JP2013055044A - Composite particle for electrochemical element electrode, electrochemical element electrode material, and electrochemical element electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite particle for an electrochemical element electrode, high in fluidity and exhibiting high adhesion with respect to a collector, and capable of providing an electrochemical element electrode high in initial capacity, low in internal resistance and excellent in high-temperature preservation characteristics.SOLUTION: There is provided a composite particle for an electrochemical element electrode, including a scale-like electrode active material, a non-water soluble polymer and a water-soluble polymer having an acidic group. The water-soluble polymer preferably contains a sulfonic acid group as the acidic group.

Description

  The present invention relates to a composite particle for an electrochemical element electrode, an electrochemical element electrode material, and an electrochemical element electrode.

  Electrochemical elements such as lithium ion secondary batteries that are small and lightweight, have high energy density, and can be repeatedly charged and discharged are rapidly expanding their demands by taking advantage of their characteristics. Lithium ion secondary batteries are used in fields such as mobile phones, notebook personal computers, and electric vehicles because of their relatively high energy density.

  With the expansion and development of applications, these electrochemical elements are required to be further improved, such as lowering resistance, increasing capacity, improving mechanical properties and productivity. Under such circumstances, there has been a demand for a more productive manufacturing method for electrochemical element electrodes, and various improvements have been made regarding a manufacturing method capable of high-speed molding and a material for electrochemical element electrodes suitable for the manufacturing method. It has been broken.

  An electrochemical element electrode is usually formed by laminating an active material layer formed by binding an electrode active material and a conductive material used as necessary with a binder on a current collector. is there. As a method of forming such an active material layer, Patent Document 1 discloses that a particulate electrode material is obtained by spray drying a slurry containing an electrode active material, rubber particles, and a dispersion medium, and the obtained electrode material A method of forming an electrode active material layer by using a metal is disclosed.

  However, in the technique described in Patent Document 1, carboxymethyl cellulose is used as a viscosity modifier that also acts as a dispersant. In the particulate electrode material, carboxymethyl cellulose is combined with a binder, thereby In some cases, the binder becomes hard, and when the obtained particulate electrode material is pressure-molded, adhesion with the current collector becomes insufficient. Further, in Patent Document 1, since a particulate active material is used as the electrode active material, the obtained particulate electrode material has poor fluidity. Therefore, when it is used as an electrode, the thickness in the electrode plane is reduced. As a result, there is a problem that the cycle characteristics are inferior.

JP 2010-109354 A

  The present invention has high fluidity, high adhesion to a current collector, high initial capacity, low internal resistance, and can provide an electrochemical device electrode excellent in high-temperature storage characteristics. An object is to provide composite particles for device electrodes. Another object of the present invention is to provide an electrochemical element electrode material and an electrochemical element electrode obtained by using such composite particles for electrochemical element electrodes.

  As a result of diligent research to achieve the above object, the present inventors have found that in the composite particles containing the electrode active material, the water-insoluble polymer, and the water-soluble polymer having an acidic group, the electrode active material has a scaly shape. By using this active material, it has high fluidity, high adhesion to the current collector, and when used as an electrode, it has high initial capacity, low internal resistance, and excellent high-temperature storage characteristics. The present invention has been completed.

That is, according to the present invention, there is provided an electrochemical element electrode composite particle comprising a scaly electrode active material, a water-insoluble polymer, and a water-soluble polymer having an acidic group.
In the composite particle for an electrochemical element electrode of the present invention, the water-soluble polymer preferably contains a sulfonic acid group as an acidic group.

According to the present invention, there is provided an electrochemical element electrode material comprising any one of the above-described composite particles for an electrochemical element electrode.
In addition, according to the present invention, there is provided an electrochemical element electrode characterized in that an active material layer formed from the above electrochemical element electrode material is laminated on a current collector.
The electrochemical element electrode of the present invention is preferably formed by laminating the active material layer on the current collector by pressure molding, and by laminating by roll pressure molding. More preferred.
Further, according to the present invention, there is provided a method for producing any one of the above composite particles for an electrochemical element electrode, wherein the electrode active material, the water-insoluble polymer, and the water-soluble polymer are dispersed in water. There is provided a method for producing composite particles for an electrochemical element electrode, comprising: a step of obtaining a slurry; and a step of spray-drying the slurry and granulating the slurry.

  According to the present invention, an electrochemical device electrode having high fluidity, high adhesion to a current collector, high initial capacity, low internal resistance, and excellent high-temperature storage characteristics can be provided. Electrochemical element electrode composite particles, and electrochemical element electrode materials and electrochemical element electrodes obtained by using such electrochemical element electrode composite particles can be provided.

  The composite particle for an electrochemical element electrode of the present invention is characterized by containing a scaly electrode active material, a water-insoluble polymer, and a water-soluble polymer having an acidic group.

(Scale-like electrode active material)
The scaly electrode active material used in the present invention is not particularly limited as long as the shape thereof is scaly. For example, the length of the major axis L1 is 0.1 to 20 μm, preferably 0.5 to 10 μm. The ratio of the length of the minor axis L2 to the thickness t (L2 / t) is 10 or more, preferably 15 or more. The ratio (L1 / L2) between the length of the major axis L1 and the length of the minor axis L2 is not particularly limited, but is preferably 1 to 5, and more preferably 1 to 2. The long diameter L1 is, for example, the length of the longest diameter on the main surface of the electrode active material, and the short diameter L2 is, for example, the length of the shortest diameter on the main surface of the electrode active material. The thickness t is, for example, the length in the direction orthogonal to the main surface of the electrode active material, and these can be measured, for example, by observing the electrode active material with an electron microscope. In the present invention, by using a scaly active material as the electrode active material, the fluidity of the composite particles for electrochemical device electrodes can be increased by the action of the scaly active material, thereby improving the moldability. Can be improved.

  Specific examples of the scaly electrode active material used in the present invention include, for example, scaly graphite, scaly lithium titanate, scaly titanium silicon alloy, scaly silicon carbide, etc. Among these, scaly graphite is preferable because the internal resistance of the obtained electrochemical element electrode can be lowered. When scaly graphite is used as the electrode active material, the composite particle for an electrochemical element electrode of the present invention is a composite particle for a negative electrode of a lithium ion secondary battery or a composite particle for a negative electrode of a lithium ion capacitor. It can be used suitably.

(Water-insoluble polymer)
The water-insoluble polymer used in the present invention is not particularly limited as long as it is a water-insoluble polymer, but from the viewpoint that a scaly electrode active material can be satisfactorily bound without inhibiting electronic conduction, Those having a particle shape are preferred. In particular, as the water-insoluble polymer, in the composite particle for an electrochemical element electrode of the present invention, a state in which the particle state is maintained, that is, on a scaly electrode active material. It is preferable to be able to exist in a state where the particle state is maintained. The presence of the particle state in the composite particle for an electrochemical element electrode can further enhance the effect that the electrode active materials can be favorably bound to each other without hindering the electron conduction. In the present invention, the “state in which the particle state is maintained” does not have to be a state in which the particle shape is completely maintained, and may be in a state in which the particle shape is maintained to some extent. As a result of binding, the electrode active materials may be crushed to some extent by each other.

  Examples of such a water-insoluble polymer include a polymer obtained by emulsion polymerization using water as a dispersion medium. In this case, the water-insoluble polymer is water as a dispersion medium. Used in a dispersed state. Specific examples of such polymers include those containing conjugated diene monomer units, ethylenically unsaturated carboxylic acid monomer units, and other monomer units copolymerizable therewith. In the present invention, the conjugated diene monomer unit is a structural unit obtained by polymerizing a conjugated diene monomer, and the ethylenically unsaturated carboxylic acid monomer unit is an ethylenically unsaturated carboxylic acid monomer. It refers to a structural unit obtained by polymerization, and the other monomer unit copolymerizable with these refers to a structural unit obtained by polymerizing other monomers copolymerizable therewith.

  Examples of the conjugated diene monomer forming the conjugated diene monomer unit include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, and 1,3. -Pentadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like. These conjugated diene monomers can be used alone or in combination of two or more. Of these, 1,3-butadiene is preferred.

  The content ratio of the conjugated diene monomer unit in the water-insoluble polymer is preferably 20 to 60% by weight, more preferably 30 to 55% by weight. By making the content rate of a conjugated diene monomer unit into the said range, adhesiveness with a collector can be improved, keeping electrolyte solution resistance favorable.

  Examples of the ethylenically unsaturated carboxylic acid monomer forming the ethylenically unsaturated carboxylic acid monomer unit include monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid, and itaconic acid, and dicarboxylic acids. Or the anhydride of dicarboxylic acid etc. are mentioned. These ethylenically unsaturated carboxylic acid monomers can be used alone or in combination of two or more. Among these, methacrylic acid and itaconic acid are preferable, and methacrylic acid is more preferable.

  The content ratio of the ethylenically unsaturated carboxylic acid monomer unit in the water-insoluble polymer is preferably 0.5 to 10% by weight, more preferably 1 to 8% by weight, and further preferably 2 to 7% by weight. %. By making the content rate of an ethylenically unsaturated carboxylic acid monomer unit into the said range, the viscosity raise at the time of slurrying can be suppressed, and the obtained slurry can be made stable.

  Other monomers that form other copolymerizable monomer units include aromatic vinyl monomers, vinyl cyanide monomers, unsaturated carboxylic acid alkyl ester monomers, and hydroxyalkyl groups. And unsaturated monomers containing carboxylic acid amide monomers. These other monomers can be used alone or in combination of two or more. Among these, aromatic vinyl monomers and vinyl cyanide monomers are preferable, and aromatic vinyl monomers are more preferable.

Examples of the aromatic vinyl monomer include styrene, α-methylstyrene, β-methylstyrene, vinyltoluene and the like.
Examples of the vinyl cyanide monomer include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, α-ethylacrylonitrile, and the like.
Examples of unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl maleate, and dimethyl itaco. Nate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like.

Examples of the unsaturated monomer containing a hydroxyalkyl group include β-hydroxyethyl acrylate, β-hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2- Examples include hydroxypropyl methacrylate, di- (ethylene glycol) maleate, di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl) maleate, 2-hydroxyethyl methyl fumarate and the like.
Examples of the unsaturated carboxylic acid amide monomer include acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N, N-dimethylacrylamide and the like.

  The content of other copolymerizable monomer units in the water-insoluble polymer is preferably 30 to 79.5% by weight, more preferably 35 to 69% by weight. By setting the content ratio of other copolymerizable monomer units in the above range, it is possible to improve the adhesion to the current collector while maintaining good resistance to the electrolytic solution.

  The weight average molecular weight of the water-insoluble polymer is preferably 10,000 to 1,000,000, more preferably 20,000 to 500,000. By setting the weight average molecular weight of the water-insoluble polymer in the above range, the strength in the case of an electrochemical element electrode can be made sufficient. In addition, the weight average molecular weight of a water-insoluble polymer can be calculated | required as a polystyrene conversion value which used tetrahydrofuran as a developing solvent by gel permeation chromatography (GPC).

  Moreover, when the water-insoluble polymer has a particle shape, the average particle diameter of the water-insoluble polymer is preferably 50 to 500 nm, more preferably 70 to 400 nm. By setting the average particle diameter of the water-insoluble polymer in the above range, the strength and flexibility in the case of an electrochemical element electrode can be improved.

  The content ratio of the water-insoluble polymer in the composite particle for an electrochemical element electrode of the present invention is preferably 0.3 to 8 parts by weight, more preferably 0 with respect to 100 parts by weight of the scaly electrode active material. .4-7 parts by weight, more preferably 0.5-5 parts by weight. By making the content rate of a water-insoluble polymer into the said range, the adhesive improvement effect with respect to a collector can be heightened more.

(Water-soluble polymer having an acidic group)
The water-soluble polymer having an acidic group used in the present invention is not particularly limited as long as it is a water-soluble polymer having an acidic group, but the acidic group includes at least a sulfonic acid group, a carboxyl group, and a phosphoric acid group. Those having one are preferable, those having at least one of a sulfonic acid group and a carboxyl group are more preferable, those having at least a sulfonic acid group are more preferable, and those having a sulfonic acid group and a carboxyl group are particularly preferable. In particular, when the water-soluble polymer having an acidic group used in the present invention has a sulfonic acid group and a carboxyl group, the sulfonic acid group-containing monomer and the carboxyl group-containing monomer, and if necessary A copolymer obtained by copolymerizing a monomer copolymerizable with these is preferably used.

  In the present invention, the water-soluble polymer having an acidic group is dispersed in water together with the scaly electrode active material and the water-insoluble polymer in the production process of the composite electrode electrode for an electrochemical device electrode to form a slurry. Acts as a dispersant and pH adjuster. And in this invention, the effect | action which improves the dispersibility of the electrode active material at the time of slurrying, and the effect which improves adhesiveness with an electrical power collector by the effect | action as a dispersing agent of the water-soluble polymer which has an acidic group. Can be realized.

  As sulfonic acid group-containing monomers, vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, sulfoethyl methacrylate, sulfopropyl methacrylate, sulfobutyl methacrylate and other functional groups other than sulfonic acid groups are included. Compound; Compound containing amide group and sulfonic acid group such as 2-acrylamido-2-methylpropanesulfonic acid (AMPS); Hydroxyl group and sulfonic acid group such as 3-allyloxy-2-hydroxypropanesulfonic acid (HAPS) And the like. These lithium salts, sodium salts, potassium salts, and the like can also be used. These may be used alone or in combination of two or more. Among these, 2-acrylamido-2-methylpropanesulfonic acid (AMPS), styrenesulfonic acid, and sulfobutyl methacrylate are preferable, and 2-acrylamido-2-methylpropanesulfonic acid (AMPS) is more preferable.

  The content ratio of the sulfonic acid group-containing monomer unit in the water-soluble polymer having an acidic group is preferably 2 to 15% by weight, more preferably 2 to 10% by weight, and further preferably 2 to 8% by weight. It is. By setting the content ratio of the sulfonic acid group-containing monomer unit within the above range, the effect of improving the dispersibility of the positive electrode active material and the effect of improving the adhesion to the current collector when slurryed can be further enhanced. In the present invention, the sulfonic acid group-containing monomer unit refers to a structural unit obtained by polymerizing a sulfonic acid group-containing monomer.

  Examples of the carboxyl group-containing monomer include monocarboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid; 2-ethylacrylic acid, isocrotonic acid, α-acetoxyacrylic acid, β-trans-aryloxyacrylic acid, and α-chloro. Derivatives of monocarboxylic acids such as β-E-methoxyacrylic acid and β-diaminoacrylic acid; dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid; maleic anhydride, acrylic anhydride, methylmaleic anhydride, dimethyl Dicarboxylic acid anhydrides such as maleic anhydride; methylmaleic acid, dimethylmaleic acid, phenylmaleic acid, chloromaleic acid, dichloromaleic acid, fluoromaleic acid, diphenyl maleate, nonyl maleate, decyl maleate, maleic acid Dodecyl, octadecyl maleate, And derivatives of dicarboxylic acids such as fluoroalkyl lanes. These may be used alone or in combination of two or more. Among these, acrylic acid and methacrylic acid are preferable.

  The content ratio of the carboxyl group-containing monomer unit in the water-soluble polymer having an acidic group is preferably 20 to 60% by weight, more preferably 20 to 50% by weight, still more preferably 20 to 40% by weight. is there. By setting the content ratio of the carboxyl group-containing monomer unit in the above range, the adhesion to the current collector can be further improved. In the present invention, the carboxyl group-containing monomer unit refers to a structural unit obtained by polymerizing a carboxylic acid group-containing monomer.

  Further, the water-soluble polymer having an acidic group used in the present invention is obtained by further copolymerizing a (meth) acrylic acid ester monomer in addition to the above-described sulfonic acid group-containing monomer and carboxyl group-containing monomer. It is preferable.

  Examples of (meth) acrylic acid ester monomers include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, and (meth) acrylic acid-2-ethylhexyl. (Meth) acrylic acid alkyl ester; carboxylic acid esters having two or more carbon-carbon double bonds such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate; These may be used alone or in combination of two or more. Among these, (meth) acrylic acid alkyl ester is preferable, and methyl (meth) acrylate, ethyl (meth) acrylate, and butyl (meth) acrylate are more preferable.

  The content ratio of the (meth) acrylic acid ester monomer unit in the water-soluble polymer having an acidic group is preferably 25 to 78% by weight, more preferably 45 to 75% by weight, and further preferably 60 to 70%. % By weight. By making the content rate of a (meth) acrylic acid ester monomer unit into the said range, the adhesive improvement effect with respect to a collector can be heightened more. In the present invention, the (meth) acrylic acid ester monomer unit refers to a structural unit obtained by polymerizing a (meth) acrylic acid ester monomer.

  The weight average molecular weight of the water-soluble polymer having an acidic group is preferably 1,000 to 100,000, more preferably 1,500 to 80,000, still more preferably 2,000 to 75,000. By making a weight average molecular weight into the said range, the adhesive improvement effect with respect to an electrical power collector can be heightened more. In addition, the weight average molecular weight of the water-soluble polymer having an acidic group was determined by using a solution obtained by dissolving 0.85 g / ml sodium nitrate in a 10% by volume aqueous solution of dimethylformamide by gel permeation chromatography (GPC). It can be determined as a value in terms of polystyrene.

  Moreover, the glass transition temperature of the water-soluble polymer which has an acidic group becomes like this. Preferably it is 0-70 degreeC, More preferably, it is 0-50 degreeC, More preferably, it is 0-40 degreeC. By setting the glass transition temperature within the above range, flexibility in the case of an electrochemical element electrode can be improved.

  Although it does not specifically limit as a manufacturing method of the water-soluble polymer which has an acidic group, For example, it can manufacture by emulsion polymerization which uses water as a dispersion medium.

  The content ratio of the water-soluble polymer having an acidic group in the composite particle for an electrochemical element electrode of the present invention is preferably 0.01 to 2 parts by weight with respect to 100 parts by weight of the scaly electrode active material. Preferably it is 0.03-1 weight part, More preferably, it is 0.05-0.5 weight part. By making the content ratio of the water-soluble polymer having an acidic group within the above range, the effect of improving the dispersibility of the electrode active material when slurried and the effect of improving the adhesion with the current collector are more appropriately It can be demonstrated.

  In the present invention, the ratio of the above-mentioned water-insoluble polymer and the water-soluble polymer having an acidic group is the weight ratio of “water-insoluble polymer / water-soluble polymer having an acidic group”. Preferably they are 80 / 20-99.9 / 0.1, More preferably, it is 85 / 15-95 / 5, More preferably, it is 83 / 17-95 / 5. By setting these proportions in the above range, the dispersibility of the electrode active material when slurryed can be further improved.

(Conductive material)
The composite particle for an electrochemical element electrode of the present invention may contain a conductive material, if necessary, in addition to the above components.

  The conductive material is not particularly limited as long as it is a particulate material having conductivity. For example, conductive carbon black such as furnace black, acetylene black, and ketjen black; graphite such as natural graphite and artificial graphite And carbon fibers such as polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, and vapor-grown carbon fibers.

  In the composite particle for an electrochemical element electrode of the present invention, the content ratio when blending the conductive material is preferably 0.1 to 50 parts by weight, more preferably 100 parts by weight of the scale-like electrode active material. 0.5 to 15 parts by weight, more preferably 1 to 10 parts by weight. By setting the content ratio of the conductive material in the above range, the internal resistance can be sufficiently reduced while keeping the capacity of the obtained electrochemical element high.

(Composite particles for electrochemical device electrodes)
The composite particle for an electrochemical element electrode of the present invention comprises a scaly electrode active material, a water-insoluble polymer, and a water-soluble polymer having an acidic group, each of which is independent of each other. What does not exist as particles but forms one particle with at least two components, preferably three components among three components of a scaly electrode active material, a water-insoluble polymer and a water-soluble polymer having an acidic group It is. In the composite particle, a water-soluble polymer having an acidic group may be present in the form of particles.

  Specifically, a plurality of the individual particles of the three components are combined to form secondary particles, and a plurality (preferably several to several tens) of electrode active materials are formed of water-insoluble heavy weight. Those which are bound by a water-soluble polymer having a coalescence and / or an acidic group to form a massive particle are preferred.

  The shape and structure of the composite particles are not particularly limited, but from the viewpoint of fluidity, the shape is preferably nearly spherical, and the structure is composed of a water-insoluble polymer and a water-soluble polymer having an acidic group. A structure that is uniformly dispersed in the composite particles without being unevenly distributed on the surface of the particles is preferable.

  The method for producing the composite particle for electrochemical element electrode of the present invention is not particularly limited, but according to the spray drying granulation method described below, the composite particle for electrochemical element electrode of the present invention can be obtained relatively easily. This is preferable. Hereinafter, the spray drying granulation method will be described.

  First, a slurry for composite particles containing a scaly electrode active material, a water-insoluble polymer, and a water-soluble polymer having an acidic group is prepared. The slurry for composite particles is prepared by dispersing or dissolving a scaly electrode active material, a water-insoluble polymer, a water-soluble polymer having an acidic group, and additives that are added as necessary in a solvent. be able to. In this case, when the water-insoluble polymer is dispersed in water as a dispersion medium, it can be added in a state dispersed in water. Moreover, when the water-soluble polymer which has an acidic group is the state melt | dissolved in water, it can add in the state dissolved in water.

  As the solvent used for obtaining the composite particle slurry, water is usually used, but a mixed solvent of water and an organic solvent may be used. Examples of the organic solvent that can be used in this case include alkyl alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol; alkyl ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran, dioxane and diglyme; diethylformamide; Amides such as dimethylacetamide, N-methyl-2-pyrrolidone and dimethylimidazolidinone; sulfur solvents such as dimethylsulfoxide and sulfolane; and the like. Among these, alcohols are preferable. By using water and an organic solvent having a lower boiling point than water, the drying rate can be increased during spray drying. Further, the dispersibility of the water-insoluble polymer and the solubility of the water-soluble polymer having an acidic group can be changed depending on the amount or type of the organic solvent used in combination with water. And thereby, the viscosity and fluidity | liquidity of the slurry for composite particles can be adjusted, and production efficiency can be improved.

  The amount of the solvent used when preparing the slurry for composite particles is such that the solid content concentration in the slurry for composite particles is preferably 1 to 50% by weight, more preferably 5 to 50% by weight, and still more preferably 10 to 30%. The amount is in the range of% by weight. By setting the solid content concentration within the above range, the water-insoluble polymer can be uniformly dispersed, which is preferable.

  The viscosity of the composite particle slurry is preferably in the range of 10 to 3,000 mPa · s, more preferably 30 to 1,500 mPa · s, and still more preferably 50 to 1,000 mPa · s at room temperature. When the viscosity of the slurry for composite particles is within this range, the productivity of the spray drying granulation step can be increased.

  Moreover, in this invention, when preparing the slurry for composite particles, you may add dispersing agents and surfactant other than the water-soluble polymer which has an acidic group mentioned above as needed.

  The dispersant other than the water-soluble polymer having an acidic group is not particularly limited as long as it is a resin that can be dissolved in a solvent. For example, carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, etc. Cellulosic polymers, and ammonium salts or alkali metal salts thereof; ammonium salts or alkali metal salts of polyacrylic acid or polymethacrylic acid; polyvinyl alcohol, modified polyvinyl alcohol, polyethylene oxide; polyvinyl pyrrolidone, polycarboxylic acid, oxidized starch, phosphorus Examples include acid starch, casein, various modified starches, chitin, and chitosan derivatives. These dispersants can be used alone or in combination of two or more. Especially, as a dispersing agent, a cellulose polymer is preferable and carboxymethylcellulose or its ammonium salt or alkali metal salt is especially preferable. The amount of the dispersant other than the water-soluble polymer having an acidic group depends on the content of the water-soluble polymer having an acidic group. The weight ratio of the “water-soluble polymer” is preferably 3/7 or less.

  Further, examples of the surfactant include amphoteric surfactants such as anionic, cationic, nonionic, and nonionic anions, but anionic or nonionic surfactants that are easily thermally decomposed are preferable. The compounding amount of the surfactant is preferably 50 parts by weight or less, more preferably 0.1 to 10 parts by weight, and further preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the scaly electrode active material. Part.

  There is no particular limitation on the method or order of dispersing or dissolving the scaly electrode active material, the water-insoluble polymer, the water-soluble polymer having an acidic group, and the additive added as necessary in a solvent. Moreover, as a mixing apparatus, a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a homomixer, a planetary mixer, etc. can be used, for example. Mixing is usually performed in the range of room temperature to 80 ° C. for 10 minutes to several hours.

  Subsequently, the obtained slurry for composite particles is granulated by spray drying. Spray drying is a method of spraying and drying a slurry in hot air. An atomizer is used as an apparatus used for spraying slurry. There are two types of atomizers: a rotating disk system and a pressurizing system. In the rotating disk system, slurry is introduced almost at the center of a disk that rotates at high speed, and the slurry is removed from the disk by the centrifugal force of the disk. In this case, the slurry is atomized. In the rotating disk system, the rotational speed of the disk depends on the size of the disk, but is usually 5,000 to 30,000 rpm, preferably 15,000 to 30,000 rpm. The lower the rotational speed of the disk, the larger the spray droplets and the larger the average particle diameter of the resulting composite particles for electrochemical device electrodes. Examples of the rotating disk type atomizer include a pin type and a vane type, and a pin type atomizer is preferable. A pin-type atomizer is a type of centrifugal spraying device that uses a spraying plate, and the spraying plate has a plurality of spraying rollers removably mounted on a concentric circle along its periphery between upper and lower mounting disks. It consists of The slurry for composite particles is introduced from the center of the spray disk, adheres to the spray roller by centrifugal force, moves outward on the roller surface, and finally sprays away from the roller surface. On the other hand, the pressurization method is a method in which the slurry for composite particles is pressurized and sprayed from a nozzle to be dried.

  The temperature of the slurry for composite particles to be sprayed is usually room temperature, but may be higher than room temperature by heating. Moreover, the hot air temperature at the time of spray-drying is 80-250 degreeC normally, Preferably it is 100-200 degreeC. In the spray drying method, the method of blowing hot air is not particularly limited. For example, the method in which the hot air and the spraying direction flow side by side, the method in which the hot air is sprayed at the top of the drying tower and descends with the hot air, and the sprayed droplets and hot air flow countercurrently. Examples include a contact method, and a method in which sprayed droplets first flow in parallel with hot air, then drop by gravity and contact countercurrent.

  The spraying method includes not only a method of spraying a slurry for composite particles containing a scaly electrode active material, a water-insoluble polymer and a water-soluble polymer having an acidic group, but also water-insoluble heavy duty. A method of spraying a slurry containing a coalesced polymer, a water-soluble polymer having an acidic group and, if necessary, other additives to the flowing electrode active material can also be used. From the standpoint of ease of particle size control, productivity, and reduction in particle size distribution, an optimal method may be appropriately selected according to the components of the composite particles.

  The average particle size of the composite particle for an electrochemical element electrode of the present invention thus obtained is preferably 0.1 to 1,000 μm, more preferably 1 to 80 μm, and further preferably 10 to 40 μm. By setting the average particle diameter in the above range, the fluidity of the composite particles for electrochemical element electrodes can be further improved. In addition, the average particle diameter of the composite particle for electrochemical element electrodes is a volume average particle diameter calculated by measuring with a laser diffraction particle size distribution analyzer (for example, SALD-3100; manufactured by Shimadzu Corporation).

<Electrochemical element electrode material>
The electrochemical element electrode material of the present invention comprises the above-described composite particle for an electrochemical element electrode of the present invention. The composite particle for an electrochemical element electrode of the present invention is used as an electrochemical element electrode material by including other binders or other additives alone or as necessary. The content of the composite particle for an electrochemical element electrode contained in the electrochemical element electrode material is preferably 50% by weight or more, more preferably 70% by weight or more, and further preferably 90% by weight or more.

  As another binder used as needed, the water-insoluble polymer contained in the composite particle for electrochemical element electrodes of the present invention described above can be used, for example. Since the composite particle for electrochemical element electrodes of the present invention already contains a water-insoluble polymer as a binder, another binder is added separately when preparing the electrochemical element electrode material. Although not necessary, another binder may be added in order to increase the binding force between the composite particles for electrochemical element electrodes. In addition, when the other binder is added, the amount of the other binder added is the total of the water-insoluble polymer in the composite electrode electrode for electrochemical devices, and the weight of the scaly electrode active material is 100 weight. The amount is preferably 0.01 to 10 parts by weight, more preferably 0.1 to 5 parts by weight with respect to parts. Other additives include molding aids such as water and alcohol, and these can be added by appropriately selecting an amount that does not impair the effects of the present invention.

<Electrochemical element electrode>
The electrochemical element electrode of the present invention is formed by laminating an active material layer made of the above-described electrochemical element electrode material of the present invention on a current collector. As the current collector material, for example, metal, carbon, conductive polymer and the like can be used, and metal is preferably used. As the metal, aluminum, platinum, nickel, tantalum, titanium, stainless steel, other alloys, etc. are usually used. Among these, it is preferable to use aluminum or an aluminum alloy in terms of conductivity and voltage resistance. In addition, when high voltage resistance is required, high-purity aluminum disclosed in JP 2001-176757 A can be suitably used. The current collector is in the form of a film or a sheet, and the thickness thereof is appropriately selected according to the purpose of use, but is usually 1 to 200 μm, preferably 5 to 100 μm, more preferably 10 to 50 μm.

  When laminating the active material layer on the current collector, the active material layer may be formed by forming the electrochemical element electrode material into a sheet and then laminating on the current collector. A method in which a chemical element electrode material is directly pressure-molded is preferred. As pressure molding, for example, a roll-type pressure molding apparatus provided with a pair of rolls is used. While feeding a current collector with a roll, an electrochemical element electrode material is roll-type pressure molded with a supply device such as a screw feeder. By supplying to the device, roll pressure forming method for forming the active material layer on the current collector, or spraying the electrochemical element electrode material on the current collector, and using the blade etc. Then, a method of adjusting the thickness and then forming with a pressurizing apparatus, a method of filling the mold with an electrochemical element electrode material, and pressurizing the mold to form are included. Among these, the roll pressure molding method is preferable. In particular, since the composite particles for electrochemical element electrodes of the present invention have high fluidity, the high fluidity enables molding by roll press molding, thereby improving productivity. It becomes.

  The temperature at the time of roll press molding is preferably 25 to 200 ° C, more preferably 50 to 150 ° C, and further preferably 80 to 120 ° C. By adjusting the temperature at the time of roll pressing to the above range, the adhesion between the active material layer and the current collector can be made sufficient. Moreover, the press linear pressure between rolls at the time of roll press molding is preferably 10 to 1,000 kN / m, more preferably 200 to 900 kN / m, and still more preferably 300 to 600 kN / m. By setting the linear pressure within the above range, the uniformity of the thickness of the active material layer can be improved. Moreover, the molding speed at the time of roll pressure molding is preferably 0.1 to 20 m / min, more preferably 1 to 10 m / min.

  Further, post-pressurization may be further performed as necessary in order to eliminate variations in the thickness of the formed electrochemical element electrode and increase the density of the active material layer to increase the capacity. The post-pressing method is generally a press process using a roll. In the roll pressing step, two cylindrical rolls are arranged vertically in parallel with a narrow interval, each is rotated in the opposite direction, and pressure is applied by interposing an electrode therebetween. In this case, the temperature of the roll may be adjusted as necessary, such as heating or cooling.

  Since the electrochemical element electrode of the present invention thus obtained is obtained by using the above-described composite particle for an electrochemical element electrode of the present invention for the active material layer, the active material layer, the current collector, In addition, the initial capacity is high, the internal resistance is low, and the high-temperature storage characteristics are excellent. Therefore, the electrochemical element electrode of the present invention can be suitably used as an electrode for various electrochemical elements such as a lithium ion secondary battery, particularly as a negative electrode.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Parts and% in each example are based on weight unless otherwise specified.
In addition, the definition and evaluation method of each characteristic are as follows.

<Flowability of composite particles for electrodes>
A powder tester P-100 (manufactured by Hosokawa Micron Corporation) was used, and sieves were set in the order of 250 μm, 150 μm, and 76 μm from the top on the vibration table. Then, the vibration amplitude is set to 1.0 mm, the vibration time is set to 60 seconds, the electrode composite particles 2 g are gently put on it to vibrate, and after the vibration is stopped, the weight remaining on each sieve is measured, and the following standards are used. The degree of aggregation (%) of the composite particles for electrodes was measured.
That is,
α (%) = [Amount of powder remaining on the upper sieve (screen with an opening of 250 μm)] ÷ 2 (g)
× 100
β (%) = [amount of powder remaining in the middle stage sieve (sieve 150 μm sieve)] ÷ 2 (g)
× 100 × 0.6
γ (%) = [the amount of powder remaining in the lower sieve (mesh with an opening of 76 μm)] ÷ 2 (g) ×
100x0.2
Based on the above, α, β and γ were calculated, and the degree of aggregation (%) = α + β + γ was calculated. And based on the calculated aggregation degree, the fluidity | liquidity of the composite particle for electrodes was evaluated by the following references | standards. It can be evaluated that the higher the fluidity, the better the moldability.
A: Aggregation degree is 0% or more and less than 5% B: Aggregation degree is 5% or more and less than 10% C: Aggregation degree is 10% or more and less than 25% D: Aggregation degree is 25% or more and less than 50% E: Aggregation degree is 50% or more

<Peel strength>
The negative electrodes obtained in Examples and Comparative Examples were fixed with the negative electrode active material layer face up, and a cellophane tape was attached to the surface of the negative electrode active material layer, and then the cellophane tape was applied from one end of the test piece to 50 mm / min. The stress when peeled in the 180 ° direction at a speed was measured. And this measurement was performed 10 times, the average value was calculated | required, this was made into peel strength, and the following reference | standard evaluated. It can be determined that the higher the peel strength, the higher the adhesion strength in the negative electrode active material layer and the adhesion strength between the negative electrode active material layer and the current collector.
A: Peel strength is 10 N / m or more B: Peel strength is less than 10 N / m, 5 N / m or more C: Peel strength is less than 5 N / m, 1 N / m or more D: Peel strength is less than 1 N / m

<Internal resistance>
The coin-type lithium ion secondary batteries obtained in the examples and comparative examples were charged at a room temperature and charged at a charge voltage of 4.2 V and a charge rate of 0.1 C after being left for 24 hours after the battery was prepared. It was. Then, in an environment of −30 ° C., discharge is performed at a discharge voltage of 3.0 V and a charge / discharge rate of 1 C, and an internal resistance is evaluated by measuring a voltage drop amount (ΔV) 10 seconds after the start of discharge. Went. It can be determined that the smaller the value of the voltage drop 10 seconds after the start of discharge, the smaller the internal resistance and the faster charge / discharge is possible.
A: Voltage drop amount is less than 0.2V B: Voltage drop amount is 0.2V or more and less than 0.3V C: Voltage drop amount is 0.3V or more and less than 0.5V D: Voltage drop amount is 0.5V or more , Less than 0.7V E: Voltage drop is 0.7V or more

<High temperature storage characteristics>
The coin-type lithium ion secondary batteries obtained in the examples and comparative examples were allowed to stand for 24 hours after the battery was prepared, and then charged / discharged at a charging voltage of 4.2 V, a discharging voltage of 3.0 V, and 0.1 C. The battery was charged and discharged, and the initial capacity _C0 was measured. Next, the battery was charged to 4.2 V, stored at 60 ° C. for 7 days, then charged and discharged at a charge voltage of 4.2 V, discharge voltage of 3.0 V, and 0.1 C, and the capacity C after high temperature storage. ₁ was measured. Then, according _{ΔC = C 1 / C 0 ×} 100 (%), to calculate a capacity retention rate, the following criteria were evaluated for high-temperature storage characteristics. It can be judged that the higher the capacity retention rate, the better the high-temperature storage characteristics.
A: ΔC is 85% or more B: ΔC is 70% or more and less than 85% C: ΔC is 60% or more and less than 70% D: ΔC is 50% or more and less than 60% E: ΔC is less than 50%

(Production Example 1: Production of water-insoluble particulate polymer (A1))
In a 5 MPa pressure vessel with a stirrer, 50 parts of styrene, 47 parts of 1,3-butadiene, 3 parts of methacrylic acid, 4 parts of sodium dodecylbenzenesulfonate, 150 parts of ion-exchanged water, t-dodecyl mercaptan 0.4 as a chain transfer agent 0.5 parts of potassium persulfate as a part and a polymerization initiator were charged and stirred sufficiently, and then heated to 50 ° C. to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction was stopped by cooling to obtain an aqueous dispersion of the water-insoluble particulate polymer (A1). The composition of the obtained water-insoluble particulate polymer (A1) was 50% styrene units, 47% 1,3-butadiene units, and 3% methacrylic acid units.

(Production Example 2: Production of water-insoluble particulate polymer (A2))
Except for changing the blending amount of styrene from 50 parts to 57 parts and the blending amount of 1,3-butadiene from 47 parts to 40 parts, respectively, a water-insoluble particulate polymer ( An aqueous dispersion of A2) was obtained. The composition of the obtained water-insoluble particulate polymer (A2) was styrene units 57%, 1,3-butadiene units 40%, and methacrylic acid units 3%.

(Production Example 3: Production of water-insoluble particulate polymer (A3))
Except for changing the blending amount of styrene from 50 parts to 40 parts and the blending amount of 1,3-butadiene from 47 parts to 57 parts, respectively, a water-insoluble particulate polymer ( An aqueous dispersion of A3) was obtained. The composition of the obtained water-insoluble particulate polymer (A3) was 40% styrene units, 57% 1,3-butadiene units, and 3% methacrylic acid units.

(Production Example 4: Production of water-insoluble particulate polymer (A4))
A water-insoluble particulate polymer was prepared in the same manner as in Production Example 1, except that the amount of 1,3-butadiene was changed from 50 parts to 47 parts and the amount of methacrylic acid was changed from 3 parts to 6 parts. An aqueous dispersion of (A4) was obtained. The composition of the obtained water-insoluble particulate polymer (A4) was styrene units 47%, 1,3-butadiene units 47%, and methacrylic acid units 6%.

(Production Example 5: Production of water-soluble polymer (B1) having an acidic group)
In a 5 MPa pressure vessel equipped with a stirrer, 50 parts of ion-exchanged water, 0.4 part of sodium bicarbonate, 0.115 part of sodium dodecyl diphenyl ether sulfonate with a concentration of 30%, 30 parts of methacrylic acid, 35 parts of ethyl acrylate, 32 parts of butyl acrylate. An emulsion aqueous solution was obtained by charging a monomer mixture consisting of 5 parts and 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and stirring sufficiently. Separately from the above, a 1 L SUS separable flask equipped with a stirrer, a reflux condenser and a thermometer was charged with demineralized water in advance and stirred sufficiently. The emulsion aqueous solution obtained above was continuously added dropwise to the potassium persulfate aqueous solution over 4 hours. Then, when the polymerization conversion rate reached 90%, the reaction temperature was changed to 80 ° C., and the reaction was further continued for 2 hours, followed by cooling to stop the reaction, and the water-soluble polymer (B1) having an acidic group was removed. An aqueous dispersion containing was obtained. The polymerization conversion is 99%, the glass transition temperature is 38 ° C., the weight average molecular weight is 25,000, and the composition of the water-soluble polymer (B1) having an acidic group is 30% methacrylic acid unit, ethyl The acrylate unit was 35%, the butyl acrylate unit was 32.5%, and the 2-acrylamido-2-methylpropanesulfonic acid unit (AMPS unit) was 2.5%.

(Production Example 6: Production of water-soluble polymer (B2) having an acidic group)
From 35 parts to 33 parts of ethyl acrylate, from 32.5 parts to 30 parts of butyl acrylate, and from 2.5 parts to 7 parts of 2-acrylamido-2-methylpropanesulfonic acid The aqueous dispersion containing the water-soluble polymer (B2) having an acidic group was obtained in the same manner as in Production Example 5 except that each was changed. The polymerization conversion is 99%, the glass transition temperature is 45 ° C., the weight average molecular weight is 50,000, and the composition of the water-soluble polymer (B2) having an acidic group is 30% methacrylic acid unit, ethyl They were 33% acrylate unit, 30% butyl acrylate unit and 7% 2-acrylamido-2-methylpropanesulfonic acid unit.

(Production Example 7: Production of water-soluble polymer having acidic group (B3))
A water-soluble polymer having an acidic group (B3) in the same manner as in Production Example 5 except that 2.5 parts of styrenesulfonic acid was used instead of 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid. An aqueous dispersion containing was obtained. The polymerization conversion is 99%, the glass transition temperature is 58 ° C., the weight average molecular weight is 70,000, and the composition of the water-soluble polymer (B3) having an acidic group is 30% methacrylic acid unit, ethyl The acrylate unit was 35%, the butyl acrylate unit was 32.5%, and the styrene sulfonic acid unit was 2.5%.

(Production Example 8: Production of water-soluble polymer (B4) having an acidic group)
In the same manner as in Production Example 5, except that 2.5 parts of 4-sulfobutylmethacrylate was used instead of 2.5 parts of 2-acrylamido-2-methylpropanesulfonic acid, a water-soluble polymer having an acidic group ( An aqueous dispersion containing B4) was obtained. The polymerization conversion is 99%, the glass transition temperature is 55 ° C., the weight average molecular weight is 40,000, and the composition of the water-soluble polymer (B4) having an acidic group is 30% methacrylic acid unit, ethyl The acrylate unit was 35%, the butyl acrylate unit was 32.5%, and the 4-sulfobutyl methacrylate unit was 2.5%.

(Production Example 9: Production of water-soluble polymer (B5) having an acidic group)
An aqueous dispersion containing a water-soluble polymer (B5) having an acidic group was obtained in the same manner as in Production Example 5 except that 30 parts of acrylic acid was used instead of 30 parts of methacrylic acid. The polymerization conversion is 99%, the glass transition temperature is 38 ° C., the weight average molecular weight is 25,000, and the composition of the water-soluble polymer (B5) having an acidic group is 30% acrylic acid unit, ethyl The acrylate unit was 35%, the butyl acrylate unit was 32.5%, and the 2-acrylamido-2-methylpropanesulfonic acid unit was 2.5%.

(Production Example 10: Production of water-soluble polymer (B6) having an acidic group)
It has an acidic group in the same manner as in Production Example 5 except that methacrylic acid is not used and the blending amount of 2-acrylamido-2-methylpropanesulfonic acid is changed from 2.5 parts to 32.5 parts. An aqueous dispersion containing a water-soluble polymer (B6) was obtained. The polymerization conversion was 99%, the glass transition temperature was 38 ° C., the weight average molecular weight was 25,000, and the composition of the water-soluble polymer (B6) having an acidic group was 35% ethyl acrylate units, butyl It was 32.5% of acrylate units and 32.5% of 2-acrylamido-2-methylpropanesulfonic acid units.

Example 1
Production of composite particles for negative electrode Scalar graphite (SLP-6, manufactured by Timcal Corporation, length of major axis L1: 3.5 μm, ratio of length of minor axis L2 to thickness t (L2 / t): 15) 100 parts, 2.7 parts in terms of solid content of the water-insoluble particulate polymer (A1) obtained in Production Example 1, and the water-soluble polymer having an acidic group obtained in Production Example 5 0.3 parts of (B1) in terms of solid content was mixed, and ion-exchanged water was further added so that the solid content concentration would be 20%, followed by mixing and dispersion to obtain a composite particle slurry. Then, the obtained slurry for composite particles was sprayed using a spray dryer (Okawara Chemical Co., Ltd.) and a rotating disk type atomizer (diameter 65 mm), rotating at 25,000 rpm, hot air temperature 150 ° C., particle recovery. Spray drying granulation was performed under conditions of an outlet temperature of 90 ° C. to obtain composite particles for a negative electrode. The average volume particle diameter of the obtained composite particles was 40 μm.

Production of Negative Electrode The negative electrode composite particles obtained above were applied to a roll (rolling rough surface heat roll, manufactured by Hirano Giken Kogyo Co., Ltd.) in a roll (roll temperature 100 ° C., press linear pressure 4.0 kN / cm). , Supplied together with an electrolytic copper foil (thickness: 20 μm) as a current collector, formed into a sheet on an electrolytic copper foil as a current collector at a molding speed of 20 m / min, and a negative electrode active material having a thickness of 80 μm A negative electrode having a layer was obtained.

Manufacture of half-cell, and the negative electrode plate is cut out into a disk shape with a diameter of 15 mm, and a separator made of a disk-shaped polypropylene porous film with a diameter of 18 mm and a thickness of 25 μm is formed on the negative electrode active material layer surface side of the negative electrode. Metals were laminated in order, and this was stored in a stainless steel coin-type outer container (diameter 20 mm, height 1.8 mm, stainless steel thickness 0.25 mm) provided with polypropylene packing. Next, an electrolytic solution (solvent: ethylene carbonate / diethyl carbonate = 1/2 (volume ratio at 20 ° C.), electrolyte: 1M LiPF ₆ ) is poured into this container so that no air remains, and a polypropylene packing is prepared. A stainless steel cap with a thickness of 0.2 mm is put on and fixed to the outer container, and the battery can is sealed to produce a half cell (secondary battery) for measuring the initial capacity with a diameter of 20 mm and a thickness of about 2 mm. did.

Manufacture of positive electrode 95 parts of LiCoO ₂ as a positive electrode active material, PVDF (polyvinylidene fluoride) as a binder for an electrode mixture layer were added so as to have a solid content of 3 parts, and further 2 parts of acetylene black, N-methyl 20 parts of pyrrolidone was added and mixed with a planetary mixer to obtain a positive electrode slurry. This positive electrode slurry was applied to an aluminum foil having a thickness of 18 μm, dried at 120 ° C. for 30 minutes, and then roll-pressed to obtain a positive electrode having a thickness of 60 μm.

Manufacture of Lithium Ion Secondary Battery The positive electrode obtained above was cut into a disk shape with a diameter of 13 mm and the negative electrode with a diameter of 14 mm, and the positive electrode active material layer side of this positive electrode had a disk-like polypropylene porous shape with a diameter of 18 mm and a thickness of 25 μm. The separator made of a film and the negative electrode obtained above were laminated in order, and this was stored in a stainless steel coin-type outer container provided with a polypropylene packing. An electrolytic solution (solvent: ethylene carbonate / diethyl carbonate = 1/2 (volume ratio at 20 ° C.), electrolyte: 1M LiPF ₆ ) is poured into this container so that no air remains, and is passed through a polypropylene packing. A 0.2 mm thick stainless steel cap was put on the outer container and fixed, and the battery can was sealed to manufacture a coin-type lithium ion secondary battery having a diameter of 20 mm and a thickness of about 3.2 mm.

  Then, evaluation of fluidity using the composite particles for negative electrode obtained above, evaluation of peel strength using negative electrode, evaluation of initial capacity using half cell, and lithium ion secondary battery The internal resistance and the high temperature storage characteristics were evaluated. The results are shown in Table 1.

(Example 2)
As a negative electrode active material, instead of scaly graphite (SLP-6, manufactured by Timcal), scaly graphite (SFG-6, manufactured by Timcar, Inc., length of major axis L1: 3.7 μm, length and thickness of minor axis L2 A composite particle for negative electrode, a negative electrode, a half cell, and a lithium ion secondary battery were produced and evaluated in the same manner as in Example 1 except that the ratio to t (L2 / t): 30) was used. It was. The results are shown in Table 1.

(Example 3)
As a negative electrode active material, instead of scaly graphite (SLP-6, manufactured by Timcal), scaly graphite (SFG-10, manufactured by Timcar, Inc., length of major axis L1: 5.5 μm, length and thickness of minor axis L2 A composite particle for negative electrode, a negative electrode, a half cell, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the ratio to t (L2 / t): 10) was used. It was. The results are shown in Table 1.

(Examples 4 to 6)
Instead of the water-insoluble particulate polymer (A1), the water-insoluble particulate polymer (A2) obtained in Production Example 2 (Example 4) and the water-insoluble particulate weight obtained in Production Example 3 A negative electrode was prepared in the same manner as in Example 1, except that the union (A3) (Example 5) and the water-insoluble particulate polymer (A4) (Example 6) obtained in Production Example 4 were used. Composite particles for electrodes, a negative electrode, a half cell, and a lithium ion secondary battery were produced and evaluated in the same manner. The results are shown in Table 1.

(Examples 7 to 10)
Instead of the water-soluble polymer (B1) having an acidic group, the water-soluble polymer (B2) having an acidic group obtained in Production Example 6 (Example 7) and having the acidic group obtained in Production Example 7 Water-soluble polymer (B3) (Example 8), water-soluble polymer (B4) having an acidic group obtained in Production Example 8 (Example 9), and water-soluble polymer having an acidic group obtained in Production Example 9 The negative electrode electrode composite particles, negative electrode, half cell and lithium ion secondary battery were produced in the same manner as in Example 1 except that the conductive polymer (B5) (Example 10) was used. went. The results are shown in Table 1.

(Examples 11-14)
Except that the blending amount of the water-insoluble particulate polymer (A1) and the water-soluble polymer (B1) having an acidic group was changed to the amount shown in Table 2, in the same manner as in Example 1, composite particles for negative electrode, A negative electrode, a half cell and a lithium ion secondary battery were produced and evaluated in the same manner. The results are shown in Table 2.

(Example 15)
For the negative electrode in the same manner as in Example 1 except that the water-soluble polymer (B6) having an acidic group obtained in Production Example 10 was used instead of the water-soluble polymer (B1) having an acidic group. Composite particles, a negative electrode, a half cell, and a lithium ion secondary battery were manufactured and evaluated in the same manner. The results are shown in Table 2.

(Comparative Example 1)
As a negative electrode active material, spherical artificial graphite (length of major axis L1: 4 μm, ratio of length of minor axis L2 to thickness t (L2 / t) instead of scaly graphite (SLP-6, manufactured by Timcal) : 1.5) was used in the same manner as in Example 1 except that composite particles for negative electrode, negative electrode, half cell and lithium ion secondary battery were produced and evaluated in the same manner. The results are shown in Table 2.

(Comparative Example 2)
A negative electrode composite particle, a negative electrode, a half cell, and a lithium ion secondary battery were produced in the same manner as in Example 1 except that carboxymethylcellulose was used instead of the water-soluble polymer (B1) having an acidic group. Evaluation was performed in the same manner. The results are shown in Table 2.

(Comparative Example 3)
In the same manner as in Example 1, a composite particle slurry was obtained, and the obtained composite particle slurry was applied onto an electrolytic copper foil as a current collector and dried at 110 ° C. A negative electrode, a half cell and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the layer was formed, and evaluated in the same manner. The results are shown in Table 2.

(Comparative Example 4)
Except that the water-insoluble particulate polymer (A1) was not blended, the composite particles for negative electrode were produced in the same manner as in Example 1. As a result, the composite particles for negative electrode were obtained with extremely poor moldability. I could not.

  As shown in Tables 1 and 2, the electrode composite material containing a scaly electrode active material, a water-insoluble polymer and a water-soluble polymer having an acidic group has high fluidity. The electrodes obtained using such composite particles for electrodes had high peel strength, low internal resistance when used as batteries, and excellent high-temperature storage characteristics (Examples 1 to 15).

On the other hand, when a spherical electrode active material is used instead of the scaly electrode active material, the fluidity of the composite particles for the negative electrode is low, the peel strength when the negative electrode is used, and the battery It was inferior to the internal resistance and the high-temperature storage characteristics when compared (Comparative Example 1).
In addition, when carboxymethyl cellulose was used instead of the water-soluble polymer having an acidic group, the peel strength when used as a negative electrode and the internal resistance when used as a battery were inferior (Comparative Example 2). ).
Furthermore, instead of obtaining composite particles for negative electrode and molding the obtained composite particles for negative electrode in a powder state, a scaly electrode active material, a water-insoluble polymer, and a water-soluble polymer having an acidic group When a negative electrode is obtained by directly applying a slurry containing benzene onto a current collector, the resulting negative electrode has a low peel strength, and further has inferior internal resistance and high-temperature storage characteristics when used as a battery. (Comparative Example 3).
Moreover, when not using a water-insoluble polymer, the molded object which can perform each evaluation was not able to be obtained (comparative example 4).

Claims (7)

  A composite particle for an electrochemical element electrode, comprising a scaly electrode active material, a water-insoluble polymer, and a water-soluble polymer having an acidic group.   The composite particle for an electrochemical element electrode, wherein the water-soluble polymer contains a sulfonic acid group as an acidic group.   An electrochemical element electrode material comprising the composite particle for an electrochemical element electrode according to claim 1.   An electrochemical element electrode, comprising an active material layer formed of the electrochemical element electrode material according to claim 3 and laminated on a current collector.   The electrochemical element electrode according to claim 4, wherein the active material layer is laminated on the current collector by pressure molding.   6. The electrochemical element electrode according to claim 5, wherein the active material layer is laminated on the current collector by roll pressing. A method for producing the composite particle for an electrochemical element electrode according to claim 1 or 2,
The electrode active material, the water-insoluble polymer, and a process for obtaining a slurry by dispersing the water-soluble polymer in water, and a process for spray drying and granulating the slurry, for an electrochemical device electrode A method for producing composite particles.