Carbon nanotube dispersion and use thereof

Abstract

To provide a carbon nanotube dispersion, a carbon nanotube resin composition, and a mixture slurry having high dispersibility and elastic modulus in order to obtain an electrode film having excellent electrode strength and conductivity, and to provide a nonaqueous electrolyte secondary battery having excellent rate properties and cycle properties.SOLUTION: A carbon nanotube (CNT) dispersion comprises carbon nanotubes, a dispersing agent, and a solvent, and satisfies (1) to (4). (1) In a Raman spectrum of the CNT, where G represents the maximum peak intensity in the range of 1560-1600 cm-1, and D represents the maximum peak intensity in the range of 1310-1350 cm-1, the ratio of G / D of the CNT is from 5 to 100. (2) With respect to 100 pts.mass of the CNT, 30 pts.mass or more and less than 250 pts.mass of the dispersing agent is contained. (3) The complex elastic modulus of the CNT dispersion is 5 Pa or more and less than 650 Pa, and the phase angle is 5° or more and less than 50°. (4) The BET specific surface area of the CNT is from 550 to 1200 m2 / g.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a carbon nanotube dispersion, more specifically to a carbon nanotube dispersion, a resin composition containing the carbon nanotube dispersion and a resin, a composite slurry containing the carbon nanotube dispersion, a resin, and an active material, an electrode film formed from the composite slurry, and a nonaqueous electrolyte secondary battery including the electrode film and an electrolyte. [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, which 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, it is known that adding carbon nanotubes to graphite or silicon negative electrodes improves the electrode's conductivity, electrode strength, such as adhesion and expansion / contraction properties, as well as the rate characteristics and cycle characteristics of lithium-ion secondary batteries (see, for example, Patent Document 1). Furthermore, studies are also being conducted to reduce electrode resistance by adding carbon nanotubes to positive electrodes (see, for example, Patent Documents 2 and 3). Multi-walled carbon nanotubes with outer diameters of 10 nm to several tens of nm are relatively inexpensive, and are expected to be put to practical use.

[0005] Using carbon nanotubes with a small average outer diameter allows for efficient formation of a conductive network with a small amount, thereby reducing the amount of conductive additive contained in the positive and negative electrodes of lithium-ion secondary batteries. It is also known that using carbon nanotubes with a long fiber length produces similar effects (see, for example, Patent Document 4). However, carbon nanotubes with these characteristics have strong cohesion and are difficult to disperse, making it impossible to obtain a carbon nanotube dispersion with sufficient dispersibility.

[0006] Therefore, methods for stabilizing the dispersion of carbon nanotubes using various dispersants have been proposed. For example, dispersion in water and NMP (N-methyl-2-pyrrolidone) using a polymer dispersant such as a water-soluble polymer has been proposed (see Patent Documents 1, 5, and 6). In Patent Document 1, single-walled carbon nanotubes are dispersed in NMP containing polyvinylpyrrolidone. Dispersion is carried out using zirconia beads in a solvent, but the dispersion time is long, which causes the particle size of the dispersed carbon nanotubes to become small, and although the conductivity of the electrode is improved, the strength of the electrode cannot be improved. In Patent Document 5, oxidation-treated double-walled carbon nanotubes are dispersed in an aqueous carboxymethyl cellulose solution using an ultrasonic homogenizer, but it is difficult to disperse carbon nanotubes in the solvent at a high concentration. In Patent Document 6, single-walled carbon nanotubes are dispersed in an NMP solvent containing polyvinylpyrrolidone. Dispersion is carried out using ultrasonic waves, but carbon nanotubes are dispersed in a solvent at high concentrations. It has been difficult to achieve this. Furthermore, a method has been proposed in which nitrile rubber is used as a dispersant to stabilize the dispersion of multi-walled carbon nanotubes (see Patent Document 7). Patent Document 7 proposes that the output characteristics of an electrode can be improved by preparing a multi-walled carbon nanotube dispersion liquid having a specific complex elastic modulus. However, with multi-walled carbon nanotubes having an outer diameter of 10 nm or more, the improvement in electrode strength is insufficient, making it difficult to improve the cycle characteristics of lithium-ion secondary batteries.

[0007] Therefore, obtaining a carbon nanotube dispersion in which single-walled carbon nanotubes are uniformly dispersed in a dispersion medium at a high concentration has been an important challenge for expanding the applications of carbon nanotubes. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 2020-105316 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-70908 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-19619 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-221672 [Patent Document 5] Japanese Patent Application Laid-Open No. 2010-254546 [Patent Document 6] Japanese Patent Application Laid-Open No. 2005-162877 [Patent Document 7] Special Publication No. 2018-533175 Summary of the Invention [Problem to be solved by the invention]

[0009] The problem to be solved by the present invention is to provide a carbon nanotube dispersion, a carbon nanotube resin composition, and a composite slurry having high dispersibility and elastic modulus in order to obtain an electrode film having excellent electrode strength and conductivity, and more specifically, to provide a nonaqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics. [Means for solving the problem]

[0010] That is, the present invention relates to a carbon nanotube dispersion liquid containing carbon nanotubes, a dispersant, and a solvent, and characterized in that the following (1) to (4) are satisfied: (1) 1560-1600 cm in the Raman spectrum of carbon nanotubes -1 The maximum peak intensity in the range of 1310 to 1350 cm is G. -1 Maximum peak intensity within the range The G / D ratio of the carbon nanotube is 5 to 100, where D is the degree of (2) The dispersant must contain 30 parts by mass or more but less than 250 parts by mass per 100 parts by mass of carbon nanotubes. (3) The carbon nanotube dispersion has a complex modulus of 5 Pa or more and less than 650 Pa at 25°C and a frequency of 1 Hz, and a phase angle of 5° or more and less than 50°. (4) The BET specific surface area of ​​the carbon nanotubes is 550 to 1200 m 2 / g

[0011] In addition, the present invention provides a method for producing carbon nanotubes having a Raman spectrum of 1560 to 1600 cm -1The maximum peak intensity in the range of 1310 to 1350 cm is G. -1 Within the range of When the maximum peak intensity is D, the G / D ratio of the carbon nanotube is 10 to 50. The present invention relates to the carbon nanotube dispersion liquid, characterized in that:

[0012] In addition, the present invention is directed to a method for measuring the shear rate of a carbon nanotube dispersion liquid at 25°C using a rheometer. -1 The carbon nanotube dispersion liquid is characterized in that the viscosity measured by the method (2) is 5 Pa·s or more and less than 40 Pa·s.

[0013] The present invention also provides a method for producing a toner having a cumulative particle size D10 measured by a dynamic light scattering method of 200 nm or more. The carbon nanotube dispersion liquid is characterized in that the particle size is less than 00 nm.

[0014] In addition, the present invention provides a method for manufacturing a carbon nanotube having a volume resistivity of 1.0×10 -3 Ω·cm~1.0×10 -2 The carbon nanotube dispersion liquid is characterized in that its viscosity is Ω·cm.

[0015] The present invention also relates to the carbon nanotube dispersion liquid, wherein the cumulative particle size D50 measured by dynamic light scattering is 500 nm or more and less than 3000 nm.

[0016] The present invention also relates to the carbon nanotube dispersion liquid, wherein the dispersant has a weight average molecular weight of 10,000 to 100,000.

[0017] The present invention also relates to the carbon nanotube dispersion liquid, wherein the solvent contains water.

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

[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, wherein at least one of the positive electrode and the negative electrode contains the above-described electrode film. [Effects of the Invention]

[0022] By using the carbon nanotube dispersion of the present invention, a resin composition, a composite slurry, and an electrode film having excellent electrode strength and adhesion can be obtained. Furthermore, a nonaqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics can be obtained. Therefore, the carbon nanotube dispersion of the present invention can be used in various fields where high conductivity and durability are required. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a graph showing the Raman spectra of the carbon nanotubes used in the examples and comparative examples of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] The carbon nanotube dispersion, resin composition, composite slurry, and electrode film formed by coating the same, and nonaqueous electrolyte secondary battery of the present invention will be described in detail below.

[0025] (1) Carbon nanotubes The carbon nanotubes of this embodiment are preferably single-walled carbon nanotubes. The single-walled carbon nanotubes may be mixed with multi-walled carbon nanotubes. Single-walled carbon nanotubes have a structure in which one layer of graphite is wrapped around them, while multi-walled carbon nanotubes have a structure in which two or more layers of graphite are wrapped around them.

[0026] The average outer diameter of the carbon nanotubes of this embodiment is 0.5 nm to 5 nm, and 1 nm to The average outer diameter of the carbon nanotubes is preferably 3 nm, and more preferably 1 nm to 2 nm. The average outer diameter of the carbon nanotubes can be calculated by observing the morphology of the carbon nanotubes using a transmission electron microscope (manufactured by JEOL Ltd.), measuring the lengths of the minor axes of 100 nanotubes, and averaging the measured values.

[0027] The BET specific surface area of ​​the carbon nanotubes of this embodiment is 550 m 2 / g~1200m 2 / g, 600-1200m 2 / g, and 800m 2 / g~1200m 2 / g is more preferable, and 800m 2 / g~1000m 2 / g is more preferred.

[0028] The carbon nanotubes of this embodiment have a Raman spectrum of 1560 to 1600 cm -1 The maximum peak intensity in the range of 1310 to 1350 cm is G. -1 When the maximum peak intensity within this range is defined as D, the G / D ratio is 5-100, more preferably 10-50, and further preferably 20-50.

[0029] The volume resistivity of the carbon nanotube of this embodiment is 1.0×10 -3 Ω·cm~3.0×10 -2 Ω·cm is preferred, and 1.0×10 -3 Ω·cm~1.0×10 -2It 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.).

[0030] The carbon purity of the carbon nanotubes of this embodiment is expressed as the carbon atom content (%) in the carbon nanotubes. The carbon purity is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more, relative to 100% by mass of the carbon nanotubes.

[0031] The amount of metal contained in the carbon nanotubes of this embodiment is preferably less than 20% by mass, more preferably less than 10% by mass, and even more preferably less than 5% by mass, based on 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. Specific examples include metals such as cobalt, nickel, aluminum, magnesium, silica, manganese, and molybdenum, as well as metal oxides and composite oxides thereof.

[0032] 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.

[0033] The carbon nanotubes of this embodiment may be pulverized carbon nanotubes. Pulverization is performed using a mill containing milling media such as beads or steel balls to pulverize the carbon nanotubes without the presence of a liquid substance, and is also called dry milling. Pulverization is performed by utilizing the crushing or destructive force generated by the collision of the milling media. Pulverization primarily reduces the size of secondary particles of the carbon nanotubes, thereby improving the dispersibility of the carbon nanotubes. Known methods, such as a dry attritor, ball mill, vibration mill, or bead mill, can be used as the dry milling device, and the milling time can be set as desired depending on the device.

[0034] The carbon nanotubes of this embodiment may be produced by any method, including but not limited to laser ablation, arc discharge, thermal CVD, plasma CVD, and combustion.

[0035] (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.

[0036] 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.

[0037] 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.

[0038] 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, and more specifically, include, but are not limited to, polyoxyethylene lauryl ethers, sorbitan fatty acid esters, and polyoxyethylene octylphenyl ethers.

[0039] 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.

[0040] 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 Examples of the cellulose ester include methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, and polyacrylonitrile polymers. Particularly preferred are methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, and polyacrylonitrile polymers.

[0041] Carboxymethylcellulose can be used in the form of a salt such as sodium carboxymethylcellulose, in which the hydroxy group of carboxymethylcellulose is substituted with a sodium carboxymethyl group.

[0042] The dispersant of this embodiment preferably has a pullulan-equivalent weight-average molecular weight of 5,000 to 30,0000, more preferably 10,000 to 10,0000, and even more preferably 10,000 to 50,000. Using a dispersant with an appropriate weight-average molecular weight improves adsorption to CNTs and the stability of the carbon nanotube dispersion. Furthermore, using a dispersant exceeding the above range increases the viscosity of the carbon nanotube dispersion, which may result in reduced dispersion efficiency when using a disperser in which the dispersion passes through a narrow channel, such as a nozzle-type high-pressure homogenizer. Resin-type dispersants may have binding properties in addition to dispersing properties. Such resin-type dispersants can also be used as binders, and the same type of resin as the resin-type dispersant may be used as the binder. When using the same type of resin as the resin-type dispersant as the binder, it is preferable to use a resin with a weight-average molecular weight greater than the weight-average molecular weight of the resin-type dispersant.

[0043] In addition to the dispersant of this embodiment, an inorganic base and an inorganic metal salt may be contained. The inorganic base and inorganic metal salt are preferably compounds containing at least one of an alkali metal and an alkaline earth metal. Specifically, examples thereof include chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, tungstates, vanadates, molybdates, niobates, and borates of alkali metals and alkaline earth metals. Among these, chlorides, hydroxides, and carbonates of alkali metals and alkaline earth metals are preferred in terms of the ease with which cations can be supplied. Examples of alkali metal hydroxides include lithium hydroxide, sodium hydroxide, and potassium hydroxide. Examples of alkaline earth metal hydroxides include calcium hydroxide and magnesium hydroxide. Examples of alkali metal carbonates include lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, and potassium bicarbonate. Examples of alkaline earth metal carbonates include calcium carbonate and magnesium carbonate. Among these, lithium hydroxide, sodium hydroxide, lithium carbonate, and sodium carbonate are more preferred.

[0044] In addition to the dispersant of this embodiment, an acid may be contained. Addition of an acid may change the charge state in the dispersion system and the balance between hydrophilic and hydrophobic moieties, thereby improving dispersibility. The type of acid is not particularly limited, and one type may be used alone or in combination with multiple types. Examples of the acid include oxalic acid, lactic acid, citric acid, polyacrylic acid, polystyrene sulfonic acid, acetic acid, malonic acid, hydrochloric acid, nitric acid, sulfuric acid, boric acid, and phosphoric acid.

[0045] In addition to the dispersant of the present embodiment, an antifoaming agent may be contained. Any antifoaming agent having an antifoaming effect may be used, such as a commercially available antifoaming agent, a wetting agent, a hydrophilic organic solvent, or a water-soluble organic solvent. One type of antifoaming agent may be used alone, or a combination of two or more types may be used. For example, alcohols such as ethanol, propanol, isopropanol, butanol, octyl alcohol, hexadecyl alcohol, acetylene alcohol, ethylene glycol monobutyl ether, methyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, acetylene glycol, polyoxyalkylene glycol, propylene glycol, and other glycols; Fatty acid esters: diethylene glycol laurate, glycerin monoricinoleate, alkenyl succinic acid derivatives, sorbitol monolaurate, sorbitol trioleate, polyoxyethylene monolaurate, polyoxyethylene sorbitol monolaurate, natural waxes, etc. Amide-based: polyoxyalkylene amide, acrylate polyamine, etc. Phosphate esters: tributyl phosphate, sodium octyl phosphate, etc. Metal soaps: aluminum stearate, calcium oleate, etc. Oils and fats: animal and vegetable oils, sesame oil, castor oil, etc. Mineral oils: kerosene, paraffin, etc. Silicone-based: dimethyl silicone oil, silicone paste, silicone emulsion, organic modified polysiloxane, fluorosilicone oil, etc.

[0046] (3) Solvent The solvent of this embodiment is not particularly limited as long as it can disperse carbon nanotubes, but is preferably water and / or a mixed solvent consisting of one or more water-soluble organic solvents, and more preferably contains water. If water is contained, it is preferably 95% by mass or more, and more preferably 98% by mass or more, relative to 100% by mass of the solvent.

[0047] Examples of water-soluble organic solvents include alcohols (methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, benzyl alcohol, etc.), polyhydric alcohols (ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, etc.), polyhydric alcohol ethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, propylene ... ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methylcaprolactam, etc.), heterocyclics (cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, etc.), sulfoxides (dimethyl sulfoxide, etc.), sulfones (hexamethylphosphorotriamide, sulfolane, etc.), lower ketones (acetone, methyl ethyl ketone, etc.), as well as tetrahydrofuran, urea, acetonitrile, etc. can be used.

[0048] (4) Carbon nanotube dispersion The carbon nanotube dispersion liquid of this embodiment contains carbon nanotubes, a dispersant, and a solvent.

[0049] The complex modulus of the carbon nanotube dispersion of this embodiment at 25°C and a frequency of 1 Hz is 5 Pa or more but less than 650 Pa, preferably 5 Pa or more but less than 400 Pa, and more preferably 10 Pa or more but less than 400 Pa. The complex modulus of the carbon nanotube dispersion indicates the hardness of the carbon nanotube dispersion, and tends to be smaller as the dispersibility of the carbon nanotubes improves and the viscosity of the carbon nanotube dispersion decreases. On the other hand, when the fiber length of the carbon nanotubes is long, even if the dispersion is good, the complex modulus may be a high value due to the structural viscosity of the carbon nanotubes themselves.

[0050] The phase angle of the carbon nanotube dispersion of this embodiment at 25°C and a frequency of 1 Hz is preferably 5° or more and less than 50°, and more preferably 10° or more and less than 50°. The phase angle refers to the phase shift of the stress wave when the strain applied to the carbon nanotube dispersion is a sine wave. In a purely elastic body, the sine wave will be in phase with the applied strain, resulting in a phase angle of 0°. On the other hand, in a purely viscous body, the stress wave will be advanced by 90°. Carbon nanotube dispersions with complex modulus and phase angle values ​​within the above ranges have good dispersed particle size and dispersion state of carbon nanotubes, and are suitable as carbon nanotube dispersions for improving electrode strength and conductivity. The complex modulus and phase angle of the carbon nanotube dispersion can be determined by dynamic viscoelasticity measurement using a rheometer with a 35 mm diameter, 2° cone, at 25°C, a frequency of 1 Hz, and a strain rate range of 0.01% to 5%. If the measured value contains decimal points, it is rounded to the nearest integer in accordance with Rule B of JIS Z 8401:1999.

[0051] A well-developed conductive network is formed by uniformly and well-dispersing the carbon nanotubes while maintaining a certain length or more so that the fiber length does not shorten due to breakage. Therefore, it is not enough for the conductive material dispersion to simply have a low viscosity and good (apparent) dispersibility; it is particularly effective to judge the dispersion state by combining the complex modulus and / or phase angle with conventional indicators such as viscosity. By setting the complex modulus and / or phase angle within the above range, a conductive material dispersion with good conductivity and electrode strength can be obtained.

[0052] The viscosity of the carbon nanotube dispersion liquid of this embodiment is measured using a rheometer at a shear rate of 1 (s -1 When measured at a shear rate of 10 (s), the viscosity is preferably 5 Pa·s or more and less than 60 Pa, more preferably 10 Pa·s or more and less than 40 Pa·s, and even more preferably 20 Pa·s or more and less than 40 Pa·s. -1 When measured at a shear rate of 1 (s), the shear pressure is preferably 1 Pa·s or more and less than 10 Pa. -1 ) the dispersibility of the carbon nanotube dispersion can be determined by measuring the shear viscosity in the above range, and the carbon nanotube dispersion in the above range has a good dispersed particle size and dispersion state of the carbon nanotubes, and is suitable as a carbon nanotube dispersion for improving electrode strength and conductivity. The viscosity of the carbon nanotube dispersion can be determined by leaving the carbon nanotube dispersion to stand in a thermostatic bath at 25°C for at least one hour, thoroughly stirring the carbon nanotube dispersion, and then measuring the shear viscosity at 25°C and at shear rates of 1 s-1 and 10 s-1 using a rheometer with a 35 mm diameter, 2° cone. If the measured value includes decimal points, it is rounded to the nearest integer in accordance with Rule B of JIS Z 8401:1999.

[0053] The cumulative particle size D10 of the carbon nanotube dispersion of this embodiment measured by dynamic light scattering is preferably 200 nm or more and less than 500 nm, more preferably 200 nm or more and less than 400 nm, and even more preferably 300 nm or more and less than 400 nm. Furthermore, the cumulative particle size D50 of the carbon nanotube dispersion measured by dynamic light scattering is preferably 500 nm or more and less than 3000 nm, more preferably 500 nm or more and less than 2000 nm, and even more preferably 500 nm or more and less than 1500 nm. The cumulative particle sizes D10 and D50 of the carbon nanotube dispersion are measured using a particle size distribution analyzer. The particle size measured by dynamic light scattering correlates with the fiber length of the carbon nanotubes, and a carbon nanotube dispersion with a cumulative particle size D10 in the above range has a good dispersion state of the carbon nanotubes in the dispersion.

[0054] To obtain the carbon nanotube dispersion of this embodiment, it is preferable to disperse the carbon nanotubes in a solvent. The dispersing device used for this process is not particularly limited.

[0055] 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 dispersing machines include, but are not limited to, 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," 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; wet jet mills (Jenus's "Jenus 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.

[0056] The amount of carbon nanotubes in the carbon nanotube dispersion of this embodiment is preferably 0.2 to 1.5 parts by mass, more preferably 0.4 to 1.2 parts by mass, and more preferably 0.4 to 1.0 parts by mass, per 100 parts by mass of the carbon nanotube dispersion.

[0057] The amount of dispersant used in the carbon nanotube dispersion liquid of this embodiment is preferably 30 to 250 parts by mass, more preferably 50 to 150 parts by mass, and even more preferably 50 to 100 parts by mass, per 100 parts by mass of carbon nanotubes.

[0058] The pH of the carbon nanotube dispersion liquid of this embodiment is preferably 6 to 11, more preferably 7 to 11, further preferably 8 to 11, and particularly preferably 9 to 11. The pH of the carbon nanotube dispersion liquid can be measured using a pH meter (manufactured by Horiba, Ltd., pH METER F-52).

[0059] (5) Binder The binder is a resin that binds substances such as carbon nanotubes together.

[0060] 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. Among these, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene, carboxymethyl cellulose, ... Dimethyl cellulose, styrene butadiene rubber, and polyacrylic acid are preferred.

[0061] Carboxymethyl cellulose as a binder resin preferably has a high viscosity, for example, a viscosity of 500 to 6000 mPa·s when a 1% aqueous solution is prepared, and more preferably 1000 to 3000 mPa·s. The viscosity of a 1% aqueous solution of carboxymethyl cellulose can be measured at 25°C with a B-type viscometer rotor rotation speed of 60 rpm.

[0062] The carboxymethyl cellulose used as the binder resin preferably has a high degree of etherification, for example, preferably 0.6 to 1.5, and more preferably 0.8 to 1.2.

[0063] The type and amount ratio of the binder are appropriately selected according to the properties of the coexisting materials such as carbon nanotubes, active material, etc. For example, the amount of carboxymethyl cellulose used is preferably 0.5 to 3.0 mass %, more preferably 1.0 to 2.0 mass %, assuming that the mass of the active material is 100 mass %.

[0064] The styrene-butadiene rubber may be any oil-in-water emulsion commonly used as a binder for electrodes. The amount of styrene-butadiene rubber used is preferably 0.5 to 3.0 mass%, more preferably 1.0 to 2.0 mass%, based on 100 mass% of the active material.

[0065] The amount of polyacrylic acid used is preferably 1 to 25% by mass, and more preferably 5 to 20% by mass, when the mass of the active material is taken as 100% by mass.

[0066] Regarding the amount of polyvinylidene fluoride used, when the mass of the active material is taken as 100 mass %, the proportion of polyacrylic acid is preferably 1 to 10 mass %, more preferably 1 to 5 mass %.

[0067] (5) Carbon nanotube resin composition The carbon nanotube resin composition of this embodiment contains carbon nanotubes, a dispersant, a solvent, and a binder.

[0068] To obtain the carbon nanotube resin composition of this embodiment, it is preferable to mix and homogenize the carbon nanotube dispersion and the binder. As a mixing method, various conventionally known methods can be used. The carbon nanotube resin composition can be produced using the dispersing device described above for the carbon nanotube dispersion.

[0069] (6) Mixture slurry The composite slurry of this embodiment contains carbon nanotubes, a dispersant, a solvent, a binder, and an active material. <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.

[0070] As the positive electrode active material, there is no particular limitation, but metal compounds such as metal oxides and metal sulfides capable of doping or intercalating lithium ions, and conductive polymers can be used. For example, oxides of transition metals such as Fe, Co, Ni, Mn, composite oxides with lithium, and inorganic compounds such as transition metal sulfides can be mentioned. Specifically, transition metal oxide powders such as MnO, V2O5, V6O 13 , TiO2, etc., lithium nickelate with a layered structure , lithium cobaltate, lithium manganate, composite oxide powders of lithium and transition metals such as lithium manganate with a spinel structure, lithium iron phosphate-based materials which are phosphate compounds with an olivine structure, transition metal sulfide powders such as TiS2, FeS, etc. can be mentioned. Also, conductive polymers such as poly aniline, polyacetylene, polypyrrole, polythiophene can be used. Further, the above inorganic compounds and organic compounds may be mixed and used.

[0071] As the negative electrode active material, there is no particular limitation as long as it can dope or intercalate lithium ions. For example, metallic Li, alloy systems such as its alloys tin alloy, silicon alloy, lead alloy, etc., Li X Fe2O^3, Li X Fe3O^4, Li X WO2 (x is a number where 0 < x < 1), metal oxide systems such as lithium titanate, lithium vanadate, lithium silicate, conductive polymer systems such as polyacetylene, poly-p-phenylene, amorphous carbonaceous materials such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbon materials, or carbonaceous powders such as natural graphite, carbon black, mesophase carbon black, resin-fired carbon materials, gas-phase grown carbon fibers, carbon fibers and other carbon-based materials can be mentioned. These negative electrode active materials can also be used alone or in combination of two or more.

[0072] As the negative electrode active material of this embodiment, a silicon-based negative electrode active material which is a negative electrode active material containing silicon such as a silicon alloy or lithium silicate is preferable.<000034​ Examples of silicon-based negative electrode active materials include so-called metallurgical grade silicon produced by reducing silicon dioxide with carbon; industrial grade silicon obtained by reducing impurities in metallurgical grade silicon by acid treatment or unidirectional solidification; high-purity silicon produced from silane obtained by reacting silicon and having different crystalline states such as high-purity single crystal, polycrystalline, and amorphous; and silicon obtained by highly purifying industrial grade silicon by sputtering or EB evaporation (electron beam evaporation) while simultaneously adjusting its crystalline state or precipitation state.

[0074] Other examples include silicon oxide, which is a compound of silicon and oxygen, silicon and various alloys, and silicon compounds obtained by adjusting the crystalline state thereof by a quenching method, etc. Among these, a silicon-based negative electrode active material having a structure in which silicon nanoparticles are dispersed in silicon oxide and the outside is coated with a carbon film is preferred.

[0075] In addition to the silicon-based negative electrode active material, the negative electrode active material of this embodiment preferably uses a carbonaceous powder such as an amorphous carbonaceous material such as soft carbon or hard carbon, artificial graphite such as a highly graphitized carbon material, or natural graphite, etc. Among these, it is preferable to use a carbonaceous powder such as artificial graphite or natural graphite.

[0076] The amount of the silicon-based negative electrode active material is preferably 3 to 50 mass %, and more preferably 5 to 25 mass %, based on 100 mass % of carbonaceous powder such as artificial graphite or natural graphite.

[0077] The BET specific surface area of ​​the active material of this embodiment is 0.1 to 10 m 2 / g is preferred, with 0. 2 to 5 m 2 / g is more preferable, and 0.3 to 3m 2 / g is more preferred.

[0078] The average particle size of the active material of this embodiment is preferably within a range of 0.5 to 50 μm, and more preferably 2 to 20 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.

[0079] (7) Manufacturing method of composite slurry

[0080] The composite slurry of this embodiment can be prepared by various conventionally known methods. For example, Examples of the method include a method of adding an active material to a carbon nanotube resin composition, and a method of adding an active material to a carbon nanotube dispersion liquid and then adding a binder.

[0081] 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 liquid.

[0082] The amount of the active material in the composite slurry of this embodiment is preferably 20 to 85 parts by mass, more preferably 30 to 75 parts by mass, and even more preferably 40 to 70 parts by mass, per 100 parts by mass of the composite slurry.

[0083] The amount of carbon nanotubes in the composite slurry of this embodiment is preferably 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass, and even more preferably 0.03 to 1 part by mass, relative to 100 parts by mass of the active material.

[0084] The amount of binder in the composite slurry of this embodiment is preferably 0.5 to 30 mass %, more preferably 1 to 25 mass %, and particularly preferably 2 to 20 mass %, relative to 100 mass % of the active material.

[0085] The amount of solid content in the composite slurry of this embodiment is preferably 30 to 90 mass %, more preferably 30 to 80 mass %, and more preferably 40 to 75 mass %, relative to 100 mass % of the composite slurry.

[0086] (8) Electrode film The electrode film of this embodiment is formed by forming a composite material slurry, for example, a coated film formed by applying the composite material slurry onto a current collector and drying it to form an electrode composite material layer.

[0087] 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 secondary batteries. Examples of materials for the current collector include metals and alloys such as aluminum, copper, nickel, titanium, and 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.

[0088] 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.

[0089] 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.

[0090] (8) Non-aqueous electrolyte secondary battery The nonaqueous electrolyte secondary battery of this embodiment includes a positive electrode, a negative electrode, and an electrolyte.

[0091] 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.

[0092] 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.

[0093] 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). Materials containing sodium salts and calcium salts can also be used. The electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolytic solution.

[0094] 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.

[0095] 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.

[0096] 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 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

[0097] 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".

[0098] <Measurement method of physical properties> The physical properties of CNT used in each of the following examples and comparative examples were measured by the following method.

[0099] <G / D ratio of CNT> 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 the measurement wavelength was 100 to 3000 cm -1 The CNT for measurement was fractionated on a slide glass and flattened using a spatula. Among the obtained peaks, the maximum peak intensity within the range of 1560 - 1600 cm -1 in the spectrum was defined as G, and the maximum peak intensity within the range of 1310 - 1350 cm -1 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> After weighing 0.03 g of CNT using an electronic balance (MSA225S100DI, manufactured by Sartorius), it was dried while degassing at 110 °C for 15 minutes. Then, the BET specific surface area of CNT was measured using a fully automatic specific surface area measuring device (HM-model1208, manufactured by MOUNTECH).

[0101] <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 for dispersion treatment under ice cooling at an amplitude of 50 % for 5 minutes to prepare a CNT dispersion. Then, the CNT dispersion was appropriately diluted, a few 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.). Observations were made at a magnification of 50,000 times, and multiple photos containing 10 or more CNTs in the field of view were taken. The outer diameters of 300 arbitrarily extracted CNTs were measured, and the average value was taken as the average outer diameter (nm) of CNT.

[0102] <Volume resistivity of CNT> Using a powder resistivity measuring device (manufactured by Mitsubishi Chemical Analytech Co., Ltd.: Loresta GP powder resistivity measuring 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), and an applied voltage limiter of 90 V, the volume resistivity [Ω·cm] of the conductive powder under various pressures was measured. At a density of 1 g / cm 3 the value of the volume resistivity of CNT was evaluated.

[0103] <Particle size distribution of CNT dispersion> After the CNT dispersion was left standing in a thermostatic bath at 25 °C for 1 hour or more, the CNT dispersion was thoroughly stirred and diluted, and then a particle size distribution analyzer (manufactured by Microtrac Bell Corporation, Nanotrac Using a UPA (model UPA-EX), the cumulative particle sizes D10 and D50 of the CNT dispersion were measured. The permeability was set to absorption, the density of CNT was 1.8, and the shape was non-spherical. The refractive index of the solvent was 1.333. 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.

[0104] <Complex elastic modulus and phase angle of CNT dispersion> The complex elastic modulus and phase angle of the CNT dispersion 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 (RheoStress1 rotational rheometer manufactured by Thermo Fisher Scientific Co., Ltd.) with a cone of diameter 35 mm and 2°.

[0105] <Viscosity of CNT dispersion> After leaving the CNT dispersion standing in a constant temperature bath at 25°C for 1 hour or more, the CNT dispersion was thoroughly stirred, and then a rheometer (RheoStress1 rotational rheometer manufactured by Thermo Fisher Scientific Co., Ltd.) with a cone of diameter 35 mm and 2° was used to measure the shear viscosity at 25°C and shear rates of 1 s -1 and 10 s -1 for evaluation.

[0106] <Peeling strength of the electrode film for the negative electrode> The composite slurry for the negative electrode was coated on a copper foil using an applicator so that the weight per unit area of the electrode was 8 mg / cm 2 and then baked in an electric oven at 120°C ± 5°C for 25 minutes The coating was then dried. Two 90mm x 20mm rectangles were then cut, with the coating direction as the long axis. Peel strength was measured using a tabletop tensile tester (Strograph E3, manufactured by Toyo Seiki Seisakusho Co., Ltd.) and evaluated using the 180-degree peel test method. 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 peel the adhesive off. The average stress value during this process was recorded as the peel strength.

[0107] <Peel strength of electrode film for positive electrode> The positive electrode composite slurry was applied to the electrode using an applicator so that the weight per unit area was 20 mg / cm. 2 After coating the aluminum foil so that the coating was uniform, 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 tabletop tensile tester (Strograph E3, manufactured by Toyo Seiki Seisaku-sho, Ltd.) using a 180° peel test method. 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 peel the layer off. The average stress measured during this process was recorded as the peel strength.

[0108] <Preparation of standard positive electrode> First, 93 parts by mass of a positive electrode active material (manufactured by BASF Toda Battery Materials LLC, HED (registered trademark) NCM-111 1100), 4 parts by mass of acetylene black (manufactured by Denka Co., Ltd., Denka Black (registered trademark) HS100), and 3 parts by mass of PVDF (manufactured by Kureha Battery Materials Japan Co., Ltd., Kureha KF Polymer W#1300) were mixed in a 150 cm 3The mixture was added to a plastic container and mixed with a spatula until the powder was uniform. 20.5 parts by mass of NMP was then added, and the mixture was stirred with a planetary centrifugal mixer (Thinky Corporation, ARE-310) at 2000 rpm for 30 seconds. The mixture in the plastic container was then mixed with a spatula until uniform, and then stirred with the planetary centrifugal mixer at 2000 rpm for 30 seconds. 14.6 parts by mass of NMP was then added, and the mixture was stirred with the planetary centrifugal mixer at 2000 rpm for 30 seconds. Finally, the mixture was stirred with a high-speed mixer at 3000 rpm for 10 minutes to obtain a positive electrode composite slurry. The positive electrode composite slurry was then applied to a 20 μm-thick aluminum foil current collector using an applicator, and then dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain an electrode with a coating weight per unit area of ​​20 mg / cm. 2 Further, a rolling treatment was carried out using a roll press (Thank Metal Co., Ltd., 3 ton hydraulic roll press) to adjust the density of the composite layer to 3.1 g / cm. 3 A standard positive electrode was fabricated.

[0109] <Preparation of standard negative electrode> A 150 ml plastic container was charged with 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 Co., Ltd., 100% nonvolatile content), and 98.4 parts by mass of water, and then stirred at 2000 rpm for 30 seconds using a planetary centrifugal mixer (Thinky Awatori Rentaro, ARE-310). Furthermore, 87 parts by mass of artificial graphite (CGB-20, manufactured by Nippon Graphite Industries Co., Ltd.) and 10 parts by mass of silicon were added 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 was 8 mg / cm. 2After coating on the copper foil so that the coating was as follows, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes. The density of the composite layer was 1.7 g / cm 3 A standard negative electrode was fabricated.

[0110] <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 11 mA (0.2 C) with a charge cutoff voltage of 4.2 V (cutoff current of 1.1 mA (0.02 C)), followed by a constant current discharge at a discharge current of 11 mA (0.2 C) with a charge cutoff voltage of 4.2 V (cutoff current of 1.1 mA (0.02 C)). This procedure was repeated three times, followed by a constant current / constant voltage charge at a charge current of 11 mA (0.2 C) with a charge cutoff voltage of 4.2 V (cutoff current of 1.1 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 1. (Formula 1) Rate characteristic = 3C discharge capacity / 3rd 0.2C discharge capacity × 100 (%)

[0111] <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: 1.38 mA (0.025 C)) was performed at a charge current of 55 mA (1 C) with a charge cutoff voltage of 4.2 V, followed by a constant-current discharge at a discharge current of 55 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 at 25°C to the 200th 1 C discharge capacity, as shown in Equation 2 below. (Formula 2) Cycle characteristics = 3rd 1C discharge capacity / 200th 1C discharge capacity × 100 (%)

[0112] <Synthesis of dispersant (A)> A reaction vessel equipped with a gas inlet tube, thermometer, condenser, and stirrer was charged with 100 parts of acetonitrile and purged with nitrogen gas. The reaction vessel was heated to 70°C, and a mixture of 85.0 parts of acrylonitrile, 15.0 parts of acrylic acid, and 5.0 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) (NOF Corporation; V-65) was added dropwise over 2 hours to carry out the polymerization reaction. After the dropwise addition, the reaction was continued for another hour at 70°C, followed by the addition of 0.5 parts of Perbutyl O, and the reaction was continued for another hour at 70°C. After that, measurement of the nonvolatile content confirmed that the conversion rate exceeded 98%, and the mixture was concentrated under reduced pressure to completely remove the dispersant, yielding Dispersant (A). The weight-average molecular weight (Mw) of Dispersant (A) was 38,000.

[0113] (Method for measuring weight average molecular weight (Mw)) The weight average molecular weight (Mw) of the produced dispersant (A) was measured by gel permeation chromatography (GPC) equipped with an RI detector under the following conditions. The molecular weight is a pullulan-equivalent value. Measurement sample: 0.1% by mass aqueous solution Device: HLC-8320GPC (Tosoh) Eluent: 0.1M NaCl aqueous solution Column: TSKgel SuperMultiporePW-M (Tosoh) Flow rate: 1.0mL / min Temperature: 25℃ Injection volume: 100μl

[0114] (Method for measuring the degree of etherification) 2.0 g of sodium carboxymethylcellulose and 100 mL of nitric acid methanol were added to a 300 mL stoppered Erlenmeyer flask and shaken for 2 hours to replace the sodium carboxymethylcellulose with carboxymethylcellulose. The carboxymethylcellulose was then suction filtered through a glass filter and washed with 200 mL of 80% methanol. The solution was then substituted with 50 mL of anhydrous methanol, suction filtered, and dried at 105°C for 2 hours. 1.0 to 1.5 g of dried carboxymethylcellulose was weighed and placed in a 300 mL stoppered Erlenmeyer flask. 15 mL of 80% methanol was added to moisten the mixture, and 50 mL of 1 / 10 N sodium hydroxide was added. The mixture was shaken for 2 hours. Then, phenolphthalein was used as an indicator to measure the Excess sodium hydroxide was back-titrated with 10N sulfuric acid, and the degree of etherification was calculated according to (Equation 3) and (Equation 4). (Formula 3) A=(50×F1−X×F2) / (Y×10) X: amount of sulfuric acid added, Y: weight of dry carboxymethyl cellulose, F1: Sulfuric acid factor, F2: Sodium hydroxide factor (Equation 4) Degree of etherification = 0.162A / (1-0.058A)

[0115] Table 1 shows the CNTs used in the examples and comparative examples, the outer diameter of the CNTs, the specific surface area of ​​the CNTs, the G / D ratio, and the volume resistivity.

[0116] [Table 1]

[0117] Table 2 shows the dispersants used in the examples, comparative examples, and reference examples.

[0118] [Table 2]

[0119] Example 1 98.25 parts of ion-exchanged water was added to a stainless steel container, and while stirring with a disperser, 0.75 parts of dispersant (A) was added and stirred until uniform. Next, 1 part of CNT (A) was weighed and added while stirring with a disperser. A high-shear mixer (L5M-A, Silverson) equipped with a square-hole high-shear screen was used, and batch dispersion was performed at 8,600 rpm until uniform. The dispersion was then fed from the stainless steel container to a high-pressure homogenizer (Starburst Lab HJP-17007, Sugino Machine) via piping, and a pass-type dispersion process was performed five times to obtain CNT dispersion (WA1). The dispersion process was performed using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa.

[0120] (Examples 2 to 15), (Examples 19 to 20), (Comparative Examples 1 and 2) CNT dispersions (WA2 to WF4) were obtained in the same manner as in Example 1, except that the CNT type, CNT addition amount, dispersant type, dispersant addition amount, ion-exchanged water addition amount, and number of passes were changed as shown in Table 3.

[0121] Example 16 Capacity 150cm 3 4 parts by mass of the CNT dispersion liquid (WA1) prepared in Example 1 and 6 parts by mass of ion-exchanged water were weighed into a plastic container. Then, using a planetary centrifugal mixer (Thinky Corporation, Awatori Rentaro, ARE-310), the mixture was stirred at 2000 rpm for 30 seconds to obtain a CNT dispersion liquid (WA13).

[0122] Example 17 A CNT dispersion (WA14) was obtained in the same manner as in Example 16, except that the CNT dispersion (WA3) prepared in Example 3 was used.

[0123] Example 18 A CNT dispersion (WA15) was obtained in the same manner as in Example 16, except that the CNT dispersion (WA11) prepared in Example 11 was used.

[0124] Example 21 20 parts of CNT (C) and 480 parts of 8 mm diameter zirconia beads were placed in a polypropylene bottle as grinding media and ground for 40 minutes using a Red Devil paint conditioner. The zirconia beads were then separated and the CNT (C) was recovered. Next, 98.38 parts of ion-exchanged water was added to a stainless steel container, and while stirring with a dispersant, 1.13 parts of dispersant (C) was added and the mixture was stirred with a dispersant until uniform. Then, 1.5 parts of the recovered CNT (C) were weighed and added while stirring with a dispersant. A high-shear mixer (L5M-A, Silverson) equipped with a square-hole high-shear screen was used for batch dispersion at 8,600 rpm until the mixture was uniform. The dispersion liquid was then fed from the stainless steel container to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine) via piping, and a pass-type dispersion process was carried out 20 times to obtain a CNT dispersion liquid (WC27). 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.

[0125] Example 22 98.40 parts of ion-exchanged water was added to a stainless steel container, and while stirring with a disperser, 0.50 parts of dispersant (C) and 0.10 parts of polyacrylic acid (Fujifilm Wako Pure Chemical Industries, Ltd., molecular weight 25,000) were added and stirred until uniform. Then, 1.0 part of CNT (A) was weighed and added while stirring with a disperser. A high-shear mixer (L5M-A, Silverson) equipped with a square-hole high-shear screen was used to mix the mixture at a speed of 8,600 rpm. Batch dispersion was performed until the entire mixture was uniform. Next, the liquid to be dispersed was fed from the stainless steel container via piping to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine), and a pass-type dispersion process was performed 20 times to obtain a CNT dispersion (WA28). The dispersion process was performed using a single nozzle chamber with a nozzle diameter of 0.25 mm and a pressure of 100 MPa.

[0126] (Comparative Example 3) A glass bottle (M-140, manufactured by Kakuyo Glass Co., Ltd.) was charged with 1 part of CNT (A), 0.75 parts of dispersant (A), 98.25 parts of ion-exchanged water, and 120 parts of zirconia beads (bead diameter 1.25 mmφ), and the mixture was dispersed for 8 hours using a paint conditioner manufactured by Red Devil. An attempt was made to separate the zirconia beads, but the viscosity was high and a CNT dispersion liquid could not be obtained.

[0127] (Comparative Examples 4 to 6) The dispersion treatment was carried out in the same manner as in Comparative Example 3, except that the CNT addition amount, dispersion time, and bead diameter were changed as shown in Table 3, and then the zirconia beads were separated to obtain CNT dispersions (WA17 to WA19).

[0128] [Table 3]

[0129] Example 23 99.3 parts of NMP was added to a stainless steel container, and while stirring with a disperser, 0.3 parts of dispersant (E) was added and stirred with a disperser until the dispersant (E) was dissolved. Then, 0.4 parts of CNT (A) was weighed and added while stirring with a disperser. A high-shear mixer (L5M-A, manufactured by Silverson) equipped with a square-hole high-shear screen was used, and batch dispersion was carried out at a speed of 8,600 rpm until the entire mixture was uniform. The dispersion was then fed from the stainless steel container to a high-pressure homogenizer (Starburst Lab HJP-17007, manufactured by Sugino Machine) via piping, and a pass-type dispersion process was carried out 20 times to obtain CNT dispersion (A20). 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.

[0130] (Examples 24 to 26) CNT dispersions (A21 to A23) were obtained in the same manner as in Example 23, except that the number of passes was changed to those shown in Table 4.

[0131] (Comparative Example 7) A glass bottle (M-140, manufactured by Kakuyo Glass Co., Ltd.) was charged with 0.4 parts of CNT (A), 0.3 parts of dispersant (E), 99.3 parts of NMP, and 120 parts of zirconia beads (bead diameter 1.25 mmφ), and the mixture was subjected to a dispersion treatment for 8 hours using a paint conditioner manufactured by Red Devil Co., Ltd. After that, the zirconia beads were separated to obtain a CNT dispersion (A24).

[0132] [Table 4]

[0133] Table 5 shows the evaluation results of the CNT dispersions produced in Examples 1 to 26 and Comparative Examples 1 to 7. The phase angle of the CNT dispersions was evaluated as ◯ (good) for values ​​of 10 or greater and less than 50, △ (passable) for values ​​of 5 or greater and less than 10, and × (unacceptable) for values ​​less than 5 or 50 or greater. The complex modulus of the CNT dispersions at 25°C and a frequency of 1 Hz was evaluated as ◯ (good) for values ​​of 5 or greater and less than 400, △ (passable) for values ​​of 400 or greater and less than 650, and × (unacceptable) for values ​​less than 5. The viscosity of the CNT dispersions was evaluated as follows: the shear viscosity at a shear rate of 1 was evaluated as ⊚ (excellent) for values ​​of 20 or greater and less than 40, ◯ (good) for values ​​of 10 or greater and less than 20 or 40 or greater and less than 60, △ (passable) for values ​​of 5 or greater and less than 10, and × (unacceptable) for values ​​less than 5. The particle size evaluation of the CNT dispersion liquid was carried out as follows: particle size distribution D10 of 200 or more and less than 300 was rated as ◎ (excellent), 300 or more and less than 500 was rated as ○ (good), and less than 200 was rated as × (unacceptable).

[0134] [Table 5]

[0135] Example 28 Capacity 150cm 30.63 parts by mass of CNT dispersion (WA1), 12.5 parts by mass of an aqueous solution containing 2% by mass of CMC (Daicel FineChem Co., Ltd., #1190), and 13.8 parts by mass of ion-exchanged water were weighed into a plastic container. The mixture was then stirred at 2000 rpm for 30 seconds using a planetary centrifugal mixer (Thinky Corporation, Awatori Rentaro, ARE-310) to obtain CNT resin composition (WA1). 2.92 parts by mass of silicon monoxide (Osaka Titanium Technology Co., Ltd., SILICON MONOOXIDE, SiO 1.3C 5μm) was then added, and the mixture was stirred at 2000 rpm for 30 seconds using the planetary centrifugal mixer. Furthermore, 21.44 parts by mass of artificial graphite (Nippon Graphite Industries Co., Ltd., CGB-20) was added, and the mixture was stirred at 2000 rpm for 30 seconds using the planetary centrifugal mixer. Thereafter, 0.78 parts by mass of styrene butadiene emulsion (TRD2001, manufactured by JSR Corporation) was further added, and the mixture was stirred at 2000 rpm for 30 seconds using the planetary centrifugal mixer to obtain a negative electrode mixture slurry (WA1).

[0136] (Examples 29 to 49), (Comparative Examples 8 to 12) CNT resin compositions (WA2 to WA19) and negative electrode composite slurries (WA2 to WA19) were obtained in the same manner as in Example 28, except that the CNT dispersion was changed to one listed in Table 6 and the amounts of CNT dispersion and ion-exchanged water added were adjusted so that the CNTs were 0.025 parts by mass per 100 parts by mass of the composite slurry. The non-volatile content of the negative electrode composite slurries was 48% by mass.

[0137] Example 50 Capacity 150cm 37.0 parts by mass of NMP containing 8% by mass of PVDF (Solef #5130, manufactured by Solvey) was weighed into a plastic container. Then, 0.19 parts by mass of CNT dispersion (A20) 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 (A20). Furthermore, 36.9 parts 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 the planetary centrifugal mixer to obtain positive electrode composite slurry (A20).

[0138] (Examples 51 to 53), (Comparative Example 13) CNT resin compositions (A21 to A24) and positive electrode composite slurries (A21 to A24) were obtained in the same manner as in Example 50, except that the CNT dispersion liquids listed in Table 6 were used.

[0139] [Table 6]

[0140] Example 54 The negative electrode composite slurry (WA1) was applied to the electrode using an applicator so that the weight per unit area of ​​the electrode was 8 mg / cm. 2 After coating on a copper foil so that the temperature was as follows, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain an electrode film (WA1).

[0141] (Examples 55 to 75), (Comparative Examples 14 to 18) Electrode membranes (WA2) to (WA19) were obtained in the same manner as in Example 54, except that the negative electrode composite slurries shown in Table 7 were used instead.

[0142] Example 76 The positive electrode composite slurry (A20) was applied to the electrode using an applicator so that the weight per unit area of ​​the electrode was 20 mg / cm. 2After that, the coating was dried in an electric oven at 120°C ± 5°C for 25 minutes to obtain an electrode film (A20).

[0143] (Examples 77 to 79), (Comparative Example 19) Electrode films (A21) to (A24) were obtained in the same manner as in Example 76, except that the positive electrode composite slurries shown in Table 7 were used.

[0144] Table 7 shows the evaluation results of the electrode films produced in Examples 54 to 79 and Comparative Examples 14 to 19. The adhesion evaluation was rated as follows: ⊚ (excellent) for a peel strength (Ω cm) of 0.5 or more, ◯ (good) for 0.3 or more and less than 0.5, △ (fair) for 0.1 or more and less than 0.3, and × (unacceptable) for less than 0.1.

[0145] [Table 7]

[0146] (Examples 80 to 101), (Comparative Examples 20 to 24) The electrode films (WA1 to WA19) were rolled using a roll press (Thank Metal Co., Ltd., 3-ton hydraulic roll press) until the density of the composite layer reached 1.7 g / cm 3 A negative electrode is created. Made.

[0147] (Examples 102 to 105), (Comparative Example 25) The electrode films (A20 to A24) were rolled using a roll press (Thank Metal Co., Ltd., 3-ton hydraulic roll press) until the density of the composite layer reached 3.2 g / cm 3 A positive electrode having the following structure was fabricated.

[0148] Table 8 shows the negative electrodes and positive electrodes produced in Examples 80 to 105 and Comparative Examples 20 to 25.

[0149] [Table 8]

[0150] Example 106 The negative electrode (WA1) and standard positive electrode were punched out to 50 mm x 45 mm and 45 mm x 40 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 3:5:2 (volume ratio) solvent, adding 1 part each of VC (vinylene carbonate) and FEC (fluoroethylene carbonate) as additives per 100 parts of the solvent, followed by 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 (WA1).

[0151] (Examples 107 to 127), (Comparative Examples 26 to 30) Laminated lithium ion secondary batteries (WA2 to WA19) were fabricated in the same manner except that the negative electrodes were changed to those listed in Table 9.

[0152] Example 128 The standard anode and cathode (A20) were punched out to 50 mm x 45 mm and 45 mm x 40 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 volume ratio of 3:5:2, with 1 part by weight of vinylene carbonate (VC) and 1 part by weight of fluoroethylene carbonate (FEC) added per 100 parts by weight of the mixed solvent, followed by 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 (A20).

[0153] (Examples 129 to 131), (Comparative Example 31) Laminated lithium ion secondary batteries (A21 to A24) were fabricated in the same manner except that the positive electrodes were changed to those listed in Table 9.

[0154] [Table 9]

[0155] Table 10 shows the evaluation results of the laminated lithium-ion secondary batteries fabricated in Examples 106 to 131 and Comparative Examples 26 to 31. Regarding rate characteristics, those with a rate characteristic of 80% or more were rated as ◎ (excellent), those with a rate characteristic of 70% or more but less than 80% were rated as ○ (good), those with a rate characteristic of 60% or more but less than 70% were △ (passable), and those with a rate characteristic of less than 60% were rated × (unacceptable). Regarding cycle characteristics, those with a cycle characteristic of 90% or more were rated as ◎ (excellent), those with a rate characteristic of 85% or more but less than 90% were ◯ (good), those with a rate characteristic of 80% or more but less than 85% were △ (passable), and those with a rate characteristic of less than 80% were rated - (unacceptable).

[0156] [Table 10]

[0157] In the above examples, a carbon nanotube dispersion containing carbon nanotubes, a dispersant, and a solvent was used, in which the G / D ratio of the carbon nanotubes was 5 to 100, and the dispersant was contained in an amount of 30 parts by mass or more but less than 250 parts by mass per 100 parts by mass of the carbon nanotubes. The carbon nanotube dispersion had a complex modulus of 5 Pa or more but less than 650 Pa at 25°C and a frequency of 1 Hz, and a phase angle of 5° or more but less than 50°. In the examples, electrode adhesion tended to be improved compared to the comparative examples. Additionally, improved conductivity and electrode strength resulted in a lithium ion secondary battery with excellent rate and cycle characteristics. Therefore, it was clear that the present invention can provide a lithium ion secondary battery with high capacity, high power, and high durability that are difficult to achieve with conventional carbon nanotube dispersions.

[0158] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above. The configuration and details of the present invention may be modified in various ways that are understandable to those skilled in the art and fall within the scope of the invention.

[0159] 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 liquid containing carbon nanotubes, a dispersant, and a solvent, characterized in that the carbon nanotube dispersion liquid satisfies the following (1) to (4): (1) 1560-1600 cm in the Raman spectrum of carbon nanotubes －１ The maximum peak intensity in the range of 1310 to 1350 cm －１ When the maximum peak intensity within the range is defined as D, the G / D ratio of the carbon nanotube is 5 to 100. (2) The dispersant is contained in an amount of 30 parts by mass or more and less than 250 parts by mass per 100 parts by mass of carbon nanotubes. (3) The carbon nanotube dispersion has a complex modulus of 5 Pa or more and less than 650 Pa at 25°C and a frequency of 1 Hz, and a phase angle of 5° or more and less than 50°. (4) The BET specific surface area of ​​the carbon nanotubes is 550 to 1200 m ２ / g

2. In the Raman spectrum of carbon nanotubes, 1560-1600 cm －１ The maximum peak intensity in the range of G, 1310 to 1350 cm －１ The maximum peak intensity within the range 2. The carbon nanotube dispersion according to claim 1, wherein the G / D ratio of the carbon nanotubes is 10 to 50, where D is the G / D ratio.

3. The carbon nanotube dispersion at 25°C was subjected to a shear rate of 1 (s －１ 3. The carbon nanotube dispersion liquid according to claim 1, wherein the viscosity measured by a method (I) is 5 Pa·s or more and less than 40 Pa·s.

4. 4. The carbon nanotube dispersion according to claim 1, wherein the cumulative particle size D10 measured by dynamic light scattering is 200 nm or more and less than 500 nm.

5. The volume resistivity of the carbon nanotube is 1.0 × 10 －３ Ω・cm~1.0×10 －２ 5. The carbon nanotube dispersion liquid according to claim 1, wherein the viscosity is Ω·cm.

6. 6. The carbon nanotube dispersion according to claim 1, wherein the cumulative particle size D50 measured by dynamic light scattering is 500 nm or more and less than 3000 nm.

7. 7. The carbon nanotube dispersion liquid according to claim 1, wherein the dispersant has a weight average molecular weight of 10,000 to 100,000.

8. 8. The carbon nanotube dispersion liquid according to claim 1, wherein the solvent contains water.

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

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

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

12. 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 contains the electrode film according to claim 11.

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