KR20160102159A - Composite particle for electrochemical element electrode - Google Patents

Abstract

A composite particle for 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) (D) in a proportion of (C) / (D) = 0.2 to 18 in terms of weight ratio.

Description

TECHNICAL FIELD [0001] The present invention relates to a composite particle for an electrochemical device electrode,

The present invention relates to a composite particle for an electrochemical device electrode.

BACKGROUND ART Electrochemical devices such as a lithium ion secondary battery, an electric double layer capacitor, and a lithium ion capacitor are rapidly expanding in demand because of their small size and light weight, high energy density, and repeatable charge / discharge characteristics. Lithium ion secondary batteries are used in mobile fields such as portable telephones and notebook personal computers because of their relatively large energy density. On the other hand, since the electric double layer capacitor can be rapidly charged and discharged, it is used as a memory backup small power source for a personal computer or the like, and the electric double layer capacitor is expected to be used as an auxiliary power source for electric vehicles and the like. In addition, lithium ion capacitors that take advantage of lithium ion secondary batteries and electric double layer capacitors have higher energy density and higher output density than electric double layer capacitors. Therefore, the application of electric double layer capacitors, and the performance of electric double layer capacitors, The application to a use that can not be satisfied is considered. Among them, in particular, lithium ion secondary batteries are being studied not only for use in automobiles such as hybrid electric vehicles and electric vehicles, but also for power storage applications.

As the expectations for these electrochemical devices increase, there is a demand for further improvement in these electrochemical devices, such as lowering the resistance, increasing the capacity, increasing the mechanical characteristics, and improving the productivity, in accordance with the expansion and development of applications. In such a situation, a production method with higher productivity is required for an electrode for an electrochemical device, and various improvements are made to the electrode material for an electrochemical device suitable for a manufacturing method capable of high-speed molding and a manufacturing method thereof have.

An electrode for an electrochemical device is generally formed by laminating an electrode active material layer formed by binding an electrode active material and a conductive auxiliary agent, which is used if necessary, with a binder resin on a current collector. The electrode for electrochemical device includes a coating electrode formed by applying a slurry for a coating electrode containing an electrode active material, a binder resin, a conductive auxiliary agent or the like onto a current collector and removing the solvent by heat or the like. It has been difficult to produce a uniform electrochemical device. In addition, this method is expensive, has a poor working environment, and tends to have a large manufacturing apparatus.

On the other hand, it has been proposed to obtain an electrochemical device having a uniform electrode active material layer by obtaining composite particles and powder-forming them. As a method for forming such an electrode active material layer, for example, Patent Document 1 discloses a method for producing composite particles by spraying and drying a slurry for composite particles containing an electrode active material, a binder resin and a dispersion medium to obtain composite particles, A method of forming an active material layer is disclosed. Such a composite particle may be broken at the time of transportation such as air transportation, and therefore, it is required to improve the strength.

Here, when the electrode active material layer is formed using the destroyed composite particles, the uniformity of the particle diameter of the composite particles is lost, whereby the fluidity of the powder is deteriorated and a uniform electrode active material layer can not be formed. In addition, the adhesion between the composite particles and the adhesion between the electrode active material layer and the current collector became weak, and the cycle characteristics of the obtained electrochemical device were not sufficient. In addition, the electrode having the electrode active material layer formed using the destroyed composite particles was inferior in flexibility, and cracks sometimes occurred in the electrode when the electrode was wound.

In addition, in Patent Document 1, although external particles coated with the fibrous conductive auxiliary agent are obtained on the surface of the composite particles, since the fibrous conductive auxiliary agent does not exist inside the composite particles, the strength of the composite particles is improved I could not.

Patent Document 2 discloses that carbon fibers are contained in a slurry for a coating electrode for coating an electrode to form an electrode layer in order to improve the adhesion of the coating electrode. However, since it relates to a method of producing the above-mentioned coated electrode, which is different from the powder forming using the composite particles, it is not described to improve the strength of the composite particles.

Patent Document 3 discloses that a finely divided cellulose fiber is contained in a slurry for a coating electrode for forming an electrode layer by coating on an electrode in order to improve the adhesion of the coated electrode. However, since it relates to a method of producing the above-mentioned coated electrode, which is different from the powder forming using the composite particles, it is not described to improve the strength of the composite particles.

International Publication No. 2009/44856 Japanese Laid-Open Patent Publication No. 2009-295666 International Publication No. 2013/42720

An object of the present invention is to provide a composite particle for an electrochemical device electrode, which has sufficient strength and can obtain sufficient adhesiveness in the case of forming an electrode and can obtain an electrode with excellent flexibility.

As a result of intensive studies to solve the above problems, the present inventors have found that the above objects can be achieved by using a water-soluble polymer and a water-insoluble polysaccharide polymer in combination at a predetermined ratio to obtain composite particles, thereby completing the present invention .

That is, according to the present invention,

(1) A composite particle for 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) The composite particle for an electrochemical device electrode, which comprises a polysaccharide polymer fiber (D) in a ratio by weight of (C) / (D) = 0.2 to 18,

(2) The composite particle for electrochemical device electrode according to (1), wherein the average degree of polymerization of the water-soluble polysaccharide polymer fiber (D) is 50 to 1000,

(3) The electrochemical device electrode composite particle according to (1) or (2), wherein the particulate binder resin (B) is a conjugated diene polymer or an acrylate polymer.

(4) 100 parts by weight of composite particles in which the amount of the water-soluble polymer (C) is 0.1 to 10 parts by weight in terms of solid content relative to 100 parts by weight of the negative electrode active material (A) (1) to (3), wherein the solid content of the composite particles is 0.1 to 2 parts by weight based on the total weight of the composite particles.

According to the present invention, it is possible to provide a composite particle for an electrochemical device electrode, which has sufficient strength and can obtain sufficient adhesiveness when forming an electrode, and which can obtain an electrode having excellent flexibility.

Hereinafter, the composite particles for an electrochemical device electrode according to the embodiment of the present invention will be described. The composite particles for an electrochemical device electrode of the present invention (hereinafter sometimes referred to as " composite particles ") are obtained by mixing the negative electrode active material (A), the particulate binder resin (B), the water- soluble polymer (C) (C) / (D) = 0.2 to 18 as a weight ratio of the water-soluble polymer (C) and the water-insoluble polysaccharide polymer fiber (D) .

Further, in the following, the "positive electrode active material" means the electrode active material for the positive electrode, and the "negative electrode active material" means the electrode active material for the negative electrode. The "positive electrode active material layer" means an electrode active material layer formed on the positive electrode, and the "negative electrode active material layer" means an electrode active material layer formed on the negative electrode.

(Negative electrode active material (A))

The negative electrode active material (A) used in the present invention includes a material capable of transferring electrons in the negative electrode of an electrochemical device. As the negative electrode active material (A) in the case where the electrochemical device is a lithium ion secondary battery, a material capable of occluding and releasing lithium can be usually used.

An example of the negative electrode active material (A) preferably used in a lithium ion secondary battery is a negative electrode active material formed of carbon. Natural graphite, artificial graphite, carbon black and the like can be mentioned as the negative electrode active material formed of carbon. Among them, graphite such as artificial graphite and natural graphite is preferable, and natural graphite is particularly preferable.

Another example of the negative electrode active material (A) preferably used in a 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.

Of the negative electrode active materials containing these metals, a negative electrode active material containing silicon is preferred. By using a negative electrode active material containing silicon, the electric capacity of the lithium ion secondary battery can be increased. In general, the negative electrode active material containing silicon expands and shrinks largely (for example, about 5 times) with charging and discharging. However, the composite particles of the present invention are capable of withstanding the expansion and contraction of the negative electrode active material containing silicon It has strength. Therefore, in the negative electrode produced using the composite particles of the present invention, deterioration of the battery performance due to expansion and contraction of the negative electrode active material containing silicon can be effectively suppressed.

Examples of the negative electrode active material containing silicon include a compound containing silicon (hereinafter sometimes referred to as &quot; silicon-containing compound &quot;) and metallic silicon. The silicon-containing compound is, for example, SiO, SiO ₂ , SiO _x (0.01? X <2), SiC, SiOC and the like as a compound of silicon and other elements. Of 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 expansion of the negative electrode. Here, SiO _x is a compound that can be formed from one or both of SiO and SiO ₂ and metal silicon. This SiO _x can be produced, for example, by cooling a silicon monoxide gas produced by heating a mixture of SiO ₂ and silicon metal and precipitating it.

When the 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 wt%, more preferably 5 to 40 wt% Particularly preferably 10 to 30% by weight. When the compounding amount of the silicon-containing compound is too small, the capacity when the lithium ion secondary battery is manufactured becomes small. When the compounding amount of the silicon-containing compound is too large, the negative electrode is swollen.

As the negative electrode active material (A), one type may be used alone, or two or more types may be used in combination at an arbitrary ratio.

It is preferable that the negative electrode active material (A) is formed into a particle shape. If 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 占 퐉, more preferably 0.5 to 50 占 퐉, and still more preferably 0.8 to 20 占 퐉. The tap density of the negative electrode active material for a lithium ion secondary battery is not particularly limited, but is preferably 0.6 g / cm &lt; 3 &gt; or more.

The negative electrode active material (A) preferably used when the electrochemical device is a lithium ion capacitor includes the negative electrode active material formed of the carbon.

(Particulate binder resin (B))

The particulate binder resin (B) to be used in the present invention is not particularly limited as long as it can bind 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 polymer compounds such as silicone polymers, fluorine-containing polymers, conjugated diene polymers, acrylate polymers, polyimide, polyamide and polyurethane, Polymers, conjugated diene-based polymers and acrylate-based polymers, more preferably conjugated diene-based polymers and acrylate-based polymers. These polymers may be used alone or as a mixture of two or more of them to be used 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, and a perfluoroethylene-propene copolymer. Among them, polytetrafluoroethylene is preferable because it is fibrillated to easily hold the negative electrode active material.

The conjugated diene polymer is a copolymer obtained by polymerizing a homopolymer of a conjugated diene monomer or a monomer mixture containing a conjugated diene monomer, or a hydrogenated product thereof. As the conjugated diene-based monomer, there can be mentioned 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, Substituted and side-chain conjugated hexadiene and the like are preferably used. From the standpoint of improving the flexibility at the time of use as an electrode and being highly resistant to cracking, 1,3-butadiene is used . In the monomer mixture, two or more kinds of these conjugated diene monomers may be contained.

When the conjugated diene polymer is a copolymer of the above-mentioned conjugated diene monomer and a monomer capable of copolymerizing with the conjugated diene monomer, examples of such a copolymerizable monomer include an?,? -Unsaturated nitrile compound and vinyl having an acid component Compounds and the like.

Specific examples of the conjugated diene-based polymer include conjugated diene-based monomer homopolymers such as polybutadiene and polyisoprene; Aromatic vinyl-based monomers and conjugated diene-based monomer copolymers such as styrene-butadiene copolymer (SBR) which may be carboxy-modified; Vinyl cyanide monomer-conjugated diene monomer copolymer such as acrylonitrile-butadiene copolymer (NBR); Hydrogenated SBR, and hydrogenated NBR.

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

(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, and R ² represents an ether group (Meth) acrylic acid ester] represented by the general formula (1), which may have a hydroxyl group, a phosphoric acid group, an amino group, a carboxyl group, a fluorine atom or an epoxy group, , Or a monomer mixture containing the compound represented by the general formula (1). Specific examples of the compound represented by the general formula (1) include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, n- Isobutyl (meth) acrylate, isobornyl (meth) acrylate, isodecyl (meth) acrylate, isobutyl (meth) acrylate, isobutyl (meth) acrylate, (Meth) acrylic acid alkyl esters such as lauryl (meth) acrylate, stearyl (meth) acrylate, and tridecyl (meth) acrylate; (Meth) acrylate, methoxypropyleneglycol, (meth) acrylic acid methoxypolyethyleneglycol, (meth) acryloxyphenoxyethyl, (meth) acrylate tetrahydro Ether group-containing (meth) acrylic acid esters such as furfuryl; (Meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2- (Meth) acrylic acid esters containing hydroxyl group such as hydroxyethyl phthalic acid; Carboxylic acid-containing (meth) acrylic acid esters such as 2- (meth) acryloyloxyethyl phthalic acid; (Meth) acrylic acid perfluorooctylethyl (meth) acrylate; (Meth) acrylic acid ester such as ethyl (meth) acrylate; (Meth) acrylic esters containing an epoxy group such as glycidyl (meth) acrylate; (Meth) acrylate, and amino group-containing (meth) acrylate esters such as dimethylaminoethyl (meth) acrylate.

Further, in the present specification, "(meth) acryl" means "acrylic" and "methacryl". In addition, "(meth) acryloyl" means "acryloyl" and "methacryloyl".

These (meth) acrylic acid esters may be used alone or in combination of two or more. Among them, alkyl (meth) acrylates are preferable, and (meth) acrylic acid methyl ester, (meth) acrylate and n-butyl (meth) acrylate or alkyl methacrylate having alkyl group of 6 to 12 carbon atoms desirable. By selecting these, the swelling property with respect to the electrolytic solution can be lowered, and the cycle characteristics can be improved.

When the acrylate polymer is a copolymer of a compound represented by the above-mentioned general formula (1) and a monomer capable of copolymerizing with it, examples of such a copolymerizable monomer include two or more carbon-carbon double Unsaturated nitrile compounds or acidic components other than the carboxylic acid esters having a bond, aromatic vinyl monomers, amide monomers, olefins, diene monomers, vinyl ketones, and heterocyclic ring-containing vinyl compounds, Vinyl compounds.

Among the above copolymerizable monomers, use of an aromatic vinyl-based monomer is preferable because it can be made strong in strength so as not to be deformed well when an electrode (negative electrode) is produced, and in that sufficient adhesion between the negative electrode active material layer and the current collector can be obtained desirable. Examples of the aromatic vinyl monomer include styrene and the like.

If the amount of the aromatic vinyl monomer is too large, sufficient adhesion between the negative electrode active material layer and the current collector tends not to be obtained. When the blending amount of the aromatic vinyl monomer is too small, the electrolyte resistance tends to decrease when the negative electrode is produced.

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

Examples of the?,? - unsaturated nitrile compound used in the polymer constituting the dispersed particulate binder resin include acrylonitrile, methacrylonitrile,? -Chloroacrylonitrile,? -Bromoacrylonitrile and the like . 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?,? - 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 still more preferably 1 to 20% by weight. When an alpha, beta -unsaturated nitrile compound unit is contained in the dispersion type binder resin, the electrode (negative electrode) can not be deformed well and thus the strength can be made strong. In addition, when the α, β-unsaturated nitrile compound unit is contained in the dispersion type binder resin, the adhesion between the negative electrode active material layer containing the composite particles and the current collector can be made sufficient.

If the amount of the?,? - 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. If the amount of the?,? - unsaturated nitrile compound unit is too small, the electrolyte resistance tends to decrease when the negative electrode is produced.

Examples of the vinyl compound having an acidic 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, and methacrylic acid and itaconic acid are more preferable, and methacrylic acid is particularly preferable in view of good adhesive strength.

The amount of the vinyl compound unit having an acid component in the dispersed particulate binder resin is preferably 0.5 to 10% by weight, more preferably 1 to 10% by weight from the viewpoint of improving the stability when the slurry for a composite particle is improved, To 8% by weight, and more preferably 2 to 7% by weight.

If the blending amount of the vinyl compound unit having an acid component is too large, the viscosity of the slurry for composite particles tends to be high, and handling tends to become difficult. If the amount of the vinyl compound unit having an acid component is too small, the stability of the composite particle slurry tends to be lowered.

The particulate binder resin of the dispersion type used in the present invention is a particulate polymer having good binding properties and can suppress deterioration due to repetition of charging and discharging at a reduced capacity of the produced electrode. Examples of the particulate binder resin (B) include those in which particles of a binder resin such as latex are dispersed in water, and those obtained in the form of a powder obtained by drying such a dispersion.

The average particle diameter of the dispersed particulate binder resin is preferably 0.001 to 100 占 퐉, more preferably 0.001 to 100 占 퐉, from the standpoint that the stability of the slurry for composite particles is good and the strength and flexibility of the obtained negative electrode become good Is 10 to 1000 nm, and more preferably 50 to 500 nm.

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

The blending amount of the particulate binder resin (B) in the composite particles for an electrochemical device electrode of the present invention is such that the adhesion between the obtained negative electrode active material layer and the current collector can be sufficiently secured and the internal resistance of the electrochemical device can be reduced , It is preferably 0.1 to 50 parts by weight, more preferably 0.5 to 20 parts by weight, and still more preferably 1 to 15 parts by weight, based on 100 parts by weight of the negative electrode active material, on a dry weight basis.

(Water-soluble polymer (C))

The water-soluble polymer (C) used in the present invention refers to a polymer having an untreated water content of less than 10.0 wt% 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 their ammonium salts or alkali metal salts, alginic acid esters such as alginic acid propylene glycol ester, and alginic acid (Meth) acrylic acid (or methacrylic acid) salts such as polyacrylic acid (or methacrylic acid) sodium, polyvinyl alcohol, modified polyvinyl alcohol, poly-N-vinyl acetamide, , Polyvinylpyrrolidone, polycarboxylic acid, oxidized starch, starch phosphate, casein, various modified starches, chitin, chitosan derivatives and the like. In the present invention, "(modified) poly" means "unmodified poly" or "modified poly".

These water-soluble polymers (C) may be used alone or in combination of two or more. Among these, cellulose-based polymers are preferable, and carboxymethylcellulose or its ammonium salt or alkali metal salt is particularly preferable from the viewpoint of good dispersibility of the water-insoluble polysaccharide polymer fibers (D) and high adhesiveness. The blending amount of the water-soluble polymer (C) is not particularly limited as long as it does not impair the effect of the present invention, but is preferably 0.1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material (A) More preferably 0.2 to 5 parts by weight, and still more preferably 0.25 to 2 parts by weight.

(Non-water-soluble polysaccharide polymer fiber (D))

The water-insoluble polysaccharide polymer fiber (D) used in the present invention belongs to a so-called polymer compound in a polysaccharide and is not particularly limited as long as it is a water-insoluble fibrous material. Usually, (Short fibers). Further, the water-insoluble polysaccharide polymer fiber used in the present invention refers to a polysaccharide polymer fiber having an unsalted amount of 90% by weight or more when 0.5 g of the polysaccharide polymer fiber is dissolved in 100 g of pure water at 25 ° C.

As the water-insoluble polysaccharide polymer fiber (D), it is preferable to use a nanofiber of a polysaccharide polymer. Since the polysaccharide polymer has flexibility in the nanofiber of the polysaccharide polymer and has a high tensile strength of the fiber, From the standpoint of improving the strength, it is more preferable to use alone or an arbitrary mixture selected from bio-derived nanon fibers such as cellulose nanofiber, chitin nanofiber and chitosan nanofiber. Among them, cellulose nanofibers are more preferably used, and it is particularly preferable to use cellulose nanofibers based on bamboo, conifer, hardwood and cotton.

Examples of the method of fibrillating (shortening the fiber) by adding a mechanical shearing force to the water-insoluble polysaccharide polymer fiber (D) include a method of dissolving the water-insoluble polysaccharide polymer fiber in water and then beating the solution, And the like. As the water-insoluble polysaccharide polymer fibers, short fibers having various fiber diameters are commercially available, and they may be dispersed in water.

The average fiber diameter of the water-insoluble polysaccharide polymer fibers (D) used in the present invention is such that the non-water-soluble polysaccharide polymer fibers (D) are present in the composite particles in a larger amount to strengthen the adhesion between the negative electrode active materials, Is preferably 5 to 3000 nm, more preferably 5 to 2000 nm, further preferably 5 to 1000 nm, particularly preferably 5 to 4000 nm, from the viewpoint that the strength of the electrochemical device is sufficient, Is 5 to 100 nm. If the average fiber diameter of the water-insoluble polysaccharide polymer fibers (D) is too large, the water-insoluble polysaccharide polymer fibers can not be sufficiently present in the composite particles, so that the strength of the composite particles can not be sufficient. Further, the fluidity of the composite particles deteriorates, and it becomes difficult to form a uniform negative electrode active material layer.

In addition, the water-insoluble polysaccharide polymer fibers (D) may be composed of short fibers which are not aligned and sufficiently separated from each other. In this case, the average fiber diameter becomes the average diameter of the short fibers. In addition, the water-soluble polysaccharide polymer fibers (D) may be one in which a plurality of short fibers are aggregated into a plurality of fibers to form one yarn. In this case, the average fiber diameter is defined as an average value of the diameter of one yarn.

The average degree of polymerization of the water-insoluble polysaccharide polymer fibers (D) can be 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 chemical properties, it is preferably 50 to 1000, more preferably 100 to 900, still more preferably 150 to 800. If the average degree of polymerization of the water-insoluble polysaccharide polymer fibers is excessively large, the internal resistance of the resultant electrochemical device increases. In addition, it is difficult to form a uniform negative electrode active material layer. When the average degree of polymerization of the water-insoluble polysaccharide polymer fibers is too small, the strength of the composite particles becomes insufficient.

In the present invention, the average degree of polymerization is determined by the viscosity method using the following copper ethylenediamine solution.

The freeze-dried, water-soluble polysaccharide polymer fibers were dissolved in copper ethylenediamine solution 1 to prepare solution 2, and the viscosity was measured using a viscometer. The intrinsic viscosity [?] Of the water-insoluble polysaccharide polymeric fiber solution is determined by the following equation, assuming that the viscosity of the solution 2 is? And the viscosity of the solution 1 is? 0.

Intrinsic viscosity [?] = (? /? 0) / {c (1 + A 占? /?

Here, c is the water-soluble polysaccharide polymer fiber concentration (g / dL), and A is a value determined according to the kind of the solution 1. When 0.5 M copper ethylene diamine solution is used as solution 1, A is 0.28.

The average degree of polymerization DP is obtained from the following formula.

Intrinsic viscosity [η] = K × DP ^a

Where K and a are the values determined by the kind of polymer. For example, in the case of cellulose, K is 5.7 × 10 ^-3 and a is 1.

The viscometer is preferably a capillary viscometer, for example a Canon-Pensche Viscometer.

The blending amount of the water-insoluble polysaccharide polymer fibers (D) is preferably 0.1 to 2 parts by weight, more preferably 0.2 to 1.5 parts by weight, more preferably 0.3 to 5 parts by weight, in terms of solid content, based on 100 parts by weight of the resultant composite particles. 1 part by weight. If the blending amount of the water-soluble polysaccharide polymer fiber is excessively large, the internal resistance of the resultant electrochemical device increases. In addition, it becomes difficult to form a uniform electrode layer (negative electrode active material layer). When the blending amount of the water-soluble polysaccharide polymer fibers (D) is too small, the reinforcing effect by the water-insoluble polysaccharide polymer fibers is small and the strength of the composite particles is insufficient. When the blending amount of the water-soluble polysaccharide polymer fibers (D) is too large, the granulation of the composite particles can not be carried out.

Further, when the viscosity of the slurry for composite particles is increased by increasing the blending amount of the water-soluble polysaccharide polymer fibers (D), the viscosity can be adjusted appropriately by reducing the amount of the water-soluble polymer blended.

The ratio of the water-soluble polymer (C) to the water-insoluble polysaccharide polymer fiber (D) to be used in the present invention is preferably in the range of a water-soluble polymeric fiber (D) in a weight ratio in terms of solid content from the viewpoint of improving the dispersibility of the water- The ratio of the polymer (C) / the water-insoluble polysaccharide polymer fiber (D) is 0.2 to 18, preferably 0.25 to 15, more preferably 0.3 to 10.

(Conductive auxiliary agent)

In the electrochemical device electrode composite particle of the present invention, in addition to the above components, a conductive auxiliary agent may be contained, if necessary.

The conductive auxiliary agent is not particularly limited as long as it is a conductive material, but a conductive particulate material is preferable, and examples thereof include conductive carbon black such as furnace black, acetylene black, and ketjen black; Graphite such as natural graphite and artificial graphite; Carbon fiber such as polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and vapor-grown carbon fiber. When the conductive auxiliary agent is a particulate material, the average particle diameter is not particularly limited, but is preferably smaller than the average particle size of the negative electrode active material. From the viewpoint of exhibiting sufficient conductivity with a smaller usage amount, it is preferably 0.001 to 10 mu m Preferably 0.05 to 5 mu m, and more preferably 0.1 to 1 mu m.

The mixing amount of the conductive auxiliary agent in the composite particles for electrochemical device electrode of the present invention is preferably in the range of 100 parts by weight to 100 parts by weight with respect to 100 parts by weight of the negative active material from the viewpoint of sufficiently reducing the internal resistance while keeping the capacitance of the obtained electrochemical device high. 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.

(Production of composite particles)

The composite particles are obtained by assembling using the other components such as the negative electrode active material (A), the particulate binder resin (B), the water-soluble polymer (C), the water-soluble polysaccharide polymer fiber (D) The composite particles contain the negative electrode active material (A) and the particulate binder resin (B), but the negative electrode active material (A) and the particulate binder resin (B) are not present as separate particles individually, (A) and the particulate binder resin (B), the particles are formed by two or more components. Specifically, a plurality of (two or more) individual particles are combined with each other to form secondary particles while maintaining substantially the shape, and a plurality of (preferably several to several tens) negative electrode active materials Is preferably bound by the particulate binder resin (B) to form particles.

The shape of the composite particles is preferably substantially spherical in terms of fluidity. That is, assuming that the short axis of the composite particle is L _s , the major axis is L ₁ , and L _a = (L _s + L ₁ ) / 2, the value of (1 - (L ₁ -L _s ) / L _a ) × 100 Is a sphericity (%), the sphericity is preferably 80% or more, and more preferably 90% or more. Here, the short axis L _s and the long axis L _l are values measured from a scanning electron microscopic photograph image.

The average particle diameter of the composite particles is preferably 0.1 to 200 占 퐉, more preferably 1 to 150 占 퐉, and still more preferably 10 to 80 占 퐉, from the viewpoint of easily obtaining an electrode layer (negative electrode active material layer) to be. In the present invention, the average particle size is the volume average particle size as measured by a laser diffraction particle size distribution analyzer (for example, SALD-3100; manufactured by Shimadzu Corporation).

The method of producing the composite particles is not particularly limited, and the production method of the composite particles may include a spray drying method, an electric layer method, a compression method, an agitation method, an extrusion method, a crushing method, a fluidized bed method, a fluidized bed multifunctional method, Whereby a composite particle can be obtained.

From the viewpoints of ease of particle diameter control, productivity, ease of control of particle size distribution, etc., the optimum method for the composite particles can be appropriately selected depending on the components of the composite particles and the like. It is preferable because the particles can be produced relatively easily. Hereinafter, the spray-drying assembly method will be described.

First, a slurry for composite particles (hereinafter sometimes referred to as &quot; slurry &quot;) containing the negative electrode active material (A) and the particulate binder resin (B) is prepared. The slurry for composite particles can be prepared by dispersing or dissolving a negative electrode active material, a binder resin, a water-soluble polymer, a water-insoluble polysaccharide polymer fiber, and a conductive auxiliary agent, if necessary, in a solvent. In this case, when the binder resin is dispersed in water as a solvent, it may be added while dispersed in water.

As the solvent used to obtain the slurry for composite particles, water is preferably used, but a mixed solvent of water and an organic solvent may be used, or an organic solvent alone or in combination of several kinds may be used. 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; And amides such as diethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone, and dimethylimidazolidinone. When an organic solvent is used, alcohols are preferable. By using an organic solvent having a lower boiling point than water and water, the drying speed can be increased at the time of spray drying. In this way, the viscosity and fluidity of the slurry for composite particles can be adjusted, and the production efficiency can be improved.

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

In the present invention, when preparing the slurry for composite particles, a dispersant or a surfactant may be added as needed. Examples of the surfactant include amphoteric surfactants such as anionic surfactants, cationic surfactants, nonionic surfactants and nonionic surfactants, which are preferred to be readily decomposed by anionic or nonionic surfactants. The blending amount of the surfactant is preferably 50 parts by weight or less, more preferably 0.1 to 10 parts by weight, and still more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the negative electrode active material.

The amount of the solvent used when preparing the slurry is preferably 1 to 50% by weight, more preferably 5 to 50% by weight, still more preferably 5 to 50% by weight, in terms of solid concentration of the slurry, from the viewpoint of uniformly dispersing the binder resin in the slurry By weight is 10 to 40% by weight.

The method of dispersing or dissolving the negative electrode active material (A), the particulate binder resin (B), the water-soluble polymer (C) and the water-insoluble polysaccharide polymer fiber (D) (A), a particulate binder resin (B), a water-soluble polymer (C), a water-insoluble polysaccharide polymer fiber (D) and a conductive auxiliary agent are added to a solvent and a method in which a solvent is mixed with a water-soluble polymer (A), a conductive auxiliary agent and a water-insoluble polysaccharide polymer fiber (D) are added and mixed. Finally, a particulate binder resin (B) (for example, latex) dispersed in a solvent (A) and a conductive auxiliary agent are added to and mixed with the particulate binder resin (B) and the water-insoluble polysaccharide polymer fiber (D) dispersed in a solvent, and a water-soluble And a method of mixing by adding a molecule (C).

As the mixing apparatus, for example, a ball mill, a sand mill, a bead mill, a pigment disperser, a brain ball, an ultrasonic disperser, a homogenizer, a homomixer, a planetary mixer and the like can be used. The mixing is preferably carried out at room temperature to 80 ° C for 10 minutes to several hours.

Then, the obtained composite particle slurry is spray dried and assembled. Spray drying is a method in which a slurry is sprayed in hot air to dry. As an apparatus used for spraying the slurry, an atomizer can be mentioned. As the atomizer, there are two types of apparatuses of a rotary disc type and a pressurization type. In the rotary disc type, a slurry is introduced into the center of a disc rotating at a high speed, and the slurry is discharged In which the slurry is misty. In the rotary disc method, the rotation speed of the disc depends on the size of the disc, 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 droplet size and the larger the average particle size of the resulting composite particles. As the rotator disk type atomizer, there can be mentioned a pin type and a vane type, but it is preferably a pin type atomizer. The fin type atomizer is a type of centrifugal spraying apparatus using a spray boom and is equipped with a plurality of atomizing rollers so as to freely attach and detach the atomizer on the almost concentric circle along the peripheral edge between the upper and lower mounting disks . The slurry for the composite particles is introduced from the middle of the spraying section and is attached to the spraying roller by centrifugal force to move the roller surface outwardly and finally spray away from the roller surface. On the other hand, the pressurizing method is a method in which the slurry for composite particles is pressurized and dried from a nozzle in the form of mist.

The temperature of the slurry for a composite particle to be sprayed is preferably room temperature, but it may be heated to a temperature higher than room temperature. The hot air temperature at 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 spraying the hot air is not particularly limited. For example, a method in which the hot air and the spray direction are cross flow in the lateral direction, a method in which the spray is sprayed from the dry tower part (top part) , A method in which the sprayed droplet and hot air make a countercurrent contact, a method in which the sprayed droplet is cocurrent with the first hot air, and then gravitationally falls and makes a countercurrent contact.

(Electrochemical device electrode)

The electrochemical device electrode (negative electrode) can be obtained by laminating the negative electrode active material layer containing the composite particles for electrochemical device electrode of the present invention on the current collector. As the material of the current collector, for example, metal, carbon, conductive polymer, or the like can be used, and a metal is preferably used. As the metal, copper, aluminum, platinum, nickel, tantalum, titanium, stainless steel and other alloys are usually used. Of these, copper, aluminum or an aluminum alloy is preferably used in terms of conductivity and withstand voltage. When high withstand voltage is required, aluminum of high purity disclosed in Japanese Laid-Open Patent Publication No. 2001-176757 can be preferably used. The collector may be a film or a sheet. The thickness of the collector is appropriately selected depending on the purpose of use, and is preferably 1 to 200 占 퐉, more preferably 5 to 100 占 퐉, and still more preferably 10 to 50 占 퐉.

When the negative electrode active material layer is laminated on the current collector, the composite particles may be formed into a sheet and then laminated on the current collector. However, a method of directly pressing the composite particles directly on the current collector is preferable. As a method of press-forming, for example, a roll-type press-molding apparatus provided with a pair of rolls is used to feed a composite particle to a roll-type press-molding apparatus by a feeding device such as a screw feeder while the current- A roll pressing method in which a negative electrode active material layer is formed on a current collector, a method in which composite particles are dispersed on a current collector, the composite particles are uniformly dispersed with a blade or the like to adjust the thickness, A method of charging the metal mold and pressing the metal mold to form the metal mold, and the like. Of these, a roll pressing method is preferred. Particularly, since the composite particles of the present invention have high fluidity, the composite particles can be formed by roll press forming due to their high fluidity, thereby making it possible to improve the productivity.

The roll temperature at the time of performing roll pressing is preferably 25 to 200 占 폚, more preferably 50 to 150 占 폚, and still more preferably 50 to 150 占 폚, from the viewpoint that sufficient adhesion between the negative electrode active material layer and the current collector can be achieved. 80 to 120 ° C. The press line pressure between the rolls during roll press forming is preferably from 10 to 1000 kN / m, more preferably from 200 to 900 kN / m, from the viewpoint of improving the uniformity of the thickness of the negative electrode active material layer, More preferably 300 to 600 kN / m. The molding speed in roll pressing is preferably 0.1 to 20 m / min, more preferably 4 to 10 m / min.

Further, in order to increase the density and increase the capacity of the negative electrode active material layer, it is also possible to perform additional post-pressurization as needed, in order to eliminate variations in thickness of the formed electrochemical device electrode (negative electrode). As a post-pressurizing method, a press process by a roll is preferable. In the roll pressing step, rolls of two cylindrical columns are vertically arranged in parallel at narrow intervals, and are rotated in opposite directions to each other, and an electrode is pressed therebetween. At this time, if necessary, the temperature of the roll may be adjusted by heating or cooling.

(Electrochemical device)

The electrochemical device can be obtained by using the electrochemical device 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 device include a lithium ion secondary battery and a lithium ion capacitor.

(Positive electrode)

A positive electrode of an electrochemical device is formed by laminating a positive electrode active material layer on a current collector. The positive electrode of the electrochemical device is a positive electrode slurry containing a positive electrode active material, a binder resin for a positive electrode, a solvent used in the production of a positive electrode, a water-soluble polymer to be used if necessary, And then drying it. That is, a positive electrode active material layer is formed on the current collector by applying the positive electrode slurry to the surface of the current collector and drying the same.

(Positive electrode active material)

The positive electrode active material in the case where the electrochemical device is a lithium ion secondary battery is roughly classified into an active material comprising an inorganic compound and an organic compound, in which an active material capable of doping and dedoping lithium ions is used.

Examples of the positive electrode active material composed of an inorganic compound include transition metal oxides, transition metal sulfides, and lithium-containing composite metal oxides of lithium and a transition metal. As the transition metal, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Mo are used.

Examples of 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 OP ₂ O ₅ , MoO ₃ , V ₂ O ₅ , V ₆ O _13, etc. Among them, MnO, V ₂ O ₅ , V ₆ O ₁₃ and TiO ₂ are preferable in terms of cycle stability and capacity. Examples of the transition metal sulfide include TiS ₂ , TiS ₃ , amorphous MoS ₂ , and FeS. 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.

The lithium-containing composite metal oxide having a layered structure includes lithium-containing cobalt oxide (LiCoO ₂ ) (hereinafter may be referred to as "LCO"), lithium-containing nickel oxide (LiNiO ₂ ) , A lithium composite oxide of Ni-Mn-Al, and a lithium composite oxide of Ni-Co-Al. Examples of the lithium-containing composite metal oxide having a spinel structure include lithium manganese oxide (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 , Fe, Co, Ni, Cu, etc.). As the lithium-containing composite metal oxide having an olivine structure, Li _X MPO ₄ (where M is Mn, Fe, Co, Ni, Cu, Mg, Zn, V, Ca, Sr, Ba, , At least one selected from B and Mo, and 0? X? 2).

As the organic compound, for example, a conductive polymer such as polyacetylene or poly-p-phenylene may be used. The iron-based oxide lacking the electric conductivity may be used as the positive electrode active material covered with the carbon material by allowing the carbon source material to exist at the time of the reduction calcination. These compounds may be partially substituted by an element. The positive electrode active material may be a mixture of the inorganic compound and the organic compound.

The positive electrode active material in the case where the electrochemical device is a lithium ion capacitor may be one capable of reversibly supporting lithium ions and anions such as tetrafluoroborate. Concretely, carbon isotopes can be preferably used, and electrode active materials used in electric double layer capacitors can be widely used. Specific examples of the carbon isotopes include activated carbon, polyacene (PAS), carbon whiskers, carbon nanotubes, and graphite.

The volume average particle diameter of the positive electrode active material is preferably from the viewpoint of reducing the blending amount of the positive electrode binder resin when preparing the positive electrode slurry and suppressing the decrease of the capacity of the battery and the viscosity suitable for applying the positive electrode slurry Is preferably from 1 to 50 mu m, and more preferably from 2 to 30 mu m from the viewpoint of obtaining a uniform electrode.

(Binder resin for positive electrode)

Examples of the binder resin for positive electrode include polyolefin resins such as polyethylene, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP) Acrylonitrile derivatives; A soft polymer such as an acrylic soft polymer, a diene soft polymer, an olefin soft polymer, a vinyl soft polymer and the like. The binder resin may be used singly or in combination of two or more in an arbitrary ratio.

(Other components)

As the water-soluble polymer and the conductive auxiliary agent to be used in the slurry for positive electrode according to need, the water-soluble polymer and the conductive auxiliary agent usable for the above-mentioned composite particles can be used, respectively.

(A solvent used for producing a positive electrode)

As the solvent used for the production of the positive electrode, either water or an organic solvent may be used. Examples of the organic solvent include cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; Aromatic hydrocarbons such as toluene and xylene; Ketones such as ethyl methyl ketone and cyclohexanone; Esters such as ethyl acetate, butyl acetate,? -Butyrolactone and? -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; And amides such as N-methylpyrrolidone and N, N-dimethylformamide. Of these, N-methylpyrrolidone (NMP) is preferable. The solvents may be used singly or in combination of two or more in an arbitrary ratio. Among them, it is preferable to use water as a solvent.

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

(Whole house)

The current collector used for the positive electrode may be the same current collector used for the above-described electrochemical device electrode (negative electrode).

(Production method of positive electrode)

The method of applying the positive electrode slurry to the surface of the current collector is not particularly limited. For example, methods such as a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, and a brush method may be used.

The drying method includes, for example, hot air, hot air, low-humidity air drying, vacuum drying, and drying by irradiation with (circle) infrared rays or electron beams. The drying time is preferably 5 minutes to 30 minutes, and the drying temperature is preferably 40 to 180 ° C.

It is also preferable that the positive electrode slurry is coated on the surface of the current collector and dried, and then the positive electrode active material layer is subjected to pressure treatment, for example, using a die press or a roll press, if 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, and 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 liable to be peeled off from the current collector. If the porosity is too large, the charging efficiency and the discharge efficiency are lowered.

When the positive electrode active material layer contains a curable polymer, it is preferable to cure the polymer after formation of the positive electrode active material layer.

(Separator)

As the separator, for example, a microporous film or nonwoven fabric containing a polyolefin resin such as polyethylene or polypropylene, or an aromatic polyamide resin; A porous resin coat containing an inorganic ceramic powder, or the like can be used. Specific examples thereof include a microporous membrane made of a resin such as a polyolefin (polyethylene, polypropylene, polybutene, polyvinyl chloride) and a mixture or copolymer thereof; A microporous membrane made of a resin such as polyethylene terephthalate, polycycloolefin, polyethersulfone, polyamide, polyimide, polyimide amide, polyaramid, nylon, and polytetrafluoroethylene; Woven or nonwoven fabric of polyolefin type fibers; And aggregates of insulating substance particles. Among them, a microporous membrane made of a polyolefin-based resin is preferable because the film thickness of the whole separator can be made thinner and the capacity per volume can be increased by raising the active material ratio in the lithium ion secondary battery.

The thickness of the separator is preferably 0.5 to 40 占 퐉, more preferably 0.5 to 40 占 퐉, from the viewpoint that the internal resistance by the separator in the lithium ion secondary battery can be reduced and the workability in the production of the lithium ion secondary battery is excellent. Preferably 1 to 30 mu m, and more preferably 1 to 25 mu m.

(Electrolytic solution)

As the electrolyte for the lithium ion secondary battery, for example, a nonaqueous electrolyte solution in which a supporting electrolyte is dissolved in a nonaqueous solvent is used. As the supporting electrolyte, a lithium salt is preferably used. Lithium salts include, for _{example, 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, and (C ₂ F ₅ SO ₂ ) NLi. In particular, the _{LiPF 6, LiClO 4, CF 3} SO 3 Li represents a high dissociation degree and easily soluble in solvents. These may be used singly or in combination of two or more in an arbitrary ratio. The higher the degree of dissociation of the supporting electrolyte, the higher the lithium ion conductivity. Therefore, the lithium ion conductivity can be controlled depending on the type of the supporting electrolyte.

The concentration of the supporting electrolyte in the electrolytic solution is preferably 0.5 to 2.5 mol / l depending on the type of the supporting electrolyte. If the concentration of the supporting electrolyte is excessively low or too high, there is a possibility that the ionic conductivity is lowered.

The non-aqueous solvent is not particularly limited as long as it can dissolve the supporting electrolyte. Examples of the nonaqueous solvent include carbonates such as dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene carbonate (BC) and methyl ethyl carbonate (MEC); esters such as? -butyrolactone and methyl formate; Ethers such as 1,2-dimethoxyethane and tetrahydrofuran; Sulfur compounds such as sulfolane and dimethylsulfoxide; And an ionic liquid which is also used as a supporting electrolyte. Of these, carbonates are preferable because of high dielectric constant and stable wide potential range. The non-aqueous solvent may be used singly or in combination of two or more at any ratio. Generally, 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. However, since both have a trade-off relationship, the lithium ion conductivity is controlled It is good to use. The nonaqueous solvent may be a combination of all or a part of hydrogen substituted with fluorine, or a total amount thereof.

The electrolytic solution may contain an additive. As the additive, for example, a carbonate type such as vinylene carbonate (VC); Sulfur compounds such as ethylene sulfite (ES); And fluorine-containing compounds such as fluoroethylene carbonate (FEC). One kind of additives may be used alone, or two or more kinds of additives may be used in combination at an arbitrary ratio.

As the electrolytic solution for the lithium ion capacitor, the same electrolytic solution that can be used for the above-described lithium ion secondary battery can be used.

(Manufacturing Method of Electrochemical Device)

A specific method for producing an electrochemical device such as a lithium ion secondary battery or a lithium ion capacitor includes a method in which a positive electrode and a negative electrode are superimposed with a separator interposed therebetween, And a method in which an electrolyte is injected into the battery container to seal the battery container. Expanded metal as needed; 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 and overcharge discharge. The shape of the lithium ion secondary battery may be a coin type, a button type, a sheet type, a cylindrical type, a square type, or a flat type. The material of the battery container is not particularly limited as long as it inhibits the penetration of moisture into the inside of the battery, such as a metal or aluminum laminate.

According to the composite particle for an electrochemical device electrode of the present invention, it is possible to obtain an electrode having sufficient strength, sufficient adhesion can be obtained when an electrode is formed, and excellent flexibility can be obtained. In addition, the composite particle for electrochemical device electrode of the present invention has excellent fluidity.

Example

EXAMPLES The present invention will be described in more detail with reference to the following examples, but it should be understood that the present invention is not limited to the following examples, but may be carried out without departing from the scope and spirit of the invention . In the following description, &quot;% &quot; and &quot; part &quot; representing amounts are based on weight unless otherwise specified.

In the Examples and Comparative Examples, the particle strength, fill strength, flexibility and cycle characteristics of the composite particles were evaluated as follows. In the following, the average fiber diameter is an average value when the fiber diameter is measured for 100 non-water-soluble polysaccharide polymer fibers in the field of an electron microscope.

<Particle Strength of Composite Particle>

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 load was applied at a load load rate of 4.46 mN / sec at the center of the composite particle at room temperature, and the compressive strength (MPa) at the time of deforming the particle until the diameter of the composite particle was displaced by 40% was measured . Further, in this measurement, composite particles having a diameter of 40 to 60 탆 were selected and compression tests were conducted.

The compression test was carried out ten times, and the average value was regarded as the compressive strength. The compressive strength was evaluated based on the following criteria, and the results are shown in Tables 1 and 2. The larger the compressive strength, the better the adhesion strength between the negative electrode active materials, and the composite particles exhibit excellent particle strength.

A: Compressive strength of not less than 1.00 MPa

B: Compressive strength of 0.90 MPa or more and less than 1.00 MPa

C: Compressive strength of 0.80 MPa or more and less than 0.90 MPa

D: Compressive strength of 0.70 MPa or more and less than 0.80 MPa

E: Compressive strength less than 0.70 MPa

<Peel Strength>

The negative electrode for a lithium ion secondary battery obtained in Examples and Comparative Examples was cut into a square shape having a width of 1 cm and a length of 10 cm. After cutting the negative electrode for the lithium ion secondary battery with the negative electrode active material layer face up and attaching the cellophane tape to the surface of the negative electrode active material layer, the cellophane tape was peeled from one end of the test piece at 180 ° The stress at the time of peeling in the direction was measured. This stress was measured 10 times, and the average value was defined as the peel strength. The peel strength was evaluated based on the following criteria, and the results are shown in Tables 1 and 2. In addition, the larger the fill strength, the better the adhesion in the negative electrode active material layer and the better the adhesion between the negative electrode active material layer and the current collector.

A: Peel strength of 15 N / m or more

B: Peel strength of 7 N / m or more and less than 15 N / m

C: Peel strength of 3 N / m or more and less than 7 N / m

D: Peel strength less than 3 N / m

E: Inability to evaluate

&Lt; Electrode flexibility &gt;

A rod having different diameters was placed on the negative electrode active material layer side of the negative electrode for a lithium ion secondary battery obtained in Examples and Comparative Examples and the negative electrode was wound on a rod to evaluate whether or not the negative electrode active material layer was cracked. 1 and Table 2, respectively. The smaller the diameter of the rod, the better the turnability of the negative electrode. If the winding property is excellent, the separation of the negative electrode active material layer can be suppressed, so that the cycle characteristics of the secondary battery are excellent.

A: Not cracked at 1.2 mm?

B: Not cracked at 1.5 mm?

C: Not cracked at 2 mm φ

D: Not cracked at 3 mmφ

E: Not cracked at 4 mmφ

<Characteristics of charge / discharge cycle>

The laminate-type lithium ion secondary battery obtained in the Examples and Comparative Examples was charged with a constant current until a voltage of 4.2 V was attained by a constant current constant voltage charging method at 60 DEG C at 0.5 DEG C and then charged at a constant voltage, Discharge cycle test in which the battery was discharged to 3.0 V at a constant current of 0.5 C. The charge-discharge cycle test was performed 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 on the basis of the following criteria, and the results are shown in Tables 1 and 2. The larger the capacity retention rate, the less the capacity decrease due to repetitive charging and discharging.

A: Capacity retention rate is 90% or more

B: Capacity retention rate is 80% or more and less than 90%

C: Capacity retention rate is 75% or more and less than 80%

D: Capacity retention ratio is 70% or more and less than 75%

E: Capacity retention rate is less than 70% or unmeasurable

[Example 1]

(Production of particulate binder resin (B)

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, 150 parts of t-dodecylmercaptan And 0.5 part of potassium persulfate as a polymerization initiator were put in a flask, and the mixture was sufficiently stirred and then heated to 50 DEG C to initiate polymerization. When the polymerization conversion rate reached 96%, the reaction mixture was cooled and the reaction was terminated to obtain a particulate binder resin (B) (styrene-butadiene copolymer (hereinafter sometimes abbreviated as "SBR")).

(Production of Slurry for Composite Particles)

91.0 parts of artificial graphite (average particle diameter: 24.5 mu m, graphite interlayer distance (plane interval (d value) of (002) plane by X-ray diffractometry): 0.354 nm), 6.6 parts of SiC as the negative electrode active material (A) (BSH-6; available from Daiichi Kogyo Seiyaku Co., Ltd.) as a water-soluble polymer (C) as a water-soluble polymer (C) (Manufactured by Chuetsu Pulp Co., Ltd.) as a non-water-soluble polysaccharide polymer fiber (D) in a 1% aqueous dispersion of cellulose nanofibers (raw material: bamboo, ) Was mixed in an amount of 0.8 parts in terms of solid content, and ion-exchanged water was further added thereto so as to have a solid content concentration of 35% and mixed and dispersed to obtain a slurry for composite particles. That is, the ratio of the water-soluble polymer (C) to the water-insoluble polysaccharide polymer fiber (D) was (C) / (D) = 0.5.

(Production of composite particles)

The slurry for the composite particles was pulverized at a rotation speed of 25,000 rpm, a hot air temperature of 150 占 폚, a temperature of the particle recovery outlet of 90 (a diameter of 65 mm) in a rotary disk type atomizer in a spray dryer (manufactured by Okawara Chemical Industry Co., Ltd.) Lt; 0 &gt; C, followed by spray drying and granulation, to obtain composite particles. The average particle diameter of the composite particles was 40 占 퐉.

(Preparation of negative electrode for lithium ion secondary battery)

Next, the obtained particles were supplied to a roll (roll temperature of 100 占 폚, press line pressure of 4.0 kN / cm) of a roll press machine (press cutting surface roughness hot roll, manufactured by Hirano Kikai Kogyo Co., Ltd.) and molded into a sheet at a forming speed of 20 m / , And a negative electrode for a lithium ion secondary battery having a thickness of 80 탆 was obtained.

(Preparation of positive electrode slurry and positive electrode for lithium ion secondary battery)

Polyvinylidene fluoride (PVDF; "KF-1100" manufactured by Kureha Chemical Industries, Ltd.) as a positive electrode binder resin was added to 92 parts of LiCoO ₂ as a positive electrode active material (hereinafter abbreviated as "LCO" , 6 parts of acetylene black ("HS-100" manufactured by Denki Kagaku Kogyo) and 20 parts of N-methylpyrrolidone were added and mixed with a planetary mixer to obtain a positive electrode slurry. The slurry for positive electrode was applied to an aluminum foil having a thickness of 18 占 퐉, dried at 120 占 폚 for 30 minutes, and then rolled to obtain a positive electrode for a lithium ion secondary battery having a thickness of 60 占 퐉.

(Preparation of separator)

A single-layered polypropylene separator (width 65 mm, length 500 mm, thickness 25 占 퐉, manufactured by the dry method, porosity of 55%) was cut out in a square of 5 占 5 cm2.

(Production of lithium ion secondary battery)

An aluminum-coated sheath was prepared as an exterior of the battery. The positive electrode for a lithium ion secondary battery obtained above was cut into a square of 4 x 4 cm 2, and the surface of the current collector side was disposed so as to be in contact with the aluminum-containing sheath. On the surface of the positive electrode active material layer of the positive electrode for a lithium ion secondary battery, a square separator obtained as described above was disposed. Further, the negative electrode for a lithium ion secondary battery obtained above was cut into a square of 4.2 x 4.2 cm 2, and the negative electrode active material layer side surface was disposed on the separator so as to face the separator. Further, a 1.0 M LiPF ₆ solution containing 2.0% of vinylene carbonate was charged. The solvent of the LiPF ₆ solution is a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC / EMC = 3/7 (volume ratio)). Further, in order to seal the openings of the aluminum foil, heat sealing was performed at 150 캜 to obtain an aluminum sheath to obtain a laminate type lithium ion secondary battery (laminate type cell).

[Example 2]

A slurry for composite particles, a composite particle, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared in the same manner as in Example 1 except that 97.6 parts of artificial graphite was used as the negative electrode active material (A).

[Example 3]

Except that 1.0% aqueous dispersion of cellulose nano fiber (raw material: softwood, degree of fibrillation: high, average degree of polymerization: 300; manufactured by Chuetsu Pulp Co., Ltd.) was used as the water-insoluble polysaccharide polymer fiber (D) Production of a slurry, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery.

[Example 4]

Except that 1.0% aqueous dispersion of cellulose nano fiber (raw material: hardwood, degree of fibrillation: low, average degree of polymerization: 600; manufactured by Chuetsu Pulp Co., Ltd.) was used as the water-insoluble polysaccharide polymer fiber (D) Production of a slurry, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery.

[Example 5]

Except that a 10% aqueous dispersion of a cotton cellulose nanofiber (fiber diameter: 0.1 to 0.01 탆, Celissi KY100G; manufactured by Daicel Fine Chemicals) was used as the water-insoluble polysaccharide polymer fiber (D) Production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery.

[Example 6]

Except that a 2% water dispersion (BiNFi-S (SFo-10002), average degree of polymerization 300, manufactured by Suginomachin Co., Ltd.) of chitin cellulose nanofibers was used as the water-insoluble polysaccharide polymer fiber (D) Production of composite particles, preparation of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery.

[Example 7]

Except that a 2% aqueous dispersion of chitosan cellulose nanofibers (BiNFi-S (EFo-10002), average degree of polymerization 480; manufactured by Suginomachin Co., Ltd.) was used as the water-insoluble polysaccharide polymer fiber (D) Production of composite particles, preparation of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery.

[Example 8]

Preparation of slurry for composite particles, production of composite particles, preparation of negative electrode for lithium ion secondary battery and production of lithium ion secondary battery were carried out in the same manner as in Example 1 except that polyacrylic resin was used as water-soluble polymer (C). The production of the polyacrylic resin was carried out as follows.

(Production of polyacrylic resin)

In a 1 L SUS separable flask equipped with a stirrer, a reflux condenser and a thermometer, demineralized water was preliminarily poured in advance and sufficiently stirred. The mixture was then brought to 70 ° C and 0.2 parts of an aqueous potassium persulfate solution was added.

50 parts of ion-exchanged water, 0.4 part of sodium hydrogencarbonate, 0.115 part of sodium dodecyldiphenyl ether sulfonate having a concentration of 30% as an emulsifier, 60 parts of methacrylic acid, 10 parts of ethyl acrylate 15 parts of butyl acrylate, 15 parts of butyl acrylate, and 10 parts of 2-acrylamide-2-methylpropanesulfonic acid as a sulfonic acid group-containing monomer copolymerizable therewith were poured into the emulsion and sufficiently stirred to prepare an emulsion aqueous solution.

The resulting aqueous emulsion solution was continuously added dropwise to the above separable flask over 4 hours. At the time when the polymerization conversion rate reached 90%, the reaction temperature was adjusted to 80 캜 and the reaction was further carried out for 2 hours, followed by cooling and quenching to obtain an aqueous dispersion containing the polyacrylic resin. The polymerization conversion rate was 99%. The weight average molecular weight of the obtained polyacrylic resin was measured by GPC and found to be 25,000. Further, when the obtained polyacrylic resin was used as a 1 wt% aqueous solution, the viscosity was 3000 (mPa · s).

[Example 9]

The procedure of Example 1 was repeated except that poly-N-vinylacetamide (PNVA, GE191-103; manufactured by Showa Denko K.K.) resin was used as the water-soluble polymer (C) Production of a negative electrode for an ion secondary battery, and production of a lithium ion secondary battery.

[Example 10]

Except that polyvinyl alcohol resin (PVA, JF-17, manufactured by Nippon SAKUVIPO Corporation) was used as the water-soluble polymer (C), the same procedure as in Example 1 was conducted except that the slurry for composite particles, And production of a lithium ion secondary battery were carried out.

[Example 11]

90.6 parts of artificial graphite and 6.6 parts of SiC as the negative electrode active material A and 1% aqueous dispersion of cellulose nanofibers as the water-insoluble polysaccharide polymer fibers (raw material: bamboo, degree of hummer: high, average degree of polymerization: 350; Manufactured by Shin-Etsu Chemical Co., Ltd.) was used in an amount of 1.2 parts in terms of solid content, the preparation of composite particles slurry, production of composite particles, preparation of negative electrode for lithium ion secondary battery and production of lithium ion secondary battery were carried out in the same manner as in Example 1. 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), 1.0 part of a 1.0% aqueous solution of CMC (BSH-6; manufactured by Daiichi Kogyo K.K.) as a water soluble polymer (C) in terms of solid content, (Raw material: bamboo, degree of fibrillation: high, average degree of polymerization: 350, manufactured by Chuetsu Pulp Co., Ltd.) as a solid dispersion conversion amount of cellulose nanofibers as a negative electrode active material (D) Production of a slurry, production of composite particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery. 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]

Except for using 91.1 parts of artificial graphite and 6.6 parts of SiC as the negative electrode active material and 0.3 part of a 1.0% aqueous solution of CMC (BSH-6; manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd.) as a water-soluble polymer (C) 1, a slurry for composite particles, a composite particle, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were prepared. 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]

Except that the amount of the negative electrode active material (A) was changed to 91.2 parts of artificial graphite and 6.6 parts of SiC and the amount of CMC as the water-soluble polymer (C) was changed to 1.0 part in terms of solid content without adding the water-soluble polysaccharide polymer fiber (D) Similar to Example 1, the slurry for composite particles, the preparation of composite particles, the preparation of a negative electrode for a lithium ion secondary battery, and the production of a lithium ion secondary battery were carried out.

[Comparative Example 2]

Preparation of a slurry for composite particles, preparation of composite particles, preparation of composite particles, mixing of LiCoO 2 and LiCoO 2 as in Example 1, except that the amount of the negative electrode active material (A) was changed to 91.4 parts of artificial graphite and 6.6 parts of SiC without adding CMC as the water- Production of a negative electrode for an ion secondary battery, and production of a lithium ion secondary battery.

[Comparative Example 3]

In the preparation of the slurry for composite particles, 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, (C) / (D) = 20 by mixing the water-soluble polymer (C) and the water-soluble polysaccharide polymer fiber (D) in an amount of 0.05 part by weight And that the amount of the negative electrode active material (A) was changed to 91.15 parts of artificial graphite and 6.6 parts of SiC, the preparation of the slurry for composite particles, the production of composite particles, the production of negative electrode for lithium ion secondary battery, A secondary battery was manufactured.

[Comparative Example 4]

In the preparation of the slurry for composite particles, 0.15 part by mass of CMC as a water-soluble polymer (C) in terms of solid content and 1% aqueous dispersion of cellulose nanofibers as a water-insoluble polysaccharide polymer fiber (raw material: bamboo, (C) / (D) = 0.15 by mixing the water-soluble polymer (C) and the water-soluble polysaccharide polymer fiber (D) in an amount of 1.0 part by mass , And that the amount of the negative electrode active material (A) was changed to 97.65 parts of artificial graphite, the same procedure as in Example 1 was repeated to prepare slurries for composite particles, to manufacture composite particles, to manufacture negative electrodes for lithium ion secondary batteries, Respectively.

[Comparative Example 5]

The water-soluble polymer (C) and the reinforcing fiber (D) were obtained by using carbon nanofibers (VGCF, manufactured by Showa Denko K.K., fiber diameter 150 nm, fiber length 20 μm) as the reinforcing fibers in place of the water- (D)) = 0.4 and the amount of the negative electrode active material (A) was changed to 97.4 parts of artificial graphite in the same manner as in Example 1, Production of particles, production of a negative electrode for a lithium ion secondary battery, and production of a lithium ion secondary battery.

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

Claims (4)

A composite particle for 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)
Wherein the water-soluble polymer (C) and the water-insoluble polysaccharide polymer fiber (D) are contained in a ratio of (C) / (D) = 0.2 to 18 in weight ratio. The method according to claim 1,
Wherein the average degree of polymerization of the water-insoluble polysaccharide polymer fibers (D) is 50 to 1,000. 3. The method according to claim 1 or 2,
The particulate binder resin (B) is a conjugated diene polymer or an acrylate polymer. 4. The method according to any one of claims 1 to 3,
The amount of the water-soluble polymer (C) to be blended is 0.1 to 10 parts by weight in terms of solid content relative to 100 parts by weight of the negative electrode active material (A)
Wherein the amount of the water-soluble polysaccharide polymer fiber (D) is 0.1 to 2 parts by weight in terms of solid content relative to 100 parts by weight of the composite particles.