Conductive carbon material dispersion and method for producing the same

Abstract

To provide a conductive material dispersion capable of securing superior dispersibility and conductivity, and a method for producing the same.SOLUTION: The present invention provides a conductive carbon material dispersion in which a conductive carbon material powder surface-treated with a compound having a catechol group is dispersed in water and / or an organic solvent.

Description

Technical Field

[0001] The present invention relates to a conductive carbon material, a conductive carbon material dispersion, and a method for producing the same, which are suitable for the production of lithium-ion batteries, sodium-ion batteries, semi-solid batteries, all-solid batteries, and capacitors, and can also be used for touch panels, conductive adhesives, antistatic agents, etc.

Background Art

[0002] Conventionally, carbon-based materials have been used as conductive materials (such as Patent Document 1, Patent Document 2, etc.). As conductive carbon materials, powdery (fine particle) materials such as carbon nanotubes, carbon fibers, graphite, graphene, acetylene black, ketjen black, and furnace black are known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] These conductive carbon material powders have the problems that they increase the contacts between the powders, have a high specific surface area, tend to have a high viscosity during dispersion, and when the dispersant is increased to lower the viscosity, the conductive performance deteriorates. For improving the dispersibility of carbon material powder, for example, it has been proposed to react hydrochloric acid dopamine with graphite oxide to obtain graphene powder having a catechol group (Patent Document 4). Regarding the use of dopamine, it has been proposed to polymerize dopamine in a carbon fiber (VGCF) dispersion to obtain a nanocarbon material surface-modified with polydopamine and use it as a material for an anode for a lithium-ion battery (Patent Document 3).

[0005] On the other hand, in recent years, carbon nanotubes have attracted attention as highly conductive carbon materials. Regarding carbon nanotubes, the specific surface area per unit mass is further increased and they are excellent in conductivity, but dispersion at a high concentration has been impossible.

[0006] Also, in order to improve the dispersibility, when the amount of the dispersant is increased, the compatibility with the binder resin deteriorates, causing problems such as the occurrence of aggregation and a decrease in the pot life.

[0007] Thus, it has been difficult for carbon nanotubes to be stabilized with high dispersibility in water and organic solvents while maintaining high conductivity. Attempts to coat carbon nanotubes with dopamine are known, and it has been proposed to mix carbon nanotubes and dopamine in a Tris solution and perform ultrasonic treatment (Patent Document 5), but the dispersibility is still not sufficient.

[0008] In view of the above problems, an object of the present invention is to provide a dispersion of a carbon-based conductive material that can solve the above problems.

Means for Solving the Problems

[0009] The present inventor has conducted various studies on the surface treatment and dispersion method of the carbon material, and found that a dispersion containing at least a surface-treated carbon material, a polymer dispersant, and a solvent, By creating a dispersion characterized in that the surface treatment agent is a compound containing a catechol group, it has been discovered that the above problems can be solved. That is, the present invention is (1) A conductive carbon material dispersion in which conductive carbon material powder surface-treated with a compound having a catechol group is dispersed in water and / or an organic solvent. (2) The conductive carbon material dispersion according to (1) above, characterized in that the conductive carbon material powder is at least one carbon material powder selected from the group consisting of carbon nanotubes, carbon fibers, graphite, graphene, acetylene black, ketjen black, and furnace black. (3) The conductive carbon material dispersion according to (1) above, characterized in that the compound having a catechol group is one or more compounds selected from the group consisting of catechol, dopamine hydrochloride, dopamine hydrobromide, dopa, norepinephrine, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol, and 4-tert-butylpyrocatechol. (4) The conductive carbon material dispersion according to (3) above, characterized in that the compound having a catechol group is dopamine hydrochloride and dopamine hydrobromide. (5) A method for producing a surface-treated carbon material powder, characterized by surface-treating the conductive carbon material powder with a compound having a catechol group. (6) The method for producing a surface-treated carbon material powder according to (5) above, characterized in that the surface treatment is performed in water. (7) The method for producing a conductive carbon material powder according to (5) above, characterized in that the conductive carbon material powder is at least one carbon material powder selected from the group consisting of carbon nanotubes, carbon fibers, graphite, graphene, acetylene black, ketjen black, and furnace black. (8) The method for producing a conductive carbon material powder according to (5) above, characterized in that the compound having a catechol group is one or more compounds selected from the group consisting of catechol, dopamine hydrochloride, dopamine hydrobromide, dopa, norepinephrine, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol, and 4-tert-butylpyrocatechol. (9) The method for producing the conductive carbon material powder according to (8) above, wherein the compound having a catechol group is hydrobromic acid dopamine, and (10) A dispersion containing the conductive carbon material powder obtained by the production method according to (5) above, a dispersant, and a dispersion medium, is present.

[0010] The dispersion of the present invention contains at least a conductive carbon material. As the conductive carbon material, at least one selected from carbon nanotubes, carbon fibers, graphite, graphene, acetylene black, ketjen black, and furnace black is preferable, and a combination of two or more kinds can also be applied. Among these, carbon nanotubes are particularly preferable.

[0011] The dispersion of the present invention may further contain a dispersion aid such as a pigment derivative.

[0012] In the dispersion of the present invention, it is preferable to use a polymer dispersant as the dispersant.

[0013] In the dispersion of the present invention, the solvent is preferably at least one selected from the group consisting of ester solvents, ketone solvents, glycol solvents, alcohol solvents, and nitrogen-containing polar solvents, in addition to water, as an organic solvent.

[0014] The conductive carbon material powder of the present invention is characterized in that it is surface-treated with a compound having a catechol group. Moreover, the method for producing the surface-treated carbon material powder of the present invention is characterized in that the conductive carbon material powder is surface-treated with a compound having a catechol group. The dispersion of the present invention can also be produced by a step (1) of surface-treating the conductive carbon material powder with a compound having a catechol group in water, a step (2) of mixing the obtained surface-treated carbon material powder with a dispersant and a solvent, and a step (3) of dispersing the obtained mixture by a media-type disperser or a media-less disperser or both dispersers.

[0015] When using carbon nanotubes as the conductive carbon material powder, it is preferable to perform a washing step with an acid solution or a metal sublimation step at high temperature prior to the above step (1).

Effects of the Invention

[0016] According to the present invention, a dispersion liquid excellent in dispersibility, good in stability over time, good in conductivity, and low in viscosity can be obtained. More specifically, according to the present invention, a conductive carbon material powder excellent in dispersibility and a dispersion liquid containing the same can be obtained. In particular, by using hydrobromic acid dopamine as the compound having a catechol group, excellent effects can be obtained not only in terms of dispersibility but also in lowering the viscosity of the dispersion liquid.

[0017] In addition, when the dispersion liquid of the present invention is used in admixture with a binder or the like, high conductivity can be imparted with a small amount of addition, there is no increase in the viscosity of the mixture, no aggregation occurs, and the pot life is also extended, so that a good conductive coating film can be obtained.

Modes for Carrying Out the Invention

[0018] The present invention is a conductive carbon material dispersion liquid containing a conductive carbon material powder surface-treated with a compound containing a catechol group, a dispersant, and a dispersion medium.

[0019] As the conductive carbon material powder, a single type selected from the group consisting of carbon nanotubes, carbon fibers, graphite, graphene, acetylene black, ketjen black, and furnace black can be used alone, or two or more types of them can be used in combination.

[0020] As applicable carbon nanotubes, it can be applied to both single-walled carbon nanotubes and multi-walled carbon nanotubes. Specifically, as single-walled carbon nanotubes, there are TUBALL manufactured by OCSiAl, ZEONANO SG101 manufactured by Nippon Zeon, HX-N-5 manufactured by Dow etc. As multi-walled carbon nanotubes, there are HX-N-4 manufactured by Dow, ENERMAX61 manufactured by Cabot, Knanos300T manufactured by Kumho, JEIO manufactured, CNANO manufactured etc.

[0021] To reduce metal impurities, it is preferable to perform cleaning with an acid solution or metal sublimation by high-temperature treatment on the carbon nanotubes.

[0022] Specifically, as carbon fibers, there are VGCF-H, VGCF-X manufactured by Showa Denko, Ensaco250G, Ensaco260G, Ensaco350G, Super-P manufactured by TIMCAL etc.

[0023] Specifically, as graphite, there are GF-1, Z-5F manufactured by Ito Graphite Industry Co., Ltd., SP-270, SP-5030, SP-5030-α manufactured by Nippon Graphite etc.

[0024] Specifically, as graphene, there are QuanteraSXM manufactured by ULVAC-PHI, graphene manufactured by NSC, GO, reduced GO etc.

[0025] Specifically, as acetylene black, there are Denka Black manufactured by Denka, Denka Black HS-100, FX-35, Li-400, acetylene black-01, acetylene black-03 manufactured by Soltex etc.

[0026] Specifically, as ketjen black, there are EC-300J, EC-600JD manufactured by Akzo etc.

[0027] As furnace black, specifically, Tokablack #4300, #4400, #4500, #5500 manufactured by Tokai Carbon Co., Ltd., Printex L, Printex L6 manufactured by Orion Engineered Carbons GmbH, Raven7000, 5750, 5250, 5000ULTRAIII, 5000ULTRA, Conductex SC ULTRA, Conductex 975ULTRA manufactured by Birla Carbon, etc., PUER BLACK100, 115, 205, #2350, #2400B, #2600B, #30050B, #3030B, #3230B, #3350B, #3400B, #5400B manufactured by Mitsubishi Chemical Corporation, MONARCH1400, 1300, 900, VulcanXC-72R, BlackPearls2000, LITX-50, LITX-200 manufactured by Cabot Corporation, etc. can be mentioned. Among these various conductive carbon material powders, carbon nanotubes are extremely preferable.

[0028] As the surface treatment agent, it is a compound containing a catechol group, and a single kind selected from the group consisting of catechol, dopamine hydrochloride, dopamine hydrobromide, dopa, norepinephrine, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol and 4-tert-butylpyrocatechol can be used alone, or two or more kinds of them can be used in combination.

[0029] The dispersant is not particularly limited as long as it can be dissolved in the solvent described later, and nonionic dispersants, anionic dispersants, and cationic dispersants can be mentioned. Furthermore, if a high molecular weight type is used, long-term dispersion stabilization due to steric hindrance is expected.

[0030] Examples of nonionic dispersants include polyvinyl alcohol, polyvinyl pyrrolidone, cellulose resins, polyalkylene oxides, polyvinyl acetals, polyvinyl ethers, chitins, chitosans, starch, etc.

[0031] Polyvinyl alcohol may be of either the fully saponified type or the partially saponified type, and any degree of polymerization, from low molecular weight forms with a degree of polymerization of 1000 or less to high molecular weight forms with a degree of polymerization of 1500 or more, can be used. Specific examples of polyvinyl alcohol include K-type series (partially saponified type) such as Gohsenol KP-06 (saponification degree: 71.0 - 75.0 mol%) and KL-05 (saponification degree: 78.5 - 81.5 mol%) manufactured by Nippon Synthetic Chemical Industry Co., Ltd., G-type series (partially saponified type) such as GL-03 (saponification degree: 86.5 - 89.0 mol%), A-type series (quasi-fully saponified type) such as C-500 (saponification degree: 95.0 - 97.0 mol%) and A-300 (saponification degree: 97.0 - 98.5 mol%), and N-type series (fully saponified type) such as NL-05 (saponification degree: 98.5 mol% or more).

[0032] For polyvinylpyrrolidone, those having a weight average molecular weight (viscosity measurement method) in the range of 8000 - 3 million are preferred. Specifically, products such as Luvitec K17 (K value: 15.0 - 19.0, low molecular weight), K30 (K value 27.0 - 33.0), K80 (K value 74.0 - 82.0), K85 (K value 84.0 - 88.0), K90 (K value 88.0 - 92.0), K90HM (K value 92.0 - 96.0, high molecular weight) manufactured by BASF Japan Ltd., and K15, K30, K90, K120, etc. manufactured by Ashland Inc. can be mentioned. From the perspective of preventing viscosity increase, polyvinylpyrrolidone preferably has a K value of 150 or less, and more preferably a K value of 100 or less.

[0033] Examples of cellulose-based resins include alcohol-soluble butyrate of cellulose, cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxyethyl cellulose, nitrocellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, ammonium carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, etc.

[0034] Examples of the polyalkylene oxide include polyethylene oxide, polypropylene oxide, and polyethylene oxide - polypropylene oxide copolymer. Specific examples of the polyethylene oxide include those manufactured by Meisei Chemical Industry Co., Ltd., with trade names: Alcox R - 150 (average molecular weight: 100,000 - 170,000), R - 400 (average molecular weight: 180,000 - 250,000), R - 1000 (average molecular weight: 250,000 - 300,000), E - 30 (average molecular weight: 300,000 - 500,000), E - 45 (average molecular weight: 600,000 - 800,000), E - 60 (average molecular weight: 1,000,000 - 1,200,000), E - 75 (average molecular weight: 2,000,000 - 2,500,000), E - 100 (average molecular weight: 2,500,000 - 3,000,000), E - 130 (average molecular weight: 3,000,000 - 3,500,000), E - 160 (average molecular weight: 3,600,000 - 4,000,000), and E - 240 (average molecular weight: 4,000,000 - 5,000,000).

[0035] Specific examples of the polyethylene oxide - polypropylene oxide copolymer include those manufactured by Meisei Chemical Industry Co., Ltd., with trade names: Alcox EP - 10X (average molecular weight: about 1,000,000) and EP - 20X (average molecular weight: about 800,000). As the average molecular weight of the polyalkylene oxide increases, its viscosity increases, and accordingly, the viscosity of the conductive material dispersion also increases. From this perspective, the average molecular weight (weight - average molecular weight) of the polyalkylene oxide is, for example, 20,000 or more and 5,000,000 or less, preferably 3,000,000 or less, and more preferably 1,000,000 or less.

[0036] Examples of the anionic dispersant include formalin condensates of β - naphthalenesulfonic acid, formalin condensates of alkylnaphthalenesulfonic acid, formalin condensates of creosote oil sulfonic acid, styrene - acrylic acid, and styrene - maleic acid.

[0037] Examples of cationic dispersants include polymers having basic functional groups such as amino groups. For example, basic functional group-containing copolymers; high molecular weight unsaturated acid esters having basic functional groups, modified polyurethanes, modified polyesters, modified poly(meth)acrylates, modified polyacrylates, or (meth)acrylic copolymers; polyethyleneimine; polyoxyethylene alkylamines; alkanolamines; alkylammonium salts, and the like.

[0038] More specific examples of cationic dispersants include those manufactured by Ajinomoto Fine-Techno Co., Ltd., trade names: Ajisper PB821, PB822, PB824, PB881; those manufactured by BASF, trade names: Efka® PX4320, PX4310, PX4300, PX4330, PX4340, PX4700, PX4701, PX4731, PX4732, PU4063, PA4400, PA4401, PA4403; those manufactured by BYK, trade name: BYK-9077; those manufactured by Lubrizol, trade name: Solsperse 76500, and the like.

[0039] The above dispersants can be used alone or in combination of two or more.

[0040] The solvent used in the present invention is not particularly limited, and water, alcohol solvents (such as methanol, ethanol, butanol, isopropanol, phenol, etc.), amine solvents (such as triethylamine, trimethanolamine, etc.), ether solvents (such as dioxane, tetrahydrofuran, etc.), ether alcohol solvents (such as 2-methoxyethanol, ethoxyethanol, methoxyethoxyethanol, phenylethanol, etc.), glycol solvents (such as ethylene glycol, ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, etc.), ester solvents (such as methyl acetate, ethyl acetate, normal butyl acetate, etc.), carbonate solvents (such as ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, butylene carbonate, etc.), ketone solvents (such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc.), hydrocarbon solvents (such as toluene, benzene, xylene, hexane, cyclohexane, etc.), chlorine-containing hydrocarbon solvents (such as chloroform, dichloromethane, chlorobenzene, etc.), lower carboxylic acids (such as acetic acid, etc.), nitrogen-containing polar solvents (such as N,N-dimethylformamide, nitromethane, N-methylpyrrolidone, etc.), sulfur compound solvents (such as dimethyl sulfoxide, etc.), etc. can be used.

[0041] These solvents can be used alone or in combination of two or more.

[0042] The dispersion of the present invention contains at least a surface-treated conductive material, a dispersant, and a solvent, but may further contain other components. Examples of other components include pH adjusters, antifoaming agents, preservatives, surface conditioners, etc.

[0043] If the dispersion of the present invention is used, a smooth coating film with good compatibility with the binder resin and good conductivity can be obtained.

[0044] The mixing method, coating method, and drying method of the above mixture are not particularly limited, and can be appropriately selected from known methods according to the solvent, resin, and mixing amount used.

[0045] Method for producing the dispersion The production method of the dispersion of the present invention is not particularly limited as long as a dispersion satisfying the requirements of the dispersion of the present invention described above is produced. However, for example, it preferably includes the following steps (1) to (3). Step (1): A step of surface-treating a carbon-based conductive material with a compound having a catechol group in water Step (2): A step of mixing the conductive material obtained in step (1) with a dispersant and a solvent Step (3): A step of mechanically pulverizing the mixture obtained in step (2)

[0046] By including the above steps (1) to (3), a dispersion having excellent dispersibility, good stability over time, good conductivity, and low viscosity can be prepared. In addition, it also has excellent compatibility with various binders, suppresses aggregation during binder mixing, and can also obtain the effect of extending the pot life of the mixed solution.

[0047] Step (1) In the step of surface-treating a carbon-based conductive material with a compound having a catechol group in water, the mixing method is not particularly limited, and known stirring and mixing devices such as a dissolver and a high-shear mixer can be used. However, in order to uniformly treat carbon materials with strong aggregation force such as CNT, it is more preferable to use a high-shear mixer or a colloid mill.

[0048] The concentration of the carbon-based conductive material during surface treatment is not particularly limited as long as it can be uniformly stirred, and it is treated at a concentration of 0.1% to 50%.

[0049] The amount of the compound having a catechol group as the surface treatment agent is added in a ratio of 10 to 200 parts by mass with respect to the carbon-based conductive material, more preferably in the range of 50 to 150 parts by mass, and still more preferably in the range of 75% to 125%.

[0050] During surface treatment, the stirring time is 1 h to 72 h in consideration of the adsorption time of the compound having a catechol group and the influence of the environmental temperature.

[0051] Step 1 includes a washing step of the compound having an excess catechol group that was not used in surface treatment. The washing method is not particularly limited, and methods such as natural filtration, suction filtration, and centrifugation can be used.

[0052] Step 1 includes a step of drying the surface-treated carbon-based conductive material to mix it with various solvents. The drying method is not particularly limited, and methods such as shelf drying and airflow drying can be used.

[0053] Step (2) This is a step of mixing the conductive material obtained in Step (1) with a dispersant and a solvent. The mixing method is not particularly limited, and known stirring and mixing devices such as a dissolver and a high-shear mixer can be used. However, in order to uniformly process carbon materials with strong cohesive force such as CNTs, it is more preferable to use a high-shear mixer or a colloid mill. Note that the surface-treated carbon-based conductive material can be used alone or in combination of two or more.

[0054] The concentration of the surface-treated carbon-based conductive material in the mixed solution is 0.01 to 50 parts by mass. More preferably, it is 0.1 to 30 parts by mass. Even more preferably, it is 0.2 to 20 parts by mass.

[0055] The addition amount of the dispersant in the mixed solution is 10 to 200 parts by mass with respect to 100 parts by mass of the surface-treated carbon-based conductive material. More preferably, it is 20 to 150 parts by mass. Even more preferably, it is 30 to 100 parts by mass.

[0056] Step (3) This is a step of mechanically pulverizing the mixture obtained in Step (2). The mechanical pulverization method is not particularly limited, and dispersers such as a homogenizer, a roll mill, a bead mill, an ultrasonic disperser, and a high-pressure disperser can be used.

[0057] By performing the above steps (1) to (3), a dispersion liquid with excellent dispersibility, good stability over time, good conductivity, and low viscosity can be obtained.

[0058] Use It is suitable for the manufacture of lithium-ion batteries, sodium-ion batteries, semi-solid batteries, all-solid batteries, and capacitors. In addition, it can also be used for touch panels, conductive adhesives, antistatic agents, etc.

[0059] Moreover, by using the dispersion liquid of the present invention, a smooth coating film with good compatibility with the binder resin and good conductivity can be obtained.

Example

[0060] Hereinafter, the present invention will be described in detail based on examples and comparative examples. However, the present invention is not limited by the examples and comparative examples.

[0061] Example 1 2 g of TUBALL (SWCNT manufactured by OCSiAl) was added to 1000 mL of ion-exchanged water and mixed. Then, 2 g of dopamine hydrobromide was added and stirred. After the dopamine hydrobromide was dissolved, 1 M Tris-HCl buffer solution (pH 8.5) was added to adjust the pH to about 8.5. This mixed solution was stirred at 3000 rpm for 24 hours using a high-shear mixer (manufactured by Silver Son) to treat dopamine on the surface of TUBALL. After stirring, suction filtration was used for washing to remove excess dopamine. The obtained product was dried in an oven at 100 °C for 5 hours to obtain dopamine-treated TUBALL (T-1).

[0062] 0.8 part of the obtained dopamine-treated TUBALL (T-1), 1.2 parts of CMC 5A (carboxymethyl cellulose manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a dispersant, 98 parts of ion-exchanged water were put into a stainless-steel tank and mixed. The mixed liquid was pulverized for 5 hours using a paint shaker with Φ2.0 mm zirconia beads.

[0063] The physical properties of the dispersion were measured by the following method. Viscosity: BM viscometer, rotor #3, 60 rpm, 25 °C Surface resistance: The binder resin (TDR302A manufactured by ENEOS, solid content 40%) and the dispersion were mixed so that the CNT concentration became 0.1%, and applied onto a glass plate with an applicator. After drying in an oven at 100 °C for 30 minutes, the surface resistance was measured with a Loresta (manufactured by Mitsubishi Chemical). Binder miscibility: The state of the mixed solution prepared for surface resistance measurement after one day was visually confirmed.

[0064] Example 2 0.4 part of the dopamine-treated TUBALL (T-1) obtained in Example 1, 0.6 part of PVP K-30 (polyvinylpyrrolidone manufactured by Ashland) as a dispersant, and 99 parts of NMP were put into a stainless steel tank and mixed. The mixed solution was pulverized for 5 hours using a paint shaker with Φ2.0 mm zirconia beads.

[0065] The physical properties of the dispersion were measured by the following method. Viscosity: BM viscometer, rotor #3, 60 rpm, 25 °C Volume resistance: Using an active material (NC-03W manufactured by Toda Kogyo) and a binder resin (KF-7208 manufactured by Kureha, solid content 8%), an electrode paste with a CNT concentration of 0.1% was prepared and applied onto a PET film with an applicator. It was dried in a dryer at 100 °C for 20 minutes, and the volume resistance was measured with a Loresta (manufactured by Mitsubishi Chemical). Binder miscibility: The state of the mixed solution prepared for volume resistance measurement after one day was visually confirmed.

[0066] Example 3 0.4 part of the dopamine-treated TUBALL (T-1) obtained in Example 1, 0.6 part of PVP K-30 (polyvinylpyrrolidone manufactured by Ashland) as a dispersant, and 99 parts of NMP were put into a stainless steel tank and mixed. The mixed solution was pulverized by a high-pressure disperser (manufactured by Mirel, Mirel mini) at 100 MPa for 5 passes. The physical properties of the dispersion were measured by the method of Example 1.

[0067] Example 4 To 1000 mL of ion-exchanged water, 2 g of TUBALL (SWCNT manufactured by OCSiAl) was added and mixed. After that, 1 g of dopamine hydrobromide was added and stirred. After the dopamine hydrobromide was dissolved, 1 M Tris-HCl buffer (pH 8.5) was added to adjust the pH to about 8.5. This mixed solution was stirred at 3000 rpm for 24 hours using a high-shear mixer (manufactured by Silverson) to treat dopamine on the surface of TUBALL. After stirring, suction filtration was used for washing to remove excess dopamine. The obtained product was dried in an oven at 100 °C for 5 hours to obtain dopamine-treated TUBALL (T-2).

[0068] 0.8 part of the obtained dopamine-treated TUBALL (T-2), 1.2 parts of Cellogen 5A (carboxymethyl cellulose manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a dispersant, 98 parts of ion-exchanged water were put into a stainless steel tank and mixed. The mixed solution was milled for 5 hours using a paint shaker with Φ2.0 mm zirconia beads. The physical properties of the dispersion were measured by the method of Example 1.

[0069] Example 5 0.4 part of the dopamine-treated TUBALL (T-2) obtained in Example 4, 0.6 part of PVP K-30 (polyvinylpyrrolidone manufactured by Ashland) as a dispersant, 99 parts of NMP were put into a stainless steel tank and mixed. The mixed solution was milled for 5 hours using a paint shaker with Φ2.0 mm zirconia beads. The physical properties of the dispersion were measured by the method of Example 2.

[0070] Example 6 To 1000 mL of ion-exchanged water, 2 g of TUBALL (SWCNT manufactured by OCSiAl) was added and mixed. After that, 2 g of dopamine hydrochloride was added and stirred. After the dopamine hydrochloride was dissolved, 1M Tris-HCl buffer (pH 8.5) was added to adjust the pH to approximately 8.5. This mixture was stirred at 3000 rpm for 24 hours using a high-shear mixer (manufactured by Silverson) to treat the TUBALL surface with dopamine. After stirring, suction filtration was used for washing to remove the excess dopamine. The resulting product was dried in an oven at 100 °C for 5 hours to obtain dopamine-treated TUBALL (T-3).

[0071] 0.8 part of the obtained dopamine-treated TUBALL (T-3), 1.2 parts of cellogen 5A (carboxymethyl cellulose manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) as a dispersant, 98 parts of ion-exchanged water were put into a stainless steel tank and mixed. The mixed solution was pulverized for 5 hours using a paint shaker with Φ2.0 mm zirconia beads. The physical properties of the dispersion were measured by the method of Example 1.

[0072] Example 7 0.4 part of the dopamine-treated TUBALL (T-3) obtained in Example 6, 0.6 part of PVP K-30 (polyvinylpyrrolidone manufactured by Ashland) as a dispersant, 99 parts of NMP were put into a stainless steel tank and mixed. The mixed solution was pulverized for 5 hours using a paint shaker with Φ2.0 mm zirconia beads. The physical properties of the dispersion were measured by the method of Example 2.

[0073] Example 8 2 g of HX-N4-GT (MWCNT manufactured by Dowtech) was added to 1000 mL of ion-exchanged water and mixed. Then, 2 g of dopamine hydrobromide was added and stirred. After the dopamine hydrobromide was dissolved, 1M Tris-HCl buffer (pH 8.5) was added to adjust the pH to approximately 8.5. This mixture was stirred at 3000 rpm for 24 hours using a high-shear mixer (manufactured by Silverson), and dopamine was treated on the surface of HX-N4-GT. After stirring, suction filtration was used for washing to remove excess dopamine. The obtained product was dried in an oven at 100 °C for 5 hours to obtain dopamine-treated HX-N4-GT (H-1).

[0074] 2.2 parts of the obtained dopamine-treated HX-N4-GT (H-1), 1.9 parts of Celogen 5A (carboxymethyl cellulose manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) as a dispersant, 95.9 parts of ion-exchanged water were charged into a stainless steel tank and mixed. The mixed liquid was pulverized for 2 hours using Φ2.0 mm zirconia beads in a paint shaker.

[0075] The physical properties of the dispersion were measured by the following method. Viscosity: BM type viscometer, rotor #2, 60 rpm, 25 °C Surface resistance: The binder resin (TDR302A manufactured by ENEOS, solid content 40%) and the dispersion were mixed so that the CNT concentration became 0.1%, and applied on a glass plate with an applicator. After drying in an oven at 100 °C for 30 minutes, the surface resistance was measured with Loresta (manufactured by Mitsubishi Chemical). Binder miscibility: The state of the mixed liquid prepared for measuring the surface resistance was visually confirmed after 1 day.

[0076] Example 9 2.2 parts of the dopamine-treated HX-N4-GT (H-1) obtained in Example 8, 1.9 parts of PVP K-30 (polyvinylpyrrolidone manufactured by Ashland) as a dispersant, and 95.9 parts of NMP were charged into a stainless steel tank and mixed. The mixed liquid was pulverized for 2 hours using Φ2.0 mm zirconia beads in a paint shaker.

[0077] The physical properties of the dispersion were measured by the following method. Viscosity: BM type viscometer, rotor #3, 60 rpm, 25 °C Volume resistivity: Using the active material (NC-03W manufactured by Toda Kogyo) and the binder resin (KF-7208 manufactured by Kreha, solid content 8%), an electrode paste with a CNT concentration of 0.3% was prepared and applied onto a PET film using an applicator. It was dried at 100 °C for 20 minutes in a dryer, and the volume resistivity was measured using Loresta (manufactured by Mitsubishi Chemical). Binder miscibility: Visually confirmed the state of the mixed solution prepared for volume resistivity measurement after one day.

[0078] Example 10 2 g of GTCO-220 (MWCNT manufactured by Dainichi Nanotech) was added to 1000 mL of ion-exchanged water and mixed. After that, 2 g of dopamine hydrobromide was added and stirred. After the dopamine hydrobromide was dissolved, 1 M Tris-HCl buffer (pH 8.5) was added to adjust the pH to approximately 8.5. This mixed solution was stirred at 3000 rpm for 24 hours using a high shear mixer (manufactured by Silverson) to treat dopamine on the surface of GTCO-220. After stirring, suction filtration was used for washing to remove the excess dopamine. The obtained product was dried in an oven at 100 °C for 5 hours to obtain dopamine-treated GTCO-220 (G-1).

[0079] One part of the obtained dopamine-treated GTCO-220 (G-1), one part of the untreated conductive material SuperP Li, 0.6 part of PVP (polyvinylpyrrolidone manufactured by Ashland) as a dispersant, and 97.4 parts of NMP were put into a stainless steel tank and mixed. The mixed solution was ground for 5 hours using a paint shaker with Φ2.0 mm zirconia beads.

[0080] The physical properties of the dispersion were measured by the following method. Viscosity: BM-type viscometer, rotor #2, 60 rpm, 25 °C Volume Resistivity: An electrode paste with a CNT concentration of 0.5% was prepared using an active material (NC-03W, manufactured by Toda Kogyo) and a binder resin (KF-7208, manufactured by Kureha, solid content 8%). The paste was applied onto a PET film using an applicator and dried in a dryer at 100 °C for 20 minutes. The volume resistivity was measured using a Loresta (manufactured by Mitsubishi Chemical). Binder Mixability: The state of the mixed solution prepared for volume resistivity measurement was visually confirmed one day later.

[0081] Example 11 10 g of Ketjenblack EC600JD (manufactured by Lion) was added to 1000 mL of ion-exchanged water and mixed. After that, 4 g of dopamine hydrobromide was added and stirred. After the dopamine hydrobromide was dissolved, 1M Tris-HCl buffer (pH 8.5) was added to adjust the pH to approximately 8.5. This mixed solution was stirred at 3000 rpm for 24 hours using a high-shear mixer (manufactured by Silverson) to treat the surface of Ketjenblack EC600JD with dopamine. After stirring, suction filtration was used for washing to remove the excess dopamine. The obtained product was dried in an oven at 100 °C for 5 hours to obtain dopamine-treated Ketjenblack EC600JD (K-1).

[0082] 4 parts of the obtained dopamine-treated Ketjenblack EC600JD (K-1), 7 parts of Solsperse 76500 (a polymeric dispersant manufactured by Lubrizol) as a dispersant, and 89 parts of toluene were put into a stainless-steel tank and mixed. The mixed solution was pulverized using a paint shaker with Φ2.0 mm zirconia beads for 2 hours.

[0083] The physical properties of the dispersion were measured by the following method. Viscosity: BM viscometer, rotor #2, 60 rpm, 25 °C Surface Resistivity: The dispersion was applied onto a glass plate using a bar coater #60 and dried in a dryer at 100 °C for 20 minutes. The surface resistivity was measured using a Loresta (manufactured by Mitsubishi Chemical).

[0084] Example 12 15 g of Li-335 (acetylene black manufactured by Denka) was added to 1000 mL of ion-exchanged water and mixed. Then, 5 g of dopamine hydrobromide was added and stirred. After the dopamine hydrobromide was dissolved, 1 M Tris-HCl buffer (pH 8.5) was added to adjust the pH to approximately 8.5. This mixed solution was stirred at 3000 rpm for 24 hours using a high-shear mixer (manufactured by Silverson) to treat dopamine on the surface of Li-335. After stirring, suction filtration was used for washing to remove excess dopamine. The obtained product was dried in an oven at 100 °C for 5 hours to obtain dopamine-treated Li-335 (A-1).

[0085] 17 parts of the obtained dopamine-treated Li-335 (A-1), 2 parts of Methocel SM-04 (methyl cellulose manufactured by Shin-Etsu Chemical Co., Ltd.) as a dispersant, and 81 parts of NMP were put into a stainless steel tank and mixed. The mixed solution was pulverized for 2 hours using a paint shaker with Φ2.0 mm zirconia beads.

[0086] The physical properties of the dispersion were measured by the following method. Viscosity: BM type viscometer, rotor #3, 60 rpm, 25 °C Surface resistance: Using a binder resin (KF-7208 manufactured by Kureha, solid content 8%), a mixed solution with an acetylene black concentration of 8% was prepared and applied onto a glass plate using an applicator. It was dried in a dryer at 100 °C for 20 minutes, and the surface resistance was measured using Loresta (manufactured by Mitsubishi Chemical). Binder miscibility: The state of the mixed solution prepared for surface resistance measurement after 1 day was visually confirmed.

[0087] Comparative Example 1 In Example 1, the same operations as in Example 1 were performed except that untreated TUBALL was used.

[0088] Comparative Example 2 In Example 2, the same operations as in Example 2 were performed except that untreated TUBALL was used.

[0089] Comparative Example 3 In Example 3, the same operations as in Example 2 were performed except that untreated TUBALL was used.

[0090] Comparative Example 4 In Example 8, the same operations as in Example 7 were performed except that untreated HX-N4-GT was used.

[0091] Comparative Example 5 In Example 9, the same operations as in Example 8 were performed except that untreated HX-N4-GT was used.

[0092] Comparative Example 6 In Example 10, the same operations as in Example 9 were performed except that untreated GTCO-220 was used.

[0093] Comparative Example 7 In Example 11, the same operations as in Example 10 were performed except that untreated Ketjenblack EC600JD was used.

[0094] Comparative Example 8 In Example 12, the same operations as in Example 11 were performed except that untreated Li-335 was used.

[0095] From Tables 1 and 2, it was confirmed that by using a carbon-based conductive material surface-treated with a compound containing a catechol group, the dispersion viscosity in water and organic solvents can be reduced by using a general dispersant, a dispersion liquid with good stability over time can be prepared, and furthermore, the compatibility with various binders is also excellent and aggregation during binder mixing is suppressed.

[0096] [Table 1]

[0097] [Table 2]

Claims

1. A conductive carbon material dispersion in which conductive carbon material powder surface-treated with a compound having a catechol group is dispersed in water and / or an organic solvent.

2. The conductive carbon material dispersion according to claim 1, wherein the conductive carbon material powder is at least one carbon material powder selected from the group consisting of carbon nanotubes, carbon fibers, graphite, graphene, acetylene black, ketjen black, and furnace black.

3. The conductive carbon material dispersion according to claim 1, wherein the compound having a catechol group is one or more compounds selected from the group consisting of catechol, dopamine hydrochloride, dopamine hydrobromide, dopa, norepinephrine, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol, and 4-tert-butylpyrocatechol.

4. The conductive carbon material dispersion according to claim 3, wherein the compound having a catechol group is dopamine hydrobromide.

5. A method for producing a surface-treated carbon material powder, characterized by surface-treating conductive carbon material powder with a compound having a catechol group.

6. The method for producing a surface-treated carbon material powder according to claim 5, wherein the surface treatment is carried out in water.

7. The method for producing a conductive carbon material powder according to claim 5, wherein the conductive carbon material powder is at least one carbon material powder selected from the group consisting of carbon nanotubes, carbon fibers, graphite, graphene, acetylene black, ketjen black, and furnace black.

8. The method for producing a conductive carbon material powder according to claim 5, wherein the compound having a catechol group is one or more compounds selected from the group consisting of catechol, dopamine hydrochloride, dopamine hydrobromide, dopa, norepinephrine, 3,4-dihydroxybenzoic acid, 3,4-dihydroxyphenylacetic acid, caffeic acid, 4-methylcatechol, and 4-tert-butylpyrocatechol.

9. The method for producing a conductive carbon material powder according to claim 8, wherein the compound having a catechol group is dopamine hydrobromide.

10. A dispersion containing the conductive carbon material powder obtained by the production method according to claim 5, a dispersant, and a dispersion medium.

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