WO2018155609A1 - Accumulateur au lithium-ion comprenant une électrode négative pour batterie à haute densité d'énergie - Google Patents

Accumulateur au lithium-ion comprenant une électrode négative pour batterie à haute densité d'énergie Download PDF

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WO2018155609A1
WO2018155609A1 PCT/JP2018/006621 JP2018006621W WO2018155609A1 WO 2018155609 A1 WO2018155609 A1 WO 2018155609A1 JP 2018006621 W JP2018006621 W JP 2018006621W WO 2018155609 A1 WO2018155609 A1 WO 2018155609A1
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negative electrode
weight
ion secondary
carbon
lithium ion
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PCT/JP2018/006621
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Japanese (ja)
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丈史 莇
卓 玉井
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日本電気株式会社
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Publication of WO2018155609A1 publication Critical patent/WO2018155609A1/fr

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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
    • H01M10/052—Li-accumulators
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • 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
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials

Definitions

  • the present invention relates to a lithium ion secondary battery, a method of manufacturing a lithium ion secondary battery, and a vehicle equipped with the lithium ion secondary battery.
  • a carbon-based material is used for the negative electrode of a lithium ion secondary battery, but in order to increase the energy density of the battery, a silicon oxide having a large amount of occlusion / release of lithium ions per unit volume is used as the negative electrode. It is being considered for use.
  • silicon oxide provides a high capacity, the expansion and contraction of the active material when lithium ions are occluded and released are large, so that the cycle characteristics are degraded due to cutting of the conductive path or peeling of the active material particles. .
  • the silicon oxide is generally used by being mixed with another negative electrode active material such as graphite so that the ratio in the negative electrode active material layer is reduced.
  • Patent Document 1 describes a lithium ion secondary battery containing silicon oxide represented by SiO x (0.3 ⁇ x ⁇ 1.6) and graphite.
  • the lithium ion secondary battery described in Patent Document 1 has room for improvement in energy density because the silicon oxide content is lower than that of graphite. It is desired to further increase the mixing ratio of silicon oxide in the negative electrode active material layer. When the mixing ratio of the silicon oxide is high, it becomes more important to select a binder having a high binding force in order to prevent the deterioration of the negative electrode active material layer due to the large expansion and contraction of the silicon oxide.
  • polyimide Since polyimide has a high binding force, it is generally used as a binder for a negative electrode having a high silicon oxide content ratio. However, in polyimide, an organic solvent having a high environmental load such as N-methylpyrrolidone (NMP) is used. In recent years, an aqueous binder is required from the viewpoint of environmental harmony and industrial applicability. In addition, polyimide also has a problem that heat treatment at a high temperature is required for imidization and that good cycle characteristics cannot be obtained when the negative electrode is densified by pressing.
  • NMP N-methylpyrrolidone
  • rubber-based binders such as styrene butadiene rubber (SBR) and polyacrylic acid are known.
  • SBR styrene butadiene rubber
  • the rubber binder can be used up to a silicon oxide mixing ratio of about 5 to 7% by weight.
  • polyacrylic acid has a higher binding force than rubber-based binders, there is little capacity deterioration.
  • polyacrylic acid has a lower binding force than polyimide, the cycle characteristics are still insufficient.
  • a battery using polyacrylic acid has a problem of high resistance.
  • an object of the present invention is to provide a lithium ion secondary battery that uses polyacrylic acid that is an aqueous binder and has a high energy density and improved cycle characteristics. There is.
  • a first lithium ion secondary battery of the present invention includes a positive electrode including a positive electrode active material layer including a lithium-containing layered nickel composite oxide, composite particles including silicon oxide and carbon, graphite particles, a conductive material, and polyacryl
  • a lithium ion secondary battery including a negative electrode including a negative electrode active material layer including an acid wherein the conductive material has a specific surface area of 40 to 800 m 2 / g, and the amount of the composite particles in the negative electrode active material layer Is 50% by weight or more, the amount of the polyacrylic acid is 3% by weight or more and 8% by weight or less, the total amount of the conductive material and the polyacrylic acid is 4% by weight or more and 13% by weight or less, and the composite In the particles, the amount of carbon is 2% by weight or more.
  • a lithium ion secondary battery using polyacrylic acid which has a high energy density and improved cycle characteristics, can be provided.
  • FIG. 1 It is a disassembled perspective view which shows the basic structure of a film-clad battery. It is sectional drawing which shows the cross section of the battery of FIG. 1 typically. It is an impedance plot of a battery using polyacrylic acid or SBR / CMC and various conductive materials in the negative electrode. It is a SEM image of the negative electrode which uses a carbon nanotube. It is a SEM image of the negative electrode which uses carbon nanohorn.
  • the positive electrode includes a current collector and a positive electrode active material layer that is provided on the current collector and includes a positive electrode active material, a binder, and, if necessary, a conductive material.
  • the positive electrode active material contains a lithium-containing layered nickel composite oxide.
  • a lithium-containing layered nickel composite oxide that is a high-capacity material, the energy density of the battery can be improved.
  • Examples of the lithium-containing layered nickel composite oxide include those represented by the following formula (1).
  • Li y Ni (1-x) M x O 2 (1) (However, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1.2, and M is at least one element selected from the group consisting of Co, Al, Mn, Fe, Ti, and B.)
  • the Ni content is high, that is, in the formula (1), x is preferably less than 0.5, and more preferably 0.4 or less.
  • x is preferably less than 0.5, and more preferably 0.4 or less.
  • LiNi 0.8 Co 0.05 Mn 0.15 O 2 , LiNi 0.8 Co 0.1 Mn 0.1 O 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2, LiNi 0.8 Co 0.1 Al can be preferably used 0.1 O 2 or the like.
  • the Ni content does not exceed 0.5, that is, in the formula (1), x is 0.5 or more. It is also preferred that the number of specific transition metals does not exceed half.
  • LiNi 0.4 Co 0.3 Mn 0.3 O 2 (abbreviated as NCM433), LiNi 1/3 Co 1/3 Mn 1/3 O 2 , LiNi 0.5 Co 0.2 Mn 0.3 O 2 (abbreviated as NCM523), LiNi 0.5 Co 0.3 Mn 0.2 O 2 (abbreviated as NCM532), etc. (however, the content of each transition metal in these compounds varies by about 10%) Can also be included).
  • NCM532 or NCM523 and NCM433 range from 9: 1 to 1: 9 (typically 2 It is also preferable to use a mixture in 1).
  • the material with high Ni content (x is 0.4 or less) and the material with Ni content not exceeding 0.5 (x is 0.5 or more, for example, NCM433) are mixed. As a result, a battery having a high capacity and high thermal stability can be formed.
  • positive electrode active materials may be used together with the lithium-containing layered nickel composite oxide.
  • positive electrode active materials for example, LiMnO 2 , Li x Mn 2 O 4 (0 ⁇ x ⁇ 2), Li 2 MnO 3 , xLi 2 MnO 3 — (1-x) LiMO 2 (x is 0.
  • M is one or more elements selected from the group consisting of Mn, Fe, Co, Ni, Ti, Al and Mg), Li x Mn 1.5 Ni 0.5 Lithium manganate having a layered structure or spinel structure such as O 4 (0 ⁇ x ⁇ 2); LiCoO 2 or a part of these transition metals replaced with another metal; chemistry in these lithium transition metal oxides Those having an excess of Li rather than the stoichiometric composition; and those having an olivine structure such as LiFePO 4 .
  • any of the positive electrode active materials described above can be used alone or in combination of two or more.
  • the content of the lithium-containing layered nickel composite oxide in the total amount of the positive electrode active material is preferably 50% by weight or more, more preferably 80% by weight or more, and may be 100% by weight.
  • the binder used for the positive electrode is not particularly limited, but polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, polytetrafluoroethylene, polypropylene, Polyethylene, polybutadiene, polyacrylic acid, polyacrylic acid ester, polystyrene, polyacrylonitrile, polyimide, polyamideimide and the like can be used.
  • the binder may be a mixture of a plurality of resins, a copolymer, and a crosslinked product thereof, such as styrene butadiene rubber (SBR). Further, when an aqueous binder such as an SBR emulsion is used, a thickener such as carboxymethyl cellulose (CMC) can also be used.
  • SBR styrene butadiene rubber
  • the amount of the binder in the positive electrode is preferably 1 part by weight or more, more preferably 2 parts by weight or more, and preferably 30 parts by weight or less, more preferably 25 parts by weight or less as the upper limit with respect to 100 parts by weight of the positive electrode active material. It is.
  • the positive electrode current collector is not particularly limited, but aluminum, nickel, silver, or an alloy thereof can be used.
  • Examples of the shape of the positive electrode current collector include a foil, a flat plate, and a mesh.
  • a conductive material may be added for the purpose of reducing the impedance.
  • the conductive material include carbonaceous fine particles such as graphite, carbon black, and acetylene black.
  • the positive electrode according to the present embodiment can be produced by preparing a slurry containing a positive electrode active material, a binder and a solvent, and applying the slurry onto a positive electrode current collector to form a positive electrode active material layer.
  • the negative electrode includes a current collector and a negative electrode active material layer provided on the current collector and including a negative electrode active material, a binder, and a conductive material.
  • a negative electrode active material e.g., composite particles and graphite particles containing silicon oxide and carbon are used as the negative electrode active material, and polyacrylic acid is used as the binder.
  • the negative electrode active material of the present embodiment includes composite particles containing silicon oxide and carbon (hereinafter, this composite particle is also simply referred to as silicon oxide particles).
  • Silicon oxide is not particularly limited, for example, expressed by a composition formula SiO x (0 ⁇ x ⁇ 2 ). Further, the silicon oxide may contain Li, and the silicon oxide containing Li is represented by, for example, SiLi y O z (y> 0, 2>z> 0). Further, the silicon oxide may contain a trace amount of a metal element or a nonmetal element. The silicon oxide can contain, for example, 0.1 to 5% by weight of one or more elements selected from nitrogen, boron and sulfur. By containing a trace amount of a metal element or a non-metal element, the electrical conductivity of the silicon oxide can be improved.
  • the silicon oxide may be crystalline or amorphous.
  • Silicon oxide particles contain carbon together with silicon oxide.
  • the carbon coats the entire surface or part of the periphery of the silicon oxide that is the core of the particle.
  • the carbon film can be formed by, for example, a sputtering method or a vapor deposition method using a carbon source.
  • Examples of the vapor deposition method include an arc vapor deposition method and a chemical vapor deposition method.
  • the chemical vapor deposition method which is chemical vapor deposition is preferable because the vapor deposition temperature and vapor deposition atmosphere can be easily controlled.
  • This chemical vapor deposition method can be performed by using silicon oxide particles in an alumina or quartz boat.
  • the chemical vapor deposition method can be performed in a state where the silicon oxide particles are suspended or transported in the gas.
  • the carbon source used in the chemical vapor deposition method can be used without particular limitation as long as it generates carbon by thermal decomposition, and can be appropriately selected according to the conditions.
  • the carbon source include hydrocarbon compounds such as methane, ethane, ethylene, acetylene, and benzene, organic solvents such as methanol, ethanol, toluene, and xylene, or CO.
  • an inert gas such as argon or nitrogen, or a mixed gas of these and hydrogen can be used.
  • the temperature in the chemical vapor deposition method is, for example, in the range of 400 to 1200 ° C.
  • the amount of carbon in the silicon oxide particles is 2% by weight or more, preferably 3% by weight or more, and more preferably 4.5% by weight or more.
  • the amount of carbon in the silicon oxide particles is preferably 8% by weight or less, more preferably 6% by weight or less.
  • the amount of silicon oxide is preferably 60% by weight or more, more preferably 70% by weight or more, and still more preferably 92% by weight or more.
  • the amount of silicon oxide in the silicon oxide particles is preferably 98% by weight or less, more preferably 95.5% by weight or less.
  • the content of silicon oxide particles in the negative electrode active material layer is preferably 50% by weight or more, more preferably 60% by weight or more, and still more preferably 70% by weight or more. By containing many silicon oxide particles in the negative electrode, the energy density of the battery can be improved.
  • the content of silicon oxide particles in the negative electrode active material layer is preferably 95% by weight or less, more preferably 90% by weight or less.
  • the average particle diameter of the silicon oxide particles is preferably 1 ⁇ m or more, more preferably 3 ⁇ m or more as a lower limit.
  • the upper limit of the average particle diameter of the silicon oxide particles is preferably 10 ⁇ m or less, more preferably 7 ⁇ m or less.
  • the average particle size represents a particle size at an integrated volume of 50%.
  • the average particle diameter can be measured by a laser diffraction / scattering particle size distribution measuring apparatus.
  • the specific surface area of the silicon oxide particles is preferably 1 m 2 / g or more, more preferably 3 m 2 / g or more as a lower limit.
  • the specific surface area of the silicon oxide particles is preferably 20 m 2 / g or less, more preferably 12 m 2 / g or less as the upper limit. Specific surface area can be measured using the BET method with nitrogen adsorption.
  • the negative electrode active material of this embodiment further contains graphite particles.
  • the graphite used in this embodiment may be artificial graphite or natural graphite.
  • Artificial graphite is graphitized in a relatively high temperature range of 2200 ° C. to 3000 ° C. using coal coke, pitch, heavy oil and the like as main raw materials.
  • natural graphite uses natural minerals as the main raw material.
  • Artificial graphite is usually not coated on the surface, while natural graphite is usually coated on the surface with carbon. Since this carbon film has a high irreversible capacity and is easily damaged by the expansion and contraction of silicon oxide, it can cause deterioration.
  • the shape of the graphite particles is not particularly limited, and for example, spherical, lump, scale-like particles can be used.
  • the content of the graphite particles in the negative electrode active material layer is preferably 1% by weight or more, more preferably 5% by weight or more, and still more preferably 10% by weight or more. Content of the graphite particle in a negative electrode active material layer becomes like this. Preferably it is 40 weight% or less, More preferably, it is 25 weight% or less.
  • the average particle diameter of the graphite particles is preferably 5 ⁇ m or more, more preferably 8 ⁇ m or more as a lower limit.
  • the average particle diameter of the graphite particles is preferably 30 ⁇ m or less, more preferably 25 ⁇ m or less as the upper limit.
  • the specific surface area of the graphite particles is preferably 1 m 2 / g or more, more preferably 2 m 2 / g or more as a lower limit.
  • the specific surface area of the graphite particles is preferably 10 m 2 / g or less, more preferably 5 m 2 / g or less as the upper limit. Specific surface area can be measured using the BET method with nitrogen adsorption.
  • the binder of this embodiment includes polyacrylic acid.
  • Polyacrylic acid is a polymer containing monomer units derived from (meth) acrylic acid represented by the following formula (2) or a metal salt thereof.
  • the amount of the monomer unit represented by the formula (2) in the polyacrylic acid is not particularly limited, but is, for example, 50% by weight or more, 70% by weight or more, and may be 100% by weight.
  • (meth) acrylic acid means acrylic acid and methacrylic acid.
  • R 1 is a hydrogen atom or a methyl group.
  • the carboxylic acid in the monomer unit represented by the formula (2) may be a carboxylic acid metal salt.
  • the metal is preferably a monovalent metal.
  • the monovalent metal include alkali metals (for example, Na, Li, K, Rb, Cs, Fr, etc.) and noble metals (for example, Ag, Au, Cu, etc.).
  • alkali metals are preferable.
  • Na, Li, and K are preferable, and Na is most preferable.
  • the adhesion with the constituent material of the negative electrode active material layer may be further improved.
  • Polyacrylic acid may contain other monomer units.
  • the polyacrylic acid further includes a monomer unit other than (meth) acrylic acid, the peel strength between the negative electrode active material layer and the current collector may be improved.
  • monomer units include monocarboxylic acid compounds such as crotonic acid and pentenoic acid, dicarboxylic acid compounds such as itaconic acid and maleic acid, sulfonic acid compounds such as vinyl sulfonic acid, and phosphonic acids such as vinyl phosphonic acid.
  • Acids having an ethylenically unsaturated group such as compounds; aromatic olefins having acidic groups such as styrene sulfonic acid and styrene carboxylic acid; (meth) acrylic acid alkyl esters; acrylonitrile; aliphatic olefins such as ethylene, propylene and butadiene; Examples include monomer units derived from monomers such as aromatic olefins such as styrene.
  • the other monomer unit may be a monomer unit constituting a known polymer used as a binder for a secondary battery. In these monomer units, if present, the acid may be a salt.
  • At least one hydrogen atom in the main chain and the side chain may be substituted with halogen (fluorine, chlorine, boron, iodine, etc.) or the like.
  • the copolymer may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer. Any of a polymer etc. and these combinations may be sufficient.
  • the content of polyacrylic acid in the negative electrode active material layer is preferably 1% by weight or more, more preferably 2% by weight or more, and further preferably 3% by weight or more.
  • the content of polyacrylic acid in the negative electrode active material layer is preferably 8% by weight or less, more preferably 7% by weight or less.
  • the negative electrode active material layer includes a conductive material in order to suppress an increase in resistance due to polyacrylic acid.
  • the conductive material used in the present embodiment has a specific surface area of 40 to 800 m 2 / g.
  • the specific surface area of the conductive material is 50 to 600 m 2 / g. Specific surface area can be measured using the BET method with nitrogen adsorption.
  • a conductive material having such a specific surface area can be present on the surface of silicon oxide particles or graphite particles, which are active materials, by polyacrylic acid used as a binder, thereby forming many conductive paths between the active materials. it can. Therefore, battery resistance can be reduced.
  • the surface of the negative electrode active material particles can be confirmed by an electron microscope such as SEM (scanning electron microscope). Observe the particle surface with an electron microscope image, and consider the ratio (%) of the area where the conductive material is attached to the confirmed particle area as the coverage of the conductive material on the active material particle surface. Can do.
  • the coverage of the conductive material on the surface of the silicon oxide particles is preferably 30% or more, more preferably 50% or more, and may be 100% in terms of the number average of the particles. .
  • Examples of the conductive material having such a specific surface area include carbon materials such as carbon black, acetylene black, ketjen black, carbon nanotube, and carbon nanohorn.
  • Carbon black is carbon fine particles produced by thermal decomposition of hydrocarbons.
  • a plurality of primary particles form a structure.
  • the average primary particle diameter of carbon black is preferably 20 nm or more and 80 nm or less.
  • the specific surface area of carbon black is preferably 40 m 2 / g or more and 80 m 2 / g or less.
  • the amount of carbon black in the negative electrode active material layer is preferably 1% by weight or more and 10% by weight or less.
  • Acetylene black is a kind of carbon black and can be produced by pyrolyzing acetylene.
  • Ketjen black is a kind of carbon black and has high conductivity.
  • the carbon nanotube may be any carbon nanotube having a single-layer or coaxial multilayer structure in which a planar graphene sheet having a six-membered ring of carbon is formed in a cylindrical shape, but is preferably a multilayer. Further, both ends of the cylindrical carbon nanotube may be open, but are preferably closed with a hemispherical fullerene containing a carbon 5-membered ring or 7-membered ring.
  • the diameter of the outermost cylinder of the carbon nanotube is preferably 10 nm or more and 30 nm or less.
  • the specific surface area of the carbon nanotube is preferably 100 m 2 / g or more and 200 m 2 / g or less.
  • the amount of carbon nanotubes in the negative electrode active material layer is preferably 1% by weight or more and 6% by weight or less.
  • a single carbon nanohorn has a shape in which a single graphene sheet is rounded into a cylindrical shape, and the tip of the carbon nanohorn has a conical shape with a tip angle of about 20 °.
  • the carbon nanohorn preferably has a diameter of 80 nm to 160 nm. Further, it is preferable that the specific surface area of the carbon nanohorn or less 200 meters 2 / g or more 400m 2 / g.
  • the amount of carbon nanohorn in the negative electrode active material layer is preferably 1% by weight or more and 6% by weight or less.
  • FIG. 3 shows impedance characteristics of a battery using polyacrylic acid or SBR / CMC and various conductive materials in the negative electrode. It can be seen from FIG. 3 that a battery using no conductive material or a battery using plate-like graphite having a specific surface area of 20 m 2 / g as the negative electrode has a large electronic resistance (Rsol) and charge transfer resistance (Rct). A battery using carbon black, carbon nanotube, or carbon nanohorn having a specific surface area of 40 to 800 m 2 / g has a small Rsol and Rct. It is considered that appropriate conductive paths are formed between these active materials and between the active materials and the current collector foil.
  • Rsol electronic resistance
  • Rct charge transfer resistance
  • the content of the conductive material in the negative electrode active material layer is preferably 1% by weight or more, more preferably 3% by weight or more.
  • the content of the conductive material in the negative electrode active material layer is preferably 10% by weight or less, more preferably 6% by weight or less.
  • the total amount of polyacrylic acid and the conductive material is 13% by weight or less, preferably 10% by weight or less of the negative electrode active material layer. It is. In order to improve the cycle characteristics, the total amount of polyacrylic acid and the conductive material is 4% by weight or more, preferably 5% by weight or more of the negative electrode active material layer.
  • the weight ratio of the conductive material to the polyacrylic acid is preferably 0.12 or more and 2 or less, more preferably 0.3 or more and 1.8 or less, and further preferably 1 or more and 1.7. It is as follows. By controlling the weight ratio of the conductive material to the polyacrylic acid, the cycle characteristics can be further improved.
  • the negative electrode current collector aluminum, nickel, stainless steel, chromium, copper, silver, and alloys thereof can be used because of electrochemical stability.
  • Examples of the shape include foil, flat plate, and mesh.
  • the copper alloy preferably contains one or more elements selected from the group consisting of Zn, Sn, and In in an amount of 0.01 to 1.0% by weight.
  • the thickness of the current collector is not particularly limited, but is preferably 1 to 15 ⁇ m, more preferably 4 to 8 ⁇ m. In these ranges of thicknesses, the current collector can have adequate strength against silicon oxide expansion and contraction.
  • the electrode density is 1.35 g / cm 3 , for example, 10 ⁇ 5 ⁇ ⁇ cm 2 or more and 10 ⁇ 2 ⁇ ⁇ cm 2 or less, or 10 ⁇ 4 ⁇ ⁇ cm 2.
  • the electrode resistance (also referred to as interface resistance) at the negative electrode / electrolyte interface can be reduced within the range of 10 ⁇ 3 ⁇ ⁇ cm 2 or less.
  • this electrode resistance value is particularly small, it is effective to use a positive electrode, electrolyte, separator, etc. to produce a cell and measure the negative electrode itself instead of measuring the AC impedance. The inventor found out.
  • the effect of the conductive material and polyacrylic acid can also be confirmed when measured by the AC impedance method as a cell, but in order to show that the effect of the present invention is remarkable, the influence of the positive electrode, the electrolyte, and the separator Therefore, the value calculated from the electrode resistance measuring instrument was used as the interface resistance value of the negative electrode of the present invention.
  • an electrode resistance measuring device capable of measuring a low resistance value.
  • Step 1 Consider the electrode sheet as a three-layer resistor and assume a three-dimensional resistance matrix model.
  • Step 2 A constant current is passed through the electrode surface, and 100 potentials generated on the surface are measured.
  • Step 3 Current is passed through the three-dimensional resistance matrix model assumed in Step 1 to calculate the potential.
  • Step 4 The measured potential is compared with the computer-simulated potential, and if it matches, the process ends.
  • the value of the three-dimensional resistance matrix model is updated in a timely manner and the recalculation is repeated. That is, while updating the resistance of the electrode layer and the interface resistance in a timely manner, the interface resistance can be obtained by calculating until the measured potential and the potential simulated by the computer match.
  • the negative electrode according to the present embodiment can be produced by preparing a slurry containing a negative electrode active material, a conductive material, polyacrylic acid and a solvent, and applying this to a negative electrode current collector to form a negative electrode active material layer.
  • the negative electrode can be prepared as follows. First, a negative electrode active material such as silicon oxide particles and graphite particles, polyacrylic acid, and a conductive material are dispersed and kneaded in a solvent in a predetermined blending amount to prepare a negative electrode slurry.
  • the solvent is preferably water.
  • the negative electrode can be produced by coating this negative electrode slurry on a negative electrode current collector and drying it.
  • the obtained negative electrode can adjust an electrode density by compressing a negative electrode active material layer by methods, such as a roll press.
  • the electrode density is preferably in the range of 1.0 g / cm 3 or more and 2.0 g / cm 3 or less.
  • the electrode density is 1.0 g / cm 3 or more, the charge / discharge capacity tends to be good.
  • the electrode density is 2.0 g / cm 3 or less, it is easy to impregnate the electrolytic solution, and the charge / discharge capacity tends to be good.
  • polyacrylic acid may be attached to the conductive material in advance, and then the negative electrode active material and the conductive material may be bound.
  • the negative electrode can be prepared as follows. First, polyacrylic acid and a conductive material are mixed in a solvent to attach polyacrylic acid to the conductive material.
  • the solvent is preferably water.
  • negative electrode active materials such as silicon oxide particles and graphite particles are further added to the mixture to prepare a negative electrode slurry.
  • the negative electrode can be produced by coating this negative electrode slurry on a negative electrode current collector and drying it.
  • the conductive material can be bound to the surface of the negative electrode active material particles such as silicon oxide particles with a higher coverage such as 70% or more or 80% or more.
  • the electrolytic solution includes a nonaqueous solvent and a supporting salt.
  • a nonaqueous solvent For example, Cyclic carbonates, such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC); Dimethyl carbonate (DMC), Diethyl carbonate (DEC) ), Chain carbonates such as ethyl methyl carbonate (MEC), dipropyl carbonate (DPC); aliphatic carboxylic acid esters such as propylene carbonate derivatives, methyl formate, methyl acetate, ethyl propionate; diethyl ether, ethyl propyl ether Aprotic organic solvents such as ethers such as trimethyl phosphate, triethyl phosphate, tripropyl phosphate, trioctyl phosphate, and triphenyl phosphate, and the number of hydrogen atoms in these compounds
  • Some fluorinated aprotic organic solvent such as propylene carbonate (PC),
  • cyclic such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (MEC), dipropyl carbonate (DPC), etc.
  • chain carbonates are included.
  • Non-aqueous solvents can be used alone or in combination of two or more.
  • the supporting salt is not particularly limited except that it contains Li.
  • the supporting salt include LiPF 6 , LiAsF 6 , LiAlCl 4 , LiClO 4 , LiBF 4 , LiSbF 6 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiC (CF 3 SO 2 ) 3 , LiN (FSO 2). ) 2 , LiN (CF 3 SO 2 ) 2 , LiN (C 2 F 5 SO 2 ) 2 , LiB 10 Cl 10 and the like.
  • Other examples of the supporting salt include lower aliphatic lithium carboxylate, lithium chloroborane, lithium tetraphenylborate, LiBr, LiI, LiSCN, LiCl, and the like.
  • a support salt can be used individually by 1 type or in combination of 2 or more types.
  • the concentration of the supporting salt in the electrolytic solution is preferably 0.5 to 1.5 mol / L. By setting the concentration of the supporting salt within this range, it becomes easy to adjust the density, viscosity, electrical conductivity, and the like to an appropriate range.
  • the electrolytic solution can further contain an additive.
  • an additive A halogenated cyclic carbonate, an unsaturated cyclic carbonate, cyclic
  • Any separator may be used as long as it suppresses the conduction between the positive electrode and the negative electrode without impeding the permeation of the charged body and has durability against the electrolytic solution.
  • Specific materials include polyolefins such as polypropylene and polyethylene, polyesters such as cellulose, polyethylene terephthalate and polybutylene terephthalate, polyimide, polyvinylidene fluoride, polymetaphenylene isophthalamide, polyparaphenylene terephthalamide and copolyparaphenylene-3, Aromatic polyamide (aramid) such as 4′-oxydiphenylene terephthalamide can be used. These can be used as porous films, woven fabrics, non-woven fabrics and the like.
  • An insulating layer may be formed on at least one surface of the positive electrode, the negative electrode, and the separator.
  • Examples of the method for forming the insulating layer include a doctor blade method, a dip coating method, a die coater method, a CVD method, and a sputtering method.
  • An insulating layer can be formed simultaneously with the formation of the positive electrode, the negative electrode, and the separator.
  • Examples of the material constituting the insulating layer include a mixture of an insulating filler such as aluminum oxide or barium titanate and a binder such as SBR or PVDF.
  • the lithium ion secondary battery of this embodiment has a structure as shown in FIGS. 1 and 2, for example.
  • This lithium ion secondary battery includes a battery element 20, a film outer package 10 that accommodates the battery element 20 together with an electrolyte, and a positive electrode tab 51 and a negative electrode tab 52 (hereinafter also referred to simply as “electrode tabs”). ing.
  • the battery element 20 is formed by alternately stacking a plurality of positive electrodes 30 and a plurality of negative electrodes 40 with a separator 25 interposed therebetween.
  • the electrode material 32 is applied to both surfaces of the metal foil 31.
  • the electrode material 42 is applied to both surfaces of the metal foil 41. Note that the present embodiment is not necessarily limited to a stacked battery, and can also be applied to a wound battery.
  • the lithium ion secondary battery may have a configuration in which the electrode tab is drawn out on one side of the outer package as shown in FIGS. 1 and 2, but the lithium ion secondary battery has the electrode tab pulled out on both sides of the outer package. It can be a thing. Although detailed illustration is omitted, each of the positive and negative metal foils has an extension on a part of the outer periphery. The extensions of the negative electrode metal foil are collected together and connected to the negative electrode tab 52, and the extensions of the positive electrode metal foil are collected together and connected to the positive electrode tab 51 (see FIG. 2). The portions gathered together in the stacking direction between the extension portions in this way are also called “current collecting portions”.
  • the film outer package 10 is composed of two films 10-1 and 10-2 in this example.
  • the films 10-1 and 10-2 are heat sealed to each other at the periphery of the battery element 20 and sealed.
  • the positive electrode tab 51 and the negative electrode tab 52 are drawn in the same direction from one short side of the film outer package 10 sealed in this way.
  • FIGS. 1 and 2 show examples in which the cup portion is formed on one film 10-1 and the cup portion is not formed on the other film 10-2.
  • a configuration in which a cup portion is formed on both films (not shown) or a configuration in which neither cup portion is formed (not shown) may be employed.
  • the lithium ion secondary battery of this embodiment has a high energy density.
  • the lithium ion secondary battery of the present embodiment can have a high volume energy density such as 540 Wh / L or more and 660 Wh / L or less, 600 Wh / or more and 660 Wh / L or less.
  • the lithium ion secondary battery according to the present embodiment can be produced according to a normal method. Taking a laminated laminate type lithium ion secondary battery as an example, an example of a method for producing a lithium ion secondary battery will be described. First, in a dry air or an inert atmosphere, an electrode element is formed by arranging a positive electrode and a negative electrode to face each other with a separator interposed therebetween. Next, this electrode element is accommodated in an exterior body (container), and an electrolytic solution is injected to impregnate the electrode with the electrolytic solution. Then, the opening part of an exterior body is sealed and a lithium ion secondary battery is completed.
  • a plurality of lithium ion secondary batteries according to this embodiment can be combined to form an assembled battery.
  • the assembled battery may have a configuration in which two or more lithium ion secondary batteries according to the present embodiment are used and connected in series, in parallel, or both. Capacitance and voltage can be freely adjusted by connecting in series and / or in parallel. About the number of the lithium ion secondary batteries with which an assembled battery is provided, it can set suitably according to battery capacity or an output.
  • the lithium ion secondary battery or its assembled battery according to this embodiment can be used in a vehicle.
  • Vehicles according to this embodiment include hybrid vehicles, fuel cell vehicles, and electric vehicles (all include four-wheel vehicles (passenger cars, trucks, buses and other commercial vehicles, light vehicles, etc.), motorcycles (motorcycles), and tricycles. ).
  • vehicle according to the present embodiment is not limited to an automobile, and may be used as various power sources for other vehicles, for example, moving bodies such as trains.
  • ⁇ Negative electrode conductive material carbon black (specific surface area: 45 m 2 / g)> [Example 1] (Production of battery) LiNi 0.8 Co 0.15 Al 0.05 O 2 (94 wt%) as the positive electrode active material, polyvinylidene fluoride (3 wt%) as the binder, and carbon black (3 wt%) as the conductive material Were mixed to obtain a positive electrode mixture.
  • a positive electrode slurry was prepared by dispersing the positive electrode mixture in N-methyl-2-pyrrolidone. This positive electrode slurry was uniformly applied to one side of a 12 ⁇ m thick aluminum current collector foil. After drying, a positive electrode was produced by compression molding with a roll press.
  • Carbon-coated SiO particles having a BET specific surface area of 4.6 m 2 / g and an average particle diameter of 5.0 ⁇ m as the negative electrode active material, and artificial graphite particles having a BET specific surface area of 2.8 m 2 / g and an average particle diameter of 12 ⁇ m was used.
  • Carbon coated SiO particles, artificial graphite particles, carbon black having a BET specific surface area of 45 m 2 / g and an average particle size (primary particles) of 0.045 ⁇ m are dispersed in a mixed solution of polyacrylic acid and water as a binder.
  • the weight ratio of each negative electrode material in the negative electrode slurry was as shown in Table 1.
  • the weight ratio of the carbon-coated SiO particles, which are the negative electrode active material, and the graphite particles is 80:20.
  • This negative electrode slurry was uniformly applied onto a high strength Cu alloy current collector foil having a thickness of 8 ⁇ m. After drying, the electrode was pressed to make the negative electrode density 1.35 g / cm 3 .
  • the resistance measuring device used was a model XF-057 probe unit manufactured by Hioki Electric. With respect to each negative electrode, the thickness of the active material layer and the thickness of the current collector foil were input, and the probe of the resistance measuring device was pressed to obtain the interface resistance value of each negative electrode.
  • the positive electrode and the negative electrode cut out to 3 cm ⁇ 3 cm were arranged so as to face each other with a separator interposed therebetween.
  • a PET nonwoven fabric with a thickness of 15 ⁇ m was used as the separator.
  • the electrolytic solution was prepared by mixing a solvent and a supporting salt.
  • a solvent ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) were used at a volume ratio of 30/60/10, and the supporting salt was LiPF having a supporting salt concentration of 0.9 mol / L. 6 was used.
  • the above positive electrode, negative electrode, separator, and electrolytic solution were placed in a laminate outer package, the laminate was sealed, and a lithium ion secondary battery was produced.
  • the positive electrode and the negative electrode were connected to a tab and electrically connected from the outside of the laminate.
  • the battery volume (L) was calculated from the basis weight and density of the electrode, the thickness of the current collector, and the thickness of the separator. Energy from specific capacity (mAh / g) of each cell, actual value (%) of aging efficiency when each cell is aged at 45 ° C. for 20 days, and actual value (V) of average operating voltage after aging of each cell The capacity (Wh) was calculated. The value obtained by dividing the energy capacity by the battery volume was defined as the volume energy density (Wh / L). As the aging efficiency, the value of the recovery capacity (mAh) after 45 days at 45 ° C. with respect to the initial charge capacity (mAh) was used.
  • ⁇ Negative electrode conductive material carbon black (specific surface area: 65 m 2 / g)> [Example 9] LiNi 0.8 Co 0.15 Al 0.05 O 2 (94 wt%) as the positive electrode active material, polyvinylidene fluoride (3 wt%) as the binder, and carbon black (3 wt%) as the conductive material Were mixed to obtain a positive electrode mixture.
  • a positive electrode slurry was prepared by dispersing the positive electrode mixture in N-methyl-2-pyrrolidone. This positive electrode slurry was uniformly applied to one side of a 12 ⁇ m thick aluminum current collector foil. After drying, a positive electrode was produced by compression molding with a roll press.
  • Carbon-coated SiO particles having a BET specific surface area of 4.6 m 2 / g and an average particle diameter of 5.0 ⁇ m as the negative electrode active material, and artificial graphite particles having a BET specific surface area of 2.8 m 2 / g and an average particle diameter of 12 ⁇ m was used.
  • Carbon coated SiO particles, artificial graphite particles, carbon black having a BET specific surface area of 65 m 2 / g and an average particle size (primary particles) of 0.065 ⁇ m are dispersed in a mixed solution of polyacrylic acid and water as a binder.
  • the weight ratio of each negative electrode material in the negative electrode slurry was as shown in Table 2.
  • the weight ratio of the carbon-coated SiO particles, which are the negative electrode active material, and the graphite particles is 80:20.
  • This negative electrode slurry was uniformly applied onto a high strength Cu alloy current collector foil having a thickness of 8 ⁇ m. After drying, the electrode was pressed to make the negative electrode density 1.35 g / cm 3 .
  • the interface resistance was evaluated in the same manner as in Example 1.
  • the positive electrode and the negative electrode cut out to 3 cm ⁇ 3 cm were arranged so as to face each other with a separator interposed therebetween.
  • a PET nonwoven fabric with a thickness of 15 ⁇ m was used as the separator.
  • the electrolytic solution was prepared by mixing a solvent and a supporting salt.
  • a solvent ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) were used at a volume ratio of 30/60/10, and the supporting salt was LiPF having a supporting salt concentration of 0.9 mol / L. 6 was used.
  • the above positive electrode, negative electrode, separator, and electrolytic solution were placed in a laminate outer package, the laminate was sealed, and a lithium ion secondary battery was produced.
  • the positive electrode and the negative electrode were connected to a tab and electrically connected from the outside of the laminate.
  • ⁇ Negative electrode conductive material carbon nanotube (specific surface area: 150 m 2 / g)> [Example 15] LiNi 0.8 Co 0.15 Al 0.05 O 2 (94 wt%) as the positive electrode active material, polyvinylidene fluoride (3 wt%) as the binder, and carbon black (3 wt%) as the conductive material Were mixed to obtain a positive electrode mixture.
  • a positive electrode slurry was prepared by dispersing the positive electrode mixture in N-methyl-2-pyrrolidone. This positive electrode slurry was uniformly applied to one side of a 12 ⁇ m thick aluminum current collector foil. After drying, a positive electrode was produced by compression molding with a roll press.
  • Carbon-coated SiO particles having a BET specific surface area of 4.6 m 2 / g and an average particle diameter of 5.0 ⁇ m as the negative electrode active material, and artificial graphite particles having a BET specific surface area of 2.8 m 2 / g and an average particle diameter of 12 ⁇ m was used.
  • Carbon-coated SiO particles, artificial graphite particles, carbon nanotubes having a specific surface area of 150 m 2 / g and an average particle diameter of 0.02 ⁇ m are dispersed in a mixed solution of polyacrylic acid and water as a binder, and a negative electrode slurry is prepared.
  • the weight ratio of each negative electrode material in the negative electrode slurry was as shown in Table 3.
  • the weight ratio of the carbon-coated SiO particles, which are the negative electrode active material, and the graphite particles is 80:20.
  • This negative electrode slurry was uniformly applied onto a current collector made of high strength Cu alloy foil having a thickness of 8 ⁇ m. After drying, the electrode was pressed to make the negative electrode density 1.35 g / cm 3 .
  • the interface resistance was evaluated in the same manner as in Example 1.
  • the positive electrode and the negative electrode cut out to 3 cm ⁇ 3 cm were arranged so as to face each other with a separator interposed therebetween.
  • a PET nonwoven fabric with a thickness of 15 ⁇ m was used as the separator.
  • the electrolytic solution was prepared by mixing a solvent and a supporting salt.
  • a solvent ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) were used at a volume ratio of 30/60/10, and the supporting salt was LiPF having a supporting salt concentration of 0.9 mol / L. 6 was used.
  • the above positive electrode, negative electrode, separator, and electrolytic solution were placed in a laminate outer package, the laminate was sealed, and a lithium ion secondary battery was produced.
  • the positive electrode and the negative electrode were connected to a tab and electrically connected from the outside of the laminate.
  • Example 19 The negative electrode produced in Example 19 was observed by SEM before charge / discharge.
  • the SEM image is shown in FIG. From the SEM image, it can be seen that the surface of silicon oxide particles of about 60 to 70% is covered with carbon nanotubes.
  • ⁇ Negative electrode conductive material carbon nanohorn (specific surface area: 300 m 2 / g)>
  • LiNi 0.8 Co 0.15 Al 0.05 O 2 (94 wt%) as the positive electrode active material, polyvinylidene fluoride (3 wt%) as the binder, and carbon black (3 wt%) as the conductive material Were mixed to obtain a positive electrode mixture.
  • a positive electrode slurry was prepared by dispersing the positive electrode mixture in N-methyl-2-pyrrolidone. This positive electrode slurry was uniformly applied to one side of a 12 ⁇ m thick aluminum current collector foil. After drying, a positive electrode was produced by compression molding with a roll press.
  • Carbon-coated SiO particles having a BET specific surface area of 4.6 m 2 / g and an average particle diameter of 5.0 ⁇ m as the negative electrode active material, and artificial graphite particles having a BET specific surface area of 2.8 m 2 / g and an average particle diameter of 12 ⁇ m was used.
  • Carbon-coated SiO particles, artificial graphite particles, carbon nanohorns having a specific surface area of 300 m 2 / g and an average particle size of 0.15 ⁇ m are dispersed in a mixed solution of polyacrylic acid and water as a binder, and a negative electrode slurry is prepared.
  • the weight ratio of each negative electrode material in the negative electrode slurry was as shown in Table 4.
  • the weight ratio of the carbon-coated SiO particles, which are the negative electrode active material, and the graphite particles is 80:20.
  • This negative electrode slurry was uniformly applied onto a high strength Cu alloy current collector foil having a thickness of 8 ⁇ m. After drying, the electrode was pressed to make the negative electrode density 1.35 g / cm 3 .
  • the interface resistance was evaluated in the same manner as in Example 1.
  • the positive electrode and the negative electrode cut out to 3 cm ⁇ 3 cm were arranged so as to face each other with a separator interposed therebetween.
  • a PET nonwoven fabric with a thickness of 15 ⁇ m was used as the separator.
  • the electrolytic solution was prepared by mixing a solvent and a supporting salt.
  • a solvent ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) were used at a volume ratio of 30/60/10, and the supporting salt was LiPF having a supporting salt concentration of 0.9 mol / L. 6 was used.
  • the above positive electrode, negative electrode, separator, and electrolytic solution were placed in a laminate outer package, the laminate was sealed, and a lithium ion secondary battery was produced.
  • the positive electrode and the negative electrode were connected to a tab and electrically connected from the outside of the laminate.
  • Example 26 The negative electrode produced in Example 26 was observed by SEM before charge / discharge.
  • the SEM image is shown in FIG. From the SEM image, it can be seen that the surface of silicon oxide particles of about 50 to 60% is covered with carbon nanohorns.
  • ⁇ Negative electrode conductive material Ketjen black (specific surface area: 800 m 2 / g)> [Example 29] LiNi 0.8 Co 0.15 Al 0.05 O 2 (94 wt%) as the positive electrode active material, polyvinylidene fluoride (3 wt%) as the binder, and carbon black (3 wt%) as the conductive material Were mixed to obtain a positive electrode mixture.
  • a positive electrode slurry was prepared by dispersing the positive electrode mixture in N-methyl-2-pyrrolidone. This positive electrode slurry was uniformly applied to one side of a 12 ⁇ m thick aluminum current collector foil. After drying, a positive electrode was produced by compression molding with a roll press.
  • Carbon-coated SiO particles having a BET specific surface area of 4.6 m 2 / g and an average particle diameter of 5.0 ⁇ m as the negative electrode active material, and artificial graphite particles having a BET specific surface area of 2.8 m 2 / g and an average particle diameter of 12 ⁇ m was used.
  • Disperse Ketjen Black having carbon-coated SiO particles, artificial graphite particles, a specific surface area of 800 m 2 / g and an average particle size (primary particles) of 0.04 ⁇ m in a mixed solution of polyacrylic acid and water as a binder.
  • the weight ratio of each negative electrode material in the negative electrode slurry was as shown in Table 5.
  • the weight ratio of the carbon-coated SiO particles, which are the negative electrode active material, and the graphite particles is 80:20.
  • This negative electrode slurry was uniformly applied onto a high strength Cu alloy current collector foil having a thickness of 8 ⁇ m. After drying, the electrode was pressed to make the negative electrode density 1.35 g / cm 3 .
  • the interface resistance was evaluated in the same manner as in Example 1.
  • the positive electrode and the negative electrode cut out to 3 cm ⁇ 3 cm were arranged so as to face each other with a separator interposed therebetween.
  • a PET nonwoven fabric with a thickness of 15 ⁇ m was used as the separator.
  • the electrolytic solution was prepared by mixing a solvent and a supporting salt.
  • a solvent ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) were used at a volume ratio of 30/60/10, and the supporting salt was LiPF having a supporting salt concentration of 0.9 mol / L. 6 was used.
  • the above positive electrode, negative electrode, separator, and electrolytic solution were placed in a laminate outer package, the laminate was sealed, and a lithium ion secondary battery was produced.
  • the positive electrode and the negative electrode were connected to a tab and electrically connected from the outside of the laminate.
  • ⁇ Negative electrode conductive material plate-like graphite (specific surface area 17 m 2 / g)>
  • LiNi 0.8 Co 0.15 Al 0.05 O 2 (94 wt%) as the positive electrode active material, polyvinylidene fluoride (3 wt%) as the binder, and carbon black (3 wt%) as the conductive material Were mixed to obtain a positive electrode mixture.
  • a positive electrode slurry was prepared by dispersing the positive electrode mixture in N-methyl-2-pyrrolidone. This positive electrode slurry was uniformly applied to one side of a 12 ⁇ m thick aluminum current collector foil. After drying, a positive electrode was produced by compression molding with a roll press.
  • Carbon-coated SiO particles having a BET specific surface area of 4.6 m 2 / g and an average particle diameter of 5.0 ⁇ m as the negative electrode active material, and artificial graphite particles having a BET specific surface area of 2.8 m 2 / g and an average particle diameter of 12 ⁇ m was used.
  • Carbon-coated SiO particles, artificial graphite particles, plate graphite having a specific surface area of 17 m 2 / g and an average particle diameter of 10 ⁇ m are dispersed in a mixed solution of polyacrylic acid and water as a binder to produce a negative electrode slurry.
  • the weight ratio of each negative electrode material in the negative electrode slurry was as shown in Table 6.
  • the weight ratio of the carbon-coated SiO particles that are the negative electrode active material and the graphite particles is 80:20.
  • This negative electrode slurry was uniformly applied onto a high strength Cu alloy current collector foil having a thickness of 8 ⁇ m. After drying, the electrode was pressed to make the negative electrode density 1.35 g / cm 3 .
  • the interface resistance was evaluated in the same manner as in Example 1.
  • the positive electrode and the negative electrode cut out to 3 cm ⁇ 3 cm were arranged so as to face each other with a separator interposed therebetween.
  • a PET nonwoven fabric with a thickness of 15 ⁇ m was used as the separator.
  • the electrolytic solution was prepared by mixing a solvent and a supporting salt.
  • a solvent ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) were used at a volume ratio of 30/60/10, and the supporting salt was LiPF having a supporting salt concentration of 0.9 mol / L. 6 was used.
  • the above positive electrode, negative electrode, separator, and electrolytic solution were placed in a laminate outer package, the laminate was sealed, and a lithium ion secondary battery was produced.
  • the positive electrode and the negative electrode were connected to a tab and electrically connected from the outside of the laminate.
  • ⁇ Negative electrode conductive material Ketjen black (specific surface area: 1270 m 2 / g)>
  • LiNi 0.8 Co 0.15 Al 0.05 O 2 (94 wt%) as the positive electrode active material, polyvinylidene fluoride (3 wt%) as the binder, and carbon black (3 wt%) as the conductive material Were mixed to obtain a positive electrode mixture.
  • a positive electrode slurry was prepared by dispersing the positive electrode mixture in N-methyl-2-pyrrolidone. This positive electrode slurry was uniformly applied to one side of a 12 ⁇ m thick aluminum current collector foil. After drying, a positive electrode was produced by compression molding with a roll press.
  • Carbon-coated SiO particles having a BET specific surface area of 4.6 m 2 / g and an average particle diameter of 5.0 ⁇ m as the negative electrode active material, and artificial graphite particles having a BET specific surface area of 2.8 m 2 / g and an average particle diameter of 12 ⁇ m was used.
  • Disperse Ketjen Black having carbon-coated SiO particles, artificial graphite particles, a specific surface area of 1270 m 2 / g and an average particle size (primary particles) of 0.035 ⁇ m in a mixed solution of polyacrylic acid and water as a binder.
  • the weight ratio of each negative electrode material in the negative electrode slurry was as shown in Table 7.
  • the weight ratio of the carbon-coated SiO particles that are the negative electrode active material and the graphite particles is 80:20.
  • This negative electrode slurry was uniformly applied onto a high strength Cu alloy current collector foil having a thickness of 8 ⁇ m. After drying, the electrode was pressed to make the negative electrode density 1.35 g / cm 3 .
  • the interface resistance was evaluated in the same manner as in Example 1.
  • the positive electrode and the negative electrode cut out to 3 cm ⁇ 3 cm were arranged so as to face each other with a separator interposed therebetween.
  • a PET nonwoven fabric with a thickness of 15 ⁇ m was used as the separator.
  • the electrolytic solution was prepared by mixing a solvent and a supporting salt.
  • a solvent ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) were used at a volume ratio of 30/60/10, and the supporting salt was LiPF having a supporting salt concentration of 0.9 mol / L. 6 was used.
  • the above positive electrode, negative electrode, separator, and electrolytic solution were placed in a laminate outer package, the laminate was sealed, and a lithium ion secondary battery was produced.
  • the positive electrode and the negative electrode were connected to a tab and electrically connected from the outside of the laminate.
  • Example 24 in which the above-described carbon nanohorn was used as the conductive material, a current collector foil made of high strength Cu alloy having a thickness of 8 ⁇ m was used for the negative electrode current collector, but as described in Table 8 below, the stainless steel foil was used. Or changed to electrolytic copper foil. Otherwise, a battery was fabricated in the same manner as in Example 24. Table 8 shows the evaluation results of the fabricated batteries.
  • the capacity deterioration was so large that the capacity retention rate could not be maintained up to 300 cycles.
  • the strength of the electrolytic copper foil is low, and it was suggested that the copper foil cannot withstand the expansion and contraction of SiO present at a high content.
  • the interfacial resistance was higher than that of the high-strength Cu alloy foil, but the capacity retention rate was the same as that of the high-strength Cu alloy foil.
  • the negative electrode produced in Examples 37 and 38 was observed by SEM before charge and discharge. From the SEM image, it was found that about 80% of the silicon oxide particles were coated with carbon nanohorns. It is thought that the coverage of the conductive material on the silicon oxide particles was increased by attaching polyacrylic acid to the carbon nanohorn in advance. As a result, compared with Examples 24 and 26 having the same design specifications, the interface resistance was lowered, the cycle characteristics were increased, and the volume energy density was also high.
  • the conductive material has a specific surface area of 40 to 800 m 2 / g, and in the negative electrode active material layer, the amount of the composite particles is 50% by weight or more, and the polyacrylic acid
  • the amount of the conductive material is 1% by weight or more, the total amount of the conductive material and the polyacrylic acid is 13% by weight or less, and in the composite particle,
  • (Appendix 2) The lithium ion secondary battery according to appendix 1, wherein a weight ratio of the conductive material to the polyacrylic acid is 0.12 or more and 2 or less.
  • (Appendix 3) The lithium ion secondary battery according to appendix 1 or 2, wherein the graphite particles are artificial graphite.
  • (Appendix 4) The graphite particles, the lithium ion secondary battery according to any one of appendices 1 to 3 having the following specific surface area average particle diameter and 2m 2 / g or more 8 ⁇ m above 25 ⁇ m or less 5 m 2 / g.
  • (Appendix 5) The lithium ion secondary battery according to any one of supplementary notes 1 to 4, wherein the composite particles have an average particle diameter of 3 ⁇ m to 7 ⁇ m and a specific surface area of 3 m 2 / g to 12 m 2 / g.
  • (Appendix 6) The lithium ion secondary battery according to any one of appendices 1 to 5, wherein the amount of the silicon oxide in the composite particles is 70% by weight or more.
  • (Appendix 7) The lithium ion secondary battery according to any one of appendices 1 to 6, wherein the conductive material covers 70% or more of the surface of the composite particle.
  • (Appendix 10) The lithium ion secondary battery according to any one of supplementary notes 1 to 9, wherein the negative electrode has an interface resistance of 10 ⁇ 5 ⁇ ⁇ cm 2 or more and 10 ⁇ 2 ⁇ ⁇ cm 2 or less.
  • (Appendix 11) The lithium ion secondary battery according to any one of supplementary notes 1 to 10, wherein the volume energy density is 540 Wh / L or more and 660 Wh / L or less.
  • (Appendix 12) A vehicle equipped with the lithium ion secondary battery according to any one of appendices 1 to 11.
  • a negative electrode slurry prepared by mixing a conductive material having a specific surface area of 40 to 800 m 2 / g, silicon oxide and carbon, and composite particles and graphite particles containing 2% by weight or more of carbon, and polyacrylic acid in a solvent.
  • the negative electrode slurry is applied to a current collector, the amount of the composite particles is 50% by weight or more, the amount of the polyacrylic acid is 3% by weight or more and 8% by weight or less, and the conductive And a step of forming a negative electrode active material layer in which the total amount of the material and the polyacrylic acid is 4% by weight or more and 13% by weight or less.
  • the lithium ion secondary battery according to the present invention can be used in, for example, all industrial fields that require a power source and industrial fields related to transport, storage, and supply of electrical energy.
  • power sources for mobile devices such as mobile phones and laptop computers
  • power sources for mobile vehicles such as electric vehicles, hybrid cars, electric motorcycles, electric assist bicycles, electric vehicles, trains, satellites, submarines, etc .
  • It can be used for backup power sources such as UPS; power storage facilities for storing power generated by solar power generation, wind power generation, etc.

Abstract

L'invention concerne un accumulateur au lithium-ion comprenant une électrode positive comportant : une couche de matériau actif d'électrode positive contenant un oxyde composite de nickel stratifié contenant du lithium; et une électrode négative comportant une couche de matériau actif d'électrode négative contenant de l'acide polyacrylique, un élément électroconducteur, des particules de graphite et des particules composites contenant du carbone et un oxyde de silicium, l'accumulateur au lithium-ion étant caractérisée en ce que : l'élément électroconducteur a une surface spécifique de 40 à 800 m2/g; la couche de matériau actif d'électrode négative a une teneur en particules composites d'au moins 50 % en poids, une teneur en acide polyacrylique de 3 à 8 % en poids, et une teneur totale en élément électroconducteur/acide polyacrylique de 4 à 13 % en poids; et les particules composites ont une teneur en carbone d'au moins 2 % en poids.
PCT/JP2018/006621 2017-02-23 2018-02-23 Accumulateur au lithium-ion comprenant une électrode négative pour batterie à haute densité d'énergie WO2018155609A1 (fr)

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JP2023512360A (ja) * 2020-12-28 2023-03-27 寧徳新能源科技有限公司 負極材料、電気化学装置及び電子装置
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CN112886050A (zh) * 2019-11-29 2021-06-01 宁德时代新能源科技股份有限公司 二次电池及含有该二次电池的装置
JP7466981B2 (ja) 2020-06-11 2024-04-15 エルジー エナジー ソリューション リミテッド 負極及びこれを含む二次電池
JP2023512360A (ja) * 2020-12-28 2023-03-27 寧徳新能源科技有限公司 負極材料、電気化学装置及び電子装置
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