WO2020137403A1 - Carbon material dispersion liquid for secondary battery electrodes, slurry composition for secondary battery electrodes, electrode for secondary batteries, and secondary battery - Google Patents

Carbon material dispersion liquid for secondary battery electrodes, slurry composition for secondary battery electrodes, electrode for secondary batteries, and secondary battery Download PDF

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Publication number
WO2020137403A1
WO2020137403A1 PCT/JP2019/047460 JP2019047460W WO2020137403A1 WO 2020137403 A1 WO2020137403 A1 WO 2020137403A1 JP 2019047460 W JP2019047460 W JP 2019047460W WO 2020137403 A1 WO2020137403 A1 WO 2020137403A1
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secondary battery
electrode
carbon material
dispersion liquid
slurry composition
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PCT/JP2019/047460
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French (fr)
Japanese (ja)
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高橋　直樹
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日本ゼオン株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • 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
    • H01M4/04—Processes of manufacture in general
    • 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

  • the present invention relates to a carbon material dispersion liquid for a secondary battery electrode, a slurry composition for a secondary battery electrode, an electrode for a secondary battery, and a secondary battery.
  • Secondary batteries such as lithium-ion secondary batteries are small and lightweight, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members such as electrodes has been studied for the purpose of further improving the performance of secondary batteries.
  • an electrode for a lithium ion secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector. Then, the electrode mixture layer, for example, an electrode active material, a conductive material, a binder or the like is dispersed or dissolved in a dispersion medium, an electrode slurry composition is applied onto a current collector, dried to form an electrode. It is formed by binding an active material and a conductive material with a binder.
  • the electrode mixture layer for example, an electrode active material, a conductive material, a binder or the like is dispersed or dissolved in a dispersion medium, an electrode slurry composition is applied onto a current collector, dried to form an electrode. It is formed by binding an active material and a conductive material with a binder.
  • a carbon material dispersion liquid obtained by dispersing a conductive material made of a carbon material having conductivity such as carbon black in a dispersion medium.
  • Patent Documents 1 and 2 as a carbon material dispersion having excellent dispersibility and storage stability, a carbon black having a predetermined BET specific surface area and a dispersant comprising a polyvinyl alcohol resin having a predetermined saponification degree are disclosed.
  • a carbon black dispersion liquid containing N-methyl-2-pyrrolidone as a dispersion medium is disclosed.
  • the conventional carbon material dispersion liquid for a secondary battery electrode is improved in rate characteristics and high temperature storage characteristics of a secondary battery including an electrode formed by using the carbon material dispersion liquid for a secondary battery electrode. There was room for improvement.
  • the present invention provides a secondary battery electrode capable of exhibiting excellent rate characteristics and high temperature storage characteristics in a secondary battery, and a carbon material dispersion liquid for a secondary battery electrode capable of forming the secondary battery electrode, It is an object to provide a slurry composition for a secondary battery electrode. Another object of the present invention is to provide a secondary battery that is excellent in both rate characteristics and high temperature storage characteristics.
  • the present inventor has conducted extensive studies in order to achieve the above object. Then, the present inventor has determined a median diameter (D50) of a dispersoid to be a predetermined value in a carbon material dispersion liquid for a secondary battery electrode in which a carbon material is dispersed in an organic dispersion medium using a polyvinyl alcohol-based polymer as a dispersant. Within the range, it was found that a secondary battery using an electrode formed by using the carbon material dispersion liquid for a secondary battery electrode can exhibit excellent rate characteristics and high temperature storage characteristics, and completed the present invention. It was
  • the present invention is intended to advantageously solve the above problems, the carbon material dispersion liquid for a secondary battery electrode of the present invention, a carbon material, a polyvinyl alcohol-based polymer, an organic dispersion medium.
  • the median diameter (D50) of the dispersoid is 0.90 ⁇ m or more and 10 ⁇ m or less.
  • the carbon material dispersion for the secondary battery electrode is dispersed.
  • a secondary battery including an electrode having an electrode mixture layer formed using a liquid can exhibit excellent rate characteristics and high-temperature storage characteristics.
  • the “median diameter (D50) of dispersoid” can be measured by the method described in Examples of the present specification.
  • the carbon material is at least one selected from the group consisting of acetylene black, furnace black, Ketjen black, carbon fibers, carbon nanotubes and graphene. It is preferable to include. If at least one selected from the group consisting of acetylene black, furnace black, Ketjen black, carbon fiber, carbon nanotube, and graphene is used as the carbon material, the rate characteristics of the secondary battery can be further improved.
  • the saponification degree of the polyvinyl alcohol-based polymer in the carbon material dispersion liquid for a secondary battery electrode of the present invention is preferably more than 60 mol% and 99.5 mol% or less.
  • the “saponification degree of the polyvinyl alcohol polymer” can be measured in accordance with JIS K0070.
  • the present invention is intended to advantageously solve the above problems, the secondary battery electrode slurry composition of the present invention, any of the above secondary battery electrode carbon material dispersion, It is characterized by containing an electrode active material and a binder.
  • the carbon material dispersion liquid for a secondary battery electrode described above is contained, it is possible to form a secondary battery electrode capable of exhibiting excellent rate characteristics and high temperature storage characteristics in a secondary battery.
  • the electrode for secondary batteries of this invention is the electrode mixture material formed using the slurry composition for secondary battery electrodes mentioned above. It is characterized by having a layer.
  • the secondary battery electrode including the electrode mixture layer formed by using the above-described secondary battery electrode slurry composition the secondary battery can exhibit excellent rate characteristics and high temperature storage characteristics. ..
  • the secondary battery of this invention is equipped with a positive electrode, a negative electrode, an electrolytic solution, and a separator, and at least one of the said positive electrode and a negative electrode is the above-mentioned. It is a secondary battery electrode as described above.
  • a secondary battery including the above-described secondary battery electrode can exhibit excellent rate characteristics and high temperature storage characteristics.
  • the carbon material dispersion liquid for a secondary battery electrode and the slurry composition for a secondary battery electrode of the present invention it is possible to form a secondary battery electrode capable of exhibiting excellent rate characteristics and high temperature storage characteristics in a secondary battery. You can Further, according to the secondary battery electrode of the present invention, the secondary battery can exhibit excellent rate characteristics and high temperature storage characteristics. Furthermore, the secondary battery of the present invention is excellent in both rate characteristics and high temperature storage characteristics.
  • the carbon material dispersion liquid for a secondary battery electrode of the present invention can be used when preparing a slurry composition for a secondary battery electrode.
  • the slurry composition for secondary battery electrodes prepared by using the carbon material dispersion liquid for secondary battery electrodes of the present invention can be used when forming electrodes of secondary batteries such as lithium ion secondary batteries. ..
  • the secondary battery of the present invention is characterized by using an electrode for a secondary battery formed by using the slurry composition for an electrode of the secondary battery of the present invention.
  • the carbon material dispersion liquid for a secondary battery electrode and the slurry composition for a secondary battery electrode of the present invention can be particularly preferably used when forming a positive electrode of a secondary battery.
  • the carbon material dispersion liquid for a secondary battery electrode of the present invention contains a carbon material, a polyvinyl alcohol-based polymer, and an organic dispersion medium, and optionally further contains other components that can be blended in the electrode of the secondary battery. To do. Furthermore, the carbon material dispersion liquid for secondary battery electrodes of the present invention requires that the median diameter (D50) of the dispersoid be 0.90 ⁇ m or more and 10 ⁇ m or less. The carbon material dispersion liquid for a secondary battery electrode usually does not contain an electrode active material.
  • the carbon material dispersion liquid for a secondary battery electrode of the present invention contains a polyvinyl alcohol-based polymer, and further, the median diameter (D50) of the dispersoid is 0.90 ⁇ m or more and 10 ⁇ m or less.
  • a secondary battery including an electrode having an electrode mixture layer formed by using the carbon material dispersion liquid for use can exhibit excellent rate characteristics and high-temperature storage characteristics.
  • the median diameter of the dispersoid is The rate property is improved by having an appropriate size, and the electrode mixture layer due to the stress generated during high temperature storage is obtained by further containing a polyvinyl alcohol polymer and adjusting the median diameter of the dispersoid to an appropriate size. It is presumed that this is because the structural change of is suppressed.
  • the carbon material is not particularly limited as long as it can be used as a conductive material in the electrode of the secondary battery, and a known carbon material can be used.
  • the carbon material is at least selected from the group consisting of acetylene black, furnace black, Ketjen Black (registered trademark), carbon fiber, carbon nanotube, and graphene. It is preferable to use one kind, more preferably to use at least one kind selected from the group consisting of acetylene black, Ketjen black and carbon nanotubes, and further preferable to use acetylene black and/or carbon nanotubes.
  • the amount of the carbon material contained in the carbon material dispersion liquid for secondary battery electrodes (100% by mass) is usually 1% by mass or more and 30% by mass or less, and 3% by mass or more and 30% by mass or less. It is preferable.
  • the polyvinyl alcohol-based polymer has the following formula: It is a polymer containing the vinyl alcohol structural unit represented by and optionally further containing other structural units derived from other monomers.
  • the polyvinyl alcohol-based polymer is, for example, a polyvinyl ester obtained by polymerizing one or more kinds of vinyl ester-based monomers and other monomers which can be optionally copolymerized with the vinyl ester-based monomers. It can be produced by saponifying a polymer.
  • vinyl ester-based monomer for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc. Can be used. Of these, vinyl acetate is preferable.
  • vinyl ester-based monomer examples include, for example, ethylene, propylene, 1-butene, isobutene and other olefins having 2 to 30 carbon atoms; (meth)acrylic acid and Salts thereof; methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, (meth)acrylate i -(Meth)acrylic acid ester such as -butyl, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate; (meth)acrylonitrile, etc.
  • (meth)acrylic acid refers to acrylic acid and/or methacrylic acid
  • (meth)acrylonitrile refers to acrylonitrile and/or methacrylonitrile
  • the polyvinyl ester-based polymer can be obtained by polymerizing the above-mentioned monomers by a conventionally known method, and is a copolymer of one or more kinds of vinyl ester-based monomers and other monomers. Or a polymer obtained by using only a vinyl ester-based monomer.
  • the proportion of structural units derived from other monomers (other structural units) in all structural units contained in the polyvinyl ester-based polymer is preferably 50% by mass or less, and 30% by mass.
  • the content is more preferably the following or less, still more preferably 5% by mass or less, and further preferably 0% by mass (that is, the polyvinyl ester-based polymer is a polymer obtained by using only a vinyl ester-based monomer). Is particularly preferable. It is even more preferable that the polyvinyl ester polymer is a polymer obtained by using only one type of vinyl ester monomer.
  • the saponification of the polyvinyl ester-based polymer is not particularly limited, and can be performed according to a known saponification method using a base such as sodium hydroxide or potassium hydroxide.
  • the degree of saponification of the polyvinyl alcohol-based polymer obtained by saponifying the polyvinyl ester-based polymer is not particularly limited, and is preferably more than 60 mol%, more preferably more than 70 mol%, and 85 mol%. % Is more preferable, it is particularly preferable that it is more than 95 mol%, and it is preferable that it is 99.5 mol% or less.
  • the saponification degree of the polyvinyl alcohol polymer is within the above range, the high temperature storage characteristics of the secondary battery can be further improved.
  • the amount of the polyvinyl alcohol-based polymer contained in the carbon material dispersion liquid for secondary battery electrode is preferably more than 0.1 parts by mass, and more than 1 part by mass, per 100 parts by mass of the carbon material. More preferably, more preferably more than 3 parts by mass, particularly preferably 10 parts by mass or more, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, 30 It is more preferable that the amount is not more than parts by mass.
  • the amount of the polyvinyl alcohol polymer is within the above range, the rate characteristics and the high temperature storage characteristics of the secondary battery can be further improved while the carbon material is well dispersed.
  • the organic dispersion medium is not particularly limited, and a known organic solvent used in the field of secondary batteries can be used.
  • a known organic solvent used in the field of secondary batteries can be used.
  • the organic dispersion medium alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol and decanol; acetone , Ketones such as methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as diethyl ether, dioxane and tetrahydrofuran; amides such as N,N-dimethylformamide and N-methyl-2-pyrrolidone (NMP) System polar organic solvents; aromatic
  • the carbon material dispersion liquid for a secondary battery electrode requires that the median diameter of the dispersoid be 0.90 ⁇ m or more and 10 ⁇ m or less, preferably 1.2 ⁇ m or more, and 1.5 ⁇ m or more. Is more preferable, 3.0 ⁇ m or more is more preferable, 7.0 ⁇ m or less is preferable, 5.0 ⁇ m or less is more preferable, and 4.0 ⁇ m or less is further preferable.
  • the median diameter of the dispersoid is at least the above lower limit, the rate characteristics and high temperature storage characteristics of the secondary battery can be further improved.
  • the rate characteristic of the secondary battery can be further improved.
  • the dispersoid contains a carbon material and a polyvinyl alcohol polymer adsorbed on the carbon material. Then, the median diameter of the dispersoid can be adjusted, for example, by changing the particle diameter of the carbon material, the type and amount of the polyvinyl alcohol-based polymer, and the preparation conditions of the carbon material dispersion liquid for secondary battery electrodes. it can.
  • carbon material dispersion liquid for secondary battery electrodes may optionally contain are not particularly limited, and examples thereof include a reinforcing material, a leveling agent, a viscosity modifier, and an electrolyte solution additive. These are not particularly limited as long as they do not affect the battery reaction, and known ones such as those described in International Publication No. 2012/115096 can be used. Moreover, these components may be used individually by 1 type, and may be used in combination of 2 or more types in arbitrary ratios.
  • the carbon material dispersion liquid for a secondary battery electrode can be prepared by mixing the above components by a known method and dispersing the carbon material or the like in an organic dispersion medium.
  • the mixing of the components described above is not particularly limited, propeller mixer, high speed mixer, dissolver, homogenizer, artemizer, wet jet mill, colloid mill, mass colloider, bead mill, sand mill, ball mill, sand grinder, It can be carried out using a mixing and dispersing machine such as an in-line mixer or a medialess type high speed stirring and dispersing machine. Among them, from the viewpoint of easy adjustment of the median diameter of the dispersoid, it is preferable to use a media stirring type mixing/dispersing machine such as a bead mill.
  • the outer diameter (media diameter) of the media used is preferably 0.1 mm or more, more preferably 0.5 mm or more, and 3 mm or less. It is preferably 2 mm or less, more preferably 1 mm or less.
  • the slurry composition for a secondary battery electrode of the present invention contains the above-mentioned carbon material dispersion liquid for a secondary battery electrode, an electrode active material, and a binder, and can be optionally blended in an electrode of a secondary battery. It further contains components. That is, the secondary battery electrode slurry composition contains a carbon material, a polyvinyl alcohol-based polymer, an organic dispersion medium, an electrode active material, and a binder, and optionally further contains other components. Since the secondary battery electrode slurry composition of the present invention contains the above-described secondary battery electrode carbon material dispersion liquid, an electrode mixture formed using the secondary battery electrode slurry composition. The electrode provided with the layer can exhibit excellent rate characteristics and high temperature storage characteristics in the secondary battery.
  • the carbon material dispersion liquid for secondary battery electrodes the carbon material dispersion liquid for secondary battery electrodes of the present invention described above can be used.
  • the amount of the secondary battery electrode carbon material dispersion liquid used for the preparation of the secondary battery electrode slurry composition is not particularly limited, for example, the amount of the carbon material contained in the slurry composition is the electrode active material. The amount can be 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the substance.
  • the electrode active material is a material that exchanges electrons in the electrode of the secondary battery. Then, for example, when the secondary battery is a lithium-ion secondary battery, a substance capable of inserting and extracting lithium is usually used as the electrode active material.
  • the slurry composition for secondary battery electrodes is a slurry composition for lithium ion secondary battery electrodes is demonstrated below as an example, this invention is not limited to the following examples.
  • the positive electrode active material for a lithium ion secondary battery is not particularly limited, and lithium-containing cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 O 4 ), lithium-containing nickel oxide (LiNiO 2 ). ), Co-Ni-Mn lithium-containing composite oxide (Li(Co Mn Ni)O 2 ), Ni-Mn-Al lithium-containing composite oxide, Ni-Co-Al lithium-containing composite oxide, olivine type Represented by lithium iron phosphate (LiFePO 4 ), olivine-type lithium manganese phosphate (LiMnPO 4 ), Li 2 MnO 3 —LiNiO 2 based solid solution, Li 1+x Mn 2-x O 4 (0 ⁇ X ⁇ 2)
  • Examples of known positive electrode active materials include lithium-excess spinel compounds, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ]O 2 and LiNi 0.5 Mn 1.5 O 4 .
  • examples of the negative electrode active material for a lithium ion secondary battery include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material combining these.
  • the carbon-based negative electrode active material refers to an active material having lithium as a main skeleton into which lithium can be inserted (also referred to as “dope”).
  • examples of the carbon-based negative electrode active material include a carbonaceous material and graphite. Quality materials.
  • Examples of the carbonaceous material include easily graphitizable carbon and non-graphitizable carbon having a structure close to an amorphous structure represented by glassy carbon.
  • examples of the graphitizable carbon include a carbon material obtained from tar pitch obtained from petroleum or coal as a raw material. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber, and pyrolytic vapor growth carbon fiber.
  • Examples of the non-graphitizable carbon include, for example, a phenol resin fired body, polyacrylonitrile-based carbon fiber, pseudo-isotropic carbon, furfuryl alcohol resin fired body (PFA), hard carbon and the like.
  • examples of the graphite material include natural graphite and artificial graphite.
  • artificial graphite for example, artificial graphite obtained by heat-treating carbon containing easily graphitizable carbon at 2800° C. or higher, graphitized MCMB obtained by heat-treating MCMB at 2000° C. or higher, and mesophase pitch-based carbon fiber at 2000° C.
  • the graphitized mesophase pitch-based carbon fiber heat-treated as described above can be used.
  • the metal-based negative electrode active material is an active material containing a metal, and usually has a structure containing an element capable of inserting lithium, and has a theoretical electric capacity of 500 mAh/unit mass per unit mass when lithium is inserted.
  • the metal-based active material include lithium metal and elemental metals capable of forming a lithium alloy (eg, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn). , Sr, Zn, Ti, etc.) and alloys thereof, and their oxides, sulfides, nitrides, silicides, carbides, phosphides and the like.
  • the metal-based negative electrode active material is preferably an active material containing silicon (silicon-based negative electrode active material). This is because the lithium-ion secondary battery can have a high capacity by using the silicon-based negative electrode active material.
  • silicon-based negative electrode active material examples include silicon (Si), alloys containing silicon, SiO, SiO x , and a compound of Si-containing material and conductive carbon obtained by coating or compounding Si-containing material with conductive carbon. And so on.
  • the above electrode active materials may be used alone or in combination of two or more.
  • the binder is not particularly limited as long as it can function as a binder for binding the electrode active material, the carbon material, etc., and a known binder used in the field of secondary batteries can be used. it can.
  • the binder is not particularly limited, but a fluorine-containing polymer such as polyvinylidene fluoride; a polymer containing a conjugated diene monomer unit such as acrylonitrile-butadiene copolymer or styrene-butadiene copolymer is used.
  • a compound (conjugated diene polymer) and its hydride; a polymer containing a (meth)acrylic acid ester monomer unit (acrylic polymer); and the like can be used.
  • One of these polymers may be used alone, or two or more of them may be used in combination.
  • the amount of the binder contained in the secondary battery electrode slurry composition is not particularly limited and can be, for example, 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the electrode active material.
  • the other components that can be added to the slurry composition are not particularly limited, and include the same components as the other components that can be added to the carbon material dispersion liquid for secondary battery electrode described above. Further, other components may be used alone or in combination of two or more at an arbitrary ratio.
  • the slurry composition for secondary battery electrodes can be manufactured by mixing the electrode active material, the binder, the above-mentioned carbon material dispersion liquid for secondary battery electrodes, and any other components.
  • the mixing of the above-mentioned components is not particularly limited, and a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, a mixer such as a fill mix is used. Can be done by The mixing may be performed by newly adding an organic dispersion medium.
  • the order of mixing the above-mentioned components is not particularly limited, and all the components may be mixed together, for example, only one of the electrode active material and the binder is used as a carbon material dispersion liquid for a secondary battery electrode. After mixing, the remaining ingredients may be further mixed.
  • the secondary battery electrode of the present invention includes an electrode mixture layer formed using the above-described secondary battery electrode slurry composition. Therefore, the electrode mixture layer contains at least an electrode active material, a binder, a carbon material, a polyvinyl alcohol-based polymer, and any other component.
  • the respective components contained in the electrode mixture layer were those contained in the slurry composition for a secondary battery electrode, and the preferable abundance ratio of these components is in the slurry composition. It is the same as the preferable abundance ratio of each component.
  • the secondary battery electrode of the present invention since the electrode mixture layer is formed using the above-described secondary battery electrode slurry composition, the conductive path is well formed, and at the time of storage at high temperature. The structural change of the electrode composite material layer due to the generated stress is suppressed. Therefore, when the secondary battery electrode of the present invention is used, the secondary battery can exhibit excellent rate characteristics and high temperature storage characteristics.
  • the electrode mixture layer of the secondary battery electrode of the present invention includes, for example, a step of applying the above-mentioned slurry composition on a current collector (application step) and a slurry composition applied on the current collector. It can be formed on the current collector through a step of drying the material to form an electrode mixture layer on the current collector (drying step).
  • the method for applying the slurry composition onto the current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method or the like can be used. At this time, the slurry composition may be applied to only one surface of the current collector, or may be applied to both surfaces. The thickness of the slurry film on the current collector after coating and before drying can be appropriately set according to the thickness of the electrode mixture layer obtained by drying.
  • the current collector for applying the slurry composition a material having electrical conductivity and electrochemical durability is used.
  • a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used.
  • the above materials may be used alone or in combination of two or more at an arbitrary ratio.
  • the method for drying the slurry composition on the current collector is not particularly limited, and known methods can be used, for example, hot air, hot air, low-humid air drying method, vacuum drying method, infrared ray, electron beam, and the like. A drying method by irradiation can be mentioned.
  • an electrode mixture layer is formed on the current collector, and a secondary battery electrode including the current collector and the electrode mixture layer can be obtained. it can.
  • the electrode mixture layer may be subjected to a pressure treatment using a die press or roll press.
  • the pressure treatment can improve the adhesion between the electrode mixture layer and the current collector.
  • the electrode mixture layer contains a curable polymer, it is preferable to cure the polymer after forming the electrode mixture layer.
  • the secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolytic solution, and a separator, and uses the secondary battery electrode described above as at least one of the positive electrode and the negative electrode. Since the secondary battery of the present invention uses the above-described secondary battery electrode as at least one of the positive electrode and the negative electrode, it can exhibit excellent rate characteristics and high temperature storage characteristics.
  • the secondary battery is a lithium ion secondary battery will be described below as an example, the present invention is not limited to the following example.
  • the electrodes other than the above-mentioned secondary battery electrodes that can be used in the secondary battery of the present invention are not particularly limited, and known electrodes used in the production of secondary batteries can be used. You can Specifically, as the electrodes other than the secondary battery electrode described above, an electrode obtained by forming an electrode mixture layer on a current collector by using a known manufacturing method can be used.
  • an organic electrolytic solution prepared by dissolving a supporting electrolyte in an organic solvent is usually used.
  • a lithium salt is used as the supporting electrolyte of the lithium ion secondary battery.
  • the lithium salt include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi. , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 )NLi, and the like.
  • LiPF 6 , LiClO 4 , and CF 3 SO 3 Li are preferable, and LiPF 6 is particularly preferable, because it is easily dissolved in a solvent and exhibits a high dissociation degree.
  • the electrolytes may be used alone or in combination of two or more at an arbitrary ratio.
  • the lithium ion conductivity tends to be higher as the supporting electrolyte having a higher dissociation degree is used, and thus the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.
  • the organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, and examples thereof include dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), Carbonates such as butylene carbonate (BC) and ethylmethyl carbonate (EMC); esters such as ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide And the like are preferably used. Further, a mixed solution of these solvents may be used. Of these, carbonates are preferably used because they have a high dielectric constant and a wide stable potential region. The concentration of the electrolyte in the electrolytic solution can be adjusted appropriately. Further, known additives can be added to the electrolytic solution.
  • DMC dimethyl carbonate
  • EC ethylene carbonate
  • DEC diethyl
  • the separator is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, the film thickness of the entire separator can be reduced, and thus the capacity per volume can be increased by increasing the ratio of the electrode active material in the secondary battery, and thus the polyolefin-based ( A microporous membrane made of a resin of polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferable.
  • the secondary battery is, for example, a positive electrode and a negative electrode are stacked via a separator, which is wound or folded according to the shape of the battery as required and put into a battery container, and the electrolytic solution is placed in the battery container. It can be manufactured by injecting and sealing.
  • the above-mentioned secondary battery electrode is used as at least one of the positive electrode and the negative electrode.
  • the secondary battery of the present invention may include a fuse, an overcurrent prevention element such as a PTC element, and an expanded metal, if necessary, in order to prevent an increase in internal pressure of the secondary battery and the occurrence of overcharging/discharging.
  • a lead plate or the like may be provided.
  • the shape of the secondary battery may be, for example, a coin type, a button type, a sheet type, a cylindrical type, a prismatic type, a flat type or the like.
  • ⁇ Saponification degree> About 1 g of the polyvinyl alcohol polymer was precisely weighed to the order of 1 mg (the precision value is S), put in a 300 mL Erlenmeyer flask, and 25 mL of 0.5 mol/L potassium hydroxide ethanol solution was added using a pipette. .. Subsequently, a cooling tube was attached to the Erlenmeyer flask and reacted at 40° C. for 30 minutes while stirring. After completion of the reaction, the mixture was cooled, 1 mL of a phenolphthalein solution was added as an indicator, and titration was performed using a 0.5 mol/L hydrochloric acid aqueous solution.
  • the amount of hydrochloric acid at this time is A.
  • the blank test was performed without adding the polyvinyl alcohol polymer.
  • the amount of hydrochloric acid at this time is B.
  • the saponification value X was calculated from the following formula.
  • f is a factor of the 0.5 mol/L hydrochloric acid aqueous solution used.
  • Saponification value X ⁇ (BA) ⁇ f ⁇ 28.05 ⁇ /S
  • the saponification degree was calculated from the following equation, where Y is the number of moles of vinyl ester monomer units contained in 1 g of the polymer (polyvinyl ester polymer) before saponification.
  • Saponification degree [ ⁇ 1-(X/0.0561) ⁇ /Y] ⁇ 100 ⁇ Median diameter>
  • the prepared carbon material dispersion liquid for a secondary battery electrode was diluted to an appropriate concentration and then subjected to ultrasonic treatment for 1 minute (output: 70 W, frequency: 35 kHz, temperature: 25° C.) to obtain a measurement sample.
  • the particle size distribution (volume basis) was measured with the solvent refractive index of 1.47 (N-methyl-2-pyrrolidone), and the median diameter (D50) was calculated. I asked.
  • the concentration of the measurement sample was set so that the absorbance at the measuring device was 0.2 or less.
  • the manufactured secondary battery was charged at a temperature of 25° C. to 4.2 V by the constant current charging method (charging rate: 0.2 C) and then charged by the constant voltage charging method until the current value became 0.02 C. After that, the capacity when discharged to 3.0 V by the constant current method with a discharge rate of 0.2 C was defined as C1. Then, the charging conditions were the same, the capacity was measured in the same manner except that the discharge rate was 2.0 C, and the capacity at this time was C2. Then, the rate characteristic was calculated from the following formula and evaluated according to the following criteria. The larger the value, the lower the battery resistance and the better the rate characteristics.
  • Rate characteristic (C2/C1) ⁇ 100 (%)
  • the manufactured secondary battery was charged at a temperature of 25° C. to 4.2 V by the constant current charging method (charging rate: 0.2 C) and then charged by the constant voltage charging method until the current value became 0.02 C. Then, the charged secondary battery was stored in a constant temperature bath at 60° C. for 30 days. After the secondary battery stored in the constant temperature bath was cooled to a temperature of 25° C., the capacity when discharged to 3.0 V by a constant current method with a discharge rate of 0.2 C was defined as C3.
  • High temperature storage characteristics (C3/C1) ⁇ 100 (%)
  • Example 1 ⁇ Preparation of carbon material dispersion liquid for positive electrode>
  • a premixing tank of a bead mill with a crushing chamber capacity of 0.6 L 2640 g of N-methyl-2-pyrrolidone (NMP) as an organic dispersion medium and 300 g of acetylene black as a carbon material (specific surface area: 39 m 2 /g)
  • NMP N-methyl-2-pyrrolidone
  • acetylene black as a carbon material (specific surface area: 39 m 2 /g)
  • 60 g of polyvinyl alcohol (saponification degree: 98 mol%) as a polyvinyl alcohol-based polymer were added and premixing was performed to obtain a preliminary dispersion liquid.
  • the peripheral speed of the bead mill was set to 12 m/sec, the preliminary dispersion was mixed while feeding at a speed of 300 g/min, and the dispersion treatment was carried out when the median diameter of the dispersoid in the dispersion became 3.4 ⁇ m.
  • the beads used were zirconia beads having a diameter of 1.0 mm.
  • PVdF polyvinylidene fluoride
  • the amount of NMP added is such that the viscosity of the obtained slurry composition for a positive electrode (measured with a single cylindrical rotary viscometer at a temperature of 25° C. and a rotation speed of 60 rpm according to JIS Z8803:1991) is 4,000 to 5,000 mPa. It was adjusted to fall within the range of s.
  • An aluminum foil having a thickness of 20 ⁇ m was prepared as a current collector.
  • the slurry composition for a positive electrode was applied on an aluminum foil with a comma coater so that the basis weight after drying was 20 mg/cm 2 , dried at 90° C. for 20 minutes and 120° C. for 20 minutes, and then at 60° C.
  • the obtained positive electrode raw material was rolled by a roll press to produce a sheet-shaped positive electrode composed of a positive electrode mixture layer having a density of 3.2 g/cm 3 and an aluminum foil.
  • the thickness of the sheet-shaped positive electrode was 70 ⁇ m. This sheet-shaped positive electrode was cut into a width of 4.8 mm and a length of 50 cm to obtain a positive electrode for a lithium ion secondary battery.
  • ⁇ Production of negative electrode> A mixture of 90 parts of spherical artificial graphite (volume average particle size: 12 ⁇ m) and 10 parts of SiO X (volume average particle size: 10 ⁇ m) as a negative electrode active material, 1 part of a styrene-butadiene copolymer as a binder, and a thickening agent. 1 part of carboxymethyl cellulose as an agent and an appropriate amount of water as a dispersion medium were stirred with a planetary mixer to prepare a slurry composition for a negative electrode. Next, a copper foil having a thickness of 15 ⁇ m was prepared as a current collector.
  • the above negative electrode slurry composition was applied onto both surfaces of a copper foil so that the applied amount after drying was 10 mg/cm 2 , and dried at 60° C. for 20 minutes and 120° C. for 20 minutes. Then, it heat-processed at 150 degreeC for 2 hours, and obtained the negative electrode original fabric.
  • This negative electrode raw material was rolled by a roll press to produce a sheet-shaped negative electrode composed of a negative electrode mixture layer (both sides) having a density of 1.7 g/cm 3 and a copper foil. Then, the sheet-shaped negative electrode was cut into a width 5.0 mm and a length 52 cm to obtain a negative electrode for a lithium ion secondary battery.
  • the positive electrode and the negative electrode were wound using a core having a diameter of 20 mm with a separator (a microporous polypropylene film having a thickness of 15 ⁇ m) interposed therebetween to obtain a wound body. Then, the obtained wound body was compressed from one direction at a speed of 10 mm/sec until the thickness became 4.5 mm.
  • the wound body after compression had an elliptical shape in plan view, and the ratio of the major axis to the minor axis (major axis/minor axis) was 7.7.
  • the compressed wound body was accommodated in an aluminum laminate case together with 3.2 g of the electrolytic solution.
  • a nickel lead wire was connected to a predetermined part of the negative electrode and an aluminum lead wire was connected to a predetermined part of the positive electrode, and then the opening of the case was sealed with heat to obtain a lithium ion secondary battery.
  • This lithium-ion secondary battery was a pouch type with a width of 35 mm, a height of 48 mm, and a thickness of 5 mm, and the nominal capacity of the battery was 700 mAh.
  • the rate characteristics and the high temperature storage characteristics of the obtained lithium ion secondary battery were evaluated. The results are shown in Table 1.
  • Example 2 When preparing the carbon material dispersion liquid for the positive electrode, polyvinyl alcohol having a saponification degree of 80 mol% was used in place of polyvinyl alcohol (saponification degree: 98 mol %), and the dispersion treatment was stopped when the median diameter reached 3.2 ⁇ m.
  • a positive electrode carbon material dispersion liquid, a positive electrode slurry composition, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
  • Example 3 At the time of preparing the carbon material dispersion liquid for the positive electrode, the amount of NMP was set to 2595 g, the amount of polyvinyl alcohol was set to 105 g, and the dispersion treatment was stopped at the time when the median diameter reached 3.3 ⁇ m. A carbon material dispersion liquid for a positive electrode, a slurry composition for a positive electrode, a positive electrode, a negative electrode and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
  • Example 4 When preparing the carbon material dispersion liquid for the positive electrode, the carbon material dispersion liquid for the positive electrode, the slurry composition for the positive electrode, and the positive electrode were prepared in the same manner as in Example 1 except that the dispersion treatment was stopped when the median diameter reached 1.8 ⁇ m. A negative electrode and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
  • Example 5 The positive electrode was prepared in the same manner as in Example 1 except that the rotor peripheral speed of the bead mill was changed to 8 m/sec and the dispersion treatment was stopped when the median diameter reached 8.4 ⁇ m when the carbon material dispersion liquid for positive electrode was prepared. A carbon material dispersion liquid, a positive electrode slurry composition, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
  • Example 6 Except that the zirconia beads having a diameter of 0.5 mm were used instead of the zirconia beads having a diameter of 1.0 mm when the dispersion of the carbon material for the positive electrode was prepared, and the dispersion treatment was stopped when the median diameter became 0.95 ⁇ m.
  • a positive electrode carbon material dispersion liquid, a positive electrode slurry composition, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
  • Example 7 When preparing the carbon material dispersion liquid for the positive electrode, 150 g of multi-walled carbon nanotubes (specific surface area: 90 m 2 /g) was used instead of 300 g of acetylene black (specific surface area: 39 m 2 /g), and the amount of NMP was 2585 g. The amount of alcohol was 37.5 g, and the carbon material dispersion liquid for the positive electrode, the slurry composition for the positive electrode, the positive electrode, which was the same as in Example 1, except that the dispersion treatment was stopped when the median diameter reached 1.2 ⁇ m. A negative electrode and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
  • Example 8 When preparing the carbon material dispersion liquid for the positive electrode, 150 g of Ketjen black (specific surface area: 300 m 2 /g) was used instead of 300 g of acetylene black (specific surface area: 39 m 2 /g), and the amount of NMP was 2585 g. The amount of alcohol was 45 g, and the carbon material dispersion for positive electrode, positive electrode slurry composition, positive electrode, negative electrode, and the like were prepared in the same manner as in Example 1 except that the dispersion treatment was stopped at the time when the median diameter became 1.6 ⁇ m. A lithium ion secondary battery was produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
  • the secondary batteries prepared using the carbon material dispersion liquids for secondary battery electrodes of Examples 1 to 8 are excellent in both rate characteristics and high temperature storage characteristics.
  • the secondary batteries produced using the carbon material dispersion liquids for secondary battery electrodes of Comparative Examples 1 to 3 in which the median diameter (D50) of the dispersoid is less than 0.90 ⁇ m or more than 10 ⁇ m have rate characteristics. It can be seen that
  • the carbon material dispersion liquid for a secondary battery electrode and the slurry composition for a secondary battery electrode of the present invention it is possible to form a secondary battery electrode capable of exhibiting excellent rate characteristics and high temperature storage characteristics in a secondary battery. You can Further, according to the secondary battery electrode of the present invention, the secondary battery can exhibit excellent rate characteristics and high temperature storage characteristics. Furthermore, the secondary battery of the present invention is excellent in both rate characteristics and high temperature storage characteristics.

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Abstract

The present invention provides a secondary battery electrode carbon material dispersion liquid capable of forming a secondary battery electrode that can cause a secondary battery to exhibit excellent rate characteristics and high temperature preservation characteristics. This carbon material dispersion liquid for secondary battery electrodes contains a carbon material, a polyvinyl alcohol-based polymer, and an organic dispersion medium, wherein the median diameter (D50) of dispersoids therein is 0.90-10 µm.

Description

二次電池電極用炭素材料分散液、二次電池電極用スラリー組成物、二次電池用電極および二次電池Carbon material dispersion liquid for secondary battery electrode, slurry composition for secondary battery electrode, secondary battery electrode and secondary battery
　本発明は、二次電池電極用炭素材料分散液、二次電池電極用スラリー組成物、二次電池用電極および二次電池に関するものである。 The present invention relates to a carbon material dispersion liquid for a secondary battery electrode, a slurry composition for a secondary battery electrode, an electrode for a secondary battery, and a secondary battery.
　リチウムイオン二次電池などの二次電池は、小型で軽量、且つエネルギー密度が高く、さらに繰り返し充放電が可能という特性があり、幅広い用途に使用されている。そのため、近年では、二次電池の更なる高性能化を目的として、電極などの電池部材の改良が検討されている。 Secondary batteries such as lithium-ion secondary batteries are small and lightweight, have high energy density, and can be repeatedly charged and discharged, and are used in a wide range of applications. Therefore, in recent years, improvement of battery members such as electrodes has been studied for the purpose of further improving the performance of secondary batteries.
　ここで、例えばリチウムイオン二次電池用の電極は、通常、集電体と、集電体上に形成された電極合材層とを備えている。そして、電極合材層は、例えば、電極活物質と、導電材と、バインダーなどとを分散媒に分散または溶解させてなる電極用スラリー組成物を集電体上に塗布し、乾燥させて電極活物質および導電材などをバインダーで結着することにより形成されている。 Here, for example, an electrode for a lithium ion secondary battery usually includes a current collector and an electrode mixture layer formed on the current collector. Then, the electrode mixture layer, for example, an electrode active material, a conductive material, a binder or the like is dispersed or dissolved in a dispersion medium, an electrode slurry composition is applied onto a current collector, dried to form an electrode. It is formed by binding an active material and a conductive material with a binder.
　また、近年では、電極合材層を形成する際の生産プロセスの効率化などの観点から、カーボンブラックなどの導電性を有する炭素材料よりなる導電材を分散媒に分散させてなる炭素材料分散液を調製した後、当該炭素材料分散液に電極活物質やバインダーを混合して電極用スラリー組成物を得る技術が提案されている。 In recent years, from the viewpoint of improving the efficiency of the production process when forming the electrode mixture layer, a carbon material dispersion liquid obtained by dispersing a conductive material made of a carbon material having conductivity such as carbon black in a dispersion medium. After preparing the above, there has been proposed a technique in which an electrode active material or a binder is mixed with the carbon material dispersion liquid to obtain an electrode slurry composition.
　そして、例えば特許文献１，２には、分散性および貯蔵安定性に優れる炭素材料分散液として、所定のＢＥＴ比表面積を有するカーボンブラックと、所定のけん化度を有するポリビニルアルコール樹脂からなる分散剤と、分散媒としてのＮ－メチル－２－ピロリドンとを含んでなるカーボンブラック分散液が開示されている。 Then, for example, in Patent Documents 1 and 2, as a carbon material dispersion having excellent dispersibility and storage stability, a carbon black having a predetermined BET specific surface area and a dispersant comprising a polyvinyl alcohol resin having a predetermined saponification degree are disclosed. A carbon black dispersion liquid containing N-methyl-2-pyrrolidone as a dispersion medium is disclosed.
特開２０１４－１９３９９６号公報JP, 2014-193996, A 特開２０１４－１９４００１号公報JP, 2014-194001, A
　しかし、上記従来の二次電池電極用炭素材料分散液には、二次電池電極用炭素材料分散液を用いて形成した電極を備える二次電池のレート特性および高温保存特性を向上させるという点において改善の余地があった。 However, the conventional carbon material dispersion liquid for a secondary battery electrode is improved in rate characteristics and high temperature storage characteristics of a secondary battery including an electrode formed by using the carbon material dispersion liquid for a secondary battery electrode. There was room for improvement.
　そこで、本発明は、二次電池に優れたレート特性および高温保存特性を発揮させ得る二次電池用電極、並びに、当該二次電池用電極を形成可能な二次電池電極用炭素材料分散液および二次電池電極用スラリー組成物を提供することを目的とする。
　また、本発明は、レート特性および高温保存特性の双方に優れる二次電池を提供することを目的とする。 Therefore, the present invention provides a secondary battery electrode capable of exhibiting excellent rate characteristics and high temperature storage characteristics in a secondary battery, and a carbon material dispersion liquid for a secondary battery electrode capable of forming the secondary battery electrode, It is an object to provide a slurry composition for a secondary battery electrode.
Another object of the present invention is to provide a secondary battery that is excellent in both rate characteristics and high temperature storage characteristics.
　本発明者は、上記目的を達成するために鋭意検討を行った。そして、本発明者は、ポリビニルアルコール系重合体を分散剤として用いて炭素材料を有機分散媒に分散させてなる二次電池電極用炭素材料分散液において分散質のメジアン径（Ｄ５０）を所定の範囲内にすれば、当該二次電池電極用炭素材料分散液を用いて形成した電極を使用した二次電池に優れたレート特性および高温保存特性を発揮させ得ることを見出し、本発明を完成させた。 The present inventor has conducted extensive studies in order to achieve the above object. Then, the present inventor has determined a median diameter (D50) of a dispersoid to be a predetermined value in a carbon material dispersion liquid for a secondary battery electrode in which a carbon material is dispersed in an organic dispersion medium using a polyvinyl alcohol-based polymer as a dispersant. Within the range, it was found that a secondary battery using an electrode formed by using the carbon material dispersion liquid for a secondary battery electrode can exhibit excellent rate characteristics and high temperature storage characteristics, and completed the present invention. It was
　即ち、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池電極用炭素材料分散液は、炭素材料と、ポリビニルアルコール系重合体と、有機分散媒とを含み、分散質のメジアン径（Ｄ５０）が０．９０μｍ以上１０μｍ以下であることを特徴とする。このように、炭素材料と、ポリビニルアルコール系重合体と、有機分散媒とを含有させると共に分散質のメジアン径（Ｄ５０）を０．９０μｍ以上１０μｍ以下とすれば、二次電池電極用炭素材料分散液を用いて形成した電極合材層を有する電極を備える二次電池に優れたレート特性および高温保存特性を発揮させることができる。
　ここで、本発明において、「分散質のメジアン径（Ｄ５０）」は、本明細書の実施例に記載の方法を用いて測定することができる。 That is, the present invention is intended to advantageously solve the above problems, the carbon material dispersion liquid for a secondary battery electrode of the present invention, a carbon material, a polyvinyl alcohol-based polymer, an organic dispersion medium. And the median diameter (D50) of the dispersoid is 0.90 μm or more and 10 μm or less. As described above, when the carbon material, the polyvinyl alcohol-based polymer, and the organic dispersion medium are contained and the median diameter (D50) of the dispersoid is 0.90 μm or more and 10 μm or less, the carbon material dispersion for the secondary battery electrode is dispersed. A secondary battery including an electrode having an electrode mixture layer formed using a liquid can exhibit excellent rate characteristics and high-temperature storage characteristics.
Here, in the present invention, the “median diameter (D50) of dispersoid” can be measured by the method described in Examples of the present specification.
　ここで、本発明の二次電池電極用炭素材料分散液は、前記炭素材料が、アセチレンブラック、ファーネスブラック、ケッチェンブラック、炭素繊維、カーボンナノチューブおよびグラフェンからなる群より選択される少なくとも１種を含むことが好ましい。アセチレンブラック、ファーネスブラック、ケッチェンブラック、炭素繊維、カーボンナノチューブおよびグラフェンからなる群より選択される少なくとも１種を炭素材料として使用すれば、二次電池のレート特性を更に向上させることができる。 Here, in the carbon material dispersion liquid for a secondary battery electrode of the present invention, the carbon material is at least one selected from the group consisting of acetylene black, furnace black, Ketjen black, carbon fibers, carbon nanotubes and graphene. It is preferable to include. If at least one selected from the group consisting of acetylene black, furnace black, Ketjen black, carbon fiber, carbon nanotube, and graphene is used as the carbon material, the rate characteristics of the secondary battery can be further improved.
　そして、本発明の二次電池電極用炭素材料分散液は、前記ポリビニルアルコール系重合体のけん化度が６０ｍｏｌ％超９９．５ｍｏｌ％以下であることが好ましい。けん化度が６０ｍｏｌ％超９９．５ｍｏｌ％以下のポリビニルアルコール系重合体を使用すれば、二次電池の高温保存特性を更に向上させることができる。
　ここで、本発明において、「ポリビニルアルコール系重合体のけん化度」は、ＪＩＳ Ｋ００７０に準拠して測定することができる。 The saponification degree of the polyvinyl alcohol-based polymer in the carbon material dispersion liquid for a secondary battery electrode of the present invention is preferably more than 60 mol% and 99.5 mol% or less. By using a polyvinyl alcohol-based polymer having a saponification degree of more than 60 mol% and 99.5 mol% or less, the high temperature storage characteristics of the secondary battery can be further improved.
Here, in the present invention, the “saponification degree of the polyvinyl alcohol polymer” can be measured in accordance with JIS K0070.
　また、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池電極用スラリー組成物は、上述した二次電池電極用炭素材料分散液の何れかと、電極活物質と、バインダーとを含むことを特徴とする。上述した二次電池電極用炭素材料分散液を含有させれば、二次電池に優れたレート特性および高温保存特性を発揮させることが可能な二次電池用電極を形成することができる。 Further, the present invention is intended to advantageously solve the above problems, the secondary battery electrode slurry composition of the present invention, any of the above secondary battery electrode carbon material dispersion, It is characterized by containing an electrode active material and a binder. When the carbon material dispersion liquid for a secondary battery electrode described above is contained, it is possible to form a secondary battery electrode capable of exhibiting excellent rate characteristics and high temperature storage characteristics in a secondary battery.
　更に、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池用電極は、上述した二次電池電極用スラリー組成物を用いて形成した電極合材層を備えることを特徴とする。上述した二次電池電極用スラリー組成物を使用して形成した電極合材層を備える二次電池用電極を使用すれば、二次電池に優れたレート特性および高温保存特性を発揮させることができる。 Furthermore, this invention aims at solving the above-mentioned subject advantageously, and the electrode for secondary batteries of this invention is the electrode mixture material formed using the slurry composition for secondary battery electrodes mentioned above. It is characterized by having a layer. By using the secondary battery electrode including the electrode mixture layer formed by using the above-described secondary battery electrode slurry composition, the secondary battery can exhibit excellent rate characteristics and high temperature storage characteristics. ..
　そして、この発明は、上記課題を有利に解決することを目的とするものであり、本発明の二次電池は、正極、負極、電解液およびセパレータを備え、前記正極および負極の少なくとも一方が上述した二次電池用電極であることを特徴とする。上述した二次電池用電極を備える二次電池は、優れたレート特性および高温保存特性を発揮し得る。 And this invention aims at solving the said subject advantageously, the secondary battery of this invention is equipped with a positive electrode, a negative electrode, an electrolytic solution, and a separator, and at least one of the said positive electrode and a negative electrode is the above-mentioned. It is a secondary battery electrode as described above. A secondary battery including the above-described secondary battery electrode can exhibit excellent rate characteristics and high temperature storage characteristics.
　本発明の二次電池電極用炭素材料分散液および二次電池電極用スラリー組成物によれば、二次電池に優れたレート特性および高温保存特性を発揮させ得る二次電池用電極を形成することができる。
　また、本発明の二次電池用電極によれば、二次電池に優れたレート特性および高温保存特性を発揮させることができる。
　更に、本発明の二次電池は、レート特性および高温保存特性の双方に優れている。 According to the carbon material dispersion liquid for a secondary battery electrode and the slurry composition for a secondary battery electrode of the present invention, it is possible to form a secondary battery electrode capable of exhibiting excellent rate characteristics and high temperature storage characteristics in a secondary battery. You can
Further, according to the secondary battery electrode of the present invention, the secondary battery can exhibit excellent rate characteristics and high temperature storage characteristics.
Furthermore, the secondary battery of the present invention is excellent in both rate characteristics and high temperature storage characteristics.
　以下、本発明の実施形態について詳細に説明する。
　ここで、本発明の二次電池電極用炭素材料分散液は、二次電池電極用スラリー組成物を調製する際に用いることができる。そして、本発明の二次電池電極用炭素材料分散液を用いて調製した二次電池電極用スラリー組成物は、リチウムイオン二次電池等の二次電池の電極を形成する際に用いることができる。更に、本発明の二次電池は、本発明の二次電池電極用スラリー組成物を用いて形成した二次電池用電極を用いたことを特徴とする。
　なお、本発明の二次電池電極用炭素材料分散液および二次電池電極用スラリー組成物は、二次電池の正極を形成する際に特に好適に用いることができる。 Hereinafter, embodiments of the present invention will be described in detail.
Here, the carbon material dispersion liquid for a secondary battery electrode of the present invention can be used when preparing a slurry composition for a secondary battery electrode. And the slurry composition for secondary battery electrodes prepared by using the carbon material dispersion liquid for secondary battery electrodes of the present invention can be used when forming electrodes of secondary batteries such as lithium ion secondary batteries. .. Furthermore, the secondary battery of the present invention is characterized by using an electrode for a secondary battery formed by using the slurry composition for an electrode of the secondary battery of the present invention.
The carbon material dispersion liquid for a secondary battery electrode and the slurry composition for a secondary battery electrode of the present invention can be particularly preferably used when forming a positive electrode of a secondary battery.
（二次電池電極用炭素材料分散液）
　本発明の二次電池電極用炭素材料分散液は、炭素材料と、ポリビニルアルコール系重合体と、有機分散媒とを含み、任意に、二次電池の電極に配合され得るその他の成分を更に含有する。更に、本発明の二次電池電極用炭素材料分散液は、分散質のメジアン径（Ｄ５０）が０．９０μｍ以上１０μｍ以下であることを必要とする。
　なお、二次電池電極用炭素材料分散液は、通常、電極活物質を含有していない。 (Carbon material dispersion for secondary battery electrode)
The carbon material dispersion liquid for a secondary battery electrode of the present invention contains a carbon material, a polyvinyl alcohol-based polymer, and an organic dispersion medium, and optionally further contains other components that can be blended in the electrode of the secondary battery. To do. Furthermore, the carbon material dispersion liquid for secondary battery electrodes of the present invention requires that the median diameter (D50) of the dispersoid be 0.90 μm or more and 10 μm or less.
The carbon material dispersion liquid for a secondary battery electrode usually does not contain an electrode active material.
　そして、本発明の二次電池電極用炭素材料分散液は、ポリビニルアルコール系重合体を含有し、更に、分散質のメジアン径（Ｄ５０）が０．９０μｍ以上１０μｍ以下であるので、二次電池電極用炭素材料分散液を用いて形成した電極合材層を有する電極を備える二次電池に優れたレート特性および高温保存特性を発揮させることができる。
　なお、本発明の二次電池電極用炭素材料分散液を用いることで二次電池に優れたレート特性および高温保存特性を発揮させることができる理由は、明らかではないが、分散質のメジアン径が適度な大きさであることによりレート特性が向上し、更に、ポリビニルアルコール系重合体を含有させると共に分散質のメジアン径を適度な大きさとすることで高温保存時に生じる応力に起因した電極合材層の構造変化が抑制されるからであると推察される。 The carbon material dispersion liquid for a secondary battery electrode of the present invention contains a polyvinyl alcohol-based polymer, and further, the median diameter (D50) of the dispersoid is 0.90 μm or more and 10 μm or less. A secondary battery including an electrode having an electrode mixture layer formed by using the carbon material dispersion liquid for use can exhibit excellent rate characteristics and high-temperature storage characteristics.
The reason why it is possible to exhibit excellent rate characteristics and high temperature storage characteristics in a secondary battery by using the carbon material dispersion liquid for a secondary battery electrode of the present invention is not clear, but the median diameter of the dispersoid is The rate property is improved by having an appropriate size, and the electrode mixture layer due to the stress generated during high temperature storage is obtained by further containing a polyvinyl alcohol polymer and adjusting the median diameter of the dispersoid to an appropriate size. It is presumed that this is because the structural change of is suppressed.
＜炭素材料＞
　ここで、炭素材料としては、二次電池の電極において導電材として使用し得るものであれば特に限定されることなく、既知の炭素材料を用いることができる。中でも、二次電池のレート特性を更に向上させる観点からは、炭素材料としては、アセチレンブラック、ファーネスブラック、ケッチェンブラック（登録商標）、炭素繊維、カーボンナノチューブおよびグラフェンからなる群より選択される少なくとも１種を用いることが好ましく、アセチレンブラック、ケッチェンブラックおよびカーボンナノチューブからなる群より選択される少なくとも１種を用いることがより好ましく、アセチレンブラックおよび／またはカーボンナノチューブを用いることが更に好ましい。 <Carbon material>
Here, the carbon material is not particularly limited as long as it can be used as a conductive material in the electrode of the secondary battery, and a known carbon material can be used. Among them, from the viewpoint of further improving the rate characteristics of the secondary battery, the carbon material is at least selected from the group consisting of acetylene black, furnace black, Ketjen Black (registered trademark), carbon fiber, carbon nanotube, and graphene. It is preferable to use one kind, more preferably to use at least one kind selected from the group consisting of acetylene black, Ketjen black and carbon nanotubes, and further preferable to use acetylene black and/or carbon nanotubes.
　そして、二次電池電極用炭素材料分散液（１００質量％）中に含まれている炭素材料の量は、通常１質量％以上３０質量％以下であり、３質量％以上３０質量％以下であることが好ましい。 Then, the amount of the carbon material contained in the carbon material dispersion liquid for secondary battery electrodes (100% by mass) is usually 1% by mass or more and 30% by mass or less, and 3% by mass or more and 30% by mass or less. It is preferable.
＜ポリビニルアルコール系重合体＞
　ポリビニルアルコール系重合体は、下記式：
Figure JPOXMLDOC01-appb-C000001
 で表されるビニルアルコール構造単位を含有し、任意にその他の単量体に由来するその他の構造単位を更に含有し得る重合体である。そして、ポリビニルアルコール系重合体は、例えば、１種類以上のビニルエステル系単量体と、任意にビニルエステル系単量体と共重合し得るその他の単量体とを重合して得られるポリビニルエステル系重合体をけん化することにより製造することができる。 <Polyvinyl alcohol polymer>
The polyvinyl alcohol-based polymer has the following formula:
Figure JPOXMLDOC01-appb-C000001
 It is a polymer containing the vinyl alcohol structural unit represented by and optionally further containing other structural units derived from other monomers. The polyvinyl alcohol-based polymer is, for example, a polyvinyl ester obtained by polymerizing one or more kinds of vinyl ester-based monomers and other monomers which can be optionally copolymerized with the vinyl ester-based monomers. It can be produced by saponifying a polymer.
　ここで、ビニルエステル系単量体としては、例えば、ギ酸ビニル、酢酸ビニル、プロピオン酸ビニル、バレリン酸ビニル、ラウリン酸ビニル、ステアリン酸ビニル、安息香酸ビニル、ピバリン酸ビニル、バーサティック酸ビニルなどを用いることができる。中でも、酢酸ビニルが好ましい。 Here, as the vinyl ester-based monomer, for example, vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, vinyl versatate, etc. Can be used. Of these, vinyl acetate is preferable.
　また、ビニルエステル系単量体と任意に共重合させ得るその他の単量体としては、例えば、エチレン、プロピレン、１－ブテン、イソブテン等の炭素数２～３０のオレフィン；（メタ）アクリル酸およびその塩；（メタ）アクリル酸メチル、（メタ）アクリル酸エチル、（メタ）アクリル酸ｎ－プロピル、（メタ）アクリル酸ｉ－プロピル、（メタ）アクリル酸ｎ－ブチル、（メタ）アクリル酸ｉ－ブチル、（メタ）アクリル酸ｔ－ブチル、（メタ）アクリル酸２－エチルへキシル、（メタ）アクリル酸ドデシル、（メタ）アクリル酸オクタデシル等の（メタ）アクリル酸エステル；（メタ）アクリロニトリル等のシアン化ビニル；などが挙げられる。これらのその他の単量体は、１種類を単独で、または、２種類以上を組み合わせて用いることができる。
　なお、本明細書において、「（メタ）アクリル酸」とは、アクリル酸および／またはメタクリル酸を指し、「（メタ）アクリロニトリル」とは、アクリロニトリルおよび／またはメタクリロニトリルを指す。 Other monomers that can be optionally copolymerized with the vinyl ester-based monomer include, for example, ethylene, propylene, 1-butene, isobutene and other olefins having 2 to 30 carbon atoms; (meth)acrylic acid and Salts thereof; methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, (meth)acrylate i -(Meth)acrylic acid ester such as -butyl, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, dodecyl (meth)acrylate, octadecyl (meth)acrylate; (meth)acrylonitrile, etc. Vinyl cyanide; and the like. These other monomers can be used alone or in combination of two or more.
In addition, in this specification, "(meth)acrylic acid" refers to acrylic acid and/or methacrylic acid, and "(meth)acrylonitrile" refers to acrylonitrile and/or methacrylonitrile.
　そして、ポリビニルエステル系重合体は、上述した単量体を従来公知の方法により重合して得ることができ、１種類以上のビニルエステル系単量体と、その他の単量体との共重合体であってもよいし、ビニルエステル系単量体のみを用いて得られる重合体であってもよい。
　なお、ポリビニルエステル系重合体に含まれる全構造単位のうち、その他の単量体に由来する構造単位（その他の構造単位）が占める割合は、５０質量％以下であることが好ましく、３０質量％以下であることがより好ましく、５質量％以下であることが更に好ましく、０質量％である（即ち、ポリビニルエステル系重合体はビニルエステル系単量体のみを用いて得られる重合体である）ことが特に好ましい。そして、ポリビニルエステル系重合体は、１種類のビニルエステル系単量体のみを用いて得られる重合体であることがより一層好ましい。 The polyvinyl ester-based polymer can be obtained by polymerizing the above-mentioned monomers by a conventionally known method, and is a copolymer of one or more kinds of vinyl ester-based monomers and other monomers. Or a polymer obtained by using only a vinyl ester-based monomer.
The proportion of structural units derived from other monomers (other structural units) in all structural units contained in the polyvinyl ester-based polymer is preferably 50% by mass or less, and 30% by mass. The content is more preferably the following or less, still more preferably 5% by mass or less, and further preferably 0% by mass (that is, the polyvinyl ester-based polymer is a polymer obtained by using only a vinyl ester-based monomer). Is particularly preferable. It is even more preferable that the polyvinyl ester polymer is a polymer obtained by using only one type of vinyl ester monomer.
　ポリビニルエステル系重合体のけん化は、特に限定されることなく、例えば水酸化ナトリウムや水酸化カリウムなどの塩基を使用し、既知のけん化方法に従って行うことができる。 The saponification of the polyvinyl ester-based polymer is not particularly limited, and can be performed according to a known saponification method using a base such as sodium hydroxide or potassium hydroxide.
　また、ポリビニルエステル系重合体をけん化して得られるポリビニルアルコール系重合体のけん化度は、特に限定されることなく、６０ｍｏｌ％超であることが好ましく、７０ｍｏｌ％超であることがより好ましく、８５ｍｏｌ％超であることが更に好ましく、９５ｍｏｌ％超であることが特に好ましく、９９．５ｍｏｌ％以下であることが好ましい。ポリビニルアルコール系重合体のけん化度が上記範囲内であれば、二次電池の高温保存特性を更に向上させることができる。 The degree of saponification of the polyvinyl alcohol-based polymer obtained by saponifying the polyvinyl ester-based polymer is not particularly limited, and is preferably more than 60 mol%, more preferably more than 70 mol%, and 85 mol%. % Is more preferable, it is particularly preferable that it is more than 95 mol%, and it is preferable that it is 99.5 mol% or less. When the saponification degree of the polyvinyl alcohol polymer is within the above range, the high temperature storage characteristics of the secondary battery can be further improved.
　そして、二次電池電極用炭素材料分散液中に含まれているポリビニルアルコール系重合体の量は、炭素材料１００質量部当たり、０．１質量部超であることが好ましく、１質量部超であることがより好ましく、３質量部超であることが更に好ましく、１０質量部以上であることが特に好ましく、５０質量部以下であることが好ましく、４０質量部以下であることがより好ましく、３０質量部以下であることが更に好ましい。ポリビニルアルコール系重合体の量が上記範囲内であれば、炭素材料を良好に分散させつつ、二次電池のレート特性および高温保存特性を更に向上させることができる。 The amount of the polyvinyl alcohol-based polymer contained in the carbon material dispersion liquid for secondary battery electrode is preferably more than 0.1 parts by mass, and more than 1 part by mass, per 100 parts by mass of the carbon material. More preferably, more preferably more than 3 parts by mass, particularly preferably 10 parts by mass or more, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, 30 It is more preferable that the amount is not more than parts by mass. When the amount of the polyvinyl alcohol polymer is within the above range, the rate characteristics and the high temperature storage characteristics of the secondary battery can be further improved while the carbon material is well dispersed.
＜有機分散媒＞
　有機分散媒としては、特に限定されることなく、二次電池の分野において用いられる既知の有機溶媒を用いることができる。具体的には、有機分散媒としては、メタノール、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、ｔ－ブタノール、ペンタノール、ヘキサノール、ヘプタノール、オクタノール、ノナノール、デカノールなどのアルコール類；アセトン、メチルエチルケトン、シクロヘキサノンなどのケトン類；酢酸エチル、酢酸ブチルなどのエステル類；ジエチルエーテル、ジオキサン、テトラヒドロフランなどのエーテル類；Ｎ，Ｎ－ジメチルホルムアミド、Ｎ－メチル－２－ピロリドン（ＮＭＰ）などのアミド系極性有機溶媒；トルエン、キシレン、クロロベンゼン、オルトジクロロベンゼン、パラジクロロベンゼンなどの芳香族炭化水素類；などが挙げられる。これらは、１種類を単独で用いてもよいし、２種類以上を混合して用いてもよい。
　これらの中でも、有機分散媒としては、Ｎ－メチル－２－ピロリドンを用いることが好ましい。 <Organic dispersion medium>
The organic dispersion medium is not particularly limited, and a known organic solvent used in the field of secondary batteries can be used. Specifically, as the organic dispersion medium, alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, t-butanol, pentanol, hexanol, heptanol, octanol, nonanol and decanol; acetone , Ketones such as methyl ethyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as diethyl ether, dioxane and tetrahydrofuran; amides such as N,N-dimethylformamide and N-methyl-2-pyrrolidone (NMP) System polar organic solvents; aromatic hydrocarbons such as toluene, xylene, chlorobenzene, orthodichlorobenzene, and paradichlorobenzene; and the like. These may be used alone or in combination of two or more.
Among these, N-methyl-2-pyrrolidone is preferably used as the organic dispersion medium.
＜メジアン径（Ｄ５０）＞
　そして、二次電池電極用炭素材料分散液は、分散質のメジアン径が、０．９０μｍ以上１０μｍ以下であることを必要とし、１．２μｍ以上であることが好ましく、１．５μｍ以上であることがより好ましく、３．０μｍ以上であることが更に好ましく、７．０μｍ以下であることが好ましく、５．０μｍ以下であることがより好ましく、４．０μｍ以下であることが更に好ましい。分散質のメジアン径が上記下限値以上であれば、二次電池のレート特性および高温保存特性を更に向上させることができる。また、分散質のメジアン径が上記上限値以下であれば、二次電池のレート特性を更に向上させることができる。
　なお、分散質には、炭素材料と、炭素材料に吸着したポリビニルアルコール系重合体等とが含まれていると推察される。そして、分散質のメジアン径は、例えば、炭素材料の粒子径、ポリビニルアルコール系重合体の種類および量、並びに、二次電池電極用炭素材料分散液の調製条件を変更することにより調整することができる。 <Median diameter (D50)>
The carbon material dispersion liquid for a secondary battery electrode requires that the median diameter of the dispersoid be 0.90 μm or more and 10 μm or less, preferably 1.2 μm or more, and 1.5 μm or more. Is more preferable, 3.0 μm or more is more preferable, 7.0 μm or less is preferable, 5.0 μm or less is more preferable, and 4.0 μm or less is further preferable. When the median diameter of the dispersoid is at least the above lower limit, the rate characteristics and high temperature storage characteristics of the secondary battery can be further improved. Further, when the median diameter of the dispersoid is not more than the above upper limit value, the rate characteristic of the secondary battery can be further improved.
It is assumed that the dispersoid contains a carbon material and a polyvinyl alcohol polymer adsorbed on the carbon material. Then, the median diameter of the dispersoid can be adjusted, for example, by changing the particle diameter of the carbon material, the type and amount of the polyvinyl alcohol-based polymer, and the preparation conditions of the carbon material dispersion liquid for secondary battery electrodes. it can.
＜その他の成分＞
　二次電池電極用炭素材料分散液が任意に含有し得るその他の成分としては、特に限定されることなく、例えば、補強材、レベリング剤、粘度調整剤、電解液添加剤などが挙げられる。これらは、電池反応に影響を及ぼさないものであれば特に限られず、公知のもの、例えば国際公開第２０１２／１１５０９６号に記載のものを使用することができる。また、これらの成分は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。 <Other ingredients>
Other components that the carbon material dispersion liquid for secondary battery electrodes may optionally contain are not particularly limited, and examples thereof include a reinforcing material, a leveling agent, a viscosity modifier, and an electrolyte solution additive. These are not particularly limited as long as they do not affect the battery reaction, and known ones such as those described in International Publication No. 2012/115096 can be used. Moreover, these components may be used individually by 1 type, and may be used in combination of 2 or more types in arbitrary ratios.
（二次電池電極用炭素材料分散液の製造方法）
　二次電池電極用炭素材料分散液は、上述した成分を既知の方法で混合し、有機分散媒中に炭素材料等を分散させて調製することができる。 (Method for producing carbon material dispersion liquid for secondary battery electrode)
The carbon material dispersion liquid for a secondary battery electrode can be prepared by mixing the above components by a known method and dispersing the carbon material or the like in an organic dispersion medium.
　ここで、上述した成分の混合は、特に限定されることなく、プロペラミキサー、ハイスピードミキサー、ディゾルバー、ホモジナイザー、アルテマイザー、湿式ジェットミル、コロイドミル、マスコロイダー、ビーズミル、サンドミル、ボールミル、サンドグラインダー、インラインミキサー、メディアレス型高速撹拌分散機などの混合分散機を用いて行うことができる。中でも、分散質のメジアン径の調整の容易性の観点からは、ビーズミル等のメディア撹拌型の混合分散機を用いることが好ましい。
　なお、メディア撹拌型の混合分散機を用いる場合、使用するメディアの外径（メディア径）は、０．１ｍｍ以上であることが好ましく、０．５ｍｍ以上であることがより好ましく、３ｍｍ以下であることが好ましく、２ｍｍ以下であることがより好ましく、１ｍｍ以下であることが更に好ましい。 Here, the mixing of the components described above is not particularly limited, propeller mixer, high speed mixer, dissolver, homogenizer, artemizer, wet jet mill, colloid mill, mass colloider, bead mill, sand mill, ball mill, sand grinder, It can be carried out using a mixing and dispersing machine such as an in-line mixer or a medialess type high speed stirring and dispersing machine. Among them, from the viewpoint of easy adjustment of the median diameter of the dispersoid, it is preferable to use a media stirring type mixing/dispersing machine such as a bead mill.
When a media agitation type mixing/dispersing machine is used, the outer diameter (media diameter) of the media used is preferably 0.1 mm or more, more preferably 0.5 mm or more, and 3 mm or less. It is preferably 2 mm or less, more preferably 1 mm or less.
（二次電池電極用スラリー組成物）
　本発明の二次電池電極用スラリー組成物は、上述した二次電池電極用炭素材料分散液と、電極活物質と、バインダーとを含み、任意に、二次電池の電極に配合され得るその他の成分を更に含有する。即ち、二次電池電極用スラリー組成物は、炭素材料と、ポリビニルアルコール系重合体と、有機分散媒と、電極活物質と、バインダーとを含有し、任意にその他の成分を更に含有する。
　そして、本発明の二次電池電極用スラリー組成物は、上述した二次電池電極用炭素材料分散液を含有しているので、当該二次電池電極用スラリー組成物を用いて形成した電極合材層を備える電極は、二次電池に優れたレート特性および高温保存特性を発揮させることができる。 (Slurry composition for secondary battery electrode)
The slurry composition for a secondary battery electrode of the present invention contains the above-mentioned carbon material dispersion liquid for a secondary battery electrode, an electrode active material, and a binder, and can be optionally blended in an electrode of a secondary battery. It further contains components. That is, the secondary battery electrode slurry composition contains a carbon material, a polyvinyl alcohol-based polymer, an organic dispersion medium, an electrode active material, and a binder, and optionally further contains other components.
Since the secondary battery electrode slurry composition of the present invention contains the above-described secondary battery electrode carbon material dispersion liquid, an electrode mixture formed using the secondary battery electrode slurry composition. The electrode provided with the layer can exhibit excellent rate characteristics and high temperature storage characteristics in the secondary battery.
＜二次電池電極用炭素材料分散液＞
　ここで、二次電池電極用炭素材料分散液としては、上述した本発明の二次電池電極用炭素材料分散液を用いることができる。
　なお、二次電池電極用スラリー組成物の調製に用いる二次電池電極用炭素材料分散液の量は、特に限定されることなく、例えば、スラリー組成物中に含まれる炭素材料の量が電極活物質１００質量部当たり０．５質量部以上５質量部以下となる量とすることができる。 <Carbon material dispersion for secondary battery electrode>
Here, as the carbon material dispersion liquid for secondary battery electrodes, the carbon material dispersion liquid for secondary battery electrodes of the present invention described above can be used.
The amount of the secondary battery electrode carbon material dispersion liquid used for the preparation of the secondary battery electrode slurry composition is not particularly limited, for example, the amount of the carbon material contained in the slurry composition is the electrode active material. The amount can be 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the substance.
＜電極活物質＞
　電極活物質は、二次電池の電極において電子の受け渡しをする物質である。そして、例えば二次電池がリチウムイオン二次電池の場合には、電極活物質としては、通常は、リチウムを吸蔵および放出し得る物質を用いる。
　なお、以下では、一例として二次電池電極用スラリー組成物がリチウムイオン二次電池電極用スラリー組成物である場合について説明するが、本発明は下記の一例に限定されるものではない。 <Electrode active material>
The electrode active material is a material that exchanges electrons in the electrode of the secondary battery. Then, for example, when the secondary battery is a lithium-ion secondary battery, a substance capable of inserting and extracting lithium is usually used as the electrode active material.
In addition, although the case where the slurry composition for secondary battery electrodes is a slurry composition for lithium ion secondary battery electrodes is demonstrated below as an example, this invention is not limited to the following examples.
　そして、リチウムイオン二次電池用の正極活物質としては、特に限定されることなく、リチウム含有コバルト酸化物（ＬｉＣｏＯ2）、マンガン酸リチウム（ＬｉＭｎ2Ｏ4）、リチウム含有ニッケル酸化物（ＬｉＮｉＯ2）、Ｃｏ－Ｎｉ－Ｍｎのリチウム含有複合酸化物（Ｌｉ（Ｃｏ Ｍｎ Ｎｉ）Ｏ2）、Ｎｉ－Ｍｎ－Ａｌのリチウム含有複合酸化物、Ｎｉ－Ｃｏ－Ａｌのリチウム含有複合酸化物、オリビン型リン酸鉄リチウム（ＬｉＦｅＰＯ4）、オリビン型リン酸マンガンリチウム（ＬｉＭｎＰＯ4）、Ｌｉ2ＭｎＯ3－ＬｉＮｉＯ2系固溶体、Ｌｉ1+xＭｎ2-xＯ4（０＜Ｘ＜２）で表されるリチウム過剰のスピネル化合物、Ｌｉ［Ｎｉ0.17Ｌｉ0.2Ｃｏ0.07Ｍｎ0.56］Ｏ2、ＬｉＮｉ0.5Ｍｎ1.5Ｏ4等の既知の正極活物質が挙げられる。
　なお、正極活物質の配合量や粒子径は、特に限定されることなく、従来使用されている正極活物質と同様とすることができる。 The positive electrode active material for a lithium ion secondary battery is not particularly limited, and lithium-containing cobalt oxide (LiCoO 2 ), lithium manganate (LiMn 2 O 4 ), lithium-containing nickel oxide (LiNiO 2 ). ), Co-Ni-Mn lithium-containing composite oxide (Li(Co Mn Ni)O 2 ), Ni-Mn-Al lithium-containing composite oxide, Ni-Co-Al lithium-containing composite oxide, olivine type Represented by lithium iron phosphate (LiFePO 4 ), olivine-type lithium manganese phosphate (LiMnPO 4 ), Li 2 MnO 3 —LiNiO 2 based solid solution, Li 1+x Mn 2-x O 4 (0<X<2) Examples of known positive electrode active materials include lithium-excess spinel compounds, Li[Ni 0.17 Li 0.2 Co 0.07 Mn 0.56 ]O 2 and LiNi 0.5 Mn 1.5 O 4 .
The amount and particle size of the positive electrode active material are not particularly limited, and may be the same as those of conventionally used positive electrode active materials.
　また、リチウムイオン二次電池用の負極活物質としては、例えば、炭素系負極活物質、金属系負極活物質、およびこれらを組み合わせた負極活物質などが挙げられる。 Further, examples of the negative electrode active material for a lithium ion secondary battery include a carbon-based negative electrode active material, a metal-based negative electrode active material, and a negative electrode active material combining these.
　ここで、炭素系負極活物質とは、リチウムを挿入（「ドープ」ともいう。）可能な、炭素を主骨格とする活物質をいい、炭素系負極活物質としては、例えば炭素質材料と黒鉛質材料とが挙げられる。 Here, the carbon-based negative electrode active material refers to an active material having lithium as a main skeleton into which lithium can be inserted (also referred to as “dope”). Examples of the carbon-based negative electrode active material include a carbonaceous material and graphite. Quality materials.
　そして、炭素質材料としては、例えば、易黒鉛性炭素や、ガラス状炭素に代表される非晶質構造に近い構造を持つ難黒鉛性炭素などが挙げられる。
　ここで、易黒鉛性炭素としては、例えば、石油または石炭から得られるタールピッチを原料とした炭素材料が挙げられる。具体例を挙げると、コークス、メソカーボンマイクロビーズ（ＭＣＭＢ）、メソフェーズピッチ系炭素繊維、熱分解気相成長炭素繊維などが挙げられる。
　また、難黒鉛性炭素としては、例えば、フェノール樹脂焼成体、ポリアクリロニトリル系炭素繊維、擬等方性炭素、フルフリルアルコール樹脂焼成体（ＰＦＡ）、ハードカーボンなどが挙げられる。 Examples of the carbonaceous material include easily graphitizable carbon and non-graphitizable carbon having a structure close to an amorphous structure represented by glassy carbon.
Here, examples of the graphitizable carbon include a carbon material obtained from tar pitch obtained from petroleum or coal as a raw material. Specific examples include coke, mesocarbon microbeads (MCMB), mesophase pitch-based carbon fiber, and pyrolytic vapor growth carbon fiber.
Examples of the non-graphitizable carbon include, for example, a phenol resin fired body, polyacrylonitrile-based carbon fiber, pseudo-isotropic carbon, furfuryl alcohol resin fired body (PFA), hard carbon and the like.
　更に、黒鉛質材料としては、例えば、天然黒鉛、人造黒鉛などが挙げられる。
　ここで、人造黒鉛としては、例えば、易黒鉛性炭素を含んだ炭素を主に２８００℃以上で熱処理した人造黒鉛、ＭＣＭＢを２０００℃以上で熱処理した黒鉛化ＭＣＭＢ、メソフェーズピッチ系炭素繊維を２０００℃以上で熱処理した黒鉛化メソフェーズピッチ系炭素繊維などが挙げられる。 Furthermore, examples of the graphite material include natural graphite and artificial graphite.
Here, as the artificial graphite, for example, artificial graphite obtained by heat-treating carbon containing easily graphitizable carbon at 2800° C. or higher, graphitized MCMB obtained by heat-treating MCMB at 2000° C. or higher, and mesophase pitch-based carbon fiber at 2000° C. The graphitized mesophase pitch-based carbon fiber heat-treated as described above can be used.
　また、金属系負極活物質とは、金属を含む活物質であり、通常は、リチウムの挿入が可能な元素を構造に含み、リチウムが挿入された場合の単位質量当たりの理論電気容量が５００ｍＡｈ／ｇ以上である活物質をいう。金属系活物質としては、例えば、リチウム金属、リチウム合金を形成し得る単体金属（例えば、Ａｇ、Ａｌ、Ｂａ、Ｂｉ、Ｃｕ、Ｇａ、Ｇｅ、Ｉｎ、Ｎｉ、Ｐ、Ｐｂ、Ｓｂ、Ｓｉ、Ｓｎ、Ｓｒ、Ｚｎ、Ｔｉなど）およびその合金、並びに、それらの酸化物、硫化物、窒化物、ケイ化物、炭化物、燐化物などが用いられる。これらの中でも、金属系負極活物質としては、ケイ素を含む活物質（シリコン系負極活物質）が好ましい。シリコン系負極活物質を用いることにより、リチウムイオン二次電池を高容量化することができるからである。 Further, the metal-based negative electrode active material is an active material containing a metal, and usually has a structure containing an element capable of inserting lithium, and has a theoretical electric capacity of 500 mAh/unit mass per unit mass when lithium is inserted. An active material having a weight of at least g. Examples of the metal-based active material include lithium metal and elemental metals capable of forming a lithium alloy (eg, Ag, Al, Ba, Bi, Cu, Ga, Ge, In, Ni, P, Pb, Sb, Si, Sn). , Sr, Zn, Ti, etc.) and alloys thereof, and their oxides, sulfides, nitrides, silicides, carbides, phosphides and the like. Among these, the metal-based negative electrode active material is preferably an active material containing silicon (silicon-based negative electrode active material). This is because the lithium-ion secondary battery can have a high capacity by using the silicon-based negative electrode active material.
　シリコン系負極活物質としては、例えば、ケイ素（Ｓｉ）、ケイ素を含む合金、ＳｉＯ、ＳｉＯx、Ｓｉ含有材料を導電性カーボンで被覆または複合化してなるＳｉ含有材料と導電性カーボンとの複合化物などが挙げられる。 Examples of the silicon-based negative electrode active material include silicon (Si), alloys containing silicon, SiO, SiO x , and a compound of Si-containing material and conductive carbon obtained by coating or compounding Si-containing material with conductive carbon. And so on.
　なお、上述した電極活物質は、１種類を単独で用いてもよいし、２種類上を組み合わせて用いてもよい。 The above electrode active materials may be used alone or in combination of two or more.
＜バインダー＞
　バインダーとしては、電極活物質や炭素材料等を結着する結着材として機能し得るものであれば特に限定されることなく、二次電池の分野において用いられている既知のバインダーを用いることができる。具体的には、バインダーとしては、特に限定されることなく、ポリフッ化ビニリデン等のフッ素含有重合体；アクリロニトリル－ブタジエン共重合体やスチレン－ブタジエン共重合体等の共役ジエン単量体単位を含む重合体（共役ジエン系重合体）およびその水素化物；（メタ）アクリル酸エステル単量体単位を含む重合体（アクリル系重合体）；などを用いることができる。これらの重合体は、１種類を単独で用いてもよいし、２種類上を組み合わせて用いてもよい。 <Binder>
The binder is not particularly limited as long as it can function as a binder for binding the electrode active material, the carbon material, etc., and a known binder used in the field of secondary batteries can be used. it can. Specifically, the binder is not particularly limited, but a fluorine-containing polymer such as polyvinylidene fluoride; a polymer containing a conjugated diene monomer unit such as acrylonitrile-butadiene copolymer or styrene-butadiene copolymer is used. A compound (conjugated diene polymer) and its hydride; a polymer containing a (meth)acrylic acid ester monomer unit (acrylic polymer); and the like can be used. One of these polymers may be used alone, or two or more of them may be used in combination.
　なお、二次電池電極用スラリー組成物に含有させるバインダーの量は、特に限定されることなく、例えば、電極活物質１００質量部当たり０．１質量部以上５質量部以下とすることができる。 The amount of the binder contained in the secondary battery electrode slurry composition is not particularly limited and can be, for example, 0.1 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the electrode active material.
＜その他の成分＞
　スラリー組成物に配合し得るその他の成分としては、特に限定することなく、上述した二次電池電極用炭素材料分散液に配合し得るその他の成分と同様のものが挙げられる。また、その他の成分は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。 <Other ingredients>
The other components that can be added to the slurry composition are not particularly limited, and include the same components as the other components that can be added to the carbon material dispersion liquid for secondary battery electrode described above. Further, other components may be used alone or in combination of two or more at an arbitrary ratio.
＜二次電池電極用スラリー組成物の製造＞
　そして、二次電池電極用スラリー組成物は、電極活物質と、バインダーと、上述した二次電池電極用炭素材料分散液と、任意のその他の成分とを混合して製造することができる。
　ここで、上述した成分の混合は、特に限定されることなく、ボールミル、サンドミル、ビーズミル、顔料分散機、らい潰機、超音波分散機、ホモジナイザー、プラネタリーミキサー、フィルミックスなどの混合機を用いて行うことができる。なお、混合は、新たに有機分散媒を追加して行ってもよい。また、上述した成分を混合する順番は特に限定されることは無く、全ての成分を一括混合してもよいし、例えば電極活物質およびバインダーの一方のみを二次電池電極用炭素材料分散液と混合した後に残りの成分を更に混合してもよい。 <Production of slurry composition for secondary battery electrode>
And the slurry composition for secondary battery electrodes can be manufactured by mixing the electrode active material, the binder, the above-mentioned carbon material dispersion liquid for secondary battery electrodes, and any other components.
Here, the mixing of the above-mentioned components is not particularly limited, and a ball mill, a sand mill, a bead mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, a planetary mixer, a mixer such as a fill mix is used. Can be done by The mixing may be performed by newly adding an organic dispersion medium. The order of mixing the above-mentioned components is not particularly limited, and all the components may be mixed together, for example, only one of the electrode active material and the binder is used as a carbon material dispersion liquid for a secondary battery electrode. After mixing, the remaining ingredients may be further mixed.
（二次電池用電極）
　本発明の二次電池用電極は、上述した二次電池電極用スラリー組成物を用いて形成した電極合材層を備える。従って、電極合材層には、少なくとも、電極活物質と、バインダーと、炭素材料と、ポリビニルアルコール系重合体と、任意のその他の成分とが含有されている。なお、電極合材層中に含まれている各成分は、上記二次電池電極用スラリー組成物中に含まれていたものであり、それら各成分の好適な存在比は、スラリー組成物中の各成分の好適な存在比と同じである。
　そして、本発明の二次電池用電極では、上述した二次電池電極用スラリー組成物を使用して電極合材層を形成しているので、導電パスが良好に形成されると共に、高温保存時に生じる応力に起因した電極合材層の構造変化が抑制される。従って、本発明の二次電池用電極を使用すれば、二次電池に優れたレート特性および高温保存特性を発揮させることができる。 (Secondary battery electrode)
The secondary battery electrode of the present invention includes an electrode mixture layer formed using the above-described secondary battery electrode slurry composition. Therefore, the electrode mixture layer contains at least an electrode active material, a binder, a carbon material, a polyvinyl alcohol-based polymer, and any other component. The respective components contained in the electrode mixture layer were those contained in the slurry composition for a secondary battery electrode, and the preferable abundance ratio of these components is in the slurry composition. It is the same as the preferable abundance ratio of each component.
Then, in the secondary battery electrode of the present invention, since the electrode mixture layer is formed using the above-described secondary battery electrode slurry composition, the conductive path is well formed, and at the time of storage at high temperature. The structural change of the electrode composite material layer due to the generated stress is suppressed. Therefore, when the secondary battery electrode of the present invention is used, the secondary battery can exhibit excellent rate characteristics and high temperature storage characteristics.
＜二次電池用電極の製造＞
　ここで、本発明の二次電池用電極の電極合材層は、例えば、上述したスラリー組成物を集電体上に塗布する工程（塗布工程）と、集電体上に塗布されたスラリー組成物を乾燥して集電体上に電極合材層を形成する工程（乾燥工程）とを経て集電体上に形成することができる。 <Manufacture of electrodes for secondary batteries>
Here, the electrode mixture layer of the secondary battery electrode of the present invention includes, for example, a step of applying the above-mentioned slurry composition on a current collector (application step) and a slurry composition applied on the current collector. It can be formed on the current collector through a step of drying the material to form an electrode mixture layer on the current collector (drying step).
［塗布工程］
　そして、上記スラリー組成物を集電体上に塗布する方法としては、特に限定されず公知の方法を用いることができる。具体的には、塗布方法としては、ドクターブレード法、ディップ法、リバースロール法、ダイレクトロール法、グラビア法、エクストルージョン法、ハケ塗り法などを用いることができる。この際、スラリー組成物を集電体の片面だけに塗布してもよいし、両面に塗布してもよい。塗布後乾燥前の集電体上のスラリー膜の厚みは、乾燥して得られる電極合材層の厚みに応じて適宜に設定しうる。 [Coating process]
The method for applying the slurry composition onto the current collector is not particularly limited, and a known method can be used. Specifically, as a coating method, a doctor blade method, a dipping method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a brush coating method or the like can be used. At this time, the slurry composition may be applied to only one surface of the current collector, or may be applied to both surfaces. The thickness of the slurry film on the current collector after coating and before drying can be appropriately set according to the thickness of the electrode mixture layer obtained by drying.
　ここで、スラリー組成物を塗布する集電体としては、電気導電性を有し、かつ、電気化学的に耐久性のある材料が用いられる。具体的には、集電体としては、例えば、鉄、銅、アルミニウム、ニッケル、ステンレス鋼、チタン、タンタル、金、白金などからなる集電体を用い得る。なお、前記の材料は、１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。 Here, as the current collector for applying the slurry composition, a material having electrical conductivity and electrochemical durability is used. Specifically, as the current collector, for example, a current collector made of iron, copper, aluminum, nickel, stainless steel, titanium, tantalum, gold, platinum, or the like can be used. The above materials may be used alone or in combination of two or more at an arbitrary ratio.
［乾燥工程］
　集電体上のスラリー組成物を乾燥する方法としては、特に限定されず公知の方法を用いることができ、例えば温風、熱風、低湿風による乾燥法、真空乾燥法、赤外線や電子線などの照射による乾燥法が挙げられる。このように集電体上のスラリー組成物を乾燥することで、集電体上に電極合材層を形成し、集電体と電極合材層とを備える二次電池用電極を得ることができる。 [Drying process]
The method for drying the slurry composition on the current collector is not particularly limited, and known methods can be used, for example, hot air, hot air, low-humid air drying method, vacuum drying method, infrared ray, electron beam, and the like. A drying method by irradiation can be mentioned. By drying the slurry composition on the current collector in this manner, an electrode mixture layer is formed on the current collector, and a secondary battery electrode including the current collector and the electrode mixture layer can be obtained. it can.
　なお、乾燥工程の後、金型プレスまたはロールプレスなどを用い、電極合材層に加圧処理を施してもよい。加圧処理により、電極合材層と集電体との密着性を向上させることができる。また、電極合材層が硬化性の重合体を含む場合は、電極合材層の形成後に前記重合体を硬化させることが好ましい。 After the drying step, the electrode mixture layer may be subjected to a pressure treatment using a die press or roll press. The pressure treatment can improve the adhesion between the electrode mixture layer and the current collector. When the electrode mixture layer contains a curable polymer, it is preferable to cure the polymer after forming the electrode mixture layer.
（二次電池）
　本発明の二次電池は、正極と、負極と、電解液と、セパレータとを備えており、上述した二次電池用電極を正極および負極の少なくとも一方として用いる。そして、本発明の二次電池は、上述した二次電池用電極を正極および負極の少なくとも一方として用いているので、優れたレート特性および高温保存特性を発揮することができる。
　なお、以下では、一例として二次電池がリチウムイオン二次電池である場合について説明するが、本発明は下記の一例に限定されるものではない。 (Secondary battery)
The secondary battery of the present invention includes a positive electrode, a negative electrode, an electrolytic solution, and a separator, and uses the secondary battery electrode described above as at least one of the positive electrode and the negative electrode. Since the secondary battery of the present invention uses the above-described secondary battery electrode as at least one of the positive electrode and the negative electrode, it can exhibit excellent rate characteristics and high temperature storage characteristics.
In addition, although the case where the secondary battery is a lithium ion secondary battery will be described below as an example, the present invention is not limited to the following example.
＜電極＞
　ここで、本発明の二次電池で使用し得る、上述した二次電池用電極以外の電極としては、特に限定されることなく、二次電池の製造に用いられている既知の電極を用いることができる。具体的には、上述した二次電池用電極以外の電極としては、既知の製造方法を用いて集電体上に電極合材層を形成してなる電極などを用いることができる。 <Electrode>
Here, the electrodes other than the above-mentioned secondary battery electrodes that can be used in the secondary battery of the present invention are not particularly limited, and known electrodes used in the production of secondary batteries can be used. You can Specifically, as the electrodes other than the secondary battery electrode described above, an electrode obtained by forming an electrode mixture layer on a current collector by using a known manufacturing method can be used.
＜電解液＞
　電解液としては、通常、有機溶媒に支持電解質を溶解した有機電解液が用いられる。リチウムイオン二次電池の支持電解質としては、例えば、リチウム塩が用いられる。リチウム塩としては、例えば、ＬｉＰＦ6、ＬｉＡｓＦ6、ＬｉＢＦ4、ＬｉＳｂＦ6、ＬｉＡｌＣｌ4、ＬｉＣｌＯ4、ＣＦ3ＳＯ3Ｌｉ、Ｃ4Ｆ9ＳＯ3Ｌｉ、ＣＦ3ＣＯＯＬｉ、（ＣＦ3ＣＯ）2ＮＬｉ、（ＣＦ3ＳＯ2）2ＮＬｉ、（Ｃ2Ｆ5ＳＯ2）ＮＬｉなどが挙げられる。なかでも、溶媒に溶けやすく高い解離度を示すので、ＬｉＰＦ6、ＬｉＣｌＯ4、ＣＦ3ＳＯ3Ｌｉが好ましく、ＬｉＰＦ6が特に好ましい。なお、電解質は１種類を単独で用いてもよく、２種類以上を任意の比率で組み合わせて用いてもよい。通常は、解離度の高い支持電解質を用いるほどリチウムイオン伝導度が高くなる傾向があるので、支持電解質の種類によりリチウムイオン伝導度を調節することができる。 <Electrolyte>
As the electrolytic solution, an organic electrolytic solution prepared by dissolving a supporting electrolyte in an organic solvent is usually used. As the supporting electrolyte of the lithium ion secondary battery, for example, a lithium salt is used. Examples of the lithium salt include LiPF 6 , LiAsF 6 , LiBF 4 , LiSbF 6 , LiAlCl 4 , LiClO 4 , CF 3 SO 3 Li, C 4 F 9 SO 3 Li, CF 3 COOLi, (CF 3 CO) 2 NLi. , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 )NLi, and the like. Of these, LiPF 6 , LiClO 4 , and CF 3 SO 3 Li are preferable, and LiPF 6 is particularly preferable, because it is easily dissolved in a solvent and exhibits a high dissociation degree. The electrolytes may be used alone or in combination of two or more at an arbitrary ratio. Usually, the lithium ion conductivity tends to be higher as the supporting electrolyte having a higher dissociation degree is used, and thus the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.
　電解液に使用する有機溶媒としては、支持電解質を溶解できるものであれば特に限定されないが、例えば、ジメチルカーボネート（ＤＭＣ）、エチレンカーボネート（ＥＣ）、ジエチルカーボネート（ＤＥＣ）、プロピレンカーボネート（ＰＣ）、ブチレンカーボネート（ＢＣ）、エチルメチルカーボネート（ＥＭＣ）等のカーボネート類；γ－ブチロラクトン、ギ酸メチル等のエステル類；１，２－ジメトキシエタン、テトラヒドロフラン等のエーテル類；スルホラン、ジメチルスルホキシド等の含硫黄化合物類；などが好適に用いられる。またこれらの溶媒の混合液を用いてもよい。中でも、誘電率が高く、安定な電位領域が広いので、カーボネート類を用いることが好ましい。
　なお、電解液中の電解質の濃度は適宜調整することができる。また、電解液には、既知の添加剤を添加することができる。 The organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte, and examples thereof include dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), Carbonates such as butylene carbonate (BC) and ethylmethyl carbonate (EMC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfur-containing compounds such as sulfolane and dimethyl sulfoxide And the like are preferably used. Further, a mixed solution of these solvents may be used. Of these, carbonates are preferably used because they have a high dielectric constant and a wide stable potential region.
The concentration of the electrolyte in the electrolytic solution can be adjusted appropriately. Further, known additives can be added to the electrolytic solution.
＜セパレータ＞
　セパレータとしては、特に限定されることなく、例えば特開２０１２－２０４３０３号公報に記載のものを用いることができる。これらの中でも、セパレータ全体の膜厚を薄くすることができ、これにより、二次電池内の電極活物質の比率を高くして体積あたりの容量を高くすることができるという点より、ポリオレフィン系（ポリエチレン、ポリプロピレン、ポリブテン、ポリ塩化ビニル）の樹脂からなる微多孔膜が好ましい。 <Separator>
The separator is not particularly limited, and for example, those described in JP 2012-204303 A can be used. Among these, the film thickness of the entire separator can be reduced, and thus the capacity per volume can be increased by increasing the ratio of the electrode active material in the secondary battery, and thus the polyolefin-based ( A microporous membrane made of a resin of polyethylene, polypropylene, polybutene, polyvinyl chloride) is preferable.
　そして、二次電池は、例えば、正極と、負極とを、セパレータを介して重ね合わせ、これを必要に応じて電池形状に応じて巻く、折るなどして電池容器に入れ、電池容器に電解液を注入して封口することにより製造することができる。ここで、本発明の二次電池では、正極および負極の少なくとも一方として、上述した二次電池用電極を使用する。なお、本発明の二次電池には、二次電池の内部の圧力上昇、過充放電等の発生を防止するために、必要に応じて、ヒューズ、ＰＴＣ素子等の過電流防止素子、エキスパンドメタル、リード板などを設けてもよい。二次電池の形状は、例えば、コイン型、ボタン型、シート型、円筒型、角形、扁平型など、何れであってもよい。 Then, the secondary battery is, for example, a positive electrode and a negative electrode are stacked via a separator, which is wound or folded according to the shape of the battery as required and put into a battery container, and the electrolytic solution is placed in the battery container. It can be manufactured by injecting and sealing. Here, in the secondary battery of the present invention, the above-mentioned secondary battery electrode is used as at least one of the positive electrode and the negative electrode. The secondary battery of the present invention may include a fuse, an overcurrent prevention element such as a PTC element, and an expanded metal, if necessary, in order to prevent an increase in internal pressure of the secondary battery and the occurrence of overcharging/discharging. A lead plate or the like may be provided. The shape of the secondary battery may be, for example, a coin type, a button type, a sheet type, a cylindrical type, a prismatic type, a flat type or the like.
　以下、本発明について実施例に基づき具体的に説明するが、本発明はこれら実施例に限定されるものではない。なお、以下の説明において、量を表す「％」及び「部」は、特に断らない限り、質量基準である。
　そして、実施例および比較例において、ポリビニルアルコール系重合体のけん化度、二次電池電極用炭素材料分散液中の分散質のメジアン径、並びに、二次電池のレート特性および高温保存特性は、以下の方法で算出、評価した。 Hereinafter, the present invention will be specifically described based on Examples, but the present invention is not limited to these Examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified.
Then, in Examples and Comparative Examples, the saponification degree of the polyvinyl alcohol-based polymer, the median diameter of the dispersoid in the carbon material dispersion for secondary battery electrodes, and the rate characteristics and high-temperature storage characteristics of the secondary battery are as follows. The method was used to calculate and evaluate.
＜けん化度＞
　ポリビニルアルコール系重合体約１ｇを１ｍｇの桁まで精秤（精秤値をＳとする）し、３００ｍＬ三角フラスコに入れ、全量ピペットを用いて０．５ｍｏｌ／Ｌ水酸化カリウムエタノール溶液を２５ｍＬ添加した。続いて、三角フラスコに冷却管をとりつけ、撹拌しながら、４０℃で３０分間反応させた。反応終了後、冷却し、指示薬としてフェノールフタレイン溶液を１ｍＬ添加し、０．５ｍｏｌ／Ｌ塩酸水溶液を用いて滴定した。この時の塩酸の量をＡとする。空試験も同様にして、ポリビニルアルコール系重合体を添加しない状態で実施した。この時の塩酸の量をＢとする。Ｓ、ＡおよびＢを用いて次式よりけん化価Ｘを算出した。ここで、ｆは使用した０．５ｍｏｌ／Ｌ塩酸水溶液のファクターである。
　けん化価Ｘ＝｛（Ｂ－Ａ）×ｆ×２８．０５｝／Ｓ
　次に、けん化前の重合体（ポリビニルエステル系重合体）１ｇ中に含まれるビニルエステル単量体単位のモル数をＹとして、次式よりけん化度を算出した。
　けん化度＝［｛１－（Ｘ／０．０５６１）｝／Ｙ］×１００
＜メジアン径＞
　作製した二次電池電極用炭素材料分散液を適切な濃度に希釈した後、１分間超音波処理（出力：７０Ｗ、周波数：３５ｋＨｚ、温度：２５℃）をしたものを測定サンプルとした。レーザー回折粒度分布計（島津製作所製、SALD-7100）を用い、溶媒屈折率を１．４７（Ｎ－メチル－２－ピロリドン）として粒度分布（体積基準）を測定し、メジアン径（Ｄ５０）を求めた。
　なお、測定サンプルの濃度は、測定装置での吸光度が０．２以下となる濃度とした。
＜レート特性＞
　作製した二次電池を、温度２５℃において、定電流充電法（充電レート：０．２Ｃ）で４．２Ｖまで充電したのち、定電圧充電法で電流値が０．０２Ｃとなるまで充電した。その後、放電レート０．２Ｃの定電流法で３．０Ｖまで放電した時の容量をＣ１とした。ついで、充電条件は同じで、放電レートを２．０Ｃとした以外は同様にして容量を測定し、この時の容量をＣ２とした。
　そして、下記の式からレート特性を算出し、以下の基準に従って評価した。値が大きいほど電池抵抗が低く、レート特性に優れていることを示す。
　レート特性＝（Ｃ２／Ｃ１）×１００　（％）
　Ａ：レート特性が８５％以上
　Ｂ：レート特性が８０％以上８５％未満
　Ｃ：レート特性が８０％未満
＜高温保存特性＞
　作製した二次電池を、温度２５℃において、定電流充電法（充電レート：０．２Ｃ）で４．２Ｖまで充電したのち、定電圧充電法で電流値が０．０２Ｃとなるまで充電した。その後、充電状態の二次電池を６０℃の恒温槽内で３０日間保存した。
　恒温槽内で保存した二次電池を温度２５℃に冷却した後、放電レート０．２Ｃの定電流法で３．０Ｖまで放電した時の容量をＣ３とした。そして、上記＜レート特性＞を算出する際に求めた容量Ｃ１と、容量Ｃ３とを用いて、下記式から高温保存特性を算出し、以下の基準に従って評価した。値が大きいほど高温保存時の容量劣化が小さく、高温保存特性に優れていることを示す。
　高温保存特性＝（Ｃ３／Ｃ１）×１００　（％）
Ａ：高温保存特性が８５％以上
Ｂ：高温保存特性が８０％以上８５％未満
Ｃ：高温保存特性が７５％以上８０％未満
Ｄ：高温保存特性が７５％未満 <Saponification degree>
About 1 g of the polyvinyl alcohol polymer was precisely weighed to the order of 1 mg (the precision value is S), put in a 300 mL Erlenmeyer flask, and 25 mL of 0.5 mol/L potassium hydroxide ethanol solution was added using a pipette. .. Subsequently, a cooling tube was attached to the Erlenmeyer flask and reacted at 40° C. for 30 minutes while stirring. After completion of the reaction, the mixture was cooled, 1 mL of a phenolphthalein solution was added as an indicator, and titration was performed using a 0.5 mol/L hydrochloric acid aqueous solution. The amount of hydrochloric acid at this time is A. Similarly, the blank test was performed without adding the polyvinyl alcohol polymer. The amount of hydrochloric acid at this time is B. Using S, A and B, the saponification value X was calculated from the following formula. Here, f is a factor of the 0.5 mol/L hydrochloric acid aqueous solution used.
Saponification value X={(BA)×f×28.05}/S
Next, the saponification degree was calculated from the following equation, where Y is the number of moles of vinyl ester monomer units contained in 1 g of the polymer (polyvinyl ester polymer) before saponification.
Saponification degree=[{1-(X/0.0561)}/Y]×100
<Median diameter>
The prepared carbon material dispersion liquid for a secondary battery electrode was diluted to an appropriate concentration and then subjected to ultrasonic treatment for 1 minute (output: 70 W, frequency: 35 kHz, temperature: 25° C.) to obtain a measurement sample. Using a laser diffraction particle size distribution analyzer (SALD-7100 manufactured by Shimadzu Corporation), the particle size distribution (volume basis) was measured with the solvent refractive index of 1.47 (N-methyl-2-pyrrolidone), and the median diameter (D50) was calculated. I asked.
The concentration of the measurement sample was set so that the absorbance at the measuring device was 0.2 or less.
<Rate characteristics>
The manufactured secondary battery was charged at a temperature of 25° C. to 4.2 V by the constant current charging method (charging rate: 0.2 C) and then charged by the constant voltage charging method until the current value became 0.02 C. After that, the capacity when discharged to 3.0 V by the constant current method with a discharge rate of 0.2 C was defined as C1. Then, the charging conditions were the same, the capacity was measured in the same manner except that the discharge rate was 2.0 C, and the capacity at this time was C2.
Then, the rate characteristic was calculated from the following formula and evaluated according to the following criteria. The larger the value, the lower the battery resistance and the better the rate characteristics.
Rate characteristic=(C2/C1)×100 (%)
A: Rate characteristic is 85% or more B: Rate characteristic is 80% or more and less than 85% C: Rate characteristic is less than 80% <High temperature storage characteristic>
The manufactured secondary battery was charged at a temperature of 25° C. to 4.2 V by the constant current charging method (charging rate: 0.2 C) and then charged by the constant voltage charging method until the current value became 0.02 C. Then, the charged secondary battery was stored in a constant temperature bath at 60° C. for 30 days.
After the secondary battery stored in the constant temperature bath was cooled to a temperature of 25° C., the capacity when discharged to 3.0 V by a constant current method with a discharge rate of 0.2 C was defined as C3. Then, using the capacitance C1 and the capacitance C3 obtained when calculating the above <rate characteristic>, the high temperature storage characteristic was calculated from the following formula and evaluated according to the following criteria. The larger the value, the smaller the capacity deterioration during high temperature storage, indicating that the high temperature storage characteristics are excellent.
High temperature storage characteristics=(C3/C1)×100 (%)
A: High temperature storage property is 85% or more B: High temperature storage property is 80% or more and less than 85% C: High temperature storage property is 75% or more and less than 80% D: High temperature storage property is less than 75%
（実施例１）
＜正極用炭素材料分散液の調製＞
　粉砕室の容量が０．６Ｌのビーズミルのプレミキシングタンクに、有機分散媒としてのＮ－メチル－２－ピロリドン（ＮＭＰ）２６４０ｇと、炭素材料としてのアセチレンブラック（比表面積：３９ｍ2／ｇ）３００ｇと、ポリビニルアルコール系重合体としてのポリビニルアルコール（けん化度：９８ｍｏｌ％）６０ｇとを投入し、プレミキシングを実施して予備分散液を得た。
　続いて、ビーズミルのローター周速を１２ｍ／秒とし、速度３００ｇ／分で送液しながら予備分散液を混合し、分散液中の分散質のメジアン径が３．４μｍとなった時点で分散処理を停止して正極用炭素材料分散液を得た。なお、使用したビーズは、直径１．０ｍｍのジルコニア製ビーズであった。
＜正極用スラリー組成物の調製＞
　上記正極用炭素材料分散液１０部（固形分換算）中に、正極活物質としてのＬｉＮｉ0.5Ｃｏ0.2Ｍｎ0.3Ｏ2（層状構造を有する三元系活物質、平均粒子径：１０μｍ）３１０部と、バインダーとしてポリフッ化ビニリデン（ＰＶｄＦ）１０．０部と、追加の有機分散媒としてのＮＭＰとを添加し、プラネタリーミキサーにて撹拌（４０ｒｐｍ、６０分）して、正極用スラリー組成物を調製した。なお、ＮＭＰの添加量は、得られる正極用スラリー組成物の粘度（ＪＩＳ Ｚ８８０３：１９９１に準拠し、温度２５℃、回転数６０ｒｐｍにて単一円筒形回転粘度計で測定）が４０００～５０００ｍＰａ・ｓの範囲内となるように調整した。
＜正極の作製＞
　集電体として、厚さ２０μｍのアルミ箔を準備した。上記正極用スラリー組成物を、コンマコーターでアルミ箔上に乾燥後の目付量が２０ｍｇ／ｃｍ2になるように塗布し、９０℃で２０分、１２０℃で２０分間乾燥した後、６０℃で１０時間加熱処理して正極原反を得た。得られた正極原反をロールプレスで圧延し、密度が３．２ｇ／ｃｍ3の正極合材層と、アルミ箔とからなるシート状正極を作製した。なお、シート状正極の厚みは７０μｍであった。このシート状正極を幅４．８ｍｍ、長さ５０ｃｍに切断して、リチウムイオン二次電池用正極とした。
＜負極の作製＞
　負極活物質としての球状人造黒鉛（体積平均粒子径：１２μｍ）９０部およびＳｉＯX（体積平均粒子径：１０μｍ）１０部の混合物と、バインダーとしてのスチレン－ブタジエン共重合体１部と、増粘剤としてのカルボキシメチルセルロース１部と、分散媒としての適量の水とをプラネタリーミキサーにて撹拌し、負極用スラリー組成物を調製した。
　次に、集電体として、厚さ１５μｍの銅箔を準備した。上記負極用スラリー組成物を銅箔の両面に乾燥後の塗布量がそれぞれ１０ｍｇ／ｃｍ2になるように塗布し、６０℃で２０分、１２０℃で２０分間乾燥した。その後、１５０℃で２時間加熱処理して、負極原反を得た。この負極原反をロールプレスで圧延し、密度が１．７ｇ／ｃｍ3の負極合材層（両面）と、銅箔とからなるシート状負極を作製した。そして、シート状負極を幅５．０ｍｍ、長さ５２ｃｍに切断して、リチウムイオン二次電池用負極とした。
＜リチウムイオン二次電池の製造＞
　上記正極と上記負極とを、セパレータ（厚さ１５μｍのポリプロピレン製の微多孔膜）を介在させて直径２０ｍｍの芯を用いて捲回し、捲回体を得た。そして、得られた捲回体を、１０ｍｍ／秒の速度で厚さ４．５ｍｍになるまで一方向から圧縮した。なお、圧縮後の捲回体は平面視楕円形をしており、その長径と短径との比（長径／短径）は７．７であった。
　また、電解液（組成：濃度１．０ＭのＬｉＰＦ6溶液（溶媒は、エチレンカーボネート／エチルメチルカーボネート＝３／７（質量比）の混合溶媒にフルオロエチレンカーボネート５％を添加した混合溶液であり、添加剤としてビニレンカーボネート２体積％を添加））を準備した。
　その後、圧縮した捲回体をアルミ製ラミネートケース内に３．２ｇの電解液とともに収容した。そして、負極の所定の箇所にニッケルリード線を接続し、正極の所定の箇所にアルミニウムリード線を接続したのち、ケースの開口部を熱で封口し、リチウムイオン二次電池を得た。このリチウムイオン二次電池は、幅３５ｍｍ、高さ４８ｍｍ、厚さ５ｍｍのパウチ形であり、電池の公称容量は７００ｍＡｈであった。得られたリチウムイオン二次電池について、レート特性および高温保存特性を評価した。結果を表１に示す。 (Example 1)
<Preparation of carbon material dispersion liquid for positive electrode>
In a premixing tank of a bead mill with a crushing chamber capacity of 0.6 L, 2640 g of N-methyl-2-pyrrolidone (NMP) as an organic dispersion medium and 300 g of acetylene black as a carbon material (specific surface area: 39 m 2 /g) And 60 g of polyvinyl alcohol (saponification degree: 98 mol%) as a polyvinyl alcohol-based polymer were added and premixing was performed to obtain a preliminary dispersion liquid.
Subsequently, the peripheral speed of the bead mill was set to 12 m/sec, the preliminary dispersion was mixed while feeding at a speed of 300 g/min, and the dispersion treatment was carried out when the median diameter of the dispersoid in the dispersion became 3.4 μm. Was stopped to obtain a carbon material dispersion liquid for the positive electrode. The beads used were zirconia beads having a diameter of 1.0 mm.
<Preparation of slurry composition for positive electrode>
310 parts of LiNi 0.5 Co 0.2 Mn 0.3 O 2 (ternary active material having a layered structure, average particle diameter: 10 μm) as a positive electrode active material in 10 parts of the carbon material dispersion liquid for a positive electrode (calculated as solid content) Then, 10.0 parts of polyvinylidene fluoride (PVdF) as a binder and NMP as an additional organic dispersion medium were added and stirred with a planetary mixer (40 rpm, 60 minutes) to prepare a positive electrode slurry composition. did. The amount of NMP added is such that the viscosity of the obtained slurry composition for a positive electrode (measured with a single cylindrical rotary viscometer at a temperature of 25° C. and a rotation speed of 60 rpm according to JIS Z8803:1991) is 4,000 to 5,000 mPa. It was adjusted to fall within the range of s.
<Production of positive electrode>
An aluminum foil having a thickness of 20 μm was prepared as a current collector. The slurry composition for a positive electrode was applied on an aluminum foil with a comma coater so that the basis weight after drying was 20 mg/cm 2 , dried at 90° C. for 20 minutes and 120° C. for 20 minutes, and then at 60° C. It heat-processed for 10 hours and obtained the positive electrode original fabric. The obtained positive electrode raw material was rolled by a roll press to produce a sheet-shaped positive electrode composed of a positive electrode mixture layer having a density of 3.2 g/cm 3 and an aluminum foil. The thickness of the sheet-shaped positive electrode was 70 μm. This sheet-shaped positive electrode was cut into a width of 4.8 mm and a length of 50 cm to obtain a positive electrode for a lithium ion secondary battery.
<Production of negative electrode>
A mixture of 90 parts of spherical artificial graphite (volume average particle size: 12 μm) and 10 parts of SiO X (volume average particle size: 10 μm) as a negative electrode active material, 1 part of a styrene-butadiene copolymer as a binder, and a thickening agent. 1 part of carboxymethyl cellulose as an agent and an appropriate amount of water as a dispersion medium were stirred with a planetary mixer to prepare a slurry composition for a negative electrode.
Next, a copper foil having a thickness of 15 μm was prepared as a current collector. The above negative electrode slurry composition was applied onto both surfaces of a copper foil so that the applied amount after drying was 10 mg/cm 2 , and dried at 60° C. for 20 minutes and 120° C. for 20 minutes. Then, it heat-processed at 150 degreeC for 2 hours, and obtained the negative electrode original fabric. This negative electrode raw material was rolled by a roll press to produce a sheet-shaped negative electrode composed of a negative electrode mixture layer (both sides) having a density of 1.7 g/cm 3 and a copper foil. Then, the sheet-shaped negative electrode was cut into a width 5.0 mm and a length 52 cm to obtain a negative electrode for a lithium ion secondary battery.
<Manufacture of lithium-ion secondary battery>
The positive electrode and the negative electrode were wound using a core having a diameter of 20 mm with a separator (a microporous polypropylene film having a thickness of 15 μm) interposed therebetween to obtain a wound body. Then, the obtained wound body was compressed from one direction at a speed of 10 mm/sec until the thickness became 4.5 mm. The wound body after compression had an elliptical shape in plan view, and the ratio of the major axis to the minor axis (major axis/minor axis) was 7.7.
Further, an electrolytic solution (composition: a LiPF 6 solution having a concentration of 1.0 M (the solvent is a mixed solution of 5% fluoroethylene carbonate added to a mixed solvent of ethylene carbonate/ethyl methyl carbonate=3/7 (mass ratio), 2% by volume of vinylene carbonate was added as an additive)).
Then, the compressed wound body was accommodated in an aluminum laminate case together with 3.2 g of the electrolytic solution. Then, a nickel lead wire was connected to a predetermined part of the negative electrode and an aluminum lead wire was connected to a predetermined part of the positive electrode, and then the opening of the case was sealed with heat to obtain a lithium ion secondary battery. This lithium-ion secondary battery was a pouch type with a width of 35 mm, a height of 48 mm, and a thickness of 5 mm, and the nominal capacity of the battery was 700 mAh. The rate characteristics and the high temperature storage characteristics of the obtained lithium ion secondary battery were evaluated. The results are shown in Table 1.
（実施例２）
　正極用炭素材料分散液の調製時に、ポリビニルアルコール（けん化度：９８ｍｏｌ％）に替えてけん化度８０ｍｏｌ％のポリビニルアルコールを使用し、メジアン径が３．２μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Example 2)
When preparing the carbon material dispersion liquid for the positive electrode, polyvinyl alcohol having a saponification degree of 80 mol% was used in place of polyvinyl alcohol (saponification degree: 98 mol %), and the dispersion treatment was stopped when the median diameter reached 3.2 μm. In the same manner as in Example 1, a positive electrode carbon material dispersion liquid, a positive electrode slurry composition, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（実施例３）
　正極用炭素材料分散液の調製時に、ＮＭＰの量を２５９５ｇとし、ポリビニルアルコールの量を１０５ｇとし、メジアン径が３．３μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Example 3)
At the time of preparing the carbon material dispersion liquid for the positive electrode, the amount of NMP was set to 2595 g, the amount of polyvinyl alcohol was set to 105 g, and the dispersion treatment was stopped at the time when the median diameter reached 3.3 μm. A carbon material dispersion liquid for a positive electrode, a slurry composition for a positive electrode, a positive electrode, a negative electrode and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（実施例４）
　正極用炭素材料分散液の調製時に、メジアン径が１．８μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Example 4)
When preparing the carbon material dispersion liquid for the positive electrode, the carbon material dispersion liquid for the positive electrode, the slurry composition for the positive electrode, and the positive electrode were prepared in the same manner as in Example 1 except that the dispersion treatment was stopped when the median diameter reached 1.8 μm. A negative electrode and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（実施例５）
　正極用炭素材料分散液の調製時に、ビーズミルのローター周速を８ｍ／秒に変更し、メジアン径が８．４μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Example 5)
The positive electrode was prepared in the same manner as in Example 1 except that the rotor peripheral speed of the bead mill was changed to 8 m/sec and the dispersion treatment was stopped when the median diameter reached 8.4 μm when the carbon material dispersion liquid for positive electrode was prepared. A carbon material dispersion liquid, a positive electrode slurry composition, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（実施例６）
　正極用炭素材料分散液の調製時に、直径１．０ｍｍのジルコニア製ビーズに替えて直径０．５ｍｍのジルコニア製ビーズを使用し、メジアン径が０．９５μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Example 6)
Except that the zirconia beads having a diameter of 0.5 mm were used instead of the zirconia beads having a diameter of 1.0 mm when the dispersion of the carbon material for the positive electrode was prepared, and the dispersion treatment was stopped when the median diameter became 0.95 μm. In the same manner as in Example 1, a positive electrode carbon material dispersion liquid, a positive electrode slurry composition, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（実施例７）
　正極用炭素材料分散液の調製時に、アセチレンブラック（比表面積：３９ｍ2／ｇ）３００ｇに替えて多層カーボンナノチューブ（比表面積：９０ｍ2／ｇ）１５０ｇを使用し、ＮＭＰの量を２５８５ｇとし、ポリビニルアルコールの量を３７．５ｇとし、メジアン径が１．２μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Example 7)
When preparing the carbon material dispersion liquid for the positive electrode, 150 g of multi-walled carbon nanotubes (specific surface area: 90 m 2 /g) was used instead of 300 g of acetylene black (specific surface area: 39 m 2 /g), and the amount of NMP was 2585 g. The amount of alcohol was 37.5 g, and the carbon material dispersion liquid for the positive electrode, the slurry composition for the positive electrode, the positive electrode, which was the same as in Example 1, except that the dispersion treatment was stopped when the median diameter reached 1.2 μm. A negative electrode and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（実施例８）
　正極用炭素材料分散液の調製時に、アセチレンブラック（比表面積：３９ｍ2／ｇ）３００ｇに替えてケッチェンブラック（比表面積：３００ｍ2／ｇ）１５０ｇを使用し、ＮＭＰの量を２５８５ｇとし、ポリビニルアルコールの量を４５ｇとし、メジアン径が１．６μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Example 8)
When preparing the carbon material dispersion liquid for the positive electrode, 150 g of Ketjen black (specific surface area: 300 m 2 /g) was used instead of 300 g of acetylene black (specific surface area: 39 m 2 /g), and the amount of NMP was 2585 g. The amount of alcohol was 45 g, and the carbon material dispersion for positive electrode, positive electrode slurry composition, positive electrode, negative electrode, and the like were prepared in the same manner as in Example 1 except that the dispersion treatment was stopped at the time when the median diameter became 1.6 μm. A lithium ion secondary battery was produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（比較例１）
　正極用炭素材料分散液の調製時に、メジアン径が１１．９μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Comparative Example 1)
When preparing the carbon material dispersion liquid for the positive electrode, the carbon material dispersion liquid for the positive electrode, the slurry composition for the positive electrode, the positive electrode were prepared in the same manner as in Example 1 except that the dispersion treatment was stopped when the median diameter became 11.9 μm. A negative electrode and a lithium ion secondary battery were produced. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（比較例２）
　正極用炭素材料分散液の調製時に、直径１．０ｍｍのジルコニア製ビーズに替えて直径１．２５ｍｍのジルコニア製ビーズを使用し、ビーズミルのローター周速を１６ｍ／秒に変更し、メジアン径が０．７μｍとなった時点で分散処理を停止した以外は実施例２と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Comparative example 2)
When the carbon material dispersion liquid for the positive electrode was prepared, zirconia beads having a diameter of 1.25 mm were used instead of zirconia beads having a diameter of 1.0 mm, the rotor peripheral speed of the bead mill was changed to 16 m/sec, and the median diameter was 0. A carbon material dispersion liquid for a positive electrode, a slurry composition for a positive electrode, a positive electrode, a negative electrode, and a lithium ion secondary battery were produced in the same manner as in Example 2 except that the dispersion treatment was stopped at the time of 0.7 μm. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
（比較例３）
　正極用炭素材料分散液の調製時に、直径１．０ｍｍのジルコニア製ビーズに替えて直径１．２５ｍｍのジルコニア製ビーズを使用し、ビーズミルのローター周速を１６ｍ／秒に変更し、メジアン径が０．７μｍとなった時点で分散処理を停止した以外は実施例１と同様にして、正極用炭素材料分散液、正極用スラリー組成物、正極、負極およびリチウムイオン二次電池を作製した。そして、実施例１と同様にして評価を行った。結果を表１に示す。 (Comparative example 3)
When the carbon material dispersion liquid for the positive electrode was prepared, zirconia beads having a diameter of 1.25 mm were used instead of zirconia beads having a diameter of 1.0 mm, the rotor peripheral speed of the bead mill was changed to 16 m/sec, and the median diameter was 0. A carbon material dispersion liquid for a positive electrode, a slurry composition for a positive electrode, a positive electrode, a negative electrode and a lithium ion secondary battery were produced in the same manner as in Example 1 except that the dispersion treatment was stopped at the time of 0.7 μm. Then, evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　表１より、実施例１～８の二次電池電極用炭素材料分散液を用いて作製した二次電池は、レート特性および高温保存特性の双方に優れていることが分かる。また、表１より、分散質のメジアン径（Ｄ５０）が０．９０μｍ未満または１０μｍ超の比較例１～３の二次電池電極用炭素材料分散液を用いて作製した二次電池は、レート特性が低下することが分かる。 From Table 1, it can be seen that the secondary batteries prepared using the carbon material dispersion liquids for secondary battery electrodes of Examples 1 to 8 are excellent in both rate characteristics and high temperature storage characteristics. In addition, from Table 1, the secondary batteries produced using the carbon material dispersion liquids for secondary battery electrodes of Comparative Examples 1 to 3 in which the median diameter (D50) of the dispersoid is less than 0.90 μm or more than 10 μm have rate characteristics. It can be seen that
　本発明の二次電池電極用炭素材料分散液および二次電池電極用スラリー組成物によれば、二次電池に優れたレート特性および高温保存特性を発揮させ得る二次電池用電極を形成することができる。
　また、本発明の二次電池用電極によれば、二次電池に優れたレート特性および高温保存特性を発揮させることができる。
　更に、本発明の二次電池は、レート特性および高温保存特性の双方に優れている。 According to the carbon material dispersion liquid for a secondary battery electrode and the slurry composition for a secondary battery electrode of the present invention, it is possible to form a secondary battery electrode capable of exhibiting excellent rate characteristics and high temperature storage characteristics in a secondary battery. You can
Further, according to the secondary battery electrode of the present invention, the secondary battery can exhibit excellent rate characteristics and high temperature storage characteristics.
Furthermore, the secondary battery of the present invention is excellent in both rate characteristics and high temperature storage characteristics.

Claims (6)

  1. 　炭素材料と、ポリビニルアルコール系重合体と、有機分散媒とを含み、
    　分散質のメジアン径（Ｄ５０）が０．９０μｍ以上１０μｍ以下である、二次電池電極用炭素材料分散液。     Including a carbon material, a polyvinyl alcohol-based polymer, and an organic dispersion medium,
    A carbon material dispersion liquid for a secondary battery electrode, wherein the median diameter (D50) of the dispersoid is 0.90 μm or more and 10 μm or less.
  2. 　前記炭素材料が、アセチレンブラック、ファーネスブラック、ケッチェンブラック、炭素繊維、カーボンナノチューブおよびグラフェンからなる群より選択される少なくとも１種を含む、請求項１に記載の二次電池電極用炭素材料分散液。 The carbon material dispersion liquid for a secondary battery electrode according to claim 1, wherein the carbon material contains at least one selected from the group consisting of acetylene black, furnace black, Ketjen black, carbon fibers, carbon nanotubes, and graphene. ..
  3. 　前記ポリビニルアルコール系重合体のけん化度が６０ｍｏｌ％超９９．５ｍｏｌ％以下である、請求項１または２に記載の二次電池電極用炭素材料分散液。 The carbon material dispersion liquid for a secondary battery electrode according to claim 1 or 2, wherein the saponification degree of the polyvinyl alcohol-based polymer is more than 60 mol% and 99.5 mol% or less.
  4. 　請求項１～３の何れかに記載の二次電池電極用炭素材料分散液と、電極活物質と、バインダーとを含む、二次電池電極用スラリー組成物。 A slurry composition for a secondary battery electrode, comprising the carbon material dispersion liquid for a secondary battery electrode according to any one of claims 1 to 3, an electrode active material, and a binder.
  5. 　請求項４に記載の二次電池電極用スラリー組成物を用いて形成した電極合材層を備える、二次電池用電極。 An electrode for a secondary battery, comprising an electrode mixture layer formed by using the slurry composition for a secondary battery electrode according to claim 4.
  6. 　正極、負極、電解液およびセパレータを備え、
    　前記正極および負極の少なくとも一方が請求項５に記載の二次電池用電極である、二次電池。     Provided with a positive electrode, a negative electrode, an electrolytic solution and a separator,
    A secondary battery in which at least one of the positive electrode and the negative electrode is the electrode for a secondary battery according to claim 5.
PCT/JP2019/047460 2018-12-27 2019-12-04 Carbon material dispersion liquid for secondary battery electrodes, slurry composition for secondary battery electrodes, electrode for secondary batteries, and secondary battery WO2020137403A1 (en)

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