Carbon nanotube dispersion paste for non-aqueous electrolyte secondary battery, composite paste, and electrode layer for non-aqueous electrolyte secondary battery

Abstract

The present invention addresses the problem of providing: a carbon nanotube dispersion paste and a composite paste that have excellent pigment dispersibility and storage stability even at high pigment concentrations; and an electrode layer for a non-aqueous electrolyte secondary battery that has excellent performance (electric conductivity, battery performance, etc.). As the solution, provided is a carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery that contains at least a dispersion resin (A), carbon nanotubes (B), and a solvent (C), wherein: the dispersion resin (A) contains at least a structural unit (a-1); and the BET specific surface area of the carbon nanotubes (B) is 100 m2 / g to 1000 m2 / g.

Description

Carbon nanotube dispersion paste for non-aqueous electrolyte secondary battery, composite paste, and electrode layer for non-aqueous electrolyte secondary battery

[0001] The present invention relates to a carbon nanotube-dispersed paste for non-aqueous electrolyte secondary batteries (also simply referred to as a carbon nanotube-dispersed paste in the present invention), a composite paste, and an electrode layer for non-aqueous electrolyte secondary batteries, which have excellent electrical conductivity, pigment dispersibility, and storage stability even at high pigment concentrations.

[0002] Paste-like pigment dispersions in which a pigment is dispersed in a mixture of a pigment dispersing resin, a solvent, and the like have conventionally been widely used in fields such as paints, battery electrodes, coating materials, coating materials, electromagnetic wave shields, display panels, touch screen panels, colored films, colored sheets, decorative materials, protective materials, magnet modifiers, printing inks, device members, electronic device members, printed wiring boards, solar cells, functional rubber members, and resin molded films. Furthermore, conductive pigments, conductive polymers, and the like are incorporated into these materials to impart functions such as electrostatic coating properties, conductivity, electromagnetic wave shielding properties, and antistatic properties.

[0003] In these fields, there is an increasing demand for improvements in performance such as pigment dispersibility, storage stability, conductivity, coatability, and finish. To this end, pigment dispersing resins and pigment pastes are being developed that have excellent pigment dispersing ability and excellent pigment dispersion stability that prevents reagglomeration of pigment particles in the formed pigment dispersion.

[0004] When designing a pigment paste, it is important to prepare a highly concentrated and uniformly dispersed pigment paste using a small amount of pigment dispersing resin, in order to prevent the pigment dispersing resin from adversely affecting the conductive properties of the final product itself, such as the coating film, and from the perspective of reducing the amounts of solvent and pigment dispersing resin used and reducing the energy used during drying.

[0005] For example, Patent Document 1 discloses a method for producing a slurry for an electrode of a lithium secondary battery, which comprises dispersing a solvent containing fibrous carbon using a media (hereinafter also referred to as "media") disperser to obtain a slurry, and kneading the slurry with an electrode active material to obtain a slurry to be applied to a current collector. However, in the case of a paste with a high pigment concentration and / or high viscosity, uniform dispersion is not possible, and storage stability is poor. In particular, if the slurry contains a large amount of water, high viscosity and gelation may occur.

[0006] JP 2014-182892 A

[0007] An object of the present invention is to provide a carbon nanotube dispersion paste and composite paste for non-aqueous electrolyte secondary batteries that have excellent pigment dispersibility and storage stability even in pastes with high pigment concentrations and / or high viscosity, and further provide an electrode layer for non-aqueous electrolyte secondary batteries that has excellent finish properties, conductivity, etc.

[0008] As a result of extensive research into solving the above problems, the present inventors have discovered a carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery, which contains at least a dispersion resin (A), carbon nanotubes (B), and a solvent (C), wherein the dispersion resin (A) contains at least a structural unit having a hydrocarbon group having 8 to 30 carbon atoms, and the carbon nanotubes (B) have a BET specific surface area of ​​100 m or less. ２ / g to 1000m ２ The present inventors have found that the above-mentioned problems can be solved by using a carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery having a surface area of ​​100 μm or less, and have completed the present invention.

[0009] That is, the present invention provides the following carbon nanotube dispersion paste for non-aqueous electrolyte secondary batteries, composite paste, and electrode layer for non-aqueous electrolyte secondary batteries: Item 1. A carbon nanotube dispersion paste for non-aqueous electrolyte secondary batteries, comprising at least a dispersion resin (A), carbon nanotubes (B), and a solvent (C), wherein the dispersion resin (A) contains at least a structural unit (a-1) represented by the following formula (1), and the carbon nanotubes (B) have a BET specific surface area of ​​100 m ２ / g to 1000m２ / g of the carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery.

[0010]

[0011] (In the formula, R １ and R ３ are the same or different and represent a hydrogen atom or a methyl group; R ２ represents a hydrogen atom, a carboxyl group, or an organic group; X represents an organic linking group; R ４ represents a hydrocarbon group having 8 to 30 carbon atoms.) Item 2. The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to Item 1, further comprising polyvinylidene fluoride (D). Item 3. The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to Item 1 or 2, wherein the dispersion resin (A) has at least one polar functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphate group, a pyridine group, an amino group, and a cyano group, and the polar functional group concentration is 0.1 to 8.5 mmol / g. Item 4. The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to any one of Items 1 to 3, further comprising a highly polar, low-molecular-weight component (E). Item 5. The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to any one of Items 1 to 4, wherein the carbon nanotubes (B) are previously dry-dispersed using a media-type grinder. Item 6. Item 7. A carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to any one of Items 1 to 5, wherein the carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery has a water content of less than 10,000 ppm. Item 8. A composite paste for a non-aqueous electrolyte secondary battery obtained by further adding an electrode active material (G) to the carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to any one of Items 1 to 6. Item 9. An electrode layer for a non-aqueous electrolyte secondary battery obtained by coating a current collector with the composite paste according to Item 7. Item 10. A non-aqueous electrolyte secondary battery comprising a positive electrode including the electrode layer according to Item 8, a negative electrode, a non-aqueous electrolyte, and a separator.

[0012] The carbon nanotube-dispersed paste for a non-aqueous electrolyte secondary battery of the present invention has excellent pigment dispersibility and storage stability even at a high pigment concentration and / or high viscosity, and can sufficiently reduce the viscosity of the paste with a relatively small amount of dispersing resin. Furthermore, the electrode layer for a non-aqueous electrolyte secondary battery produced by the paste has excellent finish, conductivity, battery performance, etc.

[0013] Hereinafter, embodiments of the present invention will be described in detail.

[0014] The present invention is not limited to the following embodiments, and should be understood to include various modified examples implemented within the scope of the present invention. In the present invention, a paste containing carbon nanotubes is called a "carbon nanotube dispersion paste," but it can also be called a "conductive pigment paste." A paste prepared by further blending at least one electrode active material and, optionally, various other components, in order to apply the carbon nanotube dispersion paste is called a "composite paste." The composite paste applied to an object to be coated and dried is called a "coating film," "composite layer," or "electrode layer." It can be said that the carbon nanotube dispersion paste is a paste that does not substantially contain an electrode active material.

[0015] Carbon nanotube dispersion paste for non-aqueous electrolyte secondary batteries The present invention provides a carbon nanotube dispersion paste for non-aqueous electrolyte secondary batteries, which paste contains at least a dispersion resin (A), carbon nanotubes (B), and a solvent (C), wherein the dispersion resin (A) contains at least a structural unit (a-1) represented by the following formula (1), and the carbon nanotubes (B) have a BET specific surface area of ​​100 m ２ / g to 1000m ２ The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery has a viscosity of 1000 MPa (1000 MPa) / g.

[0016]

[0017] (In the formula, R １ and R ３ are the same or different and represent a hydrogen atom or a methyl group; R ２represents a hydrogen atom, a carboxyl group, or an organic group; X represents an organic linking group; R ４ represents a hydrocarbon group having 8 to 30 carbon atoms.) The carbon nanotube dispersion paste of the present invention preferably has a water content of less than 10,000 ppm, more preferably less than 7,500 ppm, even more preferably less than 5,000 ppm, particularly preferably less than 2,500 ppm, and even more particularly preferably less than 1,000 ppm. Therefore, the carbon nanotube dispersion paste of the present invention can be said to be a substantially non-aqueous paste.

[0018] In the present invention, the water content of the carbon nanotube dispersion paste can be measured by Karl Fischer coulometric titration. Specifically, the water content can be measured using a Karl Fischer moisture meter (manufactured by Kyoto Electronics Manufacturing Co., Ltd., product name "MKC-610") with the temperature of the moisture vaporizer (manufactured by Kyoto Electronics Manufacturing Co., Ltd., product name "ADP-611") attached to the meter set to 130°C.

[0019] In the present invention, by making the water content of the carbon nanotube dispersion paste less than 10,000 ppm (and further making the water content of the solvent (C) less than 10,000 ppm), it is possible to prevent the paste from becoming highly viscous or gelling during storage.

[0020] Although the mechanism by which carbon nanotube dispersion pastes and composite pastes for nonaqueous electrolyte secondary batteries increase in viscosity and gelation is unclear, the following mechanism is hypothesized. For example, in carbon nanotube dispersion pastes and composite pastes containing polyvinylidene fluoride, the acidity of the protons adjacent to the fluorine groups in polyvinylidene fluoride is very high due to the electron-withdrawing properties of the fluorine groups. Therefore, proton desorption easily occurs, especially under basic conditions. It is hypothesized that this proton desorption is particularly likely to occur when moisture is present in the carbon nanotube dispersion paste and composite paste. After proton desorption, anions are generated on the carbon, which promotes the desorption of fluorine groups and creates double bonds in the main chains of the polyvinylidene fluoride molecules. It is hypothesized that multiple polyvinylidene fluoride molecules with double bonds then polymerize, further polymerizing, leading to increased viscosity and gelation. In particular, since the electrode active material in the composite paste may contain lithium hydroxide, which is a relatively strong base, the increase in viscosity and gelation are significant in the composite paste.

[0021] In the present invention, by specifying the water content of the carbon nanotube dispersion paste and the composite paste, polymerization of the polymer component (such as polyvinylidene fluoride) can be suppressed, thereby suppressing viscosity increase and gelation of the carbon nanotube dispersion paste or composite paste for non-aqueous electrolyte secondary batteries. Furthermore, the water content is virtually impossible to reduce to zero because it is carried over from various raw materials (especially solvents) or contaminated by water vapor contained in the atmosphere during the manufacturing process. Therefore, the water content of the carbon nanotube dispersion paste of the present invention is preferably 100 ppm or more, more preferably 200 ppm or more, and even more preferably 500 ppm or more. Furthermore, the water content of the solvent (C) is preferably 100 ppm or more, more preferably 200 ppm or more, and even more preferably 500 ppm or more. Within the above lower limit, production is possible without excessive water content control of the raw materials (reducing the water content) or the manufacturing process (reducing water contamination).

[0022] Dispersion Resin (A) The dispersion resin (A) contains at least a structural unit (a-1) represented by the following formula (1).

[0023]

[0024] (In the formula, R １ and R ３ are the same or different and represent a hydrogen atom or a methyl group; R ２ represents a hydrogen atom, a carboxyl group, or an organic group; X represents an organic linking group; R ４ represents a hydrocarbon group having 8 to 30 carbon atoms.) The R ４ It is believed that the presence of a hydrocarbon group (relatively bulky side chain) having 8 to 30 carbon atoms improves pigment dispersibility and storage stability due to steric repulsion. Furthermore, the hydrocarbon group (alkyl group) having 8 to 30 carbon atoms is preferably a linear or branched hydrocarbon group, and more preferably a linear hydrocarbon group. The hydrocarbon group having 8 to 30 carbon atoms is preferably a hydrocarbon group having 12 or more but less than 30 carbon atoms, more preferably a hydrocarbon group having 15 or more but less than 26 carbon atoms, and even more preferably a hydrocarbon group having 19 or more but less than 24 carbon atoms.

[0025] The method for introducing the structural unit (a-1) represented by the above formula (1) into the dispersion resin (A) is not particularly limited, and examples thereof include a (co)polymerization reaction of a monomer containing a hydrocarbon group having 8 to 30 carbon atoms, a modification reaction of a polymer (resin), and / or an addition reaction. Examples of polymerizable monomers containing a hydrocarbon group having 8 to 30 carbon atoms include octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, behenyl (meth)acrylate, lauryl (meth)acrylamide, stearyl (meth)acrylamide, and behenyl (meth)acrylamide. In these cases, the organic linking group X in the above formula (1) has a structure of "-C(=O)-O-" or "-C(=O)-NH-". These can be used alone or in combination of two or more.

[0026] Alternatively, the structural unit (a-1) of formula (1) can be introduced by (co)polymerizing a polymerizable monomer (α) having a reactive functional group, followed by reaction with a compound (β) that reacts with a hydrocarbon group having 8 to 30 carbon atoms and the reactive functional group. The types and combinations of the polymerizable monomer (α) and compound (β) are not particularly limited as long as they ultimately allow for the introduction of the structural unit (a-1) of formula (1), but examples include glycidyl (meth)acrylate and a fatty acid having a hydrocarbon group of 8 to 30 carbon atoms, glycidyl (meth)acrylate and a primary or secondary amino group compound having a hydrocarbon group of 8 to 30 carbon atoms, 2-(meth)acryloyloxyethyl isocyanate and an alcohol having a hydrocarbon group of 8 to 30 carbon atoms, and a hydroxyl group-containing (meth)acrylate and an isocyanate compound having a hydrocarbon group of 8 to 30 carbon atoms. When the structural unit (a-1) of formula (1) is introduced by reacting the polymerizable monomer (α) with compound (β), the organic linking group X in formula (1) will have a structure other than "-C(=O)-O-" or "-C(=O)-NH-". The above structure is preferable because it is relatively inexpensive, allows for a wide degree of freedom in resin design, and can be designed to meet various requirements. These may be used alone or in combination of two or more.

[0027] The type of resin serving as the skeleton is not particularly limited as long as it is a resin other than polyvinylidene fluoride (D) described later, but an acrylic resin obtained by (co)polymerizing at least one polymerizable unsaturated group-containing monomer having a (meth)acryloyl group is preferred.

[0028] Other polymerizable unsaturated group-containing monomers that can be used in the acrylic resin together with the polymerizable unsaturated group-containing monomer containing a hydrocarbon group having 8 to 30 carbon atoms can be used without any particular limitation as long as they are monomers that are usually used in the synthesis of acrylic resins, and examples thereof include alkyl (meth)acrylates having 7 or less carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, t-butyl (meth)acrylate, and n-hexyl (meth)acrylate; aromatic ring-containing polymerizable unsaturated monomers, such as vinyl naphthalene, naphthyl (meth)acrylate, naphthyl alkyl (meth)acrylate, vinyl anthracene, anthracenyl (meth)acrylate, benzyl (meth)acrylate, and styrene; 2-hydroxybenzoates, ... Examples of such polymerizable unsaturated monomers include hydroxyl group-containing polymerizable unsaturated monomers such as hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; carboxyl group-containing polymerizable unsaturated monomers such as (meth)acrylic acid and maleic acid; nitrogen-containing polymerizable unsaturated monomers not containing a urethane bond such as (meth)acrylonitrile, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, 4-vinylpyridine, 2-vinylpyridine, and adducts of glycidyl (meth)acrylate and amines; and polyalkylene glycol macromonomers such as polyethylene glycol (meth)acrylate and polypropylene glycol (meth)acrylate. These may be used alone or in combination of two or more. Among these, from the viewpoint of dispersibility or dispersion stability, it is preferable to contain at least one aromatic ring-containing polymerizable unsaturated monomer, and styrene is more preferable as the aromatic ring-containing polymerizable unsaturated monomer, because it is believed that stabilization is achieved by π-π interactions between the aromatic rings in the graphite structure on the surface of the carbon nanotubes and the pigment dispersion resin containing aromatic rings.The π-π interaction is a dispersion force acting between aromatic rings, and is also called a stacking interaction because two aromatic rings tend to be stabilized in a coin-like arrangement. In this specification, "(meth)acrylate" means acrylate and / or methacrylate, and "(meth)acrylic acid" means acrylic acid and / or methacrylic acid. Furthermore, "(meth)acryloyl" means acryloyl and / or methacryloyl. Furthermore, "(meth)acrylamide" means acrylamide and / or methacrylamide. Furthermore, the "(co)polymer" of the present invention includes both a polymer obtained by polymerizing one type of monomer and a copolymer obtained by copolymerizing two or more types of monomers.

[0029] The acrylic resin can be produced by a polymerization method known per se, and for example, solution polymerization is preferably used, but is not limited thereto, and bulk polymerization, emulsion polymerization, suspension polymerization, etc. When solution polymerization is carried out, it may be continuous polymerization or batch polymerization, and the monomers may be charged all at once or in portions, or may be added continuously or intermittently.

[0030] The polymerization initiator used in the solution polymerization is not particularly limited, but specific examples include known radical polymerization initiators such as azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, 2,2'-azobis(2-methylbutyronitrile), and azobis(4-methoxy-2,4-dimethylvaleronitrile); peroxides such as acetyl peroxide, benzoyl peroxide, lauroyl peroxide, acetylcyclohexylsulfonyl peroxide, and 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate; percarbonate compounds such as diisopropyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, and diethoxyethyl peroxydicarbonate; perester compounds such as t-butylperoxyneodecanate, α-cumylperoxyneodecanate, and t-butylperoxyneodecanate; and azobisdimethylvaleronitrile and azobismethoxyvaleronitrile.

[0031] The polymerization reaction temperature is not particularly limited, but can usually be set in the range of about 30°C or higher and 300°C or lower.

[0032] The weight average molecular weight of the acrylic resin obtainable as described above is, for example, 1,000 or more, preferably 2,000 or more, more preferably 7,000 or more, and for example, 2,000,000 or less, preferably 1,000,000 or less, more preferably 500,000 or less.

[0033] Unless otherwise specified, the weight average molecular weight in this specification is a value obtained by converting the retention time (retention volume) measured using a gel permeation chromatograph (GPC) into the molecular weight of polystyrene using the retention time (retention volume) of a standard polystyrene of known molecular weight measured under the same conditions. Specifically, the gel permeation chromatograph is "HLC8120GPC" (manufactured by Tosoh Corporation, trade name) and four columns, "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL" and "TSKgel G-2000HXL" (all manufactured by Tosoh Corporation, trade name), can be measured under the conditions of a mobile phase of tetrahydrofuran, a measurement temperature of 40 ° C, a flow rate of 1 mL / min, and a detector RI.

[0034] After completion of synthesis, the acrylic resin can be converted into a solid or a resin solution in which any solvent has been substituted by removing the solvent and / or replacing the solvent.

[0035] The solvent may be removed by heating at normal pressure or under reduced pressure. The solvent replacement method may involve adding a replacement solvent at any stage before, during, or after the solvent removal.

[0036] Furthermore, the content of the hydrocarbon group having 8 to 30 carbon atoms in the dispersion resin (A) is preferably 1 to 100 mass%, more preferably 10 to 90 mass%, even more preferably 20 to 80 mass%, and particularly preferably 30 to 60 mass%, expressed as the mass proportion of the monomer [structural unit (a-1)] when all monomers are taken as 100 mass%.

[0037] The dispersion resin (A) preferably has, in addition to a hydrocarbon group having 8 to 30 carbon atoms, at least one polar functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphate group, a pyridine group, an amino group, and a cyano group, and has a polar functional group concentration of 0.1 to 8.5 mmol / g, more preferably 0.2 to 6.0 mmol / g, even more preferably 0.3 to 4.0 mmol / g, and particularly preferably 0.4 to 2.0 mmol / g. The acid group and amino group may be in the form of a salt. Among these, the polar functional group preferably has a hydroxyl group, an acid group, a pyridine group, and / or an amino group.

[0038] When the dispersion resin (A) has an aromatic ring, the content of the aromatic ring-containing polymerizable unsaturated monomer is preferably 5 to 50 mass%, more preferably 10 to 40 mass%, in terms of the mass ratio of the monomer when all monomers are 100 mass%.

[0039] (Content of Dispersion Resin (A)) The solid content of the dispersion resin (A) is, for example, 0.1 mass% or more, preferably 1 mass% or more, more preferably 3 mass% or more, based on the total solid content of the carbon nanotube dispersion paste, and is, for example, 40 mass% or less, preferably 30 mass% or less, more preferably 20 mass% or less.

[0040] The solid content of the dispersion resin (A) is, based on the content of the carbon nanotubes (B), for example, 0.1 mass% or more, preferably 1 mass% or more, more preferably 5 mass% or more, and for example, 150 mass% or less, preferably 120 mass% or less, more preferably 100 mass% or less.

[0041] Carbon nanotubes (B) The carbon nanotubes (B) have a BET specific surface area of ​​100 m ２ / g to 1000m ２ / g. Single-walled carbon nanotubes and multi-walled carbon nanotubes can be used alone or in combination. In particular, in terms of viscosity, conductivity, and cost, it is preferable to use multi-walled carbon nanotubes.

[0042] The average outer diameter of the carbon nanotubes (B) is, for example, 1 nm or more, preferably 3 nm or more, more preferably 5 nm or more, and for example, 30 nm or less, preferably 28 nm or less, more preferably 25 nm or less.

[0043] The average length of the carbon nanotubes (B) is, for example, 0.1 μm or more, preferably 1 μm or more, more preferably 5 μm or more, and for example, 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less.

[0044] The BET specific surface area of ​​the carbon nanotubes (B) is usually 100 m ２ / g or more, preferably 130m ２ / g or more, more preferably 160m ２ / g or more, and is usually 1000m ２ / g or less, preferably 700m ２ / g or less, more preferably 400m ２ / g or less.

[0045] The BET specific surface area of ​​the present invention can be calculated by the BET method using nitrogen adsorption measurement. Specifically, for example, the BET specific surface area (m ２ / g) can be measured.

[0046] The amount of acidic groups in the carbon nanotubes (B) is, from the viewpoint of dispersibility and storage stability, usually 0.01 mmol / g or more, preferably 0.01 mmol / g or more, and usually 1.0 mmol / g or less, preferably 0.5 mmol / g or less, more preferably 0.2 mmol / g or less, and even more preferably 0.1 mmol / g or less. If the amount of acidic groups is 0.01 mmol / g or more, dispersibility will be good, and if it is 1.0 mmol / g or less, storage stability will be good.

[0047] The acidic groups can be imparted to the carbon nanotubes by the acid treatment described below.

[0048] <Acid Treatment Method> The acid treatment method is not particularly limited as long as it can bring the carbon nanotubes into contact with an acid, but a method of immersing the carbon nanotubes in an acid treatment solution (aqueous acid solution) is preferred. The acid contained in the acid treatment solution is not particularly limited, but examples include nitric acid, sulfuric acid, and hydrochloric acid. These can be used alone or in combination of two or more. Among these, nitric acid and sulfuric acid are preferred. The amount of acidic groups in the carbon nanotubes can be adjusted by the concentration, temperature, treatment time, etc. of the acid treatment solution.

[0049] After the acid treatment, excess acid components adhering to the surface can be removed by a washing method described below, thereby obtaining acid-treated carbon nanotubes. The method for washing the acid-treated carbon nanotubes is not particularly limited, but washing with water is preferred. For example, carbon nanotubes are recovered from the acid-treated carbon nanotubes by a known method such as filtration, and then the carbon nanotubes are washed with water. After the washing, if necessary, water adhering to the surface can be removed by drying, thereby obtaining acid-treated carbon nanotubes.

[0050] Furthermore, the volume-equivalent median diameter (D50) of the carbon nanotubes (B), as measured by the method described in the Examples below, is typically 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and typically 250 μm or less, preferably 200 μm or less, more preferably 150 μm or less. Here, the median diameter (D50) can be determined by irradiating carbon nanotube particles with laser light and converting the diameter of the carbon nanotubes from the scattered light into a spherical equivalent. A larger median diameter (D50) indicates more carbon nanotube agglomerates and poor dispersibility. If the median diameter (D50) is greater than 250 μm, the likelihood of carbon nanotube agglomerates being present in the electrode increases, resulting in non-uniform conductivity throughout the electrode. On the other hand, if the median diameter (D50) is less than 10 μm, the fiber length is short, resulting in insufficient conductive paths and reduced conductivity. When the median diameter (D50) is within the range of 10 μm or more and 250 μm or less, the carbon nanotubes can be uniformly dispersed in the electrode while maintaining their electrical conductivity.

[0051] In addition, in the Raman spectrum of the carbon nanotube (B), －１ More than 1600cm －１ The maximum peak intensity within the following range is G, 1310 cm －１ More than 1350cm －１ When the maximum peak intensity within the following range is defined as D, the G / D ratio is usually 0.1 or more, preferably 0.4 or more, more preferably 0.6 or more, and usually 5.0 or less, preferably 3.0 or less, more preferably 1.0 or less.

[0052] Here, it is preferable that the G / D ratio is in the range of 0.1 to 5.0, since there are fewer defects and crystal interfaces on the carbon surface and the conductivity is likely to be high.

[0053] (Content of Carbon Nanotubes (B)) The solid content of the carbon nanotubes (B) is, based on the total amount of solids in the carbon nanotube dispersion paste, for example, 10% by mass or more, preferably 20% by mass or more, more preferably 30% by mass or more, and for example, 90% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less. Also, based on the total amount of the carbon nanotube dispersion paste, it is, for example, 0.5% by mass or more, preferably 1% by mass or more, more preferably 2% by mass or more, and for example, 10% by mass or less, preferably 8% by mass or less, more preferably 6% by mass or less.

[0054] (Dry Dispersion of Carbon Nanotubes) The carbon nanotubes (B) can be dry-dispersed in a media-type mill before preparing a carbon nanotube-dispersed paste. The "dry dispersion" of the present invention refers to pulverization (including crushing) using a mill to obtain a solids concentration of 80% by mass or more (preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more). While the carbon nanotubes (B) can be pulverized together with components other than the carbon nanotubes (B), it is preferable that the carbon nanotube (B) content in the solids of the pulverized component is typically 80% by mass or more, preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 98% by mass or more, and particularly preferably carbon nanotubes (B) alone. As components other than the carbon nanotubes (B) in the pulverized component, solvents, resins, and pigments other than the carbon nanotubes (B) can be used as needed, but it is preferable that the pulverized component essentially contains only the carbon nanotubes (B). The "solids concentration" refers to the percentage of solids (% by mass) when 1 g of the sample is dried by heating at 130°C for 3 hours.

[0055] The dry dispersion method involves grinding a pigment without adding any liquid components, and since energy can be applied directly to the pigment, it allows for highly efficient and powerful grinding (disintegration). Furthermore, the grinding surface is activated and interacts with surrounding substances, resulting in good dispersibility and storage stability in the paste dispersion step described below, and the resulting coating film can have excellent conductivity and finish.

[0056] In the dry dispersion, the material is pulverized using a pulverizer equipped with pulverizing media such as glass beads, zirconia beads, or steel balls. The pulverization is carried out by utilizing the crushing or destructive force generated by the collision of the pulverizing media with each other and / or the collision of the pulverizer with the pulverizing media. Known pulverizing devices such as high-speed impact mills, jet mills, roll mills, attritors, ball mills, vibration mills, and bead mills can be used.

[0057] During pulverization, various vapors or gases can be blown into the pulverizer to further activate the surface of the carbon nanotubes (B) or adjust the activity. Suitable vapors include acidic or basic compounds, and suitable gases include oxygen, nitrogen, and the like.

[0058] The outer diameter of the grinding media is preferably 0.1 to 5 mm, more preferably 0.5 to 3 mm. Within this range, a desired grinding force can be obtained, and the pigment can be efficiently ground and disintegrated without excessively destroying the fiber shape of the carbon nanotubes.

[0059] Other conductive pigments (B1) The carbon nanotube dispersion paste used in the present invention can also contain other conductive pigments (B1) other than the carbon nanotubes (B). Examples of other conductive pigments (B1) include at least one conductive carbon selected from the group consisting of acetylene black, ketjen black, furnace black, thermal black, graphene, and graphite. Preferably, the other conductive pigments (B1) are at least one selected from the group consisting of acetylene black, ketjen black, furnace black, and thermal black, more preferably at least one selected from the group consisting of acetylene black and ketjen black, and even more preferably at least one type of acetylene black.

[0060] The average primary particle diameter of the other conductive pigment (B1) is, for example, 10 nm or more, preferably 20 nm or more, and for example, 80 nm or less, preferably 70 nm or less. Here, the average primary particle diameter refers to the average particle diameter of primary particles obtained by observing the conductive pigment (B1) with an electron microscope, determining the projected area of ​​each of 100 particles, calculating the diameter of a circle equivalent to that area, and then simply averaging the diameters of the 100 particles. Note that if the pigment is in an aggregated state, the calculation is performed using the primary particles that make up the aggregated particles.

[0061] The BET specific surface area of ​​the conductive pigment (B1) is not particularly limited. ２ / g or more, preferably 10m ２ / g or more, more preferably 20m ２ / g or more, for example, 500m ２ / g or less, preferably 250m ２ / g or less, more preferably 200m ２ / g or less.

[0062] The dibutyl phthalate (DBP) oil absorption of the conductive pigment (B1) is not particularly limited and is, in view of the relationship between pigment dispersibility and conductivity, for example, 60 ml / 100 g or more, preferably 150 ml / 100 g or more, and for example, 1,000 ml / 100 g or less, preferably 800 ml / 100 g or less.

[0063] Solvent (C) As the solvent (C), a known organic solvent can be suitably used. Specific examples include hydrocarbon solvents such as n-butane, n-hexane, n-heptane, n-octane, cyclopentane, cyclohexane, and cyclobutane; aromatic solvents such as toluene and xylene; ketone solvents such as methyl isobutyl ketone; ether solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and diethylene glycol; ethyl acetate, n-butyl acetate, isobutyl acetate, and ethylene glycol monomethyl ether acetate. ketone-based solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, etc.; alcohol-based solvents such as ethanol, isopropanol, n-butanol, sec-butanol, isobutanol, etc.; and amide-based solvents such as "Equamide" (trade name, manufactured by Idemitsu Kosan Co., Ltd.), N,N-dimethylformamide, N,N-dimethylacetamide, N-methylformamide, N-methylacetamide, N-methylpropioamide, N-methyl-2-pyrrolidone, etc.

[0064] Among these, amide solvents are preferred, and N-methyl-2-pyrrolidone is more preferred. These solvents can be used alone or in combination of two or more.

[0065] For the reasons described above, the water content (upper limit) of the solvent (C) is usually less than 10,000 ppm, preferably less than 7,500 ppm, more preferably less than 5,000 ppm, even more preferably less than 2,500 ppm, and particularly preferably less than 1,000 ppm. The water content (lower limit) is preferably 100 ppm or more, more preferably 200 ppm or more, and even more preferably 500 ppm or more.

[0066] When an amide compound (solvent) such as N-methyl-2-pyrrolidone is used, it may contain an amine component as an impurity, and in the carbon nanotube dispersion paste of the present invention, the viscosity or tendency to thicken may vary from lot to lot depending on the amine component as an impurity.

[0067] Furthermore, when the carbon nanotube dispersion paste of the present invention is applied to an electrode layer by the method described below, the solvent and the like volatilize and do not remain. However, it is preferable to recover and reuse the volatilized solvent to reduce waste, be environmentally friendly, and / or reduce raw material costs. That is, it is preferable to use a recycled product as the solvent (C). If the carbon nanotube dispersion paste of the present invention contains an amine compound (E1) as the highly polar, low-molecular-weight component (E) described below, this recycled solvent (recycled product) will also contain the amine compound (E1) originally contained therein, and similarly, the viscosity or thickening tendency of the paste will vary from lot to lot. Furthermore, amine compounds generally often have a strong odor.

[0068] Therefore, in this case, it is preferable to control and adjust the content of amine components contained as impurities in the recycled solvent (C) to a certain amount or less, and the content of amine components is usually 1% by mass or less, preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less.

[0069] The content of the amine component can be quantified by a general analysis such as ion chromatography-mass spectrometry (IC-MS). The content can be quantified by preparing a calibration curve in advance for the peaks of amine species that are expected to be mixed.

[0070] The above-mentioned "use of a recycled product as the solvent (C)" means that the solvent (C) used in the present invention contains 5% by mass or more (preferably 10% by mass or more) of the recycled product. As the recycled product, it is preferable to use a solvent recovered in the process of producing an electrode layer by heating and drying a composite paste, which will be described later.

[0071] The solvent (C) preferably contains N-methyl-2-pyrrolidone, and when N-methyl-2-pyrrolidone is contained, it is preferable to use a recycled product of N-methyl-2-pyrrolidone. Furthermore, it is suitable to control the water content in N-methyl-2-pyrrolidone to less than 10,000 ppm (preferably less than 7,500 ppm, more preferably less than 5,000 ppm, even more preferably less than 2,500 ppm, and particularly preferably less than 1,000 ppm), and the amine component to 1% by mass or less, preferably 0.5% by mass or less, and particularly preferably 0.1% by mass or less.

[0072] The content of the solvent (C) in the carbon nanotube dispersion paste is, based on the total amount of the paste, for example, 40 mass% or more, preferably 60 mass% or more, more preferably 80 mass% or more, and for example, 99 mass% or less, preferably 98 mass% or less, more preferably 97 mass% or less.

[0073] Polyvinylidene fluoride (D) The polyvinylidene fluoride (D) can be contained as a component of the carbon nanotube dispersion paste of the present invention as needed, and is a resin intended for forming a film of the electrode layer. Various modified polyvinylidene fluorides (D1) can also be suitably used, and it is preferable that the modified polyvinylidene fluoride (D1) has a polar functional group from the viewpoint of adhesion to the substrate.

[0074] The weight average molecular weight of the polyvinylidene fluoride (D) is, from the viewpoints of adhesion to the substrate, reinforcement of the film properties, and solvent resistance, for example, 100,000 or more, preferably 500,000 or more, more preferably 650,000 or more, and for example, 3,000,000 or less, preferably 2,000,000 or less.

[0075] The content of polyvinylidene fluoride (D) is, for example, 10.0 mass% or more, preferably 30.0 mass% or more, more preferably 40.0 mass% or more, based on the solid content of the carbon nanotube dispersion paste, and for example, 99.0 mass% or less, preferably 80.0 mass% or less, more preferably 60.0 mass% or less.

[0076] The process of converting the polyvinylidene fluoride (D) from a solid state into a resin solution preferably includes a step of mixing and dissolving the polyvinylidene fluoride (D) in a solvent having a liquid temperature of 40°C or higher (preferably 60°C or higher, more preferably 80°C or higher) (the upper limit is 200°C or lower, preferably 100°C or lower) to form a resin solution, from the viewpoint of solubility in the solvent. After the resin solution is formed, it is preferable to mix it with other components [components (A), (B), (C), etc.]. The "liquid temperature" refers to the temperature of the solvent or resin solution at the time of dissolution. Solid polyvinylidene fluoride (D) may be mixed and dissolved in a solvent having a liquid temperature of 40°C or higher in advance, or solid polyvinylidene fluoride (D) and a solvent may be mixed and then heated to a temperature of 40°C or higher. In addition, the polyvinylidene fluoride (D) may contain components other than the polyvinylidene fluoride (D) and the solvent. One or more solvents may be used, and the types listed above for the solvent (C) can be suitably used. Furthermore, it is preferable to cool the hot-dissolved resin solution as described above to a predetermined temperature of 10°C or higher but lower than 40°C, and from the viewpoint of preventing precipitation, it is preferable that the cooling step be performed at a cooling rate of 0.5°C / min or higher (preferably 1°C / min or higher) defined by the following formula: Cooling rate = (solution temperature at the start of cooling - solution temperature at the end of cooling) / Cooling time. Note that the polyvinylidene fluoride (D) is not contained at the time of producing the carbon nanotube dispersion paste, but can be added when producing the composite paste described below.

[0077] Mixing and Dispersion The method for producing a carbon nanotube dispersion paste of the present invention includes the steps of mixing and further dispersing components containing at least a dispersion resin (A), carbon nanotubes (B), and a solvent (C), and these steps allow a liquid carbon nanotube dispersion paste to be obtained.

[0078] The upper limit of the solid content of the carbon nanotube dispersion paste is usually less than 80% by mass, preferably less than 50% by mass, more preferably less than 20% by mass, and even more preferably less than 10% by mass. The lower limit is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more.

[0079] In the mixing and dispersing step, the components can be uniformly mixed and dispersed using a conventionally known dispersing machine, such as a paint shaker, a sand mill, a ball mill, a pebble mill, an LMZ mill, a DCP pearl mill, a planetary ball mill, a homogenizer, a twin-screw kneader, or a thin film rotary high-speed mixer (manufactured by Filmix, trade name "Clearmix", etc.). The order in which the components are mixed is not particularly limited.

[0080]

[0043] The carbon nanotube dispersion paste of the present invention may further contain a highly polar, low-molecular-weight component (E). The highly polar, low-molecular-weight component (E) is a component that increases the wettability and / or storage stability of the conductive pigment, and may be, for example, a known basic component or acidic component. Among these, it is preferable to contain a basic component, and as the basic component, an amine compound (E1) or an inorganic base (E2) is more preferable, and an inorganic base (E2) is even more preferable.

[0081] The content of the basic component in the highly polar, low-molecular-weight component (E) is, for example, 50% by mass or more, preferably 75% by mass or more, and more preferably 95% by mass or more, based on 100% by mass of the highly polar, low-molecular-weight component (E).

[0082] Examples of the amine compound (E1) include ammonia, primary amines, secondary amines, and tertiary amines.

[0083] Examples of primary amines include ethylamine, n-propylamine, sec-propylamine, n-butylamine, sec-butylamine, i-butylamine, tert-butylamine, pentylamine, hexylamine, heptylamine, octylamine, decylamine, laurylamine, myristyrylamine, 1,2-dimethylhexylamine, 3-pentylamine, 2-ethylhexylamine, allylamine, aminoethanol, 1-aminopropanol, 2-aminopropanol, aminobutanol, aminopentanol, aminohexanol, 3-ethoxypropylamine, 3-propoxypropylamine, 3-isopropoxypropylamine, 3-butoxypropylamine, 3-isobutoxypropylamine, 3-(2-ethylhexyloxy)propylamine, aminocyclopentane, aminocyclohexane, aminonorbornene, aminomethylcyclohexane, aminobenzene, benzylamine, phenethylamine, α-phenylethylamine, naphthylamine, Primary monoamines such as furfurylamine; ethylenediamine, 1,2-diaminopropane, 1,3-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, dimethylaminopropylamine, diethylaminopropylamine, bis-(3-aminopropyl)ether, 1,2-bis-(3-aminopropoxy)ethane, 1,3-bis -(3-aminopropoxy)-2,2'-dimethylpropane, aminoethylethanolamine, 1,2-bisaminocyclohexane, 1,3-bisaminocyclohexane, 1,4-bisaminocyclohexane, 1,3-bisaminomethylcyclohexane, 1,4-bisaminomethylcyclohexane, 1,3-bisaminoethylcyclohexane, 1,4-bisaminoethylcyclohexane, 1,3-bisaminopropylcyclohexane, 1,4-bisaminopropylcyclohexane, hydrogenated 4,4'-Diaminodiphenylmethane, 2-aminopiperidine, 4-aminopiperidine, 2-aminomethylpiperidine, 4-aminomethylpiperidine, 2-aminoethylpiperidine, 4-aminoethylpiperidine, N-aminoethylpiperidine, N-aminopropylpiperidine, N-aminoethylmorpholine, N-aminopropylmorpholine, isophoronediamine, menthanediamine, 1,4-bisaminopropylpiperazine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 2,4-tolylenediamine, 2,6-tolylenediamine, 2,4-toluenediamine, m-aminobenzylamine, 4-chloro-o-phenylenediamine, tetrachloro-p-xylylenediamine, 4-methoxy-6-methyl-m-phenylenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-naphthalenediamine, 2,6-naphthalenediamine, benzidine, 4,4'-bis( o-toluidine), dianisidine, 4,4'-diaminodiphenylmethane, 2,2-(4,4'-diaminodiphenyl)propane, 4,4'-diaminodiphenyl ether, 4,4'-thiodianiline, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminoditolyl sulfone, methylenebis(o-chloroaniline), 3,9-bis(3-aminopropyl)2,4,8,10-tetraoxaspiro[5.5]undecane, diethylenetriamine, Examples of the primary polyamines include iminobispropylamine, methyliminobispropylamine, bis(hexamethylene)triamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, N-aminoethylpiperazine, N-aminopropylpiperazine, 1,4-bis(aminoethylpiperazine), 1,4-bis(aminopropylpiperazine), 2,6-diaminopyridine, and bis(3,4-diaminophenyl)sulfone.

[0084] Examples of secondary amines include diethylamine, dipropylamine, di-n-butylamine, di-sec-butylamine, diisobutylamine, di-n-pentylamine, di-3-pentylamine, dihexylamine, dioctylamine, di(2-ethylhexyl)amine, methylhexylamine, diallylamine, pyrrolidine, piperidine, 2,4-lupethidine, 2,6-lupethidine, 3,5-lupethidine, diphenylamine, Secondary monoamines such as N-methylaniline, N-ethylaniline, dibenzylamine, methylbenzylamine, dinaphthylamine, pyrrole, indoline, indole, and morpholine; N,N'-dimethylethylenediamine, N,N'-dimethyl-1,2-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,2-diaminobutane, N,N'-dimethyl-1,3-diaminobutane, N,N' -dimethyl-1,4-diaminobutane, N,N'-dimethyl-1,5-diaminopentane, N,N'-dimethyl-1,6-diaminohexane, N,N'-dimethyl-1,7-diaminoheptane, N,N'-diethylethylenediamine, N,N'-diethyl-1,2-diaminopropane, N,N'-diethyl-1,3-diaminopropane, N,N'-diethyl-1,2-diaminobutane, N,N'-diethyl-1,3-diaminobutane and secondary polyamines such as hexane, N,N'-diethyl-1,4-diaminobutane, N,N'-diethyl-1,6-diaminohexane, piperazine, 2-methylpiperazine, 2,5-dimethylpiperazine, 2,6-dimethylpiperazine, homopiperazine, 1,1-di-(4-piperidyl)methane, 1,2-di-(4-piperidyl)ethane, 1,3-di-(4-piperidyl)propane, and 1,4-di-(4-piperidyl)butane.

[0085] Examples of tertiary amines include trimethylamine, triethylamine, tri-n-propylamine, tri-iso-propylamine, tri-1,2-dimethylpropylamine, tri-3-methoxypropylamine, tri-n-butylamine, tri-iso-butylamine, tri-sec-butylamine, tri-pentylamine, tri-3-pentylamine, tri-n-hexylamine, tri-n-octylamine, tri-2-ethylhexylamine, tri-dodecylamine, tri-laurylamine, dicyclohexylethylamine, cyclohexyldiethylamine, tri-cyclohexylamine, N,N-dimethylhexylamine, N-methyldihexylamine, N,N-dimethylcyclohexylamine, N-methyldicyclohexylamine, N,N-diethylethanolamine, N,N-dimethylethanolamine, N-ethyldiethanolamine, triethanolamine, tribenzylamine, N,N-dimethylbenzylamine, diethylbenzylamine, tertiary monoamines such as diphenylamine, triphenylamine, N,N-dimethylamino-p-cresol, N,N-dimethylaminomethylphenol, 2-(N,N-dimethylaminomethyl)phenol, N,N-dimethylaniline, N,N-diethylaniline, pyridine, quinoline, N-methylmorpholine, N-methylpiperidine, 2-(2-dimethylaminoethoxy)-4-methyl-1,3,2-dioxabornane, and 2-, 3-, and 4-picoline; tetramethylethylenediamine , pyrazine, N,N'-dimethylpiperazine, N,N'-bis((2-hydroxy)propyl)piperazine, hexamethylenetetramine, N,N,N',N'-tetramethyl-1,3-butanamine, 2-dimethylamino-2-hydroxypropane, diethylaminoethanol, N,N,N-tris(3-dimethylaminopropyl)amine, 2,4,6-tris(N,N-dimethylaminomethyl)phenol, heptamethylisobiguanide, and other tertiary polyamines.

[0086] These may be used alone or in combination of two or more.

[0087] Of these, primary amine compounds are preferred, and monoamine compounds (monoamines) are more preferred.

[0088] Examples of the amine compound (E1) include aliphatic amines, alicyclic amines, aromatic amines, and alkanolamines. Any of these can be suitably used, but aromatic amines and / or alkanolamines are preferred.

[0089] Since it is preferable that no amine compound remains in the electrode layer after drying, the weight-average molecular weight of the amine compound (E1) is preferably less than 1,000, more preferably 800 or less, even more preferably 500 or less, particularly preferably 350 or less, and even more particularly preferably 250 or less. For the same reason, the boiling point of the amine compound is preferably 400°C or less, more preferably 300°C or less, and even more preferably 200°C or less.

[0090] The amine value of the amine compound (E1) is usually 5 mgKOH / g or more, preferably 50 mgKOH / g or more, more preferably 105 mgKOH / g or more, and usually 1,000 mgKOH / g or less. Examples of the inorganic base (E2) include metal hydroxides (sodium hydroxide, lithium hydroxide, potassium hydroxide, etc.).

[0091] As the other highly polar, low molecular weight component, for example, one or more acidic highly polar, low molecular weight components selected from organic acids and inorganic acids can be used in combination with the basic component.

[0092] Examples of organic acids include organic carboxylic acids (formic acid, acetic acid, propionic acid, benzoic acid, phthalic acid, etc.) and organic sulfonic acids (benzenesulfonic acid, etc.), and examples of inorganic acids include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc., and acid anhydrides of these acids can also be used.

[0093] The content of the highly polar, low-molecular-weight component (E) is, for example, 1% by mass or more, preferably 2% by mass or more, and more preferably 5% by mass or more, based on 100% by mass of the solid content of the carbon nanotube dispersion paste, and is, for example, 600% by mass or less, preferably 300% by mass or less, and more preferably 100% by mass or less.

[0094] Based on 100% by mass of the solid content of the carbon nanotubes (B), the lower limit is, for example, 1% by mass or more, preferably 2% by mass or more, more preferably 5% by mass or more, and even more preferably 12% by mass or more, and the upper limit is, for example, 1,000% by mass or less, preferably 500% by mass or less, more preferably 100% by mass or less, and even more preferably 50% by mass or less.

[0095] Since the highly polar, low-molecular-weight component (E) is often irritating or has a strong odor, it may worsen the working environment during blending or the drying process. In addition, it is generally expensive, which may increase costs. Therefore, it is necessary to keep the content to the minimum necessary.

[0096] The content ratio of the solvent (C) to the highly polar, low-molecular-weight component (E), expressed as the mass ratio of the solvent (C) to the highly polar, low-molecular-weight component (E), is usually within a range of 100 / 0.01 to 100 / 10, preferably within a range of 100 / 0.02 to 100 / 7, more preferably within a range of 100 / 0.05 to 100 / 5, and even more preferably within a range of 100 / 0.1 to 100 / 4.

[0097] Other Components The carbon nanotube dispersion paste may further contain other components in addition to the components (A), (B), and (C) described above, and the components (D) and (E) that may be contained as needed.

[0098] Examples of other components include resins other than the dispersion resin (A) and polyvinylidene fluoride (D), neutralizing agents, antifoaming agents, preservatives, rust inhibitors, plasticizers, pigments other than the carbon nanotubes (B), and dehydrating agents (F).

[0099] Examples of pigments other than carbon nanotubes (B) include the other conductive pigments (B1) described above; white pigments such as titanium white and zinc oxide; blue pigments such as cyanine blue and indanthrene blue; green pigments such as cyanine green and verdigris; organic red pigments such as azo-based and quinacridone-based pigments, red pigments such as red iron oxide; organic yellow pigments such as benzimidazolone-based, isoindolinone-based, isoindoline-based, and quinophthalone-based pigments; and yellow pigments such as titanium yellow and yellow lead. These pigments can be used alone or in combination of two or more. These pigments other than carbon nanotubes (B) can be used for purposes such as color adjustment and film property reinforcement, as long as the conductivity is not significantly impaired. They may be dispersed simultaneously with the dispersion resin (A) and the carbon nanotubes (B), or they may be dispersed into a paste and then mixed as a pigment or pigment paste.

[0100] The content of pigments other than the carbon nanotubes (B) is preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 1% by mass or less, based on the total amount of pigments in the carbon nanotube dispersion paste, and it is particularly preferable that they are substantially not contained.

[0101] The viscosity of the carbon nanotube dispersion paste is determined from the viewpoint of pigment dispersibility and storage stability, and is set to a value of 2 s －１ The viscosity at 1000 kJ / min is, for example, less than 5,000 mPa s, preferably less than 2,500 mPa s, and more preferably less than 1,000 mPa s, and is, for example, 10 mPa s or more, preferably 50 mPa s or more, and more preferably 100 mPa s or more. The viscosity can be measured using, for example, a cone and plate viscometer (manufactured by HAAKE, trade name "Mars2", diameter 35 mm, 2° inclined cone and plate).

[0102] Dehydrating Agent (F) Any known dehydrating agent having a dehydrating effect can be used as the dehydrating agent (F) without any particular limitation. It may be a solid dehydrating agent that is insoluble in the solvent (C) of the paste, or a dehydrating agent that dissolves in the solvent (C). Specific examples of the dehydrating agent include solid dehydrating agents such as zeolite, silica gel, calcium oxide, molecular sieves, activated alumina, barium oxide, calcium hydride, and sodium sulfate; phosphate esters such as trimethyl phosphate, tri-2-propyl phosphate, tributyl phosphate, and tetraisopropylethylene phosphonate; phosphine oxides such as tributylphosphine oxide, trioctylphosphine oxide, and triphenylphosphine oxide; methyl orthoformate, ethyl orthoformate, and the like. orthoesters such as esters, methyl orthoacetate, ethyl orthoacetate, and ethyl orthobenzoate; and acid anhydrides such as oxalic anhydride, acetic anhydride, propionic anhydride, butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, disulfuric acid, dinitrogen pentoxide, diphosphoric acid, diphosphorus pentoxide, diphosphorus trioxide, diarsenic pentoxide, diarsenic trioxide, methanesulfonic anhydride, trifluoromethanesulfonic anhydride, and sulfobenzoic anhydride, and these can be used alone or in combination of two or more.

[0103] [Method for Producing a Composite Paste for a Non-Aqueous Electrolyte Secondary Battery] In the present invention, a carbon nanotube-dispersed paste containing carbon nanotubes (B) is first prepared by the method described above. The carbon nanotube-dispersed paste and at least one electrode active material (G) are then mixed to produce a composite paste for a non-aqueous electrolyte secondary battery.

[0104] In the above-mentioned step of mixing the electrode active material (G), the composite paste can be mixed uniformly using a conventionally known mixer and disperser.

[0105] The solid content of the dispersed resin (A) in the solid content of the composite paste is usually 0.01% by mass or more, preferably 0.05% by mass or more, and is usually 10% by mass or less, preferably 1% by mass or less, which is suitable in terms of battery performance, paste viscosity, etc.

[0106] In the composite paste of the present invention, from the viewpoint of storage stability (suppression of thickening) of the composite paste, it is preferable that the composite paste contains a high-polarity, low-molecular-weight component (E), and that the high-polarity, low-molecular-weight component (E) contains at least one amine compound (E1). From the viewpoint of alleviating aggregation between the carbon nanotubes (B) and the electrode active material (G) by contacting (wetting) the high-polarity, low-molecular-weight component (E) with the carbon nanotubes (B), it is preferable to include a sequence of first mixing the carbon nanotubes (B) and the high-polarity, low-molecular-weight component (E).

[0107] The solid content of carbon nanotubes (B) in the solid content of the composite paste of the present invention is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and usually 30% by mass or less, preferably 20% by mass or less, more preferably 10% by mass or less. This is suitable from the viewpoint of battery performance. The content of the solvent (C) in the composite paste of the present invention is usually 1% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and usually 90% by mass or less, preferably 80% by mass or less, more preferably 70% by mass or less. This is suitable from the viewpoint of electrode drying efficiency and paste viscosity.

[0108] The composite paste is suitable for use in the positive or negative electrode of a non-aqueous electrolyte secondary battery, and is preferably used for the positive electrode.

[0109] In addition, the moisture content of the composite paste is usually less than 10,000 ppm, preferably less than 7,500 ppm, more preferably less than 5,000 ppm, even more preferably less than 2,500 ppm, and particularly preferably less than 1,000 ppm, from the viewpoint of suppressing the increase in viscosity or gelation of the composite paste. The composite paste used in the present invention can be said to be a substantially non-aqueous composite paste. Furthermore, for the reasons described above (moisture carried over from raw materials or moisture contamination during the manufacturing process), the moisture content of the composite paste is preferably 100 ppm or more, more preferably 200 ppm or more, and even more preferably 500 ppm or more.

[0110] Electrode Active Material (G) Examples of the electrode active material (G) include lithium nickel oxide (LiNiO ２ ), lithium manganese oxide (LiMn ２ O ４ ), lithium cobalt oxide (LiCoO ２ ), LiNi １／３ Co １／３ Mn １／３ O ２ lithium composite oxides such as lithium iron phosphate (LiFePO ４ ), sodium composite oxide, potassium composite oxide, etc. These electrode active materials (G) can be used singly or in combination of two or more. The electrode active material containing lithium iron phosphate is inexpensive and has relatively good cycle characteristics and energy density, and therefore can be suitably used.

[0111] The particle size of the electrode active material (G) is usually 0.5 μm or more, preferably 10.5 μm or more, and usually 30 μm or less, preferably 20 μm or less.

[0112] The solid content of the electrode active material (G) in the solid content of the composite paste for a non-aqueous electrolyte secondary battery of the present invention is usually 50% by mass or more, preferably 60% by mass or more, and is preferably less than 100% by mass in terms of battery capacity, battery resistance, etc.

[0113] When the electrode active material (G) is contained in the composite paste, the viscosity may increase during storage. The reason for this is that the electrode active material (G) has alkali metal hydroxides (e.g., LiOH, KOH, NaOH, etc.) derived from the raw materials on the particle surface, and is thought to aggregate (thicken) due to the carbon nanotubes (B) having an acidic surface. Therefore, by containing a certain amount or more of the highly polar low-molecular-weight component (E) [particularly the amine compound (E1)], the storage viscosity increase of the composite paste can be suppressed.

[0114] Furthermore, the amount of water contained in the electrode active material (G) is usually less than 10,000 ppm, preferably less than 7,500 ppm, more preferably less than 5,000 ppm, even more preferably less than 2,500 ppm, and particularly preferably less than 1,000 ppm, from the viewpoint of suppressing the increase in viscosity or gelation of the composite paste described above. Furthermore, the electrode active material (G) of the present invention can be suitably used as an electrode active material composite (G-1) in which at least a portion of its surface is covered with carbon nanotubes. The composite (G-1) can be obtained by previously mixing the electrode active material (G), carbon nanotubes, and, if necessary, other components (e.g., a solvent or a dispersion resin). If necessary, a drying process can be added after mixing, allowing the carbon nanotubes to be more uniformly adsorbed and / or fixed to the electrode active material (G). Furthermore, the electrode active material composite (G-1) produced as described above can form a uniform conductive network around the electrode active material by adsorbing and / or fixing the carbon nanotubes to the surface of the electrode active material. As the carbon nanotubes that can be used in the electrode active material composite (G-1), any known carbon nanotubes can be used without any particular limitation, but the carbon nanotubes listed as the carbon nanotubes (B) can be preferably used.

[0115] As described above, an electrode layer for a non-aqueous electrolyte secondary battery (also referred to as an electrode mixture layer or a mixture layer) can be produced by applying a mixture paste for a non-aqueous electrolyte secondary battery to the surface of a core material (current collector) of a positive electrode or a negative electrode and drying the applied mixture, and is particularly preferably used for a positive electrode.

[0116] In addition, the carbon nanotube dispersion paste obtained by the manufacturing method of the present invention can be used not only as a paste for a composite layer (electrode layer), but also as a primer layer (also referred to as a functional layer or adhesive layer) between an electrode core material and a composite layer (electrode layer). The method for applying the composite paste for non-aqueous electrolyte secondary batteries can be performed by a method known per se using a die coater or the like. The amount of application of the composite paste for non-aqueous electrolyte secondary batteries is not particularly limited, but can be set so that the thickness of the composite layer after drying is, for example, 0.04 mm or more, preferably 0.06 mm or more, and, for example, 0.30 mm or less, preferably 0.24 mm or less. The temperature of the drying step can be appropriately set, for example, 80°C or more, preferably 100°C or more, and, for example, 250°C or less, preferably 200°C or less. The time of the drying step can be appropriately set, for example, 5 seconds or more, and, for example, 120 minutes or less, preferably 60 minutes or less.

[0117] In the drying step, all or part of the solvent (C) and the highly polar, low-molecular-weight component (E) that may be contained as needed volatilize. As described above, in order to reduce waste, be environmentally friendly, and / or reduce costs, it is preferable to recover and reuse the volatilized components (C) and (E).

[0118] Furthermore, in non-aqueous electrolyte secondary batteries, the presence of impurities such as moisture in the electrode layer reduces the cycle life. That is, if the carbon nanotube dispersion paste or composite paste contains more moisture than specified, or if the electrode layer is not sufficiently dried during the manufacturing process, moisture remains in the electrode layer, causing deterioration of the battery's cycle characteristics. The moisture content in the electrode layer is usually less than 1000 ppm, preferably less than 750 ppm, more preferably less than 500 ppm, even more preferably less than 250 ppm, and particularly preferably less than 100 ppm.

[0119] Furthermore, as described above, when the composite paste is applied to a current collector and dried by heating, vapor containing the solvent (C) [and, if necessary, the highly polar, low-molecular-weight component (E)] and the like can be recovered, and then impurities other than the solvent (C) can be removed by distillation, thereby producing a recycled product of the solvent (C).

[0120] The carbon nanotube dispersion paste, composite paste, and electrode layer of the present invention are particularly suitable for use in secondary batteries containing a non-aqueous electrolyte solution. The secondary battery containing a non-aqueous electrolyte solution is a secondary battery containing at least a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte solution, and is preferably a non-aqueous electrolyte type lithium ion secondary battery.

[0121] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these specific embodiments.

[0122] The present invention will be described in more detail below with reference to Production Examples, Examples, and Comparative Examples, but the present invention is not limited thereto. In each example, "parts" means parts by mass, and "%" means % by mass.

[0123] [Production of Dispersion Resin] Production Example 1: A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and water separator was charged with 75 parts of N-methyl-2-pyrrolidone (Note 1) and heated to 120°C in a nitrogen stream. Once the temperature reached 120°C, a mixture of the monomer species shown in Table 1 below (100 parts in total) and 2 parts of 2,2'-azobis(2-methylbutyronitrile) was added dropwise over 3 hours. After completion of the addition, the mixture was aged at 120°C for 30 minutes, and then a mixture of 1 part of 2,2'-azobis(2-methylbutyronitrile) and 20 parts of N-methyl-2-pyrrolidone (Note 1) was added dropwise over 1 hour. After further aging at 120°C for 1 hour, the mixture was cooled, and N-methyl-2-pyrrolidone (Note 1) was added to obtain an acrylic resin (A1) with a solids content of 50%. (Note 1) N-methyl-2-pyrrolidone: Water content 500 ppm (Note 2), amine content 500 ppm (Note 2), recycled product (Note 2) Water content and amine content were measured using a Karl Fischer moisture meter (Kyoto Electronics Manufacturing Co., Ltd., product name "MKC-610") and ion chromatography (Shimadzu Corporation, product name "Prominence HIC-NS").

[0124] Production Examples 2 to 9 Acrylic resins (A2) to (A9) with a solid content of 50% were obtained in the same manner as in Production Example 1, except that the monomer species were changed as shown in Table 1. The weight-average molecular weights of the obtained resins are shown in Table 1.

[0125]

[0126] The abbreviations of the monomer species in Table 1 above are as follows: iBA: i-butyl acrylate (having a hydrocarbon group with 4 carbon atoms) SLMA: lauryl methacrylate (having a hydrocarbon group with 12 carbon atoms) SMA: stearyl methacrylate (having a hydrocarbon group with 18 carbon atoms) BEMA: behenyl methacrylate (having a hydrocarbon group with 22 carbon atoms) St: styrene PP-800: polypropylene glycol monomethacrylate (manufactured by NOF Corporation, trade name "BLEMMER PP-800", average number of moles of PO added: 13 moles) DMAEMA: N,N-dimethylaminoethyl methacrylate

[0127] [Production of Carbon Nanotube Dispersion Paste and Composite Paste] Example 1X Using a continuous dry bead mill "Drystar SDA1" (trade name, manufactured by Ashizawa Finetech Co., Ltd.), carbon nanotubes (CNT1 (Note 3)) were pulverized at a feed rate of 0.5 kg / hr using zirconia beads (diameter 3.0 mm) at a filling rate of 70% and a mill peripheral speed of 5.0 m / s. Next, 5,000 parts of N-methyl-2-pyrrolidone (Note 1), 200 parts of the above-mentioned crushed carbon nanotubes (CNT1), 80 parts of acrylic resin (A1) (solid content 40 parts) (Note 2), 1,800 parts of a resin solution of "KF Polymer W # 7300" (manufactured by Kureha Corporation, trade name, polyvinylidene fluoride, weight average molecular weight 1,000,000) (solid content 180 parts) (Note 4), and 25 parts of lithium hydroxide were mixed with stirring, and finally N-methyl-2-pyrrolidone (Note 1) was used to adjust the total mass to 10,000 parts. Subsequently, the mixture was dispersed in a ball mill for 4 hours to produce a carbon nanotube dispersion paste (X-1). The water content of the carbon nanotube dispersion paste (X-1) was 600 ppm (Note 2). (Note 3) CNT1: Multi-walled carbon nanotube shown in Table 2 below. (Note 4) To prepare the polyvinylidene fluoride resin solution, polyvinylidene fluoride and N-methyl-2-pyrrolidone (Note 1) were mixed and dissolved at a temperature of 80°C in advance. The solution was then cooled to 30°C at a rate of approximately 1°C / min.

[0128]

[0129] The carbon nanotubes are multi-walled carbon nanotubes. The median diameter (D50), G / D ratio, specific surface area (BET specific surface area), and amount of acidic groups in Table 2 were measured by the methods described below.

[0130] Examples 2X to 7X, Comparative Examples 1X to 2X Carbon nanotube-dispersed pastes (X-2) to (X-9) were produced in the same manner as in Example 1X, except that the dispersing resin was changed to the type shown in Table 3 below. The water content of each carbon nanotube-dispersed paste was 600 ppm (Note 2). The results of the evaluation tests described below are also shown in Table 3 below.

[0131]

[0132] Example 1Y 100 parts of the carbon nanotube dispersion paste (X-1) were mixed with electrode active material particles (composition formula LiNi ０．５ Mn １．５ O ４ Lithium nickel manganese oxide particles with a spinel structure represented by the formula (I), an average particle diameter of 6 μm, and a BET specific surface area of ​​0.7 m ２ 900 parts of the cellulose acetate copolymer (C10 / g, water content 100 ppm) were mixed in a disperser to prepare a composite paste (Y-1).

[0133] Examples 2Y to 7Y, Comparative Examples 1Y to 2Y Composite pastes (Y-2) to (Y-9) were produced in the same manner as in Example 1Y, except that the carbon nanotube dispersion paste was changed to the type shown in Table 4 below. The results of the evaluation tests described below are also shown in Table 3 above.

[0134]

[0135] <Median diameter (D50)> The median diameter (D50) was measured using a laser diffraction / scattering particle size distribution analyzer "LA-960" (trade name, manufactured by HORIBA) according to the following procedure.

[0136] [Preparation of Aqueous Dispersion Medium] 0.10 g of "F10MC" (trade name, manufactured by Nippon Paper Industries Co., Ltd., carboxymethylcellulose sodium (hereinafter also referred to as CMCNa)) was added to 100 mL of distilled water, and the mixture was stirred at room temperature for 24 hours or more to dissolve, thereby preparing an aqueous dispersion medium containing 0.1% by mass of CMCNa.

[0137] [Preparation of CMCNa Aqueous Solution] 2.0 g of "F10MC" (trade name, carboxymethylcellulose sodium, manufactured by Nippon Paper Industries Co., Ltd.) was added to 100 mL of distilled water and dissolved by stirring at room temperature for 24 hours or more to prepare a 2.0 mass % aqueous solution of CMCNa.

[0138] [Pretreatment before measurement] 6.0 mg of carbon nanotubes were weighed into a vial, and 6.0 g of the aqueous dispersion medium was added. An ultrasonic homogenizer (Microtec Nichion Corporation, "SmurtNR-50") was used for pretreatment before measurement. The tip was confirmed to be free of deterioration, and the tip was adjusted so that it was immersed 10 mm or more below the surface of the sample being treated. A carbon nanotube aqueous dispersion was prepared by homogenizing the solution through ultrasonic irradiation using auto-power operation with a constant output power, with a time set (irradiation time) of 40 seconds, a power set of 50%, and a start power of 50% (output of 50%).

[0139] [Measurement] Using the carbon nanotube aqueous dispersion, the proportion of dispersed particles of carbon nanotubes having a size of 1 μm or less and the median diameter (D50) were measured according to the following methods.

[0140] The optical model of the LS 13 320 universal liquid module is set to a refractive index of 1.520 for carbon nanotubes and 1.333 for water, and after the module has been washed, approximately 1.0 mL of a CMCNa aqueous solution is filled.

[0141] After performing offset measurement, optical axis adjustment, and background measurement under conditions of 50% pump speed, the prepared carbon nanotube aqueous dispersion was added to a particle size distribution meter so that the relative concentration, which indicates the percentage of light scattered outside the beam by the particles, was 8-12%, or the PIDS was 40-55%, and the particle size distribution was measured after irradiating with ultrasound at 78 W for 2 minutes (measurement pretreatment) using the particle size distribution meter accessory, circulating for 30 seconds to remove air bubbles, and then the particle size distribution was measured. A graph of volume % versus particle size (particle diameter) was obtained, and the presence proportion of dispersed particles of 1 μm or less and the median diameter (D50) were determined.

[0142] For each carbon nanotube sample, three measurement samples were collected from different locations and particle size distribution was measured, and the proportion of dispersed particles of 1 μm or less and the median diameter (D50) were calculated as the average value.

[0143] <G / D ratio of carbon nanotubes> The Raman spectrum of the carbon nanotubes was measured by placing the carbon nanotubes in a Raman microscope (manufactured by Horiba, Ltd., product name "XploRA") and using a laser wavelength of 532 nm. －１ More than 1600cm －１ The maximum peak intensity within the following range is G, 1310 cm －１ More than 1350cm －１ The G / D ratio of the carbon nanotube was determined by setting the maximum peak intensity within the following range as D.

[0144] <Specific surface area (BET specific surface area)> The BET specific surface area of ​​the carbon nanotubes was measured in accordance with JIS Z8830:2013 using a specific surface area measuring device (manufactured by Microtrac-Bell, product name "BERSORP-MAX") as the BET specific surface area (m ２ / g) was measured.

[0145] <Amount of Acidic Groups in Carbon Nanotubes (CNT)> 2 g of CNT was precisely weighed out, immersed in 50 ml of a 0.01 M benzylamine / n-methylpyrrolidone solution, and dispersed for 1 hour using an ultrasonic irradiator. The solution was then centrifuged, and the supernatant was filtered. The benzylamine remaining in the resulting filtrate was quantitatively analyzed by potentiometric titration with 0.1 M hydrochloric acid, and the amount of acidic groups (mmol / g) per 1 g of the resulting CNT was determined.

[0146] Evaluation tests were carried out on the carbon nanotube dispersion pastes and composite pastes obtained in the above Examples and Comparative Examples. Evaluations D and E are considered to be unsatisfactory. If there is even one unsatisfactory evaluation result, the carbon nanotube dispersion paste or composite paste is deemed to be unsatisfactory.

[0147] <Dispersibility> The dispersibility of the obtained carbon nanotube dispersion paste was evaluated using a particle gauge according to the dispersibility test of JIS K-5600-2-5, based on the following criteria: A: The pigment is dispersed at less than 10 μm. Dispersibility is very good. B: The pigment is dispersed at 10 μm or more and less than 20 μm. Dispersibility is somewhat good. C: The pigment is dispersed at 20 μm or more, but no agglomerates are visible to the naked eye. Dispersibility is somewhat poor. D: Agglomerates are visible to the naked eye. Dispersibility is poor. E: Large agglomerates are visible to the naked eye. Dispersibility is very poor.

[0148] <Viscosity> The obtained composite paste was measured at a shear rate of 2.0 sec using a cone and plate viscometer (manufactured by HAAKE, product name "Mars2", diameter 35 mm, cone and plate tilted at 2°). －１ The viscosity was measured at 100°C and evaluated according to the following criteria: A: The viscosity was less than 10 Pa·s. B: The viscosity was 10 Pa·s or more and less than 20 Pa·s. C: The viscosity was 20 Pa·s or more and less than 50 Pa·s. D: The viscosity was 50 Pa·s or more.

[0149] [Production of Battery Electrode Layer] Application Examples 1Z to 7Z The composite pastes obtained in Examples 1Y to 7Y were applied to both sides of a long aluminum foil (positive electrode current collector) having an average thickness of 15 μm in a weight per side of 10 mg / cm ２ The positive electrode layer was formed by applying the mixture in a strip shape by a roller coating method so that the solid content was 100% (based on the solid content) and drying (drying temperature: 180°C, 30 minutes). The positive electrode active material layer (positive electrode layer) supported on the positive electrode current collector was rolled using a roll press to adjust the properties. The resulting electrode layer had a residual solvent content of less than 1% and was an electrode layer with good finish.

Claims

1. A carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery, comprising at least a dispersion resin (A), carbon nanotubes (B), and a solvent (C), wherein the dispersion resin (A) contains at least a structural unit (a-1) represented by the following formula (1), and the carbon nanotubes (B) have a BET specific surface area of ​​100 m ２ / g to 1000m ２ / g of the carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery. (In the formula, R １ and R ３ are the same or different and represent a hydrogen atom or a methyl group; R ２ represents a hydrogen atom, a carboxyl group, or an organic group; X represents an organic linking group; R ４ represents a hydrocarbon group having 8 to 30 carbon atoms.

2. The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to claim 1, further comprising polyvinylidene fluoride (D).

3. A carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to claim 1, characterized in that the dispersion resin (A) has at least one polar functional group selected from the group consisting of a hydroxyl group, a carboxyl group, a sulfonic acid group, a phosphate group, a pyridine group, an amino group and a cyano group, and the concentration of the polar functional group is 0.1 to 8.5 mmol / g.

4. The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to claim 1, further comprising a highly polar, low-molecular-weight component (E).

5. The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to claim 1, wherein the carbon nanotubes (B) are previously dry-dispersed using a media-type grinder.

6. The carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to claim 1, wherein the water content of the carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery is less than 10,000 ppm.

7. A composite paste for a non-aqueous electrolyte secondary battery obtained by further adding an electrode active material (G) to the carbon nanotube dispersion paste for a non-aqueous electrolyte secondary battery according to any one of claims 1 to 6.

8. An electrode layer for a non-aqueous electrolyte secondary battery obtained by coating a current collector with the composite paste according to claim 7.

9. A non-aqueous electrolyte secondary battery comprising a positive electrode containing the electrode layer according to claim 8, a negative electrode, a non-aqueous electrolyte, and a separator.

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