WO2023022064A1 - Carbon nanotube dispersion, conductive paste using same, secondary battery electrode paste, secondary battery electrode, and secondary battery - Google Patents

Carbon nanotube dispersion, conductive paste using same, secondary battery electrode paste, secondary battery electrode, and secondary battery Download PDF

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WO2023022064A1
WO2023022064A1 PCT/JP2022/030390 JP2022030390W WO2023022064A1 WO 2023022064 A1 WO2023022064 A1 WO 2023022064A1 JP 2022030390 W JP2022030390 W JP 2022030390W WO 2023022064 A1 WO2023022064 A1 WO 2023022064A1
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secondary battery
carbon nanotube
dispersion
electrode
paste
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PCT/JP2022/030390
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French (fr)
Japanese (ja)
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敬之 早川
剛 橋本
寛史 阿部
聡 佐久間
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三菱鉛筆株式会社
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Priority to CN202280056603.6A priority Critical patent/CN117836972A/en
Publication of WO2023022064A1 publication Critical patent/WO2023022064A1/en

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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D201/00—Coating compositions based on unspecified macromolecular compounds
    • C09D201/02—Coating compositions based on unspecified macromolecular compounds characterised by the presence of specified groups, e.g. terminal or pendant functional groups
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/24—Electrically-conducting paints
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
    • C09D7/40—Additives
    • C09D7/60—Additives non-macromolecular
    • C09D7/61—Additives non-macromolecular inorganic
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising carbon-silicon compounds, carbon or silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This specification describes a carbon nanotube dispersion with excellent stability and conductivity, a conductive paste using this dispersion, an electrode paste for secondary batteries that is suitable for producing secondary batteries such as lithium ion batteries, a secondary
  • the present invention relates to battery electrodes and secondary batteries.
  • lithium-ion secondary batteries using non-aqueous electrolytes have come to be used in many devices due to their characteristics of high energy density and high voltage.
  • negative electrode materials and positive electrode materials used in these lithium ion secondary batteries, especially carbon nanotube dispersion liquids for positive electrode materials it is possible to reduce electrode resistance and achieve good conductive performance and to efficiently form a conductive network with a small amount. Consideration is being given to what can be done.
  • Patent Document 1 discloses a carbon nanotube dispersion containing a carbon nanotube, a dispersing agent, and a dispersion medium, wherein the geometric standard deviation ( ⁇ D) of the distribution of the tube outer diameter of the carbon nanotube is 1.25 to 1. .70, and the average particle diameter (D50) of the carbon nanotubes in the dispersion is 400 nm or less according to the dynamic light scattering method,
  • a carbon nanotube, a water-soluble resin, and water are contained
  • the carbon nanotube (A) is a single wall, and has an average outer diameter of 0.5 to 5 nm in image analysis with a transmission electron microscope.
  • Patent Document 3 discloses a dispersion containing carbon nanotubes having an average outer diameter of 3 nm or less and a dispersing agent, wherein the average particle diameter measured by a dynamic light scattering method is 200 nm or more and 1500 nm or less.
  • Patent Document 4 discloses a method for dispersing carbon nanotubes in a dispersion medium, wherein beads having an average diameter of 0.4 to 5 mm and a specific gravity of 2 to 3 g/cm 3 are prepared in the presence of a surfactant.
  • a carbon nanotube dispersing method characterized by dispersing using In Patent Document 5, carbon nanotubes having a number average fiber diameter of 100 nm or more and carbon nanotubes having a number average fiber diameter of 30 nm or less are mixed in a 1-methyl-2-pyrrolidone solution of polyaniline with a wet jet mill, and polyaniline is obtained. and obtaining a dispersion of carbon nanotubes in which both the carbon nanotubes are dispersed in a 1-methyl-2-pyrrolidone solution of .
  • the present disclosure is intended to solve the above-described conventional problems, etc., and a carbon nanotube dispersion that can achieve both high stability and conductive performance, a conductive paste using the same, an electrode paste for a secondary battery, and two
  • An object of the present invention is to provide an electrode for a secondary battery and a secondary battery such as a lithium ion battery using this electrode.
  • the present inventors have found that a carbon nanotube dispersion containing at least a carbon nanotube, a water-soluble polymer material, and a dispersion medium, wherein the carbon nanotube in the dispersion is Using a dispersion prepared so that the median diameter (D50) by the dynamic light scattering method is within a predetermined range, the carbon nanotube dispersion for the above purpose, a conductive paste using the same, an electrode paste for a secondary battery, and a secondary battery
  • a secondary battery such as a lithium-ion battery can be obtained by using an electrode for use with the electrode.
  • the carbon nanotube dispersion of the present disclosure contains at least carbon nanotubes, a water-soluble polymer material, and a dispersion medium, and the median diameter of the carbon nanotubes measured by the dynamic light scattering method is X, the dispersion limit median It is characterized in that 1.0 ⁇ X/a ⁇ 2.0 and X ⁇ 1.0 ⁇ m, where a is the diameter.
  • the water-soluble polymeric material is preferably one or more polymeric materials selected from nonionic water-soluble polymers and anionic water-soluble polymers.
  • the conductive paste is characterized by including at least the carbon nanotube dispersion having the above configuration
  • the secondary battery electrode paste includes the carbon nanotube dispersion having the above configuration
  • the secondary battery active material characterized by including at least
  • the secondary battery electrode of the present disclosure is characterized by using the secondary battery electrode paste having the above configuration
  • the secondary battery is characterized by using the secondary battery electrode having the above configuration.
  • a carbon nanotube dispersion that can achieve both high stability and conductive performance, a conductive paste using the same, an electrode paste for a secondary battery and an electrode for a secondary battery, and a lithium ion using the electrode
  • a secondary battery suitable for a battery or the like can be provided.
  • the carbon nanotube dispersion of the present disclosure contains at least carbon nanotubes, a water-soluble polymer material, and a dispersion medium, and X is the median diameter of the carbon nanotubes measured by the dynamic light scattering method, It is characterized in that 1.0 ⁇ X/a ⁇ 2.0, where a, and X ⁇ 1.0 ⁇ m.
  • the carbon nanotube (CNT) used in the present disclosure is not particularly limited as long as it has a cylindrical shape obtained by substantially winding one face of graphite, and one face of graphite is wound in one layer. Either single-walled CNTs or multi-walled CNTs wound in two or three or more layers can be used.
  • forms of carbon nanotubes include, but are not limited to, graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. , each of these may be used alone or in combination of two or more (hereinafter simply referred to as "at least one").
  • the average outer diameter of the carbon nanotubes is preferably 1 nm or more and 90 nm or less, more preferably 3 nm or more and 30 nm or less, and 3 nm or more and 15 nm or less, from the viewpoint of the viscosity, conductivity, and stability of the dispersion. It is even more preferable to have
  • the average outer diameter of a carbon nanotube refers to the arithmetic mean value of n sufficient outer diameters measured using transmission electron microscope images at a magnification of 100,000 or more.
  • the purity of the carbon nanotubes used in the present disclosure is preferably 90 to 100% by mass, particularly preferably 95 to 100% by mass. The purity of carbon nanotubes is calculated based on the amount of impurities, with ash measured according to JIS K 1469 and JIS K 6218 as impurities.
  • Carbon nanotubes (CNT) that can be specifically used include, for example, FloTube9000 (average outer diameter 11 nm) manufactured by Cnano, MEIJO eDIPS EC2.0 (average outer diameter 2.0 nm) manufactured by Meijo Nano Carbon, etc. One type can be used.
  • the content of these carbon nanotubes (CNT) is not particularly limited and can be set to a suitable content depending on the application.
  • the content when used for conductive paste, secondary battery electrode paste, secondary battery electrode, etc., the content is It is preferably 0.1 to 15.0% by mass, more preferably 0.1 to 10.0% by mass, more preferably 0.5 to 8.0% by mass, with respect to the total amount of the liquid, 1.0 ⁇ 6.0% by mass, preferably 2.0 to 5.0% by mass.
  • the carbon nanotube (CNT) content By setting the carbon nanotube (CNT) content to 0.1% by mass or more, sufficient conductivity can be ensured, while by setting the content to 15.0% by mass or less, the stability of the dispersion liquid can be improved. And good conductivity can be secured.
  • Water-soluble polymer material used in the present disclosure can be used without particular limitation as long as it is soluble in water or dissolved in the dispersion medium (solvent other than water) used.
  • water-soluble polymeric materials include natural polymeric materials such as proteins and starches, synthetic high molecular weight materials such as polyacrylic acid, polyacrylamide, polyoxyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyvinylamide, and polyamines. Molecular materials and the like can be mentioned. These water-soluble polymeric materials function as dispersants and binders for carbon nanotubes (CNT).
  • the water-soluble polymeric material that dissolves in a solvent other than water may be in a partially dissolved state as well as in a completely dissolved state.
  • the water-soluble polymers it is possible to stably disperse carbon nanotubes (CNT) without impairing their electrical conductivity.
  • the water-soluble polymer material it is particularly preferable to use at least one kind selected from nonionic water-soluble polymers and anionic water-soluble polymers. It is particularly suitable for stably dispersing without
  • Nonionic water-soluble polymers that can be used include, for example, polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters and alkylallyl ethers, glycerol At least one of late fatty acid esters and polyoxyethylene glycerol fatty acid esters, xanthan gum, welan gum, succinoglycan, polyvinyl alcohol (PVAL or PVOH), polyvinylpyrrolidone, polyvinyl acetal, and the like.
  • PVAL polyvinyl alcohol
  • PVOH polyvinylpyrrolidone
  • polyvinyl acetal and the like.
  • Examples of usable anionic water-soluble polymers include fatty acids and their salts, polysulfonic acids and their salts, polycarboxylic acids and their salts, alkylsulfuric acid esters and their salts, alkylarylsulfonic acids and their salts, and alkylnaphthalenes.
  • Sulfonic acid and its salts dialkylsulfonic acid and its salts, dialkylsulfosuccinic acid and its salts, alkyl phosphoric acid and its salts, polyoxyethylene alkyl ether sulfuric acid and its salts, polyoxyethylene alkylaryl ether sulfuric acid and its salts, naphthalene sulfone At least one of acid-formalin condensates and salts thereof, polyoxyethylene alkyl phosphate sulfonic acid and salts thereof, acrylic polymers such as styrene acrylic resins, and cellulose polymers such as carboxymethylcellulose or sodium (Na) salts thereof is mentioned.
  • Polyvinylpyrrolidone is preferably used as the nonionic water-soluble polymer because it does not impede conductivity, and acrylic polymers and cellulose-based polymers are used as anionic water-soluble polymers. is desirable.
  • the (total) content of these water-soluble polymer materials is not particularly limited and can be set to a suitable content depending on the application.
  • the content when used as a conductive paste, a secondary battery electrode paste, a secondary battery electrode, etc., in order to achieve both high stability and conductive performance, the content is 0.005 with respect to the total amount of the dispersion liquid. It is preferably from 0.025 to 16% by mass, preferably from 0.025 to 16% by mass.
  • the content of these polymer materials is 0.005% by mass or more, the dispersion stability of carbon nanotubes (CNT) is improved, while when the content is 20% by mass or less, the stability of the dispersion is improved. Good electrical conductivity can be secured.
  • the dispersion medium used in the present disclosure is water (purified water, distilled water , pure water, ultrapure water, etc.), organic solvents, etc. can be used without particular limitation.
  • As the dispersion medium not only can it be used alone, but it is also possible to use a mixture of two or more types, and even a combination of water and an organic solvent can be used by appropriately adjusting it within a miscible range. is.
  • organic solvents for example, aromatics, alcohols, polyhydric alcohols, glycol ethers, esters, etc. can be used. These solvents may be used alone or in combination.
  • aromatics examples include benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol.
  • Monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene Glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, phenyl alkylsulfonate, butyl phthalate, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, etc. can be used.
  • alcohols include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methyl amyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n -decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, 2-methylcyclohexanol and the like can be used.
  • polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, 3 -methyl-1,3-butanediol, triethylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, hexylene glycol, octylene glycol and the like can be used. can.
  • glycol ethers include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylbutyl ether, Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3-methoxy-1 -butanol, 3-methoxy-1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol
  • esters include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, and acetic acid.
  • Additives may be added to the carbon nanotube dispersion of the present disclosure according to its use.
  • thickeners include carboxymethylcellulose sodium, anti-settling agents, wetting agents, emulsifiers, anti-sagging agents, anti-foaming agents, leveling agents, plasticizers, anti-mold/anti-algae agents, and antibacterial agents.
  • X is the median diameter of the carbon nanotubes measured by the dynamic light scattering method
  • a is the median diameter of the dispersion limit, 1.0 ⁇ X/a ⁇ 2.0 and is characterized by X ⁇ 1.0 ⁇ m.
  • the median diameter X of the carbon nanotube measured by the dynamic light scattering method is the scattering intensity reference median diameter measured in an environment of 25 ° C. (by cumulant analysis method Median diameter, particle diameter at which the cumulative frequency reaches 50%, D50), which can be measured using, for example, FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.). The measurement can be carried out by diluting with the dispersion medium used in the carbon nanotube dispersion so as to obtain an optimum concentration.
  • the median diameter X of the carbon nanotubes measured by the dynamic light scattering method and the minimum dispersion limit median diameter a are 1.0 ⁇ X/a ⁇ 2.0, and X ⁇ 1. When it is 0 ⁇ m, it is possible to obtain a carbon nanotube dispersion having both stability and conductivity at a high level.
  • a state in which the carbon nanotubes are independent and separated one by one without agglomeration is preferable in terms of conductivity, but it is difficult to achieve both stability of the carbon nanotube dispersion.
  • the present inventors have found that the median diameter X of carbon nanotubes measured by the dynamic light scattering method and the dispersion limit median diameter a are 1.0 ⁇ X/a ⁇ 2.0, and X ⁇ 1. It was discovered for the first time that a high degree of both stability and conductivity can be achieved when the thickness is 0 ⁇ m.
  • the carbon nanotubes are either insufficiently dispersed or excessively dispersed, which is not preferable because both conductivity and stability are lowered.
  • X ⁇ 1.0 ⁇ m (1000 nm) it is possible to achieve both stability and conductivity most effectively, and when X ⁇ 1.0 ⁇ m (1000 nm), stability decreases. I don't like it.
  • the carbon nanotube dispersion having the properties described above can be prepared by dispersing each component having the properties described above under suitable conditions using a dispersing device as shown below.
  • a dispersing device a dispersing machine that is commonly used for pigment dispersion or the like can be used. Homogenizers, paint conditioners, colloid mills, bead mills, cone mills, ball mills, sand mills, attritors, pearl mills, coball mills and other media-type dispersers, wet jet mills, thin-film rotating high-speed mixers and other medialess dispersers, and other roll mills. Examples include, but are not limited to. From the standpoint of stability and dispersion efficiency, preferred dispersing devices include a thin-film rotating high-speed mixer and a bead mill.
  • the distribution limit median diameter a of the carbon nanotube dispersion liquid varies slightly depending on the above-described formulation composition and the type of dispersion used, but preferably, a certain disperser is selected and dispersion is performed with that disperser. It is desirable to measure the dispersion limit median diameter a when dispersed without changing the conditions. For example, when using a bead mill, it is possible to set and specify conditions such as the media bead diameter and filling rate, dispersion peripheral speed, flow velocity of the dispersion liquid introduced into the disperser, cooling water flow rate and temperature, etc. desirable.
  • the dispersion limit median diameter of the carbon nanotubes is a and the elapsed dispersion time is Ta
  • the dispersion is dispersed for a dispersion time less than Ta
  • the median diameter range of the present invention is 1. More preferably, the carbon nanotube dispersion satisfies .0 ⁇ X/a ⁇ 2.0 and X ⁇ 1.0 ⁇ m.
  • the viscosity of the carbon nanotube dispersion of the present disclosure was measured with a cone-plate viscometer (rotor rotation speed 10 rpm (shear rate 38.3 s -1 ), temperature 25 ° C.) from the viewpoint of stability and handling.
  • the actual viscosity value is preferably 1 to 10,000 mPa ⁇ s, more preferably 1 to 5,000 mPa ⁇ s.
  • the carbon nanotube dispersion liquid of the present disclosure configured in this way can achieve both high stability and conductive performance. Since this carbon nanotube dispersion has unprecedented excellent performance, it can be used as a conductive paste, an electrode paste for secondary batteries, an electrode for secondary batteries, and a secondary battery suitable for lithium ion batteries using this electrode. It becomes available.
  • the conductive paste of the present disclosure is characterized by containing at least the carbon nanotube dispersion liquid having the above structure, and can be used for conductive resin products, conductive adhesives, printed wiring applications, and the like.
  • This conductive paste can be configured by adding at least a resin component to the above-described carbon nanotube dispersion liquid capable of achieving both high stability and conductive performance.
  • the resin component for example, a thermosetting resin, an ultraviolet curable resin, or the like can be used.
  • the secondary battery electrode paste of the present disclosure is characterized by including at least the carbon nanotube dispersion having the above configuration and the secondary battery active material, and the secondary battery electrode of the present disclosure includes: It is characterized by using the electrode paste for secondary batteries having the above structure.
  • the carbon nanotube dispersion having the above constitution can be used as it is, or after being diluted or concentrated.
  • the carbon nanotubes contained in electrode paste for secondary batteries and electrodes for secondary batteries are appropriately adjusted according to the electrode characteristics, battery capacity after cell formation, charge-discharge characteristics, etc., and the optimum content is obtained. However, it is desirable that it be contained in an amount of 1 to 15 parts by mass.
  • the active material used in the secondary battery electrode paste either a positive electrode active material or a negative electrode active material can be used.
  • the positive electrode active material for secondary batteries is not particularly limited as long as it is a normal positive electrode active material (an active material that allows lithium ions to reversibly enter and exit) that can be used for the positive electrode of a lithium ion battery.
  • transition metal sulfides such as TiS2 , FeS and MoS2
  • transition metal oxides such as MnO, V2O5 , V6O13 and TiO2 ; mentioned.
  • the olivine-type lithium phosphate is, for example, at least one selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe. It contains the elements Lithium, Phosphorus and Oxygen. These compounds may have some elements partially substituted with other elements in order to improve their properties.
  • a preferable positive electrode active material for a secondary battery is a lithium-nickel composite oxide, and more preferably the lithium-nickel composite oxide has the formula: LiNi X M1 Y M2 ZO 2 (M1 and M2 are Al , B, at least one metal element selected from alkali metals, alkaline earth metals, and transition metals, 0.8 ⁇ X ⁇ 1.0, 0 ⁇ Y ⁇ 0.2, 0 ⁇ Z ⁇ 0.2 ) is desirable.
  • These positive electrode active materials for secondary batteries may be used singly or in combination of two or more.
  • any ordinary negative electrode active material that can be used for the negative electrode of a lithium ion battery can be used without particular limitation.
  • usable negative electrode active materials for secondary batteries include inorganic compounds such as lithium metals, lithium alloys, and tin compounds; carbonaceous materials capable of intercalating and deintercalating lithium ions; composite oxides containing multiple elements; and a reactive polymer.
  • carbonaceous materials include cokes, vitreous carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers.
  • graphites such as artificial graphite and natural graphite have an operating potential close to that of metallic lithium, can be charged and discharged at a high operating voltage, and suppress self-discharge when lithium salt is used as a supporting salt. Moreover, the irreversible capacity during charging can be reduced, which is preferable.
  • composite oxides include lithium-titanium composite oxides and lithium-vanadium composite oxides.
  • metal oxide materials and carbonaceous materials are preferable as negative electrode active materials for secondary batteries from the viewpoint of safety.
  • the electrode paste for a secondary battery contains the carbon nanotube dispersion having the above structure, the active material for the positive electrode or the negative electrode for the secondary battery, and a binder.
  • binders include polyimide resins, polyvinylidene fluoride (PVdF), polytetrafluoroethylene, ethylene tetrafluoride/propylene hexafluoride/vinylidene fluoride copolymers, Fluorine resins such as propylene fluoride/vinylidene fluoride copolymers, tetrafluoroethylene/perfluorovinyl ether copolymers, polyolefin resins such as polyethylene and polypropylene, polyvinylpyrrolidone, polyvinyl alcohol, styrene-butadiene rubber (SBR), Acrylic resins and the like can be mentioned.
  • the amount of these binders is preferably from 0.2 to 0.2 with respect to the total amount of the secondary battery electrode paste, from the viewpoint of adhesion to the current collecting foil, battery capacity after cell formation, and charge/discharge characteristics. It is desirable to add 3.0 parts by mass, more preferably 0.5 to 2.5 parts by mass.
  • solvents may be added to the secondary battery electrode paste.
  • solvents include water (purified water, ion-exchanged water, distilled water, ultrapure water, etc.), aromatic solvents, alcohols, polyhydric alcohols, ether solvents, glycol ether solvents, ester solvents, Examples include amine solvents, amide solvents, heterocyclic solvents, sulfoxide solvents, sulfone solvents and the like. These solvents may be used alone or in combination of two or more.
  • the amount of these solvents is preferably 0.5 to 80 parts by mass, more than Preferably, it is desirable to add 1 to 70 parts by mass.
  • a leveling agent, a solid electrolyte material, and the like can be added as appropriate within a range that does not impair the effects of the present invention.
  • the secondary battery electrode paste configured in this way contains the carbon nanotube dispersion, the positive electrode or negative electrode active material for the secondary battery, a binder, a solvent, and the like, for example, a biaxial type It can be prepared by using a kneader or the like.
  • the obtained secondary battery electrode paste is applied onto a current collector, which is a conductive member of a lithium ion secondary battery, and dried to obtain a predetermined positive electrode and negative electrode for a lithium ion secondary battery.
  • a secondary battery electrode paste and a secondary battery electrode that achieve battery performance that can withstand repeated charging and discharging for a long period of time can be obtained.
  • the material and shape of the current collector used for the electrode are not particularly limited, and those suitable for various secondary batteries can be appropriately selected.
  • the material of the current collector includes metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel.
  • a flat foil is generally used, but a roughened surface, a perforated foil, and a mesh current collector can also be used.
  • the method of applying the electrode paste onto the current collector is not particularly limited and any known method can be used. Specific examples include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method or an electrostatic coating method.
  • the thickness of the electrode material layer is generally 1 ⁇ m or more and 500 ⁇ m or less, preferably 10 ⁇ m or more and 300 ⁇ m or less.
  • the secondary battery of the present disclosure is characterized by using the above secondary battery electrode, and is preferably a positive electrode of a lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, It is preferable to use the above secondary battery electrode as the negative electrode.
  • the positive electrode an electrode prepared by coating and drying the electrode paste containing the positive electrode active material on the current collector can be used.
  • the negative electrode an electrode prepared by coating and drying an electrode paste containing a negative electrode active material on a current collector can be used.
  • the electrolyte various conventionally known substances in which ions can move can be used.
  • the electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolytic solution.
  • non-aqueous solvents include, but are not limited to, carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate; ⁇ -butyrolactone, ⁇ -valerolactone, and ⁇ - lactones such as octanoic lactone; tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1, glymes such as 2-dibutoxyethane; esters such as methylformate, methylacetate and methylpropionate; sulfoxides such as dimethylsulfoxide and sulfolane; and nitriles such as acetonitrile. Each of these solvents may be used alone, or two or more of them may be mixed and used.
  • the lithium ion secondary battery preferably contains a separator.
  • separators include polyethylene nonwoven fabrics, polypropylene nonwoven fabrics, polyamide nonwoven fabrics, and those subjected to hydrophilic treatment, but are not particularly limited to these.
  • the structure of the lithium ion secondary battery is not particularly limited, it usually consists of a positive electrode, a negative electrode, and an optional separator. It can be of various shapes.
  • a lithium-ion secondary battery or the like which is a secondary battery of the present disclosure configured in this way, can provide a secondary battery that achieves battery performance that can withstand repeated charging and discharging for a long period of time.
  • Example 1 A carbon nanotube dispersion was obtained by dispersing for a dispersion time of Tx (minutes) using a blending composition shown in Table 1 below [each amount of carbon nanotubes, dispersant (polymer material), and dispersion medium] and dispersing apparatus A. .
  • Table 1 a blending composition shown in Table 1 below [each amount of carbon nanotubes, dispersant (polymer material), and dispersion medium] and dispersing apparatus A. .
  • the median diameter X (nm) of the resulting carbon nanotube dispersion obtained by the dynamic light scattering method and X/a showing the relationship between a and X are shown in Table 1 below, and the stability and conductivity were measured by the following method. , was evaluated according to the following evaluation criteria. These evaluation results are shown in Table 1 below.
  • Example 1 (Examples 2 to 9, 11, Comparative Examples 1 to 5) The results obtained in the same manner as in Example 1 are shown in Table 1 below.
  • Example 10 Table 1 below shows the results obtained in the same manner as in Example 1, except that dispersing apparatus B was used.
  • Evaluation method for rate of change in viscosity over time The rate of change (after 1 week/initial) is calculated from the change in viscosity value obtained by the above-mentioned viscosity measurement method when the completed dispersion is placed in an environment of 25°C for 1 week. was obtained, and the rate of change in viscosity over time was evaluated according to the following evaluation criteria. Evaluation criteria: A: Change rate is less than 200% B: Change rate is 200% or more and less than 500% C: Change rate is 500% or more
  • Stability criteria ⁇ : All three items of the above evaluation results (1) to (3) are rated A. ⁇ : Two items of the above evaluation results (1) to (3) are rated A, and there is no C rating. ⁇ : Among the evaluation results of (1) to (3) above, the A evaluation is 0 to 1 item, and there is no C evaluation. ⁇ : Among the evaluation results of the above (1) to (3), C evaluation is one or more items.
  • the completed dispersion was applied to one side of a PET film (Lumirror #100-T60, Toray Industries, Inc.) with an applicator having a gap of 50 ⁇ m, dried at a temperature of 80° C., and the resistance value of the obtained film was measured.
  • the resistance value was measured as a sheet resistance using an apparatus consisting of a 4-point probe with a probe interval of 10 mm and a milliohm high tester 3227 (manufactured by Hioki Electric Co., Ltd.), and conductivity was evaluated according to the following evaluation criteria.
  • Carbon nanotube dispersions are excellent in stability and conductive performance, and are useful as materials for fuel cells, various electrodes, electromagnetic wave shielding materials, conductive resins, field emission display members, etc., especially electrodes such as lithium ion secondary batteries. It can be used for the production of electrode paste and electrodes suitable for the production of, and can realize excellent battery performance that can withstand repeated charging and discharging for a long period of time.

Abstract

Provided are: a carbon nanotube dispersion, a conductive paste, and a secondary battery electrode paste that are ideal for production of secondary batteries, e.g., lithium ion batteries, and the like; a secondary battery electrode; and a secondary battery.　This carbon nanotube dispersion is characterized by including at least carbon nanotubes, a water-soluble polymer material, and a dispersion medium. The carbon nanotube dispersion is also characterized in that, when X is the median diameter of the carbon nanotubes as measured by dynamic light scattering and a is the dispersion limit median diameter, 1.0<X/a≤2.0, and X<1.0 μm.

Description

カーボンナノチューブ分散液、これを用いた導電ペースト、二次電池用電極ペースト、二次電池用電極、及び、二次電池Carbon nanotube dispersion liquid, conductive paste using the same, electrode paste for secondary battery, electrode for secondary battery, and secondary battery
　本明細書は、安定性と導電性能に優れたカーボンナノチューブ分散液、この分散液を用いた導電ペースト、リチウムイオン電池などの二次電池の製造に好適となる二次電池用電極ペースト、二次電池用電極、二次電池に関する。 This specification describes a carbon nanotube dispersion with excellent stability and conductivity, a conductive paste using this dispersion, an electrode paste for secondary batteries that is suitable for producing secondary batteries such as lithium ion batteries, a secondary The present invention relates to battery electrodes and secondary batteries.
　電気自動車の普及、携帯電話やノート型パーソナルコンピュータなどの携帯機器の小型軽量化及び高性能化に伴い、高いエネルギー密度を有する二次電池、さらに、その二次電池の高容量化が求められている。このような背景の下で高エネルギー密度、高電圧という特徴から非水系電解液を用いるリチウムイオン二次電池が多くの機器に使われるようになっている。
　これらリチウムイオン二次電池に用いられる負極材料や正極材料、特に正極材料にカーボンナノチューブ分散液などを用いることにより、良好な導電性能、電極抵抗を低減でき少量で効率的に導電ネットワークを形成することができることなどの検討が行われている。 With the spread of electric vehicles and the miniaturization, weight reduction and performance enhancement of mobile devices such as mobile phones and notebook personal computers, there is a demand for secondary batteries with high energy density and higher capacity secondary batteries. there is Under such circumstances, lithium-ion secondary batteries using non-aqueous electrolytes have come to be used in many devices due to their characteristics of high energy density and high voltage.
By using negative electrode materials and positive electrode materials used in these lithium ion secondary batteries, especially carbon nanotube dispersion liquids for positive electrode materials, it is possible to reduce electrode resistance and achieve good conductive performance and to efficiently form a conductive network with a small amount. Consideration is being given to what can be done.
　例えば、特許文献１には、カーボンナノチューブと、分散剤と分散媒とを含むカーボンナノチューブ分散液であって、該カーボンナノチューブのチューブ外径の分布の幾何標準偏差（σＤ）を１．２５～１．７０とし、該分散液中でのカーボンナノチューブの動的光散乱法による平均粒子径（Ｄ５０）を４００ｎｍ以下とするカーボンナノチューブ分散液が開示されており、
　特許文献２には、カーボンナノチューブ、水溶性樹脂と、水とを含有し、カーボンナノチューブ（Ａ）は、単層であり、透過型電子顕微鏡における画像解析における平均外径が０．５～５ｎｍであり、比表面積が４００～８００ｍ２／ｇであり、カーボンナノチューブ（Ａ）の炭素成分１００質量部に対して、水溶性樹脂（Ｂ）を４００質量部以上、２０００質量部以下含有し、カーボンナノチューブ分散液のレーザー回折式粒度分布測定によって算出される５０％粒子径（Ｄ５０径）が１．５～４０μｍであることを特徴とする、カーボンナノチューブ分散液が開示され、
　特許文献３には、平均外径が３ｎｍ以下であるカーボンナノチューブと分散剤を含んだ分散体であって、動的光散乱法によって測定した平均粒径が２００ｎｍ以上１５００ｎｍ以下であることを特徴とするカーボンナノチューブ水性分散液であり、分散剤がイオン性分散剤であることを特徴とする上記のカーボンナノチューブ水性分散液であることなどが開示され、
　特許文献４には、カーボンナノチューブを分散媒に分散させる方法であって、界面活性剤の存在下で、平均径が０．４～５ｍｍであり、比重が２～３ｇ／ｃｍ３であるビーズを用いて分散させることを特徴とするカーボンナノチューブの分散方法、及びその分散方法を用いて製造されたカーボンナノチューブ分散液が開示され、
　特許文献５には、ポリアニリンの１－メチル－２－ピロリドン溶液中で、数平均繊維径１００ｎｍ以上であるカーボンナノチューブと数平均繊維径３０ｎｍ以下であるカーボンナノチューブとを湿式ジェットミルで混合し、ポリアニリンの１－メチル－２－ピロリドン溶液中に前記両カーボンナノチューブが分散しているカーボンナノチューブの分散液を得ることなどが開示されている。 For example, Patent Document 1 discloses a carbon nanotube dispersion containing a carbon nanotube, a dispersing agent, and a dispersion medium, wherein the geometric standard deviation (σD) of the distribution of the tube outer diameter of the carbon nanotube is 1.25 to 1. .70, and the average particle diameter (D50) of the carbon nanotubes in the dispersion is 400 nm or less according to the dynamic light scattering method,
In Patent Document 2, a carbon nanotube, a water-soluble resin, and water are contained, the carbon nanotube (A) is a single wall, and has an average outer diameter of 0.5 to 5 nm in image analysis with a transmission electron microscope. has a specific surface area of 400 to 800 m 2 /g, contains 400 parts by mass or more and 2000 parts by mass or less of the water-soluble resin (B) with respect to 100 parts by mass of the carbon component of the carbon nanotube (A), and the carbon nanotube Disclosed is a carbon nanotube dispersion characterized in that the 50% particle diameter (D50 diameter) calculated by laser diffraction particle size distribution measurement of the dispersion is 1.5 to 40 μm,
Patent Document 3 discloses a dispersion containing carbon nanotubes having an average outer diameter of 3 nm or less and a dispersing agent, wherein the average particle diameter measured by a dynamic light scattering method is 200 nm or more and 1500 nm or less. Disclosed is the above carbon nanotube aqueous dispersion characterized in that the dispersant is an ionic dispersant, and the like,
Patent Document 4 discloses a method for dispersing carbon nanotubes in a dispersion medium, wherein beads having an average diameter of 0.4 to 5 mm and a specific gravity of 2 to 3 g/cm 3 are prepared in the presence of a surfactant. Disclosed is a carbon nanotube dispersing method characterized by dispersing using
In Patent Document 5, carbon nanotubes having a number average fiber diameter of 100 nm or more and carbon nanotubes having a number average fiber diameter of 30 nm or less are mixed in a 1-methyl-2-pyrrolidone solution of polyaniline with a wet jet mill, and polyaniline is obtained. and obtaining a dispersion of carbon nanotubes in which both the carbon nanotubes are dispersed in a 1-methyl-2-pyrrolidone solution of .
　しかしながら、これらの特許文献１～５のカーボンナノチューブ分散液等では、経時的に分散性が低下したりし、安定性と導電性能を高度に両立することが難しく、高い安定性と導電性能を両立することができるカーボンナノチューブ分散液、これを用いた導電ペースト、二次電池用電極ペースト及び二次電池用電極、この電極を用いたリチウムイオン電池などの二次電池が切望されているのが現状である。 However, in the carbon nanotube dispersions and the like of these Patent Documents 1 to 5, the dispersibility decreases over time, and it is difficult to achieve both high stability and conductive performance. Carbon nanotube dispersion, conductive paste using the same, electrode paste for secondary batteries and electrodes for secondary batteries, and secondary batteries such as lithium ion batteries using this electrode are currently in demand. is.
特開２０１７－２０６４１２号公報（特許請求の範囲、実施例等）Japanese Patent Application Laid-Open No. 2017-206412 (Claims, Examples, etc.) 特開２０２０－０１９９２４号公報（特許請求の範囲、実施例等）Japanese Patent Application Laid-Open No. 2020-019924 (Claims, Examples, etc.) 特開２０１０－２５４５４６号公報（特許請求の範囲、実施例等）Japanese Patent Application Laid-Open No. 2010-254546 (Claims, Examples, etc.) 特開２００７－１６９１２０号公報（特許請求の範囲、実施例等）Japanese Patent Application Laid-Open No. 2007-169120 (Claims, Examples, etc.) 特開２０１５－１１７１５０号公報（特許請求の範囲、実施例等）Japanese Patent Application Laid-Open No. 2015-117150 (Claims, Examples, etc.)
　本開示は、上記従来の課題等について解消しようとするものであり、高い安定性と導電性能を両立することができるカーボンナノチューブ分散液、これを用いた導電ペースト、二次電池用電極ペースト及び二次電池用電極、この電極を用いたリチウムイオン電池などの二次電池を提供することを目的とする。 The present disclosure is intended to solve the above-described conventional problems, etc., and a carbon nanotube dispersion that can achieve both high stability and conductive performance, a conductive paste using the same, an electrode paste for a secondary battery, and two An object of the present invention is to provide an electrode for a secondary battery and a secondary battery such as a lithium ion battery using this electrode.
　本開示者らは、上記従来の課題について鋭意検討した結果、カーボンナノチューブと、水溶性高分子材料と、分散媒と、を少なくとも含むカーボンナノチューブ分散液であって、該分散液中のカーボンナノチューブの動的光散乱法によるメジアン径（Ｄ５０）が所定範囲となるように調製された分散液により、上記目的のカーボンナノチューブ分散液、これを用いた導電ペースト、二次電池用電極ペースト及び二次電池用電極、この電極を用いたリチウムイオン電池などの二次電池が得られることを見出し、本開示を完成するに至ったのである。 As a result of intensive studies on the above-described conventional problems, the present inventors have found that a carbon nanotube dispersion containing at least a carbon nanotube, a water-soluble polymer material, and a dispersion medium, wherein the carbon nanotube in the dispersion is Using a dispersion prepared so that the median diameter (D50) by the dynamic light scattering method is within a predetermined range, the carbon nanotube dispersion for the above purpose, a conductive paste using the same, an electrode paste for a secondary battery, and a secondary battery The present inventors have completed the present disclosure by discovering that a secondary battery such as a lithium-ion battery can be obtained by using an electrode for use with the electrode.
　すなわち、本開示のカーボンナノチューブ分散液は、カーボンナノチューブと、水溶性高分子材料と、分散媒と、を少なくとも含み、動的光散乱法にて測定したカーボンナノチューブのメジアン径をＸ、分散限界メジアン径をａとした場合に１．０＜Ｘ／ａ≦２．０であり、Ｘ＜１．０μｍであることを特徴とする。
　前記水溶性高分子材料は、非イオン性水溶性高分子とアニオン性水溶性高分子から選ばれる1種類以上の高分子材料であることが好ましい。
　本開示において、導電ペーストは、上記構成のカーボンナノチューブ分散液を少なくとも含むことを特徴とし、また、二次電池用電極ペーストは、上記構成のカーボンナノチューブ分散液と、二次電池用活物質と、を少なくとも含むことを特徴とする。
　本開示の二次電池用電極は、上記構成の二次電池用電極ペーストを用いたことを特徴とし、また、二次電池は、上記構成の二次電池用電極を用いたことを特徴とする。 That is, the carbon nanotube dispersion of the present disclosure contains at least carbon nanotubes, a water-soluble polymer material, and a dispersion medium, and the median diameter of the carbon nanotubes measured by the dynamic light scattering method is X, the dispersion limit median It is characterized in that 1.0<X/a≦2.0 and X<1.0 μm, where a is the diameter.
The water-soluble polymeric material is preferably one or more polymeric materials selected from nonionic water-soluble polymers and anionic water-soluble polymers.
In the present disclosure, the conductive paste is characterized by including at least the carbon nanotube dispersion having the above configuration, and the secondary battery electrode paste includes the carbon nanotube dispersion having the above configuration, the secondary battery active material, characterized by including at least
The secondary battery electrode of the present disclosure is characterized by using the secondary battery electrode paste having the above configuration, and the secondary battery is characterized by using the secondary battery electrode having the above configuration. .
　本開示によれば、高い安定性と導電性能を両立することができるカーボンナノチューブ分散液、これを用いた導電ペースト、二次電池用電極ペースト及び二次電池用電極、この電極を用いたリチウムイオン電池などに好適な二次電池を提供することができる。
　本開示の目的及び効果は、特に請求項において指摘される構成要素及び組み合わせを用いることによって認識され且つ得られるものである。上述の一般的な説明及び後述の詳細な説明の両方は、例示的及び説明的なものであり、特許請求の範囲に記載されている本開示を制限するものではない。 According to the present disclosure, a carbon nanotube dispersion that can achieve both high stability and conductive performance, a conductive paste using the same, an electrode paste for a secondary battery and an electrode for a secondary battery, and a lithium ion using the electrode A secondary battery suitable for a battery or the like can be provided.
The objects and advantages of the disclosure may be realized and obtained by means of the elements and combinations particularly pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory and are not limiting of the disclosure as claimed.
本開示における分散限界メジアン径ａを説明する説明図である。It is an explanatory view explaining dispersion limit median diameter a in the present disclosure.
　以下に、本開示の実施形態を詳しく説明する。但し、本開示の技術的範囲は下記で詳述する実施の形態に限定されず、特許請求の範囲に記載された発明とその均等物に及ぶ点に留意されたい。また、本開示は、本明細書に開示されている内容と当該分野における技術常識（設計事項、自明事項を含む）に基づいて実施することができる。 The embodiments of the present disclosure will be described in detail below. However, it should be noted that the technical scope of the present disclosure is not limited to the embodiments detailed below, but extends to the invention described in the claims and equivalents thereof. In addition, the present disclosure can be implemented based on the content disclosed in this specification and common general technical knowledge (including design matters and self-evident matters) in the relevant field.
〈カーボンナノチューブ分散液〉
　本開示のカーボンナノチューブ分散液は、カーボンナノチューブと、水溶性高分子材料と、分散媒と、を少なくとも含み、動的光散乱法にて測定したカーボンナノチューブのメジアン径をＸ、分散限界メジアン径をａとした場合に１．０＜Ｘ／ａ≦２．０であり、Ｘ＜１．０μｍであることを特徴とするものである。 <Carbon nanotube dispersion>
The carbon nanotube dispersion of the present disclosure contains at least carbon nanotubes, a water-soluble polymer material, and a dispersion medium, and X is the median diameter of the carbon nanotubes measured by the dynamic light scattering method, It is characterized in that 1.0<X/a≤2.0, where a, and X<1.0 μm.
〈カーボンナノチューブ（ＣＮＴ）〉
　本開示に用いるカーボンナノチューブ（ＣＮＴ）としては、実質的にグラファイトの１枚面を巻いて筒状にした形状を有するものであれば特に限定されず、グラファイトの１枚面を１層に巻いた単層ＣＮＴ、二層又は三層以上の多層に巻いた多層ＣＮＴのいずれも用いることができる。
　また、カーボンナノチューブの形態としては、例えば、グラファイトウィスカー、フィラメンタスカーボン、グラファイトファイバー、極細炭素チューブ、カーボンチューブ、カーボンフィブリル、カーボンマイクロチューブ及びカーボンナノファイバーを挙げることができるが、これらに限定されず、これらを各単独又は二種以上組み合わせ（以下、単に「少なくとも１種」という）であってもよい。 <Carbon nanotube (CNT)>
The carbon nanotube (CNT) used in the present disclosure is not particularly limited as long as it has a cylindrical shape obtained by substantially winding one face of graphite, and one face of graphite is wound in one layer. Either single-walled CNTs or multi-walled CNTs wound in two or three or more layers can be used.
Examples of forms of carbon nanotubes include, but are not limited to, graphite whiskers, filamentous carbon, graphite fibers, ultrafine carbon tubes, carbon tubes, carbon fibrils, carbon microtubes, and carbon nanofibers. , each of these may be used alone or in combination of two or more (hereinafter simply referred to as "at least one").
　更に、カーボンナノチューブの平均外径は、分散液の粘度、導電性、安定性の点から、１ｎｍ以上９０ｎｍ以下であることが好ましく、３ｎｍ以上３０ｎｍ以下であることがより好ましく、３ｎｍ以上１５ｎｍ以下であることがさらに好ましい。
　本開示において、カーボンナノチューブの平均外径とは、透過型電子顕微鏡の１０万倍以上の倍率の画像を用いて測定した十分なｎ数の外形の算術平均値をいう。
　また、本開示に用いるカーボンナノチューブの純度は、９０～１００質量％が好ましく、特に９５～１００質量％が好ましい。なお、カーボンナノチューブの純度は、ＪＩＳ　Ｋ　１４６９やＪＩＳ　Ｋ　６２１８に準拠して測定した灰分を不純物とし、その不純物量に基づき算出される。 Furthermore, the average outer diameter of the carbon nanotubes is preferably 1 nm or more and 90 nm or less, more preferably 3 nm or more and 30 nm or less, and 3 nm or more and 15 nm or less, from the viewpoint of the viscosity, conductivity, and stability of the dispersion. It is even more preferable to have
In the present disclosure, the average outer diameter of a carbon nanotube refers to the arithmetic mean value of n sufficient outer diameters measured using transmission electron microscope images at a magnification of 100,000 or more.
Further, the purity of the carbon nanotubes used in the present disclosure is preferably 90 to 100% by mass, particularly preferably 95 to 100% by mass. The purity of carbon nanotubes is calculated based on the amount of impurities, with ash measured according to JIS K 1469 and JIS K 6218 as impurities.
　具体的に用いることができるカーボンナノチューブ（ＣＮＴ）としては、例えば、Ｃｎａｎｏ社製のＦｌｏＴｕｂｅ９０００（平均外径１１ｎｍ）、名城ナノカーボン社製のＭＥＩＪＯｅＤＩＰＳ　ＥＣ２．０（平均外径２．０ｎｍ）などの少なくとも１種を用いることができる。 Carbon nanotubes (CNT) that can be specifically used include, for example, FloTube9000 (average outer diameter 11 nm) manufactured by Cnano, MEIJO eDIPS EC2.0 (average outer diameter 2.0 nm) manufactured by Meijo Nano Carbon, etc. One type can be used.
　これらのカーボンナノチューブ（ＣＮＴ）の含有量は、用途に応じて、好適な含有量を設定することができ、特に限定されるものではない。
　例えば、導電ペースト、二次電池用電極ペースト、二次電池用電極などに用いる場合は、高い安定性と導電性能を両立する点、分散液製造時の粘度の点から、その含有量は、分散液全量に対して、０．１～１５．０質量％とすることが好ましく、さらに好ましくは０．１～１０．０質量％、より好ましくは０．５～８．０質量％、１．０～６．０質量％、特に２．０～５．０質量％とすることが望ましい。
　このカーボンナノチューブ（ＣＮＴ）の含有量を０．１質量％以上とすることにより、充分な導電性を確保できるようになり、一方、１５．０質量％以下とすることにより、分散液の安定性と良好な導電性を確保することができるものとなる。 The content of these carbon nanotubes (CNT) is not particularly limited and can be set to a suitable content depending on the application.
For example, when used for conductive paste, secondary battery electrode paste, secondary battery electrode, etc., the content is It is preferably 0.1 to 15.0% by mass, more preferably 0.1 to 10.0% by mass, more preferably 0.5 to 8.0% by mass, with respect to the total amount of the liquid, 1.0 ~6.0% by mass, preferably 2.0 to 5.0% by mass.
By setting the carbon nanotube (CNT) content to 0.1% by mass or more, sufficient conductivity can be ensured, while by setting the content to 15.0% by mass or less, the stability of the dispersion liquid can be improved. And good conductivity can be secured.
〈水溶性高分子材料〉
　本開示に用いる水溶性高分子材料は、水に可溶なもの、または、用いる分散媒（水以外の溶媒）に溶解するものであれば特に限定されずに用いることができる。
　水に可溶な高分子材料としては、例えば、タンパク質やデンプンなどの天然高分子材料の他、ポリアクリル酸、ポリアクリルアミド、ポリオキシエチレンオキシド、ポリビニルピロリドン、ポリビニルアルコール、ポリビニルアミド、ポリアミンなどの合成高分子材料などを挙げることができる。これらの水溶性高分子材料は、カーボンナノチューブ（ＣＮＴ）の分散剤や結着剤として機能するものである。
　また、上記水以外の溶媒に溶解する水溶性高分子材料としては、完全に溶解する場合のみならず、一部が溶解する状態であっても良い。これらの水溶性の高分子を用いることにより、カーボンナノチューブ（ＣＮＴ）の有する導電性を損なうことなく安定に分散することが可能となる。
　水溶性高分子材料としては、特に、非イオン性水溶性高分子とアニオン性水溶性高分子から選ばれる少なくとも１種類以上のものを用いることが好ましく、カーボンナノチューブ（ＣＮＴ）の有する導電性を損なうことなく安定に分散することに特に適したものとなる。 <Water-soluble polymer material>
The water-soluble polymeric material used in the present disclosure can be used without particular limitation as long as it is soluble in water or dissolved in the dispersion medium (solvent other than water) used.
Examples of water-soluble polymeric materials include natural polymeric materials such as proteins and starches, synthetic high molecular weight materials such as polyacrylic acid, polyacrylamide, polyoxyethylene oxide, polyvinylpyrrolidone, polyvinyl alcohol, polyvinylamide, and polyamines. Molecular materials and the like can be mentioned. These water-soluble polymeric materials function as dispersants and binders for carbon nanotubes (CNT).
Moreover, the water-soluble polymeric material that dissolves in a solvent other than water may be in a partially dissolved state as well as in a completely dissolved state. By using these water-soluble polymers, it is possible to stably disperse carbon nanotubes (CNT) without impairing their electrical conductivity.
As the water-soluble polymer material, it is particularly preferable to use at least one kind selected from nonionic water-soluble polymers and anionic water-soluble polymers. It is particularly suitable for stably dispersing without
　用いることができる非イオン性水溶性高分子としては、例えば、ポリオキシエチレンアルキルエーテル、ポリオキシアルキレン誘導体、ポリオキシエチレンフェニルエーテル、ソルビタン脂肪酸エステル、ポリオキシエチレンソルビタン脂肪酸エステル及びアルキルアリルエーテル、グリセロールボレイト脂肪酸エステル及びポリオキシエチレングリセロール脂肪酸エステル、キサンタンガム、ウェランガム、サクシノグリカン、ポリビニルアルコール（ＰＶＡＬ又はＰＶＯＨ）、ポリビニルピロリドン、ポリビニルアセタールなどの少なくとも１種が挙げられる。 Nonionic water-soluble polymers that can be used include, for example, polyoxyethylene alkyl ethers, polyoxyalkylene derivatives, polyoxyethylene phenyl ethers, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters and alkylallyl ethers, glycerol At least one of late fatty acid esters and polyoxyethylene glycerol fatty acid esters, xanthan gum, welan gum, succinoglycan, polyvinyl alcohol (PVAL or PVOH), polyvinylpyrrolidone, polyvinyl acetal, and the like.
　用いることができるアニオン性水溶性高分子としては、例えば、脂肪酸及びその塩、ポリスルホン酸及びその塩、ポリカルボン酸及びその塩、アルキル硫酸エステル及びその塩、アルキルアリールスルホン酸及びその塩、アルキルナフタレンスルホン酸及びその塩、ジアルキルスルホン酸及びその塩、ジアルキルスルホコハク酸及びその塩、アルキルリン酸及びその塩、ポリオキシエチレンアルキルエーテル硫酸及びその塩、ポリオキシエチレンアルキルアリールエーテル硫酸及びその塩、ナフタレンスルホン酸ホルマリン縮合物及びその塩、ポリオキシエチレンアルキルリン酸スルホン酸及びその塩、スチレンアクリル樹脂などのアクリル系高分子、カルボキシメチルセルロース又はそのナトリウム（Ｎａ）塩などのセルロース系高分子などの少なくとも１種が挙げられる。 Examples of usable anionic water-soluble polymers include fatty acids and their salts, polysulfonic acids and their salts, polycarboxylic acids and their salts, alkylsulfuric acid esters and their salts, alkylarylsulfonic acids and their salts, and alkylnaphthalenes. Sulfonic acid and its salts, dialkylsulfonic acid and its salts, dialkylsulfosuccinic acid and its salts, alkyl phosphoric acid and its salts, polyoxyethylene alkyl ether sulfuric acid and its salts, polyoxyethylene alkylaryl ether sulfuric acid and its salts, naphthalene sulfone At least one of acid-formalin condensates and salts thereof, polyoxyethylene alkyl phosphate sulfonic acid and salts thereof, acrylic polymers such as styrene acrylic resins, and cellulose polymers such as carboxymethylcellulose or sodium (Na) salts thereof is mentioned.
　好ましくは、導電性を阻害しない点から、用いる非イオン性水溶性高分子としては、ポリビニルピロリドンの使用が望ましく、また、アニオン性水溶性高分子では、アクリル系高分子、セルロース系高分子の使用が望ましい。 Polyvinylpyrrolidone is preferably used as the nonionic water-soluble polymer because it does not impede conductivity, and acrylic polymers and cellulose-based polymers are used as anionic water-soluble polymers. is desirable.
　これらの水溶性高分子材料の（合計）含有量は、用途に応じて、好適な含有量を設定することができ、特に限定されるものでない。
　例えば、導電ペースト、二次電池用電極ペースト、二次電池用電極などに用いる場合は、高い安定性と導電性能を両立するために、その含有量は、分散液全量に対して、０．００５～２０質量％とすることが好ましく、特に好ましくは、０．０２５～１６質量％とすることが望ましい。
　これらの高分子材料の含有量を０．００５質量％以上とすることにより、カーボンナノチューブ（ＣＮＴ）の分散安定性が良好となり、一方、２０質量％以下とすることにより、分散液の安定性と良好な導電性を確保することができるものとなる。 The (total) content of these water-soluble polymer materials is not particularly limited and can be set to a suitable content depending on the application.
For example, when used as a conductive paste, a secondary battery electrode paste, a secondary battery electrode, etc., in order to achieve both high stability and conductive performance, the content is 0.005 with respect to the total amount of the dispersion liquid. It is preferably from 0.025 to 16% by mass, preferably from 0.025 to 16% by mass.
When the content of these polymer materials is 0.005% by mass or more, the dispersion stability of carbon nanotubes (CNT) is improved, while when the content is 20% by mass or less, the stability of the dispersion is improved. Good electrical conductivity can be secured.
〈分散媒〉
　本開示に用いる分散媒は、非イオン性水溶性高分子とアニオン性水溶性高分子などの水溶性高分子材料を一部でも溶解させることができるものであれば、水（精製水、蒸留水、純水、超純水など）、有機溶媒など特に限定されることなく用いることが可能である。
　分散媒としては、単独で用いるのみならず、２種類以上を混合して用いることも可能であり、水と有機溶媒の組合せであっても、混合可能な範囲で適宜調整して用いることが可能である。 <Dispersion medium>
The dispersion medium used in the present disclosure is water (purified water, distilled water , pure water, ultrapure water, etc.), organic solvents, etc. can be used without particular limitation.
As the dispersion medium, not only can it be used alone, but it is also possible to use a mixture of two or more types, and even a combination of water and an organic solvent can be used by appropriately adjusting it within a miscible range. is.
　有機溶媒としては、例えば、芳香族類、アルコール類、多価アルコール類、グリコールエーテル類、エステル類等を用いることができる。これらの溶媒は、単独で用いてもよく、又は組み合わせて用いてもよい。 As organic solvents, for example, aromatics, alcohols, polyhydric alcohols, glycol ethers, esters, etc. can be used. These solvents may be used alone or in combination.
　芳香族類としては、例えば、ベンジルアルコール、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、エチレングリコールモノフェニルエーテル、エチレングリコールモノベンジルエーテル、プロピレングリコールモノフェニルエーテル、ジエチレングリコールモノメチルエーテル、ジエチレングリコールモノエチルエーテル、ジエチレングリコールモノブチルエーテル、ジエチレングリコールモノフェニルエーテル、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル、プロピレングリコールモノブチルエーテル、エチレングリコールモノメチルエーテルアセテート、トリエチレングリコールモノメチルエーテル、トリエチレングリコールモノエチルエーテル、トリエチレングリコールモノブチルエーテル、エチレングリコールモノフェニルエーテル、プロピレングリコールモノフェニルエーテル、アルキルスルフォン酸フェニルエステル、フタル酸ブチル、フタル酸エチルヘキシル、フタル酸トリデシル、トリメリット酸エチルヘキシル、ジエチレングリコールジベンゾエート、ジプロピレングリコールジベンゾエート等を用いることができる。 Examples of aromatics include benzyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, propylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol. Monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monophenyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene Glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, phenyl alkylsulfonate, butyl phthalate, ethylhexyl phthalate, tridecyl phthalate, ethylhexyl trimellitate, diethylene glycol dibenzoate, dipropylene glycol dibenzoate, etc. can be used.
　アルコール類としては、例えば、エタノール、ｎ－プロパノール、イソプロパノール、ｎ－ブタノール、イソブタノール、ｔｅｒｔ－ブチルアルコール、１－ペンタノール、イソアミルアルコール、ｓｅｃ－アミルアルコール、３－ペンタノール、ｔｅｒｔ－アミルアルコール、ｎ－ヘキサノール、メチルアミルアルコール、２－エチルブタノール、ｎ－ヘプタノール、２－ヘプタノール、３－ヘプタノール、ｎ－オクタノール、２－オクタノール、２－エチルヘキサノール、３，５，５－トリメチルヘキサノール、ノナノール、ｎ－デカノール、ウンデカノール、ｎ－デカノール、トリメチルノニルアルコール、テトラデカノール、ヘプタデカノール、シクロヘキサノール、２－メチルシクロヘキサノール等を用いることができる。 Examples of alcohols include ethanol, n-propanol, isopropanol, n-butanol, isobutanol, tert-butyl alcohol, 1-pentanol, isoamyl alcohol, sec-amyl alcohol, 3-pentanol, tert-amyl alcohol, n-hexanol, methyl amyl alcohol, 2-ethylbutanol, n-heptanol, 2-heptanol, 3-heptanol, n-octanol, 2-octanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, nonanol, n -decanol, undecanol, n-decanol, trimethylnonyl alcohol, tetradecanol, heptadecanol, cyclohexanol, 2-methylcyclohexanol and the like can be used.
　多価アルコール類としては、例えば、エチレングリコール、ジエチレングリコール、トリエチレングリコール、ポリエチレングリコール、プロピレングリコール、ジプロピレングリコール、ポリプロピレングリコール、ブチレングリコール、ヘキサンジオール、ペンタンジオール、グリセリン、ヘキサントリオール、チオジグリコール、３－メチル－１，３ブンタンジオール、トリエチレングリコール、ジプロピレングリコール、１，３－プロパンジオール、１，３－ブタンジオール、１，５－ペンタンジオール、ヘキシレングリコール、オクチレングリコール等を用いることができる。 Examples of polyhydric alcohols include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol, 3 -methyl-1,3-butanediol, triethylene glycol, dipropylene glycol, 1,3-propanediol, 1,3-butanediol, 1,5-pentanediol, hexylene glycol, octylene glycol and the like can be used. can.
　グリコールエーテル類としては、例えば、メチルイソプロピルエーテル、エチルエーテル、エチルプロピルエーテル、エチルブチルエーテル、イソプロピルエーテル、ブチルエーテル、ヘキシルエーテル、２－エチルヘキシルエーテル、エチレングリコールモノヘキシルエーテル、エチレングリコールモノ－２－エチルブチルエーテル、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、ジエチレングリコールモノエチルエーテル、ジエチレングリコールモノブチルエーテル、トリエチレングリコールモノブチルエーテル、テトラエチレングリコールモノブチルエーテル、３－メチル－３－メトキシ－１－ブタノール、３－メトキシ－１－ブタノール、プロピレングリコールモノメチルエーテル、プロピレングリコールモノエチルエーテル、プロピレングリコールモノプロピルエーテル、プロピレングリコールモノブチルエーテル、プロピレングリコールターシャリーブチルエーテルジプロピレングリコールモノメチルエーテル、ジプロピレングリコールモノエチルエーテル、ジプロピレングリコールモノプロピルエーテル、ジプロピレングリコールモノブチルエーテル、トリプロピレングリコールモノメチルエーテル、トリプロピレングリコールモノブチルエーテル、テトラプロピレングリコールモノブチルエーテル等を用いることができる。 Examples of glycol ethers include methyl isopropyl ether, ethyl ether, ethyl propyl ether, ethyl butyl ether, isopropyl ether, butyl ether, hexyl ether, 2-ethylhexyl ether, ethylene glycol monohexyl ether, ethylene glycol mono-2-ethylbutyl ether, Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monobutyl ether, 3-methyl-3-methoxy-1 -butanol, 3-methoxy-1-butanol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol tertiary butyl ether dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether , dipropylene glycol monopropyl ether, dipropylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, tetrapropylene glycol monobutyl ether and the like can be used.
　エステル類としては、例えば、プロピレングリコールメチルエーテルアセテート、プロピレングリコールジアセテート、３－メチル－３－メトキシブチルアセテート、プロピレングリコールエチルエーテルアセテート、エチレングリコールエチルエーテルアセテート、ギ酸ブチル、ギ酸イソブチル、ギ酸イソアミル、酢酸プロピル、酢酸ブチル、酢酸イソプロピル、酢酸イソブチル、酢酸イソアミル、プロピオン酸メチル、プロピオン酸エチル、プロピオン酸プロピル、プロピオン酸イソブチル、プロピオン酸イソアミル、酪酸メチル、酪酸エチル、酪酸プロピル、イソ酪酸メチル、イソ酪酸エチル、イソ酪酸プロピル、吉草酸メチル、吉草酸エチル、吉草酸プロピル、イソ吉草酸メチル、イソ吉草酸エチル、イソ吉草酸プロピル、トリメチル酢酸メチル、トリメチル酢酸エチル、トリメチル酢酸プロピル、カプロン酸メチル、カプロン酸エチル、カプロン酸プロピル、カプリル酸メチル、カプリル酸エチル、カプリル酸プロピル、ラウリン酸メチル、ラウリン酸エチル、オレイン酸メチル、オレイン酸エチル、カプリル酸トリグリセライド、クエン酸トリブチルアセテート、オキシステアリン酸オクチル、プロピレングリコールモノリシノレート、２－ヒドロキシイソ酪酸メチル、３－メトキシブチルアセテート等を用いることができる。 Examples of esters include propylene glycol methyl ether acetate, propylene glycol diacetate, 3-methyl-3-methoxybutyl acetate, propylene glycol ethyl ether acetate, ethylene glycol ethyl ether acetate, butyl formate, isobutyl formate, isoamyl formate, and acetic acid. Propyl, butyl acetate, isopropyl acetate, isobutyl acetate, isoamyl acetate, methyl propionate, ethyl propionate, propyl propionate, isobutyl propionate, isoamyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate , propyl isobutyrate, methyl valerate, ethyl valerate, propyl valerate, methyl isovalerate, ethyl isovalerate, propyl isovalerate, methyl trimethylacetate, ethyl trimethylacetate, propyl trimethylacetate, methyl caproate, caproic acid Ethyl, propyl caproate, methyl caprylate, ethyl caprylate, propyl caprylate, methyl laurate, ethyl laurate, methyl oleate, ethyl oleate, caprylic triglyceride, tributyl acetate citrate, octyl oxystearate, propylene glycol Monoricinolate, methyl 2-hydroxyisobutyrate, 3-methoxybutyl acetate and the like can be used.
　更に、エタノールアミン、ジエタノールアミン、トリエタノールアミン、Ｎ－メチルジエタノールアミン、Ｎ－エチルジエタノールアミン、モルホリン、Ｎ－エチルモルホリン、エチレンジアミン、ジエチレンジアミン、トリエチレンテトラミン、テトラエチレンペンタミン、ポリエチレンイミン、ペンタメチルジエチレントリアミン、テトラメチルプロピレンジアミンなどのアミン系、Ｎ－メチル－２－ピロリドン（ＮＭＰ）、Ｎ－エチル－２－ピロリドン（ＮＥＰ）、Ｎ，Ｎ－ジメチルホルムアミド、Ｎ，Ｎ－ジメチルアセトアミド、Ｎ，Ｎ－ジエチルアセトアミド、Ｎ－メチルカプロラクタムなどのアミド系，クロヘキシルピロリドン、２－オキサゾリドン、１，３－ジメチル－２－イミダゾリジノン、γ－ブチロラクトンなどの複素環系、ジメチルスルホキシドなどのスルホキシド系、ヘキサメチルホスホロトリアミド、スルホランなどのスルホン系、尿素、アセトニトリルなどの少なくとも１種を使用することができる。 Furthermore, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetra Amines such as methylpropylenediamine, N-methyl-2-pyrrolidone (NMP), N-ethyl-2-pyrrolidone (NEP), N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide , amides such as N-methylcaprolactam, heterocyclics such as chlohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, sulfoxides such as dimethylsulfoxide, hexamethylphosphorotri At least one of amides, sulfones such as sulfolane, urea, and acetonitrile can be used.
　本開示のカーボンナノチューブ分散液には、その用途に応じた添加剤を加えてもよい。例えば、増粘剤としてカルボキシメチルセルロースナトリウム、沈降防止剤、湿潤剤、乳化剤、たれ防止剤、消泡剤、レベリング剤、可塑剤、防カビ・防藻剤、抗菌剤等が挙げられる。 Additives may be added to the carbon nanotube dispersion of the present disclosure according to its use. Examples of thickeners include carboxymethylcellulose sodium, anti-settling agents, wetting agents, emulsifiers, anti-sagging agents, anti-foaming agents, leveling agents, plasticizers, anti-mold/anti-algae agents, and antibacterial agents.
　本開示のカーボンナノチューブ分散液は、さらに、動的光散乱法にて測定したカーボンナノチューブのメジアン径をＸ、分散限界メジアン径をａとした場合に、１．０＜Ｘ／ａ≦２．０であり、Ｘ＜１．０μｍであることを特徴とするものである。 In the carbon nanotube dispersion of the present disclosure, further, where X is the median diameter of the carbon nanotubes measured by the dynamic light scattering method, and a is the median diameter of the dispersion limit, 1.0 < X/a ≤ 2.0 and is characterized by X<1.0 μm.
〈メジアン径Ｘ〉
　本開示（後述する実施例、比較例を含む）において、動的光散乱法にて測定したカーボンナノチューブのメジアン径Ｘは、２５℃の環境下で測定した散乱強度基準メジアン径（キュムラント解析法による中位径、頻度の累積が５０％になる粒子径、Ｄ５０）をいい、例えば、ＦＰＡＲ－１０００（大塚電子社製）を用いて測定することができる。
　測定に際しては、カーボンナノチューブ分散液に使用されている分散媒によって適宜最適な濃度となるように希釈して行うことができる。 <Median diameter X>
In the present disclosure (including Examples and Comparative Examples described later), the median diameter X of the carbon nanotube measured by the dynamic light scattering method is the scattering intensity reference median diameter measured in an environment of 25 ° C. (by cumulant analysis method Median diameter, particle diameter at which the cumulative frequency reaches 50%, D50), which can be measured using, for example, FPAR-1000 (manufactured by Otsuka Electronics Co., Ltd.).
The measurement can be carried out by diluting with the dispersion medium used in the carbon nanotube dispersion so as to obtain an optimum concentration.
〈分散限界メジアン径ａ〉
　本開示において、分散限界メジアン径ａとは、分散時間とカーボンナノチューブのメジアン径との関係において、メジアン径の変化の割合（（変化の割合）＝（メジアン径の変化量）／（分散時間の変化量））がマイナスからゼロに変化したとき、かつ最小のメジアン径となったときのカーボンナノチューブのメジアン径として定義することができる。（図１参照）
　また、分散限界メジアン径ａは、本開示におけるカーボンナノチューブ分散液の配合組成とカーボンナノチューブ分散液を得るための分散条件から特定されるものである。 <Dispersion limit median diameter a>
In the present disclosure, the dispersion limit median diameter a, in the relationship between the dispersion time and the median diameter of the carbon nanotube, the rate of change in the median diameter ((rate of change) = (change in median diameter) / (dispersion time It can be defined as the median diameter of the carbon nanotubes when the amount of change)) changes from minus to zero and reaches the minimum median diameter. (See Figure 1)
Further, the distribution limit median diameter a is specified from the blending composition of the carbon nanotube dispersion and the dispersion conditions for obtaining the carbon nanotube dispersion in the present disclosure.
　本開示においては、上記動的光散乱法にて測定したカーボンナノチューブのメジアン径Ｘと、分散限界最小メジアン径ａとが、１．０＜Ｘ／ａ≦２．０であり、Ｘ＜１．０μｍであるときに、安定性と導電性を高度に両立するカーボンナノチューブ分散液を得ることができるものである。 In the present disclosure, the median diameter X of the carbon nanotubes measured by the dynamic light scattering method and the minimum dispersion limit median diameter a are 1.0<X/a≦2.0, and X<1. When it is 0 μm, it is possible to obtain a carbon nanotube dispersion having both stability and conductivity at a high level.
　カーボンナノチューブが凝集することなく１本ずつ独立してバラバラになっている状態は、導電性の面では好ましいが、カーボンナノチューブ分散液の安定性を両立させることが困難である。
　本開示者らは、上記動的光散乱法にて測定したカーボンナノチューブのメジアン径Ｘと、分散限界メジアン径ａとが、１．０＜Ｘ／ａ≦２．０であり、Ｘ＜１．０μｍであるときに、初めて、安定性と導電性を高度に両立することができることを見出したものである。 A state in which the carbon nanotubes are independent and separated one by one without agglomeration is preferable in terms of conductivity, but it is difficult to achieve both stability of the carbon nanotube dispersion.
The present inventors have found that the median diameter X of carbon nanotubes measured by the dynamic light scattering method and the dispersion limit median diameter a are 1.0<X/a≦2.0, and X<1. It was discovered for the first time that a high degree of both stability and conductivity can be achieved when the thickness is 0 μm.
　カーボンナノチューブ分散液のメジアン径Ｘが、Ｘ／ａ＝１．０である場合は、カーボンナノチューブが凝集することなく１本ずつ独立してバラバラになっている状態に相当するが、上記したとおり、安定性と導電性の高度な両立が困難である。また、２．０＜Ｘ／ａである場合には、カーボンナノチューブの分散が不十分であるか過剰に分散している状態であり、導電性も安定性も低下してしまい好ましくない。
　さらに、Ｘ＜１．０μｍ（１０００ｎｍ）を満たす場合に、安定性と導電性を最も効果的に両立することが可能であり、Ｘ≧１．０μｍ（１０００ｎｍ）の場合には、安定性が落ちてしまい好ましくない。 When the median diameter X of the carbon nanotube dispersion liquid is X/a=1.0, it corresponds to a state in which the carbon nanotubes are separated one by one without aggregating. It is difficult to achieve a high degree of compatibility between stability and conductivity. On the other hand, when 2.0<X/a, the carbon nanotubes are either insufficiently dispersed or excessively dispersed, which is not preferable because both conductivity and stability are lowered.
Furthermore, when X<1.0 μm (1000 nm), it is possible to achieve both stability and conductivity most effectively, and when X≧1.0 μm (1000 nm), stability decreases. I don't like it.
　本開示において、上記特性のカーボンナノチューブ分散液は、上記配合特性の各成分を下記に示すような分散装置により好適な条件で分散して調製することができる。
　例えば、分散装置としては、顔料分散等に通常用いられている分散機を使用することができ、例えば、ディスパー、ホモミキサー、自転公転ミキサー、ヘンシェルミキサー、プラネタリーミキサー等のミキサー類、（高圧）ホモジナイザー、ペイントコンディショナー、コロイドミル類、ビーズミル、コーンミル、ボールミル、サンドミル、アトライター、パールミル、コボールミル等のメディア型分散機、湿式ジェットミル、薄膜旋回型高速ミキサー等のメディアレス分散機、その他ロールミル等が挙げられるが、これらに限定されるものではない。
　好ましい分散装置としては、安定性や分散効率の点から、薄膜旋回型高速ミキサーやビーズミルなどが好ましい。 In the present disclosure, the carbon nanotube dispersion having the properties described above can be prepared by dispersing each component having the properties described above under suitable conditions using a dispersing device as shown below.
For example, as the dispersing device, a dispersing machine that is commonly used for pigment dispersion or the like can be used. Homogenizers, paint conditioners, colloid mills, bead mills, cone mills, ball mills, sand mills, attritors, pearl mills, coball mills and other media-type dispersers, wet jet mills, thin-film rotating high-speed mixers and other medialess dispersers, and other roll mills. Examples include, but are not limited to.
From the standpoint of stability and dispersion efficiency, preferred dispersing devices include a thin-film rotating high-speed mixer and a bead mill.
　本開示において、カーボンナノチューブ分散液の分散限界メジアン径ａは、上述の配合組成、用いる分散機種により若干変動するものであるが、好ましくは、ある分散機を選択して、その分散機で行う分散条件を変えずに分散した場合の分散限界メジアン径ａを計測することが望ましい。例えば、ビーズミルを用いる場合は、メディアのビーズ径や充填率、分散周速、分散機に導入する分散液の流速、冷却水の流量や温度などの条件を固定して分散し、特定することが望ましい。
　また、本開示では、カーボンナノチューブの分散限界メジアン径がａを示したときの分散経過時間をＴａとした場合に、Ｔａ未満となる分散時間で分散し、本発明のメジアン径の範囲となる１．０＜Ｘ／ａ≦２．０であり、かつＸ＜１．０μｍであるカーボンナノチューブ分散液とすることがより好ましい。 In the present disclosure, the distribution limit median diameter a of the carbon nanotube dispersion liquid varies slightly depending on the above-described formulation composition and the type of dispersion used, but preferably, a certain disperser is selected and dispersion is performed with that disperser. It is desirable to measure the dispersion limit median diameter a when dispersed without changing the conditions. For example, when using a bead mill, it is possible to set and specify conditions such as the media bead diameter and filling rate, dispersion peripheral speed, flow velocity of the dispersion liquid introduced into the disperser, cooling water flow rate and temperature, etc. desirable.
Further, in the present disclosure, when the dispersion limit median diameter of the carbon nanotubes is a and the elapsed dispersion time is Ta, the dispersion is dispersed for a dispersion time less than Ta, and the median diameter range of the present invention is 1. More preferably, the carbon nanotube dispersion satisfies .0<X/a≦2.0 and X<1.0 μm.
　また、本開示のカーボンナノチューブ分散液の粘度は、安定性の点、ハンドリングの点から、コーンプレート粘度計（ローター回転速度１０ｒｐｍ（せん断速度３８．３ｓ－１）、温度２５℃）にて測定した際の粘度値が、１～１００００ｍＰａ・ｓであることが好ましく、１～５０００ｍＰａ・ｓであることがより好ましい。 In addition, the viscosity of the carbon nanotube dispersion of the present disclosure was measured with a cone-plate viscometer (rotor rotation speed 10 rpm (shear rate 38.3 s -1 ), temperature 25 ° C.) from the viewpoint of stability and handling. The actual viscosity value is preferably 1 to 10,000 mPa·s, more preferably 1 to 5,000 mPa·s.
　このように構成される本開示のカーボンナノチューブ分散液は、高い安定性と導電性能を両立することができるものとなる。このカーボンナノチューブ分散液は、従来にない優れた性能を有するので、導電ペースト、二次電池用電極ペースト及び二次電池用電極、この電極を用いたリチウムイオン電池などに好適な二次電池などに利用することができるものとなる。 The carbon nanotube dispersion liquid of the present disclosure configured in this way can achieve both high stability and conductive performance. Since this carbon nanotube dispersion has unprecedented excellent performance, it can be used as a conductive paste, an electrode paste for secondary batteries, an electrode for secondary batteries, and a secondary battery suitable for lithium ion batteries using this electrode. It becomes available.
〈導電ペースト〉
　本開示の導電ペーストは、上記構成のカーボンナノチューブ分散液を少なくとも含むことを特徴とするものであり、導電性樹脂製品、導電性接着剤、プリント配線用途などに利用することができる。
　この導電ペーストとしては、上述の高い安定性と導電性能を両立することができるカーボンナノチューブ分散液に、少なくとも樹脂成分を添加して構成することができる。樹脂成分としては、例えば、熱硬化性樹脂、紫外線硬化性樹脂などが使用できる。 <Conductive paste>
The conductive paste of the present disclosure is characterized by containing at least the carbon nanotube dispersion liquid having the above structure, and can be used for conductive resin products, conductive adhesives, printed wiring applications, and the like.
This conductive paste can be configured by adding at least a resin component to the above-described carbon nanotube dispersion liquid capable of achieving both high stability and conductive performance. As the resin component, for example, a thermosetting resin, an ultraviolet curable resin, or the like can be used.
〈二次電池用電極ペースト、二次電池用電極〉
　本開示の二次電池用電極ペーストは、上記構成のカーボンナノチューブ分散液と、二次電池用活物質と、を少なくとも含むことを特徴とするものであり、本開示の二次電池用電極は、上記構成の二次電池用電極ペーストを用いることを特徴とするものである。 <Electrode paste for secondary battery, electrode for secondary battery>
The secondary battery electrode paste of the present disclosure is characterized by including at least the carbon nanotube dispersion having the above configuration and the secondary battery active material, and the secondary battery electrode of the present disclosure includes: It is characterized by using the electrode paste for secondary batteries having the above structure.
　上記構成のカーボンナノチューブ分散液は、そのまま、または、希釈、または、濃縮して用いることができる。
　二次電池用電極ペースト、二次電池用電極に含有されるカーボンナノチューブは、電極特性やセル化された後の電池容量、充放電特性などにより適宜調整され、最適な含有量とされるものであるが、１～１５質量部となるように含有されることが望ましい。 The carbon nanotube dispersion having the above constitution can be used as it is, or after being diluted or concentrated.
The carbon nanotubes contained in electrode paste for secondary batteries and electrodes for secondary batteries are appropriately adjusted according to the electrode characteristics, battery capacity after cell formation, charge-discharge characteristics, etc., and the optimum content is obtained. However, it is desirable that it be contained in an amount of 1 to 15 parts by mass.
　上記二次電池用電極ペーストに用いる活物質としては、正極活性物質、または負極活性物質のいずれも使用することができる。
　二次電池用正極活物質としては、リチウムイオン電池の正極に使用可能な通常の正極活物質（リチウムイオンを可逆的に出入りさせる活物質）であれば、特に限定されずに用いることができる。
　例えば、リチウム－ニッケル複合酸化物、リチウム－コバルト複合酸化物、リチウム－マンガン複合酸化物、リチウム－ニッケル－マンガン複合酸化物、リチウム－ニッケル－コバルト複合酸化物、リチウム－ニッケル－アルミニウム複合酸化物、リチウム－ニッケル－コバルト－アルミニウム複合酸化物、リチウム－ニッケル－マンガン－コバルト複合酸化物、リチウム－ニッケル－マンガン－アルミニウム複合酸化物、リチウム－ニッケル－コバルト－マンガン－アルミニウム複合酸化物等のリチウムと遷移金属との複合酸化物、ＴｉＳ２、ＦｅＳ、ＭｏＳ２等の遷移金属硫化物、ＭｎＯ、Ｖ２Ｏ５、Ｖ６Ｏ１３、ＴｉＯ２等の遷移金属酸化物、オリビン型リチウムリン酸化物等が挙げられる。オリビン型リチウムリン酸化物は、例えば、Ｍｎ、Ｃｒ、Ｃｏ、Ｃｕ、Ｎｉ、Ｖ、Ｍｏ、Ｔｉ、Ｚｎ、Ａｌ、Ｇａ、Ｍｇ、Ｂ、Ｎｂ、およびＦｅよりなる群のうちの少なくとも１種の元素と、リチウムと、リンと、酸素とを含んでいる。これらの化合物はその特性を向上させるために一部の元素を部分的に他の元素に置換したものであってもよい。
　好ましい二次電池用正極活物質としては、リチウム－ニッケル複合酸化物であり、更に好ましくは、該リチウム－ニッケル複合酸化物が、式：ＬｉＮｉＸＭ１ＹＭ２ＺＯ２（Ｍ１およびＭ２は、Ａｌ、Ｂ、アルカリ金属、アルカリ土類金属、遷移金属の元素のうち少なくとも１種以上の金属元素、０．８≦Ｘ≦１．０、０≦Ｙ≦０．２、０≦Ｚ≦０．２）で表されるリチウム－ニッケル複合酸化物が望ましい。
　これらの二次電池用正極の活物質は、一種のみを単独で用いてもよく、二種以上を組み合わせて用いてもよい。 As the active material used in the secondary battery electrode paste, either a positive electrode active material or a negative electrode active material can be used.
The positive electrode active material for secondary batteries is not particularly limited as long as it is a normal positive electrode active material (an active material that allows lithium ions to reversibly enter and exit) that can be used for the positive electrode of a lithium ion battery.
For example, lithium-nickel composite oxide, lithium-cobalt composite oxide, lithium-manganese composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-aluminum composite oxide, Lithium and transitions such as lithium-nickel-cobalt-aluminum composite oxide, lithium-nickel-manganese-cobalt composite oxide, lithium-nickel-manganese-aluminum composite oxide, lithium-nickel-cobalt-manganese-aluminum composite oxide composite oxides with metals, transition metal sulfides such as TiS2 , FeS and MoS2 ; transition metal oxides such as MnO, V2O5 , V6O13 and TiO2 ; mentioned. The olivine-type lithium phosphate is, for example, at least one selected from the group consisting of Mn, Cr, Co, Cu, Ni, V, Mo, Ti, Zn, Al, Ga, Mg, B, Nb, and Fe. It contains the elements Lithium, Phosphorus and Oxygen. These compounds may have some elements partially substituted with other elements in order to improve their properties.
A preferable positive electrode active material for a secondary battery is a lithium-nickel composite oxide, and more preferably the lithium-nickel composite oxide has the formula: LiNi X M1 Y M2 ZO 2 (M1 and M2 are Al , B, at least one metal element selected from alkali metals, alkaline earth metals, and transition metals, 0.8≦X≦1.0, 0≦Y≦0.2, 0≦Z≦0.2 ) is desirable.
These positive electrode active materials for secondary batteries may be used singly or in combination of two or more.
　二次電池用負極活物質としては、リチウムイオン電池の負極に使用可能な通常の負極活物質であれば、特に限定されずに用いることができる。
　用いることができる二次電池用負極活物質としては、例えば、リチウム金属、リチウム合金、スズ化合物などの無機化合物、リチウムイオンを吸蔵放出可能な炭素質材料、複数の元素を含む複合酸化物、導電性ポリマーなどが挙げられる。炭素質材料は、例えば、コークス類、ガラス状炭素類、グラファイト類、難黒鉛化性炭素類、熱分解炭素類、炭素繊維などが挙げられる。このうち、人造黒鉛、天然黒鉛などのグラファイト類が、金属リチウムに近い作動電位を有し、高い作動電圧での充放電が可能であり支持塩としてリチウム塩を使用した場合に自己放電を抑え、且つ充電時における不可逆容量を少なくできるため、好ましい。複合酸化物としては、例えば、リチウムチタン複合酸化物やリチウムバナジウム複合酸化物などが挙げられる。二次電池用負極活物質としては、このうち、金属酸化物材料や炭素質材料が安全性の面からみて好ましい。 As the negative electrode active material for a secondary battery, any ordinary negative electrode active material that can be used for the negative electrode of a lithium ion battery can be used without particular limitation.
Examples of usable negative electrode active materials for secondary batteries include inorganic compounds such as lithium metals, lithium alloys, and tin compounds; carbonaceous materials capable of intercalating and deintercalating lithium ions; composite oxides containing multiple elements; and a reactive polymer. Examples of carbonaceous materials include cokes, vitreous carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Among them, graphites such as artificial graphite and natural graphite have an operating potential close to that of metallic lithium, can be charged and discharged at a high operating voltage, and suppress self-discharge when lithium salt is used as a supporting salt. Moreover, the irreversible capacity during charging can be reduced, which is preferable. Examples of composite oxides include lithium-titanium composite oxides and lithium-vanadium composite oxides. Among them, metal oxide materials and carbonaceous materials are preferable as negative electrode active materials for secondary batteries from the viewpoint of safety.
　また、二次電池用電極ペーストには、上記構成のカーボンナノチューブ分散液と、二次電池用の正極又は負極の活物質と、更に結着材（バインダー）を含むことが好ましい。
　用いることができる結着材（バインダー）としては、例えば、ポリイミド系樹脂、ポリフッ化ビニリデン（ＰＶｄＦ）、ポリテトラフルオロエチレン、四フッ化エチレン・六フッ化プロピレン・フッ化ビニリデン系共重合体、六フッ化プロピレン・フッ化ビニリデン系共重合体、四フッ化エチレン・パーフルオロビニルエーテル系共重合体などのフッ素樹脂、ポリエチレン、ポリプロピレンなどのポリオレフィン樹脂、ポリビニルピロリドン、ポリビニルアルコール、スチレンブタジエンゴム（ＳＢＲ）、アクリル系樹脂などを挙げることができる。これらの結着材は２種以上を混合して用いてもよい。
　これらの結着材の量は、集電箔に対する密着性、セル化された後の電池容量や充放電特性の点から、好ましくは、二次電池用電極ペースト全量に対して、０．２～３．０質量部、より好ましくは、０．５～２．５質量部添加することが望ましい。 Moreover, it is preferable that the electrode paste for a secondary battery contains the carbon nanotube dispersion having the above structure, the active material for the positive electrode or the negative electrode for the secondary battery, and a binder.
Examples of binders that can be used include polyimide resins, polyvinylidene fluoride (PVdF), polytetrafluoroethylene, ethylene tetrafluoride/propylene hexafluoride/vinylidene fluoride copolymers, Fluorine resins such as propylene fluoride/vinylidene fluoride copolymers, tetrafluoroethylene/perfluorovinyl ether copolymers, polyolefin resins such as polyethylene and polypropylene, polyvinylpyrrolidone, polyvinyl alcohol, styrene-butadiene rubber (SBR), Acrylic resins and the like can be mentioned. Two or more of these binders may be mixed and used.
The amount of these binders is preferably from 0.2 to 0.2 with respect to the total amount of the secondary battery electrode paste, from the viewpoint of adhesion to the current collecting foil, battery capacity after cell formation, and charge/discharge characteristics. It is desirable to add 3.0 parts by mass, more preferably 0.5 to 2.5 parts by mass.
　更に、二次電池用電極ペーストには、各種溶媒を添加してもよい。溶媒としては、例えば、水（精製水、イオン交換水、蒸留水、超純水など）、芳香族系溶媒、アルコール類、多価アルコール類、エーテル系溶媒、グリコールエーテル系溶媒、エステル系溶媒、アミン系溶媒、アミド系溶媒、複素環系溶媒、スルホキシド系溶媒、スルホン系溶媒などが挙げられる。これらの溶媒は、各単独又は２種以上を混合して用いてもよい。
　これらの溶媒の量は、電極ペーストを塗工する際に、適切な粘性に仕上げる必要性の点から、好ましくは、二次電池用電極ペースト全量に対して、０．５～８０質量部、より好ましくは、１～７０質量部添加することが望ましい。
　更に、上記カーボンナノチューブ分散液、活物質、結着材の他に、本発明の効果を損なわない範囲で、レベリング剤、固体電解質材などを適宜配合することができる。 Further, various solvents may be added to the secondary battery electrode paste. Examples of solvents include water (purified water, ion-exchanged water, distilled water, ultrapure water, etc.), aromatic solvents, alcohols, polyhydric alcohols, ether solvents, glycol ether solvents, ester solvents, Examples include amine solvents, amide solvents, heterocyclic solvents, sulfoxide solvents, sulfone solvents and the like. These solvents may be used alone or in combination of two or more.
The amount of these solvents is preferably 0.5 to 80 parts by mass, more than Preferably, it is desirable to add 1 to 70 parts by mass.
Furthermore, in addition to the above carbon nanotube dispersion, active material, and binder, a leveling agent, a solid electrolyte material, and the like can be added as appropriate within a range that does not impair the effects of the present invention.
　このように構成される二次電池用電極ペーストは、上記カーボンナノチューブ分散液と、二次電池用の正極又は負極の活物質と、結着材（バインダー）、溶媒などを、例えば、二軸型の混練機などを用いることにより調製することができる。
　得られた二次電池用電極ペーストをリチウムイオン二次電池の導電性部材である集電体上に塗布して乾燥することにより所定のリチウムイオン二次電池用正極、負極が得られることとなり、本開示では、長期間の繰り返し充放電に耐えうる電池性能を実現する二次電池用電極ペースト、二次電池用電極が得られることとなる。 The secondary battery electrode paste configured in this way contains the carbon nanotube dispersion, the positive electrode or negative electrode active material for the secondary battery, a binder, a solvent, and the like, for example, a biaxial type It can be prepared by using a kneader or the like.
The obtained secondary battery electrode paste is applied onto a current collector, which is a conductive member of a lithium ion secondary battery, and dried to obtain a predetermined positive electrode and negative electrode for a lithium ion secondary battery. According to the present disclosure, a secondary battery electrode paste and a secondary battery electrode that achieve battery performance that can withstand repeated charging and discharging for a long period of time can be obtained.
　上記電極に使用する集電体の材質や形状は特に限定されず、各種二次電池にあったものを適宜選択することができる。例えば、集電体の材質としては、アルミニウム、銅、ニッケル、チタン、又はステンレス等の金属や合金が挙げられる。また、形状としては、一般的には平板上の箔が用いられるが、表面を粗面化したものや、穴あき箔状のもの、及びメッシュ状の集電体も使用できる。
　集電体上に電極ペーストを塗工する方法としては、特に制限はなく公知の方法を用いることができる。具体的には、ダイコーティング法、ディップコーティング法、ロールコーティング法、ドクターコーティング法、ナイフコーティング法、スプレーコティング法、グラビアコーティング法、スクリーン印刷法または静電塗装法等が挙げる事ができ、乾燥方法としては放置乾燥、送風乾燥機、温風乾燥機、赤外線加熱機、遠赤外線加熱機などが使用できるが、特にこれらに限定されるものではない。
　また、塗布後に平版プレスやカレンダーロール等による圧延処理を行っても良い。電極材層の厚みは、一般的には１μｍ以上、５００μｍ以下であり、好ましくは１０μｍ以上、３００μｍ以下である。 The material and shape of the current collector used for the electrode are not particularly limited, and those suitable for various secondary batteries can be appropriately selected. For example, the material of the current collector includes metals and alloys such as aluminum, copper, nickel, titanium, and stainless steel. As for the shape, a flat foil is generally used, but a roughened surface, a perforated foil, and a mesh current collector can also be used.
The method of applying the electrode paste onto the current collector is not particularly limited and any known method can be used. Specific examples include a die coating method, a dip coating method, a roll coating method, a doctor coating method, a knife coating method, a spray coating method, a gravure coating method, a screen printing method or an electrostatic coating method. As a method, drying by standing, a blow dryer, a hot air dryer, an infrared heater, a far-infrared heater, etc. can be used, but the method is not particularly limited to these.
Further, after application, a rolling treatment using a lithographic press, calendar rolls, or the like may be performed. The thickness of the electrode material layer is generally 1 μm or more and 500 μm or less, preferably 10 μm or more and 300 μm or less.
〈二次電池、リチウムイオン二次電池〉
　本開示の二次電池は、上記二次電池用電極を用いたことを特徴とするものであり、好ましくは、正極と、負極と、電解質とを具備してなるリチウムイオン二次電池の正極、負極に上記二次電池用電極を用いたものが好ましい。以下において、リチウムイオン二次電池に用いた場合について説明する。
　正極としては、上記集電体上に正極活物質を含む上述の電極用ペーストを塗工乾燥して電極を作製したものを使用することができる。
　負極としては、集電体上に負極活物質を含む電極用ペーストを塗工乾燥して電極を作製したものを使用することができる。 <Secondary battery, lithium ion secondary battery>
The secondary battery of the present disclosure is characterized by using the above secondary battery electrode, and is preferably a positive electrode of a lithium ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, It is preferable to use the above secondary battery electrode as the negative electrode. In the following, the case of using in a lithium ion secondary battery will be described.
As the positive electrode, an electrode prepared by coating and drying the electrode paste containing the positive electrode active material on the current collector can be used.
As the negative electrode, an electrode prepared by coating and drying an electrode paste containing a negative electrode active material on a current collector can be used.
　電解質としては、イオンが移動可能な従来公知の様々なものを使用することができる。例えば、ＬｉＢＦ4、ＬｉＣｌＯ4、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＳｂＦ6、ＬｉＣＦ3ＳＯ3、Ｌｉ（ＣＦ3ＳＯ2）2Ｎ、ＬｉＣ4Ｆ9ＳＯ3、Ｌｉ（ＣＦ3ＳＯ2）3Ｃ、ＬｉＩ、ＬｉＢｒ、ＬｉＣｌ、ＬｉＡｌＣｌ、ＬｉＨＦ2、ＬｉＳＣＮ、又はＬｉＢＰｈ4（ただし、Ｐｈはフェニル基である）等リチウム塩を含むものが挙げられるが、これらに限定されない。電解質は非水系の溶媒に溶解して、電解液として使用することが好ましい。 As the electrolyte, various conventionally known substances in which ions can move can be used. For example, LiBF4 , LiClO4 , LiPF6 , LiAsF6 , LiSbF6 , LiCF3SO3 , Li ( CF3SO2 ) 2N , LiC4F9SO3 , Li( CF3SO2 ) 3C , LiI , LiBr, LiCl, LiAlCl, LiHF 2 , LiSCN, or LiBPh 4 (where Ph is a phenyl group) containing lithium salts. The electrolyte is preferably dissolved in a non-aqueous solvent and used as an electrolytic solution.
　非水系の溶媒としては、特に限定はされないが、例えば、エチレンカーボネート、プロピレンカーボネート、ブチレンカーボネート、ジメチルカーボネート、エチルメチルカーボネート、及びジエチルカーボネート等のカーボネート類；γ－ブチロラクトン、γ－バレロラクトン、及びγ－オクタノイックラクトン等のラクトン類；テトラヒドロフラン、２－メチルテトラヒドロフラン、１，３－ジオキソラン、４－メチル－１，３－ジオキソラン、１，２－メトキシエタン、１，２－エトキシエタン、及び１，２－ジブトキシエタン等のグライム類；メチルフォルメート、メチルアセテート、及びメチルプロピオネート等のエステル類；ジメチルスルホキシド、及びスルホラン等のスルホキシド類；並びに、アセトニトリル等のニトリル類等が挙げられる。これらの溶媒は、それぞれ単独で使用しても良いが、２種以上を混合して使用しても良い。 Examples of non-aqueous solvents include, but are not limited to, carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, ethylmethyl carbonate, and diethyl carbonate; γ-butyrolactone, γ-valerolactone, and γ - lactones such as octanoic lactone; tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,2-methoxyethane, 1,2-ethoxyethane, and 1, glymes such as 2-dibutoxyethane; esters such as methylformate, methylacetate and methylpropionate; sulfoxides such as dimethylsulfoxide and sulfolane; and nitriles such as acetonitrile. Each of these solvents may be used alone, or two or more of them may be mixed and used.
　本開示において、リチウムイオン二次電池には、セパレーターを含むことが好ましい。セパレーターとしては、例えば、ポリエチレン不織布、ポリプロピレン不織布、ポリアミド不織布及びこれらに親水性処理を施したものが挙げられるが、特にこれらに限定されるものではない。
　リチウムイオン二次電池の構造は特に限定されないが、通常、正極及び負極と、必要に応じて設けられるセパレーターとから構成され、ペーパー型、円筒型、ボタン型、積層型等、使用する目的に応じた種々の形状とすることができる。 In the present disclosure, the lithium ion secondary battery preferably contains a separator. Examples of separators include polyethylene nonwoven fabrics, polypropylene nonwoven fabrics, polyamide nonwoven fabrics, and those subjected to hydrophilic treatment, but are not particularly limited to these.
Although the structure of the lithium ion secondary battery is not particularly limited, it usually consists of a positive electrode, a negative electrode, and an optional separator. It can be of various shapes.
　このように構成される本開示の二次電池となるリチウムイオン二次電池等は、長期間の繰り返し充放電に耐えうる電池性能を実現する二次電池が得られることとなる。 A lithium-ion secondary battery or the like, which is a secondary battery of the present disclosure configured in this way, can provide a secondary battery that achieves battery performance that can withstand repeated charging and discharging for a long period of time.
　以下に本開示を実施例により説明するが、本開示はこれらの実施例に限定されるものではない。 Although the present disclosure will be described below using examples, the present disclosure is not limited to these examples.
　〔実施例１～１１、比較例１～５：カーボンナノチューブ分散液の調製）
（分散限界メジアン径ａの特定）
　下記表１に示す配合組成〔カーボンナノチューブ、分散剤（高分子材料）、分散媒の各量〕を、横型ビーズミル（分散装置Ａ）又は薄膜旋回型高速ミキサー（分散装置Ｂ）にて分散し、任意の時間毎にサンプリングしてカーボンナノチューブの動的光散乱法によるメジアン径を測定し、実施例、比較例における分散限界メジアン径ａを求めた。
　なお、分散装置Ａ、及びＢにおける分散条件は下記のとおりである。
　分散装置Ａ：ビーズ径φ０．５ｍｍのジルコニアビーズ、分散時間０～３６０分
　分散装置Ｂ：ミキサー回転数４０ｒｐｍ、分散時間０～３６０分 [Examples 1 to 11, Comparative Examples 1 to 5: Preparation of carbon nanotube dispersions)
(Specification of dispersion limit median diameter a)
The compounding composition shown in Table 1 below [each amount of carbon nanotubes, dispersant (polymer material), and dispersion medium] was dispersed in a horizontal bead mill (dispersing device A) or a thin film swirling high-speed mixer (dispersing device B), Samples were taken every arbitrary time and the median diameter of the carbon nanotubes was measured by the dynamic light scattering method to obtain the dispersion limit median diameter a in the examples and comparative examples.
The dispersing conditions in the dispersing apparatuses A and B are as follows.
Dispersing device A: zirconia beads with a bead diameter of φ0.5 mm, dispersion time 0 to 360 minutes Dispersing device B: mixer rotation speed 40 rpm, dispersion time 0 to 360 minutes
（実施例１）
　下記表１に示す配合組成〔カーボンナノチューブ、分散剤（高分子材料）、分散媒の各量〕、分散装置Ａを用いて、分散時間Ｔｘ（分）の分散を行いカーボンナノチューブ分散液を得た。
　得られたカーボンナノチューブ分散液の動的光散乱法によるメジアン径Ｘ（ｎｍ）、ａとＸの関係を示すＸ／ａを下記表１に記載すると共に、下記方法で、安定性と導電性について、下記評価基準により評価した。これらの評価結果を下記表１に示す。 (Example 1)
A carbon nanotube dispersion was obtained by dispersing for a dispersion time of Tx (minutes) using a blending composition shown in Table 1 below [each amount of carbon nanotubes, dispersant (polymer material), and dispersion medium] and dispersing apparatus A. .
The median diameter X (nm) of the resulting carbon nanotube dispersion obtained by the dynamic light scattering method and X/a showing the relationship between a and X are shown in Table 1 below, and the stability and conductivity were measured by the following method. , was evaluated according to the following evaluation criteria. These evaluation results are shown in Table 1 below.
（実施例２～９、１１、比較例１～５）
　実施例１と同様にして得られた結果を下記表１に示す。 (Examples 2 to 9, 11, Comparative Examples 1 to 5)
The results obtained in the same manner as in Example 1 are shown in Table 1 below.
（実施例１０）
　分散装置Ｂを用いて分散したことを除いて、実施例１と同様にして得られた結果を下記表１に示す． (Example 10)
Table 1 below shows the results obtained in the same manner as in Example 1, except that dispersing apparatus B was used.
（メジアン径Ｘの測定方法）
　動的光散乱法（２５℃）により、キュムラント解析法によるメジアン径を測定した。 (Method for measuring median diameter X)
The median diameter was measured by the cumulant analysis method by the dynamic light scattering method (25° C.).
（分散液粘度の測定方法）
　コーンプレート型粘度計（東機産業社製、１°３４′Ｒ２４コーン）を用いて２５℃にて１０ｒｐｍ(せん断速度３８．３ｓ－１)の条件で、粘度を測定した。 (Method for measuring dispersion viscosity)
The viscosity was measured at 25° C. and 10 rpm (shear rate: 38.3 s −1 ) using a cone-plate viscometer (1°34′R24 cone manufactured by Toki Sangyo Co., Ltd.).
（安定性の評価方法）
　（１）経時粘度の変化率、（２）経時での液の外観、（３）経時後の液を膜にした時の状態をそれぞれ評価し、それらの結果〔（１）～（３）〕から下記評価基準で安定性を綜合評価した (Stability evaluation method)
(1) Rate of change in viscosity over time, (2) Appearance of the liquid over time, and (3) State when the liquid was formed into a film after time was evaluated, and the results [(1) to (3)] were evaluated. The stability was comprehensively evaluated according to the following evaluation criteria from
（１）経時粘度の変化率の評価方法
　完成した分散液を、２５℃環境下に１週間置いた時の上記粘度測定方法により求めた粘度値の変化から、変化率(１週間後/初期)を求め、下記評価基準で経時粘度変化率を評価した。
　評価基準：
　　　　Ａ：変化率が２００％未満
　　　　Ｂ：変化率が２００％以上５００％未満
　　　　Ｃ：変化率が５００％以上 (1) Evaluation method for rate of change in viscosity over time The rate of change (after 1 week/initial) is calculated from the change in viscosity value obtained by the above-mentioned viscosity measurement method when the completed dispersion is placed in an environment of 25°C for 1 week. was obtained, and the rate of change in viscosity over time was evaluated according to the following evaluation criteria.
Evaluation criteria:
A: Change rate is less than 200% B: Change rate is 200% or more and less than 500% C: Change rate is 500% or more
（２）経時での液の外観
　上記（１）の２５℃環境下に１週間置いた時の分散液の外観を下記評価基準で官能評価した。
　評価基準：
　　　　Ａ：分離も濃度差もなく均一
　　　　Ｂ：分離や濃度差が少し見られるが、簡単に再撹拌による均一化が可能
　　　　Ｃ：カーボンナノチューブが沈降し、再撹拌による均一化ができない (2) Appearance of liquid over time The appearance of the dispersion liquid after being placed in the above (1) environment at 25°C for one week was sensory evaluated according to the following evaluation criteria.
Evaluation criteria:
A: Uniform with no separation or concentration difference B: Some separation or concentration difference can be seen, but can be easily homogenized by re-stirring C: Carbon nanotubes have settled and cannot be homogenized by re-stirring
（３）経時後の液を膜にした時の状態
　完成した分散液を、ＰＥＴフィルム（ルミラー＃１００－Ｔ６０、東レ社）の片面に隙間が５０μｍのアプリケーターで塗布した後、温度８０℃で乾燥し、得られた膜の状態を下記評価基準で官能評価した。
　　　　Ａ：均一で平滑な塗膜が得られる
　　　　Ｂ：凝集粒が数個見られる、もしくはわずかに面内に濃度差がある
　　　　Ｃ：表面がざらついている、もしくは均一に塗れない (3) State when the liquid after aging is made into a film The completed dispersion is applied to one side of a PET film (Lumirror #100-T60, Toray Industries, Inc.) with an applicator with a gap of 50 μm, and then dried at a temperature of 80 ° C. Then, the state of the obtained film was sensory evaluated according to the following evaluation criteria.
A: A uniform and smooth coating film is obtained B: Several agglomerated grains are observed, or there is a slight difference in density within the plane C: The surface is rough or the coating cannot be applied uniformly
　安定性の評価基準：
　　　　◎：上記（１）～（３）の評価結果の３項目が共にＡ評価
　　　　〇：上記（１）～（３）の評価結果のうち２項目でＡ評価、かつＣ評価が無い。
　　　　△：上記（１）～（３）の評価結果のうちＡ評価が０～１項目、かつＣ評価が無い
　　　　×：上記（１）～（３）の評価結果のうちＣ評価が１項目以上 Stability criteria:
⊚: All three items of the above evaluation results (1) to (3) are rated A. ◯: Two items of the above evaluation results (1) to (3) are rated A, and there is no C rating.
△: Among the evaluation results of (1) to (3) above, the A evaluation is 0 to 1 item, and there is no C evaluation. ×: Among the evaluation results of the above (1) to (3), C evaluation is one or more items.
（導電性の評価方法）
　完成した分散液を、ＰＥＴフィルム（ルミラー＃１００－Ｔ６０、東レ社）の片面に隙間が５０μｍのアプリケーターで塗布した後、温度８０℃で乾燥し、得られた膜の抵抗値を測定した。抵抗値はシート抵抗として、探針間隔１０ｍｍの４探針プローブとミリオームハイテスタ３２２７（日置電機社製）からなる装置を用いて測定し、下記評価基準で導電性を評価した。
　評価基準：
　　　　◎：シート抵抗が２５０Ω／□未満
　　　　〇：シート抵抗が２５０Ω／□以上４００Ω／□未満
　　　　△：シート抵抗が４００Ω／□以上８００Ω／□未満
　　　　×：シート抵抗が８００Ω／□以上 (Conductive evaluation method)
The completed dispersion was applied to one side of a PET film (Lumirror #100-T60, Toray Industries, Inc.) with an applicator having a gap of 50 μm, dried at a temperature of 80° C., and the resistance value of the obtained film was measured. The resistance value was measured as a sheet resistance using an apparatus consisting of a 4-point probe with a probe interval of 10 mm and a milliohm high tester 3227 (manufactured by Hioki Electric Co., Ltd.), and conductivity was evaluated according to the following evaluation criteria.
Evaluation criteria:
◎: Sheet resistance less than 250 Ω/□ ○: Sheet resistance 250 Ω/□ or more and less than 400 Ω/□ △: Sheet resistance 400 Ω/□ or more and less than 800 Ω/□ ×: Sheet resistance 800 Ω/□ or more
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　上記表１の評価結果等から明らかなように、本開示の範囲内である実施例１～１１のカーボンナノチューブ分散液は、安定性と導電性とが高度に両立し、共に優れるものとなった。これに対し、比較例１～５のカーボンナノチューブ分散液は、上記特性を満足することはできなかった。 As is clear from the evaluation results and the like in Table 1 above, the carbon nanotube dispersions of Examples 1 to 11, which are within the scope of the present disclosure, were highly compatible with both stability and conductivity, and both were excellent. . On the other hand, the carbon nanotube dispersions of Comparative Examples 1 to 5 could not satisfy the above properties.
　カーボンナノチューブ分散液は、安定性と導電性能に優れ、燃料電池、各種電極、電磁波シールド材、導電性樹脂、電界放出ディスプレイ用部材などの材料として有用であり、特にリチウムイオン二次電池などの電極の製造に好適な電極ペースト、電極の製造に用いることができ、長期間の繰り返し充放電に耐えうる優れた電池性能を実現することができる。 Carbon nanotube dispersions are excellent in stability and conductive performance, and are useful as materials for fuel cells, various electrodes, electromagnetic wave shielding materials, conductive resins, field emission display members, etc., especially electrodes such as lithium ion secondary batteries. It can be used for the production of electrode paste and electrodes suitable for the production of, and can realize excellent battery performance that can withstand repeated charging and discharging for a long period of time.

Claims (6)

  1. 　カーボンナノチューブと、水溶性高分子材料と、分散媒と、を少なくとも含み、動的光散乱法にて測定したカーボンナノチューブのメジアン径をＸ、分散限界メジアン径をａとした場合に１．０＜Ｘ／ａ≦２．０であり、Ｘ＜１．０μｍであることを特徴とするカーボンナノチューブ分散液。 It contains at least a carbon nanotube, a water-soluble polymer material, and a dispersion medium, and 1.0<1.0 where X is the median diameter of the carbon nanotube measured by a dynamic light scattering method and a is the dispersion limit median diameter. A carbon nanotube dispersion characterized in that X/a≦2.0 and X<1.0 μm.
  2. 　前記水溶性高分子材料が、非イオン性水溶性高分子とアニオン性水溶性高分子から選ばれる1種類以上の高分子材料であることを特徴とする、請求項１に記載のカーボンナノチューブ分散液。 2. The carbon nanotube dispersion according to claim 1, wherein the water-soluble polymer material is one or more polymer materials selected from nonionic water-soluble polymers and anionic water-soluble polymers. .
  3. 　請求項１又は２に記載のカーボンナノチューブ分散液を少なくとも含むことを特徴とする導電ペースト。 A conductive paste comprising at least the carbon nanotube dispersion according to claim 1 or 2.
  4. 　請求項１又は２に記載のカーボンナノチューブ分散液と、二次電池用活物質と、を少なくとも含むことを特徴とする二次電池用電極ペースト。 An electrode paste for a secondary battery, comprising at least the carbon nanotube dispersion according to claim 1 or 2 and an active material for a secondary battery.
  5. 　請求項４に記載の二次電池用電極ペーストを用いたことを特徴とする二次電池用電極。 A secondary battery electrode using the secondary battery electrode paste according to claim 4.
  6. 　請求項５に記載の二次電池用電極を用いたことを特徴とする二次電池。 A secondary battery using the secondary battery electrode according to claim 5.
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JP2011070908A (en) * 2009-09-25 2011-04-07 Mikuni Color Ltd Conductive material dispersion liquid, electrode paste, and conductive material coating active substance
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JP2011070908A (en) * 2009-09-25 2011-04-07 Mikuni Color Ltd Conductive material dispersion liquid, electrode paste, and conductive material coating active substance
JP2012056788A (en) * 2010-09-08 2012-03-22 Toray Ind Inc Carbon nanotube water dispersion
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