Carbon nanotube dispersion composition, and resin composition, electrode film, secondary battery, vehicle using 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 carbon nanotube dispersion compositions. More specifically, it relates to a cobalt-containing carbon nanotube dispersion composition, a resin composition comprising a cobalt-containing carbon nanotube dispersion composition and a binder resin, a composite slurry comprising a cobalt-containing carbon nanotube dispersion composition, a binder resin and an active material, an electrode film coated therewith, a non-aqueous secondary electrolyte secondary battery comprising an electrode film and an electrolyte, and a vehicle comprising a non-aqueous secondary electrolyte secondary battery. [Background technology]

[0002] With the spread of electric vehicles and the miniaturization, weight reduction, and increased performance of portable devices, there is a growing demand for secondary batteries with high energy density and higher capacity. Against this backdrop, non-aqueous electrolyte secondary batteries, particularly lithium-ion secondary batteries, which utilize non-aqueous electrolytes due to their high energy density and high voltage characteristics, are increasingly being used in many devices.

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

[0004] Conductive additives used include carbon black, Ketjenblack, fullerene, graphene, and fine carbon materials. Carbon nanotubes, a type of fine carbon fiber, are particularly frequently used. For example, electrode films coated with a composite slurry containing a carbon nanotube dispersion composition and an active material are known to have low electrode resistance and improved battery load resistance and cycle characteristics. (See, for example, Patent Documents 1 and 2.)

[0005] Using carbon nanotubes with a small average outer diameter allows for the efficient formation of conductive networks with small amounts, thereby reducing the amount of conductive additives contained in the positive and negative electrodes of lithium-ion secondary batteries. Similar effects are known to be observed when using carbon nanotubes with long fiber lengths (see, for example, Patent Documents 3 and 4). However, carbon nanotubes with these characteristics have strong cohesive forces and are difficult to disperse.

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

[0007] Various dispersion methods have been investigated to reduce electrode resistance. For example, a method has been investigated to control the dispersion state of carbon nanotubes by using hydrogenated nitrile butadiene rubber as a dispersant and optimizing the complex modulus. (See Patent Documents 6, 7, 8, and 9) However, in Patent Document 6, the complex modulus of the CNT dispersion composition is high, and the concentration is high and It has been difficult to obtain uniformly dispersed carbon nanotubes. Furthermore, Patent Document 7 describes how to obtain highly dispersible carbon nanotubes by using various dispersants and dispersing them in a high-pressure homogenizer. It has been proposed that von nanotubes can be obtained, but high concentrations of CNTs in amide-based polar solvents Dispersing carbon nanotubes had not been considered. Furthermore, Patent Document 8 proposes a carbon nanotube dispersion composition containing a high concentration (5% by mass) of carbon nanotubes with an outer diameter of 6-15 nm in an amide-based polar solvent. However, because the entire amount of carbon nanotubes is loaded into the dispersion medium at once, there is a problem of high heat generation and a decrease in the adsorption efficiency of the dispersant. In addition, although the use of carbon nanotubes with a large BET specific surface area and high hygroscopicity has been considered, no measures have been taken to prevent water contamination of the amide-based polar solvent when preparing the carbon nanotube dispersion composition, resulting in a problem of the carbon nanotube dispersion composition containing a large amount of water. Therefore, when preparing the composite slurry, it reacts with the basic active material, causing the composite to gel and worsening the resistance. Patent Document 9 proposes a carbon nanotube dispersion composition containing a high concentration (5% by mass) of carbon nanotubes with an outer diameter of 7-12 nm by loading the carbon nanotubes in stages, but regarding CNT dispersion in an amide-based polar solvent... It was not shown at all. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Patent No. 6586197 [Patent Document 2] Japanese Patent Publication No. 2011-70908 [Patent Document 3] Patent No. 6590034 [Patent Document 4] Japanese Patent Publication No. 2012-221672 [Patent Document 5] Japanese Patent Publication No. 2019-192537 [Patent Document 6] Special Publication No. 2018-533175 [Patent Document 7] Japanese Patent Publication No. 2021-72279 [Patent Document 8] Patent No. 6933285 [Patent Document 9] Patent No. 6860740

Summary of the Invention

Problems to be Solved by the Invention

[0009] The problem to be solved by the present invention is to provide a carbon nanotube dispersion composition, a carbon nanotube resin composition, and a composite slurry having high dispersibility in order to obtain an electrode film with high adhesiveness and conductivity. More specifically, it is to provide a non-aqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics, and a vehicle equipped with the non-aqueous electrolyte secondary battery.

Means for Solving the Problems

[0010] The inventors of the present invention have intensively studied to solve the above problems. The inventors have found that when a carbon nanotube dispersion composition in which the cobalt content of the carbon nanotubes is 3000 ppm to 20000 ppm, the G / D ratio is not less than 0.5 and less than 1.5, and the BET specific surface area is 150 m 2 / g to 800 m 2 / g, and the water content of the carbon nanotube dispersion composition is 50 ppm to 1500 ppm is used, an electrode film excellent in conductivity and adhesiveness can be obtained, and a non-aqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics can be obtained. Based on such a discovery, the inventors have made the present invention.

[0011] That is, the present invention relates to a carbon nanotube dispersion composition containing carbon nanotubes, a dispersant, and an amide-based polar solvent, characterized by satisfying 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 not less than 0.5 and less than 1.5. (3) The BET specific surface area of the carbon nanotubes is 150 m 2 / g to 800 m 2 / g. (4) The water content of the carbon nanotube dispersion composition is 50 ppm to 1500 ppm.

[0012] Furthermore, in powder X-ray diffraction analysis of carbon nanotubes, the present invention provides a diffraction angle of 2θ = 45 The present invention relates to a carbon nanotube dispersion composition characterized by the presence of two peaks at ±5°, where α is the low-angle peak and β is the high-angle peak, and 0.7 < (β / α) < 1.0.

[0013] Furthermore, in this invention, when the metallic cobalt content in 100 parts by mass of a carbon nanotube dispersion composition is X (parts by mass) and the cobalt content is Y (parts by mass), 5.0 ≤ (X / Y) × 10 The present invention relates to the carbon nanotube dispersion composition characterized by having a coefficient of 0 ≤ 50.

[0014] Furthermore, the present invention relates to the carbon nanotube dispersion composition characterized in that the cumulative particle size D50 measured by dynamic light scattering is 100 nm to 500 nm.

[0015] Furthermore, the present invention relates to the carbon nanotube dispersion composition characterized by having a complex modulus of elasticity of 1 to 50 Pa and a phase angle of 20° to 70°.

[0016] Furthermore, the present invention relates to the carbon nanotube dispersion composition characterized in that the dispersant is contained in an amount of 10 to 50 parts by mass per 100 parts by mass of carbon nanotubes.

[0017] Furthermore, the present invention relates to a carbon nanotube dispersion composition characterized by a dispersion containing 2.5 to 7.0 parts by mass of carbon nanotubes in 100 parts by mass of the carbon nanotube dispersion, wherein the viscosity of the carbon nanotube dispersion at 25°C measured at a B-type viscometer rotor rotation speed of 60 rpm is 100 mPa·s to 2000 mPa·s.

[0018] Furthermore, the present invention relates to a carbon nanotube resin composition comprising the carbon nanotube dispersion composition and a binder resin.

[0019] Furthermore, the present invention relates to the carbon nanotube resin composition and the composite slurry containing the active material.

[0020] Furthermore, the present invention relates to an electrode film which is a coating film for the aforementioned asphalt slurry.

[0021] Furthermore, the present invention relates to a non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein at least one of the positive electrode or the negative electrode includes the electrode film.

[0022] Furthermore, the present invention relates to a vehicle comprising the aforementioned non-aqueous electrolyte secondary battery. [Effects of the Invention]

[0023] By using the carbon nanotube dispersion composition of the present invention, resin compositions, composite slurries, and electrode films with excellent conductivity and adhesion can be obtained. Furthermore, non-aqueous electrolyte secondary batteries with excellent rate characteristics and cycle characteristics can be obtained. Therefore, the carbon nanotube dispersion composition of the present invention can be used in various application fields, such as vehicles, where excellent non-aqueous secondary electrolyte secondary batteries are required. [Brief explanation of the drawing]

[0024] [Figure 1] Figure 1 shows the XRD spectra of CNT(D), (M), and (N). In powder X-ray diffraction analysis of carbon nanotubes, two peaks can be confirmed to exist at the diffraction angle 2θ = 45° ± 5° for CNT(D), (M), and (N). [Figure 2] Figure 2 shows the XRD spectra of CNT(D), (E), and (F). Acid treatment and 3000°C treatment of CNT(D) can be observed to reduce the height of the two peaks present at the diffraction angle 2θ = 45° ± 5° in powder X-ray diffraction analysis of carbon nanotubes. [Figure 3] Figure 3 shows the XRD spectra of coatings prepared using the CNT dispersion composition (D1) obtained in Examples 1-4. A peak was obtained around 44.05°, and the line connecting the plots at ±0.2° was used as the baseline. The peak intensity was defined as the length from the peak top to the baseline when a perpendicular line was drawn from the peak to the baseline. [Figure 4] Figure 4 shows a calibration curve for calculating the amount of metallic cobalt prepared using the CNT-dispersed composition (D1) obtained in Examples 1-4. The amount of metallic cobalt in the CNT-dispersed composition (D1) was estimated to be 35 ppm from the intercept with the X-axis. [Modes for carrying out the invention]

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

[0026] (1) Carbon nanotubes The carbon nanotubes of this embodiment have a cylindrical shape formed by winding planar graphite. The carbon nanotubes may also consist of a mixture of 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 sidewalls of the carbon nanotubes do not have to be of a graphite structure. For example, carbon nanotubes having sidewalls with an amorphous structure can also be used as carbon nanotubes.

[0027] The cobalt content of the carbon nanotubes of the present embodiment is 3000 to 20000 ppm, and more preferably 6000 to 15000 ppm. CNTs with a cobalt content less than 3000 ppm are produced using metal catalysts such as iron and nickel. When used as a conductive aid for non-aqueous electrolyte secondary batteries, the cycle characteristics may deteriorate. Also, carbon nanotubes with a cobalt content of 3000 to 20000 ppm that are purified at high temperature to have a cobalt content of 3000 ppm or less may cause the carbon nanotubes to fuse together, making it difficult to form a conductive path.

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

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

[0030] When the carbon nanotubes of the present embodiment are subjected to powder X-ray diffraction analysis, it is preferable that there is a peak at a diffraction angle 2θ = 25° ± 2°, and the half-width of the peak is 2° or more and less than 6° more preferably 2.5° or more and less than 6°.

[0031] In this embodiment, when powder X-ray diffraction analysis is performed on the carbon nanotubes, two peaks are present at the diffraction angle 2θ = 45° ± 5°. When the lower-angle peak is denoted as α and the higher-angle peak as β, it is preferable that 0.7 < (β / α) < 1.0, and more preferably that 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 non-aqueous 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 imaged using a transmission electron microscope. Next, 300 carbon nanotubes are selected from the observation images, and their outer diameters are measured. Then, the average outer diameter (nm) of the carbon nanotubes is calculated as the number average of the outer diameters.

[0034] In this embodiment, the carbon nanotube preferably has 3 to 30 layers, more preferably 3 to 20 layers, and even more preferably 3 to 10 layers.

[0035] The volume resistivity of the carbon nanotube in this embodiment is 1.0 × 10⁻⁶ -2 ~3.0×10 -2 It is preferable that the ratio is Ω·cm, and 1.0 × 10 -2 ~2.0×10 -2 It is more preferable that the volume resistivity is Ω·cm. The volume resistivity of carbon nanotubes can be measured using a powder resistivity measuring device (Mitsubishi Chemical Analytech Co., Ltd.: Rolester GP Powder Resistivity Measuring System MCP-PD-51).

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

[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, relative to 100% by mass of the carbon nanotubes. Examples of metals contained in the carbon nanotubes include metals and metal oxides used as catalysts when synthesizing carbon nanotubes. Specifically, examples include metals such as iron, cobalt, nickel, aluminum, magnesium, silica, manganese, and molybdenum, as well as metal oxides and composite oxides thereof.

[0038] In this embodiment, it is preferable that the amount of iron contained in the carbon nanotubes is less than 10 ppm. If carbon nanotubes containing 10 ppm or more of iron are used in a non-aqueous electrolyte secondary battery, the iron may dissolve into the electrolyte and precipitate at the counter electrode, potentially leading to an internal short circuit in the battery.

[0039] The carbon nanotubes of this embodiment typically exist as secondary particles. The shape of these secondary particles may be, for example, a state in which carbon nanotubes, which are typical primary particles, are intricately intertwined. They may also be aggregates of linearly shaped carbon nanotubes. Secondary particles, which are aggregates of linear carbon nanotubes, are easier to unravel than intertwined ones. Furthermore, linear nanotubes have better dispersibility than intertwined ones, making them suitable for use as carbon nanotubes.

[0040] The carbon nanotubes in 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. Furthermore, carbon nanotubes containing organic compounds, metal atoms, or substances such as fullerenes can also be used.

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

[0042] Any conventionally known raw material gas can be used as the 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 raw material gases, but are not limited to these. Particularly from the viewpoint of ease of use, it is desirable to use at least one of hydrocarbons and alcohols as the raw material gas.

[0043] (2) Dispersant The dispersant in 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 the dispersion of carbon nanotubes, a suitable type of dispersant can be used in a suitable amount.

[0044] When selecting anionic surfactants, the type is not particularly limited. Specifically, examples include, but are not limited to, fatty acid salts, polysulfonates, polycarboxylates, alkyl sulfates, alkylaryl sulfons, alkylnaphthalene sulfons, dialkyl sulfons, dialkyl sulfosuccinates, alkyl phosphates, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl phosphate sulfons, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters. Furthermore, specific examples include, but are not limited to, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene nonylphenyl ether sulfate, and sodium salts of β-naphthalene sulfonic acid formalin condensates.

[0045] Cationic surfactants include alkylamine salts and quaternary ammonium salts. Specifically, these include, but are not limited to, stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl beef tallow ammonium chloride, dimethyl dioleyl ammonium chloride, methyl oleyl diethanol chloride, tetramethyl ammonium chloride, laurylpyridinium chloride, laurylpyridinium bromide, laurylpyridinium disulfate, cetylpyridinium bromide, 4-alkyl mercaptopyridine, poly(vinylpyridine)-dodecyl bromide, and dodecylbenzyltriethylammonium chloride. Amphoteric surfactants include, but are not limited to, aminocarboxylate 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. Specifically, polyoxyethylene lauryl ether, sorbitan Examples include, but are not limited to, tan fatty acid esters and polyoxyethylene octylphenyl ethers.

[0047] The selected surfactant is not limited to a single surfactant. Therefore, it is possible to use two or more surfactants in combination. 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, the amount blended should preferably be an amount suitable for each surfactant component. A combination of an anionic surfactant and a nonionic surfactant is preferred. The anionic surfactant is preferably a polycarboxylate salt. The nonionic surfactant is preferably a polyoxyethylene phenyl ether.

[0048] Specific examples of resin-type dispersants include cellulose derivatives (cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethylcellulose, ethyl hydroxyethylcellulose, nitrocellulose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, etc.), polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, hydrogenated nitrile butadiene rubber, and polyacrylonitrile polymers. Methylcellulose, ethylcellulose, carboxymethylcellulose, polyvinyl alcohol, polyvinyl butyral, polyvinylpyrrolidone, 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] Furthermore, it is preferable to add amine compounds or inorganic bases in addition to the dispersant. Primary amines, secondary amines, and tertiary amines can be used as amine compounds, but ammonia and quaternary ammonium compounds are not included. In addition to monoamines, amine compounds such as diamines, triamines, and tetramines, which have multiple amino groups in their molecules, can also be used. Specifically, examples include, but are not limited to, primary aliphatic amines such as methylamine, ethylamine, butylamine, and octylamine; secondary aliphatic amines such as dimethylamine, diethylamine, and dibutylamine; tertiary aliphatic 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-type polar solvents Examples of amide-based organic solvents in this embodiment include N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, and N-methylcaprolactam. 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 polar solvent in this embodiment is preferably 300 ppm or less, and more preferably 100 ppm or less. By using an amide polar solvent with low water content, the carbon described later can be 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 comprises carbon nanotubes, a dispersant, and an amide-based polar solvent.

[0053] The carbon nanotube dispersion composition of this embodiment has a moisture content of 50 ppm to 1500 ppm, preferably 100 ppm to 1200 ppm, and more preferably 200 ppm to 1200 ppm. When the moisture content of the carbon nanotube dispersion composition is within the above range, it is thought that the interaction between water and cobalt causes it to exhibit basicity, improving the dispersibility of the carbon nanotube dispersion composition. On the other hand, if the moisture content exceeds the above range, and polyvinylidene fluoride is used as a binder as described later, the mixture slurry may gel, potentially degrading the performance of the electrode film and battery. The moisture content of the carbon nanotube dispersion composition can be measured using a trace moisture measuring device, with the moisture vaporization device attached to the device set to a temperature of 230°C.

[0054] The metallic 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 metallic cobalt content of the carbon nanotube dispersion composition can be calculated, for example, by creating a calibration curve and measuring the electrode film obtained by adding 75, 150, 300, and 600 ppm of metallic cobalt to the carbon nanotube dispersion composition, dispersing it, and then coating and drying it, and then performing XRD measurements of the resulting film.

[0055] The cobalt content of the carbon nanotube dispersion composition in 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, acid decomposition using a microwave sample pretreatment device (Milestone General, ETHOS1), extraction of the metals contained in the CNT dispersion composition, and then analysis using a multi-type ICP emission spectrometer (Agilent, 720-ES).

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

[0057] In this embodiment, the carbon nanotube dispersion composition preferably has a cumulative particle size D50 measured by dynamic light scattering, which is 100 nm to 600 nm, and more preferably 100 nm to 300 nm. Furthermore, the cumulative particle size D90 is preferably 900 nm or less, and 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, and more preferably 4 Pa ​​to 40 Pa. Furthermore, the phase angle is preferably 5° to 70°, and more preferably 20° to 60°. The complex modulus and phase angle of the carbon nanotubes can be evaluated by dynamic viscoelasticity measurement.

[0059] The complex modulus of elasticity indicates the hardness of a carbon nanotube dispersion composition, and decreases as the dispersibility of the carbon nanotubes is good and the viscosity of the carbon nanotube dispersion composition decreases. However, when the fiber length of the carbon nanotubes is large, even if the carbon nanotubes are uniformly and stably unraveled in the medium, the structural viscosity of the carbon nanotubes themselves is present, The complex modulus of elasticity can sometimes be a high value. Also, if the molecular weight of the dispersant is large, the structural viscosity of the dispersant itself can result in a high complex modulus of elasticity. The phase angle refers to the phase shift of the stress wave when the strain applied to the carbon nanotube dispersion composition is a sine wave; in other words, it indicates the flowability of the dispersion composition. For a purely elastic material, the stress wave is in phase with the applied strain, resulting in a phase angle of 0°. On the other hand, for a purely viscous material, the stress wave is 90° ahead. In typical viscoelasticity measurement samples, the phase angle is greater than 0° and less than 90°, and if the dispersibility of carbon nanotubes in the carbon nanotube dispersion composition is good, the phase angle approaches 90°, which is characteristic of a purely viscous material. However, similar to the complex modulus of elasticity, if 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. Carbon nanotube dispersion compositions within the above range exhibit good carbon nanotube particle size and dispersibility, making them suitable as carbon nanotube dispersion compositions 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 to 1500, and more preferably 200 to 1200.

[0061] The amount of dispersant in the carbon nanotube dispersion composition of this embodiment is preferably 10 to 100 parts by mass, and more preferably 10 to 50 parts by mass, per 100 parts by mass of 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, and more preferably 3.0 to 6.0 parts by mass, per 100 parts by mass of the carbon nanotube dispersion.

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

[0064] In this embodiment, the viscosity of the carbon nanotube dispersion composition is preferably such that, when S is the viscosity measured at 6 rpm and T is the viscosity measured at 60 rpm using a B-type viscometer, the ratio 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 perform a process in which carbon nanotubes are dispersed in a solvent. The dispersion apparatus used for such a process is not particularly limited.

[0066] As a dispersion device, dispersers commonly used for pigment dispersion can be used. For example, mixers such as dispersers, homomixers, planetary mixers, and homogenizers (BRANSON Advanced Digital Sonifer®, MODEL 450DA, M-Technique "Clearmix", PRIMI) can be used. Examples of media-type dispersants include X Company's "Filmix," Silverson's "Abramix," etc., paint conditioners (Red Devil), colloid mills (PUC's "PUC Colloid Mill," IKA's "Colloid Mill MK"), cone mills (IKA's "Corn Mill MKO," etc.), ball mills, sand mills (Shinmaru Enterprises' "Dyno Mill," etc.), attritors, pearl mills (Eirich's "DCP Mill," etc.), Coball Mills, high-pressure homogenizers (Genus' "Genus PY," Sugino Machine's "Starburst," Nanomizer's "Nanomizer," etc.), media-less dispersants such as M-Technique's "CREA SS-5" and Nara Machinery'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, vinylpyrrolidone, etc. as constituent 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 carboxymethylcellulose; rubbers such as styrene-butadiene rubber and fluororubber; conductive resins such as polyaniline and polyacetylene. Modified forms, mixtures, and copolymers of these resins are also acceptable. In particular, from a resistance standpoint, the use of polymer compounds having fluorine atoms in the molecule, such as polyvinylidene fluoride, polyvinyl fluoride, and tetrafluoroethylene, is preferred.

[0069] The weight-average molecular weight of the binder in 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. If the molecular weight is too low, the binder's resistance and adhesion may decrease. If the molecular weight is too high, the binder's resistance and adhesion improve, but the viscosity of the binder itself increases, reducing workability, and it may also act as a flocculant, causing the dispersed particles to aggregate significantly.

[0070] (5) Carbon nanotube resin composition The carbon nanotube resin composition of this embodiment comprises 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. Various conventionally known mixing methods can be used. The carbon nanotube resin composition can be prepared using the dispersion apparatus described in the section on the carbon nanotube dispersion composition.

[0072] (6)Active material In this embodiment, the active material refers to the material that forms the basis of the battery reaction. The active material can be divided into positive electrode active material and negative electrode active material based on its electromotive force.

[0073] The positive electrode active material is not particularly limited, but metal compounds such as metal oxides and metal sulfides that can be doped or intercalated with lithium ions, and conductive polymers can be used. 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. Specifically, MnO, V2O5, V6O 13Examples include transition metal oxide powders such as TiO2, lithium-transition metal composite oxide powders such as layered lithium nickelate, lithium cobaltate, lithium manganate, and spinel-structured lithium manganate, lithium iron phosphate-based materials which are olivine-structured phosphoric acid compounds, and transition metal sulfide powders such as TiS2 and FeS. Conductive polymers such as aniline, polyacetylene, polypyrrole, and polythiophene can also be used. Furthermore, the above inorganic and organic compounds may be used in mixtures.

[0074] The negative electrode active material is not particularly limited as long as it can be doped or intercalated with lithium ions. For example, metallic Li, its alloys such as tin alloys, silicon alloys, lead alloys, LiXFe2O3, LiXFe3O4, LiXWO2 (where x is 0 <x<1の Examples of anode active materials include metal oxides such as lithium titanate, lithium vanadate, and lithium siliconate; conductive polymers such as polyacetylene and poly-p-phenylene; amorphous carbonaceous materials such as soft carbon and hard carbon; artificial graphite such as high-graphitization carbon materials; carbonaceous powders such as natural graphite; carbon black; mesophase carbon black; resin-fired carbon materials; vapor-grown carbon fibers; and carbon-based materials such as carbon fibers. These anode active materials can be used individually 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 one 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 m². 2 A weight of 0.2 to 5 mg is preferred. 2 A weight of 0.3 to 3 mg is more preferable. 2Those with a weight of / g are even more preferable.

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

[0078] (7) Asphalt slurry The composite slurry of this embodiment comprises 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 the carbon nanotube resin composition and then perform a dispersion treatment. The dispersion apparatus used for this treatment is not particularly limited. The composite slurry can be obtained using the dispersion apparatus described in the carbon nanotube dispersion composition section.

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

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

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

[0083] The amount of solids in the asphalt slurry is preferably 30 to 90% by mass, and more preferably 40 to 85% by mass, based on 100% by mass of the asphalt slurry.

[0084] The moisture content in the asphalt 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 in this embodiment is a coating film of asphalt slurry. For example, it is a coating film formed by coating and drying asphalt slurry on a current collector to create an electrode asphalt 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 to suit various non-aqueous electrolyte secondary batteries. For example, the material of the current collector can be a metal or alloy such as aluminum, copper, nickel, titanium, or stainless steel. In terms of shape, a flat foil is generally used, but current collectors with roughened surfaces, perforated foils, and mesh-shaped current collectors can also be used.

[0087] There are no particular restrictions on the method for coating the current collector with the asphalt slurry, and known methods can be used. Specifically, die coating, dip coating, roll coating, doctor coating, knife coating, spray coating, gravure coating, screen printing, or electrostatic coating methods can be used, and drying methods such as standing drying, forced-air drying, hot-air drying, infrared heating, and far-infrared heating can be used, but are not limited to these.

[0088] Furthermore, rolling treatment using a flatbed press or calender roll may be performed after coating. The thickness of the electrode composite layer is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.

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

[0090] As the positive electrode, an electrode film can be prepared by coating a slurry containing the positive electrode active material onto a current collector and drying it.

[0091] As the negative electrode, an electrode film can be prepared by coating and drying a slurry containing the negative electrode active material onto the current collector.

[0092] Various conventionally known electrolytes that allow ion movement can be used. For example, 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) can be used, but are not limited to these, and sodium salts can also be used. It is preferable to dissolve the electrolyte in a non-aqueous solvent and use it as an electrolyte solution.

[0093] Non-aqueous solvents are not particularly limited, but examples 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; glycines 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 individually or in combination of two or more.

[0094] The non-aqueous electrolyte secondary battery of this embodiment preferably includes a separator. Examples of the separator include, but are not 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. Usually, it is composed of a positive electrode and a negative electrode, and a separator provided as needed, 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 it does not exceed the gist thereof. 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. Thereafter, 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 measurement was performed using a laser wavelength of 532 nm. The measurement conditions were an acquisition 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 CNTs for measurement were 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 the CNTs.

[0100] <BET specific surface area of CNTs> Using an electronic balance (manufactured by Sartorius, MSA225S100DI), 0.03 g of CNTs was weighed, and then dried while degassing at 110 °C for 15 minutes. Thereafter, using a fully automatic specific surface area measuring device (manufactured by MOUNTECH, HM-model1208), the BET specific surface area of the CNTs was measured. <Moisture in 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 performed by setting the vaporizer (manufactured by Nitto Seiko Analytic Co., Ltd., VA200) to 230 °C and placing 0.5 g to 1.0 g of CNTs at the sample installation location in the vaporizer.

[0101] <Powder X-ray diffraction analysis of CNTs> CNTs were 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. Thereafter, a sample for powder X-ray diffraction analysis of CNTs was placed in a fully automatic multi-purpose X-ray diffractometer (SmartLab, manufactured by Rigaku), and the operation was performed 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: The plots appearing at the diffraction angle 2θ = 45° ± 5° were each subjected to a simple moving average of 11 points, 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°. The plots were connected by a line. (Equation 1) Peak intensity ratio = β / α The evaluation of the peak intensity ratio was 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 (poor).

[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.). Then, 200 mL of toluene was added, and an ultrasonic homogenizer (Advanced Digital Sonifer (registered trademark), MODEL 450DA, manufactured by BRANSON) was used to perform dispersion treatment under ice cooling at an amplitude of 50% for 5 minutes to prepare a CNT dispersion. After that, the CNT dispersion was appropriately diluted, several μL was dropped in the form of a collodion film, dried at room temperature, and then observed directly using a transmission electron microscope (H-7650, manufactured by Hitachi, Ltd.). The observation was performed at a magnification of 50,000 times. A plurality of photos containing 10 or more CNTs in the field of view were taken, and the outer diameters of 300 arbitrarily extracted CNTs were measured, and the average value was taken as the average outer diameter (nm) of CNT.

[0103] <Volume resistivity of CNT> Using a powder resistivity measuring 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, a powder probe unit (four-probe ring electrode, electrode interval 5.0 mm, electrode radius 1.0 mm, sample radius 12.5 mm), the volume resistivity [Ω·cm] of the conductive powder under various pressures was measured with an applied voltage limiter of 90 V. 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. Thereafter, 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 the 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. Thereafter, 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. Thereafter, 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. Thereafter, 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 ray. 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 a 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 is X (parts by mass) and the cobalt content determined by ICP analysis is Y (parts by mass), (X / Y) × 100 is defined as the ratio of metallic cobalt in the CNT dispersion composition. The evaluation of the ratio of metallic cobalt is as follows: ⊙: 10 or more and less than 40 (excellent), ○: 5 or more and less than 10 or 40 or more and 5≤0 or less (good), ×: less than 5 or exceeding 50 (poor).

[0107] <Initial viscosity of the CNT dispersion composition> After the CNT dispersion composition was allowed to stand in a constant temperature 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 is 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 the CNT dispersion composition was allowed to stand in a constant temperature 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 is S and the viscosity measured at 60 rpm is T, S / T is defined as the TI value, and the TI value is as follows: ⊙: 2 or more and less than 4 (excellent), ○: 4 or more and less than 7 (good), ×: less than 2 or exceeding 7 (infeasible).

[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 (not acceptable).

[0110] <Measurement of Particle Size Distribution of CNT Dispersion Composition> After leaving the CNT dispersion composition to stand 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 BEL 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 was ⊙: 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 Electrode Film> The composite 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 coating film after drying was measured using a P-T610. After measurement, the volume resistivity (Ω·cm) of the electrode film was calculated by multiplying the measurement by the thickness of the electrode composite layer formed on the aluminum foil. The thickness of the electrode composite layer was determined by subtracting the thickness of the copper foil from the average value of measurements taken at three points in the electrode film using a film thickness gauge (NIKON DIGIMICRO MH-15M) to obtain the volume resistivity (Ω·cm) of the electrode film. Volume resistivity was evaluated as follows: ◎: 6Ω·cm or less (Excellent), ○: greater than 6Ω·cm but 10Ω·cm or less (Good), greater than 10Ω·cm (Unacceptable).

[0112] <Peel strength of electrode film> The asphalt slurry is applied using an applicator, and the basis weight per unit of the electrode is 20 mg / cm³. 2 After coating the aluminum foil in the manner described, the coating film was dried in an electric oven at 120°C ± 5°C for 25 minutes. Then, two 90mm x 20mm rectangles were cut with the coating direction as the long axis. For measuring the peel strength, a benchtop tensile testing machine (Strograph E3, manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used, and the 180-degree peel test method was employed. Specifically, a 100mm x 30mm double-sided tape (No. 5000NS, manufactured by Nitoms Co., Ltd.) was attached to a stainless steel plate, and the prepared battery electrode composite layer was pressed firmly against the other side of the double-sided tape. The tape was then peeled off by pulling it from bottom to top at a constant speed (50mm / min), and the average stress at this time was defined as the peel strength. The peel strength was evaluated as follows: ◎: 0.7N / cm or more (Excellent), ○: 0.5N / cm or more but less than 0.7N / cm (Good), and less than 0.5N / cm was unacceptable.

[0113] <Fabrication of standard negative electrodes> In a 150ml plastic container, 0.5 parts by mass of acetylene black (Denka Black® HS-100, manufactured by Denka), 1 part by mass of MAC500LC (carboxymethylcellulose sodium salt, Sunrose special type MAC500L, manufactured by Nippon Paper Industries, 100% non-volatile content), and 98.4 parts by mass of water were added. The mixture was then stirred at 2000 rpm for 30 seconds using a rotation / revolution mixer (Sinky Awatori Rentaro, ARE-310). Furthermore, 92 parts by mass of artificial graphite (manufactured by Nippon Graphite Industry, CGB-20) and 5 parts by mass of silicon (manufactured by Osaka Titanium Technology, SILICON MONOOXIDE SiO 1.3C 5μm, 100% non-volatile content) were added as active materials, and the mixture was stirred at 3000 rpm for 10 minutes using a high-speed stirrer. Next, 3.1 parts by mass of SBR (TRD2001, manufactured by JSR Corporation) were added, and the mixture was stirred at 2000 rpm for 30 seconds using the aforementioned rotation / revolution mixer to obtain a negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry was measured using an applicator to determine the basis weight per unit electrode of 8 mg / cm³. 2 After coating the copper foil in this manner, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes. Furthermore, it was rolled using a roll press (manufactured by Sankumetal Co., Ltd., 3t hydraulic roll press) to obtain a density of 1.6 g / cm³ in the asphalt layer. 3 A standard negative electrode was fabricated.

[0114] <Rate characteristic evaluation of lithium-ion secondary batteries> A laminated lithium-ion secondary battery was placed in a constant temperature room at 25°C, and charge / discharge measurements were performed using a charge / discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). Constant current and constant voltage charging (cutoff current 1.0mA (0.02C)) was performed with a charging current of 10mA (0.2C) and a charging termination voltage of 4.2V, followed by constant current discharge at a discharge current of 10mA (0.2C) and a discharge termination voltage of 2.5V. This operation was repeated three times, and then constant current and constant voltage charging (cutoff current (1.0mA 0.02C)) was performed with a charging current of 10mA (0.2C) and a charging termination voltage of 4.2V, followed by constant current discharge at 0.2C and 3C until the discharge termination voltage reached 2.5V, and the discharge capacity was determined for each. The rate characteristic can be expressed as the ratio of the 0.2C discharge capacity to the 3C discharge capacity, as shown in Equation 2 below. (Equation 2) Rate characteristic = 3C discharge capacity / 3rd 0.2C discharge capacity × 100 (%) Rating characteristics are evaluated as follows: ◎ (Excellent) for rating characteristics of 80% or higher, ○ (Good) for 70% to less than 80%, △ (Acceptable) for 60% to less than 70%, and × (Poor) for less than 60%. The rating was set as follows: Cycle characteristics were rated as follows: 90% or higher as +++ (Excellent), 85% or higher but less than 90% as ++ (Good), 80% or higher but less than 85% as + (Acceptable), and less than 80% as - (Unacceptable).

[0115] <Evaluation of Cycle Characteristics of Lithium-ion Secondary Batteries> A laminated lithium-ion secondary battery was placed in a constant temperature room at 25°C, and charge / discharge measurements were performed using a charge / discharge device (SM-8, manufactured by Hokuto Denko Co., Ltd.). Constant current constant voltage charging (cutoff current 1.25mA (0.025C)) was performed with a charging current of 50mA (1C) and a charging termination voltage of 4.2V, followed by constant current discharge with a discharge current of 50mA (1C) and a discharge termination voltage of 2.5V. This operation was repeated 200 times. 1C was defined as the current value required to discharge the theoretical capacity of the positive electrode in one hour. The cycle characteristics can be expressed by the ratio of the 1C discharge capacity at 25°C after the 3rd cycle to the 1C discharge capacity after the 200th cycle, as shown in Equation 3 below. (Equation 3) Cycle characteristics = 1C discharge capacity at 3rd cycle / 1C discharge capacity at 200th cycle × 100 (%) The cycle characteristic evaluation was carried out with the cycle characteristics being rated as +++ (excellent) when 90% or more, ++ (good) when 85% or more and less than 90%, + (acceptable) when 80% or more and less than 85%, and - (unacceptable) when less than 80%.

[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] [[ID=I9]] <Synthesis of cobalt hydroxide> Cobalt hydroxide in which plate-like primary particles formed spherical secondary particles was produced by the method described in

[0091] of JP-A No. 2012-72050. As a result of confirmation by ICP analysis, the residual sulfur content contained in the produced cobalt hydroxide was 1500 ppm.

[0119] <Synthesis of CNT synthesis catalyst> 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), CNT synthesis catalyst (X) was produced by the method described in paragraphs

[0147] and

[0148] of JP-A No. 2019-108256.

[0120] 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), CNT synthesis catalyst (Y) was produced by the method described in paragraph

[0117] of JP-A No. 2018-150218.

[0121] <Synthesis of CNT (A)> A heat-resistant dish made of quartz glass, in which 1 g of the catalyst (X) for CNT synthesis was sprayed, was placed in the center of a horizontal reaction tube with an internal volume of 10 L, which can be pressurized and heated with an external heater. Exhaust was carried out while injecting nitrogen gas to replace the air in the reaction tube with nitrogen gas, and the reaction tube 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 catalytic 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 to 100 °C or lower and taken out to obtain CNT (A).

[0122] <Synthesis of CNT (B) to (C)> CNT (B) to (C) were produced 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 Industries, Ltd.), 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 Industries, Ltd.) was changed to 60% nitric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0131] [[ID=z29]] <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 in 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 later.

[0133] [Table 2]

[0134] (Example 1-1) 200 g of CNT(A) was placed in a heat-resistant container made of Teflon® and dried in an electric oven at 140°C ±5°C for 24 hours. After drying, it was 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. Subsequently, according to 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 homogeneous. Then, 1.5 parts by mass of dried CNT(A) was taken and added while stirring with a disperser, and batch dispersion was performed in a high-shear mixer (L5M-A, SILVERSON) equipped with a square-hole high-shear screen at a speed of 8,600 rpm until the whole mixture was homogeneous and the dispersed particle size was 250 μm or less as measured by a grind gauge. Next, the dispersion liquid was supplied from the stainless steel container to a high-pressure homogenizer via piping, and a circulating dispersion treatment was performed. The dispersion treatment was carried out using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. After dispersion until the viscosity of the dispersion liquid at 60 rpm, measured with a B-type viscometer (TOKI SANGYO, VISCOMETER, MODEL: BL), was 3,000 mPa·s or less, 0.5 parts by mass of dry CNT(A) were added to the stainless steel container while stirring with a disperser, and the circulating dispersion treatment was performed again using the high-pressure homogenizer. After circulating dispersion using a homogenizer until the viscosity was 3,000 mPa·s or less, 0.5 parts by mass of dried CNT(A) were added to a stainless steel container while stirring with a disperser. This process was repeated a total of three times (total amount of dried CNT(A) added was 3.0 parts by mass). Subsequently, the mixture was subjected to 15-pass dispersion treatment using a high-pressure homogenizer, and then passed through a magnetic filter with a surface magnetic flux density of 17,000 gauss and a nylon mesh with a mesh opening of 20 μm to obtain a CNT dispersion composition (A) containing 3.0 parts by mass of CNT(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 amount, dispersant type, dispersant amount, and NMP amount were changed as listed in Table 3. Dried CNTs (J) to (N) were prepared in the same manner as in Example 1-1, and the moisture content of the dried CNTs (J) to (N) was 800 ppm.

[0136] (Examples 1-17, 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) 200g of CNT(M) was placed in a heat-resistant container made of Teflon® and dried in an electric oven at 140°C ±5°C for 24 hours. After drying, it was cooled in an open dry chamber (Daikin Industries, Ltd., HRG-50A) to produce dried CNT(M) with a moisture content of 800ppm. Subsequently, according to the composition shown in Table 3, 92.8 parts by mass of NMP (Kishida Chemical Co., Ltd., for LBG, moisture content 100ppm or less) and 1.2 parts by mass of dispersant (PVB) were added to a stainless steel container placed in the open dry chamber and stirred with a disperser until homogeneous. Then, 2.0 parts by mass of dried CNT(D) were taken and added while stirring with a disperser, and batch dispersion was performed using a high-shear mixer (L5M-A, SILVERSON) equipped with a square-hole high-shear screen at a speed of 8,600 rpm until the entire mixture was homogeneous and the dispersed particle size was 250 μm or less as measured by a grind gauge. Next, the dispersion liquid was supplied from the stainless steel container to a high-pressure homogenizer via piping, and a circulating dispersion treatment was performed. The dispersion treatment was carried out using a single-nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa. After dispersion until the viscosity of the dispersion liquid at 60 rpm, measured with a B-type viscometer (TOKI SANGYO, VISCOMETER, MODEL: BL), was 3,000 mPa·s or less, 0.25 parts by mass of dry CNT(M) were added to the stainless steel container while stirring with a disperser, and the circulating dispersion treatment was performed again with the high-pressure homogenizer. The process of circulating dispersion with the high-pressure homogenizer until the viscosity was 3,000 mPa·s or less, followed by adding 0.25 parts by mass of dry CNT(M) to the stainless steel container while stirring with a disperser, was repeated a total of 16 times. (The total amount of dry CNT(M) added was 6.0 parts by mass). Subsequently, a 40-pass dispersion treatment was performed using a high-pressure homogenizer to obtain a CNT dispersion composition (M2) containing 6.0 parts by mass of CNTs.

[0138] (Comparative Examples 1-5) Deionized 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 In a plastic container, 12.5 parts by mass of NMP (Natural Polymer Mixture) containing 8% by mass of PVDF (polyvinylidene fluoride, Solvey, Solvey #5130) was weighed, 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 rotation / revolution mixer (Awatori Rentaro, ARE-310) to obtain CNT resin composition (A). Subsequently, 98.7 parts by mass of positive electrode active material (BASF Toda Battery Materials LLC, HED® NCM-111 1100) was added, and the mixture was stirred at 2000 rpm for 2.5 minutes using a rotation / revolution 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 slurry (B) to (D8) were obtained by the same method except that CNT dispersion compositions (B) to (D8) were used instead of CNT dispersion composition (A).

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

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

[0144] [Table 4]

[0145] (Example 3-1) The asphalt slurry (A) is applied using an applicator, and the basis weight per unit of the electrode is 20 mg / cm³. 2 After coating the aluminum foil in this manner, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain electrode film (A). Subsequently, electrode film (A) was rolled using a roll press (Sankmetal, 3t hydraulic roll press) to obtain positive electrode (A). The basis weight per unit of the composite layer was 20 mg / cm². 2 The density of the asphalt layer after rolling was set to 3.1 g / cc.

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

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

[0148] [Table 5]

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

[0150] (Examples 4-2 to 4-19), (Comparative Examples 4-1 to 4-5) Laminated lithium-ion secondary batteries (B) to (M3) were fabricated using the same method as in Example 4-1, except that the positive electrode was changed to the 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 m². 2 / g~800m 2 A carbon nanotube dispersion composition was used, comprising carbon nanotubes in a quantity of / g, a dispersant, and an amide-based polar solvent, with a water content of 50 ppm to 1500 ppm. In the examples, lithium-ion secondary batteries with superior rate characteristics and cycle characteristics compared to the comparative example were obtained. Therefore, it has become clear that the present invention can provide lithium-ion secondary batteries 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 embodiments, the present invention is not limited thereto. Various modifications to the structure and details of the present invention can be made that are understandable to those skilled in the art within the scope of the invention.

Claims

1. A carbon nanotube dispersion composition comprising carbon nanotubes, a dispersant, and N-methyl-2-pyrrolidone, characterized in that it satisfies the following conditions (1), (2), (3), (4), and (5). (1) The cobalt content of the carbon nanotubes is between 3,000 ppm and 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 ​​carbon nanotubes is 150 m². 2 / g to 800m 2 It must be / g. (4) The carbon nanotube dispersion composition has a water content of 50 ppm to 1500 ppm. (5) The iron content of the carbon nanotubes is less than 10 ppm.

2. The carbon nanotube dispersion composition according to Claim 1, wherein when the viscosity of the carbon nanotube dispersion composition at 25°C is measured using a B-type viscometer at 6 rpm, S is the viscosity measured at 60 rpm, and T is the viscosity measured at 60 rpm, the ratio 2.0 ≤ S / T < 7.

0.

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

0.

4. A carbon nanotube dispersion composition according to any one of claims 1 to 3, characterized in that the complex modulus of elasticity is 1 to 50 Pa and the phase angle is 20° to 70°.

5. A carbon nanotube resin composition comprising a carbon nanotube dispersion composition according to any one of claims 1 to 4 and a binder resin.

6. A composite slurry containing the carbon nanotube resin composition according to claim 5 and an active material.

7. An electrode film which is a coating film of the asphalt slurry according to claim 6.

8. A method for producing the carbon nanotube dispersion composition according to any one of Claims 1 to 4, The process includes dispersing carbon nanotubes, a dispersant, and N-methyl-2-pyrrolidone. The N-methyl-2-pyrrolidone has a water content of 300 ppm or less. A method for producing a carbon nanotube dispersion composition.

9. A method for producing a carbon nanotube dispersion composition according to any one of Claims 1 to 4, Carbon nanotubes, a dispersant, and N-methyl-2-pyrrolidone are dispersed using a high-pressure homogenizer until the viscosity, measured at 60 rpm using a B-type viscometer, is 3,000 mPa·s or less. A method for producing a carbon nanotube dispersion composition.

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