Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
  • H01M4/139—Processes of manufacture
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • 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
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/13—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
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/364—Composites as mixtures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a method for producing a slurry composition for secondary battery electrodes, and a method for producing secondary battery electrodes and secondary batteries.
• Electrodes used in these secondary batteries are produced by coating and drying a composition for forming an electrode mixture layer containing an active material, a binder, and the like on a current collector.
• a composition for forming an electrode mixture layer containing an active material, a binder, and the like on a current collector.
• an aqueous binder containing styrene-butadiene rubber (SBR) latex and carboxymethyl cellulose (CMC) is used as the binder used in the negative electrode slurry composition.
• SBR styrene-butadiene rubber
• CMC carboxymethyl cellulose
• PVDF polyvinylidene fluoride
• NMP N-methyl-2-pyrrolidone
• a secondary battery electrode is obtained by applying and drying a secondary battery electrode slurry composition (hereinafter also referred to as "electrode slurry") containing an active material, a thickener and a binder on the surface of an electrode current collector. be done.
• electrode slurry a secondary battery electrode slurry composition
• Patent Document 1 discloses that a negative electrode active material, CMC and water are kneaded to form a primary kneaded body (solid content concentration: 70% by mass or less), and further adding water to the primary kneaded body to dilute it, and adding a binder to produce a negative electrode paste for manufacturing a negative electrode.
• a method for manufacturing an electrolyte secondary battery is described.
• Patent Document 1 specifically discloses a method for producing a slurry composition for a negative electrode (hereinafter also referred to as "negative electrode slurry”) using CMC as a thickener and SBR as an aqueous binder, and the output characteristics are improved.
• negative electrode slurry a method for producing a slurry composition for a negative electrode (hereinafter also referred to as "negative electrode slurry") using CMC as a thickener and SBR as an aqueous binder, and the output characteristics are improved.
• peel strength can be ensured while using CMC with high viscosity in the
• the step (B) comprises a step (B1) of obtaining a mixture (M2) by blending the liquid component in the mixture (M1), and adding a second thickener and the liquid component to the mixture (M2). and a step (B3) of obtaining the paste precursor by kneading the mixture (M3) in at least this order.
• Patent Document 2 specifically discloses a method for producing a negative electrode slurry composition (negative electrode slurry) having a solid content concentration of 51% by mass, using CMC as a thickener and SBR as an aqueous binder. It is described that it is possible to stably obtain a negative electrode for a battery having excellent adhesiveness between the body layer and the negative electrode active material layer.
• Patent Document 3 after dry-mixing a plurality of powdery materials containing at least a negative electrode active material and a thickener in a powder state, an aqueous medium and an aqueous solution containing an aqueous binder are added and wet-mixed.
• the process includes at least a first hard kneading step (solid content concentration: 68% by mass or more and 79% by mass or less) and a second hard kneading step (solid content concentration: 59% by mass or more and 66% by mass or less).
• a step-by-step process is described.
• Patent Document 3 specifically discloses a method for producing a negative electrode slurry composition (negative electrode slurry) having a solid content concentration of 59 to 66% by mass, using CMC as a thickener and SBR as an aqueous binder. It is described that the viscosity of the negative electrode slurry can be controlled within a certain range, and a secondary battery negative electrode having excellent adhesiveness between the negative electrode active material layer and the current collector layer can be stably obtained.
• the coating properties of the slurry composition for secondary battery electrodes (electrode slurry), and the adhesion between the electrode active material layer and the current collector layer (hereinafter, “ (also referred to as “peeling strength”) is required.
• Patent Documents 1 and 2 can both provide good peel strength, there is no indication of the relationship between the production methods, the viscosity of the electrode slurry, and the coatability. Moreover, it is described that the production method described in Patent Document 3 can impart good coatability and peel strength.
• the production methods described in Patent Documents 1 to 3 when a slurry composition for a secondary battery electrode is produced using a binder that is more hydrophilic than SBR as an aqueous binder, the viscosity of the composition increases. However, there is a problem that it is difficult to achieve both the coatability of the electrode slurry and the peel strength.
• the present invention has been made in view of the above circumstances, and its object is to improve coatability by reducing the viscosity of the composition when the solid content concentration of the slurry composition for secondary battery electrodes is higher than before. It is an object of the present invention to provide a method for producing the same composition, which can obtain a secondary battery electrode exhibiting excellent peel strength (binding property) while ensuring the same. In addition, it is another object of the present invention to provide a method for producing a secondary battery electrode and a method for producing a secondary battery obtained by using the slurry composition.
• a composition containing an active material, a thickener and water and having a solid content concentration within a specific range is kneaded to form a first kneaded product.
• a method for producing a slurry composition for a secondary battery electrode comprising a step C of adjusting the mass%.
• step B includes a step B1 of adding an aqueous solution of the hydrophilic binder to the first kneaded material and kneading to obtain a second kneaded material.
• a method for producing a slurry composition for a secondary battery electrode [3] The step B includes a step B2 of adding the hydrophilic binder to the first kneaded material and kneading it hard, and further adding water and kneading the hard kneaded material to obtain a second kneaded material.
• the hydrophilic binder is obtained by polymerizing a monomer component containing an ethylenically unsaturated carboxylic acid monomer.
• the hydrophilic binder is crosslinked with a crosslinkable monomer, and the amount of the crosslinkable monomer used is 0.001 mol% or more with respect to the total amount of non-crosslinkable monomers.
• the viscosity of the slurry composition is reduced to ensure coatability and excellent It is possible to obtain a secondary battery electrode exhibiting excellent peel strength (binding property).
• the slurry composition for secondary battery electrodes of the present invention contains a thickener, an active material, a hydrophilic binder and water.
• the above slurry composition is in a slurry state that can be applied to a current collector.
• a 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 copper foil or aluminum foil.
• a hydrophilic binder is preferable because the effect of the present invention is particularly large when it is used in a slurry composition for a secondary battery electrode containing a silicon-based active material, which will be described later, as an active material.
• (meth)acryl means acryl and/or methacryl
• (meth)acrylate means acrylate and/or methacrylate
• a “(meth)acryloyl group” means an acryloyl group and/or a methacryloyl group.
• the thickener is not particularly limited as long as it improves the coatability of the slurry composition for secondary battery electrodes (however, it differs from the hydrophilic binder according to the present invention).
• a thickener for example, a cellulose-based water-soluble polymer, a substituted product obtained by substituting a carboxymethyl group on a cellulose-based water-soluble polymer, or a salt thereof (hereinafter, the substituted product or a salt thereof may be collectively referred to as "CMC").
• CMC alginic acid or its salts, oxidized starch, phosphorylated starch, casein, starch and the like.
• CMC is easy to obtain an electrode slurry with excellent coatability by being adsorbed to the active material, and it is possible to obtain a secondary battery electrode that exhibits excellent peel strength (binding property). preferable.
• cellulose-based water-soluble polymer examples include alkyl celluloses such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose, and microcrystalline cellulose; Hydroxyalkylcellulose such as hydroxyethylcellulose, hydroxybutylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose stearoxyether, carboxymethylhydroxyethylcellulose, alkylhydroxyethylcellulose, nonoxynylhydroxyethylcellulose and the like.
• alkyl celluloses such as methyl cellulose, methyl ethyl cellulose, ethyl cellulose, and microcrystalline cellulose
• Hydroxyalkylcellulose such as hydroxyethylcellulose, hydroxybutylmethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, hydroxyethylmethylcellulose, hydroxypropylmethylcellulose stearoxyether, carboxymethylhydroxyethylcellulose
• a lithium salt of a transition metal oxide can be used.
• layered rock salt type and spinel type lithium-containing metal oxides can be used.
• lithium manganate etc. are mentioned as a spinel type positive electrode active material.
• phosphates include olivine-type lithium iron phosphate.
• the positive electrode active material one of the above materials may be used alone, or two or more of them may be used in combination as a mixture or composite.
• the positive electrode active material containing the layered rock salt-type lithium-containing metal oxide When the positive electrode active material containing the layered rock salt-type lithium-containing metal oxide is dispersed in water, the lithium ions on the surface of the active material are exchanged with the hydrogen ions in the water, so that the dispersion becomes alkaline. For this reason, aluminum foil (Al) or the like, which is a general positive electrode current collector material, may be corroded. In such a case, it is preferable to neutralize the alkali content eluted from the active material by using the present polymer which has not been neutralized or partially neutralized as the hydrophilic binder. In addition, the amount of the unneutralized or partially neutralized polymer used should be such that the amount of unneutralized carboxyl groups of the polymer is equal to or greater than the amount of alkali eluted from the active material. is preferred.
• conductive aids include carbon-based materials such as carbon black, carbon nanotubes, carbon fibers, graphite fine powder, and carbon fibers. is preferred. As carbon black, ketjen black and acetylene black are preferable.
• the conductive aid may be used alone or in combination of two or more. From the viewpoint of achieving both conductivity and energy density, the amount of the conductive aid 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. .2 to 10 parts by mass.
• the positive electrode active material may be surface-coated with a conductive carbonaceous material.
• examples of negative electrode active materials include carbon-based materials, lithium metals, lithium alloys, and metal oxides, and one or more of these can be used in combination.
• active materials made of carbon-based materials such as natural graphite, artificial graphite, hard carbon and soft carbon (hereinafter also referred to as "carbon-based active materials") are preferable, and graphite such as natural graphite and artificial graphite, and hard carbon are more preferred.
• graphite spherical graphite is preferably used from the standpoint of battery performance, and the preferred range of particle size is, for example, 1 to 20 ⁇ m, and for example, 5 to 15 ⁇ m.
• a metal such as silicon or tin, or a metal oxide that can occlude lithium can be used as the negative electrode active material.
• silicon has a higher capacity than graphite, and active materials made of silicon-based materials such as silicon, silicon alloys, and silicon oxides such as silicon monoxide (SiO) (hereinafter also referred to as "silicon-based active materials”) ) can be used.
• silicon-based active materials have a high capacity, it undergoes a large change in volume during charging and discharging. Therefore, it is preferable to use it together with the carbon-based active material.
• the silicon-based active material if the silicon-based active material is contained in a large amount, the electrode material may collapse and the cycle characteristics (durability) may be greatly reduced. From this point of view, when the silicon-based active material is used together, the amount used is, for example, 60% by mass or less, and for example, 30% by mass or less, relative to the carbon-based active material.
• the carbon-based active material itself has good electrical conductivity, so it is not always necessary to add a conductive aid.
• a conductive agent is added for the purpose of further reducing resistance, the amount used is, for example, 10 parts by mass or less with respect to 100 parts by mass of the total amount of active materials from the viewpoint of energy density, and for example, 5 parts by mass. Part by mass or less.
• the hydrophilic binder used in the present invention has a structural unit derived from a hydrophilic vinyl-based monomer, and the monomer may be any radically polymerizable hydrophilic vinyl-based monomer. There is no particular limitation (however, it is different from the thickening agent).
• the hydrophilic binder used in the present invention may be a crosslinked polymer (hereinafter also referred to as "the present crosslinked polymer") or a non-crosslinked polymer (hereinafter also referred to as the "present non-crosslinked polymer”). ).
• the present crosslinked polymer and the present non-crosslinked polymer may be used alone or in combination.
• the present crosslinked polymer or the present non-crosslinked polymer may be used singly or in combination of two or more.
• the hydrophilic vinyl-based monomer includes, for example, a carboxyl group, an amide group, an amino group, a phosphoric acid group, a sulfonic acid group, a hydroxyl group, a quaternary ammonium group, or a salt thereof (partially or wholly neutralized).
• a hydrophilic vinyl-based monomer having a polar group such as a polar group can be used.
• a hydrophilic vinyl-based monomer having a carboxyl group improves the adhesion to the current collector, and the lithium ion Since the desolvation effect and ionic conductivity are excellent, it is preferable in terms of obtaining an electrode with low resistance and excellent high rate characteristics.
• Ethylenically unsaturated carboxylic acid monomers include (meth)acrylic acid, itaconic acid, crotonic acid, maleic acid, fumaric acid; Carboxylic acid; ethylenically unsaturated monomers having a carboxyl group such as succinic acid monohydroxyethyl (meth)acrylate, ⁇ -carboxy-caprolactone mono(meth)acrylate, ⁇ -carboxyethyl (meth)acrylate, or their (parts ) alkali-neutralized products, and one of them may be used alone, or two or more thereof may be used in combination.
• carboxyl group such as succinic acid monohydroxyethyl (meth)acrylate, ⁇ -carboxy-caprolactone mono(meth)acrylate, ⁇ -carboxyethyl (meth)acrylate, or their (parts ) alkali-neutralized products, and one of them may be used alone, or two or more thereof may be
• a compound having an acryloyl group as a polymerizable functional group is preferable because a polymer having a long primary chain length can be obtained because the polymerization rate is high, and the binding force of the hydrophilic binder is good, and acrylic is particularly preferable.
• acrylic acid is used as the ethylenically unsaturated carboxylic acid monomer, a polymer having a high carboxyl group content can be obtained.
• a hydrophilic vinyl monomer having an amide group (hereinafter also referred to as "an amide group-containing ethylenically unsaturated monomer”) is preferable from the viewpoint of excellent binding properties of the hydrophilic binder.
• Amido group-containing ethylenically unsaturated monomers include N-alkyl (meth)acrylamide compounds such as isopropyl (meth)acrylamide and t-butyl (meth)acrylamide; Nn-butoxymethyl (meth)acrylamide, N- N-alkoxyalkyl (meth)acrylamide compounds such as isobutoxymethyl (meth)acrylamide; N,N-dialkyl (meth)acrylamide compounds such as dimethyl (meth)acrylamide and diethyl (meth)acrylamide; cyclic compounds such as N-acryloylmorpholine (Meth)acrylamide compounds may be mentioned, and one of these may be used alone, or two or more thereof may be used in combination.
• N-acrylamide compounds such
• crosslinked polymer Here, the crosslinked polymer in the case of using an ethylenically unsaturated carboxylic acid monomer as the hydrophilic vinyl monomer will be described.
• the crosslinked polymer contained in the hydrophilic binder contains 50% by mass or more and 100% by mass or less of a structural unit derived from an ethylenically unsaturated carboxylic acid monomer (hereinafter also referred to as "component (a1)"). be able to.
• the present crosslinked polymer has a carboxyl group by having such a structural unit
• the adhesion to the current collector is improved, and the lithium ion desolvation effect and ionic conductivity are excellent.
• An electrode with excellent high rate characteristics can be obtained.
• the dispersion stability of the active material and the like in the present slurry composition can be enhanced.
• the component (a1) can be introduced into the polymer, for example, by polymerizing a monomer containing an ethylenically unsaturated carboxylic acid monomer. Alternatively, it can be obtained by (co)polymerizing a (meth)acrylic acid ester monomer and then hydrolyzing it.
• Examples of the ethylenically unsaturated carboxylic acid monomer include those mentioned above.
• a compound having an acryloyl group as a polymerizable functional group is preferable because a polymer having a long primary chain length can be obtained because the polymerization rate is high, and the binding force of the hydrophilic binder is good, and acrylic is particularly preferable.
• 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 component (a1) in the present crosslinked polymer can be 50% by mass or more and 100% by mass or less with respect to the total structural units of the present crosslinked polymer.
• the content of component (a1) in the present crosslinked polymer can be 50% by mass or more and 100% by mass or less with respect to the total structural units of the present crosslinked polymer.
• the lower limit is 50% by mass or more, the dispersion stability of the present slurry composition is improved, and a higher binding force is obtained, which is preferable, and may be 60% by mass or more, or may be 70% by mass or more. , 80% by mass or more.
• the upper limit is, for example, 99.9% by mass or less, or, for example, 99.5% by mass or less, or, for example, 99% by mass or less, or, for example, 98% by mass or less, or, for example, 95% by mass. or less, or, for example, 90% by mass or less, or, for example, 80% by mass or less.
• the range can be a range in which such lower and upper limits are appropriately combined. For example, it is 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 therewith (hereinafter also referred to as "component (b1)").
• component (b1) 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, etc. derived structural units.
• 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 component (b1) can be 0% by mass or more and 50% by mass or less with respect to the total structural units of the present crosslinked polymer.
• the proportion of component (b1) may be 1% by mass or more and 50% by mass or less, may be 2% by mass or more and 50% by mass or less, or may be 5% by mass or more and 50% by mass or less. may be 10% by mass or more and 50% by mass or less.
• the component (b1) is contained in an amount of 1% by mass or more based on the total structural units of the present crosslinked polymer, the affinity for the electrolytic solution is improved, and an effect of improving the lithium ion conductivity can also be expected.
• component (b1) structural units derived from nonionic ethylenically unsaturated monomers are preferable from the viewpoint of obtaining an electrode having good bending resistance.
• monomers include amide group-containing ethylenically unsaturated monomers, nitrile group-containing ethylenically unsaturated monomers, alicyclic structure-containing ethylenically unsaturated monomers, and hydroxyl group-containing ethylenically unsaturated monomers. is mentioned.
• Examples of the amide group-containing ethylenically unsaturated monomer include those described above, and one of these may be used alone, or two or more thereof may be used in combination.
• nitrile group-containing ethylenically unsaturated monomers include (meth)acrylonitrile; cyanoalkyl (meth)acrylate compounds such as cyanomethyl (meth)acrylate and cyanoethyl (meth)acrylate; 4-cyanostyrene , cyano group-containing unsaturated aromatic compounds such as 4-cyano- ⁇ -methylstyrene; may be used.
• acrylonitrile is preferable because of its high nitrile group content.
• the alicyclic structure-containing ethylenically unsaturated monomers include, for example, cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, (meth) ) Cyclodecyl acrylate and cyclododecyl (meth) acrylate which may have an aliphatic substituent (meth) acrylic acid cycloalkyl ester; (meth) isobornyl acrylate, (meth) adamantyl acrylate, (meth) ) dicyclopentenyl acrylate, dicyclopentenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, and cyclohexanedimethanol mono(meth)acrylate and cyclodecanedimethanol mono(meth)acrylate, etc
• hydroxyl group-containing ethylenically unsaturated monomers examples include hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate and hydroxybutyl (meth)acrylate. may be used, or two or more may be used in combination.
• the present crosslinked polymer or a salt thereof has excellent binding properties with a hydrophilic binder, and is composed of an amide group-containing monounsaturated ethylenic monomer, a nitrile group-containing ethylenically unsaturated monomer, an alicyclic structure-containing ethylenic It preferably contains a structural unit derived from an unsaturated monomer 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 (c), a strong interaction with the electrode material can be achieved. , can exhibit good binding properties to the active material. As a result, it is possible to obtain an electrode mixture layer that is firm and has good integrity. Alicyclic structure-containing ethylenically unsaturated monomers are preferred.
• the present crosslinked polymer or a salt thereof preferably contains a structural unit derived from a hydroxyl group-containing ethylenically unsaturated monomer from the viewpoint of improving the cycle characteristics of the obtained secondary battery. It is preferably contained in an amount of 2.0% by mass or more and 50% by mass or less, more preferably 10.0% by mass or more and 50% by mass or less.
• (meth)acrylic acid esters may be used as other nonionic ethylenically unsaturated monomers.
• (meth)acrylic acid esters include (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, meth) acrylic acid alkyl ester compound; Aromatic (meth)acrylic acid ester compounds such as phenyl (meth)acrylate, phenylmethyl (meth)acrylate, and phenylethyl (meth)acrylate; (meth)acrylic acid alkoxyalkyl ester compounds such as 2-methoxyethyl (meth)acrylate and 2-ethoxyethyl (meth)acrylate, and the like, and one of these may be used alone or , may be used in combination of two or more.
• aromatic (meth)acrylic acid ester compounds 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 preferred, and 2-methoxyethyl (meth)acrylate is more preferred.
• nonionic ethylenically unsaturated monomers compounds having an acryloyl group are preferable because they have a high polymerization rate, so that a polymer having a long primary chain length can be obtained, and the bonding strength of the hydrophilic binder is good.
• a compound having a homopolymer glass transition temperature (Tg) of 0° C. or less is preferable because the obtained electrode has good bending resistance.
• 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, alkali metal salts such as lithium salts, sodium salts and potassium salts; alkaline earth metal salts such as magnesium salts, calcium salts and barium salts; other metal salts such as aluminum salts; salts, organic amine salts, and the like.
• alkali metal salts and alkaline earth metal salts are preferred, and alkali metal salts are more preferred, because they are less likely to adversely affect battery characteristics.
• the present polymer is preferably a polymer having a crosslinked structure (present crosslinked polymer).
• the cross-linking method for the present cross-linked polymer is not particularly limited, and examples thereof include the following methods. 1) Copolymerization of crosslinkable monomers 2) Utilization of chain transfer to polymer chains during radical polymerization 3) After synthesizing a polymer having a reactive functional group, postcrosslinking by adding a crosslinking agent as necessary By having the crosslinked structure of the present polymer, the binder containing the polymer or salt thereof can have excellent binding power.
• the method by copolymerization of a crosslinkable monomer is preferable because the operation is simple and the degree of crosslinking can be easily controlled.
• crosslinkable monomers include polyfunctional polymerizable monomers having two or more polymerizable unsaturated groups, and monomers having self-crosslinkable functional groups such as hydrolyzable silyl groups. mentioned.
• the polyfunctional polymerizable monomer is a compound having two or more polymerizable functional groups such as (meth)acryloyl groups and alkenyl groups in the molecule, and includes polyfunctional (meth)acrylate compounds, polyfunctional alkenyl compounds, ( Examples include compounds having both a meth)acryloyl group and an alkenyl group. These compounds may be used individually by 1 type, and may be used in combination of 2 or more type. Among these, a polyfunctional alkenyl compound is preferable because it is easy to obtain a uniform crosslinked structure, and a polyfunctional allyl ether compound having two or more allyl ether groups in the molecule is particularly preferable.
• polyfunctional (meth)acrylate compounds include ethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di( Di(meth)acrylates of dihydric alcohols such as meth)acrylates; Poly(meth)acrylates such as tri(meth)acrylates and tetra(meth)acrylates of trihydric or higher polyhydric alcohols such as meth)acrylates and pentaerythritol tetra(meth)acrylates; Bisamides and the like can be mentioned.
• Polyfunctional alkenyl compounds include polyfunctional allyl ether compounds such as trimethylolpropane diallyl ether, trimethylolpropane triallyl ether, pentaerythritol diallyl ether, pentaerythritol triallyl ether, tetraallyloxyethane, and polyallyl saccharose; and polyfunctional vinyl compounds such as divinylbenzene.
• Compounds having both a (meth)acryloyl group and an alkenyl group include allyl (meth)acrylate, isopropenyl (meth)acrylate, butenyl (meth)acrylate, pentenyl (meth)acrylate, and (meth)acrylic acid. 2-(2-vinyloxyethoxy)ethyl and the like can be mentioned.
• the monomer having a self-crosslinkable crosslinkable functional group include hydrolyzable silyl group-containing vinyl monomers and N-methylol(meth)acrylamide. These compounds can be used individually by 1 type or in combination of 2 or more types.
• 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.
• vinylsilanes such as vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, and vinyldimethylmethoxysilane
• silyls such as trimethoxysilylpropyl acrylate, triethoxysilylpropyl acrylate, and methyldimethoxysilylpropyl acrylate
• Group-containing acrylic acid esters silyl group-containing methacrylic acid esters such as trimethoxysilylpropyl methacrylate, triethoxysilylpropyl methacrylate, methyldimethoxysilylpropyl methacrylate, and dimethylmethoxysilylpropyl methacrylate; trimethoxysilylpropyl vinyl ether, etc. and silyl group-containing vinyl est
• the amount of the crosslinkable monomer used is the total amount of monomers other than the crosslinkable monomer (non-crosslinkable monomer) It is preferably 0.01 to 5.0 parts by mass, more preferably 0.05 to 5.0 parts by mass, and still more preferably 0.1 or more parts by mass with respect to 100 parts by mass. It is 3.0 parts by mass or less, more preferably 0.2 parts by mass or more and 2.0 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. If it is 5.0 parts by mass or less, the stability of the polymer tends to be high.
• the amount of the crosslinkable monomer used is 0.001 mol% or more and 2.5 mol% or less with respect to the total amount of monomers other than crosslinkable monomers (non-crosslinkable monomers). is preferably 0.01 mol% or more and 2.0 mol% or less, more preferably 0.03 mol% or more and 1.5 mol% or less, and 0.05 mol% or more and 1 It is more preferably 0.0 mol % or less, and even more preferably 0.10 mol % or more and 0.50 mol % or less.
• the crosslinked polymer preferably has a viscosity of 10,000 mPa ⁇ s or less in a 2% by mass aqueous solution.
• the viscosity of the 2 mass % concentration aqueous solution is 10,000 mPa ⁇ s or less, it is possible to provide durability capable of following changes in volume of the active material during charging and discharging.
• the viscosity of the 2% by mass aqueous solution may be 5,000 mPa ⁇ s or less, 3,000 mPa ⁇ s or less, or 2,000 mPa ⁇ s or less.
• the viscosity of the aqueous solution is obtained by uniformly dissolving or dispersing an amount of the present crosslinked polymer to give a predetermined concentration in water, and then measuring the B-type viscosity (25° C.) at 12 rpm.
• the crosslinked polymer or its salt absorbs water and becomes swollen.
• the degree of cross-linking the lower the degree of cross-linking, the easier the cross-linked polymer swells.
• the number of cross-linking points is the same, the greater the molecular weight (primary chain length), the more cross-linking points that contribute to the formation of a three-dimensional network, and the cross-linked polymer is less likely to swell.
• the viscosity of the aqueous crosslinked polymer solution can be adjusted by adjusting the amount of hydrophilic groups, the number of crosslinked points, the primary chain length, and the like of the crosslinked polymer.
• the number of cross-linking points can be adjusted by, for example, the amount of the cross-linking monomer used, the chain transfer reaction to the polymer chain, the post-cross-linking reaction, and the like.
• the primary chain length of the polymer can be adjusted by setting conditions related to the amount of radical generation, such as the initiator and polymerization temperature, and by selecting a polymerization solvent in consideration of chain transfer and the like.
• the present crosslinked polymer does not exist as large particle size aggregates (secondary aggregates), and is well dispersed as water-swollen particles having an appropriate particle size. Binders containing coalescence are preferred because they can exhibit good binding performance.
• the present crosslinked polymer has a particle diameter (water-swollen particle diameter) when a neutralization degree based on the carboxyl groups of the crosslinked polymer is 70 to 100 mol% is dispersed in water, and the volume-based median diameter is preferably in the range of 0.1 ⁇ m or more and 10.0 ⁇ m or less.
• a more preferable range of the particle size is 0.1 ⁇ m or more and 8.0 ⁇ m or less, a further preferable range is 0.1 ⁇ m or more and 7.0 ⁇ m or less, and a still more preferable range is 0.2 ⁇ m or more and 5.0 ⁇ m or less.
• a more preferable range is 0.5 ⁇ m or more and 3.0 ⁇ m or less.
• the particle size is in the range of 0.1 ⁇ m or more and 10.0 ⁇ m or less, the particles are uniformly present in the present slurry composition with a suitable size, so that the present slurry composition has high stability and excellent binding properties. It is possible to demonstrate If the particle size exceeds 10.0 ⁇ m, the binding properties may be insufficient as described above. In addition, since it is difficult to obtain a smooth coating surface, the coatability may be insufficient. On the other hand, when the particle size is less than 0.1 ⁇ m, there is a concern in terms of stable production. Here, the water-swollen particle size is obtained by a method according to the method described in the Examples.
• the particle diameter (dry particle diameter) of the present crosslinked polymer when dried is preferably in the range of 0.03 ⁇ m or more and 3 ⁇ m or less in terms of volume-based median diameter.
• a more preferable range of the particle size is 0.1 ⁇ m or more and 1 ⁇ m or less, and a further preferable range is 0.3 ⁇ m or more and 0.8 ⁇ m or less.
• acid groups such as carboxyl groups derived from ethylenically unsaturated carboxylic acid monomers are neutralized so that the degree of neutralization in the present slurry composition is 20 mol% or more, and salt is formed. It is preferable to use it as a mode.
• the degree of neutralization is more preferably 50 mol% or more, still more preferably 70 mol% or more, still more preferably 75 mol% or more, still more preferably 80 mol% or more, and particularly preferably 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 can be an appropriate combination of the above lower and upper limits.
• the degree of neutralization can be calculated from the charged values of the monomer having an acid group such as a carboxyl group and the neutralizing agent used for neutralization.
• ⁇ Method for producing the present crosslinked polymer> known polymerization methods such as solution polymerization, precipitation polymerization, suspension polymerization, and emulsion polymerization can be used. polymerization) is preferred. Heterogeneous polymerization methods such as precipitation polymerization, suspension polymerization, and emulsion polymerization are preferred, and precipitation polymerization is more preferred among them, in that better performance can be obtained with respect to binding properties and the like.
• Precipitation polymerization is a method of producing a polymer by carrying out a polymerization reaction in a solvent that dissolves the unsaturated monomer as the starting material but does not substantially dissolve the resulting polymer.
• a dispersion liquid of polymer particles is obtained in which primary particles of several tens of nm to several hundreds of nm are secondary aggregated to several ⁇ m to several tens of ⁇ m.
• a dispersion stabilizer can also be used to control the particle size of the polymer.
• the secondary aggregation can be suppressed by selecting a dispersion stabilizer, a polymerization solvent, and the like. In general, precipitation polymerization in which secondary aggregation is suppressed is also called dispersion polymerization.
• a solvent selected from water and various organic solvents can be used as the polymerization solvent in consideration of the type of monomers used.
• a solvent with a small chain transfer constant In order to obtain a polymer having a longer primary chain length, it is preferable to use a solvent with a small chain transfer constant.
• Specific polymerization solvents 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. , these can be used singly or in combination of two or more. Alternatively, a mixed solvent of these and water may be used.
• a water-soluble solvent in the present invention refers to a solvent having a solubility in water at 20° C. of greater than 10 g/100 ml.
• methyl ethyl ketone and acetonitrile are preferable in that they are easy to use), 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 neutralization process described later. .
• polymerization initiator known polymerization initiators such as azo compounds, organic peroxides, and inorganic peroxides can be used, but are not particularly limited. Using known methods such as thermal initiation, redox initiation using a reducing agent, and UV initiation can be used to adjust the conditions of use so that an appropriate amount of radicals is generated. In order to obtain a crosslinked polymer having a long primary chain length, it is preferable to set the conditions so that the amount of radical generation is less within the allowable production time.
• a preferred amount of the polymerization initiator to be 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 parts by mass or more, the polymerization reaction can be stably carried out, and when it is 2 parts by mass or less, it is easy to obtain a polymer having a long primary chain length.
• the polymerization temperature is preferably 0 to 100°C, more preferably 20 to 80°C, although it depends on conditions such as the type and concentration of the monomers used.
• the polymerization temperature may be constant or may vary during the polymerization reaction.
• the polymerization time is preferably 1 minute to 20 hours, more preferably 1 hour to 10 hours.
• the present non-crosslinked polymer contained in the hydrophilic binder can contain 50% by mass or more and 100% by mass or less of structural units derived from an ethylenically unsaturated carboxylic acid monomer (the component (a1)).
• the method for introducing the (a1) component of the present non-crosslinked polymer may be the same as the method described for the (a1) component of the present crosslinked polymer.
• a method of saponifying a polymer containing a structural unit derived from a (meth)acrylic acid alkyl ester compound (described above as the component (b1) of the present crosslinked polymer) may be used, and the (meth)acrylic acid
• the alkyl ester compound methyl acrylate and methyl methacrylate are preferable because the saponification reaction proceeds easily, and one of them may be used alone, or two or more may be used in combination.
• the non-crosslinked polymer has a higher viscosity than the crosslinked polymer. This is presumably because the non-crosslinked polymer has a broadened molecular chain, while the crosslinked polymer is in the form of particles, resulting in a small apparent molecular weight.
• the content of component (a1) in the present non-crosslinked polymer can be 50% by mass or more and 100% by mass or less with respect to the total structural units of the present non-crosslinked polymer in terms of solubility in water. , preferably 60% by mass or more and 100% by mass or less, more preferably 70% by mass or more and 100% by mass or less, and still more preferably 80% by mass or more and 100% by mass or less.
• the present non-crosslinked polymer can contain, in addition to the (a1) component, a structural unit (the (b1) component) derived from another ethylenically unsaturated monomer copolymerizable therewith.
• the method for introducing the component (b1) may be the same as the method described for the component (b1) of the present crosslinked polymer.
• a method of saponifying a polymer containing a structural unit derived from a vinyl ester compound such as vinyl acetate or vinyl propionate may be used. Vinyl acetate is preferred, and one kind may be used alone, or two or more kinds may be used in combination.
• the ratio of component (b1) can be 0% by mass or more and 50% by mass or less with respect to all structural units of the present non-crosslinked polymer.
• the proportion of component (b1) may be 1% by mass or more and 50% by mass or less, may be 2% by mass or more and 50% by mass or less, or may be 5% by mass or more and 50% by mass or less. may be 10% by mass or more and 50% by mass or less.
• the non-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, alkali metal salts such as lithium, sodium and potassium; magnesium salts.
• alkaline earth metal salts such as calcium salts and barium salts; other metal salts such as aluminum salts; ammonium salts and organic amine salts; Among these, alkali metal salts and alkaline earth metal salts are preferred, and alkali metal salts are more preferred, because they are less likely to adversely affect battery characteristics.
• acid groups such as carboxyl groups derived from ethylenically unsaturated carboxylic acid monomers are neutralized so that the degree of neutralization is 20 mol% or more in the present slurry composition, and salt It is preferable to use it as an aspect of.
• the degree of neutralization is more preferably 50 mol% or more, still more preferably 70 mol% or more, still more preferably 75 mol% or more, still more preferably 80 mol% or more, and particularly preferably 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 can be an appropriate combination of the above lower and upper limits.
• the degree of neutralization can be calculated from the charged values of the monomer having an acid group such as a carboxyl group and the neutralizing agent used for neutralization.
• the weight average molecular weight (Mw) of the present non-crosslinked polymer is not particularly limited, but is preferably 5,000 or more, more preferably 10, from the viewpoint of obtaining an electrode mixture layer with excellent binding properties. , 000 or more. Mw may be 100,000 or more, 500,000 or more, or 1,000,000 or more. The upper limit of Mw is not particularly limited, but from the viewpoint of handling in manufacturing, it is, for example, 10,000,000 or less, may be 7,000,000 or less, or 5,000,000 or less. It may be less than or equal to 3,000,000.
• Mw is obtained according to the method described in the Examples according to the structural unit of the present non-crosslinked polymer.
• the amount of the present non-crosslinked polymer used is 7.5 parts by mass or more and 200 parts by mass per 100 parts by mass of the total amount of the present crosslinked polymer. It is preferably no more than parts by mass.
• the amount of the non-crosslinked polymer used may be 15 parts by mass or more, 25 parts by mass or more, 35 parts by mass or more, or 45 parts by mass or more. good.
• the upper limit may be 190 parts by mass or less, 180 parts by mass or less, 170 parts by mass or less, or 160 parts by mass or less.
• the range can be a range in which such a lower limit and an upper limit are appropriately combined. It is 35 parts by mass or more and 170 parts by mass or less, and can be, for example, 35 parts by mass or more and 160 parts by mass or less.
• a specific amount of the present non-crosslinked polymer can be used together with the present crosslinked polymer, and when the solid content concentration of the secondary battery electrode slurry composition is higher than before, the electrode slurry It is possible to obtain a secondary battery that exhibits excellent cycle characteristics while ensuring coatability by reducing the viscosity of the.
• the amount of the present non-crosslinkable polymer used is 7.5 parts by mass or more, such effects can be exhibited.
• the amount of the present non-crosslinkable polymer used exceeds 200 parts by mass, sufficient coatability may not be obtained.
• ⁇ Method for producing the present non-crosslinked polymer Known polymerization methods such as solution polymerization, precipitation polymerization, suspension polymerization, and emulsion polymerization can be used for the present non-crosslinked polymer, and the polymer may be appropriately selected depending on the molecular weight, composition, or the like.
• polymerization initiator known polymerization initiators such as azo compounds, organic peroxides, and inorganic peroxides can be used, but the polymerization initiator is not particularly limited. Using known methods such as thermal initiation, redox initiation using a reducing agent, and UV initiation can be used to adjust the conditions of use so that an appropriate amount of radicals is generated. For the purpose of adjusting the molecular weight, etc., a known chain transfer agent may be used as necessary.
• the present non-crosslinked polymer preferably has a viscosity of 10,000 mPa ⁇ s or less in a 2% by mass aqueous solution.
• the viscosity of the 2 mass % concentration aqueous solution is 10,000 mPa ⁇ s or less, it is possible to provide durability capable of following changes in volume of the active material during charging and discharging.
• the viscosity of the 2% by mass aqueous solution may be 5,000 mPa ⁇ s or less, 3,000 mPa ⁇ s or less, or 2,000 mPa ⁇ s or less.
• the aqueous solution viscosity is obtained by uniformly dissolving or dispersing an amount of the present non-crosslinked polymer in water to give a predetermined concentration, and then measuring the B-type viscosity (25° C.) at 12 rpm.
• the present slurry composition may further contain other binder components such as styrene-butadiene rubber (SBR) latex, acrylic latex and polyvinylidene fluoride latex.
• SBR styrene-butadiene rubber
• acrylic latex acrylic latex
• polyvinylidene fluoride latex polyvinylidene fluoride latex.
• the amount used can be, for example, 0.1 to 5 parts by mass or less, and for example, 0.1 to 2 parts by mass, with respect to 100 parts by mass of the total amount of the active material. part or less, or, 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 may increase, resulting in insufficient high rate characteristics.
• the timing of adding the latex is preferably in step C from the viewpoint of suppressing aggregation of the latex due to shearing.
• the SBR-based latex is an aqueous dispersion of a copolymer having a structural unit derived from an aromatic vinyl monomer such as styrene and a structural unit derived from an aliphatic conjugated diene monomer such as 1,3-butadiene. Show body.
• aromatic vinyl monomer include styrene, ⁇ -methylstyrene, vinyltoluene, divinylbenzene and the like, and one or more of these can be used.
• the structural unit derived from the aromatic vinyl monomer in the copolymer can be in the range of, for example, 20 to 70% by mass, mainly from the viewpoint of binding property, and for example, 30 to 60%. It can be in the range of % by mass.
• Examples of the aliphatic conjugated diene-based monomer include 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 resulting electrode are good. and, for example, 40 to 60% by mass.
• the SBR-based latex may contain nitrile group-containing monomers such as (meth)acrylonitrile, (meth)acryl Carboxyl group-containing monomers such as acids, itaconic acid and maleic acid, and ester group-containing monomers such as methyl (meth)acrylate may be used as copolymerizable monomers.
• nitrile group-containing monomers such as (meth)acrylonitrile, (meth)acryl Carboxyl group-containing monomers such as acids, itaconic acid and maleic acid, and ester group-containing monomers such as methyl (meth)acrylate may be used as copolymerizable monomers.
• the structural units derived from the other monomers in the copolymer can be in the range of, for example, 0 to 30% by mass, and can be in the range of, for example, 0 to 20% by mass.
• Method for producing slurry composition for secondary battery electrode comprises an active material, a thickener, a hydrophilic binder and water. Including step B and step C.
• Step A A step of kneading a composition having a solid content concentration of 60 to 80% by mass containing an active material, a thickener and water to obtain a hard kneaded product.
• Step B of adding a viscous binder (but different from the thickener) and water and kneading to obtain a second kneaded product;
• Step C Step of adjusting the solid content concentration of the second hard paste to 40 to 60% by mass
• a part of the hydrophilic binder may be added in Step A. It is preferable to add all of the hydrophilic binder in the step B because the effect of reducing the viscosity of the slurry composition is high.
• the electrode slurry viscosity is reduced even when the solid content of the slurry composition is high. It can be made excellent in productivity.
• the viscosity of the slurry composition increases significantly, resulting in poor productivity. It is believed that this is because the hydrophilic binder and the thickening agent are competitively adsorbed to the active material, and the amount of the thickening agent that exists free in the medium increases.
• step A by kneading the composition containing no hydrophilic binder and containing a thickening agent, the amount of the thickening agent adsorbed to the active material increases, It is believed that the viscosity of the slurry composition can be reduced because the amount of the thickener that exists free in the medium is reduced.
• the solid content concentration of the composition in step A is 60 to 80% by mass, and a strong shearing force is applied to the composition to promote adsorption of the thickener to the active material, and the obtained electrode slurry is preferably 61 to 78% by mass, more preferably 62 to 76% by mass, even more preferably 63 to 74% by mass, and even more preferably 66 to 72% by mass, in that the viscosity of can be further reduced. %, more preferably 68 to 72% by mass, and particularly preferably 68 to 70% by mass.
• the kneading time in step A is preferably 10 minutes to 60 minutes in terms of promoting adsorption of the thickener to the active material, reducing the viscosity of the resulting electrode slurry, and achieving excellent productivity. More preferably 20 minutes to 60 minutes, still more preferably 25 minutes to 60 minutes.
• the step B can include the following step B1.
• Step B1 A step of adding an aqueous solution of a hydrophilic binder to the first kneaded product obtained in step A and kneading to obtain a second kneaded product.
• the binder as an aqueous solution instead of adding it in powder form, the viscosity of the resulting electrode slurry can be further reduced, and the occurrence of so-called "steps" can be suppressed to obtain a smooth secondary battery electrode. It is preferable in that it is
• step B can include steps B2 and B3 below.
• Step B2 A step of adding a hydrophilic binder to the first kneaded product obtained in Step A and kneading it firmly
• Step B3 Following the step B2, further adding water and kneading it hard to make a second
• the step of obtaining a hard kneaded product of Step B includes steps B2 and B3, when the hydrophilic binder is powdery, the hydrophilic binder is uniformly dispersed and dissolved in the electrode slurry by the kneading step B2. This is preferable in that the viscosity of the electrode slurry can be reduced.
• the amount of the thickening agent used in the present slurry composition is, for example, 0.1 parts 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 to 10 parts by mass, for example, 0.3 to 8 parts by mass, and for example, 0.4 to 5 parts by mass. . If the amount of the thickener used is 0.1 parts by mass or more, sufficient binding properties can be obtained. Moreover, the dispersion stability of the active material and the like can be ensured, and a uniform material mixture layer can be formed.
• the amount of the thickening agent used is 20 parts by mass or less, the present slurry composition does not become highly viscous, and the coatability onto the current collector can be ensured. As a result, a mixture layer having a uniform and smooth surface can be formed.
• the amount of the hydrophilic binder used in the present slurry composition is, for example, 0.1 parts 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 to 10 parts by mass, for example, 0.3 to 8 parts by mass, and for example, 0.4 to 5 parts by mass. . If the amount of the hydrophilic binder used is 0.1 part by mass or more, sufficient binding properties can be obtained. Moreover, the dispersion stability of the active material and the like can be ensured, and a uniform material mixture layer can be formed.
• the amount of the hydrophilic binder used is 20 parts by mass or less, the present slurry composition does not become highly viscous, and the coatability to the current collector can be ensured. As a result, a mixture layer having a uniform and smooth surface can be formed.
• the amount of active material used in the present slurry composition is, for example, in the range of 20 to 40% by mass, and for example, in the range of 25 to 40% by mass, relative to the total amount of the slurry composition.
• the amount of the active material used is 20% by mass or more, the migration of the hydrophilic binder and the like can be suppressed, and it is advantageous in terms of the drying cost of the medium.
• it is 40% by mass or less, the fluidity and coatability of the present slurry composition can be ensured, and a uniform mixture layer can be formed.
• This slurry composition uses water as a medium.
• lower alcohols such as methanol and ethanol
• carbonates such as ethylene carbonate
• ketones such as acetone, tetrahydrofuran, N-methylpyrrolidone and other water-soluble
• a mixed solvent with an organic solvent may be used.
• the proportion of water in the mixed medium is, for example, 50% by mass or more, and is, for example, 70% by mass or more.
• the content of the medium containing water in the entire slurry composition is the coatability of the slurry, and the energy cost required for drying, from the viewpoint of productivity. , 40 to 60% by weight, and for example, 40 to 55% by weight.
• the slurry composition for a secondary battery electrode according to the present invention comprises an active material, a thickener, a hydrophilic binder and water as essential constituents. can get.
• the method for mixing each component is not particularly limited, and a known method can be adopted. A method of dispersing and kneading is preferred.
• the mixing means known mixers such as a planetary mixer, a thin film swirling mixer, and a rotation-revolution mixer can be used. preferably.
• the pH of the slurry composition is not particularly limited as long as the effect of the present invention is exhibited, but is preferably less than 12.5. It is more preferably less than 0.5 and even more preferably less than 10.5.
• the viscosity of the slurry composition 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 in the range of, for example, 100 to 12,000 mPa s, Further, for example, it can be in the range of 500 to 11,000 mPa ⁇ s, or for example, in the range of 1,000 to 10,000 mPa ⁇ s. If the viscosity of the slurry is within the above range, good coatability can be ensured.
• the secondary battery electrode according to the present invention comprises a mixture layer formed from the slurry composition for a secondary battery electrode according to the present invention on the surface of a current collector made of copper, aluminum or the like. It is.
• the mixture layer is formed by applying the present slurry composition to the surface of the current collector and then removing the medium such as water by drying.
• the method of applying the present slurry composition is not particularly limited, and known methods such as doctor blade method, dip method, roll coating method, comma coating method, curtain coating method, gravure coating method and extrusion method can be employed. can be done.
• the drying can be performed by a known method such as hot air blowing, pressure reduction, (far) infrared rays, or microwave irradiation.
• the mixture layer obtained after drying is subjected to compression treatment by a die press, a roll press, or the like.
• compression treatment By compressing the active material and the hydrophilic binder, the strength of the material 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% of the thickness before compression, and the thickness of the mixture layer after compression is generally about 4 to 200 ⁇ m.
• a secondary battery can be produced by providing a separator and an electrolytic solution in the secondary battery electrode according to the present invention.
• the electrolytic solution may be liquid or gel.
• a 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 retaining an electrolytic solution to ensure ionic conductivity.
• the separator is preferably a film-like insulating microporous membrane having good ion permeability and mechanical strength. Specific materials that can be used include polyolefins such as polyethylene and polypropylene, and polytetrafluoroethylene.
• the electrolytic solution As the electrolytic solution, a commonly used known one can be used depending on the type of active material.
• specific solvents include cyclic carbonates such as propylene carbonate and ethylene carbonate, which have a high dielectric constant and high ability to dissolve the electrolyte, and low-viscosity chains such as ethylmethyl carbonate, dimethyl carbonate, and diethyl carbonate. carbonates, etc., and these can be used alone or as a mixed solvent.
• the electrolytic solution is used by dissolving lithium salts such as LiPF 6 , LiSbF 6 , LiBF 4 , LiClO 4 and LiAlO 4 in these solvents.
• a potassium hydroxide aqueous solution can be used as an electrolytic solution in a nickel-metal hydride secondary battery.
• a secondary battery is obtained by housing a positive electrode plate and a negative electrode plate partitioned by a separator in a spiral or laminated structure in a case or the like.
• a secondary battery having an electrode provided with a mixture layer formed from the slurry composition for a secondary battery electrode disclosed in the present specification has good durability even after repeated charging and discharging. (cycle characteristics), it is suitable for vehicle-mounted secondary batteries and the like.
• LiOH.H 2 O lithium hydroxide monohydrate
• the particle size in an aqueous medium measured by the following method was 1.68 ⁇ m.
• Measurement of particle size in aqueous medium (water-swollen particle size) 0.25 g of hydrophilic polymer R-1 powder and 49.75 g of deionized water were weighed into a 100 cc container and set in a rotation/revolution stirrer (Awatori Rentaro AR-250, manufactured by Thinky Co.). Next, agitation (rotation speed 2,000 rpm / revolution speed 800 rpm, 7 minutes) and further defoaming (rotation speed 2,200 rpm / revolution speed 60 rpm, 1 minute) are performed, and the hydrogel in a state where R-1 is swollen in water.
• the particle size distribution of the above hydrogel was measured with a laser diffraction/scattering particle size distribution meter (Microtrac MT-3300EXII manufactured by Microtrac Bell) using ion-exchanged water as a dispersion medium.
• a laser diffraction/scattering particle size distribution meter Microtrac MT-3300EXII manufactured by Microtrac Bell
• an amount of hydrogel that could obtain an appropriate scattered light intensity was added.
• the particle size distribution profile measured was stabilized. As soon as the stability was confirmed, the particle size distribution was measured to obtain the volume-based median diameter (D50) as a representative value of the particle diameter.
• the particle diameter in the aqueous medium measured in the same manner as in Example 1 was 1.40 ⁇ m.
• R-3 Non-crosslinked sodium polyacrylate neutralized salt.
• the product name "Aron (registered trademark) A-20P-X” manufactured by Toagosei Co., Ltd., Mw 5,000,000) was used.
• GPC Gel Permeation Chromatography HLC-8420, manufactured by Tosoh Corporation
• dimethylformamide in which lithium bromide monohydrate was dissolved at a concentration of 10 mM was used as the eluent, and polymethyl methacrylate was used as the standard substance.
• the polymerization rate of ACMO calculated from GC (gas chromatography GC-2014, manufactured by Shimadzu Corporation) was 100%.
• the obtained polymerization reaction liquid was dried at 100°C overnight and then pulverized to obtain a powder of hydrophilic polymer R-4. Since the hydrophilic polymer R-4 has hygroscopicity, it was sealed and stored in a container having water vapor barrier properties.
• Example 1 (Production of slurry composition for secondary battery electrode) 77.6 parts of artificial graphite (manufactured by Showa Denko Co., Ltd., trade name “SCMG-CF”) and silicon monoxide (Osaka Titanium Technologies) are added as an active material to a planetary mixer (Hibismix 2P-03 type manufactured by Primix) with a volume of 0.6 L. 19.4 parts of 5 ⁇ m particle size manufactured by Co., Ltd., and 1.5 parts of carboxymethyl cellulose sodium (CMC) as a thickening agent were added. Next, dry mixing was performed for 7 minutes at a rotation speed of 40 rpm to obtain a powder mixture.
• SCMG-CF artificial graphite
• silicon monoxide Osaka Titanium Technologies
• step A after adding 43.5 parts of ion-exchanged water to the powder mixture to adjust the solid content concentration to 69.4%, the mixture was kneaded for 30 minutes at a planetary mixer rotation speed of 95 rpm, A first dough was obtained. At this time, 99.4 g of the mixture was kneaded in the planetary mixer, and a current of 0.25 A was flowing at an applied voltage of 100 V (252 W/kg). Moreover, although the starting temperature of hard kneading was 26.1° C., the temperature of the hard kneaded product rose to 36.4° C. at the end of mixing due to heat generated by stirring.
• step B 1.0 parts of hydrophilic binder R-1 and 31.5 parts of ion-exchanged water are added to the first kneaded product to adjust the solid content concentration to 57.0%, and then the planet The mixture was kneaded for 20 minutes at a rotation speed of 95 rpm in a Lee mixer to obtain a second kneaded product.
• 122.15 g of the mixture was kneaded in the planetary mixer, and a current of 0.15 A was flowing at an applied voltage of 100 V (123 W/kg).
• the starting temperature of hard kneading was 31.9° C., but the temperature of the hard kneaded product was 32.6° C.
• step C after adjusting the solid content concentration to 53% by adding 1.5 parts of ion-exchanged water and styrene-butadiene rubber (SBR) latex in terms of solid content to the second kneaded product, The mixture was gently mixed for 10 minutes at a planetary mixer rotation speed of 95 rpm, and vacuum defoamed at a planetary mixer rotation speed of 10 rpm for 5 minutes to produce a negative electrode slurry composition (negative electrode slurry).
• SBR styrene-butadiene rubber
• the negative electrode slurry was applied onto a current collector (copper foil) having a thickness of 20 ⁇ m, and dried in a ventilation dryer at 80° C. for 30 minutes to form a mixture layer. . After that, after rolling so that the mixture layer has a thickness of 50 ⁇ 5 ⁇ m and a mixture density of 1.60 ⁇ 0.10 g/cm 3 , it is punched into a size of 1 cm ⁇ 6 cm for a peel strength test, and the pressure is reduced at 130° C. for 8 hours. It was dried under the conditions to obtain a negative electrode plate.
• the mixture layer surface of the negative electrode plate having a size of 1 cm ⁇ 6 cm was attached to an acrylic plate having a size of 3 cm ⁇ 9 cm via a double-sided tape (Nichiban NW-20) to prepare a sample for a peeling test.
• a tensile tester electrical stand MX-500N manufactured by Imada Corporation, digital force gauge DSY-5N manufactured by Imada Corporation
• 180 ° peeling is performed at a measurement temperature of 25 ° C and a tensile speed of 100 mm / min, and the mixture layer and copper foil
• the adhesion was evaluated by measuring the peel strength between the layers.
• the peel strength was as high as 20.8 N/m, which was good.
• Example 2 Example 1 except that in step B, 1.0 parts of hydrophilic binder R-1 was mixed with 31.5 parts of ion-exchanged water in step B1 and added as an aqueous solution of a hydrophilic binder in the form of a water-swollen gel. A negative electrode slurry was prepared by performing the same operation, and the slurry viscosity was measured.
• Examples 3, 5-14, and Comparative Examples 1-4 A negative electrode slurry was prepared in the same manner as in Example 1 except that the composition and the negative electrode slurry preparation conditions were as shown in Table 1, and the slurry viscosity was measured.
• Example 4 After obtaining a powder mixture by the same operation as in Example 1, in step A, 43.5 parts of ion-exchanged water was added to the powder mixture to adjust the solid content concentration to 69.4%. Solid kneading was carried out for 25 minutes at a rotation speed of 95 rpm in a Lee mixer. Next, in step B, 1.0 parts of hydrophilic polymer R-1 is added as step B2, and kneaded hard for 5 minutes at a planetary mixer rotation speed of 95 rpm, and 31.5 parts of ion-exchanged water is added as step B3. Then, the mixture was hard kneaded for 20 minutes with a planetary mixer at a rotational speed of 95 rpm. Except for the operations described above, the same operations as in Example 1 were performed to prepare a negative electrode slurry, and the slurry viscosity was measured.
• the step (Example 1) in which a portion of the hydrophilic binder is not added is better at the time of dry-mixing.
• the resulting electrode slurry viscosity was lower than the step of adding a portion of the hydrophilic binder (Example 3). This is because, in the former, the adsorption of the thickener to the active material has progressed sufficiently, while in the latter, the hydrophilic binder partly added in the dry mixing is added to the thickener in the first kneading step. This is thought to be due to the inhibition of adsorption to the active material.
• Example 1 (69.4%) is better than Example 8 (65.0%) and Example 9 (71 .1%), the resulting electrode slurry viscosity was lower. This is because, in Example 1, a stronger shearing force was applied to the composition in the hard kneading step in step A, and the adsorption of the thickener to the active material progressed sufficiently, resulting in a lower electrode slurry viscosity. It is thought that
• the secondary battery electrode slurry composition obtained by the production method of the present invention has excellent peel strength ( binding), it is expected to exhibit good durability (cycle characteristics). Therefore, it is expected that a secondary battery equipped with an electrode obtained using the above slurry composition can ensure good integrity and exhibit good durability (cycle characteristics) even after repeated charging and discharging. It is expected to contribute to increasing the capacity of automotive secondary batteries, etc., and can be particularly suitable for non-aqueous electrolyte secondary battery electrodes, especially useful for non-aqueous electrolyte lithium ion secondary batteries with high energy density. is.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Composite Materials (AREA)
• Power Engineering (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Battery Electrode And Active Subsutance (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (1)

Family

ID=85086851

Family Applications (1)

Country Status (5)

Families Citing this family (1)

Citations (3)

Family Cites Families (3)

• 2022
  • 2022-07-21 JP JP2023538475A patent/JP7835223B2/ja active Active
  • 2022-07-21 WO PCT/JP2022/028302 patent/WO2023008296A1/ja not_active Ceased
  • 2022-07-21 CN CN202280053050.9A patent/CN117751462A/zh active Pending
  • 2022-07-21 US US18/293,111 patent/US20240332498A1/en active Pending
  • 2022-07-21 KR KR1020247004766A patent/KR20240035539A/ko active Pending

Patent Citations (3)

Also Published As

Similar Documents

Legal Events