Classifications

• • 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
  • 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
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0562—Solid materials
• • 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
  • H01M10/058—Construction or 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
  • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
• • 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
  • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
  • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• • 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
  • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
  • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• • 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 rechargeable all-solid-state battery that is used as a power source for portable electronic devices, in-vehicle batteries, and for power storage, etc.
• This application claims priority based on Japanese Patent Application No. 2023-126539, filed on August 2, 2023, the contents of which are incorporated herein by reference.
• lithium secondary batteries have been widely used in electronic devices such as mobile phones and laptop computers, as well as power sources for electric vehicles and power storage.
• electronic devices such as mobile phones and laptop computers
• power sources for electric vehicles and power storage In particular, there has been a rapid increase in demand for high-capacity, high-output, and high-energy-density batteries that can be installed in hybrid and electric vehicles.
• Lithium secondary batteries are primarily composed of a positive electrode and a negative electrode that contain a material capable of absorbing and releasing lithium, and an electrolyte.
• the electrolyte used may be a non-aqueous electrolyte solution for batteries that contains a lithium salt and a non-aqueous solvent, or a solid electrolyte such as a sulfide-based solid electrolyte.
• a lithium secondary battery that uses a solid electrolyte as the electrolyte is called an all-solid-state battery.
• JP 2004-185931 A JP 2001-243982 A JP 2003-086249 A JP 2022-076417 A
• a problem with lithium secondary batteries is degradation caused by an increase in battery resistance over time. Therefore, there is a demand for reducing the increase in battery resistance after long-term storage so that lithium secondary batteries can be used stably for longer periods.
• the present invention aims to provide an all-solid-state battery in which the increase in battery resistance after long-term storage is suppressed, a method for producing the same, and a positive electrode active material or positive electrode used in the all-solid-state battery.
• a lithium-containing composite oxide, Additive A is a compound having a sulfur-oxygen bond;
• a positive electrode active material for a solid-state battery comprising: [2] The positive electrode active material according to [1], wherein the additive A is one or more compounds selected from the group consisting of cyclic sulfates, chain sulfates, cyclic sulfonates, and chain sulfonates. [3]
• the additive A is represented by the following general formulas (A1) to (A4):
• R 11 and R 12 each independently represent a hydrocarbon group having 1 to 6 carbon atoms]
• R 21 represents an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by general formula (A2-1), or a group represented by general formula (A2-2); in formula (A2-1), R 22 represents an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group; in formula (A2-2), R 23 represents an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms; and in formulas (A2-1) and (A2-2), * represents a bonding position] [In formula (A3), R 31 to R 34 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group
• A is an element other than Li, Ni, Mn, and Co; and a to f are real numbers satisfying 0.8 ⁇ a ⁇ 1.2, 0 ⁇ b ⁇ 0.95, 0 ⁇ c ⁇ 0.5, 0 ⁇ d ⁇ 1.0, 0.7 ⁇ b+c+d ⁇ 1.1, 0 ⁇ e ⁇ 0.1, and 1.8 ⁇ f ⁇ 2.2.
• a positive electrode for a solid-state battery comprising the positive electrode active material according to any one of [1] to [6].
• a lithium-containing composite oxide, Additive A is a compound having a sulfur-oxygen bond;
• a positive electrode for a solid-state battery comprising: [9] The positive electrode according to [8], wherein the additive A is one or more compounds selected from the group consisting of cyclic sulfates, chain sulfates, cyclic sulfonates, and chain sulfonates.
• the additive A is represented by the following general formulas (A1) to (A4):
• R 11 and R 12 each independently represent a hydrocarbon group having 1 to 6 carbon atoms]
• R 21 represents an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, a group represented by general formula (A2-1), or a group represented by general formula (A2-2); in formula (A2-1), R 22 represents an oxygen atom, an alkylene group having 1 to 6 carbon atoms, an alkenylene group having 2 to 6 carbon atoms, or an oxymethylene group; in formula (A2-2), R 23 represents an alkyl group having 1 to 6 carbon atoms, or an alkenyl group having 2 to 6 carbon atoms; and in formulas (A2-1) and (A2-2), * represents a bonding position] [In formula (A3), R 31 to R 34 each independently represent a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 3 carbon atoms, or a fluorohydrocarbon group
• A is an element other than Li, Ni, Mn, and Co; and a to f are real numbers satisfying 0.8 ⁇ a ⁇ 1.2, 0 ⁇ b ⁇ 0.95, 0 ⁇ c ⁇ 0.5, 0 ⁇ d ⁇ 1.0, 0.7 ⁇ b+c+d ⁇ 1.1, 0 ⁇ e ⁇ 0.1, and 1.8 ⁇ f ⁇ 2.2.
• An all-solid-state battery comprising the positive electrode according to any one of [7] to [12] above and a solid electrolyte.
• the method for producing an all-solid-state battery comprising the steps of: [17] A step of preparing a positive electrode containing a positive electrode active material containing a lithium-containing composite oxide and an additive A which is a compound having a sulfur-oxygen bond; joining the positive electrode, the negative electrode, and a solid electrolyte such that the solid electrolyte is present between the positive electrode and the negative electrode;
• the method for producing an all-solid-state battery comprising the steps of:
• the present invention provides a positive electrode active material for solid-state batteries that can reduce the increase in battery resistance after long-term storage, and an all-solid-state battery that uses the positive electrode active material for solid-state batteries and has reduced battery resistance after long-term storage.
• X to Y (X and Y are real numbers satisfying X ⁇ Y)" means a numerical range "greater than or equal to X and less than or equal to Y.”
• C xy (x and y are real numbers satisfying 0 ⁇ x ⁇ y) means that the number of carbon atoms is x or more and y or less.
• the positive electrode active material for a solid battery according to the present invention contains a lithium-containing composite oxide and an additive A which is a compound having a sulfur-oxygen bond.
• the positive electrode active material for a solid battery according to the present invention can suppress an increase in battery resistance after long-term storage of a solid battery in which the positive electrode active material is used. The reason why such an effect of suppressing an increase in battery resistance over time is obtained is not clear, but is presumed to be as follows.
• Lithium composite oxides with a layered rock salt structure that are mainly used as positive electrode active materials such as active materials containing transition metals (Ni, Co, Mn) called NCM, lose lithium ions during charging, making the layered structure unstable.
• the crystal structure changes as transition metal atoms move to the site left by the lithium ions, resulting in low lithium ion conductivity and a decrease in the rate at which lithium ions are inserted and removed from the positive electrode active material. This change in crystal structure is one of the reasons why positive electrode resistance increases after durability tests.
• the oxygen atom in the sulfur-oxygen bond structure can be coordinated to a transition metal atom.
• additive A which is a compound having a sulfur-oxygen bond, coordinates with the transition metal atom through its oxygen atom, thereby stabilizing the transition metal atom in the positive electrode active material.
• the S-containing compound is not particularly limited as long as it has a sulfur-oxygen bond capable of coordinating with a transition metal atom.
• the S-containing compound is preferably one or more compounds selected from the group consisting of cyclic sulfate esters, chain sulfate esters, cyclic sulfonate esters, and chain sulfonate esters, and is more preferably a compound represented by any of the following general formulas (A1) to (A4).
• R 11 and R 12 each independently represent a hydrocarbon group having 1 to 6 carbon atoms (C 1-6 hydrocarbon group).
• the C 1-6 hydrocarbon group may be linear or branched.
• the C 1-6 hydrocarbon group may be an alkenyl group having 2 to 6 carbon atoms (C 2-6 alkenyl group) or an alkynyl group having 2 to 6 carbon atoms (C 2-6 alkynyl group) having one or more unsaturated bonds, but is preferably an alkyl group having 1 to 6 carbon atoms (C 1-6 alkyl group).
• C 1-6 alkyl group examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a 2-methylbutyl group, a 1-methylpentyl group, a neopentyl group, a 1-ethylpropyl group, a hexyl group, and a 3,3-dimethylbutyl group.
• Specific examples of C2-6 alkenyl groups include vinyl, propenyl, butenyl, pentenyl, and hexenyl groups.
• C2-6 alkynyl groups include ethynyl, propynyl, butynyl, pentynyl, and hexynyl groups.
• R 11 and R 12 are each independently a linear or branched C 1-3 alkyl group, more preferably the same linear or branched C 1-3 alkyl group as each other, even more preferably the same linear C 1-3 alkyl group as each other, and particularly preferably both are a methyl group.
• the C 1-6 alkylene group may be linear or branched (excluding groups represented by general formula (A2-2)).
• Specific examples of the C 1-6 alkylene group include a methylene group, an ethylene group, a propylene group, an isopropylene group, a butylene group, an isobutylene group, a sec-butylene group, a tert-butylene group, a pentylene group, a 2-methylbutylene group, a 1-methylpentylene group, a neopentylene group, a 1-ethylpropylene group, a hexylene group, and a 3,3-dimethylbutylene group.
• the C 1-6 alkylene group is preferably a linear C 1-6 alkylene group, more preferably a linear C 1-3 alkylene group, and particularly preferably an ethylene group.
• R 21 is a C 2-6 alkenylene group
• the C 2-6 alkenylene group may be linear or branched.
• Specific examples of the C 2-6 alkenylene group include a vinylene group, a propenylene group, a butenylene group, a pentenylene group, and a hexenylene group.
• the C 2-6 alkenylene group is preferably a linear C 2-6 alkenylene group, more preferably a linear C 1-3 alkenylene group, and particularly preferably a vinylene group.
• R 22 represents an oxygen atom, a C 1-6 alkylene group, a C 2-6 alkenylene group, or an oxymethylene group (bonded to the sultone group via an oxygen atom).
• Examples of the C 1-6 alkylene group include the same groups as the C 1-6 alkylene groups listed for R 21.
• Examples of the C 2-6 alkenylene group include the same groups as the C 2-6 alkenylene groups listed for R 21 .
• R 22 is preferably an oxygen atom, a methylene group, an ethylene group, a propylene group, or an oxymethylene group, and more preferably an ethylene group or an oxymethylene group.
• R 21 is an oxymethylene group ([4,4'-bi(1,3,2-dioxathiolane)]2,2,2',2'-tetraoxide) is preferred.
• R 31 to R 34 and R 41 to R 44 are C 1-3 hydrocarbon groups
• the C 1-3 hydrocarbon groups may be linear or branched.
• the C 1-3 hydrocarbon groups may be alkenyl groups having one unsaturated bond and having 2 to 3 carbon atoms (C 2-3 alkenyl groups).
• Specific examples of the C 1-3 hydrocarbon groups include methyl, ethyl, propyl, isopropyl, vinyl, and propynyl groups.
• R 31 to R 34 and R 41 to R 44 are each a C 1-3 fluorohydrocarbon group
• specific examples of the C 1-3 fluorohydrocarbon group include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a 2,2,2-trifluoroethyl group, a perfluoroethyl group, and a perfluoropropyl group.
• Additive A other than compounds (A1) to (A4) can also be, for example, 1,4-butane sultone.
• additive A in the positive electrode active material for a solid battery according to the present invention is preferably 0.001% by mass to 10% by mass, more preferably 0.01% by mass to 5% by mass, even more preferably 0.01% by mass to 4% by mass, even more preferably 0.1% by mass to 2% by mass, and particularly preferably 0.1% by mass to 2% by mass.
• the lithium-containing composite oxide used in the present invention is preferably a composite oxide containing lithium and a transition metal atom.
• the lithium-containing composite oxide used in the present invention is preferably a compound containing at least one transition metal atom selected from the group consisting of Co, Ni, and Mn, and may contain atoms other than lithium and these transition metal atoms as necessary. Examples of such other atoms include at least one selected from the group consisting of P, Na, Mg, Ca, Sr, B, Al, Ge, Ti, V, Cr, Fe, Cu, Zr, Nb, Mo, W, Sn, Hf, and Ta (hereinafter also referred to as "additive element").
• the lithium-containing composite oxide used in the present invention contains, in particular, Al and Mg as additive elements, there is an advantage that the positive electrode structure is less likely to break.
• the additive elements include Ca and Mg, the capacity retention rate can be improved by suppressing the decrease in capacity due to the cycles of the battery without significantly decreasing the initial discharge capacity. This is thought to be because calcium ions and magnesium ions that do not contribute to the battery reaction are dissolved in the Li site, thereby reducing the distortion of the crystal structure change of the lithium-containing composite oxide due to the cycles of the battery.
• Ca by dissolving in the Li site, acts like a pillar at the Li site and contributes to stabilizing the crystal structure.
• Mg is believed to contribute to further improvement of cycle characteristics and high durability.
• Na has the effect of promoting crystal growth during firing.
• Other added elements are also believed to contribute to improving the capacity, cycle characteristics, output characteristics, safety, and durability of the battery.
• the lithium-containing composite oxide may be a compound that does not contain any of Co, Ni, and Mn.
• An example of such a compound is a lithium transition metal phosphate, typically lithium iron phosphate (LiFePO 4 ).
• the lithium-containing composite oxide used in the present invention is preferably a compound having a composition represented by the following general formula (P1) (hereinafter sometimes referred to as "compound (P1)").
• A is an element other than Li, Ni, Mn, and Co. Specific examples include the additive elements mentioned above.
• a contained in one molecule of compound (P1) may be one type of atom or two or more types of atoms.
• the compound (P1) preferably has a layered structure in which a Li layer made of lithium ions and a transition metal oxide layer containing Ni, Co, and Mn are layered.
• the compound (P1) having such a layered structure has a relatively small change in lattice volume when lithium is released, and also releases a small amount of oxygen during overcharging.
• the superlattice structure of compound (P1) can be confirmed, for example, by crystal structure analysis using electron beam diffraction measurement (TEM).
• Compound (P1) is disclosed in Japanese Patent No. 4995444, Japanese Patent No. 5277686, JP 2013-101968, JP 2013-175410, JP 4880936, JP 5271751, JP 5317390, JP 2010-282761, JP 2009-158330, JP It is possible to manufacture the compound (P1) by appropriately referring to known methods described in JP 2010-199077 A, JP 5365711 A, JP 2012-252964 A, JP 5365711 A, JP 2012-252964 A, JP 2015-176760 A, etc., and by appropriately modifying the synthesis methods described therein.
• lithium hydroxide LiOH.H 2 O
• nickel hydroxide Ni(OH) 2
• cobalt hydroxide Co(OH) 2
• manganese hydroxide Mn(OH) 2
• the positive electrode active material for a solid battery according to the present invention may contain components other than additive A and the lithium-containing composite oxide as necessary.
• the content of the lithium-containing composite oxide in the positive electrode active material for a solid battery according to the present invention is not particularly limited, but is preferably 70 mass% or more, more preferably 80 mass% or more, and even more preferably 90 mass% or more, based on the total positive electrode active material for a solid battery.
• the surface of the lithium-containing composite oxide is preferably coated with the additive A.
• the surface of the active material is the end of the crystal structure, and there are many missing oxygen atoms. For this reason, by having the additive A, which has oxygen coordinated to the transition metal atoms derived from the lithium-containing composite oxide, present on the surface of the active material, the crystal structure can be further stabilized, and the effect of additive A in suppressing an increase in the positive electrode resistance can be more fully exerted.
• the all-solid-state battery according to the present invention contains a positive electrode containing a lithium-containing composite oxide and the additive A, and a solid electrolyte.
• the all-solid-state battery according to the present invention has a positive electrode containing the additive A, and therefore has a small increase in battery resistance after long-term storage and excellent long-term storage stability.
• the positive electrode may be a positive electrode containing the positive electrode active material according to the present invention (a positive electrode active material containing a lithium-containing composite oxide and the additive A), or may be a positive electrode manufactured using a conventional positive electrode active material (a positive electrode active material containing a lithium-containing composite oxide but not the additive A) and the additive A as raw materials.
• the positive electrode active material layer can be produced by dry-mixing a positive electrode active material containing a lithium-containing composite oxide, a binder (and further, a solid electrolyte, a conductive assistant, an additive A, a thickener, and the like, which are used as necessary), forming the mixture into a sheet, and pressing the sheet onto a positive electrode current collector.
• the positive electrode active material layer can also be produced by dissolving or dispersing the positive electrode active material containing the lithium-containing composite oxide and the binder (and further, a solid electrolyte, a conductive assistant, an additive A, a thickener, and the like, which are used as necessary) in a liquid medium to form a slurry, and then applying the obtained slurry to a positive electrode current collector and drying it.
• the content of the positive electrode active material (or the content of the lithium-containing complex oxide) in the positive electrode active material layer is not particularly limited, but is usually 50 mass% or more, preferably 60 mass% or more, and more preferably 70 mass% or more, based on the total amount of the positive electrode active material layer.
• the content of the positive electrode active material (or the content of the lithium-containing complex oxide) in the positive electrode active material layer is usually 99 mass% or less, preferably 95 mass% or less, and more preferably 90 mass% or less, from the viewpoint of the ionic conductivity of the positive electrode active material layer.
• binders include resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylonitrile, polyacrylamide, aromatic polyamide, cellulose, and nitrocellulose; rubber-like polymers such as SBR (styrene-butadiene rubber), NBR (acrylonitrile-butadiene rubber), fluororubber, isoprene rubber, butadiene rubber, and ethylene-propylene rubber; styrene-butadiene-styrene block copolymers and their hydrogenated products, and EPDM (ethylene-propylene-diene ternary copolymer).
• resin-based polymers such as polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate (PMMA), polymethyl acrylate (PMA), polyacrylonitrile, polyacrylamide, aromatic polyamide, cellulose, and nitrocellulose
• rubber-like polymers such as
• suitable materials include thermoplastic elastomers such as styrene-ethylene-butadiene-ethylene copolymers, styrene-isoprene-styrene block copolymers, and hydrogenated products thereof; soft resin-like polymers such as syndiotactic-1,2-polybutadiene, polyvinyl acetate, ethylene-vinyl acetate copolymers, and propylene- ⁇ -olefin copolymers; fluorine-based polymers such as polyvinylidene fluoride, polytetrafluoroethylene, fluorinated polyvinylidene fluoride, and polytetrafluoroethylene-ethylene copolymers; and polymer compositions having ionic conductivity for alkali metal ions (especially lithium ions). These substances may be used alone or in any combination and ratio of two or more.
• the proportion of the binder in the positive electrode active material layer is usually 0.1 mass% or more, preferably 0.3 mass% or more, and more preferably 0.5 mass% or more, from the viewpoint of the mechanical strength of the positive electrode. Also, the proportion of the binder in the positive electrode active material layer is usually 50 mass% or less, preferably 30 mass% or less, more preferably 10 mass% or less, and even more preferably 5 mass% or less, from the viewpoint of further improving the battery capacity and conductivity.
• Thickeners are not particularly limited, and examples include carboxymethylcellulose, methylcellulose, hydroxymethylcellulose, ethylcellulose, polyvinyl alcohol, oxidized starch, phosphated starch, casein, and salts thereof. These substances may be used alone or in any combination and ratio of two or more.
• the proportion of the thickener in the positive electrode active material layer is usually 0.1 mass% or more, preferably 0.3 mass% or more, and more preferably 0.5 mass% or more, from the viewpoint of the stability of the positive electrode slurry.
• the proportion of the binder in the positive electrode active material layer is usually 50 mass% or less, preferably 30 mass% or less, more preferably 10 mass% or less, and even more preferably 5 mass% or less, from the viewpoint of further improving the battery capacity and conductivity.
• the positive electrode active material layer may contain a solid electrolyte from the viewpoint of ion conductivity.
• the solid electrolyte may be any of those listed as the solid electrolytes constituting the solid electrolyte layer of the all-solid-state battery described below.
• the solid electrolyte contained in the positive electrode active material layer may be one of the substances described below, or two or more of them may be used in any combination and ratio.
• the solid electrolyte contained in the positive electrode active material layer may be the same type of substance as the solid electrolyte constituting the solid electrolyte layer of the all-solid-state battery, or it may be a different substance.
• the proportion of the solid electrolyte in the positive electrode active material layer is usually 1 mass% or more, preferably 5 mass% or more, more preferably 10 mass% or more, and even more preferably 15 mass% or more, from the viewpoint of further improving the electrical conductivity. Also, the proportion of the solid electrolyte in the positive electrode active material layer is usually 50 mass% or less, preferably 40 mass% or less, more preferably 30 mass% or less, and even more preferably 20 mass% or less, from the viewpoint of containing a sufficient amount of positive electrode active material.
• the positive electrode active material layer may contain a conductive assistant in order to increase the electrical conductivity.
• a conductive assistant in order to increase the electrical conductivity.
• conductive assistant includes metal materials such as copper, nickel, etc., graphite such as natural graphite, artificial graphite, etc., carbon materials such as carbon black (e.g., acetylene black), carbon nanotubes, amorphous carbon (e.g., needle coke), etc. These substances may be used alone or in any combination and ratio of two or more.
• the proportion of the conductive assistant in the positive electrode active material layer is usually 0.01% by mass or more, preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, from the viewpoint of further improving the conductivity. Also, the proportion of the conductive assistant in the positive electrode active material layer is usually 50% by mass or less, preferably 30% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, from the viewpoint of further improving the battery capacity.
• the positive electrode current collector When a thin film is used as the positive electrode current collector, its thickness is not limited, but from the viewpoint of strength, it is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, and more preferably 5 ⁇ m or more. From the viewpoint of ease of handling, the thickness of the thin film positive electrode current collector is usually 100 mm or less, preferably 1 mm or less, and more preferably 50 ⁇ m or less.
• the liquid medium for forming the slurry is not particularly limited in type, so long as it is a solvent capable of dissolving or dispersing the lithium-containing composite oxide (e.g., powder), the binder, and the conductive assistant and thickener used as needed.
• the liquid medium may be either a polar solvent or a non-polar organic solvent.
• the polar solvent may be a protic polar solvent or an aprotic polar solvent.
• protic polar solvents examples include water; alcohol-based polar solvents such as methanol and ethanol; and amine-based polar solvents such as diethylenetriamine and N,N-dimethylaminopropylamine.
• aprotic polar solvents include ketone-based polar solvents such as cyclohexanone, N-methylpyrrolidone (NMP), methyl ethyl ketone, and acetone; amide-based polar solvents such as hexamethylphosphamide, dimethylacetamide, and dimethylformamide; ether-based polar solvents such as tetrahydrofuran (THF), dimethyl ether, and ethylene oxide; sulfoxide compounds such as dimethyl sulfoxide; and ester-based polar solvents such as methyl acrylate and methyl acetate.
• ketone-based polar solvents such as cyclohexanone, N-methylpyrrolidone (NMP), methyl
• non-polar organic solvents examples include aromatic-containing non-polar solvents such as tetralin, anisole (methoxybenzene), benzene, xylene, toluene, methylnaphthalene, quinoline, and pyridine; and aliphatic hydrocarbon-based non-polar solvents such as hexane. These solvents may be used alone or in any combination of two or more in any ratio.
• a dispersant can be added along with the thickener, and a slurry can be made using a latex such as SBR.
• the liquid solvent is preferably a non-polar organic solvent, more preferably an aromatic organic solvent, an aliphatic hydrocarbon solvent, or a mixture of these, and even more preferably an aromatic organic solvent, in order to minimize the effect on the sulfide-based solid electrolyte.
• the thickness of the positive electrode active material layer is usually about 10 ⁇ m or more and 300 ⁇ m or less.
• the positive electrode active material layer obtained by coating and drying is preferably compressed by a roller press or the like to increase the packing density of the positive electrode active material.
• the solid electrolyte contained in the all-solid-state battery according to the present invention is not particularly limited as long as it can conduct ions, and examples thereof include sulfide-based solid electrolytes, oxide-based solid electrolytes, and hydride-based solid electrolytes. Among these, from the viewpoint of high ion conductivity, it is preferable that at least a part of the solid electrolyte is a sulfide-based solid electrolyte.
• the solid electrolyte may be used alone or in any combination and ratio of two or more kinds.
• the sulfide solid electrolyte preferably has high ionic conductivity, and examples thereof include Li 2 S-P 2 S 5 , Li 2 S-P 2 S 5 -LiI, Li 2 S-P 2 S 5 -LiCl, Li 2 S-P 2 S 5 -LiBr, Li 2 S-P 2 S 5 -Li 2 O, Li 2 S-P 2 S 5 -Li 2 O-LiI, Li 2 S-P 2 S 5 -Li 3 N, Li 2 S-SiS 2 , Li 2 S-SiS 2 -LiI, Li 2 S-SiS 2 -LiBr, Li 2 S-SiS 2 -LiCl, and Li 2 S-SiS 2 -B.
• Li 2 S-P 2 S 5 Li 2 S-P 2 S 5 -LiI, Li 2 S-P 2 S 5 -LiCl, Li (7-a-2) PS (6-a-b) X a (wherein X is at least one of F, Cl, Br, and I, and 0.4 ⁇ a ⁇ 2.2, ⁇ 0.9 ⁇ b ⁇ ( ⁇ a+2)) are preferred, and x Li 2 S.(100- x )P 2 S 5 (70 ⁇ x ⁇ 80), Li (7-a-2) PS (6-a-b) X a (wherein X is at least one of F, Cl, Br, and I, and 0.4 ⁇ a ⁇ 2.2, ⁇ 0.9 ⁇ b ⁇ ( ⁇ a+2)) are more preferred.
• the other solid electrolyte can be appropriately selected from the solid electrolytes used in all-solid-state batteries.
• Specific examples of the other solid electrolyte include oxide-based solid electrolytes, dry polymer electrolytes, gel polymer electrolytes, and pseudo-solid electrolytes.
• the lower limit of the average thickness of the solid electrolyte layer in the all-solid-state battery is preferably 1 ⁇ m, and more preferably 3 ⁇ m.
• the upper limit of the average thickness of the solid electrolyte layer is preferably 50 ⁇ m, and more preferably 20 ⁇ m.
• the negative electrode may be configured by forming a negative electrode active material layer containing a negative electrode active material on a negative electrode current collector.
• the negative electrode active material layer preferably contains a binder in addition to the negative electrode active material, and further preferably contains a solid electrolyte, a conductive assistant, a thickener, and the like, as necessary.
• the binder the same binder as that in the positive electrode active material layer described above can be used.
• the solid electrolyte the same solid electrolyte as that in the positive electrode active material layer described above can be used.
• the conductive assistant the same conductive assistant as that in the positive electrode active material layer described above can be used.
• As the thickener the same thickener as that in the positive electrode active material layer described above can be used.
• the negative electrode active material used in the negative electrode of the present invention may be, for example, at least one selected from the group consisting of metallic lithium, lithium-containing alloys, metals or alloys capable of alloying with lithium, oxides capable of doping and dedoping lithium ions, transition metal nitrides capable of doping and dedoping lithium ions, and carbon materials capable of doping and dedoping lithium ions (which may be used alone or a mixture containing two or more of these may be used).
• oxides capable of doping and dedoping lithium ions include silicon oxide, lithium titanate, and the lithium-containing composite oxides listed for the positive electrode.
• Examples of metals or alloys that can be alloyed with lithium (or lithium ions) include silicon, silicon alloys, tin, and tin alloys.
• carbon materials capable of doping and dedoping lithium ions are preferred.
• Examples of such carbon materials include carbon black, activated carbon, graphite materials (artificial graphite, natural graphite), amorphous carbon materials, etc.
• the form of the carbon materials may be any of fibrous, spherical, potato-like, and flake-like forms.
• amorphous carbon material examples include hard carbon, coke, mesocarbon microbeads (MCMB) calcined at 1500° C. or less, and mesope pitch carbon fiber (MCF).
• the graphite material examples include natural graphite and artificial graphite. Examples of the artificial graphite include graphitized MCMB and graphitized MCF. Examples of the graphite material that can be used include those containing boron. Examples of the graphite material that can be used include those coated with a metal such as gold, platinum, silver, copper, or tin, those coated with amorphous carbon, and those mixed with amorphous carbon and graphite.
• These carbon materials may be used alone or in combination of two or more.
• a carbon material in which the interplanar spacing d(002) of the (002) plane measured by X-ray analysis is 0.340 nm or less is particularly preferred.
• graphite with a true density of 1.70 g/cm3 or more or a highly crystalline carbon material with properties similar thereto is also preferred. By using such carbon materials, the energy density of the battery can be increased.
• the negative electrode active material layer can be formed using a slurry containing a negative electrode active material (and preferably a binder, and further a solid electrolyte, a conductive assistant, and a thickener, which are used as needed), similar to the above-mentioned positive electrode active material layer.
• the solvent in the slurry for forming the negative electrode active material layer can be the same as the solvent in the slurry for producing the positive electrode active material layer.
• a thickener can also be contained in the slurry for forming the negative electrode active material layer.
• the negative electrode may be configured by forming a negative electrode active material layer made of the negative electrode active material on a current collector by a method such as vapor deposition, sputtering, or plating.
• the negative electrode active material layer may not contain a binder.
• the material for the negative electrode current collector examples include metal materials such as copper, nickel, stainless steel, and nickel-plated steel, with copper being particularly preferred from the standpoints of ease of processing and cost.
• the shape of the current collector may be, for example, a metal foil, a metal cylinder, a metal coil, a metal plate, a metal thin film, an expanded metal, a punched metal, a foamed metal, etc.
• a metal thin film is preferable, and a copper foil is more preferable.
• a rolled copper foil produced by a rolling method, or an electrolytic copper foil produced by an electrolytic method is even more preferable.
• a copper alloy phosphor bronze, titanium copper, Corson alloy, Cu—Cr—Zr alloy, etc.
• the thickness of the negative electrode active material layer is usually about 10 ⁇ m or more and 300 ⁇ m or less.
• the positive and negative electrode active material layers obtained by coating and drying are preferably compressed by a roller press or the like to increase the packing density of the negative electrode active material.
• the all-solid-state battery according to the present invention can have various known shapes, and can be formed into any shape such as a cylindrical shape, a coin shape, a square shape, a film shape, etc.
• the basic structure of the battery is the same regardless of the shape, and the design can be modified according to the purpose.
• the all-solid-state battery according to the present invention may be an all-solid-state battery obtained by charging and discharging an all-solid-state battery (an all-solid-state battery before charging and discharging) including a negative electrode, a positive electrode, and a solid electrolyte layer. That is, the all-solid-state battery according to the present invention may be an all-solid-state battery (a charged and discharged all-solid-state battery) produced by first preparing an all-solid-state battery before charging and discharging, the all-solid-state battery including a negative electrode, a positive electrode, and a solid electrolyte layer, and then charging and discharging the all-solid-state battery before charging and discharging at least once.
• the uses of the all-solid-state battery according to the present invention are not particularly limited, and it can be used for a variety of known uses.
• it can be widely used in notebook computers, mobile computers, mobile phones, headphone stereos, video movie players, liquid crystal televisions, handy cleaners, electronic organizers, calculators, radios, backup power supplies, motors, automobiles, electric automobiles, motorcycles, electric motorcycles, bicycles, electric bicycles, lighting equipment, game consoles, watches, power tools, cameras, and other small portable devices and large devices alike.
• a positive electrode active material was prepared using 1,3,2-dioxathiolane-2,2-dioxide (DTD) as additive A, and an all-solid-state battery was prepared using the positive electrode active material.
• the positive electrode active material (82.7 parts by mass), an argyrodite-type sulfide solid electrolyte (average particle size 0.6 ⁇ m) (15.4 parts by mass), vapor-grown carbon fiber (VGCF) (1.1 parts by mass), a rubber-based binder (0.8 parts by mass), and a tetralin/anisole mixed solution as a dispersion medium were added and kneaded to obtain a positive electrode composite slurry.
• the obtained positive electrode composite slurry was applied to an aluminum foil as a positive electrode current collector, and the dispersion medium was removed by vacuum heating and drying to obtain a positive electrode sheet equipped with a positive electrode composite layer and a current collector.
• the initial resistance of the battery cell in the all-solid-state battery obtained above was measured by a constant current/constant voltage charge/discharge (CCCV) method as follows.
• the battery cell was charged and discharged three times at 25° C. with a charge voltage of 4.35 V and a discharge voltage of 3 V at a 0.1 C CCCV termination of 0.01 C, and then charged to 3.685 V at a 0.1 C CCCV termination of 0.01 C. After charging, the DC resistance of the battery cell was measured for 10 seconds of discharge to obtain the initial resistance.
• CCCV constant current/constant voltage charge/discharge
• Battery cell float test (high temperature storage)
• the high-temperature storage stability of the battery cell was measured by a float test (60° C., charging voltage 4.35 V, 0.1 C CCCV charging, 168 hours) using the battery cell after the initial resistance measurement.
• the float test is an accelerated test that is widely used to examine the long-term storage stability of a battery.
• the resistance of the battery cells after the float test was measured by the CCCV method as follows.
• the battery cell after the float test was discharged to 3 V at 0.1 C CCCV 0.01 C termination.
• the discharged battery cell was charged and discharged for 2 cycles at 25° C. with a charge voltage of 4.35 V and a discharge voltage of 3 V at 0.1 C CCCV 0.01 C termination, and then charged to 3.685 V at 0.1 C CCCV 0.01 C termination.
• the DC resistance of the charged battery cell was measured for 10 seconds of discharge, and the resistance after the float test was calculated.
• Example 2 A positive electrode active material was prepared in the same manner as in Example 1, except that dimethyl sulfate (DMS) was used instead of DTD as additive A. An all-solid-state battery was manufactured using the positive electrode active material, and the initial resistance and the resistance after a float test of the obtained all-solid-state battery were measured.
• DMS dimethyl sulfate
• Example 1 A positive electrode active material was prepared in the same manner as in Example 1 except that additive A was not contained, and an all-solid-state battery was manufactured using the positive electrode active material. The initial resistance and the resistance after the float test of the obtained all-solid-state battery were measured.
• a positive electrode active material was prepared in the same manner as in Example 1, except that lithium bis(oxalato)borate (BOB) was used instead of DTD as additive A.
• An all-solid-state battery was manufactured using the positive electrode active material, and the initial resistance and the resistance after a float test of the obtained all-solid-state battery were measured.
• Ethylene carbonate hereinafter, "EC”
• DMC dimethyl carbonate
• EMC ethyl methyl carbonate
• a mixture of LiNi0.5Co0.2Mn0.3O2 (94 mass%) as a positive electrode active material, carbon black (3 mass%) as a conductive additive, and polyvinylidene fluoride (PVdF) (3 mass%) as a binder was obtained .
• the obtained mixture was dispersed in an N-methylpyrrolidone solvent to obtain a positive electrode composite slurry.
• An aluminum foil having a thickness of 20 ⁇ m was prepared as a positive electrode current collector.
• the obtained positive electrode mixture slurry was applied onto an aluminum foil, dried, and then rolled with a press to obtain a sheet-shaped positive electrode.
• the positive electrode was composed of a positive electrode current collector and a positive electrode active material layer.
• Graphite (96% by mass) as a negative electrode active material, carbon black (1% by mass) as a conductive assistant, 1% by mass in terms of solid content of sodium carboxymethylcellulose dispersed in pure water as a thickener, and 2% by mass in terms of solid content of styrene-butadiene rubber (SBR) dispersed in pure water as a binder were mixed together to obtain a negative electrode composite slurry.
• a copper foil having a thickness of 10 ⁇ m was prepared as a negative electrode current collector.
• the obtained negative electrode mixture slurry was applied onto a copper foil, dried, and then rolled with a press to obtain a sheet-shaped negative electrode.
• the negative electrode was composed of a negative electrode current collector and a negative electrode active material layer.
• the negative electrode was punched out into a disk shape with a diameter of 14 mm
• the positive electrode was punched out into a disk shape with a diameter of 13 mm
• the separator was punched out into a disk shape with a diameter of 17 mm, thereby obtaining a coin-shaped negative electrode, a coin-shaped positive electrode, and a coin-shaped separator.
• the obtained coin-shaped negative electrode, coin-shaped separator, and coin-shaped positive electrode were stacked in this order in a stainless steel battery can (size: 2032 size).
• the lithium secondary battery precursor was charged to 1.5 V to 4.2 V at a temperature range of 25° C. to 70° C., held for 5 to 50 hours, charged to 4.2 V, and discharged to 2.5 V, in that order, to obtain a lithium secondary battery.
• CC10s discharge means discharge at a constant current for 10 seconds.
• the DC resistance [ ⁇ ] was calculated as the initial room temperature resistance.
• the DC resistance [ ⁇ ] was similarly determined as the initial room temperature resistance.
• High temperature storage Next, the lithium secondary battery after the measurement of the initial room temperature resistance was charged to 4.2 V, and the charged lithium secondary battery was stored in a thermostatic chamber at 60° C. for 14 days (hereinafter referred to as “high temperature storage”).
• a lithium secondary battery was produced in the same manner as in Comparative Example 3, except that a nonaqueous electrolyte solution was used in which DTD was added as an additive to the base electrolyte solution used in Comparative Example 3 so that the content of DTD in the total amount of the finally obtained nonaqueous electrolyte solution was 1.0 mass %, and the room temperature resistance increase rate of the obtained lithium secondary battery during high-temperature storage was measured.
• a lithium secondary battery was produced in the same manner as in Comparative Example 3, except that a solution obtained by adding BOB as an additive to the basic electrolyte solution used in Comparative Example 3 so that the content of BOB relative to the total amount of the finally obtained nonaqueous electrolyte solution was 1.0 mass %, and the room temperature resistance of the obtained lithium secondary battery was measured in the initial state and after high-temperature storage.
• the room temperature resistance increase rate (relative value) during high temperature storage of the lithium secondary batteries of Comparative Example 4 and Comparative Example 5 was calculated, assuming that the room temperature resistance increase rate during high temperature storage of the lithium secondary battery of Comparative Example 3 was 100.
• the results are shown in Table 2.
• the lithium secondary battery of Comparative Example 4 which contained DTD as additive A and used an electrolyte solution instead of a solid electrolyte as the electrolyte, had a relative resistance value after high-temperature storage of 93% compared to the lithium secondary battery of Comparative Example 3 without an additive. From the results of Example 1 and Comparative Example 4, it was found that the effect of suppressing the increase in battery resistance after long-term storage obtained when DTD is used as additive A is superior to that of a lithium secondary battery using an electrolyte solution in an all-solid-state battery using a solid electrolyte.
• the lithium secondary battery of Comparative Example 5 which contained BOB as additive A and used an electrolyte solution instead of a solid electrolyte as the electrolyte, had a relative resistance value after high-temperature storage of 85% compared to the lithium secondary battery of Comparative Example 3 without an additive. From the results of Comparative Example 2 and Comparative Example 5, it was found that there was no difference in the effect of suppressing the increase in battery resistance after long-term storage obtained when BOB is used as additive A between a lithium secondary battery using an electrolyte solution and an all-solid-state battery using a solid electrolyte.
• additive A into the positive electrode active material in an all-solid-state battery, the increase in internal resistance over time can be suppressed, and the battery resistance after long-term storage can be reduced.

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