Carbon material dispersion liquid, and slurry composition for negative electrode for secondary battery using same

Abstract

Provided is a carbon material dispersion which does not adversely affect other compounding components, is effective on a wide range of microorganisms such as bacteria, molds, and yeasts, and can maintain a high preservative / antibacterial effect and persistence thereof over a long period of time in any environment even if a small amount of the carbon material dispersion is used. Thus, dispersibility and storage stability can be highly considered. Also provided is a slurry composition for a negative electrode for a secondary battery, which uses the dispersion liquid, and which is suitable for the production of a battery / electrode such as a lithium ion battery. This carbon material dispersion liquid contains at least a carbon material containing carbon nanotubes, a dispersant, a preservative, and a liquid medium, and is characterized in that the preservative contains a triazine compound and at least one substance selected from the group A described below. Group A: an iodo-propargyl compound, a pyridine compound, a pyrithione compound, a hydroxyquinoline compound, a benzothiazole compound, an isothiazoline compound, and a dithiol compound.

Description

Technical Field

[0001] The present specification relates to a carbon material dispersion liquid, which can prevent the growth of bacteria, molds, etc. and improve dispersibility and storage stability; it also relates to a slurry composition for negative electrode for secondary battery using the carbon material dispersion liquid, which is suitable for the manufacture of electrodes / batteries such as lithium ion batteries. Background Art

[0002] In recent years, secondary batteries have been widely used in various fields such as electric vehicles, power storage, and information equipment. By including a dispersion of carbon nanotubes in the electrode material of the secondary battery and using it for the electrode of the secondary battery, etc., it is possible to achieve good conductivity, reduce electrode resistance, and effectively form a conductive network with a small amount. Therefore, various schemes have been proposed. In addition, the electrode of the secondary battery is manufactured by coating a slurry for forming an electrode layer containing a dispersion of carbon nanotubes, a conductive material, an active material, a binder, etc. on a collector plate.

[0003] For example, Patent Document 1 discloses a slurry for a negative electrode mixture slurry of a non-aqueous electrolyte secondary battery, which is prepared by dispersing surface-modified natural graphite as an active material, a carbon nanotube dispersion, carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) as a binder in water.

[0004] In the case of such a water-based slurry, there is a problem that corrosion or mold may occur during long-term storage due to factors such as the passage of time and the storage environment.

[0005] Therefore, the following schemes have been proposed as preservatives and bactericides for aqueous slurries: 1) a scheme using acids, salts, isothiazolin-based preservatives, alcohols, etc. (for example, refer to Patent Document 2); 2) a scheme using alcohols, chlorine-containing compounds, acids, alkalis, nitrogen-containing organic sulfur compounds, etc. (for example, refer to Patent Document 3); 3) a scheme using isothiazolin compounds (CIT, MIT, OIT, BIT) and further using them in combination with pyrithione compounds (for example, refer to Patent Document 4), etc.

[0006] However, the current situation is that even if the preservatives, fungicides, etc. described in these patent documents 2 to 4 are used, there are still problems such as the occasional generation of mold or bacteria depending on the type of carbon nanotubes, carbon materials, and blending components used, as well as the influence of factors such as the manufacturing environment and storage environment, and poor dispersibility and storage stability.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2015-195143 (patent claims and examples, etc.)

[0010] Patent Document 2: International Publication No. 2015 / 16283 (patent claims and embodiments, etc.)

[0011] Patent Document 3: Japanese Patent Application Publication No. 2011-181195 (patent claims and examples, etc.)

[0012] Patent Document 4: International Publication No. 2012 / 26462 (patent claims and embodiments, etc.) Summary of the invention

[0013] Problem that the invention aims to solve

[0014] The present disclosure is completed in order to solve the above-mentioned existing problems, etc., and its purpose is to provide a carbon material dispersion liquid that can prevent the growth of bacteria, molds, etc. and thus improve dispersibility and storage stability; and to provide a slurry composition for negative electrode for secondary battery using the carbon material dispersion liquid, which is suitable for the manufacture of electrodes / batteries such as lithium ion batteries.

[0015] Solutions for solving problems

[0016] The present inventors have conducted in-depth research on the above-mentioned existing problems, and as a result, found that by preparing a carbon material dispersion containing at least a carbon material containing carbon nanotubes, a dispersant, a specific preservative and a liquid medium, the above-mentioned target carbon material dispersion can be obtained, and a slurry composition for a negative electrode for a secondary battery suitable for manufacturing a battery / electrode such as a lithium ion battery using the dispersion can be obtained, thereby completing the present disclosure.

[0017] That is, the carbon material dispersion of the present disclosure is characterized in that it contains at least a carbon material including carbon nanotubes, a dispersant, a preservative, and a liquid medium, wherein the preservative contains a triazine compound and at least one selected from the following Group A.

[0018] Group A: organic sulfur compounds, organic nitrogen sulfur compounds, organic halogen compounds, haloallyl sulfone compounds, iodopropargyl compounds, N-haloalkylthio compounds, nitrile compounds, pyridine compounds, pyridinethione compounds, 8-hydroxyquinoline compounds, benzothiazole compounds, isothiazolin compounds, dithiol compounds, pyridine oxide compounds, nitropropane compounds, organic tin compounds, phenol compounds, quaternary ammonium salt compounds, thiazine compounds, aniline compounds, adamantane compounds, dithiocarbamate compounds, indanone bromide compounds, benzyl bromoacetate compounds, and inorganic salt compounds.

[0019] Preferably, the content of the triazine compound is 0.001 to 0.2% by mass based on the total amount of the dispersion, and the total content of the preservative is 0.3% by mass or less based on the total amount of the dispersion.

[0020] Preferably, the preservative is selected from the group consisting of Fusarium, Cellulomonas, Delftia, Cupriavidus, Rhizobium (formerly known as Agrobacterium radiobacter), Micrococcus, Stomatococcus, Planococcus, Staphylococcus, Deinococcus, Streptococcus, Leuconostoc, Pediococcus, Aerococcus, Gemella, Peptococcus, Peptostreptococcus, and Streptococcus. At least one of the genera Bacillus, Bacillus, Sporolactobacillus, Clostridium, Desulfotomaculum, Sporosarcina, Oscillospira, Lactobacillus, and Listeria shows an antiseptic effect.

[0021] The slurry composition for secondary battery negative electrodes disclosed in the present invention is characterized by containing at least the carbon material dispersion having the above composition.

[0022] Effects of the Invention

[0023] According to the present disclosure, a carbon material dispersion liquid can be provided that can prevent the growth of bacteria, molds, etc. and thus improve dispersibility and storage stability; and a slurry composition for secondary battery negative electrode using the carbon material dispersion liquid can be provided, which is suitable for the production of electrodes / batteries such as lithium ion batteries.

[0024] The objects and effects of the present disclosure are realized and attained by using the constituent elements and combinations particularly pointed out in the claims.Both the above general description and the following detailed description are exemplary and explanatory and do not limit the present disclosure described in the claims. DETAILED DESCRIPTION

[0025] The following describes the embodiments of the present disclosure in detail. However, the scope of protection of the present disclosure is not limited to the embodiments described in detail below, and it should be noted that it involves the inventions and their equivalents recorded in the claims. In addition, the present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field (including conventional technical selection and obvious features).

[0026] The carbon material dispersion disclosed herein is characterized in that it contains at least a carbon material including carbon nanotubes, a dispersant, a preservative, and a liquid medium, wherein the preservative contains a triazine compound and at least one selected from the following Group A.

[0027] Group A: organic sulfur compounds, organic nitrogen sulfur compounds, organic halogen compounds, haloallyl sulfone compounds, iodopropargyl compounds, N-haloalkylthio compounds, nitrile compounds, pyridine compounds, pyridinethione compounds, 8-hydroxyquinoline compounds, benzothiazole compounds, isothiazolin compounds, dithiol compounds, pyridine oxide compounds, nitropropane compounds, organic tin compounds, phenol compounds, quaternary ammonium salt compounds, thiazine compounds, aniline compounds, adamantane compounds, dithiocarbamate compounds, indanone bromide compounds, benzyl bromoacetate compounds, and inorganic salt compounds.

[0028] 〈Carbon Nanotube (CNT)〉

[0029] The carbon nanotubes (CNTs) used in the present invention are not particularly limited as long as they have a shape in which one surface of graphite is essentially rolled into a tube. Single-layer CNTs in which one surface of graphite is rolled into a single layer can be used, and multilayer CNTs in which two or three or more layers are rolled into multiple layers can also be used.

[0030] In addition, examples of carbon nanotube forms include graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers, but are not limited to these and may be any one of these or a combination of two or more (hereinafter referred to as "at least one").

[0031] Furthermore, from the viewpoints of the viscosity, conductivity and stability of the dispersion, the average outer diameter of the carbon nanotubes is preferably 1 nm to 90 nm, more preferably 3 nm to 30 nm, and even more preferably 3 nm to 15 nm.

[0032] In the present disclosure, the average outer diameter of carbon nanotubes refers to the arithmetic mean of a sufficient number of n outer shapes measured using an image at a magnification of 100,000 or more using a transmission electron microscope.

[0033] The purity of the carbon nanotubes used in the present disclosure is preferably 90 to 100 mass %, particularly preferably 95 to 100 mass %. The purity of the carbon nanotubes is calculated based on the amount of impurities, with ash measured in accordance with JIS K 1469 and JIS K 6218 as impurities.

[0034] Specific examples of carbon nanotubes (CNTs) that can be used include NC7000 (average outer diameter 10 nm) manufactured by Nanocyl, Baytubes C150P (average outer diameter 11 nm) manufactured by Bayer, FloTube9000 (average outer diameter 19 nm), FloTube7320 (average outer diameter 9 nm), FloTube7010 (average outer diameter 9 nm), FloTube6810 (average outer diameter 8 nm), FloTube6120 (average outer diameter 8 nm), FloTube6100 (average outer diameter 8 nm), FloTube2020 (average outer diameter 4 nm) manufactured by Cnano, MEIJOeDIPS EC2.0 (average outer diameter 2.0 nm) manufactured by MEIJO NANO CARBON, KORBON-A7 (average outer diameter 1.2 nm) manufactured by KOATSU GAS KOGYO CO., LTD., NFT-7 (average outer diameter 30 nm), KOATSU At least one of NFT-15 (average outer diameter 30 nm) manufactured by GAS KOGYO CO., LTD., and the like.

[0035] The content of these carbon nanotubes (CNT) can be set to a suitable content, and is not particularly limited. Preferably, from the aspect of both high stability and conductive performance, and from the aspect of preferred coating liquid viscosity, its content is preferably 0.1 to 15.0 mass %, more preferably 0.1 to 10.0 mass %, more preferably 0.1 to 8.0 mass %, 0.1 to 6.0 mass %, and particularly 0.1 to 5.0 mass % relative to the total amount of the dispersion.

[0036] When the content of the carbon nanotubes (CNT) is 0.1% by mass or more, sufficient conductivity can be ensured, whereas when the content is 15.0% by mass or less, stability of the coating liquid and good conductivity can be ensured.

[0037] 〈Carbon Materials〉

[0038] Examples of carbon materials other than the carbon nanotubes (CNTs) include graphene, graphite, and carbon particles such as carbon black such as acetylene black and Ketjen black, which may be used alone or in combination.

[0039] The shape of these carbon particles is not particularly limited, and may be, for example, flat, array-like, spherical, or the like.

[0040] The average particle size of these carbon particles can be more than 100nm, more than 200nm, more than 300nm, more than 500nm, more than 700nm, more than 1μm, more than 2μm or more than 3μm, or can be less than 20μm, less than 15μm, less than 10μm or less than 7μm. Here, the average particle size used in this specification is appropriately selected according to the size of the carbon particles to be targeted. In the case of particles approximately less than 1μm, the particle size is the value of the histogram average particle size (D50) of the scattering intensity distribution measured by the dynamic light scattering method, and in the case of particles greater than 1μm, it is the value of the median particle size (D50) calculated based on the volume basis in the laser diffraction method. The determination based on the dynamic light scattering method can be carried out using, for example, DelsaMax CORE (BeckmanCoulter). The determination based on the laser diffraction method can be carried out using, for example, a particle size distribution measuring device MT3300II (MicrotracBEL).

[0041] The content of these carbon particles can be set to a suitable content without particular limitation. Preferably, from the aspect of both high stability and conductive performance and from the aspect of preferred coating liquid viscosity, the content is preferably 0.1 to 15.0% by mass relative to the total amount of the dispersion, more preferably 0.1 to 10.0% by mass, more preferably 0.1 to 8.0% by mass, 0.1 to 6.0% by mass, and particularly 0.1 to 5.0% by mass is ideal.

[0042] (Dispersant)

[0043] The dispersant used in the present disclosure is a component that significantly improves the dispersibility of the above-mentioned carbon material containing carbon nanotubes, and examples thereof include at least one of carboxymethyl cellulose (CMC) or its salts (sodium salt, ammonium salt), cellulose nanofibers (CeNF), anionic, cationic, nonionic and amphoteric dispersants, polymer dispersants, etc.

[0044] Examples of carboxymethyl cellulose (CMC) include a combination of a cellulose having a mass average molecular weight of 300,000 or less and a cellulose having a mass average molecular weight of 1 to 3,000,000. Examples of cellulose nanofibers (CeNF) include a cellulose having a crystallinity of 70% or less when measured by X-ray diffraction.

[0045] As the anionic dispersant, for example, acrylic resins such as styrene acrylic resins, polyurethane resins, polyester resins, polyvinyl chloride resins, and epoxy resins can be used.

[0046] The crystallinity of cellulose is the cellulose I type crystallinity calculated by the Segal method based on the diffraction intensity value obtained by X-ray diffraction method and can be obtained by the following formula (1).

[0047] Cellulose I type crystallinity (%) = (I 22.6 -I 18.5 ) / I 22.6 〕×100……(1)

[0048] In the above formula (1), I 22.6 It represents the diffraction intensity of the lattice (002 plane) (diffraction angle 2θ = 22.6°) in X-ray diffraction, I 18.5 It represents the diffraction intensity of the amorphous part (diffraction angle 2θ=18.5°). It should be noted that type I cellulose refers to the crystal form of natural cellulose, and type I crystallinity of cellulose refers to the proportion of the amount of crystalline regions in the entire cellulose.

[0049] The content of these dispersants can be set to a suitable content, and is not particularly limited. For example, when used in secondary battery electrode pastes, secondary battery electrodes, etc., from the perspective of both high stability and conductive performance, and from the perspective of viscosity when manufacturing the dispersion, its content is preferably 0.01 to 10% by mass relative to the total amount of the dispersion, more preferably 0.05 to 5% by mass, and more preferably 0.1 to 1% by mass is ideal.

[0050] (preservative)

[0051] The preservative used in the present invention is a triazine compound and at least one preservative selected from the following Group A. By using this selective combination type, the antibacterial spectrum can be applied over a wide range (effective against a wide range of microorganisms such as bacteria, molds, yeasts, etc.), and even when used in small amounts, a high preservative / antibacterial effect and its sustainability can be maintained for a long time. Even depending on the type of carbon nanotubes, carbon materials, type of compounding components, etc., as well as the manufacturing environment, storage environment, etc., including the combination of these factors, the reproduction of molds, bacteria, yeasts, etc. can be effectively prevented, thereby obtaining a carbon material dispersion that can highly balance dispersibility and storage stability.

[0052] Group A: organic sulfur compounds, organic nitrogen sulfur compounds, organic halogen compounds, haloallyl sulfone compounds, iodopropargyl compounds, N-halogenated alkylthio compounds, nitrile compounds, pyridine compounds, pyridinethione compounds, 8-hydroxyquinoline compounds, benzothiazole compounds, isothiazolin compounds, dithiol compounds, pyridine oxide compounds, nitropropane compounds, organic tin compounds, phenol compounds, quaternary ammonium salt compounds, thiazine compounds, aniline compounds, adamantane compounds, dithiocarbamate compounds, indanone bromide compounds, benzyl bromoacetate compounds, inorganic salt compounds, ethanol, isopropanol, propanol, sec-butanol, tert-butanol, phenoxyethanol, benzalkonium chloride.

[0053] The triazine compound used is a nitrogen-containing six-membered ring compound, and examples thereof include 2,4-bis(N,N'-dipropylamino)-6-chloro-1,3,5-triazine, 2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine, 2,4-diethyl-6-octylamino-1,3,5-triazine, hexahydro-1,3,5-triethyl-s-triazine, hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine, hexahydro-1,3,5-tris(2-hydroxyethyl)-1,3,5-triazine and other hexahydro-1,3,5-trisubstituted-s-triazine compounds, n-caprinoguanamine, 5-ethylhexylaminoguanamine, and the like. Commercially available products may be used.

[0054] Examples of the organic halogen compounds in the above group A include sodium pentachlorophenol. Specific examples of the pyridine oxide compounds include sodium 2-pyridinethiol-1-oxide. Examples of the isothiazolin-based compounds include 1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one, 5-chloro-2-methyl-4-isothiazolin-3-one magnesium chloride, 5-chloro-2-methyl-4-isothiazolin-3-one calcium chloride, and 2-methyl-4-isothiazolin-3-one calcium chloride. Examples of the pyridinethione-based compounds include sodium 1-oxo-1λ(5)-pyridine-2-thiol (sodium pyridinethione), zinc pyridinethione, copper pyridinethione, and pyridinethione chitosan. Commercially available products may be used.

[0055] In the above-mentioned Group A, examples of effective combinations with triazine compounds include organic sulfur compounds, organic nitrogen sulfur compounds, organic halogen compounds, and pyridinethione compounds. More preferred are combinations of triazine compounds and pyridinethione compounds, and combinations of triazine compounds and organic nitrogen sulfur compounds. In particular, a combination of a triazine compound and a pyridinethione compound in combination with a nitrogen-containing six-membered ring compound is ideal.

[0056] The content of the triazine compound is preferably 0.001 to 0.2% by mass, more preferably 0.005 to 0.1% by mass, based on the total amount of the dispersion. The total content of the preservative including the group A is preferably 0.3% by mass or less, more preferably 0.005 to 0.2% by mass, based on the total amount of the dispersion. This allows the dispersion to have a broad antimicrobial spectrum (effective against a broad range of microorganisms such as bacteria, molds, and yeasts) without adversely affecting other compounding components. In addition, even when the amount used is small, a high antiseptic / antimicrobial effect and its sustainability can be maintained for a long period of time. Even depending on the type of compounding components of the dispersion, the production environment, the storage environment, and the combination of these factors, the growth of molds, fungi, yeasts, etc. can be effectively prevented, thereby enabling a carbon material dispersion that can achieve both high dispersibility and storage stability.

[0057] In the present disclosure, the triazine compound and at least one preservative selected from the group A can effectively prevent the growth of targeted microorganisms such as bacteria, molds, yeasts, etc. in the carbon material dispersion, that is, the growth of a wide range of molds, fungi, yeasts, etc., and especially when used in a small amount, can also be selected from Fusarium, Cellulomonas, Delftia, Cupriavidus, Rhizobium (formerly known as Agrobacterium) for a long time. radiobacter), Micrococcus, Stomatococcus, Planococcus, Staphylococcus, Deinococcus, Streptococcus, Leuconostoc, Pediococcus, Aerococcus, Gemella, Peptococcus, Peptostreptococcus, The antiseptic / antimicrobial effect of at least one microorganism of the genus Sphaerocephalus, the genus Ruminococcus, the genus Coprococcus, the genus Sarcina, the genus Bacillus, the genus Sporolactobacillus, the genus Clostridium, the genus Desulfotomaculum, the genus Sporosarcina, the genus Oscillospira, the genus Lactobacillus, and the genus Listeria is particularly excellent.

[0058] The liquid medium used in the present disclosure is water (eg, purified water, distilled water, pure water, ultrapure water, tap water, ion-exchanged water, etc.), and in addition to water, a water-soluble solvent may be used as needed.

[0059] Examples of the water-soluble solvent that can be used include ethylene glycol, triethylene glycol, tetraethylene glycol, propylene glycol, dipropylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butylene glycol, 2,3-butylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 1,2-pentanediol, 1,5-pentanediol, 2,5-hexanediol, 3-methyl-1,3-butylene glycol, 2-methyl-2,4-pentanediol, 3- At least one of alkylene glycols such as methyl-1,3,5-pentanetriol and 1,2,3-hexanetriol, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, glycerols such as glycerol, dipropylene glycol and tripropylene glycol, lower alkyl ethers of glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether and diethylene glycol mono-n-butyl ether, N-methyl-2-pyrrolidone and 1,3-dimethyl-2-imidazolidinone.

[0060] Furthermore, water-soluble solvents such as amides such as dimethylformamide and dimethylacetamide and ketones such as acetone may be mixed.

[0061] The content of these water-soluble solvents varies depending on the solid content of the dispersion, and is preferably 0.1 to 7% by mass relative to the total amount of the dispersion, more preferably less than 10% by mass, and further preferably 0.1 to 5% by mass, from the perspective of improving the mixing properties of the slurry and the drying properties.

[0062] The carbon material dispersion of the present disclosure may contain additives suitable for its application, such as anti-settling agents, wetting agents, emulsifiers, anti-dripping agents, defoaming agents, leveling agents, plasticizers, and the like.

[0063] The carbon material dispersion of the present disclosure can be produced by, for example, adding at least a carbon material including carbon nanotubes, a dispersant, a preservative, and a liquid medium (water) and stirring / mixing the mixture, followed by a dispersion step.

[0064] The dispersion treatment of the above-mentioned dispersion liquid can be carried out using, for example, mixers such as ultrasonic dispersers, dispersers, homomixers, rotation and revolution mixers, Henschel mixers, planetary mixers, (high-pressure) homogenizers, paint conditioners, colloid mills, bead mills, cone mills, ball mills, sand mills, attritors, pearl mills, annular gap ball mills and other media-type dispersers, wet jet mills, thin film rotary high-speed mixers and other media-free dispersers, and roller mills and other dispersing devices, but are not limited to these.

[0065] As a preferable dispersion apparatus, a thin film rotating high-speed mixer, a bead mill, etc. are preferable from the viewpoint of stability and dispersion efficiency.

[0066] In addition, from the perspective of obtaining the fluidity of the electrode slurry prepared by adding it, the carbon material dispersion disclosed in the present invention is ideally a carbon material dispersion having a viscosity value (mPa·s) of 5 to 700, and more preferably 5 to 200, at 25°C at a rotation speed of 10 rpm using an E-type rotational viscometer [TV-25 (manufactured by Toki Sangyo Co., Ltd.) rotor (1°34'×R24mm)].

[0067] The carbon material dispersion of the present invention thus constituted can apply a wide range of antimicrobial spectrum (effective against a wide range of microorganisms such as bacteria, molds, yeasts, etc., especially the above-mentioned Fusarium genus to Listeria genus, etc.) without adversely affecting other compounding components, and can maintain high antiseptic / antimicrobial effects and their sustainability for a long time even when used in a small amount. Even depending on the types of compounding components of the dispersion, the manufacturing environment, the storage environment, etc., including the combination of these factors, the growth of molds, fungi, yeasts, etc. can be effectively prevented, thereby making it possible to prepare a carbon material dispersion that can highly balance dispersibility and storage stability. Therefore, when the dispersion is used for electrode manufacturing, etc., it is possible to balance high stability and conductive performance without adversely affecting Li + The carbon nanotubes and the like are uniformly dispersed without adversely affecting the ingress and egress of plasma or the reduction in the resistance value of the electrode, and the dispersion stability is excellent.

[0068] By using the carbon material dispersion for negative electrodes of batteries such as lithium-ion batteries, an electrode composition suitable for manufacturing battery electrodes of high-efficiency lithium-ion batteries, etc. is obtained, which can evenly distribute the conductive agent and active material when coating to form the electrode, and has no adverse effects on the resistance value of the electrode itself while highly maintaining the cycle characteristics and self-discharge characteristics.

[0069] This carbon material dispersion has excellent properties not previously available, and therefore can be used as electrode slurry, positive electrode slurry, negative electrode slurry, etc. suitable for secondary batteries such as lithium ion batteries by further adding various components.

[0070] <Slurry composition for negative electrode for secondary battery of the present disclosure>

[0071] The slurry composition for negative electrode of secondary battery disclosed in the present invention is characterized in that it contains at least a carbon material dispersion of the above-mentioned composition, and preferably can be prepared using appropriate amounts of negative electrode active material, binder component, and carbon particles that become the above-mentioned conductive agent as required, dispersant, preservative (a combination of triazine compound and group A), liquid medium, etc.

[0072] The negative electrode active material that can be used is not particularly limited, and for example, metal oxide-based active material particles, silicon-based active material particles, and particularly metal oxide-based negative electrode active material particles can be used.

[0073] As metal oxide-based negative electrode active material particles, for example, titanium oxide can be used. As titanium oxide, there is no particular limitation as long as it can absorb and release lithium, for example, spinel lithium titanate, ramsdellite lithium titanate, titanium-containing metal composite oxides, titanium dioxide (TiO2(B)) having a monoclinic crystal structure, and anatase titanium dioxide can be used.

[0074] As spinel lithium titanate, Li4+xTi5O 12 (x varies in the range of -1≤x≤3 according to the charge and discharge reaction), etc. Examples of ramsdellite-type lithium titanate include Li2+yTi3O7 (y varies in the range of -1≤y≤3 according to the charge and discharge reaction), etc. Examples of TiO2(B) and anatase-type titanium dioxide include Li1+zTiO2 (z varies in the range of -1≤z≤0 according to the charge and discharge reaction), etc.

[0075] As the titanium-containing metal composite oxide, there can be mentioned a metal composite oxide containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni and Fe, etc. As the metal composite oxide containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni and Fe, for example, there can be mentioned TiO2-P2O5, TiO2-V2O5, TiO2-P2O5-SnO2, TiO2-P2O5-MeO (Me is at least one element selected from the group consisting of Cu, Ni and Fe), etc.

[0076] Such a metal composite oxide preferably has a microstructure in which the crystal phase and the amorphous phase coexist or the amorphous phase exists independently, and the cycle performance can be further improved by having a microstructure.

[0077] In the secondary battery negative electrode slurry composition disclosed herein, the content of the negative electrode active material is preferably 30 to 60% by mass, more preferably 35 to 55% by mass, based on the total amount of the negative electrode slurry, from the perspective of ensuring battery capacity and slurry fluidity.

[0078] (Binder ingredients)

[0079] As the binder component, for example, various emulsion-type polymers can be used, specifically, fluorine-based emulsion-type polymers such as polyvinylidene fluoride (PVdF) and polytetrafluoroethylene (PTFE), elastomeric emulsion-type polymers such as ethylene-propylene-diene copolymer (EPDM), nitrile rubber (NBR) and styrene-butadiene rubber (SBR), acrylic emulsion-type polymers, etc. can be used.

[0080] As the polymer, from the viewpoint of conductivity, it is preferable to use an elastic emulsion type polymer, particularly a styrene-based elastic emulsion type polymer, particularly styrene-butadiene rubber.

[0081] In addition, as the polymer, for example, natural polymers such as polysaccharides and synthetic polymers can be used. Such polymers are sometimes used as thickeners.

[0082] As the polysaccharide, for example, gum arabic, tragacanth gum, guar gum, locust bean gum, alginic acid, carrageenan, gelatin, xanthan gum, welan gum, succinoglycan, diutan gum, dextran, methylcellulose, ethylcellulose, hydroxyethylcellulose, starch glycolic acid and salts thereof can be used.

[0083] As the synthetic polymer, for example, water-soluble resins such as polyvinyl methyl ether, polyacrylic acid and its salts, polyethylene oxide, vinyl acetate-polyvinyl pyrrolidone copolymer, styrene-acrylic acid copolymer and its salts, isobutylene maleic anhydride copolymer and its salts can be used.

[0084] In addition, as the polymer, for example, nonionic dispersants such as polyalkylene oxides, polyvinyl acetals, polyvinyl ethers, chitins, chitosans, and starches can be used. These polymers may be used as dispersing aids.

[0085] The content of these binder components can be set to a suitable content, and is not particularly limited. Preferably, from the aspect of the preferred coating liquid viscosity and the aspect of electrode stability, its content is preferably 0.1 to 2 mass %, more preferably 0.2 to 1 mass %, and more preferably 0.2 to 0.8 mass % relative to the total amount of the slurry composition.

[0086] The slurry composition for negative electrode for secondary battery disclosed in the present invention contains the above-mentioned carbon material dispersion, negative electrode active material, dispersant, binder component, and carbon particles as required that become the above-mentioned conductive material, dispersant, preservative (a combination of triazine compound and group A, the content is within the above-mentioned range), liquid medium, etc. in appropriate amounts, and further contains a pH adjuster, a leveling agent, a solid electrolyte material, a stripping agent, etc. within a range that does not impair the effects of the present invention.

[0087] (pH adjuster)

[0088] The pH of the slurry composition for a negative electrode for a secondary battery of the present disclosure is preferably 4 to 9 from the viewpoint of corrosion of the current collector and from the viewpoint of composition stability.

[0089] As the pH adjuster that can be used, for example, at least one of ammonia, urea, monoethanolamine, diethanolamine, triethanolamine, aminomethylpropanol, sodium tripolyphosphate, alkali metal salts of carbonic acid or phosphoric acid such as sodium carbonate, and alkali metal hydroxides such as sodium hydroxide can be used.

[0090] The slurry composition for negative electrode for secondary battery disclosed in the present invention contains at least the above-mentioned carbon material dispersion, preferably contains negative electrode active material and binder component, and its production can be obtained by, for example, adding carbon material dispersion, negative electrode active material, conductive material, etc. and stirring / mixing them using the following apparatus, and then undergoing a dispersion process.

[0091] As the above-mentioned manufacturing apparatus, for example, mixers such as ultrasonic dispersers, dispersers, homomixers, rotation and revolution mixers, Henschel mixers, planetary mixers, (high-pressure) homogenizers, paint conditioners, colloid mills, bead mills, cone mills, ball mills, sand mills, attritors, bead mills, annular gap ball mills and other media-type dispersers, wet jet mills, thin film rotary high-speed mixers and other media-free dispersers, and roller mills and other dispersing devices can be used for dispersion treatment, but are not limited to these.

[0092] As a preferable apparatus, a planetary mixer, a bead mill, etc. are preferable from the viewpoint of stability and dispersion efficiency.

[0093] In addition, from the perspective of sedimentation stability and coating properties, the shear rate of the secondary battery negative electrode slurry composition disclosed in the present invention is 1000 s -1 The viscosity at the bottom is preferably 0.1 to 1.5 Pa·s.

[0094] The viscosity can be adjusted by appropriately combining a dispersant, a sedimentation inhibitor, a slurry material concentration, and the like.

[0095] The negative electrode slurry composition for secondary batteries of the present disclosure thus constituted contains a carbon material dispersion liquid that can maintain a high anticorrosion / antibacterial effect and its sustainability for a long time even in a small amount, and highly combines dispersibility and storage stability, or contains the above-mentioned preservative (a combination of a triazine compound and group A) when preparing the negative electrode slurry composition. Therefore, when coating is performed to form an electrode, the carbon material containing carbon nanotubes that serves as a conductive material and the active material can be uniformly distributed, and a negative electrode with high stability and a low resistance value when the electrode is prepared can be formed.

[0096] In addition, in the present disclosure, it is further described in detail in Test Example 3, but if the above-mentioned preservative (a combination of a triazine compound and Group A) is used, the dispersibility is particularly improved in relation to the pH of the carbon material dispersion, and a carbon material dispersion with low viscosity can be obtained.

[0097] Example

[0098] Hereinafter, the present disclosure will be described using Test Examples 1 to 3 corresponding to Examples and Comparative Examples, but the present disclosure is not limited to these Test Examples.

[0099] (Test Example 1)

[0100] [Test and evaluation of the growth of fungi and mold in carbon material dispersions with different preservatives]

[0101] Using samples A to J having the blending compositions shown in Table 1 below, a test of bacterial / mold growth (bioburden test: culture medium immersion method) and its antiseptic effect (antibacterial / antifungal properties) were conducted by the following method.

[0102] (Evaluation method)

[0103] The carbon material dispersion (total amount 100 mass %: basic composition) is as follows: carbon nanotube (FT612) 1.2 mass % + dispersant (polyvinyl pyrrolidone: PVP K30, manufactured by Sumitomo Pharma Food & Chemical Co., Ltd.) 0.6 mass % + water (balance).

[0104] Next, a negative electrode slurry composition was prepared using the carbon material dispersion, and each preservative (mass %) described in the following Table 1 was added to prepare specimens A to J.

[0105] Contaminated slurry was further added to the specimens A to J, and the specimens were placed at a constant temperature (culture temperature 32.5°C, the same below) to test the preservative effect (antibacterial / antifungal properties) over time using general live bacteria (culture medium SCDLPA) and fungi (culture medium CPPDA).

[0106] The antiseptic effect (antibacterial / antifungal properties on the 1st, 7th and 14th day after inoculation) is shown in Table 1 below. The final contamination concentration was about 3E+04 cfu / ml. For the general live bacteria (culture medium SCDLPA), molds (culture medium CPPDA) and the like of the above-mentioned contaminated slurry, MALDI-TOF (matrix-assisted laser ionization time-of-flight mass spectrometry) was used to identify the bacterial species using the bacterial identification method. As a result, four bacterial genera were identified as shown in Table 2 below [Cellulomonas, Delftia, Cupriavidus, Rhizobium (formerly known as Agrobacterium radiobacter)].

[0107] (Test Example 2)

[0108] [Anticorrosive agent: Test and evaluation of bacterial / fungal growth in carbon material dispersion based on the presence or absence of triazine-based compounds and pyrithione-based compounds]

[0109] Using samples 1 to 4 having the blending compositions shown in Table 3 below, a test on the growth of general live bacteria / fungi and their antiseptic effects (antibacterial properties) were conducted by the following method.

[0110] (Evaluation method)

[0111] For the specimen 1, the negative electrode slurry composition (basic composition) using the above-mentioned carbon material dispersion was sterilized at a material temperature of 70°C for 60 minutes.

[0112] Sample 2 was prepared by adding a negative electrode slurry composition contaminated with common live bacteria or fungi to sample 1.

[0113] Sample 3 was prepared by adding the triazine compound listed in Table 1: + pyrithione compound: 0.067% by mass in total to sample 2.

[0114] For the specimen 4, the negative electrode slurry composition (basic composition) using the above-mentioned carbon material dispersion liquid was used.

[0115] The specimens 1 to 4 were placed at a constant temperature, and the preservative effects (antibacterial / antifungal properties) and the shear rate over time of 0.2 s were evaluated immediately after inoculation, 2 weeks after inoculation, and 1 month (30 days) after inoculation using general live bacteria (SCDLPA culture medium) and fungi (CPPDA culture medium). -1 , shear speed 1000s -1 The viscosity changes of each.

[0116] Shear speed 0.2s -1, shear speed 1000s -1 The viscosity of each sample was measured by the following method.

[0117] Rheometer (MCR302, cone and plate from Anton Paar) 2°), and measure the shear rate at 25°C for 0.2s -1 , shear speed 1000s -1 The viscosity values ​​of .

[0118] The antiseptic effect (antibacterial / antifungal properties) and the shear rate over time were 0.2 s. -1 , shear speed 1000s -1 The viscosity changes are shown in Table 4 and Table 5 below.

[0119] (Test Example 3)

[0120] [Anticorrosive agent: Evaluation of viscosity change when using each carbon material dispersion containing a triazine compound + a pyridinethione compound and a pH of 3.7 to 9.6, and evaluation of electrode characteristics such as sheet resistance when used as a negative electrode slurry composition]

[0121] Test Examples 3-1 to 3-10 having the compounding compositions shown in Table 6 below were used to perform a bead mill dispersion treatment, and the pH (before dispersion, after dispersion), viscosity (viscosity immediately after addition of the preservative, 2 hours after addition), average particle size, L*, sheet resistance, and glossiness were measured and evaluated by the following methods.

[0122] These results are shown in Table 6 below.

[0123] (pH determination)

[0124] The pH (25° C.) was measured using a pH meter F72 (manufactured by Kuba Manufacturing Co., Ltd.).

[0125] (Viscosity measurement)

[0126] The viscosity (immediately after adding the preservative and 2 hours after adding the preservative) was measured using an E-type rotational viscometer [TV-25 (manufactured by Toki Sangyo Co., Ltd.) rotor (1°34'×R24mm)] at a rotation speed of 10 rpm and a viscosity value (mPa·s) at 25°C.

[0127] (Measurement of particle size)

[0128] The median particle size was measured by cumulant analysis using a dynamic light scattering method (25°C).

[0129] (Measurement of gloss)

[0130] The coating was applied to one side of a PET film (Lumirror #100-T60, Toray Industries, Inc.) using an applicator with a gap of 50 μm, and then dried at 80° C. The gloss was measured using a gloss meter (manufactured by Suga Test Instruments Co., Ltd.).

[0131] (Sheet resistance)

[0132] The carbon material dispersion was further transferred to a planetary mixer, a binder material of SBR was added, the revolution speed was set to 10 rpm, and the composition was kneaded for 120 minutes to obtain an electrode slurry.

[0133] The obtained slurry for electrode was measured by the following measurement method to evaluate the conductivity of the thin-layer resistor.

[0134] The finished electrode slurry was applied to one side of a PET film (Lumirror #100-T60, Toray) using an applicator with a gap of 50 μm, and then dried at 80°C to measure the resistance of the resulting film. The resistance value was measured using a device consisting of 4 probes with a probe interval of 10 mm and mΩ HiTESTER 3227 (Hioki Electric).

[0135] When the sheet resistance is 1.0 kΩ / □ or less, it can be confirmed that the conductivity is excellent.

[0136] [Table 1]

[0137]

[0138] [Table 2]

[0139]

[0140] [Table 3]

[0141]

[0142] [Table 4]

[0143]

[0144] [Table 5]

[0145]

[0146] [Table 6]

[0147]

[0148] The evaluation results in Tables 1 to 5 above indicate that in the case of a carbon material dispersion containing a carbon material including carbon nanotubes, a dispersant, a preservative and a liquid medium within the scope of the present disclosure, the combined use of the triazine compounds and group A (pyridinethione compounds) of specimen D (Table 1) and specimen 3 (Tables 3 to 5) also showed excellent preservative effects on four genera of bacteria, compared with the case where a preservative (isopropyl alcohol, an organic nitrogen sulfur compound, a pyridinethione compound) is used alone as a preservative, and the viscosity changes less over time, and the stability and dispersibility are excellent.

[0149] In addition, the results in Table 6 indicate that the dispersibility of the carbon material dispersion containing carbon nanotubes can be controlled by adding these preservatives and adjusting the pH.

[0150] Industrial Applicability

[0151] The carbon material dispersion has excellent temporal stability and dispersibility, and is useful as a material for fuel cells, various electrodes, electromagnetic wave shielding materials, conductive resins, components for field emission displays, etc., and can be particularly used in the manufacture of anode electrode slurry compositions and electrodes suitable for manufacturing electrodes for lithium ion secondary batteries, etc., and can achieve excellent battery performance.

Claims

1. A carbon material dispersion, characterized in that: The invention at least comprises: a carbon material containing carbon nanotubes, a dispersant, a preservative and a liquid medium, wherein the preservative comprises a triazine compound and at least one selected from the following group A, Group A: organic sulfur compounds, organic nitrogen sulfur compounds, organic halogen compounds, haloallyl sulfone compounds, iodopropargyl compounds, N-haloalkylthio compounds, nitrile compounds, pyridine compounds, 8-hydroxyquinoline compounds, benzothiazole compounds, isothiazolin compounds, dithiol compounds, pyridine oxide compounds, nitropropane compounds, organic tin compounds, phenol compounds, quaternary ammonium salt compounds, thiazine compounds, aniline compounds, adamantane compounds, dithiocarbamate compounds, indanone bromide compounds, benzyl bromoacetate compounds, and inorganic salt compounds.

2. The carbon material dispersion according to claim 1, characterized in that The content of the triazine compound is 0.001 to 0.2% by mass based on the total amount of the dispersion, and the total content of the preservative is 0.5% by mass or less based on the total amount of the dispersion.

3. The carbon material dispersion according to claim 1 or 2, characterized in that The preservative is selected from the group consisting of Fusarium, Cellulomonas, Delftia, Cupriavidus, Rhizobium (formerly known as Agrobacterium radiobacter), Micrococcus, Stomatococcus, Planococcus, Staphylococcus, Deinococcus, Streptococcus, Leuconostoc, Pediococcus, Aerococcus, Gemella, Peptococcus, Peptostreptococcus, and Streptococcus. At least one of the genera Bacillus, Bacillus, Sporolactobacillus, Clostridium, Desulfotomaculum, Sporosarcina, Oscillospira, Lactobacillus, and Listeria shows an antiseptic effect.

4. A slurry composition for a negative electrode for a secondary battery, characterized in that: Contains the carbon material dispersion according to claim 1 or 2.

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