WO2023180868A1 - リチウムイオン電池 - Google Patents

リチウムイオン電池 Download PDF

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Publication number
WO2023180868A1
WO2023180868A1 PCT/IB2023/052424 IB2023052424W WO2023180868A1 WO 2023180868 A1 WO2023180868 A1 WO 2023180868A1 IB 2023052424 W IB2023052424 W IB 2023052424W WO 2023180868 A1 WO2023180868 A1 WO 2023180868A1
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Prior art keywords
positive electrode
active material
electrode active
lithium
ion battery
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PCT/IB2023/052424
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English (en)
French (fr)
Japanese (ja)
Inventor
比護大地
田中文子
島田知弥
村椿将太郎
荻田香
栗城和貴
鈴木邦彦
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Semiconductor Energy Laboratory Co Ltd
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Semiconductor Energy Laboratory Co Ltd
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Application filed by Semiconductor Energy Laboratory Co Ltd filed Critical Semiconductor Energy Laboratory Co Ltd
Priority to JP2024508824A priority Critical patent/JPWO2023180868A1/ja
Priority to US18/849,321 priority patent/US20250226451A1/en
Priority to CN202380028702.8A priority patent/CN118901159A/zh
Priority to DE112023001569.4T priority patent/DE112023001569T5/de
Priority to KR1020247031672A priority patent/KR20240167817A/ko
Publication of WO2023180868A1 publication Critical patent/WO2023180868A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M4/36—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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0034—Fluorinated solvents
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • 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

  • One aspect of the present invention relates to a lithium ion battery.
  • one embodiment of the present invention is not limited to the above field, but relates to a semiconductor device, a display device, a light emitting device, a power storage device, a lighting device, an electronic device, a vehicle, and a manufacturing method thereof.
  • the lithium ion battery of one embodiment of the present invention can be used as a necessary power source in the semiconductor device, display device, light-emitting device, power storage device, lighting device, electronic device, and vehicle described above.
  • the above-mentioned electronic devices include information terminal devices equipped with lithium ion batteries.
  • the above-mentioned power storage device includes a stationary power storage device and the like.
  • a lithium ion battery (sometimes referred to as a lithium ion secondary battery) refers to a battery that uses lithium ions as carrier ions.
  • a lithium ion battery is a secondary battery that can be used repeatedly by charging and discharging.
  • the carrier ions of the present invention are not limited to lithium ions, and alkali metal ions or alkaline earth metal ions can be used as carrier ions. Specifically, sodium ions, magnesium ions, etc. can be applied. In this case, the present invention can be understood by reading lithium ions as sodium ions, magnesium ions, etc.
  • Patent Document 1 proposes a fluorinated chain carboxylic acid ester as a non-aqueous electrolyte in order to suppress a decrease in battery capacity at high temperatures. Furthermore, in Non-Patent Document 1, in order to improve the output characteristics at sub-zero temperatures, methyl 3,3,3-trifluoropropionate (MTFP):fluoroethylene carbonate (FEC) was mixed at a ratio of 9:1 as an electrolyte. is proposed. Furthermore, Non-Patent Document 2 reports the crystal structure of a positive electrode active material.
  • MTFP 3,3,3-trifluoropropionate
  • FEC fluoroethylene carbonate
  • Example 1 of Patent Document 1 lithium cobalt oxide (LiCoO 2 ) in which Al and Mg are each dissolved as a solid solution and Zr added to the particle surface is used as the positive electrode active material, and 4-fluoroethylene carbonate is used as the positive electrode active material. It is described that a mixture of (4-FEC) and CF 3 CH 2 COOCH 3 at a volume ratio of 2:8 is used as an organic solvent for a non-aqueous electrolyte. However, in Patent Document 1, battery characteristics at sub-zero temperatures were not studied.
  • Non-Patent Document 1 in order to study battery characteristics at sub-zero temperatures, a mixture of methyl 3,3,3-trifluoropropionate (MTFP) and fluoroethylene carbonate (FEC) at a ratio of 9:1 was subjected to non-aqueous electrolysis. It is described that NMC811 is used as an organic solvent for a liquid, and it is described that NMC811 is used as a positive electrode active material in a cycle test. However, in Non-Patent Document 1, battery characteristics under high temperatures were not studied.
  • MTFP methyl 3,3,3-trifluoropropionate
  • FEC fluoroethylene carbonate
  • the present invention provides a lithium ion battery having an electrolyte containing a new organic solvent and a new positive electrode active material in order to enable charging and discharging in a wide temperature range from sub-zero to high temperatures. is one of the challenges.
  • one embodiment of the present invention includes a positive electrode having a positive electrode active material and an electrolyte
  • the positive electrode active material includes lithium cobalt oxide having Mg, F, Ni, and Al
  • the electrolyte is a lithium ion battery containing a fluorinated cyclic carbonate and a fluorinated chain carbonate.
  • Another embodiment of the present invention includes a positive electrode having a positive electrode active material and an electrolyte
  • the positive electrode active material includes lithium cobalt oxide having Mg, F, Ni, and Al
  • the electrolyte includes fluoroethylene carbonate and an electrolyte.
  • methyl trifluoropropionate and when the total content of fluoroethylene carbonate and methyl trifluoropropionate is 100 vol%, the volume ratio of fluoroethylene carbonate and methyl trifluoropropionate is x:100 -x (5 ⁇ x ⁇ 30).
  • the median diameter (D50) of the lithium cobalt oxide according to another embodiment of the present invention is preferably 10 ⁇ m or more and 14 ⁇ m or less.
  • the median diameter (D50) of the lithium cobalt oxide according to another embodiment of the present invention is preferably 5 ⁇ m or more and 9 ⁇ m or less.
  • a lithium ion battery including a positive electrode active material containing lithium cobalt oxide having Mg, F, Ni, and Al, and an electrolyte containing a fluorinated cyclic carbonate and a fluorinated chain carbonate.
  • a half cell comprising a positive electrode having the above positive electrode active material, the above electrolyte, and lithium metal as a counter electrode is prepared, the half cell is placed at an environmental temperature of 25° C., and a voltage of 4.6 V is applied.
  • Another aspect of the present invention is a lithium ion battery including a positive electrode having a positive electrode active material containing lithium cobalt oxide containing Mg, F, Ni, and Al, and an electrolyte, the battery having the above positive electrode active material.
  • a voltage of 4.6V is obtained.
  • Charge with a constant current at a rate of 0.1C (1C 200mA/g (current per weight of positive electrode active material is 200mA/g)) until the current value reaches 0.05C, and then charge at a constant rate of 4.6V until the current value reaches 0.05C.
  • the discharge capacity value determined by placing it at an environmental temperature of -40°C and discharging at a constant current at a rate of 0.1C until the voltage reaches 2.5V is 50% or more.
  • a lithium-ion battery is 50% or more.
  • Another embodiment of the present invention is a lithium ion battery including a positive electrode active material having nickel, cobalt, and manganese, and an electrolyte including a fluorinated cyclic carbonate and a fluorinated chain carbonate, the positive electrode active material A half cell comprising a positive electrode having a After constant current charging at a rate of 200 mA/g (current per weight of material) and constant voltage charging at 4.5 V until the current value reaches 0.05 C, place it at an environmental temperature of -40°C. Then, the discharge capacity value obtained by discharging at a constant current at a rate of 0.1C until the voltage reaches 2.5V becomes 4.5V when the half cell is placed at an environmental temperature of 25°C.
  • Another embodiment of the present invention is a lithium ion battery comprising a positive electrode active material containing nickel, cobalt, and manganese, and an electrolyte, the electrolyte comprising fluoroethylene carbonate and methyl trifluoropropionate.
  • the volume ratio of fluoroethylene carbonate and methyl trifluoropropionate is x:100-x (however, 5 ⁇ x ⁇
  • the ratio of nickel:cobalt:manganese in the positive electrode active material satisfies 8:1:1 or around 8:1:1.
  • the proportion of nickel in the positive electrode active material is preferably higher than the proportion of cobalt and the proportion of manganese.
  • the positive electrode active material preferably has a median diameter (D50) of 4 ⁇ m or more and 7 ⁇ m or less.
  • the half-cell separator preferably includes polyimide.
  • the half-cell separator preferably comprises polypropylene.
  • a lithium ion battery having an electrolyte having a new organic solvent and a new positive electrode active material it is possible to provide a lithium ion battery having an electrolyte having a new organic solvent and a new positive electrode active material. According to one embodiment of the present invention, a lithium ion battery that can be charged and discharged over a wide temperature range from below freezing to high temperatures can be provided.
  • FIGS. 1A and 1B are diagrams illustrating a lithium ion battery according to one embodiment of the present invention.
  • 2A to 2C are diagrams illustrating a method for manufacturing a positive electrode according to one embodiment of the present invention.
  • 3A to 3F are diagrams illustrating a positive electrode active material according to one embodiment of the present invention.
  • FIG. 4 is a diagram illustrating the crystal structure of a positive electrode active material according to one embodiment of the present invention.
  • FIG. 5 is a diagram illustrating the crystal structure of the positive electrode active material.
  • FIG. 6 is a diagram illustrating the diffraction peak of the positive electrode active material.
  • FIG. 7 is a diagram illustrating the diffraction peak of the positive electrode active material.
  • FIG. 8A and 8B are diagrams illustrating diffraction peaks of the positive electrode active material.
  • FIG. 9 is a diagram illustrating a method for manufacturing a positive electrode according to one embodiment of the present invention.
  • FIG. 10 is a diagram illustrating a method for manufacturing a positive electrode according to one embodiment of the present invention.
  • FIG. 11 is a diagram illustrating a method for manufacturing a positive electrode according to one embodiment of the present invention.
  • FIG. 12 is a diagram illustrating a method for manufacturing a positive electrode according to one embodiment of the present invention.
  • FIG. 13 is a diagram illustrating a method for manufacturing a positive electrode according to one embodiment of the present invention.
  • 14A to 14D are diagrams illustrating a positive electrode according to one embodiment of the present invention.
  • 15A to 15D are diagrams illustrating a positive electrode according to one embodiment of the present invention.
  • 16A and 16B are diagrams illustrating a lithium ion battery according to one embodiment of the present invention.
  • 17A to 17C are diagrams illustrating a lithium ion battery according to one embodiment of the present invention.
  • 18A to 18D are diagrams illustrating a lithium ion battery and a power storage system according to one embodiment of the present invention.
  • 19A to 19C are diagrams illustrating a lithium ion battery according to one embodiment of the present invention.
  • 20A to 20C are diagrams illustrating a lithium ion battery according to one embodiment of the present invention.
  • 21A to 21C are diagrams illustrating an electric vehicle according to one embodiment of the present invention.
  • 22A to 22D are diagrams illustrating a transportation vehicle according to one embodiment of the present invention.
  • 23A to 23C are diagrams illustrating a two-wheeled vehicle and the like according to one embodiment of the present invention.
  • 24A to 24D are diagrams illustrating an electronic device and the like according to one embodiment of the present invention.
  • 25A to 25D are diagrams showing an example of space equipment.
  • 26A and 26B are diagrams showing NMR of an organic solvent of an electrolyte that is one embodiment of the present invention.
  • FIGS. 27A and 27B are diagrams showing NMR of an organic solvent of an electrolyte, which is one embodiment of the present invention.
  • FIGS. 28A and 28B are diagrams showing NMR of an organic solvent of an electrolyte that is one embodiment of the present invention.
  • FIGS. 29A and 29B are diagrams illustrating AC impedance measurement.
  • 30A to 30C are diagrams showing results of AC impedance measurement of a sample having an electrolyte and a positive electrode active material according to one embodiment of the present invention.
  • 31A to 31C are diagrams showing the results of AC impedance measurement of a sample having an electrolyte and a positive electrode active material according to one embodiment of the present invention.
  • 32A and 32B are diagrams showing the charge capacity and discharge capacity of a sample having an electrolyte and a positive electrode active material according to one embodiment of the present invention.
  • 33A and 33B are diagrams showing the charge capacity and discharge capacity of a sample having an electrolyte and a positive electrode active material according to one embodiment of the present invention.
  • 34A and 34B are diagrams showing the charge capacity and discharge capacity of a sample having an electrolyte and a positive electrode active material according to one embodiment of the present invention.
  • FIGS. 35A and 35B are diagrams showing charging and discharging curves of a sample having an electrolyte and a positive electrode active material according to one embodiment of the present invention.
  • 36A to 36C are diagrams showing cycle characteristics of a sample having an electrolyte and a positive electrode active material according to one embodiment of the present invention.
  • FIG. 37 is a diagram showing the viscosity of the organic solvent of the electrolyte, which is one embodiment of the present invention.
  • FIGS. 38A and 38B are diagrams showing the charge capacity and discharge capacity of a sample having an electrolyte and a positive electrode active material according to one embodiment of the present invention.
  • FIGS. 39A and 39B are graphs showing DSC results of organic liquids.
  • FIG. 40 is a diagram showing a model used for calculation.
  • FIG. 41 is a graph showing the activation barrier for lithium ion diffusion.
  • FIG. 42A and FIG. 42B are diagrams showing charge/discharge curves (25° C.) of a full cell.
  • FIGS. 43A and 43B are diagrams showing the cycle characteristics (25° C.) of a full cell.
  • the positive electrode active material refers to a compound containing a transition metal and oxygen that can insert and extract carrier ions.
  • Compounds containing oxygen are sometimes called oxides or composite oxides.
  • Lithium ions are typically used as carrier ions, but sodium ions, magnesium ions, etc. may also be used.
  • Carbonic acid, hydroxyl groups, etc. adsorbed after the production of the positive electrode active material are not included in the positive electrode active material. Further, it is assumed that the positive electrode active material does not include the electrolyte, organic solvent, binder, conductive material, or compounds derived from these that adhere to the positive electrode active material.
  • homogeneous refers to a phenomenon in which a certain element (for example, A) is distributed with similar characteristics in a specific region in a solid composed of multiple elements (for example, A, B, and C). say. Specifically, it is sufficient that the concentrations of the elements in the specific regions are substantially the same. For example, it is sufficient that the difference in element concentration between specific regions is within 10%, and this may be referred to as having substantially the same concentration. Specific regions include, for example, the surface layer, convex portions, concave portions, or the interior of the active material, and if the concentration of the element is substantially the same between the convex portion and the interior, the element is homogeneous in the convex portion and the interior. It can be said that it exists.
  • “segregation” refers to a phenomenon in which a certain element (for example, B) is spatially non-uniformly distributed in a solid consisting of multiple elements (for example, A, B, C), and a certain element ( For example, B) has a different concentration between a specific region and another specific region.
  • “Segregation” has the same meaning as uneven distribution, precipitation, non-uniformity, deviation, or a mixture of regions with high concentration and regions with low concentration.
  • particles used for active material particles and the like are not limited to referring only to spherical shapes (having a circular cross-sectional shape).
  • the particles include an elliptical cross-sectional shape, an asymmetrical shape, and the like, and the individual particles do not necessarily have to be uniform, but may have irregular shapes.
  • low freezing point refers to 0°C or lower
  • high temperature refers to 25°C or higher
  • room temperature refers to higher than 0°C and lower than 25°C.
  • temperature range from below freezing to high temperatures includes the above-mentioned room temperature.
  • nonaqueous electrolyte includes an organic solvent exhibiting carrier ion conductivity, and generally refers to a liquid, but is not limited to a liquid in the present invention. Therefore, in this specification and the like, the concept related to the nonaqueous electrolyte is referred to as "electrolyte.” That is, the electrolyte that is one aspect of the present invention is not limited to that state, and includes, for example, those whose viscosity has increased from a liquid state as a result of adjusting the viscosity. Further, the electrolyte includes solid or semi-solid forms. Semi-solid refers to a state intermediate between liquid and solid. Specific semi-solids include flexible solids, typically gels.
  • a semi-solid electrolyte may be generally referred to as a semi-solid electrolyte, and the electrolyte that is one embodiment of the present invention also includes a semi-solid electrolyte.
  • the above-mentioned liquid, solid, or semi-solid state or viscosity shall be confirmed when the lithium ion battery is placed at 25°C.
  • carbonate refers to a compound having at least one carbonate ester in its molecular structure, and includes “cyclic carbonate” and “chain carbonate” unless otherwise specified.
  • chain includes both linear and branched chains.
  • viscosity a value representing the magnitude of viscosity
  • appropriate viscosity refers to having a viscosity suitable for a lithium ion battery.
  • a full cell means a battery cell that is assembled so that different electrodes are located, such as a positive electrode/negative electrode unit cell.
  • a half cell means a battery cell assembled using lithium metal as a negative electrode (counter electrode).
  • FIG. 1A illustrates the configuration of a lithium ion battery 100.
  • the lithium ion battery 100 can be seen to have a negative electrode 106, a separator 108, and a positive electrode 107 in a cross-sectional view.
  • the electrolyte 109 is in a liquid state, and is present throughout the negative electrode 106, separator 108, and positive electrode 107. As described above, the electrolyte 109 is not limited to a liquid state.
  • the negative electrode 106 includes a negative electrode current collector 101 and a negative electrode active material layer 102.
  • the negative electrode active material layer 102 includes at least a negative electrode active material, and may include a conductive material and/or a binder.
  • a known material can be used as the negative electrode active material, and the details will be described later.
  • the positive electrode 107 includes a positive electrode current collector 105 and a positive electrode active material layer 104.
  • the positive electrode active material layer 104 includes at least a positive electrode active material, and may include a conductive material and/or a binder.
  • the positive electrode active material can withstand high voltage charging and can increase the discharge capacity of a lithium ion battery.
  • the positive electrode active material of one embodiment of the present invention will be described later.
  • the conductive material has a function of assisting the current path between the positive electrode active materials and/or between the positive electrode active material and the current collector. Further, the conductive material has a function of assisting the current path between the negative electrode active materials and/or between the negative electrode active material and the current collector.
  • a known material can be used as the conductive material, and the details will be described later.
  • the binder is also called a binding agent, and has a function of assisting in adhesion between positive electrode active materials and/or between a positive electrode active material and a current collector. Further, the binder has a function of assisting the adhesion between the negative electrode active materials and/or between the negative electrode active material and the current collector. A known material can be used for the binder, and the details will be described later.
  • FIG. 1B illustrates a lithium ion battery 100 that does not have a negative electrode active material layer 102, unlike FIG. 1A. Depending on the material of the negative electrode current collector 101, the negative electrode active material layer 102 can be made unnecessary. The rest of the configuration of the lithium ion battery 100 in FIG. 1B is the same as that of the lithium ion battery 100 in FIG. 1A, so a description thereof will be omitted.
  • a lithium ion battery having excellent discharging characteristics and/or excellent charging characteristics over a wide temperature range from below freezing to high temperatures. Especially at any temperature below freezing (e.g., 0°C or lower, -20°C or lower, preferably -30°C or lower, more preferably -40°C or lower, still more preferably -50°C or lower, even more preferably -60°C or lower).
  • a lithium ion battery having excellent discharge characteristics and/or excellent charging characteristics can be realized.
  • the explanation will focus on the configuration of the lithium ion battery required for this purpose. Specifically, the description will focus on the positive electrode active material and electrolyte. Details of the configuration other than the positive electrode active material and electrolyte of the lithium ion battery will be described in Embodiment 3 and thereafter.
  • the positive electrode active material has a function of taking in and/or releasing lithium ions, which are carrier ions, during charging and discharging.
  • the positive electrode active material used as an embodiment of the present invention is a material that can be charged and discharged at least at a high charging voltage (hereinafter also referred to as "high charging voltage") below freezing, and that is less likely to deteriorate due to charging and discharging (or has a low resistance).
  • high charging voltage refers to a charging voltage of, for example, 4.4V or higher, preferably 4.5V or higher, and more preferably 4.6V or higher.
  • the positive electrode active material is not limited to one type, but two or more types of materials with different median diameters (D50) may be mixed, as long as the material has little deterioration due to charging and discharging, at least at subzero temperatures and high charging voltages. Two or more materials having different values may be mixed.
  • “different composition” refers to cases where the composition of elements contained in the materials is different, as well as cases where the proportions of the elements contained are different even if the composition of the elements contained in the materials is the same. shall also be included.
  • high charging voltage is defined as 4.5 V or higher based on the potential when the negative electrode is made of lithium metal, but when the negative electrode is made of carbon material (for example, graphite),
  • a voltage of 4.4 V or higher is referred to as a "high charging voltage.”
  • a charging voltage of 4.5 V or more is called high charging voltage
  • a carbon material e.g. graphite
  • a charging voltage of .4V or higher is referred to as a high charging voltage.
  • the charging capacity and/or discharge capacity can be maintained even at temperatures below freezing.
  • Large lithium-ion batteries can be realized.
  • the value of charge capacity and/or discharge capacity at any temperature below freezing is 50% or more (preferably 60% or more, more preferably 70% or more, most preferably 80% or more).
  • the temperature during charging or discharging described in this specification, etc. refers to the temperature of the environment in which the lithium ion battery is placed (hereinafter sometimes referred to as "environmental temperature” in this specification, etc.). say.
  • environment temperature the temperature of the environment in which the lithium ion battery is placed
  • a constant temperature bath that is stable at a desired temperature is used, so the environmental temperature is equal to the temperature of the constant temperature bath.
  • the test cell to be measured e.g., full cell or half cell
  • wait for sufficient time e.g., 1 hour or more
  • the measurement of battery characteristics is not necessarily limited to this method.
  • the electrolyte used as an embodiment of the present invention can be used at any temperature below freezing (for example, 0°C, -20°C, preferably -30°C, more preferably -40°C, still more preferably -50°C or -60°C).
  • a material with excellent ionic conductivity can be used.
  • the electrolyte has an organic solvent
  • the organic solvent of the electrolyte that is one embodiment of the present invention is not limited to being liquid at 25°C, and may be solid at 25°C or semi-solid at 25°C. Good too.
  • the organic solvent of the electrolyte that is one aspect of the present invention may be heated at any temperature below freezing (for example, 0°C, -20°C, preferably -30°C, more preferably -40°C, still more preferably -50°C, or -60°C), but is not limited thereto.
  • the organic solvent of the electrolyte that is one aspect of the present invention may be liquid, solid, or semi-solid at any temperature below freezing.
  • the organic solvent described in this embodiment mode may include a fluorinated cyclic carbonate (sometimes referred to as a fluorinated cyclic carbonate) or a fluorinated chain carbonate (sometimes referred to as a fluorinated chain carbonate). Furthermore, it is preferable that the organic solvent contains both a fluorinated cyclic carbonate and a fluorinated chain carbonate. Both fluorinated cyclic carbonates and fluorinated linear carbonates have substituents that exhibit electron-withdrawing properties, and the solvation energy of lithium ions is lower than that of organic compounds that do not have substituents that exhibit electron-withdrawing properties. is low. Therefore, both the fluorinated cyclic carbonate and the fluorinated chain carbonate are suitable as organic solvents.
  • fluorinated cyclic carbonate examples include fluoroethylene carbonate (also referred to as fluorinated ethylene carbonate, fluoroethylene carbonate, FEC, and F1EC), difluoroethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3EC), or tetrafluoroethylene carbonate (F4EC). ) etc. can be used.
  • fluoroethylene carbonate also referred to as fluorinated ethylene carbonate, fluoroethylene carbonate, FEC, and F1EC
  • DFEC, F2EC difluoroethylene carbonate
  • F3EC trifluoroethylene carbonate
  • F4EC tetrafluoroethylene carbonate
  • the following structural formula (H10) is the structural formula of FEC.
  • the electron-withdrawing substituent is the F group.
  • fluorinated chain carbonate is methyl 3,3,3-trifluoropropionate.
  • the following structural formula (H22) is the structural formula of methyl 3,3,3-trifluoropropionate.
  • the abbreviation for methyl 3,3,3-trifluoropropionate is "MTFP".
  • MTFP the electron-withdrawing substituent is the CF3 group.
  • fluorinated chain carbonate is trifluoromethyl propionate.
  • the following structural formula (H24) is the structural formula of trifluoromethyl propionate.
  • the electron-withdrawing substituent is the CF3 group.
  • fluorinated chain carbonate is methyl 2,2-difluoropropionate.
  • the following structural formula (H25) is the structural formula of methyl 2,2-difluoropropionate.
  • the electron-withdrawing substituent is the CF2 group.
  • the organic solvent of the electrolyte that is one aspect of the present invention may preferably contain one or more selected from the above-mentioned fluorinated cyclic carbonates and one or more selected from the fluorinated chain carbonates.
  • the organic solvent described in this embodiment mode may include FEC and MTFP. Let me explain the reason.
  • FEC is one of the cyclic carbonates and has a high dielectric constant, so when used in an organic solvent, it has the effect of promoting the dissociation of lithium salt. Furthermore, since FEC has a substituent that exhibits electron-withdrawing properties, it is easily bonded to lithium ions by Coulomb force or the like. Specifically, FEC has a lower solvation energy than ethylene carbonate (abbreviated as "EC"), which does not have an electron-withdrawing substituent, so it can be said to easily generate solvation with lithium ions. .
  • EC ethylene carbonate
  • FEC is considered to have a deep highest occupied molecular orbital (HOMO) level, and the deeper the HOMO is, the less likely it is to be oxidized and the oxidation resistance will be improved.
  • FEC has a high viscosity, and when only FEC is used as an organic solvent, it is difficult to use it at sub-zero temperatures. Therefore, the organic solvent specifically explained as one aspect of the present invention further includes not only FEC but also MTFP.
  • MTFP is one of the chain carbonates and has the effect of lowering or maintaining the viscosity of the electrolyte.
  • MTFP also has a lower solvation energy than methyl propionate (abbreviated as "MP"), which does not have an electron-withdrawing substituent, so even if it may form a solvate with lithium ions, good.
  • MP methyl propionate
  • FEC and MTFP having such physical properties are prepared at a volume ratio of x:100-x (5 ⁇ x ⁇ 30, preferably 10 ⁇ x ⁇ 20, assuming that the total content of these two organic solvents is 100 vol%). It is best to mix and use them so that In the organic solvent, it is preferable to mix the organic solvents so that the amount of MTFP is larger than that of FEC. Note that the above volume ratio may be a volume ratio measured before mixing the organic solvent, and the outside air when mixing the organic solvent may be at room temperature (typically, 25 ° C.). . An organic solvent in which FEC and MTFP are mixed is preferable because it exhibits a viscosity that allows operation as a lithium ion battery and maintains an appropriate viscosity even at subzero temperatures.
  • the organic solvent that is one embodiment of the present invention contains a fluorinated cyclic carbonate and a fluorinated linear carbonate, it is possible to provide a lithium ion battery that can be charged and discharged over a wide temperature range including at least sub-zero temperatures. can.
  • the organic solvent mentioned above must be highly purified and have a low content of particulate waste or elements other than the constituent elements of the organic solvent (hereinafter also simply referred to as "impurities" and include water or moisture). is preferred.
  • the ratio of impurities to the organic solvent is preferably 1 mol% or less, preferably 0.1 mol% or less, more preferably 0.01 mol% or less.
  • lithium salt dissolved in the organic solvent examples include LiPF 6 , LiClO 4 , LiAsF 6 , LiBF 4 , LiAlCl 4 , LiSCN, LiBr, LiI, Li 2 SO 4 , Li 2 B 10 Cl 10 , Li 2 B 12 Cl 12 , LiCF3SO3 , LiC4F9SO3, LiC ( CF3SO2 ) 3 , LiC ( C2F5SO2 ) 3 , LiN ( CF3SO2 ) 2 , LiN ( C4F9SO 2 ) At least one of (CF 3 SO 2 ), LiN (C 2 F 5 SO 2 ) 2 , and lithium bis(oxalate)borate (LiBOB) can be used, and any combination of the above-mentioned lithium salts can be used. It may be used at a ratio of Although a lithium salt is one of the constituents of the electrolyte of one embodiment of the present invention, it does not necessarily have to be
  • additives may be mixed with the organic solvent in order to form a film at the interface between the active material and the electrolyte.
  • the additives include vinylene carbonate (VC), propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), SUN (suberonitrile) or succinonitrile or One or more dinitrile compounds selected from adiponitrile and dinitrile compounds may be used.
  • the concentration of the additive may be, for example, 0.1 wt% or more and 5 wt% or less based on the total organic solvent.
  • the additive is one of the components that the electrolyte of one embodiment of the present invention has, it does not necessarily have to be included. Furthermore, it is preferable to select a material for the additive that is different from that of the organic solvent.
  • the electrolyte that can be used in the lithium ion battery of one embodiment of the present invention has been described; however, the electrolyte that can be used in the lithium ion battery of one embodiment of the present invention is limited to this example. It is not something that will be done. Other materials can also be used as long as they have appropriate viscosity even at subzero temperatures and have excellent lithium ion conductivity.
  • a lithium ion battery according to one embodiment of the present invention includes at least the above-described positive electrode active material and an electrolyte, thereby realizing a lithium ion battery that can be charged and discharged over a wide temperature range including at least subzero temperatures.
  • a cathode active material that can be used for a lithium ion battery that is one embodiment of the present invention (hereinafter referred to as "a cathode active material that can be used as an embodiment of the present invention") is described using FIGS. 2A to 2C. ) and its manufacturing method will be explained.
  • any material can be used as the positive electrode active material that can be used in the lithium ion battery, which is one embodiment of the present invention, as long as it is less likely to deteriorate due to charging and discharging at a high charging voltage.
  • the positive electrode active material that can be used in the lithium ion battery disclosed in this specification etc. does not need to be interpreted as being limited to the specific materials described in this embodiment mode etc., and the high charging voltage ( For example, it is also possible to use a material known as a material that exhibits little deterioration due to charging and discharging even when the voltage is 4.5 V or higher.
  • a method for manufacturing a positive electrode active material that can be used as one embodiment of the present invention will be described below.
  • a positive electrode active material is manufactured using a solid phase method.
  • the lithium ion battery of the present invention can also be manufactured using a positive electrode active material using a coprecipitation method, a hydrothermal method, etc. in addition to the solid phase method. Active materials can be applied. Note that the flow used to explain the manufacturing method and the like in this embodiment indicates the order of elements connected by lines, and does not indicate the order of elements not connected by lines.
  • the transition metal M source it is preferable to use a compound having the transition metal M described above, and for example, an oxide of the metal exemplified as the transition metal M or a hydroxide of the metal exemplified above can be used.
  • an oxide of the metal exemplified as the transition metal M or a hydroxide of the metal exemplified above can be used.
  • a cobalt source cobalt oxide, cobalt hydroxide, etc.
  • a manganese source manganese oxide, manganese hydroxide, etc.
  • nickel source nickel oxide, nickel hydroxide, etc.
  • an aluminum source aluminum oxide, aluminum hydroxide, etc. can be used.
  • step S12 the Li source and the M source are mixed while being crushed to produce a mixed material.
  • the step of mixing while pulverizing can be performed in a dry or wet manner. If using a wet method, prepare a solvent.
  • the solvent ketones such as acetone, alcohols such as ethanol and isopropanol, ethers, dioxane, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used.
  • acetones acetone with a water content of 10 ppm or less and a purity of 99.5% or more is referred to as "dehydrated acetone," and it is preferable to use dehydrated acetone as a solvent.
  • step S13 shown in FIG. 2A the mixed material is heated.
  • the heating temperature is preferably 800°C or higher and 1100°C or lower, more preferably 900°C or higher and 1000°C or lower. If the temperature is too low, the decomposition and melting of the Li source, M source, etc. may become insufficient. On the other hand, if the temperature is too high, lithium may sublimate from the Li source and/or the transition metal used as the M source may be excessively reduced. If the heating time is too short, a composite oxide containing lithium and transition metal M will not be synthesized, but if the heating time is too long, productivity will decrease.
  • the heating time is preferably 1 hour or more and 100 hours or less, and preferably 2 hours or more and 20 hours or less.
  • the temperature increase rate depends on the temperature reached by the heating temperature, but is preferably 80° C./h or more and 250° C./h or less, more preferably 100° C./h or more and 250° C./h or less.
  • the heating atmosphere is preferably an atmosphere containing little water.
  • the atmosphere with a small amount of water can be defined using the dew point, and for example, the heating atmosphere may be an atmosphere with a dew point of -50°C or lower, more preferably a dew point of -80°C or lower.
  • an atmosphere containing oxygen such as dry air is preferable.
  • the flow rate of oxygen is preferably 5 L/min or more and 15 L/min or less. The state in which oxygen is continuously introduced into the reaction chamber and the oxygen is flowing within the reaction chamber is called "flow."
  • the heating atmosphere may be made into an oxygen-containing atmosphere, for example, by reducing the pressure in the reaction chamber, introducing oxygen, and then controlling the oxygen so that it does not enter or leave the reaction chamber.
  • This is called "purge.”
  • oxygen may be introduced to a pressure of 50 hPa, and the flow of oxygen in and out may be stopped. This state is sometimes referred to as filling the reaction chamber with oxygen.
  • Cooling after heating may be allowed to cool naturally, but it is preferable that the time for cooling from the specified temperature to room temperature falls within 10 hours or more and 50 hours or less. However, cooling to room temperature is not necessarily required, and cooling to a temperature permitted by the next step is sufficient.
  • the heating in this step may be performed using a rotary kiln or a roller hearth kiln.
  • a rotary kiln is a rotary firing device and is preferable because it can heat the raw materials while stirring them.
  • a roller hearth kiln is a baking device in which the raw material is conveyed by rollers, and is preferable because the raw material can continuously pass through a heating zone, a cooling zone, and the like.
  • a batch type baking device may be used for heating in this step.
  • the container in which the mixed materials are placed during heating should be made of heat-resistant materials such as aluminum oxide (referred to as alumina), mullite/cordierite, magnesia, zirconia, etc. It is preferable that it is made of a material with a high Further, during heating, it is preferable to place a lid on the crucible or sheath, and by placing the lid, sublimation of the raw materials etc. can be prevented.
  • alumina aluminum oxide
  • mullite/cordierite mullite/cordierite
  • magnesia magnesia
  • zirconia zirconia
  • the mixed material may be transferred from the crucible or pod to a mortar and then crushed and recovered.
  • the mortar is made of a material with high heat resistance such as alumina, mullite/cordierite, magnesia, zirconia, or the like. Note that the same heating conditions as in step S13 can be applied to heating steps other than step S13, which will be described later.
  • the recovered mixture may be agglomerated.
  • the recovered mixture may be crushed to break up the agglomerated state.
  • the recovered mixture may be sieved to further break up any agglomerations. Sieving may be performed after crushing, sieving may be performed while crushing, or only sieving may be performed in place of crushing.
  • a composite oxide (LiMO 2 ) containing lithium and transition metal M can be obtained in step S14 shown in FIG. 2A.
  • the composite oxide is represented by LiMO 2
  • the composite oxide may also be produced by a coprecipitation method.
  • the composite oxide may be produced by a hydrothermal method.
  • step S15 shown in FIG. 2A the composite oxide is heated. Since the complex oxide is heated for the first time, the heating in step S15 may be referred to as initial heating. Alternatively, since it is heated before step S20 described below, it may be called preheating or pretreatment.
  • the heating temperature in step S15 is more preferably 500°C or more and 1000°C or less, even more preferably 500°C or more and 950°C or less, and even more preferably 500°C or more and 900°C or less. Further, the temperature is preferably 700°C or more and 1000°C or less, 700°C or more and 950°C or less, and more preferably 700°C or more and 900°C or less. Further, the temperature is preferably 800°C or more and 1000°C or less, 800°C or more and 950°C or less, and more preferably 800°C or more and 900°C or less. Note that the heating temperature in step S15 is preferably lower than that in step S13.
  • lithium may be desorbed from a part of the composite oxide. Further, it can be expected to have the effect of increasing the crystallinity of the composite oxide. Further, although impurities may be mixed in the Li source and/or the M source prepared in step S11 etc., it is possible to reduce the impurities from the composite oxide by initial heating.
  • the initial heating has the effect of smoothing the surface of the composite oxide.
  • a smooth surface means that there are few irregularities, that the surface of the composite oxide is rounded overall, and that the corners are rounded. Also, a state in which there are few foreign substances attached to the surface is sometimes called smooth.
  • the heating conditions can be selected from the heating conditions explained in step S13.
  • the heating temperature in this step is preferably lower than the temperature in step S13 in order to maintain the crystal structure of the composite oxide.
  • the heating time in this step is preferably shorter than the time in step S13 in order to maintain the crystal structure of the composite oxide.
  • heating is preferably performed at a temperature of 700° C. or more and 1000° C. or less for 2 hours or more and 20 hours or less.
  • the effect of increasing the crystallinity of the composite oxide includes, for example, the effect of alleviating strain resulting from the difference in shrinkage caused by heating the composite oxide, the effect of alleviating the shift resulting from the difference in shrinkage, and the like.
  • a temperature difference may occur between the surface and the inside of the composite oxide due to the heating in step S13. Temperature differences may also induce differential shrinkage. It is also thought that the temperature difference causes a difference in shrinkage due to the difference in fluidity between the surface and the inside.
  • the energy associated with differential shrinkage imparts internal stress differentials to the composite oxide, which causes distortion.
  • the above energy is sometimes called strain energy. It is considered that the internal stress is removed by the initial heating in step S15, and in other words, the strain energy is reduced by the initial heating in step S15. As the strain energy decreases, the strain in the composite oxide is relaxed. Therefore, the surface of the composite oxide may become smooth after step S15. In other words, it is considered that after step S15, the shrinkage difference that occurs in the composite oxide is alleviated, and the surface of the composite oxide becomes smooth.
  • Step S15 may also be called tempering or annealing of the composite oxide.
  • the difference in shrinkage may cause micro-shifts in the composite oxide, such as shifts in crystal planes.
  • This step may also be carried out in order to reduce the deviation. Through this step, it is possible to reduce the deviation of the composite oxide. If the misalignment is made uniform, the surface of the composite oxide may become smooth. It is also said that crystal grains have been aligned. In other words, it is considered that after step S15, the displacement of crystals, etc. that occurs in the composite oxide is alleviated, and the surface of the composite oxide becomes smooth.
  • a state in which the surface of the composite oxide is smooth can be said to have a surface roughness of at least 10 nm or less when surface unevenness information is quantified from measurement data in one cross section of the composite oxide.
  • One cross section is a cross section obtained when observing with a scanning transmission electron microscope (abbreviated as STEM), for example.
  • step S14 a composite oxide containing lithium and transition metal M that has been synthesized in advance may be used. In this case, steps S11 to S13 can be omitted.
  • step S15 By performing step S15 on a composite oxide synthesized in advance, a composite oxide with a smooth surface can be obtained.
  • lithium in the composite oxide may be reduced due to initial heating. Due to the decrease in lithium, there is a possibility that the additive elements described in the next step S20_1 and the like may more easily enter the composite oxide. Furthermore, if the additive element is added to a composite oxide with a smooth surface, the additive element can be added evenly, so it is preferable to add the additive element after the initial heating. The step of adding an additive element will be explained using FIG. 2B.
  • step S20_1 Details of step S20_1 shown in FIG. 2A are shown in FIG. 2B.
  • step S21_1 of FIG. 2B an additive element A1 source (A1 source) to be added to the composite oxide is prepared.
  • A1 source an additive element A1 source to be added to the composite oxide.
  • a lithium source may be prepared together with the source of the additive element A1.
  • Additional elements A1 include nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic can be used.
  • the source of the additive element A1 can be called a magnesium source (Mg source).
  • Mg source magnesium fluoride, magnesium oxide, magnesium hydroxide, magnesium carbonate, or the like can be used. Further, a plurality of the above-mentioned magnesium sources may be used.
  • the source of the additive element A1 can be called a fluorine source (F source).
  • F source fluorine source
  • the fluorine source include lithium fluoride, magnesium fluoride, aluminum fluoride, titanium fluoride, cobalt fluoride, nickel fluoride, zirconium fluoride, vanadium fluoride, manganese fluoride, iron fluoride, and chromium fluoride.
  • niobium fluoride zinc fluoride, calcium fluoride, sodium fluoride, potassium fluoride, barium fluoride, cerium fluoride, lanthanum fluoride, or sodium aluminum hexafluoride.
  • lithium fluoride is preferable because it has a relatively low melting point of 848° C. and is easily melted in the heating step described below.
  • FIG. 2B shows an example in which an Mg source and an F source are used as the additive element A1 source.
  • Magnesium fluoride can be used both as a fluorine source and as a magnesium source. Lithium fluoride can also be used as a lithium source. Other lithium sources used in step S21_1 include lithium carbonate.
  • lithium fluoride is prepared as a fluorine source
  • magnesium fluoride is prepared as a fluorine source and a magnesium source.
  • the amount of magnesium added is preferably higher than 0.1 atomic % and 3 atomic % or less, and 0.5 atomic % or more and 2 atomic % or less, based on the number of Co atoms in LiMO 2 in step S14, typically LiCoO 2 .
  • the following is more preferable, and 0.5 atomic % or more and 1 atomic % or less is even more preferable. If the amount of magnesium added is 0.1 atomic % or less, the initial discharge capacity is high, but repeating high voltage charging may cause the discharge capacity to decrease rapidly.
  • step S22_1 shown in FIG. 2B the magnesium source and the fluorine source are mixed while being crushed.
  • This step can be carried out by selecting from the pulverization conditions and mixing conditions described in step S12.
  • step S23_1 shown in FIG. 2B the material crushed and mixed above can be recovered to obtain an additive element A1 source (A1 source).
  • the additive element A1 source shown in step S23_1 may include a plurality of raw materials such as an Mg source and an F source, and in this case, the A1 source can be called a mixture.
  • the particle size of the above mixture preferably has a median diameter (D50) of 600 nm or more and 20 ⁇ m or less, more preferably 1 ⁇ m or more and 10 ⁇ m or less. Even when one type of material is used as the source of additive element A1, the median diameter (D50) is preferably 600 nm or more and 20 ⁇ m or less, more preferably 1 ⁇ m or more and 10 ⁇ m or less.
  • the mixture when mixed with the composite oxide in a later step, the mixture will not adhere uniformly to the surface of the composite oxide. Easy to do. It is preferable that the mixture adheres uniformly to the surface of the composite oxide because it is easy to uniformly distribute or diffuse fluorine and/or magnesium in the surface layer of the composite oxide after heating.
  • the region in which fluorine and/or magnesium is distributed can also be called a surface layer portion. If there is a region in the surface layer that does not contain fluorine and/or magnesium, it may be difficult to form an O3' type crystal structure, which will be described later, in a charged state.
  • fluorine fluorine may also be chlorine, and can be read as halogen as a substance containing these.
  • step S31 shown in FIG. 2A the composite oxide and the additive element A1 source (A1 source) are mixed.
  • the mixing in step S31 is preferably performed under milder conditions than the pulverizing and mixing conditions in step S12 so as not to destroy the composite oxide.
  • the rotational speed is lower or the time is shorter than the mixing in step S12.
  • the dry method is more suitable than the wet method because the conditions are milder.
  • the above mixing is preferably performed in an atmosphere with a dew point of -100°C or more and -10°C or less.
  • mixing can take place in a dry room.
  • the atmosphere of the dry room preferably has dry air.
  • Step S32 of FIG. 2A the materials mixed above are collected to obtain a mixture 903.
  • the mixture 903 may be crushed to loosen the agglomerated state. Further, the mixture 903 may be sieved to loosen any agglomerates. Sieving may be performed after crushing, sieving may be performed while crushing, or only sieving may be performed in place of crushing.
  • a method of adding lithium fluoride as a fluorine source and magnesium fluoride as a magnesium source to a composite oxide that has undergone initial heating has been described, but the present invention is not limited to the above method.
  • a magnesium source, a fluorine source, etc. can be prepared together with a Li source and an M source, and then the process can proceed to step S12. Thereafter, LiMO 2 added with magnesium and fluorine can be obtained by heating in step S13.
  • a composite oxide to which magnesium and fluorine are added in advance may be used. If a composite oxide to which magnesium and fluorine are added is used, steps S11 to S32 and step S20_1 can be omitted. It can be said that this is a simple and highly productive method.
  • a magnesium source and a fluorine source may be further added in accordance with step S20_1 to the composite oxide to which magnesium and fluorine have been added in advance.
  • a nickel source and an aluminum source may be added instead of or in addition to the magnesium source and fluorine source.
  • Step S33 the mixture 903 is heated.
  • the heating conditions can be selected from the heating conditions explained in step S13.
  • the heating time is preferably 2 hours or more.
  • the lower limit of the heating temperature in step S33 needs to be equal to or higher than the temperature at which the reaction between the composite oxide (LiMO 2 ) and the additive element A1 source proceeds.
  • the temperature at which the reaction proceeds may be a temperature at which the elements of the composite oxide and the additive element A1 source can diffuse into each other, and may be lower than the melting temperature of these materials.
  • the heating temperature in step S33 may be 500° C. or higher.
  • the temperature is higher than the temperature at which at least a portion of the mixture 903 melts, the reaction will more easily proceed.
  • the eutectic point of LiF and MgF 2 is around 742°C, so the lower limit of the heating temperature in step S33 is preferably 742°C or higher.
  • a higher heating temperature is preferable because the reaction progresses more easily, heating time is shorter, and productivity is higher.
  • the upper limit of the heating temperature is lower than the decomposition temperature of the composite oxide.
  • the temperature is lower than the decomposition temperature of 1130°C.
  • the temperature is more preferably 1000°C or lower, even more preferably 950°C or lower, and even more preferably 920°C or lower.
  • the heating temperature in step S33 is preferably 500°C or more and less than 1130°C, more preferably 500°C or more and 1000°C or less, even more preferably 500°C or more and 950°C or less, and even more preferably 500°C or more and 920°C or less.
  • the temperature is preferably 500°C or more and 900°C or less.
  • the temperature is preferably 830°C or more and less than 1130°C, more preferably 830°C or more and less than 1000°C, even more preferably 830°C or more and less than 950°C, even more preferably 830°C or more and less than 920°C, and even more preferably 830°C or more and less than 900°C. .
  • the heating temperature in step S33 is preferably lower than that in step S13. This is to prevent the composite oxide (LiMO 2 ) from decomposing. Note that the heating temperature in step S33 is preferably higher than that in step S15.
  • the heating temperature can be lowered to below the decomposition temperature of the composite oxide (LiMO 2 ), for example from 742°C to 950°C, and by distributing additive elements A1 including magnesium in the surface layer, good properties can be achieved.
  • a positive electrode active material can be produced.
  • the mixture 903 in an atmosphere containing LiF, that is, to heat the mixture 903 in a state where the partial pressure of LiF in the processing chamber is high.
  • Such heating can suppress sublimation of LiF in the mixture 903.
  • sublimation of LiF in the mixture 903 can also be suppressed by placing a lid on the container as described above.
  • the mixture 903 it is preferable to heat the mixture 903 in this step so that the mixture 903 does not stick to each other. If the mixture 903 sticks to each other during heating, the contact area with oxygen in the atmosphere will be reduced and the diffusion path of the additive element A1 (e.g. magnesium and/or fluorine) will be inhibited. , and/or fluorine) may become difficult to diffuse.
  • the additive element A1 e.g. magnesium and/or fluorine
  • the heating time varies depending on conditions such as the heating temperature, the size of LiMO 2 in step S14, and the composition.
  • the median diameter (D50) of LiMO 2 is small, a lower temperature or a shorter time may be more preferable than when the median diameter (D50) is large.
  • the median diameter (D50) can be determined using a laser diffraction particle size distribution analyzer.
  • the heating temperature in step S33 is, for example, 800° C. or more and 920° C.
  • the temperature is preferably 850°C or higher and 920°C or lower, more preferably 850°C or higher and 920°C or lower.
  • the heating time in step S33 is, for example, more preferably 10 hours or more, even more preferably 20 hours or more, and may be 60 hours or more.
  • the median diameter (D50) When the median diameter (D50) is large, the volume of the composite oxide (LiMO 2 ) becomes large, and the internal stress is relaxed or removed in the bulk layer of the composite oxide. Heating time may be required. If the median diameter (D50) is large, it takes time for the additive element A1 including magnesium to be uniformly distributed in the surface layer, so the heating time may become longer as described above.
  • the median diameter (D50) of lithium cobalt oxide may increase through heat treatment, it is preferable that the median diameter (D50) satisfies 10 ⁇ m or more and 14 ⁇ m or less even after heat treatment. That is, it is preferable that the median diameter (D50) of the positive electrode active material satisfies 10 ⁇ m or more and 14 ⁇ m or less.
  • the heating temperature in step S33 is such that the median diameter (D50) is about 12 ⁇ m.
  • the heating time in step S33 can be shorter than the heating time when the median diameter (D50) is about 12 ⁇ m.
  • the time period is preferably 1 hour or more and 10 hours or less, more preferably 5 hours or more and 10 hours or less.
  • the median diameter (D50) When the median diameter (D50) is small, the time during which the additive element A1 including magnesium is distributed in the surface layer portion becomes short, so that the heating time can be shortened as described above. When the median diameter (D50) is small, the volume of the composite oxide (LiMO 2 ) is small, so the time required to temper or anneal the bulk layer of the composite oxide can be shortened.
  • the median diameter (D50) of lithium cobalt oxide may increase after heat treatment, it is preferable that the median diameter (D50) satisfies 5 ⁇ m or more and 9 ⁇ m or less even after heat treatment. That is, it is preferable that the median diameter (D50) of the positive electrode active material satisfies 5 ⁇ m or more and 9 ⁇ m or less.
  • step S33 it is preferable to provide a step of further adding an additive element different from the aforementioned additive element A1. This step will be explained using FIG. 2C.
  • step S20_2 Details of step S20_2 shown in FIG. 2A are shown in FIG. 2C.
  • step S21_2 of FIG. 2C an additive element A2 source (A2 source) to be added to the composite oxide is prepared.
  • a lithium source may be prepared together with the source of additive element A2.
  • Additional elements A2 include nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic can be used. Although it is preferable to use at least an element not selected as the additive element A1 as the additive element A2, the element selected as the additive element A1 may be included. Note that FIG. 2C shows an example in which a Ni source and an Al source are used as the additive element A2 source.
  • nickel hydroxide is prepared as a nickel source
  • aluminum hydroxide is prepared as an aluminum source.
  • Nickel oxide or nickel carbonate may be used instead of nickel hydroxide.
  • Aluminum oxide or aluminum carbonate may be used instead of aluminum hydroxide.
  • step S22_2 shown in FIG. 2C the nickel source is mixed while being crushed, and the aluminum source is further mixed while being crushed.
  • This step can be carried out by selecting from the pulverization conditions and mixing conditions described in step S12. Note that this step may be performed by combining the nickel source and the aluminum source as in step S22_1 in FIG. 2B, and then mixing them while pulverizing them.
  • a heating step may be performed after step S22_2 if necessary.
  • the heating step in this case can be carried out by selecting from the heating conditions explained in step S13.
  • Step S23_2 the material pulverized or mixed above can be recovered to obtain an additive element A2 source (A2 source).
  • A2 source additive element A2 source
  • step S34 shown in FIG. 2A the composite oxide heated in step S33 and an additive element A2 source (A2 source) are mixed.
  • A2 source an additive element A2 source
  • A2 sources a plurality of additive element A2 sources (A2 sources) may be prepared.
  • Step S35 of FIG. 2A the materials mixed above are collected to obtain a mixture 904.
  • the mixture 904 may be crushed to break up the agglomerated state.
  • the mixture 904 may be sieved to loosen the agglomerated state. Sieving may be performed after crushing, sieving may be performed while crushing, or only sieving may be performed in place of crushing.
  • Step S36 the mixture 904 is heated.
  • the heating conditions can be selected from the heating conditions explained in step S33.
  • the heating time is preferably 2 hours or more.
  • the heating temperature in step S36 is preferably 500°C or more and 1130°C or less, more preferably 500°C or more and 1000°C or less, even more preferably 500°C or more and 950°C or less, and even more preferably 500°C or more and 900°C or less.
  • the temperature is preferably 742°C or more and 1130°C or less, more preferably 742°C or more and 1000°C or less, even more preferably 742°C or more and 950°C or less, and even more preferably 742°C or more and 900°C or less.
  • the temperature is preferably 800°C or more and 1100°C or less, 830°C or more and 1130°C or less, more preferably 830°C or more and 1000°C or less, even more preferably 830°C or more and 950°C or less, and even more preferably 830°C or more and 900°C or less.
  • the heating temperature in step S36 is preferably lower than that in step S13.
  • the heating temperature in step S36 is preferably lower than that in step S33.
  • the mixture 904 it is preferable to heat the mixture 904 in this step so that the mixture 904 does not stick to each other. If the mixtures 904 stick to each other during heating, the contact area with oxygen in the atmosphere will be reduced and the diffusion path of the additive element A2 will be inhibited, which may deteriorate the distribution of the additive element A2.
  • step S37 shown in FIG. 2A the heated material is collected and crushed as necessary to obtain the positive electrode active material 10. At this time, it is preferable to further sieve the recovered positive electrode active material 10.
  • the positive electrode active material 10 of one embodiment of the present invention can be manufactured.
  • the positive electrode active material of one embodiment of the present invention has a smooth surface. The above is an example of a method for producing a positive electrode active material.
  • FIG. 3A shows a cross section of the positive electrode active material 10 in which the crystal grain boundaries 15 are clearly indicated by dashed lines.
  • the positive electrode active materials 10 shown in FIGS. 3A and 3B both have a surface layer 10a and an interior (the interior is referred to as a "bulk") 10b, and their boundaries are indicated by broken lines. Note that it is more preferable that the surface layer portion 10a covers 90% or more of the bulk portion 10b.
  • the broken line in the figure of FIG. 3A and FIG. 3B is an example
  • the dashed-dotted line in the figure of FIG. 3B is an example
  • the ratio of the covered surface layer part is also an example.
  • the grain boundaries 15 shown in FIG. 3B are, for example, areas where the positive electrode active materials 10 are fixed to each other, areas where the crystal orientation changes inside the positive electrode active materials 10, in other words, repeating bright lines and dark lines in a STEM image etc. are discontinuous. This refers to areas where the crystal structure is disordered, areas with many crystal defects, or areas where the crystal structure is disordered.
  • a crystal defect refers to a defect that can be observed in a cross-sectional TEM (transmission electron microscope) image, a cross-sectional STEM image, etc., and the defect can also be called a structure in which another element has entered between the lattices, or a cavity. In other words, the grain boundaries 15 can be said to be one of the planar defects.
  • the vicinity of the grain boundary 15 is a region within 20 nm, preferably within 10 nm, centered on the grain boundary 15, and the vicinity of the grain boundary exists both inside and outside the grain. These can be distinguished by indicating the vicinity of the grain boundary on the inside of the grain or the vicinity of the grain boundary on the outside of the grain.
  • the positive electrode active material 10 Since the positive electrode active material 10 has a composite oxide containing a transition metal and oxygen that can insert and extract lithium, it contains a transition metal M (such as Co, Ni, Mn, Fe, etc.) that oxidizes and reduces as lithium inserts and extracts. ) can be defined as the "surface" of the positive electrode active material. Additional elements may be present in regions where they are not present. A newly generated surface due to slips, cracks, and/or cracks may also be referred to as the surface of the positive electrode active material.
  • a transition metal M such as Co, Ni, Mn, Fe, etc.
  • the surface layer portion 10a is, for example, a region within 50 nm from the surface toward the inside, more preferably within 35 nm, still more preferably within 20 nm, and most preferably within 10 nm.
  • the surface layer portion may be referred to as near-surface, near-surface region, or shell.
  • the region within 50 nm, more preferably within 35 nm, still more preferably within 20 nm, and most preferably within 10 nm from the surface toward the inside refers to the distance in the depth direction along the perpendicular or substantially perpendicular direction from the surface.
  • Perpendicular or substantially perpendicular to the surface refers to a direction in which the angle formed with a tangent to the surface is 80° or more and 100° or less.
  • the bulk portion 10b refers to a region deeper than the surface layer portion 10a.
  • the bulk portion 10b may be referred to as the inside, and may also be referred to as the core.
  • the bulk portion 10b may include a central portion of the positive electrode active material.
  • the region where lithium is intercalated and deintercalated may be defined as the "surface". Therefore, the "surface” can be considered as the region of the positive electrode active material 10 that comes into contact with the electrolyte.
  • the surface of the positive electrode active material 10 includes the surface of the surface layer portion 10a, and in a region where the bulk portion 10b is exposed, the bulk portion 10b may be the surface.
  • carbonate groups, hydroxyl groups, etc. chemically adsorbed after production are considered to be regions in which lithium cannot be intercalated and desorbed, and these do not constitute the surface of the positive electrode active material 10 .
  • the electrolyte, binder, conductive material, or compound derived from these adhered to the positive electrode active material 10 does not constitute the surface of the positive electrode active material 10 .
  • the positive electrode active material must contain a transition metal capable of redox in order to maintain charge neutrality even when lithium ions are intercalated and deintercalated.
  • the positive electrode active material 10 of one embodiment of the present invention mainly uses cobalt as the transition metal M responsible for the redox reaction, but in addition to cobalt, at least one or more selected from nickel and manganese may be used.
  • cobalt is 75 at % or more, preferably 90 at % or more, and more preferably 95 at % or more of the transition metal M included in the positive electrode active material 10, it is relatively easy to synthesize, easy to handle, and has excellent cycle characteristics. It is preferable because it has many advantages.
  • the raw material may be cheaper than when the amount of cobalt is large. , and the discharge capacity per weight may increase, which is preferable.
  • additive elements A included in the positive electrode active material 10 are listed again, and include nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, and chromium. It is preferable to use one or more selected from , niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic.
  • the positive electrode active material 10 can be called lithium cobalt oxide to which the additive element A is added.
  • the additive element A can further stabilize the crystal structure of the positive electrode active material 10.
  • additive elements A do not necessarily include nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, and boron. , and arsenic.
  • FIGS. 4 to 8 changes in the crystal structure due to changes in x in LixCoO 2 will be explained while comparing the cathode active material 10 that can be used as an embodiment of the present invention with a conventional cathode active material.
  • the crystal structure of a positive electrode active material 10 that can be used as one embodiment of the present invention is shown in FIG. 4, and the crystal structure of a conventional positive electrode active material is shown in FIG.
  • the conventional positive electrode active material shown in FIG. 5 is lithium cobalt oxide (LiCoO 2 ) without any particular additive element.
  • this crystal structure lithium occupies octahedral sites, and three CoO 2 layers exist in the unit cell. Therefore, this crystal structure is sometimes called an O3 type crystal structure.
  • the CoO 2 layer refers to a structure in which an octahedral structure in which six oxygen atoms are coordinated with cobalt is continuous in a plane in a shared edge state.
  • the CoO 2 layer is sometimes referred to as a layer consisting of an octahedron of cobalt and oxygen.
  • R-3m(O3) is attached to the crystal structure when x in Li x CoO 2 is 1.
  • the crystal structure when x in Li x CoO 2 is 1 is the same as the crystal structure shown in FIG. 4, and is similarly designated by R-3m(O3).
  • Layered rock salt type composite oxides have high discharge capacity, have two-dimensional lithium ion diffusion paths, are suitable for lithium ion insertion/extraction reactions, and are excellent as positive electrode active materials for lithium ion batteries. Therefore, it is preferable that the bulk portion 10b, which occupies most of the positive electrode active material 10, has a layered rock salt type crystal structure.
  • the crystal structure of the surface layer portion 10a of the positive electrode active material 10 that can be used as one embodiment of the present invention does not have to be a layered rock salt type. It is preferable that the surface layer portion 10a has a function of reinforcing the layered structure of the bulk portion 10b, which is composed of octahedrons of cobalt and oxygen, so that it does not break even if lithium is removed from the positive electrode active material 10 due to charging. Alternatively, it is preferable that the surface layer portion 10a functions as a barrier film for the positive electrode active material 10. Alternatively, it is preferable that the surface layer portion 10a, which is the outer peripheral portion of the positive electrode active material 10, reinforces the positive electrode active material 10.
  • Reinforcement here refers to suppressing structural changes in the surface layer portion 10a and bulk portion 10b of the positive electrode active material 10, including desorption of oxygen, and/or suppressing oxidative decomposition of the electrolyte on the surface of the positive electrode active material 10. It means to suppress something.
  • the surface layer portion 10a is a region where lithium ions are first desorbed during charging, and is a region where the lithium concentration tends to be lower than that of the bulk portion 10b. Further, when the lithium ions are detached from the atoms on the surface of the positive electrode active material 10 that the surface layer portion 10a has, some of the bonds are broken. Therefore, the surface layer portion 10a is likely to become unstable and can be said to be a region where changes in the crystal structure, that is, deterioration is likely to occur.
  • the surface layer part 10a can be made sufficiently stable, the layered structure of the two CoO layers in the bulk part 10b can be made difficult to break even when x in Li x CoO 2 is small, for example, when x is 0.24 or less. . Furthermore, displacement of the CoO 2 layer in the bulk portion 10b can be suppressed.
  • the surface layer portion 10a preferably contains an additive element A, and more preferably contains a plurality of additive elements A. Further, it is preferable that the concentration of one or more of the additive elements A is higher in the surface layer portion 10a than in the bulk portion 10b. Moreover, it is preferable that one or more selected from the additive elements A included in the positive electrode active material 10 have a concentration gradient. Moreover, it is more preferable that the distribution of the positive electrode active material 10 differs depending on the additive element A. For example, it is more preferable that the depth of the concentration peak from the surface differs depending on the additive element A. The concentration peak here refers to the maximum value of the concentration in the surface layer portion 10a or 50 nm or less from the surface.
  • FIGS. 3C and 3D show enlarged views of the area around AB in FIG. 3A.
  • 3C and 3D are cross-sectional views of a surface layer having a (001) plane (hereinafter referred to as (001) plane, sometimes referred to as c-plane or basal plane), that is, a cross-sectional view of a region oriented in (001). It can be said.
  • a layered rock salt crystal structure cations are arranged parallel to the (001) plane.
  • This can be said to be a structure in which two CoO layers and a lithium layer are alternately stacked parallel to the (001) plane. Therefore, the diffusion path of lithium ions exists parallel to the (001) plane. Since the CoO 2 layer is relatively stable, the (001) plane on which the CoO 2 layer exists is relatively stable, and the main diffusion route of lithium ions during charging and discharging is not exposed on the (001) plane. Not yet.
  • FIG. 3C showing such a (001) plane shows the distribution of magnesium and the like as an example of the additive element A.
  • the shading in FIG. 3C corresponds to the change in magnesium concentration. Since the CoO 2 layer on the (001) plane is relatively stable, the additive element A may not be detected.
  • the additive element A is present at the highest concentration at or near the surface of the surface layer portion 10a, and the concentration of the additive element A decreases toward the bulk portion 10b.
  • concentration peak of magnesium, etc. at the position showing the highest concentration.
  • the manner in which the concentration decreases is sometimes referred to as a concentration gradient. Note that in this specification and the like, the additive element A exhibiting a distribution as shown in FIG. 3C on the (001) plane will be referred to as the additive element X.
  • a distribution like that of the additive element X or a distribution like that of the additive element Y may be shown, and the distributions may be different from each other.
  • a concentration peak position like that of the additive element X or a concentration peak position like that of the additive element Y may be shown, and the concentration peak positions may be different from each other.
  • FIGS. 3E and 3F show enlarged views of the area around CD in FIG. 3A.
  • Figures 3E and 3F can be said to be cross-sectional views of the surface layer having planes other than the (001) plane (hereinafter sometimes referred to as a-b planes or edge planes), and the planes other than the (001) plane are of the layered rock salt type. In the crystal structure, this is the surface where the diffusion path for lithium ions exists.
  • FIG. 3E which shows planes other than the (001) plane, shows the distribution of magnesium and the like as an example of the additive element X.
  • the concentration of the additive element X may be higher in planes other than the (001) plane in FIG. 3E.
  • the concentration peak of magnesium or the like may be located at or near the surface of the surface layer portion 10a, and may exhibit a higher intensity than the concentration peak on the (001) plane in FIG. 3C.
  • the additive element X may be distributed over a wide range other than the (001) plane in FIG. 3E.
  • FIG. 3F shows the distribution of aluminum and the like as an example of the additive element Y.
  • the concentration peak of aluminum is preferably located in a region of 5 nm or more and 50 nm or less from the surface toward the inside, whether on the (001) plane in FIG. 3D or on a plane other than the (001) plane in FIG. 3F.
  • the aluminum concentration peak may be deeper on planes other than the (001) plane in FIG. 3F than on the (001) plane in FIG. 3D.
  • the distribution of additive elements may vary depending on the plane direction of the positive electrode active material.
  • the lithium ion diffusion path exists on surfaces other than the (001) plane, and the lithium ion diffusion path is exposed on surfaces other than the (001) plane. Therefore, as shown in FIGS. 3E and 3F, the surface layer 10a corresponding to the plane other than the (001) plane is an important area for maintaining the diffusion path of lithium ions, and at the same time is the area where lithium ions are first desorbed. Because it is a region where Therefore, in order to maintain the crystal structure of the entire positive electrode active material 10, it is preferable to reinforce planes other than the (001) plane and the corresponding surface layer portion 10a preferentially. That is, it is preferable that the additive element A is preferentially present in planes other than the (001) plane and in the surface layer portion 10a corresponding thereto.
  • the manufacturing method is to mix an additive element into LiCoO 2 formed through initial heating and heat it, the additive element spreads through the diffusion path of lithium ions. Therefore, the distribution of the additive elements in the plane other than (001) and the surface layer 10a corresponding to the plane as shown in FIGS. 3C and 3D can be easily set within a preferable range.
  • the surface of the positive electrode active material 10 is preferably smooth and has few irregularities, the entire surface of the positive electrode active material 10 does not necessarily have to be smooth.
  • the positive electrode active material 10 may have unevenness due to slip occurring on a plane parallel to the (001) plane, for example, a plane on which lithium is arranged. Slip is also called stacking fault.
  • pressing is performed when producing a positive electrode, and LiCoO 2 may be deformed along the lattice pattern direction (ab-plane direction) due to the pressing, and this deformation is also included in slip.
  • the deformation includes shifting the checkered stripes back and forth. When the checkered stripes are shifted back and forth, a step is created on the surface in the direction perpendicular to the checkered stripes (c-axis direction).
  • the surface resulting from slipping and its surface layer 10a are often (001) planes, and the surface layer 10a corresponding to the (001) plane may be free of additive elements or may be below the detection limit.
  • the diffusion path of lithium ions is not exposed on the (001) plane and it is relatively stable, so there is almost no problem even if the additive element is not present or is below the detection limit.
  • Magnesium which is one of the additive elements X, is divalent, and since magnesium ions are more stable in lithium sites than in cobalt sites in a layered rock salt crystal structure, they easily enter the lithium sites.
  • the presence of magnesium at an appropriate concentration in the lithium sites of the surface layer 10a facilitates reinforcing the layered rock salt crystal structure of the bulk portion 10b and the like. This is presumed to be because the magnesium present at the lithium site functions as a pillar that supports the two CoO layers.
  • the presence of magnesium can suppress desorption of oxygen around magnesium in a state where x in Li x CoO 2 (described later) is, for example, 0.24 or less.
  • the presence of magnesium can be expected to increase the density of the positive electrode active material 10. Furthermore, if the magnesium concentration in the surface layer portion 10a is high, it can be expected that corrosion resistance against hydrofluoric acid produced by decomposition of the electrolytic solution will be improved.
  • magnesium is at an appropriate concentration, it will not have a negative effect on the insertion and desorption of lithium during charging and discharging, and the above advantages can be enjoyed.
  • magnesium is in excess, there is a possibility that intercalation and deintercalation of lithium will be adversely affected.
  • the effect on stabilizing the crystal structure may be reduced. This is thought to be because magnesium enters the cobalt site in addition to the lithium site.
  • unnecessary magnesium compounds oxides, fluorides, etc.
  • the discharge capacity of the positive electrode active material may decrease. This is thought to be because too much magnesium enters the lithium site, reducing the amount of lithium that contributes to charging and discharging.
  • the entire positive electrode active material 10 has an appropriate amount of magnesium.
  • the number of magnesium atoms is preferably 0.001 to 0.1 times the number of cobalt atoms, more preferably more than 0.01 times and less than 0.04 times, and even more preferably about 0.02 times.
  • the amount of magnesium contained in the entire cathode active material 10 herein refers to the amount of magnesium that the entire cathode active material 10 has, for example, by using GD-MS (glow discharge mass spectrometry), ICP-MS (inductively coupled plasma mass spectrometry), etc. It may be a value obtained by elemental analysis of the entire active material 10, or it may be a value based on the blending of raw materials in the process of producing the positive electrode active material 10.
  • nickel which is one of the additive elements X, can exist at both the cobalt site and the lithium site.
  • the redox potential becomes lower than that of cobalt, which is preferable because it leads to an increase in discharge capacity.
  • the entire positive electrode active material 10 has an appropriate amount of nickel.
  • the number of nickel atoms in the positive electrode active material 10 is preferably higher than 0% and less than 7.5% of the number of cobalt atoms, preferably 0.05% or more and 4% or less, and 0.1% or more and 2% or less. It is preferably 0.2% or more and 1% or less. Alternatively, it is preferably higher than 0% and 4% or less. Alternatively, it is preferably higher than 0% and 2% or less. Or preferably 0.05% or more and less than 7.5%. Or preferably 0.05% or more and 2% or less. Or preferably 0.1% or more and less than 7.5%. Or preferably 0.1% or more and 4% or less.
  • the amount of nickel shown here may be a value obtained by elemental analysis of the entire positive electrode active material using, for example, GD-MS, ICP-MS, etc., or a value obtained by mixing raw materials in the process of producing the positive electrode active material. may be based on the value of
  • aluminum which is one of the additive elements Y, may exist in cobalt sites in a layered rock salt crystal structure.
  • Aluminum is a typical trivalent element and its valence does not change, so lithium around aluminum is difficult to move during charging and discharging. Therefore, aluminum and the lithium surrounding it function as pillars and can suppress changes in the crystal structure. Additionally, aluminum has the effect of suppressing the elution of surrounding cobalt and improving continuous charging resistance. Furthermore, since the Al--O bond is stronger than the Co--O bond, desorption of oxygen around aluminum can be suppressed. These effects improve thermal stability. Therefore, safety can be improved when a positive electrode active material containing aluminum as an additive element is used in a lithium ion battery. In addition, the positive electrode active material 10 can have a crystal structure that does not easily collapse even after repeated charging and discharging.
  • aluminum which is one of the additive elements Y
  • the peak concentration of aluminum is in a region deeper than the peak concentration of the additive element X.
  • the entire positive electrode active material 10 has an appropriate amount of aluminum.
  • the number of aluminum atoms contained in the entire positive electrode active material 10 is preferably 0.05% or more and 4% or less, preferably 0.1% or more and 2% or less, and 0.3% or more and 1.5% or less of the number of cobalt atoms. % or less is more preferable. Or preferably 0.05% or more and 2% or less. Or preferably 0.1% or more and 4% or less.
  • the amount that the entire positive electrode active material 10 has here may be, for example, a value obtained by elemental analysis of the entire positive electrode active material 10 using GD-MS, ICP-MS, etc. It may also be based on the value of the blending of raw materials in the process of manufacturing No. 10.
  • fluorine which is one of the additive elements X
  • fluorine is a monovalent anion
  • fluorine in the surface layer portion 10a when a part of oxygen is replaced with fluorine in the surface layer portion 10a, the lithium desorption energy becomes small.
  • the valence of cobalt ions changes from trivalent to tetravalent when fluorine is not present, and from divalent to trivalent when fluorine is present, resulting in a difference in redox potential. Therefore, if part of the oxygen in the surface layer 10a of the positive electrode active material 10 is replaced with fluorine, it can be said that desorption and insertion of lithium ions near fluorine tend to occur smoothly. Therefore, when used in a lithium ion battery, charging/discharging characteristics, large current characteristics, etc. can be improved.
  • a fluxing agent also called a fluxing agent
  • the surface layer portion 10a contains both magnesium and nickel, there is a possibility that divalent magnesium can exist more stably near divalent nickel. Therefore, elution of magnesium can be suppressed even when x in Li x CoO 2 is small. Therefore, it can contribute to stabilization of the surface layer portion 10a.
  • additive element X and additive element Y it is preferable to have additional elements having different distributions, such as additive element X and additive element Y, because the crystal structure can be stabilized over a wider region.
  • additional elements having different distributions such as additive element X and additive element Y
  • the crystal structure in a wider area is stabilized than when it has only one of the additive element X and the additive element Y. can be converted into In this way, when the positive electrode active material 10 has both the additive element X and the additive element Y, the additive element do not have.
  • each additive element can be synergized and contribute to further stabilization of the surface layer portion 10a.
  • magnesium, nickel, and aluminum are highly effective in providing a stable composition and crystal structure, and are therefore preferable.
  • the surface layer portion 10a is occupied only by the compound of the additive element and oxygen, it is not preferable because it becomes difficult to insert and extract lithium.
  • the surface layer portion 10a is occupied only by MgO, a structure in which MgO and NiO(II) are dissolved in solid solution, and/or a structure in which MgO and CoO(II) are dissolved in solid solution. Therefore, it is preferable that the surface layer portion 10a contains at least cobalt, and also contains lithium in the discharge state, so that a path for inserting and extracting lithium is ensured.
  • the surface layer portion 10a has a higher concentration of cobalt than magnesium. Further, it is preferable that the surface layer portion 10a has a higher concentration of cobalt than nickel. Further, it is preferable that the surface layer portion 10a has a higher concentration of cobalt than aluminum. Further, it is preferable that the surface layer portion 10a has a higher concentration of cobalt than fluorine.
  • the surface layer portion 10a has a higher concentration of magnesium than nickel.
  • some of the additive elements particularly magnesium and nickel, have a higher concentration in the surface layer part 10a than in the bulk part 10b, and it is preferable that they also exist randomly and dilutely in the bulk part 10b.
  • aluminum which is a part of the additive element, also exists randomly and sparsely in the bulk portion 10b.
  • magnesium and aluminum are present at appropriate concentrations in the lithium sites of the bulk portion 10b, there is an effect that the layered rock salt type crystal structure can be easily maintained as described above.
  • nickel is present in the bulk portion 10b at an appropriate concentration, displacement of the layered structure consisting of octahedrons of cobalt and oxygen can be suppressed, as described above.
  • magnesium and nickel are contained together, a synergistic effect of suppressing the elution of magnesium can be expected as described above.
  • the crystal structure of the lithium cobalt oxide changes continuously from the bulk portion 10b toward the surface layer portion 10a due to the concentration gradient of the additive element.
  • the surface layer portion 10a preferably has a composition and crystal structure that are more stable at room temperature (25° C.) than the bulk portion 10b.
  • at least a portion of the surface layer portion 10a of the positive electrode active material 10 that can be used as an embodiment of the present invention has a rock salt crystal structure.
  • the surface layer portion 10a preferably has both a layered rock salt type crystal structure and a rock salt type crystal structure.
  • the surface layer portion 10a preferably has characteristics of both a layered rock salt type and a rock salt type crystal structure.
  • the crystal orientations of the surface layer portion 10a and the bulk portion 10b are approximately the same.
  • the surface layer portion 10a and the bulk portion 10b are topotaxy.
  • topotoxy means having three-dimensional structural similarity such that the crystal orientations roughly match, or having the same crystallographic orientation.
  • epitaxy refers to structural similarity of two-dimensional interfaces.
  • a pit refers to a hole formed as a defect progresses in a positive electrode active material.
  • the positive electrode active material 10 that can be used as an embodiment of the present invention has the above-mentioned distribution of additive elements and/or crystal structure, so that the positive electrode active material 10 is in a charged state, that is, a state in which x in Li x CoO 2 is small.
  • the crystal structure of this material is different from that of conventional positive electrode active materials.
  • "x is small” means 0.1 ⁇ x ⁇ 0.24.
  • P2/m monoclinic O1
  • lithium cobalt oxide has a trigonal space group P-3m1 crystal structure as shown in Figure 5, and the CoO 2 layer is in the unit cell. There is one layer. Therefore, this crystal structure is sometimes called trigonal O1 type or O1 type. In addition, the trigonal crystal is sometimes converted into a complex hexagonal lattice and is called the hexagonal O1 type.
  • P-3m1 trigonal O1
  • This structure can be said to be a structure in which a CoO 2 structure like trigonal O1 type and a LiCoO 2 structure like R-3m(O3) are alternately stacked. Therefore, this crystal structure is sometimes called an H1-3 type crystal structure.
  • the H1-3 type crystal structure has twice the number of cobalt atoms per unit cell as other structures.
  • the c-axis of the H1-3 type crystal structure is shown as 1/2 of the unit cell in order to facilitate comparison with other crystal structures.
  • the H1-3 type crystal structure has the coordinates of cobalt and oxygen in the unit cell as Co(0, 0, 0.42150 ⁇ 0.00016), O1(0, 0, 0.27671 ⁇ 0.00045), O2( 0, 0, 0.11535 ⁇ 0.00045).
  • O1 and O2 are each oxygen atoms.
  • Which unit cell should be used to represent a certain crystal structure can be determined, for example, by Rietveld analysis using X-ray diffraction (referred to as XRD). In the Rietveld analysis, a unit cell with a small value of GOF (goodness of fit) may be adopted.
  • the two crystal structures that cause dynamic structural changes also have a large difference in volume.
  • the difference in volume between the H1-3 type crystal structure and the R-3m(O3) type crystal structure in the discharge state is higher than 3.5%, typically 3.9% or more. It is.
  • the positive electrode active material 10 that can be used as one embodiment of the present invention shown in FIG .
  • the positive electrode active material 10 can reduce the deviation of the CoO 2 layer between the state where x is 1 and the state where x is 0.24 or less.
  • the positive electrode active material 10 can reduce the change in volume when compared per cobalt atom. Therefore, even if the cathode active material 10 is repeatedly charged and discharged such that x becomes 0.24 or less, the crystal structure does not easily collapse, and excellent cycle characteristics can be achieved.
  • the positive electrode active material 10 can have a more stable crystal structure than conventional positive electrode active materials when x in Li x CoO 2 is 0.24 or less. Therefore, in the positive electrode active material 10, when x in Li x CoO 2 is maintained at 0.24 or less, short circuits are less likely to occur, thereby improving the safety of the lithium ion battery.
  • x is approximately 0.2, it can be expressed as, for example, 0.18 ⁇ x ⁇ 0.24, typically 0.18 ⁇ x ⁇ 0.22.
  • the crystal structure of the O3' type has the coordinates of cobalt and oxygen in the unit cell within the range of Co(0,0,0.5), O(0,0,x), 0.20 ⁇ x ⁇ 0.25. It can be shown as
  • the positive electrode active material 10 has a crystal structure belonging to the monoclinic space group P2/m. This means that two layers of CoO exist in the unit cell. Therefore, in this specification and the like, this crystal structure will be referred to as a "monoclinic O1 (15) type crystal structure.”
  • P2/m monoclinic O1(15)
  • x is approximately 0.15, it can be expressed as, for example, 0.13 ⁇ x ⁇ 0.24, typically 0.13 ⁇ x ⁇ 0.18.
  • the monoclinic O1 (15) type crystal structure has the coordinates of cobalt and oxygen in the unit cell as Co1 (0.5, 0, 0.5), Co2 (0, 0.5, 0.5), O1 (X O1 ,0, Z O1 ), 0.23 ⁇ X O1 ⁇ 0.24, 0.61 ⁇ Z O1 ⁇ 0.65, O2 (X O2 ,0.5, Z O2 ), 0.75 ⁇ X It can be shown within the range of O2 ⁇ 0.78, 0.68 ⁇ Z O2 ⁇ 0.71.
  • c 0.484 ⁇ 0.001 (nm). ).
  • this crystal structure can also be fitted to the space group R-3m if a certain amount of error is allowed.
  • the coordinates of cobalt oxygen in the unit cell in this case are shown within the range of Co(0,0,0.5), O(0,0,Z O ), 0.21 ⁇ Z O ⁇ 0.23. be able to.
  • ions such as cobalt, nickel, and magnesium occupy six oxygen coordination positions. Note that a light element such as lithium may occupy a 4-coordination position of oxygen.
  • the difference in volume per same number of cobalt atoms between R-3m(O3) in the discharge state and the O3' type crystal structure is 2.5% or less, more specifically 2.2% or less, typically 1 .8%.
  • the difference in volume per the same number of cobalt atoms between R-3m(O3) in the discharge state and monoclinic O1(15) type crystal structure is less than 3.3%, more specifically less than 3.0%, typical Specifically, it is 2.5%.
  • the positive electrode active material 10 changes in the crystal structure when x in Li x CoO 2 is small, that is, when a large amount of lithium is released, are suppressed more than in conventional positive electrode active materials.
  • changes in volume are also suppressed when comparing the same number of cobalt atoms. Therefore, it can be seen that the crystal structure of the positive electrode active material 10 does not easily collapse even after repeated charging and discharging such that x becomes 0.24 or less, and a decrease in charge/discharge capacity during charge/discharge cycles is suppressed.
  • the positive electrode active material 10 since more lithium can be stably utilized than conventional positive electrode active materials, the positive electrode active material 10 has a large discharge capacity per weight and per volume. Therefore, by using the positive electrode active material 10, a lithium ion battery with high discharge capacity per weight and per volume can be manufactured.
  • the positive electrode active material 10 may have an O3' type crystal structure when x in Li x CoO 2 is 0.15 or more and 0.24 or less, and when x is higher than 0.24. It is estimated that it has an O3' type crystal structure even when it is 0.27 or less.
  • the positive electrode active material 10 is monoclinic O1 (15) type when x in Li x CoO 2 is higher than 0.1 and lower than 0.2, typically when x is 0.13 or higher and 0.18 or lower. It has been confirmed that it may have a crystalline structure.
  • the crystal structure is influenced not only by x in Li x CoO 2 but also by the number of charge/discharge cycles, charge/discharge current, temperature, electrolyte, etc., it is not necessarily limited to the above range of x.
  • the positive electrode active material 10 may have only an O3' type crystal structure, or may have a monoclinic O1 (15) type crystal structure. It may have only one crystal structure, or it may have both crystal structures. Furthermore, the entire bulk portion 10b of the positive electrode active material 10 does not have to have an O3' type and/or a monoclinic O1 (15) type crystal structure. It may contain other crystal structures, or may be partially amorphous.
  • the state in which x in Li x CoO 2 is small can be rephrased as a state in which the battery is charged at a high charging voltage.
  • the positive electrode active material 10 is preferable because it can maintain the R-3m(O3) crystal structure even when charged at a high charging voltage, for example, at a voltage of 4.6 V or higher at 25°C.
  • the positive electrode active material 10 is preferable because it can take an O3' type crystal structure when charged at a higher charging voltage, for example, at a voltage of 4.65 V or more and 4.7 V or less at 25° C.
  • the positive electrode active material 10 is preferable because it can assume a monoclinic O1 (15) type crystal structure when charged at a higher charging voltage, for example, at a voltage higher than 4.7V and lower than 4.8V at 25°C. be able to.
  • the crystal structure is affected by the number of charge/discharge cycles, charge/discharge current, electrolyte, etc., so when the charging voltage is lower, for example, even if the charging voltage is 4.5 V or more and less than 4.6 V at 25°C, the The positive electrode active material 10 that can be used as one embodiment of the invention may have an O3' type crystal structure. Similarly, when charged at a voltage of 4.65 V or more and 4.7 V or less at 25° C., a monoclinic O1 (15) type crystal structure may be obtained.
  • the voltage of the lithium ion battery is lowered by the potential of graphite than the above.
  • the potential of graphite is about 0.01V to 0.7V based on the potential of lithium metal. Therefore, in the case of a lithium ion battery that uses graphite as the negative electrode active material, it has a similar crystal structure when the voltage obtained by subtracting the potential of graphite from the above voltage is applied.
  • lithium is shown to exist at all lithium sites with equal probability, but the present invention is not limited to this. It may be present unevenly at some lithium sites.
  • the distribution of lithium can be analyzed, for example, by neutron diffraction.
  • the O3' type crystal structure and the monoclinic O1 (15) type crystal structure are similar to the CdCl 2 type crystal structure, although they have lithium randomly between the layers.
  • This crystal structure similar to CdCl type 2 is close to the crystal structure when lithium nickelate is charged to Li 0.06 NiO 2 , but pure lithium cobalt oxide or a layered rock salt type positive electrode active material containing a large amount of cobalt is It is known that CdCl does not normally have a type 2 crystal structure.
  • the concentration gradient of the additive element be the same at a plurality of locations in the surface layer portion 10a of the positive electrode active material 10.
  • the reinforcement derived from the additive element exists homogeneously in the surface layer portion 10a. Even if a portion of the surface layer 10a is reinforced, if there is a portion without reinforcement, stress may be concentrated on the portion without reinforcement. When stress concentrates on a portion of the positive electrode active material 10, defects such as cracks may occur there, leading to cracks in the positive electrode active material and a decrease in discharge capacity.
  • the additive elements do not necessarily have to have the same concentration gradient in all the surface layer portions 10a of the positive electrode active material 10.
  • the additive elements included in the positive electrode active material 10 that can be used as an embodiment of the present invention are at least partially unevenly distributed in and near the grain boundaries 15 as shown in FIG. 3B. is more preferable.
  • the magnesium concentration at and near the grain boundaries 15 of the positive electrode active material 10 is higher than in other regions of the bulk portion 10b.
  • the fluorine concentration in the grain boundaries 15 and the vicinity thereof is also higher than in other regions of the bulk portion 10b.
  • the nickel concentration in the grain boundaries 15 and the vicinity thereof is also higher than in other regions of the bulk portion 10b.
  • the aluminum concentration in the grain boundaries 15 and the vicinity thereof is also higher than in other regions of the bulk portion 10b.
  • the grain boundaries 15 are one of the planar defects, they tend to become unstable like the surface, and the crystal structure tends to change. Therefore, by increasing the concentration of the additive element at and near the grain boundaries 15, such changes in the crystal structure can be more effectively suppressed.
  • the cracks may be caused by the cracks. Magnesium and fluorine concentrations increase near the exposed surface. Therefore, the corrosion resistance against hydrofluoric acid can be improved even in the positive electrode active material after cracks have occurred.
  • the positive electrode active material 10 that can be used as an embodiment of the present invention has an O3' type and/or monoclinic O1 (15) type crystal structure. Whether or not the positive electrode has a positive electrode active material in a charged state where x in Li x CoO 2 is small is examined by This can be determined by analysis using magnetic resonance (NMR) or the like.
  • XRD can analyze the symmetry of transition metals such as cobalt in the positive electrode active material with high resolution, compare the height of crystallinity and crystal orientation, and analyze the periodic distortion of the lattice and crystallite size. This method is preferable because sufficient accuracy can be obtained even if the positive electrode obtained by disassembling a lithium ion battery is directly measured.
  • powder XRD provides a diffraction peak that reflects the crystal structure of the bulk portion 10b of the positive electrode active material 10, which occupies most of the volume of the positive electrode active material 10.
  • the measurement sample is a powder
  • the powder it is sometimes referred to as the powder XRD measurement described above
  • the powder can be set using methods such as placing it in a glass sample holder or sprinkling the sample on a greased silicone non-reflective plate. can.
  • the measurement sample is a positive electrode
  • the positive electrode can be attached to the substrate with double-sided tape, and the positive electrode active material layer can be set according to the measurement surface required by the apparatus.
  • the positive electrode active material 10 that can be used as an embodiment of the present invention, if x is too small, such as 0.1 or less, or if the charging voltage exceeds 4.9V, the H1-3 type or three-way type A crystal O1 type crystal structure may also occur. Therefore, in order to determine whether or not the positive electrode active material 10 can be used as an embodiment of the present invention, analysis of the crystal structure such as XRD, and information such as charging capacity or charging voltage are required. .
  • the positive electrode active material in a state where x is small may undergo a change in crystal structure when exposed to the atmosphere.
  • the O3' type and monoclinic O1(15) type crystal structures may change to the H1-3 type crystal structure. Therefore, it is preferable that all samples subjected to crystal structure analysis be handled in an inert atmosphere such as an argon atmosphere.
  • whether the distribution of additive elements in a certain positive electrode active material is in the state described above can be determined by, for example, XPS, energy dispersive X-ray spectroscopy (EDX), or EPMA. (Electron Probe Micro Analysis).
  • the crystal structure of the surface layer portion 10a, grain boundaries 15, etc. can be analyzed by electron beam diffraction or the like of a cross section of the positive electrode active material 10.
  • the evaluation conditions for determining whether a certain composite oxide is a positive electrode active material 10 that can be used as an embodiment of the present invention are a coin cell having lithium metal as a counter electrode (for example, CR2032 type, diameter 20 mm, height 3 .2mm) and charging it under predetermined conditions. Furthermore, the evaluation conditions for determining whether a certain electrolyte is an electrolyte that can be used as an embodiment of the present invention are a coin cell (for example, CR2032 type, diameter 20 mm, height 3.2 mm) having lithium metal as a counter electrode. An example is a method in which the battery is manufactured and then charged under predetermined conditions.
  • Procedure 1 described below is an example for confirming the physical properties of the positive electrode active material 10 that can be used as one embodiment of the present invention. Therefore, the electrolyte is different from the structure of the lithium ion battery, which is one embodiment of the present invention.
  • ⁇ Evaluation procedure 1 ⁇ A certain lithium-ion battery is disassembled, the positive electrode impregnated with electrolyte is removed, and the positive electrode is punched out into a size that will fit into a prepared coin cell.
  • the positive electrode includes a conductive material and a binder in addition to the positive electrode active material. Further, electrolyte and the like are removed before punching out the positive electrode. For example, after taking out the positive electrode, the positive electrode may be cleaned using an organic solvent or the like.
  • the coin cell has lithium metal as the counter electrode. Note that materials other than lithium metal may be used for the counter electrode.
  • the potential in this specification and the like is the potential of the positive electrode when lithium metal is used as the counter electrode, unless otherwise specified.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • VC vinylene carbonate
  • Lithium fluorophosphate (LiPF 6 ) may be dissolved therein.
  • the coin cell has a porous polypropylene film with a thickness of 25 ⁇ m as a separator.
  • stainless steel (SUS) is used as a positive electrode can, and stainless steel (SUS) is used as a negative electrode can.
  • Coin cell A for evaluation produced under the above conditions is heated to a current of any voltage (for example, 4.5V, 4.55V, 4.6V, or 4.65V, 4.7V, 4.75V, 4.8V).
  • Constant current charging also called CC charging
  • 10 mA/g corresponding to 0.05 C when 1 C is 200 mA/g per weight of positive electrode active material.
  • the temperature during charging of the coin cell A for evaluation can be 25°C.
  • the temperature during charging may be the temperature of a constant temperature bath in which the coin cell A is placed.
  • the coin cell A After charging under such conditions, the coin cell A is disassembled in a glove box with an argon atmosphere and the positive electrode is taken out, thereby obtaining a positive electrode active material with an arbitrary charging capacity.
  • XRD can be performed in a sealed container with an argon atmosphere.
  • ⁇ Evaluation procedure 2 ⁇ A certain lithium ion battery is disassembled, the positive electrode impregnated with electrolyte is taken out, and the electrolyte is measured by nuclear magnetic resonance (for example, 1 H NMR) to identify at least the organic solvent. Using nuclear magnetic resonance, the mixing ratio (volume ratio) of organic solvents can also be identified. In addition, it is also possible to identify lithium salts, additives, etc. that the electrolyte has.
  • nuclear magnetic resonance for example, 1 H NMR
  • the positive electrode includes a conductive material and a binder in addition to the positive electrode active material. Further, the electrolyte and the like are removed after the nuclear magnetic resonance measurement and before punching out the positive electrode. For example, after taking out the positive electrode, the positive electrode may be cleaned using an organic solvent or the like.
  • the coin cell has lithium metal as the counter electrode. Note that materials other than lithium metal may be used for the counter electrode.
  • the coin cell is prepared with an electrolyte specified using nuclear magnetic resonance method.
  • the electrolyte is an electrolyte that is one embodiment of the present invention.
  • the coin cell has a porous polypropylene film with a thickness of 25 ⁇ m as a separator.
  • stainless steel (SUS) is used as a positive electrode can, and stainless steel (SUS) is used as a negative electrode can.
  • Coin cell B for evaluation produced under the above conditions is charged to an arbitrary voltage (for example, 4.5V, 4.55V, 4.6V, or 4.65V, 4.7V, 4.75V, 4.8V). , then discharge.
  • an arbitrary voltage for example, 4.5V, 4.55V, 4.6V, or 4.65V, 4.7V, 4.75V, 4.8V.
  • the temperature during charging of the coin cell B for evaluation can be 25° C., which is below freezing, and it can be confirmed how much the charge/discharge capacity at below freezing temperature is compared to the charge/discharge capacity at 25° C.
  • XRD device Bruker AXS, D8 ADVANCE
  • X-ray source CuK ⁇ 1- ray output: 40KV, 40mA
  • ⁇ Powder XRD pattern> The ideal XRD patterns using the CuK ⁇ 1 line calculated from the models of the O3' type crystal structure, the monoclinic O1 (15) type crystal structure, and the H1-3 type crystal structure are shown in Figures 6, 7, Shown in FIGS. 8A and 8B.
  • 8A and 8B show the XRD patterns of O3' type, monoclinic O1(15) type, and H1-3 type, and FIG. 8A shows the area where the 2 ⁇ range is 18° or more and 21° or less, FIG.
  • FIG. 8B is an enlarged view of a region in which the 2 ⁇ range is 42° or more and 46° or less.
  • the patterns of LiCoO 2 (O3) and CoO 2 (O1) were obtained from Reflex Powder D, one of the modules of Materials Studio (BIOVIA), based on crystal structure information obtained from ICSD (Inorganic Crystal Structure Database). Created using iffraction did.
  • the pattern of the H1-3 type crystal structure was similarly created from the crystal structure information described in Non-Patent Document 2.
  • the crystal structure patterns of the O3' type and the monoclinic O1 (15) type were estimated from the XRD pattern of the positive electrode active material that can be used as an embodiment of the present invention, and the crystal structures were estimated using TOPAS ver. 3 (crystal structure analysis software manufactured by Bruker), and an XRD pattern was created in the same manner as the others.
  • the positive electrode active material 10 that can be used as an embodiment of the present invention has an O3' type and/or monoclinic O1 (15) type crystal structure when x in Li x CoO 2 is small; ' type and/or monoclinic O1 (15) type crystal structure. It may contain other crystal structures, or may be partially amorphous. However, when performing Rietveld analysis on the XRD pattern, the O3' type and/or monoclinic O1(15) type crystal structure is preferably 50% or more, more preferably 60% or more, More preferably, it is 66% or more. If the O3' type and/or monoclinic O1(15) type crystal structure is 50% or more, more preferably 60% or more, and still more preferably 66% or more, the positive electrode active material has sufficiently excellent cycle characteristics. be able to.
  • the O3' type and/or monoclinic O1(15) type crystal structure remains 35% or more when Rietveld analysis is performed. It is more preferably 40% or more, and even more preferably 43% or more.
  • each diffraction peak after charging be sharp, that is, have a narrow half-width.
  • the half width varies depending on the XRD measurement conditions or the 2 ⁇ value even for peaks generated from the same crystal phase.
  • the half-width is preferably 0.2° or less, more preferably 0.15° or less, and 0.12° or less. More preferred. Note that not all peaks necessarily satisfy this requirement. If some peaks satisfy this requirement, it can be said that the crystallinity of the crystal phase is high. Therefore, it sufficiently contributes to stabilizing the crystal structure after charging.
  • the positive electrode active material 10 that can be used as one embodiment of the present invention has a smooth surface and few irregularities.
  • the fact that the surface is smooth and has few irregularities indicates that the effect of the flux described below was sufficiently exerted and the surface of the additive element source and lithium cobalt oxide were melted (solid solution). Therefore, this is one factor indicating that the distribution of the additive elements in the surface layer portion 10a is good.
  • the positive electrode active material 10 may have a covering portion outside the surface layer portion 10a.
  • the covering portion does not need to cover all of the positive electrode active material.
  • the covering portion may be an inorganic compound formed during the production of the positive electrode active material, or may be formed by depositing decomposition products of the electrolyte and organic electrolyte during charging and discharging.
  • the covering portion contains an electrolyte and a decomposition product of an organic electrolyte, it preferably contains carbon, oxygen, and fluorine. Furthermore, when LiBOB and/or SUN (suberonitrile) are used as part of the electrolyte, it is easy to obtain a high-quality film. Therefore, a coating having one or more selected from boron, nitrogen, sulfur, and fluorine is preferable because it may be a high-quality coating.
  • a method for manufacturing a positive electrode active material that can be used in the lithium ion battery of the present invention will be described.
  • a positive electrode active material is manufactured using a coprecipitation method.
  • the lithium ion battery of the present invention can also be manufactured using a positive electrode active material using a solid phase method, a hydrothermal method, etc. in addition to the coprecipitation method. Active materials can be applied.
  • the flowchart used to explain the manufacturing method and the like in this embodiment shows the order of elements connected by lines, and does not show the order of elements not connected by lines.
  • a precursor is a precursor of the oxide, for example, a hydroxide, which is a precursor.
  • Step S201 of FIG. 9 raw materials corresponding to the type of positive electrode active material are prepared.
  • an aqueous solution in which at least a transition metal salt is dissolved is prepared.
  • An aqueous solution in which a transition metal salt is dissolved can be referred to as a transition metal source.
  • the pH value of the aqueous solution in which the transition metal salt is dissolved is less than 7, preferably when the pH value is 1 or more and 6 or less, the aqueous solution exhibits acidity and can be described as an acidic aqueous solution.
  • transition metals selected from manganese, cobalt, and nickel can be used.
  • the transition metal only cobalt is used, only nickel is used, two types of cobalt and manganese are used, two types of cobalt and nickel are used, or cobalt, manganese and nickel are used. Three types may be used.
  • Nickel cobalt manganese composite oxide refers to lithium nickel cobalt manganese composite oxide before lithium is mixed.
  • lithium nickel cobalt manganese composite oxide is referred to as "NCM”.
  • NCM can be represented by the chemical formula LiNix Co y Mn z O 2 (x>0, y>0, 0.8 ⁇ x+y+z ⁇ 1.2). In NCM, Li is not limited to 1 based on the above chemical formula, but Li is 0.58 or more and 1.10 or less, preferably 0.90 or more and 1.05 or less, preferably 0.92 or more and 1. 01 or less can be satisfied. Note that NCM may further contain elements other than nickel, cobalt, and manganese.
  • x, y, and z may be referred to as the mixing ratio of nickel, cobalt, and manganese, and the mixing ratio is the ratio of each element used at least when weighing the raw materials. It is preferable that the mixing ratios described above as x, y, and z are satisfied because a layered rock salt type crystal structure can be obtained.
  • the proportion of each element obtained when NCM is measured by analysis using X-ray photoelectron spectroscopy (XPS), inductively coupled plasma mass spectrometry (ICP-MS), or energy dispersive X-ray spectroscopy (TEM-EDX), that is, x , y, and z are called the ratios of nickel, cobalt, and manganese, and the ratios do not have to match the mixing ratios. For example, if unreacted raw materials remain during the manufacturing process, the mixing ratio may differ from the ratio. If some of the raw materials for nickel are unreacted, the ratio of nickel will be smaller than the mixing ratio.
  • the proportion of nickel in the transition metals is high, it is preferable because it is possible to provide an inexpensive positive electrode active material and also to provide a high potential or high capacity positive electrode active material.
  • the number of atoms of nickel is preferably 33 or more, more preferably 50 or more, and 80 or more. and even more preferable.
  • the proportion of nickel is too high, chemical stability and heat resistance may decrease. Therefore, when the sum of the numbers of atoms of nickel, cobalt, and manganese contained in the positive electrode active material is 100, it is preferable that the number of atoms of nickel is 95 or less.
  • cobalt When cobalt is used as the transition metal, the average discharge voltage is high, and since cobalt contributes to stabilizing the layered rock salt structure, a secondary battery with improved cycle characteristics or high reliability can be obtained.
  • cobalt is more expensive than nickel and manganese and is unstable, so if the proportion of cobalt is too high, production costs may increase. Therefore, for example, when the sum of the numbers of atoms of nickel, cobalt, and manganese contained in the positive electrode active material is 100, it is preferable that the number of cobalt atoms is 2.5 or more and 34 or less.
  • manganese as the transition metal because heat resistance and chemical stability are improved. However, if the proportion of manganese is too high, the discharge voltage and discharge capacity tend to decrease. Therefore, for example, when the sum of the numbers of atoms of nickel, cobalt, and manganese contained in the positive electrode active material is 100, it is preferable that the number of atoms of manganese is 2.5 or more and 33 or less.
  • an aqueous solution in which a transition metal salt is dissolved will be explained.
  • an aqueous solution in which the transition metal salt is dissolved an aqueous solution in which the above-mentioned nickel salt is dissolved or an aqueous solution containing a water-soluble salt of nickel can be used.
  • nickel sulfate or nickel nitrate is dissolved in water.
  • Aqueous solutions can be used.
  • nickel ions may be present, and nickel may be present as a complex.
  • an aqueous solution in which a cobalt salt is dissolved or an aqueous solution containing a water-soluble salt of cobalt can be used as the aqueous solution in which the transition metal salt is dissolved.
  • a cobalt salt is dissolved or an aqueous solution containing a water-soluble salt of cobalt
  • cobalt sulfate or cobalt nitrate is dissolved in water.
  • Aqueous solutions can be used.
  • Cobalt ions may be present in the aqueous solution, and cobalt may be present as a complex.
  • an aqueous solution in which a manganese salt is dissolved or an aqueous solution containing a water-soluble salt of manganese can be used, and an aqueous solution in which manganese sulfate, manganese nitrate, etc. is dissolved in water can be used.
  • an aqueous solution in which manganese sulfate, manganese nitrate, etc. is dissolved in water can be used.
  • Manganese ions may be present in the aqueous solution, and manganese may be present as a complex.
  • the aqueous solution in which the transition metal salt is dissolved has high purity, and it is preferable to use pure water as the aqueous solution.
  • the concentration of transition metal ions in the aqueous solution in which the transition metal salt is dissolved is 1 mol/L or more and 5 mol/L or less, preferably 2 mol/L or more and 3 mol/L or less.
  • the aqueous solution contains a plurality of transition metal salts, it is sufficient that the total concentration of transition metal ions satisfies the above range.
  • an aqueous solution in which cobalt salt, manganese salt, and nickel salt are dissolved can be used as the aqueous solution in which transition metal salts are dissolved.
  • an aqueous solution in which nickel sulfate, cobalt sulfate, and manganese sulfate are dissolved can be used as an aqueous solution in which a transition metal salt is dissolved.
  • an aqueous solution exhibiting alkalinity (referred to as an alkaline aqueous solution) is prepared.
  • the alkaline aqueous solution refers to an aqueous solution having a pH value of greater than 7, preferably an aqueous solution having a pH value of 8 or more.
  • an aqueous solution containing sodium hydroxide, potassium hydroxide, lithium hydroxide, or ammonia can be used as the alkaline aqueous solution.
  • an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, or ammonia dissolved in water can be used.
  • An aqueous solution in which a plurality of selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, or ammonia are dissolved in water may be used. It is preferable to use pure water as the water.
  • the alkali concentration of the alkaline aqueous solution is 1 mol/L or more and 10 mol/L or less, preferably 3 mol/L or more and 7 mol/L or less. When the aqueous solution contains a plurality of alkalis, the total concentration of the alkalis should just satisfy the above range.
  • the pure water used for the aqueous solution in which the transition metal salt is dissolved and the alkaline aqueous solution is water with a specific resistance of 1 M ⁇ cm or more, more preferably water with a specific resistance of 10 M ⁇ cm or more, and still more preferably 15 M ⁇ cm or more. water is preferred. Water that satisfies the specific resistance has high purity and contains very few impurities.
  • Step S203 of FIG. 9 the above two aqueous solutions are mixed to produce a mixed aqueous solution (referred to as a mixed solution or coprecipitated mixed solution).
  • a mixed aqueous solution referred to as a mixed solution or coprecipitated mixed solution.
  • pure water may be prepared separately from the above two aqueous solutions, and a mixed aqueous solution may be produced in the pure water.
  • the aqueous solution in which the transition metal salt is dissolved can be reacted with the alkaline aqueous solution.
  • the reaction may be referred to as a neutralization reaction, an acid-base reaction, or a coprecipitation reaction. As the reaction progresses in this step, a coprecipitate is precipitated.
  • the product of the reaction is referred to as a coprecipitate.
  • a coprecipitate When an aqueous solution in which the transition metal salt is dissolved and an alkaline aqueous solution are mixed, a hydroxide is formed as a coprecipitate.
  • the temperature of the mixed liquid and the pH value of the mixed liquid may be kept constant, and the mixed liquid may be further stirred.
  • the above temperature is preferably 40°C or more and 90°C or less, preferably 45°C or more and 70°C or less.
  • the pH value is preferably 9.0 or more and 13.0 or less, preferably 10.5 or more and 11.5 or less.
  • the rotational speed of the stirring is preferably 800 rpm or more and 1200 rpm or less, preferably 900 rpm or more and 1100 rpm or less.
  • a coprecipitate is precipitated in the mixed solution as a reaction product.
  • a coprecipitate may precipitate in a mixed solution and is sometimes referred to as a precipitate.
  • the mixture may become a suspension.
  • a suspension refers to a liquid in which coprecipitate particles are dispersed in a liquid.
  • Step S205 of FIG. 9 the mixed liquid is filtered to obtain a coprecipitate from the mixed liquid. Specifically, the coprecipitate is taken out from the mixed solution. It is recommended to use suction filtration for filtration.
  • the coprecipitate has a size (long axis) of 1 ⁇ m or more and 20 ⁇ m or less. Further, an ordinal number may be attached to the coprecipitate obtained by filtration to distinguish it from the coprecipitate present in the mixed solution, and this may be referred to as a filtered powder.
  • a hydroxide containing a transition metal is obtained as a coprecipitate.
  • a hydroxide containing cobalt, manganese, and nickel is produced as a coprecipitate (composite hydroxide containing cobalt, manganese, and nickel). ) is obtained.
  • the coprecipitate obtained by filtration typically hydroxide, contains impurities such as water.
  • the hydroxide obtained as a coprecipitate may become secondary particles in which primary particles are aggregated.
  • the primary particles refer to the smallest unit particles (agglomerates) that are observed when observed at a magnification of 20,000 times using a SEM (scanning electron microscope) or the like. In other words, primary particles are the smallest unit particles.
  • secondary particles refers to particles (independent particles) in which the primary particles aggregate so as to share part of the grain boundaries (such as the outer periphery of the primary particles) and are not easily separated.
  • Step S207 in FIG. 9 the coprecipitate is washed to obtain hydroxide from which impurities have been removed.
  • cleaning using water can be applied.
  • Cleaning using water is sometimes referred to as water washing.
  • washing with water can be repeated once or multiple times.
  • Impurities and the like can be removed to some extent from the coprecipitate by washing with water.
  • Distilled water or pure water may be used as the water.
  • pure water the content explained in step S201 can be referred to.
  • suction filtration may be performed after washing the coprecipitate with water. Furthermore, when washing with water is repeated multiple times, it is advisable to perform suction filtration after washing with water.
  • cleaning using an organic solvent can be applied to the cleaning in the above step.
  • cleaning using an organic solvent can be repeated once or multiple times.
  • the coprecipitate can be dried by washing with an organic solvent. The drying process includes removing water or moisture that has adhered due to the previous washing or the like.
  • acetone or alcohol such as isopropanol (typically isopropyl alcohol) may be used.
  • suction filtration may be performed after washing the coprecipitate with an organic solvent. Further, when washing with an organic solvent is repeated multiple times, it is preferable to perform suction filtration after washing with the organic solvent.
  • a combination of washing with water and washing using an organic solvent can be applied.
  • Suction filtration may be used.
  • a step of washing with water and then suction filtration can be carried out, and then a step of washing with an organic solvent and then suction filtration can be carried out.
  • the number of times of washing with water is preferably greater than the number of times of washing with an organic solvent.
  • Step S209 in FIG. 9 is a step of heating the coprecipitate, and sufficient impurities are removed, but this step may be omitted if there are few impurities.
  • this step allows hydrogen and oxygen to be removed from the coprecipitate as water. Since removing hydrogen and oxygen as water is called dehydration, the heating process in this step includes a dehydration process. Furthermore, this step allows water or moisture contained in the coprecipitate to be removed. Since removing water, moisture, etc. is called drying, the heating process in this step includes a drying process. In addition to water or moisture, impurities can also be gasified and removed in the heating process of this step. For example, the organic solvent used in step S207 can also be removed by the heating process of this step.
  • the upper limit of the heating temperature in this step is preferably lower than the temperature at which hydroxide, which is a coprecipitate, begins to change into an oxide. That is, it is preferable not to change the hydroxide to the oxide in this step.
  • the temperature at which hydroxide changes to oxide can be determined by thermogravimetry-differential thermal analysis (TG-DTA).
  • TG-DTA thermogravimetry-differential thermal analysis
  • 220°C is derived as the temperature at which hydroxide begins to decompose, dehydrate, or reduce, that is, the temperature at which hydroxide begins to change to oxide, and 220°C can be set as the upper limit of the temperature for heat treatment. .
  • the temperature of the heat treatment is higher because the treatment progresses more easily, the treatment time is shorter, and the productivity is higher.
  • the lower limit of the heat treatment temperature may be at least a temperature that can remove water or moisture from the hydroxide.
  • the removal of water or moisture is also called drying.
  • the specific temperature of the heat treatment is preferably 130°C or more and 220°C or less, preferably 150°C or more and 220°C or less, and more preferably 180°C or more and 220°C or less.
  • a vacuum drying furnace when heating is performed in a vacuum atmosphere, a vacuum drying furnace may be used, and the vacuum drying furnace has a vacuum pump connected to the drying furnace.
  • a dry pump, a turbo molecular pump, an oil rotary pump, a cryopump, or a mechanical booster pump can be used as the vacuum pump included in the bell jar type vacuum device and the vacuum drying furnace.
  • the vacuum atmosphere in the bell jar type vacuum device and the vacuum drying furnace includes an atmosphere in which the pressure is reduced so that the differential pressure gauge of each device is ⁇ 0.1 MPa or more and less than ⁇ 0.08 MPa.
  • a gas containing nitrogen may be flowed into a container included in a bell jar type vacuum device and a vacuum drying furnace.
  • the heat treatment in this step may be performed in multiple stages. For example, it can be carried out at a first temperature for a first time and then at a second temperature for a second time. It is sufficient that the second temperature satisfies the temperature range of the heat treatment described above.
  • the first temperature is lower than the second temperature, for example, in a range of 80°C or higher and lower than 90°C.
  • the second time may satisfy the range of the heat treatment time described above.
  • the first time is shorter than the second time, for example, 0.5 hours or more and 1 hour or less.
  • the multi-stage treatment is preferred because impurities can be easily removed from the hydroxide.
  • a lithium source is prepared.
  • the ratio of the lithium source to the hydroxide (lithium source/hydroxide) is set to be 0.90 or more and 1.05 or less, preferably 0.92 or more and 1.01 or less.
  • a lithium compound can be used as the lithium source.
  • Lithium compounds include lithium hydroxide, lithium carbonate, or lithium nitrate. It is preferable that the lithium source has high purity. Further, it is preferable that the lithium source is pulverized so that the solid phase reaction can proceed easily.
  • lithium hydroxide has a melting point of 462° C., which is the lowest among lithium compounds.
  • a lithium compound with a low melting point such as lithium hydroxide, is preferably used when producing a positive electrode active material containing a high proportion of nickel.
  • a ball mill, bead mill, kneader, or the like can be used for mixing.
  • a ball mill it is preferable to use zirconia balls as the media, for example.
  • Step S213 Heating process>
  • the mixture is heated. Since it becomes an oxide after the main heating step, the mixture is called a precursor.
  • an ordinal number may be attached to the heating process of this step.
  • the heating conditions for this step are preferably heating at a first temperature and then heating at a second temperature. Heating at the first temperature may be referred to as first firing, and heating at the second temperature may be referred to as second firing. Note that in the present invention, the second firing may be performed without performing the first firing. That is, this step may be performed only once.
  • the second temperature is preferably higher than the first temperature.
  • heating at the first temperature may be referred to as preliminary firing
  • heating at the second temperature may be referred to as main firing.
  • main firing may be performed without performing preliminary firing.
  • lithium hydroxide used as a lithium source, it is preferable to perform temporary calcination.
  • the first temperature is preferably higher than the melting point of the lithium source.
  • the first temperature is preferably 500°C or higher and 700°C or lower.
  • the second temperature is preferably higher than 500°C and lower than 1050°C, and when the second temperature is higher than the first temperature, the second temperature is preferably higher than 700°C and lower than 1050°C.
  • the heating time at the first temperature and the heating time at the second temperature are preferably 1 hour or more and 20 hours or less, respectively.
  • the time for heating at the first temperature may be equal to, longer, or shorter than the time for heating at the second temperature.
  • heating at the first temperature and heating at the second temperature are preferably performed in an oxygen atmosphere, and particularly preferably performed while supplying oxygen.
  • the rate may be 2 L/min or more and 15 L/min, preferably 5 L/min and 10 L/min per 1 L of internal volume of the furnace.
  • the heating atmosphere at the first temperature may be the same as or different from the heating atmosphere at the second temperature.
  • an electric furnace or a rotary kiln can be used as the firing device used for heating at the first temperature and the second temperature.
  • the firing device used for heating at the first temperature may be the same as or different from the firing device used for heating at the second temperature.
  • the mixture may be placed in a crucible or sheath during heating.
  • the crucible or sheath is preferably made of a material with high heat resistance, such as alumina (aluminum oxide), mullite/cordierite, magnesia, or zirconia.
  • aluminum oxide is preferred because it is a material that is difficult to mix with impurities.
  • an alumina crucible or sheath with a purity of 99% or higher, preferably 99.5% or higher may be used.
  • a crucible made of aluminum oxide with a purity of 99.9% is used.
  • it is preferable to heat the crucible or pod with a lid which can prevent sublimation of the materials contained in the mixture.
  • the lid may be placed so that the inside of the crucible is isolated from the air inside the furnace, or it may be placed so that it is partially open so that the inside of the crucible can come into contact with the inside air of the furnace.
  • the present invention it is preferable to crush or crush in a mortar between the heating step at the first temperature and the heating step at the second temperature.
  • a state where the mixtures are stuck to each other or agglomerated between the mixtures can be loosened by crushing or crushing. If the mixture sticks to each other during heating, the contact area with oxygen in the atmosphere may decrease, so it is preferable to crush or crush the mixture as described above. Furthermore, after pulverization or crushing, it may be classified using a sieve.
  • the mortar is also preferably made of a material that does not easily release impurities. Specifically, it is suitable to use an alumina mortar with a purity of 90% or more, preferably 99% or more.
  • NCM can be obtained as a positive electrode active material according to the prepared raw materials. It is preferable to use the obtained NCM because high discharge capacity can be obtained in terms of battery characteristics.
  • the median diameter (D50) of the NCM is 3 ⁇ m or more and 13 ⁇ m or less, and 4 ⁇ m or more and 10 ⁇ m or less. If the median diameter (D50) is small, the discharge capacity increases, so the median diameter (D50) of the NCM is preferably 4 ⁇ m or more and 7 ⁇ m or less.
  • a complexing agent may be added as the raw material prepared in step S201 of FIG.
  • a complexing agent is a compound that can form a complex with a transition metal ion in an aqueous solution.
  • Complexing agents include ammonia or ammonium salts. Note that an aqueous solution obtained by dissolving these in water, for example pure water, serves as a complexing agent. When ammonia is used, it can be described as an aqueous ammonia solution.
  • a chelating agent which is a complexing agent for forming a chelate compound
  • Chelating agents include glycine, oxine, 1-nitroso-2-naphthol, 2-mercaptobenzothiazole or EDTA (ethylenediaminetetraacetic acid).
  • an aqueous solution obtained by dissolving these in water for example, pure water, serves as a chelating agent.
  • glycine it can be described as a glycine aqueous solution.
  • the glycine concentration is preferably 0.05 mol/L or more and 0.15 mol/L or less, preferably 0.07 mol/L or more and 0.12 mol/L or less.
  • the use of a chelating agent suppresses unnecessary generation of crystal nuclei, a hydroxide with a good particle size distribution can be obtained. Furthermore, by using a chelating agent, it is possible to delay the acid-base reaction, and as the reaction progresses gradually, secondary particles having a nearly spherical shape can be obtained. For this reason, the chelating agent is preferably a common complexing agent, such as an aqueous ammonia solution.
  • a complexing agent specifically a chelating agent
  • the complexing agent is preferably placed in the reaction tank.
  • an ordinal number may be assigned to the complexing agent or chelating agent.
  • the materials that can be used as the complexing agent or the chelating agent are as described above.
  • the glycine concentration in the aqueous glycine solution is preferably 0.05 mol/L or more and 0.15 mol/L or less, preferably 0.07 mol/L or more and 0.12 mol/L or less.
  • the glycine concentration in the present glycine aqueous solution is preferably equal to the glycine concentration mixed in the aqueous solution in which the transition metal salt is dissolved.
  • steps S203 and subsequent steps are performed in the same manner as in manufacturing method 1.
  • the coprecipitation synthesis apparatus 170 used in this production method 2 will be explained using FIG. 10.
  • the coprecipitation synthesis apparatus 170 can be installed in a draft chamber, and has at least a reaction tank 171.
  • a reaction vessel can be used as the reaction tank 171.
  • Separable flasks may be cylindrical or round. In the case of a cylindrical type, the separable flask has a flat bottom.
  • the separable cover has a plurality of inlets, for example four inlets.
  • the atmosphere inside the reaction tank 171 can be controlled using at least one inlet of the separable cover. For example, it is preferable to control the atmosphere so that it contains nitrogen. In that case, it is preferable to control the flow of nitrogen into the reaction tank 171. At this time, it is preferable that the amount of air flow is necessary to exhaust the gas generated by the thermal decomposition reaction. Furthermore, nitrogen may be bubbled into the aqueous solution 203 placed in the reaction tank 171.
  • the coprecipitation synthesis apparatus 170 may be equipped with a reflux condenser connected to another inlet of the separable cover, and the reflux condenser discharges atmospheric gas, for example, nitrogen, from the reaction tank 171 while discharging water. can be returned to the reaction tank 171.
  • the above-mentioned chelating agent is added as an aqueous solution 203.
  • an aqueous solution such as the aqueous solution 203, initially placed in the reaction tank 171 may be referred to as a filling liquid.
  • the filling liquid is sometimes referred to as the adjustment liquid.
  • the filling liquid and the adjustment liquid refer to an aqueous solution before the reaction, that is, an aqueous solution in an initial state.
  • An aqueous solution in which a transition metal salt is dissolved is prepared as an aqueous solution 201.
  • the aqueous solution 201 is placed in the first tank 180.
  • an alkaline aqueous solution is prepared as the aqueous solution 202. Since the alkaline aqueous solution is used to maintain a constant pH value, it is sometimes referred to as a pH adjusting solution.
  • the aqueous solution 202 is kept in the second tank 186. Oxygen in each aqueous solution may be removed by bubbling nitrogen in the first tank 180 and the second tank 186.
  • a tank separate from the first tank 180 and the second tank 186 may be prepared and the above-mentioned chelating agent may be stored therein.
  • the first tank 180 has a pump 182 and a tube (also referred to as pipe) 181 connected to the pump 182.
  • the tube 181 is fixed to the inlet of the separable cover, and the aqueous solution 201 is reacted from the tip of the tube 181. It can be dropped into the tank 171.
  • the second tank 186 also has a pump 188 and a pipe 187 connected to the pump 188.
  • the pipe 187 is fixed to the inlet of the separable cover, and the aqueous solution 202 is dripped into the reaction tank 171 from the tip of the pipe 187. be done.
  • each raw material is prepared in the reaction tank 171, the first tank 180, and the second tank 186 according to step S201.
  • Step S203 Mixing step> Next, the mixing process in step S203 will be explained. First, the conditions for the coprecipitation method related to this step are shown.
  • the pH value of the aqueous solution 203 in the reaction tank 171 is 9.0 or more and 13.0 or less, preferably 10.5 or more and 11.5 or less.
  • the temperature of the aqueous solution 203 in the reaction tank 171 is 40°C or more and 90°C or less, preferably 45°C or more and 70°C or less.
  • the water temperature can also be controlled according to the temperature inside the reaction tank 171.
  • the temperature in the reaction tank 171 may be equal to or deviate from the water temperature by less than 5°C, preferably by less than 2°C. Therefore, the temperature in the reaction tank 171 is set to 35°C or more and 95°C or less, preferably 40°C or more and 75°C or less.
  • the rotation speed for stirring the aqueous solution 203 in the reaction tank 171 is 800 rpm or more and 1200 rpm or less, preferably 900 rpm or more and 1100 rpm or less.
  • the concentration of transition metal ions in the aqueous solution 201 is 1 mol/L or more and 5 mol/L or less, preferably 2 mol/L or more and 3 mol/L or less. When having a plurality of transition metals, the total concentration of transition metal ions satisfies the above range.
  • the dropping rate of the aqueous solution 201 is 0.03 mL/min or more and 1.0 mL/min or less, preferably 0.03 mL/min or more and 0.5 mL/min.
  • the size of the hydroxide that is, the median diameter (D50)
  • the size of the hydroxide that is, the median diameter (D50)
  • the size of the hydroxide is small
  • the positive electrode active material also becomes small
  • the size of the hydroxide is large
  • the positive electrode active material also becomes large.
  • the hydroxide that affects the size of the positive electrode active material which is a lithium composite oxide, can be called a precursor.
  • the alkali concentration of the aqueous solution 202 is 1 mol/L or more and 10 mol/L or less, preferably 3 mol/L or more and 7 mol/L or less.
  • the concentration of the chelating agent in the aqueous solution 203 is 0.05 mol/L or more and 0.15 mol/L or less, preferably 0.07 mol/L or more and 0.12 mol/L or less.
  • a stirring section 172 is provided in the reaction tank 171 in FIG.
  • the stirring section 172 can stir the aqueous solution 203 in the reaction tank 171, and further includes a stirring motor 173 as a power source for rotating the stirring section 172.
  • the stirring section 172 has paddle-shaped stirring blades (referred to as paddle blades), and the paddle blades have two or more and six or less blades, and the blades have an inclination of 40 degrees or more and 70 degrees or less. You can leave it there.
  • the blades in the stirring section 172 may be moved up and down.
  • the rotation speed of the stirring section 172 is preferably set to 800 rpm or more and 1200 rpm or less, preferably 900 rpm or more and 1100 rpm or less.
  • a baffle plate may be installed inside the reaction tank 171.
  • thermometer 174 is provided to measure the temperature of the reaction tank 171 or the water temperature of the aqueous solution 203.
  • the temperature of the reaction tank 171 can be controlled using a thermoelectric element so that the temperature of the aqueous solution 203 is constant.
  • thermoelectric elements include Peltier elements.
  • the tip of the thermometer 174 is immersed in the aqueous solution 203.
  • the aqueous solution 203 may be heated to a temperature of 40° C. or higher and 90° C. or lower, preferably 45° C. or higher and 70° C. or lower.
  • the temperature of the reaction tank 171 may be controlled using a thermometer 174.
  • the coprecipitation synthesis apparatus 170 includes a control device 190 and the like to control the dropping conditions or stirring conditions from each pump.
  • the control device 190 can control the rotation speed of the stirring section 172, the amount of each aqueous solution dropped, etc. based on the information obtained from the thermometer 174.
  • the dropping rate of the aqueous solution 201 is set to 0.05 mL/min or more and 1.0 mL/min or less, preferably 0.08 mL/min or more and 0.5 mL/min.
  • the concentration of transition metal ions in the aqueous solution 201 is preferably 1 mol/L or more and 5 mol/L or less, preferably 2 mol/L or more and 3 mol/L or less.
  • the total concentration of each transition metal ion preferably satisfies the above range.
  • a pH meter is also placed in the reaction tank 171 and can measure the pH of the aqueous solution 203.
  • the pH value may be set within a range of 9.0 or more and 13.0 or less, preferably 10.5 or more and 11.5 or less.
  • the concentration of the chelating agent in the aqueous solution 203 is preferably 0.05 mol/L or more and 0.15 mol/L or less, preferably 0.07 mol/L or more and 0.12 mol/L or less.
  • the alkali concentration of the aqueous solution 202 is preferably 1 mol/L or more and 10 mol/L or less, preferably 3 mol/L or more and 7 mol/L or less.
  • reaction product precipitates in the reaction tank 171.
  • the reaction product is a coprecipitate, specifically a hydroxide.
  • step S205 onwards are the same as those in manufacturing method 1, and therefore their description will be omitted.
  • the positive electrode active material can be manufactured.
  • NCM with a good particle size distribution can be obtained as a positive electrode active material.
  • the discharge capacity increases in terms of battery characteristics, which is preferable.
  • the NCM may have one or more selected from calcium and aluminum at a concentration of 0.1 atm% or more and 5 atm% or less based on the NCM.
  • Calcium and aluminum at the above concentrations may be referred to as additive elements.
  • the additive element is often located in the surface layer of the active material, and the surface layer refers to a region up to 50 nm from the surface of the active material, preferably a region up to 30 nm, and more preferably a region up to 10 nm.
  • the surface layer part can be considered to be located in the same way whether the active material is a primary particle or a secondary particle, and includes a region up to 50 nm from the surface of the primary particle or the surface of the secondary particle, preferably a region up to 30 nm, More preferably, a region up to 10 nm is called a surface layer portion.
  • the surface of a primary particle or the surface of a secondary particle is an interface between a region where a transition metal (for example, Co, Ni, Mn, Fe, etc.) that undergoes oxidation and reduction as lithium is intercalated and withdrawn exists and a region where it does not exist.
  • a transition metal for example, Co, Ni, Mn, Fe, etc.
  • NCMA The NCM containing aluminum as a main component is sometimes referred to as NCMA.
  • NCMA is sometimes referred to as a lithium composite oxide containing Ni, Co, Mn, and Al.
  • NCA a lithium composite oxide containing Ni and Co containing aluminum as a main component
  • NCA is sometimes referred to as a lithium composite oxide containing Ni, Co, and Al.
  • FIG. 11 a case will be described using FIG. 11 in which the above-mentioned additive element source is added in the same step as the raw material prepared in step S201, that is, at the same time.
  • This manufacturing method 3 shown in FIG. 11 is the same as manufacturing method 1 from step S203 to step S213, but a new step S215 is added.
  • Step S215 of FIG. 11 an additive element source is prepared.
  • an aqueous solution in which a salt of the additive element source is dissolved can be used.
  • an aqueous solution in which aluminum sulfate, aluminum chloride, aluminum nitrate, calcium oxide, calcium carbonate, calcium hydroxide, or calcium sulfate is dissolved can be used.
  • the additive element source is weighed so that the additive element is 0.1 atm % or more and 5 atm % or less of NCM.
  • a plurality of additive elements may be included. In the case of having a plurality of additive elements, the total concentration of the additive elements may satisfy 0.1 atm % or more and 5 atm % or less of NCM.
  • Step S203 Mixing step>
  • a mixed solution is manufactured by mixing an aqueous solution in which a transition metal salt is dissolved, an alkaline aqueous solution, and an aqueous solution in which a salt as an additive element source is dissolved.
  • the mixing in this step is similar to step S203 in manufacturing method 1.
  • step S205 onwards are the same as those in manufacturing method 1, and therefore their description will be omitted.
  • the positive electrode active material can be manufactured.
  • NCM having an additive element can be obtained as a positive electrode active material.
  • the additive element is preferably located in the surface layer of the NCM.
  • NCMA or NCA can also be obtained as the positive electrode active material.
  • Step S215 of FIG. 12 an additive element source is prepared.
  • an additive element source is prepared.
  • the additive element source is weighed so that the additive element is 0.1 atm % or more and 5 atm % or less of NCM.
  • a plurality of additive elements may be included. In the case of having a plurality of additive elements, the total concentration of the additive elements may satisfy 0.1 atm % or more and 5 atm % or less of NCM.
  • Step S211 Mixing step>
  • the hydroxide, the lithium source, and the additive element source are mixed to produce a mixture.
  • the mixing in this step is similar to step S211 in manufacturing method 1.
  • step S213 onward are the same as those in manufacturing method 1, and therefore their description will be omitted.
  • the positive electrode active material can be manufactured.
  • NCM having an additive element can be obtained as a positive electrode active material.
  • the additive element is preferably located in the surface layer of the NCM.
  • NCMA or NCA can also be obtained as the positive electrode active material.
  • Step S215 of FIG. 13 an additive element source is prepared.
  • a source of additional elements aluminum sulfate, aluminum chloride, aluminum nitrate, calcium oxide, calcium carbonate, calcium hydroxide, or calcium sulfate can be used.
  • the additive element source is weighed so that the additive element is 0.1 atm % or more and 5 atm % or less of NCM.
  • a plurality of additive elements may be included. In the case of having a plurality of additive elements, the total concentration of the additive elements may satisfy 0.1 atm % or more and 5 atm % or less of NCM.
  • Step S216 Mixing step>
  • step S216 of FIG. 13 the composite oxide and the additive element source are mixed to produce a mixture.
  • the mixing in this step is similar to step S211 in manufacturing method 1.
  • Step S217 Heating process>
  • the mixture is heated.
  • the heating in this step is similar to step S213 in manufacturing method 1.
  • the positive electrode active material can be manufactured.
  • NCM having an additive element can be obtained as a positive electrode active material.
  • the additive element is preferably located in the surface layer of the NCM.
  • NCMA or NCA can also be obtained as the positive electrode active material.
  • the positive electrode has a positive electrode active material layer and a positive electrode current collector.
  • the positive electrode active material layer includes a positive electrode active material and may further include at least one of a conductive additive and a binder.
  • the positive electrode active material the material described in Embodiment 1 can be used.
  • FIG. 14A shows an example of a schematic diagram of a cross section of a positive electrode.
  • metal foil can be used as the current collector 550.
  • the positive electrode can be formed by applying a slurry onto a metal foil and drying it. Note that pressing may be applied after drying.
  • the positive electrode has an active material layer formed on a current collector 550.
  • the positive electrode active material 561 has a function of taking in and/or releasing lithium ions during charging and discharging.
  • a material that is less likely to deteriorate due to charging and discharging even at a high charging voltage can be used.
  • charging voltage is expressed based on the potential of lithium metal.
  • a high charging voltage is, for example, a charging voltage of 4.6V or higher, preferably 4.65V or higher, more preferably 4.7V or higher, even more preferably 4.75V or higher, and most preferably shall be 4.8V or higher.
  • the positive electrode active material 561 used as one embodiment of the present invention any material can be used as long as it exhibits little deterioration due to charging and discharging even at a high charging voltage, and the material described in Embodiment 1 or 2 can be used. can be used. Note that the positive electrode active material 561 can be made of two or more types of materials with different particle sizes, as long as they are less likely to deteriorate due to charging and discharging even at high charging voltages.
  • the conductive aid is also called a conductive agent or a conductive material, and a carbon material can be used as the conductive aid.
  • a conductive additive between the plurality of active materials, the plurality of active materials are electrically connected to each other, thereby increasing conductivity.
  • adheresion does not only mean that the active material and the conductive agent are in close physical contact with each other, but also that when a covalent bond occurs, they are bonded by van der Waals force.
  • the concept includes cases where the conductive agent covers part of the surface of the active material, cases where the conductive agent fits into the unevenness of the surface of the active material, and cases where the conductive agent is electrically connected even if they are not in contact with each other.
  • FIG. 14A illustrates carbon black 553 as a conductive aid.
  • a binder As a positive electrode of a lithium ion battery, a binder (resin) may be mixed in order to fix the current collector 550 such as metal foil and the active material.
  • a binder is also called a binding agent.
  • the binder is a polymeric material, and when a large amount of the binder is included, the proportion of the active material in the positive electrode decreases, and the discharge capacity of the lithium ion battery decreases. Therefore, it is preferable to mix the amount of binder to a minimum.
  • a region not filled with the positive electrode active material 561, the second active material 562, and the carbon black 553 indicates a void or a binder.
  • FIG. 14A shows an example in which the positive electrode active material 561 is spherical, it is not particularly limited.
  • the cross-sectional shape of the positive electrode active material 561 may be an ellipse, a rectangle, a trapezoid, a pyramid, a polygon with rounded corners, or an asymmetric shape.
  • FIG. 14B shows an example in which the positive electrode active material 561 has a polygonal shape with rounded corners.
  • graphene 554 is used as a carbon material used as a conductive additive.
  • a positive electrode active material layer including a positive electrode active material 561, graphene 554, and carbon black 553 is formed on a current collector 550.
  • the weight of the carbon black to be mixed is 1.5 times to 20 times, preferably 2 times to 9.5 times, the weight of graphene. It is preferable to do so.
  • the dispersion stability of the carbon black 553 is excellent during slurry preparation, and agglomerated portions are less likely to occur.
  • the mixture of graphene 554 and carbon black 553 is within the above range, it is possible to obtain a higher electrode density than a positive electrode using only carbon black 553 as a conductive additive.
  • the capacity per unit weight can be increased.
  • the density of the positive electrode active material layer measured by weight can be 3.5 g/cc or more.
  • the electrode density is lower than that of a positive electrode that uses only graphene as a conductive additive, by mixing the first carbon material (graphene) and the second carbon material (acetylene black) within the above range, rapid charging is possible. can correspond to Therefore, it is particularly effective when used as a lithium ion battery for vehicles.
  • FIG. 14C illustrates an example of a positive electrode using carbon fiber 555 instead of graphene.
  • FIG. 14C shows an example different from FIG. 14B.
  • carbon fiber 555 is used, agglomeration of carbon black 553 can be prevented and dispersibility can be improved.
  • a region not filled with the positive electrode active material 561, carbon fibers 555, and carbon black 553 indicates a void or a binder.
  • FIG. 14D is illustrated as an example of another positive electrode.
  • FIG. 14C shows an example in which carbon fiber 555 is used in addition to graphene 554. When both graphene 554 and carbon fiber 555 are used, agglomeration of carbon black such as carbon black 553 can be prevented and dispersibility can be further improved.
  • regions not filled with the positive electrode active material 561, carbon fibers 555, graphene 554, and carbon black 553 indicate voids or binder.
  • a lithium ion battery can be produced by filling the battery with .
  • the positive electrode has a positive electrode active material layer and a positive electrode current collector.
  • the positive electrode active material layer includes a positive electrode active material and may further include a conductive material. Further, the positive electrode active material layer may further include a binder. Further, the positive electrode active material layer may include a conductive material and a binder.
  • FIG. 15A shows an example of the positive electrode active material 10.
  • the positive electrode active material for example, the materials described in Embodiment Mode 2 and the like can be used.
  • the positive electrode active material manufactured according to Embodiment 2 and the like is composed of secondary particles 12 having primary particles 11 and the like. Voids 13 may be observed between the aggregated primary particles 11 . Furthermore, there is an interface 14 between adjacent primary particles 11 .
  • the positive electrode active material manufactured by the manufacturing methods 3 to 5 of the third embodiment described above can have an additive element.
  • FIG. 15B shows the concentration distribution of the additive element in the EF cross section shown by the dashed line in FIG. 15A. Since the E-F cross section passes through the interface 14, FIG. 15B shows the concentration distribution of the additive element inside the primary particle from the interface 14.
  • the concentration distribution is sometimes referred to as a concentration gradient, and the vicinity of the interface refers to a region of primary particles less than 10 nm from the interface, preferably a region of primary particles less than 8 nm from the interface 14.
  • the region of the primary particle less than 10 m from the interface may be referred to as the surface layer portion of the primary particle.
  • the horizontal axis in FIG. 15B corresponds to the distance of the E-F cross section, and the vertical axis corresponds to the concentration of the additive element.
  • the concentration peak of the additive element is preferably located at a position overlapping the interface 14. Calcium is an example of the additive element.
  • a positive electrode active material containing an additive element having such a concentration peak is preferable because cycle deterioration is suppressed.
  • the concentration peak position may differ depending on the additive elements.
  • the concentration of the additive element decreases from the surface toward the inside, as shown in FIG. 15B. That is, in the primary particles, it is preferable that the concentration of the additive element is higher in the surface layer than in the inside. For example, it is preferable that the concentration of calcium, which is an example of an additive element, decreases from the surface toward the inside, as shown in FIG. 15B. Further, when a positive electrode active material is manufactured using a plurality of additive elements, the shape of the concentration distribution may differ depending on the additive elements.
  • FIG. 15C shows an example of a cross-sectional view of the positive electrode 107.
  • the positive electrode 107 includes a positive electrode current collector 105 and a positive electrode active material layer 104.
  • ⁇ Positive electrode current collector For example, metal foil can be used for the positive electrode current collector 105.
  • the positive electrode can be formed by applying a slurry onto a metal foil and drying it. Note that pressing may be applied after drying.
  • the positive electrode has a positive electrode active material layer 104 formed on a positive electrode current collector 105.
  • the metal foil highly conductive materials such as metals such as stainless steel, gold, platinum, aluminum, titanium, and alloys thereof can be used. Further, it is preferable that the material used for the positive electrode current collector does not elute at the potential of the positive electrode. Furthermore, an aluminum alloy to which an element that improves heat resistance, such as silicon, titanium, neodymium, scandium, or molybdenum is added, can be used. Alternatively, it may be formed of a metal element that reacts with silicon to form silicide. Examples of metal elements that react with silicon to form silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel.
  • the current collector may have a foil shape, a plate shape, a sheet shape, a net shape, a punched metal shape, an expanded metal shape, or the like as appropriate.
  • the current collector preferably has a thickness of 5 ⁇ m or more and 30 ⁇ m or less.
  • Slurry is a material liquid used to form the cathode active material layer 104 on the cathode current collector 105, and contains an active material, a binder, and a solvent, preferably further mixed with a conductive material.
  • the slurry is sometimes called an electrode slurry or an active material slurry, and when forming a positive electrode active material layer, a positive electrode slurry is used, and when forming a negative electrode active material layer, it is called a negative electrode slurry.
  • a negative electrode slurry it is also.
  • the positive electrode active material layer 104 includes secondary particles 12a and secondary particles 12b as positive electrode active materials.
  • the secondary particles 12a have a different median diameter (D50) from the secondary particles 12b.
  • the conductive material is also called a conductivity imparting agent or a conductivity aid, and a carbon material can be used.
  • a conductive material By attaching a conductive material between the plurality of active materials, the plurality of active materials are electrically connected to each other, thereby increasing conductivity.
  • adheresion does not only mean that the active material and the conductive material are in close physical contact with each other, but also refers to the case where a covalent bond occurs or the case where they are bonded by van der Waals force.
  • the concept includes cases in which a conductive material covers part of the surface of an active material, cases in which a conductive material fits into irregularities on the surface of an active material, cases in which the conductive material is electrically connected even though they are not in contact with each other.
  • graphene includes carbon, has a shape such as a flat plate or a sheet, and has a two-dimensional structure formed by a 6-membered carbon ring. etc. are included. Graphene may also be curled to resemble carbon nanofibers. Furthermore, graphene having a two-dimensional structure formed of six-membered carbon rings may also be referred to as a carbon sheet.
  • the graphene compound has a shape such as a flat plate or a sheet, and includes graphene oxide, multilayer graphene oxide, multi-oxide graphene, reduced graphene oxide, reduced multi-layer graphene oxide, and reduced multi-layer graphene oxide. , graphene quantum dots, etc. Further, the graphene compound may be curled into a nanofiber-like shape. Furthermore, the graphene compound may have a functional group, and the functional group is preferably an epoxy group, a carboxy group, or a hydroxy group.
  • reduced graphene oxide, reduced multilayer graphene oxide, or reduced multi-oxide graphene refers to a portion in which the carbon concentration is greater than 80 atomic% and the oxygen concentration is 2 atomic% or more and 15 atomic% or less. It is preferable to have. With such carbon and oxygen concentrations, even a small amount can function as a highly conductive material. Further, it is preferable that the reduced graphene oxide, the reduced multilayer graphene oxide, and the reduced multilayer graphene oxide have an intensity ratio G/D of G band and D band in the Raman spectrum of 1 or more. With such an intensity ratio, even a small amount can function as a highly conductive material. Furthermore, by reducing graphene oxide, multilayer graphene oxide, and multi-layer graphene oxide, it is possible to provide pores in the graphene compound in some cases.
  • FIG. 15C illustrates carbon black 553 as a conductive material.
  • Carbon black 553 is often agglomerated because it is a fine particle.
  • the carbon black 553 can be located between the secondary particles 12a, etc., and can serve as a current path between adjacent secondary particles 12a.
  • carbon black 553 can be located between the positive electrode current collector 105 and the secondary particles, and can play a role in the current path between the positive electrode current collector 105 and the secondary particles.
  • a binder As a positive electrode of a lithium ion battery, a binder (resin) may be mixed in order to fix the positive electrode current collector 105 and the active material.
  • a binder is also called a binding agent.
  • the binder it is preferable to use rubber materials such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, and ethylene-propylene-diene copolymer.
  • SBR styrene-butadiene rubber
  • fluororubber can be used as the binder.
  • the binder it is preferable to use, for example, a water-soluble polymer.
  • a water-soluble polymer for example, polysaccharides can be used.
  • the polysaccharide one or more of cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, regenerated cellulose, starch, etc. can be used. Further, it is more preferable to use these water-soluble polymers in combination with the above-mentioned rubber material.
  • CMC carboxymethyl cellulose
  • ethyl cellulose methyl cellulose
  • hydroxypropyl cellulose diacetyl cellulose
  • regenerated cellulose starch, etc.
  • the binder may be used in combination of two or more of the above binders.
  • a material with particularly excellent viscosity adjusting effect may be used in combination with other materials.
  • rubber materials have excellent adhesive strength and/or elasticity, it may be difficult to adjust the viscosity when mixed with a solvent. In such cases, for example, it is preferable to mix with a material that is particularly effective in controlling viscosity.
  • a material having a particularly excellent viscosity adjusting effect for example, a water-soluble polymer may be used.
  • the aforementioned polysaccharides such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, cellulose derivatives such as regenerated cellulose, starch, etc. are used. be able to.
  • the above-mentioned binder is a polymeric material, and when a large amount of binder is included, the proportion of active material in the positive electrode or negative electrode decreases, and the discharge capacity of the lithium ion battery decreases. Therefore, it is preferable to mix the amount of binder to a minimum.
  • secondary particles 12a and 12b are illustrated as being spherical (having a circular cross-sectional shape) in FIG. 15C, they are not particularly limited. Irregularities, which are part of the primary particles, are often observed on the surface of the cross-sectional shape of the secondary particles where the primary particles aggregate.
  • FIG. 15D shows a positive electrode using carbon black 553 and graphene 554 as carbon materials used as conductive materials.
  • the weight of the carbon black to be mixed is 1.5 times to 20 times, preferably 2 times to 9.5 times, the weight of graphene. It is preferable to do so.
  • the graphene 554 and carbon black 553 are mixed within the above range because the dispersion stability of the carbon black 553 is excellent during slurry preparation. Further, when the mixture of graphene 554 and carbon black 553 is within the above range, it is possible to achieve a higher electrode density than a positive electrode using only carbon black 553 as a conductive material. By increasing the electrode density, the capacity per unit weight can be increased. Specifically, the density of the positive electrode active material layer measured by weight can be 3.5 g/cc or more.
  • the electrode density is lower than that of a positive electrode using only graphene as a conductive material, by setting the mixture of graphene 554 and carbon black 553 within the above range, it is possible to support rapid charging. Therefore, it is effective to mix graphene 554 and carbon black 553 when producing a lithium ion battery for use in a vehicle.
  • carbon fibers may be used instead of the graphene.
  • carbon fibers carbon nanotubes
  • agglomeration of carbon black 553 can be prevented.
  • FIGS. 15C and 15D Using either one of the positive electrodes shown in FIGS. 15C and 15D, place a separator on top of the positive electrode, place it in a container (exterior body, metal can, etc.) that accommodates the laminate in which the negative electrode is stacked on top of the separator, and fill the container with electrolyte. By filling it, a lithium ion battery can be manufactured. That is, in FIGS. 15C and 15D, the areas that are voids are impregnated with electrolyte.
  • the negative electrode has a negative electrode active material layer and a negative electrode current collector. Further, the negative electrode active material layer includes a negative electrode active material, and may further include a conductive material and a binder.
  • Niobium electrode active material for example, an alloy material and/or a carbon material can be used.
  • an element that can perform a charge/discharge reaction by alloying/dealloying reaction with lithium can be used as the negative electrode active material.
  • one or more materials selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used. These elements have a larger capacity than carbon, and silicon in particular has a high theoretical capacity of 4200 mAh/g. For this reason, it is preferable to use silicon as the negative electrode active material. Further, compounds having these elements may also be used.
  • an element that can perform a charging/discharging reaction by alloying/dealloying reaction with lithium, a compound having the element, etc. may be referred to as an alloy-based material.
  • SiO refers to silicon monoxide, for example.
  • SiO can also be expressed as SiO x .
  • x preferably has a value of 1 or a value close to 1.
  • x is preferably 0.2 or more and 1.5 or less, and preferably 0.3 or more and 1.2 or less.
  • Examples of graphite include artificial graphite and natural graphite.
  • Examples of the artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite.
  • MCMB mesocarbon microbeads
  • spherical graphite having a spherical shape can be used as the artificial graphite.
  • MCMB may have a spherical shape, which is preferred.
  • it is relatively easy to reduce the surface area of MCMB which may be preferable.
  • Examples of natural graphite include flaky graphite and spheroidized natural graphite.
  • Graphite exhibits a potential as low as that of lithium metal (0.05 V or more and 0.3 V or less vs. Li/Li + ) when lithium ions are inserted into graphite (when a lithium-graphite intercalation compound is generated). This allows lithium ion batteries using graphite to exhibit high operating voltage. Furthermore, graphite is preferable because it has advantages such as a relatively high capacity per unit volume, a relatively small volumetric expansion, low cost, and higher safety than lithium metal.
  • titanium dioxide TiO 2
  • lithium titanium composite oxide Li 4 Ti 5 O 12
  • lithium-graphite intercalation compound Li x C 6
  • niobium pentoxide Nb 2 O 5
  • tungsten dioxide WO 2
  • MoO 2 molybdenum dioxide
  • Li 2.6 Co 0.4 N has a large discharge capacity (900 mAh/g (per weight of negative electrode active material), 1890 mAh/cm 3 ) and is preferred.
  • the negative electrode active material contains lithium ions, it can be combined with materials such as V 2 O 5 and Cr 3 O 8 that do not contain lithium ions as the positive electrode active material, which is preferable. Note that even when a material containing lithium ions is used as the positive electrode active material, a nitride of lithium and a transition metal can be used as the negative electrode active material by removing the lithium ions contained in the positive electrode active material in advance.
  • a material that causes a conversion reaction can also be used as the negative electrode active material.
  • transition metal oxides that do not form an alloy with lithium such as cobalt oxide (CoO), nickel oxide (NiO), and iron oxide (FeO)
  • CoO cobalt oxide
  • NiO nickel oxide
  • FeO iron oxide
  • Materials that cause conversion reactions include oxides such as Fe 2 O 3 , CuO, Cu 2 O, RuO 2 , and Cr 2 O 3 , sulfides such as CoS 0.89 , NiS, and CuS, and Zn 3 N 2 , Cu 3 N, Ge 3 N 4 and other nitrides, NiP 2 , FeP 2 and CoP 3 and other phosphides, and FeF 3 and BiF 3 and other fluorides.
  • the same materials as the conductive material and binder that can be included in the positive electrode active material layer can be used.
  • ⁇ Negative electrode current collector> In addition to the same materials as the positive electrode current collector, copper or the like can also be used for the negative electrode current collector. Note that it is preferable to use a material that does not form an alloy with carrier ions such as lithium for the negative electrode current collector.
  • Electrolyte those described in Embodiment 1 and the like can be used.
  • separator When the electrolyte contains an electrolytic solution, a separator is placed between the positive electrode and the negative electrode.
  • separators include fibers containing cellulose such as paper, nonwoven fabrics, glass fibers, ceramics, nylon (polyamide), vinylon (polyvinyl alcohol fiber), polypropylene (denoted as PP), polyimide (denoted as PI).
  • synthetic fibers using polyester, acrylic, polyolefin, polyurethane, etc. can be used.
  • the porosity of the separator can be set to 35% or more and 90% or less, preferably 60% or more and 85% or less.
  • a separator using polypropylene can have a porosity of 35% or more and 45% or less.
  • a separator using polyimide can have a porosity of 75% or more and 85% or less.
  • the thickness of the separator is preferably 10 ⁇ m or more and 80 ⁇ m or less, more preferably 20 ⁇ m or more and 60 ⁇ m or less.
  • a separator using polyimide is preferable because it can have a high porosity and can be made thick (typically, the thickness is 50 ⁇ m or more and 60 ⁇ m or less).
  • the separator is processed into a bag shape and arranged so as to surround either the positive electrode or the negative electrode.
  • the separator may have a multilayer structure.
  • a film of an organic material such as polypropylene or polyethylene can be coated with a ceramic material, a fluorine material, a polyamide material, or a mixture thereof.
  • the ceramic material for example, aluminum oxide particles, silicon oxide particles, etc. can be used.
  • the fluorine-based material for example, PVDF, polytetrafluoroethylene, etc. can be used.
  • the polyamide material for example, nylon, aramid (meta-aramid, para-aramid), etc. can be used.
  • the safety of the lithium ion battery can be maintained even if the overall thickness of the separator is thin, so the capacity per volume of the lithium ion battery can be increased.
  • a coin cell for example, CR2032 type, diameter 20 mm, height 3.2 mm
  • Li metal as a counter electrode
  • a certain lithium ion battery is disassembled, the positive electrode impregnated with electrolyte is taken out, and the electrolyte is measured by nuclear magnetic resonance (for example, 1 H NMR) to identify at least the organic solvent.
  • nuclear magnetic resonance for example, 1 H NMR
  • the mixing ratio (volume ratio) of organic solvents can also be identified.
  • the positive electrode includes a conductive material and a binder in addition to the positive electrode active material. Further, the electrolyte and the like are removed after the nuclear magnetic resonance measurement and before punching out the positive electrode. For example, after taking out the positive electrode, the positive electrode may be cleaned using an organic solvent or the like.
  • the coin cell has lithium metal as the counter electrode. Note that materials other than lithium metal may be used for the counter electrode.
  • An electrolyte specified using nuclear magnetic resonance method is prepared as the electrolyte for the coin cell.
  • the electrolyte is an electrolyte that is one embodiment of the present invention.
  • the coin cell has a porous polypropylene film with a thickness of 25 ⁇ m as a separator.
  • stainless steel (SUS) is used as a positive electrode can, and stainless steel (SUS) is used as a negative electrode can.
  • the temperature during charging of the coin cell for evaluation can be 25° C., which is below freezing, and it can be confirmed how much the charge/discharge capacity at below freezing temperature is compared to the charge/discharge capacity at 25° C.
  • This embodiment can be used in combination with other embodiments.
  • FIGS. 16A and 16B An example of a laminate type lithium ion battery 100 is shown in FIGS. 16A and 16B.
  • 16A and 16B are external views, and the lithium ion battery 100 includes the electrolyte and separator (not shown in FIG. 16), the negative electrode 106, and the positive electrode 107 described in the above embodiment.
  • the negative electrode 106 preferably has a larger area than the positive electrode 107.
  • the lithium ion battery 100 has a negative lead electrode 510 electrically connected to the negative electrode 106 and a positive lead electrode 511 electrically connected to the positive electrode 107.
  • FIG. 16A shows an example in which the negative lead electrode 510 and the positive lead electrode 511 protrude from the same side of the exterior body 509, and the adhesive area 508 is formed at least on the side from which each lead electrode protrudes and on two sides adjacent to the side. Located in . Further, FIG.
  • 16B shows an example in which the side where the negative lead electrode 510 protrudes from the exterior body 509 and the side where the positive lead electrode 511 protrudes from the exterior body 509 are opposite to each other, and the adhesive area 508 is such that at least each lead electrode It is located on two protruding sides and one side sandwiched between the two sides.
  • the side where the adhesive region 508 is not located may correspond to the side where the exterior body 509 is folded.
  • the organic solvent and positive electrode active material of the present invention are used in the laminate type lithium ion battery 100, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • FIG. 17A is an exploded perspective view of a coin-shaped (single-layer flat type) lithium ion battery
  • FIG. 17B is an external view
  • FIG. 17C is a cross-sectional view thereof.
  • Coin-shaped lithium-ion batteries are mainly used in small electronic devices.
  • coin-type lithium ion batteries include button-type lithium ion batteries.
  • FIG. 17A is a schematic diagram so that the overlapping (vertical relationship and positional relationship) of members can be seen. Therefore, FIGS. 17A and 17B are not completely corresponding diagrams.
  • FIG. 17A shows a state in which the positive electrode 304, the negative electrode 307, the spacer 342, and the washer 332 are overlapped and sealed with the negative electrode can 302 and the positive electrode can 301. Note that in FIG. 17A, the electrolyte and separator described in the above embodiment are not illustrated.
  • the spacer 342 and the washer 332 are used to protect the inside or fix the position inside the can when the positive electrode can 301 and the negative electrode can 302 are crimped together.
  • the spacer 342 or washer 332 is made of stainless steel or an insulating material.
  • a positive electrode 304 has a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305 .
  • FIG. 17B is a perspective view of the completed coin-shaped lithium ion battery 100.
  • a positive electrode can 301 that also serves as a positive electrode terminal and a negative electrode can 302 that also serves as a negative electrode terminal may be insulated and sealed with a gasket 303 made of polypropylene or the like.
  • the positive electrode 304 is formed by a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector 305 .
  • the negative electrode 307 is formed of a negative electrode current collector 308 and a negative electrode active material layer 309 provided in contact with the negative electrode current collector 308.
  • the positive electrode can 301 is electrically connected to the positive electrode 304
  • the negative electrode can 302 is electrically connected to the negative electrode 307.
  • the active material layer of each of the positive electrode 304 and negative electrode 307 used in the coin-shaped lithium ion battery 100 may be formed only on one side.
  • the positive electrode 304, the negative electrode 307, and the negative electrode can 302 are stacked in this order with the positive electrode can 301 facing down, and the positive electrode can 301 and the negative electrode can 302 are crimped together via the gasket 303 to form a coin shape.
  • a lithium ion battery 100 is manufactured.
  • the organic solvent and positive electrode active material of the present invention are used in the coin-shaped lithium ion battery 100, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • the cylindrical lithium ion battery 616 has a positive electrode cap (battery lid) 601 on the top surface and a battery can (exterior can) 602 on the side and bottom surfaces. These positive electrode cap 601 and battery can (exterior can) 602 are insulated by a gasket (insulating packing) 610.
  • FIG. 18B is a diagram schematically showing a cross section of a cylindrical lithium ion battery.
  • the cylindrical lithium ion battery shown in FIG. 18B has a positive electrode cap (battery lid) 601 on the top surface and a battery can (exterior can) 602 on the side and bottom surfaces.
  • These positive electrode caps and the battery can (exterior can) 602 are insulated by a gasket (insulating packing) 610.
  • a battery element is provided inside the hollow cylindrical battery can 602, in which a band-shaped positive electrode 604 and a negative electrode 606 are wound with a separator 605 in between.
  • the battery element is wound around a central axis.
  • the battery can 602 has one end closed and the other end open.
  • a battery element in which a positive electrode, a negative electrode, and a separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609.
  • an electrolyte (not shown) according to one embodiment of the present invention is injected into the inside of the battery can 602 in which the battery element is provided.
  • FIGS. 18A to 18D illustrate the lithium ion battery 616 in which the height of the cylinder is larger than the diameter of the cylinder
  • the present invention is not limited to this.
  • a lithium ion battery may be used in which the diameter of the cylinder is larger than the height of the cylinder. With such a configuration, it is possible to downsize a lithium ion battery, for example.
  • a positive electrode terminal (positive electrode current collector lead) 603 is connected to the positive electrode 604, and a negative electrode terminal (negative electrode current collector lead) 607 is connected to the negative electrode 606.
  • Both the positive electrode terminal 603 and the negative electrode terminal 607 can be made of a metal material such as aluminum.
  • the positive terminal 603 and the negative terminal 607 are resistance welded to the safety valve mechanism 613 and the bottom of the battery can 602, respectively.
  • the safety valve mechanism 613 is electrically connected to the positive electrode cap 601 via a PTC (Positive Temperature Coefficient) element 611. The safety valve mechanism 613 disconnects the electrical connection between the positive electrode cap 601 and the positive electrode 604 when the increase in the internal pressure of the battery exceeds a predetermined threshold value.
  • FIG. 18C shows an example of the power storage system 615.
  • the power storage system 615 includes a plurality of lithium ion batteries 616 and is sometimes referred to as a battery pack.
  • the positive electrode of each lithium ion battery contacts and is electrically connected to a conductor 624 separated by an insulator 625.
  • the conductor 624 is electrically connected to the control circuit 620 via the wiring 623.
  • the negative electrode of each lithium ion battery is electrically connected to the control circuit 620 via a wiring 626.
  • As the control circuit 620 a protection circuit or the like that prevents overcharging or overdischarging can be applied.
  • FIG. 18D shows an example of the power storage system 615.
  • the power storage system 615 includes a plurality of lithium ion batteries 616, and the plurality of lithium ion batteries 616 are sandwiched between a conductive plate 628 and a conductive plate 614.
  • the plurality of lithium ion batteries 616 are electrically connected to a conductive plate 628 and a conductive plate 614 by wiring 627.
  • the plurality of lithium ion batteries 616 may be connected in parallel, connected in series, or connected in parallel and then further connected in series.
  • a temperature control device may be provided between the plurality of lithium ion batteries 616. When the lithium ion battery 616 is overheated, the temperature control device can cool it down, and when the lithium ion battery 616 is too cold, the temperature control device can heat it up. Therefore, the performance of power storage system 615 is less affected by outside temperature.
  • power storage system 615 is electrically connected to control circuit 620 via wiring 621 and wiring 622.
  • the wiring 621 is electrically connected to the positive electrodes of the plurality of lithium ion batteries 616 via the conductive plate 628
  • the wiring 622 is electrically connected to the negative electrodes of the plurality of lithium ion batteries 616 via the conductive plate 614.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in the cylindrical lithium ion battery 100, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • FIGS. 19 and 20 A structural example of a lithium ion battery will be described using FIGS. 19 and 20.
  • a lithium ion battery 913 shown in FIG. 19A has a wound body 950 in which a terminal 951 and a terminal 952 are provided inside a housing 930.
  • the wound body 950 is impregnated with an electrolyte of one form of the present invention inside the housing 930.
  • the terminal 952 is in contact with the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like.
  • the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930.
  • a metal material for example, aluminum
  • a resin material can be used as the housing 930.
  • the housing 930 shown in FIG. 19A may be formed of a plurality of materials.
  • a housing 930a and a housing 930b are bonded together, and a wound body 950 is provided in an area surrounded by the housing 930a and the housing 930b.
  • an insulating material such as organic resin can be used.
  • a material such as an organic resin on the surface where the antenna is formed shielding of the electric field by the lithium ion battery 913 can be suppressed.
  • an antenna may be provided inside the housing 930a.
  • a metal material can be used as the housing 930b.
  • the wound body 950 includes a negative electrode 931, a positive electrode 932, and a separator 933.
  • the wound body 950 is a wound body in which a negative electrode 931 and a positive electrode 932 are stacked on top of each other with a separator 933 in between, and the laminated sheet is wound. Note that a plurality of layers of the negative electrode 931, the positive electrode 932, and the separator 933 may be stacked.
  • a lithium ion battery 913 having a wound body 950a as shown in FIGS. 20A to 20C may be used.
  • a wound body 950a shown in FIG. 20A includes a negative electrode 931, a positive electrode 932, and a separator 933.
  • the negative electrode 931 has a negative electrode active material layer 931a.
  • the positive electrode 932 has a positive electrode active material layer 932a.
  • the separator 933 has a width wider than the negative electrode active material layer 931a and the positive electrode active material layer 932a, and is wound so as to overlap with the negative electrode active material layer 931a and the positive electrode active material layer 932a. Further, from the viewpoint of safety, it is preferable that the width of the negative electrode active material layer 931a is wider than that of the positive electrode active material layer 932a. Further, the wound body 950a having such a shape is preferable because it has good safety and productivity.
  • negative electrode 931 is electrically connected to terminal 951.
  • Terminal 951 is electrically connected to terminal 911a.
  • the positive electrode 932 is electrically connected to the terminal 952.
  • Terminal 952 is electrically connected to terminal 911b.
  • the casing 930 covers the wound body 950a, forming a lithium ion battery 913. It is preferable that the housing 930 is provided with a safety valve, an overcurrent protection element, and the like.
  • the safety valve is a valve that opens the inside of the casing 930 at a predetermined internal pressure in order to prevent the battery from exploding.
  • the lithium ion battery 913 may have a plurality of wound bodies 950a. By using a plurality of wound bodies 950a, the lithium ion battery 913 can have a larger charge/discharge capacity.
  • the description of the lithium ion battery 913 shown in FIGS. 19A to 19C can be referred to.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in the lithium ion battery 913 having a wound body, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • the electric vehicle is equipped with first batteries 1301a and 1301b as main driving lithium-ion batteries, and a second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304.
  • first batteries 1301a and 1301b as main driving lithium-ion batteries
  • second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in the first batteries 1301a and 1301b, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • the second battery 1311 is also called a cranking battery (also called a starter battery).
  • the second battery 1311 only needs to have a high output, and a large capacity is not required, and the capacity of the second battery 1311 is smaller than that of the first batteries 1301a and 1301b.
  • the internal structure of the first battery 1301a may be of a wound type or a laminated type. Furthermore, the all-solid-state battery of Embodiment 5 may be used as the first battery 1301a. By using the all-solid-state battery of Embodiment 5 as the first battery 1301a, high capacity can be achieved, safety can be improved, and the battery can be made smaller and lighter.
  • first batteries 1301a and 1301b are connected in parallel, but three or more may be connected in parallel. Furthermore, if the first battery 1301a can store sufficient power, the first battery 1301b may not be necessary.
  • a large amount of electric power can be extracted by configuring a battery pack that includes multiple lithium ion batteries.
  • the plurality of lithium ion batteries may be connected in parallel or in series, or may be connected in parallel and then further connected in series.
  • a plurality of lithium ion batteries is also called an assembled battery.
  • the first battery 1301a has a service plug or circuit breaker that can cut off high voltage without using tools. provided.
  • the power of the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but is also used to power 42V in-vehicle components (electric power steering 1307, heater 1308, defogger 1309, etc.) via a DCDC circuit 1306. to supply power. Even when the rear motor 1317 is provided on the rear wheel, the first battery 1301a is used to rotate the rear motor 1317.
  • the second battery 1311 supplies power to 14V vehicle components (audio 1313, power window 1314, lamps 1315, etc.) via the DCDC circuit 1310.
  • FIG. 21B shows an example in which nine prismatic lithium ion batteries 1300 are used as one battery pack 1415. Further, nine prismatic lithium ion batteries 1300 are connected in series, one electrode is fixed by a fixing part 1413 made of an insulator, and the other electrode is fixed by a fixing part 1414 made of an insulator.
  • this embodiment shows an example in which the battery is fixed using the fixing parts 1413 and 1414, it may also be configured to be housed in a battery housing box (also referred to as a housing). Since it is assumed that the vehicle is subjected to vibrations or shaking from the outside (road surface, etc.), it is preferable to fix the plurality of lithium ion batteries using the fixing parts 1413 and 1414, the battery housing box, and the like.
  • one electrode is electrically connected to the control circuit section 1320 by a wiring 1421.
  • the other electrode is electrically connected to the control circuit section 1320 by a wiring 1422.
  • control circuit section 1320 may use a memory circuit including a transistor using an oxide semiconductor.
  • a charging control circuit or a battery control system having a memory circuit including a transistor using an oxide semiconductor may be referred to as a BTOS (Battery operating system or Battery oxide semiconductor).
  • a metal oxide that functions as an oxide semiconductor is preferable to use.
  • In-M-Zn oxide element M is aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium
  • a metal oxide such as one or more selected from hafnium, tantalum, tungsten, and magnesium.
  • In-M-Zn oxide that can be applied as an oxide is CAAC-OS (C-Axis Aligned Crystal Oxide Semiconductor), CAC-OS (Cloud-Aligned Composite Oxide) Semiconductor) is preferable.
  • CAAC-OS C-Axis Aligned Crystal Oxide Semiconductor
  • CAC-OS Cloud-Aligned Composite Oxide
  • an In-Ga oxide or an In-Zn oxide may be used.
  • CAAC-OS is an oxide semiconductor that has a plurality of crystal regions, and the c-axes of the plurality of crystal regions are oriented in a specific direction. Note that the specific direction is the thickness direction of the CAAC-OS film, the normal direction to the surface on which the CAAC-OS film is formed, or the normal direction to the surface of the CAAC-OS film.
  • a crystal region is a region having periodicity in atomic arrangement. Note that if the atomic arrangement is regarded as a lattice arrangement, a crystal region is also a region with a uniform lattice arrangement.
  • the CAAC-OS has a region where a plurality of crystal regions are connected in the a-b plane direction, and this region may have distortion. Note that distortion refers to a region where a plurality of crystal regions are connected, where the direction of the lattice arrangement changes between a region with a uniform lattice arrangement and another region with a uniform lattice arrangement.
  • CAAC-OS is an oxide semiconductor that has c-axis orientation and no obvious orientation in the a-b plane direction.
  • CAC-OS is, for example, a structure of a material in which elements constituting a metal oxide are unevenly distributed in a size of 0.5 Nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or less, or in the vicinity thereof.
  • the metal oxide one or more metal elements are unevenly distributed, and the region having the metal element has a size of 0.5 Nm or more and 10 nm or less, preferably 1 nm or more and 3 nm or less, or a size in the vicinity thereof.
  • the mixed state is also called a mosaic or a patch.
  • control circuit portion 1320 can be used in a low-temperature environment, it is preferable to use a transistor using an oxide semiconductor.
  • the control circuit section 1320 may be formed using unipolar transistors.
  • a transistor using an oxide semiconductor in its semiconductor layer has an operating ambient temperature wider than that of single crystal Si, ranging from -40° C. to 150° C., and even when a lithium ion battery is heated, its characteristics change less than that of a single crystal.
  • the off-state current of a transistor using an oxide semiconductor is below the measurement lower limit regardless of the temperature even at 150° C., the off-state current characteristics of a single-crystal Si transistor are highly temperature dependent. For example, at 150° C., the off-state current of a single-crystal Si transistor increases, and the current on/off ratio does not become sufficiently large.
  • the control circuit section 1320 can improve safety.
  • the control circuit unit 1320 using a memory circuit including a transistor using an oxide semiconductor can also function as an automatic control device for a lithium ion battery in response to ten causes of instability such as micro shorts.
  • the functions that eliminate the causes of instability in 10 areas include overcharging prevention, overcurrent prevention, overheating control during charging, cell balance in assembled batteries, overdischarge prevention, fuel gauge, and temperature-based charging. Examples include automatic control of voltage and current amount, control of charging current amount according to the degree of deterioration, micro-short abnormal behavior detection, and abnormal prediction regarding micro-short, and the control circuit unit 1320 has at least one of these functions. Furthermore, it is possible to miniaturize the automatic control device for lithium ion batteries.
  • a micro short circuit refers to a minute short circuit inside a lithium ion battery.
  • One of the causes of micro shorts is that multiple charging and discharging cycles cause local current concentration in a part of the positive electrode and part of the negative electrode due to uneven distribution of the positive electrode active material. It is said that micro short circuits occur due to the generation of side reactants during the reaction.
  • control circuit unit 1320 can also be said to detect the terminal voltage of the lithium ion battery and manage the charging/discharging state of the lithium ion battery. For example, to prevent overcharging, both the output transistor and the cutoff switch of the charging circuit can be turned off almost simultaneously.
  • FIG. 21C an example of a block diagram of the battery pack 1415 shown in FIG. 21B is shown in FIG. 21C.
  • the control circuit section 1320 includes a switch section 1324 including at least a switch for preventing overcharging and a switch for preventing overdischarge, a control circuit 1322 for controlling the switch section 1324, and a voltage measuring section for the first battery 1301a. has.
  • the control circuit section 1320 has an upper limit voltage and a lower limit voltage set for the lithium ion battery to be used, and limits the upper limit of the current from the outside and the upper limit of the output current to the outside.
  • the range of the lithium ion battery from the lower limit voltage to the upper limit voltage is within the voltage range recommended for use, and when it is outside that range, the switch section 1324 is activated and functions as a protection circuit.
  • control circuit section 1320 can also be called a protection circuit because it controls the switch section 1324 to prevent overdischarge and overcharge. For example, when the control circuit 1322 detects a voltage that is likely to cause overcharging, the switch section 1324 is turned off to cut off the current. Furthermore, a PTC element may be provided in the charging/discharging path to provide a function of cutting off the current in response to a rise in temperature. Further, the control circuit section 1320 has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).
  • the switch portion 1324 can be configured by combining an n-channel transistor and a p-channel transistor.
  • the switch section 1324 is not limited to a switch having an Si transistor using single crystal silicon, but includes, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (phosphide).
  • the switch portion 1324 may be formed of a power transistor having a material such as indium (indium), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaO x (gallium oxide; x is a real number greater than 0), or the like. .
  • a memory element using an OS transistor can be freely arranged by stacking it on a circuit using a Si transistor, it can be easily integrated.
  • the first batteries 1301a and 1301b mainly supply power to 42V system (high voltage system) in-vehicle equipment, and the second battery 1311 supplies power to 14V system (low voltage system) in-vehicle equipment.
  • the second battery 1311 a lead-acid battery is often used because it is advantageous in terms of cost.
  • using a lithium ion battery as the second battery 1311 has the advantage of being maintenance-free, if it is used for a long period of time, for example three years or more, there is a risk that an abnormality that cannot be determined at the time of manufacture may occur.
  • the second battery 1311 that starts the inverter becomes inoperable, the second battery 1311 is powered by a lead-acid In the case of a storage battery, power is supplied from the first battery to the second battery, and the battery is charged so as to always maintain a fully charged state.
  • lithium ion batteries are used as both the first battery 1301a and the second battery 1311, but the second battery 1311 uses a lead acid battery, an all-solid battery, or an electric double layer capacitor. It's okay.
  • the electrolyte and positive electrode active material of one embodiment of the present invention are used in the above-mentioned lithium ion battery, excellent charge-discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • regenerated energy due to the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305, and charged to the second battery 1311 from the motor controller 1303 and the battery controller 1302 via the control circuit section 1321.
  • the first battery 1301a is charged from the battery controller 1302 via the control circuit section 1320.
  • the first battery 1301b is charged from the battery controller 1302 via the control circuit unit 1320. In order to efficiently charge the regenerated energy, it is desirable that the first batteries 1301a and 1301b can be rapidly charged.
  • the battery controller 1302 can set the charging voltage, charging current, etc. of the first batteries 1301a and 1301b.
  • the battery controller 1302 can set charging conditions according to the charging characteristics of the lithium ion battery to be used and perform rapid charging.
  • the outlet of the charger or the connection cable of the charger is electrically connected to the battery controller 1302.
  • Power supplied from an external charger charges the first batteries 1301a and 1301b via the battery controller 1302.
  • a control circuit is provided and the function of the battery controller 1302 is not used in some cases, but in order to prevent overcharging, the first batteries 1301a and 1301b are charged via the control circuit section 1320. It is preferable.
  • the connection cable or the connection cable of the charger is provided with a control circuit.
  • the control circuit section 1320 is sometimes called an ECU (Electronic Control Unit).
  • the ECU is connected to a CAN (Controller Area Network) provided in the electric vehicle.
  • CAN is one of the serial communication standards used as an in-vehicle LAN.
  • the ECU includes a microcomputer. Further, the ECU uses a CPU or a GPU.
  • External chargers installed at charging stations and the like include 100V outlets, 200V outlets, and 3-phase 200V and 50kW. It is also possible to charge the battery by receiving power from an external charging facility using a non-contact power supply method or the like.
  • a lithium ion battery which is one embodiment of the present invention, is mounted in a vehicle, typically a transportation vehicle, will be described.
  • next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), or plug-in hybrid vehicles (PHV)
  • HV hybrid vehicles
  • EV electric vehicles
  • PSV plug-in hybrid vehicles
  • agricultural machinery, motorized bicycles including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing aircraft and rotary-wing aircraft, rockets, artificial satellites, space probes, Lithium-ion batteries can also be installed in transportation vehicles such as planetary probes and spacecraft.
  • a car 2001 shown in FIG. 22A is an electric car that uses an electric motor as a power source for driving. Alternatively, it is a hybrid vehicle that can appropriately select and use an electric motor and an engine as a power source for driving.
  • a lithium ion battery is mounted on a vehicle
  • the example of the lithium ion battery shown in the above embodiment is installed at one or more locations.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in a lithium ion battery installed in a vehicle, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • a car 2001 shown in FIG. 22A includes a battery pack 2200, and the battery pack includes a battery module to which a plurality of lithium ion batteries are connected. Further, battery pack 2200 preferably includes a charging control device electrically connected to the battery module.
  • the automobile 2001 can be charged by receiving power from an external charging facility using a plug-in method, a non-contact power supply method, or the like to a lithium ion battery of the automobile 2001.
  • a predetermined charging method and connector standard such as CHAdeMO (registered trademark) or combo may be used as appropriate.
  • the lithium ion battery may be a charging station located in a commercial facility or may be a home power source.
  • plug-in technology it is possible to charge the power storage device mounted on the vehicle 2001 by supplying power from the outside. Charging can be performed by converting AC power into DC power via a conversion device such as an ACDC converter.
  • a power receiving device can be mounted on a vehicle and electrical power can be supplied from a ground power transmitting device in a non-contact manner for charging.
  • this contactless power supply method by incorporating a power transmission device into the road or an outer wall, charging can be performed not only while the vehicle is stopped but also while the vehicle is running. Further, electric power may be transmitted and received between two vehicles using this contactless power supply method.
  • a solar cell may be provided on the exterior of the vehicle to charge the lithium ion battery when the vehicle is stopped and when the vehicle is running.
  • an electromagnetic induction method or a magnetic resonance method can be used.
  • FIG. 22B shows a large transport vehicle 2002 having an electrically controlled motor as an example of a transport vehicle.
  • the battery module of the transportation vehicle 2002 has a maximum voltage of 170V, with 48 cells connected in series, for example, a four-cell unit of lithium ion batteries with a nominal voltage of 3.0V or more and 5.0V or less. Except for the difference in the number of lithium ion batteries in the battery pack 2201, etc., it has the same functions as those in FIG. 21B, so a description thereof will be omitted.
  • the electrolyte and positive electrode active material of one embodiment of the present invention are used in the lithium ion battery of the battery pack 2201, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • FIG. 22C shows, by way of example, a large transport vehicle 2003 with an electrically controlled motor.
  • the battery module of the transportation vehicle 2003 has a maximum voltage of 600V, for example, by connecting in series 100 or more lithium ion batteries with a nominal voltage of 3.0 V or more and 5.0 V or less. Except for the difference in the number of batteries, etc., it has the same functions as those in FIG. 22B, so a description thereof will be omitted.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in the lithium ion battery included in the module, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • FIG. 22D shows an example aircraft 2004 with an engine that burns fuel. Since the aircraft 2004 shown in FIG. 22D has wheels for takeoff and landing, it can be said to be part of a transportation vehicle, and a battery module is configured by connecting a plurality of lithium ion batteries, and the battery module and charging control device are connected to each other. It has a battery pack 2203 that includes.
  • the battery module of the aircraft 2004 is, for example, eight 4V lithium ion batteries connected in series and has a maximum voltage of 32V. Except for the difference in the number of lithium ion batteries constituting the battery module of the battery pack 2203, it has the same functions as those in FIG. 21B, so a description thereof will be omitted.
  • a lithium ion battery which is one embodiment of the present invention, is mounted on a vehicle such as a two-wheeled vehicle or a bicycle.
  • FIG. 23A is an example of an electric bicycle using a lithium ion battery according to one embodiment of the present invention.
  • the lithium ion battery of one embodiment of the present invention can be applied to the electric bicycle 8700 shown in FIG. 23A.
  • the lithium ion battery of one embodiment of the present invention may have a protection circuit.
  • Electric bicycle 8700 includes a power storage device 8702.
  • the power storage device 8702 can supply electricity to a motor that assists the driver. Further, the power storage device 8702 is portable, and FIG. 23B shows a state in which it is removed from the bicycle. Further, the power storage device 8702 includes a plurality of built-in lithium ion batteries 8701 according to one embodiment of the present invention, and can display the remaining battery power and the like on a display portion 8703.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in the lithium ion battery 8701, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • Power storage device 8702 also includes a control circuit 8704 that can control charging or detect abnormality of the lithium ion battery, an example of which is shown in Embodiment 7.
  • the control circuit 8704 is electrically connected to the positive and negative electrodes of the lithium ion battery 8701. This can greatly contribute to eradicating accidents such as fires caused by lithium-ion batteries.
  • FIG. 23C is an example of a two-wheeled vehicle using the lithium ion battery of one embodiment of the present invention.
  • a scooter 8600 shown in FIG. 23C includes a power storage device 8602, a side mirror 8601, and a direction indicator light 8603.
  • the power storage device 8602 can supply electricity to the direction indicator light 8603.
  • excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • a scooter 8600 shown in FIG. 23C can store a power storage device 8602 in an under-seat storage 8604.
  • the power storage device 8602 can be stored in the under-seat storage 8604 even if the under-seat storage 8604 is small.
  • Electrode 8 In this embodiment, an example in which a lithium ion battery, which is one embodiment of the present invention, is mounted in an electronic device will be described.
  • Electronic devices that incorporate lithium ion batteries include, for example, television devices (also called televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, and mobile phones (mobile phones, etc.).
  • Examples include mobile phone devices (also referred to as mobile phone devices), portable game machines, personal digital assistants, audio playback devices, and large game machines such as pachinko machines.
  • portable information terminals include notebook personal computers, tablet terminals, electronic book terminals, and mobile phones.
  • FIG. 24A shows an example of a mobile phone.
  • the mobile phone 2100 includes a display section 2102 built into a housing 2101, as well as operation buttons 2103, an external connection port 2104, a speaker 2105, a microphone 2106, and the like.
  • the mobile phone 2100 includes a lithium ion battery 2107.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in a lithium ion battery, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • the mobile phone 2100 can run various applications such as mobile telephony, e-mail, text viewing and creation, music playback, Internet communication, computer games, and so on.
  • the operation button 2103 can have various functions such as turning on and off the power, turning on and off wireless communication, executing and canceling silent mode, and executing and canceling power saving mode.
  • the functions of the operation buttons 2103 can be freely set using the operating system built into the mobile phone 2100.
  • the mobile phone 2100 is capable of performing short-range wireless communication according to communication standards. For example, by communicating with a headset capable of wireless communication, it is also possible to make hands-free calls.
  • the mobile phone 2100 is equipped with an external connection port 2104, and can directly exchange data with other information terminals via a connector. Charging can also be performed via the external connection port 2104. Note that the charging operation may be performed by wireless power supply without using the external connection port 2104.
  • mobile phone 2100 has a sensor.
  • the sensor includes, for example, a human body sensor such as a fingerprint sensor, a pulse sensor, and a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, and the like.
  • FIG. 24B is an unmanned aircraft 2300 with multiple rotors 2302.
  • Unmanned aerial vehicle 2300 is sometimes called a drone.
  • Unmanned aircraft 2300 includes a lithium ion battery 2301, which is one embodiment of the present invention, a camera 2303, and an antenna (not shown).
  • Unmanned aerial vehicle 2300 can be remotely controlled via an antenna.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in a lithium ion battery, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • FIG. 24C shows an example of a robot.
  • the robot 6400 shown in FIG. 24C includes a lithium ion battery 6409, an illuminance sensor 6401, a microphone 6402, an upper camera 6403, a speaker 6404, a display portion 6405, a lower camera 6406, an obstacle sensor 6407, a movement mechanism 6408, a calculation device, and the like.
  • the microphone 6402 has a function of detecting the user's speaking voice, environmental sounds, and the like. Furthermore, the speaker 6404 has a function of emitting sound.
  • the robot 6400 can communicate with a user using a microphone 6402 and a speaker 6404.
  • the display unit 6405 has a function of displaying various information.
  • the robot 6400 can display information desired by the user on the display section 6405.
  • the display unit 6405 may include a touch panel. Further, the display unit 6405 may be a removable information terminal, and by installing it at a fixed position on the robot 6400, charging and data exchange are possible.
  • the upper camera 6403 and the lower camera 6406 have a function of capturing images around the robot 6400. Further, the obstacle sensor 6407 can detect the presence or absence of an obstacle in the direction of movement of the robot 6400 when the robot 6400 moves forward using the moving mechanism 6408.
  • the robot 6400 uses an upper camera 6403, a lower camera 6406, and an obstacle sensor 6407 to recognize the surrounding environment and can move safely.
  • the robot 6400 includes a lithium ion battery 6409 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal area.
  • a lithium ion battery 6409 according to one embodiment of the present invention
  • a semiconductor device or an electronic component in its internal area.
  • FIG. 24D shows an example of a cleaning robot.
  • the cleaning robot 6300 includes a display portion 6302 placed on the top surface of a housing 6301, a plurality of cameras 6303 placed on the side, a brush 6304, operation buttons 6305, a lithium ion battery 6306, various sensors, and the like.
  • the cleaning robot 6300 is equipped with tires, a suction port, and the like.
  • the cleaning robot 6300 is self-propelled, detects dirt 6310, and can suck the dirt from a suction port provided on the bottom surface.
  • the cleaning robot 6300 can analyze the image taken by the camera 6303 and determine the presence or absence of obstacles such as walls, furniture, or steps. Furthermore, if an object such as wiring that is likely to become entangled with the brush 6304 is detected through image analysis, the rotation of the brush 6304 can be stopped.
  • the cleaning robot 6300 includes a lithium ion battery 6306 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal area. When the electrolyte and positive electrode active material according to one embodiment of the present invention are used in a lithium ion battery, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • This embodiment can be implemented in combination with other embodiments as appropriate.
  • FIG. 25A shows an artificial satellite 6800 as an example of space equipment.
  • the artificial satellite 6800 includes a body 6801, a solar panel 6802, an antenna 6803, and a lithium ion battery 6805.
  • Solar panels are sometimes called solar modules.
  • the satellite 6800 By irradiating the solar panel 6802 with sunlight, electric power necessary for the operation of the artificial satellite 6800 is generated. However, for example, in a situation where the solar panel is not irradiated with sunlight or in a situation where the amount of sunlight irradiated onto the solar panel is small, less electric power is generated. Therefore, the power necessary for satellite 6800 to operate may not be generated. In order to operate the satellite 6800 even under conditions where generated power is low, the satellite 6800 may be provided with a lithium ion battery 6805. When the electrolyte and positive electrode active material according to one embodiment of the present invention are used in a lithium ion battery, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • Satellite 6800 can generate signals.
  • the signal is transmitted via antenna 6803 and can be received by, for example, a ground-based receiver or other satellite.
  • a ground-based receiver or other satellite By receiving the signal transmitted by the artificial satellite 6800, it is possible to measure, for example, the position of the receiver that received the signal.
  • the artificial satellite 6800 can constitute, for example, a satellite positioning system.
  • the artificial satellite 6800 can be configured to include a sensor.
  • the artificial satellite 6800 can have a function of detecting sunlight reflected by hitting an object provided on the ground.
  • the artificial satellite 6800 can have a function of detecting thermal infrared rays emitted from the earth's surface.
  • the artificial satellite 6800 can have the function of, for example, an earth observation satellite.
  • FIG. 25B shows a spacecraft 6900 having a solar sail (also referred to as a solar sail) as an example of space equipment.
  • the probe 6900 includes a fuselage 6901, a solar sail 6902, and a lithium ion battery 6905.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in a lithium ion battery, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • the surface of the solar sail 6902 preferably has a thin film with high reflectance, and further preferably faces toward the sun.
  • the solar sail 6902 may be designed to be folded into a small size until it exits the atmosphere, and to be unfolded into a large sheet outside the Earth's atmosphere (outer space) as shown in FIG. 25B.
  • FIG. 25C shows a spacecraft 6910 as an example of space equipment.
  • Spacecraft 6910 includes a fuselage 6911, a solar panel 6912, and a lithium ion battery 6913.
  • the fuselage 6911 can have, for example, a pressurized chamber and a non-pressurized chamber.
  • the pressurized chamber may be designed so that a crew member can enter it. Power generated by sunlight irradiating the solar panel 6912 can charge the lithium ion battery 6913.
  • FIG. 25D shows a rover 6920 as an example of space equipment.
  • the rover 6920 has a fuselage 6921 and a lithium ion battery 6923.
  • the electrolyte and positive electrode active material according to one embodiment of the present invention are used in a lithium ion battery, excellent charge/discharge characteristics are expected over a wide temperature range from below freezing to high temperatures.
  • Rover 6920 may have a solar panel 6922.
  • the rover 6920 may be designed to accommodate a passenger.
  • the lithium ion battery 6923 may be charged with the electric power generated by sunlight irradiating the solar panel 6912, or the electric power generated by other power sources such as a fuel cell, a radioisotope thermoelectric converter, etc.
  • a lithium ion battery 6923 may be charged.
  • FIGS. 27A and 27B Charts of the measurement results are shown in FIGS. 27A and 27B.
  • the peak position of MTFP can be read.
  • MTFP can be read to have a peak at 3 ppm or more and 4 ppm or less when analyzed by 1 H-NMR.
  • FIG. 28B which is an enlarged view, both the peak corresponding to FEC confirmed in FIG. 26B and the peak corresponding to MTFP confirmed in FIG. 27B were confirmed. That is, FEC and MTFP are not combined, and it is presumed that FEC, which forms a solvate with the lithium salt, and MTFP coexist in the mixed solution.
  • the MTFP may be considered to be mixed to maintain proper viscosity. MTFP may also form a solvate with a lithium salt.
  • ⁇ HOMO level and solvation energy> the HOMO level and solvation energy were calculated.
  • solvation energy refers to the energy for the organic solvent used in the electrolyte to bond with lithium ions through Coulomb force or the like. Connecting is also called coordination.
  • FEC which has a substituent that exhibits electron-withdrawing property
  • MTFP substituent that exhibits electron-withdrawing property
  • EC and MP including organic compounds that do not have a substituent that exhibits electron-withdrawing property, are HOMO-compliant.
  • the position and solvation energy were calculated. Note that here, the stabilizing energy when four molecules of the organic solvent used in the electrolyte are coordinated with one Li ion is calculated as the solvation energy.
  • DFT Density functional theory
  • 6-311G (a basis function of a triple split valence basis set using three shortening functions for each valence orbital) was applied to all atoms.
  • basis functions for example, in the case of a hydrogen atom, 1s to 3s orbits are taken into consideration, and in the case of a carbon atom, 1s to 4s and 2p to 4p orbits are taken into consideration.
  • a p function to hydrogen atoms and a d function to non-hydrogen atoms as polarization basis sets. The table below summarizes the above calculation conditions.
  • the calculation results of the HOMO level and solvation energy are shown in the table below, and the measured values of the melting point are also attached to the table below.
  • the solvation energies of MTFP and MP which are chain-type organic compounds, change due to the influence of rotational coordinates, so the solvation energies are shown as ranges.
  • HOMO level a difference was confirmed between an organic compound having a substituent that exhibits electron-withdrawing property and an organic compound having no such substituent. Specifically, FEC having the above substituent had a deeper HOMO level than EC having no above substituent. Furthermore, MTFP having the above substituent had a deeper HOMO level than MP having no above substituent.
  • FEC having the above substituent had a deeper HOMO level than EC having no above substituent.
  • MTFP having the above substituent had a deeper HOMO level than MP having no above substituent.
  • lithium-ion batteries can be used over a wide temperature range, and battery characteristics can also be improved when lithium-ion batteries are placed at sub-zero temperatures. There is expected.
  • Sample 1, Sample 2, and Reference Example 1 were prepared in order to measure AC impedance and evaluate charge/discharge characteristics. The manufacturing conditions for each sample will be explained.
  • step S15 the lithium cobalt oxide was heated at 850° C. for 2 hours in a furnace into which oxygen was introduced. No oxygen was supplied into the furnace during heating.
  • step S22_1 LiF and MgF 2 were ground and mixed in dehydrated acetone to obtain a mixture A1, that is, an A1 source.
  • step S31 of FIG. 2A the lithium cobalt oxide that has been heat-treated in step S15 is mixed with the mixture A1 to obtain a mixture 903 in step S32, and the mixture 903 is heated at 900° C. for 20 hours in step S33. , heated in a furnace where oxygen was introduced.
  • step S20_2 No oxygen was supplied into the furnace during heating.
  • an A2 source for step S20_2 was prepared. Ni(OH) 2 and Al(OH) 3 shown in step S21_2 of FIG. 2C were each weighed to be 0.5 mol% with respect to lithium cobalt oxide, and each was placed in dehydrated acetone as in step S22_2. Mixing while grinding yielded mixture A2, ie source A2. Thereafter, mixture 903 and mixture A2 were mixed as in step S34 of FIG. 2A, and mixture 904 was obtained as in step S35. Next, as in step S36, the mixture 904 was heated at 850° C. for 10 hours in a furnace into which oxygen was introduced. No oxygen was supplied into the furnace during heating. In this way, a positive electrode active material of Sample 1 was obtained.
  • the positive electrode active material of Sample 1 is LCO containing Mg, F, Ni, and Al, and the positive electrode active material corresponds to the above-mentioned discharge state where x in Li x CoO 2 is 1 and x is 0.24 or less.
  • the above positive electrode active material, acetylene black (AB) as a conductive aid, and polyvinylidene fluoride (PVDF) as a binder were prepared as the positive electrode of Sample 1.
  • PVDF was prepared in a state in which it was dissolved in N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 5%.
  • NMP N-methyl-2-pyrrolidone
  • a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) using Sample 1 as a positive electrode was assembled.
  • the coin cell used lithium metal as the counter electrode.
  • Stainless steel (SUS) was used for the positive electrode can and negative electrode can of the coin cell, respectively.
  • Such coin cells are sometimes called half cells or test batteries.
  • Sample 2 differs from Sample 1 in the positive electrode active material.
  • LCO obtained by the solid phase method shown in Embodiment 2 is used.
  • lithium cobalt oxide manufactured by Nippon Kagaku Kogyo, product name: This sample differs from Sample 1 in that C-5H (hereinafter referred to as "C-5H") was prepared.
  • C-5H has a median diameter (D50) of approximately 7.0 ⁇ m.
  • steps S15 and subsequent steps were performed in the same manner as in sample 1, and as a heating condition different from that in sample 1, in step S33, the mixture 903 was heated at 850° C. for 10 hours in a furnace into which oxygen was introduced.
  • the heating time for Sample 2 was shorter than that for Sample 1 because the median diameter (D50) was smaller. Further, the heating time of sample 2 was also made shorter than that of sample 1 in step S36. In addition, for Sample 2, steps S20_2 and subsequent steps were performed in the same manner as Sample 1. In this way, sample 2 of positive electrode active material was obtained.
  • the positive electrode active material of Sample 2 is LCO containing Mg, F, Ni, and Al, and the positive electrode active material corresponds to the above-mentioned discharge state where x in Li x CoO 2 is 1 and x is 0.24 or less.
  • the above positive electrode active material, acetylene black (AB) as a conductive aid, and polyvinylidene fluoride (PVDF) as a binder were prepared as the positive electrode of Sample 2.
  • PVDF was prepared in a state in which it was dissolved in N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 5%.
  • NMP N-methyl-2-pyrrolidone
  • Sample 2 As in Sample 1, PP and PI were prepared as separators. When distinguishing Sample 2 by the material of the separator, it is written as "Sample 2_P” and “Sample 2_I”, respectively.
  • a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) was assembled using Sample 2 as the positive electrode and lithium metal as the counter electrode.
  • Stainless steel (SUS) was used for the positive electrode can and negative electrode can of the coin cell, respectively.
  • Such coin cells are sometimes called half cells or test batteries.
  • sample 1_P As an example, conditions for producing an evaluation cell for AC impedance measurement will be described. Aging treatment was performed on the half cell having sample 1_P. As aging treatment, two cycles of charging under the following conditions and discharging under the following conditions were repeated. As charging conditions, the environmental temperature at which sample 1_P is placed was 25°C, and constant current charging (hereinafter referred to as CC charging) was performed at a rate of 0.1C until the final voltage reached 4.6V, and then the current decreased to 0.01C. Constant voltage charging (hereinafter referred to as CV charging) was performed at 4.6V until the voltage reached 4.6V.
  • CC charging constant current charging
  • CV charging Constant voltage charging
  • the environmental temperature at which sample 1_P was placed was set to 25° C., and constant current discharge (hereinafter referred to as CC discharge) was performed at a rate of 0.1 C until the final voltage reached 2.5 V.
  • CC discharge constant current discharge
  • a subsequent third cycle of charging was performed.
  • the conditions for the charging were as follows: CC charging was performed at a rate of 0.1C until the final voltage reached 4.5V at an environmental temperature of 25°C, and then CV charging was performed until the current reached 0.01C.
  • the environmental temperature is the temperature of a constant temperature bath (manufactured by ESPEC) in which each sample is placed, and is hereinafter simply referred to as the environmental temperature.
  • 1C 200 mA/g (current per weight of positive electrode active material was 200 mA/g).
  • the half cell containing Sample 1 was left in a constant temperature bath for 6 hours.
  • the positive electrode of sample 1_P was taken out from the half cell under an argon atmosphere. The positive electrode taken out was in a state of being impregnated with electrolyte.
  • FIGS. 29A and 29B a Nyquist diagram and an equivalent circuit diagram used for fitting are shown in FIGS. 29A and 29B, respectively.
  • Z' on the horizontal axis indicates resistance [ ⁇ ]
  • -Z'' on the vertical axis indicates reactance [ ⁇ ].
  • CPE HF and CPE LF are 29A and 29B
  • the resistance marked R S corresponds to the resistance of the electrolyte
  • the resistance marked R HF relates to electron conduction within the electrode or adsorption and desorption of lithium ions on the electrode surface.
  • the resistor with RLF corresponds to solvation and desolvation of lithium ions, charge transfer resistance corresponding to insertion and desorption of lithium ions, and surface film resistance.Surface
  • the film can be formed by decomposing the electrolytic solution and depositing it on the active material. Note that W in FIGS. 29A and 29B is a diffusion coefficient corresponding to the diffusion of lithium ions in a solid.
  • AC impedance measurement was performed using a potentio/galvanostat (hereinafter referred to as "P/G") while controlling the environmental temperature in which the symmetrical cell is placed to be 25 °C, 0 °C, -20 °C, -40 °C, and 25 °C.
  • P/G potentio/galvanostat
  • the measurements were carried out using a measurement device that combines a frequency response analyzer (hereinafter referred to as "FRA”) and a frequency response analyzer (hereinafter referred to as "FRA”).
  • FRA the alternating current amplitude
  • AC amplitude was set to 10 mV
  • the frequency applied to the symmetric cell was varied within 0.3 mHz to 100 kHz.
  • the frequency is changed from 1 mHz to 100 kHz
  • the frequency is changed from 0.5 mHz to 100 kHz
  • the frequency is changed.
  • the frequency was changed from 0.3mHz to 100kHz.
  • FIG. 30A shows the results of AC impedance measurement of Sample 1_P and Reference Example 1 under the lowest environmental temperature of -40° C. among the AC impedance conditions.
  • sample 1_P the frequency at the apex of the circular arc corresponding to R LF was 2.1 mHz, and the resistance was 1.3 ⁇ 10 5 ( ⁇ ).
  • Reference Example 1 the frequency at the apex of the circular arc corresponding to RLF was 1.0 mHz, and the resistance was 2.7 ⁇ 10 5 ( ⁇ ).
  • FIG. 30B shows an enlarged view of a region in which the resistance Z' in FIG. 30A is around 50 ( ⁇ ) and is marked with a square.
  • sample 1_P the frequency at the apex of the circular arc corresponding to R HF was 988 Hz, and the resistance was 62 ( ⁇ ).
  • Reference Example 1 the frequency at the apex of the arc corresponding to RHF was 916 Hz, and the resistance was 35 ( ⁇ ).
  • FIG. 30C R S , R HF , and R LF of Sample 1_P and Reference Example 1 are shown together.
  • FIG. 31A shows the results of AC impedance measurement of Sample 1_P and Reference Example 1 when the environmental temperature was 25°C.
  • the frequency at the apex of the circular arc corresponding to R LF was 3.8 Hz, and the resistance was 76 ( ⁇ ).
  • the frequency at the apex of the circular arc corresponding to RLF was 1.7 Hz, and the resistance was 126 ( ⁇ ).
  • FIG. 31B shows an enlarged view of a region in which Z′ in FIG. 31A is around 50 ( ⁇ ) and is marked with a square.
  • the frequency at the apex of the circular arc corresponding to R HF was 14094 Hz, and the resistance was 3.6 ( ⁇ ).
  • Sample 1_P had a lower RLF value than Reference Example 1 at both environmental temperatures of -40°C and 25°C.
  • the separator material is common to Sample 1_P and Reference Example 1, it can be said that Sample 1 has a lower RLF value than Reference Example 1 at both environmental temperatures of -40°C and 25°C.
  • RLF is a charge transfer resistance corresponding to solvation and desolvation of lithium ions, insertion and desorption of lithium ions, and a surface film resistance component. It was also found that R LF is the resistance that should be considered the most at subzero temperatures because R LF is larger than R S and R HF at -40° C.
  • Sample 1 had a low RLF at -40°C, it was assumed that the lithium ion battery had excellent charge/discharge characteristics at subzero temperatures. Furthermore, since sample 1 has a low RLF even at 25°C, it is assumed that a lithium-ion battery with an electrolyte like sample 1 can achieve excellent charge-discharge characteristics over a wide temperature range from sub-zero to high temperatures. It was done.
  • ⁇ Charge/discharge characteristics> The charge capacity, discharge capacity, and cycle characteristics of Sample 1, Sample 2, etc. described above were measured using a charge/discharge measuring system (TOSCAT-3100) manufactured by Toyo System Co., Ltd. as a charge/discharge measuring instrument.
  • TOSCAT-3100 charge/discharge measuring system manufactured by Toyo System Co., Ltd.
  • the rate includes a discharge rate, and the discharge rate is a relative ratio of the current value during discharge to the battery capacity, and is expressed in units of C.
  • the current equivalent to 1C is X (A).
  • the rate also includes the charge rate, but the charge rate can be understood by replacing the above-mentioned discharge rate and discharge with the charge rate and charge, respectively.
  • 1C 200 mA/g (current per weight of positive electrode active material is 200 mA/g).
  • the above charging was performed by CC charging at a charging rate of 0.1C until the final voltage reached 4.6V, and the above discharging was performed by CC discharging at a discharge rate of 0.1C until the final voltage reached 2.5V.
  • 1C 200 mA/g (current per weight of positive electrode active material was 200 mA/g).
  • the table below shows the test conditions.
  • FIG. 32A shows the charging capacity (mAh/g) per weight of positive electrode active material for each sample.
  • the temperature shown on the horizontal axis of FIG. 32A is the environmental temperature under the charging conditions shown in the above table.
  • the table below shows the charging capacity at each environmental temperature normalized to the charging capacity at 25°C.
  • the normalized value may be expressed as a percentage, and a normalized value of 0.5 is equal to 50%.
  • ⁇ Discharge characteristics> in order to confirm the discharge capacity below freezing point, the environmental temperatures at which Sample 1_P, Sample 1_I, Sample 2_P, and Sample 2_I (collectively referred to as each sample) are placed were set to 25°C, 0°C, -20°C, - The discharge capacity was measured at each environmental temperature while lowering the temperature in the order of 40°C, -45°C, and -50°C. Note that charging was performed after each discharge at each environmental temperature, and the environmental temperature was 25° C. for the charging. In the above charging, CC charging was performed at a charging rate of 0.1C until the final voltage reached 4.6V, and then CV charging was performed at 4.6V until the current reached 0.05C.
  • CC discharge was performed at a discharge rate of 0.1C until the final voltage reached 2.5V.
  • 1C 200 mA/g (current per weight of positive electrode active material was 200 mA/g).
  • the table below shows the test conditions.
  • FIG. 32B shows the results of discharge capacity (mAh/g) per weight of positive electrode active material for each sample.
  • the temperature shown on the horizontal axis of FIG. 32B is the environmental temperature under the discharge conditions shown in the above table.
  • the table below shows the discharge capacity at each environmental temperature normalized by the discharge capacity at 25°C.
  • the normalized value may be expressed as a percentage, and a normalized value of 0.5 is equal to 50%.
  • each sample can obtain discharge capacity in a wide temperature range including sub-zero temperatures, and the discharge capacity at -20°C and -40°C is 80% or more, preferably 85% or more, of the charge capacity at 25°C. I knew it would satisfy. It was also found that sample 2 had a higher discharge capacity than sample 1 at each environmental temperature. As described above, it was found that the lithium ion battery using the organic solvent of the electrolyte and the positive electrode active material, which is one embodiment of the present invention, exhibits excellent charge/discharge characteristics in a wide temperature range including sub-zero temperatures.
  • the positive electrode was produced in the same manner as Sample 1_P and Sample 2_P above. Note that the positive electrode active material layer was coated on one side of the current collector.
  • ⁇ Preparation of negative electrode> Artificial graphite (MCMB-High rate discharge-G10 manufactured by Linyi Gelon) was used as the negative electrode active material, VGCF (registered trademark) (VGCF-H manufactured by Showa Denko) was used as the conductive agent, and SBR (JSR) was used as the binder.
  • a negative electrode active material layer was prepared using CMC (manufactured by Kishida Chemical) as a thickener.
  • the mixing ratio (weight ratio) of artificial graphite, VGCF, CMC, and SBR was set to 96:1:1:2.
  • the slurry corresponding to the negative electrode active material layer used water as a solvent.
  • the slurry was coated on one side of a copper foil using a coater equipped with a dryer, and the solvent was dried to prepare a negative electrode. No press was done.
  • FEC fluoroethylene carbonate
  • MTFP methyl 3,3,3-trifluoropropionate
  • An organic electrolyte solution was prepared in which LiPF 6 was dissolved in a mixed solvent containing 1 mol/L. No additives were used.
  • the area of the negative electrode was 45 mm x 53 mm (23.841 cm 2 ), and the area of the positive electrode was 41 mm x 50 mm (20.493 cm 2 ).
  • the amount of the positive electrode active material supported was approximately 10.6 mg/cm 2
  • the amount of the negative electrode supported was approximately 7.6 mg/cm 2
  • the capacity ratio was approximately 80%.
  • the capacity ratio is the ratio of the negative electrode capacity to the positive electrode capacity.
  • the product of the capacity of 300 mAh/g and the area of the negative electrode active material layer was defined as the negative electrode capacity.
  • FIG. 33A shows the charging capacity (mAh/g) per weight of positive electrode active material for each sample.
  • the temperature shown on the horizontal axis of FIG. 33A is the environmental temperature under the charging conditions shown in the above table.
  • the table below shows the charging capacity at each environmental temperature normalized to the charging capacity at 25°C.
  • the normalized value may be expressed as a percentage, and a normalized value of 0.5 is equal to 50%.
  • each sample was able to obtain charging capacity over a wide temperature range including sub-zero temperatures, and the charging capacity at -20°C was found to be 50% or more of the charging capacity at 25°C.
  • a lithium ion battery using an organic solvent for an electrolyte and a positive electrode active material which is an embodiment of the present invention, exhibits excellent charging characteristics in a wide temperature range including sub-zero temperatures.
  • CC discharge was performed at a discharge rate of 0.1C until the final voltage reached 2.5V.
  • 1C 200 mA/g (current per weight of positive electrode active material was 200 mA/g).
  • the table below shows the test conditions.
  • FIG. 33B shows the charging capacity (mAh/g) per weight of positive electrode active material for each sample.
  • the temperature shown on the horizontal axis of FIG. 33B is the environmental temperature under the charging conditions shown in the above table.
  • the table below shows the charging capacity at each environmental temperature normalized to the charging capacity at 25°C.
  • the normalized value may be expressed as a percentage, and a normalized value of 0.5 is equal to 50%.
  • each sample was able to obtain discharge capacity in a wide temperature range including below freezing point, and the discharge capacity at -20°C was found to be 50% or more of the discharge capacity at 25°C. It was also found that sample 2F_P had a discharge capacity at -40°C that was 50% or more of the discharge capacity at 25°C. As described above, it was found that the lithium ion battery using the organic solvent of the electrolyte and the positive electrode active material, which is one embodiment of the present invention, exhibits excellent discharge characteristics in a wide temperature range including sub-zero temperatures.
  • ⁇ Aging conditions> After holding sample 25F_P at room temperature for 24 hours, it was charged at a rate of 15 mAh/g at a 0.01 C rate, and further charged at a rate of 120 mAh/g at a rate of 0.1 C. Here, the calculation was performed using a positive electrode capacity of 200 mAh/g. After holding sample 25F_P in a charged state of 135 mAh/g in a constant temperature bath set at 40° C. for 24 hours, vacuuming was performed until the differential pressure gauge showed ⁇ 60 kPa, and the exterior body was sealed.
  • CCCV charging at 0.1C rate with 0.01C cut condition at upper limit voltage 4.5V then CV discharge at 0.2C to lower limit voltage 2.5V once, then 0.2C at upper limit voltage 4.5V
  • CCCV charging at a rate of 0.02C cut condition then CV discharging at 0.2C to a lower limit voltage of 2.5V is repeated three times, and then a cycle of 0.2C rate and 0.02C cut condition at an upper limit voltage of 4.5V is repeated three times.
  • a cycle of CCCV charging and then CV discharging at 0.2C to a lower limit voltage of 3.0V was repeated three times.
  • FIG. 42A shows a charge/discharge curve obtained by repeating 500 cycles of CCCV charging at an upper limit voltage of 4.5 V at a 0.2 C rate and 0.1 C cut condition, and then CV discharging to a lower limit voltage of 3.0 V.
  • the vertical axis represents voltage (V)
  • the horizontal axis represents capacity (Wh/kg) per active material. Note that the capacity indicates charge capacity when a charge curve is used, and the discharge capacity when a discharge curve is used. Further, FIG.
  • FIG. 42B shows a charge/discharge curve obtained by repeating 500 cycles of CCCV charging at a 0.2C rate and 0.02C cut condition at an upper limit voltage of 4.6V, and then CV discharging to a lower limit voltage of 3.0V.
  • the vertical axis represents voltage (V)
  • the horizontal axis represents capacity per active material (Wh/kg). Note that the capacity indicates charge capacity when a charge curve is used, and the discharge capacity when a discharge curve is used.
  • a charge-discharge curve is the superimposition of the charge voltage (V) for charge capacity (Wh/kg, per weight of positive electrode active material) and the discharge voltage (V) for discharge capacity (Wh/kg, per weight of positive electrode active material). This is what is shown.
  • the initial discharge capacity was 187.2mAh/g.
  • the initial energy density when the upper limit voltage was 4.5 V was 727.7 Wh/kg.
  • the initial discharge capacity was 200.1 mAh/g when the upper limit voltage was 4.6V.
  • the initial energy density was 782.8 Wh/kg when the upper limit voltage was 4.6 V.
  • the discharge voltage of sample 25F_P decreased less. This is considered to be due to the fact that no alteration or reduction in crystallinity that would impede Li diffusion on the LCO surface occurred.
  • FIG. 43B shows the results of a cycle test in which a cycle of CCCV charging at an upper limit voltage of 4.6 V at a 0.2 C rate and 0.02 C cut condition, and then CV discharging to a lower limit voltage of 3.0 V was repeated 500 times.
  • the horizontal axis shows the discharge energy density and charging/discharging efficiency with respect to the number of cycles. Therefore, the left vertical axis in FIG. 43A represents the discharge energy density (Wh/kg), and the right vertical axis represents the charging/discharging efficiency (%).
  • the initial discharge capacity in each cycle test was about 40 mAh when the upper limit voltage was 4.5V, and 44 mAh when the upper limit voltage was 4.6V. Further, when the upper limit voltage was 4.5 V, the energy density maintenance rate after 500 cycles was 89% (650 Wh/kg). When the upper limit voltage was 4.6 V, the energy density maintenance rate after 500 cycles was 75.8% (593.7 Wh/kg). As described above, it was found that a lithium ion battery using an organic solvent for an electrolyte and a positive electrode active material, which is an embodiment of the present invention, exhibits excellent cycle characteristics even at room temperature (typically 25° C.).
  • a lithium composite oxide (Li 1.01 Ni 0.8 Co 0.1 Mn 0.1 O 2 ) was used. A method for producing the lithium composite oxide will be explained. First, an aqueous solution A in which nickel sulfate, cobalt sulfate, manganese sulfate, and glycine were dissolved in pure water was prepared as a raw material in step S201 in FIG.
  • step S201 sodium hydroxide was prepared, and an aqueous solution B was prepared by dissolving this in pure water.
  • concentration of sodium hydroxide in aqueous solution B was adjusted to 5 mol/L.
  • step S201 glycine was prepared and an aqueous solution C in which glycine was dissolved in pure water was prepared.
  • concentration of glycine in aqueous solution C was adjusted to 0.1 mol/L.
  • aqueous solution C 300 mL was placed in the reaction tank 171 of the coprecipitation synthesis apparatus, 250 mL of aqueous solution A was placed in the first tank 180, and 200 mL of aqueous solution B was placed in the second tank 186. Nitrogen was supplied to the reaction tank 171 at a flow rate of 1 L/min.
  • the temperature of the reaction tank 171 of the coprecipitation synthesis apparatus was set to 50° C., the pH value of the aqueous solution C was adjusted to 11.0, and mixing was started.
  • Aqueous solution A was supplied from the first tank 180 to the reaction tank 171 at a feeding rate of 0.1 mL/min, and stirring was continued at 1000 rpm using three swept blades. A baffle plate was placed during stirring.
  • the aqueous solution B in the second tank 186 was appropriately supplied to the reaction tank 171 so that the pH value of the aqueous solution C in the reaction tank 171 of the coprecipitation synthesis apparatus was kept constant.
  • the deposited coprecipitate was filtered. Thereafter, using a suction filtration device, the coprecipitate in the suction funnel was suction filtered while being washed with pure water. Thereafter, the coprecipitate in the suction funnel was suction-filtered using a suction filtration device while being washed with acetone.
  • the coprecipitate that had undergone the suction filtration step was transferred to a Petri dish, the Petri dish was placed in a bell jar type vacuum device, the pressure was reduced until the differential pressure gauge read -0.1 MPa, and the mixture was heated at 80° C. for 1 hour.
  • the heating process can be called a drying process.
  • a hydroxide corresponding to the precursor of the positive electrode active material of Sample 11 was obtained.
  • lithium hydroxide was prepared by pulverizing and classifying it at 10,000 rpm for 1 hour. It was weighed so that the ratio of lithium hydroxide to the hydroxide corresponding to the precursor of the positive electrode active material of Sample 11 was 0.95. Lithium hydroxide and a hydroxide corresponding to the precursor of the positive electrode active material of Sample 11 were mixed at 1500 rpm for 1.5 minutes to prepare a mixture.
  • the mixture was placed in an alumina crucible, put into a muffle furnace without a lid, and heated at 700° C. for 10 hours. Oxygen was supplied to the muffle furnace at a flow rate of 5 L/min.
  • the mixture was transferred to a mortar and crushed, and then passed through a sieve.
  • the sieved mixture was put into the alumina crucible again, put into a muffle furnace without a lid, and heated at 800° C. for 10 hours.
  • Oxygen was supplied to the muffle furnace at a flow rate of 5 L/min.
  • NCM corresponding to the positive electrode active material of Sample 11 positive electrode active material was 9.2 ⁇ m.
  • SALD-2200 manufactured by Shimadzu Corporation.
  • the above positive electrode active material, acetylene black (AB) as a conductive aid, and polyvinylidene fluoride (PVDF) as a binder were prepared as the positive electrode of Sample 11.
  • PVDF was prepared in a state in which it was dissolved in N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 5%.
  • NMP N-methyl-2-pyrrolidone
  • a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) was assembled using Sample 11 as a positive electrode and lithium metal as a counter electrode.
  • the above positive electrode active material, acetylene black (AB) as a conductive aid, and polyvinylidene fluoride (PVDF) as a binder were prepared as the positive electrode of Sample 12.
  • PVDF was prepared in a state in which it was dissolved in N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 5%.
  • NMP N-methyl-2-pyrrolidone
  • sample 12_P PP was used as the separator for Sample 12. This will be referred to as “sample 12_P.”
  • a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) was assembled using sample 12 as a positive electrode and lithium metal as a counter electrode.
  • the table below shows the main conditions regarding Sample 11_P, Sample 11_I, and Sample 12_P.
  • FIG. 34A shows the results of charge capacity (mAh/g) per weight of positive electrode active material in Sample 11_P and Sample 11_I.
  • the temperature shown on the horizontal axis of FIG. 34A is the environmental temperature under the charging conditions shown in the above table.
  • FIG. 35A shows charging curves of sample 11_P and sample 12_P at 25° C. and ⁇ 40° C.
  • the table below shows the charging capacity at each environmental temperature normalized to the charging capacity at 25°C.
  • the normalized value may be expressed as a percentage, and a normalized value of 0.5 is equal to 50%.
  • each sample can obtain charging capacity in a wide temperature range including sub-zero temperatures, and the charging capacity at -20°C, -40°C, and -45°C is different from that at 25°C. It was found that 50% or more of the charging capacity was satisfied. Furthermore, each sample could be charged even at -50°C, and sample 12_P had a charging capacity at -50°C that was 50% or more compared to the charging capacity at 25°C. It was also found that sample 11_I had a higher charging capacity than sample 11_P at each environmental temperature. It was also found that sample 12_P had a higher charging capacity than sample 11_P at each temperature. As described above, it was found that a lithium ion battery using an organic solvent for an electrolyte and a positive electrode active material, which is an embodiment of the present invention, exhibits excellent charging characteristics in a wide temperature range including sub-zero temperatures.
  • ⁇ Discharge characteristics> in order to confirm the discharge capacity below freezing point, the environmental temperatures at which Sample 11_P, Sample 11_I, and Sample 12_P (collectively referred to as each sample) are placed were set to 25°C, 0°C, -20°C, -40°C, The discharge capacity was measured at each environmental temperature while lowering the temperature in the order of -45°C, -50°C, -55°C, and -60°C. Note that charging was performed after each discharge at each environmental temperature, and the environmental temperature was 25° C. for the charging. In the above charging, CC charging was performed at a charging rate of 0.1C until the final voltage reached 4.5V, and then CV charging was performed at 4.5V until the current value reached 0.05C.
  • CC discharge was performed at a discharge rate of 0.1C until the final voltage reached 2.5V.
  • 1C 200 mA/g (current per weight of positive electrode active material was 200 mA/g).
  • the table below shows the test conditions.
  • FIG. 34B shows the results of discharge capacity (mAh/g) per weight of positive electrode active material in Sample 11_P and Sample 11_I.
  • the temperature shown on the horizontal axis of FIG. 34B is the environmental temperature under the discharge conditions shown in the above table.
  • FIG. 35B shows the discharge curves of sample 11_P and sample 12_P at 25° C. and ⁇ 40° C.
  • the table below shows the discharge capacity at each environmental temperature normalized by the discharge capacity at 25°C.
  • the normalized value may be expressed as a percentage, and a normalized value of 0.5 is equal to 50%.
  • each sample can obtain charging capacity in a wide temperature range including sub-zero temperatures, and the discharge capacity at -20°C to -55°C is compared to the charging capacity at 25°C. It was found that more than 50% of the criteria were met. Furthermore, each sample was able to discharge at -55°C or -60°C. It was also found that sample 11_I had a higher discharge capacity than sample 11_P at each environmental temperature. It was also found that sample 12_P had a higher charging capacity than sample 11_P at each environmental temperature. As described above, it was found that the lithium ion battery using the organic solvent of the electrolyte and the positive electrode active material, which is one embodiment of the present invention, exhibits excellent charge/discharge characteristics in a wide temperature range including sub-zero temperatures.
  • sample 11_P and sample 12_P were evaluated as cycle characteristics at high temperatures.
  • the temperature (environmental temperature) of the constant temperature bath in which Sample 11_P and Sample 12_P are placed was controlled to be any one of 25° C., 45° C., and 65° C., and cycle characteristics were measured at each temperature. 45°C and 65°C in this cycle test are included in the high temperature.
  • CC charging was performed at a charging rate of 0.5C until the final voltage reached 4.5V, and then CV charging was performed until the current reached 0.05C.
  • the battery was held for 10 minutes as a pause period after CV charging, and then discharging was started.
  • CC discharge was performed at a discharge rate of 0.5C until the final voltage reached 2.5V.
  • 1C 200 mA/g (current per weight of positive electrode active material was 200 mA/g).
  • the above charging and discharging are considered as one cycle, the number of cycles is repeated 50 times, and the value calculated by (discharge capacity at 50th cycle/maximum value of discharge capacity during 50 cycles) x 100 is the discharge capacity maintenance rate at the 50th cycle. (capacity retention) (%).
  • the value of the discharge capacity measured at the 50th cycle is the maximum value of the discharge capacity (maximum discharge) during all 50 cycles.
  • the percentage of the discharge capacity (denoted as capacity) was calculated and used as the discharge capacity maintenance rate (%). The higher the discharge capacity retention rate, the more desirable the battery characteristics are because the decrease in capacity of the battery after repeated charging and discharging is suppressed.
  • a current is actually measured, and it is preferable that the current be measured using a four-terminal method.
  • the charging current flows from the negative terminal through the charge/discharge meter to the positive terminal.
  • the discharge current is defined as flowing from the positive terminal through the charging/discharging measuring device to the negative terminal.
  • the charging current and the discharging current are measured by an ammeter included in the charging/discharging measuring device, and the integrated amount of current flowing in one charging and one discharging corresponds to the charging capacity and the discharging capacity, respectively.
  • the cumulative amount of discharge current that flowed during the 1st cycle of discharge can be called the 1st cycle discharge capacity
  • the cumulative amount of discharge current that flowed during the 50th cycle of discharge can be called the 50th cycle of discharge. It can be called capacity.
  • FIG. 36A shows the discharge capacity maintenance rate at an environmental temperature of 25° C.
  • FIG. 36B shows the discharge capacity maintenance rate at an environmental temperature of 45° C.
  • FIG. 36C shows the discharge capacity maintenance rate at an environmental temperature of 65° C.
  • the horizontal axis shows the number of cycles (times)
  • the vertical axis shows the discharge capacity retention rate (%). It was found that Sample 11_P and Sample 12_P had a discharge capacity retention rate of 85% or more, preferably 90% or more, at any temperature, especially at high temperature, and exhibited good cycle characteristics. It was found that lithium ion batteries using Sample 11_P and Sample 12_P exhibit excellent battery characteristics over a wide temperature range from below freezing to high temperatures.
  • Figure 37 shows the results of viscosity measurement.
  • mixed liquid B had a lower viscosity than mixed liquid A at all temperatures.
  • the carrier ion conductivity that is, the lithium ion conductivity increases, so it is estimated that the mixture B, like the mixture A, exhibits excellent charge and discharge characteristics at subzero temperatures.
  • sample 31 was prepared and its charge/discharge characteristics at low temperatures were investigated.
  • sample 31A, sample 31B, and sample 31C depending on the mixed liquid.
  • ⁇ Cathode active material of sample 31> As a positive electrode active material, the same positive electrode active material as Sample 1 described above was prepared again.
  • FIG. 38A shows the charging capacity (mAh/g) per weight of positive electrode active material for Sample 31A, Sample 31B, and Sample 31C.
  • the temperature shown on the horizontal axis of FIG. 38A is the environmental temperature under the charging conditions shown in the above table.
  • a lithium ion battery using an organic solvent for an electrolyte and a positive electrode active material which is an embodiment of the present invention, can exhibit excellent charge-discharge characteristics over a wide temperature range including sub-zero temperatures, regardless of the volume ratio of the organic solvent. Understood.
  • ⁇ Discharge characteristics> in order to confirm the discharge capacity below freezing, the environmental temperatures at which samples 31A, 31B, and 31C (collectively referred to as each sample) are placed are set to 25°C, 0°C, -20°C, -40°C, The discharge capacity was measured at each environmental temperature while lowering the temperature in the order of -45°C, -50°C, -55°C, and -60°C. Note that charging was performed after each discharge at each environmental temperature, and the environmental temperature was 25° C. for the charging. In the above charging, CC charging was performed at a charging rate of 0.1C until the final voltage reached 4.6V, and then CV charging was performed at 4.6V until the current reached 0.05C.
  • CC discharge was performed at a discharge rate of 0.1C until the final voltage reached 2.5V.
  • 1C 200 mA/g (current per weight of positive electrode active material was 200 mA/g).
  • the table below shows the test conditions.
  • FIG. 38B shows the results of discharge capacity (mAh/g) per weight of positive electrode active material in Sample 31A, Sample 31B, and Sample 31C.
  • the temperature shown on the horizontal axis of FIG. 38B is the environmental temperature under the discharge conditions shown in the table above.
  • a lithium ion battery using an organic solvent for an electrolyte and a positive electrode active material which is an embodiment of the present invention, can exhibit excellent charge-discharge characteristics over a wide temperature range including sub-zero temperatures, regardless of the blending ratio of the organic solvent. Understood.
  • FIG. 39A shows the amount of heat (Heat Flow, mW) with respect to temperature (Temperature)
  • FIG. 39B shows the amount of heat (Heat Flow, W/g) with respect to temperature.
  • the nail penetration test is a test in which a full cell is fully charged and a nail satisfying a predetermined diameter selected from 2 mm to 10 mm is inserted into the full cell at a predetermined speed.
  • a full cell was assembled using Sample 1-P as the positive electrode and spheroidized natural graphite as the negative electrode, and a nail penetration test was conducted.
  • the table below shows the conditions for full cell.
  • the nail penetration test was conducted using an Advanced Safety Tester manufactured by ESPEC Co., Ltd. at room temperature, specifically at 25°C. Further, in the nail penetration test, a nail with a diameter of 3 mm was used, the nail penetration speed was 5 mm/s, and the nail penetration amount was 10 mm. Regarding other points, the nail penetration test was conducted in accordance with the description of SAE J2464 "Safety and abuse test for electric/hybrid vehicle power storage system".
  • the weight of the active material layer can be determined by subtracting the weight of other than the active material, such as the current collector, conductive aid, binder, and thickener, from the weight of the electrode.
  • the weight of the active material is obtained by specifying the blending ratio of the active material, conductive aid, binder, thickener, etc. that constitute the active material layer.
  • a first area includes only a current collector without being coated with an active material layer, and a second area where an active material layer coated with an active material layer and a current collector are laminated. Equal areas are taken out of the area and the weight of each is measured.
  • the weight of the active material layer can be determined from the difference in weight. Thereafter, the weight of the active material can be determined by specifying the blending ratio of the active material, conductive aid, binder, and thickener.
  • the amount of supported active material is determined by dividing the weight of the active material by the area taken out.
  • ignition in a nail penetration test means that flame is observed outside the exterior body within 1 minute after nail penetration, or that thermal runaway of the secondary battery occurs.
  • the full cell using Sample 1-P as the positive electrode did not ignite.
  • the left diagram in Figure 40 shows the state in which one cyclic molecule was adsorbed on the surface and the molecule interacted with lithium ions. show.
  • the left diagram in FIG. 40 is called the starting state.
  • the right diagram in FIG. 40 shows a state in which lithium ions have diffused into the pores of lithium cobalt oxide.
  • the right diagram in FIG. 40 is called the final state.
  • the transition from the initial state to the final state corresponds to discharge because lithium ions diffuse into the interior. Also, from the final state to the initial state, lithium ions diffuse to the surface, which corresponds to charging.
  • FIG. 41 shows the activation barrier for lithium ion diffusion on the lithium cobalt oxide (104) surface in energy (eV) in the initial state shown in the left diagram of FIG. 40, the final state shown in the right diagram of FIG. 40, and an intermediate state between them. Shown as The table below shows the activation barrier for lithium ion diffusion in each state.
  • the activation barrier for lithium ion diffusion during discharge is 0.12 eV lower for FEC, and lithium ions It was found that it is easy to spread. It is also thought that the ease with which the Li-O coordination bond formed in the initial state is broken has an effect. In FEC, since fluorine withdraws electrons from oxygen coordinating with lithium ions, the Li-O coordination bond is easily broken. Furthermore, the difference in the activation barrier for lithium ion diffusion during charging was small.

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JP2017208246A (ja) * 2016-05-19 2017-11-24 株式会社Ｇｓユアサ 非水電解液二次電池用非水電解液、非水電解液二次電池、及び非水電解液二次電池の製造方法
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JP2017208246A (ja) * 2016-05-19 2017-11-24 株式会社Ｇｓユアサ 非水電解液二次電池用非水電解液、非水電解液二次電池、及び非水電解液二次電池の製造方法
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CN117878298B (zh) * 2024-03-13 2024-05-28 湖南顺隆新能源科技有限公司 一种动力型锰酸锂制备方法及装置

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