Binder composition for electrode, coating liquid composition for electrode, electrode for electrical storage device, and electrical storage device

Abstract

The present invention provides a technology related to an adhesive having excellent workability while maintaining adhesiveness. An adhesive composition for an electrode contains: a polyurethane resin aqueous dispersion obtained by dispersing a polyurethane resin in water, carbon nanotubes, and a surfactant, wherein the surfactant contains at least one selected from the group consisting of a nonionic surfactant, a silicone surfactant, and a fluorosurfactant, and the content of the surfactant is 0.1% by mass or more and 20% by mass or less based on the total amount of the polyurethane resin, the carbon nanotubes, and the surfactant.

Description

Technical Field

[0001] The present invention relates to a binder composition for an electrode, a coating liquid composition for an electrode, an electrode for an electric storage device, and an electric storage device. Background Art

[0002] Conventionally, as a power source for portable terminals such as notebook personal computers, mobile phones, and PDAs (Personal Digital Assistant), a secondary battery has been known (for example, Patent Document 1).

[0003] In Patent Documents 1, 2, and 3, styrene-butadiene rubber (SBR) is used as a binder used in an electrode of a secondary battery.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Laid-Open No. 5-21068

[0007] Patent Document 2: Japanese Patent Laid-Open No. 11-7948

[0008] Patent Document 3: Japanese Patent Laid-Open No. 2001-210318 Summary of the Invention

[0009] Technical Problem to be Solved by the Invention

[0010] Generally, for a binder used in an electrode of a secondary battery, not only excellent adhesiveness but also excellent workability is required. As specific characteristics of workability, for example, smoothness of a coating film surface, defoaming property of a coating material, etc. can be cited. Generally, as a method for improving the smoothness of a coating film surface and the defoaming property of a coating material, a method of mixing a surfactant into the binder can be considered. However, generally, if a surfactant is added to the binder, there is a tendency for the adhesiveness of the binder to decrease. Therefore, it is desired to develop a technology related to a binder having excellent adhesiveness and workability.

[0011] Technical Means for Solving the Problem

[0012] The present invention has been completed to solve the above problems and can be achieved by the following means.

[0013] (1) According to one aspect of the present invention, there is provided a binder composition for an electrode. The binder composition for an electrode is characterized by containing: a polyurethane resin aqueous dispersion obtained by dispersing a polyurethane resin in water, carbon nanotubes, and a surfactant, wherein the surfactant contains at least one selected from the group consisting of a nonionic surfactant, a silicone surfactant, and a fluorosurfactant, and the content of the surfactant is 0.1% by mass or more and 20% by mass or less based on the total amount of the polyurethane resin, the carbon nanotubes, and the surfactant.

[0014] According to this aspect, a binder excellent in adhesiveness and workability can be provided.

[0015] (2) In the binder composition for an electrode according to the above aspect, it may also be that the ratio (surfactant / carbon nanotubes) of the content of the surfactant to the content of the carbon nanotubes is 0.05 or more and 10 or less.

[0016] According to this aspect, a binder excellent in adhesiveness and workability can be provided.

[0017] (3) In the binder composition for an electrode according to the above aspect, it may also be that the ratio (surfactant / polyurethane resin) of the content of the surfactant to the content of the polyurethane resin is 0.001 or more and 0.3 or less.

[0018] According to this aspect, a binder excellent in adhesiveness and workability can be provided.

[0019] (4) In the binder composition for an electrode according to the above aspect, it may also be that the surfactant is a nonionic surfactant, and the content of the nonionic surfactant is 0.5% by mass or more and 15% by mass or less based on the total amount of the polyurethane resin, the carbon nanotubes, and the nonionic surfactant.

[0020] According to this aspect, a binder excellent in adhesiveness and workability can be provided.

[0021] (5) In the binder composition for an electrode according to the above aspect, it may also be that the surfactant is a silicone surfactant, and the content of the silicone surfactant is 0.5% by mass or more and 13% by mass or less based on the total amount of the polyurethane resin, the carbon nanotubes, and the silicone surfactant.

[0022] According to this aspect, a binder excellent in workability and more excellent in adhesiveness can be provided.

[0023] (6) In the binder composition for an electrode in the above-described manner, the surfactant may be a fluorosurfactant, and the content of the fluorosurfactant is 0.5% by mass or more and 15% by mass or less with respect to the total amount of the polyurethane resin, the carbon nanotubes, and the fluorosurfactant.

[0024] According to this manner, a binder having excellent workability and more excellent adhesiveness can be provided.

[0025] (7) In the binder composition for an electrode in the above-described manner, it may also contain carboxymethyl cellulose or a salt thereof.

[0026] According to this manner, a binder having excellent dispersion stability can be provided.

[0027] (8) In the binder composition for an electrode in the above-described manner, the ratio (carbon nanotubes / polyurethane resin) of the content of the carbon nanotubes to the content of the polyurethane resin may be 0.001 or more and 0.2 or less.

[0028] According to this manner, a binder having excellent adhesiveness and workability can be provided.

[0029] (9) According to another aspect of the present invention, an electrode coating liquid composition containing the binder composition for an electrode in the above-described manner can be provided.

[0030] (10) According to another aspect of the present invention, an electrode for a power storage device containing the solid component of the electrode coating liquid composition in the above-described manner can be provided.

[0031] (11) According to another aspect of the present invention, a power storage device including the electrode for a power storage device in the above-described manner can be provided. Detailed Embodiments

[0032] Hereinafter, preferred embodiments of the present invention will be described.

[0033] <Binder Composition for Electrode>

[0034] The binder composition for an electrode according to an embodiment of the present invention includes: a polyurethane resin aqueous dispersion in which a polyurethane resin is dispersed in water; carbon nanotubes; and a surfactant. The surfactant in the present embodiment includes at least one selected from the group consisting of a nonionic surfactant, a silicone surfactant, and a fluorosurfactant. And the content of the surfactant in the present embodiment is 0.1% by mass or more and 20% by mass or less with respect to the total amount of the polyurethane resin, the carbon nanotubes, and the surfactant.

[0035] Generally, when a surfactant is added to a binder, there is a tendency for the adhesiveness to decrease. However, according to the electrode binder composition of this method, by using a predetermined amount of a specific surfactant, a binder with excellent workability while maintaining adhesiveness can be provided.

[0036] <Polyurethane resin aqueous dispersion>

[0037] The polyurethane resin aqueous dispersion uses a polyisocyanate compound and a polyol as constituent monomers.

[0038] (Polyisocyanate compound)

[0039] The polyisocyanate compound is not particularly limited. For example, organic polyisocyanates etc. can be cited. As the organic polyisocyanate, there is no particular limitation, and examples can include: aliphatic polyisocyanates, alicyclic polyisocyanates, aromatic polyisocyanates, araliphatic polyisocyanates, etc. As the aliphatic polyisocyanate, examples can include: tetramethylene diisocyanate, dodecamethylene diisocyanate, hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, etc. As the alicyclic polyisocyanate, examples can include: isophorone diisocyanate, hydrogenated xylylene diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate, methylcyclohexylene diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane, etc. As the aromatic polyisocyanate, examples can include: toluene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate (MDI), 4,4'-dibenzyl diisocyanate, 1,5-naphthalene diisocyanate, xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, hydrogenated diphenylmethane diisocyanate, etc. As the araliphatic polyisocyanate, examples can include: dialkyldiphenylmethane diisocyanate, tetraalkyldiphenylmethane diisocyanate, α,α,α,α-tetramethylxylylene diisocyanate, etc. In addition, as the polyisocyanate compound, modified products such as dimers or trimers of these organic polyisocyanates, biuretized isocyanates, etc. can be cited. The polyisocyanate compound can be used alone or two or more kinds can be used in combination.

[0040] As the polyisocyanate compound, aromatic polyisocyanates and alicyclic polyisocyanates are preferred, and alicyclic polyisocyanates are more preferred. Specifically, as the polyisocyanate compound, 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate are preferred, and 4,4'-dicyclohexylmethane diisocyanate is more preferred.

[0041] (Polyol)

[0042] The polyol is not particularly limited, and examples thereof include polybutadiene polyol, polyisoprene polyol, polychloroprene polyol, etc. Among them, polybutadiene polyol and polyisoprene polyol are preferred, and polybutadiene polyol is more preferred.

[0043] In addition, as the polyol, polycarbonate polyol can also be used. The polycarbonate polyol is not particularly limited, and for example, polycarbonate polyols commonly used in this technical field can be used. Examples of the polycarbonate polyol include: carbonate polyol of 1,6-hexanediol, carbonate polyol of 1,4-butanediol and 1,6-hexanediol, carbonate polyol of 1,5-pentanediol and 1,6-hexanediol, carbonate polyol of 3-methyl-1,5-pentanediol and 1,6-hexanediol, etc. More specifically, examples include PCDL T-6001, T-6002, T-5651, T-5652, T-5650J, T-4671, T-4672 manufactured by Asahi Kasei Corporation, Kuraray Polyol C-590, C-1050, C-1050R, C-1090, C-2050, C-2050R, C-2070, C-2070R, C-2090, C-2090R, C-3090, C-3090R, C-4090, C-4090R, C-5090, C-5090R, C-1065N, C-2065N, C-1015N, C-2015N manufactured by Kuraray Co., Ltd., ETERNACOLL (registered trademark) UH-50, UH-100, UH-200, UH-300, UM-90(3 / 1), UM-90(1 / 1), UM-90(1 / 3), UC-100 manufactured by Ube Industries, Ltd., etc.

[0044] (Other constituent monomers)

[0045] In addition to polyisocyanate compounds and polyols, the polyurethane resin aqueous dispersion may also contain, for example, a compound having a hydrophilic group and one or more active hydrogen groups as a constituent monomer. In the present specification, examples of the "hydrophilic group" include an anionic hydrophilic group, a cationic hydrophilic group, and a nonionic hydrophilic group. Examples of the anionic hydrophilic group include a carboxyl group and its salts, and a sulfonic acid group and its salts. Examples of the cationic hydrophilic group include a tertiary ammonium salt and a quaternary ammonium salt. Examples of the nonionic hydrophilic group include a group containing ethylene oxide repeating units, a group containing ethylene oxide repeating units and other alkylene oxide repeating units, and the like.

[0046] Examples of the compound having one or more active hydrogen groups and one or more carboxyl groups (or their salts) include carboxylic acid-containing compounds such as 2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid, 2,2-dimethylolvaleric acid, dihydroxymaleic acid, 2,6-dihydroxybenzoic acid, 3,4-diaminobenzoic acid, and their derivatives and their salts, and polyester polyols obtained by using them. In addition, amino acids such as alanine, aminobutyric acid, aminohexanoic acid, glycine, glutamic acid, aspartic acid, and histidine can be cited; carboxylic acids such as succinic acid, adipic acid, maleic anhydride, phthalic acid, and trimellitic anhydride can be cited.

[0047] Examples of the compound having one or more active hydrogen groups and one or more sulfonic acid groups (or their salts) include sulfonic acid-containing compounds such as 2-hydroxyethyl sulfonate, phenol sulfonic acid, sulfobenzoic acid, sulfosuccinic acid, 5-sulfoisophthalic acid, aminobenzenesulfonic acid, 1,3-phenylenediamine-4,6-disulfonic acid, 2,4-diaminotoluene-5-sulfonic acid, and their derivatives, and polyester polyols, polyamide polyols, polyamide polyester polyols, etc. obtained by copolymerizing them.

[0048] By neutralizing these carboxyl groups or sulfonic acid groups to form salts, the finally obtained polyurethane can be made water-dispersible. Examples of the neutralizing agent in this case include non-volatile bases such as sodium hydroxide and potassium hydroxide, or tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine, methyldiethanolamine, and triethanolamine, and volatile bases such as ammonia. The neutralization can be carried out either before, during, or after the urethane formation reaction.

[0049] Examples of the compound having one or more active hydrogen groups and a tertiary ammonium salt include alkanolamines such as methylaminoethanol and methyldiethanolamine. By neutralizing them with an organic carboxylic acid such as formic acid or acetic acid or an inorganic acid such as hydrochloric acid or sulfuric acid to form salts, the polyurethane can be made water-dispersible. The neutralization can be carried out either before, during, or after the urethane formation reaction. Among them, from the viewpoint of ease of emulsification, a substance obtained by neutralizing methyldiethanolamine with an organic carboxylic acid is preferred.

[0050] Examples of the compound having one or more active hydrogen groups and a quaternary ammonium salt include, for example, compounds obtained by quaternizing the aforementioned alkanolamines such as methylaminoethanol and methyldiethanolamine with a haloalkyl such as chloromethane and bromomethyl, or a dialkyl sulfate such as dimethyl sulfate. Among them, from the viewpoint of ease of emulsification, a compound obtained by quaternizing methyldiethanolamine with dimethyl sulfate or the like is preferred.

[0051] The compound having one or more active hydrogen groups and one or more nonionic hydrophilic groups is not particularly limited. Preferably, it is a compound containing at least 30% by mass or more of ethylene oxide repeating units and having a number average molecular weight of 300 to 20,000. Examples thereof include nonionic group-containing compounds such as polyethylene glycol, polyethylene oxide-polypropylene oxide copolymer diol, polyethylene oxide-polybutylene oxide copolymer diol, polyethylene oxide-polyalkylene oxide copolymer diol or its monoalkyl ether, or polyester polyether polyols obtained by copolymerizing them.

[0052] (Chain extender)

[0053] The chain extender for the polyurethane resin is not particularly limited, and examples thereof include diamines, triamines, and tetraamines. Examples of the diamine include ethylenediamine, trimethylenediamine, piperazine, and isophoronediamine. Examples of the triamine include diethylenetriamine and dipropylenetriamine. Examples of the tetraamine include triethylenetetramine. As the chain extender, diamines are preferred, and ethylenediamine is more preferred.

[0054] The blending amount of the chain extender is not particularly limited. Relative to 100 parts by mass of the polyurethane resin, it is preferably 0.1 part by mass or more and 3 parts by mass or less, and more preferably 0.2 part by mass or more and 1 part by mass or less.

[0055] The solid content of the polyurethane resin in the polyurethane resin aqueous dispersion is not particularly limited. From the viewpoint of operability, relative to 100 parts by mass of the polyurethane resin aqueous dispersion, it is preferably 1 part by mass or more and 60 parts by mass or less, more preferably 3 parts by mass or more and 55 parts by mass or less, and further preferably 4 parts by mass or more and 50 parts by mass or less.

[0056] <Preparation method of polyurethane resin aqueous dispersion>

[0057] As a method for producing a polyurethane resin aqueous dispersion, there is no particular limitation, and known methods can be used. As a method for producing a polyurethane resin aqueous dispersion, for example, the following method can be cited. First, a polyisocyanate compound, a polyol, etc. are reacted under reaction conditions of 30°C to 130°C for about 0.5 hours to 10 hours, and then it is cooled to 5°C to 45°C as needed to obtain a urethane prepolymer. In addition, as the solvent, any organic solvent such as acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, ethyl acetate, butyl acetate, etc. can be used. Then, the urethane prepolymer is emulsified and chain-extended to produce a polyurethane resin aqueous dispersion. Water is added during emulsification. The water used during emulsification is preferably 100 to 900 parts by mass relative to 100 parts by mass of the urethane prepolymer.

[0058] <Carbon nanotubes>

[0059] The carbon nanotubes of the present embodiment are not particularly limited, and examples thereof include single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), etc. Since the electron conductivity can be improved with a small amount, single-walled carbon nanotubes (SWCNT) are preferably used as the carbon nanotubes.

[0060] The fiber diameter and fiber length of the carbon nanotubes are not particularly limited. The number-average fiber diameter is preferably 0.5 nm or more and 20 nm or less, and the number-average fiber length is preferably 0.5 μm or more and 1 mm or less. By setting the number-average fiber diameter to 0.5 nm or more, the viscosity can be prevented from becoming too high, and thus the preparation of the coating composition for the electrode becomes easy. In addition, by making the number-average fiber diameter 20 nm or less, the flexibility is improved, and thus the durability when making a battery is improved. The number-average fiber diameter is more preferably 1 nm or more and 10 nm or less, and further preferably 2 nm or more and 8 nm or less. In addition, by making the number-average fiber length 0.5 μm or more, the durability of the obtained electrode is improved, and the cycle life of the obtained battery is improved. By setting the number-average fiber length to 1 mm or less, the rheological control of the carbon nanotubes becomes easy. The number-average fiber length is more preferably 1 μm or more and 10 μm or less, and further preferably 2 μm or more and 7 μm or less. The number-average fiber length and the number-average fiber diameter can be measured by, for example, measuring the major axis and diameter of 100 randomly selected carbon nanotubes in a transmission electron microscope photograph or a scanning probe microscope photograph and calculating their number average.

[0061] The carbon nanotubes are preferably used in a state of being dispersed in a specified medium. The dispersion of the carbon nanotubes is prepared by dispersing the carbon nanotubes in the medium to the nanometer size by a known method. Water is usually used as the medium, but polar solvents such as alcohols and ketone solvents, or a mixed solvent of these polar organic solvents and water can also be used.

[0062] As a dispersant for dispersing carbon nanotubes, cellulose-based materials such as hydroxymethylcellulose, carboxymethylcellulose and its alkali metal salts, methylcellulose, ethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylmethylcellulose can be used. Among them, carboxymethylcellulose or its salt is more preferably used, and the sodium salt of carboxymethylcellulose is particularly preferably used. Although the binder composition for electrodes in the present embodiment does not contain nanofibrillated cellulose, nanofibrillated cellulose may also be contained.

[0063] <Surfactant>

[0064] The binder composition for electrodes in the present embodiment contains a surfactant. The surfactant in the present embodiment contains at least one selected from the group consisting of nonionic surfactants, silicone surfactants, and fluorosurfactants. Moreover, the content of the surfactant is 0.1% by mass or more and 20% by mass or less based on the total amount of the polyurethane resin, carbon nanotubes, and the surfactant.

[0065] In this specification, a nonionic surfactant refers to a surfactant that does not exhibit ionic properties but exhibits surface activity even when dissolved in water. There is no particular limitation on the nonionic surfactant, and for example, acetylene glycol-based nonionic surfactants can be cited. As acetylene glycol-based nonionic surfactants, for example, SURFYNOL 420, SURFYNOL 423, SURFYNOL 424, SURFYNOL 425, SURFYNOL 440, SURFYNOL465 manufactured by Nissin Chemical Industry Co., Ltd., TRITON (registered trademark) HW-1000 manufactured by Dow Chemical Company, etc. can be cited.

[0066] When the surfactant is a nonionic surfactant, from the viewpoint of improving adhesiveness, the content of the nonionic surfactant is more preferably 0.5% by mass or more and 15% by mass or less, and further preferably 1% by mass or more and 10% by mass or less based on the total amount of the polyurethane resin, carbon nanotubes, and the nonionic surfactant.

[0067] As the silicone surfactant, there is no particular limitation. For example, DOWSIL (registered trademark) FS Antifoam 92, DOWSIL (registered trademark) FS Antifoam 1277, DOWSIL (registered trademark) FS Antifoam 013A, DOWSIL (registered trademark) 1313 Antifoam Emulsion manufactured by Dow Toray can be cited. BYK-345, BYK-346, BYK-347, BYK-348, BYK-349, BYK-3400, BYK-3410, BYK-3441, BYK-3450, BYK-3451, BYK-3480, BYK-3481, etc. manufactured by BYK-Chemie Japan can be cited.

[0068] When the surfactant is a silicone surfactant, from the viewpoint of improving adhesiveness, the content of the silicone surfactant is more preferably 0.5% by mass or more and 13% by mass or less, further preferably 1% by mass or more and 8% by mass or less, based on the total amount of the polyurethane resin, carbon nanotubes, and silicone surfactant.

[0069] As the fluorosurfactant, there is no particular limitation. For example, Ftergent 100(100C), Ftergent 150(150CH), Ftergent 212M, Ftergent 251, Ftergent 400SW manufactured by NEOS can be cited. Surflon S-211, Surflon S-221, Surflon S-231, Surflon S-232, Surflon S-233, etc. manufactured by AGC SEIMICHEMICAL can be cited. FC-4430, FC-4432, etc. manufactured by 3M can be cited.

[0070] When the surfactant is a fluorosurfactant, from the viewpoint of improving adhesiveness, the content of the fluorosurfactant is more preferably 0.5% by mass or more and 15% by mass or less, further preferably 1% by mass or more and 10% by mass or less, based on the total amount of the polyurethane resin, carbon nanotubes, and fluorosurfactant.

[0071] In the electrode binder composition of the present embodiment, the ratio of the content of the surfactant to the content of the carbon nanotubes (surfactant / carbon nanotubes) is not particularly limited, preferably 0.05 or more and 10 or less, more preferably 0.5 or more and 8 or less, further preferably 0.5 or more and 3 or less, and particularly preferably 1 or more and 2 or less.

[0072] In the binder composition for electrodes of the present embodiment, the ratio of the content of carbon nanotubes to the content of polyurethane resin (carbon nanotubes / polyurethane resin) is not particularly limited, and is preferably 0.006 or more and 0.2 or less, more preferably 0.01 or more and 0.1 or less, still more preferably 0.02 or more and 0.1 or less, and particularly preferably 0.03 or more and 0.08 or less.

[0073] In the binder composition for electrodes of the present embodiment, the ratio of the content of surfactant to the content of polyurethane resin (surfactant / polyurethane resin) is not particularly limited, and is preferably 0.001 or more and 0.3 or less, more preferably 0.01 or more and 0.15 or less, still more preferably 0.02 or more and 0.1 or less, and particularly preferably 0.025 or more and 0.05 or less.

[0074] Furthermore, in the binder composition for electrodes of the present embodiment, various commonly used additives can be used as needed. Such additives are not particularly limited, and examples thereof include weathering agents, antibacterial agents, antifungal agents, pigments, rust preventives, dyes, film-forming aids, silane coupling agents, anti-blocking agents, viscosity regulators, leveling agents, defoaming agents, dispersion stabilizers, light stabilizers, antioxidants, ultraviolet absorbers, inorganic fillers, organic fillers, plasticizers, lubricants, antistatic agents, and the like.

[0075] Next, the coating liquid composition for electrodes of other embodiments of the present invention will be described. The coating liquid composition for electrodes may contain a binder composition for electrodes, an active material, a conductive auxiliary agent, and a dispersant, which will be described later.

[0076] In the coating liquid composition for electrodes, the polyurethane resin is preferably 0.1% by mass or more and 10% by mass or less with respect to the solid content of the coating liquid composition for electrodes. When the polyurethane resin is within the above range, the adhesiveness of the electrode composite layer and the electron conductivity of the electrode can be taken into account. In addition, the carbon nanotubes are preferably 0.06% by mass or more and 2% by mass or less with respect to the solid content of the coating liquid composition for electrodes. When the content of the carbon nanotubes is within the above range, the rheological properties of the coating liquid composition for electrodes, the adhesiveness of the electrode composite layer, and the electron conductivity of the electrode can be taken into account. The surfactant is preferably 0.005% by mass or more and 3% by mass or less with respect to the solid content of the coating liquid composition for electrodes. In addition, with respect to the solid content of the coating liquid composition for electrodes, it is preferably contains 0.4% by mass or more and 10% by mass or less of a dispersant. With respect to the solid content of the coating liquid composition for electrodes, it is preferably contains 80% by mass or more and 93% by mass or less of an active material. With respect to the solid content of the coating liquid composition for electrodes, it is preferably contains 0.5% by mass or more and 3% by mass or less of a conductive auxiliary agent.

[0077] As the dispersant, there is no particular limitation, and known dispersants having a dispersing function can be used. For example, cellulose-based materials such as hydroxymethylcellulose, carboxymethylcellulose and its alkali metal salts, methylcellulose, ethylcellulose, hydroxypropylmethylcellulose, and hydroxyethylmethylcellulose can be used; cellulose nanofibers such as those described in Japanese Patent No. 5626828 and Japanese Patent No. 5921960; polycarboxylic acid-based compounds such as polyacrylic acid and sodium polyacrylate; compounds having a vinylpyrrolidone structure such as polyvinylpyrrolidone; polyurethane resins, polyester resins, polyacrylamide, polyethylene oxide, polyvinyl alcohol, sodium alginate, xanthan gum, carrageenan, guar gum, agar, starch, etc. One or more of them can be used. Among them, carboxymethylcellulose salts are preferably used.

[0078] As the conductive additive, an electron conductive material that does not have an adverse effect on battery performance can be used. Generally, carbon blacks such as acetylene black and Ketjen black are used, but natural graphite (flake graphite, flaky graphite, amorphous graphite, etc.), artificial graphite, carbon whiskers, carbon fibers, or metal (copper, nickel, aluminum, silver, gold, etc.) powders, metal fibers, conductive ceramic materials, etc. can also be used. One or a mixture of two or more of them can be used. The addition amount is preferably 0.1 to 30% by weight, particularly preferably 0.2 to 20% by weight, based on the amount of the active material. In addition, carbon nanotubes, which are components of the electrode binder composition of the present embodiment, also function as conductive additives.

[0079] It should be noted that there is no particular limitation on the method, order, etc. of mixing the above electrode materials in the electrode coating liquid composition of the energy storage device of the present embodiment. For example, the conductive additive, dispersant, and electrode binder composition can be premixed and used. There is no particular limitation on the mixing and dispersing device used for the mixing and dispersing treatment of the composition. For example, a homogenizer, planetary mixer, propeller mixer, kneader, homogenizer, ultrasonic homogenizer, colloid mill, bead mill, sand mill, high-pressure homogenizer, etc. can be used.

[0080] As the energy storage device of the present invention, known energy storage devices can be cited, and there is no particular limitation. For example, lithium secondary batteries, lithium ion capacitors, etc. can be cited.

[0081] Next, a lithium secondary battery as the energy storage device of the present embodiment will be described. The positive electrode and negative electrode used in the lithium secondary battery of the present embodiment are composed of an electrode active material, a conductive agent, a current collector of the electrode active material, and a binder that binds the electrode active material and the conductive agent to the current collector, etc.

[0082] The lithium secondary battery of the present embodiment is composed of electrodes manufactured using the electrode binder composition of the above-described embodiment. The above binder can be used in both the positive electrode and the negative electrode, or can be used in either the positive electrode or the negative electrode.

[0083] In the lithium secondary battery of the present embodiment, as the electrode binder for those not using the above electrode binder composition, the following can be used: polyvinylidene fluoride, polyvinylidene fluoride copolymers such as copolymers of polyvinylidene fluoride with hexafluoropropylene, perfluoromethyl vinyl ether, and tetrafluoroethylene, fluorine-based resins such as polytetrafluoroethylene and fluororubber, polymers such as styrene-butadiene rubber, ethylene-propylene rubber, and styrene-acrylonitrile copolymer, but are not limited thereto.

[0084] As the positive electrode active material used in the positive electrode of the lithium secondary battery of the present embodiment, there is no particular limitation as long as it can perform insertion and extraction of lithium ions. As examples, there can be mentioned: metal oxides such as CuO, Cu2O, MnO2, MoO3, V2O5, CrO3, MoO3, Fe2O3, Ni2O3, CoO3; Li x CoO2, Li x NiO2, Li x Mn2O4, LiFePO4 and other composite oxides of lithium and transition metals; metal chalcogenides such as TiS2, MoS2, NbSe3; conductive polymer compounds such as polyacene, polyphenylene, polypyrrole, and polyaniline. Among the above, from the aspects of easy release of lithium ions and high voltage, a composite oxide of one or more selected from transition metals such as cobalt, nickel, and manganese and lithium, which is generally referred to as a high voltage type, is preferred. As specific examples of the composite oxide of cobalt, nickel, manganese and lithium, there can be mentioned: LiCoO2, LiMnO2, LiMn2O4, LiNiO2, LiNi x Co (1-x) O2, LiMn a Ni b Co c (a + b + c = 1), etc. In addition, substances obtained by doping a small amount of elements such as fluorine, boron, aluminum, chromium, zirconium, molybdenum, and iron in these lithium composite oxides, or substances obtained by surface-treating the particle surfaces of lithium composite oxides with carbon, MgO, Al2O3, SiO2, etc. can also be used. Two or more of the above positive electrode active materials can also be used in combination.

[0085] As the negative electrode active material used in the negative electrode of the present embodiment, as long as it can insert / extract metallic lithium or lithium ions, known active materials can be used without particular limitation. For example, carbon materials such as natural graphite, artificial graphite, hard carbon, and soft carbon can be used. In addition, metallic materials such as metallic lithium, alloys, and tin compounds, lithium transition metal nitrides, crystalline metal oxides, amorphous metal oxides, silicon compounds, and conductive polymers can also be used. As specific examples, Li4Ti5O 12 , NiSi5C6, etc. can be cited.

[0086] The positive electrode and negative electrode of the lithium secondary battery of the present embodiment use a conductive agent. As the conductive agent, as long as it is an electron conductive material that does not have an adverse effect on the battery performance, it can be used without particular limitation. Usually, carbon blacks such as acetylene black and Ketjen black are used, but natural graphite (flake graphite, scaly graphite, earthy graphite, etc.), artificial graphite, carbon whiskers, carbon fibers, or powders of metals (copper, nickel, aluminum, silver, gold, etc.), metal fibers, and conductive ceramic materials can also be used. They can also be used as a mixture of two or more. The addition amount is preferably 0.1 to 30% by mass, particularly preferably 0.2 to 20% by mass, relative to the amount of the active material.

[0087] As the current collector of the electrode active material of the lithium secondary battery of the present embodiment, any electron conductor that does not have an adverse effect on the constructed battery can be used. For example, as the current collector for the positive electrode, in addition to aluminum, titanium, stainless steel, nickel, fired carbon, conductive polymers, conductive glass, etc., for the purpose of improving adhesiveness, conductivity, and oxidation resistance, substances obtained by treating the surfaces of aluminum, copper, etc. with carbon, nickel, titanium, silver, etc. can be used. In addition, as the current collector for the negative electrode, in addition to copper, stainless steel, nickel, aluminum, titanium, fired carbon, conductive polymers, conductive glass, Al-Cd alloys, etc., for the purpose of improving adhesiveness, conductivity, and oxidation resistance, a current collector obtained by treating the surface of copper, etc. with carbon, nickel, titanium, silver, etc. can be used. These current collector materials can also be subjected to surface oxidation treatment. In addition, regarding its shape, in addition to foil-like, film-like, sheet-like, net-like, punched or expanded objects, strip-shaped bodies, porous bodies, foamed bodies, etc. can also be used. The thickness is not particularly limited, and a thickness of 1 to 100 μm is usually used.

[0088] The electrode of the lithium secondary battery of the present embodiment can be manufactured by mixing an electrode active material, a conductive agent, a current collector of the electrode active material, and a binder that binds the electrode active material and the conductive agent to the current collector to prepare a slurry-like electrode material, and coating it on an aluminum foil or copper foil that serves as the current collector to volatilize the dispersion medium.

[0089] In the electrode material of this embodiment, as a viscosity modifier for slurry formation, a thickener such as a water-soluble polymer can be used. Specifically, one or more selected from cellulose-based materials such as carboxymethyl cellulose salts, methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose; polycarboxylic acid-based compounds such as polyacrylic acid and sodium polyacrylate; compounds having a vinylpyrrolidone structure such as polyvinylpyrrolidone; polyacrylamide, polyethylene oxide, polyvinyl alcohol, sodium alginate, xanthan gum, carrageenan, guar gum, agar, starch, etc. can be used, and among them, carboxymethyl cellulose salts are preferred.

[0090] There are no particular limitations on the method, order, etc. of mixing the above-mentioned electrode materials. For example, the active material and the conductive agent can be premixed and used. In this case of mixing, a ball mill such as a mortar, a grinding mill, a planetary ball mill or a shaking ball mill, mechanical fusion, etc. can be used.

[0091] The separator used in the lithium secondary battery of this embodiment can be a separator commonly used in a lithium secondary battery without particular limitation. Examples thereof include porous resins, ceramics, non-woven fabrics, etc. composed of polyethylene, polypropylene, polyolefin, polytetrafluoroethylene, etc.

[0092] The electrolyte used in the lithium secondary battery of this embodiment may be an electrolyte commonly used in a lithium secondary battery, and general electrolytes such as organic electrolytes and ionic liquids can be used.

[0093] As the electrolyte salt used in the lithium secondary battery of this embodiment, for example, LiPF6, LiBF4, LiClO4, LiAsF6, LiCl, LiBr, LiCF3SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiI, LiAlCl4, NaClO4, NaBF4, NaI, etc. can be cited. Inorganic lithium salts such as LiPF6, LiBF4, LiClO4, LiAsF6, etc. and those composed of LiN(SO2C x F 2x+1 )(SO2C y F 2y+1) The organolithium salts shown below. Here, x and y represent integers of 0 or 1 to 4, and in addition, x + y is 2 to 8. Examples of the organolithium salts include: LiN(SO2F)2, LiN(SO2CF3)(SO2C2F5), LiN(SO2CF3)(SO2C3F7), LiN(SO2CF3)(SO2C4F9), LiN(SO2C2F5)2, LiN(SO2C2F5)(SO2C3F7), LiN(SO2C2F5)(SO2C4F9), etc. Among them, when LiPF6, LiBF4, LiN(CF3SO2)2, LiN(SO2F)2, LiN(SO2C2F5)2, etc. are used for the electrolyte, the electrical characteristics are excellent, and thus they are preferred. One kind of the above electrolyte salts can be used, or two or more kinds can be used. Such lithium salts are usually contained in the electrolytic solution at a concentration of 0.1 to 2.0 mol / L, preferably at a concentration of 0.3 to 1.5 mol / L.

[0094] As the organic solvent for dissolving the electrolyte salt of the lithium secondary battery of the present embodiment, there is no particular limitation as long as it is an organic solvent used in a non-aqueous electrolyte of a general lithium secondary battery. For example, carbonate compounds, lactone compounds, ether compounds, sulfolane compounds, dioxolane compounds, ketone compounds, nitrile compounds, halogenated hydrocarbon compounds, etc. can be cited. Specifically, carbonate esters such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, ethylene carbonate, propylene carbonate, ethylene glycol dimethyl carbonate, propylene glycol dimethyl carbonate, ethylene glycol diethyl carbonate, vinylene carbonate, etc., lactones such as γ-butyrolactone, etc., ethers such as dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,4-dioxane, etc., sulfolanes such as sulfolane, 3-methylsulfolane, etc., dioxolanes such as 1,3-dioxolane, etc., ketones such as 4-methyl-2-pentanone, etc., nitriles such as acetonitrile, propionitrile, valeronitrile, benzonitrile, etc., halogenated hydrocarbons such as 1,2-dichloroethane, etc., and other methyl formate, dimethylformamide, diethylformamide, dimethyl sulfoxide, imidazolium salts, quaternary ammonium salts, and other ionic liquids. Furthermore, it can also be a mixture thereof.

[0095] Among these organic solvents, since they are excellent in terms of solubility of the electrolyte, dielectric constant, and viscosity, it is particularly preferred to contain one or more non-aqueous solvents selected from the group consisting of carbonate esters.

[0096] In the lithium secondary battery of the present embodiment, in the case of using a polymer electrolyte or a polymer gel electrolyte, examples of those that can be used include: polymers of ethers, esters, siloxanes, acrylonitrile, vinylidene fluoride, hexafluoropropylene, acrylate, methacrylate, styrene, vinyl acetate, vinyl chloride, oxetane, etc. as polymer compounds, or polymers having a copolymer structure thereof, or crosslinked bodies thereof, etc. The polymer may be one kind or two or more kinds. The polymer structure is not particularly limited, and polymers having an ether structure such as polyethylene oxide are particularly preferred.

[0097] In the lithium secondary battery of the present embodiment, the battery of the liquid system is an electrolytic solution, the battery of the gel system is a precursor solution obtained by dissolving a polymer in the electrolytic solution, and the solid electrolyte battery stores a crosslinked polymer in which an electrolyte salt is dissolved in a battery container.

[0098] The lithium secondary battery of the present embodiment can be formed into a cylindrical shape, a coin shape, a square shape, or any other shape. The basic structure of the battery is the same regardless of the shape, and can be designed and changed according to the purpose. For example, in the case of a cylindrical shape, a negative electrode formed by coating a negative electrode active material on a negative electrode current collector and a positive electrode formed by coating a positive electrode active material on a positive electrode current collector are wound via a separator, and the obtained wound body is housed in a battery can, a non-aqueous electrolytic solution is injected, and it is sealed in a state where insulating plates are placed above and below to obtain. In addition, in the case of being applied to a coin-type lithium secondary battery, it is housed in a coin-type battery can in a state where a disk-shaped negative electrode, a separator, a disk-shaped positive electrode, and a stainless steel plate are laminated, and a non-aqueous electrolytic solution is injected and sealed.

[0099] Examples

[0100] Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[0101] <Preparation of polyurethane resin aqueous dispersion>

[0102] (Polyurethane resin aqueous dispersion A1)

[0103] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 71.3 parts by mass of polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd., Poly bd R-45HT, average hydroxyl value 46.5 mgKOH / g, number of active hydrogen groups 2.32), 4.2 parts by mass of 4,4'-dihydroxymethylpropionic acid (number of active hydrogen groups 2), 24.5 parts by mass of dicyclohexylmethane diisocyanate, and 100 parts by mass of methyl ethyl ketone were added. Then, the reaction was carried out at 75 °C for 4 hours to obtain a methyl ethyl ketone solution of a polyurethane prepolymer. The content of free isocyanate groups was 2.5% relative to the non-volatile components of the solution.

[0104] Next, after cooling the solution to 45°C, 1.25 parts by mass of sodium hydroxide was added to carry out neutralization. Then, while slowly adding 300 parts by mass of water to the solution, emulsification and dispersion were carried out using a homogenizer. After adding an aqueous solution obtained by dissolving 1.6 parts by mass of ethylenediamine (number of active hydrogen groups 2) in 100 parts by mass of water to the obtained emulsified dispersion, a chain extension reaction was carried out for 1 hour. Then, methyl ethyl ketone as a reaction solvent was distilled under reduced pressure at 50°C to obtain a polyurethane resin aqueous dispersion A1 with a concentration of non-volatile components (solid components) of about 30% by mass.

[0105] (Polyurethane resin aqueous dispersion A2)

[0106] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 34.2 parts by mass of polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd., Poly bd R-45HT, average hydroxyl value 46.5 mgKOH / g, number of active hydrogen groups 2.32), 34.0 parts by mass of polycarbonate polyol (manufactured by Ube Industries, Ltd., ETERNACOLL UH-100, average hydroxyl value 110.0 mgKOH / g, number of active hydrogen groups 2.0), 4.2 parts by mass of dimethylolpropionic acid (number of active hydrogen groups 2), 27.8 parts by mass of 4,4'-dicyclohexylmethane diisocyanate, and 100 parts by mass of methyl ethyl ketone were added. Then, the reaction was carried out at 75°C for 4 hours to obtain a methyl ethyl ketone solution of a polyurethane prepolymer. The content of free isocyanate groups was 2.0% relative to the non-volatile components of the solution.

[0107] Next, after cooling the solution to 45°C, 3.13 parts by mass of triethylamine was added to carry out neutralization. Then, while slowly adding 300 parts by mass of water to the solution, emulsification and dispersion were carried out using a homogenizer. An aqueous solution obtained by dissolving 1.3 parts by mass of ethylenediamine (number of active hydrogen groups 2) in 100 parts by mass of water was added to the obtained emulsified dispersion, and then a chain extension reaction was carried out for 1 hour. Then, methyl ethyl ketone as a reaction solvent was distilled under reduced pressure at 50°C to obtain a polyurethane resin aqueous dispersion A2 with a concentration of non-volatile components (solid components) of about 30% by mass.

[0108] (Polyurethane resin aqueous dispersion A3)

[0109] In a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer, and a nitrogen inlet tube, 51.3 parts by mass of a polycarbonate polyol (manufactured by Ube Industries, Ltd., ETERNACOLL UH-100, average hydroxyl value 110.0 mgKOH / g, number of active hydrogen groups 2.0), 5.1 parts by mass of dimethylolpropionic acid (number of active hydrogen groups 2), 2.6 parts by mass of trimethylolpropane (number of active hydrogen groups 2), 41.0 parts by mass of 4,4'-dicyclohexylmethane diisocyanate, and 100 parts by mass of methyl ethyl ketone were added. Then, the reaction was carried out at 75 °C for 4 hours to obtain a methyl ethyl ketone solution of a polyurethane prepolymer. The content of free isocyanate groups was 3.0% relative to the non-volatile components of the solution.

[0110] Next, after cooling the solution to 45 °C, 3.8 parts by mass of triethylamine was added to carry out neutralization. Then, while slowly adding 300 parts by mass of water to the solution, emulsification and dispersion were carried out using a homogenizer. An aqueous solution obtained by dissolving 1.9 parts by mass of ethylenediamine (number of active hydrogen groups 2) in 100 parts by mass of water was added to the obtained emulsified dispersion, and then a chain extension reaction was carried out for 1 hour. Then, methyl ethyl ketone as a reaction solvent was distilled off under reduced pressure at 50 °C to obtain a polyurethane resin aqueous dispersion A3 with a non-volatile component (solid component) concentration of about 30% by mass.

[0111] <Manufacture of Carbon Nanotube Aqueous Dispersion>

[0112] In a beaker, 1.0 g of single-walled carbon nanotubes (SWCNT) (TUBALL BATT manufactured by OCSiAl, CNT purity > 93%, average diameter 1.6 ± 0.5 nm) was mixed with 50 g of a 2 wt% aqueous solution of carboxymethyl cellulose salt (CELLOGEN 7A manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). After stirring, using a beaker, an ultrasonic homogenizer (US-600T manufactured by Nippon Seiki Co., Ltd.), a circulation unit, and a tube pump, while circulating the slurry, dispersion was carried out at an output of 100 μA for 90 minutes to obtain an aqueous dispersion of carbon nanotubes. The number-average fiber diameter of the obtained carbon nanotubes was 3 nm, the number-average fiber length was 3000 nm, and the aspect ratio was 1000.

[0113] It should be noted that the number-average fiber diameter and number-average fiber length of the carbon nanotubes were measured using a scanning probe microscope (SPM) (AFM-5300E manufactured by JEOL Ltd.). That is, after diluting the carbon nanotubes with water to a solid component concentration of 0.01 wt%, they were spread on a mica substrate and the solvent was evaporated. Then, the AFM image of the sample was observed, and the number-average fiber diameter and average fiber length were calculated according to the method described above. In addition, the aspect ratio was calculated using these values according to the following formula 1.

[0114] Aspect ratio = average fiber length (nm) / average fiber diameter (nm) (Equation 1)

[0115] <Method for fabricating the electrode used in the experiment>

[0116] (Fabrication of the negative electrode)

[0117] 89 parts by mass of SiO (average particle size 4.5 μm, specific surface area 5.5 m 2 / g) as the negative electrode active material, 2 parts by mass of acetylene black (Li-400 manufactured by DENKA) as the conductive assistant, 0.45 parts by mass of carboxymethyl cellulose salt (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., BSH-6) as the dispersant, and an electrode binder were mixed, and then stirred using a homogenizer to prepare a negative electrode slurry (electrode coating liquid) with a solid content of 40% by mass. Pure water was used for the preparation of the solid content. The electrode coating liquid was coated on an electrolytic copper foil with a thickness of 10 μm using a roll coater (manufactured by Sanki Mento Co., Ltd., Titanium Coater), and then dried at 120 °C and subjected to a roll pressing treatment, thereby obtaining a negative electrode with a negative electrode active material of 7 - 8 mg / cm 2 of the negative electrode.

[0118] Here, in Example 1, as the electrode binder, 9 parts by mass of polyurethane resin aqueous dispersion A1, 0.2 parts by mass of carbon nanotubes, and 0.3 parts by mass of SURFYNOL 420 (manufactured by Nikko Chemical Industry Co., Ltd.) as a nonionic surfactant were used.

[0119] <Examples 2 - 10, Comparative Examples 1 - 2>

[0120] Except for changing to the compositions shown in the following table, the negative electrode was fabricated in the same manner as described in Example 1. It should be noted that in Examples 2, 3, and 6, in addition to SiO, graphite (average particle size 18 μm, specific surface area 3.2 m 2 / g) was also used as the negative electrode active material.

[0121] <Operability evaluation>

[0122] (Smoothness of the coating film surface)

[0123] Using an optical microscope, visually observe the coating film surface of the obtained electrode. Then, evaluate the smoothness of the coating film surface based on the number of pinholes per 1 m 2 of the coating film surface. Hereinafter, the negative electrode was used as the electrode. The fewer the number of pinholes, the more excellent the smoothness of the coating film surface.

[0124] Evaluation criteria

[0125] 5 points: Less than 1 pinhole per 1 m 2 of the coating film

[0126] 4 points: per 1 m 2 the number of pinholes is more than 1 and less than 5

[0127] 3 points: per 1 m 2 the number of pinholes is more than 5 and less than 20

[0128] 2 points: per 1 m 2 the number of pinholes is more than 20 and less than 100

[0129] 1 point: per 1 m 2 the number of pinholes is more than 100

[0130] (Defoaming property of coating)

[0131] The above-mentioned negative electrode paste (coating liquid for electrode) is stirred using a planetary mixer while reducing the pressure to perform defoaming. The time until the bubbles disappear is visually confirmed. The shorter the time until the bubbles disappear, the more excellent the defoaming property of the coating.

[0132] Evaluation criteria

[0133] 5 points: defoaming in less than 30 minutes

[0134] 4 points: defoaming in 30 minutes or more and less than 1 hour

[0135] 3 points: defoaming in 1 hour or more and less than 3 hours

[0136] 2 points: defoaming in 3 hours or more and less than 5 hours

[0137] 1 point: no defoaming in 5 hours

[0138] <Adhesion evaluation>

[0139] With the coating film surface of the above-obtained electrode as the outside, after bending the electrode 180° and returning it, the degree of shedding of the active material on the coating film surface is visually judged. The less the shedding of the active material, the more excellent the adhesion.

[0140] Evaluation criteria:

[0141] 5 points: no shedding

[0142] 4 points: shedding is more than 0% and 25% or less

[0143] 3 points: shedding is more than 25% and 50% or less

[0144] 2 points: shedding is more than 50% and 75% or less

[0145] 1 point: shedding is more than 75%

[0146] The experimental results are shown below.

[0147] [Table 1]

[0148]

[0149] By comparing Examples 1 to 10 with Comparative Example 1, it can be seen that by using the surfactant of the present embodiment, excellent operability can be achieved while maintaining adhesiveness. In addition, by comparing Examples 1 to 10 with Comparative Example 2, it can be seen that by making the content of the surfactant 20% by mass or less based on the total amount of the polyurethane resin, carbon nanotubes, and surfactant, excellent operability can be achieved while maintaining adhesiveness.

[0150] Industrial Applicability

[0151] The binder composition for an electrode of the present embodiment can be used as a binder for an electrode of a power storage device (for example, an electrode for a lithium secondary battery, etc.), and the electrode using this binder is used in the manufacture of various power storage devices. That is, an electrode coating liquid composition containing the binder composition for an electrode of the present embodiment can be prepared, and a power storage device having an electrode containing the solid component of the electrode coating liquid can be obtained. The obtained power storage device can be used in various portable devices such as mobile phones, laptop computers, personal digital assistants (PDAs), video cameras, digital cameras, etc., and medium or large-sized power storage devices mounted on electric bicycles, electric vehicles, etc.

[0152] The present invention is not limited to the above embodiments and can be implemented in various structures without departing from its gist. For example, for the technical features in the embodiments and examples corresponding to the technical features in each mode described in the Summary of the Invention, in order to solve part or all of the above problems, or to achieve part or all of the above effects, appropriate substitution and combination can be made. In addition, if the technical feature is not described as an essential technical feature in this specification, it can be appropriately deleted.

Claims

1. An adhesive composition for an electrode, characterized in that, the adhesive composition for an electrode contains: a polyurethane resin aqueous dispersion obtained by dispersing a polyurethane resin in water, carbon nanotubes, and a surfactant, the surfactant is a nonionic surfactant, relative to the total amount of the polyurethane resin, the carbon nanotubes, and the surfactant, the content of the surfactant is 0.1% by mass or more and 20% by mass or less, the number-average fiber diameter of the carbon nanotubes is 0.5 nm or more and 20 nm or less, and the number-average fiber length is 0.5 μm or more and 1 mm or less; and the adhesive composition for an electrode further contains a conductive auxiliary agent, the conductive auxiliary agent is at least one selected from carbon black, natural graphite, artificial graphite, carbon whiskers, carbon fibers, metal powders, metal fibers, and conductive ceramic materials, and the content of the conductive auxiliary agent relative to the electrode active material is 0.1% by mass to 30% by mass.

2. The binder composition for an electrode according to claim 1, wherein Relative to the total amount of the polyurethane resin, the carbon nanotubes, and the nonionic surfactant, the content of the nonionic surfactant is 0.5% by mass or more and 15% by mass or less.

3. An adhesive composition for an electrode, characterized in that, the adhesive composition for an electrode contains: a polyurethane resin aqueous dispersion obtained by dispersing a polyurethane resin in water, carbon nanotubes, and a surfactant, the surfactant is a silicone-based surfactant, relative to the total amount of the polyurethane resin, the carbon nanotubes, and the surfactant, the content of the surfactant is 0.1% by mass or more and 20% by mass or less, the number-average fiber diameter of the carbon nanotubes is 0.5 nm or more and 20 nm or less, and the number-average fiber length is 0.5 μm or more and 1 mm or less; and the adhesive composition for an electrode further contains a conductive auxiliary agent, the conductive auxiliary agent is at least one selected from carbon black, natural graphite, artificial graphite, carbon whiskers, carbon fibers, metal powders, metal fibers, and conductive ceramic materials, and the content of the conductive auxiliary agent relative to the electrode active material is 0.1% by mass to 30% by mass.

4. The adhesive composition for an electrode according to claim 3, characterized in that, relative to the total amount of the polyurethane resin, the carbon nanotubes, and the silicone-based surfactant, the content of the silicone-based surfactant is 0.5% by mass or more and 13% by mass or less.

5. An adhesive composition for an electrode, characterized in that, the adhesive composition for an electrode contains: a polyurethane resin aqueous dispersion obtained by dispersing a polyurethane resin in water, carbon nanotubes, and a surfactant, the surfactant is a fluorine-based surfactant, relative to the total amount of the polyurethane resin, the carbon nanotubes, and the surfactant, the content of the surfactant is 0.1% by mass or more and 20% by mass or less, the number-average fiber diameter of the carbon nanotubes is 0.5 nm or more and 20 nm or less, and the number-average fiber length is 0.5 μm or more and 1 mm or less; and The binder composition for electrodes further contains a conductive aid, the conductive aid being at least one selected from carbon black, natural graphite, artificial graphite, carbon whiskers, carbon fibers, metal powders, metal fibers, and conductive ceramic materials, and the content of the conductive aid relative to the electrode active material being 0.1% by mass to 30% by mass.

6. The binder composition for electrodes according to claim 5, wherein relative to the total amount of the polyurethane resin, the carbon nanotubes, and the fluorosurfactant, the content of the fluorosurfactant is 0.5% by mass or more and 15% by mass or less.

7. The binder composition for electrodes according to any one of claims 1 to 6, wherein the ratio of the content of the surfactant to the content of the carbon nanotubes (surfactant / carbon nanotubes) is 0.05 or more and 10 or less.

8. The binder composition for electrodes according to any one of claims 1 to 6, wherein the ratio of the content of the surfactant to the content of the polyurethane resin (surfactant / polyurethane resin) is 0.001 or more and 0.3 or less.

9. The binder composition for electrodes according to any one of claims 1 to 6, wherein the binder composition for electrodes further contains carboxymethyl cellulose or a salt thereof.

10. The binder composition for electrodes according to any one of claims 1 to 6, wherein the ratio of the content of the carbon nanotubes to the content of the polyurethane resin (carbon nanotubes / polyurethane resin) is 0.001 or more and 0.2 or less.

11. An electrode coating liquid composition, wherein the electrode coating liquid composition contains the binder composition for electrodes according to any one of claims 1 to 10.

12. An electrode for an electrical storage device, wherein the electrode for an electrical storage device contains the solid component of the electrode coating liquid composition according to claim 11.

13. An electrical storage device, wherein the electrical storage device includes the electrode for an electrical storage device according to claim 12.

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