WO2009098986A1

WO2009098986A1 - Aqueous paste for forming electrode of electrical storage device

Info

Publication number: WO2009098986A1
Application number: PCT/JP2009/051382
Authority: WO
Inventors: Ryoji Yamada
Original assignee: Asahi Glass Company, Limited
Priority date: 2008-02-08
Filing date: 2009-01-28
Publication date: 2009-08-13
Also published as: JP2011086378A

Abstract

Disclosed is an aqueous paste for forming an electrode of electrical storage devices, wherein an electrode active material, a conductive assistant and a binder are finely and uniformly dispersed. The aqueous paste exhibits high processability, while having a low risk of placing burden on the environment or impairing human health. Also disclosed is an electrode for electrical storage devices, which is made from the aqueous paste. Specifically disclosed is an aqueous paste for forming an electrode of electrical storage devices, which is characterized by containing an electrode active material, a conductive assistant and a binder. The aqueous paste is also characterized in that the conductive assistant is composed of a hydrophilic conductive carbonaceous material.

Description

Aqueous paste for storage element electrode formation

The present invention relates to an aqueous paste for forming an electric storage element electrode and an electric storage element having an electric storage element electrode formed from the aqueous paste.

Storage elements are widely used in various mechanisms and forms, such as energy sources for mobile devices, in-vehicle storage / discharge systems / energy sources, and power storage systems. These devices have characteristics such as high output and high energy density, reliability that can be used with peace of mind even in various environments such as low and high temperatures, and safety for unforeseen circumstances. Is required. Conventionally, the study for improving the characteristics has been on the improvement of the main material responsible for the function. However, it is extremely important to study a manufacturing method for realizing an element structure that can exhibit the characteristics of these materials as much as possible, particularly an electrode composite structure.

The electrode of the electricity storage element is composed of a composite of at least an electrode active material having a main function, a conductive additive, a binder and the like. In the formation of composites, the technology that the electrode active material, which is powder particles, and the conductive additive are dispersed as finely and as homogeneously as possible and then supported by the binder is a characteristic that each constituent material has. It is important to get the most out of it. The composite is formed by preparing a paste in which each electrode constituent material is dispersed in a medium, and applying and drying the paste on a current collector. Conventionally, an organic solvent has been used as a medium for preparing the paste. In order to support the electrode constituent material using a small amount of the polymer for the binder, it has been considered preferable to use a polymer solution (see Patent Document 1).

On the other hand, water-based pastes that use water as a medium have been proposed in the past, and it was expected that the environmental burden and cost could be greatly reduced in terms of materials, equipment, and equipment operation. However, since the conductive carbonaceous material usually used as a conductive auxiliary agent is hydrophobic and is very difficult to disperse in water, an electrode having good battery characteristics cannot be produced from an aqueous paste. In addition, in the case of non-aqueous power storage elements, since the intrusion of water greatly impairs the element characteristics, it has been considered not to bring water into the manufacturing process.

In order to solve this problem, ammonium perfluorooctanoate (hereinafter referred to as APFO), which is an emulsifier used in the production of an aqueous fluoropolymer dispersion, and carboxymethyl cellulose (hereinafter referred to as CMC) coexist. It has been proposed that a conductive carbonaceous material is finely dispersed in water (see Patent Document 2). In this case, an aqueous paste in which the electrode forming material is uniformly dispersed can be prepared. Since an electrode manufactured from such an aqueous paste can exhibit good electric storage element characteristics, an electrode manufactured from an aqueous paste has been adopted in lithium batteries, lithium ion batteries, electric double layer capacitors and the like.

However, PFOAs typified by APFO (in this specification, PFOAs include APFO and ammonium perfluorooctane sulfonate, and perfluoroalkanoic acid and salts thereof and perfluoroalkanesulfonic acid and salts thereof which are similar to these. It was found that fluorinated surfactants such as, etc.) have high in vivo persistence and accumulation. Although there are still many unclear points about the toxicity and danger of PFOAs remaining in the living body to the human body, it is required not to use them as much as possible because they are compounds that do not exist in nature. For this reason, in the production of an aqueous dispersion of a fluoropolymer, after emulsion polymerization using PFOAs, a hydrocarbon-based surfactant such as sodium lauryl sulfate or polyoxyethylene alkyl ether is added to the resulting emulsion of the fluoropolymer. In addition, after stabilization, a technique has been developed in which PFOAs are removed to obtain a fluoropolymer aqueous dispersion having a significantly low PFOA content.

However, an aqueous paste using a fluorine-containing polymer aqueous dispersion containing a small amount of PFOA as a binder cannot be applied to the surface of the current collector as a result of abnormally thickening of the paste. There has been a problem that it is not possible to form an electrode composite layer that is excellent in workability such as winding and that can exhibit good characteristics of an electric storage element.
As a solution to this problem, measures such as weakening the hydrophobicity of the hydrophobic conductive carbonaceous material or imparting hydrophilicity are effective to make the conductive carbonaceous material finely dispersed in water. it was thought.

Carbon blacks such as acetylene black, etc., whose surface has been hydrophilized by treating the surface of acetylene black with extremely strong hydrophobicity (in this specification, carbon black is a carbonaceous material that normally exhibits black color, and what are carbon blacks? , Which is a general term for conductive carbonaceous materials, including acetylene black, ketjen black, etc.), an aqueous paste with good dispersibility could be prepared, and an electrode capable of exhibiting good battery characteristics could be formed. (For example, refer to Patent Document 3). However, since such surface treatment reduces the electronic conductivity of the carbon blacks, the battery characteristics were not improved with the electrode in which the electrode active material and the surface oxidized carbon black were dispersed.

Japanese Patent Publication No. 08-4007 Japanese Patent Publication No. 07-40485 Japanese Patent No. 3555213

In the present invention, the electrode active material, the conductive additive, and the binder are each finely divided and uniformly dispersed, have high processability, and contain very little or no PFOA, which is represented by APFO. An object of the present invention is to provide an aqueous paste for forming a storage element electrode, and a storage element electrode formed from the aqueous paste.

The present inventor used a conductive carbonaceous material having hydrophilicity (hereinafter referred to as conductive carbonaceous material having hydrophilicity in the present invention) instead of a conductive carbonaceous material such as acetylene black having a strong hydrophobic property as a conductive assistant. The material refers to a conductive carbonaceous material determined to have hydrophilicity in the following hydrophilicity evaluation test.), So that it is possible to use PFOAs, organic solvents with high environmental impact, and the like. The inventors have found that the above problems can be solved and have completed the present invention.
That is, this invention provides the aqueous | water-based paste for electrical storage element electrode formation of the following structures, and the electrical storage element formed from it.

[1] A conductive carbonaceous material that contains an electrode active material, a conductive additive, and a binder, and that is determined to have hydrophilicity in the following hydrophilicity evaluation test. An aqueous paste for forming a storage element electrode.
Hydrophilic evaluation test:
10 mg of conductive carbonaceous material powder dried at 120 ° C. for 24 hours is accurately weighed, and its mass is defined as W ₁ . Next, the above conductive carbonaceous material powder and 300 g of ion exchange water are added into the 500 ml separatory funnel from the upper mouth, and 30 g of ion exchange water is further added to the inner wall surface of the separatory funnel. Pour the adhering conductive carbonaceous material powder. Next, the separating funnel was shaken for 1 minute and then allowed to stand for 30 minutes. Next, the cock of the separatory funnel is opened, and ion-exchanged water and 300 g of conductive carbonaceous material powder mixed with ion-exchanged water are extracted from the bottom, and the conductive carbonaceous material powder is filtered from the extracted liquid. Separated, dried at 120 ° C. for 24 hours, weighed, and the mass is defined as W ₂ . When the charged mass W _{1 of} the conductive carbonaceous material powder charged into the separating funnel and the mass W ₂ mixed with water satisfy the relationship of (W ₂ / W ₁ ) × 100 ≧ 1, the conductive carbonaceous material Is determined to have hydrophilicity.

[2] The aqueous paste for forming a storage element electrode according to [1], wherein the hydrophilic conductive carbonaceous material is a boron-modified conductive carbonaceous material.
[3] The aqueous paste for forming a storage element electrode according to [2], wherein the boron content is 0.01 to 10% by mass.
[4] The conductive carbonaceous material is acetylene black, thermal black, furnace black, channel black, lamp black, graphite such as natural graphite, artificial graphite, ketjen black, needle coke, carbon fiber, carbon tube, and The aqueous paste for forming a storage element electrode according to any one of [1] to [3], which is at least one selected from the group consisting of carbon coils.
[5] The aqueous paste for forming a storage element electrode according to any one of [1] to [4], wherein the binder is an aqueous dispersion of a polymer.
[6] The aqueous paste for forming a storage element electrode according to any one of [1] to [4], wherein the binder is an aqueous dispersion of a fluorine-containing polymer.
[7] The electricity storage according to [6], wherein the aqueous dispersion of the fluorine-containing polymer is prepared by mixing an aqueous dispersion of the crystalline fluorine-containing polymer and an aqueous dispersion of the amorphous fluorine-containing polymer. An aqueous paste for device electrode formation.
[8] Further, surfactants are contained, and the surfactants are anionic surfactants of carboxylate type, sulfonate type, sulfate type, phosphate type, etc .; quaternary ammonium salts Type, imidazolinium salt type, pyrodinium salt type cationic surfactants; betaine type, aminocarboxylate type, imidazoline derivative type, alkylamine oxide type amphoteric surfactants; and ether type, ether Any one of [1] to [7], which is one or more selected from the group consisting of nonionic surfactants such as ester type, ester type, nitrogen-containing type, block copolymer of ethylene oxide and propylene oxide, etc. The aqueous paste for electricity storage element electrode formation of description.
[9] Further containing a water-soluble polymer compound, wherein the water-soluble polymer compound is a cellulose such as methyl cellulose, carboxymethyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose; oligosaccharide, dextrin, water-soluble dietary fiber The storage element electrode formation according to any one of [1] to [8], which is at least one selected from the group consisting of saccharides such as: crown ethers; polyacrylic acids; polyethylene oxide; and polyvinyl alcohol Aqueous paste for use.
[10] A power storage device comprising a power storage device electrode formed from the aqueous paste for forming a power storage device electrode according to any one of [1] to [9].

In the aqueous paste for forming a storage element electrode according to the present invention, the conductive auxiliary agent is refined and uniformly dispersed in the aqueous paste. The aqueous paste for forming a storage element electrode of the present invention can form an electrode composite layer while maintaining a state in which a plurality of finely divided components are uniformly dispersed even after being coated on a substrate, Since it is not necessary to use PFOA, which has a storage property and is an environmental concern, it is useful for the production of a storage element.
Further, the obtained electricity storage device electrode has excellent adhesion to the substrate, excellent solvent resistance, heat resistance, high workability, and refined electrode active material, conductive additive, and binder, respectively. Since the agent is uniformly dispersed, the agent functions to perform smooth interfacial charge transfer reaction, ionic conduction, and electronic conduction, and exhibits excellent power storage device characteristics.

The conductive auxiliary agent in the present invention is a conductive carbonaceous material determined to have hydrophilicity in a hydrophilicity evaluation test.
The hydrophilicity evaluation test of the present invention is shown below.
10 mg of conductive carbonaceous material powder dried at 120 ° C. for 24 hours is accurately weighed, and its mass is defined as W ₁ . Next, the above conductive carbonaceous material powder and 300 g of ion exchange water are added into the 500 ml separatory funnel from the upper mouth, and 30 g of ion exchange water is further added to the inner wall surface of the separatory funnel. Pour the adhering conductive carbonaceous material powder. Next, the separating funnel is shaken for 1 minute and then allowed to stand for 30 minutes. Next, the cock of the separatory funnel is opened, and ion-exchanged water and 300 g of conductive carbonaceous material powder mixed with ion-exchanged water are extracted from the bottom, and the conductive carbonaceous material powder is filtered from the extracted liquid. It separated Te, weighed and dried for 24 hours at 120 ° C., to its mass and W _2. When the charged mass W _{1 of} the conductive carbonaceous material powder charged into the separating funnel and the mass W ₂ mixed with water satisfy the relationship of (W ₂ / W ₁ ) × 100 ≧ 1, the conductive carbonaceous material Is determined to have hydrophilicity.

In the hydrophilicity evaluation test, it can be clearly evaluated whether or not the conductive carbonaceous material has hydrophilicity.
Usually, those that are hydrophilic and miscible with water will sink in water in less than a minute after shaking, while those that are not hydrophilic will sink in water even if shaken continuously for one day. Absent. From the conductive carbonaceous material determined to be hydrophilic in the evaluation test, a good aqueous paste for forming a storage element electrode can be prepared which is finely divided and uniformly dispersed.
The value of (W ₂ / W ₁ ) × 100 is preferably 2 or more, more preferably 5 or more, and most preferably 10 or more. The upper limit of (W ₂ / W ₁ ) × 100 is 100.

Preferable specific examples of the conductive carbonaceous material having hydrophilicity include boron-modified conductive carbonaceous material. As the boron-modified conductive carbonaceous material, boron-modified acetylene black is particularly preferable because it exhibits high characteristics as a power storage element and can maintain the characteristics over a long period of time.
A method for synthesizing such a boron-modified conductive carbonaceous material is known (Japanese Patent No. 3667144) and can be preferably used in the present invention. For example, boron-modified carbon blacks can be produced by mixing pulverized carbon blacks and pulverized boron carbide and then heating at about 2500 ° C. As carbon blacks, acetylene black, thermal black, furnace black, channel black, lamp black and the like are used. In addition, graphites such as natural graphite and artificial graphite, and other carbonaceous materials such as ketjen black, needle coke and carbon fiber can also be used as carbon blacks.

Furthermore, as a boron-modified conductive carbonaceous material, boron is synthesized by spraying a mixed gas of acetylene gas and vaporized trimethyl borate onto a cylindrical furnace heated to about 2000 ° C. and thermally decomposing it. Boron-modified acetylene black solid-dissolved in (3) can also be used. In this boron-modified acetylene black, the boron content can be variously controlled by adjusting the mixing amount of acetylene gas and trimethyl borate.

The boron content of the boron-modified conductive carbonaceous material used in the present invention is preferably 0.01 to 10% by mass on average. If it is less than 0.01% by mass, it is determined that the hydrophilicity evaluation test of the present invention does not have hydrophilicity, the hydrophilicity is not sufficient, and dispersion in water becomes difficult. On the other hand, if boron is contained in excess of 10% by mass, the electron conductivity is impaired, which is not preferable. More preferably, the content is 0.05 to 5% by mass, still more preferably 0.1 to 3% by mass, and most preferably 0.15 to 2% by mass. Within this range, the dispersibility in water is high, a homogeneous dispersion state can be stably maintained, and higher conductivity can be exhibited than a conductive carbonaceous material not containing boron.

The mechanism by which boron-modified acetylene black, etc. becomes hydrophilic is not yet well understood. However, the unpaired electrons of acetylene black increase due to solid solution of boron to increase electron conductivity, and the increased polarity is compatible with water. It is interpreted that it became soaked in water. Boron-modified acetylene black does not express hydrophilicity by forming hydrophilic functional groups on the surface, such as surface oxidation treatment or sulfonation treatment, so hygroscopicity maintains the characteristics of acetylene black itself Therefore, the coating film is preferable because it is easy to dry.

Other specific examples of the conductive carbonaceous material having hydrophilicity include, for example, carbon black (US Pat. No. 5,571,311) dispersed in an aqueous dispersion medium after adsorbing alcohol, surfactant or the like on the surface. Carbon black grafted with nonionic, anionic or cationic hydrophilic groups on the surface (JP-A-5-230410, JP-A-6-128517, JP-A-6-166554, etc.), sulfuric acid, three Carbon black (JP-A-10-120958, JP-A-2002-324557, etc.) treated with a sulfonating agent such as sulfur sulfide or sulfonated pyridine salt to introduce a sulfone group on the surface, ozone treatment or plasma treatment Carbon black oxidized by the gas phase method such as nitric acid, hydrogen peroxide solution, sodium perchlorate, etc. (Japanese Patent Laid-Open No. 10-110112, Japanese Patent Laid-Open No. 2004-253379, etc.), carbon black treated with a reducing agent such as hydrogen or lithium aluminum hydride (Japanese Patent Laid-Open No. 2002-129065, Japanese Patent Laid-Open No. 2004-339428) Etc.). In the present invention, a conductive carbonaceous material imparted with hydrophilicity by any of these methods can be used.
The average particle diameter of the conductive carbonaceous material having hydrophilicity is usually preferably 3 to 1000 nm, and more preferably 5 to 200 nm.

The binder used in the present invention is preferably an aqueous dispersion in which a crystalline resin, an amorphous resin, or a polymer such as rubber or elastomer is dispersed in water. As the polymer, a polymer containing no fluorine or a polymer containing fluorine can be preferably used. Fluorine-free binder polymers include natural rubbers: styrene butadiene copolymers, acrylic modified styrene butadiene copolymers, vinyl acetate copolymers, nitrile butyl rubber, hydrogenated nitrile butyl rubber, acrylic rubber, epichlorohydrin rubber, Synthetic rubbers and elastomers such as polyurethane; and synthetic resins such as acrylic resin, methacrylic resin, vinyl resin, polyolefin, polycarbonate, nylon, and polyimide.

As the binder in the present invention, an aqueous dispersion of a fluorine-containing polymer is more preferable. Examples of the fluorine-containing polymer include tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, general formula (1): CF ₂ ═C (OR _f ) _n F _2-n (wherein R _f has 1 to 8 carbon atoms) A perfluoroalkyl group or a perfluoroalkyloxyalkyl group containing one or more ether bonds in the molecule, n is 1 or 2, and any carbon chain has a linear, branched or cyclic structure. Or a combination of at least one or a combination of two or more fluorine-containing monomers selected from the group consisting of perfluoro (alkyl or alkyloxyalkyl vinyl ethers) represented by chlorotrifluoroethylene. A polymer is mentioned.

In addition to the fluorine-containing monomer, the general formula (2): CH ₂ = CHOR (wherein R is an alkyloxyalkyl group having 1 to 8 carbon atoms or one or more ether bonds, The carbon chain may also have a linear, branched, or cyclic structure.) One or two or more kinds of alkyl or alkyloxyalkyl vinyl ethers represented by formula (1) and copolymerizable monomers such as ethylene and propylene. It may be copolymerized.
As the copolymerizable monomer, in addition to the above monomers, 1-bromo-1,1,2,2-tetrafluoroethyl trifluorovinyl ether, vinyl crotonic acid, vinyl methacrylate, maleic anhydride, itaconic anhydride, maleic acid And itaconic acid.

When a fluorine-containing polymer is used as the binder of the aqueous paste for forming an electricity storage element electrode of the present invention (hereinafter sometimes referred to as the aqueous paste of the present invention), a homogeneously dispersed electrode active material and a conductive assistant are used for a long time. It is also preferable to use a mixture of a crystalline fluorine-containing polymer and an amorphous fluorine-containing polymer for the purpose of stably supporting the electrode and further improving the adhesion between the current collector and the electrode composite layer.
Examples of the crystalline fluorine-containing polymer include tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, perfluoro (alkyl or alkyloxyalkyl vinyl ethers) of the above general formula (1), chlorotrifluoroethylene, and the like. A crystalline homopolymer obtained by polymerizing one selected from these monomers or a crystalline copolymer obtained by polymerizing at least two of the monomers is preferred.

The amorphous fluorine-containing polymer is an amorphous copolymer obtained by polymerizing at least two selected from the following first group monomers, or at least one selected from the following first group monomers: Amorphous copolymers obtained by copolymerizing a seed and at least one selected from the following second group of monomers are preferred.
Monomers of the first group: tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, perfluoro (alkyl or alkyloxyalkyl vinyl ethers) of the above general formula (1), chlorotrifluoroethylene and the like.
Second group of monomers: alkyl or alkyloxyalkyl vinyl ethers of the above general formula (2), ethylene, propylene and the like.

The crystalline fluorine-containing polymer and the amorphous fluorine-containing polymer may be those obtained by copolymerizing other copolymerizable monomers copolymerizable with the above monomers. Other copolymerizable monomers that can be copolymerized include 1-bromo-1,1,2,2-tetrafluoroethyl trifluorovinyl ether, vinyl crotonic acid, vinyl methacrylate, maleic anhydride, itaconic anhydride, maleic acid And itaconic acid.
The mixing ratio (mass ratio) of the crystalline fluoropolymer and the amorphous fluoropolymer is preferably in the range of 0.1: 9.9 to 9.9: 0.1, and 0.2: 9.8 to 9 The range of .8: 0.2 is more preferable, and the range of 0.3: 9.7 to 9.7: 0.3 is more preferable. When the ratio of the crystalline fluorine-containing polymer to the amorphous fluorine-containing polymer is within this range, the electricity storage device electrode is excellent in adhesion to the substrate and excellent in solvent resistance and heat resistance.

Production of an aqueous dispersion of a fluorine-containing polymer is usually carried out by emulsion polymerization. As the emulsifier in this emulsion polymerization, fluorinated emulsifiers such as PFOA and fluorine-containing ether carboxylic acid compounds having a small chain transfer constant are used. After the emulsion polymerization, these fluorine-based emulsifiers are removed, and the dispersion is stabilized with a hydrocarbon-based emulsifier. The removal of the fluorine-based emulsifier can be performed by a known method. The fluorine-based emulsifier composed of an anionic surfactant can be removed by adsorbing to an anion exchange resin. The fluorine-based emulsifier can also be obtained by concentration using an ED method (Electro-decantation method) or a phase separation method (described in fluorine resin handbook (edited by Takaomi Satokawa, published by Nikkan Kogyo Shimbun, 1990)). Can be removed.
For the aqueous paste for forming a storage element electrode of the present invention, an aqueous dispersion of a fluorine-containing polymer from which a fluorine-based emulsifier has been removed or reduced by such a method can be suitably used.
When an aqueous polymer dispersion is used as the binder, the polymer concentration of the aqueous polymer dispersion is usually preferably 10 to 80% by mass, more preferably 20 to 70% by mass.

Examples of the electrode active material used in the present invention include electrode active materials of various power storage elements. For example, metal oxides, metal sulfides, conductive organic compounds and the like are generally used as the positive electrode active material for lithium batteries. In particular, metal oxides such as lithium metal composite oxides and lithium metal phosphoolivines are preferably used because stable battery characteristics can be expressed over a long period of time. These metal oxides are sometimes used as a composite oxide of Li and another metal, but are also used as a composite oxide composed of Li and other metals. For example, some lithium nickel composite oxides, it is hardly to the positive electrode of the intact lithium ion batteries LiNiO _2, Co part of lithium or nickel, Mn, Al, B, Cr , Cu, F, Fe, A material substituted with one or more elements selected from the group consisting of Ga, Mg, Mo, Nb, O, Sn, Ti, V, Zn, Zr, and other elements is preferably used.

Examples of the negative electrode active material for lithium batteries include graphite-based carbon, non-graphite-based carbon, and metal-based materials, and any material can be preferably applied to the present invention. Examples of carbonaceous materials such as graphite-based carbon and non-graphite-based carbon include natural graphite, artificial graphite, coal-based coke, petroleum-based coke, coal-based pitch carbide, petroleum-based pitch carbide, needle coke, and pitch coke. Examples thereof include carbides such as phenol resin and cellulose, partially graphitized products of these carbides, furnace black, acetylene black, and carbon fibers. Examples of the metal material include tin, silicon, titanium, metal nitride, lithium, and lithium alloy.
Activated carbon is used as the electrode active material for the electric double layer capacitor, and it is also preferably used in the present invention. There are also proposals to perform boric acid treatment for the purpose of increasing load characteristics and capacitance, and these modified activated carbons are also preferably used in the present invention.
As an active material for a nickel metal hydride battery, a nickel hydroxide compounded with nickel hydroxide or cobalt oxide is used for the positive electrode, and a nickel-based or titanium-based hydrogen storage alloy is used for the negative electrode. Used for.
The average particle diameter of the electrode active material is usually preferably 0.05 to 500 μm, more preferably 0.1 to 100 μm.

The aqueous paste of the present invention is not limited in the content of the electrode active material, but is generally prepared in the range of 5 to 65% by mass, preferably 10 to 60% by mass with respect to the total amount of the aqueous paste. . Even if the amount is less than 5% by mass, the formed electrode itself has no problem in characteristics, but it is not preferable because of low productivity and inefficiency.
The content of the conductive assistant and the binder is determined according to the type of electrode active material and its characteristics, but the content of the conductive assistant is usually 0 with respect to the mass of the electrode active material. 0.01 to 15% by mass is preferable, and more preferably 0.1 to 12% by mass. The content of the binder is usually preferably 0.01 to 15% by mass with respect to the mass of the electrode active material, More preferably, the content is 0.1 to 12% by mass.
The main material responsible for the characteristics of the storage element is an electrode active material. Therefore, materials other than the electrode active material that do not contribute to the storage capacity are preferably added in the minimum amount capable of expressing the required function.

In the aqueous paste of the present invention, it is preferable to use a dispersant or a dispersion stabilizer in order to disperse the hydrophilic conductive carbonaceous material in water. Examples of the dispersant or the dispersion stabilizer include general-purpose general surfactants and water-soluble polymer compounds other than the fluorine-containing dispersant. Thereby, even if it does not use the dispersing agent containing the above-mentioned fluorine, the conductive carbonaceous material which has hydrophilicity can be refined | miniaturized in water, and can be uniformly disperse | distributed. This dispersed state does not change even in the presence of an electrode active material or a binder.
The dispersant may be a dispersant contained in an aqueous dispersion that is a binder. In addition, surfactants can also be used by adding to the aqueous paste for forming a storage element electrode of the present invention. Further, the water-soluble polymer may be a water-soluble polymer selected for the purpose of improving the coating processability from the aqueous slurry.

As the surfactant, anionic surfactants such as carboxylate type, sulfonate type, sulfate type, and phosphate type; cations such as quaternary ammonium salt type, imidazolinium salt type, and pyrodinium salt type Surfactants: amphoteric surfactants such as betaine type, aminocarboxylate type, imidazoline derivative type, alkylamine oxide type; ether type, ether ester type, ester type, nitrogen-containing type, ethylene oxide and propylene oxide Nonionic surfactants such as block copolymers are exemplified. Of these, anionic surfactants and nonionic surfactants are preferred because they have a small impact on the environment.
The total content of the surfactant is preferably 0.01 to 10% by mass and more preferably 0.05 to 5% by mass with respect to the total amount of the aqueous paste.
Examples of water-soluble polymer compounds include celluloses such as methylcellulose, carboxymethylcellulose, ethylcellulose, hydroxyethylcellulose, and hydroxypropylmethylcellulose; saccharides such as oligosaccharides, dextrin, and water-soluble dietary fibers; crown ethers; polyacrylic acids; ; Polyvinyl alcohol etc. are mentioned. Among them, carboxymethyl cellulose can be suitably used in the present invention because it functions well as a dispersion stabilizer.
The content of the water-soluble polymer compound is preferably 0.01 to 10% by mass and more preferably 0.05 to 5% by mass with respect to the total amount of the aqueous paste.

In the aqueous paste of the present invention, for the purpose of improving the adhesion between the electrode composite and the current collector, a water-soluble compound having a boiling point higher than that of water can be added as an aqueous medium in addition to water. Examples thereof include organic solvents such as dimethylformamide, dimethylacetamide, dimethyl sulfoxide, tetramethylene sulfone, N-methylpyrrolidone, ethylene glycols, propylene glycols and glycerin. The content of the organic solvent is usually preferably 0 to 50% by mass and more preferably 0 to 35% by mass with respect to the total amount of water and the organic solvent.
In the aqueous paste of the present invention, the content of the aqueous medium is preferably 30 to 90% by mass, and more preferably 33 to 70% by mass.
The aqueous paste of the present invention is obtained by mixing an electrode active material, a conductive carbonaceous material having hydrophilicity as a conductive additive, a binder and an aqueous medium, and further mixing other components as necessary. Can be manufactured. When an aqueous polymer dispersion is used as the binder, an aqueous medium is contained in the aqueous polymer dispersion. Therefore, it is not necessary to add another aqueous medium or add an aqueous medium. Good.

Examples of a method for forming a storage element electrode from the aqueous paste of the present invention include a method of applying the aqueous paste of the present invention to a substrate, drying, and heat-treating. As the substrate, an aluminum foil is used for the positive electrode of the lithium ion battery, a copper foil is used for the negative electrode, an aluminum foil is used for the capacitor electrode, and a nickel foil or a nickel mesh is used for the nickel metal hydride battery electrode. A good electrode composite layer can be formed on any of these substrates from the aqueous paste of the present invention. A good coating film can be formed on other substrates.
Examples of the electricity storage device of the present invention include lithium batteries such as lithium ion batteries, lithium polymer batteries, and lithium primary batteries; primary and secondary batteries such as nickel metal hydride batteries; and capacitors such as electric double layer capacitors. The aqueous paste of the present invention is suitably used for forming an electrode composite layer of these electricity storage elements.

Since the composite electrode formed by applying the aqueous paste of the present invention can realize a structure in which the electrode active material, the conductive additive, the binder, and other composite components are uniformly dispersed as described above, it is smooth. Can develop a positive charge transfer reaction. A power storage device using the electrode of the present invention having such features has a large charge / discharge capacity and a high energy density, and can realize excellent cycle characteristics, high load characteristics, low temperature characteristics, high temperature characteristics, and safety. In particular, since both high energy density and high load characteristics and highly reliable safety can be achieved, high output, high energy density, high reliability and safety can be realized even in medium and large-sized power storage devices.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples.
[Hydrophilicity evaluation test method]
10 mg of conductive carbonaceous material powder dried at 120 ° C. for 24 hours is accurately weighed, and its mass is defined as W ₁ . Next, the above conductive carbonaceous material powder and 300 g of ion exchange water are added into the 500 ml separatory funnel from the upper mouth, and 30 g of ion exchange water is further added to the inner wall surface of the separatory funnel. Pour the adhering conductive carbonaceous material powder. Next, the separating funnel was shaken for 1 minute and then allowed to stand for 30 minutes. Next, the cock of the separatory funnel is opened, and ion-exchanged water and 300 g of conductive carbonaceous material powder mixed with ion-exchanged water are extracted from the bottom, and the conductive carbonaceous material powder is filtered from the extracted liquid. The sample was dried at 120 ° C. for 24 hours and weighed, and the mass was defined as W ₂ . When the charged mass W _{1 of} the conductive carbonaceous material powder charged into the separating funnel and the mass W ₂ mixed with water satisfy the relationship of (W ₂ / W ₁ ) × 100 ≧ 1, the conductive carbonaceous material Was determined to have hydrophilicity.

(1) Synthesis of boron-modified acetylene black (A) A tube furnace controlled at 750 to 800 ° C. was sprayed with acetylene gas at a supply rate of 200 liters / hour and trimethyl borate at 6 milliliters / hour, and boron-containing acetylene. Got black. This boron-containing acetylene black was treated at 2800 ° C. in an argon atmosphere to obtain acetylene black (A) in which boron was dissolved. This acetylene black (A) has a boron content of 0.13% by mass and a carbon content of 95.0% by mass. The result of the hydrophilicity evaluation test of the present invention is (W ₂ / W ₁ ) × 100. It was determined to be 10 and hydrophilic.

(2) Synthesis of boron-modified acetylene black (B) Acetylene black (B) in which boron is dissolved in the same manner as in the synthesis of (A) except that the trimethyl borate supply rate is 12 ml / hour. Got. This acetylene black (B) has a boron content of 0.37% by mass and a carbon content of 95.1% by mass. The result of the hydrophilicity evaluation test of the present invention is (W ₂ / W ₁ ) × 100. It was 30 and was determined to have hydrophilicity.
(3) Synthesis of boron-modified acetylene black (C) Acetylene black (C) in which boron is dissolved in the same manner as in the synthesis of (A) except that the trimethyl borate supply rate is 36 ml / hour. Got. This acetylene black (C) has a boron content of 1.21% by mass and a carbon content of 94.3% by mass. The result of the hydrophilicity evaluation test of the present invention is (W ₂ / W ₁ ) × 100. It was determined to have a hydrophilicity of 75.
In addition, commercially available acetylene black and ketjen black for battery use were obtained. These boron contents were less than the detection limit and were judged to be almost 0% by mass. In addition, as a result of the hydrophilicity evaluation test of the present invention, both of the values of (W ₂ / W ₁ ) × 100 were 0, and it was determined that the hydrophilic property was not hydrophilic at all.

(4) Production of Crystalline Fluoropolymer Aqueous Dispersion (D) Containing Fluorosurfactant 7100 g of paraffin wax, 59 L of ultrapure water, and 15 g of APFO were charged into a 100 L pressure-resistant polymerization tank. After raising the temperature to 70 ° C., purging with nitrogen and then degassing, tetrafluoroethylene was introduced to an internal pressure of 1.9 MPa while stirring. 1 L of 0.5% by mass aqueous succinic acid peroxide solution was injected into this to initiate polymerization. The polymerization was carried out for 45 minutes while maintaining the polymerization pressure at 1.9 MPa while supplying tetrafluoroethylene. Thereafter, the temperature was raised to 90 ° C., 1 L of a 2.5 mass% APFO aqueous solution was added, and the mixture was continued for 95 minutes. Agglomerates, paraffin and the like are removed from the obtained emulsion, and used for a binder having a polytetrafluoroethylene (hereinafter referred to as PTFE) content of 26.0% by mass and an APFO content of 0.12% by mass. 25.1 kg of an aqueous crystalline fluoropolymer dispersion (D) was obtained. As a result of thermal analysis, the polymer taken out from a part of (D), purified and dried was a crystalline polymer having a melting point of 327 ° C.

(5) Production of crystalline fluoropolymer aqueous dispersion (E) containing a trace amount of fluorosurfactant 0.2 kg of polyoxyethylene (average polymerization degree 9) lauryl ether in the aqueous dispersion of (D) above The nonionic surfactant containing the main component is added and dissolved, 0.3 kg of anion exchange resin (Mitsubishi Chemical Corporation, Diaion WA-30) is dispersed, stirred for 24 hours, and filtered to obtain the anion exchange resin. Removed. Subsequently, 0.04 kg of 28 mass% ammonia water was added to the filtrate, and it concentrated at 80 degreeC for 10 hours by the phase-separation method. Next, after removing the supernatant, 0.1 kg of the nonionic surfactant is newly added, and the crystalline content for the binder having a PTFE content of 59.7% by mass and an APFO content of 0.01% by mass is added. 10.5 kg of fluoropolymer aqueous dispersion (E) was obtained. As a result of thermal analysis, the polymer taken out from a part of (E), purified and dried was a crystalline polymer having a melting point of 327 ° C.

(6) Production of crystalline fluoropolymer aqueous dispersion (F) containing a trace amount of a fluorosurfactant C ₂ F ₅ OCF ₂ CF ₂ OCF ₂ COONH ₄ (hereinafter referred to as EEA) instead of 15 g of APFO .) Was used to produce an aqueous dispersion having a PTFE content of 24.3% by mass in the same manner as in the production of the aqueous dispersion (D). From this aqueous dispersion, 0.5 kg of anion exchange resin is used instead of 0.3 kg of anion exchange resin, and an anionic surfactant made of sodium lauryl sulfate is used instead of the newly added nonionic surfactant. In the same manner as in the production of the liquid (E), the fluoroemulsifier is removed and concentrated, and the crystalline content for the binder having a PTFE content of 57.8% by mass and an EEA content of 0.005% by mass is obtained. 10.9 kg of fluoropolymer aqueous dispersion (F) was obtained. As a result of thermal analysis, the polymer taken out from a part of (F), purified and dried was a crystalline polymer having a melting point of 327 ° C.

(7) Production of Amorphous Fluoropolymer Aqueous Dispersion (G) Containing a Small Amount of Fluorosurfactant 1.5 L of ion-exchanged water and 40 g of disodium hydrogen phosphate 12 hydrate in a 3 L pressure-resistant polymerization tank Sodium hydroxide 0.5 g, tertiary butanol 198 g, APFO 7 g, and ammonium persulfate 2.5 g were charged and dissolved. Subsequently, 200 g of an aqueous solution in which 0.4 g of ethylenediaminetetraacetic acid disodium salt dihydrate and 0.3 g of ferrous sulfate heptahydrate were dissolved was added, and the mixture was stirred and tetrahydrate with a molar ratio of 85/15. A fluoroethylene / propylene mixed gas was charged to an internal pressure of 2.5 MPa, and 2.5% by mass of a Rongalite aqueous solution was added to initiate polymerization. The polymerization was carried out for 5.5 hours while maintaining a polymerization pressure of 2.5 MPa while additionally supplying 800 g of a tetrafluoroethylene / propylene mixed gas having a molar ratio of 56/44. Aggregates and the like were removed from the obtained emulsion to prepare an aqueous dispersion having a tetrafluoroethylene / propylene copolymer content of 30.8% by mass and APFO of 0.3% by mass. To this aqueous dispersion, a nonionic surfactant mainly composed of 20 g of polyoxyethylene (average degree of polymerization 9) lauryl ether was added and dissolved. 35 g of the anion exchange resin was dispersed and stirred for 24 hours, followed by filtration. The anion exchange resin was removed. To the filtrate, 5 g of 28% by mass aqueous ammonia was added and concentrated at 80 ° C. for 10 hours by a phase separation method. Next, after removing the supernatant, 10 g of the anionic surfactant is newly added, and the amorphous fluorine-containing binder for binder having a copolymer content of 60.3% by mass and an APFO content of 0.01% by mass. 1150 g of polymer aqueous dispersion (G) was obtained. The polymer taken out of a part of the aqueous dispersion (G), purified and dried was an amorphous copolymer having a tetrafluoroethylene / propylene copolymer molar ratio of 56.3 / 43.7 and no crystal melting point.

(8) Production of Amorphous Fluoropolymer Aqueous Dispersion (H) Containing a Trace Amount of Fluorosurfactant 8G of EEA was used instead of 7 g of APFO in the same manner as in the production of aqueous dispersion (G). 1050 g of an amorphous fluoropolymer aqueous dispersion (H) for a binder having a copolymer content of 61.9% by mass and an EEA content of 0.01% by mass was obtained. A polymer taken out of a part of the aqueous dispersion (H), purified and dried was an amorphous copolymer having a tetrafluoroethylene / propylene copolymer molar ratio of 55.8 / 44.2 and no crystalline melting point.

(9) Production of Amorphous Fluoropolymer Aqueous Dispersion (I) Containing No Fluorosurfactant: 1.0 L of ion exchange water, 2.2 g of potassium carbonate, 0.7 g of ammonium persulfate in a 3 L pressure-resistant polymerization tank, 31 g of polyoxyethylene alkyl ether, 1 g of sodium lauryl sulfate, 161 g of ethyl vinyl ether, 178 g of cyclohexyl vinyl ether, and 141 g of 4-hydroxybutyl vinyl ether were charged, and degassing was repeated by repeating cooling and nitrogen gas pressurization. Thereafter, 482 g of chlorotrifluoroethylene was charged, and a polymerization reaction was performed at 30 ° C. for 12 hours. Aggregates were removed from the obtained emulsion to obtain 1250 g of an amorphous fluoropolymer aqueous dispersion (I) for a binder having a polymer content of 50.1% by mass. The polymer taken out from a part of the aqueous dispersion (I), purified and dried was an amorphous copolymer having no crystalline melting point.

(10) Production of Amorphous Hydrocarbon Polymer Aqueous Dispersion (J) Containing No Fluorosurfactant 1000 g of ion-exchanged water, 2.5 g of sodium dodecylbenzenesulfonate, potassium persulfate in a 3 L pressure resistant reactor 5 g, 2.5 g of sodium bisulfite, 235 g of styrene, 195 g of butadiene, 50 g of methyl methacrylate, and 20 g of itaconic acid were charged, and deaeration was repeated by repeating cooling and nitrogen gas pressurization. Thereafter, a polymerization reaction was carried out at 45 ° C. for 6 hours. Aggregates were removed from the obtained emulsion to obtain 1300 g of an acrylic modified styrene butadiene rubber aqueous dispersion (J) for a binder having a polymer content of 35.5% by mass. The polymer taken out from a part of the aqueous dispersion (J), purified and dried was an amorphous copolymer having no crystalline melting point.

(11) Synthesis of positive electrode active material for lithium ion battery (K) [lithium (nickel / manganese / cobalt) composite oxide] 3.3 mol of nickel oxide prepared by baking nickel carbonate at 700 ° C. for 15 hours in the air Then, 3.3 mol of manganese dioxide prepared by baking manganese carbonate at 700 ° C. for 15 hours in the atmosphere, 3.3 mol of cobalt oxyhydroxide having low crystallinity, and 5.1 mol of lithium carbonate were dispersed in pure water. The bead mill was treated with zirconia beads having a diameter of 0.1 mm for 2 hours and then spray-dried to obtain a dry powder. This was calcined in the atmosphere at 850 ° C. for 15 hours to obtain a lithium (nickel / manganese / cobalt) composite oxide having an average particle size of 3.6 μm.

(12) Synthesis of Lithium Ion Battery Positive Electrode Active Material (L) [Lithium Iron Phosphate] 313.1 g of 85% phosphoric acid was diluted with 1000 g of pure water. While stirring this aqueous phosphoric acid solution, 100.3 g of lithium carbonate was added and dissolved to obtain an aqueous solution of lithium phosphate.
To this aqueous solution, iron oxyhydroxide having a molecular weight of 92.4 per equivalent of iron was added, and 400 g of pure water was further added to obtain an aqueous paste as a raw material for lithium iron phosphate. This aqueous paste was subjected to bead mill treatment with zirconia beads having a diameter of 0.5 mm for 1 hour, and then an aqueous solution prepared by dissolving 51.4 g of dextrin having a number average molecular weight of 8500 in 115 g of pure water was dissolved and spray-dried. A dry powder was obtained. The dry powder was heated to 600 ° C. at a temperature rising rate of 5 ° C./min while supplying nitrogen gas containing 5% by volume of hydrogen gas at a flow rate of 0.8 liter / min, and held at 600 ° C. for 5 hours. did. Then, it cooled by the setting of the temperature-fall rate of 5 degree-C / min, and obtained the lithium iron phosphate whose average particle diameter is 4.2 micrometers.

(13) Synthesis of Lithium Ion Battery Negative Electrode Active Material (M) [Disproportionated Silicon] 240 g of silicon monoxide having an average particle size of 0.38 μm was added to 630 g of pure water, stirred, and spray-dried from the obtained paste. To prepare a dry powder. The dry powder was heated to 1200 ° C. at a temperature rising rate of 5 ° C./min while supplying argon gas at a flow rate of 1 liter / min, and held at 1200 ° C. for 5 hours. Thereafter, cooling was performed at a temperature decrease rate of 5 ° C./min to obtain disproportionated silicon having an average particle diameter of 4.2 μm.
In addition, lithium cobalt composite oxide as a positive electrode active material for a lithium ion secondary battery, natural graphite as a negative electrode active material for a lithium ion secondary battery, nickel hydroxide as a positive electrode active material for a nickel hydrogen secondary battery, A commercial product was used as the activated carbon as the electrode active material for the multilayer capacitor.

(Example 1) (Comparative example)
After 0.74 g of carboxymethylcellulose was dissolved in 75 g of ion-exchanged water, 2.3 g of commercially available acetylene black was added and dispersed by stirring for 1 minute while rotating a three-one motor equipped with a disk turbine blade at a speed of 450 rpm. To this was added 7.1 g of a crystalline fluoropolymer aqueous dispersion (D) containing a fluorosurfactant (the polymer component corresponds to 1.85 g), and the mixture was stirred and dispersed for 1 minute in the same manner as above. An electrode-forming aqueous paste model (1) was obtained. The suitability of the aqueous paste model (1) as an aqueous paste for electrode formation was examined by measuring the dispersion viscosity. The results are shown in Table 1.
It is empirically known that the suitability as an electrode-forming aqueous paste can be determined from a change in viscosity when a binder polymer dispersion is added to a conductive additive dispersion. That is, if the viscosity change before and after the addition is less than ± 20%, it is determined that the combination of the conductive aid, the binder, and the dispersion stabilizer that are compatible with the aqueous paste for electrode formation.
From Table 1, it can be said that the aqueous paste model (1) is compatible with the aqueous paste for electrode formation, but it cannot be used because it contains APFO that cannot satisfy the PFOA regulations at a relatively high concentration.

(Example 2) (Comparative example)
Instead of the crystalline fluoropolymer aqueous dispersion (D), 3.1 g of the crystalline fluoropolymer aqueous dispersion (E) containing a trace amount of a fluorosurfactant (the polymer component corresponds to 1.85 g) is used. Except that, an aqueous paste model for electrode formation (2) was prepared in the same manner as in Example 1, and the suitability as an aqueous paste for electrode formation was examined. The results are shown in Table 1. From Table 1, an aqueous paste containing a conductive auxiliary agent made of general-purpose acetylene black having no hydrophilicity and a fluorine-containing polymer aqueous dispersion containing only a small amount of a fluorosurfactant is an aqueous solution for electrode formation. It was determined not to fit the paste.

(Example 3) (Comparative example)
In place of the crystalline fluoropolymer aqueous dispersion (E), 3.1 g of the amorphous fluoropolymer aqueous dispersion (G) containing a trace amount of a fluorosurfactant (corresponding to 1.85 g of the polymer component) Except that it was used, an electrode forming aqueous paste model (3) was prepared in the same manner as in Example 1, and the compatibility as an electrode forming aqueous paste was examined. The results are shown in Table 1. From Table 1, an aqueous paste using an amorphous fluoropolymer aqueous dispersion (G) having a trace amount of a conductive auxiliary agent made of general-purpose acetylene black having no hydrophilicity and a fluorosurfactant as an electrode is used as an electrode. It was found to be incompatible with the aqueous pastes for use.

(Example 4) (Comparative example)
In place of the amorphous fluoropolymer aqueous dispersion (G), 3.7 g of the amorphous fluoropolymer aqueous dispersion (I) containing no fluorosurfactant (the polymer component corresponds to 1.85 g) Except that it was used, an electrode forming aqueous paste model (4) was prepared in the same manner as in Example 1, and the compatibility as an electrode forming aqueous paste was examined. The results are shown in Table 1. From Table 1, an aqueous paste using a conductive auxiliary agent made of general-purpose acetylene black having no hydrophilicity and a fluoropolymer aqueous dispersion containing no fluorosurfactant as a binder is an aqueous paste for electrode formation. It turned out not to fit.

(Example 5) (Comparative example)
Instead of the amorphous fluoropolymer aqueous dispersion (I), 5.2 g of an amorphous hydrocarbon polymer aqueous dispersion (J) containing no fluorosurfactant (corresponding to 1.85 g of the polymer component) ) Was used in the same manner as in Example 1 to prepare an aqueous paste model for electrode formation (5), and the suitability as an aqueous paste for electrode formation was examined. The results are shown in Table 1. From Table 1, an aqueous paste using a conductive auxiliary agent made of general-purpose acetylene black having no hydrophilicity and a fluoropolymer aqueous dispersion containing no fluorosurfactant as a binder is an aqueous paste for electrode formation. It turned out not to fit.

(Example 6) (Comparative example)
An aqueous paste model for electrode formation (6) was prepared in the same manner as in Example 2 except that 2.3 g of commercially available ketjen black was used instead of commercially available acetylene black, and suitability as an aqueous paste for electrode formation was prepared. I investigated. The results are shown in Table 1. From Table 1, an aqueous paste using a conductive auxiliary agent made of general-purpose ketjen black having no hydrophilicity and a polymer aqueous dispersion containing only a small amount of a fluorosurfactant as a binder is an aqueous paste for electrode formation. It turned out not to fit.

(Example 7)
Example except that 2.3 g of boron-modified acetylene black (A) having a value of (W ₂ / W ₁ ) × 100 of 10 of the hydrophilicity evaluation test of the present invention of 10 was used instead of commercially available acetylene black In the same manner as in No. 2, an electrode forming aqueous paste model (7) was prepared, and the suitability as an electrode forming aqueous paste was examined. The results are shown in Table 1. From Table 1, when boron-modified acetylene black having hydrophilicity is used as a conductive additive, an aqueous paste using a fluoropolymer aqueous dispersion having only a small amount of a fluorosurfactant as a binder can be used for electrode formation. It was found that it can be suitably used as an aqueous paste.

(Example 8)
Example except that 2.3 g of boron-modified acetylene black (B) having a value of (W ₂ / W ₁ ) × 100 of 30 of the hydrophilicity evaluation test of the present invention of 30 was used instead of commercially available acetylene black In the same manner as in No. 2, an electrode forming aqueous paste model (8) was prepared, and the suitability as an electrode forming aqueous paste was examined. The results are shown in Table 1. From Table 1, when boron-modified acetylene black having hydrophilicity is used as a conductive additive, an aqueous paste using a fluoropolymer aqueous dispersion having only a small amount of a fluorosurfactant as a binder can be used for electrode formation. It was found that it can be suitably used as an aqueous paste.

(Example 9)
Example except that 2.3 g of boron-modified acetylene black (C) having a value of (W ₂ / W ₁ ) × 100 of 75 of the hydrophilicity evaluation test of the present invention was used in place of commercially available acetylene black In the same manner as in No. 2, an electrode forming aqueous paste model (9) was prepared and examined for suitability as an electrode forming aqueous paste. The results are shown in Table 1. From Table 1, when boron-modified acetylene black having hydrophilicity is used as a conductive additive, an aqueous paste using a fluoropolymer aqueous dispersion having only a small amount of a fluorosurfactant as a binder can be used for electrode formation. It was found that it can be suitably used as an aqueous paste.

(Example 10)
Instead of the crystalline fluoropolymer aqueous dispersion (E), the fluorosurfactant is contained in a trace amount as in 1.6 g of the crystalline fluoropolymer aqueous dispersion (F) containing only a trace amount of the fluorosurfactant. 1.5 g of the amorphous fluorine-containing polymer aqueous dispersion (H) containing only the content (the mass ratio of the crystalline polymer to the amorphous polymer is 5 to 5, corresponding to 1.85 g of both polymers) Except that, an aqueous paste model for electrode formation (10) was prepared in the same manner as in Example 8, and the suitability as an aqueous paste for electrode formation was examined. The results are shown in Table 1. From Table 1, when boron-modified acetylene black having hydrophilicity is used as a conductive additive, an aqueous paste using a fluoropolymer aqueous dispersion having only a small amount of a fluorosurfactant as a binder can be used for electrode formation. It was found that it can be suitably used as an aqueous paste.

(Example 11)
Instead of boron-modified acetylene black (B), 2.3 g of boron-modified acetylene black (C), 1.6 g of crystalline fluoropolymer aqueous dispersion (F) and amorphous fluoropolymer aqueous dispersion (H ) Of 1.5 g of the crystalline fluoropolymer aqueous dispersion (F) and 2.7 g of the amorphous fluoropolymer aqueous dispersion (H) (crystalline polymer and amorphous polymer) The electrode forming aqueous paste model (11) was prepared in the same manner as in Example 10 except that the weight ratio of 1: 9 was used and the polymer of both was equivalent to 1.85 g. The suitability as a paste was examined. The results are shown in Table 1. From Table 1, when boron-modified acetylene black having hydrophilicity is used as a conductive additive, an aqueous paste using a fluoropolymer aqueous dispersion having only a small amount of a fluorosurfactant as a binder can be used for electrode formation. It was found that it can be suitably used as an aqueous paste.

(Example 12)
Instead of 0.3 g of the crystalline fluoropolymer aqueous dispersion (F) and 2.7 g of the amorphous fluoropolymer aqueous dispersion (H), the crystalline fluoropolymer aqueous dispersion (F) of 2. 9 g and 0.3 g of the amorphous fluorine-containing polymer aqueous dispersion (H) (the mass ratio of the crystalline polymer to the amorphous polymer is 9 to 1, corresponding to 1.85 g of both polymers). Except for this, an aqueous paste model for electrode formation (12) was prepared in the same manner as in Example 11 and examined for suitability as an aqueous paste for electrode formation. The results are shown in Table 1. Table 1 shows that when boron-modified acetylene black having hydrophilicity is used as a conductive additive, an aqueous paste using a polymer-containing aqueous dispersion containing only a small amount of a fluorosurfactant as a binder can be used for electrode formation. It was found that it can be suitably used as an aqueous paste.

(Example 13)
In place of 0.3 g of the crystalline fluorine-containing polymer aqueous dispersion (F) and 2.7 g of the amorphous fluorine-containing polymer aqueous dispersion (H), the amorphous fluorine-containing material does not contain any fluorosurfactant. An electrode-forming aqueous paste model (13) was prepared in the same manner as in Example 12 except that 3.7 g of the polymer aqueous dispersion (I) (the polymer component corresponds to 1.85 g) was used. The suitability as an aqueous paste was examined. The results are shown in Table 1. Table 1 shows that when boron-modified acetylene black having hydrophilicity is used as a conductive aid, an aqueous paste for electrode formation can be used even with an aqueous paste containing a fluoropolymer aqueous dispersion containing no fluorosurfactant. It was found that it can be suitably used as.

(Example 14)
Instead of 3.7 g of the amorphous fluoropolymer aqueous dispersion (I), 5.2 g of the amorphous hydrocarbon polymer aqueous dispersion (J) containing no fluorosurfactant (polymer component) Was equivalent to 1.85 g), and an aqueous paste model for electrode formation (14) was prepared in the same manner as in Example 13 and examined for suitability as an aqueous paste for electrode formation. The results are shown in Table 1. From Table 1, when boron-modified acetylene black having hydrophilicity is used as a conductive additive, an aqueous paste for forming an electrode can be used even with an aqueous paste using a hydrocarbon-based polymer aqueous dispersion containing no fluorosurfactant as a binder. It turned out that it can be used conveniently as a paste.

(Example 15) (Comparative example)
After 0.74 g of carboxymethylcellulose was dissolved in 75 g of ion-exchanged water, 2.3 g of commercially available acetylene black was added and dispersed by stirring for 1 minute while rotating a three-one motor equipped with a disk turbine blade at a speed of 450 rpm. Similarly to 2.5 g of the crystalline fluoropolymer aqueous dispersion (E) containing only a trace amount of the fluorosurfactant, an amorphous fluoropolymer aqueous dispersion containing only a trace amount of the fluorosurfactant (E) G) 0.6 g (the ratio of the crystalline polymer to the amorphous polymer is 8 to 2 and corresponds to 1.85 g of both polymers) and the positive electrode active for lithium ion battery dispersed in 25 g of ion-exchanged water 60 g of the substance (K) was added and stirred for 1 minute in the same manner as above to obtain an aqueous paste for electrode formation (15).

Subsequently, the paste (15) was applied onto the aluminum sheet, dried at 120 ° C. for 2 hours, then heat-treated at 300 ° C. for 10 minutes and roll-press-rolled to adjust the electrode composite layer thickness to 120 μm. A test piece cut out to a size of 2 cm in width and 10 cm in length from the obtained electrode plate was bent 100 times along a round bar having a diameter of 2 mm, and the strength of the electrode composite layer and the electrode active material holding power were examined. The adhesion to the substrate was evaluated by measuring the number of remaining eyes by cutting off a 100-cell grid pattern and making an adhesive tape (cello tape (registered trademark)) lightly adhered and then peeled off. The remaining number is indicated by the ratio of the number of remaining eyes to the 100th. The larger the number of numerators relative to the denominator 100, the higher the remaining ratio and the higher the adhesion.
The results are shown in Table 2. From Table 2, the positive electrode plate for a lithium ion battery formed from the paste (15) had low electrode active material carrying ability and adhesion to the substrate, and was difficult to use in a battery. It was judged that this was because the electrode active material, the highly hydrophobic conductive assistant and the binder could not be uniformly dispersed and mixed in the paste (15) due to the small amount of the fluorine-based dispersant.

(Example 16) (Comparative example)
In place of 2.5 g of the crystalline fluoropolymer aqueous dispersion (E) and 0.6 g of the amorphous fluoropolymer aqueous dispersion (G), amorphous fluorine-free containing no fluorosurfactant An aqueous electrode-forming paste (16) was prepared in the same manner as in Example 15 except that 3.7 g of the polymer aqueous dispersion (I) (the polymer component was equivalent to 1.85 g) was used. An electrode plate was obtained. However, this electrode plate has low electrode active material carrying ability and adhesion to the substrate, and is difficult to use for batteries. It was judged that this was because the paste (16) containing only the hydrocarbon-based dispersant could not uniformly disperse and mix the electrode active material, the conductive additive, and the binder.

(Example 17) (Comparative example)
Instead of 3.7 g of the amorphous fluoropolymer aqueous dispersion (I), 5.2 g of the amorphous hydrocarbon polymer aqueous dispersion (I) containing no fluorosurfactant (polymer component) Was equivalent to 1.85 g), and an aqueous electrode forming paste (17) was prepared in the same manner as in Example 15 to obtain an electrode plate for a lithium ion battery. However, this electrode plate has low electrode active material carrying ability and adhesion to the substrate, and is difficult to use for batteries. It was judged that this was because the electrode active material, the conductive additive and the binder could not be uniformly dispersed and mixed in the paste (17) containing only the hydrocarbon-based dispersant.

(Example 18)
An electrode-forming aqueous paste (18) was prepared in the same manner as in Example 15 except that 2.3 g of boron-modified acetylene black (A) was used in place of commercially available acetylene black to obtain an electrode plate for a lithium ion battery. It was. From Table 2, the positive electrode plate for a lithium ion battery formed from the paste (18) had good electrode active material carrying ability and adhesion to the substrate. This is because the use of boron-modified acetylene black, which has a hydrophilic property that is relatively easy to disperse in water, makes it possible to prepare an aqueous paste for electrode formation with good dispersion, with little use of a fluorosurfactant. It was determined that it was due to the accident.

(Example 19)
Instead of boron-modified acetylene black (A), 2.3 g of boron-modified acetylene black (B) was used, and 2.5 g of crystalline fluoropolymer aqueous dispersion (E) and amorphous fluoropolymer aqueous dispersion ( In place of 0.6 g of G), a fluorosurfactant containing only a trace amount is similar to 2.6 g of the crystalline fluoropolymer aqueous dispersion (F) containing only a trace amount. Except for using 0.6 g of the aqueous fluoropolymer dispersion (H) (the ratio of the crystalline polymer to the amorphous polymer is 8 to 2, corresponding to 1.85 g of both polymers). In the same manner as in No. 18, an electrode-forming aqueous paste (19) was prepared to obtain an electrode plate for a lithium ion battery. From Table 2, the positive electrode plate for a lithium ion battery formed from the paste (19) had good electrode active material carrying ability and adhesion to the substrate. This is because, in the paste (19), the use of boron-modified acetylene black having hydrophilicity, which is relatively easy to disperse in water, makes it possible to form an electrode with good dispersibility without using almost any fluorosurfactant. It was judged that the aqueous paste was prepared.

(Example 20)
Instead of boron-modified acetylene black (B), 2.3 g of boron-modified acetylene black (C) was used. 2.6 g of crystalline fluoropolymer aqueous dispersion (F) and amorphous fluoropolymer aqueous dispersion ( In place of 0.6 g of H), 2.2 g of (F) and 1.1 g of amorphous fluoropolymer aqueous dispersion (I) containing no fluorosurfactant (crystalline polymer and amorphous) The electrode-forming aqueous paste (20) was prepared in the same manner as in Example 19 except that the ratio of the conductive polymer was 7 to 3, and the amount of both polymers was equivalent to 1.85 g. An electrode plate was obtained. From Table 2, the positive electrode plate for a lithium ion battery formed from the paste (20) had good electrode active material carrying power and adhesion to the substrate. This is because, in the paste (20), the use of boron-modified acetylene black having hydrophilicity, which is relatively easy to disperse in water, makes it possible to form an electrode with good dispersion even with little use of a fluorosurfactant. It was judged that the aqueous paste was prepared.

(Example 21)
Instead of 2.2 g of the crystalline fluoropolymer aqueous dispersion (F) and 1.1 g of the amorphous fluoropolymer aqueous dispersion (I), 2.9 g of (F) and the fluorosurfactant are 0.5 g of amorphous hydrocarbon polymer aqueous dispersion (J) not containing at all (mass ratio of crystalline polymer to amorphous polymer is 9 to 1, corresponding to 1.85 g of both polymers) A lithium ion battery electrode plate was obtained by preparing an aqueous electrode-forming paste (21) in the same manner as in Example 20 except that was used. From Table 2, the positive electrode plate for a lithium ion battery formed from the paste (21) had good electrode active material carrying ability and adhesion to the substrate. This is because, even in the paste (21), boron-modified acetylene black having hydrophilicity that is relatively easy to disperse in water is used, so that it is possible to form an electrode with good dispersibility even with little use of a fluorosurfactant. It was judged that the aqueous paste was prepared.

(Example 22)
In place of 2.9 g of crystalline fluoropolymer aqueous dispersion (F) and 1.1 g of amorphous fluoropolymer aqueous dispersion (I), amorphous carbonization containing no fluorosurfactant An aqueous electrode-forming paste (22) was prepared in the same manner as in Example 20 except that 5.2 g (the polymer component was equivalent to 1.85 g) of the aqueous hydrogen-based polymer dispersion (J) was used. A battery electrode plate was obtained. From Table 2, the lithium ion battery positive electrode plate formed from the paste (22) had good electrode active material carrying power and adhesion to the substrate. This is because, even in the paste (22), boron-modified acetylene black having hydrophilicity that is relatively easy to disperse in water is used, so that it is possible to form an electrode with good dispersion without using any fluorosurfactant. It was judged that the aqueous paste was prepared.

(Example 23)
An electrode forming paste (23) was prepared in the same manner as in Example 19 except that the positive electrode active material (L) for lithium ion batteries was used in place of the positive electrode active material (K) for lithium ion batteries. A battery electrode plate was obtained. This electrode plate also had good electrode active material carrying power and adhesion to the substrate.
(Example 24)
An electrode forming paste (24) was prepared in the same manner as in Example 19 except that a commercially available lithium cobalt composite oxide (average particle size 5.8 μm) was used instead of the positive electrode active material (K) for the lithium ion battery. It prepared and obtained the electrode plate for lithium ion batteries. This electrode plate also had good electrode active material carrying power and adhesion to the substrate.

(Example 25)
A paste for electrode formation (25) was prepared in the same manner as in Example 19 except that commercially available activated carbon (BET specific surface area was 2900 m ² / g) was used instead of the positive electrode active material (K) for lithium ion batteries. An electrode plate for an electric double layer capacitor was obtained. This electrode plate also had good electrode active material carrying power and adhesion to the substrate.
(Example 26)
Instead of 2.6 g of the crystalline fluorine-containing polymer aqueous dispersion (F) and 0.6 g of the amorphous fluorine-containing polymer aqueous dispersion (H), 0. 3 g and 2.7 g of the amorphous fluorine-containing polymer aqueous dispersion (H) (the mass ratio of the crystalline polymer to the amorphous polymer is 1: 9, corresponding to 1.85 g of both polymers) Example 19 except that 30 g of the negative electrode active material (M) for lithium ion batteries and 30 g of commercially available natural graphite (average particle size 3.3 μm) were used instead of 60 g of the positive electrode active material (K) for ion batteries. Similarly, an electrode forming paste (26) was prepared to obtain an electrode plate for a lithium ion battery. This electrode plate also had good electrode active material carrying power and adhesion to the substrate.

(Example 27)
Instead of 2.3 g of boron-modified acetylene black (B), 4.0 g of cobalt oxyhydroxide and 0.5 g of boron-modified acetylene black (C), 30 g of lithium ion battery negative electrode active material (M) and commercially available A paste for electrode formation (25) was prepared in the same manner as in Example 25 except that 60 g of commercially available nickel hydroxide (average particle size: 8.0 μm) was used instead of 30 g of natural graphite. I got a plate. This electrode plate also had good electrode active material carrying power and adhesion to the substrate.

(Example 28)
When the electrode plate of Example 20 is punched to a predetermined size, a positive electrode plate is obtained, and when the lithium foil is cut to a predetermined size, a negative electrode plate is obtained. A lead wire is attached to each of the positive electrode plate and the negative electrode plate thus obtained, accommodated in a stainless steel cell case via a polyolefin separator, and 1 mol / liter of lithium hexafluorophosphate is dissolved in a mixed solution of ethylene carbonate and diethylene carbonate. When the electrolyte solution is injected, it becomes a model cell of a lithium secondary battery. Attach the model cell charge and discharge tester, corresponds to the charge coulometry 0.6 mA / cm ² was charged to a battery voltage 4.3V, the discharge coulometric 2.0mA ^/ cm 2 (1.25C rate at 25 ° C. ), The model cell is a lithium secondary battery with good storage element characteristics.

[Supplement under rule 26 23.02.2009]

[Supplement under rule 26 23.02.2009]

The aqueous paste for forming a storage element electrode of the present invention can form an electrode composite layer while maintaining a state in which a plurality of finely divided components are uniformly dispersed even after being coated on a substrate. Electrode active material, conductive additive, and binder are homogeneously dispersed, functioning to carry out smooth interfacial charge transfer reaction, ionic conduction, and electronic conduction, and exhibiting good storage element characteristics Play. Furthermore, it is industrially useful because it does not need to use PFOAs, which have in-vivo residues and accumulation properties, and are environmentally concerned.

The entire contents of the specification, claims, and abstract of Japanese Patent Application No. 2008-029626 filed on Feb. 8, 2008 are incorporated herein as the disclosure of the specification of the present invention. Is.

Claims

An electrical storage element electrode comprising an electrode active material, a conductive assistant and a binder, wherein the conductive assistant is a conductive carbonaceous material determined to have hydrophilicity in the following hydrophilicity evaluation test Aqueous paste for forming.
Hydrophilic evaluation test:
10 mg of conductive carbonaceous material powder dried at 120 ° C. for 24 hours is accurately weighed, and its mass is defined as W 1 . Next, the above conductive carbonaceous material powder and 300 g of ion exchange water are added into the 500 ml separatory funnel from the upper mouth, and 30 g of ion exchange water is further added to the inner wall surface of the separatory funnel. Pour the adhering conductive carbonaceous material powder. Next, the separating funnel is shaken for 1 minute and then allowed to stand for 30 minutes. Next, the cock of the separatory funnel is opened, and ion-exchanged water and 300 g of conductive carbonaceous material powder mixed with ion-exchanged water are extracted from the bottom, and the conductive carbonaceous material powder is filtered from the extracted liquid. Separated, dried at 120 ° C. for 24 hours, weighed, and the mass is defined as W 2 . When the charged mass W 1 of the conductive carbonaceous material powder charged into the separatory funnel and the mass W 2 mixed with water satisfy the relationship of (W 2 / W 1 ) × 100 ≧ 1, the conductive carbonaceous material The material is determined to be hydrophilic.
The aqueous paste for forming a storage element electrode according to claim 1, wherein the conductive carbonaceous material having hydrophilicity is a boron-modified conductive carbonaceous material.
The aqueous paste for forming a storage element electrode according to claim 2, wherein the boron content is 0.01 to 10% by mass.
The conductive carbonaceous material includes acetylene black, thermal black, furnace black, channel black, lamp black, graphite such as natural graphite, artificial graphite, ketjen black, needle coke, carbon fiber, carbon tube, and carbon coil. The aqueous paste for forming a storage element electrode according to any one of claims 1 to 3, which is at least one member selected from the group consisting of:
The aqueous paste for forming a storage element electrode according to any one of claims 1 to 4, wherein the binder is an aqueous dispersion of a polymer.
The aqueous paste for forming a storage element electrode according to any one of claims 1 to 4, wherein the binder is an aqueous dispersion of a fluorine-containing polymer.
The aqueous storage element electrode forming water according to claim 6, wherein the aqueous dispersion of the fluoropolymer is prepared by mixing an aqueous dispersion of a crystalline fluoropolymer and an aqueous dispersion of an amorphous fluoropolymer. paste.
Further, it contains surfactants, and the surfactants are anionic surfactants such as carboxylate type, sulfonate type, sulfate type and phosphate type; quaternary ammonium salt type, imidazo Cationic surfactants such as linium salt type and pyrodinium salt type; amphoteric surfactants such as betaine type, aminocarboxylate type, imidazoline derivative type, alkylamine oxide type; and ether type, ether ester type, The electricity storage device electrode according to any one of claims 1 to 7, which is at least one selected from the group consisting of nonionic surfactants such as ester type, nitrogen-containing type, block copolymer of ethylene oxide and propylene oxide. Aqueous paste for forming.
Furthermore, it contains a water-soluble polymer compound, and the water-soluble polymer compound is a cellulose such as methylcellulose, carboxymethylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose; saccharides such as oligosaccharides, dextrin, and water-soluble dietary fibers. The aqueous paste for forming a storage element electrode according to any one of claims 1 to 8, which is at least one selected from the group consisting of crown ethers; polyacrylic acids; polyethylene oxide; and polyvinyl alcohol.
A power storage element comprising a power storage element electrode formed from the aqueous paste for forming a power storage element electrode according to any one of claims 1 to 9.