰＶＰ　Ｋ１５）の代わりに、ポリエチレングリコール（ＰＥＧ）を用いた以外は、実施例１と同様にして、バインダー組成物を得た。 (Comparative Example 5)
A binder composition was obtained in the same manner as in Example 1 except that polyethylene glycol (PEG) was used instead of polyvinyl pyrrolidone (PVP K15) which is a polymer additive.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が６９質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 69% by mass, the electrode mixture and the electrode Was made.
　（比較例６）
　ポリマー添加剤であるポリビニルピロリドン（ＰＶＰ　Ｋ１５）の代わりに、ポリアクリル酸（ＰＡＡ）を用いた以外は、実施例１と同様にして、バインダー組成物を得た。 (Comparative Example 6)
A binder composition was obtained in the same manner as in Example 1 except that polyacrylic acid (PAA) was used instead of polyvinyl pyrrolidone (PVP K15) which is a polymer additive.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が６８質量％である以外は、実施例１と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, an electrode mixture and an electrode were obtained in the same manner as in Example 1 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 68% by mass. Was made.
　（比較例７）
　実施例１で用いたフッ化ビニリデン共重合体のみからなるバインダー組成物を得た。 (Comparative Example 7)
A binder composition consisting only of the vinylidene fluoride copolymer used in Example 1 was obtained.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７６質量％である以外は、実施例９と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, in the same manner as in Example 9 except that the total solid concentration of the binder composition, the electrode active material and the conductive additive is 76% by mass, the electrode mixture and the electrode Was made.
　（比較例８）
　実施例１０で用いたフッ化ビニリデン共重合体のみからなるバインダー組成物を得た。 (Comparative Example 8)
A binder composition consisting only of the vinylidene fluoride copolymer used in Example 10 was obtained.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７２質量％である以外は、実施例９と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, an electrode mixture and an electrode were obtained in the same manner as in Example 9, except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 72% by mass. Was made.
　（比較例９）
　フッ化ビニリデン単独重合体（インヘレント粘度２．１ｄＬ／ｇ、株式会社クレハ製）のみからなるバインダー組成物を調製した。 (Comparative Example 9)
A binder composition consisting only of a vinylidene fluoride homopolymer (inherent viscosity 2.1 dL / g, manufactured by Kureha Corporation) was prepared.
　上記で得られたバインダー組成物を用いて、バインダー組成物、電極活物質および導電助剤の合計固形分濃度が７８質量％である以外は、実施例９と同様にして、電極合剤および電極を作製した。 Using the binder composition obtained above, an electrode mixture and an electrode were obtained in the same manner as in Example 9, except that the total solid concentration of the binder composition, the electrode active material and the conductive additive was 78% by mass. Was made.
　［電極合剤スラリーのチキソトロピー係数λの測定試験］
　電極スラリーを、Ｅ型粘度計（東機産業（株）、ＲＥ－８０）を用いて、２５℃、せん断速度２ｓ－１で３００秒間測定を行った。チキソトロピー係数λは、測定開始後の最大の粘度τ０および継時的な粘度変化が無くなった時点での粘度τ∞を用いて、下記式から求めることができる。 [Measurement test of thixotropy coefficient λ of electrode mixture slurry]
The electrode slurry was measured for 300 seconds at 25 ° C. and a shear rate of 2 s −1 using an E-type viscometer (Toki Sangyo Co., Ltd., RE-80). The thixotropy coefficient λ can be obtained from the following equation using the maximum viscosity τ0 after the start of measurement and the viscosity τ∞ at the time when the change in viscosity over time has disappeared.
　　　　　　λ＝（τ０－τ∞）／τ∞
　［ゲル化評価試験］
　作成した電極スラリーを、窒素雰囲気下、４０℃のオーブンで１日間保管した。１日保管後の電極スラリーを、自転公転ミキサー（シンキー（株）製、ＡＲ－３１０）を用いて２０００ｒｐｍで３０秒間混練した後、目視で流動性を確認し、流動性が見られなかった場合をゲル化有りとした。 λ = (τ0-τ∞) / τ∞
[Gelification evaluation test]
The prepared electrode slurry was stored in an oven at 40 ° C. for 1 day under a nitrogen atmosphere. When the electrode slurry after storage for 1 day is kneaded at 2000 rpm for 30 seconds using a rotating and revolving mixer (manufactured by Shinky Co., Ltd., AR-310), the fluidity is confirmed visually and no fluidity is observed. Was gelled.
　結果を表１に示す。 The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１に示すように、実施例１～１０は、測定初期のせん断応力（τ０）と平衡状態のせん断応力（τ∞）との差が小さく、チキソトロピー係数λが０～０．２であり、せん断に伴う粘度変化がほとんど生じず、チキソトロピー性が良好に抑制されていた。また、電極合剤スラリーは、一定時間経過後もゲル化が生じず、アルミニウム箔上に塗布し乾燥させることにより、平滑な電極合剤層を形成した。 As shown in Table 1, in Examples 1 to 10, the difference between the initial shear stress (τ0) and the equilibrium shear stress (τ∞) is small, and the thixotropic coefficient λ is 0 to 0.2. The viscosity change accompanying shearing hardly occurred, and the thixotropic property was well suppressed. In addition, the electrode mixture slurry did not gel after a certain period of time, and was applied onto an aluminum foil and dried to form a smooth electrode mixture layer.
　これに対し、比較例１～８は、本発明のポリマー材料からなるポリマー添加剤を含まないため、せん断に伴う粘度変化が生じ、チキソトロピー係数が高値を示した。 On the other hand, Comparative Examples 1 to 8 did not contain the polymer additive made of the polymer material of the present invention, so that the viscosity change caused by shearing occurred and the thixotropy coefficient showed a high value.
　また、比較例９は、バインダー組成物として、フッ化ビニリデン単独重合体を用いたため、電極合剤スラリーが、時間経過に伴い増粘し、流動性を失ってゲル化した。 Moreover, since the vinylidene fluoride homopolymer was used as the binder composition in Comparative Example 9, the electrode mixture slurry thickened with the passage of time and lost its fluidity to gel.
　本発明は、非水系電解質二次電池において集電体と電極活物質との結着に用いられるバインダー組成物として利用することができる。 The present invention can be used as a binder composition used for binding a current collector and an electrode active material in a non-aqueous electrolyte secondary battery.
　１　　　正極
　２　　　負極
　３　　　セパレータ
　５　　　金属ケーシング
　１０　　電極
　１１　　集電体
　１２ａ　電極合剤層
　１２ｂ　電極合剤層
　１００　電池 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 5 Metal casing 10 Electrode 11 Current collector 12a Electrode mixture layer 12b Electrode mixture layer 100 Battery

Claims (7)

  1. 　電極活物質を集電体に結着させるために用いられるバインダー組成物であって、
    　上記バインダー組成物は、フッ化ビニリデン重合体とポリマー添加剤とを含み、
    　上記フッ化ビニリデン重合体は、フッ化ビニリデンに由来する構造単位とクロロトリフルオロエチレンに由来する構造単位とを含むフッ化ビニリデン共重合体を含み、
    　上記ポリマー添加剤は、以下の繰り返し単位：
    －［ＣＨ２－ＣＨＲ］－
    を有するポリマー材料であることを特徴とするバインダー組成物。
    （上記繰り返し単位において、Ｒは、鎖状若しくは環状アミド基、ニトリル基、ヒドロキシ基、エステル含有基、または、炭素数１～４のアルキル基であって、当該アルキル基の水素原子の少なくとも１つが鎖状若しくは環状アミド基、ニトリル基またはヒドロキシ基で置換されている置換基を示す。）     A binder composition used for binding an electrode active material to a current collector,
    The binder composition includes a vinylidene fluoride polymer and a polymer additive,
    The vinylidene fluoride polymer includes a vinylidene fluoride copolymer including a structural unit derived from vinylidene fluoride and a structural unit derived from chlorotrifluoroethylene,
    The polymer additive includes the following repeating units:
    -[CH 2 -CHR]-
    A binder composition characterized by being a polymer material.
    (In the above repeating unit, R is a chain or cyclic amide group, a nitrile group, a hydroxy group, an ester-containing group, or an alkyl group having 1 to 4 carbon atoms, and at least one hydrogen atom of the alkyl group is Indicates a substituent substituted with a chain or cyclic amide group, a nitrile group or a hydroxy group.)
  2. 　上記繰り返し単位において、Ｒは、鎖状若しくは環状アミド基、ニトリル基またはヒドロキシ基であることを特徴とする請求項１に記載のバインダー組成物。 The binder composition according to claim 1, wherein R is a chain or cyclic amide group, a nitrile group or a hydroxy group in the repeating unit.
  3. 　上記ポリマー添加剤は、ポリビニルピロリドン、ポリアクリロニトリルまたはポリビニルアルコールであることを特徴とする請求項１または２に記載のバインダー組成物。 The binder composition according to claim 1 or 2, wherein the polymer additive is polyvinylpyrrolidone, polyacrylonitrile, or polyvinyl alcohol.
  4. 　上記ポリマー添加剤は、上記フッ化ビニリデン重合体と上記ポリマー添加剤との合計を１００質量％としたときに、１質量％以上かつ５０質量％以下含まれていることを特徴とする請求項１から３のいずれか１項に記載のバインダー組成物。 2. The polymer additive is contained in an amount of 1% by mass to 50% by mass when the total of the vinylidene fluoride polymer and the polymer additive is 100% by mass. 4. The binder composition according to any one of items 1 to 3.
  5. 　上記フッ化ビニリデン共重合体は、カルボキシル基を有する単量体成分に由来する構造単位をさらに含むことを特徴とする請求項１から４のいずれか１項に記載のバインダー組成物。 The binder composition according to any one of claims 1 to 4, wherein the vinylidene fluoride copolymer further includes a structural unit derived from a monomer component having a carboxyl group.
  6. 　請求項１から５のいずれか１項に記載のバインダー組成物と、溶媒と、電極活物質とを含むことを特徴とする電極合剤。 An electrode mixture comprising the binder composition according to any one of claims 1 to 5, a solvent, and an electrode active material.
  7. 　請求項６に記載の電極合剤から形成された電極合剤層を備えていることを特徴とする非水電解質二次電池。 A nonaqueous electrolyte secondary battery comprising an electrode mixture layer formed from the electrode mixture according to claim 6.
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