WO2021215380A1 - Polymère réticulé contenant un groupe carboxyle ou sel de celui-ci, et son utilisation - Google Patents

Polymère réticulé contenant un groupe carboxyle ou sel de celui-ci, et son utilisation Download PDF

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WO2021215380A1
WO2021215380A1 PCT/JP2021/015807 JP2021015807W WO2021215380A1 WO 2021215380 A1 WO2021215380 A1 WO 2021215380A1 JP 2021015807 W JP2021015807 W JP 2021015807W WO 2021215380 A1 WO2021215380 A1 WO 2021215380A1
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crosslinked polymer
mass
salt
less
polymer
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PCT/JP2021/015807
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Japanese (ja)
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朋子 仲野
篤史 西脇
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
    • C08F20/00—Homopolymers and 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
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/04—Acids, Metal salts or ammonium salts thereof
    • 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
    • C08F20/00—Homopolymers and 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
    • C08F20/02—Monocarboxylic acids having less than ten carbon atoms, Derivatives thereof
    • C08F20/10—Esters
    • C08F20/20—Esters of polyhydric alcohols or polyhydric phenols, e.g. 2-hydroxyethyl (meth)acrylate or glycerol mono-(meth)acrylate
    • 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
    • C08F22/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals each having only one carbon-to-carbon double bond, and at least one being terminated by a carboxyl radical and containing at least one other carboxyl radical in the molecule; Salts, anhydrides, esters, amides, imides or nitriles thereof
    • C08F22/02—Acids; Metal salts or ammonium salts thereof, e.g. maleic acid or itaconic acid
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a carboxyl group-containing crosslinked polymer or a salt thereof, and its use.
  • Carboxyl group-containing polymers are used in various applications such as thickeners and viscosity modifiers for cosmetics, binders for non-aqueous electrolyte secondary battery electrodes, sedimentation inhibitors for pigments, and dispersion stabilizers for metal powders. ing.
  • a thickener for cosmetics when the carboxyl group-containing polymer is linear, it has a spinnability and feels sticky, but as the degree of cross-linking is increased, the spinnability becomes higher. It has the characteristic that it decreases and you can feel the freshness. Therefore, in cosmetics that do not require spinnability and require freshness, a carboxyl group-containing crosslinked polymer is often used because of the advantage that high viscosity can be obtained with a small amount of use.
  • a binder for a non-aqueous electrolyte secondary battery electrode a carboxyl group-containing crosslinked polymer is often used because of the advantages of being able to impart good binding properties and cycle characteristics.
  • various secondary batteries such as nickel hydrogen secondary batteries, lithium ion secondary batteries, and electric double layer capacitors expand, the demand for improving energy density, reliability, and durability tends to increase.
  • specifications for using a silicon-based active material as a negative electrode active material are increasing.
  • Patent Document 1 discloses a crosslinked acrylic acid-based polymer having a specific particle size in a 1% NaCl aqueous solution.
  • the microcrosslinked acrylic acid system disclosed in Patent Documents 1 and 2 as a binder of particles in the slurry (for example, a binder of the active material in the lithium ion secondary battery electrode slurry).
  • the fine cross-linking of the acrylic acid-based polymer can enhance the binding property between the particles in the slurry, while the spread of the polymer in water is increased and the viscosity is increased even with a small amount of addition.
  • the coatability and the coating performance for example, the cycle characteristics of the lithium ion secondary battery
  • the binders for secondary battery electrodes disclosed in Patent Documents 1 and 2 can all impart good cycle characteristics and binding properties, but as the performance of the secondary battery is improved, the cycle characteristics become more favorable. There is an increasing demand for improveable binders.
  • the secondary battery electrode is generally obtained by applying a composition for an electrode mixture layer containing an active material and a binder (hereinafter, also referred to as “electrode slurry”) to the surface of an electrode current collector and drying it. At this time, it is advantageous to increase the solid content concentration of the electrode slurry from the viewpoint of increasing the drying efficiency of the electrode slurry and improving the productivity of the electrode. However, usually, as the solid content concentration increases, it becomes difficult to ensure good coatability. As described above, the binders disclosed in Patent Documents 1 and 2 have a large increase in viscosity even when added in a small amount, so that it is difficult to increase the solid content concentration.
  • the present invention has been made in view of such circumstances, and an object of the present invention is to achieve both coatability and coating performance of a composition containing a carboxyl group-containing crosslinked polymer or a salt thereof. It is to provide a crosslinked polymer or a salt thereof. Furthermore, when the solid content concentration of the composition for the electrode mixture layer is higher than before, it is possible to obtain a secondary battery that exhibits excellent cycle characteristics while ensuring coatability by reducing the viscosity of the electrode slurry. It is to provide a binder for a secondary battery electrode that can be made. In addition, 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 non-uniform network structure size obtained by measurement by the small-angle X-ray scattering method is a specific value or less, or a carboxyl group-containing crosslinked polymer or a crosslinked polymer thereof.
  • the present invention has been completed by finding that by using a salt, excellent coating performance can be exhibited while ensuring the coatability of the crosslinked polymer or a composition containing the salt thereof.
  • the solid content concentration of the composition for the secondary battery electrode mixture layer containing the binder for the secondary battery electrode containing the carboxyl group-containing crosslinked polymer or a salt thereof, the active material and water is high, the composition may be used.
  • the non-uniform network structure size obtained by the small angle X-ray scattering method measurement is less than a specific value.
  • a carboxyl group-containing crosslinked polymer or a salt thereof By containing a carboxyl group-containing crosslinked polymer or a salt thereof, the coatability is ensured by reducing the viscosity of the electrode slurry. At the same time, they have found that a secondary battery exhibiting excellent cycle characteristics can be obtained, and have completed the present invention.
  • the present invention is as follows.
  • Non-uniform network structure size of the crosslinked polymer calculated by curve fitting with the following formula (1) to the scattering intensity curve I (q) obtained by measuring a 1% by mass concentration aqueous solution of the crosslinked polymer.
  • a carboxyl group-containing crosslinked polymer or a salt thereof, wherein ⁇ (hereinafter, also referred to as “ ⁇ 1”) is 80 or less.
  • the crosslinked polymer or a salt thereof is neutralized to a degree of neutralization of 80 to 100 mol%, and then the particle size measured in an aqueous medium is 0.1 ⁇ m or more and 5.0 ⁇ m or less in terms of volume-based median diameter.
  • a binder for a secondary battery electrode which comprises the carboxyl group-containing crosslinked polymer according to any one of [1] to [6] or a salt thereof.
  • a secondary battery electrode comprising a mixture layer formed from the composition for the secondary battery electrode mixture layer according to [8] on the surface of a current collector.
  • the coatability and the coating film performance of the composition containing the crosslinked polymer or the salt thereof can be compatible with each other. Furthermore, according to the binder for the secondary battery electrode containing the carboxyl group-containing crosslinked polymer of the present invention or a salt thereof, the viscosity of the electrode slurry is higher than the conventional one when the solid content concentration of the composition for the electrode mixture layer is higher. It is possible to obtain a secondary battery that exhibits excellent cycle characteristics while ensuring coatability by reducing the amount.
  • the carboxyl group-containing crosslinked polymer of the present invention or a salt thereof (hereinafter, also referred to as “the present crosslinked polymer”) has a degree of neutralization by a small angle X-ray scattering method (measurement temperature: 25.0 ⁇ 0.1 ° C.). Calculated by curve fitting with the above formula (1) to the scattering intensity curve I (q) obtained by measuring a 1% by mass concentration aqueous solution of the present crosslinked polymer neutralized to 50 to 100 mol%. , The non-uniform network structure size ⁇ ( ⁇ 1) of this crosslinked polymer is 80 or less. ⁇ will be described in detail in "3. Characteristics of the Crosslinked Polymer" and “Examples” described later.
  • the binder for a secondary battery electrode containing the crosslinked polymer or a salt thereof is a composition for a secondary battery electrode mixture layer by mixing with an active material and water.
  • the present composition is in a slurry state that can be applied to a 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.
  • this 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.
  • the 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 by 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 material 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 alkyl such as (meth) acrylamide hexane acid and (meth) acrylamide dodecanoic acid.
  • Carboxylic acid; ethylenically unsaturated monomers having carboxyl groups such as monohydroxyethyl succinate (meth) acrylate, ⁇ -carboxy-caprolactone mono (meth) acrylate, ⁇ -carboxyethyl (meth) acrylate, or (partial) thereof.
  • Alkali neutralized products may be mentioned, 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.
  • 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 present crosslinked polymer is not particularly limited, but may be, for example, 10% by mass or more and 100% by mass or less with respect to all the structural units of the present crosslinked polymer.
  • the lower limit is, for example, 20% by mass or more, for example, 30% by mass or more, and for example, 40% by mass or more.
  • the lower limit is 50% by mass or more, the dispersion stability of the present composition becomes good and a higher binding force can be obtained, which is preferable, and it may be 60% by mass or more, or 70% by mass or more. It may be 80% by mass or more.
  • the upper limit is, for example, 99.9% by mass or less, for example, 99.5% by mass or less, for example, 99% by mass or less, for example, 98% by mass or less, and for example, 95% by mass. It is less than or equal to, for example, 90% by mass or less, and for example, 80% by mass or less.
  • the range may be a range in which such a lower limit and an upper limit are appropriately combined, and is, for example, 10% by mass or more and 100% by mass or less, and for example, 50% by mass or more and 100% by mass or less, and for example. It can be 50% by mass or more and 99.9% by mass or less, and can be, for example, 50% by mass or more and 99% by mass or less, and can be, for example, 50% by mass or more and 98% by mass or less.
  • the crosslinked polymer may contain a structural unit derived from another ethylenically unsaturated monomer copolymerizable with the component (hereinafter, also referred to as “component (b)”).
  • component (b) includes, for example, 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 nonionic ethylenically unsaturated monomer.
  • the structural unit from which it is derived can be mentioned.
  • These structural units are ethylenically unsaturated monomer compounds having anionic groups other than carboxyl groups such as sulfonic acid groups and phosphoric acid groups, or monomers containing nonionic ethylenically unsaturated monomers. Can be introduced by copolymerizing.
  • the ratio of the component (b) can be 0% by mass or more and 90% by mass or less with respect to all the structural units of the present crosslinked polymer.
  • the ratio of the component (b) may be 1% by mass or more and 60% by mass or less, 2% by mass or more and 50% by mass or less, and 5% by mass or more and 40% by mass or less. It may be 10% by mass or more and 30% by mass or less. Further, when the component (b) is contained in an amount of 1% by mass or more with respect to all the structural units of the crosslinked polymer, the affinity for the electrolytic solution is improved, so that the effect of improving the lithium ion conductivity can be expected.
  • nonionic ethylenically unsaturated monomers are preferable from the viewpoint of obtaining electrodes having good bending resistance, and nonionic ethylenically unsaturated monomers are preferable.
  • the monomer include (meth) acrylamide and its derivatives, a nitrile group-containing ethylenically unsaturated monomer, an alicyclic structure-containing ethylenically unsaturated monomer, and the like.
  • Examples of the (meth) acrylamide derivative include N-alkyl (meth) acrylamide compounds such as isopropyl (meth) acrylamide and t-butyl (meth) acrylamide; Nn-butoxymethyl (meth) acrylamide and N-isobutoxymethyl.
  • N-alkoxyalkyl (meth) acrylamide compounds such as (meth) acrylamide; N, N-dialkyl (meth) acrylamide compounds such as dimethyl (meth) acrylamide and diethyl (meth) acrylamide include one of them. It may be used alone or in combination of two or more.
  • nitrile group-containing ethylenically unsaturated monomer examples include (meth) achlorinitrile; (meth) cyanomethyl acrylate, (meth) cyanoethyl acrylate and other (meth) acrylate cyanoalkyl ester compounds; 4-cyanostyrene. , 4-Cyano- ⁇ -methylstyrene and other unsaturated aromatic compounds containing cyano groups; 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, and (meth).
  • Cyclodecyl acrylate and cyclododecyl (meth) acrylate and other aliphatic substituents may have (meth) cycloalkyl acrylate; isobornyl (meth) acrylate, adamantyl (meth) acrylate, (meth).
  • Cycloalkyl polyalcohol mono (meth) acrylate and the like can be mentioned, and one of these may be used alone, or two or more thereof may be used in combination.
  • the crosslinked polymer or a salt thereof has excellent binder binding properties, and is an amount of (meth) acrylamide and its derivatives, a nitrile group-containing ethylenically unsaturated monomer, and an alicyclic structure-containing ethylenically unsaturated monomer. It is preferable to include a structural unit derived from a body or the like. Further, 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 as the component (b), a strong interaction with the electrode material can be achieved. , Can exhibit good binding properties to active materials.
  • 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) methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, and the like.
  • Aromatic (meth) acrylic acid ester compounds such as (meth) phenyl acrylate, (meth) phenylmethyl acrylate, and (meth) phenylethyl acrylate; Examples thereof include (meth) acrylic acid alkoxyalkyl ester compounds such as 2-methoxyethyl (meth) acrylic acid and 2-ethoxyethyl (meth) acrylic acid, and one of these may be used alone. Two or more types may be used in combination.
  • 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, from the viewpoint of further improving lithium ion conductivity and high-rate characteristics. Is preferable, and 2-methoxyethyl (meth) acrylate is more preferable.
  • 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 binding force of the binder is improved. Further, as the nonionic ethylenically unsaturated monomer, a compound having a homopolymer glass transition temperature (Tg) of 0 ° C. or lower is preferable in terms of improving the bending resistance of the obtained electrode.
  • Tg homopolymer glass transition temperature
  • the crosslinked polymer may be in the form of a salt in which some or all of the carboxyl groups contained in the polymer are neutralized.
  • the type of salt is not particularly limited, but alkali metal salts such as lithium salt, sodium salt and potassium salt; alkaline earth metal salts such as calcium salt and barium salt; other metal salts such as magnesium salt and aluminum salt; ammonium. Examples thereof include salts and organic amine salts. Among these, alkali metal salts and magnesium 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 crosslinked 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) Copolymerization of crosslinkable monomers 2) Utilizing chain transfer to polymer chains during radical polymerization 3) After synthesizing a polymer having a reactive functional group, post-crosslinking is performed by adding a crosslinking agent as necessary. Since the present crosslinked polymer has a crosslinked structure, the crosslinked polymer or the binder containing a salt thereof can have an excellent binding force.
  • the method by copolymerization of crosslinkable monomers 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) acrylate 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.
  • polyfunctional (meth) acrylate compound examples 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) acrylate.
  • Di (meth) acrylates of dihydric alcohols such as meta) acrylate; trimethylol propantri (meth) acrylate, tri (meth) acrylate of trimethyl propanethylene oxide modified product, glycerin tri (meth) acrylate, pentaerythritol tri (meth) Tri (meth) acrylates of trivalent or higher polyhydric alcohols such as meta) acrylates and pentaerythritol tetra (meth) acrylates, poly (meth) acrylates such as tetra (meth) acrylates; 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, tetraallyloxyethane, and polyallyl saccharose; diallyl phthalate and the like.
  • Polyfunctional allyl compound examples thereof include polyfunctional vinyl compounds such as divinylbenzene.
  • Compounds having both (meth) acryloyl group and alkenyl group include allyl (meth) acrylate, isopropenyl (meth) acrylate, butenyl (meth) acrylate, pentenyl (meth) acrylate, and (meth) acrylate. 2- (2-Vinyloxyethoxy) ethyl and the like can be mentioned.
  • the monomer having a self-crosslinkable crosslinkable functional group include a hydrolyzable silyl group-containing vinyl monomer, N-methylol (meth) acrylamide, N-methoxyalkyl (meth) acrylate and the like. Can be mentioned. 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, vinyl methyl dimethoxysilane, vinyl dimethyl methoxysilanen; silyl such as trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, methyldimethoxysilylpropyl acrylate and the like.
  • Group-containing acrylic acid esters silyl group-containing methacrylate 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 monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.05 parts by mass or more and 5.0 parts by mass or less, more preferably 0.1 parts by mass or more and 5.0 parts by mass or less, and further preferably 0.2 parts by mass or more with respect to 100 parts by mass. It is 4.0 parts by mass or less, more preferably 0.3 parts by mass or more and 3.0 parts by mass or less.
  • the amount of the crosslinkable monomer used is 0.05 parts by mass or more, it is preferable in that the binding property and the stability of the electrode slurry are improved.
  • the amount of the crosslinkable monomer used may be 0.02 to 1.7 mol% with respect to the total amount of the monomers other than the crosslinkable monomer (non-crosslinkable monomer). It is preferably 0.10 to 1.0 mol%, more preferably 0.10 to 1.0 mol%.
  • the crosslinked polymer is a monomer component containing the above ethylenically unsaturated carboxylic acid monomer in the presence of an exchange chain transfer mechanism type control agent (hereinafter, also referred to as “the present monomer”). It is obtained by precipitation polymerization or dispersion polymerization.
  • 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 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 in which secondary agglutination is suppressed 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 polymerization method using an organic tellurium compound (TERP method)
  • TRIP method organic tellurium compound
  • SBRP method organic antimony compound
  • BIRP method organic bismuth compound
  • the exchange chain transfer mechanism type control agent a polymer 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 (hereinafter, simply "the first polymer").
  • a control agent other than the polymer can be used, which will be described in detail in paragraphs [0052] to [0078] described later.
  • the first polymer and the control agent other than the polymer may be used alone or in combination.
  • Precipitation polymerization or dispersion polymerization of this monomer in the presence of an exchange chain transfer mechanism type control agent shortens the primary chain length, and the same chain length forms a uniform crosslinked structure. It is possible to increase the degree of water swelling of the polymer.
  • the RAFT agent and the control agent in the iodine transfer polymerization method are preferable, and the RAFT agent is more preferable, because the crosslinked structure of the present crosslinked polymer can be made more uniform.
  • RAFT agents include a first polymer having a living radical polymerization active unit by a reversible addition-cleavage chain transfer method (detailed below) and / or a RAFT agent (dithioester) other than the first polymer.
  • RAFT agent dithioester
  • Compounds, xanthate compounds, trithiocarbonate compounds, dithiocarbamate compounds, etc. can be used.
  • Specific examples of the RAFT agent other than the first polymer include 2-cyano-2-propylbenzodithioate, 2-phenyl-2-propylbenzodithioate, trithiocarbonate, and 2-cyano-.
  • 2-propyldodecyltrithiocarbonate 2- (dodecylthiocarbonothio oil thio) propionic acid, 3-((1-carboxyethylthio) carbonothio oil thio)) propionic acid, 2- (dodecylthio carbonothio oil thio) Methyl 2-methylpropanoate, 1,4-bis (n-dodecylsulfanylthiocarbonylsulfanylmethyl) benzene, dibenzyltrithiocarbonate, distyryltrithiocarbonate, dicumyltrithiocarbonate, cyanomethyl-N-methyl-N- Examples thereof include phenyldithiocarbamate.
  • the RAFT agents those having trithiocarbonate in the molecule are particularly preferable in that the crosslinked structure of the present crosslinked polymer can be made more uniform.
  • a first polymer having a living radical active unit by the iodine transfer polymerization method (detailed later) and / or a control agent other than the first polymer shall be used.
  • the control agent other than the first polymer include alkyl groups such as methyl iodide, methylene iodide, iodoform, carbon tetraiodide, 1-phenylethyl iodide, and benzyl iodide.
  • Examples thereof include -2-phenylacetic acid) ethylene glycol, bis (2-iodoisobutyric acid) ethylene glycol, 1,5-diiodo-2,4-dimethylbenzene, and 2-iodopropionitrile.
  • the exchange chain transfer mechanism type control agent may be a monofunctional one having one active site, or a bifunctional or more agent having two or more active sites.
  • a bifunctional or higher exchange chain transfer mechanism type control agent is one in which a polymer chain is extended in a bidirectional or higher direction. From the viewpoint of producing the present 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 exchange chain transfer mechanism type control agent used is 0.0001 to 0.50 mol% 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 more preferable, it is more preferably 0.0001 to 0.40 mol%, further preferably 0.0001 to 0.30 mol%, and more preferably 0.0002 to 0.30 mol%. More preferred.
  • polymerization initiator used together with the exchange chain transfer mechanism type control agent 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.
  • an azo compound is preferable because it is easy to handle for safety and side reactions during radical polymerization are unlikely to occur.
  • azo compounds 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 used is, for example, 0.001 to 2 parts by mass and, for example, 0.005 to 1 part by mass, when the total amount of the monomer components used is 100 parts by mass. Further, for example, it is 0.01 to 0.1 parts by mass.
  • 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. It is preferably less than or equal to 0.2 mol or less. Further, from the viewpoint of stably performing the polymerization reaction, 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 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.
  • Specific examples of 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.
  • the water-soluble solvent refers to a solvent having a solubility in water at 20 ° C. of more than 10 g / 100 ml.
  • Methyl ethyl ketone and acetonitrile are different in that they are easy to unravel), that a polymer with a small chain transfer constant and a large degree of polymerization (primary chain length) can be obtained, and that the operation is easy 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 to 20.0% by mass, more preferably 0.1 to 10.0% by mass, still more preferably 0.1 to 5% by mass based on the total mass of the medium. It is 0.0% by mass, more preferably 0.1 to 1.0% by mass.
  • 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.
  • a highly polar solvent 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 exchange chain transfer mechanism type controller 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 higher. It is below ° C.
  • 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.
  • the crosslinked polymer dispersion obtained through the polymerization step can be obtained in a powder state by subjecting the dispersion to a reduced pressure and / or heat treatment in the drying step and distilling off the solvent.
  • a solid-liquid separation step such as centrifugation and filtration, an organic solvent or an organic solvent / water. It is preferable to include a cleaning step using a mixed solvent.
  • an alkaline compound is added to the dispersion of the crosslinked polymer obtained in the polymerization step to add weight.
  • step neutralization After neutralizing the coalescence (hereinafter, also referred to as "step neutralization"), the solvent may be removed in a drying step.
  • post-neutralization an alkaline compound is added when preparing the slurry composition to neutralize the polymer (hereinafter, "post-neutralization”). It may also be called).
  • post-neutralization is added when preparing the slurry composition to neutralize the polymer. It may also be called).
  • process neutralization is preferable because the secondary aggregates tend to be easily disintegrated.
  • first monomer a polymerized chain of one kind or two or more kinds of vinyl-based monomers (hereinafter, also simply referred to as “first monomer”)
  • first monomer a polymer (first polymer) having a living radical polymerization active unit by an exchange chain transfer mechanism and a “first polymer chain”
  • the first polymer is used as a starting point for the polymerization of the present monomer and the polymerization of the crosslinked polymer.
  • the present crosslinked 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 first polymer, is obtained as dispersed fine particles. Can be done. By doing so, the polymerization stability, that is, the aggregation of the present crosslinked polymer during the polymerization step is suppressed, the generation of coarse aggregated particles is suppressed, the particle size is small, and the particle size distribution is narrow. You can get coalescence.
  • the first polymer In order to make the first polymer function as a dispersion stabilizer in producing the present crosslinked polymer by polymerizing the present monomer in the presence of the first polymer, for example, the first polymer is 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 it in such a range, it is possible to produce the present crosslinked polymer mainly containing the present monomer while allowing the first polymer to function as a dispersion stabilizer.
  • the amount of the first polymer 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 first polymer can be used with respect to 100 parts by mass of the total mass of the present monomer, for example, 0.5 parts by mass or more, and for example, 1 part by mass or more. Further, the first polymer 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 first polymer used with respect to 100 parts by mass of the total mass of the present monomer can be set by appropriately combining the above upper limit and lower limit.
  • the polymerization conditions for producing the first polymer 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 described in the above paragraphs [0040] to [0043] and [0045] to [0049].
  • 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 first polymer.
  • 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 first polymer can be reduced.
  • the concentration at the time of producing the first polymer 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 functionalitys is used.
  • a control agent when used, it is branched in two or more directions with the living polymerization active unit as a base point, and each of them is provided with a first polymerization chain.
  • the other polymerized chain when another polymerized chain is provided, 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 first polymer may also include two or more 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 first polymer having a first polymerization 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 first polymer 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 50,000 or less, for example, 30,000 or less, and for example, 25,000 or less, and for example, 20,000 or less, and for example, 15,000 or less. And, for example, 14,000 or less, and for example, 12,000 or less.
  • the range of Mn can be set by appropriately combining the above-mentioned lower limit and upper limit, and is, for example, 5,000 or more and 25,000 or less, and for example, 10,000 or more and 25,000 or less. For example, it is 10,000 or more and 15,000 or less, and for example, 10,000 or more and 14,000 or less.
  • the weight average molecular weight (Mw) of the first polymer 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 60,000 or less, 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, and for example, 35,000 or less, and for example, 30,000 or less, and for example, 25,000 or less.
  • the range of Mw can be set by appropriately combining the above-mentioned lower limit and upper limit, and is, for example, 1,000 or more and 40,000 or less, and for example, 10,000 or more and 35,000 or less. For example, it is 10,000 or more and 30,000 or less, and for example, 15,000 or more and 25,000 or less.
  • Both Mw and Mn of the first polymer can be measured by gel permeation chromatography using polystyrene as a standard substance.
  • the details of the chromatography conditions the conditions disclosed in the subsequent examples can be adopted.
  • the molecular weight distribution (Mw / Mn) of the first polymer 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. For example, 1.1 or more and 2.5 or less, for example, 1.1 or more and 2.4 or less, and for example, 1 It can be 1 or more and 2.3 or less, and for example, 1.1 or more and 2.0 or less.
  • 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.
  • first monomer examples include styrenes, (meth) acrylonitrile compounds, maleimide compounds, unsaturated acid anhydrides and unsaturated carboxylic acid compounds. One or a combination of two or more of these can be used.
  • Styrenes include styrene and its derivatives. Specific compounds include styrene, ⁇ -methylstyrene, ⁇ -methylstyrene, vinyltoluene, vinylxylene, vinylnaphthalene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o-ethylstyrene, and m-.
  • 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, acrylonitrile, ⁇ -methylacrylonitrile, and the like.
  • 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-butyl.
  • N-alkyl-substituted maleimide compounds such as maleimide, N-pentylmaleimide, N-hexylmaleimide, N-heptylmaleimide, N-octylmaleimide, N-laurylmaleimide, N-stearylmaleimide; N-cyclopentylmaleimide, N-cyclohexylmaleimide, etc.
  • N-Cycloalkyl-substituted maleimide compounds N-phenylmaleimide, N- (4-hydroxyphenyl) maleimide, N- (4-acetylphenyl) maleimide, N- (4-methoxyphenyl) maleimide, N- (4-ethoxy) Examples thereof include N-aryl-substituted maleimide compounds such as phenyl) maleimide, N- (4-chlorophenyl) maleimide, N- (4-bromophenyl) maleimide, and N-benzylmaleimide, and one or more of these. Can be used. For example, 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 compounds include (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, citraconic acid, silicic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, maleic anhydride, and anhydrous.
  • unsaturated dicarboxylic acids such as itaconic acid and citraconic anhydride, and monoalkyl esters of unsaturated dicarboxylic acids, and one or more of them can be used.
  • the first monomer preferably contains, for example, at least styrenes.
  • styrenes are easy to carry out 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 present crosslinked polymer is produced by the dispersion polymerization method in a polar organic solvent, the first polymer tends to be present on the surface layer of the present crosslinked polymer. The dispersion stability of the crosslinked polymer is improved.
  • Styrene is, for example, 20% by mass or more of the total mass of the first monomer. This is because if 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, and 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, and are, for example, 95% by mass or less, and are, for example, 90% by mass or less, and are, for example, 85% by mass or less, and are, 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, and is, for example, 20% by mass or more and 95% by mass or less, and for example, 30% by mass or more and 75% by mass or more. And, for example, 35% by mass or more and 85% by mass or less.
  • 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 first polymer 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 for example, 30% by mass or more, and for example, 35% by mass or more, and for example, 40% by mass or more, and 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 of the total mass, and is, 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. 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 lower limit and upper limit, and is, for example, 20% by mass or more and 65% by mass or less, and for example, 25% by mass or more and 50% by mass or more. It is as follows.
  • 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 first polymer may include 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.
  • a radical polymerization initiator and another vinyl-based monomer are continuously or newly supplied to the first polymer having the first polymer chain to have a composition different from that of the first polymer chain. It is possible to obtain a first polymer having another polymer chain (block) composed of units derived from a monomer other than the first monomer.
  • 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 first polymer.
  • the first polymer has a living radical polymerization active unit by an exchange chain transfer mechanism, it can be used as a solubility or dispersion stabilizer in the polymerization solvent of the first polymer in the precipitation polymerization or dispersion polymerization of this monomer.
  • Various monomers can be selected for the function of.
  • RAFT method reversible addition-cleavage chain transfer polymerization method
  • iodine transfer polymerization method a polymerization method using an organic tellurium compound
  • TMP method a polymerization method using an organic tellurium compound
  • 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 crosslinked polymer or a salt thereof is 1% by mass of the crosslinked polymer neutralized to a neutralization degree of 50 to 100 mol% by a small-angle X-ray scattering method (measurement temperature: 25.0 ⁇ 0.1 ° C.).
  • the non-uniform network structure size ⁇ ( ⁇ 1) of the crosslinked polymer calculated by curve fitting with the following formula (1) is 80 or less with respect to the scattering intensity curve I (q) obtained by measuring the concentrated aqueous solution. Is.
  • the above equation (1) is a correlation between the “Lorentz square model” (Shibayama M.
  • ⁇ 1 is the coatability and coating performance of the composition containing the crosslinked polymer or a salt thereof (in the case of a composition containing a binder for a secondary battery electrode containing the crosslinked polymer or a salt thereof, an active material and water).
  • 5 of the crosslinked polymer neutralized to a degree of neutralization of 50 to 100 mol% by the above-mentioned ⁇ 1 and the small-angle X-ray scattering method (measurement temperature: 25.0 ⁇ 0.1 ° C.).
  • the non-uniform network structure size ⁇ ( ⁇ 5) of the crosslinked polymer calculated by curve fitting with the above formula (1) with respect to the scattering intensity curve I (q) obtained by measuring the mass% concentration aqueous solution.
  • the difference ⁇ ( ⁇ 1- ⁇ 5) is preferably 50 or less, more preferably 30 or less, further preferably 20 or less, further preferably 10 or less, and 5.0 or less. Is even more preferable.
  • ⁇ 1 and ⁇ 5 are obtained by a method according to the method described in Examples.
  • the crosslinked polymer or a salt thereof 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 crosslinked polymer or a salt thereof absorbs water and becomes swollen in water.
  • the crosslinked polymer has an appropriate degree of crosslinkage, the larger the amount of hydrophilic groups contained in 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 crosslinked 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-crosslinking reaction, and the like.
  • the primary chain length of the polymer can be adjusted by setting conditions related to the amount of radicals generated such as the initiator and the polymerization temperature, and selecting the polymerization solvent in consideration of chain transfer and the like.
  • the crosslinked polymer does not exist as a mass (secondary agglomerate) having a large particle size, but is well dispersed as water-swelled particles having an appropriate particle size.
  • a binder containing the above 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 5.0 ⁇ m or less.
  • the more preferable range of the particle size is 0.1 ⁇ m or more and 4.0 ⁇ m or less, the more preferable range is 0.1 ⁇ m or more and 3.0 ⁇ m or less, and the more preferable range is 0.2 ⁇ m or more and 3.0 ⁇ m or less. Yes, and even more preferable ranges are 0.3 ⁇ m or more and 3.0 ⁇ m or less.
  • the composition When the particle size is in the range of 0.1 ⁇ m or more and 5.0 ⁇ 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 to do. If the particle size exceeds 5.0 ⁇ 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.
  • 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 degree of neutralization is 20 mol% or more, the water swelling property is good and the dispersion stabilizing effect is easily obtained, which is preferable.
  • the degree of neutralization can be calculated by calculation from the charged values of a monomer having an acid group such as a carboxyl group and a neutralizing agent used for neutralization.
  • the crosslinked polymer or a salt thereof preferably has a water swelling degree of 20 or more and 80 or less at pH 8.
  • the degree of water swelling is within the above range, the crosslinked polymer or a salt thereof swells appropriately in an aqueous medium, so that a sufficient adhesive area to the active material and the current collector is provided when forming the electrode mixture layer. It becomes possible to secure it, and the binding property tends to be good.
  • 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 or a salt thereof 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, and is, for example, 23 or more and 70 or less, and for example, 25 or more and 65 or less, and for example, 25. It is 55 or less.
  • the degree of water swelling at pH 8 can be obtained by measuring the degree of swelling of the crosslinked polymer or a salt thereof 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.
  • a person skilled in the art can adjust the degree of water swelling by controlling the composition and structure of the crosslinked polymer or a salt thereof.
  • 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 secondary battery electrode mixture layer of the present invention contains the present binder, 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 parts by mass or more, sufficient binding property can be obtained.
  • the dispersion stability of the active material and 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 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.
  • a lithium salt of a transition metal oxide can be used as the positive electrode active material, and for example, a layered rock salt type and a spinel type lithium-containing metal oxide can be used.
  • a spinel type positive electrode active material lithium manganate and the like can be mentioned.
  • phosphates 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 dispersion liquid becomes alkaline by exchanging lithium ions on the surface of the active material and hydrogen ions in water. Therefore, there is a risk that aluminum foil (Al) or the like, which is a general current collector material for positive electrodes, will be corroded. In such a case, it is preferable to neutralize the alkali content eluted from the active material by using the present crosslinked polymer which has not been neutralized or partially neutralized as the binder.
  • the amount of the unneutralized or partially neutralized present crosslinked polymer used is such that the amount of unneutralized carboxyl groups 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.
  • a conductive auxiliary agent since all positive electrode active materials have low electrical conductivity, they are generally used by adding a conductive auxiliary agent.
  • 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.
  • the conductive auxiliary agent one of the above types may be used alone, or two or more types 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 whose surface is coated 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 a combination of two or more of these can be used.
  • 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 such as silicon or tin that can occlude lithium or a metal oxide can 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 charging and discharging 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 additive 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 a part by mass.
  • 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 the drying cost of the medium is also advantageous. 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, and water-soluble organic substances such as tetrahydrofuran and N-methylpyrrolidone. It may be a mixed solvent with a 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 become insufficient.
  • SBR-based latex and CMC are preferable, and SBR
  • the SBR 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 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. It can be in the range of% by mass.
  • aliphatic conjugated diene-based monomer in addition to 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3- Butadiene and the like can be mentioned, and one or more of these can be used.
  • 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.
  • styrene / butadiene-based monomers include nitrile group-containing monomers such as (meth) acrylonitrile and (meth) as other monomers in order to further improve performance such as binding properties.
  • a carboxyl group-containing monomer such as acrylic acid, itanconic acid, and maleic acid, and an ester group-containing monomer such as methyl (meth) acrylate may be used as the copolymerization monomer.
  • 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 CMC refers to a substitute obtained by substituting a nonionic cellulosic semi-synthetic 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, hydroxybutyl methyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl 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 the respective components using 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 material, a conductive additive and a binder are dry-blended and then mixed with a dispersion medium such as water.
  • the method of dispersion kneading is preferable.
  • the present composition is obtained in a slurry state, it is preferable to finish the composition into a slurry having no poor dispersion or aggregation.
  • 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 effects of the present invention are exhibited, but is preferably less than 12.5. For example, when CMC is blended, there is little concern about hydrolysis thereof, and 11.5. 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, the range of 1,000 to 4,000 mPa ⁇ s.
  • the viscosity of the slurry is within the above range, good coatability can be ensured.
  • Secondary battery electrode The secondary battery electrode of the present invention is provided with 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 can be adopted. can.
  • 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 mold press, a roll press or the like. By compressing, the active material and the binder can be brought into close contact with each other, and the strength of the mixture layer and the adhesion to the current collector can be improved.
  • the thickness of the mixture layer can be adjusted to, for example, about 30 to 80% before compression by 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 the secondary battery electrode of the present invention with a separator and an electrolytic solution.
  • 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 membrane 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 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 form carbonates, which 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 secondary battery provided with the electrode having the mixture layer formed from the composition for the mixture layer for the secondary battery electrode containing the binder for the secondary battery electrode disclosed in the present specification It is suitable for in-vehicle secondary batteries and the like because it exhibits good durability (cycle characteristics) even after repeated charging and discharging.
  • image processing software Igor Pro8
  • the two-dimensional scattering image for analysis was converted into a one-dimensional scattering spectrum. Specifically, the two-dimensional scattering image for analysis is read into X-ray data processing software (Igor Pro8) and integrated over all directional angles, so that the horizontal axis is the scattering vector q ( ⁇ -1 ) and the vertical axis is the vertical axis. A one-dimensional scattering spectrum (scattering intensity curve I (q)) was obtained. Next, as the baseline correction, the minimum value of the scattering intensity in the analysis target region was obtained, and the minimum value was subtracted over the entire region to perform the baseline correction.
  • X-ray data processing software Igor Pro8
  • the obtained corrected one-dimensional scattering profile was fitted using the following formula (1) to determine ⁇ ( ⁇ 1) in a 1% by mass aqueous solution and ⁇ ( ⁇ 5) in a 5% by mass aqueous solution.
  • ⁇ means the structural size of the non-uniform network of the crosslinked polymer, and as shown in FIG. 1, when there is a portion having a dense degree of crosslink, the size is described by ⁇ . .. Waveform separation software (Igor Pro8) was used for fitting.
  • the measuring device is shown in FIG.
  • the measuring device is composed of ⁇ 1> to ⁇ 3> in FIG. ⁇ 1> It is composed of a burette 1, a pinch cock 2, a silicon tube 3 and a polytetrafluoroethylene tube 4 having a branch tube for venting air.
  • a support cylinder 8 having a large number of holes on the bottom surface is installed on the funnel 5, and a filter paper 10 for an apparatus is installed on the support cylinder 8.
  • the sample 6 (measurement sample) of the crosslinked polymer or a salt thereof is sandwiched between two sample fixing filter papers 7, and the sample fixing filter paper is fixed by the adhesive tape 9.
  • All the filter papers used are ADVANTEC No. 2.
  • the inner diameter is 55 mm.
  • ⁇ 1> and ⁇ 2> are connected by a silicon tube 3.
  • the heights of the funnel 5 and the support cylinder 8 are fixed with respect to the burette 1, and the lower end of the polytetrafluoroethylene tube 4 installed inside the burette branch pipe and the bottom surface of the support cylinder 8 are at the same height. (Dotted line in FIG. 1).
  • the measuring method will be described below.
  • the pinch cock 2 in ⁇ 1> is removed, ion-exchanged water is poured from the upper part of the burette 1 through the silicon tube 3, and the burette 1 to the filter paper 10 for the device are filled with the ion-exchanged water 12.
  • the pinch cock 2 is closed, and air is removed from the polytetrafluoroethylene tube 4 connected to the burette branch pipe with a rubber stopper. In this way, the ion-exchanged water 12 is continuously supplied from the burette 1 to the filter paper 10 for the apparatus.
  • the reading (a) of the scale of the burette 1 is recorded.
  • the water absorption amount (d) of only two filter papers 7 containing no sample of the crosslinked polymer or a salt thereof is measured.
  • the above operation was performed, and the degree of water swelling was calculated from the following formula.
  • the value measured by the method described later was used.
  • Water swelling degree ⁇ dry weight of measurement sample (g) + (cd) ⁇ / ⁇ dry weight of measurement sample (g) ⁇
  • the dry weight (g) of the measurement sample the weight (g) of the measurement sample ⁇ (solid content (%) ⁇ 100)
  • the particle size distribution of the hydrogel was measured with a laser diffraction / scattering particle size distribution meter (Microtrack MT-3300EXII, manufactured by Microtrac Bell) using ion-exchanged water as a dispersion medium.
  • a laser diffraction / scattering particle size distribution meter Microtrack MT-3300EXII, manufactured by Microtrac Bell
  • the particle size distribution shape measured after several 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.
  • a hydrogel fine particle dispersion in which the polymer salt was swollen in water was prepared. After adjusting each of the obtained hydrogel fine particle dispersions to 25 ° C. ⁇ 1 ° C., the viscosity at a rotor speed of 12 rpm was measured using a B-type viscometer (TVB-10 manufactured by Toki Sangyo Co., Ltd.).
  • the reaction rate of the obtained polymer 1 was 72%.
  • the molecular weight of the polymer 1 was Mn11,900, Mw15,500, and Mw / Mn was 1.30. Styrene and acrylonitrile correspond to the first monomer.
  • the molecular weight of the first polymer was measured by gel permeation chromatography (GPC). That is, a polystyrene-equivalent number average molecular weight (Mn) and a weight average molecular weight (Mw) were obtained by THF-based GPC. Moreover, the molecular weight distribution (Mw / Mn) was calculated from the obtained values.
  • GPC gel permeation chromatography
  • LiOH / H 2 O 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 to remove the supernatant was repeated twice.
  • the precipitate was recovered and dried at 80 ° C. for 3 hours under reduced pressure conditions to remove volatile components to obtain a powder of the carboxyl group-containing polymer salt R-1. Since the carboxyl group-containing polymer salt R-1 has hygroscopicity, it was stored in a container having a water vapor barrier property.
  • the degree of water swelling was 36.4, the particle size in the aqueous medium was 1.72 ⁇ m, and the viscosity of the 2% by mass aqueous solution was 9,110 mPa ⁇ s.
  • Table 1 shows the degree of water swelling of R-2 to R-17, the particle size in the aqueous medium, and the viscosity of the 2% by mass aqueous solution.
  • the particle diameter in an aqueous medium of R-3 (degree of neutralization 70 mol%) was measured after adjusting the neutralization degree of 90 mol% by LiOH ⁇ H 2 O.
  • FIG. 1 An example of the small-angle X-ray scattering measurement result is shown in FIG. 1 (Production Example 2: R-2, Comparative Production Example 2: R-17).
  • a broad peak was observed in the vicinity of q of 0.03 to 0.10 ⁇ -1 in a 1% by mass aqueous solution. This is a peak due to scattering of charged groups derived from carboxyl groups existing inside the particles in which the hydrogel fine particles are dispersed in water.
  • a peak was observed in the vicinity of q 0.07 to 0.20 ⁇ -1. It can be considered that this is because the hydrogel fine particles were densely packed in water and the structure was apparently uniform, so that the peak derived from the cross-linking was confirmed.
  • R-2 showed a small value of ⁇ in a 1% by mass aqueous solution and a small value of ⁇ as compared with R-17, it is considered that R-2 has a more uniform crosslinked structure. be able to.
  • ⁇ 1, ⁇ 5 calculated by curve fitting the scattering intensity curve I (q) obtained by measuring R-1, R-3 to R-16 by small-angle X-ray scattering by the following formula (1). And ⁇ are shown in Table 1.
  • composition containing carboxyl group-containing crosslinked polymer salt >> (Example 1: Evaluation of composition containing carboxyl group-containing crosslinked polymer salt R-1) ⁇ Preparation of slurry composition (composition for electrode mixture layer)> Prepare a SiOx (0.8 ⁇ x ⁇ 1.2) surface coated with 10% carbon by the CVD method (hereinafter referred to as "Si-based active material"), and prepare artificial graphite and Si-based active material. The mixture was used as the active material.
  • Si-based active material a SiOx (0.8 ⁇ x ⁇ 1.2) surface coated with 10% carbon by the CVD method
  • Si-based active material As the binder, a mixture of the present crosslinked polymer salt R-1, styrene-butadiene rubber (SBR) -based latex, and carboxymethyl cellulose (CMC) was used.
  • NMP N-methylpyrrolidone
  • VGCF vapor layer carbon fiber
  • PVDF polyvinylidene fluoride
  • a mixture layer was formed by applying the positive electrode composition to an aluminum current collector (thickness: 15 ⁇ m) and drying it. Then, after rolling so that the thickness of the mixture layer was 88 ⁇ m and the packing density was 3.1 g / cm 3 , the mixture was punched 3 cm square to obtain a positive electrode plate.
  • a lithium ion secondary battery of a laminated cell was produced.
  • the electrolytic solution one in which LiPF 6 was dissolved at a concentration of 1.0 mol / liter in a mixed solvent containing ethylene carbonate (EC) and ethyl methyl carbonate (DEC) at a volume ratio of 25:75 was used.
  • the performance of the coating film obtained from the electrode slurry was evaluated by measuring the cycle characteristics of the lithium ion secondary battery.
  • the lithium-ion secondary battery of the laminated cell produced above is charged / discharged at a charge / discharge rate of 0.2 C under the conditions of 2.7 to 3.4 V by CC discharge to obtain an initial capacity of C0. It was measured. Further, charging and discharging were repeated in an environment of 25 ° C., and the capacity C50 after 50 cycles was measured.
  • the cycle characteristic ( ⁇ C) calculated by the following formula was 91.8%, and the cycle characteristic based on the following criteria was evaluated as “ ⁇ ”. The higher the value of ⁇ C, the better the cycle characteristics.
  • ⁇ C C50 / C0 ⁇ 100 (%) ⁇ Evaluation criteria> ⁇ : Charge / discharge capacity retention rate is 95.0% or more ⁇ : Charge / discharge capacity retention rate is 90.0% or more and less than 95.0% ⁇ : Charge / discharge capacity retention rate is 85.0% or more and less than 90.0% ⁇ : Charge / discharge capacity retention rate is less than 85.0%
  • Example 2 to 15 and Comparative Examples 1 to 2 An electrode slurry was prepared as a slurry composition by performing the same operation as in Example 1 except that the crosslinked polymer salt was as shown in Table 2, and the slurry viscosity was measured. In addition, the coatability of the electrode slurry and the cycle characteristics of the secondary battery obtained by using the electrode slurry were evaluated. The results are shown in Table 2.
  • the non-uniform network structure size ⁇ 1 was smaller than when the iodine transfer polymerization control agent was used (Example 13), and ⁇ ( ⁇ 1- ⁇ 5) was used. ) Is also a small value, so that the coating performance is excellent (in this embodiment, the charge / discharge capacity retention rate is high and the cycle characteristics are excellent).
  • a slurry composition containing a crosslinked polymer having a non-uniform network structure size ⁇ 1 of more than 80 either the coating film performance (cycle characteristics of the secondary battery) or the coatability was significantly inferior (). Comparative Examples 1 and 2).
  • the composition containing the carboxyl group-containing crosslinked polymer of the present invention or a salt thereof is excellent in both coatability and coating performance, it is a thickener for cosmetics, a viscosity modifier, and a non-aqueous electrolyte secondary battery electrode. It is expected to be applied to various applications such as binders for plastics, anti-settling agents for pigments, and dispersion stabilizers for metal powders.
  • a secondary battery provided with an electrode obtained by using a composition for a secondary battery electrode mixture layer containing a binder for a secondary battery electrode containing the carboxyl group-containing crosslinked polymer of the present invention or a salt thereof. Is expected to be applied to in-vehicle secondary batteries because it exhibits good durability (cycle characteristics). It is also useful for the use of active materials containing silicon, and is expected to contribute to increasing the capacity of batteries. Above all, it is useful for a non-aqueous electrolyte lithium ion secondary battery having a high energy density.

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Abstract

La présente invention concerne un polymère réticulé contenant un groupe carboxyle ou un sel de celui-ci, qui peut atteindre à la fois une aptitude au revêtement et une performance de film de revêtement d'une composition contenant le polymère réticulé ou le sel de celui-ci.　Le polymère réticulé contenant un groupe carboxyle ou le sel de celui-ci est fourni de telle sorte que la taille de structure de réseau non uniforme Ξ du polymère réticulé est au maximum égale à 80, telle que calculée par ajustement de courbe, avec l'équation (1), la courbe d'intensité de diffusion I (q) qui est obtenue par mesure d'une solution aqueuse à 1 % en masse du polymère réticulé neutralisé à un degré de neutralisation de 50 à 100 % en moles par le biais d'un procédé de diffusion de rayons X à petit angle (température de mesure : 25,0 ± 0,1 °C). FIG. : I(q)%%%Intensité de rayonnement diffusé Ξ%%%Taille de structure de réseau non uniforme de polymère réticulé A%%%Paramètre d'ajustement B%%%Paramètre d'ajustement q%%%Vecteur de diffusion q*%%%Distance entre groupes chargés L%%%Longueur de blindage électrostatique de la chaîne polymère m%%%Paramètre d'ajustement
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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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