JP2022181696A - Electrical conduction material slurry - Google Patents

Abstract

To provide an electrical conduction material slurry with an excellent dispersibility of a carbon nano-tube.SOLUTION: The present invention discloses, in one aspect, an electrical conduction material slurry containing: an electrical conduction material; a dispersant; and an organic solvent. In the electrical conduction material, 50 mass% or more is a carbon nano-tube. The dispersant is a polymer containing 60 to 99 mass% of vinyl alcohol unit in one molecular. A content amount of the vinyl alcohol unit in the electrical conduction material slurry is 17.0 to 60.0 mass part to 100 mass part of the content amount of the carbon nano-tube. The electrical conduction material slurry preferably further contains a binding agent, and the content amount of the binding agent in the electrical conduction material slurry is preferably 150 to 700 mass part against 100 mass part of the content amount of the vinyl alcohol unit.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a conductive material slurry, a battery positive electrode paste, and a battery positive electrode.

BACKGROUND ART In recent years, electric vehicles that do not emit carbon dioxide have been actively developed from the viewpoint of global warming suppression. Compared to gasoline vehicles, electric vehicles have short mileage and take a long time to charge their batteries. In order to shorten the charging time, it is necessary to speed up the movement of electrons in the positive electrode. At present, carbon black is used as a conductive aid (conductive material) in positive electrodes for non-aqueous electrolyte batteries, but the use of conductive materials with lower electronic resistance than carbon black is desired.

Carbon nanotubes (hereinafter sometimes referred to as "CNT") are known as conductive materials having lower electronic resistance than carbon black, and are expected to be applied to various fields due to their physical and chemical properties. there is CNT has a high aspect ratio and can form a conductive path with a small amount. A CNT is a carbon nanomaterial having a shape in which a single graphite sheet is substantially wound into a cylindrical shape. A single-layered CNT is called a single-walled CNT, and coaxially wound multiple-layered CNT is called a multi-layered CNT.

It is required to uniformly disperse the carbon material in the organic solvent. Patent Document 1 discloses a carbon material dispersion containing a copolymer of stearyl methacrylate and polyoxypropylene (average number of added moles: 14) methacrylate as a dispersant, a carbon material such as CNT, and an organic solvent. . Patent Document 2 describes a carbon nanotube slurry and a battery positive electrode paste containing carbon nanotubes, a polyvinyl alcohol resin having a degree of saponification of 71 mol% (56% by mass in terms of the content of vinyl alcohol units) and an average degree of polymerization of 1000 or less. is disclosed.

JP 2012-166154 A JP 2019-102259 A

In order to obtain a positive electrode paste for batteries that can efficiently form a conductive path with a small number of CNTs in the positive electrode mixture layer, a thick bundle (bundle) consisting of several tens of CNTs or a bundle of CNTs between CNTs is required in the positive electrode paste for batteries. Firm agglomeration must be resolved and CNTs must be highly dispersed. As means for obtaining such a positive electrode paste, it is necessary to use a CNT dispersion liquid in which CNTs are highly dispersed in a solvent for preparing the positive electrode paste.

Therefore, the present disclosure provides a conductive material slurry having good CNT dispersibility. The present invention also provides a battery positive electrode paste prepared using the conductive material slurry.

In one aspect, the present disclosure is a conductive material slurry containing a conductive material, a dispersant, and an organic solvent,
50% by mass or more of the conductive material is carbon nanotubes,
The dispersant is a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule,
The present invention relates to the conductive material slurry, wherein the content of the vinyl alcohol unit in the conductive material slurry is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of the content of the carbon nanotubes.

In one aspect, the present disclosure is a battery positive electrode paste containing a positive electrode active material, a binder, a conductive material, a dispersant, and an organic solvent,
50% by mass or more of the conductive material is carbon nanotubes,
The dispersant is a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule,
It relates to a battery positive electrode paste, wherein the content of the vinyl alcohol unit in the conductive material slurry is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of the content of the carbon nanotubes.

In one aspect, the present disclosure provides a positive electrode for a battery comprising a positive electrode mixture layer,
The positive electrode mixture layer includes a positive electrode active material, a conductive material, a polymer, and a binder,
50% by mass or more of the conductive material is carbon nanotubes,
The polymer contains 60 to 99% by mass of vinyl alcohol units in one molecule,
The positive electrode for a battery, wherein the content of the vinyl alcohol unit in the positive electrode mixture layer is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of the carbon nanotube content.

The conductive material slurry of the present disclosure contains a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule as a dispersant, and the content of vinyl alcohol units in the conductive material slurry is equal to the content of carbon nanotubes of 100 mass. Since it is 17.0 to 60.0 parts by mass per part, the CNTs can be well dispersed in the conductive material slurry.
In addition, since the positive electrode paste for battery of the present disclosure is prepared using the conductive material slurry, it is possible to reduce the coating film resistance of the positive electrode mixture layer.

The conductive material slurry of the present disclosure contains, as a dispersant, a polymer containing vinyl alcohol units in one molecule at a specific mass ratio, and the amount of vinyl alcohol units relative to 100 parts by mass of CNTs in the conductive material slurry is set to a specific amount. It is based on the knowledge that the dispersibility of CNTs in the conductive material slurry is improved.

Although the details of the mechanism by which the dispersibility of CNTs in the conductive material slurry is improved are not clear in the present disclosure, it is speculated as follows.
In the present disclosure, a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule is used as a CNT dispersant, and the content of vinyl alcohol units in the conductive material slurry is contained within the range of 17.0 to 60.0 parts by mass. Therefore, in a state in which the vinyl alcohol units adsorbed to the CNTs hold the CNTs, the vinyl structure, which is the main chain, spreads over the CNT surface, and the steric repulsion exerts a strong steric repulsive force between the CNTs. It is speculated that it is highly dispersible in
When the vinyl alcohol unit in one molecule of the polymer is 60% by mass or more, the solubility of the polymer in organic solvents such as N-methyl-2-pyrrolidone (NMP) is suppressed, and the polymer adsorbs to CNT. It is thought that this increases the dispersibility and contributes to the improvement of dispersibility.
Moreover, when the content of the vinyl alcohol unit is 17.0 parts by mass or more per 100 parts by mass of CNTs, the dispersibility is enhanced, the aggregation of CNTs is suppressed, and the stability of the conductive material slurry can be maintained. On the other hand, when the content of vinyl alcohol units is 60.0 parts by mass or less with respect to 100 parts by mass of CNTs, aggregation of vinyl alcohol units during solvent drying is suppressed, and contact between CNTs is maintained. , the coating resistance of the positive electrode coating is considered to be low.
However, the present invention should not be construed as being limited to these mechanisms. The dispersibility of CNTs in the conductive material slurry can be evaluated by the viscosity of the conductive material slurry. The smaller the viscosity, the better the CNT dispersibility.

<Conductive material slurry>
In one aspect, the present disclosure includes a conductive material, a dispersant, and an organic solvent, wherein 50% by mass or more of the conductive material is composed of CNTs, and the dispersant is a weight containing 60 to 99% by mass of vinyl alcohol units. It relates to the conductive material slurry, which is coalesced and the content of the vinyl alcohol unit in the conductive material slurry is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of CNTs. In the conductive material slurry of the present disclosure, CNTs can be well dispersed in the conductive material slurry.

[Conductive material]
In the conductive material slurry of the present disclosure, 50% by mass or more of the conductive material is composed of CNTs. The conductive material is preferably 80% by mass or more, more preferably 90% by mass or more, still more preferably 95% by mass or more, still more preferably 98% by mass or more, still more preferably substantially 100% by mass, and still more Preferably 100% by mass is CNT. Examples of conductive materials other than CNT contained in the conductive material slurry of the present disclosure include carbon materials such as acetylene black, ketjen black, and graphite, and these can be used alone or in combination of two or more.

In the present disclosure, CNT means an aggregate including a plurality of CNTs. The form of the CNTs used for preparing the conductive material slurry of the present disclosure is not particularly limited, and for example, a plurality of CNTs may be independent, or may be in a form such as a bundle or entanglement of a plurality of CNTs. However, a form in which these forms are mixed may be used. The CNTs may be CNTs of various layer numbers or diameters. CNTs may contain impurities (eg, catalysts and amorphous carbon) from the process in which the CNTs are manufactured.

CNTs, in one or more embodiments, have a shape in which one sheet of graphite is wound into a cylindrical shape, and those wound in one layer are single-walled CNTs (SWCNTs), and those wound in two layers. are also called double-layered CNTs (DWCNTs), and those wound in three or more layers are called multi-layered CNTs (MWCNTs). Depending on the characteristics required for the positive electrode mixture layer obtained using the battery positive electrode paste containing the conductive material slurry of the present disclosure (hereinafter sometimes abbreviated as “positive electrode paste”), a single layer, two layers, or multiple layers and mixtures thereof can be used. Multilayer CNTs are preferably used in order to obtain a positive electrode mixture layer with good CNT dispersion and low resistance.

The average diameter of CNTs is measured by scanning electron microscope (SEM) or atomic force microscope (AFM). In the present disclosure, the average diameter is not particularly limited, but from the viewpoint of improving the dispersibility of CNTs, it is preferably 3 nm or more, more preferably 5 nm or more, and still more preferably 8 nm or more. It is preferably 100 nm or less, more preferably 50 nm or less, even more preferably 30 nm or less, even more preferably 20 nm or less, and even more preferably 15 nm or less. Specifically, the average diameter of CNTs is preferably 3 to 100 nm, more preferably 3 to 50 nm, still more preferably 3 to 30 nm, even more preferably 5 to 20 nm, still more preferably 8 to 20 nm, and even more preferably is 8-15 nm.

The average length of CNTs is measured by scanning electron microscope (SEM) or atomic force microscope (AFM). In the present disclosure, the average length is not particularly limited, but from the viewpoint of improving conductivity, it is preferably 2 μm or more, more preferably 5 μm or more, still more preferably 10 μm or more, and even more preferably 30 μm or more. From the viewpoint of improving properties, the thickness is preferably 500 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, and even more preferably 120 μm or less. Specifically, the average length of CNTs is preferably 2 to 500 μm, more preferably 5 to 300 μm, even more preferably 10 to 200 μm, still more preferably 30 to 120 μm.

The content of impurities in CNTs is measured by a method such as thermogravimetric analysis, but in the present disclosure, the lower the better. The content of impurities in CNTs is preferably 40% by mass or less, more preferably 30% by mass or less, even more preferably 20% by mass or less, and even more preferably 10% by mass, from the viewpoint of increasing the effective content of CNTs. Below, it is more preferably substantially 0% by mass.

The content of the conductive material in the conductive material slurry of the present disclosure is preferably 0.5% by mass or more, more preferably 1% by mass or more, and still more preferably 1.5% by mass or more, from the viewpoint of improving the convenience of adjusting the concentration of the positive electrode paste. It is 5% by mass or more and preferably 10% by mass or less, more preferably 5% by mass or less, and even more preferably 3% by mass or less from the viewpoint of making the conductive material slurry easy to handle. Specifically, the content of the conductive material in the conductive material slurry of the present disclosure is preferably 0.5 to 10% by mass, more preferably 1 to 5% by mass, and still more preferably 1.5 to 3% by mass. be.

[Dispersant]
The dispersant contained in the conductive material slurry of the present disclosure is a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule. If the vinyl alcohol unit in one molecule of the polymer is less than 60% by mass, the solubility of the polymer in an organic solvent such as N-methyl-2-pyrrolidone (NMP) is high, and the adsorption of the polymer to CNT is poor. Therefore, it is considered that it is not effective for improving the dispersibility of CNT. On the other hand, if the vinyl alcohol unit in one molecule is more than 99% by mass, the polymer is difficult to dissolve in an organic solvent such as NMP, and it takes an excessive amount of time to prepare the conductive material slurry or the positive electrode paste, which reduces productivity. Unfortunately, the stability of the conductive material slurry is not sufficient. In addition, when the vinyl alcohol unit in one molecule of the polymer is less than 60% by mass, even if the vinyl alcohol unit is adsorbed to the CNT, the vinyl structure, which is the main chain, cannot be maintained on the CNT surface, As a result, effective steric repulsion is not generated by the polymer, and thus the dispersibility is presumed to be poor. On the other hand, a polymer containing 60 to 99% by mass of vinyl alcohol units preferably has appropriate solubility in organic solvents such as NMP, adsorption to CNTs, and steric repulsion after adsorption. It is believed that it functions particularly effectively as a dispersant because it can be balanced.

The content of vinyl alcohol units in one molecule of the polymer is 60% by mass or more, preferably 75% by mass or more, more preferably 83% by mass or more, and still more preferably, from the viewpoint of improving the dispersibility of CNTs. 84% by weight or more, more preferably 85% by weight or more, and from the viewpoint of productivity and stability of the conductive material slurry, 99% by weight or less, preferably 95% by weight or less, more preferably 92% by weight or less, and further It is preferably 90% by weight or less, more preferably 88% by weight or less, and even more preferably 87% by weight or less. In the present disclosure, the content of vinyl alcohol units in one molecule of the polymer is specifically preferably 75 to 95% by mass, more preferably 83 to 92% by mass, and still more preferably 83 to 90% by mass. , more preferably 84 to 88% by mass, and even more preferably 85 to 87% by mass.

If the mass ratio of the vinyl alcohol unit in one molecule of the polymer is within the above range, the polymer may contain vinyl ester units, vinyl butyral units, and polyalkylene glycol (meth) as structural units other than the vinyl alcohol units. ) One or more structural units selected from acrylate units, styrene units, ethylene units, and butadiene units. A vinyl ester unit originates in the vinyl ester monomer used as a raw material monomer of a polymer. Vinyl ester monomers include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl laurate and the like.

If the mass ratio of vinyl alcohol units in one molecule of the polymer is within the above range, the polymer may contain polyvinyl alcohol as a functional group other than a hydroxyl group, an acetyl group, an acetal group, or a formal group, for example. , For example, those into which one or more kinds of acetoacetyl groups, sulfonic acid groups, carboxyl groups, carbonyl groups, amino groups are introduced, those functional groups modified with various salts, other anions or cations Modified ones and those having structures such as ethers and esters are also included. The polymer may contain one or more of these modified polyvinyl alcohols, or may contain both modified polyvinyl alcohol and non-modified polyvinyl alcohol.

The content of vinyl alcohol units in the conductive material slurry of the present disclosure is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of the CNT content. If the content of vinyl alcohol units is less than 17.0 parts by mass with respect to 100 parts by mass of CNTs, the CNTs aggregate, and the stability of the conductive material slurry cannot be maintained. If the content of the vinyl alcohol units exceeds 60.0 parts by mass with respect to 100 parts by mass of CNTs, contact between the CNTs is inhibited due to the aggregation effect of the vinyl alcohol units during drying of the solvent. Increases coating resistance. Here, "the content of vinyl alcohol units in the conductive material slurry" means the total amount of vinyl alcohol units contained in the conductive material slurry.

The preferable content of vinyl alcohol units in the conductive material slurry of the present disclosure is preferably 23.0 parts by mass or more with respect to 100 parts by mass of CNTs, from the viewpoint of high dispersibility of CNTs and stability of the conductive material slurry. It is preferably 25.0 parts by mass or more, and from the viewpoint of coating film resistance, preferably 55.0 parts by mass or less, more preferably 40.0 parts by mass or less, and even more preferably 30.0 parts by mass or less per 100 parts by mass of CNTs. It is 0 mass part or less. Specifically, the preferable content of the vinyl alcohol unit in the conductive material slurry of the present disclosure is preferably 23.0 to 55.0 parts by mass, more preferably 23.0 parts by mass, with respect to 100 parts by mass of the CNT content. 0 to 40.0 parts by mass, more preferably 25.0 to 30.0 parts by mass.

The degree of polymerization of the polymer is preferably 20 or more, more preferably 50 or more, still more preferably 200 or more, and even more preferably 300 or more, from the viewpoint of improving the dispersibility of CNTs by suitably coating the CNTs with a vinyl structure. is preferably 5000 or less, more preferably 3000 or less, still more preferably 2000 or less, and still more preferably 1000 or less from the viewpoint of improving the dispersibility of CNT by improving the dispersibility of the polymer itself. In the present disclosure, specifically, the degree of polymerization of the polymer is preferably 20-5000, more preferably 50-3000, even more preferably 200-2000% by mass, and even more preferably 300-1000.

[Method for producing polymer]
A method for synthesizing the polymer is not particularly limited, and the polymer can be obtained by a known method. For example, it can be obtained by saponifying polyvinyl acetate obtained by polymerizing vinyl acetate as a raw material.

[Organic solvent]
The solvent contained in the conductive material slurry of the present disclosure is preferably an organic solvent capable of dissolving the binder contained in the battery positive electrode paste. Examples of organic solvents include amide-based polar organic solvents such as dimethylformamide (DMF), diethylformamide, dimethylacetamide (DMAc), and N-methylpyrrolidone (NMP); methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol (n-butanol), 2-methyl-1-propanol (isobutanol), 2-butanol (sec-butanol), 1-methyl-2-propanol (tert-butanol), pentanol, hexanol , heptanol, or octanol; glycols such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, or hexylene glycol; polyhydric alcohols such as glycerin, trimethylolpropane, pentaerythritol, or sorbitol; ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, triethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monoethyl Ethers, glycol ethers such as triethylene glycol monoethyl ether, tetraethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, or tetraethylene glycol monobutyl ether; acetone, methyl ethyl ketone, methyl propyl ketone , or ketones such as cyclopentanone; esters such as ethyl acetate, γ-butyllactone, and ε-propiolactone. The organic solvent contained in the conductive material slurry may be one kind or a combination of two or more kinds. When the binder is PVDF (polyvinylidene fluoride resin) contained in conventional battery positive electrode paste, the organic solvent is generally N-methyl-2-pyrrolidone (NMP). From the viewpoint of improving the dispersibility of CNTs, the organic solvent is particularly preferably NMP.

[Binder]
The binder contained in the positive electrode paste of the present disclosure, which will be described later, may be added to the conductive material slurry or the positive electrode active material of the present disclosure when preparing the positive electrode paste. may be included in advance in the conductive material slurry of the present disclosure.

The binder is not particularly limited, and known binders used in the production of battery electrodes can be used. Examples include polyvinylidene fluoride (PVDF), hexafluoropropylene, and monochlorotrifluoroethylene. A vinylidene fluoride polymer such as a vinylidene fluoride copolymer of No. 2 or a modified product obtained by modifying vinylidene fluoride with a carboxylic acid can be used. The weight average molecular weight of these vinylidene fluoride polymers is not particularly limited, but vinylidene fluoride polymers having a weight average molecular weight of 100,000 to 1,500,000 are generally used. A vinylidene fluoride polymer may be mixed with styrene-butadiene rubber, polyacrylonitrile, or the like.

The amount of the binder contained in the conductive material slurry or the positive electrode paste is set to is preferably 150 parts by mass or more, more preferably 300 parts by mass or more, and still more preferably 350 parts by mass or more with respect to 100 parts by mass of the vinyl alcohol unit of the CNT dispersibility and the conductive material accompanying the addition of the binder From the viewpoint of suppressing deterioration of the dispersion stability of the conductive material slurry or positive electrode paste due to an increase in viscosity of the slurry or positive electrode paste, preferably 700 vinyl alcohol units per 100 parts by mass in the conductive material slurry or positive electrode paste. It is not more than 650 parts by mass, more preferably not more than 620 parts by mass. Specifically, the amount of the binder contained in the conductive material slurry or positive electrode paste is preferably 150 to 700 parts by mass, more preferably 150 to 700 parts by mass, with respect to 100 parts of vinyl alcohol units in the conductive material slurry or positive electrode paste. 300 to 650 parts by mass, more preferably 350 to 620 parts by mass.

[Nitrogen-containing organic compound]
The positive electrode paste of the present disclosure, which will be described later, may further contain a nitrogen-containing organic compound as one aspect. The nitrogen-containing organic compound may be added to the conductive material slurry of the present disclosure and other components when preparing the positive electrode paste. In one aspect, the nitrogen-containing organic compound is added to the conductive material slurry of the present disclosure. may be included in advance. By adding a nitrogen-containing organic compound, it is possible to prepare a low-viscosity conductive material slurry and a positive electrode paste that are easy to handle.

Although the details of the mechanism of viscosity reduction by the addition of a nitrogen-containing organic compound are not clear, the polymer containing 60 to 99% by mass of vinyl alcohol units does not cover the entire surface of the carbon material-based conductive material, and the carbon An exposed part exists on the surface of the material-based conductive material. Therefore, adjacent carbon material-based conductive materials aggregate in an organic solvent due to π-π interaction and hydrogen bonding between polar groups partially present on the surface of the carbon material-based conductive material. However, when the nitrogen-containing organic compound is contained, the nitrogen-containing organic compound suppresses hydrogen bonding between the carbon material-based conductive materials by interacting with the polar group (neutralization reaction or dipole interaction). . Furthermore, the amine (cation) interacts with the π electrons on the carbon material-based conductive material and the cation-π interaction to suppress the π-π interaction between the carbon material-based conductive materials. By suppressing the hydrogen bonding and suppressing the π-π interaction, the dispersibility of the carbon material-based conductive material is improved, and as a result, the viscosity is reduced compared to the case where the nitrogen-containing organic compound is not added. It is speculated that However, the present disclosure should not be construed as being limited to these mechanisms.

The nitrogen-containing organic compound is preferably a compound having at least one primary to tertiary amino group in the molecule (hereinafter referred to as primary to tertiary amine). In the present application, a primary to tertiary amino group means a structure in which all three bonds to the central nitrogen atom are single bonds. As long as the nitrogen-containing organic compound has one such primary to tertiary amino group, it may have other nitrogen atoms in the molecule, and the other nitrogen atoms are primary to tertiary Even if it is an amino group, it may constitute an imino group having a double bond. When other nitrogen atoms are present in the molecule, they are preferably not adjacent to the nitrogen atom of the amino group.

The primary to tertiary amines are preferably aliphatic amines, which may be chain (branched or linear) or cyclic. For cyclic amines, saturated rings are preferred. When it is not a cyclic amine, it may have an unsaturated group such as an imino group together with the amino group. Moreover, the hydrocarbon group portion of the aliphatic amine may be substituted with OH, an amino group, COOH, or the like. -CH ₂ - in the aliphatic group may be replaced with O (oxygen atom), in which case O (oxygen atom) is preferably not adjacent to the nitrogen atom of the amino group. Examples of the primary to tertiary amines include alkylamines, amino group-containing alcohols, carboxyl-substituted alkylamines, imidazoles, piperazines, guanidines, piperidines and pyrrolidines.

The alkylamines are preferably primary to tertiary amines in which the existing alkyl groups are independently branched or linear alkyl groups, more preferably alkyl groups such that the total number of carbon atoms in the molecule is 15 or less. have Specific examples include hexylamine, octylamine, diethylamine, dibutylamine, trimethylamine, triethylamine, tributylamine, N-propylethylamine, N-butylethylamine, N,N-dimethylcyclohexylamine and the like. The alkyl group may also be substituted with an amino group, in which case it will contain two or more primary to tertiary amino groups, and examples thereof include di- or triamines such as ethylenediamine and diethylenediaminetriamine.

As the amino group-containing alcohols, compounds in which the hydrogen of the alkyl group in the above alkylamine is substituted with OH are preferable, such as monoethanolamine, diethanolamine, triethanolamine, N-butyldiethanolamine, N,N-dimethylaminoethanol. , Nn-butylethanolamine, 2-(methylamino)ethanol, N-methylethanolamine, N-ethylethanolamine, 2-amino-1-propanol, 2-amino-2-methyl-1-propanol, 1 -amino-2-propanol, 2-amino-1,3-propanediol and the like. Among them, 2-amino-1,3-propanediol is preferred.

Examples of carboxyl-substituted alkylamines include compounds in which the hydrogen of the alkyl group in the above alkylamines is replaced with COOH, such as ethylenediaminetetraacetic acid, 1,3-propanediaminetetraacetic acid, and 1,2-propanediaminetetraacetic acid. , 1,3-diamino-2-hydroxypropanetetraacetic acid, glycol etherdiaminetetraacetic acid, trans-1,2-cyclohexanediaminetetraacetic acid, hexamethylenediaminetetraacetic acid, dicarboxymethylglutamic acid, dicarboxymethylaspartic acid, S,S - ethylenediaminedisuccinic acid, ethylenediaminedi(o-hydroxyphenyl)acetic acid, hydroxyethyliminodiacetic acid, ethylenediaminediacetic acid, iminodiacetic acid, ethylenediaminedipropionic acid, nitrilotriacetic acid, hydroxyethylenediaminetriacetic acid, nitrilotripropionic acid, Methylglycinediacetic acid, diethylenetriaminepentaacetic acid, triethylenetetraminehexaacetic acid and the like can be mentioned. Moreover, some or all of the carboxyl groups may form a salt with an alkali metal such as Na.

Specific examples of imidazoles include 1,2-dimethylimidazole, 2-methylimidazole, 2-ethyl-4-methylimidazole, 4-ethyl-2-methylimidazole, 1-methyl-4-ethylimidazole and the like. be done.

Piperazines are preferably unsubstituted or alkyl-substituted piperazines, where the alkyl group may further have an amino group. The substitution position of the alkyl group may be any position in the piperazine ring, and may be on the nitrogen atom or the carbon atom. Specifically, piperazine, 1-methylpiperazine, 1-ethylpiperazine, 1-propylpiperazine, 1,4-dimethylpiperazine, 1,4-diethylpiperazine, 1,4-dipropylpiperazine, 2-methylpiperazine, 2 -ethylpiperazine, 3-propylpiperazine, 2,6-dimethylpiperazine, 2,6-diethylpiperazine, 2,6-dipropylpiperazine, 2,5-dimethylpiperazine, 2,5-diethylpiperazine, 2,5-di Propylpiperazine and the like can be mentioned. Also preferred are piperazines substituted with aminoalkyl groups, such as 1-aminoethylpiperazine.

In addition, nitrogen-containing organic compounds include guanidines, piperidines, pyrrolidines, specifically guanidine and guanidine salts, piperidine, 1-methylpiperidine, 1-ethylpiperidine, 1-propylpiperidine, 2, 3 or 4-methylpiperidine, 2,3 or 4-ethylpiperidine, 2,6-dimethylpiperidine, 2,6-diethylpiperidine, 2,6-dipropylpiperidine, 2,4-dimethylpiperidine, 2,4-diethylpiperidine, 1-aminoethylpiperidine, morpholine, pyrrolidine, 1-methylpyrrolidine, 1-ethylpyrrolidine, 1-propylpyrrolidine, 2 or 3-methylpyrrolidine, 2 or 3-ethylpyrrolidine, 2,5-dimethylpyrrolidine, 2,5- Diethylpyrrolidine, 2,5-dipropylpyrrolidine, 2,4-dimethylpiperidine, 2,4-diethylpiperidine, 1-aminoethylpyrrolidine and the like can be mentioned.

From the viewpoint of improving the dispersibility of the conductive material, the content of the nitrogen-containing organic compound contained in the conductive material slurry or positive electrode paste is preferably 0.5 parts by mass or more, more preferably It is 1 part by mass or more, more preferably 5 parts by mass or more, and from the viewpoint of high conductivity, it is preferably 2000 parts by mass or less, more preferably 1000 parts by mass or less, and still more preferably 500 parts by mass or less. From the same viewpoint, the content of the nitrogen-containing organic compound contained in the conductive material slurry or the positive electrode paste is preferably 0.5 to 2000 parts by mass, more preferably 0.5 to 2000 parts by mass with respect to 100 parts by mass of the conductive material. is 1 to 1000 parts by mass, more preferably 5 to 500 parts by mass.

The conductive material slurry of the present disclosure may further contain other components as long as the effects of the present disclosure are not hindered. Other components include, for example, antioxidants, neutralizers, antifoaming agents, preservatives, dehydrating agents, rust preventives, plasticizers, etc. (hereinafter also referred to as additives).

[Method for producing conductive material slurry]
In one or more embodiments, the conductive material slurry of the present disclosure contains a conductive material, a dispersant, an organic solvent, and, if necessary, each component such as a binder, a nitrogen-containing organic compound, or an additive. , using a mixing and dispersing machine, and dispersing until the composition becomes uniform. In one aspect of the method for producing a conductive material slurry of the present disclosure, after dissolving a dispersant in an organic solvent to obtain a dispersant solution, adding a conductive material to the dispersant solution; and a step of subjecting the dispersant solution to dispersion treatment using a mixer disperser.

Examples of the mixing and dispersing machine include at least one selected from ultrasonic homogenizers, vibration mills, jet mills, ball mills, bead mills, sand mills, roll mills, homogenizers, high-pressure homogenizers, ultrasonic devices, attritors, desolvers, and paint shakers. seeds.

The dispersion treatment is preferably carried out while circulating, for example, discharging the coarse dispersion from the mixer-disperser and then re-injecting it into the mixer-disperser. The circulation is preferably 2 to 40 times, and the dispersion The discharge and injection rate of the liquid is preferably 10-60 g/min.

In the method for producing a conductive material slurry of the present disclosure, a part of the components of the conductive material slurry may be mixed and then mixed with the rest, or the entire amount of each component may be added at once. Alternatively, each may be added in multiple batches. The conductive material may be dried and mixed with other components, or may be mixed with a solvent and then mixed with other components. Examples of the solvent include the same organic solvents as described above. The binder is preferably dissolved in a solvent, ie, the binder solution is mixed with other components. Examples of the solvent include the same organic solvents as described above.

When preparing the conductive material slurry of the present disclosure containing a binder, a coarse dispersion containing a conductive material, a dispersant, an organic solvent, and, if necessary, a nitrogen-containing organic compound or an additive, etc. Preferably, the mixture containing the coarse dispersion and the binder solution is stirred with a mixer or the like, and then supplied to a mixing/dispersing machine.

The viscosity of the conductive material slurry of the present disclosure at 25° C. is preferably as low as possible, and from the viewpoint of improving handling during preparation of the positive electrode paste, it is preferably 90 Pa s or less, more preferably 70 Pa s or less, and even more preferably 60 Pa s. s or less.

<Battery positive electrode paste>
In one aspect, the present disclosure relates to a positive electrode paste for a battery comprising the conductive material slurry of the present disclosure and a positive electrode active material. By using the positive electrode paste for battery prepared using the conductive material slurry of the present disclosure, the dispersibility of CNTs in the positive electrode mixture layer is improved, so that the coating resistance of the positive electrode mixture layer can be reduced.

Further, in one aspect, the present disclosure is a battery positive electrode paste containing a positive electrode active material, a binder, a conductive material, a dispersant, and an organic solvent, wherein 50% by mass or more of the conductive material is carbon nanotubes and the dispersant is a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule, and the content of the vinyl alcohol units in the conductive material slurry is equal to the content of the carbon nanotubes of 100 mass. It relates to a positive electrode paste for batteries, which is 17.0 to 60.0 parts by mass per part.
The battery positive electrode paste of the present disclosure contains a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule as a dispersant, and the content of vinyl alcohol units in the battery positive electrode paste is equal to the content of carbon nanotubes. Since it is 17.0 to 60.0 parts by mass with respect to 100 parts by mass, the CNTs can be well dispersed in the battery positive electrode paste, and the coating film resistance of the positive electrode mixture layer can be reduced.

[Positive electrode active material]
As the positive electrode active material, any active _{material capable of} intercalating and deintercalating lithium and capable of _charge -discharge reaction may be used. _{LiNixMnyCozO2 ,} Li-rich type (Li _{( LixMe1 -x ) O2} (Me=Co, Ni, Mn _, etc.), _Ni -rich type ( _{LiNixCoyAlzO2 )} , etc. Examples include lithium metal composite oxides, and the positive electrode active material is used as a particulate matter, with an average particle size of, for example, 1 μm or more and 40 μm or less.

(Content of positive electrode active material in positive electrode paste)
The content of the positive electrode active material in the positive electrode paste of the present disclosure is preferably 80% by mass or more, more preferably 90% by mass or more, in terms of solid content, from the viewpoint of energy density and high capacity. From the viewpoint of improving the binding strength of the agent layer to the current collector, the content is preferably 99.5% by mass or less, more preferably 99% by mass or less. In the present application, the content of the positive electrode active material, the binder, the dispersant (polymer), and the conductive material in terms of solid content is the solid content of the positive electrode active material, the binder, the dispersant, and the conductive material. It is a value calculated assuming that the total is 100% by mass.

The content of the positive electrode active material in the positive electrode paste is expressed by the mass ratio to the vinyl alcohol unit in the positive electrode paste (positive electrode active material/vinyl alcohol unit) from the viewpoint of suppressing aggregation of the positive electrode active materials and the stability of the positive electrode paste. and is preferably 350 or more, more preferably 400 or more, and still more preferably 450 or more, and the positive electrode active material in the positive electrode mixture layer after solvent removal due to the positive electrode active material being covered with an excessive amount of dispersant. From the viewpoint of suppressing the aggregation of substances and suppressing the increase in the coating resistance of the positive electrode mixture layer, the content of the positive electrode active material in the positive electrode paste is the above-mentioned mass ratio (positive electrode active material/vinyl alcohol unit). Expressed as such, it is preferably 900 or less, more preferably 800 or less, and even more preferably 700 or less. Specifically, the content of the positive electrode active material in the positive electrode paste is preferably 350 to 900, more preferably 400 to 800, and still more preferably 450, in terms of the mass ratio (positive electrode active material/vinyl alcohol unit). ~700.

(Content of dispersant in positive electrode paste)
The content of the dispersant (polymer) in the positive electrode paste of the present disclosure is preferably 0.05% by mass or more, more preferably 0.10, in terms of solid content, from the viewpoint of reducing the resistance of the positive electrode mixture layer. % by mass or more, and preferably 1% by mass or less, more preferably 0.5% by mass or less, from the viewpoint of maintaining a high energy density of the battery. Specifically, the content of the dispersant (polymer) in the positive electrode paste of the present disclosure is preferably 0.05 to 1% by mass, more preferably 0.10 to 0.5% by mass.

(Content of conductive material in positive electrode paste)
The content of the conductive material in the positive electrode paste of the present disclosure is preferably 0.3% by mass or more, more preferably 0.5% by mass or more in terms of solid content, from the viewpoint of the conductivity of the positive electrode mixture layer, From the viewpoint of maintaining a high energy density of the battery, the content is preferably 2% by mass or less, more preferably 1% by mass or less. Specifically, the content of the conductive material in the positive electrode paste of the present disclosure is preferably 0.3 to 2% by mass, more preferably 0.5 to 1% by mass.

(Content of binder in positive electrode paste)
The content of the binder in the positive electrode paste of the present disclosure is preferably 0.5% by mass or more in terms of solid content, from the viewpoint of the coating properties of the positive electrode mixture layer and the binding property with the current collector. The content is more preferably 0.8% by mass or more, and from the viewpoint of maintaining a high energy density of the battery, it is preferably 1.5% by mass or less, more preferably 1.2% by mass or less. Specifically, the content of the binder in the positive electrode paste of the present disclosure is preferably 0.5 to 1.5% by mass, more preferably 0.8 to 1.2% by mass.

In addition, each of the positive electrode pastes of the present disclosure may further contain other components as long as the effects of the present disclosure are not hindered. Other components include, for example, antioxidants, neutralizers, antifoaming agents, preservatives, dehydrating agents, rust preventives, plasticizers and the like.

(Manufacturing method of positive electrode paste)
In one or more embodiments, the positive electrode paste of the present disclosure includes a positive electrode active material, a conductive material slurry of the present disclosure, a solvent (additional solvent) for adjusting the solid content, etc., and if necessary, a binder, etc. and stirring to produce. Each component may be mixed in any order. Examples of the solvent (additional solvent) include the same organic solvents as those described above, and among them, NMP is preferable. A planetary mixer, a bead mill, a jet mill, or the like can be used for mixing and stirring, and these can also be used in combination.

The positive paste of the present disclosure can also be prepared by premixing some of the total components used to make the positive paste and then mixing it with the remainder. Also, each component may be added in multiple batches instead of adding the entire amount at once. As a result, the mechanical load on the stirrer can be reduced. The solid content concentration of the positive electrode paste of the present disclosure can be adjusted according to the viscosity suitable for applying the positive electrode paste to the current collector. Alternatively, the components other than the positive electrode active material may be mixed and dispersed until they are homogenous, then the positive electrode active material may be added, and these may be stirred until they are homogeneous. A method for producing a positive electrode paste of the present disclosure, in one aspect, includes a step of adding and dispersing a positive electrode active material in the conductive slurry of the present disclosure. Further, in one aspect of the method for producing the positive electrode paste of the present disclosure, in the above step, a binder solution obtained by dissolving a binder in an organic solvent is added to the conductive slurry of the present disclosure, and these are mixed. Then, the positive electrode active material is added and dispersed.

<Positive electrode for battery>
In one aspect, the present disclosure relates to a positive electrode for a battery formed using the positive electrode paste of the present disclosure. A positive electrode for a battery of the present disclosure includes a current collector and a positive electrode mixture layer joined to the current collector, and the positive electrode mixture layer is formed using the positive electrode paste of the present disclosure. In the positive electrode for a battery formed using the positive electrode paste of the present disclosure, the coating film resistance of the positive electrode mixture layer is low because the dispersibility of CNTs in the positive electrode mixture layer is good.

The positive electrode paste of the present disclosure is applied, for example, to a current collector such as an aluminum foil, and dried to form a positive electrode mixture layer. In order to increase the density of the positive electrode, compaction can also be performed using a pressing machine. A die head, a comma reverse roll, a direct roll, a gravure roll, or the like can be used for coating the positive electrode paste. Drying after coating can be carried out by heating, air flow, infrared irradiation, etc. alone or in combination. The positive electrode can be pressed using a roll press machine or the like.

Further, in one aspect, the present disclosure is a positive electrode for a battery including a positive electrode mixture layer, the positive electrode mixture layer includes a positive electrode active material, a conductive material, a polymer, and a binder, 50% by mass or more of the conductive material is carbon nanotubes, the polymer contains 60 to 99% by mass of vinyl alcohol units in one molecule, and the content of the vinyl alcohol units in the positive electrode mixture layer is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of the carbon nanotube content. In the battery positive electrode of the present disclosure, the positive electrode mixture layer is formed using the positive electrode paste containing the polymer as a dispersant. The coating film resistance of the material layer is low.

The present invention will be described in more detail below with reference to Production Examples, Examples and Comparative Examples.

<Production of dispersant>
(Dispersant a1)
A reaction vessel equipped with a thermometer, a reflux condenser, a nitrogen gas inlet tube and a stirrer was charged with 100 parts of vinyl acetate as a polymerizable monomer, methanol as a solvent, and azobisisobutyronitrile as a polymerization initiator at 60°C. After the copolymerization reaction, unreacted monomers were removed under reduced pressure to obtain a resin solution. Next, a solution of sodium hydroxide in methanol was added to the resin solution to cause a saponification reaction, which was thoroughly washed and then dried with a hot air dryer. Finally, dispersant a1, which is a polyvinyl alcohol resin having a degree of polymerization of 200 and a degree of saponification of 99 mol % (vinyl alcohol unit; PV-OH 98.1 mass %) was obtained. 6 parts of the obtained dispersant a1 (solid content 6 parts) was added to 962 parts of N-methyl-2-pyrrolidone (NMP) heated to 80 ° C. and mixed to completely dissolve the dispersant a1. An NMP solution of a1 was obtained. At this time, the time required for complete dissolution was 6 hours. The time required for complete dissolution refers to the amount of undissolved matter visually observed in a state in which 962 parts of N-methyl-2-pyrrolidone (NMP) and 6 parts of dispersant a1 are mixed and heated to 80°C. The time until the existence of a certain aggregate disappeared.

Dispersants a2 to a9 shown in Table 1 were prepared by controlling the copolymerization reaction time and saponification reaction described in (dispersant a1) above. Table 2 shows the time required for complete dissolution of the resulting dispersant in NMP.

<Preparation of CNT slurry>
As an example of the conductive material slurry, the following CNT slurries A1 to A13 were prepared by the following method.

(CNT slurry A1)
Multi-walled carbon nanotubes (MWCNT, average diameter 12 nm, average length 40 um) as fibrous carbon nanostructures were added to 100 g (solid content 0.624 g) of NMP solution of dispersant a1 (vinyl alcohol unit 98.1% by mass). 2 g was added to obtain a crude dispersion. Then, the coarse dispersion containing MWCNT and dispersant a1 is filled into a high-pressure homogenizer (product name “BERYU MINI” manufactured by Mitsuku Co., Ltd.) having a multi-stage pressure control device (multi-stage pressure reducer) that applies back pressure during dispersion. Then, the coarse dispersion was subjected to dispersion treatment at a pressure of 100 MPa. Specifically, while applying a back pressure, a shearing force was applied to the coarse dispersion to disperse the MWCNTs, thereby obtaining a CNT slurry A1 as a fibrous carbon nanostructure dispersion. The dispersion treatment was performed while circulating the dispersion by discharging it from the high-pressure homogenizer and then injecting it into the high-pressure homogenizer again. This circulation was repeated 20 times, and the discharge and injection rate of the dispersion was 30 g/min. The content of vinyl alcohol units in the CNT slurry A1 was 30.6 parts per 100 parts of the CNT content.

(CNT slurry A2 to A5, A7, A8, A11, A12)
CNT slurries A2 to A5, A7, A8, A11, and A12 were each prepared in the same manner as the preparation of CNT slurry A1 so as to have the compositions shown in Table 2.

(CNT slurry A6)
CNT slurry A6 was prepared in the same manner as in the preparation of CNT slurry A1, except that dispersant a5 was used as a dispersant and the amount of multi-walled carbon nanotubes MWCNT (average diameter 12 nm, average length 40 um) added was changed to 1 g. prepared.

(CNT slurry A9)
2 g of multi-walled carbon nanotubes MWCNT (average diameter 12 nm, average length 40 um) as fibrous carbon nanostructures were added to 100 g (solid content 0.624 g) of NMP solution of dispersant a3 (vinyl alcohol unit 87.0% by mass). , 2-amino-1,3, which is a nitrogen-containing organic compound, and 0.3 g of propanediol were added to obtain a crude dispersion. Then, a coarse dispersion containing MWCNTs, a dispersant a3, and a nitrogen-containing organic compound was subjected to dispersion treatment under the same conditions as the preparation of (CNT slurry A1) to prepare CNT slurry A9.

(CNT slurry A10)
0.64 g of dispersant a3 (vinyl alcohol unit: 87.0% by weight) was added to 94.3 g of N-methyl-2-pyrrolidone heated to 80° C. and mixed to completely dissolve dispersant a3. After cooling to room temperature, 3.4 g of PVDF powder (KF Polymer L#7200, manufactured by Kureha Co., Ltd.) was added, followed by stirring for 5 minutes with a rotation/revolution mixer (AR-100, manufactured by Thinky Co., Ltd.). Further, 2.1 g of multi-walled carbon nanotubes MWCNT (average diameter 12 nm, average length 40 um) as a fibrous carbon nanostructure were added to obtain a coarse dispersion. Thereafter, dispersion treatment was performed under the same conditions as the preparation of (CNT slurry A1) to prepare CNT slurry A10. The content of PVDF (binder) with respect to 100 parts by mass of vinyl alcohol units in the CNT slurry A10 was 611 parts by mass.

(CNT slurry A13)
10 g of MWCNT (average diameter: 12 nm, average length: 40 um) as a fibrous carbon nanostructure was added to 190 g of NMP solution of dispersant a6 (solid content: 2 g) to obtain a crude dispersion. Then, the coarse dispersion containing MWCNTs and dispersant a6 was subjected to dispersion treatment under the same conditions as the preparation of (CNT slurry A1) to prepare CNT slurry A13.

[Viscosity measurement]
The viscosities of the CNT slurries A1 to A13 (25° C.) produced as described above were measured. Specifically, an MCR302 rheometer from Anton Paar was equipped with a parallel plate PP50, the shear rate was set in the range of 0.1 to 1000 (1/s), and the CNT slurry at a shear rate of 1 (1/s) The viscosities are listed in Table 2.

[Particle size measurement]
Each of the CNT slurries A1 to A13 prepared as described above was diluted 500-fold with NMP. Each of them was placed in a glass cell as an object to be measured, and the cell was attached to ZETASIZER Nano-S manufactured by Malvern Panalytical, and the particle size of CNT was measured when the temperature of the object to be measured was 20°C.

[Preparation of positive electrode paste]
(Preparation of positive electrode pastes B1 to B9, B11, and B12)
7.5 g of CNT slurries A1 to A9, A11, and A12, 4.3 g of NMP, and 3.0 g of PVDF (8%) NMP solution (KF Polymer L #7208, manufactured by Kureha Co., Ltd.) were weighed into a 50 ml sample bottle. , stirred evenly with a spatula. After that, 24.0 g of LCO (lithium cobaltate, manufactured by Nippon Kagaku Kogyo Co., Ltd., Cellseed C-8hV) was added as a positive electrode active material, and the mixture was stirred again with a spatula until uniform. Further, the mixture was stirred for 5 minutes using a rotation/revolution mixer (AR-100, manufactured by Thinky Co., Ltd.) to obtain positive electrode pastes B1 to B9, B11, and B12.

(Preparation of positive electrode paste B10)
7.5 g of CNT slurry A10 and 4.3 g of NMP were weighed into a 50 ml sample bottle and uniformly stirred with a spatula. After that, 24.0 g of LCO (lithium cobaltate, manufactured by Nippon Kagaku Kogyo Co., Ltd., Cellseed C-8hV) was added as a positive electrode active material, and the mixture was stirred again with a spatula until uniform. Further, the mixture was stirred for 5 minutes with a rotation/revolution mixer (AR-100 manufactured by Thinky Co., Ltd.) to obtain positive electrode paste B10.

(Preparation of positive electrode paste B13)
1.24 g of CNT slurry A13, 5 g of NMP, and 3.8 g of PVDF (8%) NMP solution (KF Polymer L#7208, manufactured by Kureha Co., Ltd.) were weighed into a 50 ml sample bottle and uniformly stirred with a spatula. After that, 24.0 g of LCO (lithium cobaltate, manufactured by Nippon Kagaku Kogyo Co., Ltd., Cellseed C-8hV) was added as a positive electrode active material, and the mixture was stirred again with a spatula until uniform. Further, the mixture was stirred for 5 minutes with a rotation/revolution mixer (AR-100 manufactured by Thinky Co., Ltd.) to obtain positive electrode paste B13.

The contents (% by mass) of the positive electrode active material, the binder (PVDF), the dispersant (polymer), and the conductive material (CNT) in the positive electrode pastes B1 to B13 are as follows in terms of solid content.

(Mass ratio)
Positive electrode paste B1 to B5, B7 to B9, B11, B12 (solid content concentration: 63% by mass)
Positive electrode active material: binder: dispersant: conductive material = 98.23: 0.98: 0.19: 0.60
Positive electrode paste B6 (solid content concentration: 63% by mass)
Positive electrode active material: binder: dispersant: conductive material = 98.52: 0.99: 0.19: 0.30
Positive electrode paste B10 (solid content concentration: 68% by mass)
Positive electrode active material: binder: dispersant: conductive material = 98.21: 0.99: 0.19: 0.61
Positive electrode paste B13 (solid content concentration: 72% by mass)
Positive electrode active material: binder: dispersant: conductive material = 98.45: 1.25: 0.05: 0.25

[Measurement of coating film resistance value of positive electrode mixture layer]
The positive electrode paste prepared according to the above [Preparation of positive electrode paste] was dripped onto a polyester film and uniformly coated with an applicator of 100 μm. The coated polyester film was dried at 100° C. for 1 hour to obtain a 40 μm-thick positive electrode mixture layer. The coating film resistance was measured at a threshold voltage of 10 V using a Loresta-GP (manufactured by Mitsubishi Chemical Analytech Co., Ltd.) equipped with a PSP probe. The results are shown in Table 2.

As shown in Table 2, a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule is included as a dispersant, and the content of vinyl alcohol units in the conductive material slurry is equal to the content of 100 parts by mass of CNT. On the other hand, when it was 17.0 to 60.0 parts by mass, the viscosity of the conductive material slurry was remarkably low, and the dispersibility of CNTs was good. As can be seen from the comparison between Example 3 and Example 9 in Table 2, when the conductive material slurry contains a nitrogen-containing organic compound, the viscosity of the conductive material slurry is further lowered, and the CNTs are dispersed. further improved.

As shown in Table 2, Examples 2 to 4, in which the content of vinyl alcohol units in one molecule in the polymer was 83 to 92% by mass, were lower in productivity than Examples 1 and 5 to 8. , the dispersibility of CNT, and the balance of coating film resistance.

The conductive material slurry of the present disclosure has good CNT dispersibility, and as a result, the viscosity of the conductive material slurry can be reduced. Further, if the conductive material slurry of the present disclosure is used for preparing the positive electrode paste, the viscosity of the positive electrode paste is also low, which can contribute to the reduction of the resistance of the positive electrode coating film.

Claims (12)

A conductive material slurry containing a conductive material, a dispersant and an organic solvent,
50% by mass or more of the conductive material is carbon nanotubes,
The dispersant is a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule,
The conductive material slurry, wherein the content of the vinyl alcohol unit in the conductive material slurry is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of the content of the carbon nanotubes. further containing a binder,
2. The conductive material slurry according to claim 1, wherein the content of said binder in said conductive material slurry is 150 to 700 parts by mass with respect to 100 parts by mass of said vinyl alcohol unit content. 3. The conductive material slurry according to claim 1, further comprising a nitrogen-containing organic compound. The conductive material slurry according to any one of claims 1 to 3, wherein the polymer contains 83 to 92% by mass of vinyl alcohol units in one molecule. A battery positive electrode paste containing a positive electrode active material, a binder, a conductive material, a dispersant and an organic solvent,
50% by mass or more of the conductive material is carbon nanotubes,
The dispersant is a polymer containing 60 to 99% by mass of vinyl alcohol units in one molecule,
The positive electrode paste for battery, wherein the content of the vinyl alcohol unit in the conductive material slurry is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of the content of the carbon nanotubes. 6. The positive electrode paste for battery according to claim 5, wherein the content of said binder in said positive electrode paste for battery is 150 to 700 parts by mass with respect to 100 parts by mass of said vinyl alcohol unit content. 7. The battery positive electrode paste according to claim 5, wherein the mass ratio of said positive electrode active material to said vinyl alcohol units in said battery positive electrode ( said positive electrode active material/vinyl alcohol units) is 350-900. The battery positive electrode paste according to any one of claims 5 to 7, further comprising a nitrogen-containing organic compound. The battery positive electrode paste according to any one of claims 5 to 8, wherein the polymer contains 83 to 92% by mass of vinyl alcohol units in one molecule. A positive electrode for a battery comprising a positive electrode mixture layer,
The positive electrode mixture layer includes a positive electrode active material, a conductive material, a polymer, and a binder,
50% by mass or more of the conductive material is carbon nanotubes,
The polymer contains 60 to 99% by mass of vinyl alcohol units in one molecule,
The positive electrode for a battery, wherein the content of the vinyl alcohol unit in the positive electrode mixture layer is 17.0 to 60.0 parts by mass with respect to 100 parts by mass of the carbon nanotubes. 11. The positive electrode for battery according to claim 10, wherein the content of said binder in said positive electrode for battery is 150 to 700 parts by mass with respect to 100 parts by mass of said vinyl alcohol unit content. 12. The positive electrode for battery according to claim 10, wherein the mass ratio of said positive electrode active material to said vinyl alcohol unit in said positive electrode for battery (said positive electrode active material/vinyl alcohol unit) is 350-900.