Conductive material composition, method for producing conductive material composition, slurry for secondary battery electrode containing said conductive material composition, electrode, and secondary battery

Abstract

Disclosed is a conductive material composition which contains a conductive material that is composed of at least one selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, and graphene, a resin type dispersant, a binder resin, and a solvent, wherein: the binder resin contains a water-soluble resin (X) that contains a copolymer having a constituent unit based on a hydroxyl group-containing monomer and a constituent unit based on an acid group-containing monomer; and the content of the binder resin with respect to the conductive material is 30 times by mass to 1,000 times by mass inclusive.

Description

Conductive material composition, method for manufacturing the conductive material composition, slurry for secondary battery electrode containing the conductive material composition, electrode, and secondary battery

[0001] The present invention relates to a conductive material composition, a method for manufacturing the same, a slurry for a secondary battery electrode containing the conductive material composition, an electrode, and a secondary battery.

[0002] Secondary batteries such as lithium-ion secondary batteries are rapidly expanding into hybrid vehicles, electric vehicles, household storage batteries, etc., taking advantage of their high energy density and ability to be repeatedly charged and discharged, and their range of use is expanding. In recent years, with the progress of high-performance and miniaturization of various portable electronic devices and communication devices, there is an increasing demand for secondary batteries that are small, lightweight, have a higher capacity, and have further improved various battery characteristics such as cycle characteristics and discharge rate characteristics. For the purpose of further improving performance, improvements in various battery components such as electrodes are being studied. The capacity of a lithium-ion secondary battery largely depends on the positive electrode active material and the negative electrode active material, which are the main materials, and research on various materials is active. However, the charge capacities of the active materials that have been put into practical use have all reached near the theoretical values. On the other hand, if the amount of active material filled in the battery can be increased, the capacity can be simply increased. Therefore, attempts have been made to reduce the addition amounts of conductive materials and binders that do not directly contribute to the battery capacity. Since the conductive material forms a conductive path inside the battery and plays a role such as preventing the disconnection of the conductive path due to the expansion and contraction of the active material particles by connecting the active material particles, from the perspective of forming an efficient conductive network while reducing the addition amount and maintaining the battery capacity and battery characteristics, the use of the conductive material as a dispersion liquid has been studied. In addition, as a conductive material, carbon nanotubes, which are a type of micro carbon fiber, have attracted attention because of their large specific surface area and the ability to efficiently form the above-mentioned conductive network with a small amount.

[0003] For example, Patent Document 1 proposes a carbon nanotube dispersion containing carbon nanotubes, a specific carboxymethyl cellulose or its salt, and water, in which the product of the complex elastic modulus X and the phase angle Y is within a predetermined range. Patent Document 2 discloses a carbon nanotube dispersion containing specific carbon nanotubes, a predetermined amount of a dispersant, and a solvent, in which the complex elastic modulus and the phase angle at 25°C and a frequency of 1 Hz are within a specific range. Patent Document 3 discloses a conductive material dispersion containing single-walled carbon nanotubes having a predetermined average outer diameter, a copolymer containing a predetermined amount of units derived from (meth)acrylonitrile, a specific base, and water, in which the solid content mass ratio of the copolymer and the base is within a specific range. Patent Document 4 discloses a carbon nanotube dispersion containing at least carbon nanotubes in which the median diameter and the dispersion limit median diameter are in a predetermined relationship, a water-soluble polymer material, and a dispersion medium. Further, Patent Document 5 discloses a method for producing a carbon material dispersion having a step 1 of obtaining a wet mixture by stirring a raw material containing a carbon material containing carbon nanotubes, a specific dispersant, and a liquid medium, and a step 2 of dispersing the wet mixture by performing a two-stage treatment using a high-pressure homogenizer of a specific type while changing the inner diameter of the discharge nozzle, the treatment pressure, and the discharge frequency.

[0004] JP-A-2023-024526 JP-A-2022-063234 JP-A-2021-190330 JP-A-2023-028960 JP-A-2023-054746

[0005] The dispersions disclosed in Patent Documents 1 to 4 are said to have excellent dispersibility, compatibility with binders, storage stability, conductivity, and adhesion, and when used as compositions for secondary battery electrodes, they can provide electrode films, electrodes, and even secondary batteries with excellent output and cycle characteristics. Furthermore, the manufacturing method in Patent Document 5 is said to be able to easily produce a dispersion with excellent viscosity stability in which carbon materials are well dispersed without substantially forming coarse aggregates. However, carbon nanotubes are highly hydrophobic, and when their specific surface area is large, their cohesive force becomes strong, making them difficult to disperse in water or water-containing solvents. In addition, the dispersibility and dispersion stability of electrode compositions prepared using the dispersions disclosed in Patent Documents 1 to 5 still have room for improvement depending on the selection of active material species. Furthermore, from the viewpoint of maintaining battery characteristics, there is still room for improvement in the dispersibility of carbon nanotubes in the dispersion and its long-term dispersion stability depending on the selection of binder species that have binding force capable of accommodating the volume changes associated with charging and discharging of the positive electrode active material and negative electrode active material.

[0006] The inventors have found that a composition containing a specific conductive material containing carbon nanotubes, a resin-type dispersant, and a specific water-soluble binder resin, wherein the content of the binder resin relative to the conductive material is within a specific range, preferably with water as the solvent, is produced by mixing these materials in a predetermined order, preferably using a specific high-pressure disperser, and that this composition exhibits excellent dispersibility. Furthermore, they have found that when such a composition is used as a slurry for secondary battery electrodes, the resulting active material layer (electrode film) exhibits excellent adhesion to the current collector, swelling resistance, and uniformity, as well as excellent battery characteristics such as charge-discharge efficiency and capacity retention rate, thus completing the present invention. The object of the present invention is to provide a conductive material composition and a method for producing the same, as well as a slurry for secondary battery electrodes that can prepare a slurry for secondary battery electrodes that exhibits excellent dispersibility of the conductive material and excellent dispersion stability of the active material and conductive material. Another object of the present invention is to provide an electrode formed from such a slurry for secondary battery electrodes, and a secondary battery equipped with such an electrode.

[0007] The present invention has the following embodiments: [1] A conductive material composition comprising a conductive material selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, and graphene, a resin-type dispersant, a binder resin, and a solvent, wherein the binder resin comprises a water-soluble resin (X) having a copolymer having constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers, and the content of the binder resin relative to the conductive material is 3 times by mass or more and 1000 times by mass or less. [2] The conductive material composition according to [1], wherein the content of the resin-type dispersant relative to the conductive material is 1 time by mass or more and 4 times by mass or less. [3] The conductive material composition according to [1] or [2], wherein the solvent is water. [4] A conductive material composition according to any one of [1] to [3], wherein the conductive material is a single-walled carbon nanotube, and the volume-based cumulative 10% diameter (D10) in the particle size distribution obtained by laser diffraction is in the range of 0.01 to 20 μm, the volume-based cumulative 50% diameter (D50) is in the range of 0.01 to 50 μm, and the volume-based cumulative 90% diameter (D90) is in the range of 0.02 to 200 μm. [5] The conductive material composition according to [4], wherein the ratio of D10 to D50 is 0.20 or more, and D90 is less than 22.0 μm. [6] In the Raman spectrum of a dried film formed by coating the conductive material composition onto a substrate and drying it, the range is 1320 to 1360 cm⁻¹. －１ For the maximum peak intensity ratio D within the range of 1520-1560 cm －１A conductive material composition according to any one of [1] to [5], wherein the ratio of the maximum peak intensity G within the range (G / D) is 40 to 160. [7] A conductive material composition according to any one of [1] to [6], wherein the water-soluble resin (X) contains a copolymer having constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers, the weight-average molecular weight measured using an aqueous GPC measuring device is 700,000 or more, and the swelling rate after immersing a dry film of the copolymer in a carbonate-based mixed solvent (EC (ethylene carbonate) / DEC (diethylene carbonate) = 50 / 50 (mass ratio)) at 45°C for 72 hours is 0 to 10% by mass. [8] A conductive material composition according to any one of [1] to [7], wherein the hydroxyl group-containing monomer is at least one selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate. [9] A conductive material composition according to any one of [1] to [8], wherein the acid group-containing monomer is neutralized with a basic composition or a light metal salt.

[10] A conductive material composition according to any one of [1] to [9], wherein the acid group-containing monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, monomethylmaleic acid, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate, and itaconic acid.

[11] A conductive material composition according to any one of [1] to

[10] , wherein the water-soluble resin (X) further comprises a constituent unit based on at least one selected from the group consisting of acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, and N-hydroxymethylacrylamide.

[12] A conductive material composition according to any one of [1] to

[11] , wherein the total content of the constituent unit based on the hydroxyl group-containing monomer and the constituent unit based on the acid group-containing monomer is 5 to 80% by mass, relative to the total amount of the water-soluble resin (X).

[13] A conductive material composition according to any one of [1] to

[12] , wherein the binder resin is a resin composition further comprising an aqueous latex resin (Y).

[14] The conductive material composition according to

[13] , wherein the aqueous latex resin (Y) is one or more of styrene-butadiene copolymer (SBR), styrene acrylate copolymer, and acrylate copolymer.

[15] A conductive material composition according to any one of [1] to

[14] , wherein the amount of precipitate when centrifuged at 10,000 rpm for 10 minutes is 1% by mass or less relative to the amount of solids before centrifugation.

[16] A conductive material composition according to any one of [1] to

[15] for forming electrodes of a secondary battery.

[0008]

[17] A method for producing any of the conductive material compositions of [1] to

[16] , comprising the following steps: Step 1: Mix a conductive material, which is at least one selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, and graphene, a resin-type dispersant, and a solvent using a high-pressure disperser at a pressure in the range of 50 to 270 MPa to obtain a dispersion. Step 2: Mix the dispersion obtained in Step 1 with a binder resin containing a water-soluble resin (X) having a copolymer having constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers using a high-pressure disperser at a pressure in the range of 15 to 170 MPa to obtain a conductive material composition containing the conductive material, the resin-type dispersant, the binder resin, and the solvent.

[18] A method for producing the conductive material composition of

[17] , wherein the conductive material is a single-walled carbon nanotube, and in the conductive material composition obtained in step 2, the volume-based cumulative 10% diameter (D10) in the volume-based particle size distribution obtained by laser diffraction of the conductive material is in the range of 0.01 to 20 μm, the volume-based cumulative 50% diameter (D50) is in the range of 0.01 to 50 μm, and the volume-based cumulative 90% diameter (D90) is in the range of 0.02 to 200 μm.

[19] A slurry for a secondary battery electrode comprising any of the conductive material compositions of [1] to

[16] and an active material.

[20] An electrode comprising at least a current collector and an active material layer formed by hardening the electrode slurry of

[19] .

[21] A secondary battery comprising the electrode of

[20] .

[0009] The present invention provides a conductive material composition with excellent dispersibility and a method for producing the same. A slurry for secondary battery electrodes containing such a conductive material composition and an active material exhibits excellent dispersion stability of the active material and conductive material, and the active material layer (electrode film) formed by the curing of such electrode slurry exhibits excellent adhesion to the current collector, swelling resistance, and uniformity. Therefore, a secondary battery equipped with an electrode having such an active material layer exhibits excellent battery characteristics such as charge / discharge efficiency and capacity retention rate.

[0010] The present invention relates to a conductive material composition (hereinafter also simply referred to as "the conductive material composition of the present invention") comprising a conductive material selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, and graphene, a resin-type dispersant, a binder resin, and a solvent, wherein the binder resin comprises a water-soluble resin (X) having a copolymer having constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers, and the content of the binder resin relative to the conductive material is 3 times by mass or more and 1000 times by mass or less. Embodiments of the present invention will now be described in detail. In this specification, numerical ranges indicated using "~" indicate a range that includes the numerical values ​​before and after "~" as the minimum and maximum values, respectively. First, each component of the conductive material composition of the present invention will be described.

[0011] The conductive material contained in the conductive material composition of the present invention is at least one selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, and graphene. In this specification, carbon nanotubes will also be referred to as "CNT".

[0012] CNTs have a cylindrical shape formed by winding planar graphite. Single-walled CNTs have a structure in which one layer of graphite is wound, while multi-walled CNTs have a structure in which two or more layers of graphite are wound. In addition, even if the side walls of the CNT have a graphite structure, at least a part of them may have an amorphous structure. Examples of CNT shapes include needle-shaped, cylindrical tube-shaped, fishbone-shaped, playing card-shaped (platelet), and coil-shaped. These shapes may be one type only or two or more types may be mixed. Among these, needle-shaped or cylindrical tube-shaped are preferred. Examples of CNT forms include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. CNTs may have one of these forms alone or two or more forms in combination.

[0013] Examples of carbon black include acetylene black, furnace black, hollow carbon black, channel black, thermal black, and Ketjen black. The carbon black may be neutral, acidic, or basic, and may have undergone treatments such as oxidation or graphitization.

[0014] The conductive material is at least one selected from the group consisting of single-walled carbon nanotubes (WNTs), multi-walled carbon nanotubes (WNTs), carbon black, and graphene, and two or more may be used in combination. Single-walled carbon nanotubes or multi-walled carbon nanotubes are preferred as the conductive material, and single-walled carbon nanotubes are more preferred. The particle size distribution of the conductive material is preferably such that the volume-based cumulative 10% diameter (D10) obtained by laser diffraction is in the range of 0.01 to 20 μm, the volume-based cumulative 50% diameter (D50) is in the range of 0.01 to 50 μm, and the volume-based cumulative 90% diameter (D90) is in the range of 0.02 to 200 μm. D10 is preferably in the range of 0.01 μm or more and less than 20 μm, more preferably in the range of 0.01 μm or more and less than 0.1 μm, and even more preferably in the range of 0.01 μm or more and less than 0.05 μm. D50 is preferably in the range of 0.01 μm or more and less than 50 μm, more preferably in the range of 0.01 μm or more and less than 0.5 μm, and even more preferably in the range of 0.02 μm or more and less than 0.2 μm. D90 is preferably 0.02 μm or more, more preferably 0.04 μm or more. D90 is preferably less than 200 μm, more preferably less than 100 μm, and even more preferably 30 μm or less. In other words, D90 is more preferably in the range of 0.04 μm or more and less than 100 μm, and even more preferably in the range of 0.02 μm or more and 30 μm or less.

[0015] In particular, it is preferable that the conductive material is single-walled carbon nanotubes (WNTs), and that the volume-based cumulative 10% diameter (D10) in the particle size distribution obtained by laser diffraction is in the range of 0.01 to 20 μm, the volume-based cumulative 50% diameter (D50) is in the range of 0.01 to 50 μm, and the volume-based cumulative 90% diameter (D90) is in the range of 0.02 to 200 μm. Furthermore, if the conductive material is single-walled carbon nanotubes (WNTs), it is even more preferable that its D10 is in the range of 0.01 to 0.1 μm, its D50 is in the range of 0.01 to 30 μm, and its D90 is in the range of 0.05 to 100 μm.

[0016] Furthermore, it is preferable that the ratio of D10 to D50 of the conductive material is 0.20 or greater, and that D90 is less than 200 μm. More preferably, the ratio of D10 to D50 of the conductive material is 0.20 or greater and 1.0 or less. When D10, D50, and D90 of the conductive material satisfy the above-mentioned numerical ranges and relationships, the dispersibility and dispersion stability of the conductive material composition of the present invention are more easily improved. In addition, the slurry for secondary battery electrodes described later, which contains the conductive material composition of the present invention and the active material, exhibits excellent dispersion stability, excellent uniformity of the active material layer formed from the slurry for secondary battery electrodes, and furthermore, a secondary battery having an electrode comprising such an active material layer and a current collector tends to exhibit excellent battery characteristics.

[0017] In this specification, D10, D50, and D90 of the conductive material are values ​​obtained by measuring the particle diameters at the points on the cumulative curve where the cumulative volume reaches 10%, 50%, and 90%, respectively, using a laser diffraction particle size distribution analyzer "MASTERSIZER LMS-3000" manufactured by MALVERN PANALITICAL, under the measurement conditions of "particle type: non-spherical, refractive index 1.75, absorptive rate 0.01, dispersion solvent: water, refractive index 1.33".

[0018] Furthermore, in the Raman spectrum of a dried film formed by coating a substrate with the conductive material composition of the present invention and drying it, the range was 1320 to 1360 cm⁻¹. －１ For the maximum peak intensity ratio D within the range of 1520-1560 cm －１ The ratio of the maximum peak intensity G within the specified range (G / D) is preferably 40 to 160. When this ratio (G / D) is within the specified range, the dispersibility and dispersion stability of the conductive material composition of the present invention, in which the conductive material is preferably single-walled carbon nanotubes, is more easily improved while maintaining the crystal structure of the carbon nanotubes, and good conductivity is more easily achieved. The Raman spectrum was obtained by placing the above-mentioned dried film on a Raman microscope ("NRS-5500", manufactured by JASCO Corporation) and measuring under the following conditions: excitation wavelength 532 nm, light-reducing filter 5%, laser intensity 0.6 mW, objective lens magnification 20x, slit width 100 × 1000 μm, at a range of 100 to 3000 cm⁻¹. －１ Measurements were taken within the specified range.

[0019] The resin-type dispersant contained in the conductive material composition of the present invention plays a role in improving the dispersion stability of the conductive material in the dispersion obtained by processing with a high-pressure disperser under specific conditions in step 1 of the method for manufacturing the conductive material composition of the present invention, as described later. Furthermore, through a synergistic effect with the binder resin containing a water-soluble resin (X) that is mixed by processing with a high-pressure disperser under specific conditions in step 2, it plays a role in improving the dispersion stability of the conductive material and active material when preparing a slurry for secondary battery electrodes containing the conductive material composition of the present invention and the active material, thereby improving the battery characteristics of the secondary battery equipped with the resulting electrode.

[0020] Examples of resin-type dispersants include cellulose derivatives such as methylcellulose, ethylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, ethylhydroxyethylcellulose, nitrocellulose, cyanoethylcellulose, cellulose acetate, cellulose acetate butyrate, cellulose butyrate, and alkali metal salts thereof; polystyrene sulfonic acid and its salts; polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone (PVP), polyacrylonitrile polymers, and polyvinylidene fluoride (PVDF).

[0021] From the viewpoint that the solvent constituting the conductive material composition of the present invention is preferably water, or a mixed solvent of water and an organic solvent miscible with water (aqueous medium), as described later, a water-soluble resin-type dispersant is preferred, and a resin-type dispersant that is an anionic water-soluble polymer, such as carboxymethylcellulose (CMC) or its salts, or polystyrene sulfonic acid or its salts, is more preferred. When CMC or its salts are used as the resin-type dispersant, it is preferable that the weight-average molecular weight of CMC is 10,000 or more and 1,000,000 or less, from the viewpoint that the balance of intermolecular forces between CMC and the conductive material, and between CMC and the solvent (water or aqueous medium) is improved, and the dispersion stability of the conductive material in the conductive material composition of the present invention is improved.

[0022] The conductive material composition of the present invention comprises a water-soluble resin (X) in which the binder resin contains a copolymer (hereinafter also simply referred to as "copolymer α") having constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers. The weight-average molecular weight (Mw) of copolymer α contained in the water-soluble resin (X), as measured using an aqueous GPC measuring device, is preferably 700,000 or more, more preferably 750,000 to 1,500,000, and even more preferably 800,000 to 1,200,000. When the Mw of such copolymer is 700,000 or more, the dispersion stability of the conductive material composition of the present invention tends to be good. Furthermore, the swelling resistance at high temperatures of the active material layer (electrode film) formed from the slurry for secondary battery electrodes described later, which contains the conductive material composition of the present invention, is improved, and the expansion rate is easily suppressed.

[0023] For aqueous GPC measurement devices, for example, the "Shimadzu / L20 system" manufactured by Shimadzu Corporation can be used. Using a column with a common polymer-based packing material such as polyhydroxymethacrylate (for example, the SB-806 HQ, SB-806M HQ, etc. from the "Shodex OHpak" series manufactured by Showa Denko Corporation), and using a neutral salt solution (concentration of about 0.1 to 0.3 mol / L) such as aqueous sodium nitrate solution, aqueous sodium hydrogen hydrochloride solution, aqueous sodium sulfate solution, or phosphate buffer as the eluent, Mw can be measured as a converted value based on a calibration curve prepared with standard polystyrene or pullulan (for example, "STANDARD P-82 (Pullulan)," etc., manufactured by Showa Denko Corporation).

[0024] Furthermore, the swelling rate after immersing a dry film of copolymer α containing the water-soluble resin (X) in a carbonate-based mixed solvent (EC (ethylene carbonate) / DEC (diethylene carbonate) = 50 / 50 (mass ratio)) at 45°C for 72 hours is preferably 0 to 10% by mass, more preferably 0.1 to 6% by mass, and even more preferably 0.1 to 4% by mass. When the swelling rate is within the above range, for example, the adhesion of the active material layer (electrode film) formed from a slurry for secondary battery electrodes, described later, which contains the conductive material composition of the present invention, to a current collector such as copper is easily improved. Moreover, secondary batteries having such electrodes tend to exhibit good charge-discharge characteristics even at high cycle counts. A lower swelling rate is preferable. The swelling rate described above is determined by preparing a dried film (dried coating) from the conductive material composition of the present invention, for example by drying it at 25°C for 72 hours, then at 150°C for 30 minutes, and then immersing this dried film in a carbonate-based mixed solvent (EC / DEC = 50 / 50 (mass ratio)) at 45°C for 72 hours, and measuring the rate of change in the film mass before and after immersion.

[0025] The hydroxyl group-containing monomer in copolymer α is preferably at least one selected from the group consisting of, for example, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate, with 2-hydroxyethyl acrylate being more preferred. The content of the constituent units based on the hydroxyl group-containing monomer relative to the total amount of monomers constituting copolymer α is preferably in the range of 20 to 80% by mass, and more preferably in the range of 30 to 70% by mass. When the content of the constituent units based on the hydroxyl group-containing monomer is within the above range, the dispersion stability of the conductive material composition of the present invention tends to be good. Furthermore, the swelling resistance at high temperatures of the active material layer (electrode film) formed from the slurry for secondary battery electrodes described later, which contains the conductive material composition of the present invention, is improved, and the rate of expansion is easily suppressed.

[0026] In copolymer α, the acid group-containing monomer is preferably neutralized with a basic composition or a light metal salt. Examples of basic compositions include ammonia, and examples of light metal salts include alkali metal salts such as sodium. The acid group-containing monomer in copolymer α preferably has a carboxyl group as the acid group, and is preferably at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, monomethylmaleic acid, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate, maleic acid, and itaconic acid, with acrylic acid being more preferred. The content of constituent units based on the acid group-containing monomer relative to the total amount of monomers constituting copolymer α is preferably in the range of 10 to 60% by mass, and more preferably in the range of 20 to 50% by mass. Preferably, when the content of constituent units based on the acid group-containing monomer, neutralized with a basic composition or a light metal salt, is within the above range, the dispersion stability of the conductive material composition of the present invention tends to be good. Furthermore, the swelling resistance at high temperatures of the active material layer (electrode film) formed from the slurry for secondary battery electrodes described later, which contains the conductive material composition of the present invention, is improved, and the rate of expansion is easily suppressed.

[0027] The total content of constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers relative to the total amount of water-soluble resin (X) is preferably 5 to 80% by mass, and more preferably 10 to 70% by mass. When the total content is within this range, the dispersion stability of the conductive material composition of the present invention tends to be good. In addition, the swelling resistance at high temperatures of the active material layer (electrode film) formed from the slurry for secondary battery electrodes described later, which contains the conductive material composition of the present invention, is improved, and the rate of expansion is easily suppressed.

[0028] The copolymer α contained in the water-soluble resin (X) may further contain structural units based on monomers other than hydroxyl group-containing monomers and acid group-containing monomers. Preferably, such other monomers are at least one selected from the group consisting of acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, and N-hydroxymethylacrylamide, with acrylamide being more preferred from the viewpoint of easily improving the toughness of the film formed from the conductive material composition of the present invention. If the copolymer further contains structural units based on other monomers, the content thereof is preferably 80% by mass or less relative to the total amount of monomers constituting the copolymer α, more preferably in the range of 2 to 60% by mass, and even more preferably in the range of 5 to 40% by mass. When the content of other monomers is within the above range, the swelling resistance at high temperatures of the active material layer (electrode film) formed from the slurry for secondary battery electrodes, described later, containing the conductive material composition of the present invention, is improved, and the expansion rate is easily suppressed. The copolymer α contained in the water-soluble resin (X) is obtained by copolymerizing a hydroxyl group-containing monomer and an acid group-containing monomer, and other monomers as needed, in the presence of a solvent such as water, using a polymerization initiator such as ammonium persulfate.

[0029] The binder resin constituting the conductive material composition of the present invention may be a resin composition further comprising a water-soluble resin (X) and an aqueous latex resin (Y). The aqueous latex resin (Y) preferably contains one or more of styrene-butadiene copolymer (SBR), styrene acrylate copolymer, and acrylate copolymer, with styrene acrylate copolymer being more preferred.

[0030] Examples of styrene acrylate copolymers and acrylate copolymers include methyl acrylate, methyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, acrylamide, acrylonitrile, and glycidyl methacrylate. Among these, it is preferable to include constituent units based on butyl acrylate. The content of styrene-based constituent units in the styrene acrylate copolymer is preferably 40 to 65% by mass, and more preferably 50 to 60% by mass. The content of butyl acrylate-based constituent units is preferably 20 to 40% by mass, and more preferably 25 to 35% by mass. Furthermore, from the viewpoint of ensuring good adhesion between the active material layer (electrode film) formed from the slurry for secondary battery electrodes containing the conductive material composition of the present invention (described later) and the current collector, it is more preferable that the content of styrene-based constituent units in the styrene acrylate copolymer is 40 to 60% by mass, and the content of butyl acrylate-based constituent units is 20 to 40% by mass. The styrene acrylate copolymer and the acrylate copolymer may further have constituent units based on acrylic acid or methacrylic acid. When the binder resin constituting the conductive material composition of the present invention is a resin composition further containing an aqueous latex resin (Y), the content of the aqueous latex resin (Y) is preferably in the range of 20 to 80% by mass, and more preferably in the range of 30 to 70% by mass, relative to the entire binder composition.

[0031] In this specification, resin-type dispersants and binder resins are distinguished. However, from the viewpoint that the conductive material composition of the present invention exhibits the effect of improving the dispersion stability of the conductive material, and that a slurry for secondary battery electrodes containing the conductive material composition of the present invention and an active material exhibits excellent dispersion stability, as well as excellent adhesion, swelling resistance, and uniformity of the formed active material layer with the current collector, and furthermore, that a secondary battery having an electrode comprising such an active material layer and a current collector exhibits excellent battery characteristics, the resin-type dispersant may have at least a part of the role of a binder resin, and the binder resin may have at least a part of the role of a resin-type dispersant.

[0032] The solvent constituting the conductive material composition of the present invention may be water, an organic solvent, or a mixed solvent of an organic solvent miscible with water and water (aqueous medium). Here, the organic solvent is preferably an organic solvent miscible with water, and examples include methanol, ethanol, propanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, glycerin, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, acetone, tetrahydrofuran, acetonitrile, propionitrile, N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide, diethylformamide, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphoric triamide, and the like.

[0033] When preparing a negative electrode from a slurry for secondary battery electrodes, described later, which contains the conductive material composition of the present invention and an active material, it is preferable that the solvent constituting the conductive material composition of the present invention is water or an aqueous medium, and more preferably water, from the viewpoint of reducing environmental impact, since an anionic water-soluble polymer such as CMC or its salt, polystyrene sulfonic acid or its salt is suitable as a resin dispersant.

[0034] In the conductive material composition of the present invention, the binder resin content relative to the conductive material is 3 times or more and 1000 times or less by mass. Because the binder resin content relative to the conductive material is within the above range, the slurry for secondary battery electrodes, described later, containing the conductive material composition of the present invention and the active material, exhibits excellent dispersion stability, as well as excellent adhesion, swelling resistance, and uniformity of the active material layer formed from the slurry for secondary battery electrodes with the current collector. Furthermore, the secondary battery having electrodes comprising such an active material layer and current collector exhibits excellent battery characteristics. When multilayer CNTs, carbon black, or graphene are used as the conductive material, the binder resin content relative to the conductive material is more preferably 3 times or more and 500 times or less by mass. When single-walled CNTs are used as the conductive material, the binder resin content relative to the single-walled CNTs is more preferably 30 times or more and 500 times or less by mass. The content of the conductive material relative to the total solid content in the conductive material composition of the present invention is preferably in the range of 0.1% to 3.3% by mass, for example, when single-walled CNTs are used as the conductive material. When multilayer CNTs, graphene, or carbon black are used as the conductive material, the content is preferably in the range of 10% to 33% by mass relative to the total solid content in the conductive material composition of the present invention. Furthermore, the content of the conductive material relative to the entire conductive material composition of the present invention is preferably in the range of 0.02% to 1% by mass, for example, when single-walled CNTs are used as the conductive material, and it is preferable to adjust the solvent content to fall within this range. The content of the binder resin relative to the entire conductive material composition of the present invention is preferably in the range of 3% to 30% by mass.

[0035] In the conductive material composition of the present invention, the content of the resin-type dispersant relative to the conductive material is preferably 1 to 4 times the mass of the conductive material. Because the content of the binder resin relative to the conductive material is within the above range, the conductive material composition of the present invention exhibits excellent dispersion stability. Furthermore, a slurry for secondary battery electrodes, described later, containing the conductive material composition of the present invention and an active material, exhibits excellent dispersion stability, as well as excellent adhesion, swelling resistance, and uniformity of the active material layer formed from the slurry for secondary battery electrodes with the current collector. Moreover, a secondary battery having electrodes comprising such an active material layer and a current collector exhibits excellent battery characteristics. It is more preferable that the content of the resin-type dispersant relative to the conductive material is 1 to 2 times the mass of the conductive material.

[0036] The conductive material composition of the present invention may further contain various additives as needed, such as other resins, surfactants, antioxidants, light stabilizers, plasticizers, viscosity modifiers, and organic or inorganic fillers, to the extent that they do not impair the effects of the present invention.

[0037] The conductive material composition of the present invention preferably has a precipitate amount of 1% by mass or less, more preferably 0.5% by mass or less, and may even be 0% by mass, when centrifuged at 10,000 rpm for 10 minutes, relative to the solid content before centrifugation. When the precipitate amount is within the above range, the dispersion stability of the conductive material in the conductive material composition of the present invention is good. The viscosity of the conductive material composition of the present invention is determined, for example, using a rheometer ("Kinexus pro+", manufactured by MALVERN PANALITICAL) at 25°C for 100 seconds. －１ from 0.1s －１ It can be determined by measurement within a certain range.

[0038] The conductive material composition of the present invention can be effectively used for forming electrodes in secondary batteries. Specifically, it can be suitably used as a slurry for secondary battery electrodes, as described later, containing the conductive material composition of the present invention and an active material.

[0039] The present invention also provides a method for producing the conductive material composition of the present invention described above, comprising the following steps: Step 1: Mix a conductive material, which is at least one selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, and graphene, a resin-type dispersant, and a solvent using a high-pressure disperser at a pressure in the range of 50 to 270 MPa to obtain a dispersion. Step 2: Mix the dispersion obtained in Step 1 with a binder resin containing a water-soluble resin (X) having a copolymer (polymer α) having constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers, using a high-pressure disperser at a pressure in the range of 15 to 170 MPa to obtain a conductive material composition containing the conductive material, the resin-type dispersant, the binder resin, and the solvent.

[0040] In step 1, a conductive material, a resin-type dispersant, and a solvent are processed and mixed using a high-pressure disperser to obtain a dispersion. The details of the conductive material, resin-type dispersant, and solvent are the same as those described in the conductive material composition of the present invention above. Examples of high-pressure dispersers include those that atomize pressurized liquid samples by causing them to collide with each other, or those that atomize pressurized liquid samples by introducing them into a collision chamber or a ball collision chamber equipped with balls to which pressurized liquid samples are collided. Both high-pressure dispersers are dispersion devices that atomize a liquid sample with applied processing pressure by causing it to collide with a target, and then discharge the atomized sample from a discharge nozzle. Commercially available high-pressure dispersers can be used, such as the "NAGS" series from Jōkōsha; the "Microfluidizer" series from Pawrec; the "Starburst" series from Sugino Machine; the "Nanoveta" series from Yoshida Machinery Industry; pressure homogenizers from SMT; and the "OMEGA®" series from Ashizawa Finetech. Before proceeding to step 1 described above, the conductive material, resin-type dispersant, and solvent may be pre-mixed and wetted or simply dispersed. Such mixing can be done using the high-pressure dispersers mentioned above, as well as mixers such as dispersers, homomixers, rotational mixers, Henschel mixers, and planetary mixers; media-type dispersers such as paint conditioners, colloid mills, bead mills, cone mills, ball mills, sand mills, attritors, pearl mills, and coball mills; media-less dispersers such as wet jet mills and thin-film swirling high-speed mixers; and roll mills.

[0041] In step 1, the processing pressure in the high-pressure disperser is preferably in the range of 50 to 270 MPa, and more preferably in the range of 70 to 150 MPa. The processing temperature is usually preferably in the range of 10°C to 60°C, and the number of processing cycles is usually preferably in the range of 3 to 20. The processing method in the high-pressure disperser may be any of the following methods: batch type, pass type, circulating dispersion, etc., and two or more methods may be combined. The amount of conductive material added in step 1 is preferably in the range of 0.1 to 10% by mass, and more preferably in the range of 0.3 to 5% by mass, relative to the total amount of dispersion obtained in step 1. The amount of resin-type dispersant added in step 1 is preferably in the range of 0.1 to 15% by mass, and more preferably in the range of 0.3 to 7.5% by mass, relative to the total amount of dispersion obtained in step 1.

[0042] In step 2, the dispersion obtained in step 1 and a binder resin containing a water-soluble resin (X) are processed and mixed using a high-pressure disperser to obtain the conductive material composition of the present invention, which comprises a conductive material, a resin-type dispersant, a binder resin, and a solvent. The details of the binder resin containing the water-soluble resin (X) and the copolymer α contained in such water-soluble resin (X) are the same as those of the binder resin containing the water-soluble resin (X) described in the conductive material composition of the present invention described above. The high-pressure disperser in step 2 is the same as the high-pressure disperser exemplified in the description of step 1. In step 2, the processing pressure in the high-pressure disperser is in the range of 15 to 170 MPa, and more preferably in the range of 30 to 100 MPa. The temperature during processing is usually preferably in the range of 10°C to 60°C, and the number of processing cycles is usually preferably in the range of 1 to 10. The high-pressure disperser used in step 2 may be the same type as the high-pressure disperser used in step 1 or different. If the same type of high-pressure disperser used in step 1 is also used in step 2, the dispersion obtained in step 1 may not be removed from the high-pressure disperser, but instead a binder resin containing a water-soluble resin (X) may be added and mixed by processing at a specific pressure range to carry out step 2.

[0043] The details of the particle size distribution of the conductive material used in the method for producing the conductive material composition of the present invention are the same as those described in the description of the conductive material composition of the present invention. In particular, it is preferable that the conductive material in the conductive material composition of the present invention obtained in step 2 is single-walled carbon nanotubes (WNTs), with D10 in the range of 0.01 to 20 μm, D50 in the range of 0.01 to 50 μm, and D90 in the range of 0.02 to 200 μm. Furthermore, when the conductive material is single-walled carbon nanotubes (WNTs), it is even more preferable that its D10 is in the range of 0.01 to 0.1 μm, D50 in the range of 0.01 to 30 μm, and D90 in the range of 0.05 to 100 μm. It is also preferable that the ratio of D10 to D50 of the conductive material is 0.20 or more, and D90 is less than 22.0 μm. It is even more preferable that the ratio of D10 to D50 of the conductive material is 0.20 or more and 0.80 or less.

[0044] In step 1, a conductive material, a resin-type dispersant, and a solvent are processed and mixed using a high-pressure disperser at the specific pressure range defined in this invention to obtain a dispersion. Then, in step 2, the dispersion and a binder resin are processed and mixed using a high-pressure disperser at the specific pressure range defined in this invention, thereby improving the dispersibility (dispersion stability) of the conductive material composition of the present invention, i.e., the dispersibility (dispersion stability) of the conductive material. In particular, when single-walled carbon nanotubes (WNTs) are used as the conductive material, the method for manufacturing the conductive material composition of the present invention makes it easier for the D10, D50, and D90 of the WNTs in the resulting conductive material composition to satisfy the aforementioned range, thus further improving the dispersion stability of the conductive material composition. Furthermore, a slurry for secondary battery electrodes, described later, containing the conductive material composition of the present invention and an active material exhibits excellent dispersion stability, excellent uniformity of the active material layer formed from the slurry, and a secondary battery having an electrode comprising such an active material layer and a current collector exhibits excellent battery characteristics.

[0045] The present invention also relates to a slurry for secondary battery electrodes (hereinafter also simply referred to as "the electrode slurry of the present invention") comprising the conductive material composition and active material of the present invention described above. The active material contained in the electrode slurry of the present invention may be either a negative electrode active material or a positive electrode active material.

[0046] The negative electrode active material is capable of doping or intercalating lithium ions, such as metallic lithium; an alloy of metallic lithium and tin, silicon, lead, etc.; Li Ｘ Fe ２ O ３ 、Li Ｘ Fe ３ O ４ 、Li Ｘ WO ２ (x is a positive number where 0 < x < 1), metal oxides such as lithium titanate, lithium vanadate, lithium silicate, etc.; conductive polymers such as polyacetylene, poly-p-phenylene, etc.; amorphous carbonaceous materials such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbon materials, carbonaceous powders such as natural graphite, resin-fired carbon materials, gas-phase grown carbon fibers, carbon-based materials such as carbon fibers; silicon-based materials such as silicon, silicon alloys, lithium silicate, silicon oxide, composite particles having a structure in which silicon particles are dispersed in a silicon-based matrix phase; etc. These may be used alone or in combination of two or more.

[0047] The average particle size of the negative electrode active material is not particularly limited, and it is usually preferably 0.01 μm or more and 100 μm or less. When the average particle size of the negative electrode active material is within the above range, when used as a secondary battery, the negative electrode expansion rate during charge and discharge is small, and it is easy to prevent a decrease in the reversible charge and discharge capacity per unit volume. Furthermore, it is easy to suppress the peeling of the active material layer (negative electrode material layer) from the current collector during the production of the electrode film. The average particle size of the negative electrode active material is the particle size (D50) at which the cumulative volume distribution curve is drawn from the small diameter side in the particle size distribution measured by the dynamic light scattering method using a laser diffraction particle size analyzer or the like and reaches 50% in terms of cumulative volume. The surface of at least a part of the negative electrode active material may be coated with a coating material. As the coating material, substances that can be expected to have electronic conductivity, lithium ion conductivity, and an effect of suppressing the decomposition of the electrolytic solution are preferable, and examples include electronic conductive substances such as carbon, titanium, and nickel.

[0048] The positive electrode active material is not particularly limited, and in the case of secondary batteries, for example, when manufacturing lithium-ion secondary batteries, examples include metal compounds, metal oxides, metal sulfides, and conductive polymers that can dope or intercalate lithium ions. For example, lithium cobalt oxide (LiCoO) ２ Lithium-cobalt composite oxides (LCOs), lithium nickelate (LiNiO), etc. ２ ), lithium manganese (LiMnO ２ ) and their composite oxides (LiCoxNiyMnzo ２ x + y + z = 1; Lithium nickel manganese cobalt composite oxide (NMC); Lithium manganese spinel (LiMn ２ O ４ ), lithium vanadium compound, V ２ O ５ , V ６ O １３ , VO ２ MnO ２ , TiO ２ MoV ２ O ８ TiS ２ , V ２ S ５ , VS ２ MoS ２ MoS ３ , Cr ３ O ８ , Cr ２ O ５ Olivine type LiMPO ４ (wherein M is Co, Ni, Mn, or Fe); examples include conductive polymers such as polyacetylene, polyaniline, polypyrrole, polythiophene, and polyacene, and porous carbon. These may be used individually or in combination of two or more.

[0049] The average particle size of the positive electrode active material is not particularly limited, but is preferably between 0.01 μm and 100 μm. When the average particle size of the positive electrode active material is within the above range, the positive electrode expansion rate is small during charging and discharging when used as a secondary battery, and it is easier to prevent a decrease in the reversible charge-discharge capacity per unit volume. Furthermore, it is easier to suppress the peeling of the active material layer (positive electrode material layer) from the current collector during electrode film fabrication. The average particle size of the positive electrode active material is the particle size (D50) at which the cumulative volume reaches 50% when the volume cumulative distribution curve is drawn from the smallest diameter side in the particle size distribution measured by dynamic light scattering using a laser diffraction particle size analyzer or the like.

[0050] The positive electrode active material may have at least a portion of its surface covered with a coating material. The coating material is preferably a substance that exhibits electronic conductivity, lithium ion conductivity, and an effect of suppressing the decomposition of the electrolyte, and examples of electronically conductive materials include carbon, titanium, and nickel.

[0051] The electrode slurry of the present invention may further contain other conductive materials other than those contained in the conductive material composition of the present invention described above, as long as the effects of the present invention are not impaired. Examples of such other conductive materials include graphite, acetylene black, conductive oxides and nitrides, conductive polymers such as polyacetylene, polyaniline, polypyrrole, polythiophene, and polyacene, and porous carbon. These may be used individually or in combination of two or more.

[0052] The electrode slurry of the present invention is obtained by mixing and dispersing the active material, which is the negative electrode active material or positive electrode active material as described above, the conductive material composition of the present invention, and other conductive materials as necessary. There are no particular restrictions on the order of addition during mixing. Furthermore, a non-aqueous solvent may be added as appropriate from the viewpoint of adjusting the viscosity of the resulting electrode slurry of the present invention and improving dispersion stability. Dispersion can be carried out using dispersion equipment such as a stirrer, a rotary-orbit mixer, a ball mill, a super sand mill, or a pressurized kneader.

[0053] The present invention also provides an electrode comprising at least a current collector and an active material layer formed by hardening the electrode slurry of the present invention described above. The electrode of the present invention can be obtained, for example, by applying the electrode slurry of the present invention described above to a current collector to form an active material layer as a thin film. Alternatively, the electrode slurry of the present invention may be molded into a sheet, pellet, or other shape and integrated with the current collector to obtain the electrode. Here, if the electrode slurry of the present invention contains a negative electrode active material as the active material, the formed active material layer becomes a negative electrode material layer and an electrode as a negative electrode is obtained. On the other hand, if it contains a positive electrode active material as the active material, the formed active material layer becomes a positive electrode material layer and an electrode as a positive electrode is obtained.

[0054] Examples of materials for the current collector include copper, nickel, titanium, and stainless steel. The current collector is preferably in the form of a strip, such as foil, perforated foil, or mesh. Porous materials such as porous metal (foamed metal) and carbon paper can also be used as current collectors.

[0055] Methods for applying the electrode slurry of the present invention to a current collector include, for example, metal mask printing, electrostatic coating, dip coating, spray coating, roll coating, doctor blade coating, gravure coating, and screen printing. After application, it is preferable to perform rolling treatment using a flat plate press, calender roll, etc., as necessary. Alternatively, the paste-like electrode slurry of the present invention may be formed into a sheet or pellet, and then integrated with the current collector by rolling, pressing, or a combination thereof to obtain an active material layer. When forming a negative electrode material layer with the electrode slurry of the present invention, carbon materials such as natural graphite, artificial graphite, hard carbon, or amorphous carbon such as soft carbon may be further added to the slurry to form the negative electrode material layer, provided that the effects of the present invention are not impaired.

[0056] The active material layer formed on the current collector or the active material layer integrated with the current collector is preferably heat-treated. This heat treatment removes solvents derived from the conductive material composition of the present invention, promotes increased strength through curing of the resin-type dispersant and binder resin, and improves adhesion between active materials, between the active material and the conductive material, and between the active material and the current collector. The heat treatment temperature is preferably in the range of 50 to 220°C, and more preferably in the range of 100 to 200°C. There are no particular restrictions on the heat treatment time, but it is usually in the range of 1 minute to 20 hours. It is preferable to perform the heat treatment in a non-oxidizing gas atmosphere such as helium, argon, or nitrogen, or in a vacuum atmosphere, from the viewpoint of preventing oxidation of the current collector during heat treatment. Furthermore, after heat treatment, the electrode consisting of the active material layer formed on the current collector or the active material layer integrated with the current collector is preferably pressurized from the viewpoint of adjusting the electrode density. The electrode density of the negative electrode is usually 1 to 1.8 g / cm³. ３ Preferably, it is 1.1 to 1.7 g / cm³. ３ It is more preferable that the concentration be 1.2 to 1.6 g / cm³. ３ It is even more preferable that the electrode density is as follows: While higher electrode density tends to improve adhesion and electrode volumetric density, if it is too high, the voids within the electrode decrease, making it difficult to suppress the electrode's expansion rate and potentially reducing the volume retention rate. Therefore, an optimal range for electrode density is selected.

[0057] The binder resin content in the active material layer of the lithium-ion secondary battery electrode is preferably 1 to 30% by mass, more preferably 2 to 20% by mass, and even more preferably 3 to 15% by mass. When the binder resin content is 1% by mass or more, adhesion is improved, and the destruction of the electrode structure due to expansion or contraction during charging and discharging is more easily suppressed. On the other hand, when it is 30% by mass or less, the increase in electrode resistance is more easily suppressed.

[0058] The present invention also relates to a secondary battery comprising such an electrode. The secondary battery of the present invention preferably comprises an electrode in which at least the negative electrode comprises an active material layer formed by hardening the electrode slurry of the present invention described above, and an electrolyte and a separator. The electrode slurry of the present invention has excellent dispersion stability of the active material and conductive material. Therefore, the active material layer formed from the electrode slurry of the present invention has excellent uniformity, excellent adhesion to the current collector, excellent swelling resistance, and excellent charge / discharge capacity and capacity retention rate. In other words, the secondary battery of the present invention having an electrode with such an active material layer exhibits good charge / discharge characteristics and also has excellent capacity retention rate, thus having excellent battery characteristics.

[0059] As a separator, nonwoven fabrics, cloths, microporous films, or combinations thereof, mainly composed of polyolefins such as polyethylene and polypropylene can be used. However, if the positive and negative electrodes of the non-aqueous electrolyte secondary battery being manufactured are not in direct contact, a separator is not required.

[0060] Examples of electrolytes include LiClO ４ LiPF ６ LiAsF ６ LiBF ４ LiSO ３ CF ３ A so-called organic electrolyte can be used, which is obtained by dissolving lithium salts such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, fluoroethylene carbonate, cyclopentanone, sulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, 3-methyl-1,3-oxazolidine-2-one, γ-butyrolactone, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, butyl methyl carbonate, ethyl propyl carbonate, butyl ethyl carbonate, dipropyl carbonate, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, methyl acetate, ethyl acetate, etc., in one or more non-aqueous solvents.

[0061] The secondary batteries of the present invention are preferably non-aqueous electrolyte secondary batteries and solid-state electrolyte secondary batteries, and in particular, non-aqueous electrolyte secondary batteries having electrodes with an active material layer formed using the electrode slurry of the present invention tend to exhibit superior performance. For example, if the secondary battery of the present invention is a wet-type electrolyte secondary battery, it can be constructed by arranging a negative electrode and a positive electrode opposite each other via a separator, with the negative electrode having an active material layer formed using the electrode slurry of the present invention containing a negative electrode active material, and injecting an electrolyte.

[0062] The structure of a secondary battery using the conductive material composition of the present invention is not particularly limited, but it is common to have a structure in which a positive electrode, a negative electrode, and a separator (if necessary) are wound in a flat spiral shape to form a wound electrode plate group, or these are stacked as flat plates to form a stacked electrode plate group, and these electrode plate groups are sealed in an outer casing. Secondary batteries using the conductive material composition of the present invention can be used as, for example, paper type batteries, button type batteries, coin type batteries, stacked type batteries, cylindrical batteries, prismatic batteries, etc. The conductive material composition of the present invention can also be applied to electrochemical devices in general that use the insertion and removal of lithium ions as a charge and discharge mechanism, such as hybrid capacitors and solid lithium secondary batteries.

[0063] The conductive material composition, its manufacturing method, electrode slurry, electrode, and secondary battery equipped with the electrode of the present invention have been described above. However, the present invention is not limited to the configurations of the embodiments described above. For example, the conductive material composition, electrode slurry, electrode, and secondary battery having the electrode of the present invention may each have additional configurations in the configurations of the embodiments described above, or may be replaced with any configuration that performs a similar function. Furthermore, the manufacturing method of the conductive material composition of the present invention may have additional steps in the embodiments described above, or may be replaced with any step that performs a similar function.

[0064] The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the following examples. The raw materials used in each example and comparative example are listed below. <Conductive materials> SWCNT: Single-walled carbon nanotube (OCSiAl "TUBALL® 01RW03") MWCNT: Multi-walled carbon nanotube (Cnano "FT6810") Graphene: Graphene powder (Graphene Platform "GNH-XZ") AB: Acetylene black (Denka "Li400")

[0065] <Resin-type dispersants> CMC: Carboxymethylcellulose (Nippon Paper Industries Co., Ltd. "Sunrose (registered trademark) MAC350") PSS: Poly(4-styrene sulfonate sodium) (SIGMA-ALDRICH Co., Ltd.) PVP: Polyvinylpyrrolidone (Nippon Shokubai Co., Ltd. "K30") PVDF: Polyvinylidene fluoride (Kureha Corporation "#1100")

[0066] <Binder Resin> [Synthesis Example of Binder Resin A] Stirrer, thermometer, cooler and N ２ A reaction vessel with a blower and a capacity of 1 L is filled with 500.0 parts by mass of ion-exchanged water, and N ２ After blowing for 3 hours, the mixture was heated to 75°C. A mixture of 20.0 parts by mass of acrylic acid, 20.0 parts by mass of hydroxyethyl acrylate, 60.0 parts by mass of acrylamide, 0.405 parts by mass of ammonium persulfate (1500 ppm relative to the total number of moles of monomer), and 50.0 parts by mass of deionized water was added dropwise over 3 hours. After the addition was complete, the mixture was kept at 75°C for 2 hours to carry out the polymerization reaction. The reaction mixture was cooled, and 25% aqueous ammonia and distilled water were added at a temperature below 40°C to obtain a solution of binder resin A with a pH of 7.0, a non-volatile content of 15.0% by mass, and a viscosity of 12500 mPa·s. The weight-average molecular weight of the obtained binder resin A, measured by aqueous GPC, was 780000. [Example of synthesis of binder resin B] Stirrer, thermometer, condenser and N ２ A reaction vessel with a blower and a capacity of 1 L is filled with 500.0 parts by mass of ion-exchanged water, and N ２After blowing for 3 hours, the mixture was heated to 75°C. A mixture of 30.0 parts by mass of acrylic acid, 60.0 parts by mass of hydroxyethyl acrylate, 10.0 parts by mass of acrylamide, 0.443 parts by mass of ammonium persulfate (1500 ppm relative to the total number of moles of monomer), and 50.0 parts by mass of deionized water was added dropwise over 3 hours. After the addition was complete, the mixture was kept at 75°C for 2 hours to carry out the polymerization reaction. The reaction mixture was cooled, and a 5 mol / L aqueous sodium hydroxide solution and distilled water were added at a temperature below 40°C to obtain a binder resin B solution with a pH of 7.1, a non-volatile content of 15.0% by mass, and a viscosity of 3100 mPa·s. The weight-average molecular weight of the obtained binder resin B, measured by aqueous GPC, was 730,000. [Binder Resin C] "LA136D" manufactured by Indigo Technology Inc. [Binder Resin D] Carboxymethylcellulose ("Sunrose® MAC350" manufactured by Nippon Paper Industries Co., Ltd.)

[0067] Furthermore, the details of the high-pressure dispersers used in each example and comparative example are described below. Disperser A: High-pressure homogenizer "NAGS20" (product name) manufactured by Jokosha, H-type nozzle (nozzle diameter 15 μm) Disperser B: High-pressure homogenizer "NanoVeta L-ES" (product name) manufactured by Yoshida Machinery Industry Co., Ltd., X-type nozzle or I-type nozzle Disperser C: High-pressure homogenizer "Starburst Mini" (product name) manufactured by Sugino Machine Co., Ltd., single nozzle chamber (nozzle diameter 14 μm)

[0068] 1. Example 1 of the preparation of conductive material composition, electrodes and batteries (1) Preparation of conductive material composition (Step 1) 3 parts by mass of CMC as a resin-type dispersant was added to 495 parts by mass of ion-exchanged water and dissolved completely. Next, 2 parts by mass of SWCNT as a conductive material was added, and the dispersion treatment was carried out 10 times at 100 MPa using disperser A to obtain CNT dispersion 1. The temperature during the dispersion treatment was 20 to 25°C. (Step 2) Next, 82.5 parts by mass of ion-exchanged water and 5 parts by mass of binder resin A were added to 12.5 parts by mass of the CNT dispersion 1 obtained above, and the dispersion treatment was carried out 5 times at 100 MPa using disperser A to obtain conductive material composition 1. The temperature during the dispersion treatment was 20 to 25°C.

[0069] (2) Preparation of the negative electrode 11.0 parts by mass of artificial graphite (initial charge capacity 390 mAh / g, initial discharge capacity 350 mAh / g), 85.0 parts by mass of SiO (initial charge capacity 2200 mAh / g, initial discharge capacity 1680 mAh / g), and 0.97 parts by mass of acetylene black were weighed out and stirred for 60 seconds in a rotating-orbit mixer (Thinky "ARE-310 (product name)") at a rotation speed of 1000 rpm and an orbit speed of 2000 rpm. Thereafter, stirring using the rotating-orbit mixer was carried out with the same apparatus and conditions unless otherwise specified. Next, 46.0 parts by mass (3.03 parts by mass in terms of solid content) of the conductive material composition 1 obtained above (non-volatile content concentration 6.5%) was added and mixed until the whole thing became a paste, and then stirred in a rotating-orbit mixer for 2 minutes. The mixture was heated by stirring, so it was cooled to room temperature with ice water, stirred again for 2 minutes in a rotary-orbit mixer, and then cooled to room temperature with ice water. Next, 50 parts by mass of distilled water were added to this mixture, and it was stirred again for 30 seconds in a rotary-orbit mixer to prepare negative electrode mixture slurry 1. The coating amount (surface density) of the mixture after drying was 8.7 mg / cm². ２ The gap of the bar coater was adjusted so that the negative electrode mixture slurry 1 prepared above was coated onto the copper current collector foil (10 μm thick, 180 mm wide), which is the current collector, using this bar coater, and dried for 8 minutes in a forced-air dryer set to 80°C. After drying, the negative electrode mixture was pressed using a roll press to a mixture density of 1.50 g / cm³. ３ After pressing in this manner, the surface density is reduced to 8.7 mg / cm² by vacuum drying at 110°C for 10 hours. ２ A negative electrode 1 was fabricated.

[0070] (3) Preparation of the positive electrode LiMn as the positive electrode active material ０．６ Co ０．２ Ni ０．２ O ２ A cathode mixture slurry was formed by dispersing 94.0 parts by mass of (initial charge capacity 191 mAh / g, initial discharge capacity 171 mAh / g), 3.0 parts by mass of acetylene black, and 3.0 parts by mass of polyvinylidene fluoride in N-methyl-2-pyrrolidone (NMP). The non-volatile content in the cathode mixture slurry was 50% by mass relative to the total mass of the slurry. Specifically, in a dry room controlled to a dew point of -30°C or lower, the cathode material LiMn ０．６ Co ０．２Ni ０．２ O ２ 94.0 parts by mass of (initial charge capacity 191 mAh / g, initial discharge capacity 171 mAh / g) and 3.0 parts by mass of acetylene black were weighed out and stirred for 30 seconds in a rotary-orbit mixer. Next, 30.0 parts by mass (3.0 parts by mass in terms of solid content) of a 10% NMP solution of polyvinylidene fluoride (PVDF, #1100, manufactured by Kureha Corporation) were added and mixed until the mixture became a paste, then stirred for 1 minute in a rotary-orbit mixer. Since heat was generated by the stirring, the mixture was allowed to cool to room temperature. This stirring and cooling operation with the rotary-orbit mixer was repeated three more times. Subsequently, 10.0 parts by mass of NMP was added to this mixture and mixed until the mixture was uniform, then stirred for 1 minute in a rotary-orbit mixer, and since heat was generated by the stirring, the mixture was allowed to cool to room temperature. After repeating the stirring and cooling operation with the rotational mixer three more times, 10.0 parts by mass of NMP was added and stirred with the rotational mixer for 2 minutes to prepare cathode mixture slurry 1. The coating amount (surface density) of the mixture after drying was 25.0 mg / cm². ２ The gap of the bar coater was adjusted so that the positive electrode mixture slurry 1 prepared above was coated onto the aluminum current collector foil (15 μm thick, 180 mm wide), which is the current collector, using this bar coater, and dried for 15 minutes in a forced-air dryer set to 80°C. After drying, the positive electrode mixture was pressed using a roll press to obtain a mixture density of 3.40 g / cm³. ３ After pressing in this manner, the surface density is reduced to 25.0 mg / cm² by vacuum drying at 110°C for 10 hours. ２ Positive electrode 1 was fabricated.

[0071] (4) Fabrication of the secondary battery The negative electrode 1 fabricated above was cut into a 24 mm x 24 mm square with a tab, and the positive electrode 1 fabricated above was cut into a 22 mm x 22 mm square with a tab, using a die-cutting blade. Nickel tab leads were welded to the tab portion of the cut electrodes, and aluminum tab leads were welded to the tab portion of the negative electrode 1 and positive electrode 1 1. Meanwhile, a 20 μm thick polyethylene microporous membrane was cut into a 28 mm x 38 mm rectangle using a die-cutting blade as a separator. The positive electrode 1 and the negative electrode were placed opposite each other via this separator, wrapped in laminate film, and the tab portion was fixed by heat sealing. Then, LiPF ６A laminate-type secondary battery 1 was fabricated by dissolving the compound in a 30 / 30 / 40 mixed solution of ethylene carbonate / dimethyl carbonate / methyl ethyl carbonate at a concentration of 1 mol / L, adding 1 vol% vinyl carbonate and 5 vol% fluoroethylene carbonate to obtain a non-aqueous electrolyte solution, adding 300 μL of the solution, and completely sealing it by vacuum lamination.

[0072] Examples 2-27, 31-32, 35-36, Comparative Examples 1-2 Conductive material compositions 2-27, 31-32, 35-36, C1-C2 were obtained in the same manner as in Example 1(1), except that the type, amount, and amount of resin-type dispersant used in Step 1 of Example 1(1), the type and pressure of the high-pressure disperser used, and the type and amount of binder resin used in Step 2 of Example 1(1), as well as the type and pressure of the high-pressure disperser used, were changed as shown in Table 1. Next, negative electrodes 2-27, 31-32, 35-36, C1-C2, and laminate-type secondary batteries 2-27, 31-32, 35-36, C1-C2 were produced using each conductive material composition by performing the same operations as in Examples 1(2)-(4).

[0073] Examples 28-30 Conductive material compositions 28-30 were obtained in the same manner as in Example 1(1), except that the amount of CMC used in (Step 1) of Example 1(1), the type and amount of conductive material used, and the amount of binder resin A used and the pressure of the high-pressure disperser in (Step 2) of Example 1(1) were changed as shown in Table 1. Subsequently, negative electrodes 28-30 were prepared by performing the same procedure as in Example 1(2), except that acetylene black was not added in Example 1 "(2) Preparation of negative electrode". Then, laminate-type secondary batteries 28-30 were prepared by performing the same procedure as in Examples 1(3)-(4).

[0074] Examples 33-34 Conductive material compositions 33-34 were obtained in the same manner as in Example 1(1), except that the type and amount of resin-type dispersant used in (Step 1) of Example 1(1), and the pressure of the high-pressure disperser in (Step 2) of Example 1(1), were changed as shown in Table 1. Subsequently, in Example 1 "(3) Preparation of positive electrode", the positive electrode material LiMn ０．６ Co ０．２ Ni ０．２ O２ A positive electrode mixture slurry was formed in the same manner as in Example 1 (3), except that 94.0 parts by mass of (initial charge capacity 191 mAh / g, initial discharge capacity 171 mAh / g), 2.9 parts by mass of acetylene black, 0.1 parts by mass of the conductive material composition 33 or 34 obtained above, and 3.0 parts by mass of polyvinylidene fluoride were dispersed in NMP, and positive electrodes 33 to 34 were prepared. On the other hand, a negative electrode 1 was prepared according to Examples 1 (1) and (2). Then, in Example 1 "(4) Preparation of a secondary battery", the same procedure as in Example 1 (4) was performed, except that the positive electrodes 33 to 34 prepared above were used instead of positive electrode 1, and laminate-type secondary batteries 33 to 34 were prepared.

[0075] 2. Evaluation 2-1. Particle size distribution of conductive material compositions (D10, D50, D90) The conductive material compositions obtained in each example and comparative example were diluted 100 times by mass with water, and the particle size distribution (D10, D50, D90) was measured using a particle size distribution analyzer (MASTERSIZER LMS-3000, manufactured by MALVERN PANALITICAL). Non-spherical measurement was performed under the following conditions: refractive index of water 1.33, refractive index of carbon material 1.75, absorptivity 0.01, blue laser characteristics wavelength 1.0, absorptivity 0.02, and particle size standard was volume.

[0076] 2-2. G / D ratio of conductive material composition (Raman spectroscopy) One mL of the conductive material composition obtained in each example and comparative example was coated onto a substrate made of fluororesin and dried at 25°C for 24 hours, then under vacuum at 110°C for 10 hours to create a film with a thickness of 10 to 50 μm. The film obtained above was placed in a Raman microscope ("NRS-5500", manufactured by JASCO Corporation) and observed under measurement conditions of excitation wavelength 532 nm, attenuation filter 5%, laser intensity 0.6 mW, objective lens magnification 20x, and slit width 100 × 1000 μm, at 1320 to 1360 cm⁻¹. －１ The maximum peak intensity within the range is D, 1520–1560 cm. －１ The maximum peak intensity within the specified range was defined as G, and the G / D ratio was calculated and evaluated according to the following criteria: <Evaluation Criteria> ◎: G / D ratio is greater than 120 〇: G / D ratio is between 100 and 120 △: G / D ratio is between 60 and 100 ×: G / D ratio is less than 60

[0077] 2-3. Stability of Conductive Material Compositions (1) Viscosity Stability over Time The conductive material compositions obtained in each example and comparative example were measured for 100 seconds at 25°C using a rheometer ("kinexus pro+", manufactured by MALVERN PANALITICAL). －１ from 0.1s －１ Viscosity was measured within the specified range. Measurements were taken again one week later under the same conditions. A circle (○) indicated no change, while a triangle (△) indicated a decrease in viscosity.

[0078] (2) Sedimentation: 40 mL of the conductive material composition obtained in each example and comparative example was centrifuged in a high-speed refrigerated centrifuge ("CR22N", manufactured by Himac) at 10,000 rpm for 10 minutes at 10°C. The precipitate after removing the supernatant after centrifugation was weighed, and ○ was used if there was no precipitate, and △ if there was a precipitate.

[0079] (3) Film Formation Uniformity One mL of the conductive material composition obtained in each example and comparative example was applied to a glass substrate and dried at 25°C for 24 hours, then under vacuum at 110°C for 10 hours to create a film with a thickness of 10 to 50 μm. The surface of the obtained film was visually observed and its uniformity was evaluated according to the following criteria. <Evaluation Criteria> ○: The film after drying is black and there are no aggregates ×: The black areas where CNTs have aggregated and the transparent areas consisting only of resin are visible separately; or there are aggregates of several μm to 1 mm in size and the surface is rough

[0080] 2-4. Battery Characteristics (1) Initial Charge / Discharge Efficiency (Chemical Treatment) The secondary batteries prepared in each example and comparative example were sandwiched between two Gore Hypersheets, and then between two acrylic plates, and secured with two double clips, so that a constant and uniform pressure was applied to the electrode area. This was then attached to a charge / discharge device and left at 25°C for 3 hours, after which one charge / discharge cycle was performed at a charge / discharge rate of 0.1C, and the initial charge / discharge capacity was measured.

[0081] (2) DC Resistance (DCR) The secondary battery, after its initial charge and discharge, was charged once at 25°C and a charge / discharge rate of 0.1C. It was discharged at 4mA for 30 seconds, and the current value after 30 seconds was I １ , the voltage is V １ Next, discharge was performed at 20mA for 30 seconds, and the current value after 30 seconds was I ２ , the voltage is V ２Based on these current and voltage values, the DC resistance (DCR) was calculated using the following formula. Using the DCR value of secondary battery C1 obtained in Comparative Example 1 as a reference, the relative values ​​(relative rate of change) of the DCR values ​​of the secondary batteries obtained in each example were evaluated as follows: DCR = (V １ ―V ２ ) / (I １ ―I ２ ) <Evaluation Criteria> ○: Good DCR value (improvement of 5% or more) △: Slightly good DCR value (improvement between 0% and less than 5%) ×: Same or decreased DCR value (decreased to 0%)

[0082] (3) Electrode expansion rate (Swelling) Thickness L of the electrode composite layer of the secondary battery prepared in each example and comparative example. １ The thickness was measured using a thickness measuring instrument (Digimicro MF-501, manufactured by Nicon). The secondary battery after the cycle test described in (3) above was charged once at 45°C and a charge / discharge rate of 0.1C. After charging, the thickness L of the disassembled negative electrode was measured. ２ The thickness was measured using a thickness measuring instrument (Digimicro MF-501, manufactured by Nicon). The rate of change in thickness was calculated using the following formula and defined as the electrode expansion rate. Using the electrode expansion rate of secondary battery C1 obtained in Comparative Example 1 as a reference, the relative values ​​(relative expansion rates) of the electrode expansion rates of the negative electrodes of the secondary batteries obtained in each example were evaluated according to the following criteria: Electrode expansion rate = 100 × L ２ / L １ 《Evaluation Criteria》 ○: Good relative expansion rate (improvement of 5% or more) △: Slightly good relative expansion rate (improvement between 0% and less than 5%) ×: Relative expansion rate is the same or decreased (decreased to 0%)

[0083] The results above are summarized in Tables 1 and 2.

[0084]

[0085] The results in Tables 1 and 2 show that the conductive material composition of the present invention exhibits excellent dispersibility of conductive materials, particularly single-walled carbon nanotubes (WNTs). Furthermore, electrodes having an active material layer formed from a slurry for secondary battery electrodes containing the conductive material composition of the present invention and an active material exhibit excellent uniformity of the active material layer, and secondary batteries equipped with such electrodes exhibit an excellent balance of battery characteristics such as initial charge-discharge efficiency and capacity retention rate.

[0086] The conductive material composition of the present invention exhibits excellent dispersibility of the conductive material, and the slurry for secondary battery electrodes containing the conductive material composition of the present invention and the active material exhibits excellent dispersion stability of the active material. Therefore, an electrode comprising an active material layer and a current collector formed from such a slurry for secondary battery electrodes exhibits excellent adhesion between the active material layer and the current collector, swelling resistance, and uniformity of the active material layer, enabling the formation of a secondary battery with excellent battery characteristics such as charge-discharge efficiency and capacity retention rate. A secondary battery equipped with such an electrode has excellent battery characteristics such as charge-discharge characteristics and can be effectively used in portable electronic devices, for example, as a paper battery, button battery, coin battery, stacked battery, cylindrical battery, or prismatic battery.

Claims

1. A conductive material composition comprising: a conductive material selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, and graphene; a resin-type dispersant; a binder resin; and a solvent, wherein the binder resin comprises a water-soluble resin (X) having a copolymer having constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers, and the content of the binder resin relative to the conductive material is 3 times or more and 1000 times or less by mass.

2. The conductive material composition according to claim 1, wherein the content of the resin-type dispersant relative to the conductive material is 1 to 4 times by mass.

3. The conductive material composition according to claim 1, wherein the solvent is water.

4. The conductive material composition according to claim 1, wherein the conductive material is a single-walled carbon nanotube, and the volume-based cumulative 10% diameter (D10) in the particle size distribution obtained by laser diffraction is in the range of 0.01 to 20 μm, the volume-based cumulative 50% diameter (D50) is in the range of 0.01 to 50 μm, and the volume-based cumulative 90% diameter (D90) is in the range of 0.02 to 200 μm.

5. The conductive material composition according to claim 4, wherein the ratio of D10 to D50 is 0.20 or more, and D90 is less than 22.0 μm.

6. In the Raman spectrum of the dried film formed by coating the conductive material composition onto a substrate and drying it, the range was 1320 to 1360 cm⁻¹. －１ For the maximum peak intensity ratio D within the range of 1520-1560 cm －１ The conductive material composition according to claim 1, wherein the ratio of the maximum peak intensity G within the range (G / D) is 40 to 160.

7. The conductive material composition according to claim 1, wherein the copolymer contained in the water-soluble resin (X), having constituent units based on hydroxyl group-containing monomers and constituent units based on acid group-containing monomers, has a weight-average molecular weight of 700,000 or more as measured using an aqueous GPC measuring device, and the swelling rate after immersion of a dry film of the copolymer in a carbonate-based mixed solvent (EC (ethylene carbonate) / DEC (diethylene carbonate) = 50 / 50 (mass ratio)) at 45°C for 72 hours is 0 to 10% by mass.

8. The conductive material composition according to claim 1, wherein the hydroxyl group-containing monomer is at least one selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, and 4-hydroxybutyl methacrylate.

9. The conductive material composition according to claim 1, wherein the acid group-containing monomer is neutralized with a basic composition or a light metal salt.

10. The conductive material composition according to claim 1, wherein the acid group-containing monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, monomethylmaleic acid, 2-carboxyethyl acrylate, 2-carboxyethyl methacrylate, and itaconic acid.

11. The conductive material composition according to claim 1, wherein the water-soluble resin (X) further comprises a constituent unit based on at least one selected from the group consisting of acrylamide, methacrylamide, N-methylacrylamide, N,N-dimethylacrylamide, and N-hydroxymethylacrylamide.

12. The conductive material composition according to claim 1, wherein the total content of constituent units based on the hydroxyl group-containing monomer and constituent units based on the acid group-containing monomer is 5 to 80% by mass, relative to the total amount of the water-soluble resin (X).

13. The conductive material composition according to claim 1, wherein the binder resin is a resin composition further comprising an aqueous latex resin (Y).

14. The conductive material composition according to claim 13, wherein the aqueous latex resin (Y) is one or more of styrene-butadiene copolymer (SBR), styrene acrylate copolymer, and acrylate copolymer.

15. The conductive material composition according to claim 1, wherein the amount of precipitate when centrifuged at 10,000 rpm for 10 minutes is 1% by mass or less relative to the amount of solids before centrifugation.

16. A conductive material composition according to any one of claims 1 to 15, for use in forming electrodes for secondary batteries.

17. A method for producing a conductive material composition according to any one of claims 1 to 15, comprising the following steps: Step 1: Mix a conductive material, which is at least one selected from the group consisting of single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon black, and graphene, a resin-type dispersant, and a solvent using a high-pressure disperser at a pressure in the range of 50 to 270 MPa to obtain a dispersion. Step 2: Mix the dispersion obtained in Step 1 and a binder resin containing a water-soluble resin (X) having a copolymer based on hydroxyl group-containing monomers and acid group-containing monomers using a high-pressure disperser at a pressure in the range of 15 to 170 MPa to obtain a conductive material composition containing the conductive material, the resin-type dispersant, the binder resin, and the solvent.

18. A method for producing a conductive material composition according to claim 17, wherein the conductive material is a single-walled carbon nanotube, and in the conductive material composition obtained in step 2, the volume-based cumulative 10% diameter (D10) in the volume-based particle size distribution obtained by laser diffraction of the conductive material is in the range of 0.01 to 20 μm, the volume-based cumulative 50% diameter (D50) is in the range of 0.01 to 50 μm, and the volume-based cumulative 90% diameter (D90) is in the range of 0.02 to 200 μm.

19. A slurry for secondary battery electrodes comprising a conductive material composition according to any one of claims 1 to 15 and an active material.

20. An electrode comprising at least a current collector and an active material layer formed by hardening the electrode slurry described in claim 19.

21. A secondary battery comprising the electrode described in claim 20.

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