WO2022131239A1 - Liant pour électrode de batterie rechargeable et son procédé de production, composition de couche de mélange d'électrode de batterie rechargeable, électrode de batterie rechargeable et batterie rechargeable - Google Patents

Liant pour électrode de batterie rechargeable et son procédé de production, composition de couche de mélange d'électrode de batterie rechargeable, électrode de batterie rechargeable et batterie rechargeable Download PDF

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WO2022131239A1
WO2022131239A1 PCT/JP2021/045978 JP2021045978W WO2022131239A1 WO 2022131239 A1 WO2022131239 A1 WO 2022131239A1 JP 2021045978 W JP2021045978 W JP 2021045978W WO 2022131239 A1 WO2022131239 A1 WO 2022131239A1
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polymer
secondary battery
mass
less
crosslinked polymer
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PCT/JP2021/045978
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English (en)
Japanese (ja)
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健一 吉森
朋子 仲野
晃嗣 柴田
直彦 斎藤
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東亞合成株式会社
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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/04—Acids; Metal salts or ammonium salts thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/22—Electrodes
    • H01G11/30—Electrodes characterised by their material
    • H01G11/32—Carbon-based
    • H01G11/38—Carbon pastes or blends; Binders or additives therein
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES OR LIGHT-SENSITIVE DEVICES, OF THE ELECTROLYTIC TYPE
    • H01G11/00—Hybrid capacitors, i.e. capacitors having different positive and negative electrodes; Electric double-layer [EDL] capacitors; Processes for the manufacture thereof or of parts thereof
    • H01G11/84—Processes for the manufacture of hybrid or EDL capacitors, or components thereof
    • H01G11/86—Processes for the manufacture of hybrid or EDL capacitors, or components thereof specially adapted for electrodes
    • 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
    • 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
    • H01M4/04—Processes of manufacture in general
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

Definitions

  • the present invention relates to a binder for a secondary battery electrode, a composition for a secondary battery electrode mixture layer, a secondary battery electrode, and a secondary battery.
  • a secondary battery various power storage devices such as a nickel hydrogen secondary battery, a lithium ion secondary battery, and an electric double layer capacitor have been put into practical use.
  • the electrodes used in these secondary batteries are produced by applying, drying, or the like on a current collector a composition for forming an electrode mixture layer containing an active material, a binder, and the like.
  • a composition for forming an electrode mixture layer containing an active material, a binder, and the like for example, in a lithium ion secondary battery, an aqueous binder containing styrene butadiene rubber (SBR) latex and carboxymethyl cellulose (CMC) is used as the binder used in the composition for the negative electrode mixture layer.
  • SBR styrene butadiene rubber
  • CMC carboxymethyl cellulose
  • a binder used for the positive electrode mixture layer a solution of polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP) is widely used
  • a binder is used to firmly bind the active substances together (bonding property), the size of the active material is reduced to alleviate the stress associated with swelling and shrinkage, or the electrolyte solution is used. Studies are being conducted to improve durability by devising additives.
  • Patent Document 1 discloses a binder containing a crosslinked acrylic acid-based polymer obtained by cross-linking polyacrylic acid with a specific cross-linking agent, and even when an active material containing silicon is used, an electrode is used. It is disclosed to exhibit good cycle characteristics without disrupting the structure. Although the binder disclosed in Patent Document 1 can impart good binding property, a binder having higher binding property is required as the performance of the secondary battery is improved.
  • Patent Document 2 describes structural units derived from an ethylenically unsaturated carboxylic acid compound in an amount of 20.0% by mass or more and 79.5% by mass or less, and 100 g of water at 20 ° C.
  • Cross-linked acrylic having a water swelling degree in a specific range, containing 20.0% by mass or more and 79.5% by mass or less of structural units derived from a copolymerizable compound having an ethylenically unsaturated bond having a solubility in water of 7 g or more.
  • a binder containing an acid polymer is disclosed.
  • the binder for a secondary battery electrode disclosed in Patent Document 2 exhibits even higher binding properties.
  • the active material tends to settle when the composition for the electrode mixture layer containing the binder, the active material and water (hereinafter, also referred to as “electrode slurry”) is stored for a long period of time.
  • the settling stability of the electrode slurry may be a problem.
  • the present invention has been made in view of such circumstances, and an object thereof is to ensure the sedimentation stability of the electrode slurry and to exhibit excellent binding properties to improve the cycle characteristics of the secondary battery. It is to provide a binder for a secondary battery electrode which can be improved. Further, the present invention also provides a composition for a secondary battery electrode mixture layer containing the above binder, a secondary battery electrode obtained by using the composition, and a secondary battery.
  • the binder for the secondary battery electrode which contains the metal salt of the crosslinked polymer in which the abundance ratio of the carboxyl group metal salt of the crosslinked polymer based on X-ray photoelectron spectroscopic analysis (XPS) is 85 mol% or less, is The present invention has been completed by finding that it is possible to improve the cycle characteristics of a secondary battery by exhibiting excellent binding properties while ensuring the sedimentation stability of the electrode slurry.
  • the abundance ratio is a value based on XPS, it means the abundance ratio of the carboxyl group metal salt present in the surface layer from the surface of the crosslinked polymer to a depth of about 20 nm.
  • the unit includes 80% by mass or more and 99.9% by mass or less.
  • the carboxyl-based metal of the crosslinked polymer based on XPS which is calculated by the following formula (1) by X-ray photoelectron spectroscopic analysis (XPS) of the metal salt (neutralization degree N mol%) [hereinafter, polymer salt S].
  • the salt abundance ratio (X) is 85 mol% or less.
  • the type of the metal salt is the same for the crosslinked polymer salt R and the polymer salt S.
  • the exchange chain transfer mechanism is a reversible addition-cleavage chain transfer mechanism.
  • the crosslinked polymer contains 0.5% by mass or more and 20% by mass or less of structural units derived from the hydroxyl group-containing ethylenically unsaturated monomer with respect to all the structural units [1] to [4].
  • the binder for a secondary battery electrode according to any one of the above.
  • the crosslinked polymer is crosslinked with a crosslinkable monomer, and the amount of the crosslinkable monomer used is 0.001 mol% or more with respect to the total amount of the non-crosslinkable monomer 2 5.
  • the metal salt of the crosslinked polymer is neutralized to a neutralization degree of 80 to 100 mol%, and then the particle size measured in an aqueous medium is 0.1 ⁇ m or more and 10.0 ⁇ m or less in terms of volume-based median diameter.
  • the binder for a secondary battery electrode according to any one of [1] to [6].
  • a step of polymerizing a monomer component containing an ethylenically unsaturated carboxylic acid monomer by precipitation polymerization or dispersion polymerization and During the step, an exchange chain transfer mechanism type control agent is added in an amount of 0.0001 mol% or more and 0.50 mol% or less with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer.
  • the exchange chain transfer mechanism type control agent is a polymer (A) having a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by the exchange chain transfer mechanism.
  • a composition for a secondary battery electrode mixture layer which comprises the binder for a secondary battery electrode according to any one of [1] to [7], an active material, and water.
  • a secondary battery electrode comprising a mixture layer formed from the composition for the secondary battery electrode mixture layer according to [12] on the surface of a current collector.
  • a secondary battery comprising the secondary battery electrode according to [13].
  • the binder for a secondary battery electrode of the present invention it is possible to improve the cycle characteristics of the secondary battery by exhibiting excellent binding property while ensuring the sedimentation stability of the electrode slurry.
  • the binder for a secondary battery electrode of the present invention (hereinafter, also referred to as “the binder”) is a metal salt of a carboxyl group-containing crosslinked polymer (hereinafter, also referred to as “the present crosslinked polymer”) (hereinafter, “the present crossbridge”). It also contains “polymer salt”), and can be mixed with an active material and water to obtain a composition for a secondary battery electrode binder layer (hereinafter, also referred to as "this composition”). .. It is preferable that the above composition is an electrode slurry in a slurry state that can be applied to the current collector from the viewpoint of achieving the effect of the present invention, but it is prepared in a wet powder state and applied to the surface of the current collector.
  • the secondary battery electrode of the present invention can be obtained by forming a mixture layer formed from the above composition on the surface of a current collector such as a copper foil or an aluminum foil.
  • a current collector such as a copper foil or an aluminum foil.
  • the present binder is used in a composition for a secondary battery electrode mixture layer containing a silicon-based active material described later as an active material, the effect of the present invention is particularly large, which is preferable.
  • (meth) acrylic means acrylic and / or methacrylic
  • (meth) acrylate means acrylate and / or methacrylate
  • (meth) acryloyl group means an acryloyl group and / or a methacryloyl group.
  • This crosslinked polymer has a structural unit derived from an ethylenically unsaturated carboxylic acid monomer (hereinafter, also referred to as “component (a)”), and is a single amount containing an ethylenically unsaturated carboxylic acid monomer.
  • component (a) ethylenically unsaturated carboxylic acid monomer
  • the body component can be introduced into the polymer by precipitation polymerization or dispersion polymerization.
  • the crosslinked polymer has a carboxyl group due to having such a structural unit, the adhesiveness to the current collector is improved, and the lithium ion desolvation effect and the ionic conductivity are excellent, so that the resistance is small. , An electrode having excellent high rate characteristics can be obtained. Further, since water swelling property is imparted, the dispersion stability of the active substance or the like in the present composition can be enhanced.
  • Examples of the ethylenically unsaturated carboxylic acid monomer include (meth) acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid; and (meth) acrylamide hexane acid and (meth) acrylamide dodecanoic acid.
  • (Partial) Examples thereof include alkali neutralized products, and one of these may be used alone, or two or more thereof may be used in combination.
  • a compound having an acryloyl group as a polymerizable functional group is preferable, and acrylic acid is particularly preferable in that a polymer having a long primary chain length can be obtained due to a high polymerization rate and the binder has a good binding force. be.
  • acrylic acid is used as the ethylenically unsaturated carboxylic acid monomer, a polymer having a high carboxyl group content can be obtained.
  • the content of the component (a) in the crosslinked polymer is 80% by mass or more and 99.9% by mass or less with respect to all the structural units of the crosslinked polymer.
  • the component (a) in such a range excellent adhesiveness to the current collector can be easily ensured.
  • the lower limit is 80% by mass or more, the sedimentation stability of the present composition becomes good and a higher binding force can be obtained, which is preferable.
  • it may be 82.5% by mass or more, and for example, 85% by mass or more. It may be present, and may be, for example, 87.5% by mass or more.
  • the upper limit is, for example, 97.5% by mass or less, for example 95% by mass or less, for example 92.5% by mass or less, and for example 90% by mass or less.
  • the range of the content of the component (a) may be a range in which such a lower limit and an upper limit are appropriately combined.
  • the crosslinked polymer may contain, in addition to the component (a), structural units derived from other ethylenically unsaturated monomers copolymerizable with the component (hereinafter, also referred to as “component (b)”).
  • component (b) examples include a hydroxyl group-containing ethylenically unsaturated monomer (a monomer represented by the following formula (1), a monomer represented by the formula (2)), a sulfonic acid group and a sulfonic acid group.
  • Examples thereof include a structural unit derived from an ethylenically unsaturated monomer compound having an anionic group other than a carboxyl group such as a phosphoric acid group, or a nonionic ethylenically unsaturated monomer.
  • These structural units are an ethylenically unsaturated monomer compound having an anionic group other than a carboxyl group such as a sulfonic acid group and a phosphoric acid group, or a monomer containing a nonionic ethylenically unsaturated monomer. Can be introduced by copolymerizing.
  • R 1 represents a hydrogen atom or a methyl group
  • R 2 is a monovalent organic group having a hydroxyl group and having 1 to 8 carbon atoms
  • (R 3 O) m H or R 4 O [CO (CH 2 ). ) 5 O] represents n H.
  • R 3 represents an alkylene group having 2 to 4 carbon atoms
  • R 4 represents an alkylene group having 1 to 8 carbon atoms
  • m represents an integer of 2 to 15
  • n represents an integer of 1 to 15. show.
  • the ratio of the component (b) can be 0.1% by mass or more and 20% by mass or less with respect to all the structural units of the present crosslinked polymer.
  • the ratio of the component (b) may be 0.5% by mass or more and 17.5% by mass or less, 1.0% by mass or more and 15% by mass or less, or 2% by mass or more and 12.5% by mass. % Or less, and may be 3% by mass or more and 10% by mass or less.
  • a hydroxyl group-containing ethylenically unsaturated monomer is preferable because it is excellent in binding property of the binder containing the present crosslinked polymer salt.
  • a structural unit derived from a nonionic ethylenically unsaturated monomer is preferable from the viewpoint of obtaining an electrode having good bending resistance, and the nonionic ethylenically unsaturated monomer is (meth). Examples thereof include acrylamide and its derivatives, nitrile group-containing ethylenically unsaturated monomers, and alicyclic structure-containing ethylenically unsaturated monomers.
  • the monomer represented by the above formula (1) is a (meth) acrylate compound having a hydroxyl group.
  • R 2 is a monovalent organic group having 1 to 8 carbon atoms having a hydroxyl group, the number of the hydroxyl groups may be only one or two or more.
  • the monovalent organic group is not particularly limited, and examples thereof include an alkyl group which may have a linear, branched or cyclic structure, an aryl group, an alkoxyalkyl group and the like. Be done.
  • R 2 is (R 3 O) m H or R 4 O [CO (CH 2 ) 5 O] n H
  • the alkylene group represented by R 3 or R 4 may be linear. It may be branched.
  • Examples of the monomer represented by the above formula (1) include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and hydroxyhexyl (meth) acrylate.
  • hydroxyalkyl (meth) acrylates having hydroxyalkyl groups with 1 to 8 carbon atoms such as hydroxyoctyl (meth) acrylates; polyethylene glycol mono (meth) acrylates, polypropylene glycol mono (meth) acrylates, polybutylene glycol mono (meth).
  • Acrylate and Polyalkylene Glycol Mono (meth) Acrylate such as Polypropylene Glycol Mono (Meta) Acrylate; Dihydroxyalkyl (Meta) Acrylate such as Glycerin Mono (Meta) Acrylate; Examples thereof include “Plaxel FM1", “Plaxel FM5", etc.), caprolactone-modified hydroxyacrylate (manufactured by Daicel Co., Ltd., trade names "Plaxel FA1", “Plaxel FA10L”, etc.) and the like. As the monomer represented by the above formula (1), one of these may be used alone, or two or more thereof may be used in combination.
  • the monomer represented by the above formula (2) is a (meth) acrylamide derivative having a hydroxyl group or a hydroxyalkyl group having 1 to 8 carbon atoms.
  • R 7 represents a hydrogen atom or a monovalent organic group.
  • the monovalent organic group is not particularly limited, and examples thereof include an alkyl group which may have a linear, branched or cyclic structure, an aryl group, an alkoxyalkyl group and the like. Therefore, it is preferably an organic group having 1 to 8 carbon atoms.
  • R 7 may be a hydroxyl group or a hydroxyalkyl group having 1 to 8 carbon atoms.
  • Examples of the monomer represented by the above formula (2) include hydroxy (meth) acrylamide; N-hydroxyethyl (meth) acrylamide, N-hydroxypropyl (meth) acrylamide, N-hydroxybutyl (meth) acrylamide, and the like. N-hydroxyhexyl (meth) acrylamide, N-hydroxyoctyl (meth) acrylamide, N-methylhydroxyethyl (meth) acrylamide, N-ethylhydroxyethyl (meth) acrylamide, and other hydroxyalkyl groups with 1 to 8 carbon atoms.
  • (Meta) acrylamide derivative N, N-di-hydroxyalkyl (meth) acrylamide such as N, N-dihydroxyethyl (meth) acrylamide and N, N-dihydroxyethyl (meth) acrylamide and the like can be mentioned.
  • N, N-di-hydroxyalkyl (meth) acrylamide such as N, N-dihydroxyethyl (meth) acrylamide and N, N-dihydroxyethyl (meth) acrylamide and the like can be mentioned.
  • the monomer represented by the above formula (2) one of these may be used alone, or two or more of them may be used in combination.
  • Examples of the (meth) acrylamide derivative include N-alkyl (meth) acrylamide compounds such as N-isopropyl (meth) acrylamide and Nt-butyl (meth) acrylamide; Nn-butoxymethyl (meth) acrylamide, N. -N-alkoxyalkyl (meth) acrylamide compounds such as isobutoxymethyl (meth) acrylamide; N, N-dialkyl (meth) acrylamides such as N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide. Examples thereof include compounds, and one of these may be used alone, or two or more thereof may be used in combination.
  • nitrile group-containing ethylenically unsaturated monomer examples include (meth) achlorinitrile; (meth) acrylate cyanoalkyl ester compounds such as (meth) cyanomethyl acrylate and (meth) cyanoethyl acrylate; 4-cyanostyrene. , 4-Cyano- ⁇ -methylstyrene and other cyano group-containing unsaturated aromatic compounds; examples thereof include vinylidene cyanide, and one of these may be used alone or in combination of two or more. You may use it.
  • acrylonitrile is preferable because it has a high nitrile group content.
  • Examples of the alicyclic structure-containing ethylenically unsaturated monomer include cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclodecyl (meth) acrylate and the like.
  • aliphatic substituent such as cyclododecyl (meth) acrylate (meth) acrylic acid cycloalkyl ester; isobornyl (meth) acrylate, adamantyl (meth) acrylate, cyclopentenyl (meth) acrylate, dicyclopentenyl.
  • examples thereof include oxyethyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and cycloalkylpolyalcohol mono (meth) acrylate such as cyclohexanedimethanol mono (meth) acrylate and
  • the crosslinked polymer salt has an excellent binding property of the binder, and is a monomer represented by the above formula (1), a monomer represented by the above formula (2), (meth) acrylamide and the like. It is preferable to contain a derivative and a structural unit derived from a nitrile group-containing ethylenically unsaturated monomer, an alicyclic structure-containing ethylenically unsaturated monomer, or the like.
  • hydroxyalkyl (meth) acrylate having a hydroxyalkyl group having 1 to 8 carbon atoms is more preferable, and 2-hydroxyethyl (meth) acrylate is more preferable because it is excellent in the effect of improving the binding property of the binder.
  • 3-Hydroxypropyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate are more preferred.
  • the component (b) when a structural unit derived from a hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less is introduced, a strong interaction with the electrode material can be exhibited. It can exhibit good binding properties to active materials. As a result, a solid and well-integrated electrode mixture layer can be obtained. Therefore, the above-mentioned "hydrophobic ethylenically unsaturated monomer having a solubility in water of 1 g / 100 ml or less" is particularly selected. An alicyclic structure-containing ethylenically unsaturated monomer is preferable.
  • (meth) acrylic acid ester examples include (meth) acrylics such as methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate.
  • Acrylic acid ester compound Aromatic (meth) acrylic acid ester compounds such as phenyl (meth) acrylate, phenylmethyl (meth) acrylate, phenylethyl (meth) acrylate, and phenoxyethyl (meth) acrylate; Examples thereof include (meth) acrylic acid alkoxyalkyl ester compounds such as 2-methoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate, and one of these may be used alone or 2 You may use a combination of seeds or more.
  • an aromatic (meth) acrylic acid ester compound can be preferably used.
  • compounds having an ether bond such as (meth) acrylic acid alkoxyalkyl esters such as 2-methoxyethyl (meth) acrylate and 2-ethoxyethyl (meth) acrylate are preferable.
  • 2-Methoxyethyl (meth) acrylate is more preferred.
  • nonionic ethylenically unsaturated monomers a compound having an acryloyl group is preferable in that a polymer having a long primary chain length can be obtained due to its high polymerization rate and the binder has a good binding force.
  • a compound having a glass transition temperature (Tg) of a homopolymer of 0 ° C. or lower is preferable in terms of improving the bending resistance of the obtained electrode.
  • the metal salt of the crosslinked polymer is in the form of a salt in which a part or all of the carboxyl groups contained in the polymer is neutralized.
  • the type of metal salt is not particularly limited, but alkali metal salts such as lithium salt, sodium salt and potassium salt; alkaline earth metal salts such as magnesium salt, calcium salt and barium salt; other metal salts such as aluminum salt; Examples thereof include ammonium salts and organic amine salts.
  • alkali metal salts and alkaline earth metal salts are preferable, and alkali metal salts are more preferable, from the viewpoint that adverse effects on battery characteristics are unlikely to occur.
  • the present crosslinked polymer is a polymer having a crosslinked structure.
  • the cross-linking method in the present cross-linked polymer is not particularly limited, and examples thereof include the following methods. 1) Crosslinking of crosslinkable monomers 2) Utilizing the chain transfer to the polymer chain during radical polymerization 3) After synthesizing a polymer having a reactive functional group, if necessary, a crosslinking agent is added for post-crosslinking. Since the crosslinked polymer has a crosslinked structure, the binder containing the crosslinked polymer salt can have an excellent binding force.
  • the method by copolymerizing the crosslinkable monomer is preferable because the operation is simple and the degree of crosslinking can be easily controlled.
  • crosslinkable monomer examples include a polyfunctional polymerizable monomer having two or more polymerizable unsaturated groups, a monomer having a self-crosslinkable crosslinkable functional group such as a hydrolyzable silyl group, and the like. Can be mentioned.
  • the polyfunctional polymerizable monomer is a compound having two or more polymerizable functional groups such as a (meth) acryloyl group and an alkenyl group in the molecule, and is a polyfunctional (meth) acryloyl compound, a polyfunctional alkenyl compound, ( Meta) Examples thereof include compounds having both an acryloyl group and an alkenyl group. These compounds may be used alone or in combination of two or more. Among these, a polyfunctional alkenyl compound is preferable because a uniform crosslinked structure can be easily obtained, and a polyfunctional allyl ether compound having two or more allyl ether groups in the molecule is particularly preferable.
  • Examples of the polyfunctional (meth) acryloyl compound include ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, and polypropylene glycol.
  • Di (meth) acrylates of dihydric alcohols such as di (meth) acrylates; trimethylol propantri (meth) acrylates, tri (meth) acrylates of trimethylol propaneethylene oxide modified products, glycerin tri (meth) acrylates, pentaerythritols.
  • Tri (meth) acrylates of trivalent or higher polyhydric alcohols such as tri (meth) acrylates and pentaerythritol tetra (meth) acrylates, poly (meth) acrylates such as tetra (meth) acrylates; methylenebisacrylamide, hydroxyethylenebisacrylamide. And the like, bisamides and the like can be mentioned.
  • polyfunctional alkenyl compound examples include polyfunctional allyl ether compounds such as trimethylolpropanediallyl ether, trimethylolpropanetriallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, tetraallyloxyetane, and polyallyl saccharose; Polyfunctional allyl compounds such as phthalate; polyfunctional vinyl compounds such as divinylbenzene and the like can be mentioned.
  • polyfunctional allyl ether compounds such as trimethylolpropanediallyl ether, trimethylolpropanetriallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, tetraallyloxyetane, and polyallyl saccharose
  • Polyfunctional allyl compounds such as phthalate
  • polyfunctional vinyl compounds such as divinylbenzene and the like can be mentioned.
  • Examples of compounds having both (meth) acryloyl group and alkenyl group include (meth) allyl acrylate, (meth) isopropenyl acrylate, (meth) butenyl acrylate, (meth) pentenyl acrylate, (meth). 2- (2-Vinyloxyethoxy) ethyl acrylate and the like can be mentioned.
  • the above-mentioned monomer having a crosslinkable functional group include a hydrolyzable silyl group-containing vinyl monomer, N-methoxyalkyl (meth) acrylamide and the like. These compounds can be used alone or in combination of two or more.
  • the hydrolyzable silyl group-containing vinyl monomer is not particularly limited as long as it is a vinyl monomer having at least one hydrolyzable silyl group.
  • vinyl silanes such as vinyl trimethoxysilane, vinyl triethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilanen; silyls such as trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, methyldimethoxysilylpropyl acrylate and the like.
  • Group-containing acrylic acid esters silyl group-containing methacrylic acid esters such as trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, methyldimethoxysilylpropyl methacrylate, dimethylmethoxysilylpropyl methacrylate; trimethoxysilylpropyl vinyl ether and the like.
  • Cyril group-containing vinyl ethers examples thereof include silyl group-containing vinyl esters such as trimethoxysilyl undecanoate vinyl.
  • the amount of the crosslinkable monomer used is the total amount of the monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.01 parts by mass or more and 5.0 parts by mass or less, more preferably 0.05 parts by mass or more and 3.0 parts by mass or less, and further preferably 0.1 parts by mass or more with respect to 100 parts by mass. It is 2.0 parts by mass or less, more preferably 0.1 parts by mass or more and 1.7 parts by mass or less, and even more preferably 0.5 parts by mass or more and 1.5 parts by mass or less.
  • the range of the amount of the crosslinkable monomer used may be a range in which such a lower limit and an upper limit are appropriately combined.
  • the amount of the crosslinkable monomer used is 0.01 parts by mass or more, it is preferable in that the binding property and the sedimentation stability of the electrode slurry are better. If it is 5.0 parts by mass or less, the stability of precipitation polymerization or dispersion polymerization tends to be high.
  • the amount of the crosslinkable monomer used is 0.001 mol% or more and 2.5 mol% with respect to the total amount of the monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.01 mol% or more and 2.0 mol% or less, more preferably 0.05 mol% or more and 1.75 mol% or less, and further preferably 0.05 mol%. It is more preferably 1.5 mol% or more, and further preferably 0.1 mol% or more and 1.0 mol% or less.
  • the range of the amount of the crosslinkable monomer used may be a range in which such a lower limit and an upper limit are appropriately combined.
  • the crosslinked polymer polymerizes a monomer component containing an ethylenically unsaturated carboxylic acid monomer (hereinafter, also referred to as “the present monomer”) by precipitation polymerization or dispersion polymerization.
  • the polymer (A) described later is 0.0001 as an exchange chain transfer mechanism type control agent with respect to the total amount of the monomer components containing the ethylenically unsaturated carboxylic acid monomer. It is obtained by a method comprising a step of adding mol% or more and 0.50 mol% or less.
  • the above-mentioned “intermediate” means "0.3T to 0.8T" when the time from the start of the step of polymerizing the present monomer to the end of the step is T.
  • the crosslinked polymer salt is preferably 0.4T to 0.8T, preferably 0.5T to 0.8T, in that it can achieve both excellent binding properties and sedimentation stability. More preferably, it is more preferably 0.5T to 0.7T.
  • the above lower limit and upper limit can be set in combination as appropriate.
  • Precipitation polymerization is a method for producing a polymer by carrying out a polymerization reaction in a solvent that dissolves a monomer as a raw material but does not substantially dissolve the polymer to be produced.
  • dispersion liquid of the polymer particles in which the primary particles of several tens of nm to several hundred nm are secondarily aggregated to several ⁇ m to several tens of ⁇ m can be obtained.
  • Dispersion stabilizers can also be used to control the particle size of the polymer.
  • the secondary aggregation can also be suppressed by selecting a dispersion stabilizer, a polymerization solvent, or the like. In general, precipitation polymerization that suppresses secondary aggregation is also called dispersion polymerization.
  • the exchange chain transfer mechanism type control agent includes a control agent (hereinafter, also referred to as “RAFT agent”) in the reversible addition-cleaving chain transfer polymerization method (RAFT method).
  • RAFT agent a control agent in the iodine transfer polymerization method
  • the control agent in the polymerization method using an organic tellurium compound (TERP method) the control agent in the polymerization method using an organic antimony compound (SBRP method), and the polymerization method using an organic bismuth compound (BIRP method).
  • a polymer having a polymer chain of one or more kinds of vinyl-based monomers and a living radical polymerization active unit by an exchange chain transfer mechanism includes a control agent and the like. .) Is preferably used. Only one type of the polymer (A) may be used, or two or more types may be used in combination.
  • ethylenic property is formed on the polar surface of the particles. It is possible to surface-modify other than the unsaturated carboxylic acid monomer. Along with this, it is presumed that both excellent binding properties and sedimentation stability can be achieved at the same time.
  • the RAFT agent and the control agent in the iodine transfer polymerization method are preferable, and the RAFT agent is more preferable, in that the crosslinked structure of the present crosslinked polymer can be made more uniform.
  • RAFT agent a polymer (A) having a living radical polymerization active unit by a reversible addition-cleaving chain transfer method can be used.
  • RAFT agents those having a trithiocarbonate in the molecule are particularly preferable in that the crosslinked structure of the present crosslinked polymer can be made more uniform.
  • the polymer (A) having a living radical active unit by the iodine transfer polymerization method can be used as the control agent in the iodine transfer polymerization method.
  • the polymer (A) may be a monofunctional polymer having one active site, or a polymer (A) having two or more active sites and having two or more functional sites.
  • a bifunctional or higher exchange chain transfer mechanism type control agent is one in which the polymerized chain is extended in a bidirectional or higher direction. From the viewpoint of producing the crosslinked polymer, it may be preferable to use a bifunctional or trifunctional or higher exchange chain transfer mechanism type control agent.
  • the amount of the polymer (A) used is 0.0001 mol% or more and 0.50 mol% or less with respect to the total amount of the present monomer in that the crosslinked structure of the crosslinked polymer can be made more uniform. It is preferably 0.0001 mol% or more and 0.40 mol% or less, further preferably 0.0001 mol% or more and 0.30 mol% or less, and 0.0002 mol% or more and 0. It is even more preferable that it is .30 mol% or less.
  • polymerization initiator used together with the polymer (A) known polymerization initiators such as azo compounds, organic peroxides, and inorganic peroxides can be used, but are not particularly limited.
  • the conditions of use can be adjusted by known methods such as heat initiation, redox initiation with a reducing agent, and UV initiation so that the amount of radicals generated is appropriate.
  • azo compounds are preferable because they are easy to handle for safety and side reactions during radical polymerization are unlikely to occur.
  • azo compound examples include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), and 2,2'-azobis (4-methoxy-). 2,4-dimethylvaleronitrile), dimethyl-2,2'-azobis (2-methylpropionate), 2,2'-azobis (2-methylbutyronitrile), 1,1'-azobis (cyclohexane-) 1-Carbonitrile), 2,2'-azobis [N- (2-propenyl) -2-methylpropionamide], 2,2'-azobis (N-butyl-2-methylpropionamide) and the like. Only one kind of the radical polymerization initiator may be used, or two or more kinds thereof may be used in combination.
  • the preferable amount of the polymerization initiator to be used is, for example, 0.001 part by mass or more and 2 parts by mass or less, and for example, 0.005 part by mass or more and 1 by mass, when the total amount of the monomer components to be used is 100 parts by mass. It is not less than a part by mass, and is, for example, 0.01 part by mass or more and 0.1 part by mass or less.
  • the amount of the polymerization initiator used is 0.001 part by mass or more, the polymerization reaction can be stably carried out, and when it is 2 parts by mass or less, a polymer having a long primary chain length can be easily obtained.
  • the proportion of the polymerization initiator used is not particularly limited, but the amount of the polymerization initiator used per 1 mol of the exchange chain transfer mechanism type control agent is 0.5 mol from the viewpoint that the crosslinked structure of the present crosslinked polymer can be made uniform.
  • the value is preferably 0.2 mol or less, and more preferably 0.2 mol or less.
  • the lower limit of the amount of the polymerization initiator used with respect to 1 mol of the exchange chain transfer mechanism type control agent is 0.001 mol.
  • the amount of the polymerization initiator used with respect to 1 mol of the exchange chain transfer mechanism type control agent is preferably in the range of 0.001 mol or more and 0.5 mol or less, and more preferably in the range of 0.005 mol or more and 0.2 mol or less.
  • the polymerization solvent a solvent selected from water, various organic solvents and the like can be used in consideration of the type of the monomer used and the like. In order to obtain a polymer having a longer primary chain length, it is preferable to use a solvent having a small chain transfer constant.
  • the polymerization solvent include water-soluble solvents such as methanol, t-butyl alcohol, acetone, methyl ethyl ketone, acetonitrile and tetrahydrofuran, as well as benzene, ethyl acetate, dichloroethane, n-hexane, cyclohexane and n-heptane. One of these can be used alone or in combination of two or more.
  • the water-soluble solvent refers to a solvent having a solubility in water at 20 ° C. of more than 10 g / 100 ml.
  • Methylethylketone and acetonitrile are used in terms of being easy to unravel), obtaining a polymer with a small chain transfer constant and a large degree of polymerization (primary chain length), and being easy to operate during the process neutralization described later. preferable.
  • a highly polar solvent preferably include water and methanol.
  • the amount of the highly polar solvent used is preferably 0.05% by mass or more and 20.0% by mass or less, more preferably 0.1% by mass or more and 10.0% by mass or less, based on the total mass of the medium. It is more preferably 0.1% by mass or more and 5.0% by mass or less, and further preferably 0.1% by mass or more and 1.0% by mass or less.
  • the proportion of the highly polar solvent is 0.05% by mass or more, the effect on the neutralization reaction is recognized, and when it is 20.0% by mass or less, no adverse effect on the polymerization reaction is observed. Further, in the polymerization of a highly hydrophilic ethylenically unsaturated carboxylic acid monomer such as acrylic acid, the polymerization rate is improved when a highly polar solvent is added, and it becomes easy to obtain a polymer having a long primary chain length.
  • the highly polar solvents water is particularly preferable because it has a large effect of improving the polymerization rate.
  • the reaction temperature during the polymerization reaction in the presence of the polymer (A) is preferably 30 ° C. or higher and 120 ° C. or lower, more preferably 40 ° C. or higher and 110 ° C. or lower, and further preferably 50 ° C. or higher and 100 ° C. or lower. Is.
  • the reaction temperature is 30 ° C. or higher, the polymerization reaction can proceed smoothly.
  • the reaction temperature is 120 ° C. or lower, side reactions can be suppressed and restrictions on the initiators and solvents that can be used are relaxed.
  • first monomer a polymer chain (hereinafter, simply referred to as “first monomer”) of one kind or two or more kinds of vinyl-based monomers (hereinafter, also simply referred to as “first monomer”).
  • first monomer a polymer chain having a living radical polymerization active unit by an exchange chain transfer mechanism and a "first polymer chain”
  • the polymer (A) is used as a starting point for the polymerization of the present monomer, and the cross-linked polymer is polymerized.
  • the present cross-linked polymer which can be used as a dispersion stabilizer in a solvent and has a polymer chain having a structural unit derived from the present monomer bonded to the polymer chain of the polymer (A) is obtained as dispersed fine particles. Can be done.
  • the polymerization stability that is, the aggregation of the main crosslinked polymer during the polymerization step is suppressed, the generation of coarse aggregated particles is suppressed, and the main crosslinked weight having a small particle size and a narrow particle size distribution is suppressed. You can get coalescence.
  • the polymer (A) In order to make the polymer (A) function as a dispersion stabilizer in producing the crosslinked polymer by polymerizing the present monomer in the presence of the polymer (A), for example, the polymer (A) may be used. , 0.3 parts by mass or more and 50 parts by mass or less can be used with respect to 100 parts by mass of the total mass of this monomer. By using the polymer (A) in such a range, it is possible to produce the present crosslinked polymer mainly containing the present monomer while allowing the polymer (A) to function as a dispersion stabilizer.
  • the polymer (A) when the polymer (A) is less than 0.3 parts by mass, it is difficult to obtain a sufficient dispersion stabilizing effect, and the particle size of the crosslinked polymer tends to exceed 0.3 ⁇ m, even if it exceeds 50 parts by mass. This is because it is difficult to improve the functionality as a dispersion stabilizer, and the effect of reducing the particle size of the crosslinked polymer is also reduced.
  • the polymer (A) can be used with respect to 100 parts by mass of the total mass of this monomer, for example, 0.5 parts by mass or more, and for example, 1 part by mass or more. Further, the polymer (A) can be used, for example, 40 parts by mass or less, for example, 30 parts by mass or less, and for example, 20 parts by mass or less.
  • the range of the amount of the polymer (A) used with respect to 100 parts by mass of the total mass of this monomer can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • Method for Producing Polymer (A) A structural unit derived from the first monomer by polymerizing a monomer composition containing the first monomer in the presence of a known exchange chain transfer mechanism type control agent. It is possible to obtain a polymer (A) having a first polymerized chain having the above and a living polymerization active unit by an exchange chain transfer mechanism.
  • the polymerization conditions for producing the polymer (A) are well known to those skilled in the art, and examples of the polymerization process include various processes such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. Considering that it is a polymerization starting point in the production of coalescence and that it functions as a dispersion stabilizer, solution polymerization can be used, for example. Further, the polymerization conditions such as the type of the exchange chain transfer mechanism control agent, the type and amount of the polymerization initiator, the polymerization solvent, and the reaction temperature are appropriately selected according to the above paragraphs [0045] and [0051] to [0055].
  • the amount of the exchange chain transfer mechanism control agent used is appropriately adjusted according to the number average molecular weight (Mn) of the target polymer (A).
  • Mn number average molecular weight
  • a RAFT agent and a control agent in the iodine transfer polymerization method are preferable in that the molecular weight distribution of the polymer (A) can be narrowed.
  • the concentration at the time of producing the polymer (A) is not particularly limited with respect to the total mass of the amount charged such as the polymerization solvent and the first monomer, but is, for example, 10% by mass or more and 80% by mass. % Or less, for example, 15% by mass or more and 70% by mass or less, and for example, 20% by mass or more and 70% by mass or less.
  • a living polymerization active unit is provided at the end of the first polymerization chain, and the exchange chain transfer mechanism type having two or more functionalities is provided.
  • the mode is such that the living polymerization active unit is used as a base point to branch in two or more directions, and each of them is provided with a first polymerization chain.
  • the other polymerized chain is directly bonded to the living polymerization active unit, and the first polymerization is carried out more distally to the living polymerization active unit.
  • the first polymerized chain is bonded to the distal end of the other polymerized chain so that the chain is provided.
  • the polymer (A) can also include two or more kinds of first polymerized chains. For example, after performing living radical polymerization or the like using one or more first monomers of a certain composition, one or more first monomers of another composition are used. By carrying out living radical polymerization or the like, a polymer (A) having a first polymerized chain (block) having a structural unit derived from the first monomer having a different composition can be obtained.
  • the number average molecular weight (Mn) of the polymer (A) is not particularly limited, but is, for example, 3,000 or more, for example, 5,000 or more, and for example, 7,000 or more. Also, for example, 8,000 or more, and for example, 10,000 or more. Further, the Mn is, for example, 150,000 or less, for example, 100,000 or less, for example, 80,000 or less, and for example, 50,000 or less, and for example, 25, It is 000 or less, and is, for example, 15,000 or less, and is, for example, 12,000 or less.
  • Mn is less than 3,000, the binding property of the present crosslinked polymer salt is insufficient, and if it is more than 150,000, it becomes difficult to dissolve in the polymerization solvent of the dispersion polymerization to obtain the present crosslinked polymer. Will be difficult.
  • the range of Mn can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the weight average molecular weight (Mw) of the polymer (A) is not particularly limited, but is, for example, 5,000 or more, for example, 7,000 or more, and for example, 9,000 or more. Also, for example, 10,000 or more, for example, 13,000 or more, and for example, 15,000 or more. Further, the Mw is, for example, 200,000 or less, for example, 150,000 or less, for example, 100,000 or less, and for example, 80,000 or less, and 60,000 or less. Yes, for example 55,000 or less, and for example 50,000 or less, and for example 45,000 or less, and for example 40,000 or less, and for example 36,000 or less. Yes, for example, 35,000 or less, for example, 30,000 or less, and for example, 25,000 or less.
  • Mw is less than 5,000, the binding property of the present crosslinked polymer salt is insufficient, and if it is more than 200,000, it becomes difficult to dissolve in the polymerization solvent of the dispersion polymerization, and the present crosslinked polymer is obtained. Will be difficult.
  • the range of Mw can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • Both Mw and Mn of the polymer (A) can be measured by gel permeation chromatography using polystyrene as a standard substance. As for the details of the chromatography conditions, the conditions disclosed in the subsequent examples can be adopted.
  • the molecular weight distribution (Mw / Mn) of the polymer (A) is not particularly limited, but is, for example, 2.5 or less, for example, 2.4 or less, and for example, 2.3 or less. Yes, for example 2.0 or less, and for example 1.6 or less, and for example 1.5 or less, and for example 1.4 or less, and for example 1.3 or less. be. Further, the molecular weight distribution is, for example, 1.1 or more, for example, 1.2 or more, and for example, 1.3 or more, and for example, 1.4 or more, and for example, 1.5 or more. Is. The range of the molecular weight distribution can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the molecular weight distribution is preferably 2.4 or less, and in order to obtain the present crosslinked polymer having a smaller particle size, it is preferably 1.7 or less, and more preferably 1. It is 6 or less, and more preferably 1.4 or less.
  • the SP value of the polymer (A) is not particularly limited, but is, for example, 17 to 27 ((MPa) 1/2 ) in that the present crosslinked polymer having excellent sedimentation stability and binding property can be produced. Is preferable.
  • the SP value of the polymer (A) is, for example, 27 ((MPa) 1/2 ) or less, for example, 26 ((MPa) 1/2 ) or less, and for example, 25 ((MPa) 1 ). / 2 ) It is as follows.
  • the SP value of the polymer (A) is, for example, 17 ((MPa) 1/2 ) or more, for example, 18 ((MPa) 1/2 ) or more, and for example, 19 ((MPa) 1/2) or more. ) 1/2 ) or more.
  • the range of the SP value can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • first monomer examples include styrenes, (meth) acrylonitrile compounds, maleimide compounds, unsaturated acid anhydrides, unsaturated carboxylic acid compounds and the like. One of these or two or more of them can be used in combination.
  • Styrenes include styrene and its derivatives.
  • the styrene derivative include ⁇ -methylstyrene, ⁇ -methylstyrene, vinylxylene, vinylnaphthalene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, m-ethylstyrene and p-.
  • Ethylstyrene, pn-butylstyrene, p-isobutylstyrene, pt-butylstyrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-chloromethylstyrene, p-chloromethylstyrene, o -Chlorostyrene, p-chlorostyrene, o-hydroxystyrene, m-hydroxystyrene, p-hydroxystyrene, divinylbenzene and the like are exemplified, and one or more of these can be used.
  • styrene, o-methoxystyrene, m-methoxystyrene, p-methoxystyrene, o-hydroxystyrene, m-hydroxystyrene, and p-hydroxystyrene are preferable from the viewpoint of polymerizable property.
  • Examples of the (meth) acrylonitrile compound include (meth) acrylonitrile and ⁇ -methylacrylonitrile.
  • acrylonitrile is used.
  • the maleimide compound includes a maleimide and an N-substituted maleimide compound.
  • the N-substituted maleimide compound include N-methylmaleimide, N-ethylmaleimide, Nn-propylmaleimide, N-isopropylmaleimide, Nn-butylmaleimide, N-isobutylmaleimide, and N-tert-butylmaleimide.
  • N-alkyl-substituted maleimide compounds such as N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide; N-Cycloalkyl-substituted maleimide compound; N-phenylmaleimide, N- (4-hydroxyphenyl) maleimide, N- (4-acetylphenyl) maleimide, N- (4-methoxyphenyl) maleimide, N- (4-ethoxyphenyl) ) N-aryl substituted maleimide compounds such as maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) maleimide, N-benzylmaleimide, etc., and one or more of these may be mentioned.
  • N-phenylmaleimide is used.
  • examples of the unsaturated acid anhydride include maleic anhydride, itaconic anhydride, citraconic anhydride and the like, and one or more of these can be used.
  • unsaturated carboxylic acid compound examples include (meth) acrylic acid, silicic acid, crotonic acid, and monoalkyl of unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, and citraconic acid, and unsaturated dicarboxylic acids. Esters and the like can be mentioned, and one or more of them can be used.
  • the first monomer includes, for example, at least styrenes or a hydroxyl group-containing ethylenically unsaturated monomer (a monomer represented by the above formula (1), represented by the formula (2)). It is preferable to contain the monomer), and it is more preferable to contain the hydroxyl group-containing ethylenically unsaturated monomer. This is because styrenes are easy to polymerize in the living room and can impart appropriate hydrophobicity and affinity to organic solvents. It is possible to impart hydrophobicity or affinity to an organic solvent to the first polymerized chain.
  • the polymer (A) tends to be present on the surface layer of the present crosslinked polymer.
  • the dispersion stability of the crosslinked polymer is improved. This is because the hydroxyl group-containing ethylenically unsaturated monomer can impart the water dispersibility of the binder containing the crosslinked polymer salt and the affinity for the active material. By doing so, the binding property can be improved.
  • Styrene is, for example, 20% by mass or more of the total mass of the first monomer. This is because when the content is 20% by mass or more, the living polymerization is facilitated, and an appropriate hydrophobicity and an affinity for an organic solvent can be appropriately imparted. Further, for example, it is 30% by mass or more, and for example, 35% by mass or more, for example, 40% by mass or more, and for example, 50% by mass or more, and for example, 60% by mass or more. Further, for example, it is 65% by mass or more, for example, 70% by mass or more, and for example, 75% by mass or more.
  • the styrenes are 100% by mass or less of the total mass, for example, 95% by mass or less, for example, 90% by mass or less, and for example, 85% by mass or less, and for example, for example. It is 80% by mass or less, and for example, 75% by mass or less.
  • the range of the styrenes with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the (meth) acrylonitrile compound, maleimide compound, acid anhydride and unsaturated carboxylic acid compound can be used alone, and it is preferable to use one or more of these four types in combination with styrenes. This is because all of these four types can maintain, regulate or impart the hydrophobicity or organic solvent affinity of the first polymerized chain.
  • one or more of (meth) acrylonitrile compounds such as acrylonitrile, maleimide compounds such as N-phenylmaleimide, and acid anhydrides.
  • a combination of styrene and acrylonitrile, styrene and N-phenylmaleimide and the like is preferable.
  • the unsaturated carboxylic acid compound is preferable in that the polarity of the polymer (A) can be easily changed.
  • the total amount of these one or more first monomers other than styrenes is the first monomer for polymerizing the first polymerized chain (first). It is, for example, 20% by mass or more of the total mass of the first monomer unit of the polymerized chain). Further, for example, it is 25% by mass or more, and is, for example, 30% by mass or more, and is, for example, 35% by mass or more, and is, for example, 40% by mass or more, and is, for example, 50% by mass or more. Further, for example, it is 60% by mass or more.
  • the (meth) acrylonitrile compound is 80% by mass or less, for example, 75% by mass or less, and is, for example, 70% by mass or less, and is, for example, 65% by mass or less, based on the total mass. Further, for example, it is 60% by mass or less, for example, 55% by mass or less, and for example, 50% by mass or less.
  • the range of the styrenes with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the hydroxyl group-containing ethylenically unsaturated monomer is, for example, 50% by mass or more and 90% by mass or less of the total mass of the first monomer. This is because when it is 50% by mass or more, the precipitation stability of the electrode slurry containing the present crosslinked polymer salt can be imparted. Further, for example, 52.5% by mass or more, for example, 55% by mass or more, and for example, 57.5% by mass or more, and for example, 60% by mass or more, and for example, 62.5. It is 5% by mass or more, and is, for example, 65% by mass or more, and is, for example, 67.5% by mass or more, and is, for example, 70% by mass or more.
  • the hydroxyl group-containing ethylenically unsaturated monomer is, for example, 87.5% by mass or less, for example, 85% by mass or less, and for example, 82.5% by mass or less, based on the total mass. Further, for example, it is 80% by mass or less, for example, 77.5% by mass or less, and for example, 75% by mass or less.
  • the range of the hydroxyl group-containing ethylenically unsaturated monomer with respect to the total mass can be set by appropriately combining the above-mentioned lower limit and upper limit.
  • the first polymerized chain may be a polymerized chain containing only the first monomer described above, but if necessary, other vinyl-based monomers other than the above may be used as the first monomer. be able to.
  • known vinyl-based monomers such as (meth) acrylic acid esters such as (meth) acrylic acid and alkyl (meth) acrylic acid can be used.
  • these other monomers are, for example, 10% by mass or less, for example, 5% by mass or less, for example, 3% by mass or less, or, for example, the total mass of the monomers constituting the first polymerized chain. 1, 1% by mass or less, and for example, 0.5% by mass or less.
  • the polymer (A) may be provided with a block (another polymer chain) different from that of the first polymer chain.
  • Such other polymerized chains may be added, for example, in another synthetic step after the formation of the first polymerized chain.
  • the polymer (A) having the first polymerized chain is continuously or newly supplied with a radical polymerization initiator and another vinyl-based monomer to have a composition different from that of the first polymerized chain.
  • a polymer (A) having another polymer chain (block) consisting of units derived from a monomer other than the first monomer can be obtained.
  • a part of the monomer common to the present monomer used in the present crosslinked polymer can be partially linked in advance. It can be provided in the polymer (A).
  • the polymer (A) has a living radical polymerization active unit by an exchange chain transfer mechanism, it can be used as a solubility or dispersion stabilizer for the polymer (A) in the polymerization solvent in the precipitation polymerization or dispersion polymerization of this monomer.
  • Various monomers can be selected for the function of.
  • the exchange chain transfer mechanism of the living radical polymerization active unit in the polymer (A) includes a reversible addition-cleavage chain transfer polymerization method (RAFT method), an iodine transfer polymerization method, and a polymerization method using an organic tellurium compound (TERP method).
  • RAFT method reversible addition-cleavage chain transfer polymerization method
  • TERP method a polymerization method using an organic tellurium compound
  • Examples thereof include a polymerization method using an organic antimony compound (SBRP method), a polymerization method using an organic bismuth compound (BIRP method), and the like.
  • SBRP method organic antimony compound
  • BIRP method organic bismuth compound
  • the RAFT method and the iodine transfer polymerization method are preferable, and the RAFT method is more preferable, because the particle size of the crosslinked polymer can be reduced.
  • the abundance ratio (X) of the carboxyl group metal salt is 85 mol% or less (however, N is a value of 20 or more and 100 or less, and is the same for the crosslinked polymer salt R and the polymer salt S. Also, the type of metal salt. Is the same for the crosslinked polymer salt R and the polymer salt S).
  • X is 85 mol% or less, the sedimentation stability and binding property of the electrode slurry are excellent, more preferably 82.5 mol% or less, further preferably 80 mol% or less, and 75 mol%. The following is even more preferable.
  • X is obtained by a method according to the method described in the examples.
  • the crosslinked polymer salt preferably has a viscosity of 100 mPa ⁇ s or more in a 2% by mass aqueous solution thereof.
  • the viscosity of the 2 mass% concentration aqueous solution may be 1,000 mPa ⁇ s or more, 10,000 mPa ⁇ s or more, or 50,000 mPa ⁇ s or more.
  • the viscosity of the aqueous solution is predetermined. It is obtained by uniformly dissolving or dispersing the present cross-linked polymer salt in an amount to be a concentration in water, and then measuring the B-type viscosity (25 ° C.) at 12 rpm according to the method described in Examples.
  • This crosslinked polymer salt absorbs water and becomes swollen in water.
  • the crosslinked polymer has an appropriate degree of crosslinking
  • the larger the amount of hydrophilic groups of the crosslinked polymer the easier it is for the crosslinked polymer to absorb water and swell.
  • the degree of cross-linking the lower the degree of cross-linking, the easier it is for the cross-linked polymer to swell.
  • the number of cross-linking points is the same, the larger the molecular weight (primary chain length), the more cross-linking points that contribute to the formation of the three-dimensional network, so that the cross-linked polymer is less likely to swell.
  • the viscosity of the crosslinked polymer aqueous solution can be adjusted by adjusting the amount of hydrophilic groups of the crosslinked polymer, the number of crosslinking points, the primary chain length, and the like.
  • the number of the cross-linking points can be adjusted by, for example, the amount of the cross-linking monomer used, the chain transfer reaction to the polymer chain, the post-cross-linking reaction, and the like.
  • the primary chain length of the polymer can be adjusted by setting conditions related to the amount of radical generation such as the initiator and the polymerization temperature, and selecting the polymerization solvent in consideration of chain transfer and the like.
  • the crosslinked polymer salt does not exist as a mass (secondary agglomerate) having a large particle size, but is well dispersed as water-swelling particles having an appropriate particle size.
  • a binder containing a coalesced salt is preferable because it can exhibit good binding performance.
  • the particle size (water-swelling particle size) when a crosslinked polymer having a degree of neutralization based on a carboxyl group of 80 to 100 mol% is dispersed in water is a volume-based median diameter. It is preferably in the range of 0.1 ⁇ m or more and 10.0 ⁇ m or less. A more preferable range of the particle size is 0.15 ⁇ m or more and 8.0 ⁇ m or less, a further preferable range is 0.20 ⁇ m or more and 6.0 ⁇ m or less, and a further preferable range is 0.25 ⁇ m or more and 4.0 ⁇ m or less. A more preferable range is 0.30 ⁇ m or more and 2.0 ⁇ m or less.
  • the composition When the particle size is in the range of 0.30 ⁇ m or more and 2.0 ⁇ m or less, the composition is uniformly present in a suitable size in the present composition, so that the present composition is highly stable and exhibits excellent binding properties. It becomes possible. If the particle size exceeds 10.0 ⁇ m, the binding property may be insufficient as described above. In addition, there is a risk that the coatability will be insufficient because it is difficult to obtain a smooth coated surface. On the other hand, when the particle size is less than 0.1 ⁇ m, there is concern from the viewpoint of stable manufacturability.
  • the water-swelling particle size can be measured by the method described in the examples of the present specification.
  • the crosslinked polymer is unneutralized or has a neutralization degree of less than 80 mol%, it is neutralized to a neutralization degree of 80 to 100 mol% with an alkali metal hydroxide or the like, and the particle size when dispersed in water is measured. do it.
  • the crosslinked polymer or a salt thereof often exists as agglomerated particles in which primary particles are associated and aggregated in the state of powder or solution (dispersion liquid).
  • the particle size when dispersed in water is in the above range, the crosslinked polymer or a salt thereof has extremely excellent dispersibility, and is neutralized to a neutralization degree of 80 to 100 mol% to be water.
  • the agglomerated particles are disintegrated, and even if it is a dispersion of almost primary particles or a secondary agglomerate, a stable dispersed state is formed in which the particle size is in the range of 0.1 to 10.0 ⁇ m. It is a thing.
  • acid groups such as a carboxyl group derived from an ethylenically unsaturated carboxylic acid monomer are neutralized so that the degree of neutralization is 20 mol% or more in the present composition, and the mode of the salt is It is preferable to use as.
  • the degree of neutralization is more preferably 50 mol% or more, further preferably 70 mol% or more, still more preferably 75 mol% or more, still more preferably 80 mol% or more, and particularly preferably. It is 85 mol% or more.
  • the upper limit of the degree of neutralization is 100 mol%, and may be 98 mol% or 95 mol%.
  • the range of the degree of neutralization may be appropriately combined with the above lower limit value and upper limit value, and may be, for example, 50 mol% or more and 100 mol% or less, or 75 mol% or more and 100 mol% or less. , 80 mol% or more and 100 mol% or less.
  • the crosslinked polymer salt preferably has a water swelling degree of 20 or more and 80 or less at pH 8.
  • the degree of water swelling may be, for example, 21 or more, 23 or more, 25 or more, 27 or more, or 30 or more.
  • the degree of water swelling is 20 or more, the crosslinked polymer salt spreads on the surface of the active material or the current collector, and a sufficient adhesive area can be secured, so that good binding property can be obtained.
  • the upper limit of the degree of water swelling at pH 8 may be 75 or less, 70 or less, 65 or less, 60 or less, or 55 or less.
  • the range of the degree of water swelling at pH 8 can be set by appropriately combining the above upper limit value and lower limit value.
  • the degree of water swelling at pH 8 can be obtained by measuring the degree of swelling of the crosslinked polymer salt in water at pH 8.
  • the water having a pH of 8 for example, ion-exchanged water can be used, and the pH value may be adjusted by using an appropriate acid or alkali, a buffer solution or the like, if necessary.
  • the pH at the time of measurement is, for example, in the range of 8.0 ⁇ 0.5, preferably in the range of 8.0 ⁇ 0.3, more preferably in the range of 8.0 ⁇ 0.2, and further. It is preferably in the range of 8.0 ⁇ 0.1.
  • the measurement is performed at 25 ⁇ 5 ° C.
  • a person skilled in the art can adjust the degree of water swelling by controlling the composition and structure of the crosslinked polymer salt.
  • the degree of water swelling can be increased by introducing an acidic functional group or a highly hydrophilic structural unit into the crosslinked polymer. Further, by lowering the degree of cross-linking of the cross-linked polymer, the degree of water swelling is usually increased.
  • composition for a secondary battery electrode mixture layer of the present invention contains the present binder, an active material and water.
  • the amount of the binder used in the composition is, for example, 0.1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total amount of the active material.
  • the amount used is, for example, 0.2 parts by mass or more and 10 parts by mass or less, for example, 0.3 parts by mass or more and 8 parts by mass or less, and for example, 0.4 parts by mass or more and 5 parts by mass or less. ..
  • the amount of the binder used is 0.1 part by mass or more, sufficient binding property can be obtained.
  • the dispersion stability of the active material or the like can be ensured, and a uniform mixture layer can be formed.
  • the amount of the binder used is 20 parts by mass or less, the present composition does not have a high viscosity, and the coatability to the current collector can be ensured. As a result, a mixture layer having a uniform and smooth surface can be formed.
  • the lithium salt of the transition metal oxide can be used as the positive electrode active material, and for example, layered rock salt type and spinel type lithium-containing metal oxides can be used.
  • ⁇ Li (Ni 1-ab Co a Al b ) ⁇ and the like can be mentioned.
  • a spinel type positive electrode active material lithium manganate and the like can be mentioned.
  • Phosphate, silicate, sulfur and the like are used in addition to the oxide, and examples of the phosphate include olivine-type lithium iron phosphate and the like.
  • the positive electrode active material one of the above may be used alone, or two or more thereof may be combined and used as a mixture or a composite.
  • the amount of the unneutralized or partially neutralized present crosslinked polymer used is such that the amount of the unneutralized carboxyl group of the present crosslinked polymer is equal to or more than the amount of alkali eluted from the active material. It is preferable to use it.
  • the conductive auxiliary agent include carbon-based materials such as carbon black, carbon nanotubes, carbon fibers, graphite fine powder, and carbon fibers. Among these, carbon black, carbon nanotubes, and carbon fibers are easy to obtain excellent conductivity. Is preferable. Further, as the carbon black, Ketjen black and acetylene black are preferable. As the conductive auxiliary agent, one of the above may be used alone, or two or more thereof may be used in combination.
  • the amount of the conductive auxiliary agent used can be, for example, 0.2 to 20 parts by mass with respect to 100 parts by mass of the total amount of the active material from the viewpoint of achieving both conductivity and energy density, and for example, 0. It can be 2 to 10 parts by mass.
  • the positive electrode active material a material having a surface coating with a conductive carbon-based material may be used.
  • examples of the negative electrode active material include carbon-based materials, lithium metals, lithium alloys, metal oxides, and the like, and one or more of these can be used in combination.
  • active materials made of carbon-based materials such as natural graphite, artificial graphite, hard carbon and soft carbon (hereinafter, also referred to as “carbon-based active material”) are preferable, and graphite such as natural graphite and artificial graphite, Also, hard carbon is more preferred.
  • graphite spherical graphite is preferably used from the viewpoint of battery performance, and the preferable range of the particle size thereof is, for example, 1 to 20 ⁇ m, and for example, 5 to 15 ⁇ m.
  • a metal or a metal oxide capable of storing lithium such as silicon or tin can also be used as the negative electrode active material.
  • silicon has a higher capacity than graphite, and is an active material made of a silicon-based material such as silicon, a silicon alloy, and a silicon oxide such as silicon monoxide (SiO) (hereinafter, also referred to as "silicon-based active material").
  • silicon-based active material has a high capacity, the volume change due to charge / discharge is large. Therefore, it is preferable to use it in combination with the above carbon-based active material.
  • the amount of the silicon-based active material is large, the electrode material may be disintegrated and the cycle characteristics (durability) may be significantly deteriorated.
  • the amount used is, for example, 60% by mass or less, and for example, 30% by mass or less, based on the carbon-based active material.
  • the carbon-based active material itself has good electrical conductivity, it is not always necessary to add a conductive additive.
  • a conductive auxiliary agent is added for the purpose of further reducing resistance, the amount used is, for example, 10 parts by mass or less with respect to 100 parts by mass of the total amount of the active material, and for example, 5 from the viewpoint of energy density. It is less than the mass part.
  • the amount of the active material used is, for example, in the range of 10 to 75% by mass, and for example, in the range of 30 to 65% by mass, based on the total amount of the composition. If the amount of the active material used is 10% by mass or more, migration of the binder or the like can be suppressed, and it is also advantageous in terms of the drying cost of the medium. On the other hand, if it is 75% by mass or less, the fluidity and coatability of the present composition can be ensured, and a uniform mixture layer can be formed.
  • This composition uses water as a medium. Further, for the purpose of adjusting the properties and dryness of the composition, lower alcohols such as methanol and ethanol, carbonates such as ethylene carbonate, ketones such as acetone, tetrahydrofuran, N-methyl-2-pyrrolidone and the like. It may be a mixed solvent with a water-soluble organic solvent.
  • the proportion of water in the mixing medium is, for example, 50% by mass or more, and for example, 70% by mass or more.
  • the content of the medium containing water in the entire composition is, for example, from the viewpoint of the coatability of the slurry, the energy cost required for drying, and the productivity. , 25-60% by mass, and can be, for example, 35-60% by mass.
  • the present composition may further contain other binder components such as styrene-butadiene rubber (SBR) -based latex, carboxymethyl cellulose (CMC), acrylic-based latex and polyvinylidene fluoride-based latex.
  • SBR styrene-butadiene rubber
  • CMC carboxymethyl cellulose
  • acrylic-based latex acrylic-based latex
  • polyvinylidene fluoride-based latex polyvinylidene fluoride-based latex.
  • the amount used may be, for example, 0.1 to 5 parts by mass or less, and for example, 0.1 to 2 parts by mass, based on 100 parts by mass of the total amount of the active material. It can be less than or equal to parts, and can be, for example, 0.1 to 1 part by mass or less. If the amount of the other binder component used exceeds 5 parts by mass, the resistance increases and the high rate characteristics may be insufficient.
  • SBR-based latex and CMC are preferable, and SBR-
  • the SBR-based latex is an aqueous dispersion of a copolymer having a structural unit derived from an aromatic vinyl monomer such as styrene and a structural unit derived from an aliphatic conjugated diene-based monomer such as 1,3-butadiene. Show the body.
  • aromatic vinyl monomer include ⁇ -methylstyrene, vinyltoluene, divinylbenzene and the like in addition to styrene, and one or more of these can be used.
  • the structural unit derived from the aromatic vinyl monomer in the copolymer can be, for example, in the range of 20 to 70% by mass, and for example, 30 to 60, mainly from the viewpoint of binding property.
  • the structural unit derived from the aliphatic conjugated diene-based monomer in the copolymer is, for example, 30 to 70% by mass in that the binding property of the binder and the flexibility of the obtained electrode are good. It can be in the range of 40 to 60% by mass, for example.
  • the styrene / butadiene-based latex includes nitrile group-containing monomers such as (meth) acrylonitrile and (meth) as other monomers in order to further improve the performance such as binding property.
  • nitrile group-containing monomers such as (meth) acrylonitrile and (meth) as other monomers in order to further improve the performance such as binding property.
  • a carboxyl group-containing monomer such as acrylic acid, itaconic acid, and maleic acid
  • an ester group-containing monomer such as methyl (meth) acrylate
  • the structural unit derived from the other monomer in the copolymer can be, for example, in the range of 0 to 30% by mass, or can be, for example, in the range of 0 to 20% by mass.
  • the above-mentioned CMC refers to a substituent obtained by substituting a nonionic cellulose-based semisynthetic polymer compound with a carboxymethyl group and a salt thereof.
  • the nonionic cellulose-based semi-synthetic polymer compound include alkyl celluloses such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose, and microcrystallin cellulose; Examples thereof include hydroxyethyl cellulose, hydroxybutylmethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, hydroxyethylmethyl cellulose, hydroxypropylmethyl cellulose stearoxy ether, carboxymethyl hydroxyethyl cellulose, alkyl hydroxyethyl cellulose, hydroxyalkyl cellulose such as nonoxynyl hydroxyethyl cellulose and the like.
  • the composition for the secondary battery electrode mixture layer of the present invention contains the above-mentioned active material, water and a binder as essential constituents, and can be obtained by mixing each component by a known means.
  • the mixing method of each component is not particularly limited, and a known method can be adopted.
  • powder components such as an active substance, a conductive auxiliary agent and a binder are dry-blended and then mixed with a dispersion medium such as water. The method of dispersion and kneading is preferable.
  • a known mixer such as a planetary mixer, a thin film swirl mixer, or a self-revolving mixer can be used, but a thin film swirl mixer is used because a good dispersion state can be obtained in a short time. It is preferable to do this.
  • a thin film swirl mixer it is preferable to pre-disperse in advance with a stirrer such as a disper.
  • the pH of the slurry is not particularly limited as long as the effect of the present invention is exhibited, but it is preferably less than 12.5. It is more preferably less than 10.5 and even more preferably less than 10.5.
  • the viscosity of the slurry is not particularly limited as long as the effect of the present invention is exhibited, but the B-type viscosity (25 ° C.) at 20 rpm can be, for example, in the range of 100 to 6,000 mPa ⁇ s, and for example. , 500 to 5,000 mPa ⁇ s, or, for example, 1,000 to 4,000 mPa ⁇ s.
  • the viscosity of the slurry is within the above range, good coatability can be ensured.
  • the secondary battery electrode of the present invention comprises a mixture layer formed from the composition for the mixture layer of the secondary battery electrode of the present invention on the surface of a current collector such as copper or aluminum. ..
  • the mixture layer is formed by applying the present composition to the surface of the current collector and then drying and removing a medium such as water.
  • the method for applying the present composition is not particularly limited, and known methods such as a doctor blade method, a dip method, a roll coating method, a comma coating method, a curtain coating method, a gravure coating method and an extrusion method may be adopted. can. Further, the drying can be performed by a known method such as blowing warm air, reducing the pressure, (far) infrared rays, and irradiating microwaves.
  • the mixture layer obtained after drying is subjected to a compression treatment by a die press, a roll press or the like.
  • a compression treatment by a die press, a roll press or the like.
  • the thickness of the mixture layer can be adjusted to, for example, about 30 to 80% before compression, and the thickness of the mixture layer after compression is generally about 4 to 200 ⁇ m.
  • Secondary battery A secondary battery can be manufactured by providing a separator and an electrolytic solution on the secondary battery electrode of the present invention.
  • the electrolytic solution may be in the form of a liquid or in the form of a gel.
  • the separator is arranged between the positive electrode and the negative electrode of the battery, and plays a role of preventing a short circuit due to contact between the two electrodes and holding an electrolytic solution to ensure ionic conductivity.
  • the separator is preferably a film-like insulating microporous film having good ion permeability and mechanical strength.
  • polyolefins such as polyethylene and polypropylene, polytetrafluoroethylene and the like can be used.
  • the electrolytic solution a known one that is generally used depending on the type of the active material can be used.
  • specific solvents include cyclic carbonates having a high dielectric constant and a high dissolving ability of an electrolyte such as propylene carbonate and ethylene carbonate, and low-viscosity chains such as ethylmethyl carbonate, dimethyl carbonate and diethyl carbonate. Examples thereof include state carbonate and the like, and these can be used alone or as a mixed solvent.
  • the electrolytic solution is used by dissolving lithium salts such as LiPF 6 , LiSbF 6 , LiBF 4 , LiClO 4 , and LiAlO 4 in these solvents.
  • an aqueous potassium hydroxide solution can be used as the electrolytic solution.
  • the secondary battery is obtained by forming a positive electrode plate and a negative electrode plate partitioned by a separator into a spiral or laminated structure and storing them in a case or the like.
  • the electrode slurry containing the binder for the secondary battery electrode disclosed in the present specification has excellent settling stability, it has excellent adhesion to the electrode material and excellent adhesion to the current collector in the mixture layer. Is expected to indicate. Therefore, the secondary battery provided with the electrodes obtained by using the above binder is expected to ensure good integrity and to show good durability (cycle characteristics) even after repeated charging and discharging, and is in-vehicle. Suitable for secondary batteries and the like.
  • EA ethyl acrylate
  • HOA 2-hydroxyethyl acrylate
  • the reaction of the obtained polymer 1 was obtained.
  • the calculated SP value based on the composition ratio was 26.5 ((MPa) 1/2 ).
  • the molecular weight of the polymer 1 was 82,100 for Mn, 118,300 for Mw, and 1 for Mw / Mn. It was .44.
  • EA and HEA correspond to the first vinyl-based monomer.
  • EA ethyl acrylate
  • BA n-butyl acrylate
  • HEA 2-hydroxyethyl acrylate
  • St styrene
  • AN acrylonitrile
  • DBTTC dibenzyltrithiocarbonate
  • V-65 2,2'-azobis (2, 4-Dimethylvaleronitrile) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name "V-65”)
  • -ABN-E 2,2'-azobis (2-methylbutyronitrile) (manufactured by Japan Finechem Company, Inc., trade name "ABN-E”)
  • the above measurement sample is measured by an X-ray photoelectron spectroscopic analyzer, and the abundance ratio (X) of the carboxyl group metal salt of each crosslinked polymer based on the X-ray photoelectron spectroscopic analysis (XPS) is calculated by the following formula (1).
  • N is a value of 20 or more and 100 or less, and is the same for the crosslinked polymer salt R and the polymer salt S.
  • the type of the metal salt is the same for the crosslinked polymer salt R and the polymer salt S.) ..
  • I 1 is a value calculated by the following formula (2) for the crosslinked polymer salt R based on XPS
  • I 2 is a value calculated by the following formula (3) for the polymer salt S based on XPS. It is a calculated value.
  • I 2 (atom%) AM2 / ( AM2 + AC2 + AO2 ) (3)
  • the XPS measurement was performed under the following conditions.
  • the particle size distribution of the hydrogel was measured with a laser diffraction / scattering particle size distribution meter (Microtrac MT-3300EXII, manufactured by Microtrac Bell) using ion-exchanged water as a dispersion medium.
  • a laser diffraction / scattering particle size distribution meter Microtrac MT-3300EXII, manufactured by Microtrac Bell
  • the particle size distribution shape measured after a few minutes became stable.
  • the particle size distribution was measured to obtain a volume-based median diameter (D50) as a representative value of the particle size.
  • LiOH ⁇ H2O lithium hydroxide monohydrate
  • the obtained polymerization reaction solution was centrifuged to settle the polymer particles, and then the supernatant was removed. Then, after redispersing the precipitate in acetonitrile having the same weight as the polymerization reaction solution, the washing operation of precipitating the polymer particles by centrifugation and removing the supernatant was repeated twice.
  • the precipitate was recovered and dried at 80 ° C. for 3 hours under reduced pressure to remove volatile components to obtain a powder of the metal salt R-1 of the carboxyl group-containing polymer. Since the metal salt R-1 of the carboxyl group-containing polymer has hygroscopicity, it was stored in a sealed container having a water vapor barrier property.
  • the particle size in the aqueous medium was 1.52 ⁇ m.
  • the XPS measurement result of the metal salt R-1 of the carboxyl group-containing crosslinked polymer is shown.
  • I 1 of the lithium salt R-1 neutralization degree 90 mol% of the carboxyl group-containing crosslinked polymer
  • I 2 using a lithium salt of 000) neutralization degree 90 mol%
  • I 2 using a lithium salt of 000 neutralization degree 90 mol%
  • Example 1 (Preparation of composition for electrode mixture layer) Prepare a SiOx (0.8 ⁇ x ⁇ 1.2) surface coated with carbon by the CVD method (hereinafter, also referred to as "Si-based active material"), and graphite (manufactured by Nippon Graphite Co., Ltd., trade name ". A mixture of CGB-10 ") and a Si-based active material was used as the active material.
  • Si-based active material SiOx (0.8 ⁇ x ⁇ 1.2) surface coated with carbon by the CVD method
  • graphite manufactured by Nippon Graphite Co., Ltd., trade name ". A mixture of CGB-10 ”
  • a metal salt of a crosslinked polymer containing graphite: Si-based active material: carboxyl group R-1 90: using water as a diluting solvent so that the solid content concentration of the composition for the electrode mixture layer is 40.0% by mass.
  • the electrode slurry was applied onto a current collector (copper foil) having a thickness of 20 ⁇ m, and dried in a ventilation dryer at 100 ° C. for 15 minutes to form a mixture layer. .. Then, the mixture layer was rolled so that the thickness was 50 ⁇ 5 ⁇ m and the packing density was 1.60 ⁇ 0.10 g / cm 3 , to obtain a negative electrode plate.
  • the 90 ° peel strength that is, the binder binding property
  • the rate of change in the solid content of the supernatant was determined by the following formula, and the sedimentation stability was evaluated by the following criteria (pass level: B evaluation or higher).
  • the change rate (%) of the supernatant solid content was 0.3%, which was an A rating.
  • Change rate of supernatant solid content (%) 100- (concentration of supernatant solid content after standing for 1 week) / (concentration of supernatant solid content immediately after preparation) x 100
  • a sample for a peeling test was prepared by pasting the mixture layer surface of the negative electrode electrode plate having a size of 100 mm ⁇ 25 mm on a 120 mm ⁇ 30 mm acrylic plate via a double-sided tape (Nichiban Co., Ltd. Nystack NW-20). After drying under reduced pressure conditions at 60 ° C. overnight, 90 ° peeling was performed at a measurement temperature of 25 ° C. and a tensile speed of 50 mm / min using a tensile tester (TENSILON universal test material machine RTE-1210 manufactured by ORIENTEC). The binding property was evaluated by measuring the peel strength between the mixture layer and the copper foil. The peel strength was as high as 15.3 N / m, which was good.
  • Examples 2 to 13 and Comparative Examples 1 to 4 An electrode slurry was prepared by performing the same operation as in Example 1 except that the metal salt of the carboxyl group-containing crosslinked polymer used as the binder was used as shown in Table 3. The 90 ° peel strength was evaluated for each electrode slurry. The results are shown in Table 3.
  • the composition for the secondary battery electrode mixture layer (electrode slurry) containing the binder for the secondary battery electrode of the present invention is excellent in sedimentation stability and binding property.
  • Met focusing on the structural units of the crosslinked polymer, when all the structural units include structural units derived from the hydroxyl group-containing ethylenically unsaturated monomer (Examples 1 and 7), the monomer is concerned. The result was that the binding property was further excellent as compared with the case where the structural unit derived from (Example 9) was not contained.
  • the composition for the secondary battery electrode mixture layer (electrode slurry) containing the binder for the secondary battery electrode of the present invention is excellent in sedimentation stability, and also has excellent adhesion and collection with the electrode material in the electrode mixture layer. Since it shows excellent adhesion to the electric body, it is expected to show good durability (cycle characteristics). Therefore, the secondary battery provided with the electrodes obtained by using the above binder is expected to ensure good integrity and to show good durability (cycle characteristics) even after repeated charging and discharging, and is in-vehicle. It is expected to contribute to increasing the capacity of secondary batteries for use.
  • the binder for a secondary battery electrode of the present invention can be particularly preferably used for a non-aqueous electrolyte secondary battery electrode, and is particularly useful for a non-aqueous electrolyte lithium ion secondary battery having a high energy density.

Abstract

La présente invention concerne un liant pour électrode de batterie rechargeable qui préserve la stabilité de sédimentation d'une suspension d'électrode tout en présentant d'excellentes propriétés de liaison et en permettant une amélioration des caractéristiques de cycle d'une batterie rechargeable.　La présente invention concerne un liant d'électrode de batterie rechargeable comprenant un sel métallique d'un polymère réticulé contenant un groupe carboxyle, le polymère réticulé comprenant, par rapport à tous ses motifs structuraux, 80 à 99,9 % en masse d'un motif structural issu d'un monomère d'acide carboxylique éthyléniquement insaturé, et le rapport de présence du sel métallique du groupe carboxyle du polymère réticulé obtenu par spectroscopie photoélectronique à rayons X (XPS) étant égal ou inférieur à 85 % en moles.
PCT/JP2021/045978 2020-12-18 2021-12-14 Liant pour électrode de batterie rechargeable et son procédé de production, composition de couche de mélange d'électrode de batterie rechargeable, électrode de batterie rechargeable et batterie rechargeable WO2022131239A1 (fr)

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WO2024024772A1 (fr) * 2022-07-27 2024-02-01 東亞合成株式会社 Liant pour électrode de batterie secondaire à électrolyte non aqueux

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WO2020129750A1 (fr) * 2018-12-18 2020-06-25 東亞合成株式会社 Liant destiné à des électrodes de batterie secondaire et son utilisation
WO2021215381A1 (fr) * 2020-04-23 2021-10-28 東亞合成株式会社 Procédé de production d'un polymère réticulé, contenant un groupe carboxyle, ou d'un sel de celui-ci
CN111668485A (zh) * 2020-05-22 2020-09-15 远景动力技术(江苏)有限公司 锂离子电池用粘结剂及其制备方法和应用

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2024024772A1 (fr) * 2022-07-27 2024-02-01 東亞合成株式会社 Liant pour électrode de batterie secondaire à électrolyte non aqueux

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