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 dispersion of carbon nanotubes. More specifically, it relates 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 into a film shape therefrom, and a non-aqueous electrolyte secondary battery comprising the electrode film and an electrolyte.

Background Art

[0002] With the spread of electric vehicles and the miniaturization, light weight and high performance of portable devices, there is a demand for secondary batteries having a high energy density, and further, an increase in the capacity of such secondary batteries. Under such circumstances, non-aqueous electrolyte secondary batteries using non-aqueous electrolytes, particularly lithium ion secondary batteries, have come to be used in many devices due to their characteristics of high energy density and high voltage.

[0003] As negative electrode materials used in these lithium ion secondary batteries, carbon materials typified by graphite, which have a low potential close to lithium (Li) and a large charge-discharge capacity per unit mass, are used. However, these electrode materials are used up to a point where the charge-discharge capacity per mass is close to the theoretical value, and the energy density per mass of the battery is approaching its limit. Therefore, in order to increase the utilization rate as an electrode, attempts have been made to reduce conductive aids and binders that do not contribute to the discharge capacity.

[0004] As conductive aids, carbon black, Ketjen black, fullerene, graphene, fine carbon materials, etc. are used. In particular, carbon nanotubes, which are a type of fine carbon fiber, are widely used. For example, by adding carbon nanotubes to graphite or a silicon negative electrode, it is known that the conductivity, adhesion, electrode strength such as expansion and contraction properties, rate characteristics, and cycle characteristics of a lithium-ion secondary battery are improved. (See, for example, Patent Document 1.) Also, studies have been conducted on reducing the electrode resistance by adding carbon nanotubes to the positive electrode. (See, for example, Patent Documents 2 and 3.) Among them, multi-walled carbon nanotubes with an outer diameter of 10 nm to several tens of nm are relatively inexpensive and are expected to be put into practical use.

[0005] When using carbon nanotubes with a small average outer diameter, a conductive network can be efficiently formed with a small amount, and the amount of conductive aid contained in the positive and negative electrodes for lithium-ion secondary batteries can be reduced. Also, it is known that the same effect is obtained when using carbon nanotubes with a large fiber length. (See, for example, Patent Document 4.) However, due to the strong cohesive force and difficulty in dispersion of carbon nanotubes having these characteristics, a carbon nanotube dispersion liquid having sufficient dispersibility could not be obtained.

[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-based dispersant such as a water-soluble polymer has been proposed. (See Patent Documents 1, 5, and 6.) In Cited Document 1, single-walled carbon nanotubes are dispersed in NMP containing polyvinylpyrrolidone Zirconia beads are used for dispersion in a solvent, but there is a problem that the dispersion time is long and the dispersed particle size of carbon nanotubes becomes small. Although the conductivity of the electrode is improved, the electrode strength cannot be improved. In Cited Document 5, oxidized double-walled carbon nanotubes are dispersed in an aqueous carboxymethyl cellulose solution using an ultrasonic homogenizer, but it was difficult to disperse carbon nanotubes at a high concentration in the solvent. Further, in Cited Document 6, single-walled carbon nanotubes are dispersed in an NMP solvent containing polyvinylpyrrolidone using ultrasonic waves, but it was difficult to disperse carbon nanotubes at a high concentration in the solvent. Further, a method for stabilizing the dispersion of multi-walled carbon nanotubes using nitrile rubber as a dispersant has been proposed (see Patent Document 7). In Cited Document 7, it has been proposed that the output characteristics of the electrode are improved by preparing a multi-walled carbon nanotube dispersion having a specific complex modulus. However, for multi-walled carbon nanotubes having an outer diameter of 10 nm or more, the improvement of the electrode strength was insufficient, and it was difficult to improve the cycle characteristics of the lithium-ion secondary battery.

[0007] Therefore, obtaining a carbon nanotube dispersion in which single-walled carbon nanotubes are dispersed at a high concentration and uniformly in a dispersion medium has been an important issue for expanding applications.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

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 liquid, a carbon nanotube resin composition, and a composite material slurry having high dispersibility and elastic modulus in order to obtain an electrode film excellent in electrode strength and conductivity. More specifically, it is to provide a non-aqueous electrolyte secondary battery having excellent rate characteristics and cycle characteristics.

Means for Solving the Problems

[0010] That is, the present invention relates to a carbon nanotube dispersion liquid containing carbon nanotubes, a dispersant, and a solvent, and is characterized by satisfying the following (1) to (4). (1) When the maximum peak intensity in the range of 1560 to 1600 cm in the Raman spectrum of the carbon nanotubes is G, and the maximum peak intensity in the range of 1310 to 1350 cm is D, the G / D ratio of the carbon nanotubes is 5 to 100. -1 of the range, and the maximum peak intensity in the range of 1310 to 1350 cm -1 of the range, and the maximum peak intensity When the degree is D, the G / D ratio of the carbon nanotubes is 5 to 100. (2) Containing 30 parts by mass or more and less than 250 parts by mass of the dispersant with respect to 100 parts by mass of the carbon nanotubes. (3) The complex elastic modulus of the carbon nanotube dispersion liquid at 25 °C and a frequency of 1 Hz 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 carbon nanotubes is 550 to 1200 m 2 / g.

[0011] Also, in the Raman spectrum of the carbon nanotubes of the present invention, 1560 to 1600 cm -1The maximum peak intensity within the range is G, and within the range of 1310 - 1350 cm -1 Within the range of When the maximum peak intensity within the range is D, the G / D ratio of the carbon nanotubes is 10 - 50, and It relates to the carbon nanotube dispersion liquid characterized by the above.

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

[0013] In addition, the present invention relates to the carbon nanotube dispersion liquid characterized in that the cumulative particle size D10 measured by the dynamic light scattering method is 200 nm or more and less than 5 00 nm.

[0014] In addition, the present invention relates to the carbon nanotube dispersion liquid characterized in that the volume resistivity of the carbon nanotubes is 1.0×10 -3 Ω·cm to 1.0×10 -2 Ω·cm.

[0015] In addition, the present invention relates to the carbon nanotube dispersion liquid characterized in that the cumulative particle size D50 measured by the dynamic light scattering method is 500 nm or more and less than 3000 nm.

[0016] In addition, the present invention relates to the carbon nanotube dispersion liquid characterized in that the weight average molecular weight of the dispersant is 10,000 - 100,000.

[0017] In addition, the present invention relates to the carbon nanotube dispersion liquid characterized in that the solvent contains water.

[0018] In addition, the present invention relates to a carbon nanotube resin composition characterized by including the carbon nanotube dispersion liquid and a binder.

[0019] The present invention also relates to a composite material slurry characterized by 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 material slurry.

[0021] The present invention also 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 and the negative electrode contains the electrode film.

Advantages of the Invention

[0022] By using the carbon nanotube dispersion of the present invention, a resin composition, a composite material slurry, and an electrode film excellent in electrode strength and adhesion can be obtained. Further, a non-aqueous electrolyte secondary battery excellent in rate characteristics and cycle characteristics can be obtained. Therefore, it is possible to use the carbon nanotube dispersion of the present invention in various application fields requiring high conductivity and durability.

Brief Description of the Drawings

[0023]

Figure 1

Embodiments for Carrying Out the Invention

[0024] Hereinafter, the carbon nanotube dispersion, resin composition, composite material slurry, electrode film which is a coating film thereof, and non-aqueous electrolyte secondary battery of the present invention will be described in detail.

[0025] (1) Carbon Nanotubes The carbon nanotubes of the present embodiment are preferably single-walled carbon nanotubes. The single-walled carbon nanotubes may contain multi-walled carbon nanotubes. The single-walled carbon nanotubes have a structure in which one layer of graphite is wound, and the multi-walled carbon nanotubes have a structure in which two or more layers of graphite are wound.

[0026] The average outer diameter of the carbon nanotubes of the present embodiment is 0.5 nm to 5 nm, preferably 1 nm to 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 with a transmission electron microscope (manufactured by JEOL Ltd.) and measuring the lengths of the short axes of 100 carbon nanotubes and taking the number average value.

[0027] The BET specific surface area of the carbon nanotubes of the present embodiment is 550 m 2 / g to 1200 m 2 / g, preferably 600 to 1200 m 2 / g, more preferably 800 m 2 / g to 1200 m 2 / g, and even more preferably 800 m 2 / g to 1000 m 2 / g.

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

[0029] The volume resistivity of the carbon nanotubes of the present embodiment is preferably 1.0×10 -3 Ω·cm to 3.0×10 -2 Ω·cm, more preferably 1.0×10 -3 Ω·cm to 1.0×10 -2More preferably, it is Ω·cm. The volume resistivity of the carbon nanotubes can be measured using a powder resistivity measuring apparatus (manufactured by Mitsubishi Chemical Analytech Co., Ltd.: Loresta GP Powder Resistivity Measuring System MCP-PD-51).

[0030] The carbon purity of the carbon nanotubes of this embodiment is represented by the content rate (%) of carbon atoms 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 with respect 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 with respect to 100% by mass of the carbon nanotubes. Examples of the metal contained in the carbon nanotubes include metals and metal oxides used as catalysts when synthesizing the carbon nanotubes. Specifically, metals such as cobalt, nickel, aluminum, magnesium, silica, manganese, and molybdenum, metal oxides, and composite oxides thereof can be mentioned.

[0032] The carbon nanotubes of this embodiment may be carbon nanotubes subjected to surface treatment. Further, the carbon nanotubes may be carbon nanotube derivatives having a functional group typified by a carboxyl group. Also, carbon nanotubes encapsulating a substance typified by an organic compound, a metal atom, or fullerene can also be used.

[0033] The carbon nanotubes of this embodiment may be pulverized carbon nanotubes. Pulverization treatment refers to pulverizing carbon nanotubes using a pulverizer containing pulverization media such as beads and steel balls, substantially without intervening liquid substances, and is also called dry pulverization. Pulverization is performed by utilizing the pulverizing force and destructive force caused by the collision of the pulverization media. Pulverization mainly has the effect of reducing the secondary particles of carbon nanotubes and can improve the dispersibility of carbon nanotubes. As a dry pulverization device, known methods such as a dry attritor, ball mill, vibration mill, and bead mill can be used, and the pulverization time can be arbitrarily set depending on the device.

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

[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. Appropriate types of dispersants can be used in appropriate blending amounts according to the characteristics required for the dispersion of carbon nanotubes.

[0036] When selecting an anionic surfactant, its type is not particularly limited. Specifically, fatty acid salts, polysulfonate salts, polycarboxylate salts, alkyl sulfate esters, alkylaryl sulfonate salts, alkylnaphthalene sulfonate salts, dialkyl sulfonate salts, dialkyl sulfosuccinate salts, alkyl phosphate salts, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylaryl ether sulfates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl phosphate sulfonate salts, glycerol borate fatty acid esters, and polyoxyethylene glycerol fatty acid esters can be mentioned, but are not limited thereto. Further specifically, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium polyoxyethylene lauryl ether sulfate, polyoxyethylene nonylphenyl ether sulfate ester salt, and sodium salt of β-naphthalene sulfonic acid formalin condensate can be mentioned, but are not limited thereto.

[0037] In addition, examples of cationic surfactants include alkylamine salts and quaternary ammonium salts. Specifically, stearylamine acetate, trimethyl coconut ammonium chloride, trimethyl tallow ammonium chloride, dimethyldioleyl ammonium chloride, methyloleyl diethanol chloride, tetramethylammonium chloride, lauryl pyridinium chloride, lauryl pyridinium bromide, lauryl pyridinium disulfate, cetyl pyridinium bromide, 4-alkyl mercapto pyridine, poly(vinyl pyridine)-dodecyl bromide, and dodecylbenzyltriethylammonium chloride can be mentioned, but are not limited thereto. Also, examples of amphoteric surfactants include aminocarboxylate salts, but are not limited thereto.

[0038] 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, examples include, but are not limited to, polyoxyethylene lauryl ether, sorbitan fatty acid ester, and polyoxyethylene octyl phenyl ether.

[0039] The selected surfactant 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. The blending amount at that time is preferably a suitable blending amount for each surfactant component. As the combination, a combination of an anionic surfactant and a nonionic surfactant is preferable. The anionic surfactant is preferably a polycarboxylate. The nonionic surfactant is preferably polyoxyethylene phenyl ether.

[0040] Specific examples of the resin type dispersant include cellulose derivatives (such as cellulose acetate, cellulose acetate butyrate, cellulose butyrate, cyanoethyl cellulose, ethyl hydroxyethyl cellulose, nitrocellulose, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, etc.), polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, polyacrylonitrile-based polymers, etc. In particular, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral, polyvinyl pyrrolidone, and polyacrylonitrile-based polymers are preferable.

[0041] Carboxymethyl cellulose can be used in the form of salts such as the sodium salt of carboxymethyl cellulose in which the hydroxy groups of carboxymethyl cellulose are substituted with carboxymethyl sodium groups.

[0042] The dispersant of this embodiment preferably has a weight average molecular weight in terms of pullulan of 5,000 or more and 300,000 or less, more preferably 10,000 or more and 100,000 or less, and even more preferably 10,000 or more and 50,000 or less. When a dispersant having an appropriate weight average molecular weight is used, the adsorptivity to CNTs is improved, and the stability of the carbon nanotube dispersion is further improved. Also, when a dispersant exceeding the above range is used, the viscosity of the carbon nanotube dispersion becomes high, and when a disperser through which the dispersion liquid passes through a narrow flow path such as a nozzle-type high-pressure homogenizer is used, the dispersion efficiency may decrease. In addition, the resin-type dispersant may have a binding ability in addition to the dispersing ability, and the resin-type dispersant as described above can also be used as a binder, and the same type of resin as the resin-type dispersant may be used as the binder. When the same type of resin as the resin-type dispersant is used as the binder, it is preferable to use a resin having a weight average molecular weight larger than the weight average molecular weight of the resin-type dispersant.

[0043] In addition to the dispersant of the present embodiment, an inorganic base and an inorganic metal salt may be included. The inorganic base and the inorganic metal salt are preferably compounds having at least one of an alkali metal and an alkaline earth metal. Specifically, chlorides, hydroxides, carbonates, nitrates, sulfates, phosphates, tungstates, vanadates, molybdates, niobates, and borates of an alkali metal and an alkaline earth metal can be mentioned. Among these, chlorides, hydroxides, and carbonates of an alkali metal and an alkaline earth metal are preferable in terms of easily supplying cations. Examples of the hydroxide of an alkali metal include lithium hydroxide, sodium hydroxide, potassium hydroxide, etc. Examples of the hydroxide of an alkaline earth metal include calcium hydroxide, magnesium hydroxide, etc. Examples of the carbonate of an alkali metal include lithium carbonate, lithium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, etc. Examples of the carbonate of an alkaline earth metal include calcium carbonate, magnesium carbonate. Among these, lithium hydroxide, sodium hydroxide, lithium carbonate, and sodium carbonate are more preferable.

[0044] In addition to the dispersant of the present embodiment, an acid may be included. By adding an acid, the charge state in the dispersion system and the balance between the hydrophilic part and the hydrophobic part may change, and the dispersibility may be improved. The type of acid is not particularly limited, and it may be used alone or in combination of a plurality. For example, oxalic acid, lactic acid, citric acid, polyacrylic acid, polystyrene sulfonic acid, acetic acid, malonic acid, hydrochloric acid, nitric acid, sulfuric acid, boric acid, phosphoric acid, etc. can be mentioned.

[0045] In addition to the dispersant of the present embodiment, an antifoaming agent may be included. The antifoaming agent can be arbitrarily used as long as it has an antifoaming effect, such as a commercially available antifoaming agent, wetting agent, hydrophilic organic solvent, water-soluble organic solvent, etc., and it may be used alone or in combination of a plurality. For example, alcohol-based; 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, other glycols, etc., Fatty acid ester-based; diethylene glycol laurate, glycerin monolinoleate, alkenyl succinic acid derivatives, sorbitol monolaurate, sorbitol trioleate, polyoxyethylene monolaurate, polyoxyethylene sorbitol monolaurate, natural waxes, etc., Amide-based; polyoxyalkylene amide, acrylate polyamine, etc., Phosphate ester-based; tributyl phosphate, sodium octyl phosphate, etc., Metal soap-based; aluminum stearate, calcium oleate, etc., Oil and fat-based; animal and vegetable oils, sesame oil, castor oil, etc., Mineral oil-based: kerosene, paraffin, etc., Silicone-based; dimethyl silicone oil, silicone paste, silicone emulsion, organically modified polysiloxane, fluorosilicone oil, etc. may be mentioned.

[0046] (3) Solvent The solvent of this embodiment is not particularly limited as long as the carbon nanotubes can be dispersed, but it is preferably a mixed solvent composed of any one or two or more of water and / or a water-soluble organic solvent, and more preferably contains water. When water is contained, it is preferably 95% by mass or more, more preferably 98% by mass or more, based on 100% by mass of the solvent.

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

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

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

[0050] The phase angle of the carbon nanotube dispersion of this embodiment at 25°C and a frequency of 1 Hz is 5° or more and less than 50°, and more preferably 10° or more and less than 50°. The phase angle means the phase shift of the stress wave when the strain applied to the carbon nanotube dispersion is a sine wave. For a pure elastic body, it becomes a sine wave in phase with the applied strain, so the phase angle is 0°. On the other hand, for a pure viscous body, it becomes a stress wave advanced by 90°. A carbon nanotube dispersion with the values of the complex elastic modulus and the phase angle within the above ranges has a good dispersion particle size and dispersion state of the carbon nanotubes and is suitable as a carbon nanotube dispersion for improving electrode strength and conductivity., The complex elastic modulus and phase angle of the carbon nanotube dispersion can be determined by performing dynamic viscoelasticity measurements at 25°C and a frequency of 1 Hz in the strain rate range of 0.01% to 5% using a rheometer with a cone having a diameter of 35 mm and an angle of 2°. When the measured value includes digits after the decimal point, it shall be rounded to the integer place according to Rule B of JIS Z8401:1999.

[0051] By uniformly and favorably dispersing while maintaining a length of a certain level or more so that the fiber length of the carbon nanotubes does not become shorter due to breakage, a developed conductive network is formed. Therefore, it is not simply sufficient that the viscosity of the conductive material dispersion is low (apparent) and the dispersibility is good, but it is particularly effective to judge the dispersion state by combining the complex elastic modulus and / or the phase angle with conventional indexes such as viscosity. By setting the complex elastic modulus and / or the 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 of the present embodiment 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 when measured using a rheometer at a shear rate of 1 (s -1 )). Also, when measured using a rheometer at a shear rate of 10 (s -1 ), it is preferably 1 Pa·s or more and less than 10 Pa. By measuring the shear viscosity at a shear rate of 1 (s -1 ), the dispersibility of the carbon nanotube dispersion can be judged, and the carbon nanotube dispersion within the above range has a good dispersion particle size and dispersion state of 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 allowing the carbon nanotube dispersion to stand in a thermostatic bath at 25°C for 1 hour or more, thoroughly stirring the carbon nanotube dispersion, and then measuring the shear viscosity at 25°C, a shear rate of 1 s-1 and 10 s-1 using a rheometer with a cone having a diameter of 35 mm and an angle of 2°. When the measured value includes a decimal fraction, it is rounded to the integer place in accordance with Rule B of JIS Z8401:1999.

[0053] The cumulative particle size D10 measured by the dynamic light scattering method of the carbon nanotube dispersion of the present embodiment 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. Further, the cumulative particle size D50 measured by the dynamic light scattering method of the carbon nanotube dispersion 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 (manufactured by Microtrac BEL Corporation, Nanotrac UPA, model UPA-EX). The particle size measured by the dynamic light scattering method is correlated with the fiber length of the carbon nanotubes, and the carbon nanotube dispersion in which the cumulative particle size D10 is within the above range has a good dispersion state of the carbon nanotubes in the dispersion.

[0054] To obtain the carbon nanotube dispersion of the present embodiment, it is preferable to perform a treatment of dispersing carbon nanotubes in a solvent. The dispersion device used for performing such treatment is not particularly limited.

[0055] As the dispersion device, a disperser commonly used for pigment dispersion or the like can be used. For example, mixers such as a disper, a homomixer, and a planetary mixer, a homogenizer (Advanced Digital Sonifer (registered trademark) manufactured by BRANSON, MODEL 450DA, "Claremix" manufactured by M-Technique Co., Ltd., PRIMI Media type dispersers such as "Filmix" of Company X, "Abramix" etc. manufactured by Silver Son Co., paint conditioner (manufactured by Red Devil Co.), colloid mills ("PUC Colloid Mill" manufactured by PUC Co., "Colloid Mill MK" manufactured by IKA Co.), corn mills ("Corn Mill MKO" etc. manufactured by IKA Co.), ball mills, sand mills ("Dynomill" etc. manufactured by Shinmaru Enterprises Co.), attritors, pearl mills ("DCP Mill" etc. manufactured by Ehrlich Co.), coball mills, etc., media - less dispersers such as wet jet mills ("Genus PY" manufactured by Genus Co., "Starburst" manufactured by Sugino Machine Co., "Nanomizer" manufactured by Nanomizer Co.), "Clear SS - 5" manufactured by M. Technique Co., "MICROS" manufactured by Nara Machinery Co., and other roll mills etc. may be mentioned, but are not limited thereto.

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

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

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

[0059] (5) Binder A binder is a resin for binding substances such as carbon nanotubes.

[0060] Examples of the binder in this embodiment include polymers or copolymers containing, as constituent units, ethylene, propylene, vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic esters, methacrylic acid, methacrylic esters, acrylonitrile, styrene, vinyl butyral, vinyl acetal, vinyl pyrrolidone, etc.; polyurethane resins, polyester resins, phenol resins, epoxy resins, phenoxy resins, urea resins, melamine resins, alkyd resins, acrylic resins, formaldehyde resins, silicone resins, fluorine resins; cellulose resins such as carboxymethyl cellulose; rubbers such as styrene-butadiene rubber and fluororubber; conductive resins such as polyaniline and polyacetylene. Also, modified products, mixtures, and copolymers of these resins may be used. Among these, polyvinylidene fluoride, polyvinyl fluoride, tetrafluoroethylene, carboxymethyl cellulose, styrene-butadiene rubber, and polyacrylic acid are preferred. Carboxymethyl cellulose as the binder resin is preferably highly viscous. For example, when a 1% aqueous solution is prepared, the viscosity is preferably 500 to 6000 mPa·s, more preferably 1000 to 3000 mPa·s. The viscosity of a 1% aqueous solution of carboxymethyl cellulose can be measured at 25°C using a B-type viscometer with a rotor rotation speed of 60 rpm.

[0061] Carboxymethyl cellulose as the binder resin preferably has a high degree of etherification. For example, the degree of etherification is preferably 0.6 to 1.5, more preferably 0.8 to 1.2.

[0062]

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

[0064] If styrene-butadiene rubber is an oil-in-water emulsion, generally, the one that is used as a binder for an electrode can be used. Regarding the amount of styrene-butadiene rubber used, when the mass of the active material is 100% by mass, the ratio of styrene-butadiene rubber is preferably 0.5 to 3.0% by mass, and more preferably 1.0 to 2.0% by mass.

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

[0066] Regarding the amount of polyvinylidene fluoride used, when the mass of the active material is 100% by mass, the ratio of polyacrylic acid is preferably 1 to 10% by mass, and more preferably 1 to 5% by 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 a carbon nanotube dispersion and a binder. As the mixing method, various conventionally known methods can be performed. The carbon nanotube resin composition can be produced using the dispersion device described in the carbon nanotube dispersion.

[0069] (6) Composite material slurry The composite material slurry of this embodiment contains carbon nanotubes, a dispersant, a solvent, a binder, and an active material. <Active material> The active material of this embodiment is a material that serves as the basis for the battery reaction. The active material is divided into a positive electrode active material and a negative electrode active material based on the 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, and 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 and FeS can be mentioned. Also, poly conductive polymers such as aniline, polyacetylene, polypyrrole, and 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, metal Li, alloy systems such as its alloys like tin alloys, silicon alloys, and lead alloys, Li X Fe2O3, Li X Fe3O4, Li X WO2 (x is a number where 0 < x < 1.), metal oxide systems such as lithium titanate, lithium vanadate, and lithium silicate, conductive polymer systems such as polyacetylene and poly-p-phenylene, amorphous carbonaceous materials such as soft carbon and hard carbon, artificial graphite such as highly graphitized carbon materials, or carbonaceous powders such as natural graphite, carbon black, mesophase carbon black, resin-fired carbon materials, gas-phase grown carbon fibers, carbon fibers, etc. 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.

[0073] 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 through acid treatment, unidirectional solidification, etc., high-purity single crystals, polycrystals, amorphous, etc. of different crystal states of high-purity silicon produced from silane obtained by reacting silicon, and silicon with adjusted crystal state and precipitation state obtained by making industrial grade silicon highly pure by sputtering method, EB evaporation (electron beam evaporation) method, etc.

[0074] In addition, silicon dioxide which is a compound of silicon and oxygen, and silicon compounds with adjusted crystal states of silicon and various alloys by rapid cooling method, etc. are also included. Among them, a silicon-based negative electrode active material having a structure in which silicon nanoparticles are dispersed in silicon dioxide and the outer side is coated with a carbon film is preferable.

[0075] In addition to the silicon-based negative electrode active material, the negative electrode active material of this embodiment preferably uses 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. Among them, it is preferable to use carbonaceous powders such as artificial graphite and natural graphite.

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

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

[0078] The average particle diameter of the active material in this embodiment is preferably in the range of 0.5 to 50 μm, more preferably 2 to 20 μm. The average particle diameter of the active material as used herein refers to the average value of the particle diameters measured by an electron microscope for the active material.

[0079] (7) Method for manufacturing composite material slurry

[0080] The composite material slurry of this embodiment can be produced by various conventionally known methods. For example, a method of adding an active material to a carbon nanotube resin composition for production, or a method of adding an active material to a carbon nanotube dispersion and then adding a binder for production can be mentioned.

[0081] To obtain the composite material slurry of this embodiment, after adding the active material to the carbon nanotube resin composition, it is preferable to perform a dispersion treatment. The dispersion device used for performing such treatment is not particularly limited. The composite material slurry can be obtained using the dispersion device described for the carbon nanotube dispersion.

[0082] The amount of the active material in the composite material 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 with respect to 100 parts by mass of the composite material slurry.

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

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

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

[0086] (8) Electrode film The electrode film of this embodiment is formed by forming a composite material slurry. For example, it is a coating film in which an electrode composite material layer is formed by coating and drying the composite material slurry on a current collector.

[0087] The material and shape of the current collector used for the electrode film of this embodiment are not particularly limited, and those suitable for various secondary batteries can be appropriately selected. For example, examples of the material of the current collector include metals and alloys such as aluminum, copper, nickel, titanium, or stainless steel. Further, as the shape, generally a foil on a flat plate is used, but those with a roughened surface, perforated foil-like ones, and mesh-like current collectors can also be used.

[0088] There is no particular limitation on the method of coating the composite material slurry on the current collector, and known methods can be used. Specifically, examples include the die coating method, dip coating method, roll coating method, doctor coating method, knife coating method, spray coating method, gravure coating method, screen printing method, or electrostatic coating method. As the drying method, air drying, hot air drying, infrared heating, far-infrared heating, etc. can be used, but it is not particularly limited to these.

[0089] Further, a rolling treatment may be performed by a flat plate press, a calendar roll, etc. after coating. The thickness of the electrode composite material layer is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.

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

[0091] As the positive electrode, one obtained by coating and drying a composite material slurry containing a positive electrode active material on a current collector to form an electrode film can be used.

[0092] As the negative electrode, one obtained by coating and drying a composite material slurry containing a negative electrode active material on a current collector to form an electrode film can be used.

[0093] As the electrolyte, various conventionally known ones in which ions can move can be used. For example, 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) can be mentioned, but it is not limited to these, and those containing sodium salts or 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. For example, 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 can be mentioned. These solvents can be used alone or in combination of two or more.

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

Examples

[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 neutral density filter of 10%, an objective lens magnification of 20 times, a confocal hole of 500, a slit width of 100 μm, and a measurement wavelength of 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 in the spectrum within the range of 1560 to 1600 cm -1 was defined as G, and the maximum peak intensity within the range of 1310 to 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> The CNT was weighed to 0.03 g using an electronic balance (MSA225S100DI manufactured by Sartorius), and then dried while degassing at 110 °C for 15 minutes. Thereafter, the BET specific surface area of the 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. Thereafter, the CNT dispersion was appropriately diluted, several μL was dropped in the form of a collodion film, dried at room temperature, and then observed using a transmission electron microscope (H-7650, manufactured by Hitachi, Ltd.). Observation was performed at a magnification of 50,000 times, and a plurality of photographs containing 10 or more CNTs in the visual field 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 the 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, using a powder probe unit (four-probe ring electrode, electrode interval 5.0 mm, electrode radius 1.0 mm, sample radius 12.5 mm), with the applied voltage limiter set to 90 V, the volume resistivity [Ω·cm] of the conductive powder under various pressures was measured. The value of the volume resistivity of CNT at a density of 1 g / cm 3 was evaluated.

[0103] <Particle size distribution of CNT dispersion> After the CNT dispersion was allowed to stand in a constant temperature bath at 25 °C for 1 hour or more, the CNT dispersion was sufficiently 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 the CNTs 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 in a thermostatic bath at 25 °C for 1 hour or more and then sufficiently stirring the CNT dispersion, a rheometer (RheoStress1 rotational rheometer manufactured by Thermo Fisher Scientific Co., Ltd.) with a cone of diameter 35 mm and 2° was used at 25 °C and shear rates of 1 s -1 and 10 s -1 to measure the shear viscosity for evaluation.

[0106] <Peeling Strength of Electrode Film for 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 placed in an electric oven at 120 °C ± 5 °C for 25 minutes , the coating film was dried. Then, it was cut into two rectangles of 90 mm × 20 mm with the coating direction as the major axis. For the measurement of the peel strength, a tabletop tensile testing machine (manufactured by Toyo Seiki Seisakusho, Strograph E3) was used and evaluated by the 180-degree peel test method. Specifically, a double-sided tape with a size of 100 mm × 30 mm (No. 5000NS, manufactured by Nitto Denko Corporation) was attached onto a stainless steel plate, and the prepared battery electrode composite layer was adhered to the other side of the double-sided tape. It was peeled off while being pulled from the bottom to the top at a constant speed (50 mm / min), and the average value of the stress at this time was taken as the peel strength.

[0107] <Peel Strength of the Electrode Film for the Positive Electrode> The positive electrode composite slurry was coated onto an aluminum foil using an applicator so that the basis weight per unit of the electrode was 20 mg / cm 2 Then, the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes. Then, it was cut into two rectangles of 90 mm × 20 mm with the coating direction as the major axis. For the measurement of the peel strength, a tabletop tensile testing machine (manufactured by Toyo Seiki Seisakusho, Strograph E3) was used and evaluated by the 180-degree peel test method. Specifically, a double-sided tape with a size of 100 mm × 30 mm (No. 5000NS, manufactured by Nitto Denko Corporation) was attached onto a stainless steel plate, and the prepared battery electrode composite layer was adhered to the other side of the double-sided tape. It was peeled off while being pulled from the bottom to the top at a constant speed (50 mm / min), and the average value of the stress at this time was taken as the peel strength.

[0108] <Fabrication of the Standard Positive Electrode> First, 93 parts by mass of a positive electrode active material (manufactured by BASF Toda Battery Materials Co., Ltd., 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 Kuraray Battery Materials Japan Co., Ltd., Kuraray KF Polymer W#1300) were placed in a container with a volume of 150 cm 3After adding to a plastic container, it was mixed with a spatula until the powder became uniform. Then, 20.5 parts by mass of NMP was added, and using a planetary mixer (Avataro Ryorotaro, ARE-310 manufactured by Shinchi Co., Ltd.), it was stirred at 2000 rpm for 30 seconds. Then, the mixture in the plastic container was mixed with a spatula until it became uniform, and using the planetary mixer, it was stirred at 2000 rpm for 30 seconds. Further, 14.6 parts by mass of NMP was added, and using the planetary mixer, it was stirred at 2000 rpm for 30 seconds. Finally, using a high-speed stirrer, it was stirred at 3000 rpm for 10 minutes to obtain a composite slurry for the positive electrode. Then, the composite slurry for the positive electrode was coated on an aluminum foil with a thickness of 20 μm serving as a current collector using an applicator, and then dried in an electric oven at 120 °C ± 5 °C for 25 minutes so that the mass per unit area of the electrode was 20 mg / cm 2 and adjusted. Further, rolling treatment was performed using a roll press (3t hydraulic roll press manufactured by Sanku Metal Co., Ltd.) so that the density of the composite layer was 3.1 g / cm 3 to produce a standard positive electrode.

[0109] <Fabrication of Standard Negative Electrode> To a plastic container with a volume of 150 ml, 0.5 part by mass of acetylene black (Denka Black (registered trademark) HS-100, manufactured by Denka), 1 part by mass of MAC500LC (sodium carboxymethyl cellulose salt, Sanrose special type MAC500L, manufactured by Nippon Paper Industries Co., Ltd., non-volatile content 100%), and 98.4 parts by mass of water were added. Then, using a planetary mixer (Avataro Ryorotaro manufactured by Shinchi, ARE-310), it was stirred at 2000 rpm for 30 seconds. Further, 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 using a high-speed stirrer, it was stirred at 3000 rpm for 10 minutes. Subsequently, 3.1 parts by mass of SBR (TRD2001, manufactured by JSR Corporation) was added, and using the planetary mixer, it was stirred at 2000 rpm for 30 seconds to obtain a composite slurry for the negative electrode. Then, the composite slurry for the negative electrode was coated using an applicator so that the mass per unit area of the electrode was 8 mg / cm 2After coating on the copper foil so as to achieve [the desired state], the coating film was dried in an electric oven at 120 °C ± 5 °C for 25 minutes. Further, rolling treatment was performed using a roll press (manufactured by Sanku Metal Co., Ltd., 3t hydraulic roll press) to produce a standard negative electrode with a density of the composite material layer of 1.7 g / cm 3 and the density of the composite material layer of 1.7 g / cmto obtain a standard negative electrode with a density of 1.7 g / cm

[0110] <Rate Characteristics Evaluation of Lithium-Ion Secondary Battery> The laminated lithium-ion secondary battery was placed in a constant temperature chamber at 25 °C, and charge and discharge measurements were performed using a charge and discharge device (manufactured by Hokuto Denko Corporation, SM-8). After performing constant current and constant voltage charging (cut-off current: 1.1 mA (0.02C)) at a charging current of 11 mA (0.2C) and a charging cut-off voltage of 4.2V, constant current discharge was performed at a discharge current of 11 mA (0.2C) and a discharge cut-off voltage of 2.5V. After repeating this operation three times, constant current and constant voltage charging (cut-off current: 1.1 mA (0.02C)) was performed at a charging current of 11 mA (0.2C) and a charging cut-off voltage of 4.2V, and constant current discharge was performed at discharge currents of 0.2C and 3C until the discharge cut-off voltage of 2.5V was reached, and the discharge capacities were obtained respectively. The rate characteristics can be expressed by the ratio of the 0.2C discharge capacity to the 3C discharge capacity, as shown in Equation 1 below. (Equation 1) Rate characteristics = 3C discharge capacity / 0.2C discharge capacity of the third cycle × 100 (%)

[0111] <Cycle Characteristics Evaluation of Lithium-Ion Secondary Battery> The laminated lithium-ion secondary battery was placed in a constant temperature chamber at 25 °C, and charge and discharge measurements were performed using a charge and discharge device (manufactured by Hokuto Denko Corporation, SM-8). After performing constant current and constant voltage charging (cut-off current: 1.38 mA (0.025C)) at a charging current of 55 mA (1C) and a charging cut-off voltage of 4.2V, constant current discharge was performed at a discharge current of 55 mA (1C) and a discharge cut-off voltage of 2.5V. This operation was repeated 200 times. 1C was defined as the current value for discharging the theoretical capacity of the positive electrode in one hour. The cycle characteristics can be expressed by the ratio of the 1C discharge capacity of the third cycle at 25 °C to the 1C discharge capacity of the 200th cycle, as shown in Equation 2 below. (Equation 2) Cycle characteristics = 1C discharge capacity of the third cycle / 1C discharge capacity of the 200th cycle × 100 (%)

[0112] <Synthesis of Dispersant (A)> 100 parts of acetonitrile was charged into a reaction vessel equipped with a gas introduction tube, a thermometer, a condenser, and a stirrer, and replaced with nitrogen gas. The inside of 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) (manufactured by NOF Corporation; V-65) was added dropwise over 2 hours to conduct a polymerization reaction. After completion of the dropwise addition, the reaction was further carried out at 70 °C for 1 hour. Then, 0.5 part of Perbutyl O was added, and the reaction was continued at 70 °C for 1 hour. Thereafter, it was confirmed that the conversion rate exceeded 98% by non-volatile content measurement, and the dispersion medium was completely removed by concentration under reduced pressure to obtain 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 in terms of pullulan conversion. Measurement sample: 0.1 mass% aqueous solution Apparatus: HLC-8320GPC (manufactured by Tosoh Corporation) Eluent: 0.1 M NaCl aqueous solution Column: TSKgel SuperMultiporePW-M (manufactured by Tosoh Corporation) Flow rate: 1.0 mL / min Temperature: 25 °C Injection volume: 100 μl

[0114] (Method for Measuring Degree of Etherification) Into a 300 mL conical flask with a stopper, add 2.0 g of sodium carboxymethyl cellulose and 100 mL of methanol nitrate, and shake for 2 hours to replace sodium carboxymethyl cellulose with carboxymethyl cellulose. Then, filter the carboxymethyl cellulose by suction through a glass filter, and wash it with 200 mL of 80% methanol. Then, replace it with 50 mL of anhydrous methanol, filter by suction, and dry at 105 °C for 2 hours. Weigh 1.0 - 1.5 g of the dried carboxymethyl cellulose, put it into a 300 mL conical flask with a stopper, add 15 mL of 80% methanol to moisten it, and add 50 mL of 1 / 10N sodium hydroxide and shake for 2 hours. Then, using phenolphthalein as an indicator, back-titrate the excess sodium hydroxide with 1 / 10N sulfuric acid, and calculate the degree of etherification according to (Equation 3) and (Equation 4). (Equation 3) A = (50 × F1 ― X × F2) / (Y × 10) X: Drop volume of sulfuric acid, Y: Weight of dried carboxymethyl cellulose, F1: Factor of sulfuric acid, F2: Factor of sodium hydroxide (Equation 4) Degree of etherification = 0.162A / (1 - 0.058A)

[0115] Table 1 shows the CNTs, outer diameters of CNTs, specific surface areas of CNTs, G / D ratios, and volume resistivities used in the examples and comparative examples.

[0116]

Table 1

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

[0118]

Table 2

[0119] (Example 1) Add 98.25 parts of ion-exchanged water to a stainless steel container, and while stirring with a disperser, add 0.75 part of dispersant (A), and stir until uniform with a disperser. Then, weigh 1 part of CNT (A), add it while stirring with a disperser, attach a square-hole high-shear screen to a high-shear mixer (L5M-A, manufactured by SILVERSON), and perform batch dispersion at a speed of 8,600 rpm until the whole becomes uniform. Subsequently, supply the liquid to be dispersed from the stainless steel container to a high-pressure homogenizer (Starburst Labo HJP-17007, manufactured by Sugino Machine) through a pipe, and perform the pass-type dispersion treatment 5 times to obtain a CNT dispersion liquid (WA1). The dispersion treatment was carried out using a single-nozzle chamber at 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 to 2) Except for changing the CNT type, CNT addition amount, dispersant type, dispersant addition amount, ion-exchanged water addition amount, and number of passes listed in Table 3, CNT dispersion liquids (WA2 to WF4) were obtained in the same manner as in Example 1.

[0121] (Example 16) A plastic container with a volume of 150 cm 3 was weighed with 4 parts by mass of the CNT dispersion liquid (WA1) prepared in Example 1 and 6 parts by mass of ion-exchanged water. Then, using a rotation-revolution mixer (Sinky Co., Ltd. Awatori Rentaro, ARE-310), it was stirred at 2,000 rpm for 30 seconds to obtain a CNT dispersion liquid (WA13).

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

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

[0124] (Example 21) A polypropylene bottle container was charged with 20 parts of CNT (C) and 480 parts of zirconia beads with a diameter of 8 mm as grinding media, and ground for 40 minutes using a paint conditioner manufactured by Red Devil. Subsequently, the zirconia beads were separated and CNT (C) was recovered. Next, 98.38 parts of ion-exchanged water was added to a stainless steel container, and while stirring with a disper, 1.13 parts of dispersant (C) was added and stirred with the disper until it became uniform. Then, 1.5 parts of the recovered CNT (C) was weighed and added while stirring with a disper. A square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,600 rpm until the whole became uniform. Subsequently, the dispersion liquid was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Labo HJP-17007, manufactured by Sugino Machine) through a pipe, and the pass-through dispersion treatment was performed 20 times to obtain a CNT dispersion liquid (WC27). The dispersion treatment was performed using a single nozzle chamber at 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 disper, 0.50 part of dispersant (C) and 0.10 part of polyacrylic acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., molecular weight 25,000) were added and stirred with the disper until it became uniform. Then, 1.0 part of CNT (A) was weighed and added while stirring with a disper. A square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch dispersion was performed at a speed of 8,600 rpm until the whole became uniform. Subsequently, the dispersion liquid was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Labo HJP-17007, manufactured by Sugino Machine) through a pipe, and the pass-through dispersion treatment was performed 20 times to obtain a CNT dispersion liquid (WA28). The dispersion treatment was performed using a single nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa.

[0126] (Comparative Example 3) A glass bottle (M-140, manufactured by Kashiwa Glass Co., Ltd.) was charged with 1 part of CNT (A), 0.75 part of dispersant (A), 98.25 parts of ion-exchanged water, and 120 parts of zirconia beads (bead diameter 1.25 mmφ). After performing a dispersion treatment 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) Except for changing the CNT addition amount, dispersion time, and bead diameter listed in Table 3, a dispersion treatment was performed in the same manner as in Comparative Example 3. After that, the zirconia beads were separated to obtain CNT dispersion liquids (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 disper, 0.3 part of dispersant (E) was added and stirred with the disper until the dispersant (E) was dissolved. Then, 0.4 part of CNT (A) was weighed and added while stirring with the disper. A square-hole high-shear screen was attached to a high-shear mixer (L5M-A, manufactured by SILVERSON), and batch-type dispersion was performed at a speed of 8,600 rpm until the whole became uniform. Subsequently, the dispersion liquid was supplied from the stainless steel container to a high-pressure homogenizer (Starburst Turbo HJP-17007, manufactured by Sugino Machine) through a pipe, and a pass-type dispersion treatment was performed 20 times to obtain a CNT dispersion liquid (A20). The dispersion treatment was performed using a single-nozzle chamber at a nozzle diameter of 0.25 mm and a pressure of 100 MPa.

[0130] (Examples 24 to 26) Except for changing the number of passes listed in Table 4, CNT dispersion liquids (A21 to A23) were obtained in the same manner as in Example 23.

[0131] (Comparative Example 7) 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) were charged into a glass bottle (M-140, manufactured by Kashiwa Glass Co., Ltd.). After performing a dispersion treatment for 8 hours using a paint conditioner manufactured by Red Devil, 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 prepared in Examples 1 to 26 and Comparative Examples 1 to 7. For the evaluation of the phase angle of the CNT dispersion, a value of 10 or more and less than 50 was rated as ○ (good), 5 or more and less than 10 was rated as △ (fair), and less than 5 or 50 or more was rated as × (poor). For the evaluation of the complex elastic modulus of the CNT dispersion at 25°C and a frequency of 1 Hz, a value of 5 or more and less than 400 was rated as ○ (good), 400 or more and less than 650 was rated as △ (fair), and less than 5 was rated as × (poor). For the viscosity evaluation of the CNT dispersion, when the shear viscosity at a shear rate of 1 was 20 or more and less than 40, it was rated as ⊙ (excellent), 10 or more and less than 20, or 40 or more and less than 60 was rated as ○ (good), 5 or more and less than 10 was rated as △ (fair), and less than 5 was rated as × (poor). For the particle size evaluation of the CNT dispersion, when the particle size distribution at D10 was 200 or more and less than 300, it was rated as ⊙ (excellent), 300 or more and less than 500 was rated as ○ (good), and less than 200 was rated as × (poor).

[0134]

Table 5

[0135] (Example 28) Volume 150 cm 3To a plastic container, 0.63 parts by mass of CNT dispersion (WA1), 12.5 parts by mass of an aqueous solution in which 2% by mass of CMC (manufactured by Daicel Finechem Ltd., #1190) was dissolved, and 13.8 parts by mass of ion-exchanged water were measured. Then, using a rotation-revolution mixer (Sumiki Corporation's Awatori Renkatarou, ARE-310), it was stirred at 2000 rpm for 30 seconds to obtain a CNT resin composition (WA1). Thereafter, 2.92 parts by mass of silicon monoxide (manufactured by Osaka Titanium Technology Co., Ltd., SILICON MONOOXIDE, SiO 1.3C 5μm) was added, and using the rotation-revolution mixer, it was stirred at 2000 rpm for 30 seconds. Further, 21.44 parts by mass of artificial graphite (manufactured by Nippon Graphite Industry Co., Ltd., CGB-20) was added, and using the rotation-revolution mixer, it was stirred at 2000 rpm for 30 seconds. Thereafter, 0.78 parts by mass of styrene-butadiene emulsion (manufactured by JSR Corporation, TRD2001) was added, and using the rotation-revolution mixer, it was stirred at 2000 rpm for 30 seconds to obtain a composite material slurry (WA1) for the negative electrode.

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

[0137] (Example 50) Volume 150 cm 37.0 parts by mass of NMP in which 8% by mass of PVDF (manufactured by Solvay, Solef#5130) was dissolved was measured into a plastic container. Thereafter, 0.19 part by mass of CNT dispersion (A20) was added, and using a planetary mixer (Avatomaro, ARE-310), it was stirred at 2000 rpm for 30 seconds to obtain a CNT resin composition (A20). Further thereafter, 36.9 parts of a positive electrode active material (manufactured by BASF Toda Battery Materials Co., Ltd., HED (registered trademark) NCM-111 1100) was added, and using the planetary mixer, it was stirred at 2000 rpm for 2.5 minutes to obtain a 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 dispersions listed in Table 6 were changed.

[0139]

Table 6

[0140] (Example 54) The negative electrode composite slurry (WA1) was applied onto a copper foil using an applicator so that the basis weight per unit of the electrode was 8 mg / cm 2 Thereafter, the coating film 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 films (WA2) to (WA19) were obtained in the same manner as in Example 54, except that the negative electrode composite slurries listed in Table 7 were changed.

[0142] (Example 76) The positive electrode composite slurry (A20) was applied onto an electrode using an applicator so that the basis weight per unit of the electrode was 20 mg / cm 2After coating on the copper foil so as to obtain, the coating film was dried at 120 ° C ± 5 ° C for 25 minutes in an electric oven 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 slurry listed in Table 7 was changed.

[0144] Table 7 shows the evaluation results of the electrode films prepared in Examples 54 to 79 and Comparative Examples 14 to 19. For the adhesion evaluation, the peel strength (Ω·cm) of 0.5 or more was rated as ◎ (excellent), 0.3 or more and less than 0.5 was rated as 〇 (good), 0.1 or more and less than 0.3 was rated as △ (fair), and less than 0.1 was rated as × (poor).

[0145]

Table 7

[0146] (Examples 80 to 101), (Comparative Examples 20 to 24) The electrode films (WA1 to WA19) were subjected to rolling treatment using a roll press (3t hydraulic roll press manufactured by Sanku Metal Co., Ltd.) to produce a negative electrode having a density of the composite layer of 1.7 g / cm 3 to make manufactured.

[0147] (Examples 102 to 105), (Comparative Example 25) The electrode films (A20 to A24) were subjected to rolling treatment using a roll press (3t hydraulic roll press manufactured by Sanku Metal Co., Ltd.) to produce a positive electrode having a density of the composite layer of 3.2 g / cm 3 to make.

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

[0149]

Table 8

[0150] (Example 106) The negative electrode (WA1) and the standard positive electrode were each punched out to 50 mm × 45 mm and 45 mm × 40 mm, and a separator (porous polypropylene film) inserted therebetween was inserted into an aluminum laminate bag and dried in an electric oven at 60°C for 1 hour. Thereafter, in a glove box filled with argon gas, an electrolytic solution (a mixed solvent prepared by mixing ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate at a ratio of 3:5:2 (volume ratio), and further, as additives, VC (vinylene carbonate) and FEC (fluoroethylene carbonate) were each added in an amount of 1 part by mass per 100 parts by mass of the mixed solvent, and then LiPF6 was dissolved at a concentration of 1 M to prepare a non-aqueous electrolytic solution) was injected in an amount of 2 mL, and then the aluminum laminate was sealed to fabricate a laminate-type lithium ion secondary battery (WA1).

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

[0152] (Example 128) The standard negative electrode and the positive electrode (A20) were each punched out to 50 mm × 45 mm and 45 mm × 40 mm, and a separator (porous polypropylene film) inserted therebetween was inserted into an aluminum laminate bag and dried in an electric oven at 60°C for 1 hour. Thereafter, in a glove box filled with argon gas, an electrolytic solution (a mixed solvent prepared by mixing ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate at a ratio of 3:5:2 (volume ratio), and further, as additives, VC (vinylene carbonate) and FEC (fluoroethylene carbonate) were each added in an amount of 1 part by mass per 100 parts by mass of the mixed solvent, and then LiPF6 was dissolved at a concentration of 1 M to prepare a non-aqueous electrolytic solution) was injected in an amount of 2 mL, and then the aluminum laminate was sealed to fabricate 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 as in Example 106, except that the positive electrode shown in Table 9 was used instead.

[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. For the rate characteristics, those with a rate characteristic of 80% or more were rated as ◎ (excellent), those with a rate characteristic of 70% or more and less than 80% were rated as 〇 (good), those with a rate characteristic of 60% or more and less than 70% were rated as △ (fair), and those with a rate characteristic of less than 60% were rated as × (poor). For the cycle characteristics, those with a cycle characteristic of 90% or more were rated as ◎ (excellent), those with a cycle characteristic of 85% or more and less than 90% were rated as 〇 (good), those with a cycle characteristic of 80% or more and less than 85% were rated as △ (fair), and those with a cycle characteristic of less than 80% were rated as - (poor).

[0156]

Table 10

[0157] In the above-described embodiment, a carbon nanotube dispersion liquid containing carbon nanotubes, a dispersant, and a solvent was used. 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 and less than 250 parts by mass with respect to 100 parts by mass of the carbon nanotubes. The complex elastic modulus of the carbon nanotube dispersion liquid at 25°C and a frequency of 1 Hz was 5 Pa or more and less than 650 Pa, and the phase angle was 5° or more and less than 50°. In the embodiment, compared with the comparative example, the adhesion of the electrode tended to be improved. In addition, since the conductivity and the electrode strength were improved, a lithium ion secondary battery excellent in rate characteristics and cycle characteristics was obtained. Therefore, it has become clear that the present invention can provide a lithium ion secondary battery having high capacity, high output, and high durability, which is difficult to achieve with conventional carbon nanotube dispersion liquids.

[0158] As described above, the present invention of the present application has been described with reference to the embodiments, but the present invention of the present application is not limited thereto. Various modifications that can be understood by those skilled in the art within the scope of the invention can be made to the configuration and details of the present invention.

[0159] As described above, the present invention of the present application has been described with reference to the embodiments, but the present invention of the present application is not limited thereto. Various modifications that can be understood by those skilled in the art within the scope of the invention can be made to the configuration and details of the present 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 to 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 cumulative particle size D10 measured by dynamic light scattering is 200 nm or more and less than 500 nm.

2. The carbon nanotube dispersion according to claim 1, wherein the carbon nanotubes have an average outer diameter of 0.5 to 5 nm.

3. The volume resistivity of the carbon nanotube is 1.0 × 10 －３ Ω・cm~3.0×10 －２ 3. The carbon nanotube dispersion liquid according to claim 1, wherein the viscosity is Ω·cm.

4. A carbon nanotube dispersion liquid according to any one of claims 1 to 3, wherein the dispersant is one or more selected from methyl cellulose, ethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, polyvinyl butyral, and polyacrylonitrile-based polymers.

5. 5. 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.

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

7. A carbon nanotube dispersion liquid described in any one of claims 1 to 6, having a pH of 6 to 11.

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

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

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

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

12. A method for producing a carbon nanotube dispersion liquid according to any one of claims 1 to 7, comprising: A method for producing a carbon nanotube dispersion liquid, comprising a step of performing a dispersion treatment using a wet jet mill.

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