WO2015098632A1

WO2015098632A1 - Composite particle for electrochemical element electrode

Info

Publication number: WO2015098632A1
Application number: PCT/JP2014/083339
Authority: WO
Inventors: 梓増田
Original assignee: 日本ゼオン株式会社
Priority date: 2013-12-26
Filing date: 2014-12-17
Publication date: 2015-07-02
Also published as: CN105794025B; CN105794025A; JPWO2015098632A1; KR20160102159A; JP6485359B2; KR102330766B1

Abstract

A composite particle for electrochemical element electrodes, including a negative electrode active material (A), a particulate binder resin (B), a water-soluble polymer (C), and non-water-soluble polysaccharide polymer fibers (D). The water-soluble polymer (C) and the non-water-soluble polysaccharide polymer fibers (D) are included at a weight ratio of (C)/(D) = 0.2-18.

Description

Composite particles for electrochemical device electrodes

The present invention relates to composite particles for electrochemical element electrodes.

The demand for electrochemical devices such as lithium-ion secondary batteries, electric double-layer capacitors, and lithium-ion capacitors is rapidly expanding by taking advantage of the small size, light weight, high energy density, and the ability to repeatedly charge and discharge. is doing. Lithium ion secondary batteries have a relatively high energy density and are used in mobile fields such as mobile phones and notebook personal computers. On the other hand, since the electric double layer capacitor can be rapidly charged and discharged, the electric double layer capacitor is expected to be used as an auxiliary power source for an electric vehicle or the like in addition to being used as a memory backup small power source for a personal computer or the like. Furthermore, the lithium ion capacitor that takes advantage of the lithium ion secondary battery and the electric double layer capacitor has higher energy density and output density than the electric double layer capacitor. Application to applications that could not meet the specifications for capacitor performance is being considered. Among these, in particular, lithium ion secondary batteries have been studied for application not only to in-vehicle applications such as hybrid electric vehicles and electric vehicles, but also to power storage applications.

While expectations for these electrochemical devices have increased, these electrochemical devices have further improvements such as lower resistance, higher capacity, and improved mechanical properties and productivity as applications expand and develop. It has been demanded. Under such circumstances, there is 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 an electrochemical element electrode material suitable for the manufacturing method. Has been done.

Electrodes for electrochemical devices are usually formed by laminating an electrode active material layer formed by binding an electrode active material and a conductive aid used as necessary with a binder resin on a current collector. It will be. An electrode for an electrochemical element includes a coated electrode manufactured by a method in which a slurry for a coated electrode containing an electrode active material, a binder resin, a conductive auxiliary agent, etc. is coated on a current collector and the solvent is removed by heat or the like. However, it has been difficult to manufacture a uniform electrochemical device due to migration of a binder resin or the like. In addition, this method has a high cost and a poor working environment, and the manufacturing apparatus tends to be large.

On the other hand, it has been proposed to obtain an electrochemical element having a uniform electrode active material layer by obtaining composite particles and powder molding. As a method of forming such an electrode active material layer, for example, Patent Document 1 discloses composite particles obtained by spraying and drying a slurry for composite particles containing an electrode active material, a binder resin, and a dispersion medium. A method of forming an electrode active material layer using composite particles is disclosed. Since such composite particles may be destroyed during transfer such as pneumatic transportation, improvement in strength is required.

Here, when the electrode active material layer is formed using the broken composite particles, the uniformity of the particle size of the composite particles is lost, so that the fluidity of the powder is deteriorated and a uniform electrode active material layer is formed. Can not be. In addition, the adhesion between the composite particles and the adhesion between the electrode active material layer and the current collector were weakened, and the cycle characteristics of the resulting electrochemical device were not sufficient. Moreover, the electrode which has the electrode active material layer formed using the broken composite particle is inferior in a softness | flexibility, and when the electrode was wound, the electrode might crack.

Further, in Patent Document 1, externally added particles obtained by coating the surface of the composite particles with a fibrous conductive assistant are obtained, but since the fibrous conductive assistant is not present inside the composite particles, the composite particles It was not possible to improve the strength.

In addition, Patent Document 2 describes that carbon fiber is contained in a slurry for a coating electrode that is applied to an electrode to form an electrode layer in order to improve adhesion in the coating electrode. However, since it relates to a method for producing the coated electrode, which is different from powder molding using composite particles, it has not been described to improve the strength of the composite particles.

Further, Patent Document 3 describes that, in order to enhance the adhesion in the coated electrode, the coated electrode slurry for forming the electrode layer by coating the electrode contains finely divided cellulose fibers. However, since it relates to a method for producing the coated electrode, which is different from powder molding using composite particles, it has not been described to improve the strength of the composite particles.

International Publication No. 2009/44856 JP 2009-295666 A International Publication No. 2013/42720

An object of the present invention is to provide a composite particle for an electrochemical element electrode that has sufficient strength, can provide sufficient adhesion when forming an electrode, and can provide an electrode having excellent flexibility. That is.

As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by obtaining composite particles by combining a water-soluble polymer and a water-insoluble polysaccharide polymer in a predetermined ratio. The present invention has been completed.

That is, according to the present invention,
(1) Electrochemical element electrode composite particles comprising a negative electrode active material (A), a particulate binder resin (B), a water-soluble polymer (C) and a water-insoluble polysaccharide polymer fiber (D), An electrochemical element comprising water-soluble polymer (C) and water-insoluble polysaccharide polymer fiber (D) in a weight ratio of (C) / (D) = 0.2-18 Composite particles for electrodes,
(2) The composite particle for an electrochemical element electrode according to (1), wherein the water-insoluble polysaccharide polymer fiber (D) has an average degree of polymerization of 50 to 1000,
(3) The particulate binder resin (B) is a conjugated diene polymer or an acrylate polymer, (1) or (2) the composite particle for an electrochemical element electrode,
(4) The amount of the water-soluble polymer (C) is 0.1 to 10 parts by weight in terms of solid content with respect to 100 parts by weight of the negative electrode active material (A), and the water-insoluble polysaccharide polymer fiber The electrochemical element electrode according to any one of (1) to (3), wherein the blending amount of (D) is 0.1 to 2 parts by weight in terms of solid content with respect to 100 parts by weight of composite particles obtained Composite particles,
Is provided.

ADVANTAGE OF THE INVENTION According to this invention, it has sufficient intensity | strength, can provide sufficient adhesiveness when forming an electrode, and provides the composite particle for electrochemical element electrodes which can obtain the electrode which is further excellent in a softness | flexibility. be able to.

Hereinafter, the composite particle for an electrochemical element electrode according to an embodiment of the present invention will be described. The composite particle for an electrochemical element electrode of the present invention (hereinafter sometimes referred to as “composite particle”) includes a negative electrode active material (A), a particulate binder resin (B), a water-soluble polymer (C), and a non-particle. A composite particle for an electrochemical device electrode comprising a water-soluble polysaccharide polymer fiber (D), wherein the water-soluble polymer (C) and the water-insoluble polysaccharide polymer fiber (D) are in a weight ratio (C) /(D)=0.2-18.

In the following, “positive electrode active material” means an electrode active material for a positive electrode, and “negative electrode active material” means an electrode active material for a negative electrode. The “positive electrode active material layer” means an electrode active material layer provided on the positive electrode, and the “negative electrode active material layer” means an electrode active material layer provided on the negative electrode.

(Negative electrode active material (A))
Examples of the negative electrode active material (A) used in the present invention include materials that can transfer electrons in the negative electrode of an electrochemical element. As the negative electrode active material (A) in the case where the electrochemical device is a lithium ion secondary battery, a material that can occlude and release lithium can be generally used.

Examples of the negative electrode active material (A) preferably used for the lithium ion secondary battery include a negative electrode active material formed of carbon. Examples of the negative electrode active material formed of carbon include natural graphite, artificial graphite, and carbon black. Among them, graphite such as artificial graphite and natural graphite is preferable, and natural graphite is particularly preferable.

Also, another example of the negative electrode active material (A) preferably used for the lithium ion secondary battery is a negative electrode active material containing a metal. In particular, a negative electrode active material containing at least one selected from the group consisting of tin, silicon, germanium and lead is preferable. The negative electrode active material containing these elements can reduce the irreversible capacity.

Among these negative electrode active materials containing metals, negative electrode active materials containing silicon are preferable. By using a negative electrode active material containing silicon, the electric capacity of the lithium ion secondary battery can be increased. In general, a negative electrode active material containing silicon expands and contracts greatly (for example, about 5 times) with charge and discharge, but the composite particles of the present invention have a strength that can withstand the expansion and contraction of the negative electrode active material containing silicon. Have. Therefore, in the negative electrode manufactured using the composite particles of the present invention, it is possible to effectively suppress a decrease in battery performance due to expansion and contraction of the negative electrode active material containing silicon.

Examples of the negative electrode active material containing silicon include silicon-containing compounds (hereinafter sometimes referred to as “silicon-containing compounds”) and metallic silicon. The silicon-containing compound is a compound of silicon and another element, and examples thereof include SiO, SiO ₂ , SiO _x (0.01 ≦ x <2), SiC, and SiOC. Among these, SiO _x , SiOC, and SiC are preferable, SiO _x and SiOC are more preferable from the viewpoint of battery life, and SiO _x is particularly preferable from the viewpoint of suppressing swelling of the negative electrode. Here, SiO _x is a compound that can be formed from one or both of SiO and SiO ₂ and metallic silicon. This SiO _x can be produced, for example, by cooling and precipitating silicon monoxide gas generated by heating a mixture of SiO ₂ and metal silicon.

In addition, when a silicon-containing compound is used as the negative electrode active material (A), the amount of the silicon-containing compound in the negative electrode active material (A) is preferably 1 to 50% by weight, more preferably 5 to 40% by weight, particularly Preferably, it is 10 to 30% by weight. If the compounding amount of the silicon-containing compound is too small, the capacity when a lithium ion secondary battery is produced becomes small. Moreover, when there are too many compounding quantities of a silicon-containing compound, a negative electrode will swell.
Moreover, as a negative electrode active material (A), one type may be used independently and it may be used combining two or more types by arbitrary ratios.

The negative electrode active material (A) preferably has a particle size. Here, when the shape of the particles of the negative electrode active material (A) is spherical, a high-density electrode can be obtained when forming the negative electrode. The volume average particle diameter of the negative electrode active material for a lithium ion secondary battery is preferably 0.1 to 100 μm, more preferably 0.5 to 50 μm, and still more preferably 0.8 to 20 μm. Furthermore, the tap density of the negative electrode active material for the lithium ion secondary battery is not particularly limited, but those having a density of 0.6 g / cm ³ or more are preferably used.
Moreover, as a negative electrode active material (A) preferably used when an electrochemical element is a lithium ion capacitor, the negative electrode active material formed with the said carbon is mentioned.

(Particulate binder resin (B))
The particulate binder resin (B) used in the present invention is not particularly limited as long as it is a substance capable of binding the above-described negative electrode active materials to each other. As the particulate binder resin (B), a dispersion type particulate binder resin having a property of being dispersed in a solvent is preferable. Examples of the dispersion type particulate binder resin include high molecular compounds such as silicon-based polymers, fluorine-containing polymers, conjugated diene-based polymers, acrylate-based polymers, polyimides, polyamides, and polyurethanes, preferably fluorine. A containing polymer, a conjugated diene polymer, and an acrylate polymer, more preferably a conjugated diene polymer and an acrylate polymer. These polymers can be used alone or in combination as a dispersion type particulate binder resin.

The fluorine-containing polymer is a polymer containing a monomer unit containing a fluorine atom. Specific examples of the fluorine-containing polymer include polytetrafluoroethylene, polyvinylidene fluoride, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, ethylene / tetrafluoroethylene copolymer, ethylene / chlorotrifluoroethylene copolymer, A perfluoroethylene propene copolymer may be mentioned. Among them, it is preferable to include polytetrafluoroethylene because it is easy to fibrillate and hold the negative electrode active material.

The conjugated diene polymer is a homopolymer of a conjugated diene monomer, a copolymer obtained by polymerizing a monomer mixture containing a conjugated diene monomer, or a hydrogenated product thereof. 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, substituted linear conjugated pentadiene as conjugated diene monomer Preferably, 1,3-butadiene is used in that the flexibility when used as an electrode can be improved and the resistance to cracking can be increased. It is more preferable. Further, the monomer mixture may contain two or more of these conjugated diene monomers.

When the conjugated diene polymer is a copolymer of the above conjugated diene monomer and a monomer copolymerizable therewith, examples of the copolymerizable monomer include α, Examples thereof include a β-unsaturated nitrile compound and a vinyl compound having an acid component.

Specific examples of conjugated diene polymers include conjugated diene monomer homopolymers such as polybutadiene and polyisoprene; aromatic vinyl monomers such as carboxy-modified styrene-butadiene copolymer (SBR). Monomer / conjugated diene monomer copolymer; vinyl cyanide monomer / conjugated diene monomer copolymer such as acrylonitrile / butadiene copolymer (NBR); hydrogenated SBR, hydrogenated NBR, etc. Is mentioned.

The amount of the conjugated diene monomer unit in the conjugated diene polymer is preferably 20 to 60% by weight, more preferably 30 to 55% by weight. When the compounding amount of the conjugated diene monomer unit is too large, the electrolytic solution resistance tends to be lowered when the negative electrode is produced using composite particles containing a binder resin. If the blending amount of the conjugated diene monomer unit is too small, sufficient adhesion between the composite particles and the current collector tends not to be obtained.

The acrylate polymer has the general formula (1): CH ₂ ═CR ¹ —COOR ² (wherein R ¹ represents a hydrogen atom or a methyl group, R ² represents an alkyl group or a cycloalkyl group. R ² further represents A monomer unit derived from a compound represented by an ether group, a hydroxyl group, a phosphate group, an amino group, a carboxyl group, a fluorine atom, or an epoxy group. Copolymer obtained by polymerizing a polymer containing, specifically, a homopolymer of a compound represented by the general formula (1) or a monomer mixture containing the compound represented by the general formula (1) It is a coalescence. Specific examples of the compound represented by the general formula (1) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylate n. -Butyl, isobutyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isopentyl (meth) acrylate, isooctyl (meth) acrylate, isobornyl (meth) acrylate, (meth) (Meth) acrylic acid alkyl esters such as isodecyl acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and tridecyl (meth) acrylate; butoxyethyl (meth) acrylate, ethoxydiethylene glycol (meth) acrylate , (Meth) acrylic acid methoxydipropylene Recall, (meth) acrylic acid methoxypolyethylene glycol, (meth) acrylic acid phenoxyethyl, ether-containing (meth) acrylic acid ester such as (meth) acrylic acid tetrahydrofurfuryl; (meth) acrylic acid-2-hydroxyethyl, Hydroxyl-containing (meth) acrylic such as (meth) acrylic acid-2-hydroxypropyl, (meth) acrylic acid-2-hydroxy-3-phenoxypropyl, 2- (meth) acryloyloxyethyl-2-hydroxyethylphthalic acid, etc. Acid ester; 2- (meth) acryloyloxyethylphthalic acid-containing (meth) acrylic acid ester; (meth) acrylic acid perfluorooctylethyl fluorine-containing (meth) acrylic acid ester; (meth) Phosphoric acid group-containing (meth) acrylates such as ethyl acrylate Acrylic acid esters; (meth) epoxy group-containing (meth) acrylic acid esters of glycidyl acrylate; (meth) containing amino group such as dimethylaminoethyl acrylate (meth) acrylic acid ester; and the like.

In this specification, “(meth) acryl” means “acryl” and “methacryl”. “(Meth) acryloyl” means “acryloyl” and “methacryloyl”.

These (meth) acrylic acid esters can be used alone or in combination of two or more. Among these, (meth) acrylic acid alkyl esters are preferable, and methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, and alkyl groups have 6 to 12 carbon atoms. (Meth) acrylic acid alkyl ester is more preferred. By selecting these, it becomes possible to reduce the swellability with respect to the electrolytic solution, and to improve the cycle characteristics.

In addition, when the acrylate polymer is a copolymer of the compound represented by the general formula (1) and a monomer copolymerizable therewith, as the copolymerizable monomer, For example, carboxylic acid esters having two or more carbon-carbon double bonds, aromatic vinyl monomers, amide monomers, olefins, diene monomers, vinyl ketones, and heterocyclic rings In addition to vinyl compounds, examples include α, β-unsaturated nitrile compounds and vinyl compounds having an acid component.

Among the above copolymerizable monomers, the electrode (negative electrode) can be made difficult to be deformed when the electrode (negative electrode) is produced, and the strength can be strong, and sufficient adhesion between the negative electrode active material layer and the current collector is obtained. In view of the obtained point, it is preferable to use an aromatic vinyl monomer. Examples of the aromatic vinyl monomer include styrene.

In addition, when there is too much compounding quantity of an aromatic vinyl-type monomer, there exists a tendency for sufficient adhesiveness of a negative electrode active material layer and a collector to be not acquired. Moreover, when there are too few compounding quantities of an aromatic vinyl-type monomer, there exists a tendency for electrolyte solution resistance to fall, when manufacturing a negative electrode.

The blending amount of the (meth) acrylic acid ester unit in the acrylate-based polymer is preferably 50 to 50% from the viewpoint of improving flexibility when used as an electrode (negative electrode) and increasing resistance to cracking. It is 95% by weight, more preferably 60 to 90% by weight.

Examples of the α, β-unsaturated nitrile compound used in the polymer constituting the dispersed particulate binder resin include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile, and α-bromoacrylonitrile. These may be used alone or in combination of two or more. Among these, acrylonitrile and methacrylonitrile are preferable, and acrylonitrile is more preferable.

The blending amount of the α, β-unsaturated nitrile compound unit in the dispersion type binder resin is preferably 0.1 to 40% by weight, more preferably 0.5 to 30% by weight, and further preferably 1 to 20% by weight. It is. When an α, β-unsaturated nitrile compound unit is contained in the dispersion-type binder resin, it is difficult to be deformed when the electrode (negative electrode) is produced, and the strength can be increased. Further, when an α, β-unsaturated nitrile compound unit is contained in the dispersion-type binder resin, the adhesion between the negative electrode active material layer containing composite particles and the current collector can be made sufficient.

Note that if the amount of the α, β-unsaturated nitrile compound unit is too large, sufficient adhesion between the negative electrode active material layer and the current collector tends not to be obtained. On the other hand, if the amount of the α, β-unsaturated nitrile compound unit is too small, the resistance to electrolyte solution tends to decrease when the negative electrode is produced.

Examples of the vinyl compound having an acid component include acrylic acid, methacrylic acid, itaconic acid, maleic acid, and fumaric acid. These may be used alone or in combination of two or more. Among these, acrylic acid, methacrylic acid, and itaconic acid are preferable, methacrylic acid and itaconic acid are more preferable, and methacrylic acid is particularly preferable in terms of improving adhesive strength.

The blending amount of the vinyl compound unit having an acid component in the dispersion type particulate binder resin is preferably 0.5 to 10% by weight, more preferably from the viewpoint of improving the stability of the composite particle slurry. Is 1 to 8% by weight, more preferably 2 to 7% by weight.

In addition, when there are too many compounding quantities of the vinyl compound unit which has an acid component, there exists a tendency for the viscosity of the slurry for composite particles to become high, and for handling to become difficult. Moreover, when there are too few compounding quantities of the vinyl compound unit which has an acid component, there exists a tendency for stability of the slurry for composite particles to fall.

The dispersion type particulate binder resin used in the present invention is in the form of particles, so that it has good binding properties, and can suppress deterioration of the capacity of the produced electrode and repeated charge / discharge. Examples of the particulate binder resin (B) include those in which binder resin particles such as latex are dispersed in water, and powders obtained by drying such a dispersion.

The average particle size of the dispersion type particulate binder resin is preferably from the viewpoint that the strength and flexibility of the obtained negative electrode are improved while the stability in the case of the composite particle slurry is improved. The thickness is from 001 to 100 μm, more preferably from 10 to 1000 nm, still more preferably from 50 to 500 nm.

The method for producing the particulate binder resin (B) used in the present invention is not particularly limited, and a known polymerization method such as an emulsion polymerization method, a suspension polymerization method, a dispersion polymerization method or a solution polymerization method may be employed. it can. Among these, it is preferable to produce by an emulsion polymerization method because the particle diameter of the particulate binder resin (B) can be easily controlled. The particulate binder resin (B) used in the present invention may be particles having a core-shell structure obtained by stepwise polymerization of a mixture of two or more monomers.

The compounding amount of the particulate binder resin (B) in the composite particle for an electrochemical element electrode of the present invention can ensure sufficient adhesion between the obtained negative electrode active material layer and the current collector, and the electrochemical element From the viewpoint of reducing the internal resistance of the negative electrode active material, it is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 20 parts by weight, and still more preferably 100 parts by weight of the negative electrode active material on a dry weight basis. 1 to 15 parts by weight.

(Water-soluble polymer (C))
The water-soluble polymer (C) used in the present invention refers to a polymer having an undissolved content of less than 10.0% by weight when 0.5 g of the polymer is dissolved in 100 g of pure water at 25 ° C.

Specific examples of the water-soluble polymer (C) include cellulosic polymers such as carboxymethylcellulose, methylcellulose, ethylcellulose and hydroxypropylcellulose, and ammonium salts or alkali metal salts thereof, alginates such as propylene glycol alginate, and alginic acid. Alginates such as sodium, polyacrylic acid, and polyacrylic acid (or methacrylic acid) salts such as sodium polyacrylic acid (or methacrylic acid), polyvinyl alcohol, modified polyvinyl alcohol, poly-N-vinylacetamide, polyethylene oxide, polyvinyl Examples include pyrrolidone, polycarboxylic acid, oxidized starch, phosphate starch, casein, various modified starches, chitin, and chitosan derivatives. It is. In the present invention, “(modified) poly” means “unmodified poly” or “modified poly”.

These water-soluble polymers (C) can be used alone or in combination of two or more. Among these, from the viewpoint of improving the dispersibility of the water-insoluble polysaccharide polymer fiber (D) and high adhesiveness, a cellulose-based polymer is preferable, and carboxymethyl cellulose or its ammonium salt or alkali metal salt is particularly preferable. The blending amount of these water-soluble polymers (C) is not particularly limited as long as the effect of the present invention is not impaired, but with respect to 100 parts by weight of the negative electrode active material (A) in solid part equivalent amount, The amount is preferably 0.1 to 10 parts by weight, more preferably 0.2 to 5 parts by weight, still more preferably 0.25 to 2 parts by weight.

(Water-insoluble polysaccharide polymer fiber (D))
The water-insoluble polysaccharide polymer fiber (D) used in the present invention belongs to a so-called polymer compound among polysaccharides, and there is no other limitation as long as it is a water-insoluble fibrous form. Usually, it is a fiber (short fiber) fibrillated by a mechanical shearing force. In addition, the water-insoluble polysaccharide polymer fiber used in the present invention is a high-polysaccharide fiber having an undissolved content of 90% by weight or more when 0.5 g of polysaccharide polymer fiber is dissolved in 100 g of pure water at 25 ° C. Refers to molecular fiber.

As the water-insoluble polysaccharide polymer fiber (D), it is preferable to use polysaccharide polymer nanofibers. Among the polysaccharide polymer nanofibers, they are flexible and have a high tensile strength. From the viewpoint of enhancing the particle reinforcing effect and enhancing the particle strength, it is more preferable to use a single or any mixture selected from bio-derived nanofibers such as cellulose nanofibers, chitin nanofibers and chitosan nanofibers. preferable. Among these, it is more preferable to use cellulose nanofibers, and it is particularly preferable to use cellulose nanofibers made from bamboo, conifers, hardwoods, and cotton.

As a method for fibrillating (shortening fiber) by applying mechanical shearing force to these water-insoluble polysaccharide polymer fibers (D), a method in which water-insoluble polysaccharide polymer fibers are dispersed in water and then beaten. And a method of passing through an orifice. As the water-insoluble polysaccharide polymer fiber, short fibers having various fiber diameters are commercially available, and these may be used by dispersing in water.

The average fiber diameter of the water-insoluble polysaccharide polymer fiber (D) used in the present invention is such that more water-insoluble polysaccharide polymer fiber (D) is present in the composite particles and the adhesion between the negative electrode active materials is strengthened. From the viewpoint of ensuring sufficient strength of the composite particles and the electrode (negative electrode), and from the viewpoint of excellent electrochemical characteristics of the obtained electrochemical device, it is preferably 5 to 3000 nm, more preferably 5 to 2000 nm, and still more preferably. It is 5 to 1000 nm, particularly preferably 5 to 100 nm. If the average fiber diameter of the water-insoluble polysaccharide polymer fiber (D) is too large, the water-insoluble polysaccharide polymer fiber cannot sufficiently exist in the composite particle, so that the strength of the composite particle should be sufficient. I can't. Further, the fluidity of the composite particles is deteriorated, and it is difficult to form a uniform negative electrode active material layer.

In addition, the water-insoluble polysaccharide polymer fiber (D) may be made of a single fiber that is sufficiently separated without being aligned. In this case, the average fiber diameter is the average diameter of single fibers. In addition, the water-insoluble polysaccharide polymer fiber (D) may be one in which a plurality of single fibers are aggregated in a bundle to form one yarn. In this case, the average fiber diameter is defined as the average value of the diameters of one yarn.

Further, the average degree of polymerization of the water-insoluble polysaccharide polymer fiber (D) is obtained from the viewpoint that the strength of the composite particles and the electrode (negative electrode) is sufficient, and a uniform negative electrode active material layer can be formed. From the viewpoint of excellent electrochemical characteristics of the chemical element, it is preferably 50 to 1000, more preferably 100 to 900, and still more preferably 150 to 800. If the average degree of polymerization of the water-insoluble polysaccharide polymer fiber is too large, the internal resistance of the resulting electrochemical device increases. In addition, it becomes difficult to form a uniform negative electrode active material layer. Moreover, when the average degree of polymerization of the water-insoluble polysaccharide polymer fiber is too small, the strength of the composite particles becomes insufficient.

In the present invention, the average degree of polymerization is determined by a viscosity method using the following copper ethylenediamine solution.
A freeze-dried water-insoluble polysaccharide polymer fiber is dissolved in a copper ethylenediamine solution 1 to prepare a solution 2, and the viscosity is measured using a viscometer. The intrinsic viscosity [η] of the water-insoluble polysaccharide polymer fiber solution is obtained by the following calculation formula where the viscosity of the solution 2 is η and the viscosity of the solution 1 is η0.

Intrinsic viscosity [η] = (η / η0) / {c (1 + A × η / η0)}
Here, c is the water-insoluble polysaccharide polymer fiber concentration (g / dL), and A is a value determined by the type of the solution 1. When 0.5 M copper ethylenediamine solution is used as solution 1, A is 0.28.

And average polymerization degree DP is calculated | required from the following formula | equation.
Intrinsic viscosity [η] = K × DP ^a
Here, K and a are values determined by the type of polymer. For example, in the case of cellulose, K is 5.7 × 10 ⁻³ and a is 1.

The soot viscometer is preferably a capillary viscometer, examples of which include a Canon-Fenske viscometer.

The blending amount of the water-insoluble polysaccharide polymer fiber (D) is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1. part by weight in terms of solid content with respect to 100 parts by weight of the resulting composite particles. 5 parts by weight, more preferably 0.3 to 1 part by weight. When the blending amount of the water-insoluble polysaccharide polymer fiber is too large, the internal resistance of the obtained electrochemical element increases. In addition, it becomes difficult to form a uniform electrode layer (negative electrode active material layer). Moreover, when there are too few compounding quantities of water-insoluble polysaccharide polymer fiber (D), the reinforcement effect by water-insoluble polysaccharide polymer fiber will be small, and the intensity | strength of composite particle will become inadequate. Moreover, when there are too many compounding quantities of a water-insoluble polysaccharide polymer fiber (D), granulation of a composite particle cannot be performed.

In addition, when the viscosity of the slurry for composite particles increases by increasing the blending amount of the water-insoluble polysaccharide polymer fiber (D), the viscosity is appropriately adjusted by reducing the blending amount of the water-soluble polymer. Can do.

The ratio of the water-soluble polymer (C) and the water-insoluble polysaccharide polymer fiber (D) used in the present invention is determined from the viewpoint of improving the dispersibility of the water-insoluble polysaccharide polymer fiber (D). In terms of weight ratio in terms of conversion, water-soluble polymer (C) / water-insoluble polysaccharide polymer fiber (D) = 0.2 to 18, preferably 0.25 to 15, more preferably 0.3 to 10. .

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

The conductive auxiliary agent is not particularly limited as long as it is a conductive material, but a conductive particulate material is preferable. For example, conductive carbon black such as furnace black, acetylene black, and ketjen black; natural And graphite such as graphite and artificial graphite; and carbon fibers such as polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and vapor grown carbon fiber. The average particle diameter when the conductive additive is a particulate material is not particularly limited, but is preferably smaller than the average particle diameter of the negative electrode active material, from the viewpoint of expressing sufficient conductivity with a smaller amount of use. The thickness is preferably 0.001 to 10 μm, more preferably 0.05 to 5 μm, and still more preferably 0.1 to 1 μm.

In the composite particle for an electrochemical element electrode of the present invention, the compounding amount of the conductive assistant is 100 parts by weight of the negative electrode active material from the viewpoint of sufficiently reducing the internal resistance while keeping the capacity of the obtained electrochemical element high. On the other hand, it is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 15 parts by weight, still more preferably 1 to 10 parts by weight.

(Manufacture of composite particles)
The composite particles include a negative electrode active material (A), a particulate binder resin (B), a water-soluble polymer (C), a water-insoluble polysaccharide polymer fiber (D), and a conductive additive added as necessary. It is obtained by granulating using the above ingredients. The composite particles include the negative electrode active material (A) and the particulate binder resin (B), but each of the negative electrode active material (A) and the particulate binder resin (B) exists as independent particles. Instead, one particle is formed by two or more components including the negative electrode active material (A) and the particulate binder resin (B), which are constituent components. Specifically, a plurality of (preferably several to several tens) secondary particles are formed by combining a plurality of the individual particles of the two or more components while maintaining the shape substantially. It is preferable that the negative electrode active material (A) is bound by the particulate binder resin (B) to form particles.

The shape of the composite particles is preferably substantially spherical from the viewpoint of fluidity. That is, the short axis diameter of the composite particles is L _s , the long axis diameter is L _l , L _a = (L _s + L _l ) / 2, and a value of (1− (L _l −L _s ) / L _a ) × 100 Is a sphericity (%), the sphericity is preferably 80% or more, more preferably 90% or more. Here, the minor axis diameter L _s and the major axis diameter L _l are values measured from a scanning electron micrograph image.

The average particle diameter of the composite particles is preferably 0.1 to 200 μm, more preferably 1 to 150 μm, and still more preferably 10 to 10 from the viewpoint that an electrode layer (negative electrode active material layer) having a desired thickness can be easily obtained. 80 μm. In the present invention, the average particle size is a volume average particle size calculated by measuring with a laser diffraction particle size distribution analyzer (for example, SALD-3100; manufactured by Shimadzu Corporation).

The production method of the composite particles is not particularly limited, but is spray drying granulation method, rolling bed granulation method, compression granulation method, stirring granulation method, extrusion granulation method, crushing granulation method, fluidized bed granulation method. Composite particles can be obtained by production methods such as a granulation method, a fluidized bed multifunctional granulation method, and a melt granulation method.

The production method of the composite particles may be appropriately selected from the viewpoints of ease of particle size control, productivity, ease of control of particle size distribution, etc. according to the components of the composite particles, etc. The spray-drying granulation method described in 1 is preferable because the composite particles can be produced relatively easily. Hereinafter, the spray drying granulation method will be described.

First, a slurry for composite particles (hereinafter sometimes referred to as “slurry”) containing a negative electrode active material (A) and a particulate binder resin (B) is prepared. The composite particle slurry is prepared by dispersing or dissolving a negative electrode active material, a binder resin, a water-soluble polymer and a water-insoluble polysaccharide polymer fiber, and a conductive additive added as necessary, in a solvent. Can do. In this case, when the binder resin is dispersed in water as a solvent, it can be added in a state dispersed in water.

As the solvent used for obtaining the composite particle slurry, water is preferably used, but a mixed solvent of water and an organic solvent may be used, or only an organic solvent may be used alone or in combination of several kinds. Examples of the organic solvent that can be used in this case include 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, dimethyl Amides such as acetamide, N-methyl-2-pyrrolidone, dimethylimidazolidinone; and the like. When using an organic solvent, alcohols are preferred. By using water and an organic solvent having a lower boiling point than water, the drying rate can be increased during spray drying. Thereby, the viscosity and fluidity of the slurry for composite particles can be adjusted, and the production efficiency can be improved.

In addition, the viscosity of the composite particle slurry is preferably 10 to 3,000 mPa · s, more preferably 30 to 1,500 mPa · s, more preferably at room temperature, from the viewpoint of improving the productivity of the spray drying granulation step. Is 50 to 1,000 mPa · s.

In the present invention, when preparing the composite particle slurry, a dispersant or a surfactant may be added as necessary. Examples of the surfactant include amphoteric surfactants such as anionic, cationic, nonionic, and nonionic anions, and 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 negative electrode active material. .

The amount of the solvent used in preparing the slurry is such that the solid content concentration of the slurry is preferably 1 to 50% by weight, more preferably 5 to 50% by weight, from the viewpoint of uniformly dispersing the binder resin in the slurry. More preferably, the amount is 10 to 40% by weight.

A negative electrode active material (A), a particulate binder resin (B), a water-soluble polymer (C), a water-insoluble polysaccharide polymer fiber (D), and a conductive additive added as necessary are dispersed in a solvent or The method or order of dissolution is not particularly limited. For example, the negative electrode active material (A), the particulate binder resin (B), the water-soluble polymer (C), and the water-insoluble polysaccharide polymer fiber (D) are used in the solvent. And after adding water-soluble polymer (C) in a solvent, adding a negative electrode active material (A), a conductive agent and water-insoluble polysaccharide polymer fiber (D) Method of mixing and finally adding particulate binder resin (B) (for example, latex) dispersed in a solvent, mixing, particulate binder resin (B) dispersed in solvent and water-insoluble polysaccharide A negative electrode active material (A) and a conductive additive are added to and mixed with the molecular fiber (D), and a solvent is added to the mixture. A method in which added to and mixed with dissolved water-soluble polymer (C) can be mentioned.

Also, as the mixing device, for example, a ball mill, a sand mill, a bead mill, a pigment disperser, a pulverizer, an ultrasonic disperser, a homogenizer, a homomixer, a planetary mixer, or the like can be used. The mixing is preferably performed at room temperature to 80 ° C. for 10 minutes to several hours.

Next, the obtained composite particle slurry is spray-dried and granulated. 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 preferably 5,000 to 30,000 rpm, more 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 size of the resulting composite particles. 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 preferably room temperature, but may be higher than room temperature by heating. The hot air temperature during spray drying is preferably 25 to 250 ° C, more preferably 50 to 200 ° C, and still more preferably 80 to 150 ° C. 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.

(Electrochemical element electrode)
An electrochemical element electrode (negative electrode) can be obtained by laminating a negative electrode active material layer containing the composite particles for electrochemical element electrodes of the present invention on a current collector. As a material for the current collector, for example, metal, carbon, conductive polymer, and the like can be used, and metal is preferably used. As the metal, copper, aluminum, platinum, nickel, tantalum, titanium, stainless steel, other alloys and the like are usually used. Among these, it is preferable to use copper, 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 depending on the purpose of use, but is preferably 1 to 200 μm, more preferably 5 to 100 μm, and still more preferably 10 to 50 μm.

When laminating the negative electrode active material layer on the current collector, the composite particles may be formed into a sheet shape and then laminated on the current collector, but the composite particles are directly pressure-molded on the current collector. Is preferred. As a method for pressure molding, for example, a roll type pressure molding apparatus provided with a pair of rolls is used, and a roll type pressure molding apparatus is used to feed composite particles with a feeder such as a screw feeder while feeding a current collector with the roll. Roll pressure molding method for forming a negative electrode active material layer on a current collector, or dispersing composite particles on a current collector, adjusting the thickness by smoothing the composite particles with a blade, Next, a method of forming with a pressurizing apparatus, a method of filling composite particles into a mold, and pressurizing the mold to form are included. Among these, the roll pressure molding method is preferable. In particular, since the composite particles of the present invention have high fluidity, they can be molded by roll press molding due to the high fluidity, thereby improving productivity.

The roll temperature at the time of roll press molding is preferably 25 to 200 ° C., more preferably 50 to 150 ° C., from the viewpoint of ensuring sufficient adhesion between the negative electrode active material layer and the current collector. More preferably, it is 80 to 120 ° C. In addition, the press linear pressure between the rolls during roll press molding is preferably 10 to 1000 kN / m, more preferably 200 to 900 kN / m, from the viewpoint of improving the uniformity of the thickness of the negative electrode active material layer. More preferably, it is 300 to 600 kN / m. Further, the molding speed at the time of roll press molding is preferably 0.1 to 20 m / min, more preferably 4 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 (negative electrode) and increase the density of the negative electrode active material layer to increase the capacity. The post-pressing method is preferably a pressing 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.

(Electrochemical element)
An electrochemical element can be obtained by using the electrochemical element electrode obtained as described above as a negative electrode and further including a positive electrode, a separator, and an electrolytic solution. Examples of the electrochemical element include a lithium ion secondary battery and a lithium ion capacitor.

(Positive electrode)
The positive electrode of the electrochemical element is formed by laminating a positive electrode active material layer on a current collector. The positive electrode of the electrochemical element is a positive electrode slurry containing a positive electrode active material, a binder resin for the positive electrode, a solvent used for preparing the positive electrode, a water-soluble polymer used as necessary, and other components such as a conductive additive. It can be obtained by applying to the surface of the electric body and drying. That is, the positive electrode active material layer is formed on the current collector by applying the slurry for the positive electrode to the surface of the current collector and drying it.

(Positive electrode active material)
When the electrochemical device is a lithium ion secondary battery, the positive electrode active material is an active material that can be doped and dedoped with lithium ions, and is broadly classified into an inorganic compound and an organic compound. The

Examples of the positive electrode active material made of an inorganic compound include transition metal oxides, transition metal sulfides, lithium-containing composite metal oxides of lithium and transition metals, and the like. Examples of the transition metal include Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo.

Transition metal oxides include MnO, MnO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , Cu ₂ V ₂ O ₃ , amorphous V ₂ O—P ₂ O ₅ , MoO ₃ , V ₂ O. ₅ , V ₆ O _{13 and the} like. Among them, MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ are preferable from the viewpoint of cycle stability and capacity. The transition metal sulfide, TiS _2, TiS _3, amorphous MoS _2, FeS, and the like. Examples of the lithium-containing composite metal oxide include a lithium-containing composite metal oxide having a layered structure, a lithium-containing composite metal oxide having a spinel structure, and a lithium-containing composite metal oxide having an olivine structure.

Examples of the lithium-containing composite metal oxide having a layered structure include lithium-containing cobalt oxide (LiCoO ₂ ) (hereinafter sometimes referred to as “LCO”), lithium-containing nickel oxide (LiNiO ₂ ), and Co—Ni—Mn. Examples thereof include lithium composite oxides, lithium composite oxides of Ni—Mn—Al, and lithium composite oxides of Ni—Co—Al. Examples of the lithium-containing composite metal oxide having a spinel structure include lithium manganate (LiMn ₂ O ₄ ) and Li [Mn _3/2 M _1/2 ] O _{4 in} which a part of Mn is substituted with another transition metal (here, M may be Cr, Fe, Co, Ni, Cu or the like. Li _x MPO ₄ (wherein, M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, Ti, Al, and the like) is a lithium-containing composite metal oxide having an olivine structure. An olivine type lithium phosphate compound represented by at least one selected from Si, B, and Mo, 0 ≦ X ≦ 2) may be mentioned.

As the organic compound, for example, a conductive polymer such as polyacetylene or poly-p-phenylene can be used. An iron-based oxide having poor electrical conductivity may be used as a positive electrode active material covered with a carbon material by allowing a carbon source material to be present during reduction firing. These compounds may be partially element-substituted. The positive electrode active material may be a mixture of the above inorganic compound and organic compound.

When the electrochemical device is a lithium ion capacitor, the positive electrode active material may be any material that can reversibly carry lithium ions and anions such as tetrafluoroborate. Specifically, carbon allotropes can be preferably used, and electrode active materials used in electric double layer capacitors can be widely used. Specific examples of the allotrope of carbon include activated carbon, polyacene (PAS), carbon whisker, carbon nanotube, and graphite.

The volume average particle diameter of the positive electrode active material can reduce the blending amount of the binder resin for the positive electrode when preparing the positive electrode slurry, and can suppress the decrease in battery capacity, and the positive electrode slurry. From the viewpoint of easily preparing a viscosity suitable for application and obtaining a uniform electrode, the viscosity is preferably 1 to 50 μm, more preferably 2 to 30 μm.

(Binder resin for positive electrode)
Examples of the positive electrode binder resin include polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polyacrylic acid derivatives, polyacrylonitrile derivatives, and the like. A soft polymer such as an acrylic soft polymer, a diene soft polymer, an olefin soft polymer, and a vinyl soft polymer. In addition, a binder resin may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios.

(Other ingredients)
As the water-soluble polymer and conductive additive used as necessary for the positive electrode slurry, the water-soluble polymer and conductive aid that can be used for the composite particles described above can be used.

(Solvent used for preparation of positive electrode)
As a solvent used for producing the positive electrode, either water or an organic solvent may be used. Examples of the organic solvent include cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; ketones such as ethyl methyl ketone and cyclohexanone; ethyl acetate, butyl acetate, and γ-butyrolactone Esters such as ε-caprolactone; alkyl nitriles such as acetonitrile and propionitrile; ethers such as tetrahydrofuran and ethylene glycol diethyl ether: alcohols such as methanol, ethanol, isopropanol, ethylene glycol, and ethylene glycol monomethyl ether; N Amides such as -methylpyrrolidone and N, N-dimethylformamide; among them, N-methylpyrrolidone (NMP) is preferred. In addition, a solvent may be used individually by 1 type and may be used combining two or more types by arbitrary ratios. Of these, water is preferably used as the solvent.

The amount of the solvent may be adjusted so that the viscosity of the positive electrode slurry is suitable for coating. Specifically, the solid content concentration of the positive electrode slurry is preferably adjusted to 30 to 90% by weight, more preferably 40 to 80% by weight.

(Current collector)
As the current collector used for the positive electrode, the same current collector as the current collector used for the electrochemical element electrode (negative electrode) can be used.

(Production method of positive electrode)
The method for applying the positive electrode slurry to the surface of the current collector is not particularly limited. Examples of the method include a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush coating method.

Examples of the drying method include drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. The drying time is preferably 5 to 30 minutes, and the drying temperature is preferably 40 to 180 ° C.

In addition, after applying and drying the positive electrode slurry on the surface of the current collector, it is preferable to apply pressure treatment to the positive electrode active material layer, for example, using a die press or a roll press as necessary. By the pressure treatment, the porosity of the positive electrode active material layer can be lowered. The porosity is preferably 5% or more, more preferably 7% or more, preferably 30% or less, more preferably 20% or less. When the porosity is too small, it is difficult to obtain a high volume capacity, and the positive electrode active material layer is easily peeled off from the current collector. On the other hand, when the porosity is too large, the charging efficiency and the discharging efficiency are lowered.
Furthermore, when the positive electrode active material layer includes a curable polymer, it is preferable to cure the polymer after the positive electrode active material layer is formed.

(separator)
As the separator, for example, a polyolefin resin such as polyethylene or polypropylene, or a microporous film or nonwoven fabric containing an aromatic polyamide resin; a porous resin coat containing an inorganic ceramic powder; Specific examples include microporous membranes made of polyolefin resins (polyethylene, polypropylene, polybutene, polyvinyl chloride), and resins such as mixtures or copolymers thereof; polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, Examples thereof include a microporous film made of a resin such as polyimide, polyimide amide, polyaramid, nylon, and polytetrafluoroethylene; a polyolefin fiber woven or non-woven fabric thereof; and an aggregate of insulating substance particles. Among these, since the film thickness of the entire separator can be reduced and the active material ratio in the lithium ion secondary battery can be increased to increase the capacity per volume, a microporous film made of polyolefin resin is used. preferable.

The thickness of the separator is preferably 0.5 to 40 μm from the viewpoint of reducing the internal resistance due to the separator in the lithium ion secondary battery and from the viewpoint of excellent workability when manufacturing the lithium ion secondary battery. More preferably, the thickness is 1 to 30 μm, still more preferably 1 to 25 μm.

(Electrolyte)
As an electrolytic solution for a lithium ion secondary battery, for example, a nonaqueous electrolytic solution in which a supporting electrolyte is dissolved in a nonaqueous solvent is used. As the supporting electrolyte, a lithium salt is preferably used. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and the like. Among these, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferable. One of these may be used alone, or two or more of these may be used in combination at any ratio. Since the lithium ion conductivity increases as the supporting electrolyte having a higher degree of dissociation is used, the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.

The concentration of the supporting electrolyte in the electrolytic solution is preferably used at a concentration of 0.5 to 2.5 mol / L depending on the type of the supporting electrolyte. If the concentration of the supporting electrolyte is too low or too high, the ionic conductivity may decrease.

The non-aqueous solvent is not particularly limited as long as it can dissolve the supporting electrolyte. Examples of non-aqueous solvents include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC), methyl ethyl carbonate (MEC); Examples thereof include esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide; ionic liquids used also as supporting electrolytes. Among these, carbonates are preferable because they have a high dielectric constant and a wide stable potential region. A non-aqueous solvent may be used individually by 1 type, and may be used combining two or more types by arbitrary ratios. In general, the lower the viscosity of the non-aqueous solvent, the higher the lithium ion conductivity, and the higher the dielectric constant, the higher the solubility of the supporting electrolyte, but since both are in a trade-off relationship, the lithium ion conductivity depends on the type of solvent and the mixing ratio. It is recommended to adjust the conductivity. In addition, the nonaqueous solvent may be used in combination or in whole or in a form in which all or part of hydrogen is replaced with fluorine.

Moreover, the electrolyte solution may contain an additive. Examples of the additive include carbonates such as vinylene carbonate (VC); sulfur-containing compounds such as ethylene sulfite (ES); and fluorine-containing compounds such as fluoroethylene carbonate (FEC). An additive may be used individually by 1 type and may be used combining two or more types by arbitrary ratios.
In addition, as an electrolyte solution for lithium ion capacitors, the same electrolyte solution that can be used for the above-described lithium ion secondary battery can be used.

(Method for producing electrochemical element)
As a specific method for producing an electrochemical element such as a lithium ion secondary battery or a lithium ion capacitor, for example, a positive electrode and a negative electrode are overlapped via a separator, and this is wound or folded according to the shape of the battery. Examples of the method include putting the battery in a battery container, injecting an electrolyte into the battery container, and sealing the battery. Further, if necessary, an expanded metal; an overcurrent prevention element such as a fuse or a PTC element; a lead plate or the like may be inserted to prevent an increase in pressure inside the battery or overcharge / discharge. The shape of the lithium ion secondary battery may be any of a coin type, a button type, a sheet type, a cylindrical type, a square type, a flat type, and the like. The material of the battery container is not particularly limited as long as it inhibits the penetration of moisture into the battery, and is not particularly limited, such as a metal or a laminate such as aluminum.

According to the composite particle for an electrochemical element electrode of the present invention, an electrode having sufficient strength, sufficient adhesion when forming an electrode, and excellent flexibility can be obtained. Moreover, the composite particle for electrochemical element electrodes of the present invention has excellent fluidity.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily changed without departing from the gist and equivalent scope of the present invention. Can be implemented. In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified.

In the examples and comparative examples, the particle strength, peel strength, flexibility, and cycle characteristics of the composite particles were evaluated as follows. Moreover, in the following, an average fiber diameter is an average value when a fiber diameter is measured about 100 water-insoluble polysaccharide polymer fibers in the visual field of an electron microscope.

<Particle strength of composite particles>
The composite particles obtained in Examples and Comparative Examples were subjected to a compression test using a micro compression tester (“MCT-W500” manufactured by Shimadzu Corporation). In the compression test, a compressive strength (MPa) is measured when a particle is deformed until the diameter of the composite particle is displaced by 40% by applying a load at a loading speed of 4.46 mN / sec in the center direction of the composite particle at room temperature. did. In this measurement, a composite particle having a diameter of 40 to 60 μm was selected and a compression test was performed.

Further, the compression test was performed 10 times, and the average value was set as the compression strength. The compressive strength was evaluated according to the following criteria, and the results are shown in Tables 1 and 2. In addition, it shows that it is excellent in the adhesive strength of negative electrode active materials, and a composite particle is excellent in particle strength, so that compressive strength is large.
A: Compressive strength is 1.00 MPa or more B: Compressive strength is 0.90 MPa or more and less than 1.00 MPa C: Compressive strength is 0.80 MPa or more and less than 0.90 MPa D: Compressive strength is 0.70 MPa or more, 0.80 MPa Less than E: Compressive strength is less than 0.70 MPa

<Peel strength>
The negative electrodes for lithium ion secondary batteries obtained in the examples and comparative examples were cut into a rectangular shape having a width of 1 cm and a length of 10 cm. After fixing the cut negative electrode for a lithium ion secondary battery with the negative electrode active material layer side up, the cellophane tape was applied to the surface of the negative electrode active material layer, and then the cellophane tape was applied at a speed of 50 mm / min from one end of the test piece. The stress when peeled in the 180 ° direction was measured. This stress was measured 10 times, and the average value was defined as the peel strength. The peel strength was evaluated according to the following criteria, and the results are shown in Tables 1 and 2. In addition, it shows that the adhesiveness in a negative electrode active material layer and the adhesiveness between a negative electrode active material layer and a collector are so favorable that peel strength is large.
A: Peel strength is 15 N / m or more B: Peel strength is 7 N / m or more and less than 15 N / m C: Peel strength is 3 N / m or more and less than 7 N / m D: Peel strength is less than 3 N / m E: Unevaluable

<Electrode flexibility>
A rod having a different diameter was placed on the negative electrode active material layer side of the negative electrode for lithium ion secondary batteries obtained in Examples and Comparative Examples, and the negative electrode was wound around the rod to evaluate whether or not the negative electrode active material layer was cracked. The results are shown in Tables 1 and 2. It shows that it is excellent in the winding property of a negative electrode, so that the diameter of a stick | rod is small. When the winding property is excellent, peeling of the negative electrode active material layer can be suppressed, and thus the cycle characteristics of the secondary battery are excellent.
A: Unbreakable at 1.2 mmφ B: Unbreakable at 1.5 mmφ C: Unbreakable at 2 mmφ D: Unbreakable at 3 mmφ E: Unbreakable at 4 mmφ

<Charge / discharge cycle characteristics>
The laminate-type lithium ion secondary batteries obtained in the examples and comparative examples were charged at a constant current until reaching 4.2 V by a constant current constant voltage charging method of 0.5 C at 60 ° C. A charge / discharge cycle test was performed in which the battery was charged with a voltage and then discharged to 3.0 V at a constant current of 0.5C. The charge / discharge cycle test was conducted up to 100 cycles, and the ratio of the discharge capacity at the 100th cycle to the initial discharge capacity was defined as the capacity retention rate. The capacity retention rate was evaluated according to the following criteria, and the results are shown in Tables 1 and 2. It shows that the capacity | capacitance maintenance factor is so large that there is little decrease in the capacity | capacitance by repeated charging / discharging.
A: Capacity maintenance ratio is 90% or more B: Capacity maintenance ratio is 80% or more and less than 90% C: Capacity maintenance ratio is 75% or more and less than 80% D: Capacity maintenance ratio is 70% or more and less than 75% E: Capacity maintenance rate is less than 70% or cannot be evaluated

[Example 1]
(Production of particulate binder resin (B))
In a 5 MPa pressure vessel equipped with a stirrer, 47 parts of styrene, 50 parts of 1,3-butadiene, 3 parts of methacrylic acid, 4 parts of sodium dodecylbenzenesulfonate, 150 parts of ion-exchanged water, 0.4 part of t-dodecyl mercaptan as a chain transfer agent Then, 0.5 part of potassium persulfate was added as a polymerization initiator, and after sufficiently stirring, the mixture was heated to 50 ° C. to initiate polymerization. When the polymerization conversion rate reaches 96%, the reaction is stopped by cooling to obtain a particulate binder resin (B) (styrene / butadiene copolymer; hereinafter abbreviated as “SBR”). It was.

(Manufacture of slurry for composite particles)
As the negative electrode active material (A), artificial graphite (average particle size: 24.5 μm, graphite interlayer distance (surface distance (d value) of (002) plane by X-ray diffraction method): 0.354 nm) was 91.0 parts. 6.6 parts of SiC, 1.2 parts of the above-mentioned particulate binder resin (B) in terms of solid content, and carboxymethyl cellulose (hereinafter “CMC”) may be abbreviated as water-soluble polymer (C). ) 1.0% aqueous solution (BSH-6; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) in terms of solid content, 1% aqueous dispersion of cellulose nanofibers as water-insoluble polysaccharide polymer fiber (D) (Raw material: bamboo, degree of defibration: high, average polymerization degree 350; manufactured by Chuetsu Pulp Co., Ltd.) is mixed with 0.8 part in terms of solid content, and ion exchange water is added so that the solid content concentration is 35%. Then, a slurry for composite particles was obtained by mixing and dispersing. That is, the ratio of the water-soluble polymer (C) to the water-insoluble polysaccharide polymer fiber (D) was (C) / (D) = 0.5.

(Manufacture of composite particles)
The slurry for composite particles in a spray dryer (manufactured by Okawara Kako Co., Ltd.) was used with a rotary disk type atomizer (diameter 65 mm), rotation speed 25,000 rpm, hot air temperature 150 ° C., and particle recovery outlet temperature 90 ° C. Then, spray drying granulation was performed to obtain composite particles. The composite particles had an average volume particle diameter of 40 μm.

(Manufacture of negative electrodes for lithium ion secondary batteries)
Next, the obtained particles are supplied to a roll (roll temperature 100 ° C., press linear pressure 4.0 kN / cm) of a roll press machine (pressed rough surface heat roll, manufactured by Hirano Giken Kogyo Co., Ltd.), and a molding speed of 20 m / min. To obtain a negative electrode for a lithium ion secondary battery having a thickness of 80 μm.

(Production of slurry for positive electrode and positive electrode for lithium ion secondary battery)
92 parts of LiCoO ₂ (hereinafter sometimes abbreviated as “LCO”) as the positive electrode active material and polyvinylidene fluoride (PVDF; “KF-1100” manufactured by Kureha Chemical Co., Ltd.) as the positive electrode binder resin Add 6 parts of acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) and 20 parts of N-methylpyrrolidone and mix with a planetary mixer to obtain a slurry for positive electrode. It was. 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 for a lithium ion secondary battery having a thickness of 60 μm.

(Preparation of separator)
A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm, manufactured by dry method, porosity 55%) was cut into a square of 5 × 5 cm ² .

(Manufacture of lithium ion secondary batteries)
An aluminum packaging exterior was prepared as the battery exterior. The positive electrode for a lithium ion secondary battery obtained above was cut into a 4 × 4 cm ² square and placed so that the current collector-side surface was in contact with the aluminum packaging exterior. The square separator obtained above was disposed on the surface of the positive electrode active material layer of the positive electrode for a lithium ion secondary battery. Further, the negative electrode for a lithium ion secondary battery obtained above was cut into a square of 4.2 × 4.2 cm ² and arranged on the separator so that the surface on the negative electrode active material layer side faced the separator. Further, containing the vinylene carbonate 2.0%, was charged with LiPF ₆ solution having a concentration of 1.0 M. The solvent of this LiPF ₆ solution is a mixed solvent (EC / EMC = 3/7 (volume ratio)) of ethylene carbonate (EC) and ethyl methyl carbonate (EMC). Furthermore, in order to seal the opening of the aluminum packaging material, heat sealing was performed at 150 ° C. to close the aluminum exterior, and a laminate type lithium ion secondary battery (laminated cell) was manufactured.

[Example 2]
Except for using 97.6 parts of artificial graphite as the negative electrode active material (A), the production of slurry for composite particles, the production of composite particles, the production of negative electrodes for lithium ion secondary batteries, lithium ion The next battery was manufactured.

[Example 3]
Carried out except that 1.0% aqueous dispersion of cellulose nanofiber (raw material: softwood, degree of defibration: high, average polymerization degree 300; manufactured by Chuetsu Pulp Co., Ltd.) was used as the water-insoluble polysaccharide polymer fiber (D). In the same manner as in Example 1, production of a slurry for composite particles, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were performed.

[Example 4]
Carried out except that 1.0% aqueous dispersion of cellulose nanofiber (raw material: hardwood, defibration degree: low, average polymerization degree 600; manufactured by Chuetsu Pulp Co., Ltd.) was used as the water-insoluble polysaccharide polymer fiber (D). In the same manner as in Example 1, production of a slurry for composite particles, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were performed.

[Example 5]
Example 1 except that a 10% aqueous dispersion of cotton cellulose nanofibers (fiber diameter 0.1 to 0.01 μm, serisch KY100G; manufactured by Daicel Finechem) was used as the water-insoluble polysaccharide polymer fiber (D). Similarly, production of a slurry for composite particles, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were performed.

[Example 6]
Example 1 except that a 2% aqueous dispersion of chitincellulose nanofibers (BiNFi-S (SFo-120002), average polymerization degree 300; manufactured by Sugino Machine Co., Ltd.) was used as the water-insoluble polysaccharide polymer fiber (D). In the same manner as above, production of a slurry for composite particles, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were performed.

[Example 7]
Example 1 except that a 2% aqueous dispersion of chitosan cellulose nanofiber (BiNFi-S (EFo-120002), average polymerization degree 480; manufactured by Sugino Machine Co., Ltd.) was used as the water-insoluble polysaccharide polymer fiber (D). In the same manner as above, production of a slurry for composite particles, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were performed.

[Example 8]
Production of slurry for composite particles, production of composite particles, production of negative electrode for lithium ion secondary battery, lithium ion secondary, as in Example 1, except that polyacrylic resin was used as the water-soluble polymer (C) The battery was manufactured. The polyacrylic resin was produced as follows.

(Manufacture of polyacrylic resin)
Into a 1 L SUS separable flask equipped with a stirrer, a reflux condenser and a thermometer, demineralized water was charged in advance and stirred sufficiently, and then the temperature was adjusted to 70 ° C., and 0.2 part of an aqueous potassium persulfate solution was added.

In another 5 MPa pressure vessel with a stirrer, 50 parts of ion-exchanged water, 0.4 part of sodium hydrogen carbonate, 0.115 part of sodium dodecyl diphenyl ether sulfonate having a concentration of 30% as an emulsifier, 60 parts of methacrylic acid, ethyl 15 parts of acrylate and 15 parts of butyl acrylate, and a monomer mixture composed of 10 parts of 2-acrylamido-2-methylpropanesulfonic acid as a sulfonic acid group-containing monomer copolymerizable therewith are stirred sufficiently. An aqueous emulsion was prepared.

The obtained emulsion aqueous solution was continuously dropped into the separable flask over 4 hours. When the polymerization conversion rate reached 90%, the reaction temperature was set to 80 ° C., and the reaction was further carried out for 2 hours. Then, the reaction was stopped by cooling to obtain an aqueous dispersion containing a polyacrylic resin. The polymerization conversion rate was 99%. Moreover, it was 25000 when the weight average molecular weight of the obtained polyacrylic resin was measured by GPC. Moreover, the viscosity when the obtained polyacrylic resin was made into 1 weight% aqueous solution was 3000 (mPa * s).

[Example 9]
A slurry for composite particles was prepared in the same manner as in Example 1 except that poly-N-vinylacetamide (PNVA, GE191-103; Showa Denko) resin was used as the water-soluble polymer (C). Production, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were carried out.

[Example 10]
Production of slurry for composite particles, production of composite particles, lithium, except that polyvinyl alcohol resin (PVA, JF-17; manufactured by Nihon Vinegar Bipoval) was used as the water-soluble polymer (C). A negative electrode for an ion secondary battery and a lithium ion secondary battery were manufactured.

[Example 11]
Artificial graphite 90.6 parts and SiC 6.6 parts as negative electrode active material (A), 1% aqueous dispersion of cellulose nanofibers as water-insoluble polysaccharide polymer fiber (D) (raw material: bamboo, degree of defibration: high , Average polymerization degree 350; manufactured by Chuetsu Pulp Co., Ltd.), except for using 1.2 parts in terms of solid content, producing composite particle slurry, producing composite particles, lithium ion secondary battery as in Example 1. A negative electrode for a battery and a lithium ion secondary battery were manufactured. That is, the ratio of the water-soluble polymer (C) to the water-insoluble polysaccharide polymer fiber (D) was (C) / (D) = 0.33.

[Example 12]
91.1 parts of artificial graphite and 6.6 parts of SiC as the negative electrode active material (A), and 1.0% aqueous solution of CMC (BSH-6; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as the water-soluble polymer (C) 1.0 part in terms of converted amount, 1% aqueous dispersion of cellulose nanofibers (raw material: bamboo, degree of defibration: high, average polymerization degree 350; manufactured by Chuetsu Pulp Co., Ltd.) as water-insoluble polysaccharide polymer fiber (D) Except for using 0.06 parts in terms of solid content, the production of negative electrode particle slurry, the production of composite particles, the production of a negative electrode for a lithium ion secondary battery, and the production of a lithium ion secondary battery were conducted in the same manner as in Example 1. went. That is, the ratio of the water-soluble polymer (C) to the water-insoluble polysaccharide polymer fiber (D) was (C) / (D) = 16.7.

[Example 13]
91.1 parts of artificial graphite and 6.6 parts of SiC as the negative electrode active material (A), and 1.0% aqueous solution of CMC (BSH-6; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as the water-soluble polymer (C) Except that 0.3 parts was used in terms of conversion amount, the production of composite particle slurry, the production of composite particles, the production of negative electrodes for lithium ion secondary batteries, and the production of lithium ion secondary batteries were performed in the same manner as in Example 1. It was. That is, the ratio of the water-soluble polymer (C) to the water-insoluble polysaccharide polymer fiber (D) was (C) / (D) = 0.38.

[Comparative Example 1]
Without adding water-insoluble polysaccharide polymer fiber (D), the amount of negative electrode active material (A) was 91.2 parts of artificial graphite and 6.6 parts of SiC, and the amount of CMC as water-soluble polymer (C) was Production of slurry for composite particles, production of composite particles, production of negative electrode for lithium ion secondary battery, production of lithium ion secondary battery, as in Example 1, except that the solid content equivalent amount was 1.0 part. went.

[Comparative Example 2]
For composite particles as in Example 1, except that CMC as the water-soluble polymer (C) was not added and the amount of the negative electrode active material (A) was 91.4 parts of artificial graphite and 6.6 parts of SiC. Production of slurry, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were performed.

[Comparative Example 3]
In the production of the composite particle slurry, 1.0 part of CMC as the water-soluble polymer (C) in terms of solid content and 1% aqueous dispersion of cellulose nanofibers as the water-insoluble polysaccharide polymer fiber (D) ( Raw material: bamboo, defibration degree: high, average polymerization degree 350; manufactured by Chuetsu Pulp Co., Ltd.) is mixed in an amount of 0.05 parts in terms of solid content, so that water-soluble polymer (C) and water-insoluble polysaccharide polymer fiber are mixed. Example 1 except that the ratio to (D) was (C) / (D) = 20 and the amount of the negative electrode active material (A) was 91.15 parts of artificial graphite and 6.6 parts of SiC. In the same manner as above, production of a slurry for composite particles, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were performed.

[Comparative Example 4]
In the production of the composite particle slurry, 0.15 part of CMC as the water-soluble polymer (C) in terms of solid content, and 1% aqueous dispersion of cellulose nanofibers as the water-insoluble polysaccharide polymer fiber (D) ( Raw material: bamboo, degree of defibration: high, average degree of polymerization 350; manufactured by Chuetsu Pulp Co., Ltd.) is mixed with 1.0 part in terms of solid content, so that water-soluble polymer (C) and water-insoluble polysaccharide polymer fiber are mixed. The ratio to (D) was set to (C) / (D) = 0.15, and the composite material was the same as in Example 1 except that the amount of the negative electrode active material (A) was 97.65 parts of artificial graphite. Production of slurry for particles, production of composite particles, production of negative electrode for lithium ion secondary battery, and production of lithium ion secondary battery were performed.

[Comparative Example 5]
Instead of water-insoluble polysaccharide polymer fiber (D), by using carbon nanofiber (VGCF: manufactured by Showa Denko KK, fiber diameter 150 nm, fiber length 20 μm) as a reinforcing fiber, water-soluble polymer (C) and Example 1 except that the ratio to the reinforcing fiber (D ′) was (C) / (D ′) = 0.4 and the amount of the negative electrode active material (A) was 97.4 parts of artificial graphite. In the same manner as above, production of a slurry for composite particles, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery were performed.

As shown in Tables 1 and 2, an electrochemical device electrode comprising a negative electrode active material (A), a particulate binder resin (B), a water-soluble polymer (C), and a water-insoluble polysaccharide polymer fiber (D) Composite particles for water, comprising water-soluble polymer (C) and water-insoluble polysaccharide polymer fiber (D) in a weight ratio of (C) / (D) = 0.2-18 The particle strength of the composite particles for chemical element electrodes was good, and the peel strength and electrode flexibility of the negative electrode obtained using the composite particles were good. Moreover, the charge / discharge cycle characteristics of the lithium ion secondary battery obtained using the composite particles were good.

Claims

Electrochemical element electrode composite particles comprising a negative electrode active material (A), a particulate binder resin (B), a water-soluble polymer (C) and a water-insoluble polysaccharide polymer fiber (D),
An electrochemical element comprising water-soluble polymer (C) and water-insoluble polysaccharide polymer fiber (D) in a weight ratio of (C) / (D) = 0.2-18 Composite particles for electrodes.
The composite particle for an electrochemical element electrode according to claim 1, wherein the water-insoluble polysaccharide polymer fiber (D) has an average degree of polymerization of 50 to 1,000.
The composite particle for an electrochemical element electrode according to claim 1 or 2, wherein the particulate binder resin (B) is a conjugated diene polymer or an acrylate polymer.
The amount of the water-soluble polymer (C) is 0.1 to 10 parts by weight in terms of solid content with respect to 100 parts by weight of the negative electrode active material (A),
The amount of the water-insoluble polysaccharide polymer fiber (D) is 0.1 to 2 parts by weight in terms of solid content with respect to 100 parts by weight of the composite particles obtained. The composite particle for an electrochemical element electrode according to any one of the above.