WO2023209474A1 - 正極活物質、リチウムイオン電池、電子機器、および車両 - Google Patents

正極活物質、リチウムイオン電池、電子機器、および車両 Download PDF

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WO2023209474A1
WO2023209474A1 PCT/IB2023/053724 IB2023053724W WO2023209474A1 WO 2023209474 A1 WO2023209474 A1 WO 2023209474A1 IB 2023053724 W IB2023053724 W IB 2023053724W WO 2023209474 A1 WO2023209474 A1 WO 2023209474A1
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Prior art keywords
positive electrode
active material
electrode active
lithium
less
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English (en)
French (fr)
Japanese (ja)
Inventor
斉藤丞
川月惇史
門馬洋平
吉富修平
中西健太
掛端哲弥
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Semiconductor Energy Laboratory Co Ltd
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Semiconductor Energy Laboratory Co Ltd
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Priority to KR1020247037756A priority Critical patent/KR20250004277A/ko
Priority to CN202380035560.8A priority patent/CN119072799A/zh
Priority to JP2024517594A priority patent/JPWO2023209474A1/ja
Priority to US18/858,957 priority patent/US20250279425A1/en
Publication of WO2023209474A1 publication Critical patent/WO2023209474A1/ja
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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
    • H01M10/056—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
    • H01M10/0568—Liquid materials characterised by the solutes
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/66—Complex oxides containing nickel and at least one other metal element containing alkaline earth metals, e.g. SrNiO3 or SrNiO2
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—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
    • H01M10/0569—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L50/00—Electric propulsion with power supplied within the vehicle
    • B60L50/50—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells
    • B60L50/60—Electric propulsion with power supplied within the vehicle using propulsion power supplied by batteries or fuel cells using power supplied by batteries
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/76—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by a space-group or by other symmetry indications
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/77—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by unit-cell parameters, atom positions or structure diagrams
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/85—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by XPS, EDX or EDAX data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • 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
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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
    • H01M2300/004—Three 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

  • the invention disclosed in this specification etc. (hereinafter sometimes referred to as "the present invention” in this specification etc.) relates to a power storage device, a secondary battery, etc. In particular, it relates to lithium ion batteries.
  • the present invention relates to a product, a method, or a manufacturing method.
  • the invention relates to a process, machine, manufacture, or composition of matter.
  • the present invention relates to a semiconductor device, a display device, a light emitting device, a power storage device, a lighting device, an electronic device, a vehicle, or a manufacturing method thereof.
  • lithium-ion batteries with high output and high energy density are used in mobile phones, smartphones, portable information terminals such as notebook computers, portable music players, digital cameras, medical equipment, hybrid vehicles (HVs), and electric vehicles.
  • HVs hybrid vehicles
  • electric vehicles such as EVs (EVs) and plug-in hybrid vehicles (PHVs) has rapidly expanded, and they have become essential in today's information society as a source of repeatedly rechargeable energy. It has become a thing.
  • the charging characteristics and/or discharging characteristics of a lithium ion battery vary depending on the battery charging environment and/or the battery discharging environment. For example, it is known that the discharge capacity of lithium ion batteries changes depending on the temperature during discharge.
  • ImageJ Non-Patent Documents 1 to 3
  • ImageJ Non-Patent Documents 1 to 3
  • Rasband, W. S. ImageJ, U. S. National Institutes of Health, Bethesda, Maryland, USA, http://rsb. info. nih. gov/ij/, 1997-2012. Schneider, C. A. , Rasband, W. S. , Eliceiri, K. W. “NIH Image to ImageJ: 25 years of image analysis”. Nature Methods 9, 671-675, 2012. Abramoff, M. D. , Magelhaes, P. J. , Ram, S. J. “Image Processing with ImageJ”. Biophotonics International, volume 11, issue 7, pp. 36-42, 2004.
  • Patent Document 1 describes that by using the nonaqueous solvent described in Patent Document 1, a lithium ion battery that can operate even in a low temperature environment (for example, 0° C. or lower) can be realized. However, even the lithium ion battery described in Patent Document 1 cannot be said to have a large discharge capacity when discharged in a low-temperature environment, and further improvements are desired.
  • One aspect of the present invention aims to provide a positive electrode active material that can be applied to lithium ion batteries and has excellent discharge characteristics even in a low-temperature environment.
  • one of the objectives is to provide a positive electrode active material that can be applied to lithium ion batteries that have a large discharge capacity and/or a large discharge energy density even when discharged in a low-temperature environment.
  • under a low-temperature environment refers to a temperature of 0° C. or lower.
  • under a low-temperature environment it is possible to select any temperature below 0°C.
  • 0°C or lower -10°C or lower, -20°C or lower, -30°C or lower, -40°C or lower, -50°C or lower, -60°C or lower , -80°C or lower, and -100°C or lower.
  • an object of one embodiment of the present invention is to provide a lithium ion battery that has excellent discharge characteristics even in a low-temperature environment. Another objective is to provide a lithium ion battery that has excellent charging characteristics even in a low-temperature environment.
  • An object of the present invention is to provide a lithium ion battery that has a large discharge capacity and/or a large discharge energy density even when discharged at temperatures below -60°C.
  • One object of the present invention is to provide a lithium ion battery whose discharge capacity value decreases less when discharged at a temperature (preferably -50°C or lower, most preferably -60°C or lower).
  • Another object of the present invention is to provide a lithium ion battery whose discharge energy density value decreases less when discharged at a temperature (more preferably -50°C or lower, most preferably -60°C or lower).
  • one of the challenges is to provide a secondary battery with a high charging voltage.
  • one of the challenges is to provide a secondary battery with high safety or reliability.
  • one of the challenges is to provide a secondary battery with less deterioration.
  • one of the challenges is to provide a long-life secondary battery.
  • one of the challenges is to provide a new secondary battery.
  • Another object of the present invention is to provide a new material, active material, power storage device, or method for producing the same.
  • One embodiment of the present invention is a positive electrode active material containing cobalt, oxygen, magnesium, aluminum, and nickel, wherein the positive electrode active material has a median diameter of 1 ⁇ m or more and 12 ⁇ m or less, and the positive electrode The active material has magnesium and aluminum in the surface layer, and the surface layer is a region within 50 nm from the surface of the positive electrode active material. This is a positive electrode active material having a region where the aluminum is distributed closer to the surface of the positive electrode active material than aluminum.
  • the positive electrode active material has a layered rock salt type crystal structure belonging to space group R-3m, and the surface layer part includes a basal region having a surface parallel to the (00l) plane of the crystal structure, and a (00l) plane. an edge region having a surface in a direction intersecting with the positive electrode active material, and when performing EDX-ray analysis in the depth direction, the positive electrode active material has a region in which the distribution of magnesium and the distribution of nickel overlap in the edge region. It is preferable.
  • the basal region may be substantially free of nickel.
  • the number of magnesium atoms (Mg/Co) with respect to the number of cobalt atoms is 0.400 or more and 1.500 or less
  • the number of nickel atoms with respect to the number of cobalt atoms is 0.400 or more and 1.500 or less.
  • the number of atoms (Ni/Co) is preferably 0.050 or more and 0.150 or less.
  • the positive electrode active material has fluorine, and when the positive electrode active material is analyzed by XPS, the number of fluorine atoms relative to the number of cobalt atoms (F/Co) is 0.100 or more and 1.000 or less. preferable.
  • one embodiment of the present invention includes a positive electrode having the positive electrode active material according to any one of the above, and an electrolyte, the electrolyte comprising lithium hexafluorophosphate, ethylene carbonate, and ethyl methyl carbonate. and dimethyl carbonate.
  • the electrolyte has a volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate of x: It is preferable that y: 100-x-y (5 ⁇ x ⁇ 35 and 0 ⁇ y ⁇ 65).
  • the electrolyte contains lithium hexafluorophosphate in an amount of 0.5 mol/L or more and 1.5 mol/L or less, based on the volume of the total content of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate. It is preferable to have.
  • one embodiment of the present invention is an electronic device including the above lithium ion battery.
  • one embodiment of the present invention is a vehicle including the above lithium ion battery.
  • a composite oxide positive electrode active material
  • a positive electrode active material that is applicable to lithium ion batteries and has excellent discharge characteristics even in a low-temperature environment.
  • a positive electrode active material that can be applied to lithium ion batteries that have a large discharge capacity and/or a large discharge energy density even when discharged in a low-temperature environment.
  • a low temperature environment for example, 0°C or lower, -10°C, -20°C or lower, preferably -30°C or lower, more preferably -40°C or lower, even more preferably -50°C or lower
  • a lithium ion battery that has a large discharge capacity and/or a large discharge energy density even when discharged at a temperature of (most preferably ⁇ 60° C. or lower).
  • a lithium ion battery under a low temperature environment (for example, 0°C or lower, -10°C, -20°C or lower, preferably -30°C or lower, more preferably -40°C or lower, or even It is possible to provide a lithium ion battery whose discharge capacity value decreases less when discharged at a temperature (preferably -50°C or lower, most preferably -60°C or lower).
  • a secondary battery with high charging voltage can be provided.
  • a highly safe or reliable secondary battery can be provided.
  • a secondary battery with less deterioration can be provided.
  • a long-life secondary battery can be provided.
  • a new secondary battery can be provided.
  • one embodiment of the present invention can provide a novel substance, active material, power storage device, or method for manufacturing them.
  • FIG. 1A is a sectional view illustrating the internal structure of a secondary battery
  • FIG. 1B is a sectional view illustrating the positive electrode and electrolyte of the secondary battery.
  • 2A and 2B are cross-sectional views illustrating the positive electrode active material.
  • 3A to 3F are cross-sectional views illustrating the positive electrode active material.
  • FIG. 4 is a diagram illustrating the crystal structure of the positive electrode active material.
  • FIG. 5 is a diagram illustrating the crystal structure of a conventional positive electrode active material.
  • FIG. 6 is a diagram showing an XRD pattern calculated from the crystal structure.
  • FIG. 7 is a diagram showing an XRD pattern calculated from the crystal structure.
  • FIGS. 8A to 8D are diagrams illustrating a method for manufacturing a positive electrode active material.
  • FIG. 9 is a diagram illustrating a method for producing a positive electrode active material.
  • 10A to 10C are diagrams illustrating a method for producing a positive electrode active material.
  • 11A to 11D are cross-sectional views illustrating an example of a positive electrode of a secondary battery.
  • FIG. 12A is an exploded perspective view of a coin-type secondary battery
  • FIG. 12B is a perspective view of the coin-type secondary battery
  • FIG. 12C is a cross-sectional perspective view thereof.
  • FIG. 13A shows an example of a cylindrical secondary battery.
  • FIG. 13B shows an example of a cylindrical secondary battery.
  • FIG. 13C shows an example of a plurality of cylindrical secondary batteries.
  • FIG. 13D shows an example of a power storage system having a plurality of cylindrical secondary batteries.
  • FIG. 14A and 14B are diagrams illustrating an example of a secondary battery
  • FIG. 14C is a diagram illustrating the inside of the secondary battery
  • 15A to 15C are diagrams illustrating examples of secondary batteries.
  • 16A and 16B are diagrams showing the appearance of the secondary battery.
  • 17A to 17C are diagrams illustrating a method for manufacturing a secondary battery.
  • 18A to 18C are diagrams illustrating configuration examples of battery packs.
  • FIG. 19A is a perspective view of a battery pack showing one embodiment of the present invention
  • FIG. 19B is a block diagram of the battery pack
  • FIG. 19C is a block diagram of a vehicle having the battery pack.
  • 20A to 20D are diagrams illustrating an example of a transportation vehicle.
  • 20E is a diagram illustrating an example of an artificial satellite.
  • 21A and 21B are diagrams illustrating a power storage device according to one embodiment of the present invention.
  • FIG. 22A is a diagram showing an electric bicycle
  • FIG. 22B is a diagram showing a secondary battery of the electric bicycle
  • FIG. 22C is a diagram explaining a scooter.
  • 23A to 23D are diagrams illustrating an example of an electronic device.
  • FIG. 24A shows an example of a wearable device
  • FIG. 24B shows a perspective view of a wristwatch-type device
  • FIG. 24C is a diagram illustrating a side view of the wristwatch-type device.
  • 25A and 25B are graphs showing the particle size distribution of lithium cobalt oxide explained in Example 1.
  • 26A and 26B are SEM images of the sample.
  • FIGS. 27A to 27C are diagrams illustrating one method for quantifying the smoothness of a positive electrode active material.
  • FIGS. 28A to 28C are diagrams illustrating one method for quantifying the smoothness of a positive electrode active material.
  • FIGS. 29A and 29B are graphs showing discharge curves of temperature-specific charge/discharge test 1 described in Example 2.
  • FIG. 30 is a graph showing a discharge curve of temperature-specific charge/discharge test 2 explained in Example 2.
  • FIG. 31 is a graph showing the discharge capacity measured by rate at ⁇ 40° C., which will be explained in Example 2.
  • 32A and 32B are graphs showing the charge/discharge cycle test described in Example 3.
  • 33A and 33B are graphs showing the charge/discharge cycle test described in Example 3.
  • 34A to 34C are graphs showing XRD analysis of the high voltage charging state described in Example 3.
  • 35A and 35B are graphs showing STEM-EDX analysis described in Example 3.
  • 36A to 36C are graphs showing STEM-EDX analysis described in Example 3.
  • 37A to 37C are graphs showing STEM-EDX analysis described in Example 3.
  • electro-optical device having a power storage device
  • information terminal device having a power storage device
  • power storage device refers to elements and devices in general that have a power storage function. Examples include power storage devices such as lithium ion batteries (also referred to as “secondary batteries”), lithium ion capacitors, electric double layer capacitors, and the like.
  • space groups are expressed using short notation in international notation (or Hermann-Mauguin symbol).
  • crystal planes and crystal directions are expressed using Miller indices.
  • Individual planes indicating crystal planes are written using parentheses.
  • Space groups, crystal planes, and crystal directions are expressed in terms of crystallography by adding a superscript bar to the number, but in this specification, etc., due to formatting constraints, instead of adding a bar above the number, they are written in front of the number. It is sometimes expressed by adding a - (minus sign) to it.
  • the individual orientation that indicates the direction within the crystal is [ ]
  • the collective orientation that indicates all equivalent directions is ⁇ >
  • the individual plane that indicates the crystal plane is ( )
  • the collective plane that has equivalent symmetry is ⁇ ⁇ .
  • the trigonal crystal represented by the space group R-3m is generally represented by a complex hexagonal lattice of hexagonal crystals for ease of understanding the structure, and unless otherwise mentioned in this specification, the space group R-3m is expressed as a complex hexagonal lattice.
  • not only (hkl) but also (hkil) may be used as the Miller index.
  • i is -(h+k).
  • any integer greater than or equal to 1 may be expressed as h, k, i, or l.
  • (00l) includes (001), (003) and (006).
  • the space group of the crystal structure is identified by XRD, electron beam diffraction, neutron beam diffraction, or the like. Therefore, in this specification and the like, belonging to a certain space group, belonging to a certain space group, or being a certain space group can be rephrased as identifying with a certain space group.
  • the theoretical capacity of a positive electrode active material refers to the amount of electricity when all of the lithium that can be inserted and extracted from the positive electrode active material is released.
  • the theoretical capacity of LiCoO 2 is 274 mAh/g
  • the theoretical capacity of LiNiO 2 is 275 mAh/g
  • the theoretical capacity of LiMn 2 O 4 is 148 mAh/g.
  • x in Li x CoO 2 occupancy rate of Li at lithium sites.
  • x (theoretical capacity ⁇ charge capacity)/theoretical capacity.
  • LiCoO 2 charge capacity
  • x 0.2.
  • the state where x in Li x CoO 2 is small is, for example, x ⁇ 0.24, and considering the practical range when used as a positive electrode active material of a secondary battery, for example, 0.1 ⁇ x ⁇ 0. 24.
  • the charging capacity and/or discharging capacity used to calculate x in Li x CoO 2 is preferably measured under conditions where there is no or little influence of short circuits and/or electrolyte decomposition. For example, it is not preferable to use data from a secondary battery in which a sudden change in voltage that appears to be due to a short circuit has occurred for the calculation of x.
  • Cubic close-packed anion arrangement means that the anions in the second layer are placed above the voids of the anions filled in the first layer, and the anions in the third layer are placed above the voids of the anions filled in the first layer. Refers to a state in which the anion is placed directly above the void and not directly above the anion in the first layer. Therefore, the anion does not have to be strictly in a cubic lattice. Furthermore, since actual crystals always have defects, the analysis results do not necessarily have to be as theoretical.
  • a spot may appear at a position slightly different from the theoretical position. For example, if the orientation with respect to the theoretical position is 5 degrees or less, or 2.5 degrees or less, it can be said that the structure has a cubic close-packed structure.
  • FFT fast Fourier transform
  • the term "layered rock-salt type crystal structure of a composite oxide containing lithium and a transition metal” means that it has a rock-salt type ion arrangement in which cations and anions are arranged alternately, A crystal structure in which lithium is regularly arranged to form a two-dimensional plane, allowing for two-dimensional diffusion of lithium. Note that it may have defects such as cation or anion deficiency. Strictly speaking, the layered rock salt crystal structure may have a structure in which the lattice of the rock salt crystal is distorted.
  • a "rock salt type crystal structure” refers to a structure in which cations and anions are arranged alternately. Note that there may be a deficiency of cations or anions.
  • 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 consisting 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 if the difference in element concentration between specific regions is within 10%.
  • Specific areas include, for example, the surface layer, the surface, protrusions, recesses, and the inside.
  • separation refers to a phenomenon in which a certain element (for example, B) is spatially non-uniformly distributed in a solid composed of a plurality of elements (for example, A, B, and C). Or, it refers to the fact that the concentration of one element is different from that of another. It has the same meaning as uneven distribution, precipitation, non-uniformity, deviation, or a mixture of areas with high concentration and areas with low concentration.
  • the "surface layer" of a particle such as an active material 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. be.
  • a surface caused by a crack or a crack can be considered a surface.
  • a region deeper than the surface layer may be referred to as "inside.”
  • grain boundaries refer to, for example, areas where grains are stuck together, areas where the crystal orientation changes inside the grains (including the center), areas with many defects, and areas where the crystal structure is disordered.
  • grain boundaries can also be said to be one of planar defects.
  • near the grain boundary refers to a region within 20 nm, preferably within 10 nm from the grain boundary.
  • particle is not limited to only spherical shapes (circular cross-sectional shapes), but also particles with individual particle cross-sectional shapes of elliptical, rectangular, trapezoidal, triangular, or rounded corners. Examples include square, asymmetrical shapes, and the individual particles may also be irregularly shaped.
  • the characteristics of individual particles of the positive electrode active material in the following embodiments and the like, not all particles necessarily have the characteristics. For example, if 50% or more, preferably 70% or more, more preferably 90% or more of three or more randomly selected positive electrode active material particles have the characteristic, it is sufficient to have the positive electrode active material and the same. It can be said that this has the effect of improving the characteristics of the secondary battery.
  • a lithium ion battery includes a positive electrode, a negative electrode, and an electrolyte. Moreover, when the electrolyte contains an electrolytic solution, a separator is provided between the positive electrode and the negative electrode. Furthermore, it may have an exterior body that covers at least a portion of the periphery of the positive electrode, negative electrode, and electrolyte.
  • the present invention is performed in a low temperature environment (for example, 0°C or lower, -10°C, -20°C or lower, preferably -30°C or lower, more preferably -40°C or lower, still more preferably -50°C or lower, most preferably
  • the structure of the lithium ion battery is required to realize a lithium ion battery that has excellent discharge characteristics even at temperatures below -60°C and/or a lithium ion battery that has excellent charging characteristics even in low temperature environments. Focus and explain. Specifically, the description will focus on the positive electrode active material and electrolyte contained in the positive electrode.
  • a method for manufacturing a positive electrode active material of a lithium ion battery will be described in Embodiment 2, and details of the remaining structure of the lithium ion battery of one embodiment of the present invention will be described in Embodiment 3.
  • FIG. 1A is a schematic cross-sectional diagram illustrating the internal structure of the lithium ion battery 10.
  • Lithium ion battery 10 includes a positive electrode 11, a negative electrode 12, and a separator 13.
  • the positive electrode 11 has a positive electrode current collector 21 and a positive electrode active material layer 22 on the positive electrode current collector 21
  • the negative electrode 12 has a negative electrode current collector 31 and a negative electrode active material layer 32 .
  • the positive electrode active material layer 22 and the negative electrode active material layer 32 face each other with the separator 13 in between.
  • the lithium ion battery 10 has an electrolyte in the voids of the positive electrode active material layer 22, the voids of the separator 13, and the voids of the negative electrode active material layer 32.
  • the lithium ion battery of one embodiment of the present invention is not limited to this structure.
  • the structure may include two positive electrodes 11, two negative electrodes 12, and two separators 13, or a greater number of layers may be stacked. Further, instead of the laminated structure shown in FIG. 1A, a wound structure may be used.
  • FIG. 1B is an enlarged view of a portion A surrounded by a broken line in FIG. 1A.
  • the positive electrode active material layer 22 includes a positive electrode active material 100 and a conductive material 41. Further, although not shown, in addition to the positive electrode active material 100 and the conductive material 41, a binder may be included.
  • the voids that the positive electrode active material layer 22 has are preferably filled with an electrolyte 51 as shown in the figure.
  • 60% or more of the voids in the positive electrode active material layer 22 are preferably filled with the electrolyte 51, more preferably 70% or more of the voids, more preferably 80% or more of the voids, and 90% or more of the voids are filled with the electrolyte 51.
  • 95% or more of the voids are more preferred, and most preferably 99% or more of the voids.
  • the voids that the positive electrode active material layer 22 has refer to regions other than the solid components (positive electrode active material, conductive material, etc.) in the positive electrode active material layer 22.
  • the voids included in the negative electrode active material layer 32 are also filled with the electrolyte 51, similar to the above description of the positive electrode active material layer 22.
  • the voids that the negative electrode active material layer 32 has refer to regions other than the solid components (negative electrode active material, conductive material, etc.) in the negative electrode active material layer 32.
  • the energy barrier when desorbing lithium ions from the positive electrode active material tends to become high.
  • the lower the temperature of the charging environment the greater the overvoltage required to desorb lithium ions from the positive electrode active material.
  • the positive electrode active material may be exposed to high voltage (higher potential than lithium potential) during charging in a low-temperature environment.
  • high voltage high potential than lithium potential
  • a positive electrode active material that can withstand high voltage and obtain high charging capacity when charging in a low temperature environment is used as the positive electrode active material of a lithium ion battery that has excellent charging and discharging characteristics even in a low temperature environment. It is preferable.
  • the electrolyte of a lithium ion battery that has excellent charging and discharging characteristics even in a low-temperature environment (e.g., 0°C, -10°C, -20°C, preferably -30°C, more preferably It is preferable to use a material that has excellent lithium ion conductivity even when charging and/or discharging (charging and discharging) at -40°C, more preferably -50°C, most preferably -60°C.
  • a preferred positive electrode active material and electrolyte for a lithium ion battery having excellent charging and discharging characteristics even in a low-temperature environment will be described in detail below.
  • 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 material and a binder.
  • the positive electrode active material has a function of taking in lithium ions and a function of releasing lithium ions during charging and discharging.
  • the positive electrode active material used as an embodiment of the present invention is a material that exhibits less deterioration (or less resistance increase) due to charging and/or discharging in a low-temperature environment even at a high charging voltage (hereinafter also referred to as "high charging voltage"). material) can be used.
  • a positive electrode active material composite oxide
  • D50 median diameter
  • This positive electrode active material contains one or more of additive element X, additive element Y, and additive element Z. The details of the additive element X, the additive element Y, and the additive element Z will be explained in ⁇ Contained elements>.
  • the particle size of the positive electrode active material is preferably 1 ⁇ m or more.
  • the particle size of the positive electrode active material is preferably 100 nm or more even as the smallest particle.
  • the particle size of the positive electrode active material is larger than the thickness of the active material layer, which will be described later, the particle density of the active material layer cannot be increased, so the maximum particle size should be 50 ⁇ m or less. preferable.
  • the particle size can be measured using a particle size distribution meter using a laser diffraction/scattering method.
  • D50 is the particle diameter when the cumulative amount occupies 50% in the cumulative particle amount curve of the particle size distribution measurement result. Measurement of particle size is not limited to laser diffraction particle size distribution measurement, and the major axis of a particle cross section may be measured by analysis using SEM or TEM. In addition, as a method of measuring D50 from analysis such as SEM or TEM, for example, 20 or more particles are measured, an integrated particle amount curve is created, and the particle diameter when the integrated amount accounts for 50% is defined as D50. be able to.
  • charging voltage is expressed based on the potential of lithium metal.
  • high charging voltage refers to a charging voltage of, for example, 4.5V or higher, preferably 4.55V or higher, more preferably 4.6V or higher, 4.65V or higher, or 4.7V.
  • x in Li x CoO 2 is small, for example, 0.1 ⁇ x ⁇ 0.24.
  • two or more types of materials with different particle sizes and/or compositions as the positive electrode active material as long as the material is less likely to deteriorate due to charging and discharging even at a high charging voltage.
  • “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 more 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 discharge capacity in a low temperature environment for example, 0°C, -10°C, -20°C, preferably -30°C, more preferably -40°C, still more preferably -50°C, most preferably -60°C
  • a lithium ion battery whose discharge capacity value is 50% or more (preferably 60% or more, more preferably 70% or more, still more preferably 80% or more, most preferably 90% or more) compared to the discharge capacity value at 20°C. can be realized.
  • the above values are the values when both charging and discharging are performed in a low-temperature environment, and charging and discharging in a low-temperature environment and charging and discharging at 20 ° C. (Sometimes referred to as "charge/discharge temperature.") Other measurement conditions are the same.
  • the discharge capacity when charging and discharging at 0°C is preferably 85% or more, and preferably 90% or more of the discharge capacity when charging and discharging at 20°C. It is more preferable that it is 95% or more, and even more preferably that it is 98% or more.
  • the discharge capacity when charging and discharging at -10°C is preferably 80% or more, more preferably 85% or more, compared to the discharge capacity when charging and discharging at 20°C. It is preferably 90% or more, more preferably 95% or more.
  • the discharge capacity when charging and discharging at -20°C is preferably 75% or more, more preferably 80% or more, compared to the discharge capacity when charging and discharging at 20°C.
  • the discharge capacity when charging and discharging at -30°C is preferably 70% or more, more preferably 75% or more, compared to the discharge capacity when charging and discharging at 20°C. It is preferably 80% or more, more preferably 85% or more.
  • the discharge It is possible to create lithium-ion batteries with high energy density.
  • discharge energy density in a low temperature environment for example, 0°C, -10°C, -20°C, preferably -30°C, more preferably -40°C, still more preferably -50°C, most preferably -60°C
  • Lithium whose value is 50% or more (preferably 60% or more, more preferably 70% or more, still more preferably 80% or more, most preferably 90% or more) compared to the value of discharge energy density at 20 ° C.
  • Ion batteries can be realized. Note that the measurement conditions other than temperature are the same for charging and discharging in a low-temperature environment and charging and discharging at 20°C.
  • the temperature during charging or discharging described in this specification and the like refers to the temperature of a lithium ion battery.
  • a constant temperature bath that is stable at a desired temperature is used, and after placing the battery to be measured (for example, a test battery or half cell) in the constant temperature bath, the test cell is The measurement can be started after a sufficient period of time (for example, one hour or more) has elapsed until the temperature reaches the same level as that of the constant temperature bath, but the method is not necessarily limited to this method.
  • a positive electrode active material 100 that exhibits little deterioration due to repeated charging and discharging at a high charging voltage will be described with reference to FIGS. 2 and 3.
  • FIGS. 3A and 3B are cross-sectional views of a positive electrode active material 100 that is one embodiment of the present invention.
  • FIGS. 3A to 3C are enlarged views of the area around AB in FIG. 2B.
  • enlarged views of the area around CD in FIG. 2B are shown in FIGS. 3D to 3F.
  • the positive electrode active material 100 has a surface layer portion 100a and an interior portion 100b.
  • the boundary between the surface layer portion 100a and the interior portion 100b is indicated by a broken line.
  • the surface layer 100a of the positive electrode active material 100 is, for example, within 50 nm from the surface toward the inside, more preferably within 35 nm from the surface toward the inside, still more preferably within 20 nm from the surface toward the inside, most preferably the surface.
  • the surface layer portion 100a has the same meaning as near-surface, near-surface region, or shell.
  • Interior 100b is synonymous with interior region or core.
  • the surface layer portion 100a has an edge region 100a1 and a basal region 100a2, as shown in FIG. 2B. Note that in FIGS. 2A and 2B, the straight line labeled (00l) represents the (00l) plane.
  • the edge region 100a1 has a surface exposed in a direction intersecting the (00l) plane, and is within 50 nm from the surface toward the inside, more preferably within 35 nm from the surface toward the inside, and even more preferably A region within 20 nm from the surface toward the inside, and most preferably within 10 nm vertically or substantially perpendicularly from the surface toward the inside from the surface, is called an edge region 100a1.
  • intersect here means that the angle between the perpendicular to the first surface ((00l) plane) and the normal to the second surface (the surface of the positive electrode active material 100) is 10 degrees or more. It means 90 degrees or less, more preferably 30 degrees or more and 90 degrees or less.
  • the basal region 100a2 has a surface parallel to the (00l) plane, and is within 50 nm from the surface toward the inside, more preferably within 35 nm from the surface toward the inside, and even more preferably from the surface toward the inside.
  • parallel means that the angle between the perpendicular to the first surface ((00l) plane) and the normal to the second surface (the surface of the positive electrode active material 100) is 0 degrees or more and 10 degrees. less than 0 degrees, preferably 0 degrees or more and 5 degrees or less, more preferably 0 degrees or more and 2.5 degrees or less.
  • the surface of the positive electrode active material 100 refers to the surface of the composite oxide including the surface layer portion 100a and the interior portion 100b. Therefore, the positive electrode active material 100 is made of materials to which metal oxides such as aluminum oxide (Al 2 O 3 ) that do not have lithium sites that can contribute to charging and discharging are attached, and carbonates chemically adsorbed after the production of the positive electrode active material. , hydroxyl group, etc. are not included. Note that the deposited metal oxide refers to, for example, a metal oxide whose crystal orientation does not match that of the interior 100b.
  • metal oxides such as aluminum oxide (Al 2 O 3 ) that do not have lithium sites that can contribute to charging and discharging are attached, and carbonates chemically adsorbed after the production of the positive electrode active material. , hydroxyl group, etc. are not included.
  • the deposited metal oxide refers to, for example, a metal oxide whose crystal orientation does not match that of the interior 100b.
  • TEM Transmission Electron Microscope
  • STEM Scanning Transmission Electron Microscope
  • HAADF-STEM High-angle Annular Dark Field Scanning TEM, high-angle scattering annular dark-field scanning transmission electron microscope
  • ABF-STEM Annular Bright-Field Scanning Transmission Microscope, annular bright-field scanning transmission electron microscope
  • XRD X-ray diffraction
  • neutron beam diffraction etc. can also be used as materials for judgment.
  • the electrolyte attached to the positive electrode active material 100 a decomposed product of the electrolyte, an organic solvent, a binder, a conductive material, or a compound derived from these is not included.
  • the positive electrode active material 100 is a compound containing a transition metal and oxygen that are capable of intercalating and deintercalating lithium, the transition metal M (for example, Co, Ni, Mn, Fe, etc.) and oxygen that undergo oxidation and reduction as lithium intercalates and deintercalates.
  • the interface between the region where is present and the region where is not is defined as the surface of the positive electrode active material.
  • the surface caused by slips and/or cracks can also be referred to as the surface of the positive electrode active material.
  • a protective film is sometimes attached to the surface, but the protective film is not included in the positive electrode active material.
  • the protective film a single layer film or a multilayer film of carbon, metal, oxide, resin, etc. may be used.
  • the positive electrode active material 100 includes lithium, cobalt, oxygen, and additional elements.
  • the positive electrode active material 100 may include lithium cobalt oxide (LiCoO 2 ) to which additional elements are added.
  • the positive electrode active material of a lithium ion secondary battery needs to contain a transition metal capable of redox in order to maintain charge neutrality even when lithium ions are intercalated and deintercalated. It is preferable that the positive electrode active material 100 of one embodiment of the present invention mainly uses cobalt as the transition metal responsible for the redox reaction. In addition to cobalt, one or both of nickel and manganese may be used. Among the transition metals contained in the positive electrode active material 100, if cobalt accounts for 75 atomic % or more, preferably 90 atomic % or more, and more preferably 95 atomic % or more, it is relatively easy to synthesize, easy to handle, and has excellent cycle characteristics. It is preferable as it has many advantages.
  • nickel such as lithium nickelate (LiNiO 2 ) accounts for the majority of the transition metals.
  • the stability is better when x in Li x CoO 2 is small compared to complex oxides in which the amount of x in Li x CoO 2 is small. This is thought to be because cobalt is less affected by distortion due to the Jahn-Teller effect than nickel.
  • the strength of the Jahn-Teller effect in transition metal compounds differs depending on the number of electrons in the d orbital of the transition metal.
  • Layered rock-salt complex oxides such as lithium nickelate, in which octahedral-coordinated low-spin nickel (III) accounts for the majority of the transition metal, are strongly influenced by the Jahn-Teller effect, and are separated from the octahedral structure of nickel and oxygen. Distortion is likely to occur in the layers. Therefore, there is a growing concern that the crystal structure will collapse during charge/discharge cycles. Also, nickel ions are larger than cobalt ions and are close to the size of lithium ions. Therefore, in layered rock salt type composite oxides in which nickel accounts for the majority of the transition metal, such as lithium nickelate, there is a problem that cation mixing of nickel and lithium tends to occur.
  • Additional elements included in the positive electrode active material 100 include magnesium, fluorine, nickel, aluminum, titanium, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, boron, barium, bromine, and It is preferable to use one or more selected from beryllium. Moreover, the sum of transition metals among the additional elements is preferably less than 25 atom %, more preferably less than 10 atom %, and even more preferably less than 5 atom %.
  • the positive electrode active material 100 includes lithium cobalt oxide containing magnesium, lithium cobalt oxide containing magnesium and aluminum, lithium cobalt oxide containing magnesium, aluminum, and titanium, lithium cobalt oxide containing magnesium and nickel, magnesium, aluminum, and Lithium cobalt oxide with nickel, lithium cobalt oxide with magnesium and fluorine, lithium cobalt oxide with magnesium, fluorine and titanium, lithium cobalt oxide with magnesium, fluorine and aluminum, cobalt oxide with magnesium, fluorine, titanium and aluminum Any one or more of lithium cobalt oxide containing lithium, magnesium, fluorine and nickel, lithium cobalt oxide containing magnesium, fluorine, nickel and aluminum, etc. can be used.
  • a positive electrode active material having cobalt, oxygen, and magnesium a positive electrode active material having cobalt, oxygen, magnesium, and aluminum, cobalt, oxygen, and magnesium
  • a positive electrode active material having aluminum and titanium A positive electrode active material having cobalt, oxygen, magnesium, and nickel;
  • a positive electrode active material having cobalt, oxygen, magnesium, aluminum, and nickel a positive electrode active material having cobalt, oxygen, magnesium, and fluorine, a positive electrode active material having cobalt, oxygen, magnesium, fluorine, and titanium, cobalt, oxygen, magnesium, and fluorine and aluminum
  • a positive electrode active material having cobalt, oxygen, magnesium, fluorine, titanium, and aluminum a positive electrode active material having cobalt, oxygen, magnesium, fluorine, titanium, and aluminum, cobalt, oxygen, magnesium, fluorine, and nickel
  • Any one or more of the following can be used in a lithium ion battery: a positive electrode active material having cobalt, oxygen, magnesium, fluorine, nickel, aluminum, etc.
  • the additive element is preferably dissolved in the positive electrode active material 100.
  • the depth at which the detected amount of the additive element increases is deeper than the depth at which the detected amount of transition metal M increases, that is, the positive electrode active material 100 It is preferable that it be located inside.
  • the additive element has the same meaning as a mixture or a part of raw materials.
  • additive elements do not necessarily include magnesium, fluorine, nickel, aluminum, titanium, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, boron, barium, bromine, or beryllium. Good too.
  • the positive electrode active material 100 is substantially free of manganese, the above-mentioned advantages such as being relatively easy to synthesize, easy to handle, and having excellent cycle characteristics are further enhanced. It is preferable that the weight of manganese contained in the positive electrode active material 100 is, for example, 600 ppm or less, more preferably 100 ppm or less.
  • the surface layer portion 100a 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 in the interior portion 100b. Further, it can be said that some of the bonds of the atoms on the surface of the particles of the positive electrode active material 100 included in the surface layer portion 100a are in a state of being broken. Therefore, the surface layer portion 100a tends to become unstable, and can be said to be a region where the crystal structure tends to deteriorate.
  • the surface layer 100a can be made sufficiently stable, even when x in Li x CoO 2 is small, for example, even when x is 0.24 or less, the layered structure made of cobalt and oxygen octahedrons in the interior 100b will be difficult to break. I can do it. Furthermore, it is possible to suppress misalignment of the layer made of cobalt and oxygen octahedrons in the interior 100b.
  • the surface layer portion 100a preferably contains an additive element, and more preferably contains a plurality of additive elements. Further, it is preferable that the concentration of one or more selected additive elements is higher in the surface layer portion 100a than in the interior portion 100b. Further, it is preferable that one or more selected from the additive elements included in the positive electrode active material 100 have a concentration gradient. Further, it is more preferable that the distribution of the positive electrode active material 100 differs depending on the added element. For example, it is more preferable that the depth of the concentration peak from the surface differs depending on the added element. The concentration peak here refers to the maximum value of the concentration in the surface layer portion 100a or 50 nm or less from the surface.
  • FIGS. 3A to 3C are enlarged views of the vicinity of AB in FIG. 2B, and are diagrams illustrating the edge region 100a1 of the positive electrode active material 100. Further, FIGS. 3D to 3F are enlarged views of the vicinity of CD in FIG. 2B, and are diagrams for explaining the basal region 100a2 of the positive electrode active material 100.
  • some of the additive elements such as magnesium, fluorine, titanium, silicon, phosphorus, boron, calcium, etc., preferably have a concentration gradient that increases from the interior 100b toward the surface, as shown by the gradation in FIGS. 3A and 3D. .
  • An additive element having such a concentration gradient will be referred to as an additive element X.
  • additive elements such as aluminum and manganese
  • concentration gradient as shown by the hatched density in FIGS. 3B and 3E, and the concentration is deeper than the additive element X shown in FIGS. 3A and 3D.
  • concentration peak may exist in the surface layer portion 100a or may be deeper than the surface layer portion 100a.
  • An additive element having such a concentration gradient will be referred to as an additive element Y.
  • edge region 100a1 Although other additive elements, such as nickel and barium, are clearly present in the edge region 100a1, as shown by the presence or absence of hatching and the density of hatching in FIGS. 3C and 3F, they are substantially not present in the basal region 100a2. There may be cases where it is not available. Note that clearly existing here refers to a case where a characteristic X-ray energy spectrum of the element is detected in cross-sectional STEM-EDX analysis of the positive electrode active material 100.
  • substantially free refers to a case where the characteristic X-ray energy spectrum of the element is not detected in cross-sectional STEM-EDX analysis of the positive electrode active material 100. In this case, it is also said that the element is below the detection limit in STEM-EDX analysis.
  • An additive element having such a distribution will be referred to as an additive element Z.
  • 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 100a makes it easier to maintain the layered rock salt crystal structure. 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 when x in Li x CoO 2 is, for example, 0.24 or less.
  • the presence of magnesium can be expected to increase the density of the positive electrode active material 100.
  • the magnesium concentration in the surface layer portion 100a is high, it can be expected that the corrosion resistance against hydrofluoric acid produced by decomposition of the electrolytic solution will be improved.
  • magnesium is at an appropriate concentration, it will not adversely affect insertion and desorption of lithium during charging and discharging, and the above advantages can be enjoyed.
  • an excess of magnesium may have an adverse effect on lithium intercalation and deintercalation.
  • 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.
  • excess 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 100 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 positive electrode active material 100 herein may be a value obtained by elemental analysis of the entire positive electrode active material 100 using, for example, GD-MS, ICP-MS, etc. It may be based on the value of the composition of raw materials in the process of producing the substance 100.
  • aluminum which is one of the additive elements Y, can 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, when aluminum is included as an additive element, safety can be improved when the positive electrode active material 100 is used in a secondary battery. Moreover, the positive electrode active material 100 can be made such that the crystal structure does not easily collapse even after repeated charging and discharging.
  • the entire positive electrode active material 100 has an appropriate amount of aluminum.
  • the number of aluminum atoms contained in the entire positive electrode active material 100 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 100 has here may be, for example, a value obtained by elemental analysis of the entire positive electrode active material 100 using GD-MS, ICP-MS, etc., or the amount that the entire positive electrode active material 100 has. It may also be based on the value of the composition of raw materials during the production process.
  • nickel which is one of the additive elements Z, can exist at both the cobalt site and the lithium site.
  • the oxidation-reduction potential becomes lower than that of cobalt, which leads to an increase in discharge capacity, which is preferable.
  • the shift of the layered structure consisting of cobalt and oxygen octahedrons can be suppressed. Further, changes in volume due to charging and discharging are suppressed. Also, the elastic modulus becomes larger, that is, it becomes harder. This is presumably because nickel present at the lithium site also functions as a pillar supporting the two CoO layers. Therefore, it is expected that the crystal structure will become more stable especially in a charged state at a high temperature, for example, 45° C. or higher, which is preferable.
  • the entire positive electrode active material 100 has an appropriate amount of nickel.
  • the number of nickel atoms in the positive electrode active material 100 is preferably more than 0% and less than 7.5% of the number of cobalt atoms, preferably 0.05% or more and 4% or less, and preferably 0.1% or more and 2% or less. is preferable, and more preferably 0.2% or more and 1% or less.
  • it is preferably more than 0% and 4% or less.
  • it is preferably more than 0% and 2% or less.
  • preferably 0.05% or more and 2% or less Or preferably 0.1% or more and 7.5% or less.
  • the amount of nickel shown here may be, for example, a value obtained by elemental analysis of the entire positive electrode active material using 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
  • fluorine which is one of the additive elements X
  • fluorine is a monovalent anion
  • fluorine in the surface layer portion 100a when a part of oxygen is replaced with fluorine in the surface layer portion 100a, 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 100a of the positive electrode active material 100 is replaced with fluorine, it can be said that desorption and insertion of lithium ions near fluorine are likely to occur smoothly. Therefore, when the positive electrode active material 100 is used in a secondary battery, charging/discharging characteristics, large current characteristics, etc.
  • a fluxing agent also called a fluxing agent
  • titanium oxide which is one of the additive elements X, has superhydrophilicity. Therefore, by using the positive electrode active material 100 having titanium oxide in the surface layer portion 100a, the wettability with respect to a highly polar solvent may be improved. When used as a secondary battery, the interface between the positive electrode active material 100 and the highly polar electrolytic solution becomes good, and there is a possibility that an increase in internal resistance can be suppressed.
  • additive element X additive element Y
  • additive element Z additive element Z
  • the crystal structure can be stabilized over a wider region.
  • the positive electrode active material 100 includes magnesium as one of the additive elements X, aluminum as one of the additive elements Y, and nickel as one of the additive elements Z
  • the additive elements X, Y, and The crystal structure can be stabilized over a wider area than when only one or two of the elements Z are present.
  • additive element X such as magnesium
  • additive element Z such as nickel.
  • aluminum, and other additive elements Y are not essential to the surface.
  • aluminum is widely distributed in a deeper region.
  • aluminum is continuously detected in a region from the surface in a depth direction of 1 nm or more and 25 nm or less.
  • the crystal structure be widely distributed in a region of 0 nm or more and 50 nm or less from the surface, preferably 1 nm or more and 50 nm or less from the surface because the crystal structure can be stabilized over a wider region.
  • the additive element Z when the additive element Z is contained in a large amount in the edge region 100a1 (also referred to as preferentially contained, selectively contained, etc.) as shown in FIG. 3C and FIG. 3F, charging of the lithium ion battery and This is preferable because the stability of the crystal structure of the edge region 100a1 where lithium ions enter and leave the positive electrode active material 100 during discharge is improved.
  • the additive element Z has the above distribution, for example, when the positive electrode active material 100 is lithium cobalt oxide, the effects of adding the additive element Z, such as a decrease in discharge voltage or a decrease in discharge capacity, can be reduced. This is preferable because it can be kept to a minimum.
  • the effects of each additive element are synergized and can contribute to further stabilization of the surface layer portion 100a.
  • magnesium, nickel and aluminum are highly effective in providing a stable composition and crystal structure.
  • the surface layer portion 100a of the positive electrode active material 100 has a region where magnesium is distributed closer to the surface than aluminum.
  • the edge region 100a1 of the surface layer portion 100a of the positive electrode active material 100 has a region where the nickel distribution and the magnesium distribution overlap.
  • 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 secondary batteries. Therefore, it is particularly preferable that the interior 100b, which occupies most of the volume of the positive electrode active material 100, has a layered rock salt crystal structure.
  • the surface layer 100a of the positive electrode active material 100 is configured so that even if lithium is removed from the positive electrode active material 100 due to charging, the layered structure made of the transition metal M and oxygen octahedron in the interior 100b is not broken. It is preferable to have a reinforcing function. Alternatively, it is preferable that the surface layer portion 100a functions as a barrier film for the positive electrode active material 100. Alternatively, it is preferable that the surface layer portion 100a, which is the outer peripheral portion of the positive electrode active material 100, reinforces the positive electrode active material 100.
  • Reinforcement here refers to suppressing structural changes in the surface layer 100a and interior 100b of the positive electrode active material 100, including desorption of oxygen, and/or oxidative decomposition of the electrolyte on the surface of the positive electrode active material 100. It means to suppress something.
  • the surface layer portion 100a has a crystal structure different from that of the interior portion 100b. Further, it is preferable that the surface layer portion 100a has a composition and crystal structure that are more stable at room temperature (25° C.) than the interior portion 100b. For example, it is preferable that at least a portion of the surface layer portion 100a of the positive electrode active material 100 according to one embodiment of the present invention has a rock salt crystal structure. Alternatively, the surface layer portion 100a preferably has both a layered rock salt type crystal structure and a rock salt type crystal structure. Alternatively, the surface layer portion 100a preferably has characteristics of both a layered rock salt type and a rock salt type crystal structure.
  • some of the additive elements A particularly magnesium, nickel, and aluminum, preferably have a higher concentration in the surface layer 100a than in the interior 100b, but are also preferably randomly and dilutely present in the interior 100b.
  • magnesium and aluminum are present at appropriate concentrations in the lithium sites in the interior 100b, there is an effect that the layered rock salt type crystal structure can be easily maintained, similar to the above.
  • nickel is present in the interior 100b at an appropriate concentration, the shift of the layered structure consisting of the octahedron of transition metal M and oxygen can be suppressed in the same way as described above.
  • divalent magnesium may exist more stably near divalent nickel, so a synergistic effect of suppressing the elution of magnesium can be expected.
  • the crystal structure changes continuously from the interior 100b toward the surface due to the concentration gradient of the additive element A as described above.
  • the crystal orientations of the surface layer portion 100a and the interior portion 100b are approximately the same.
  • the crystal structure changes continuously from the interior 100b of a layered rock salt type toward the surface and surface layer portion 100a having characteristics of the rock salt type or both of the rock salt type and the layered rock salt type.
  • the crystal orientations of the surface layer portion 100a which has the characteristics of a rock salt type or both of a rock salt type and a layered rock salt type, and the crystal orientation of the layered rock salt type interior 100b are generally the same.
  • the layered rock-salt crystal structure belonging to space group R-3m which a composite oxide containing a transition metal M such as lithium and cobalt has, is defined as a structure in which cations and anions alternate. It has a rock salt-type ion arrangement, and the transition metal M and lithium are regularly arranged to form a two-dimensional plane, so it is a crystal structure that allows two-dimensional diffusion of lithium. Note that there may be defects such as cation or anion deficiency. Strictly speaking, the layered rock salt crystal structure may have a structure in which the lattice of the rock salt crystal is distorted.
  • the rock salt type crystal structure has a cubic crystal structure including a space group Fm-3m, and refers to a structure in which cations and anions are arranged alternately. Note that there may be a deficiency of cations or anions.
  • rock salt type and rock salt type crystal structure characteristics can be determined by electron beam diffraction, TEM image, cross-sectional STEM image, etc.
  • the rock salt type has no distinction in cation sites, but the layered rock salt type has two types of cation sites in its crystal structure, one mostly occupied by lithium and the other occupied by the transition metal M.
  • the layered structure in which two-dimensional planes of cations and two-dimensional planes of anions are arranged alternately is the same for both the rock salt type and the layered rock salt type.
  • the central spot transparent spot
  • the bright spot closest to the central spot is the ideal one.
  • a state rock salt type has a (111) plane
  • a layered rock salt type has a (003) plane, for example.
  • the bright spot on the (003) plane of LiCoO 2 is at a distance of about half the distance of the bright spot on the (111) plane of MgO. observed in position. Therefore, when the analysis region has two phases, for example, rock salt type MgO and layered rock salt type LiCoO2 , in the electron beam diffraction image, there is a plane orientation in which bright spots with strong brightness and bright spots with weak brightness are arranged alternately. do. Bright spots common to the halite type and layered halite type have strong brightness, and bright spots that occur only in the layered halite type have weak brightness.
  • Layered rock salt crystals and anions of rock salt crystals have a cubic close-packed structure (face-centered cubic lattice structure).
  • the anions are also presumed to have a cubic close-packed structure. Therefore, when a layered rock salt crystal and a rock salt crystal come into contact, there is a crystal plane in which the cubic close-packed structure composed of anions is oriented in the same direction.
  • Anions in the ⁇ 111 ⁇ plane of the cubic crystal structure have a triangular lattice.
  • the layered rock salt type has a space group R-3m and has a rhombohedral structure, but to facilitate understanding of the structure, it is generally expressed as a complex hexagonal lattice, and the (0001) plane of the layered rock salt type has a hexagonal lattice.
  • the triangular lattice of the cubic ⁇ 111 ⁇ plane has an atomic arrangement similar to the hexagonal lattice of the (0001) plane of the layered rock salt type. When both lattices are consistent, it can be said that the orientations of the cubic close-packed structures are aligned.
  • the space group of layered rock salt crystals and O3' type crystals is R-3m, which is different from the space group Fm-3m of rock salt crystals (the space group of general rock salt crystals), so the above conditions are
  • the Miller index of the crystal planes to be satisfied is different between a layered rock salt type crystal and an O3' type crystal and a rock salt type crystal.
  • a layered rock salt type crystal, an O3' type crystal, and a rock salt type crystal when the directions of the cubic close-packed structures constituted by anions are aligned, it may be said that the orientations of the crystals approximately coincide.
  • the positive electrode active material 100 of one embodiment of the present invention has the above-mentioned distribution of the additive element A and/or crystal structure in the discharge state, so that the positive electrode active material 100 has a crystal structure in which x in Li x CoO 2 is small.
  • the structure is different from conventional positive electrode active materials. Note that x is small here, which means 0.1 ⁇ x ⁇ 0.24.
  • FIGS. 4 to 7 A change in the crystal structure due to a change in x in Li x CoO 2 will be explained using FIGS. 4 to 7 while comparing a conventional cathode active material and the cathode active material 100 of one embodiment of the present invention.
  • FIG. 5 shows changes in the crystal structure of conventional positive electrode active materials.
  • the conventional positive electrode active material shown in FIG. 5 is lithium cobalt oxide (LiCoO 2 ) that does not particularly contain the additive element A.
  • 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. This is sometimes referred to as a layer consisting of cobalt and oxygen octahedrons.
  • one CoO 2 layer exists in the unit cell. Therefore, it is sometimes called O1 type or monoclinic O1 type.
  • the positive electrode active material has a crystal structure of trigonal space group P-3m1, and one CoO 2 layer is also present in the unit cell. Therefore, this crystal structure is sometimes called O1 type or trigonal O1 type.
  • the trigonal crystal is sometimes converted into a complex hexagonal lattice and is called the hexagonal O1 type.
  • This structure can also 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 stacked alternately. 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.
  • the coordinates of cobalt and oxygen in the unit cell are Co(0, 0, 0.42150 ⁇ 0.00016), O1(0, 0, 0.27671 ⁇ 0.00045), It can be expressed as O2 (0, 0, 0.11535 ⁇ 0.00045).
  • O1 and O2 are each oxygen atoms.
  • Which unit cell should be used to represent the crystal structure of the positive electrode active material can be determined, for example, by Rietveld analysis of the XRD pattern. In this case, a unit cell with a small GOF (goodness of fit) value may be used.
  • conventional lithium cobalt oxide has an H1-3 type crystal structure, an R-3m O3 structure in a discharged state, The crystal structure changes (that is, non-equilibrium phase changes) repeatedly between the two.
  • the crystal structure of conventional lithium cobalt oxide collapses.
  • the collapse of the crystal structure causes deterioration of cycle characteristics. This is because as the crystal structure collapses, the number of sites where lithium can exist stably decreases, and insertion and extraction of lithium becomes difficult.
  • the positive electrode active material 100 of one embodiment of the present invention 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 cathode active material 100 of one embodiment of the present invention, short circuits are unlikely to occur when x in Li x CoO 2 is maintained at 0.24 or less. In such a case, the safety of the secondary battery is further improved, which is preferable.
  • FIG. 4 shows the crystal structure that the interior 100b of the positive electrode active material 100 has when x in Li x CoO 2 is about 1 and 0.2. Since the interior 100b occupies most of the volume of the positive electrode active material 100 and is a part that greatly contributes to charging and discharging, it can be said that the displacement of the CoO 2 layer and the change in volume are the most problematic part.
  • the positive electrode active material 100 has the same R-3mO3 crystal structure as conventional lithium cobalt oxide.
  • the positive electrode active material 100 forms a crystal with a different structure.
  • ions such as cobalt, nickel, and magnesium occupy six oxygen coordination positions. Note that a light element such as lithium may occupy the 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. It is 8%.
  • the cathode active material 100 of one embodiment of the present invention 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 cathode active materials. has been done.
  • changes in volume are also suppressed when comparing the same number of cobalt atoms. Therefore, the crystal structure of the positive electrode active material 100 does not easily collapse even after repeated charging and discharging such that x becomes 0.24 or less. Therefore, in the positive electrode active material 100, a decrease in charge/discharge capacity during charge/discharge cycles is suppressed.
  • the positive electrode active material 100 has a large discharge capacity per weight and per volume. Therefore, by using the positive electrode active material 100, a secondary battery with high discharge capacity per weight and per volume can be manufactured.
  • the positive electrode active material 100 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 exceeds 0.24 and 0. It is estimated that even if it is less than .27, it has an O3' type crystal 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 entire interior 100b of the positive electrode active material 100 does not need to have an O3' type crystal structure. It may contain other crystal structures, or may be partially amorphous.
  • the H1-3 type crystal structure may be finally observed when the charging voltage is further increased. Furthermore, as mentioned above, the crystal structure is affected by the number of charge/discharge cycles, charge/discharge current, temperature, electrolyte, etc., so if the charging voltage is lower, for example, if the charging voltage is 4.5 V or more and less than 4.6 V at 25°C, In some cases, the positive electrode active material 100 of one embodiment of the present invention can have an O3' type crystal structure.
  • lithium is shown to exist at all lithium sites with equal probability, but the present invention is not limited to this. It may be concentrated in some lithium sites, or it may have a symmetry such as monoclinic O1 (Li 0.5 CoO 2 ) shown in FIG. 5, for example.
  • the distribution of lithium can be analyzed, for example, by neutron diffraction.
  • the O3' type crystal structure is similar to the CdCl2 type crystal structure, although it has 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 A be the same at a plurality of locations in the surface layer portion 100a of the positive electrode active material 100.
  • the reinforcement derived from the additive element A exists homogeneously in the surface layer portion 100a. Even if a portion of the surface layer portion 100a is reinforced, if there is a portion without reinforcement, stress may be concentrated on the portion without reinforcement. When stress is concentrated on a portion of the positive electrode active material 100, defects such as cracks may occur there, leading to cracking of the positive electrode active material and a decrease in discharge capacity.
  • the additive element A does not necessarily have to have the same concentration gradient in all the surface layer portions 100a of the positive electrode active material 100.
  • the area near CD has a layered rock salt type crystal structure of R-3m, and the surface has a (001) orientation.
  • the (001) oriented surface may have a different distribution of the additive element A from other surfaces.
  • the (001) oriented surface and its surface layer 100a have a distribution of one or more concentration peaks selected from the additive element It may be limited to a shallow portion.
  • the (001) oriented surface and its surface layer portion 100a may have a lower concentration of one or more selected from additive element X and additive element Y compared to other orientations.
  • one or more elements selected from the additive element X and the additive element Y may be below the detection limit.
  • the surface of the positive electrode active material 100 is more stable if it has a (001) orientation.
  • the main diffusion path of lithium ions during charging and discharging is not exposed on the (001) plane.
  • the surface other than the (001) orientation and the surface layer portion 100a are important regions for maintaining the diffusion path of lithium ions, and at the same time are the regions from which lithium ions are first desorbed, so they tend to become unstable. Therefore, it is extremely important to reinforce the surface other than the (001) orientation and the surface layer portion 100a in order to maintain the crystal structure of the entire positive electrode active material 100.
  • the positive electrode active material 100 it is important that the distribution of the additive element A on the surface other than (001) and the surface layer 100a is as shown in FIGS. 3A and 3C. It is. On the other hand, in the (001) plane and its surface layer portion 100a, the concentration of the additive element A may be low or absent as described above.
  • the additive element A spreads mainly through the diffusion path of lithium ions. Therefore, the distribution of the additive element A on the surface other than (001) and its surface layer 100a can be easily set within a preferable range.
  • the additive element A that the positive electrode active material 100 of one embodiment of the present invention has is unevenly distributed at least partially in the grain boundaries and their vicinity.
  • maldistribution means that the concentration of an element in a certain region is different from that in other regions. It has the same meaning as segregation, precipitation, non-uniformity, deviation, or a mixture of areas with high concentration and areas with low concentration.
  • the magnesium concentration at and near the grain boundaries of the positive electrode active material 100 is higher than in other regions of the interior 100b.
  • the fluorine concentration at the grain boundaries and the vicinity thereof is also higher than that in other regions of the interior 100b.
  • the nickel concentration at the grain boundaries and the vicinity thereof is also higher than in other regions of the interior 100b.
  • the aluminum concentration at the grain boundaries and the vicinity thereof is also higher than that in other regions of the interior 100b.
  • Grain boundaries are one type of surface defect. Therefore, like the surface, it tends to become unstable and the crystal structure tends to change. Therefore, if the concentration of the additive element A at the grain boundaries and the vicinity thereof is high, changes in the crystal structure can be suppressed more effectively.
  • the concentration near the surface where the cracks occur is Magnesium and fluorine concentrations increase. Therefore, the corrosion resistance against hydrofluoric acid can be improved even in the positive electrode active material after cracks have occurred.
  • Whether a certain positive electrode active material is the positive electrode active material 100 of one embodiment of the present invention having an O3' type crystal structure when x in Li x CoO 2 is small is determined by whether x in Li x CoO 2 is small. This can be determined by analyzing a positive electrode containing a positive electrode active material using XRD, electron beam diffraction, neutron beam diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), or the like.
  • XRD can analyze the symmetry of transition metals such as cobalt contained in positive electrode active materials with high resolution, compare the height of crystallinity and crystal orientation, and analyze periodic lattice distortion and crystallite size. This is preferable because sufficient accuracy can be obtained even if the positive electrode obtained by disassembling the secondary battery is directly measured.
  • powder XRD provides a diffraction peak that reflects the crystal structure of the interior 100b of the positive electrode active material 100, which occupies most of the volume of the positive electrode active material 100.
  • the positive electrode active material 100 of one embodiment of the present invention is characterized by a small change in crystal structure between when x in Li x CoO 2 is 1 and when x is 0.24 or less.
  • a material in which 50% or more of the crystal structure changes significantly when charged at a high voltage is not preferable because it cannot withstand repeated high voltage charging and discharging.
  • the O3' type crystal structure may not be obtained simply by adding additional elements.
  • x in Li x CoO 2 may be 0.24 or less.
  • the O3' type crystal structure accounts for 60% or more, and in other cases, the H1-3 type crystal structure accounts for 50% or more.
  • the positive electrode active material 100 of one embodiment of the present invention if x is too small, such as 0.1 or less, or under conditions where the charging voltage exceeds 4.9 V, the crystal structure of the H1-3 type or trigonal O1 type will change. This may occur in some cases. Therefore, in order to determine whether the positive electrode active material 100 of one embodiment of the present invention is used, 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 crystal structure 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 the positive electrode active material is in the state described above can be determined by, for example, XPS, energy dispersive X-ray spectroscopy (EDX), EPMA ( This can be determined by analysis using methods such as electronic probe microanalysis.
  • the crystal structure of the surface layer 100a, grain boundaries, etc. can be analyzed by electron beam diffraction or the like of a cross section of the positive electrode active material 100.
  • Charging to determine whether the composite oxide is the positive electrode active material 100 of one embodiment of the present invention is performed by, for example, preparing a coin cell (CR2032 type, diameter 20 mm and height 3.2 mm) with lithium counter electrode and charging it. can do.
  • the positive electrode may be prepared by coating a positive electrode current collector made of aluminum foil with a slurry in which a positive electrode active material, a conductive material, and a binder are mixed.
  • Lithium metal can be used for the counter electrode. Note that when a material other than lithium metal is used for the counter electrode, the potential of the secondary battery and the potential of the positive electrode are different. Voltages and potentials in this specification and the like are the potentials of the positive electrode unless otherwise mentioned.
  • LiPF 6 lithium hexafluorophosphate
  • DEC diethyl carbonate
  • VC vinylene carbonate
  • a polypropylene porous film with a thickness of 25 ⁇ m can be used as the separator.
  • the positive electrode can and the negative electrode can may be made of stainless steel (SUS).
  • the coin cell produced under the above conditions is charged at an arbitrary voltage (for example, 4.5V, 4.55V, 4.6V, 4.65V, 4.7V, 4.75V or 4.8V).
  • the charging method is not particularly limited as long as it can be charged at any voltage for a sufficient amount of time.
  • the current in CC charging can be 20 mA/g or more and 100 mA/g or less.
  • CV charging can be completed at 2 mA/g or more and 10 mA/g or less.
  • the temperature is 25°C or 45°C.
  • the coin cell After charging in this manner, the coin cell 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. At this time, it is necessary to tightly close the container and maintain an argon atmosphere during the measurement.
  • the conditions for charging and discharging the plurality of times may be different from the above-mentioned charging conditions.
  • charging is performed by constant current charging at a current value of 20 mA/g or more and 100 mA/g or less to an arbitrary voltage (for example, 4.6 V, 4.65 V, 4.7 V, 4.75 V or 4.8 V), and then the current value is Constant voltage charging can be performed until the voltage is 2 mA/g or more and 10 mA/g or less, and discharging can be performed at a constant current of 2.5 V and 20 mA/g or more and 100 mA/g or less.
  • constant current discharge can be performed at, for example, 2.5 V and a current value of 20 mA/g or more and 100 mA/g or less.
  • XRD> The equipment and conditions for XRD measurement are not particularly limited. For example, it can be measured using the following equipment and conditions.
  • XRD device Bruker AXS, D8 ADVANCE
  • X-ray source CuK ⁇ 1- ray output: 40KV, 40mA
  • Slit width Div. Slit
  • 0.5° Detector LynxEye Scan method: 2 ⁇ / ⁇ continuous scan Measurement range (2 ⁇ ): 15° or more and 90° or less (100 minutes) Step width (2 ⁇ ): 0.01° Setting Counting time: 1 second/step Sample table rotation: 15 rpm
  • the sample to be measured is a powder, it can be set by placing it in a glass sample holder or by sprinkling the sample on a greased silicone non-reflective plate.
  • 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.
  • Ideal powder XRD patterns using the CuK ⁇ 1 ray calculated from the models of the O3′ type crystal structure and the H1-3 type crystal structure are shown in FIGS. 6 and 7.
  • the patterns of LiCoO 2 (O3) and CoO 2 (O1) were created using Reflex Powde, one of the modules of Materials Studio (BIOVIA), based on crystal structure information obtained from ICSD (Inorganic Crystal Structure Database).
  • the XRD pattern of the H1-3 type crystal structure was created in the same manner as above based on the information on the H1-3 type crystal structure shown in FIG.
  • the XRD pattern of the O3' type crystal structure was obtained by estimating the crystal structure from the XRD pattern of the positive electrode active material of one embodiment of the present invention, and 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 100 has an O3' type crystal structure when x in Li x CoO 2 is small, all of the positive electrode active material 100 does not have to have an O3' type crystal structure. It may contain other crystal structures, or may be partially amorphous. However, when Rietveld analysis is performed on the XRD pattern, the O3' type crystal structure is preferably 50% or more, more preferably 60% or more, and even more preferably 66% or more. If the O3' type crystal structure is 50% or more, more preferably 60% or more, even more preferably 66% or more, the positive electrode active material can have sufficiently excellent cycle characteristics.
  • the O3' type crystal structure is preferably 35% or more, more preferably 40% or more, and 43% or more when subjected to Rietveld analysis. It is more preferable that it is above.
  • 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. Such high crystallinity contributes to sufficient stabilization of the crystal structure after charging.
  • XPS> With X-ray photoelectron spectroscopy (XPS), in the case of inorganic oxides, if monochromatic aluminum K ⁇ rays are used as the X-ray source, it is possible to analyze a region from the surface to a depth of about 2 to 8 nm (usually 5 nm or less). Therefore, it is possible to quantitatively analyze the concentration of each element in a region approximately half of the depth of the surface layer 100a. Additionally, narrow scan analysis allows the bonding state of elements to be analyzed. Note that the quantitative accuracy of XPS is about ⁇ 1 atomic % in most cases, and the lower limit of detection is about 1 atomic %, although it depends on the element.
  • the concentration of one or more selected additive elements is higher in the surface layer portion 100a than in the interior portion 100b.
  • concentration of one or more selected additive elements in the surface layer portion 100a is preferably higher than the average of the entire positive electrode active material 100. Therefore, for example, the concentration of one or more additive elements selected from the surface layer 100a measured by It can be said that it is preferable that the concentration of the added element be higher than the average concentration of the added element of the entire positive electrode active material 100 measured by .
  • the magnesium concentration in at least a portion of the surface layer portion 100a measured by XPS or the like is higher than the magnesium concentration in the entire positive electrode active material 100.
  • the nickel concentration in at least a portion of the surface layer portion 100a is higher than the nickel concentration in the entire positive electrode active material 100.
  • the aluminum concentration in at least a portion of the surface layer portion 100a is higher than the aluminum concentration in the entire positive electrode active material 100.
  • the fluorine concentration in at least a portion of the surface layer portion 100a is higher than the fluorine concentration in the entire positive electrode active material 100.
  • the surface and surface layer portion 100a of the positive electrode active material 100 do not contain carbonate, hydroxyl groups, etc. that are chemically adsorbed after the positive electrode active material 100 is produced. It is also assumed that the electrolytic solution, binder, conductive material, or compounds derived from these adhered to the surface of the positive electrode active material 100 are not included. Therefore, when quantifying the elements contained in the positive electrode active material, correction may be made to exclude carbon, hydrogen, excess oxygen, excess fluorine, etc. that can be detected by surface analysis such as XPS. For example, in XPS, it is possible to separate the types of bonds by analysis, and correction may be performed to exclude binder-derived C-F bonds.
  • samples such as the positive electrode active material and the positive electrode active material layer are washed to remove the electrolyte, binder, conductive material, or compounds derived from these that have adhered to the surface of the positive electrode active material. You may do so. At this time, lithium may dissolve into the solvent used for cleaning, but even in that case, the additive elements are difficult to dissolve, so the atomic ratio of the additive elements is not affected.
  • the concentration of the additive element may be compared in terms of its ratio to cobalt.
  • the ratio Mg/Co of the number of atoms of magnesium and cobalt as determined by XPS analysis is preferably 0.400 or more, more preferably 0.500 or more, and even more preferably 0.600 or more. , more preferably 0.700 or more, more preferably 0.800 or more, more preferably 0.900 or more, and even more preferably 1.000 or more.
  • Mg/Co is preferably 2.000 or less, preferably 1.500 or less, preferably 1.400 or less, preferably 1.300 or less, or 1. It is preferable that it is 200 or less.
  • the ratio Ni/Co of the number of atoms of nickel and cobalt, as determined by XPS analysis is preferably 0.05 or more, more preferably 0.06 or more, and even more preferably 0.07 or more. It is preferably 0.08 or more, and more preferably 0.09 or more. Further, Ni/Co is preferably 0.200 or less, preferably 0.150 or less, preferably 0.140 or less, preferably 0.130 or less, and 0.120 or less. It is preferably at most 0.110, or preferably at most 0.110.
  • the ratio F/Co of the number of atoms of fluorine and cobalt, as determined by XPS analysis, is preferably 0.100 or more, more preferably 0.200 or more, and even more preferably 0.300 or more. It is preferably 0.400 or more, more preferably 0.500 or more, more preferably 0.600 or more, and even more preferably 0.700 or more. Further, F/Co is preferably 1.500 or less, preferably 1.200 or less, preferably 1.100 or less, preferably 1.000 or less, and 0.900 or less. It is preferable that it is below.
  • the above range indicates that these additive elements are not attached to a narrow area on the surface of the positive electrode active material 100, but are widely distributed in the surface layer 100a of the positive electrode active material 100 at a preferable concentration. It can be said that it shows.
  • the fact that it is in the above range means that even if x is repeatedly charged and discharged so that x becomes 0.24 or less, the crystal structure does not collapse easily, making it an excellent material. cycle characteristics can be achieved.
  • the take-out angle may be, for example, 45°.
  • the take-out angle may be, for example, 45°.
  • it can be measured using the following equipment and conditions.
  • the peak indicating the bond energy between fluorine and another element is preferably 682 eV or more and less than 685 eV, and more preferably about 684.3 eV. This value is different from both the binding energy of lithium fluoride, 685 eV, and the binding energy of magnesium fluoride, 686 eV. That is, when the positive electrode active material 100 of one embodiment of the present invention contains fluorine, the bond is preferably other than lithium fluoride and magnesium fluoride.
  • the peak indicating the bond energy between magnesium and other elements is preferably 1302 eV or more and less than 1304 eV, and more preferably about 1303 eV. This value is different from the binding energy of magnesium fluoride, 1305 eV, and is close to the binding energy of magnesium oxide. That is, when the positive electrode active material 100 of one embodiment of the present invention contains magnesium, it is preferable that the bond is other than magnesium fluoride.
  • ⁇ EDX> It is preferable that one or more selected from the additive elements included in the positive electrode active material 100 have a concentration gradient. Further, it is more preferable that the depth of the concentration peak from the surface of the positive electrode active material 100 differs depending on the added element.
  • the concentration gradient of the additive element can be determined by, for example, exposing a cross section of the positive electrode active material 100 using FIB (Focused Ion Beam) or the like, and then subjecting the cross section to energy dispersive X-ray spectroscopy (EDX) or EPMA (electronic electron beam). It can be evaluated by analysis using probe microanalysis).
  • EDX surface analysis measuring while scanning the area and evaluating the area two-dimensionally. Furthermore, measuring while scanning linearly and evaluating the distribution of atomic concentration within the positive electrode active material is called EDX-ray analysis. Furthermore, data in a linear region extracted from EDX surface analysis is sometimes called EDX-ray analysis. Also, measuring a certain area without scanning is called EDX point analysis.
  • EDX plane analysis for example, element mapping
  • concentration distribution and maximum value of the added element can be analyzed by EDX-ray analysis.
  • analysis in which the sample is sliced into thin sections such as STEM-EDX, can analyze the concentration distribution in the depth direction from the surface of the positive electrode active material toward the center in a specific region without being affected by the distribution in the depth direction. More suitable.
  • the concentration of each additive element, especially the additive element X, in the surface layer portion 100a is higher than that in the interior portion 100b.
  • the surface of the positive electrode active material in STEM-EDX-ray analysis, etc. means that the characteristic X-rays derived from cobalt are 50% of the sum of the average detected amount MAVE inside and the average background value MBG .
  • a point, or a point where the characteristic X-ray originating from oxygen is 50% of the sum of the average value OAVE of the internal detection amount and the average value OBG of the background.
  • the above cobalt and oxygen differ in the 50% point of the sum of the interior and background, this is considered to be due to the influence of oxygen-containing metal oxides, carbonates, etc. that adhere to the surface.
  • a point that is 50% of the sum of the detected amount average value M AVE and the background average value M BG can be adopted.
  • the average value MBG of the cobalt background can be obtained by averaging the outer range of 2 nm or more, preferably 3 nm or more, avoiding the vicinity where the detected amount of cobalt starts to increase, for example.
  • the average value MAVE of the internal detected amounts is 2 nm or more in a region where the cobalt and oxygen counts are saturated and stable, for example, at a depth of 30 nm or more, preferably 50 nm or more from the region where the detected amount of cobalt starts to increase. , preferably on average over a range of 3 nm or more.
  • the average background value OBG of oxygen and the average value OAVE of the internal detected amount of oxygen can also be determined in the same manner.
  • the surface of the positive electrode active material 100 in a cross-sectional STEM (scanning transmission electron microscope) image, etc. is the boundary between a region where an image derived from the crystal structure of the positive electrode active material is observed and a region where it is not observed.
  • the outermost region is where an atomic column originating from the nucleus of a metal element with a higher atomic number than lithium among the metal elements constituting lithium is confirmed.
  • Surfaces in STEM images and the like may be determined in conjunction with analysis with higher spatial resolution.
  • a peak in STEM-EDX-ray analysis refers to the maximum value in a graph with the vertical axis representing the intensity of the characteristic X-ray of each element and the horizontal axis representing the analysis position, and is the maximum value of the detected intensity or the characteristic X-ray of each element. It can also be said to be the maximum value.
  • noise in STEM-EDX-ray analysis may include a measured value of half-width that is less than the spatial resolution (R), for example, less than R/2.
  • the magnesium concentration in the surface layer portion 100a is higher than the magnesium concentration in the interior portion 100b.
  • the peak of the magnesium concentration in the surface layer 100a preferably exists within a depth of 3 nm from the surface of the positive electrode active material 100 toward the center, and more preferably exists within a depth of 1 nm.
  • the magnesium concentration attenuates to 60% or less of the peak at a depth of 1 nm from the peak top. Further, it is preferable that the attenuation decreases to 30% or less of the peak at a depth of 2 nm from the peak top.
  • the peak of concentration herein refers to the maximum value of concentration. Note that due to the influence of spatial resolution in EDX-ray analysis, the position where the magnesium concentration peak exists may take a negative value as the depth from the surface toward the inside.
  • the distribution of fluorine preferably overlaps with the distribution of magnesium.
  • the difference in the depth direction between the peak of fluorine concentration and the peak of magnesium concentration is preferably within 10 nm, more preferably within 3 nm, and even more preferably within 1 nm.
  • the peak of fluorine concentration in the surface layer 100a preferably exists within a depth of 3 nm from the surface of the positive electrode active material 100 toward the center, and more preferably exists within a depth of 1 nm. Preferably, it is more preferable to exist at a depth of 0.5 nm. Alternatively, it is preferably within ⁇ 1 nm from the surface. Further, it is more preferable that the peak of the fluorine concentration be present slightly closer to the surface than the peak of the magnesium concentration, since this increases resistance to hydrofluoric acid. For example, the peak of fluorine concentration is more preferably 0.5 nm or more closer to the surface than the peak of magnesium concentration, and even more preferably 1.5 nm or more closer to the surface.
  • the peak of nickel concentration in the surface layer 100a preferably exists within a depth of 3 nm from the surface of the positive electrode active material 100 toward the center, and preferably within a depth of 1 nm from the surface of the positive electrode active material 100 toward the center. It is more preferable that it exists, and even more preferably that it exists within a depth of 0.5 nm. Alternatively, it is preferably within ⁇ 1 nm from the surface. Further, in the positive electrode active material 100 containing magnesium and nickel, the distribution of nickel preferably overlaps with the distribution of magnesium. For example, the difference in the depth direction between the peak of nickel concentration and the peak of magnesium concentration is preferably within 10 nm, more preferably within 3 nm, and even more preferably within 1 nm.
  • the peak of the concentration of magnesium, nickel, or fluorine is closer to the surface than the peak of the aluminum concentration in the surface layer portion 100a when subjected to EDX-ray analysis.
  • the peak of aluminum concentration preferably exists at a depth of 0.5 nm or more and 50 nm or less from the surface of the positive electrode active material 100 toward the center, and more preferably exists at a depth of 3 nm or more and 30 nm or less.
  • the ratio of the number of atoms of magnesium Mg and cobalt Co (Mg/Co) at the peak of magnesium concentration is preferably 0.05 or more and 0.6 or less. , more preferably 0.1 or more and 0.4 or less.
  • the ratio of the number of atoms of aluminum Al and cobalt Co (Al/Co) at the peak of the aluminum concentration is preferably 0.01 or more and 0.6 or less, more preferably 0.05 or more and 0.45 or less.
  • the ratio of the number of atoms of nickel Ni and cobalt Co (Ni/Co) at the peak of nickel concentration is preferably 0 or more and 0.2 or less, more preferably 0.01 or more and 0.1 or less, and 0.05 or more and 0.1 or less. is more preferable.
  • the ratio of the number of atoms of fluorine F and cobalt Co (F/Co) at the peak of the fluorine concentration is preferably 0 or more and 1.6 or less, more preferably 0.1 or more and 1.4 or less.
  • grain boundaries are, for example, areas where particles of the positive electrode active material 100 are stuck together, areas where the crystal orientation changes inside the positive electrode active material 100, and areas where repeating bright lines and dark lines in a STEM image are discontinuous. This refers to areas with a large number of crystal defects, areas with a disordered crystal structure, etc.
  • crystal defects refer to defects that can be observed in cross-sectional TEM (transmission electron microscopy), cross-sectional STEM images, etc., that is, structures where other atoms enter between lattices, cavities, etc.
  • Grain boundaries can be said to be one of the planar defects.
  • the vicinity of a grain boundary refers to a region within 10 nm from a grain boundary.
  • the ratio of the number of atoms of additive element A to cobalt Co (A/Co) near the grain boundary is preferably 0.020 or more and 0.50 or less. More preferably, it is 0.025 or more and 0.30 or less. More preferably, it is 0.030 or more and 0.20 or less. Or preferably 0.020 or more and 0.30 or less. Or preferably 0.020 or more and 0.20 or less. Or preferably 0.025 or more and 0.50 or less. Or preferably 0.025 or more and 0.20 or less. Or preferably 0.030 or more and 0.50 or less. Or preferably 0.030 or more and 0.30 or less.
  • the ratio of the number of magnesium and cobalt atoms near the grain boundary is 0.020 or more and 0.50 or less is preferred. More preferably, it is 0.025 or more and 0.30 or less. More preferably, it is 0.030 or more and 0.20 or less. Or preferably 0.020 or more and 0.30 or less. Or preferably 0.020 or more and 0.20 or less. Or preferably 0.025 or more and 0.50 or less. Or preferably 0.025 or more and 0.20 or less. Or preferably 0.030 or more and 0.50 or less. Or preferably 0.030 or more and 0.30 or less.
  • the additive element will not adhere to a narrow area on the surface of the positive electrode active material 100, but will preferably be applied to the surface layer 100a of the positive electrode active material 100. This can be said to indicate that the concentration is widely distributed.
  • the positive electrode active material 100 of one embodiment of the present invention at least a portion of the surface layer portion 100a preferably has a rock salt crystal structure. Therefore, when the positive electrode active material 100 and the positive electrode containing the same are analyzed by Raman spectroscopy, it is preferable that not only the layered rock salt crystal structure but also the cubic crystal structure including the rock salt type is observed.
  • the STEM image and the ultrafine electron beam diffraction pattern described below the STEM image and the ultrafine electron beam diffraction pattern will be different if there is no cobalt substituted at the lithium position with a certain frequency in the depth direction at the time of observation, and cobalt present at the 4-coordination position of oxygen.
  • Raman spectroscopy is an analysis that captures the vibrational mode of bonds such as Co-O, even if the amount of the corresponding Co-O bond is small, it may be possible to observe the wavenumber peak of the corresponding vibrational mode. be. Furthermore, since Raman spectroscopy can measure a surface area of several ⁇ m 2 and a depth of about 1 ⁇ m, it is possible to sensitively capture states that exist only on the particle surface.
  • the integrated intensity of each peak is 470 cm -1 to 490 cm -1 as I1, 580 cm -1 to 600 cm -1 as I2, and 665 cm -1 to 685 cm -1 as I3, the value of I3/I2 is 1% or more. It is preferably 10% or less, and more preferably 3% or more and 9% or less.
  • the surface layer 100a of the positive electrode active material 100 has a rock salt type crystal structure in a preferable range.
  • the characteristics of the rock salt type crystal structure as well as the layered rock salt crystal structure be observed in the ultrafine electron diffraction pattern as well as in Raman spectroscopy.
  • the characteristics of the rock salt crystal structure should not be too strong at the surface layer 100a, especially at the outermost surface (for example, at a depth of 1 nm from the surface). is preferred.
  • the difference in the lattice constants calculated from them is Smaller is preferable.
  • the difference in lattice constant calculated from a measurement point at a depth of 1 nm or less from the surface and a measurement point at a depth of 3 nm or more and 10 nm or less is preferably 0.1 ( ⁇ 10 -1 nm) or less about the a-axis.
  • the c-axis is preferably 1.0 ( ⁇ 10 ⁇ 1 nm) or less. Further, it is more preferable that the a-axis is 0.03 ( ⁇ 10 ⁇ 1 nm) or less, and the c-axis is more preferably 0.6 ( ⁇ 10 ⁇ 1 nm) or less. Further, it is more preferable that the a-axis is 0.04 ( ⁇ 10 ⁇ 1 nm) or less, and even more preferable that the c-axis is 0.3 ( ⁇ 10 ⁇ 1 nm) or less.
  • an electrolytic solution including a solvent and an electrolyte dissolved in the solvent can be used.
  • aprotic organic solvents are preferred, such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, chloroethylene carbonate, vinylene carbonate, ⁇ -butyrolactone, ⁇ -valerolactone, and dimethyl carbonate.
  • DMC diethyl carbonate
  • DEC diethyl carbonate
  • EMC ethyl methyl carbonate
  • methyl formate methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, 1,3-dioxane, 1,4 -
  • DME dimethoxyethane
  • DME dimethyl sulfoxide
  • diethyl ether methyl diglyme
  • acetonitrile benzonitrile
  • tetrahydrofuran sulfolane
  • sultone etc., or any combination and ratio of two or more of these. It can be used in
  • Ionic liquids are composed of cations and anions, and include organic cations and anions.
  • Examples of the organic cation used in the electrolytic solution include aliphatic onium cations such as quaternary ammonium cations, tertiary sulfonium cations, and quaternary phosphonium cations, and aromatic cations such as imidazolium cations and pyridinium cations.
  • examples of anions used in the electrolytic solution include monovalent amide anions, monovalent methide anions, fluorosulfonic acid anions, perfluoroalkylsulfonic acid anions, tetrafluoroborate anions, perfluoroalkylborate anions, and hexafluorophosphate anions. , or perfluoroalkyl phosphate anion.
  • electrolytes to be dissolved in the above 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 Cl12 , LiCF3SO3 , LiC4F9SO3 , LiC ( CF3SO2 ) 3 , LiC( C2F5SO2 ) 3 , LiN( CF3SO2 ) 2 , LiN ( C4F9 One type of lithium salt such as SO 2 )(CF 3 SO 2 ), LiN(C 2 F 5 SO 2 ) 2 , lithium bis(oxalate)borate (Li(C 2 O 4 ) 2 , LiBOB), or any of these Two or more of these can be used in any combination and ratio.
  • the electrolyte includes vinylene carbonate, propane sultone (PS), tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate) borate (LiBOB), and dinitrile compounds such as succinonitrile and adiponitrile.
  • Additives may also be added.
  • the concentration of the additive may be, for example, 0.1 wt% or more and 5 wt% or less based on the solvent in which the electrolyte is dissolved.
  • a polymer gel electrolyte in which a polymer is swollen with an electrolytic solution may be used.
  • silicone gel acrylic gel, acrylonitrile gel, polyethylene oxide gel, polypropylene oxide gel, fluorine polymer gel, etc.
  • polymers having a polyalkylene oxide structure such as polyethylene oxide (PEO), PVDF, polyacrylonitrile, and copolymers containing them can be used.
  • PVDF-HFP which is a copolymer of PVDF and hexafluoropropylene (HFP)
  • the polymer formed may also have a porous shape.
  • the electrolyte used as an embodiment of the present invention can be used in a low temperature environment (for example, 0°C, -10°C, -20°C, preferably -30°C, more preferably -40°C, still more preferably -50°C, most preferably A material with excellent lithium ion conductivity can be used even when charging and/or discharging (charging and discharging) at -60°C).
  • a low temperature environment for example, 0°C, -10°C, -20°C, preferably -30°C, more preferably -40°C, still more preferably -50°C, most preferably
  • a material with excellent lithium ion conductivity can be used even when charging and/or discharging (charging and discharging) at -60°C).
  • electrolyte An example of the electrolyte will be described below.
  • the electrolyte described in this embodiment mode as an example is one in which a lithium salt is dissolved in an organic solvent, and can also be called an electrolyte solution; however, the electrolyte is a liquid electrolyte (electrolyte solution) that is liquid at room temperature. It is also possible to use a solid electrolyte without being limited to. Alternatively, it is also possible to use an electrolyte (semi-solid electrolyte) containing both a liquid electrolyte that is liquid at room temperature and a solid electrolyte that is solid at room temperature.
  • the organic solvent described in this embodiment includes ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), and the ethylene carbonate, the ethyl methyl carbonate, and the dimethyl
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DMC dimethyl carbonate
  • volume ratio may be the volume ratio before mixing the organic solvent, and the outside air when mixing the organic solvent may be at room temperature (typically, 25° C.).
  • proportion of compounds contained in the organic solvent can be analyzed by, for example, nuclear magnetic resonance (NMR), gas chromatography (GC/MS), high performance liquid chromatography (HPLC), or the like.
  • EC is a cyclic carbonate and has a high relative dielectric constant, so it has the effect of promoting dissociation of lithium salt.
  • EC has a high viscosity and a high freezing point (melting point) of 38° C., so when EC alone is used as an organic solvent, it is difficult to use it in a low-temperature environment. Therefore, the organic solvent specifically explained as one aspect of the present invention does not include EC alone, but also includes EMC and DMC.
  • EMC is a chain carbonate, which has the effect of lowering the viscosity of the electrolytic solution and has a freezing point of -54°C.
  • DMC is also a chain carbonate, which has the effect of lowering the viscosity of the electrolytic solution and has a freezing point of -43°C.
  • EC, EMC, and DMC having such physical properties have a volume ratio of x:y:100-x-y (where 5 ⁇ x ⁇ 35 and the total content of these three organic solvents is 100 vol%).
  • An electrolyte prepared using an organic solvent mixed such that 0 ⁇ y ⁇ 65) has a freezing point of -40°C or lower.
  • the general electrolyte used in lithium ion batteries solidifies at about -20°C, it is difficult to produce a battery that can be charged and discharged at -40°C. Since the electrolyte described as an example in this embodiment has a freezing point of -40°C or lower, a lithium ion battery that can be charged and discharged even in an extremely low temperature environment of -40°C can be realized.
  • a lithium salt can be used as the electrolyte to be dissolved in the above solvent.
  • the electrolyte dissolved in the above solvent is preferably 0.5 mol/L or more and 1.5 mol/L or less, and preferably 0.7 mol/L or more and 1.3 mol/L or less, based on the volume of the solvent. It is preferably 0.8 mol/L or more and 1.2 mol/L or less.
  • LiPF 6 is preferably 0.5 mol/L or more and 1.5 mol/L or less, and 0.7 mol/L or more and 1.3 mol/L or less relative to the volume of the above solvent. It is preferably 0.8 mol/L or more and 1.2 mol/L or less.
  • the electrolytic solution has a low content of particulate dust or elements other than the constituent elements of the electrolytic solution (hereinafter also simply referred to as "impurities") and is highly purified. Specifically, it is preferable that the weight ratio of impurities to the electrolytic solution is 1% or less, preferably 0.1% or less, and more preferably 0.01% or less.
  • vinylene carbonate (VC), propane sultone (PS) is added to the electrolyte.
  • tert-butylbenzene (TBB), fluoroethylene carbonate (FEC), lithium bis(oxalate)borate (LiBOB), or dinitrile compounds of succinonitrile or adiponitrile may be added.
  • concentration of each additive may be, for example, 0.1 wt% or more and 5 wt% or less relative to the solvent.
  • the organic solvent of the electrolyte which is one aspect of the present invention, preferably contains two or more selected from fluorinated cyclic carbonates and fluorinated chain carbonates.
  • the organic solvent described in this embodiment mode may include fluoroethylene carbonate (FEC) and methyl 3,3,3-trifluoropropionate (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. . Furthermore, FEC is considered to have a deep HOMO, and when the HOMO is deep, it is difficult to be oxidized and the oxidation resistance is improved.
  • EC ethylene carbonate
  • 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.
  • 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 described as an example in this embodiment mode can have a freezing point of -40°C or lower, preferably -50°C or lower, and can realize a lithium ion battery that can be charged and discharged even in a sub-zero environment. . As a result, it is possible to realize a lithium ion battery that can be charged and discharged over a wide temperature range, including at least 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.
  • Electrolyte Example 2 the materials described in Electrolyte Example 1 can be used as the lithium salt. Moreover, the materials described in Example 1 of the electrolyte can also be used as additives.
  • electrolytes that can be used in the lithium ion battery of one embodiment of the present invention have been described; however, the electrolytes that can be used in the lithium ion battery of one embodiment of the present invention are limited to these examples. It is not something that will be done. It is also possible to use other materials as long as they have excellent lithium ion conductivity even during charging and discharging in a low-temperature environment.
  • a lithium ion battery according to one embodiment of the present invention includes at least the above-described positive electrode active material and electrolyte, and thus has excellent discharge characteristics even in a low temperature environment and/or has excellent charging characteristics even in a low temperature environment.
  • a lithium ion battery having these characteristics can be realized. More specifically, when a test battery is made that includes at least the above-mentioned positive electrode active material and electrolyte and uses lithium metal as a negative electrode, the discharge capacity when charging and discharging the test battery at 20 ° C. Thus, it is possible to realize a lithium ion battery whose discharge capacity is 70% or more when charging and discharging at -40°C.
  • 1C an arbitrary temperature
  • the lithium ion battery is It is expressed as being operable at T°C.
  • Example 1 of method for producing positive electrode active material> An example of a method for manufacturing a positive electrode active material that can be used as one embodiment of the present invention (Example 1 of a method for manufacturing a positive electrode active material) will be described with reference to FIGS. 8A to 8D. Note that in ⁇ Example 1 of method for producing positive electrode active material>, the additive elements described as additive element X, additive element Y, and additive element Z in Embodiment 1 are collectively referred to as additive element A.
  • lithium cobalt oxide as a starting material is prepared.
  • Lithium cobalt oxide serving as a starting material may have a particle size (strictly speaking, median diameter (D50)) of 10 ⁇ m or less (preferably 8 ⁇ m or less).
  • D50 median diameter
  • As the lithium cobalt oxide having a median diameter (D50) of 10 ⁇ m or less a known or publicly used (in short, commercially available) lithium cobalt oxide may be used, or a cobalt oxide prepared through steps S11 to S14 shown in FIG. 8B. Lithium may also be used.
  • a representative example of commercially available lithium cobalt oxide having a median diameter (D50) of 10 ⁇ m or less includes lithium cobalt oxide (trade name “Cellseed C-5H”) manufactured by Nihon Kagaku Kogyo Co., Ltd. Lithium cobalt oxide manufactured by Nihon Kagaku Kogyo Co., Ltd. (trade name "Cellseed C-5H”) has a median diameter (D50) of about 7 ⁇ m. Further, a manufacturing method for obtaining lithium cobalt oxide having a median diameter (D50) of 10 ⁇ m or less through steps S11 to S14 will be described below.
  • Step S11 In step S11 shown in FIG. 8B, a lithium source (Li source) and a cobalt source (Co source) are prepared as starting materials for lithium and transition metal materials, respectively.
  • Li source Li source
  • Co source cobalt source
  • the lithium source it is preferable to use a compound containing lithium, such as lithium carbonate, lithium hydroxide, lithium nitrate, or lithium fluoride. It is preferable that the lithium source has high purity; for example, a material with a purity of 99.99% or more may be used.
  • the cobalt source it is preferable to use a compound containing cobalt, and for example, tricobalt tetroxide, cobalt hydroxide, etc. can be used.
  • the cobalt source preferably has a high purity, for example, the purity is 3N (99.9%) or higher, preferably 4N (99.99%) or higher, more preferably 4N5 (99.995%) or higher, and even more preferably 5N (99%) or higher. .999%) or more is preferably used.
  • high-purity materials impurities in the positive electrode active material can be controlled. As a result, the capacity of the secondary battery increases and the reliability of the secondary battery improves.
  • the cobalt source preferably has high crystallinity, eg, has single crystal grains.
  • the crystallinity of the transition metal source can be evaluated using a TEM (transmission electron microscope) image, a STEM (scanning transmission electron microscope) image, a HAADF-STEM (high-angle scattering annular dark-field scanning transmission electron microscope) image, and an ABF-STEM (annular bright-field scanning transmission electron microscope) image. Judgments can be made by images (field scanning transmission electron microscope), or by X-ray diffraction (XRD), electron beam diffraction, neutron beam diffraction, etc. Note that the above method for evaluating crystallinity can be applied not only to transition metal sources but also to evaluating other crystallinities.
  • a lithium source and a cobalt source are ground and mixed to produce a mixed material. Grinding and mixing can be done dry or wet. Wet crushing and mixing is preferable for obtaining lithium cobalt oxide having a median diameter (D50) of 10 ⁇ m or less as a starting material because it can crush the particles into smaller pieces.
  • a solvent As a solvent, ketones such as acetone, alcohols such as ethanol and isopropanol, ether, dioxane, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc.
  • dehydrated acetone with a purity of 99.5% or more is used. It is preferable to mix the lithium source and the transition metal source with dehydrated acetone having a purity of 99.5% or more and suppressing the water content to 10 ppm or less, and perform the pulverization and mixing. By using dehydrated acetone of the purity described above, possible impurities can be reduced.
  • a ball mill, a bead mill, or the like can be used for grinding and mixing.
  • a ball mill aluminum oxide balls or zirconium oxide balls may be used as the grinding media.
  • Zirconium oxide balls are preferable because they emit fewer impurities.
  • the peripheral speed is preferably set to 100 mm/s or more and 2000 mm/s or less in order to suppress contamination from the media.
  • step S13 shown in FIG. 8B the above mixed material is heated.
  • the heating temperature is preferably 800°C or more and 1100°C or less, more preferably 900°C or more and 1000°C or less, and even more preferably about 950°C or less and 1000°C or less. If the temperature is too low, the lithium source and the transition metal source may be insufficiently decomposed and melted. On the other hand, if the temperature is too high, lithium may evaporate from the lithium source and/or cobalt may be excessively reduced, which may cause defects. For example, cobalt changes from trivalent to divalent, which may induce oxygen defects.
  • the heating time may be 1 hour or more and 100 hours or less, preferably 2 hours or more and 20 hours or less, and more preferably 2 hours or more and 10 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. For example, when heating at 1000°C for 10 hours, the temperature increase rate is preferably 200°C/h.
  • Heating is preferably carried out in an atmosphere with little water such as dry air, for example an atmosphere with a dew point of -50°C or less, more preferably -80°C or less. In this embodiment, heating is performed in an atmosphere with a dew point of -93°C. Further, in order to suppress impurities that may be mixed into the material, the concentration of impurities such as CH 4 , CO, CO 2 , H 2 , etc. in the heating atmosphere is preferably set to 5 ppb (parts per billion) or less.
  • an atmosphere containing oxygen is preferable.
  • the flow rate of dry air is preferably 10 L/min.
  • the method in which oxygen is continuously introduced into the reaction chamber and the oxygen flows within the reaction chamber is called flow.
  • a method without flow may be used.
  • a method may be used in which the reaction chamber is depressurized and then filled with oxygen to prevent the oxygen from entering or exiting the reaction chamber, and this is called purge.
  • the reaction chamber may be depressurized to -970 hPa and then filled with oxygen to 50 hPa.
  • 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. Heating with a rotary kiln can be carried out while stirring in either a continuous type or a batch type.
  • the container used for heating is preferably an aluminum oxide crucible or an aluminum oxide sheath.
  • a crucible made of aluminum oxide is a material that contains almost no impurities.
  • an aluminum oxide sheath with a purity of 99.9% is used. Note that it is preferable to heat the crucible or pod after placing a lid on it, since this can prevent the material from volatilizing.
  • the material may be crushed and further sieved if necessary.
  • it may be transferred from the crucible to the mortar and then recovered. Further, it is preferable to use a mortar made of zirconium oxide or agate. 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.
  • Lithium cobalt oxide (LiCoO 2 ) shown in step S14 shown in FIG. 8B can be synthesized.
  • Lithium cobalt oxide (LiCoO 2 ) shown in step S14 is an oxide containing a plurality of metal elements in its structure, so it can be called a composite oxide.
  • composite oxide refers to an oxide containing multiple metal elements in its structure. Note that after step S13, a crushing step and a classification step may be performed to adjust the particle size distribution, and then lithium cobalt oxide (LiCoO 2 ) shown in step S14 may be obtained.
  • the composite oxide may also be produced by a coprecipitation method.
  • the composite oxide may be produced by a hydrothermal method.
  • lithium cobalt oxide can be obtained as a starting material for obtaining a positive electrode active material applicable to lithium ion batteries that has excellent discharge characteristics even in low-temperature environments.
  • lithium cobalt oxide having a median diameter of 10 ⁇ m or less can be obtained as the starting material lithium cobalt oxide.
  • step S15 shown in FIG. 8A the starting material, lithium cobalt oxide, is heated. Since the heating in step S15 is the first heating of lithium cobalt oxide, it may be referred to as initial heating in this specification and the like. Alternatively, since it is heated before step S31 described below, it may be called preheating or pretreatment.
  • lithium compounds unintentionally remaining on the surface of lithium cobalt oxide are removed. Further, it can be expected to have the effect of increasing internal crystallinity. Furthermore, impurities may be mixed in the lithium source and/or cobalt source prepared in step S11 etc., but it is possible to reduce the impurities from the starting material lithium cobalt oxide by initial heating. Note that the effect of increasing internal crystallinity is, for example, the effect of alleviating distortion, displacement, etc. resulting from the shrinkage difference of the lithium cobalt oxide produced in step S14.
  • the initial heating has the effect of smoothing the surface of lithium cobalt oxide.
  • the initial heating has the effect of alleviating cracks, crystal defects, etc. that lithium cobalt oxide has.
  • smooth refers to a surface that has few irregularities, is rounded overall, and has rounded corners. Also, the state in which there are few foreign substances attached to the surface is also called “smooth.” Foreign matter is considered to be a cause of unevenness, and it is preferable not to allow it to adhere to the surface.
  • heating time in this step is too short, a sufficient effect will not be obtained, but if it is too long, productivity will decrease.
  • An appropriate heating time range can be selected from, for example, the heating conditions explained in step S13.
  • the heating temperature in step S15 is preferably lower than the temperature in step S13 in order to maintain the crystal structure of the composite oxide.
  • the heating time in step S15 is preferably shorter than the time in step S13 in order to maintain the crystal structure of the composite oxide.
  • heating may be performed at a temperature of 700° C. or more and 1000° C. or less (more preferably 800° C. or more and 900° C. or less) for 1 hour or more and 20 hours or less (more preferably 1 hour or more and 5 hours or less).
  • a temperature difference may occur between the surface and the inside of the lithium cobalt oxide. Temperature differences can 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 differential internal stress to lithium cobalt oxide.
  • the difference in internal stress is also called strain, and the 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 homogenized by the initial heating in step S15. When the strain energy is homogenized, the strain in the lithium cobalt oxide is relaxed. As a result, the surface of lithium cobalt oxide becomes smooth. Alternatively, it can be said that the surface has been improved. That is, by going through step S15, the shrinkage difference that occurs in lithium cobalt oxide is alleviated, and the surface of the composite oxide can be made smooth.
  • the differential shrinkage may cause microscopic shifts in lithium cobalt oxide, such as crystal shifts.
  • step S15 it is preferable to perform step S15. By going through step S15, it is possible to equalize the misalignment of the composite oxide (to alleviate the misalignment of crystals, etc. that has occurred in the composite oxide, or to align the crystal grains). As a result, the surface of the composite oxide becomes smooth.
  • lithium cobalt oxide with a smooth surface When lithium cobalt oxide with a smooth surface is used as a positive electrode active material, there is less deterioration during charging and discharging as a secondary battery, and cracking of the positive electrode active material can be prevented.
  • step S10 lithium cobalt oxide synthesized in advance and having a median diameter of 10 ⁇ m or less may be used. In this case, steps S11 to S13 can be omitted. By performing step S15 on previously synthesized lithium cobalt oxide, lithium cobalt oxide with a smooth surface can be obtained.
  • step S15 is not an essential configuration in one aspect of the present invention, an aspect in which step S15 is omitted is also included in one aspect of the present invention.
  • Step S20 Next, details of step S20 of preparing the additive element A as the A source will be explained using FIGS. 8C and 8D.
  • Step S20 shown in FIG. 8C includes steps S21 to S23.
  • step S21 additive element A is prepared.
  • Specific examples of additive element A include one or more selected from magnesium, fluorine, nickel, aluminum, titanium, zirconium, vanadium, iron, manganese, chromium, niobium, arsenic, zinc, silicon, sulfur, phosphorus, and boron. can be used. Alternatively, one or more selected from bromine and beryllium can also be used.
  • FIG. 8C illustrates a case where a magnesium source (Mg source) and a fluorine source (F source) are prepared. Note that in step S21, in addition to the additive element A, a lithium source may be separately prepared.
  • the source of additive element A can be called a magnesium source.
  • the magnesium source magnesium fluoride (MgF 2 ), magnesium oxide (MgO), magnesium hydroxide (Mg(OH) 2 ), magnesium carbonate (MgCO 3 ), or the like can be used.
  • a plurality of magnesium sources may be used.
  • the source of the additive element A can be called a fluorine source.
  • fluorine sources include lithium fluoride (LiF), magnesium fluoride (MgF 2 ), aluminum fluoride (AlF 3 ), titanium fluoride (TiF 4 ), cobalt fluoride (CoF 2 , CoF 3 ), and fluoride.
  • 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.
  • 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 include lithium carbonate.
  • the fluorine source may be a gas, such as fluorine (F 2 ), fluorocarbon, sulfur fluoride, or fluorinated oxygen (OF 2 , O 2 F 2 , O 3 F 2 , O 4 F 2 , O 5 F 2 , O 6 F 2 , O 2 F), etc. may be used and mixed in the atmosphere in the heating step described below.
  • F 2 fluorine
  • fluorocarbon such as fluorine (F 2 ), fluorocarbon, sulfur fluoride, or fluorinated oxygen (OF 2 , O 2 F 2 , O 3 F 2 , O 4 F 2 , O 5 F 2 , O 6 F 2 , O 2 F), etc.
  • fluorinated oxygen OF 2 , O 2 F 2 , O 3 F 2 , O 4 F 2 , O 5 F 2 , O 6 F 2 , O 2 F
  • a plurality of fluorine sources may be used.
  • lithium fluoride (LiF) is prepared as a fluorine source
  • magnesium fluoride (MgF 2 ) is prepared as a fluorine source and a magnesium source.
  • Lithium fluoride and magnesium fluoride are most effective in lowering the melting point when mixed at a molar ratio of about 65:35 (LiF:MgF 2 ). Furthermore, if the proportion of lithium fluoride is increased too much, there is a concern that lithium will become excessive and the cycle characteristics will deteriorate.
  • a certain value or its vicinity is a value greater than 0.9 times and less than 1.1 times that value, unless otherwise specified.
  • step S22 shown in FIG. 8C the magnesium source and the fluorine source are ground and mixed. This step can be carried out by selecting from the pulverization and mixing conditions described in step S12.
  • step S23 shown in FIG. 8C the materials crushed and mixed above can be recovered to obtain an additive element A source (A source).
  • a source an additive element A source
  • the additive element A source shown in step S23 has a plurality of starting materials and can also be called a mixture.
  • the particle size of the above mixture preferably has a median diameter (D50) of 100 nm or more and 10 ⁇ m or less, more preferably 300 nm or more and 5 ⁇ m or less. Further, even when one type of material is used as the source of additive element A, the median diameter (D50) is preferably 100 nm or more and 10 ⁇ m or less, more preferably 300 nm or more and 5 ⁇ m or less.
  • step S22 When the mixture pulverized in step S22 (including the case where only one type of additive element is added) is mixed with lithium cobalt oxide in a later step, it is easy to uniformly adhere the mixture to the surface of lithium cobalt oxide. It is preferable that the mixture adheres uniformly to the surface of the lithium cobalt oxide because it is easy to uniformly distribute or diffuse the additive element in the surface layer portion 100a of the composite oxide after heating.
  • Step S21> A process different from that in FIG. 8C will be explained using FIG. 8D.
  • Step S20 shown in FIG. 8D includes steps S21 to S23.
  • step S21 shown in FIG. 8D four types of additive element A sources to be added to lithium cobalt oxide are prepared. That is, FIG. 8D is different from FIG. 8C in the type of additive element A source. Moreover, in addition to the additive element A source, a lithium source may be separately prepared.
  • a magnesium source Mg source
  • a fluorine source F source
  • a nickel source Ni source
  • an aluminum source Al source
  • the magnesium source and the fluorine source can be selected from the compounds described in FIG. 8C.
  • nickel source nickel oxide, nickel hydroxide, etc.
  • aluminum source aluminum oxide, aluminum hydroxide, etc. can be used.
  • step S22 and step S23 shown in FIG. 8D are similar to step S22 and step S23 described in FIG. 8C.
  • step S31 shown in FIG. 8A the lithium cobalt oxide that has undergone step S15 (initial heating) and the additive element A source (A source) are mixed.
  • the number of nickel atoms in the nickel source is 0.05% or more and 4% or less of the number of cobalt atoms in the lithium cobalt oxide that has passed through step S15. It is preferable to perform the mixing in step S31.
  • the number of aluminum atoms in the aluminum source is 0.05% or more and 4% or less with respect to the number of cobalt atoms in the lithium cobalt oxide that has undergone step S15. It is preferable to perform the mixing in step S31.
  • the mixing in step S31 is preferably performed under milder conditions than the grinding and mixing in step S12.
  • the number of revolutions is lower or the mixing time is shorter than that of the mixing in step S12.
  • the dry method has milder conditions than the wet method.
  • a ball mill, a bead mill, etc. can be used.
  • zirconium oxide balls it is preferable to use, for example, zirconium oxide balls as the media.
  • dry mixing is performed at 150 rpm for 1 hour using a ball mill using zirconium oxide balls with a diameter of 1 mm. Further, the mixing is performed in a dry room with a dew point of -100°C or more and -10°C or less.
  • Step S32 of FIG. 8A the materials mixed above are collected to obtain a mixture 903. During recovery, sieving may be performed after crushing if necessary.
  • step S33 shown in FIG. 8A the mixture 903 is heated.
  • the heating in step S33 is preferably performed at a temperature of 800°C or more and 1100°C or less, more preferably 800°C or more and 950°C or less, and even more preferably 850°C or more and 900°C or less.
  • the heating time in step S33 may be 1 hour or more and 100 hours or less, but preferably 1 hour or more and 10 hours or less.
  • 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 lithium cobalt oxide and the additive element A source proceeds.
  • the temperature at which the reaction proceeds may be any temperature at which interdiffusion of the elements of the lithium cobalt oxide and the additive element A source occurs, and may be lower than the melting temperature of these materials.
  • the heating temperature in step S33 may be 500° C. or higher.
  • the reaction progresses more easily.
  • 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 lithium cobalt oxide (1130° C.). At temperatures near the decomposition temperature, there is concern that lithium cobalt oxide will decompose, albeit in a small amount. Therefore, the temperature is preferably 1000°C or lower, more preferably 950°C or lower, and even more preferably 900°C or lower.
  • some materials for example, LiF, which is a fluorine source, may function as a flux.
  • the heating temperature can be lowered to below the decomposition temperature of lithium cobalt oxide, for example from 742°C to 950°C, and by distributing additive elements such as magnesium in the surface layer, a positive electrode active material with good characteristics can be produced. It can be made.
  • LiF has a lower specific gravity in a gaseous state than oxygen
  • LiF may volatilize or sublimate due to heating, and if volatilized or sublimed, LiF in the mixture 903 will decrease.
  • the function as a flux becomes weak. Therefore, it is preferable to heat while suppressing the volatilization of LiF.
  • LiF is not used as a fluorine source
  • the heating in this step be performed so that the particles of the mixture 903 do not stick to each other. If the particles of the mixture 903 stick to each other during heating, the contact area with oxygen in the atmosphere decreases and the diffusion path of the added elements (e.g. fluorine) is inhibited, thereby preventing the addition of the added elements (e.g. magnesium and fluorine) to the surface layer. Fluorine) distribution may deteriorate.
  • the added elements e.g. fluorine
  • the additive element for example, fluorine
  • a positive electrode active material that is smooth and has few irregularities can be obtained. Therefore, in order for the surface to remain smooth or to become even smoother after the heating in step S15 in this process, it is better that the particles of the mixture 903 do not stick to each other.
  • the flow rate of the atmosphere containing oxygen in the kiln it is preferable to control the flow rate of the atmosphere containing oxygen in the kiln. For example, it is preferable to reduce the flow rate of the atmosphere containing oxygen, to purge the atmosphere first, and to not allow the atmosphere to flow after introducing the oxygen atmosphere into the kiln. Flowing oxygen may cause the fluorine source to evaporate, which is not preferable for maintaining surface smoothness.
  • the mixture 903 can be heated in an atmosphere containing LiF by placing a lid on the container containing the mixture 903, for example.
  • step S34 shown in FIG. 8A the heated material is collected and crushed as necessary to obtain the positive electrode active material 100. At this time, it is preferable to further sieve the recovered positive electrode active material 100.
  • a positive electrode active material 100 composite oxide having a median diameter of 12 ⁇ m or less (preferably 10.5 ⁇ m or less, more preferably 8 ⁇ m or less) can be produced. Note that the positive electrode active material 100 contains the additive element A.
  • Example 2 of method for producing positive electrode active material> Another example of a method for manufacturing a positive electrode active material that can be used as one embodiment of the present invention (Example 2 of a method for manufacturing a positive electrode active material) will be described with reference to FIGS. 9 and 10.
  • Example 2 of the method for producing a positive electrode active material differs from Example 1 of the method for producing a positive electrode active material described above in the number of times of adding additional elements and the mixing method, but the other descriptions are the same as Example 1 of the method for producing a positive electrode active material. can be applied.
  • additive element X described in Embodiment 1 is shown as additive element A1.
  • the additive element Y and the additive element Z described in Embodiment 1 are collectively shown as an additive element A2.
  • step S10 and step S15 are performed in the same manner as in FIG. 8A to prepare lithium cobalt oxide that has undergone initial heating. Note that since step S15 is not an essential configuration in one aspect of the present invention, an aspect in which step S15 is omitted is also included in one aspect of the present invention.
  • step S20a a first additive element A1 source (A1 source) is prepared. Details of step S20a will be explained with reference to FIG. 10A.
  • a first additive element A1 source (A1 source) is prepared.
  • the A1 source can be selected from among the additive elements A described in step S21 shown in FIG. 8C.
  • the additive element A1 one or more selected from magnesium, fluorine, and calcium can be used.
  • FIG. 10A illustrates a case where a magnesium source (Mg source) and a fluorine source (F source) are used as the additive element A1.
  • Steps S21 to S23 shown in FIG. 10A can be manufactured under the same conditions as steps S21 to S23 shown in FIG. 8C.
  • an additive element A1 source (A1 source) can be obtained in step S23.
  • steps S31 to S33 shown in FIG. 9 can be manufactured under the same conditions as steps S31 to S33 shown in FIG. 8A.
  • Step S34a the material heated in step S33 is recovered to obtain lithium cobalt oxide having the additive element A1.
  • the lithium cobalt oxide (first composite oxide) that has passed through step S15 it is also referred to as a second composite oxide.
  • Step S40 In step S40 shown in FIG. 9, a second additive element A2 source (A2 source) is prepared. Step S40 will be described with reference also to FIGS. 10B and 10C.
  • a second additive element A2 source (A2 source) is prepared.
  • the A2 source can be selected from among the additive elements A described in step S20 shown in FIG. 8C.
  • the additive element A2 one or more selected from nickel, titanium, boron, zirconium, and aluminum can be suitably used.
  • FIG. 10B illustrates a case where a nickel source (Ni source) and an aluminum source (Al source) are used as the additive element A2.
  • Steps S41 to S43 shown in FIG. 10B can be performed under the same conditions as steps S21 to S23 shown in FIG. 8C.
  • an additive element A2 source (A2 source) can be obtained in step S43.
  • Steps S41 to S43 shown in FIG. 10C are a modification of FIG. 10B.
  • a nickel source (Ni source) and an aluminum source (Al source) are prepared, and in step S42a, they are each independently pulverized.
  • a plurality of second additive element A2 sources (A2 sources) are prepared.
  • step S40 in FIG. 10C differs from step S40 in FIG. 10B in that the additive element source is independently pulverized in step S42a.
  • steps S51 to S53 shown in FIG. 9 can be performed under the same conditions as steps S31 to S34 shown in FIG. 8A.
  • the conditions for step S53 regarding the heating process are preferably a lower temperature and/or a shorter time than step S33 shown in FIG.
  • the heating is preferably performed at a temperature of 800°C or higher and 950°C or lower, more preferably 820°C or higher and 870°C or lower, and even more preferably 850°C ⁇ 10°C.
  • the heating time is preferably 0.5 hours or more and 8 hours or less, and more preferably 1 hour or more and 5 hours or less.
  • the number of nickel atoms in the nickel source is 0.05% or more and 4% or less with respect to the number of cobalt atoms in the lithium cobalt oxide that has passed through step S15. It is preferable to perform the mixing in step S51.
  • the number of aluminum atoms in the aluminum source is 0.05% or more and 4% or less with respect to the number of cobalt atoms in the lithium cobalt oxide that has passed through step S15. It is preferable to perform the mixing in step S51.
  • step S54 shown in FIG. 9 the heated material is collected and crushed if necessary to obtain the positive electrode active material 100.
  • a positive electrode active material 100 composite oxide having a median diameter of 12 ⁇ m or less (preferably 10.5 ⁇ m or less, more preferably 8 ⁇ m or less) can be produced.
  • a positive electrode active material 100 that can be applied to lithium ion batteries that has excellent discharge characteristics even in a low-temperature environment can be produced.
  • the positive electrode active material 100 includes an additive element A1 and an additive element A2.
  • Example 2 of the manufacturing method described above the additive elements to lithium cobalt oxide are introduced separately into a first additive element A1 and a second additive element A2.
  • the distribution of each additive element in the depth direction can be changed.
  • the first additive element can be distributed to have a higher concentration in the surface layer than in the interior
  • the second additive element can be distributed to have a higher concentration in the interior than in the surface layer.
  • the positive electrode active material 100 produced through the steps shown in FIGS. 8A and 8D has the advantage that it can be produced at low cost because multiple types of additive element A sources are added at once.
  • the positive electrode active material 100 manufactured through the steps shown in FIGS. 9 and 10 has a relatively high manufacturing cost because multiple types of additive element A sources are added in multiple steps, but each additive element This is preferable because the distribution of A in the depth direction can be controlled more accurately.
  • This embodiment can be used in combination with other embodiments.
  • 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 material and a binder.
  • the positive electrode active material the material described in Embodiment 1 can be used.
  • FIG. 11A shows an example of a schematic cross-sectional view of the positive electrode.
  • the positive electrode current collector 21 for example, metal foil can be used.
  • 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 positive electrode current collector 21.
  • the slurry is a material liquid used to form an active material layer on the positive electrode current collector 21, and includes 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. There is also.
  • the positive electrode active material 100 has a function of taking in lithium ions and a function of releasing lithium ions during charging and discharging.
  • a material that exhibits little deterioration due to charging and discharging even at a high charging voltage can be used. Note that, in this specification and the like, unless otherwise specified, charging voltage is expressed based on the potential of lithium metal.
  • the cathode active material 100 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 any material can be used as described in Embodiment 1 or 2. can be used.
  • the positive electrode active material 100 can be made of two or more types of materials with different particle sizes as long as they are materials that exhibit little deterioration due to charging and discharging even at high charging voltages.
  • FIGS. 11A to 11D Modifications of the positive electrode active material layer shown in FIG. 1B are shown in FIGS. 11A to 11D.
  • FIG. 11A illustrates carbon black 43, which is an example of a conductive material, and electrolyte 51 contained in the voids located between particles of the positive electrode active material 100, and shows not only the positive electrode active material 100 but also the second An example further including a positive electrode active material 110 is shown.
  • a binder As a positive electrode of a secondary battery, a binder (resin) may be mixed in order to fix the positive electrode current collector 21 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 secondary battery decreases. Therefore, it is preferable to mix the amount of binder to a minimum.
  • FIG. 11A shows an example in which the positive electrode active material 100 is spherical
  • the shape is not particularly limited.
  • the cross-sectional shape of the positive electrode active material 100 may be an ellipse, a rectangle, a trapezoid, a triangle, a polygon with rounded corners, or an asymmetric shape.
  • FIG. 11B shows an example in which the positive electrode active material 100 has a polygonal shape with rounded corners.
  • graphene 42 is used as a carbon material used as a conductive material.
  • a positive electrode active material layer including a positive electrode active material 100, graphene 42, and carbon black 43 is formed on the positive electrode current collector 21.
  • the weight of the carbon black to be mixed is 1.5 times or more and 20 times or less, preferably 2 times or more and 9.5 times or less of the weight of graphene. It is preferable to do so.
  • the dispersion stability of the carbon black 43 is excellent during slurry preparation, and agglomerated portions are less likely to occur.
  • the mixture of graphene 42 and carbon black 43 is within the above range, it is possible to have a higher electrode density than a positive electrode using only carbon black 43 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 that uses only graphene as the conductive material, by mixing the first carbon material (graphene) and the second carbon material (acetylene black) within the above range, rapid charging is possible. can be accommodated. Therefore, it is particularly effective when used as an on-vehicle secondary battery.
  • FIG. 11C illustrates an example of a positive electrode using carbon fiber 44 instead of graphene.
  • FIG. 11C shows an example different from FIG. 11B.
  • Use of carbon fibers 44 can prevent agglomeration of carbon black 43 and improve dispersibility.
  • the region not filled with the positive electrode active material 100, the carbon fibers 44, and the carbon black 43 indicates a void or a binder.
  • FIG. 11D is illustrated as an example of another positive electrode.
  • FIG. 11C shows an example in which carbon fiber 44 is used in addition to graphene 42. When both graphene 42 and carbon fiber 44 are used, agglomeration of carbon black such as carbon black 43 can be prevented and dispersibility can be further improved.
  • regions not filled with the positive electrode active material 100, carbon fibers 44, graphene 42, and carbon black 43 indicate voids or binder.
  • a secondary battery can be produced by filling the battery.
  • ⁇ Binder> As 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. Furthermore, fluororubber can be used as the binder.
  • 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.
  • polysaccharide cellulose derivatives such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, regenerated cellulose, or starch can be used. Further, it is more preferable to use these water-soluble polymers in combination with the above-mentioned rubber material.
  • polystyrene polymethyl acrylate, polymethyl methacrylate (polymethyl methacrylate, PMMA), sodium polyacrylate, polyvinyl alcohol (PVA), polyethylene oxide (PEO), polypropylene oxide, polyimide, polyvinyl chloride
  • PVA polyvinyl alcohol
  • PEO polyethylene oxide
  • PEO polypropylene oxide
  • polyimide polyvinyl chloride
  • materials such as polytetrafluoroethylene, polyethylene, polypropylene, polyisobutylene, polyethylene terephthalate, nylon, polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), ethylene propylene diene polymer, polyvinyl acetate, nitrocellulose, 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 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 above-mentioned polysaccharides such as carboxymethyl cellulose (CMC), methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, cellulose derivatives such as regenerated cellulose, or starch are used. be able to.
  • solubility of cellulose derivatives such as carboxymethylcellulose is increased by converting them into salts such as sodium salts or ammonium salts of carboxymethylcellulose, making it easier to exhibit the effect as a viscosity modifier.
  • the increased solubility can also improve the dispersibility with the active material or other components when preparing an electrode slurry.
  • cellulose and cellulose derivatives used as binders for electrodes include salts thereof.
  • the water-soluble polymer stabilizes the viscosity by dissolving in water, and other materials combined as the active material and binder, such as styrene-butadiene rubber, can be stably dispersed in the aqueous solution. Furthermore, since it has a functional group, it is expected that it will be easily adsorbed stably on the surface of the active material. In addition, many cellulose derivatives such as carboxymethylcellulose have functional groups such as hydroxyl or carboxyl groups, and because of these functional groups, polymers interact with each other and may exist widely covering the surface of the active material. Be expected.
  • the binder When the binder forms a film that covers or is in contact with the surface of the active material, it is expected to serve as a passive film and suppress decomposition of the electrolyte.
  • the "passive film” is a film with no electrical conductivity or a film with extremely low electrical conductivity.
  • the passive film when a passive film is formed on the surface of an active material, the battery reaction potential In this case, decomposition of the electrolytic solution can be suppressed. Further, it is more desirable that the passive film suppresses electrical conductivity and can conduct lithium ions.
  • the conductive material is also called a conductivity imparting agent or a conductivity aid, and a carbon material is 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 when a covalent bond occurs or when they bond due to van der Waals forces, the surface of the active material
  • the concept includes cases where a conductive material covers a part of the active material, cases where the conductive material fits into the unevenness of the surface of the active material, cases where the active material is electrically connected even if they are not in contact with each other.
  • active material layers such as a positive electrode active material layer and a negative electrode active material layer include a conductive material.
  • Examples of the conductive material include carbon black such as acetylene black and furnace black, graphite such as artificial graphite and natural graphite, carbon fibers such as carbon nanofibers and carbon nanotubes, and graphene compounds. More than one species can be used.
  • carbon fibers such as mesophase pitch carbon fiber and isotropic pitch carbon fiber can be used.
  • carbon nanofibers, carbon nanotubes, or the like can be used as the carbon fibers.
  • Carbon nanotubes can be produced, for example, by a vapor phase growth method.
  • graphene compounds refer to graphene, multilayer graphene, multigraphene, graphene oxide, multilayer graphene oxide, multilayer graphene oxide, reduced graphene oxide, reduced multilayer graphene oxide, reduced multilayer graphene oxide, graphene Including quantum dots, etc.
  • a graphene compound refers to a compound that contains carbon, has a shape such as a flat plate or a sheet, and has a two-dimensional structure formed of a six-membered carbon ring. The two-dimensional structure formed by the six-membered carbon ring may be called a carbon sheet.
  • the graphene compound may have a functional group. Further, it is preferable that the graphene compound has a bent shape. Further, the graphene compound may be curled into a shape similar to carbon nanofibers.
  • the content of the conductive material relative to the total amount of the active material layer is preferably 1 wt% or more and 10 wt% or less, and more preferably 1 wt% or more and 5 wt% or less.
  • graphene compounds Unlike granular conductive materials such as carbon black, which make point contact with the active material, graphene compounds enable surface contact with low contact resistance. It is possible to improve electrical conductivity with Therefore, the ratio of active material in the active material layer can be increased. Thereby, the discharge capacity of the battery can be increased.
  • Particulate carbon-containing compounds such as carbon black and graphite, or fibrous carbon-containing compounds such as carbon nanotubes, easily enter minute spaces.
  • the minute space refers to, for example, a region between a plurality of active materials.
  • ⁇ Positive electrode current collector> As the positive electrode current collector, highly conductive materials such as metals such as stainless steel, gold, platinum, aluminum, and 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.
  • 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.
  • 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 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.
  • a material containing at least one of 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, more preferably 0.3 or more and 1.2 or less.
  • carbon material graphite, graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon fiber (carbon nanotube), graphene, carbon black, etc. may be used.
  • 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 oxide Li 4 Ti 5 O 12
  • lithium-graphite intercalation compound Li x C 6
  • niobium pentoxide Nb 2 O 5
  • oxidized Oxides such as tungsten (WO 2 ) and molybdenum oxide (MoO 2 ) can be used.
  • Li 2.6 Co 0.4 N 3 is preferable because it exhibits a large discharge capacity (900 mAh/g, 1890 mAh/cm 3 ).
  • 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 double nitride of lithium and a transition metal can be used as the negative electrode active material by removing 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)
  • 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 , nitrides such as Cu 3 N and Ge 3 N 4 , phosphides such as NiP 2 , FeP 2 and CoP 3 , and fluorides such as FeF 3 and BiF 3 .
  • the negative electrode it may be a negative electrode that does not have a negative electrode active material at the time of completion of battery production.
  • An example of a negative electrode that does not have a negative electrode active material is a negative electrode that has only a negative electrode current collector at the end of battery production, and the lithium ions that are released from the positive electrode active material when the battery is charged are deposited on the negative electrode current collector. It can be a negative electrode that is precipitated as lithium metal to form a negative electrode active material layer.
  • a battery using such a negative electrode is sometimes called a negative electrode-free (anode-free) battery, a negative electrode-less (anode-less) battery, or the like.
  • a film may be provided on the negative electrode current collector to uniformly deposit lithium.
  • a solid electrolyte having lithium ion conductivity can be used as a membrane for uniformly depositing lithium.
  • the solid electrolyte sulfide-based solid electrolytes, oxide-based solid electrolytes, polymer-based solid electrolytes, and the like can be used.
  • a polymer solid electrolyte is suitable as a film for uniformly depositing lithium because it is relatively easy to form a uniform film on the negative electrode current collector.
  • a metal film that forms an alloy with lithium can be used as a metal film that forms an alloy with lithium can be used.
  • a magnesium metal film can be used as the metal film that forms an alloy with lithium. Since lithium and magnesium form a solid solution over a wide composition range, it is suitable as a film for uniformizing the precipitation of lithium.
  • a negative electrode current collector having unevenness can be used.
  • the concave portions of the negative electrode current collector become cavities in which the lithium contained in the negative electrode current collector is likely to precipitate, so when lithium is precipitated, it is suppressed from forming a dendrite-like shape. can do.
  • 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 As the electrolyte, the one described in Embodiment 1 can be used.
  • a separator When the electrolyte contains an electrolytic solution, a separator is placed between the positive electrode and the negative electrode.
  • a separator for example, fibers containing cellulose such as paper, nonwoven fabrics, glass fibers, ceramics, synthetic fibers using nylon (polyamide), vinylon (polyvinyl alcohol fiber), polyester, acrylic, polyolefin, polyurethane, etc. It is possible to use one formed of . It is preferable that 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.
  • Coating with a ceramic material improves oxidation resistance, thereby suppressing deterioration of the separator during high voltage charging and improving the reliability of the secondary battery. Furthermore, coating with a fluorine-based material makes it easier for the separator and electrode to come into close contact with each other, thereby improving output characteristics. Coating with a polyamide-based material, especially aramid, improves heat resistance, thereby improving the safety of the secondary battery.
  • a polypropylene film may be coated on both sides with a mixed material of aluminum oxide and aramid.
  • the surface of the polypropylene film in contact with the positive electrode may be coated with a mixed material of aluminum oxide and aramid, and the surface in contact with the negative electrode may be coated with a fluorine-based material.
  • the safety of the secondary battery can be maintained even if the overall thickness of the separator is thin, so that the capacity per volume of the secondary battery can be increased.
  • a metal material such as aluminum or a resin material can be used, for example.
  • a film-like exterior body can also be used.
  • a film for example, a highly flexible metal thin film such as aluminum, stainless steel, copper, or nickel is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, or polyamide, and an exterior coating is further applied on the metal thin film.
  • a three-layer film can be used in which an insulating synthetic resin film such as polyamide resin or polyester resin is provided on the outer surface of the body.
  • This embodiment can be used in combination with other embodiments.
  • FIG. 12A is an exploded perspective view of a coin-shaped (single-layer flat type) secondary battery
  • FIG. 12B is an external view
  • FIG. 12C is a cross-sectional view thereof.
  • Coin-shaped secondary batteries are mainly used in small electronic devices.
  • FIG. 12A is a schematic diagram so that the overlapping (vertical relationship and positional relationship) of members can be seen. Therefore, FIGS. 12A and 12B are not completely identical corresponding views.
  • a positive electrode 304, a separator 310, a negative electrode 307, a spacer 322, and a washer 312 are stacked. These are sealed with a negative electrode can 302 and a positive electrode can 301 with a gasket. Note that in FIG. 12A, a gasket for sealing is not shown.
  • the spacer 322 and the washer 312 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 322 and washer 312 are 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. 12B is a perspective view of the completed coin-shaped secondary battery.
  • 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 are 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. Further, the negative electrode 307 is not limited to a laminated structure, and lithium metal foil or lithium-aluminum alloy foil may be used.
  • the positive electrode 304 and the negative electrode 307 used in the coin-shaped secondary battery 300 may each have an active material layer formed only on one side.
  • the positive electrode can 301 and the negative electrode can 302 metals such as nickel, aluminum, titanium, etc., which are corrosion resistant to electrolyte, or alloys thereof, or alloys of these and other metals (for example, stainless steel, etc.) can be used. can. Further, in order to prevent corrosion due to electrolyte and the like, it is preferable to coat with nickel, aluminum, or the like.
  • 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.
  • negative electrode 307, positive electrode 304, and separator 310 are immersed in an electrolytic solution, and as shown in FIG. 12C, the positive electrode 304, separator 310, negative electrode 307, and negative electrode can 302 are stacked in this order with the positive electrode can 301 facing down. 301 and a negative electrode can 302 are crimped together via a gasket 303 to produce a coin-shaped secondary battery 300.
  • the coin-shaped secondary battery 300 can have a high discharge capacity and excellent cycle characteristics.
  • the cylindrical secondary 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. 13B is a diagram schematically showing a cross section of a cylindrical secondary battery.
  • the cylindrical secondary battery shown in FIG. 13B 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.
  • metals such as nickel, aluminum, titanium, etc., which are corrosion resistant to electrolyte, or alloys thereof, or alloys of these and other metals (for example, stainless steel, etc.) can be used. .
  • 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. Furthermore, a non-aqueous electrolyte (not shown) is injected into the inside of the battery can 602 in which the battery element is provided.
  • the non-aqueous electrolyte the same one as a coin-type secondary battery can be used.
  • the positive electrode and negative electrode used in a cylindrical storage battery are wound, it is preferable to form an active material on both sides of the current collector.
  • 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 element (Positive Temperature Coefficient) 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.
  • the PTC element 611 is a heat-sensitive resistance element whose resistance increases when the temperature rises, and the increase in resistance limits the amount of current to prevent abnormal heat generation.
  • Barium titanate (BaTiO 3 )-based semiconductor ceramics or the like can be used for the PTC element.
  • FIG. 13C shows an example of the power storage system 615.
  • Power storage system 615 includes a plurality of secondary batteries 616.
  • the positive electrode of each secondary battery contacts a conductor 624 separated by an insulator 625 and is electrically connected.
  • the conductor 624 is electrically connected to the control circuit 620 via the wiring 623.
  • the negative electrode of each secondary battery is electrically connected to the control circuit 620 via a wiring 626.
  • As the control circuit 620 a charging/discharging control circuit that performs charging and discharging, or a protection circuit that prevents overcharging and/or overdischarging can be applied.
  • FIG. 13D shows an example of the power storage system 615.
  • the power storage system 615 includes a plurality of secondary batteries 616, and the plurality of secondary batteries 616 are sandwiched between a conductive plate 628 and a conductive plate 614.
  • the plurality of secondary batteries 616 are electrically connected to a conductive plate 628 and a conductive plate 614 by wiring 627.
  • the plurality of secondary batteries 616 may be connected in parallel, connected in series, or connected in parallel and then further connected in series.
  • the plurality of secondary batteries 616 may be connected in parallel and then further connected in series.
  • a temperature control device may be provided between the plurality of secondary batteries 616.
  • the secondary battery 616 When the secondary battery 616 is overheated, it can be cooled by the temperature control device, and when the secondary battery 616 is too cold, it can be heated by the temperature control device. Therefore, the performance of power storage system 615 is less affected by outside temperature.
  • the power storage system 615 is electrically connected to the control circuit 620 via wiring 621 and wiring 622.
  • the wiring 621 is electrically connected to the positive electrodes of the plurality of secondary batteries 616 via the conductive plate 628
  • the wiring 622 is electrically connected to the negative electrodes of the plurality of secondary batteries 616 via the conductive plate 614.
  • a secondary battery 913 shown in FIG. 14A includes a wound body 950 in which a terminal 951 and a terminal 952 are provided inside a housing 930.
  • the wound body 950 is immersed in the electrolyte 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. 14A 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 secondary 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 secondary battery 913 having a wound body 950a as shown in FIG. 15 may be used.
  • a wound body 950a shown in FIG. 15A 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.
  • the negative electrode 931 is electrically connected to the terminal 951 by ultrasonic bonding, welding, or crimping.
  • Terminal 951 is electrically connected to terminal 911a.
  • the positive electrode 932 is electrically connected to the terminal 952 by ultrasonic bonding, welding, or crimping.
  • Terminal 952 is electrically connected to terminal 911b.
  • the housing 930 covers the wound body 950a and the electrolytic solution, forming a secondary 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 secondary battery 913 may have a plurality of wound bodies 950a. By using a plurality of wound bodies 950a, the secondary battery 913 can have a larger discharge capacity.
  • the description of the secondary battery 913 shown in FIGS. 14A to 14C can be referred to.
  • FIGS. 16A and 16B an example of an external view of an example of a laminate type secondary battery is shown in FIGS. 16A and 16B.
  • 16A and 16B have a positive electrode 503, a negative electrode 506, a separator 507, an exterior body 509, a positive lead electrode 510, and a negative lead electrode 511.
  • FIG. 17A shows an external view of the positive electrode 503 and the negative electrode 506.
  • the positive electrode 503 has a positive electrode current collector 501 , and the positive electrode active material layer 502 is formed on the surface of the positive electrode current collector 501 . Further, the positive electrode 503 has a region (hereinafter referred to as a tab region) where the positive electrode current collector 501 is partially exposed.
  • the negative electrode 506 has a negative electrode current collector 504 , and the negative electrode active material layer 505 is formed on the surface of the negative electrode current collector 504 . Further, the negative electrode 506 has a region where the negative electrode current collector 504 is partially exposed, that is, a tab region. Note that the area or shape of the tab regions of the positive electrode and the negative electrode is not limited to the example shown in FIG. 17A.
  • FIG. 17B shows a stacked negative electrode 506, separator 507, and positive electrode 503.
  • an example is shown in which five sets of negative electrodes and four sets of positive electrodes are used. It can also be called a laminate consisting of a negative electrode, a separator, and a positive electrode.
  • the tab regions of the positive electrodes 503 are joined together, and the positive lead electrode 510 is joined to the tab region of the outermost positive electrode. For example, ultrasonic welding or the like may be used for joining.
  • the tab regions of the negative electrodes 506 are bonded to each other, and the negative lead electrode 511 is bonded to the tab region of the outermost negative electrode.
  • a negative electrode 506, a separator 507, and a positive electrode 503 are placed on the exterior body 509.
  • the exterior body 509 is bent at the portion indicated by the broken line. After that, the outer peripheral portion of the exterior body 509 is joined. For example, thermocompression bonding or the like may be used for joining. At this time, a region (hereinafter referred to as an inlet) that is not joined is provided in a part (or one side) of the exterior body 509 so that the electrolyte can be introduced later.
  • an inlet a region (hereinafter referred to as an inlet) that is not joined is provided in a part (or one side) of the exterior body 509 so that the electrolyte can be introduced later.
  • the electrolytic solution is introduced into the interior of the exterior body 509 through an inlet provided in the exterior body 509 .
  • the electrolytic solution is preferably introduced under a reduced pressure atmosphere or an inert atmosphere. Finally, connect the inlet. In this way, a laminate type secondary battery 500 can be manufactured.
  • Example of battery pack An example of a secondary battery pack according to one embodiment of the present invention that can be wirelessly charged using an antenna will be described with reference to FIG. 18.
  • FIG. 18A is a diagram showing the appearance of the secondary battery pack 531, which has a thin rectangular parallelepiped shape (also called a thick flat plate shape).
  • FIG. 18B is a diagram illustrating the configuration of the secondary battery pack 531.
  • the secondary battery pack 531 includes a circuit board 540 and a secondary battery 513. A label 529 is attached to the secondary battery 513. Circuit board 540 is fixed by seal 515. Further, the secondary battery pack 531 has an antenna 517.
  • the inside of the secondary battery 513 may have a structure having a wound body or a structure having a laminated body.
  • the secondary battery pack 531 includes a control circuit 590 on a circuit board 540, as shown in FIG. 18B, for example. Further, the circuit board 540 is electrically connected to the terminal 514. Further, the circuit board 540 is electrically connected to the antenna 517, one of the positive and negative leads 551, and the other 552 of the positive and negative leads of the secondary battery 513.
  • a circuit system 590a provided on the circuit board 540 and a circuit system 590b electrically connected to the circuit board 540 via the terminal 514 may be included.
  • the antenna 517 is not limited to a coil shape, and may be, for example, a wire shape or a plate shape. Further, antennas such as a planar antenna, an aperture antenna, a traveling wave antenna, an EH antenna, a magnetic field antenna, and a dielectric antenna may be used. Alternatively, the antenna 517 may be a flat conductor. This flat conductor can function as one of the conductors for electric field coupling. In other words, the antenna 517 may function as one of the two conductors of the capacitor. This allows power to be exchanged not only by electromagnetic and magnetic fields but also by electric fields.
  • Secondary battery pack 531 has a layer 519 between antenna 517 and secondary battery 513.
  • the layer 519 has a function of shielding an electromagnetic field from the secondary battery 513, for example.
  • a magnetic material can be used as the layer 519.
  • This embodiment can be used in combination with other embodiments.
  • a secondary battery can typically be applied to an automobile.
  • automobiles include next-generation clean energy vehicles such as hybrid vehicles (HV), electric vehicles (EV), and plug-in hybrid vehicles (PHEV or PHV).
  • a secondary battery can be applied.
  • Vehicles are not limited to automobiles.
  • vehicles include trains, monorails, ships, submersibles (deep sea exploration vehicles, unmanned submarines), flying vehicles (helicopters, unmanned aerial vehicles (drones), airplanes, rockets, artificial satellites), electric bicycles, electric motorcycles, etc.
  • the secondary battery of one embodiment of the present invention can be applied to these vehicles.
  • the electric vehicle is installed with first batteries 1301a and 1301b as main secondary batteries for driving, and a second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304.
  • 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 a wound type shown in FIG. 14C or FIG. 15A, or a stacked type shown in FIG. 16A or FIG. 16B.
  • 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 battery pack that includes a plurality of secondary batteries, a large amount of electric power can be extracted.
  • a plurality of secondary batteries may be connected in parallel, may be connected in series, or may be connected in parallel and then further connected in series.
  • a plurality of secondary 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. 19A shows an example in which nine square secondary batteries 1300 are used as one battery pack 1415. Further, nine prismatic secondary 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 secondary batteries using fixing parts 1413, 1414, a battery housing box, or 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 it is preferable to use a metal oxide that functions as an oxide semiconductor.
  • a metal oxide In-M-Zn oxide (element M is aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium) , hafnium, tantalum, tungsten, or one or more selected from magnesium, etc.) may be used.
  • In-M-Zn oxides that can be applied as metal oxides are 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 as the metal oxide.
  • 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
  • CAC-OS has a mosaic-like structure in which the material is separated into a first region and a second region, and the first region is distributed in the film (hereinafter referred to as a cloud-like structure). ). That is, CAC-OS is a composite metal oxide having a configuration in which the first region and the second region are mixed. However, it may be difficult to observe a clear boundary between the first region and the second region.
  • CAC-OS When CAC-OS is used in a transistor, the conductivity caused by the first region and the insulation caused by the second region act complementary to each other, resulting in a switching function (on/off function). can be provided to the CAC-OS.
  • a part of the material has a conductive function
  • a part of the material has an insulating function
  • the entire material has a semiconductor function.
  • Oxide semiconductors have a variety of structures, each with different properties.
  • the oxide semiconductor of one embodiment of the present invention includes two or more of an amorphous oxide semiconductor, a polycrystalline oxide semiconductor, an a-like OS, a CAC-OS, an nc-OS, and a CAAC-OS. It's okay.
  • control circuit portion 1320 can be used in a high-temperature environment, it is preferable to use a transistor using an oxide semiconductor.
  • the control circuit section 1320 may be formed using unipolar transistors. Transistors that use oxide semiconductors in their semiconductor layers have a wider operating ambient temperature than single-crystal Si transistors, ranging from -40°C to 150°C, and their characteristics change even when the secondary battery overheats compared to single-crystal Si transistors. small. Although 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.
  • 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. Moreover, a synergistic effect regarding safety can be obtained by combining the positive electrode active material 100 obtained in Embodiments 1, 2, etc. with a secondary battery using the positive electrode.
  • the secondary battery and control circuit section 1320 using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode can greatly contribute to eradicating accidents such as fires caused by secondary batteries.
  • 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 secondary battery to prevent instability such as a micro short circuit.
  • Functions that eliminate the causes of instability in secondary batteries include overcharging prevention, overcurrent prevention, overheat control during charging, cell balance in assembled batteries, overdischarge prevention, fuel gauge, and Examples include automatic control of charging voltage and current amount, control of charging current amount according to the degree of deterioration, micro short abnormal behavior detection, abnormal prediction regarding micro short, etc., and the control circuit unit 1320 has at least one of these functions. Further, it is possible to miniaturize the automatic control device for the secondary battery.
  • micro short refers to a minute short circuit inside the secondary battery, and it is not so much that the positive and negative electrodes of the secondary battery are short-circuited, making it impossible to charge or discharge, but rather a minute short circuit inside the secondary battery. This refers to the phenomenon in which a small amount of short-circuit current flows in a short-circuited part. Since a large voltage change occurs even in a relatively short period of time and at a small location, the abnormal voltage value may affect subsequent estimation.
  • micro short circuits occur due to the occurrence of parts where some parts no longer function or the generation of side reactants due to side reactions.
  • control circuit unit 1320 can also be said to detect the terminal voltage of the secondary battery and manage the charging/discharging state of the secondary 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. 19B shows an example of a block diagram of the battery pack 1415 shown in FIG. 19A.
  • 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 secondary battery to be used, and limits the upper limit of the current from the outside or the upper limit of the output current to the outside.
  • the range of the secondary battery's lower limit voltage to upper limit voltage is within the recommended voltage range, and when the voltage is outside of 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 over-discharging and/or over-charging. 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 n-channel transistors or p-channel transistors.
  • 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 using a power transistor including indium (indium), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaOx (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. Furthermore, since an OS transistor can be manufactured using the same manufacturing equipment as a Si transistor, it can be manufactured at low cost. That is, the control circuit section 1320 using an OS transistor can be stacked on the switch section 1324 and integrated into one chip. Since the volume occupied by the control circuit section 1320 can be reduced, miniaturization is possible.
  • the first batteries 1301a and 1301b mainly supply power to 42V system (high voltage HV) in-vehicle equipment, and the second battery 1311 supplies power to 14V system (low voltage LV) in-vehicle equipment.
  • a lead-acid battery is often used because it is advantageous in terms of cost. Lead-acid batteries have the disadvantage that they have greater self-discharge than lithium-ion batteries and are more susceptible to deterioration due to a phenomenon called sulfation.
  • a lithium ion battery as the second battery 1311 has the advantage of being maintenance-free, but if it is used for a long period of time, for example three years or more, there is a risk that an abnormality that is difficult to identify 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.
  • the second battery 1311 may be a lead-acid battery, an all-solid-state battery, or an electric double layer capacitor.
  • 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 or 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 unit 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 secondary 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 charger outlet or the charger connection cable 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 outlet-200V outlet, or 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.
  • the capacity decrease is suppressed even when the electrode layer is made thicker and the loading amount is increased, and the synergistic effect of maintaining high capacity has resulted in a secondary battery with significantly improved electrical characteristics.
  • It is particularly effective for secondary batteries used in vehicles, and provides a vehicle with a long cruising range, specifically a cruising range of 500 km or more on one charge, without increasing the weight ratio of the secondary battery to the total vehicle weight. be able to.
  • the operating voltage of the secondary battery can be increased by using the positive electrode active material 100 described in Embodiments 1, 2, etc., and as the charging voltage increases. , the available capacity can be increased. Further, by using the positive electrode active material 100 described in Embodiments 1, 2, etc. as a positive electrode, a secondary battery for a vehicle with excellent cycle characteristics can be provided.
  • next-generation clean energy such as a hybrid vehicle (HV), electric vehicle (EV), or plug-in hybrid vehicle (PHV) can be realized.
  • HV hybrid vehicle
  • EV electric vehicle
  • PSV plug-in hybrid vehicle
  • a car can be realized.
  • secondary batteries in agricultural machinery, motorized bicycles including electric assist bicycles, motorcycles, electric wheelchairs, electric carts, ships, submarines, aircraft, rockets, artificial satellites, space probes, planetary probes, or spacecraft. It can also be installed.
  • the secondary battery of one embodiment of the present invention can be a high capacity secondary battery. Therefore, the secondary battery of one embodiment of the present invention is suitable for reduction in size and weight, and can be suitably used for transportation vehicles.
  • a car 2001 shown in FIG. 20A 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 secondary battery is mounted on a vehicle, the example of the secondary battery shown in Embodiment 4 is installed at one location or at multiple locations.
  • An automobile 2001 shown in FIG. 20A includes a battery pack 2200, and the battery pack includes a secondary battery module to which a plurality of secondary batteries are connected. Furthermore, it is preferable to include a charging control device electrically connected to the secondary 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 secondary battery of the automobile 2001.
  • a predetermined charging method or connector standard such as CHAdeMO (registered trademark) or combo may be used as appropriate.
  • the charging device may be a charging station provided at 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 non-contact power supply method by incorporating a power transmission device into the road or outside 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, and the secondary battery may be charged when the vehicle is stopped or traveling.
  • an electromagnetic induction method or a magnetic resonance method can be used.
  • FIG. 20B shows a large transport vehicle 2002 having an electrically controlled motor as an example of a transport vehicle.
  • the secondary battery module of the transport vehicle 2002 has a maximum voltage of 170V, for example, in which four secondary batteries with a nominal voltage of 3.0 V or more and 5.0 V or less are connected in series, and 48 cells are connected in series. Except for the difference in the number of secondary batteries constituting the secondary battery module of the battery pack 2201, it has the same functions as those in FIG. 20A, so a description thereof will be omitted.
  • FIG. 20C shows, by way of example, a large transport vehicle 2003 with an electrically controlled motor.
  • the secondary battery module of the transportation vehicle 2003 has a maximum voltage of 600V, for example, by connecting in series 100 or more secondary batteries with a nominal voltage of 3.0 V or more and 5.0 V or less. Therefore, a secondary battery with small variations in characteristics is required.
  • a secondary battery in which the positive electrode active material 100 described in Embodiments 1 and 2 is used as a positive electrode a secondary battery having stable battery characteristics can be manufactured at low cost from the viewpoint of yield. Mass production is possible.
  • it since it has the same functions as those in FIG. 23A except for the difference in the number of secondary batteries configuring the secondary battery module of the battery pack 2202, a description thereof will be omitted.
  • FIG. 20D shows an example aircraft 2004 with an engine that burns fuel. Since the aircraft 2004 shown in FIG. 20D has wheels for takeoff and landing, it can be said to be a type of transportation vehicle, and a plurality of secondary batteries are connected to form a secondary battery module, and the secondary battery module and charging control are performed. It has a battery pack 2203 that includes a device.
  • the maximum voltage of the secondary battery module of the aircraft 2004 is 32V, which is obtained by connecting eight 4V secondary batteries in series, for example. Since it has the same functions as those in FIG. 20A except for the difference in the number of secondary batteries constituting the secondary battery module of the battery pack 2203, a description thereof will be omitted.
  • FIG. 20E shows an artificial satellite 2005 equipped with a secondary battery 2204 as an example. Since the artificial satellite 2005 is used in outer space at extremely low temperatures, it is preferable to include a secondary battery 2204, which is an embodiment of the present invention and has excellent low-temperature resistance. Furthermore, it is more preferable that the secondary battery 2204 is mounted inside the artificial satellite 2005 while being covered with a heat insulating member.
  • This embodiment can be used in combination with other embodiments.
  • the house shown in FIG. 21A includes a power storage device 2612 including a secondary battery, which is one embodiment of the present invention, and a solar panel 2610.
  • Power storage device 2612 is electrically connected to solar panel 2610 via wiring 2611 and the like. Further, the power storage device 2612 and the ground-mounted charging device 2604 may be electrically connected. Electric power obtained by the solar panel 2610 can charge the power storage device 2612. Further, the power stored in the power storage device 2612 can be charged to a secondary battery included in the vehicle 2603 via the charging device 2604.
  • the power storage device 2612 is preferably installed in the underfloor space. By installing it in the underfloor space, the space above the floor can be used effectively. Alternatively, power storage device 2612 may be installed on the floor.
  • the power stored in the power storage device 2612 can also be supplied to other electronic devices in the house. Therefore, even when power cannot be supplied from a commercial power source due to a power outage or the like, electronic devices can be used by using the power storage device 2612 according to one embodiment of the present invention as an uninterruptible power source.
  • FIG. 21B shows an example of a power storage device according to one embodiment of the present invention.
  • a power storage device 791 according to one embodiment of the present invention is installed in an underfloor space 796 of a building 799.
  • the control circuit described in Embodiment 5 may be provided in the power storage device 791, and a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode may be used in the power storage device 791.
  • a synergistic effect on safety can be obtained.
  • the control circuit described in Embodiment 5 and the secondary battery using the positive electrode active material 100 described in Embodiments 1, 2, etc. as a positive electrode are greatly effective in eradicating accidents such as fire caused by power storage device 791 having a secondary battery. can contribute.
  • a control device 790 is installed in the power storage device 791, and the control device 790 is connected to a distribution board 703, a power storage controller 705 (also referred to as a control device), a display 706, and a router 709 through wiring. electrically connected.
  • Electric power is sent from a commercial power source 701 to a distribution board 703 via a drop-in line attachment section 710. Further, power is sent to the power distribution board 703 from the power storage device 791 and the commercial power source 701, and the power distribution board 703 sends the sent power to the general load through an outlet (not shown). 707 and a power storage system load 708.
  • the general load 707 is, for example, an electrical device such as a television or a personal computer
  • the power storage system load 708 is, for example, an electrical device such as a microwave oven, a refrigerator, or an air conditioner.
  • the power storage controller 705 includes a measurement section 711, a prediction section 712, and a planning section 713.
  • the measurement unit 711 has a function of measuring the amount of power consumed by the general load 707 and the power storage system load 708 during one day (for example, from 0:00 to 24:00). Further, the measurement unit 711 may have a function of measuring the amount of power of the power storage device 791 and the amount of power supplied from the commercial power source 701.
  • the prediction unit 712 calculates the demand for consumption by the general load 707 and the power storage system load 708 during the next day based on the amount of power consumed by the general load 707 and the power storage system load 708 during one day. It has a function to predict the amount of electricity.
  • the planning unit 713 has a function of making a plan for charging and discharging the power storage device 791 based on the amount of power demand predicted by the prediction unit 712.
  • the amount of power consumed by the general load 707 and the power storage system load 708 measured by the measurement unit 711 can be confirmed on the display 706. Further, the information can also be confirmed in an electrical device such as a television or a personal computer via the router 709. Furthermore, the information can also be confirmed using a portable electronic terminal such as a smartphone or a tablet via the router 709. Furthermore, the amount of power required for each time period (or each hour) predicted by the prediction unit 712 can be confirmed using the display 706, electrical equipment, and portable electronic terminal.
  • This embodiment can be used in combination with other embodiments.
  • FIG. 22A is an example of an electric bicycle using the power storage device of one embodiment of the present invention.
  • the power storage device of one embodiment of the present invention can be applied to an electric bicycle 8700 illustrated in FIG. 22A.
  • a power storage device according to one embodiment of the present invention includes, for example, a plurality of storage batteries and 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. 22B shows a state in which it is removed from the bicycle. Further, the power storage device 8702 has a plurality of built-in storage batteries 8701 included in the power storage device of one embodiment of the present invention, and can display the remaining battery level and the like on a display portion 8703.
  • Power storage device 8702 also includes a control circuit 8704 that can control charging or detect abnormality of a secondary battery, an example of which is shown in Embodiment 5. The control circuit 8704 is electrically connected to the positive and negative electrodes of the storage battery 8701.
  • the positive electrode active material 100 obtained in Embodiments 1, 2, etc. with a secondary battery using the positive electrode, a synergistic effect regarding safety can be obtained.
  • the secondary battery and control circuit 8704 using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode can greatly contribute to eradicating accidents such as fires caused by secondary batteries.
  • FIG. 22C is an example of a two-wheeled vehicle using the power storage device of one embodiment of the present invention.
  • a scooter 8600 shown in FIG. 22C 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.
  • the power storage device 8602 that houses a plurality of secondary batteries using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode can have a high capacity and can contribute to miniaturization.
  • the scooter 8600 shown in FIG. 22C 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.
  • This embodiment can be used in combination with other embodiments.
  • a secondary battery which is one embodiment of the present invention, is mounted in an electronic device
  • electronic devices incorporating secondary batteries include television devices (also called televisions or television receivers), computer monitors, digital cameras, digital video cameras, digital photo frames, mobile phones (mobile phones, 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. 23A 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 secondary battery 2107.
  • a secondary battery 2107 By providing a secondary battery 2107 using the positive electrode active material 100 described in Embodiments 1, 2, etc. as a positive electrode, high capacity can be achieved, and a configuration that can accommodate space saving due to the miniaturization of the housing is provided. It can be realized.
  • 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.
  • the mobile phone 2100 has a sensor.
  • a human body sensor such as a fingerprint sensor, a pulse sensor, a body temperature sensor, a touch sensor, a pressure sensor, an acceleration sensor, or the like.
  • FIG. 23B is an unmanned aircraft 2300 with multiple rotors 2302.
  • Unmanned aerial vehicle 2300 is sometimes called a drone.
  • Unmanned aircraft 2300 includes a secondary 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.
  • a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode has a high energy density and is highly safe, so it can be used safely for a long time and can be used unattended. It is suitable as a secondary battery mounted on the aircraft 2300.
  • FIG. 23C shows an example of a robot.
  • the robot 6400 shown in FIG. 23C includes a secondary 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 secondary battery 6409 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal area.
  • a secondary battery using the cathode active material 100 obtained in Embodiments 1, 2, etc. as a cathode has a high energy density and is highly safe, so it can be used safely for a long time and can be used for robots. It is suitable as the secondary battery 6409 mounted on the 6400.
  • FIG. 23D 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, an operation button 6305, a secondary 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 secondary battery 6306 according to one embodiment of the present invention and a semiconductor device or an electronic component in its internal area.
  • a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode has a high energy density and is highly safe, so it can be used safely for a long time and is easy to clean. It is suitable as the secondary battery 6306 mounted on the robot 6300.
  • FIG. 24A shows an example of a wearable device.
  • Wearable devices use secondary batteries as a power source.
  • wearable devices that can be charged wirelessly in addition to wired charging with exposed connectors are being developed to improve splash-proof, water-resistant, and dust-proof performance when used in daily life or outdoors. desired.
  • a secondary battery which is one embodiment of the present invention, can be mounted in a glasses-type device 4000 as shown in FIG. 24A.
  • Glasses-type device 4000 includes a frame 4000a and a display portion 4000b.
  • the eyeglass-type device 4000 can be lightweight, have good weight balance, and can be used for a long time.
  • a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode has a high energy density, and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.
  • a secondary battery which is one embodiment of the present invention, can be mounted in the headset type device 4001.
  • the headset type device 4001 includes at least a microphone section 4001a, a flexible pipe 4001b, and an earphone section 4001c.
  • a secondary battery can be provided within the flexible pipe 4001b or within the earphone portion 4001c.
  • a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode has a high energy density, and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.
  • a secondary battery which is one embodiment of the present invention, can be mounted in the device 4002 that can be directly attached to the body.
  • a secondary battery 4002b can be provided in a thin housing 4002a of the device 4002.
  • a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode has a high energy density, and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.
  • a secondary battery which is one embodiment of the present invention, can be mounted on the device 4003 that can be attached to clothing.
  • a secondary battery 4003b can be provided in a thin housing 4003a of the device 4003.
  • a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode has a high energy density, and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.
  • a secondary battery which is one embodiment of the present invention, can be mounted on the belt-type device 4006.
  • the belt-type device 4006 includes a belt portion 4006a and a wireless power receiving portion 4006b, and a secondary battery can be mounted in an internal area of the belt portion 4006a.
  • a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode has a high energy density, and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.
  • the wristwatch-type device 4005 can be equipped with a secondary battery, which is one embodiment of the present invention.
  • the wristwatch type device 4005 has a display portion 4005a and a belt portion 4005b, and a secondary battery can be provided in the display portion 4005a or the belt portion 4005b.
  • a secondary battery using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as a positive electrode has a high energy density, and can realize a configuration that can accommodate space saving due to the miniaturization of the housing.
  • the display section 4005a can display not only the time but also various information such as incoming mail or telephone calls.
  • the wristwatch-type device 4005 is a wearable device that is worn directly around the arm, it may be equipped with a sensor that measures the user's pulse, blood pressure, and the like. It is possible to accumulate data on the amount of exercise and health of the user and manage his/her health.
  • FIG. 24B shows a perspective view of the wristwatch type device 4005 removed from the wrist.
  • FIG. 24C shows a state in which a secondary battery 913 is built in the internal area.
  • Secondary battery 913 is the secondary battery shown in Embodiment 4.
  • the secondary battery 913 is provided at a position overlapping the display portion 4005a, and the wristwatch type device 4005 can have high density and high capacity, and is small and lightweight.
  • the wristwatch-type device 4005 is required to be small and lightweight, by using the positive electrode active material 100 obtained in Embodiments 1, 2, etc. as the positive electrode of the secondary battery 913, it can achieve high energy density, Moreover, the secondary battery 913 can be made small.
  • This embodiment can be used in combination with other embodiments.
  • lithium cobalt oxide (LiCoO 2 ) shown in step S10 of FIG. 9 As the starting material lithium cobalt oxide (LiCoO 2 ) shown in step S10 of FIG. 9, commercially available lithium cobalt oxide (Cellseed C-5H, manufactured by Nihon Kagaku Kogyo Co., Ltd.) containing no additional elements was prepared. Hereinafter, in this specification etc., it is simply written as "C-5H".
  • C-5H has a median diameter of about 7.0 ⁇ m and satisfies the condition that the median diameter is 10 ⁇ m or less.
  • step S15 C-5H was placed in a pod (container), covered with a lid, and then heated in a muffle furnace at 850° C. for 2 hours. After creating an oxygen atmosphere in the muffle furnace, no flow occurred ( O2 purge).
  • the height (also referred to as bulk) of the powder was set to be 10 mm or less and flat inside the pod.
  • an additive element A1 source was produced according to step S20a shown in FIG. 10A.
  • LiF lithium fluoride
  • MgF 2 magnesium fluoride
  • the ratio of LiF and MgF 2 was measured so that the ratio of LiF:MgF 2 was 1:3 (molar ratio).
  • LiF and MgF2 were mixed in dehydrated acetone and stirred at a rotation speed of 500 rpm for 20 hours.
  • a ball mill was used for mixing, and zirconium oxide balls were used as the grinding media.
  • step S31 shown in FIG. 9 the lithium cobalt oxide obtained by heating in step S15 (lithium cobalt oxide after initial heating) and the additive element A1 source obtained in step S20a were mixed. Specifically, after weighing so that the number of magnesium atoms was 1 atomic % with respect to the number of cobalt atoms possessed by lithium cobalt oxide, the lithium cobalt oxide after initial heating and the additive element A1 source were mixed in a dry method. . At this time, the mixture was stirred for 1 hour at a rotational speed of 150 rpm. Thereafter, it was sieved through a sieve having meshes of 300 ⁇ m to obtain a mixture 903 (Step S32).
  • step S33 the mixture 903 was heated.
  • the heating conditions were 900° C. for 5 hours.
  • a lid was placed on the pod containing mixture 903 during heating.
  • the interior of the pod had an atmosphere containing oxygen, and entry and exit of the oxygen was blocked (purge).
  • a composite oxide containing Mg and F lithium cobalt oxide containing Mg and F
  • a source of additive element A2 was produced.
  • nickel hydroxide (Ni(OH) 2 ) was prepared as a Ni source
  • aluminum hydroxide (Al(OH) 3 ) was prepared as an Al source.
  • nickel hydroxide and aluminum hydroxide were each separately stirred in dehydrated acetone at a rotation speed of 500 rpm for 20 hours.
  • a ball mill was used for mixing
  • zirconium oxide balls were used as the grinding media.
  • About 10 g of nickel hydroxide and aluminum hydroxide were placed in separate containers with 20 mL of dehydrated acetone, 22 g of zirconium oxide balls (1 mm diameter), and stirred in a 45 mL container of a mixing ball mill. Thereafter, each sample was sieved through a sieve having a mesh size of 300 ⁇ m to obtain a source of additive element A2.
  • step S51 a composite oxide containing Mg and F and a source of additive element A2 were mixed in a dry manner. Specifically, the mixture was mixed by stirring at a rotational speed of 150 rpm for 1 hour. The mixing ratio was such that nickel hydroxide and aluminum hydroxide contained in the source of additive element A2 were each 0.5 atomic % based on the number of cobalt atoms contained in lithium cobalt oxide. A ball mill was used for mixing, and zirconium oxide balls were used as the grinding media.
  • Step S52 For the capacity of the mixing ball mill container of 45 mL, a total of about 7.5 g of Ni source, Al source, and the composite oxide (lithium cobalt oxide containing Mg and F) obtained in step S34 together with 22 g of zirconium oxide balls (1 mm diameter) ) and mixed. Finally, it was sieved through a sieve having mesh size of 300 ⁇ m to obtain a mixture 904 (Step S52).
  • step S53 the mixture 904 was heated.
  • the heating conditions were 850° C. for 2 hours.
  • the pod containing the mixture 904 was placed with a lid and heated in a muffle furnace. After creating an oxygen atmosphere in the muffle furnace, no flow occurred ( O2 purge).
  • O2 purge By heating, lithium cobalt oxide (composite oxide) containing Mg, F, Ni, and Al was obtained (step S54). In this way, sample 1 of positive electrode active material was obtained.
  • Sample 2 was produced under different conditions from Sample 1. As a method for producing sample 2, in step S33, the heating conditions were 900° C. and 20 hours when heating the mixture 903, and in step S53, the heating conditions were 850° C. and 10 hours when heating the mixture 904. . It was produced in the same manner as Sample 1 except for the above heating temperature. Sample 2 of positive electrode active material was thus obtained.
  • Comparative Sample 1 As Comparative Sample 1, commercially available lithium cobalt oxide (Cellseed C-5H, manufactured by Nihon Kagaku Kogyo Co., Ltd.) that did not contain any additional elements was prepared.
  • FIG. 25A shows the result of particle size distribution measurement of Sample 1
  • FIG. 25B shows the result of particle size distribution measurement of Sample 2.
  • the measured data of Sample 1 and Sample 2 are shown by solid lines
  • the measured data of Comparative Sample 1 is shown by dotted lines.
  • the median diameter (D50) of Sample 1 was approximately 9.7 ⁇ m, and the median diameter (D50) of Sample 2 was approximately 9.5 ⁇ m. As a result, it was confirmed that the median diameters of Sample 1 and Sample 2 both satisfied 12 ⁇ m or less (10.5 ⁇ m or less).
  • the median diameter (D50) of Comparative Sample 1 was approximately 7.0 ⁇ m. Note that the median diameter (D50) can be measured, for example, by observation using a SEM (scanning electron microscope) or TEM, or by a particle size distribution meter using a laser diffraction/scattering method. In this example, the measurement was performed using a laser diffraction particle size distribution analyzer SALD-2200 manufactured by Shimadzu Corporation.
  • Preprocessing for analysis will be explained. 250 mg of Sample 1 and 2 ml of 0.05M H 2 SO 4 aqueous solution were prepared, placed in a glass container with a lid, and mixed to obtain a first mixed solution. Note that ultrasonic waves were applied for 1 hour for mixing. Thereafter, the container was allowed to stand at room temperature for 12 hours or more. Thereafter, 1 ml of the filtrate obtained by filtering the first mixed solution and 9 ml of pure water were mixed to obtain a second mixed solution. In this way, the pretreatment of Sample 1 was completed. Further, Comparative Sample 1 was also pretreated in the same manner as Sample 1.
  • ion chromatography was performed using the second mixed solution obtained in the above pretreatment.
  • anion analysis and cation analysis were performed.
  • Cation analysis was performed at 30°C using Dionex IonPac CG16 (3 x 50 mm) and Dionex IonPac CS16 (3 x 250 mm) columns.
  • the eluent was an aqueous methanesulfonic acid (MSA) solution, and the flow rate was 0.36 ml/min. Isocratic measurements were performed with the concentration of the MSA aqueous solution kept constant.
  • the detector used was an electrical conductivity detector.
  • a cation mixed standard solution manufactured by Kanto Kagaku Co., Ltd. was used to create the calibration curve.
  • Table 1 shows the results of ion chromatography. The numerical values shown in the table indicate the weight ppm of each element relative to the sample weight (Sample 1 or Comparative Sample 1).
  • FIG. 26A shows a surface SEM image of sample 1
  • FIG. 26B shows a surface SEM image of sample 2. Comparison of surface SEM images revealed that Sample 1 had higher smoothness than Sample 2.
  • FIGS. 27 and 28 A method for calculating the convex portion will be explained using FIGS. 27 and 28.
  • An arbitrary SEM image is shown in FIG. 27A.
  • label portions that are not used for image analysis are trimmed from the SEM image. Trimming can be performed using well-known image processing software, for example, product name: imageJ.
  • imageJ image processing software
  • FIG. 27A when a plurality of positive electrode active materials are aggregated, that is, when a plurality of positive electrode active materials are adjacent or in close contact, the boundaries of the positive electrode active materials are extracted.
  • FIG. 27B shows an image in which the boundary portion is extracted.
  • FIG. 27A shows an image in which the positive electrode active material in the foreground is extracted.
  • FIG. 27B obtained by the above procedure is superimposed on FIG. 27C using the Add Image function of ImageJ with transparency set to 50%. Thereafter, binarization is performed using the Threshold function (Otsu algorithm) of imageJ, and an image as shown in FIG. 28A in which the background and the inside of the particle are separated can be obtained.
  • Threshold function Otsu algorithm
  • particles with an area of 0.8 ⁇ m 2 or more in FIG. 28A that is, an area on the image, are identified by the Analyze particle function (FIG. 28B), and the number thereof is counted.
  • the particles correspond to the positive electrode active material.
  • Particles with an area of 0.8 ⁇ m 2 or more were selected, which corresponds to a median diameter (D50) of 1 ⁇ m or more, and it can be said that the area was selected without discrepancy with the particle size distribution measurement.
  • D50 median diameter
  • the identified particles that is, fine particles of 0.25 ⁇ m 2 or less existing on the surface of the positive electrode active material, are identified using the Analyze particle function of ImageJ, and their number is calculated. At this time, anything smaller than 10 pixels on the image is excluded as noise.
  • FIG. 28C shows the image with noise removed. The fine particles correspond to convex portions.
  • a coin-shaped half cell was manufactured using Sample 1 and Sample 2 manufactured in Example 1 as positive electrode active materials, respectively. Furthermore, using the produced half cells, temperature-specific charge/discharge tests and rate-specific discharge capacity measurements were conducted.
  • Sample 1 was prepared as a positive electrode active material, acetylene black (AB) was prepared as a conductive material, and polyvinylidene fluoride (PVDF) was prepared as a binder. PVDF was prepared in advance by dissolving it in N-methyl-2-pyrrolidone (NMP) at a weight ratio of 5%. Next, a positive electrode active material: AB:PVDF was mixed at a ratio of 95:3:2 (weight ratio) to prepare a slurry, and the slurry was applied to an aluminum positive electrode current collector. NMP was used as a solvent for the slurry.
  • NMP N-methyl-2-pyrrolidone
  • the solvent was evaporated to form a positive electrode active material layer on the positive electrode current collector.
  • pressing treatment was performed using a roll press machine.
  • the conditions for the press treatment were a linear pressure of 210 kN/m.
  • both the upper roll and lower roll of the roll press machine were set to 120 degreeC.
  • the amount of active material supported on the positive electrode was approximately 7 mg/cm 2 .
  • the electrolytic solution used in the half cell contains an organic solvent.
  • Lithium hexafluorophosphate LiPF 6
  • electrolytic solution A Lithium hexafluorophosphate
  • the electrolytic solution used in this example has a freezing point of -40°C or lower, which is a necessary condition for realizing a lithium ion battery that can be charged and discharged even in an extremely low temperature environment of -40°C.
  • a porous polypropylene film was used as the separator. Moreover, lithium metal was used for the negative electrode (counter electrode).
  • half cell 1 having Sample 1 as the positive electrode active material was manufactured.
  • Half Cell 2 was manufactured, which had Sample 2 as the positive electrode active material.
  • a current of 0.1 C can be said to be a current of 20 mA/g per weight of the positive electrode active material, and a current of 0.01 C can be said to be a current of 2 mA/g per the weight of the positive electrode active material.
  • ⁇ Temperature charging/discharging test 1> Using half cell 1 and half cell 2 that had been subjected to the above aging treatment, charging capacity and discharging capacity were measured in a low temperature environment as temperature-specific charging/discharging test 1. Measurements include charging and discharging in a 0°C environment, charging and discharging in a 25°C environment, charging and discharging in a -20°C environment, charging and discharging in a 25°C environment, and charging and discharging in a -40°C environment. The charging and discharging characteristics under each temperature environment were measured in the following order: , and charging and discharging under a 25° C. environment.
  • charging is performed by constant current charging at a charging current of 0.1C until the voltage reaches 4.60V, followed by constant voltage charging at 4.60V, and charging at a charging current of 4.60V. This was continued until the temperature reached 0.01C or less.
  • the conditions for discharging were such that constant current was discharged at a discharge rate of 0.1 C until the voltage reached 2.5 V (cutoff voltage).
  • FIG. 29A is a diagram showing the charging and discharging characteristics of half cell 1
  • FIG. 29B is a diagram showing the charging and discharging characteristics of half cell 2.
  • the dotted line shows the result when the temperature during charging and discharging is 25°C
  • the broken line shows the result when the temperature during charging and discharging is -20°C
  • the solid line shows the result when the temperature during charging and discharging is -20°C. This shows the results when the temperature during charging and discharging was -40°C.
  • half cell 1 and half cell 2 that is, lithium ion batteries equipped with the positive electrode active material obtained by the manufacturing method described in Embodiment Mode 1, etc., are at least -40°C or higher. It has become clear that charging and discharging operations are possible in a temperature range of 25° C. or lower.
  • Sample 1 and Sample 2 had extremely high discharge capacities of 170 mAh/g or more even at -40° C. for charging and discharging temperatures. From another point of view, excellent results were obtained in which the discharge capacity in charge and discharge at -40°C was 80% or more compared to the discharge capacity in charge and discharge at 25°C. In this way, the discharge capacity when the charging temperature and the discharging temperature are -40°C is 170 mAh/g or more, and the discharge capacity at -40°C discharge is 80% or more compared to the discharge capacity at 25°C discharge. The results showed that this was achieved.
  • ⁇ Temperature-specific charge/discharge test 2> Using the half cell 1 subjected to the above aging treatment (a different half cell from the one subjected to the temperature-specific charge-discharge test 1), as a temperature-specific charge-discharge test 2, in more detail, the charging capacity in a low-temperature environment, And the discharge capacity was measured. Measurements include charging and discharging in a 20°C environment, charging and discharging in a minus 40°C environment, charging and discharging in a minus 30°C environment, charging and discharging in a minus 20°C environment, and charge and discharge in a minus 10°C environment. The charging capacity and the discharging capacity under each temperature environment were measured in the order of charging and discharging, and charging and discharging in a 0° C. environment.
  • a current of 0.1 C can be said to be a current of 20 mA/g per weight of the positive electrode active material, and a current of 0.01 C can be said to be a current of 2 mA/g per the weight of the positive electrode active material.
  • the measurement results are shown in Table 3.
  • the first column shows the temperature conditions
  • the second column shows the charge capacity per positive electrode active material weight
  • the third column shows the discharge capacity per positive electrode active material weight
  • the fourth column shows half cell 1.
  • the fifth column shows the discharge capacity under each temperature environment as a discharge capacity ratio (%), assuming that the discharge capacity at 20° C. is 100%.
  • FIG. 30 shows discharge curves under each temperature environment.
  • Half Cell 1 which is a secondary battery of one embodiment of the present invention, has the following values when the discharge capacity value measured during charging and discharging in a 20°C environment is taken as 100%. Good results were obtained.
  • the discharge capacity value measured during charging and discharging in a ⁇ 40° C. environment was 77.2%, which was a good result exceeding 75%.
  • the discharge capacity value measured during charging and discharging in a -30°C environment was 88.1%, which was a good result exceeding 85%.
  • the discharge capacity value measured during charging and discharging in a -20°C environment was 94.2%, which was a good result exceeding 90%.
  • the discharge capacity value measured during charging and discharging in a -10°C environment was 96.9%, which was a good result exceeding 95%. Further, the discharge capacity value measured during charging and discharging in a 0° C. environment was 98.1%, which was a good result exceeding 98%.
  • ⁇ Discharge capacity measurement by rate> Discharging by rate (also referred to as by discharge current value, discharge speed, etc.) using half cell 1 (a different half cell from the one subjected to temperature-specific charge/discharge tests 1 and 2) subjected to the above aging treatment.
  • rate also referred to as by discharge current value, discharge speed, etc.
  • charging capacity and discharging capacity were measured in a -40°C environment under six types of discharging conditions.
  • the discharge current values were different for the six types of discharge conditions, and measurements were performed under each discharge condition in the order of 0.02C, 0.1C, 0.2C, 0.3C, 0.5C, and 1C. . Before discharging under each discharging condition, charging was performed under common charging conditions.
  • a current of 0.02C can be said to be a current of 4mA/g per weight of the positive electrode active material
  • a current of 0.1C can be said to be a current of 20mA/g per weight of the positive electrode active material
  • a current of 0.2C can be said to be a current of 4mA/g per weight of the positive electrode active material.
  • the current can be said to be 40 mA/g per weight of the positive electrode active material
  • a current of 0.3 C can be said to be a current of 60 mA/g per the weight of the positive electrode active material
  • a current of 0.5 C can be said to be a current of 60 mA/g per the weight of the positive electrode active material.
  • the current is 100 mA/g per weight
  • a current of 1C can be said to be a current of 200 mA/g per weight of the positive electrode active material.
  • constant current charging was performed at a charging current of 0.1C until the voltage reached 4.60V, and then constant voltage charging was performed at 4.60V until the charging current became 0.01C or less. Further, the discharge was performed under the conditions of constant current discharge under the six types of discharge current conditions described above until the voltage reached 2.5 V (cutoff voltage).
  • the measurement results are shown in Table 4.
  • the first column shows the discharge current conditions
  • the second column shows the charge capacity per weight of positive electrode active material
  • the third column shows the discharge capacity per weight of positive electrode active material
  • the fourth column shows the half cell 1 It shows the discharge capacity of .
  • the fifth column shows the discharge capacity under each discharge current condition as a discharge capacity ratio (%) when the discharge capacity at 0.1C is taken as 100%.
  • FIG. 31 shows a graph of discharge capacity at each discharge rate.
  • half cell 1 which is a secondary battery of one embodiment of the present invention, has the following values when the discharge capacity value measured under a discharge current condition of 0.1C is taken as 100%. Good results were obtained.
  • the discharge capacity value measured under the discharge current condition of 0.2C was 82.7%, which was a good result exceeding 80%.
  • the discharge capacity value measured under the discharge current condition of 0.3C was 72.7%, which was a good result exceeding 70%.
  • the discharge capacity value measured under the discharge current condition of 0.5C was 57.3%, which was a good result exceeding 50%.
  • half cell 1 was able to discharge even under the discharge current condition of 1 C, and its discharge capacity value was 18.8%.
  • the secondary battery of one embodiment of the present invention has high discharge characteristics in a low temperature environment of -40°C.
  • a lithium ion battery equipped with a positive electrode active material obtained by the manufacturing method described in Embodiment Mode 2, etc. can perform charging operation in a temperature range of at least -40°C or higher and 20°C or lower. It has become clear that discharge operation is possible. Furthermore, it has been revealed that by providing the electrolyte described in Embodiment 1, very excellent charging and discharging operations are possible in a temperature range of -40°C to 20°C.
  • a coin-shaped half cell was manufactured using each of Sample 1, Sample 2, and Comparative Sample 1 manufactured in Example 1 as positive electrode active materials. Further, a charge/discharge cycle test was conducted using the produced half cell.
  • a half cell 1B was created using Sample 1 as a positive electrode active material.
  • Carbonate (VC) was added at 2 wt %, and 1 mol/L of lithium hexafluorophosphate (LiPF 6 ) was used as the electrolyte of the electrolytic solution.
  • electrolytic solution B this electrolytic solution will be referred to as "electrolytic solution B" in this specification and the like.
  • the method for manufacturing the half cell except for the electrolytic solution was the same as the method described in ⁇ Production of half cell 1> of Example 1.
  • a half cell 2B having Sample 2 as the positive electrode active material was manufactured using the same manufacturing method as the half cell 1B.
  • Comparative Sample 1 As the positive electrode active material was produced using the same production method as Half Cell 1B.
  • FIGS. 32A and 32B The charge/discharge cycle characteristics of half cell 1B, half cell 2B, and comparative cell are shown in FIGS. 32A and 32B. Charging was performed by constant current charging at 0.5C to 4.60V, and then constant voltage charging until the current value reached 0.05C. Further, the discharge was carried out at a constant current of 0.5C up to 2.5V. In addition, 1C was set to 200mA/g here. Two temperature conditions were used: 25°C or 45°C. Charging and discharging were repeated 50 times in this manner.
  • FIG. 32A shows the results of a charge/discharge cycle test at a temperature of 25° C.
  • FIG. 32B shows the results of a charge/discharge cycle test at a temperature of 45° C.
  • half cell 1B with sample 1 and half cell 2B with sample 2 have good charge/discharge cycle characteristics under the high voltage condition of 4.6V and at 25°C and 45°C, respectively. I was able to confirm that this is true.
  • the half cell 1B containing Sample 1 exhibits excellent charge/discharge cycle characteristics under all conditions.
  • FIGS. 33A and 33B show the charge/discharge cycle characteristics of half cell 1B and half cell 2B at higher voltages. Charging was performed by constant current charging at 0.5C to 4.65V or 4.70V, and then constant voltage charging until the current value reached 0.05C. Further, the discharge was carried out at a constant current of 0.5C up to 2.5V. In addition, 1C was set to 200mA/g here. The temperature was 25°C. Charging and discharging were repeated 50 times in this manner.
  • FIG. 33A shows the results of a charge/discharge cycle test under a charging condition of 4.65V
  • FIG. 33B shows the results of a charge/discharge cycle test under a charging condition of 4.70V.
  • half cell 1B having sample 1 exhibited superior charge-discharge cycle characteristics compared to half cell 2B having sample 2.
  • both half cell 1B having sample 1 and half cell 2B having sample 2 had excellent charge/discharge cycle characteristics.
  • half cell 1B having sample 1 and half cell 2B having sample 2 have different charge/discharge cycle characteristics, and The comparison showed that sample 1 was superior.
  • charging and discharging were performed using the half cell 1B produced in Example 3 (a different half cell from the one used in the charge/discharge cycle test). Charging was performed by constant current charging at 0.2C to 4.50V, and then constant voltage charging until the current value reached 0.05C. Further, the discharge was carried out at a constant current of 0.2C up to 3.0V. Note that, similarly to other tests, 1C was set to 200 mA/g.
  • Charging was performed before XRD analysis in a high voltage charging state. Charging was performed by constant current charging at 0.2C to 4.60V, and then constant voltage charging until the current value reached 0.02C.
  • the half cell 1B was disassembled within one hour after the above charging was completed.
  • an insulating tool was used and disassembly was carried out carefully to avoid short-circuiting.
  • a glove box filled with argon with controlled dew point and oxygen concentration was used. Note that the dew point of the glove box is preferably ⁇ 70° C. or lower, and the oxygen concentration is preferably 5 ppm or lower.
  • the crystal structure of the cathode active material may change due to self-discharge after a long period of time has elapsed since the above-mentioned charging, it is preferable to disassemble the cathode active material as soon as possible and conduct analysis.
  • the above sample 1 obtained by disassembling the half cell 1B was set on a sealable XRD measurement stage in the glove box to obtain sample 1 sealed on the XRD measurement stage with argon. .
  • XRD measurement was started within 15 minutes.
  • the XRD apparatus and conditions are as follows.
  • XRD device Bruker AXS, D8 ADVANCE
  • X-ray source CuK ⁇ 1 -ray output: 40kV, 40mA
  • Divergence angle Div. Slit
  • 0.5° Detector LynxEye Scan method: 2 ⁇ / ⁇ continuous scan Measurement range (2 ⁇ ): 15° or more and 75° or less (100 minutes)
  • Step width (2 ⁇ ) 0.01°
  • Setting Counting time 1 second/step Sample table rotation: 15 rpm
  • FIGS. 34A to 34C The XRD measurement data of Sample 1 in the high voltage charging state measured above are shown in FIGS. 34A to 34C.
  • 34A to 34C reference data of O3' structure (O3'), reference data of H1-3 structure (H1-3), and reference data of CoO2 ( CoO2 ) are shown together.
  • FIG. 34A shows a range in which 2 ⁇ is 15° or more and 75° C. or less in XRD measurement.
  • FIGS. 34B and 34C show a part of FIG. 34A enlarged and the enlargement ratio of the vertical axis of the measurement data of sample 1 partially changed.
  • Measurement spectrum wide scan, narrow scan for each detected element
  • Table 5 shows the atoms of each element when the total number of atoms of Li, Co, Ni, Al, O, Mg, F, C, Ca, Na, S, Cl, and Ti in each sample is taken as 100%. The numbers are shown in %.
  • the total amount listed in Table 5 may be 100.1% or 99.9% due to rounding of the numerical values after analysis in order to show it as a table, but in the XPS analysis, the total atomic amount is The calculation is based on the number of 100.0%.
  • Sample 2 requires a longer heating time after mixing the A1 source and a longer heating time after mixing the A2 source.
  • F in Table 5 looking at F in Table 5, compared to sample 2, the number of atoms of F in sample 1 is significantly larger. In other words, compared to the number of F atoms detected on the surface of Sample 1, the number of F atoms detected on the surface of Sample 2 is significantly smaller.
  • the heating time after mixing the A1 source under the production conditions of Sample 2 If the heating time after mixing the A2 source is long, F may be reduced from the surface layer of the positive electrode active material to be produced. As the number of F atoms decreases in the surface layer, the effect of retaining Ni and Mg in the surface layer decreases, preventing Ni and Mg from diffusing from the surface layer into the inside of the positive electrode active material. Conceivable.
  • the number of Ni atoms relative to the number of Co atoms is 0.099
  • the number of Mg atoms relative to the number of Co atoms is 1.092
  • the number of Co atoms The number of F atoms (F/Co) was 0.794.
  • the number of Ni atoms relative to the number of Co atoms is 0.048
  • the number of Mg atoms relative to the number of Co atoms is 0.396
  • the number of Ni atoms relative to the number of Co atoms (Mg/Co) is 0.396.
  • the number of F atoms relative to the number of atoms (F/Co) was 0.021.
  • Ni/Co is preferably 0.200 or less, preferably 0.150 or less, preferably 0.140 or less, preferably 0.130 or less, and 0.120 or less. It can be said that it is preferably 0.110 or less, or 0.110 or less.
  • the number of Mg atoms relative to the number of Co atoms is 0. It is preferably .400 or more, more preferably 0.500 or more, more preferably 0.600 or more, more preferably 0.700 or more, and preferably 0.800 or more. More preferably, it is 0.900 or more, and even more preferably 1.000 or more. Further, Mg/Co is preferably 2.000 or less, preferably 1.500 or less, preferably 1.400 or less, preferably 1.300 or less, or 1. It can be said that it is preferable that it is 200 or less.
  • the number of F atoms relative to the number of Co atoms is 0. It is preferably .100 or more, more preferably 0.200 or more, more preferably 0.300 or more, more preferably 0.400 or more, and more preferably 0.500 or more. It can be said that it is more preferable, more preferably 0.600 or more, and even more preferably 0.700 or more. Further, F/Co is preferably 1.500 or less, preferably 1.200 or less, preferably 1.100 or less, preferably 1.000 or less, and 0.900 or less. It can be said that the following is preferable.
  • Sample 1 has the above-mentioned features, allowing high-voltage charging and excellent charge/discharge characteristics in an environment of -40°C, as well as being able to charge in medium-temperature environments of 25°C and 45°C. It is thought that particularly excellent battery characteristics were achieved in that there was little deterioration due to repeated discharges.
  • sample 1 was subjected to line analysis using STEM-EDX.
  • sample 1 was sliced by the FIB method ( ⁇ -sampling method).
  • STEM and EDX used the following equipment and conditions.
  • 35A, 36A, 36B, and 36C show graphs of characteristic X-ray detection intensity of STEM-ED X-ray analysis in the basal region ((001) orientation plane) of Sample 1. Further, FIGS. 35B, 37A, 37B, and 37C show graphs of the characteristic X-ray detection intensity of STEM-ED X-ray analysis in the edge region of Sample 1 (surface that is not (001) oriented). Note that the data at each measurement point in the characteristic X-ray detection intensity graphs shown in FIGS. 35A to 37C was smoothed to be the average value of 5 points including 4 adjacent points. Note that since the interval between the measurement points is about 0.2 nm, the above five-point average can also be said to be the average value over a region of about 0.8 nm.
  • FIG. 36A, 36B, and 36C are graphs in which the vertical axis of FIG. 35A is enlarged.
  • FIG. 36A shows a graph of characteristic X-ray detection intensity of cobalt and magnesium
  • FIG. 36B shows a graph of characteristic X-ray detection intensity of cobalt and aluminum.
  • a graph of detection intensity is shown
  • FIG. 36C shows a graph of characteristic X-ray detection intensity of cobalt and nickel.
  • the graph of nickel shown in FIG. 36C is not derived from the characteristic X-rays of nickel, but is derived from the characteristic X-rays of cobalt, which is close to nickel on the energy spectrum.
  • the surface was estimated to be a point at a distance of 44.3 nm. Specifically, a region avoiding the vicinity where the detected amount of cobalt starts to increase was set at a distance of 10 to 20 nm in FIG. 35A. Further, the region in which cobalt counts were stable was set at a distance of 94 to 98 nm. From the graph of the characteristic X-ray detection intensity of cobalt, the 50% point of the sum of M AVE and M BG was calculated to be 276.8 counts, and the surface was estimated to be 44.3 nm by finding a regression line.
  • FIG. 37A, FIG. 37B, and FIG. 37C are graphs in which the vertical axis of FIG. 35B is enlarged.
  • FIG. 37A shows a graph of characteristic X-ray detection intensity of cobalt and magnesium
  • FIG. 37B shows a graph of characteristic X-ray detection intensity of cobalt and aluminum.
  • a graph of detection intensity is shown
  • FIG. 37C shows a graph of characteristic X-ray detection intensity of cobalt and nickel. Note that in the energy spectrum in the edge region of Sample 1, a peak derived from the characteristic X-rays of nickel was clearly observed.
  • the surface was estimated to be at a point at a distance of 50.5 nm. Specifically, a region avoiding the vicinity where the detected amount of cobalt starts to increase was set at a distance of 10 to 20 nm in FIG. 35B. Further, the region where the cobalt count was stable was set at a distance of 97 to 100 nm. From the graph of the characteristic X-ray detection intensity of cobalt, the 50% point of the sum of M AVE and M BG was calculated to be 610.2 counts, and the surface was estimated to be 50.5 nm by finding a regression line.
  • the peak positions of the added elements are -0.9 nm for Mg and 4.0 nm for Al, with the inner direction of the particle as the positive direction based on the surface position estimated above.
  • the thickness of Ni was 1.9 nm.
  • the half-width of the magnesium distribution was 4.5 nm
  • the half-width of the nickel distribution was 8.1 nm.
  • Sample 1 had a region where magnesium was distributed closer to the surface of the positive electrode active material than aluminum in both the basal region and the edge region. Furthermore, it was confirmed that in the edge region, there was a region where magnesium and nickel were distributed closer to the surface of the positive electrode active material than aluminum. Note that in the edge region, the peak position of magnesium and the peak position of nickel were close to each other, and it was confirmed that the distribution of magnesium had a region overlapping with the distribution of nickel.

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WO2025180096A1 (zh) * 2024-03-01 2025-09-04 宁德新能源科技有限公司 一种二次电池以及电子装置

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JP2006351378A (ja) * 2005-06-16 2006-12-28 Matsushita Electric Ind Co Ltd リチウムイオン二次電池
JP2016095980A (ja) * 2014-11-13 2016-05-26 日立金属株式会社 正極活物質、正極、及びリチウムイオン二次電池
JP2020140954A (ja) * 2018-12-13 2020-09-03 株式会社半導体エネルギー研究所 正極活物質および正極活物質の作製方法、及び二次電池
JP2021097051A (ja) * 2016-11-18 2021-06-24 株式会社半導体エネルギー研究所 リチウムイオン二次電池

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JP6342230B2 (ja) 2013-06-21 2018-06-13 株式会社半導体エネルギー研究所 非水溶媒、非水電解質および蓄電装置

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JP2006351378A (ja) * 2005-06-16 2006-12-28 Matsushita Electric Ind Co Ltd リチウムイオン二次電池
JP2016095980A (ja) * 2014-11-13 2016-05-26 日立金属株式会社 正極活物質、正極、及びリチウムイオン二次電池
JP2021097051A (ja) * 2016-11-18 2021-06-24 株式会社半導体エネルギー研究所 リチウムイオン二次電池
JP2020140954A (ja) * 2018-12-13 2020-09-03 株式会社半導体エネルギー研究所 正極活物質および正極活物質の作製方法、及び二次電池

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2025180096A1 (zh) * 2024-03-01 2025-09-04 宁德新能源科技有限公司 一种二次电池以及电子装置

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