Dispersed carbon nanotube composition, and resin composition, electrode film, secondary battery, and vehicle with the same

Abstract

To provide a dispersed carbon nanotube composition having high dispersibility, a carbon nanotube resin composition, and mixed material slurry and to provide a non-aqueous electrolyte secondary battery having an excellent rate property and cycle property and a vehicle including the non-aqueous electrolyte secondary battery.SOLUTION: The present invention relates to a dispersed carbon nanotube composition including a carbon nanotube, a dispersant, and an amide polar solvent and satisfies the following (1), (2), (3), and (4): (1) the carbon nanotube has a cobalt content of 3000 ppm to 20000 ppm; (2) the carbon nanotube has a G / D ratio of 0.5 or more and less than 1.5; (3) the carbon nanotube has a BET specific surface area of 150 m2 / g to 800 m2 / g; and (4) the dispersed carbon nanotube composition has a water content of 50 ppm to 1500 ppm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon nanotube dispersion composition, more specifically to a cobalt-containing carbon nanotube dispersion composition, a resin composition containing the cobalt-containing carbon nanotube dispersion composition and a binder resin, a composite slurry containing the cobalt-containing carbon nanotube dispersion composition, a binder resin, and an active material, an electrode film formed by coating the same, a nonaqueous secondary electrolyte secondary battery including the electrode film and an electrolyte, and a vehicle including the nonaqueous secondary electrolyte secondary battery. [Background technology]

[0002] With the spread of electric vehicles and the trend toward smaller, lighter, and more powerful portable devices, secondary batteries with high energy density and even higher capacity are required. Against this background, non-aqueous electrolyte secondary batteries, particularly lithium-ion secondary batteries, which use a non-aqueous electrolyte solution, are being used in many devices due to their high energy density and high voltage characteristics.

[0003] The negative electrode materials used in these lithium-ion secondary batteries are carbon materials, such as graphite, which have a large charge / discharge capacity per unit mass at a base potential close to that of lithium (Li). However, these electrode materials are being used to achieve charge / discharge capacities per mass close to the theoretical value, and the energy density per mass of the battery is approaching its limit. Therefore, in order to increase the electrode utilization rate, attempts are being made to reduce the conductive additives and binders that do not contribute to discharge capacity.

[0004] Examples of conductive additives that have been used include carbon black, ketjen black, fullerene, graphene, and fine carbon materials. Carbon nanotubes, a type of fine carbon fiber, are particularly widely used. For example, an electrode film, which is a coating film of a composite slurry containing a carbon nanotube dispersion composition and an active material, is known to have low electrode resistance and improve the load resistance and cycle characteristics of a battery (see, for example, Patent Documents 1 and 2).

[0005] Carbon nanotubes with small average outer diameters can efficiently form conductive networks with small amounts, allowing for a reduction in the amount of conductive additives contained in the positive and negative electrodes of lithium-ion secondary batteries. It is also known that carbon nanotubes with long fiber lengths can achieve similar effects. (See, for example, Patent Documents 3 and 4.) However, carbon nanotubes with these characteristics have strong cohesion and are difficult to disperse.

[0006] Therefore, methods have been proposed for stabilizing the dispersion of carbon nanotubes using various dispersants. For example, dispersion in water and NMP (N-methyl-2-pyrrolidone) using a polymer dispersant such as water-soluble polymer polyvinylpyrrolidone has been proposed (see Patent Documents 1, 2, 3, and 5). However, these patent documents evaluate electrodes made using carbon nanotubes with outer diameters of 5 to 150 nm, but have the problem of high electrode resistance.

[0007] Various dispersion methods have been investigated to reduce electrode resistance. For example, a method has been investigated in which hydrogenated nitrile butadiene rubber is used as a dispersant to optimize the complex modulus, thereby controlling the dispersion state of carbon nanotubes (see Patent Documents 6, 7, 8, and 9). However, Patent Document 6 describes a method in which the complex modulus of the CNT dispersion composition is high, and the CNT dispersion composition is highly concentrated and It has been difficult to obtain uniformly dispersed carbon nanotubes. In addition, Patent Document 7 discloses that highly dispersible carbon nanotubes are obtained by using various dispersants and dispersing them with a high-pressure homogenizer. It has been proposed that carbon nanotubes can be obtained by the method described above, but the high concentration of CNTs in the amide-based polar solvent Furthermore, Patent Document 8 proposes a carbon nanotube dispersion composition containing a high concentration (5 mass%) of carbon nanotubes with an outer diameter of 6 to 15 nm in an amide-based polar solvent. However, because all of the carbon nanotubes are added to the dispersion medium at once, there is a problem of large heat generation and reduced adsorption efficiency of the dispersant. Furthermore, the use of carbon nanotubes with a large BET specific surface area and high moisture absorption has been considered, but no measures were taken to prevent moisture from being mixed into the amide-based polar solvent when preparing the carbon nanotube dispersion composition, resulting in the problem of a large amount of moisture being contained in the carbon nanotube dispersion composition. As a result, there was a problem of the carbon nanotube reacting with the basic active material during the preparation of the composite slurry, causing the composite to gel and resulting in a deterioration in resistance. Patent Document 9 proposes a carbon nanotube dispersion composition containing a high concentration (5 mass%) of carbon nanotubes with an outer diameter of 7 to 12 nm by adding carbon nanotubes in stages. However, there is no information on dispersing CNTs in an amide-based polar solvent. Nothing was shown. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Patent No. 6586197 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-70908 [Patent Document 3] Patent No. 6590034 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-221672 [Patent Document 5] Japanese Patent Application Publication No. 2019-192537 [Patent Document 6] Special Publication No. 2018-533175 [Patent Document 7] Patent Publication No. 2021-72279 [Patent Document 8] Patent No. 6933285 [Patent Document 9] Patent No. 6860740 Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention aims to provide a carbon nanotube dispersion composition, a carbon nanotube resin composition, and a composite slurry having high dispersibility to obtain an electrode film with high adhesion and conductivity. More specifically, the present invention aims to provide a non-aqueous electrolyte secondary battery and a vehicle equipped with the non-aqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics. [Means for solving the problem]

[0010] The inventors of the present invention have conducted extensive research to solve the above problems. The inventors have discovered a carbon nanotube having a cobalt content of 3000 ppm to 20000 ppm, a G / D ratio of 0.5 or more and less than 1.5, and a BET specific surface area of 150 m 2 / g~800m 2 The inventors have found that by using a carbon nanotube dispersion composition in which the water content is 50 ppm to 1500 ppm, an electrode film with excellent conductivity and adhesion can be obtained, and a non-aqueous electrolyte secondary battery with excellent rate characteristics and cycle characteristics can be obtained. Based on these findings, the inventors have arrived at the present invention.

[0011] That is, the present invention provides: The present invention relates to a carbon nanotube dispersion composition comprising carbon nanotubes, a dispersant, and an amide-based polar solvent, and characterized in that the carbon nanotube dispersion composition satisfies the following (1), (2), (3), and (4): (1) The cobalt content of the carbon nanotubes is 3000 ppm to 20000 ppm. (2) The G / D ratio of the carbon nanotubes is 0.5 or more and less than 1.5. (3) The BET specific surface area of carbon nanotubes is 150m 2 / g~800m 2 / g. (4) The water content of the carbon nanotube dispersion composition is 50 ppm to 1500 ppm.

[0012] In addition, the present invention provides a method for analyzing carbon nanotubes at a diffraction angle of 2θ=45° in powder X-ray diffraction analysis. The carbon nanotube dispersion composition is characterized in that there are two peaks at 1°±5°, and when the peak on the low-angle side is α and the peak on the high-angle side is β, the relationship is 0.7<(β / α)<1.0.

[0013] Furthermore, the present invention provides a carbon nanotube dispersion composition having a metal cobalt content of 100 parts by mass, X (parts by mass), and a cobalt content of 100 parts by mass, wherein the metal cobalt content is X (parts by mass), and the cobalt content is Y (parts by mass), the carbon nanotube dispersion composition has a content of 5.0≦(X / Y)×10 The carbon nanotube dispersion composition is characterized in that 0≦50.

[0014] The present invention also relates to the carbon nanotube dispersion composition, wherein the cumulative particle size D50 measured by dynamic light scattering is 100 nm to 500 nm.

[0015] The present invention also relates to the carbon nanotube dispersion composition, which has a complex modulus of elasticity of 1 to 50 Pa and a phase angle of 20° to 70°.

[0016] The present invention also relates to the carbon nanotube dispersion composition, wherein the dispersant is contained in an amount of 10 to 50 parts by mass relative to 100 parts by mass of the carbon nanotubes.

[0017] The present invention also relates to the carbon nanotube dispersion composition, which is a dispersion containing 2.5 parts by mass to 7.0 parts by mass of carbon nanotubes in 100 parts by mass of the carbon nanotube dispersion, and is characterized in that the viscosity of the carbon nanotube dispersion at 25°C when measured with a Brookfield viscometer rotor at a rotation speed of 60 rpm is 100 mPa·s to 2000 mPa·s.

[0018] The present invention also relates to a carbon nanotube resin composition containing the carbon nanotube dispersion composition and a binder resin.

[0019] The present invention also relates to a composite slurry containing the carbon nanotube resin composition and an active material.

[0020] The present invention also relates to an electrode film which is a coating film of the composite slurry.

[0021] The present invention also relates to a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, in which at least one of the positive electrode and the negative electrode includes the electrode film.

[0022] The present invention also relates to a vehicle comprising the nonaqueous electrolyte secondary battery. [Effects of the Invention]

[0023] By using the carbon nanotube dispersion composition of the present invention, a resin composition, a composite slurry, and an electrode film having excellent electrical conductivity and adhesion can be obtained. Furthermore, a non-aqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics can be obtained. Therefore, the carbon nanotube dispersion composition of the present invention can be used in various fields, such as vehicles, where excellent non-aqueous electrolyte secondary batteries are required. [Brief explanation of the drawings]

[0024] [Figure 1] Figure 1 shows the XRD spectra of CNT(D), (M), and (N). In powder X-ray diffraction analysis of carbon nanotubes, CNT(D), (M), and (N) show two peaks at a diffraction angle of 2θ = 45° ± 5°. [Figure 2] Figure 2 shows the XRD spectra of CNT(D), (E), and (F). It can be seen that, after acid treatment and 3000°C treatment of CNT(D), the powder X-ray diffraction analysis of the carbon nanotube shows that of the two peaks present at a diffraction angle 2θ = 45° ± 5°, the peak on the higher angle side is smaller. [Figure 3] 3 shows the XRD spectrum of a coating film produced using the CNT dispersion composition (D1) obtained in Example 1-4. A peak was observed near 44.05°, and the line connecting the plots at ±0.2° was used as the baseline. A perpendicular line was drawn from the peak to the baseline, and the length from the peak top to the baseline was used as the peak intensity. [Figure 4] 4 is a calibration curve for calculating the amount of metallic cobalt prepared using the CNT dispersion composition (D1) obtained in Example 1-4. The amount of metallic cobalt in the CNT dispersion composition (D1) was estimated to be 35 ppm from the intercept with the X-axis. DETAILED DESCRIPTION OF THE INVENTION

[0025] The carbon nanotube dispersion composition, resin composition, composite slurry, and electrode film and nonaqueous electrolyte secondary battery coated therewith according to the present invention will be described in detail below.

[0026] (1) Carbon nanotubes The carbon nanotube of this embodiment has a cylindrical shape of planar graphite. The carbon nanotube may also contain single-walled carbon nanotubes. Single-walled carbon nanotubes have a structure in which one layer of graphite is wound. Multi-walled carbon nanotubes have a structure in which two or more layers of graphite are wound. Furthermore, the sidewall of the carbon nanotube does not have to have a graphite structure. For example, carbon nanotubes with sidewalls having an amorphous structure can also be used as the carbon nanotube.

[0027] The cobalt content of the carbon nanotubes of this embodiment is 3,000 to 20,000 ppm, and more preferably 6,000 to 15,000 ppm. CNTs with a cobalt content of less than 3,000 ppm are produced using a metal catalyst such as iron or nickel, and when used as a conductive additive for a non-aqueous electrolyte secondary battery, there is a possibility that the cycle characteristics will deteriorate. Furthermore, carbon nanotubes with a cobalt content of 3,000 to 20,000 ppm are purified at high temperatures to reduce the cobalt content to 3,000 ppm or less, and the carbon nanotubes may fuse together, making it difficult to form conductive paths.

[0028] The G / D ratio (peak ratio between G-band and D-band) of the carbon nanotubes of this embodiment is 0.5 to 1.5, and more preferably 0.7 to 1.0, where G is the maximum peak intensity in the range of 1560 to 1600 cm-1 in a Raman spectrum and D is the maximum peak intensity in the range of 1310 to 1350 cm-1. The G / D ratio of the carbon nanotubes of this embodiment can be determined by Raman spectroscopy.

[0029] The BET specific surface area of the carbon nanotubes of this embodiment is 150 m 2 / g~800m 2 / g, 180-600m 2 / g, and 200m 2 / g~500m 2 / g is more preferred.

[0030] The carbon nanotubes of this embodiment preferably have a peak at a diffraction angle 2θ=25°±2° when subjected to powder X-ray diffraction analysis, and the half-width of the peak is 2° or more and less than 6°. It is preferable that the angle be equal to or greater than 2.5° and less than 6°.

[0031] When the carbon nanotubes of this embodiment are subjected to powder X-ray diffraction analysis, two peaks are present at a diffraction angle 2θ=45°±5°, and when the lower-angle peak is designated as α and the higher-angle peak is designated as β, the relationship preferably satisfies 0.7<(β / α)<1.0, and more preferably 0.8<(β / α)<1.0. The higher-angle peak corresponds to metallic cobalt, and carbon nanotubes within the above range are suitable as conductive materials for nonaqueous secondary electrolyte batteries.

[0032] The carbon nanotubes of this embodiment preferably have an average outer diameter of 4 to 25 nm, more preferably 4 to 20 nm, and even more preferably 4 to 15 nm.

[0033] The outer diameter and average outer diameter of the carbon nanotubes in this embodiment are determined as follows. First, the carbon nanotubes are observed and photographed using a transmission electron microscope. Next, 300 carbon nanotubes are randomly selected from the photograph and the outer diameter of each is measured. Next, the average outer diameter (nm) of the carbon nanotubes is calculated as the number average of the outer diameters.

[0034] The carbon nanotube of this embodiment preferably has 3 to 30 walls, more preferably 3 to 20 walls, and even more preferably 3 to 10 walls.

[0035] The volume resistivity of the carbon nanotube of this embodiment is 1.0×10 -2 ~3.0×10 -2 Ω·cm is preferred, and 1.0×10 -2 ~2.0×10 -2 It is more preferably Ω·cm. The volume resistivity of carbon nanotubes can be measured using a powder resistivity measuring device (Loresta GP Powder Resistivity Measuring System MCP-PD-51, manufactured by Mitsubishi Chemical Analytech Co., Ltd.).

[0036] The carbon purity of the carbon nanotubes of this embodiment is expressed as the content (%) of carbon atoms in the carbon nanotubes. The carbon purity is more preferably 95% by mass or more, and even more preferably 98% by mass or more, relative to 100% by mass of the carbon nanotubes.

[0037] The amount of metal contained in the carbon nanotubes of this embodiment is preferably less than 5% by mass, and more preferably less than 2% by mass, based on 100% by mass of the carbon nanotubes. Metals contained in the carbon nanotubes include metals and metal oxides used as catalysts when synthesizing carbon nanotubes. Specific examples include metals such as iron, cobalt, nickel, aluminum, magnesium, silica, manganese, and molybdenum, as well as metal oxides and composite oxides thereof.

[0038] The amount of iron contained in the carbon nanotubes of this embodiment is preferably less than 10 ppm. When carbon nanotubes containing 10 ppm or more of iron are used in a nonaqueous electrolyte secondary battery, the iron may dissolve into the electrolyte and deposit on the counter electrode, which may lead to an internal short circuit in the battery.

[0039] The carbon nanotubes of this embodiment are usually present as secondary particles. The shape of these secondary particles may be, for example, a state in which carbon nanotubes, which are general primary particles, are intricately entangled. They may also be an aggregate of straight carbon nanotubes. Secondary particles that are an aggregate of straight carbon nanotubes are easier to disentangle than entangled ones. Furthermore, straight ones have better dispersibility than entangled ones, so they can be suitably used as carbon nanotubes.

[0040] The carbon nanotubes of this embodiment may be surface-treated carbon nanotubes. Alternatively, the carbon nanotubes may be carbon nanotube derivatives to which functional groups such as carboxyl groups have been added. Alternatively, carbon nanotubes encapsulating organic compounds, metal atoms, or substances such as fullerenes may also be used.

[0041] The carbon nanotubes of this embodiment may be produced by any method. Carbon nanotubes can generally be produced by laser ablation, arc discharge, thermal CVD, plasma CVD, and combustion methods, but are not limited to these. For example, carbon nanotubes can be produced by catalytically reacting a carbon source with a catalyst at 500 to 1000°C in an atmosphere with an oxygen concentration of 1% by volume or less. The carbon source may be at least one of a hydrocarbon and an alcohol.

[0042] Any conventionally known source gas can be used as a carbon source for carbon nanotubes. For example, hydrocarbons such as methane, ethylene, propane, butane, and acetylene, carbon monoxide, and alcohols can be used as carbon-containing source gases, but they are not limited to these. From the viewpoint of ease of use, it is particularly desirable to use at least one of hydrocarbons and alcohols as the source gas.

[0043] (2) Dispersant The dispersant of this embodiment is not particularly limited as long as it can disperse and stabilize carbon nanotubes, and surfactants and resin-type dispersants can be used. Surfactants are mainly classified into anionic, cationic, nonionic, and amphoteric. Depending on the properties required for dispersing carbon nanotubes, a suitable type of dispersant can be used in a suitable amount.

[0044] When selecting an anionic surfactant, its type is not particularly limited.Specific examples include, but are not limited to, fatty acid salts, polysulfonates, polycarboxylates, alkyl sulfates, alkylaryl sulfonates, alkylnaphthalenesulfonates, dialkylsulfonates, dialkylsulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalenesulfonic acid formalin condensates, polyoxyethylene alkyl phosphate sulfonates, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters.Further examples include, but are not limited to, sodium dodecylbenzenesulfonate, sodium laurate sulfate, polyoxyethylene lauryl ether sodium sulfate, polyoxyethylene nonylphenyl ether sulfate, and sodium salt of β-naphthalenesulfonic acid formalin condensates.

[0045] Cationic surfactants include alkylamine salts and quaternary ammonium salts. Specific examples include, but are not limited to, stearylamine acetate, trimethyl palmitate ammonium chloride, trimethyl tallow ammonium chloride, dimethyldioleylammonium chloride, methyl oleyldiethanol chloride, tetramethylammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide, 4-alkylmercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyltriethylammonium chloride. Amphoteric surfactants include, but are not limited to, aminocarboxylic acid salts.

[0046] Examples of nonionic surfactants include, but are not limited to, polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, and alkyl allyl ethers. Examples of suitable olefin polyols include, but are not limited to, tungstate fatty acid esters and polyoxyethylene octylphenyl ether.

[0047] The surfactant to be selected is not limited to a single surfactant. Therefore, it is also possible to use a combination of two or more surfactants. For example, a combination of an anionic surfactant and a nonionic surfactant, or a combination of a cationic surfactant and a nonionic surfactant can be used. In this case, it is preferable to blend an appropriate amount for each surfactant component. A combination of an anionic surfactant and a nonionic surfactant is preferred. The anionic surfactant is preferably a polycarboxylate. The nonionic surfactant is preferably polyoxyethylene phenyl ether.

[0048] Specific examples of resin-type dispersants include cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, ethylhydroxyethyl cellulose, nitrocellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, carboxymethyl cellulose, etc.), polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, hydrogenated nitrile butadiene rubber, and polyacrylonitrile polymers. Methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, hydrogenated nitrile butadiene rubber, and polyacrylonitrile polymers are particularly preferred. The molecular weight of the resin-type dispersant is preferably 10,000 to 300,000, and more preferably 10,000 to 150,000.

[0049] In addition to the dispersant, it is preferable to add an amine compound or an inorganic base. As the amine compound, primary amines (primary amines), secondary amines (secondary amines), and tertiary amines (tertiary amines) are used, and ammonia and quaternary ammonium compounds are not included. As the amine compound, in addition to monoamines, amine compounds such as diamines, triamines, and tetramines having multiple amino groups in the molecule can also be used. Specific examples of inorganic bases include, but are not limited to, aliphatic primary amines such as methylamine, ethylamine, butylamine, and octylamine, aliphatic secondary amines such as dimethylamine, diethylamine, and dibutylamine, aliphatic tertiary amines such as trimethylamine, triethylamine, and dimethyloctylamine, amino acids such as alanine, methionine, proline, serine, asparagine, glutamine, lysine, arginine, histidine, aspartic acid, glutamic acid, and cysteine, alkanolamines such as dimethylaminoethanol, monoethanolamine, diethanolamine, methylethanolamine, and triethanolamine, and alicyclic nitrogen-containing heterocyclic compounds such as hexamethylenetetramine, morpholine, and piperidine. Examples of inorganic bases include alkali metal hydroxides, alkaline earth metal hydroxides, alkali metal carbonates, alkaline earth metal carbonates, alkali metal phosphates, and alkaline earth metal phosphates.

[0050] (3) Amide-based polar solvents Examples of the amide organic solvent of the present embodiment include N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methylcaprolactam, etc. In particular, it is more preferable to include at least one selected from the group consisting of N-methyl-2-pyrrolidone and N-ethyl-2-pyrrolidone.

[0051] The water content of the amide-based polar solvent of this embodiment is preferably 300 ppm or less, more preferably 100 ppm or less. By using an amide-based polar solvent with a low water content, the carbon The water content in the nanotube dispersion composition can be controlled.

[0052] (4) Carbon nanotube dispersion composition The carbon nanotube dispersion composition of this embodiment contains carbon nanotubes, a dispersant, and an amide-based polar solvent.

[0053] The carbon nanotube dispersion composition of this embodiment has a water content of 50 ppm to 1500 ppm, preferably 100 ppm to 1200 ppm, and more preferably 200 ppm to 1200 ppm. When the water content of the carbon nanotube dispersion composition is within the above range, the interaction between water and cobalt causes basicity, which is thought to improve the dispersibility of the carbon nanotube dispersion composition. On the other hand, when the water content exceeds the above range, when polyvinylidene fluoride is used as the binder described below, the composite slurry may gel, potentially resulting in a decrease in the performance of the electrode film or battery. The water content of the carbon nanotube dispersion composition can be measured using a trace water content measuring device, with the temperature of the water vaporizer attached to the device set to 230°C.

[0054] The metal cobalt content of the carbon nanotube dispersion composition of this embodiment is preferably 10 ppm to 200 ppm, more preferably 20 to 100 ppm, and even more preferably 30 to 100 ppm. The metal cobalt content of the carbon nanotube dispersion composition can be calculated, for example, by adding 75, 150, 300, or 600 ppm of metal cobalt to the carbon nanotube dispersion composition, dispersing the mixture, and then coating and drying the resulting electrode film, and then preparing a calibration curve by XRD measurement of the resulting film.

[0055] The cobalt content of the carbon nanotube dispersion composition of this embodiment is preferably 80 ppm to 1200 ppm, and more preferably 80 ppm to 800 ppm. The cobalt content of the carbon nanotube dispersion composition can be determined by drying the CNT dispersion composition, then acid-decomposing it using a microwave sample pretreatment device (Milestone General, ETHOS1), extracting the metals contained in the CNT dispersion composition, and then analyzing it using a multi-type ICP optical emission spectrometer (Agilent, 720-ES).

[0056] In the carbon nanotube dispersion composition of this embodiment, when the amount of metallic cobalt determined by X-ray diffraction analysis in 100 parts by mass of the carbon nanotube dispersion composition is X (parts by mass) and the amount of cobalt determined by ICP analysis is Y (parts by mass), it is preferable that 5.0≦(X / Y)×100≦50, and more preferably 8.0≦(X / Y)×100≦40.

[0057] The carbon nanotube dispersion composition of this embodiment preferably has a cumulative particle size D50 measured by dynamic light scattering of 100 nm to 600 nm, more preferably 100 nm to 300 nm, and preferably has a cumulative particle size D90 of 900 nm or less, more preferably 700 nm or less.

[0058] The carbon nanotube dispersion composition of this embodiment preferably has a complex modulus of 1 Pa to 50 Pa, more preferably 4 Pa to 40 Pa. The phase angle is preferably 5° to 70°, more preferably 20° to 60°. The complex modulus and phase angle of the carbon nanotubes can be measured and evaluated by dynamic viscoelasticity measurement.

[0059] The complex modulus indicates the hardness of the carbon nanotube dispersion composition, and decreases as the carbon nanotube dispersibility improves and the viscosity of the carbon nanotube dispersion composition decreases. However, when the carbon nanotube fiber length is long, even if the carbon nanotubes are uniformly and stably dissolved in the medium, the carbon nanotubes themselves have structural viscosity, and The complex modulus may be high. Furthermore, when the molecular weight of the dispersant is high, the dispersant itself may have structural viscosity, resulting in a high complex modulus. The phase angle indicates the phase shift of the stress wave when the strain applied to the carbon nanotube dispersion composition is a sine wave, i.e., indicates the flowability of the dispersion composition. A purely elastic material produces a sine wave in phase with the applied strain, resulting in a phase angle of 0°. On the other hand, a purely viscous material produces a stress wave that is 90° ahead. Typical viscoelasticity measurement samples produce sine waves with phase angles greater than 0° and less than 90°. If the carbon nanotubes in the carbon nanotube dispersion composition are well dispersed, the phase angle approaches 90°, which is the phase angle for a purely viscous material. However, similar to the complex modulus, when the carbon nanotubes or dispersant themselves have structural viscosity, the phase angle may be low even if the conductive material is uniformly and stably dissolved in the medium. A carbon nanotube dispersion composition within the above range has good dispersed particle size and dispersibility of carbon nanotubes, and is suitable as a carbon nanotube dispersion composition for non-aqueous electrolyte secondary batteries.

[0060] The product of the complex modulus and the phase angle of the carbon nanotube dispersion composition of this embodiment is preferably 100-1,500, and more preferably 200-1,200.

[0061] The amount of the dispersant in the carbon nanotube dispersion composition of this embodiment is preferably 10 to 100 parts by mass, more preferably 10 to 50 parts by mass, per 100 parts by mass of the carbon nanotubes.

[0062] The amount of carbon nanotubes in the carbon nanotube dispersion composition of this embodiment is preferably 2.5 to 7.0 parts by mass, more preferably 3.0 to 6.0 parts by mass, relative to 100 parts by mass of the carbon nanotube dispersion liquid.

[0063] The viscosity of the carbon nanotube dispersion composition of this embodiment, measured at 60 rpm using a Brookfield viscometer, is preferably 100 mPa·s to 2000 mPa·s, and more preferably 100 mPa·s to 500 mPa·s.

[0064] In the carbon nanotube dispersion composition of this embodiment, when the viscosity of the carbon nanotube dispersion composition is measured using a Brookfield viscometer at 6 rpm, S is the viscosity, and T is the viscosity measured at 60 rpm, it is preferable that S / T is 2.0≦S / T<7.0, and more preferably 2.0≦S / T≦4.0.

[0065] To obtain the carbon nanotube dispersion composition of this embodiment, it is preferable to carry out a treatment for dispersing the carbon nanotubes in a solvent. The dispersing device used for this treatment is not particularly limited.

[0066] As the dispersing device, a dispersing machine that is normally used for dispersing pigments, etc., can be used. For example, mixers such as a Disper, a Homomixer, and a Planetary Mixer, homogenizers (Advanced Digital Sonifer (registered trademark), Model 450DA manufactured by Branson, "Clearmix" manufactured by M Technique, PRIMI Examples of media-type dispersers include media-type dispersers such as X's "Filmix" and Silverson's "Abramix," paint conditioners (manufactured by Red Devil), colloid mills (PUC's "PUC Colloid Mill" and IKA's "Colloid Mill MK"), cone mills (IKA's "Cone Mill MKO," etc.), ball mills, sand mills (Shinmaru Enterprises' "Dyno Mill," etc.), attritors, pearl mills (Eirich's "DCP Mill," etc.), and Coball mills; high-pressure homogenizers (Genus' "Genus PY," Sugino Machine's "Starburst," Nanomizer's "Nanomizer," etc.); media-less dispersers such as M-Technique's "Claire SS-5" and Nara Kikai's "MICROS," and other roll mills, but are not limited to these.

[0067] (4) Binder A binder is a resin that binds substances together.

[0068] Examples of binders in this embodiment include polymers or copolymers containing ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic acid esters, methacrylic acid, methacrylic acid esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, or the like as structural units; polyurethane resins, polyester resins, phenolic resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, fluororesins; cellulose resins such as carboxymethyl cellulose; rubbers such as styrene-butadiene rubber and fluororubber; and conductive resins such as polyaniline and polyacetylene. Modified resins, mixtures, and copolymers of these resins are also acceptable. In particular, polymeric compounds containing fluorine atoms in the molecule, such as polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene, are preferred in terms of durability.

[0069] The weight-average molecular weight of the binder of this embodiment is preferably 10,000 to 2,000,000, more preferably 100,000 to 1,000,000, and particularly preferably 200,000 to 1,000,000. A small molecular weight may result in a decrease in the resistance and adhesion of the binder. A large molecular weight may improve the resistance and adhesion of the binder, but may increase the viscosity of the binder itself, reducing workability, and may act as a flocculant, causing significant aggregation of dispersed particles.

[0070] (5) Carbon nanotube resin composition The carbon nanotube resin composition of this embodiment contains carbon nanotubes, a dispersant, an amide-based polar solvent, and a binder.

[0071] To obtain the carbon nanotube resin composition of this embodiment, it is preferable to mix and homogenize the carbon nanotube dispersion composition and the binder. As a mixing method, various conventionally known methods can be used. The carbon nanotube resin composition can be produced using the dispersion device described above for the carbon nanotube dispersion composition.

[0072] (6) Active material The active material in this embodiment is a material that is the basis of a battery reaction. Active materials are classified into positive electrode active materials and negative electrode active materials based on electromotive force.

[0073] The positive electrode active material is not particularly limited, but may be a metal compound such as a metal oxide or metal sulfide capable of doping or intercalating lithium ions, or a conductive polymer. Examples include oxides of transition metals such as Fe, Co, Ni, and Mn, composite oxides with lithium, and inorganic compounds such as transition metal sulfides. Specific examples include MnO, VO, and VO. 13Examples of the powder include transition metal oxide powders such as TiO2, composite oxide powders of lithium and transition metals such as layered lithium nickel oxide, lithium cobalt oxide, lithium manganate, and spinel-structured lithium manganate, lithium iron phosphate-based materials which are phosphate compounds with an olivine structure, and transition metal sulfide powders such as TiS2 and FeS. It is also possible to use conductive polymers such as aniline, polyacetylene, polypyrrole, polythiophene, etc. Furthermore, the above inorganic compounds and organic compounds may be mixed and used.

[0074] The negative electrode active material is not particularly limited as long as it can dope or intercalate lithium ions. For example, metal Li, its alloys such as tin alloys, silicon alloys, and lead alloys, LiXFe2O3, LiXFe3O4, and LiXWO2 (x is 0), <x<1の (The number is 1.0). Examples of the negative electrode active material include metal oxides such as lithium titanate, lithium vanadate, and lithium silicate; conductive polymers such as polyacetylene and poly-p-phenylene; amorphous carbonaceous materials such as soft carbon and hard carbon; artificial graphite such as highly graphitized carbon materials; carbonaceous powders such as natural graphite; carbon black, mesophase carbon black, resin-baked carbon materials, vapor-grown carbon fiber, and carbon fiber. These negative electrode active materials can be used alone or in combination.

[0075] The positive electrode active material is preferably a composite oxide of lithium containing a transition metal such as Al, Fe, Co, Ni, or Mn, more preferably a composite oxide of lithium containing any of Al, Co, Ni, or Mn, and particularly preferably a composite oxide of lithium containing Ni and / or Mn. When these active materials are used, particularly good effects can be obtained.

[0076] The BET specific surface area of the active material is 0.1 to 10 m 2 / g is preferred, and 0.2 to 5m 2 / g is more preferable, and 0.3 to 3m 2 / g is more preferred.

[0077] The average particle size of the active material is preferably within a range of 0.05 to 100 μm, and more preferably within a range of 0.1 to 50 μm. The average particle size of the active material as referred to in this specification is the average value of particle sizes measured by an electron microscope.

[0078] (7) Mixture slurry The composite slurry of this embodiment contains carbon nanotubes, a dispersant, an amide-based polar solvent, a binder, and an active material.

[0079] To obtain the composite slurry of this embodiment, it is preferable to add an active material to a carbon nanotube resin composition and then perform a dispersion treatment. The dispersion device used for this treatment is not particularly limited. The composite slurry can be obtained using the dispersion device described above for the carbon nanotube dispersion composition.

[0080] The amount of the active material in the composite slurry is preferably 20 to 85 mass %, and particularly preferably 40 to 85 mass %, relative to 100 mass % of the composite slurry.

[0081] The amount of carbon nanotubes in the mixture slurry is preferably 0.05 to 10 mass %, more preferably 0.1 to 5 mass %, and even more preferably 0.1 to 3 mass %, relative to 100 mass % of the active material.

[0082] The amount of binder in the composite slurry is preferably 0.5 to 20 mass %, more preferably 1 to 10 mass %, and particularly preferably 1 to 5 mass %, relative to 100 mass % of the active material.

[0083] The amount of solid content in the composite slurry is preferably 30 to 90% by mass, and more preferably 40 to 85% by mass, relative to 100% by mass of the composite slurry.

[0084] The water content in the composite slurry is preferably 500 ppm or less, more preferably 300 ppm or less, and particularly preferably 100 ppm or less.

[0085] (8) Electrode film The electrode film of this embodiment is a coating film of a composite material slurry, for example, a coating film formed by coating a current collector with the composite material slurry and drying it to form an electrode composite material layer.

[0086] The material and shape of the current collector used in the electrode film of this embodiment are not particularly limited, and can be appropriately selected from those suitable for various nonaqueous electrolyte secondary batteries. For example, the current collector material can be metals or alloys such as aluminum, copper, nickel, titanium, or stainless steel. Furthermore, while flat foils are generally used, current collectors with roughened surfaces, perforated foils, and mesh-shaped current collectors can also be used.

[0087] The method for applying the composite slurry onto the current collector is not particularly limited, and any known method can be used, such as die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, or electrostatic painting, and the drying method can be, but is not limited to, standing to dry, or using a blower dryer, hot air dryer, infrared heater, or far-infrared heater.

[0088] After coating, the mixture may be rolled using a lithographic press, a calendar roll, etc. The thickness of the electrode mixture layer is generally 1 μm or more and 500 μm or less, and preferably 10 μm or more and 300 μm or less.

[0089] (9) Non-aqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery of this embodiment includes a positive electrode, a negative electrode, and an electrolyte.

[0090] The positive electrode may be prepared by applying a composite slurry containing a positive electrode active material onto a current collector and drying the applied slurry to form an electrode film.

[0091] The negative electrode may be prepared by coating a current collector with a composite slurry containing a negative electrode active material and drying the coated slurry to form an electrode film.

[0092] As the electrolyte, various conventionally known materials capable of ion mobility can be used. Examples include, but are not limited to, those containing lithium salts such as LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, Li(CF3SO2)3C, LiI, LiBr, LiCl, LiAlCl, LiHF2, LiSCN, or LiBPh4 (where Ph is a phenyl group). Those containing sodium salts can also be used. The electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolytic solution.

[0093] The non-aqueous solvent is not particularly limited, but examples thereof include carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate; lactones such as γ-butyrolactone, γ-valerolactone, and γ-octanoic lactone; glymes such as tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1,2-dibutoxyethane; esters such as methyl formate, methyl acetate, and methyl propionate; sulfoxides such as dimethyl sulfoxide and sulfolane; and nitriles such as acetonitrile. These solvents may be used alone or in combination.

[0094] The non-aqueous electrolyte secondary battery of this embodiment preferably includes a separator. Examples of the separator include, but are not particularly limited to, polyethylene non-woven fabric, polypropylene non-woven fabric, polyamide non-woven fabric, and those obtained by subjecting these to hydrophilic treatment.

[0095] The structure of the non-aqueous electrolyte secondary battery of this embodiment is not particularly limited, but it is usually composed of a positive electrode and a negative electrode, and a separator provided as necessary, and can have various shapes according to the purpose of use, such as a paper type, a cylindrical type, a button type, a laminated type, etc.

Examples

[0096] The present invention will be described more specifically with reference to the following examples. The present invention is not limited to the following examples as long as the gist thereof is not exceeded. In the examples, "carbon nanotube" may be abbreviated as "CNT". Unless otherwise specified, "parts" represents "parts by mass" and "%" represents "% by mass".

[0097] <Measurement method of physical properties> The physical properties of the CNT used in each of the following examples and comparative examples were measured by the following method.

[0098] <Cobalt content of CNT> The CNT was acid-decomposed using a microwave sample pretreatment apparatus (ETHOS1 manufactured by Milestone General Co., Ltd.) to extract the metals contained in the CNT. Then, analysis was performed using a multi-type ICP emission spectroscopic analyzer (720-ES manufactured by Agilent Co., Ltd.) to calculate the iron and cobalt contents of the CNT.

[0099] <G / D ratio of CNT> The CNT was placed on a Raman microscope (XploRA, manufactured by Horiba, Ltd.) and measured using a laser wavelength of 532 nm. The measurement conditions were an integration time of 60 seconds, an integration number of 2 times, a dimming filter of 10%, a magnification of the objective lens of 20 times, a confocal hole of 500, a slit width of 100 μm, and a measurement wavelength of 100 to 3000 cm -1It was used. The CNT for measurement was separated on a slide glass and flattened using a spatula. Among the obtained peaks, the maximum peak intensity within the range of 1560 to 1600 cm -1 in the spectrum was defined as G, and the maximum peak intensity within the range of 1310 to 1350 cm -1 in the spectrum was defined as D, and the ratio of G / D was defined as the G / D ratio of CNT.

[0100] <BET specific surface area of CNT> Using an electronic balance (manufactured by Sartorius, MSA225S100DI), 0.03 g of CNT was weighed, and then it was dried while degassing at 110 °C for 15 minutes. Then, using a fully automatic specific surface area measuring device (manufactured by MOUNTECH, HM-model1208), the BET specific surface area of CNT was measured. <Moisture of CNT dispersion composition> The CNT dispersion composition was measured using a trace moisture measuring device (manufactured by Nitto Seiko Analytic Co., Ltd., CA200). The measurement was carried out by setting the vaporization device (manufactured by Nitto Seiko Analytic Co., Ltd., VA200) at 230 °C and placing 0.5 g to 1.0 g of CNT at the sample installation location in the vaporization device.

[0101] <Powder X-ray diffraction analysis of CNT> CNT was placed in the recess of a glass sample plate (outer diameter 5.0 cm × 3.5 cm, thickness 3 mm, sample part 2.0 cm × 2.0 cm, thickness 2 mm) and flattened using a slide glass. Then, a sample for powder X-ray diffraction analysis of CNT was placed in a fully automatic multi-purpose X-ray diffractometer (SmartLab, manufactured by Rigaku), and the operation was carried out from 40° to 50° for analysis. Sampling was performed every 0.01°, and the scan speed was 1° / min. The voltage was 40 kV, the current was 40 mA, and the X-ray source was CuKα ray. The intensity ratio of the two peaks observed at the diffraction angle 2θ = 45° ± 5° obtained at this time was calculated as follows: For the plots appearing at the diffraction angle 2θ = 45° ± 5°, the simple moving average of 11 points was taken for each, and the peak on the low angle side was defined as α and the peak on the high angle side was defined as β. At this time, the baseline was the line connecting the plots at 2θ = 40° and 2θ = 50°. It was the line connecting the plots. (Equation 1) Peak intensity ratio = β / α The evaluation of the peak intensity ratio was defined as follows: ⊙: 0.8 or more and 1.0 or less (excellent), ○: 0.7 or more and less than 0.8 or 1.0 or more and 1.1 or less (good), ×: less than 0.7 or exceeding 1.1 (bad).

[0102] <Average outer diameter of CNT> Using an electronic balance (MSA225S100DI, manufactured by Sartorius), 0.2 g of CNT was weighed into a 450 mL SM sample bottle (manufactured by Sansho Co., Ltd.). 200 mL of toluene was added, and an ultrasonic homogenizer (Advanced Digital Sonifer (registered trademark), MODEL 450DA, manufactured by BRANSON) was used to perform a dispersion treatment under ice cooling for 5 minutes at an amplitude of 50%, thereby preparing a CNT dispersion liquid. Thereafter, the CNT dispersion liquid was appropriately diluted, and several μL was dropped in the form of a collodion film and dried at room temperature. Then, observation was carried out using a transmission electron microscope (H-7650, manufactured by Hitachi, Ltd.). Observation was performed at a magnification of 50,000 times, and a plurality of photos containing 10 or more CNTs in the visual field were taken. The outer diameters of 300 arbitrarily extracted CNTs were measured, and the average value thereof was taken as the average outer diameter (nm) of CNT.

[0103] <Volume resistivity of CNT> Using a powder resistivity measurement device (manufactured by Mitsubishi Chemical Analytech Co., Ltd.: Loresta GP Powder Resistivity Measurement System MCP-PD-51), with a sample mass of 1.2 g, using a powder probe unit (four-probe ring electrode, electrode interval 5.0 mm, electrode radius 1.0 mm, sample radius 12.5 mm), with the applied voltage limiter set to 90 V, the volume resistivity [Ω·cm] of the conductive powder under various pressures was measured. The value of the volume resistivity of CNT at a density of 1 g / cm 3 was evaluated.

[0104] <Iron and cobalt contents of CNT dispersion composition> The CNT dispersion composition was placed in a heat-resistant container made of Teflon (registered trademark) and dried in a hot air oven at 140 ± 5°C. Then, a microwave sample pretreatment device (ETHOS1, manufactured by Milestone General) was used for acid decomposition to extract the metals contained in the CNT dispersion composition. Subsequently, analysis was performed using a multi-type ICP emission spectrometer (720-ES, manufactured by Agilent) to calculate the iron and cobalt contents of the CNTs.

[0105] <Metal cobalt content of CNT dispersion composition> The carbon nanotube dispersion compositions described in the examples and comparative examples below were each added to five glass bottles (M-140, manufactured by Kashiwa Yoko Co., Ltd.) at 80 g each. Then, metal cobalt (cobalt powder, standard content 99+%, manufactured by Fujifilm Wako Pure Chemical Corporation) was added at 0 ppm, 75 ppm, 150 ppm, 300 ppm, and 600 ppm respectively, and 140 g of zirconia beads (bead diameter 1.25 mmφ) were charged. After performing a dispersion treatment for 1 hour using a paint conditioner manufactured by Red Devil, the mixture was passed through a nylon mesh with a mesh opening of 350 μm to separate the zirconia beads, and a carbon nanotube dispersion composition containing metal cobalt was obtained. Subsequently, the carbon nanotube dispersion composition containing metal cobalt was coated on a polyethylene terephthalate (PET) film using a #7 bar coater, and then dried at 120 ± 5°C for 5 minutes. Then, a sample with a diameter of φ16 mm was prepared using an electrode punching punch (manufactured by Nogami Giken Co., Ltd.) with a diameter of φ16 mm and placed in the recess of a glass sample plate for X-ray diffraction analysis. Each coating film was operated from 40° to 50° using a fully automatic multi-purpose X-ray diffractometer (SmartLab, manufactured by Rigaku) for analysis. Sampling was performed every 0.01°, and the scan speed was 1° / min. The voltage was 40 kV, the current was 40 mA, and the X-ray source was CuKα radiation. The peak at 2θ = 44.5 ± 1.0° obtained at this time was the peak derived from metal cobalt, and the amount of metal cobalt was calculated from this peak intensity. The amount of metal cobalt was calculated from the calibration curve of the peak intensity difference obtained by the internal standard addition method. The baseline was defined as the line connecting the plots of ±0.2° from the plot of the peak at 2θ = 44.5 ± 1.0°.

[0106] <Ratio of metallic cobalt in the CNT dispersion composition> When the metallic cobalt content determined by the above X-ray diffraction analysis was X (parts by mass) and the cobalt content determined by ICP analysis was Y (parts by mass), (X / Y) × 100 was defined as the ratio of metallic cobalt in the CNT dispersion composition. The evaluation of the ratio of metallic cobalt was defined as follows: ⊙: 10 or more and less than 40 (excellent), ○: 5 or more and less than 10 or 40 or more and less than 50 (good), ×: less than 5 or exceeding 50 (poor).

[0107] <Initial viscosity of the CNT dispersion composition> After leaving the CNT dispersion composition standing in a thermostatic bath at 25°C for 1 hour or more, the CNT dispersion composition was sufficiently stirred and then immediately measured at a B-type viscometer rotor rotation speed of 60 rpm. The rotor used for the measurement was No. 1 when the viscosity value was less than 100 mPa·s, No. 2 when it was 100 or more and less than 500 mPa·s, No. 3 when it was 500 or more and less than 2000 mPa·s, and No. 4 when it was 2000 or more and less than 10000 mPa·s, respectively. The evaluation of the initial viscosity was defined as follows: ⊙: 100 mPa·s or more and 500 mPa·s or less (excellent), ○: exceeding 500 mPa·s and less than 2000 mPa·s (good), ×: less than 100 mPa·s or 2000 mPa·s or more (poor).

[0108] <Thixotropy (TI value) of the CNT dispersion composition> After leaving the CNT dispersion composition standing in a thermostatic bath at 25°C for 24 hours, the CNT dispersion composition was sufficiently stirred and then immediately measured at a B-type viscometer rotor rotation speed of 6 rpm. Then, it was immediately measured at a B-type viscometer rotor rotation speed of 60 rpm. When the viscosity measured at 6 rpm was S and the viscosity measured at 60 rpm was T, S / T was defined as the TI value, and the TI value was defined as follows: ⊙: 2 or more and less than 4 (excellent), ○: 4 or more and less than 7 (good), ×: less than 2 or exceeding 7 (inferior).

[0109] <Complex elastic modulus and phase angle of the CNT dispersion composition> The complex elastic modulus and phase angle of the CNT dispersion composition were evaluated by performing dynamic viscoelasticity measurements at 25 °C and a frequency of 1 Hz in the range of strain rates from 0.01% to 5% using a rheometer (RheoStress 1 rotational rheometer manufactured by Thermo Fisher Scientific Co., Ltd.) with a cone having a diameter of 60 mm and an angle of 2°. The criteria for the complex elastic modulus were as follows: ⊙: 4 Pa or more and less than 40 Pa (excellent), ○: 1 Pa or more and less than 4 Pa, or 40 Pa or more and less than 50 Pa (good), ×: less than 1 Pa, or exceeding 50 Pa (non-conforming).

[0110] <Measurement of the particle size distribution of the CNT dispersion composition> After leaving the CNT dispersion composition standing in a constant temperature bath at 25 °C for 1 hour or more, the CNT dispersion composition was sufficiently stirred and diluted, and then the cumulative particle diameters D50 and D90 of the CNT dispersion composition were measured using a particle size distribution meter (Nanotrac UPA, model UPA-EX manufactured by Microtrac Bell Co., Ltd.). The refractive index of the CNT particles was 1.8, and the shape was non-spherical. The refractive index of the solvent was 1.47. During the measurement, the concentration of the CNT dispersion was diluted so that the value of the loading index was in the range of 0.8 to 1.2. The criteria for particle size evaluation were as follows: D50: ⊙: 100 or more and 300 or less (excellent), ○: exceeding 300 and 600 or less (good), less than 100 or exceeding 600 (poor).

[0111] <Volume resistivity of the electrode film> The composite material slurry was applied onto an aluminum foil using an applicator so that the coating weight per unit area of the electrode was 20 mg / cm 2 After that, the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes. Then, Loresta GP, MC manufactured by Mitsubishi Chemical Analytech Co., Ltd. The surface resistivity (Ω / □) of the dried coating was measured using a P-T610. After measurement, this was multiplied by the thickness of the electrode composite layer formed on the aluminum foil to obtain the volume resistivity (Ω·cm) of the electrode film. The thickness of the electrode composite layer was measured at three points in the electrode film using a film thickness meter (NIKON, DIGIMICRO MH-15M), and the copper foil film thickness was subtracted from the average value to obtain the volume resistivity (Ω·cm) of the electrode film. The volume resistivity was evaluated as follows: ◎: 6 Ω·cm or less (excellent), 〇: over 6 Ω·cm to 10 Ω·cm or less (good), and over 10 Ω·cm (unacceptable).

[0112] <Peel strength of electrode film> The composite slurry was applied to the electrode using an applicator so that the weight per unit area was 20 mg / cm 2 The coating was then applied to aluminum foil so that the coating was uniform, and the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes. Two 90mm x 20mm rectangles were then cut, with the coating direction as the long axis. Peel strength was measured using a benchtop tensile tester (Strograph E3, manufactured by Toyo Seiki Seisakusho Co., Ltd.) using a 180° peel test. Specifically, a 100mm x 30mm double-sided tape (No. 5000NS, manufactured by Nitoms Inc.) was attached to a stainless steel plate, and the prepared battery electrode composite layer was attached to the other side of the double-sided tape. The adhesive was then pulled upward at a constant speed (50mm / min) to remove the adhesive. The average stress measured during this process was recorded as the peel strength. Peel strength was evaluated as follows: Excellent: 0.7N / cm or more; Good: 0.5N / cm or more but less than 0.7N / cm; Unacceptable: less than 0.5N / cm.

[0113] <Preparation of standard negative electrode> A 150 ml plastic container was charged with 0.5 parts by weight of acetylene black (Denka Black® HS-100, manufactured by Denka), 1 part by weight of MAC500LC (carboxymethylcellulose sodium salt, Sunrose Special Type MAC500L, manufactured by Nippon Paper Industries Co., Ltd., 100% nonvolatile content), and 98.4 parts by weight of water, and then stirred at 2000 rpm for 30 seconds using a centrifugal mixer (Thinky Awatori Rentaro, ARE-310). Further added were 92 parts by weight of artificial graphite (Nippon Graphite Industries, CGB-20) and 5 parts by weight of silicon (Osaka Titanium Technology, SILICON MONOOXIDE SiO 1.3C 5 μm, 100% nonvolatile content) as active materials, and the mixture was stirred at 3000 rpm for 10 minutes using a high-speed mixer. Next, 3.1 parts by mass of SBR (TRD2001, manufactured by JSR Corporation) was added, and the mixture was stirred at 2000 rpm for 30 seconds using the planetary centrifugal mixer to obtain a negative electrode composite slurry. Thereafter, the negative electrode composite slurry was applied to the electrode using an applicator so that the weight per unit area of the electrode became 8 mg / cm. 2 After coating on copper foil so that the density of the composite layer became 1.6 g / cm, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes. Then, the coating was rolled using a roll press (Thank Metal Co., Ltd., 3 ton hydraulic roll press) until the density of the composite layer became 1.6 g / cm. 3 A standard negative electrode was fabricated.

[0114] <Evaluation of rate characteristics of lithium-ion secondary batteries> The laminated lithium-ion secondary battery was placed in a thermostatic chamber at 25°C and subjected to charge / discharge measurements using a charge / discharge device (Hokuto Denko Corporation, SM-8). The battery was charged at a constant current / constant voltage of 10 mA (0.2 C) with a charge cutoff voltage of 4.2 V (cutoff current of 1.0 mA (0.02 C)), followed by a constant current discharge at a discharge current of 10 mA (0.2 C) with a charge cutoff voltage of 4.2 V (cutoff current of 1.0 mA (0.02 C)). This procedure was repeated three times, followed by a constant current / constant voltage charge at a charge current of 10 mA (0.2 C) with a charge cutoff voltage of 4.2 V (cutoff current of 1.0 mA (0.02 C)). The battery was then discharged at both 0.2 C and 3 C until the discharge cutoff voltage of 2.5 V was reached. The discharge capacity was calculated for each battery. The rate characteristic can be expressed as the ratio of the 0.2 C discharge capacity to the 3 C discharge capacity, as shown in Equation 2. (Equation 2) Rate characteristic = 3C discharge capacity / 3rd 0.2C discharge capacity × 100 (%) The rate characteristic evaluation is as follows: ◎ (excellent) for rate characteristics of 80% or more, 〇 (good) for 70% or more but less than 80%, △ (passable) for 60% or more but less than 70%, and × (poor) for less than 60%. The cycle characteristics were rated as +++ (excellent) if the cycle characteristics were 90% or more, ++ (good) if they were 85% or more but less than 90%, + (passable) if they were 80% or more but less than 85%, and - (unacceptable) if they were less than 80%.

[0115] <Evaluation of cycle characteristics of lithium-ion secondary batteries> The laminated lithium-ion secondary battery was placed in a thermostatic chamber at 25°C and subjected to charge / discharge measurements using a charge / discharge device (Hokuto Denko Corporation, SM-8). A constant-current, constant-voltage charge (cutoff current 1.25 mA (0.025 C)) was performed at a charge current of 50 mA (1 C) with a charge cutoff voltage of 4.2 V, followed by a constant-current discharge at a discharge current of 50 mA (1 C) with a discharge cutoff voltage of 2.5 V. This procedure was repeated 200 times. 1 C was defined as the current value required to discharge the theoretical capacity of the positive electrode in 1 hour. The cycle performance can be expressed as the ratio of the 3rd 1 C discharge capacity to the 200th 1 C discharge capacity at 25°C, as shown in Equation 3 below. (Formula 3) Cycle characteristics = 3rd 1C discharge capacity / 200th 1C discharge capacity × 100 (%) The cycle characteristic evaluation was carried out as follows: when the cycle characteristic was 90% or more, it was rated as +++ (excellent); when it was 85% or more but less than 90%, it was rated as ++ (good); when it was 80% or more but less than 85%, it was rated as + (acceptable); when it was less than 80%, it was rated as - (unacceptable).

[0116] <Dispersant> · Polyvinylpyrrolidone (manufactured by Nippon Shokubai Co., Ltd., K-30, weight average molecular weight 40,000), hereinafter abbreviated as PVP. · Polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd., BL-10, calculated molecular weight 15,000), hereinafter abbreviated as PVB. · Hydrogenated nitrile butadiene rubber (dispersant 6 described in paragraph

[0194] of Patent No. 6933285), hereinafter abbreviated as H-NBR.

[0117] <Additive> · 2-Aminoethanol (manufactured by Fujifilm Wako Pure Chemical Corporation, Wako Grade 1)

[0118] <Synthesis of Cobalt Hydroxide> Cobalt hydroxide in which plate-like primary particles formed spherical secondary particles was prepared by the method described in

[0091] of JP-A-2012-072050. The remaining sulfur content in the prepared cobalt hydroxide was 1500 ppm as confirmed by ICP analysis.

[0119] <Synthesis of Catalyst for CNT Synthesis> A catalyst (X) for CNT synthesis was prepared by the method described in paragraphs

[0147] and

[0148] of JP-A-2019-108256, except that 30 parts of the cobalt hydroxide in which plate-like primary particles formed spherical secondary particles were used instead of 30 parts of cobalt hydroxide (II).

[0120] A catalyst (Y) for CNT synthesis was prepared by the method described in paragraph

[0117] of JP-A-2018-150218, except that 30 parts of the cobalt hydroxide in which plate-like primary particles formed spherical secondary particles were used instead of 30 parts of cobalt hydroxide (II).

[0121] <Synthesis of CNT (A)> A heat-resistant dish made of quartz glass, which can be pressurized and heated by an external heater, and has an internal volume of 10 L, was placed at the center of a horizontal reaction tube. 1 g of the catalyst (X) for CNT synthesis was sprinkled on the heat-resistant dish. While injecting nitrogen gas, the air in the reaction tube was evacuated, and the air in the reaction tube was replaced with nitrogen gas. Then, it was heated until the ambient temperature in the horizontal reaction tube reached 700 °C. After reaching 700 °C, propane gas as a hydrocarbon was introduced into the reaction tube at a flow rate of 2 L per minute and subjected to a contact reaction for 60 minutes. After the reaction was completed, the gas in the reaction tube was replaced with nitrogen gas, and the reaction tube was cooled until the temperature reached 100 °C or lower and then taken out to obtain CNT (A).

[0122] <Synthesis of CNT (B) to (C)> CNT (B) to (C) were prepared in the same manner as <Synthesis of CNT (A)>, except that the catalyst for CNT synthesis, reaction temperature, carbon source, and gas flow rate were changed as listed in Table 1.

[0123]

Table 1

[0124] Multi-walled carbon nanotubes (manufactured by JEIO Co., Ltd., JENOTUBE10B) were designated as CNT (D), multi-walled carbon nanotubes (manufactured by LG Chem, BT1001) were designated as CNT (E), multi-walled carbon nanotubes (manufactured by Timesnano, MwCNT) were designated as CNT (F), multi-walled carbon nanotubes (manufactured by Nanocyl, NC7000) were designated as CNT (G), and multi-walled carbon nanotubes (manufactured by KUMHOPETCROCHEMICAL Co., Ltd., 100T) were designated as CNT (H).

[0125] <Synthesis of CNT (I)> CNT (I) was obtained by the method described in

[0096] of Patent No. 6586197.

[0126] <Synthesis of CNT (J)> Weighed 10 g of CNT(A) into a 1-L glass container, added 500 g of 20% hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Corporation), and then stirred well using a stirrer. After that, it was sufficiently diluted with ion-exchanged water, and vacuum filtration was performed using a membrane filter. After repeating the dilution and filtration operations, the CNT was transferred to a PTFE vat, and then dried at 140 °C using an oven to obtain CNT(J).

[0127] <Synthesis of CNT(K)> CNT(K) was obtained by the same method as <Synthesis of CNT(J)> except that CNT(B) was used instead of CNT(A).

[0128] <Synthesis of CNT(L)> CNT(L) was obtained by the same method as <Synthesis of CNT(J)> except that CNT(C) was used instead of CNT(A).

[0129] <Synthesis of CNT(M)> CNT(M) was obtained by the same method as <Synthesis of CNT(J)> except that CNT(D) was used instead of CNT(A).

[0130] <Synthesis of CNT(N)> CNT(N) was obtained by the same method as <Synthesis of CNT(J)> except that 20% hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Corporation) was changed to 60% nitric acid (manufactured by Fujifilm Wako Pure Chemical Corporation). CNT(N) was obtained by the same method as <Synthesis of CNT(J)> except that 20% hydrochloric acid (manufactured by Fujifilm Wako Pure Chemical Corporation) was changed to 60% nitric acid (manufactured by Fujifilm Wako Pure Chemical Corporation).

[0131] <Synthesis of CNT(O)> Weighed 1000 g of CNT(D) into a 7-L carbon heat-resistant container, placed the heat-resistant container containing CNT into the furnace. Then, nitrogen gas was introduced into the furnace to discharge the air in the furnace while maintaining a positive pressure. After the oxygen concentration in the furnace reached 0.1% or less, the temperature in the furnace was raised to 3000 °C over 30 hours, and then held at 3000 °C for 1 hour. After that, the heating in the furnace was stopped, and the sample was cooled to obtain CNT(O).

[0132] Table 2 shows the CNTs used in the examples and comparative examples described below.

[0133] [Table 2]

[0134] (Example 1-1) 200 g of CNT (A) was placed in a heat-resistant Teflon (registered trademark) container and dried in an electric oven at 140 °C ± 5 °C for 24 hours. The resulting mixture was then cooled in an open dry chamber (Daikin Industries, Ltd., HRG-50A) to produce dried CNT (A) with a moisture content of 300 ppm or less. Following the composition shown in Table 3, 96.4 parts by mass of NMP (Kishida Chemical Co., Ltd., for LBG, moisture content 100 ppm or less) and 0.6 parts by mass of dispersant (PVP) were added to a stainless steel container placed in the open dry chamber and stirred with a disperser until uniform. Next, 1.5 parts by mass of dried CNT (A) was added while stirring with a disperser. A high-shear mixer (SILVERSON, L5M-A) equipped with a square-hole high-shear screen was used for batch dispersion at 8,600 rpm until the mixture was uniform and the dispersion particle size measured by a grind gauge was 250 μm or less. Next, the liquid to be dispersed was supplied from the stainless steel container to the high-pressure homogenizer via piping, and a circulation-type dispersion process was carried out. The dispersion process was carried out using a single nozzle chamber, with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. After the viscosity of the liquid to be dispersed, measured at 60 rpm using a B-type viscometer (TOKI SANGYO, VISCOMETER, MODEL: BL), was dispersed to a value of 3,000 mPa·s or less, 0.5 parts by mass of dried CNT (A) was further added to the stainless steel container while stirring with a disperser, and a circulation-type dispersion process was again carried out using the high-pressure homogenizer. After circulating and dispersing using a homogenizer until the viscosity reached 3,000 mPa s or less, 0.5 parts by mass of dried CNTs (A) were added to the stainless steel container while stirring with a disperser. This process was repeated three times in total (total amount of dried CNTs (A) added was 3.0 parts by mass). Subsequently, a dispersion process was performed 15 times using a high-pressure homogenizer, and then the mixture was passed through a mag filter with a surface magnetic flux density of 17,000 gauss and a nylon mesh with 20 μm openings to obtain a CNT dispersion composition (A) containing 3.0 parts by mass of CNTs (A).

[0135] (Examples 1-2 to 1-16), (Comparative Examples 1-1 to 1-4) CNT dispersion compositions (B) to (O) were obtained in the same manner as in Example 1-1, except that the CNT type, CNT addition amount, dispersant type, dispersant addition amount, and NMP addition amount were changed as shown in Table 3. Dried CNTs (J) to (N) were produced in the same manner as in Example 1-1, but the moisture content of the dried CNTs (J) to (N) was 800 ppm.

[0136] (Examples 1-17 and 1-18) CNT dispersions (D7) to (D8) were obtained in the same manner as in Example 1-1, except that the number of pass-type dispersions was changed to 10 and 30, respectively.

[0137] (Examples 1-19) 200 g of CNT (M) was placed in a heat-resistant Teflon container and dried in an electric oven at 140°C ±5°C for 24 hours. The resulting mixture was then cooled in an open dry chamber (Daikin Industries, Ltd., HRG-50A) to produce dried CNT (M) with a moisture content of 800 ppm. Following this, 92.8 parts by mass of NMP (Kishida Chemical Co., Ltd., for LBG, moisture content 100 ppm or less) and 1.2 parts by mass of dispersant (PVB) were added to a stainless steel container placed in the open dry chamber according to the composition shown in Table 3, and the mixture was stirred with a disperser until uniform. Next, 2.0 parts by mass of dried CNT (D) was added while stirring with a disperser. A high-shear mixer (SILVERSON, L5M-A) equipped with a square-hole high-shear screen was used for batch dispersion at 8,600 rpm until the mixture was uniform and the dispersion particle size measured by a grind gauge was 250 μm or less. Next, the dispersion liquid was fed from the stainless steel container to a high-pressure homogenizer via piping, and a circulation-type dispersion process was performed. The dispersion process was performed using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. After the viscosity of the dispersion liquid measured at 60 rpm using a B-type viscometer (TOKI SANGYO, VISCOMETER, MODEL: BL) reached 3,000 mPa·s or less, 0.25 parts by mass of dried CNTs (M) were added to the stainless steel container while stirring with a disperser, and the circulation-type dispersion process was repeated again using the high-pressure homogenizer. After circulation-type dispersion using the high-pressure homogenizer until the viscosity reached 3,000 mPa·s or less, 0.25 parts by mass of dried CNTs (M) were added to the stainless steel container while stirring with a disperser. This process was repeated 16 times in total (total amount of dried CNTs (M) added was 6.0 parts by mass). Subsequently, a dispersion treatment was carried out using a high-pressure homogenizer with 40 passes to obtain a CNT dispersion composition (M2) containing 6.0 parts by mass of CNTs.

[0138] (Comparative Examples 1-5) Ion-exchanged water was added to the CNT dispersion composition (M2) to prepare a CNT dispersion composition (M3) containing 5000 ppm of water.

[0139] [Table 3]

[0140] Example 2-1 Capacity 150cm 3 Into a plastic container, 12.5 parts by mass of NMP containing 8% by mass of PVDF (polyvinylidene fluoride, Solvey, Solef #5130) dissolved therein and 13.8 parts by mass of NMP were weighed. Then, 8.3 parts by mass of CNT dispersion composition (A) was added, and the mixture was stirred at 2000 rpm for 30 seconds using a planetary centrifugal mixer (Awatori Rentaro, ARE-310) to obtain CNT resin composition (A). Furthermore, 98.7 parts by mass of a positive electrode active material (HED (registered trademark) NCM-111 1100, manufactured by BASF Toda Battery Materials, LLC) was added, and the mixture was stirred at 2000 rpm for 2.5 minutes using a planetary centrifugal mixer (Awatori Rentaro, ARE-310) to obtain composite slurry (A).

[0141] (Examples 2-2 to 2-18), (Comparative Examples 2-1 to 2-4) CNT resin compositions (B) to (D8) and composite slurries (B) to (D8) were obtained in the same manner as above, except that CNT dispersion compositions (B) to (D8) were used instead of CNT dispersion composition (A).

[0142] (Example 2-19) A CNT resin composition (M2) and a composite slurry (M2) were obtained in the same manner as in Example 2-1, except that the amount of CNT dispersion composition (M2) added was 4.2 parts by mass instead of the CNT dispersion composition (A), and the amount of NMP added was 18.0 parts by mass.

[0143] (Comparative Example 2-5) A CNT resin composition (M3) and a composite slurry (M3) were obtained in the same manner as in Comparative Example 2-19, except that the CNT dispersion composition (M3) was used instead of the CNT dispersion composition (M2).

[0144] [Table 4]

[0145] Example 3-1 The composite slurry (A) was applied to the electrode using an applicator so that the weight per unit area of the electrode was 20 mg / cm. 2 After coating on aluminum foil so that the coating was as follows: the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain an electrode film (A). The electrode film (A) was then rolled using a roll press (Thank Metal, 3 ton hydraulic roll press) to obtain a positive electrode (A). The weight per unit area of the composite layer was 20 mg / cm. 2 The density of the composite layer after the rolling treatment was 3.1 g / cc.

[0146] (Examples 3-2 to 3-19), (Comparative Examples 3-1 to 3-5) Electrode membranes (B) to (M3) and positive electrodes (B) to (M3) were produced in the same manner as in Example 3-1, except that the composite slurry (A) was changed to composite slurries (B) to (M3).

[0147] Table 5 shows the electrode films produced in Examples 3-1 to 3-19 and Comparative Examples 3-1 to 3-5 and the evaluation results of the electrode films.

[0148] [Table 5]

[0149] Example 4-1 The positive electrode (A) and standard negative electrode were punched out to 45 mm x 40 mm and 50 mm x 45 mm, respectively. The separator (porous polypropylene film) between them was inserted into an aluminum laminate bag and dried in an electric oven at 60 °C for 1 hour. Then, in an argon-filled glove box, 2 mL of electrolyte (a nonaqueous electrolyte prepared by mixing ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a 1:1:1 (volume ratio) solvent, adding 2 parts by weight of VC (vinylene carbonate) per 100 parts by weight of the solvent mixture, and dissolving LiPF6 at a concentration of 1 M) was poured into the bag. The aluminum laminate was then sealed to prepare a laminate-type lithium-ion secondary battery (A).

[0150] (Examples 4-2 to 4-19), (Comparative Examples 4-1 to 4-5) Laminate type lithium ion secondary batteries (B) to (M3) were produced in the same manner as in Example 4-1, except that the positive electrode was changed to one shown in Table 6.

[0151] [Table 6]

[0152] In the above example, the cobalt content is 3000 ppm to 20000 ppm, the G / D ratio is 0.5 or more and less than 1.5, and the BET specific surface area is 150 m 2 / g~800m 2 A carbon nanotube dispersion composition containing carbon nanotubes with a water content of 50 ppm to 1500 ppm, a dispersant, and an amide-based polar solvent, and having a water content of 50 ppm to 1500 ppm was used. In the examples, lithium ion secondary batteries with superior rate characteristics and cycle characteristics compared to the comparative examples were obtained. Therefore, it has become clear that the present invention can provide a lithium ion secondary battery with high capacity, high output, and high durability that are difficult to achieve with conventional carbon nanotube dispersion compositions.

[0153] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the invention.

Claims

1. A carbon nanotube dispersion composition comprising carbon nanotubes, a dispersant, and an amide-based polar solvent, the carbon nanotube dispersion composition being characterized by satisfying the following (1), (2), (3), and (4): (1) The cobalt content of the carbon nanotubes is 3,000 ppm to 20,000 ppm. (2) The G / D ratio of the carbon nanotubes is 0.5 or more and less than 1.

5. (3) The BET specific surface area of the carbon nanotube is 150 m ２ / g~800m ２ / g. (4) The water content of the carbon nanotube dispersion composition is 50 ppm to 1500 ppm.

2. The carbon nanotube dispersion composition according to claim 1, characterized in that in powder X-ray diffraction analysis of the carbon nanotubes, two peaks are present at a diffraction angle 2θ = 45° ± 5°, and when the peak on the lower angle side is α and the peak on the higher angle side is β, 0.7 < (β / α) < 1.

0.

3. The content of metallic cobalt in 100 parts by mass of the carbon nanotube dispersion composition is X (parts by mass).

3. The carbon nanotube dispersion composition according to claim 1, wherein the cobalt content is Y (parts by mass), and the relationship is 5.0≦(X / Y)×100≦50.

4. 4. The carbon nanotube dispersion composition according to claim 1, wherein the cumulative particle size D50 measured by dynamic light scattering is 100 nm to 500 nm.

5. 5. The carbon nanotube dispersion composition according to claim 1, wherein the carbon nanotube dispersion composition has a complex modulus of 1 to 50 Pa and a phase angle of 20° to 70°.

6. 6. The carbon nanotube dispersion composition according to claim 1, wherein the dispersant is contained in an amount of 10 to 50 parts by mass per 100 parts by mass of the carbon nanotubes.

7. 7. The carbon nanotube dispersion composition according to any one of claims 1 to 6, characterized in that the carbon nanotube dispersion contains 2.5 parts by mass to 7.0 parts by mass of carbon nanotubes in 100 parts by mass of the carbon nanotube dispersion, and the viscosity of the carbon nanotube dispersion at 25°C measured with a Brookfield viscometer rotor at a rotation speed of 60 rpm is 100 mPa·s to 2000 mPa·s.

8. A carbon nanotube resin composition comprising the carbon nanotube dispersion composition according to any one of claims 1 to 7 and a binder resin.

9. A composite slurry comprising the carbon nanotube resin composition according to claim 8 and an active material.

10. An electrode film which is a coating film of the composite slurry according to claim 9.

11. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein at least one of the positive electrode and the negative electrode comprises the electrode film according to claim 10.

12. A vehicle comprising the nonaqueous electrolyte secondary battery according to claim 11.

Images