WO2024201266A1 - リチウムイオン二次電池 - Google Patents

リチウムイオン二次電池 Download PDF

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Publication number
WO2024201266A1
WO2024201266A1 PCT/IB2024/052825 IB2024052825W WO2024201266A1 WO 2024201266 A1 WO2024201266 A1 WO 2024201266A1 IB 2024052825 W IB2024052825 W IB 2024052825W WO 2024201266 A1 WO2024201266 A1 WO 2024201266A1
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Prior art keywords
positive electrode
active material
electrode active
lithium
lithium ion
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PCT/IB2024/052825
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English (en)
French (fr)
Japanese (ja)
Inventor
山崎舜平
荻田香
比護大地
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Semiconductor Energy Laboratory Co Ltd
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Semiconductor Energy Laboratory Co Ltd
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Priority to KR1020257031635A priority Critical patent/KR20250166125A/ko
Priority to JP2025509045A priority patent/JPWO2024201266A1/ja
Priority to CN202480018667.6A priority patent/CN120917592A/zh
Publication of WO2024201266A1 publication Critical patent/WO2024201266A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • One aspect of the present invention relates to a lithium-ion secondary battery.
  • one embodiment of the present invention is not limited to the above fields, and relates to a semiconductor device, a display device, a light-emitting device, a power storage device, a lighting device, an electronic device, a vehicle, and a manufacturing method thereof.
  • the above-mentioned semiconductor device, display device, light-emitting device, power storage device, lighting device, electronic device, and vehicle can use the lithium-ion secondary battery of one embodiment of the present invention as a necessary power source.
  • the above-mentioned electronic device includes an information terminal device equipped with a lithium-ion secondary battery.
  • the above-mentioned power storage device includes a stationary power storage device.
  • a lithium-ion secondary battery (sometimes called a lithium-ion battery) is a battery that uses lithium ions as the carrier ion.
  • Lithium-ion batteries are secondary batteries that can be used repeatedly by charging and discharging.
  • lithium-ion secondary batteries lithium-ion capacitors
  • air batteries air batteries
  • all-solid-state batteries all-solid-state batteries.
  • high-output, high-capacity lithium-ion secondary batteries has rapidly expanded in line with the development of the semiconductor industry, and they have become indispensable in today's information society as a rechargeable energy source.
  • Non-Patent Document 1 proposes an electrolyte that is a mixture of 3,3,3-methyl trifluoropropionate (MTFP):fluoroethylene carbonate (FEC) in a ratio of 9:1 to improve output characteristics below freezing.
  • Non-Patent Document 2 reports the crystal structure of the positive electrode active material.
  • Lithium-ion secondary batteries still have room for improvement in various areas, such as discharge capacity, cycle characteristics, reliability, safety, and cost.
  • An object of one embodiment of the present invention is to provide a secondary battery in which the decrease in charge/discharge capacity during charge/discharge cycles is suppressed.
  • an object of the present invention is to provide a secondary battery that has a large charge/discharge capacity and is safe or highly reliable.
  • an object of the present invention is to provide a positive electrode active material or composite oxide that can be used in a lithium ion secondary battery and in which the decrease in discharge capacity during charge/discharge cycles is suppressed.
  • an object of the present invention is to provide a positive electrode active material or composite oxide whose crystal structure is not easily destroyed even after repeated charge/discharge.
  • an object of the present invention is to provide a positive electrode active material or composite oxide that has a large charge/discharge capacity.
  • Another object of one embodiment of the present invention is to provide a positive electrode active material, a composite oxide, a power storage device, or a manufacturing method thereof.
  • Another aspect of the present invention is to provide a lithium-ion battery that has an electrolyte containing a new organic solvent and a new positive electrode active material, enabling charging and discharging over a wide temperature range, including temperatures from below freezing to high temperatures.
  • One aspect of the present invention is a lithium ion secondary battery comprising a positive electrode having a positive electrode active material and an electrolyte, the positive electrode active material having lithium cobalt oxide containing magnesium, the magnesium concentration in the surface layer of the positive electrode active material being higher than the magnesium concentration inside the positive electrode active material, and the electrolyte containing a fluorinated cyclic carbonate and a fluorinated chain carbonate.
  • the positive electrode active material is lithium cobalt oxide that further contains aluminum, nickel, and fluorine.
  • the impedance value at a frequency of 1 kHz satisfies the requirement of less than 90 m ⁇ .
  • no additives are mixed into the organic solvent to form a coating (Solid Electrolyte Interface: SEI film) at the interface between the electrode (active material layer) and the electrolyte.
  • SEI film Solid Electrolyte Interface
  • the electrolyte used in the battery of one aspect of the present invention does not contain VC.
  • the positive electrode active material lithium cobalt oxide
  • the positive electrode active material refers to a compound containing a transition metal and oxygen that can insert and remove carrier ions.
  • Compounds containing oxygen are sometimes called oxides or composite oxides.
  • Lithium ions are typically used as carrier ions, but sodium ions or magnesium ions may also be used.
  • Carbonates and hydroxyl groups adsorbed after the preparation of the positive electrode active material are not included in the positive electrode active material.
  • electrolytes, organic solvents, binders, conductive materials, or compounds derived from these that are attached to the positive electrode active material are also not included in the positive electrode active material.
  • low freezing refers to 0°C or below
  • high temperature refers to 25°C or above
  • room temperature refers to temperatures higher than 0°C and lower than 25°C.
  • a temperature range including temperatures higher than 0°C and high temperatures includes the room temperature.
  • particles as used to describe active material particles and the like is not limited to referring to only spherical shapes (cross-sectional shape being circular).
  • particles may have cross-sectional shapes such as elliptical and asymmetric shapes, and further, the individual particles do not need to be uniform and may be irregular in shape.
  • non-aqueous electrolyte refers to an organic solvent that exhibits carrier ion conductivity, and generally refers to a liquid electrolyte, but is not limited to a liquid electrolyte in the present invention. Therefore, in this specification, the concept of a non-aqueous electrolyte is described as "electrolyte".
  • the electrolyte which is one embodiment of the present invention, is not limited in its state, and includes electrolytes whose viscosity has been increased from a liquid state as a result of adjusting the viscosity, for example.
  • the electrolyte also includes a solid state or a semi-solid state.
  • a semi-solid state refers to an intermediate state between a liquid state and a solid state.
  • Specific examples of semi-solid states include flexible solid states, and typically include gel-like electrolytes.
  • Semi-solid electrolytes are generally referred to as semi-solid electrolytes, and the electrolyte, which is one embodiment of the present invention, also includes a semi-solid electrolyte.
  • the above-mentioned liquid, solid, or semi-solid state, or viscosity, is confirmed when the lithium ion battery is placed at 25°C.
  • viscosity the value that indicates the magnitude of viscosity
  • appropriate viscosity means that the viscosity is appropriate for a lithium-ion battery.
  • segregation of an element refers to a state in which an element (e.g., A) is distributed unevenly in a solid composed of multiple elements (e.g., A, B, C).
  • the distribution of a certain element refers to the spread of locations where the element is continuously present when the element is detected in a range that is not noise using any analytical method.
  • the continuous change in concentration of the element is sometimes called a concentration gradient.
  • the maximum value in the distribution is sometimes called a peak.
  • identifying a peak a distribution limited to a certain region can be targeted.
  • the above-mentioned distribution is not limited to a normal distribution. When it corresponds to a normal distribution, the half-width of the distribution can also be determined.
  • uneven distribution refers to the concentration of an element in one area being different from that in other areas. It is synonymous with bias, or the presence of a mixture of areas of high concentration and areas of low concentration. Uneven distribution through solid solution is called segregation.
  • One aspect of the present invention enables charging and discharging over a wide temperature range, including from freezing to high temperatures.
  • one aspect of the present invention makes it possible to suppress deterioration of secondary batteries and improve their reliability.
  • the aging process to form a coating on the positive electrode active material is no longer necessary.
  • the aging process is sometimes called initial charge/discharge or conditioning.
  • FIGS. 1A and 1B are diagrams illustrating a lithium ion battery according to one embodiment of the present invention.
  • 2A to 2C illustrate a method for manufacturing a positive electrode active material of one embodiment of the present invention.
  • 3A to 3F illustrate a positive electrode active material of one embodiment of the present invention.
  • FIG. 4 illustrates a crystal structure of a positive electrode active material of one embodiment of the present invention.
  • FIG. 5 is a diagram illustrating the crystal structure of the positive electrode active material.
  • FIG. 6 is a diagram illustrating the diffraction peaks of the positive electrode active material.
  • FIG. 7 is a diagram illustrating the diffraction peaks of the positive electrode active material.
  • 8A and 8B are diagrams illustrating the diffraction peaks of the positive electrode active material.
  • 9A to 9D illustrate a positive electrode of one embodiment of the present invention.
  • 10A and 10B are diagrams illustrating a lithium-ion battery of one embodiment of the present invention.
  • 11A to 11C illustrate a lithium-ion battery of one embodiment of the present invention.
  • 12A to 12D are diagrams illustrating a lithium-ion battery and a power storage system of one embodiment of the present invention.
  • 13A to 13C are diagrams illustrating a lithium-ion battery of one embodiment of the present invention.
  • 14A to 14C illustrate a lithium-ion battery of one embodiment of the present invention.
  • 15A to 15C are diagrams illustrating an electric vehicle according to one embodiment of the present invention.
  • 16A to 16D are diagrams illustrating a transportation vehicle according to one embodiment of the present invention.
  • FIG. 17A to 17C are diagrams illustrating a two-wheeled vehicle etc. according to one embodiment of the present invention.
  • 18A to 18D are diagrams illustrating electronic devices and the like according to one embodiment of the present invention.
  • 19A to 19D are diagrams showing an example of space equipment.
  • FIG. 20A shows the cycle characteristics of Sample 1 having the electrolyte and the positive electrode active material of one embodiment of the present invention at 25° C. and an end voltage of 4.7 V.
  • FIG. 20B shows the cycle characteristics of Sample 1 having the electrolyte and the positive electrode active material of one embodiment of the present invention at 45° C. and an end voltage of 4.7 V.
  • FIG. 21 shows the cycle characteristics of Sample 1 having an end voltage of 4.8 V and including the electrolyte and positive electrode active material of one embodiment of the present invention.
  • FIG. 22 is a graph showing the charge/discharge characteristics of Sample 1.
  • FIG. 23A is a graph of Sample 1 with the capacity on the vertical axis and the number of cycles on the horizontal axis
  • FIG. 23B is a graph of Sample 1 with the charge/discharge efficiency on the vertical axis and the number of cycles on the horizontal axis.
  • 24A and 24B are diagrams illustrating AC impedance measurement.
  • 25A to 25C are diagrams showing the results of AC impedance measurement of sample 1_P.
  • a lithium ion battery according to one embodiment of the present invention has an electrolyte that allows charging and discharging in a wide temperature range including at least below freezing and even up to high temperatures.
  • the lithium ion battery has a negative electrode, a positive electrode, a separator between the negative electrode and the positive electrode, and an exterior body that covers the periphery of the negative electrode and the positive electrode.
  • the battery is called a laminated lithium ion battery, a coin cell lithium ion battery, or a cylindrical lithium ion battery, but the present invention is not limited to the form of the exterior body.
  • the separator can be omitted when the electrolyte is solid or semi-solid.
  • FIG. 1A illustrates an example of the configuration of a lithium ion battery 100.
  • the lithium ion battery 100 has a negative electrode 106, a separator 108, and a positive electrode 107.
  • the electrolyte 109 is liquid, and the electrolyte 109 is present throughout the negative electrode 106, the separator 108, and the positive electrode 107.
  • the electrolyte 109 is not limited to being liquid.
  • the negative electrode 106 has a negative electrode current collector 101 and a negative electrode active material layer 102.
  • the negative electrode active material layer 102 has at least an active material, and may have a conductive material and/or a binder.
  • a known material can be used for the negative electrode active material, and details will be described later.
  • the positive electrode 107 has a positive electrode current collector 105 and a positive electrode active material layer 104.
  • the positive electrode active material layer 104 has at least an active material, and may have a conductive material and/or a binder.
  • a known material may be used for the positive electrode active material, but when a positive electrode active material of one embodiment of the present invention is applied, it is possible to withstand high voltage charging and increase the discharge capacity of the lithium ion battery.
  • the positive electrode active material of one embodiment of the present invention will be described later.
  • the conductive material functions to assist the current path between active materials and/or between the active material and the current collector. Any known material can be used as the conductive material, and details will be described later.
  • the binder is also called a binding agent, and functions to assist the adhesion between active materials and/or between the active material and the current collector. Any known material can be used as the binder, and details will be described later.
  • FIG. 1B illustrates a lithium ion battery 100 that does not have the negative electrode active material layer 102, unlike FIG. 1A.
  • the material of the negative electrode current collector 101 can make the negative electrode active material layer 102 unnecessary.
  • the other configuration of the lithium ion battery 100 in FIG. 1B is similar to that of the lithium ion battery 100 in FIG. 1A, so a description thereof will be omitted.
  • a lithium-ion battery having excellent discharge characteristics and/or excellent charge characteristics over a wide temperature range, including temperatures from below freezing to high temperatures, can be realized.
  • the following description focuses on the configuration of the lithium-ion battery required for this purpose. Specifically, the description focuses on the positive electrode active material and electrolyte. Details of the configuration of the lithium-ion battery other than the positive electrode active material and electrolyte will be described in the third embodiment and onwards.
  • the positive electrode active material has a function of taking in and/or releasing lithium ions, which are carrier ions, during charging and discharging.
  • the positive electrode active material used as one embodiment of the present invention can be charged and discharged even at a high charging voltage (hereinafter also referred to as "high charging voltage”) in a wide temperature range from below freezing to high temperatures, and can be made of a material that is less likely to deteriorate (or has a small increase in resistance) during charging and discharging.
  • the “charging voltage” is expressed based on the potential of lithium metal.
  • the "high charging voltage” refers to a charging voltage of, for example, 4.5 V or more, preferably 4.6 V or more, and more preferably 4.65 V or more.
  • the positive electrode active material is not limited to one type, and two or more materials with different median diameters (D50) may be mixed, or two or more materials with different compositions may be mixed, as long as the materials exhibit little deterioration during charging and discharging even at high charging voltages over a wide temperature range, including from below freezing to high temperatures.
  • “different compositions” includes cases where the composition of elements contained in the materials is different, as well as cases where the composition of elements contained in the materials is the same but the ratio of the elements contained is different.
  • a “high charging voltage” is defined as 4.5 V or more based on the potential when the negative electrode is lithium metal, but when the potential when the negative electrode is a carbon material (e.g., graphite) is used as the reference, a “high charging voltage” is 4.4 V or more.
  • a charging voltage of 4.5 V or more is called a high charging voltage
  • a charging voltage of 4.4 V or more is called a high charging voltage.
  • the temperature during charging or discharging described in this specification refers to the temperature of the environment in which the lithium-ion battery is placed (hereinafter, sometimes referred to as "environmental temperature" in this specification).
  • environment temperature the temperature of the thermostatic bath.
  • measurement can be started after a sufficient time (e.g., one hour or more) has elapsed until the test cell reaches the same temperature as the thermostatic bath, but measurement of battery characteristics is not necessarily limited to this method.
  • Electrolyte As the electrolyte used in one embodiment of the present invention, a material having excellent lithium ion conductivity in a wide temperature range including from below freezing to high temperatures can be used.
  • the electrolyte has an organic solvent, but the organic solvent of the electrolyte according to one embodiment of the present invention is not limited to being liquid at 25°C, and may be solid at 25°C or semi-solid at room temperature. It is preferable that the organic solvent of the electrolyte according to one embodiment of the present invention is liquid over a wide temperature range, including temperatures from below freezing to high temperatures, but is not limited to this.
  • the organic solvent may be liquid, solid, or semi-solid over a wide temperature range, including temperatures from below freezing to high temperatures.
  • the organic solvent described in this embodiment may contain a fluorinated cyclic carbonate (sometimes referred to as a fluorinated cyclic carbonate) or a fluorinated chain carbonate (sometimes referred to as a fluorinated chain carbonate). Furthermore, the organic solvent preferably contains both a fluorinated cyclic carbonate and a fluorinated chain carbonate. Both the fluorinated cyclic carbonate and the fluorinated chain carbonate have a substituent that exhibits electron-withdrawing properties, and have a lower solvation energy of lithium ions than an organic compound that does not have a substituent that exhibits electron-withdrawing properties. Therefore, both the fluorinated cyclic carbonate and the fluorinated chain carbonate are suitable as organic solvents.
  • Fluoroethylene carbonate fluorinated ethylene carbonate, fluoroethylene carbonate, FEC, F1EC), difluoroethylene carbonate (DFEC, F2EC), trifluoroethylene carbonate (F3EC), tetrafluoroethylene carbonate (F4EC), etc.
  • DFEC has isomers such as cis-4,5 and trans-4,5. All of the fluorinated cyclic carbonates have electron-withdrawing substituents, so they are considered to have low solvation energy for lithium ions.
  • the following structural formula (H10) is the structural formula of FEC.
  • the electron-withdrawing substituent is an F group.
  • Methyl 3,3,3-trifluoropropionate is an example of a fluorinated chain carbonate.
  • the following structural formula (H22) is the structural formula of methyl 3,3,3-trifluoropropionate.
  • the abbreviation for methyl 3,3,3-trifluoropropionate is "MTFP".
  • MTFP the electron-withdrawing substituent is a CF3 group.
  • An example of a fluorinated chain carbonate is trifluoromethyl 3,3,3-trifluoropropionate.
  • the following structural formula (H23) is the structural formula of trifluoromethyl 3,3,3-trifluoropropionate.
  • the electron-withdrawing substituent is a CF3 group.
  • fluorinated chain carbonate is trifluoromethyl propionate.
  • the following structural formula (H24) is the structural formula of trifluoromethyl propionate.
  • the electron-withdrawing substituent is a CF3 group.
  • Methyl 2,2-difluoropropionate is an example of a fluorinated chain carbonate.
  • the following structural formula (H25) is the structural formula of methyl 2,2-difluoropropionate.
  • the electron-withdrawing substituent is a CF2 group.
  • the organic solvent of the electrolyte which is one aspect of the present invention, may contain two or more selected from the above-mentioned fluorinated cyclic carbonates and fluorinated chain carbonates.
  • the organic solvent described in this embodiment may contain FEC and MTFP. The reason for this will be explained below.
  • FEC is a cyclic carbonate and has a high relative dielectric constant, so when used in an organic solvent, it has the effect of promoting the dissociation of lithium salts. Since FEC has a smaller solvation energy than ethylene carbonate (abbreviated as "EC"), which does not have a substituent that exhibits electron-withdrawing properties, it can be said that the bond between the lithium ion and the solvent is easily separated. Furthermore, since FEC has a deep HOMO, if the HOMO is deep, it is less likely to be oxidized and the oxidation resistance is improved.
  • the organic solvent specifically described as one embodiment of the present invention further includes not only FEC but also MTFP.
  • MTFP is a chain carbonate and has the effect of reducing or maintaining the viscosity of the entire electrolyte.
  • MTFP also has a smaller solvation energy than methyl propionate (abbreviated as "MP"), which does not have a substituent that exhibits electron-withdrawing properties, so the bond between the lithium ion and the solvent is easily separated.
  • MP methyl propionate
  • FEC and MTFP having such physical properties by mixing them in a volume ratio of x:100-x (where 5 ⁇ x ⁇ 30, preferably 10 ⁇ x ⁇ 20), with the total amount of these two organic solvents being 100%. It is preferable to mix the organic solvents so that MTFP is greater than FEC.
  • the above volume ratio may be the volume ratio measured before mixing the organic solvents, and the outside air when mixing the organic solvents may be room temperature (typically 25° C.).
  • An organic solvent mixed with FEC and MTFP is preferable because it exhibits a viscosity that allows it to operate as a lithium ion battery and maintains an appropriate viscosity over a wide temperature range, including from below freezing to high temperatures.
  • FEC has been described above as a representative example, but any of the organic compounds described as fluorinated cyclic carbonates have the effect of promoting dissociation of lithium salts, have small solvation energy so that the bonds between lithium ions and the solvent are easily separated, and have high viscosity, making them difficult to use below freezing when used alone.
  • MTFP has been described above as a representative example, but any of the organic compounds described as fluorinated chain carbonates have the effect of reducing or maintaining the viscosity of the electrolyte.
  • the organic solvent which is one aspect of the present invention, contains a fluorinated cyclic carbonate and a fluorinated chain carbonate, it is possible to provide a lithium ion battery that can be charged and discharged over a wide temperature range, including at least below freezing.
  • the organic solvent described above is preferably highly purified with a low content of particulate dust or molecules other than the constituent molecules of the organic solvent (hereinafter simply referred to as "impurities", including oxygen ( O2 ), water ( H2O ) or moisture).
  • impurities including oxygen ( O2 ), water ( H2O ) or moisture.
  • the amount of the impurities contained in the organic solvent is 100 ppm or less, preferably 50 ppm or less, and more preferably less than 10 ppm.
  • the organic solvent In order to reduce the amount of impurities contained in the organic solvent to less than 10 ppm, it is preferable to heat the organic solvent under reduced pressure before use in a secondary battery to remove the above-mentioned impurities inside.
  • the secondary battery when using the organic solvent in a secondary battery, the secondary battery is manufactured by injecting the organic solvent in a dry room where moisture has been sufficiently reduced.
  • moisture can be detected by Karl Fischer titration, and moisture with different binding strengths (e.g., crystal water, combined water, or attached water) can be quantified by changing the heating conditions. For example, if the heating conditions are 120°C and 30 minutes, moisture generated around 100°C can be mainly detected.
  • the unit ppm for the amount of impurities contained in organic solvents refers to mass fraction, i.e. ppm (mass/mass).
  • lithium salt dissolved in the organic solvent examples include LiPF6 , LiClO4 , LiAsF6 , LiBF4 , LiAlCl4 , LiSCN, LiBr, LiI, Li2SO4 , Li2B10Cl10 , Li2B12Cl12, LiCF3SO3 , LiC4F9SO3 , LiC( CF3SO2 ) 3 , LiC ( C2F5SO2 ) 3 , LiN ( CF3SO2 ) 2 , LiN ( C4F9SO2 ) ( CF3SO2 ) , LiN ( C2F5SO2 ) 2 .
  • lithium bis(oxalato)borate LiBOB
  • LiBOB lithium bis(oxalato)borate
  • the lithium salt is one of the components of the electrolyte of one embodiment of the present invention, but is not necessarily included.
  • the lithium-ion battery of one embodiment of the present invention contains at least the above-mentioned positive electrode active material and an electrolyte, thereby maintaining a state in which there is no or almost no coating on the surface of the positive electrode active material, and realizing a lithium-ion battery that can be charged and discharged over a wide temperature range, including from below freezing to high temperatures.
  • the positive electrode active material that can be used in the lithium ion battery of one aspect of the present invention can be any material that is less prone to deterioration due to charging and discharging at a high charging voltage. Therefore, the positive electrode active material that can be used in the lithium ion battery disclosed in this specification and the like does not need to be interpreted as being limited to the specific materials described in this embodiment and the like, and materials that are known at the time of filing this application as being less prone to deterioration due to charging and discharging even at high charging voltages (e.g., 4.5 V or higher) can also be used.
  • high charging voltages e.g., 4.5 V or higher
  • a method for producing a positive electrode active material that can be used as one aspect of the present invention is described below.
  • a positive electrode active material is produced using a solid-phase method
  • a positive electrode active material produced using a co-precipitation method or a hydrothermal method other than the solid-phase method can also be applied to the lithium-ion battery of the present invention.
  • the flow used to explain the production method in this embodiment shows the order of elements connected by lines, and does not show the order of elements not connected by lines.
  • a lithium source (Li source) and a transition metal M source (M source) are prepared as the starting materials of lithium and transition metal M, respectively.
  • 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.
  • the transition metal M may be, for example, one or more of manganese, cobalt, and nickel.
  • LCO lithium cobalt oxide
  • NCM nickel-cobalt-manganese composite oxide
  • Aluminum may also be used in addition to the transition metal M.
  • the transition metal M source it is preferable to use a compound having the transition metal M.
  • an oxide of a metal exemplified as the transition metal M or a hydroxide of the metal exemplified above can be used.
  • a cobalt source cobalt oxide, cobalt hydroxide, etc. can be used.
  • a manganese source manganese oxide, manganese hydroxide, etc. can be used.
  • nickel source nickel oxide, nickel hydroxide, etc.
  • aluminum source aluminum oxide, aluminum hydroxide, etc. can be used.
  • step S12 the lithium source and the cobalt source are pulverized and mixed to prepare a mixed material.
  • the pulverization and mixing can be performed in a dry or wet manner.
  • the wet method is preferable because it can be crushed into smaller pieces.
  • a solvent is prepared.
  • ketones such as acetone, alcohols such as ethanol and isopropanol, ether, dioxane, acetonitrile, N-methyl-2-pyrrolidone (NMP), etc. can be used. It is more preferable to use an aprotic solvent that is less likely to react with lithium.
  • dehydrated acetone with a purity of 99.5% or more is used. It is preferable to mix the lithium source and the cobalt source with dehydrated acetone with a purity of 99.5% or more, in which the moisture content is suppressed to 10 ppm or less, and then pulverize and mix them.
  • dehydrated acetone with the above-mentioned purity it is possible to reduce impurities that may be mixed in.
  • a ball mill, a bead mill, or the like can be used as a means for grinding and mixing.
  • a ball mill aluminum oxide balls or zirconium oxide balls are used as grinding media. Zirconium oxide balls are preferred because they emit less impurities.
  • the peripheral speed is set to 100 mm/s or more and 2000 mm/s or less in order to suppress contamination from the media. In this embodiment, the peripheral speed is set to 838 mm/s (rotation speed 400 rpm, ball mill diameter 40 mm).
  • step S13 shown in FIG. 2A the mixed material is heated.
  • the heating is preferably performed at 800° C. or more and 1100° C. or less, more preferably at 900° C. or more and 1000° C. or less, and even more preferably at about 950° C. If the temperature is too low, the decomposition and melting of the Li source and M source may be insufficient. On the other hand, if the temperature is too high, lithium may sublime from the Li source, and/or the transition metal used as the M source may be excessively reduced. If the heating time is too short, a composite oxide having lithium and the transition metal M is not synthesized, but if it is too long, the productivity decreases.
  • the heating time is preferably 1 hour or more and 100 hours or less, and more preferably 2 hours or more and 20 hours or less.
  • the temperature rise rate depends on the reaching temperature of the heating temperature, but is preferably 80° C./h or more and 250° C./h or less, more preferably 100° C./h or more and 250° C./h or less.
  • the heating atmosphere is preferably an atmosphere with little water.
  • the atmosphere with little water can be defined by the dew point.
  • the heating atmosphere is an atmosphere with a dew point of -50°C or less, more preferably an atmosphere with a dew point of -80°C or less.
  • the heating atmosphere is preferably an atmosphere containing oxygen, such as dry air.
  • oxygen is continuously introduced into the reaction chamber.
  • the flow rate of oxygen is preferably 5 L/min or more and 15 L/min or less. The state in which oxygen is continuously introduced into the reaction chamber and flows through the reaction chamber is called "flow".
  • the heating atmosphere can be made to contain oxygen by, for example, reducing the pressure in the reaction chamber before introducing oxygen, and then controlling the oxygen so that it does not enter or leave the reaction chamber. This is called "purging."
  • the reaction chamber can be reduced in pressure to -970 hPa, and then oxygen can be introduced to 50 hPa, and the oxygen can then stop entering or leaving the chamber. This state is sometimes referred to as filling the reaction chamber with oxygen.
  • the material can be allowed to cool naturally, but it is preferable that the time required for the temperature to drop from the specified temperature to room temperature is within a range of 10 to 50 hours, for example, 80°C/h to 250°C/h, and more preferably 180°C/h to 210°C/h.
  • cooling to room temperature is not necessarily required, as long as the material is cooled to a temperature acceptable for the next step.
  • the heating in this process may be performed using a rotary kiln or a roller hearth kiln. Heating using a rotary kiln can be performed while stirring, whether it is a continuous or batch type.
  • the crucible used for heating is preferably an aluminum oxide crucible.
  • An aluminum oxide crucible is a material that does not easily release impurities. In this embodiment, an aluminum oxide crucible with a purity of 99.9% is used. It is preferable to place a lid on the crucible when heating. This can prevent the material from volatilizing or sublimating. Placing a lid on the crucible means that it is possible to prevent the material from volatilizing or sublimating from the time the temperature is increased to the time the temperature is decreased in this step, and it is not necessary to seal the crucible with a lid. For example, as described above, by filling the reaction chamber with oxygen, it is possible to carry out this step without sealing the crucible.
  • a used crucible refers to one that has undergone the process of putting lithium, transition metal M, and/or materials containing additive elements into it and heating it two or less times.
  • a used crucible refers to one that has undergone the process of putting lithium, transition metal M, and/or materials containing additive elements into it and heating it three or more times. This is because when a new crucible is used, there is a risk that some of the materials, including lithium fluoride, may be absorbed, diffused, moved, and/or attached to the sheath during heating.
  • the material After heating, the material may be crushed and sieved as necessary. When recovering the heated material, it may be transferred from the crucible to a mortar and then recovered.
  • the mortar is preferably made of aluminum oxide or zirconium oxide.
  • Aluminum oxide mortars are made of a material that does not easily release impurities. Specifically, an aluminum oxide mortar with a purity of 90% or more, preferably 99% or more, is used. Note that the same heating conditions as those in step S13 can be applied to the heating steps described below other than step S13.
  • a composite oxide ( LiMO2 ) containing lithium and a transition metal M can be obtained in step S14.
  • the composite oxide is produced by a solid phase method, but the composite oxide may also be produced by a coprecipitation method.
  • the composite oxide may also be produced by a hydrothermal method.
  • step S15 shown in FIG. 2A the composite oxide is heated. Since this is the first heating of the composite oxide, the heating in step S15 may be called initial heating. Or, since it is heating before step S20 described below, it may be called preheating or pretreatment.
  • the crucible and/or lid used in this step are the same as those used in step S13. Although the following effects are expected from the initial heating, the initial heating is not essential to obtain the positive electrode active material which is one aspect of the present invention.
  • the initial heating may cause lithium to be released from part of the composite oxide. It is also expected to have the effect of increasing the crystallinity of the composite oxide.
  • the Li source and/or the M source prepared in step S11, etc. may contain impurities, but the initial heating can reduce the impurities from the composite oxide.
  • the initial heating has the effect of smoothing the surface of the complex oxide.
  • a smooth surface means that there are few irregularities, the surface of the complex oxide is generally rounded, and the corners are also rounded. A surface with little foreign matter adhering to it is sometimes called smooth.
  • the heating conditions can be selected from those described in step S13.
  • the heating temperature in this step is preferably lower than the temperature in step S13 in order to maintain the crystal structure of the complex oxide.
  • the heating time in this step is, for example, 2 to 20 hours at a temperature of 700°C to 1000°C in order to maintain the crystal structure of the complex oxide.
  • the effect of increasing the crystallinity of the complex oxide also includes, for example, the effect of alleviating distortion resulting from the difference in shrinkage caused by heating the complex oxide, and the effect of alleviating the misalignment resulting from the difference in shrinkage.
  • the heating in step S13 may cause a temperature difference between the surface and the inside of the composite oxide.
  • the temperature difference may induce a contraction difference. It is also believed that the temperature difference causes the contraction difference because the fluidity of the surface and the inside is different.
  • the energy related to the contraction difference gives the composite oxide a difference in internal stress, which causes distortion.
  • the above energy is sometimes called strain energy.
  • the internal stress is removed by the initial heating in step S15, or in other words, the strain energy is thought to be reduced by the initial heating in step S15.
  • the strain energy is thought to be reduced by the initial heating in step S15.
  • the surface of the composite oxide may become smooth after step S15.
  • Step S15 may be called tempering or annealing of the composite oxide.
  • the shrinkage difference may cause microscopic misalignment in the composite oxide, for example misalignment in the crystal plane.
  • this step it is preferable to carry out this step. By going through this step, it is possible to reduce the misalignment in the composite oxide. If the misalignment is made uniform, the surface of the composite oxide may become smooth. This is also referred to as the alignment of crystal grains. In other words, it is believed that by going through step S15, the misalignment of the crystals etc. that has occurred in the composite oxide is alleviated, and the surface of the composite oxide becomes smooth.
  • a smooth surface of a complex oxide can be said to have a surface roughness of at least 10 nm or less when the surface irregularity information of a cross section of the complex oxide is quantified from measurement data.
  • a cross section is, for example, a cross section obtained when observing with a scanning transmission electron microscope (referred to as STEM).
  • step S14 a composite oxide containing lithium and a transition metal M that has been synthesized in advance can also be used. In this case, steps S11 to S13 can be omitted.
  • step S15 By carrying out step S15 on a composite oxide that has been synthesized in advance, a composite oxide with a smooth surface can be obtained.
  • the initial heating reduces the amount of lithium in the composite oxide. This reduction in lithium may make it easier for the additive elements, which will be described in the next step S20_1, to enter the composite oxide.
  • the additive elements can be added evenly, so it is preferable to add the additive elements after the initial heating. The step of adding the additive elements will be described with reference to FIG. 2B.
  • step S20_1 ⁇ Step S20_1> and ⁇ Step S21_1>
  • the details of step S20_1 shown in Fig. 2A are shown in Fig. 2B.
  • step S21_1 in Fig. 2B an additive element A1 source (A1 source) to be added to the composite oxide is prepared.
  • a lithium source may be prepared together with the additive element A1 source.
  • the additive element A1 can be one or more selected from nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic.
  • the source of the additive element A1 can be called a magnesium source (Mg source).
  • Mg source magnesium fluoride, magnesium oxide, magnesium hydroxide, magnesium carbonate, or the like can be used.
  • multiple magnesium sources described above may be used.
  • the source of the additive element A1 can be called a fluorine source (F source).
  • F source for example, lithium fluoride, magnesium fluoride, aluminum fluoride, titanium fluoride, cobalt fluoride, nickel fluoride, zirconium fluoride, vanadium fluoride, manganese fluoride, iron fluoride, chromium fluoride, niobium fluoride, zinc fluoride, calcium fluoride, sodium fluoride, potassium fluoride, barium fluoride, cerium fluoride, lanthanum fluoride, or sodium aluminum hexafluoride can be used.
  • lithium fluoride is preferable because it has a relatively low melting point of 848°C and is easily melted in the heating process described below.
  • FIG. 2B shows an example in which a Mg source and a F source are used as the additive element A1 source.
  • Magnesium fluoride can be used as both a fluorine source and a magnesium source.
  • Lithium fluoride can be used as a lithium source.
  • Other lithium sources that can be used in step S21_1 include lithium carbonate.
  • lithium fluoride is prepared as the fluorine source
  • magnesium fluoride is prepared as the fluorine source and magnesium source.
  • the amount of lithium fluoride is large, there is a concern that the lithium becomes excessive and the cycle characteristics deteriorate.
  • “in the vicinity” refers to a value that is greater than 0.9 times and less than 1.1 times the value.
  • the amount of magnesium added is preferably 0.1 atomic % or more and 3 atomic % or less relative to the number of Co atoms in LiMO 2 , typically LiCoO 2 , in step S14, more preferably 0.5 atomic % or more and 2 atomic % or less, and even more preferably 0.5 atomic % or more and 1 atomic % or less. If the amount of magnesium added is 0.1 atomic % or less, the initial discharge capacity is high, but the discharge capacity may drop rapidly by repeating high voltage charging.
  • both the initial discharge characteristic and the charge-discharge cycle characteristic are good even if the high voltage charging is repeated.
  • the amount of magnesium added exceeds 3 atomic %, the initial discharge capacity is low, and the charge-discharge cycle characteristic also tends to gradually deteriorate.
  • Step S22_1> 2B the magnesium source and the fluorine source are mixed while being pulverized.
  • This step can be performed under the pulverization conditions and the mixing conditions selected from those described in step S12.
  • a heating step may be performed after step S22_1.
  • the heating step can be performed under heating conditions selected from those described in step S13.
  • the heating time is preferably 2 hours or more, and the heating temperature is preferably 800°C or more and 1100°C or less.
  • step S23_1 shown in Fig. 2B the material crushed and mixed above can be collected to obtain an additive element A1 source (A1 source).
  • A1 source the additive element A1 source shown in step S23_1 may have multiple raw materials such as an Mg source and an F source, and in this case, the A1 source can be called a mixture.
  • the composite oxide and a source of an additive element A1 are mixed.
  • the mixing in step S31 is preferably performed under milder conditions than the grinding and mixing conditions in step S12 in order not to destroy the composite oxide.
  • milder conditions For example, it is preferable to use conditions with a lower rotation speed or shorter time than in step S12.
  • a dry method is more preferable than a wet method because it has milder conditions.
  • the above mixing is preferably carried out in an atmosphere with a dew point of -100°C or higher and -10°C or lower.
  • the mixing can be carried out in a dry room.
  • the atmosphere of the dry room is dry air.
  • step S32 of Fig. 2A the mixed materials are collected to obtain a mixture 903.
  • the mixture 903 may be crushed to break up the aggregated state.
  • the mixture 903 may be sieved to break up the aggregated state. Sieving may be performed after crushing, sieving may be performed while crushing, or only sieving may be performed instead of crushing.
  • step S11 that is, in the stage of the starting material of the composite oxide, a magnesium source, a fluorine source, etc. can be prepared together with a Li source and an M source, and the process can proceed to step S12. Then, LiMO2 to which magnesium and fluorine have been added can be obtained by heating in step S13. In this case, it is not necessary to separate the steps from step S11 to step S14 from the steps from step S21_1 to step S23_1. It can be said that this is a simple and highly productive method.
  • a composite oxide to which magnesium and fluorine have been added in advance may be used. If a composite oxide to which magnesium and fluorine have been added is used, steps S11 to S32 and step S20_1 can be omitted. This is a simple and highly productive method.
  • a magnesium source and a fluorine source may be further added to the composite oxide to which magnesium and fluorine have already been added according to step S20_1.
  • a nickel source and an aluminum source may be added instead of or in addition to the magnesium source and the fluorine source.
  • Step S33> 2A the mixture 903 is heated.
  • the heating conditions can be selected from those described in step S13.
  • the heating time is preferably 2 hours or more.
  • the lower limit of the heating temperature in step S33 must be equal to or higher than the temperature at which the reaction between the composite oxide (LiMO 2 ) and the additive element A1 source proceeds.
  • the temperature at which the reaction proceeds is a temperature at which the elements of the composite oxide and the additive element A1 source can diffuse into each other, and may be lower than the melting temperatures of these materials.
  • An oxide is used as an example for explanation, and it is known that solid-phase diffusion occurs from the Tammann temperature T d (a temperature calculated as 0.757 times the melting point T m of the oxide).
  • the heating temperature in step S33 is set to 500° C. or higher.
  • the reaction proceeds more easily if the temperature is equal to or higher than the temperature at which at least a part of the mixture 903 melts.
  • the eutectic point of LiF and MgF2 is around 742°C, so that the lower limit of the heating temperature in step S33 is preferably set to 742°C or higher.
  • a mixture 903 obtained by mixing LiCoO 2 :LiF:MgF 2 100:0.33:1 (molar ratio) shows an endothermic peak at about 830° C. in differential scanning calorimetry (DSC). Therefore, the lower limit of the heating temperature is more preferably 830° C. or higher.
  • the upper limit of the heating temperature is lower than the decomposition temperature of the composite oxide.
  • the decomposition temperature of the composite oxide For example, in the case of LiCoO2 , it is lower than 1130°C, which is the decomposition temperature.
  • the temperature is 1000°C or lower, more preferably 950°C or lower, and even more preferably 920°C or lower.
  • the heating temperature in step S33 is preferably 500°C or higher and lower than 1130°C, more preferably 500°C or higher and lower than 1000°C, even more preferably 500°C or higher and lower than 950°C, even more preferably 500°C or higher and lower than 920°C, and even more preferably 500°C or higher and lower than 900°C.
  • 742°C or higher and lower than 1130°C is preferred, more preferably 742°C or higher and lower than 1000°C, even more preferably 742°C or higher and lower than 950°C, even more preferably 742°C or higher and lower than 920°C, and even more preferably 742°C or higher and lower than 900°C.
  • 800°C or higher and lower than 1130°C is preferred, more preferably 800°C or higher and lower than 1000°C, even more preferably 800°C or higher and lower than 950°C, even more preferably 800°C or higher and lower than 920°C, and even more preferably 800°C or higher and lower than 900°C.
  • 830°C or more and less than 1130°C is preferable, 830°C or more and 1000°C or less is more preferable, 830°C or more and 950°C or less is even more preferable, 830°C or more and 920°C or less is even more preferable, and 830°C or more and 900°C or less is even more preferable.
  • the mixture 903 when the mixture 903 is heated, it is preferable to control the partial pressure of fluorine or fluoride resulting from a fluorine source or the like in the treatment chamber or the crucible to an appropriate range.
  • some materials for example, LiF, which is a fluorine source, may function as a flux. This function allows the heating temperature to be lowered to a temperature lower than the decomposition temperature of the complex oxide (LiMO 2 ), for example, to 742° C. or higher and 950° C. or lower, and the additive element A1 including magnesium can be distributed in the surface layer portion to manufacture a positive electrode active material with good characteristics.
  • LiF may sublime when heated, and since LiF has a lower specific gravity in a gaseous state than oxygen, it is conceivable that the amount of LiF in the mixture 903 may decrease. This weakens its function as a flux. Therefore, it is necessary to heat while suppressing the sublimation of LiF. Even if LiF is not used as the fluorine source, etc., Li on the LiMO2 surface may react with F of the fluorine source to produce LiF, which may then sublime. Therefore, even if a fluoride with a higher melting point than LiF is used, it is necessary to suppress sublimation in the same manner.
  • the heating in this step is preferably performed so that the mixture 903 does not stick to itself. If the mixture 903 sticks to itself during heating, the contact area with oxygen in the atmosphere decreases, and the route for the added element A1 (e.g., magnesium and/or fluorine) to diffuse is blocked, which may make it difficult for the added element A1 (e.g., magnesium and/or fluorine) to diffuse.
  • the added element A1 e.g., magnesium and/or fluorine
  • the additive element A1 e.g., fluorine
  • the additive element A1 e.g., fluorine
  • the mixture 903 does not stick to itself.
  • the heating time varies depending on conditions such as the heating temperature, the size of LiMO2 in step S14, and the composition.
  • the median diameter (D50) of LiMO2 is small, a lower temperature or a shorter time may be more preferable than when the median diameter (D50) is large.
  • the median diameter (D50) can be determined by a laser diffraction particle size distribution analyzer.
  • the heating temperature in step S33 is, for example, preferably 800° C. or more and 920° C. or less, and more preferably 850° C. or more and 920° C. or less.
  • the heating time in step S33 is, for example, more preferably 10 hours or more, and even more preferably 20 hours or more.
  • the median diameter (D50) is large, the volume of the complex oxide (LiMO 2 ) becomes large, and the internal stress is relaxed or removed in the bulk layer of the complex oxide, so that a heating time may be required. If the median diameter (D50) is large, it takes time for the additive element A1, including magnesium, to be uniformly distributed in the surface layer, so that the heating time may be long as described above.
  • the median diameter (D50) of lithium cobalt oxide may increase after heat treatment, it is preferable that the median diameter (D50) after heat treatment is 10 ⁇ m or more and 14 ⁇ m or less. In other words, it is preferable that the median diameter (D50) of the positive electrode active material is 10 ⁇ m or more and 14 ⁇ m or less.
  • the heating temperature in step S33 is preferably in the same range as the heating temperature when the median diameter (D50) is about 12 ⁇ m.
  • the heating time in step S33 can be shorter than the heating time when the median diameter (D50) is about 12 ⁇ m. For example, 1 hour or more and 10 hours or less are preferable, and 5 hours or more and 10 hours or less are more preferable.
  • the median diameter (D50) When the median diameter (D50) is small, the time during which the additive element A1, including magnesium, is distributed in the surface layer is shortened, so that the heating time can be shortened as described above.
  • the median diameter (D50) When the median diameter (D50) is small, the volume of the composite oxide (LiMO 2 ) is small, so that the time for tempering or annealing the bulk layer of the composite oxide is short.
  • the median diameter (D50) of lithium cobalt oxide may increase after heat treatment, it is preferable that the median diameter (D50) is 5 ⁇ m or more and 9 ⁇ m or less even after heat treatment. In other words, it is preferable that the median diameter (D50) of the positive electrode active material is 5 ⁇ m or more and 9 ⁇ m or less.
  • step S33 a step of further adding an additional element different from the additional element A1 described above may be provided. This step will be described with reference to FIG. 2C.
  • step S20_2 a source of an additive element A2 (A2 source) to be added to the composite oxide is prepared.
  • a lithium source may be prepared together with the additive element A2 source.
  • the additive element A2 may be one or more selected from nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic. It is preferable that the additive element A2 is at least an element that is not selected as the additive element A1, but it may contain an element selected as the additive element A1. Note that FIG. 2C shows an example in which a Ni source and an Al source are used as the source of the additive element A2.
  • nickel hydroxide is prepared as the nickel source
  • aluminum hydroxide is prepared as the aluminum source.
  • Nickel oxide or nickel carbonate can be used instead of nickel hydroxide.
  • Aluminum oxide or aluminum carbonate can be used instead of aluminum hydroxide.
  • step S22_2 shown in Fig. 2C the nickel source is mixed while being pulverized, and further the aluminum source is mixed while being pulverized.
  • This step can be carried out by selecting from the pulverization conditions and mixing conditions described in step S12. Note that this step can also be carried out by mixing the nickel source and the aluminum source while being pulverized after combining them as in step S22_1 in Fig. 2B.
  • a heating step can be performed after step S22_2.
  • the heating step can be performed under the heating conditions selected from those described in step S13.
  • Step S23_2 the material ground or mixed above can be recovered to obtain a source of the additional element A2 (A2 source).
  • step S34 shown in FIG. 2A the composite oxide heated in step S33 is mixed with the additive element A2 source (A2 source).
  • A2 source the additive element A2 source
  • a M 100: y (0.1 ⁇ y ⁇ 3)
  • a M 100: y (0.3 ⁇ y ⁇ 1).
  • the mixing conditions in step S34 can be selected from the mixing conditions described in step S31.
  • Step S35 of Fig. 2A the mixed materials are collected to obtain a mixture 904.
  • the mixture 904 can be crushed to break up any agglomerated materials.
  • the mixture 904 can also be sieved to further break up any agglomerated materials. Sieving can be performed after crushing, sieving can be performed while crushing, or only sieving can be performed instead of crushing.
  • Step S36> 2A the mixture 904 is heated.
  • the heating conditions can be selected from those described in step S33.
  • the heating time is preferably 2 hours or more.
  • the heating temperature in step S36 is preferably 500°C to 1130°C, more preferably 500°C to 1000°C, even more preferably 500°C to 950°C, and even more preferably 500°C to 900°C.
  • 742°C to 1130°C is preferred, more preferably 742°C to 1000°C, even more preferably 742°C to 950°C, and even more preferably 742°C to 900°C.
  • 800°C to 1100°C, 830°C to 1130°C is preferred, 830°C to 1000°C is preferred, more preferably 830°C to 950°C, and even more preferably 830°C to 900°C.
  • the heating in this process is preferably performed so that the mixture 904 does not stick to itself. If the mixture 904 sticks to itself during heating, the contact area with oxygen in the atmosphere decreases and the path for the added element A2 to diffuse is blocked, which may result in a poor distribution of the added element A2.
  • step S37 shown in FIG. 2A the heated material is recovered and crushed as necessary to obtain the positive electrode active material 10. At this time, it is preferable to further sieve the recovered positive electrode active material 10.
  • the positive electrode active material 10 of one embodiment of the present invention can be produced.
  • the positive electrode active material of one embodiment of the present invention has a smooth surface. The above is an example of a method for producing a positive electrode active material.
  • FIG. 3A shows a cross section of the positive electrode active material 10 in which the grain boundary 11 is clearly indicated by a dashed line, unlike FIG. 3A.
  • Both the positive electrode active material 10 shown in FIG. 3A and FIG. 3B have a surface layer portion 10a and an inside (the inside is referred to as a "bulk portion") 10b, and the boundary between them is shown by a dashed line. It is more preferable that the surface layer portion 10a covers 90% or more of the bulk portion 10b.
  • the dashed lines in FIG. 3A and FIG. 3B are examples, the dashed lines in FIG. 3B are examples, and the proportion of the surface layer portion that is covered is also an example.
  • the surface layer 10a does not have to cover the entire bulk portion 10b.
  • Figures 3A and 3B show a positive electrode active material 10 in which the surface layer 10a covers 50% or more of the outer periphery of the bulk portion 10b, specifically 65% to 75%.
  • the positive electrode active material 10 may have an area where the bulk portion 10b is exposed.
  • the grain boundary 11 shown in FIG. 3B refers to, for example, a portion where the positive electrode active material 10 is stuck together, a portion where the crystal orientation changes inside the positive electrode active material 10, that is, a portion where the repetition of bright and dark lines in the STEM image is discontinuous, a portion containing many crystal defects, or a portion where the crystal structure is disordered.
  • the crystal defect refers to a defect that can be observed in a cross-sectional TEM (transmission electron microscope) image, a cross-sectional STEM image, etc., and the defect can also be called a structure in which other elements have entered between the lattices, or a cavity, etc. In other words, the grain boundary 11 can be said to be one of the plane defects.
  • the vicinity of the grain boundary 11 refers to a region within 20 nm, preferably within 10 nm, of the grain boundary 11, and the vicinity of the grain boundary exists both inside and outside the particle. These can be distinguished by indicating the vicinity of the grain boundary inside the particle or the vicinity of the grain boundary outside the particle.
  • the positive electrode active material 10 has a composite oxide containing oxygen and a transition metal capable of inserting and removing lithium
  • the interface between the region where the transition metal M (e.g., Co, Ni, Mn, Fe, etc.) that is oxidized and reduced with the insertion and removal of lithium is present and the region where it is not present can be regarded as the "surface" of the positive electrode active material.
  • the region where no transition metal M is present may contain an added element. New surfaces created by slips, cracks, and/or cracks may also be regarded as the surface of the positive electrode active material.
  • the surface layer 10a is, for example, a region within 50 nm, more preferably within 35 nm, even more preferably within 20 nm, and most preferably within 10 nm from the surface toward the inside.
  • the surface layer may be referred to as the vicinity of the surface, the region near the surface, or the shell.
  • the region within 50 nm, more preferably within 35 nm, even more preferably within 20 nm, and most preferably within 10 nm from the surface toward the inside refers to the distance in the depth direction along a perpendicular or nearly perpendicular direction from the surface.
  • Perpendicular or nearly perpendicular to the surface refers to a direction that forms an angle of 80° or more and 100° or less with a tangent line at the surface.
  • the bulk portion 10b refers to a region deeper than the surface layer 10a.
  • the bulk portion 10b may be referred to as the inside, and may also be referred to as the core.
  • the bulk portion 10b may include the center of the positive electrode active material.
  • the region where lithium is inserted and removed may be referred to as the "surface". Therefore, the "surface” can be considered to be the region of the positive electrode active material 10 that is in contact with the electrolyte.
  • the surface of the positive electrode active material 10 includes the surface of the surface layer 10a, and in a region where the bulk portion 10b is exposed, the bulk portion 10b may be the surface.
  • the carbonate groups, hydroxyl groups, and the like that are chemically adsorbed after preparation of the positive electrode active material 10 are considered to be regions into which lithium cannot be inserted or removed, and these do not constitute the surface of the positive electrode active material 10.
  • the electrolyte, binder, conductive material, or compounds derived from these that are attached to the positive electrode active material 10 do not constitute the surface of the positive electrode active material 10.
  • the "surface" of the positive electrode active material 10 in a cross-sectional STEM (scanning transmission electron microscope) image or the like is the boundary between the area where an electron beam bond image is observed and the area where it is not observed, and can be the outermost part of the area where bright spots originating from the atomic nuclei of metal elements with atomic numbers larger than that of lithium are confirmed.
  • the surface in a cross-sectional STEM image or the like can also be determined in conjunction with the results of an analysis with higher spatial resolution, such as electron energy loss spectroscopy (EELS).
  • EELS electron energy loss spectroscopy
  • the positive electrode active material must have a transition metal capable of oxidation and reduction in order to maintain charge neutrality even when lithium ions are inserted and removed.
  • the positive electrode active material 10 mainly uses cobalt as the transition metal M responsible for the oxidation and reduction reaction, but in addition to cobalt, at least one or more selected from nickel and manganese can also be used. If the transition metal M contained in the positive electrode active material 10 is 75 atomic % or more, preferably 90 atomic % or more, and more preferably 95 atomic % or more, cobalt has many advantages, such as being relatively easy to synthesize and easy to handle, and having excellent cycle characteristics, and is therefore preferred.
  • the raw material may be cheaper than when there is a large amount of cobalt, and the discharge capacity per weight may be increased, which is preferable.
  • additive elements A contained in the positive electrode active material 10 are listed again, and it is preferable to use one or more selected from nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic.
  • the positive electrode active material 10 can be called lithium cobalt oxide to which the additive element A has been added.
  • the additive element A can further stabilize the crystal structure of the positive electrode active material 10.
  • Additive element A does not necessarily have to include one or more selected from nickel, cobalt, magnesium, calcium, chlorine, fluorine, aluminum, manganese, titanium, zirconium, yttrium, vanadium, iron, chromium, niobium, lanthanum, hafnium, zinc, silicon, sulfur, phosphorus, boron, and arsenic.
  • the positive electrode active material 10 does not substantially contain manganese as the additive element A, the above-mentioned advantages of being relatively easy to synthesize and easy to handle, and having excellent cycle characteristics, are even greater.
  • the weight of manganese contained in the positive electrode active material 10 is preferably, for example, 600 ppm or less, more preferably 100 ppm or less.
  • the weight of manganese can be analyzed, for example, using a glow discharge mass spectrometer (GD-MS).
  • ⁇ Crystal structure> The change in crystal structure accompanying the change in x in LixCoO 2 will be described by comparing a cathode active material 10 that can be used as one embodiment of the present invention with a conventional cathode active material using Figs. 4 to 8.
  • the crystal structure of the cathode active material 10 that can be used as one embodiment of the present invention is shown in Fig. 4, and the crystal structure of the conventional cathode active material is shown in Fig. 5.
  • the conventional cathode active material shown in Fig. 5 is lithium cobalt oxide (LiCoO 2 ) that does not have any added elements.
  • does not have any added elements refers to the case where the amount of added elements is below the lower limit of detection when measured using an analytical means, or when the amount of added elements is close to the lower limit of detection, the amount of added elements is within a range that does not affect the presence or absence of the action or effect.
  • this crystal structure lithium occupies an octahedral site, and three CoO 2 layers exist in a unit cell. Therefore, this crystal structure may be called an O3 type crystal structure.
  • the CoO 2 layer refers to a structure in which an octahedral structure in which oxygen is coordinated to cobalt six times is continuous on a plane in a state of edge sharing.
  • the CoO 2 layer may also be called a layer consisting of an octahedron of cobalt and oxygen.
  • R-3m (O3) is attached to the crystal structure when x in Li x CoO 2 is 1.
  • the crystal structure when x in Li x CoO 2 is 1 is the same as the crystal structure shown in FIG. 4, and is similarly denoted by R-3m(O3).
  • Layered rock-salt complex oxides have a high discharge capacity, two-dimensional lithium ion diffusion paths, and are suitable for lithium ion insertion/extraction reactions, making them excellent as positive electrode active materials for lithium ion batteries. Therefore, it is preferable that the bulk portion 10b, which accounts for the majority of the positive electrode active material 10, has a layered rock-salt crystal structure.
  • the crystal structure of the surface layer 10a of the positive electrode active material 10 that can be used as one embodiment of the present invention does not have to be a layered rock salt type.
  • the surface layer 10a preferably has a function of reinforcing the layered structure of the bulk portion 10b, which is made up of octahedra of cobalt and oxygen, so that it is not destroyed even if lithium is removed from the positive electrode active material 10 by charging.
  • the surface layer 10a functions as a barrier film for the positive electrode active material 10.
  • the surface layer 10a which is the outer periphery of the positive electrode active material 10, reinforces the positive electrode active material 10.
  • the reinforcement here means suppressing structural changes in the surface layer 10a and bulk portion 10b of the positive electrode active material 10, including oxygen desorption, and/or suppressing oxidative decomposition of the electrolyte on the surface of the positive electrode active material 10.
  • the surface layer 10a is the region where lithium ions are first desorbed during charging, and is the region where the lithium concentration is likely to be lower than that of the bulk portion 10b.
  • the surface layer 10a is likely to become unstable, and is the region where the crystal structure is likely to change, that is, deterioration is likely to begin.
  • the surface layer 10a can be sufficiently stabilized, the layered structure of the CoO 2 layer in the bulk portion 10b can be made less likely to break even when x in Li x CoO 2 is small, for example, when x is 0.24 or less. Furthermore, the displacement of the CoO 2 layer in the bulk portion 10b can be suppressed.
  • the surface layer 10a contains an additive element A, and more preferably contains a plurality of additive elements A. It is also preferable that the surface layer 10a has a higher concentration of one or more selected from the additive elements A than the bulk layer 10b. It is also preferable that the one or more selected from the additive elements A contained in the positive electrode active material 10 have a concentration gradient. It is also more preferable that the distribution of the positive electrode active material 10 differs depending on the additive element A. For example, it is more preferable that the depth from the surface of the concentration peak differs depending on the additive element A.
  • the concentration peak here refers to the maximum concentration value in the surface layer 10a or within 50 nm from the surface.
  • FIG. 3C and 3D show enlarged views of the vicinity of A-B in FIG. 3A.
  • FIG. 3C and 3D are cross-sectional views of the surface layer having the (001) plane (hereinafter, referred to as the (001) plane, and may also be referred to as the c-plane or basal plane), that is, cross-sectional views of the region oriented in (001).
  • the layered rock salt type crystal structure cations are arranged parallel to the (001) plane.
  • This can be said to be a structure in which the CoO 2 layer and the lithium layer are alternately stacked parallel to the (001) plane. Therefore, the diffusion path of the lithium ions exists parallel to the (001) plane. Since the CoO 2 layer is relatively stable, the (001) plane on which the CoO 2 layer exists on the surface is relatively stable, and the main diffusion path of the lithium ions during charging and discharging is not exposed to the (001) plane.
  • FIG. 3C shows such a (001) plane, and shows the distribution of magnesium and the like as an example of the additive element A.
  • the shading in FIG. 3C corresponds to the change in magnesium concentration. Since the CoO 2 layer is relatively stable on the (001) plane, the additive element A may not be detected.
  • FIG. 3C shows an example of the distribution of the additive element A, in which the additive element A is present at the highest concentration on or near the surface of the surface layer portion 10a, and the concentration of the additive element A decreases toward the bulk portion 10b. It can be said that there is a concentration peak of magnesium and the like at the position showing the highest concentration. The decrease in concentration may be referred to as a concentration gradient.
  • the additive element A that shows the distribution as shown in FIG. 3C on the (001) plane is referred to as the additive element X.
  • FIG. 3D shows the distribution of aluminum as another example of the additive element A.
  • the shading in FIG. 3D corresponds to the change in the concentration of aluminum. Since the CoO 2 layer is relatively stable on the (001) plane, the additive element A may not be detected.
  • FIG. 3D shows an example of the distribution of the additive element A, in which the additive element A is present at the highest concentration at a position deeper than the surface or near the surface in the surface layer portion 10a, and the concentration of the additive element A decreases toward the surface and bulk portion 10b. It can be said that there is a concentration peak of aluminum at the position showing the highest concentration, and the concentration peak position of the aluminum may be located slightly deeper than the concentration peak position of the magnesium and the like. The decrease in concentration may be referred to as a concentration gradient.
  • the additive element A showing a distribution as shown in FIG. 3D on the (001) plane is referred to as the additive element Y.
  • a distribution like that of the added element X or a distribution like that of the added element Y may be shown, and the distributions may differ from each other.
  • a concentration peak position like that of the added element X or a concentration peak position like that of the added element Y may be shown, and the concentration peak positions may differ from each other.
  • Figures 3E and 3F show enlarged views of the vicinity of C-D in Figure 3A.
  • Figures 3E and 3F can be said to be cross-sectional views of a surface layer having faces other than the (001) face (hereinafter, sometimes referred to as ab faces or edge faces), and faces other than the (001) face are faces where diffusion paths for lithium ions exist in a layered rock-salt crystal structure.
  • FIG. 3E which shows a surface other than the (001) surface
  • the distribution of magnesium and the like is shown as an example of the added element X.
  • the concentration of the added element X may be higher in the surface other than the (001) surface in FIG. 3E.
  • the concentration peak of magnesium and the like may be located at or near the surface of the surface layer 10a, and may show a higher intensity than the concentration peak in the (001) surface in FIG. 3C.
  • the added element X may be distributed over a wide range in the surface other than the (001) surface in FIG. 3E.
  • Figure 3F shows the distribution of aluminum as an example of an added element Y. It is preferable that the aluminum concentration peak is located in a region of 5 nm to 50 nm from the surface toward the inside, whether it is the (001) plane in Figure 3D or a plane other than the (001) plane in Figure 3F. Depending on the heat treatment conditions, the aluminum concentration peak may be deeper in a plane other than the (001) plane in Figure 3F than in the (001) plane in Figure 3D.
  • the distribution of the added elements may differ depending on the surface direction of the positive electrode active material.
  • the diffusion paths of lithium ions exist on surfaces other than the (001) plane, and the diffusion paths of lithium ions are exposed on surfaces other than the (001) plane. Therefore, as shown in Figures 3E and 3F, the surface layer 10a corresponding to the surface other than the (001) plane is an important region for maintaining the diffusion paths of lithium ions, and at the same time, it is the region from which lithium ions are first desorbed and is therefore prone to becoming unstable. Therefore, in order to maintain the crystal structure of the entire positive electrode active material 10, it is preferable to preferentially reinforce the surfaces other than the (001) plane and the surface layer 10a corresponding thereto. In other words, it is preferable that the additive element A is preferentially present on the surfaces other than the (001) plane and the surface layer 10a corresponding thereto.
  • the manufacturing method involves mixing the additive elements into LiCoO 2 formed through initial heating and then heating the mixture, the additive elements spread through the diffusion path of lithium ions. Therefore, it is easy to make the distribution of the additive elements in the surface layer 10a corresponding to the surfaces other than (001) as shown in Figures 3C and 3D be in a preferred range.
  • the surface of the positive electrode active material 10 is preferably smooth and has few irregularities, the positive electrode active material 10 does not necessarily have to be smooth in its entirety.
  • the positive electrode active material 10 may have irregularities caused by slips occurring on a surface parallel to the (001) plane, for example, on a surface on which lithium is arranged. Slips are also called stacking faults.
  • pressing is performed during the preparation of the positive electrode, and the LiCoO 2 may be deformed along the lattice fringe direction (the ab plane direction) by the pressing, and this deformation is also included in slips. Deformation includes the shifting of the lattice fringes back and forth. When the lattice fringes shift back and forth, a step occurs on the surface in the direction perpendicular to the lattice fringes (the c-axis direction).
  • the surface and its surface layer 10a resulting from the slip are often the (001) plane, and the surface layer 10a corresponding to the (001) plane may not have any added elements or may have elements below the detection limit.
  • the (001) plane does not expose the diffusion path of lithium ions and is relatively stable, so there is almost no problem even if the added elements are not present or are below the detection limit.
  • Magnesium which is one of the additive elements X, is divalent, and magnesium ions are more stable at the lithium site than at the cobalt site in the layered rock salt crystal structure, so they tend to enter the lithium site.
  • the presence of magnesium at an appropriate concentration at the lithium site of the surface layer 10a makes it easier to reinforce the layered rock salt crystal structure of the bulk portion 10b and the like. This is presumably because the magnesium present at the lithium site functions as a pillar supporting the CoO 2 layers.
  • the presence of magnesium can suppress the detachment of oxygen around magnesium when x in Li x CoO 2 described below is, for example, 0.24 or less.
  • the presence of magnesium can be expected to increase the density of the positive electrode active material 10.
  • the magnesium concentration of the surface layer 10a is high, it can also be expected that the corrosion resistance to hydrofluoric acid generated by the decomposition of the organic solvent will be improved.
  • magnesium does not adversely affect the insertion and desorption of lithium during charging and discharging, and the above benefits can be enjoyed. However, if there is an excess of magnesium, it may have an adverse effect on the insertion and desorption of lithium. Furthermore, the effect of stabilizing the crystal structure may be reduced. This is thought to be because magnesium enters the cobalt site in addition to the lithium site. In addition, unnecessary magnesium compounds (oxides, fluorides, etc.) that do not substitute for either the lithium site or the cobalt site may segregate on the surface of the positive electrode active material, and may become resistance components in lithium-ion batteries. In addition, as the magnesium concentration of the positive electrode active material increases, 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 amount of magnesium contained in the entire positive electrode active material 10 is appropriate.
  • the number of magnesium atoms is preferably 0.001 to 0.1 times the number of cobalt atoms, more preferably greater than 0.01 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 10 here may be a value obtained by performing an elemental analysis of the entire positive electrode active material 10 using, for example, GD-MS (glow discharge mass spectrometry) or ICP-MS (inductively coupled plasma mass spectrometry), or may be based on the value of the composition of raw materials in the process of producing the positive electrode active material 10.
  • nickel which is one of the added elements X, can exist on either the cobalt site or the lithium site. When it exists on the cobalt site, it has a lower redox potential compared to cobalt, which leads to an increase in discharge capacity, which is preferable.
  • nickel when nickel is present at the lithium site, the shift of the layered structure consisting of octahedra of cobalt and oxygen can be suppressed. Also, the change in volume caused by charging and discharging is suppressed. Also, the elastic modulus becomes large, that is, it becomes hard. This is presumably because nickel present at the lithium site also functions as a pillar supporting the CoO2 layers.
  • an excess of nickel is undesirable because it increases the influence of distortion due to the Jahn-Teller effect. Also, an excess of nickel may adversely affect the insertion and extraction of lithium.
  • the amount of nickel contained in the entire positive electrode active material 10 is appropriate.
  • the number of nickel atoms contained in the positive electrode active material 10 is preferably higher than 0% and less than 7.5% of the number of cobalt atoms, preferably 0.05% to 4%, preferably 0.1% to 2%, and more preferably 0.2% to 1%. Or, it is preferably higher than 0% and less than 4%. Or, it is preferably higher than 0% and less than 2%. Or, it is preferably 0.05% to 7.5%. Or, it is preferably 0.05% to 2%. Or, it is preferably 0.1% to 7.5%. Or, it is preferably 0.1% to 4%.
  • the amount of nickel shown here may be a value obtained by performing an elemental analysis of the entire positive electrode active material using, for example, GD-MS, ICP-MS, etc., or may be based on the value of the raw material composition in the process of producing the positive electrode active material.
  • aluminum which is one of the additive elements Y
  • aluminum can be present at the cobalt site in the layered rock salt crystal structure. Since aluminum is a typical trivalent element and its valence does not change, lithium around the aluminum is unlikely to move even during charging and discharging. Therefore, the aluminum and the lithium around it function as columns and can suppress changes in the crystal structure. Aluminum also has the effect of suppressing the elution of surrounding cobalt and improving continuous charging resistance. In addition, since the Al-O bond is stronger than the Co-O bond, it can suppress the detachment of oxygen around the aluminum. These effects improve thermal stability. Therefore, the safety can be improved when a positive electrode active material having aluminum as an additive element is used in a lithium ion battery. In addition, it is possible to obtain a positive electrode active material 10 whose crystal structure is unlikely to collapse even when repeatedly charged and discharged.
  • aluminum which is one of the added elements Y
  • the aluminum concentration peak is in a region deeper than the concentration peak of the added element X.
  • the presence of aluminum, which is one of the added elements Y is confirmed in a region deeper than the deepest position where the presence of the added element X is confirmed. This is because lithium present near the aluminum substituted for the lithium site is fixed, and if aluminum is substituted for the lithium site on the surface, it may block the diffusion path of lithium.
  • the amount of aluminum contained in the entire positive electrode active material 10 is appropriate.
  • the number of aluminum atoms contained in the entire positive electrode active material 10 is preferably 0.05% to 4% of the number of cobalt atoms, preferably 0.1% to 2%, and more preferably 0.3% to 1.5%.
  • 0.05% to 2% is preferable.
  • 0.1% to 4% is preferable.
  • the amount contained in the entire positive electrode active material 10 here may be, for example, a value obtained by performing elemental analysis of the entire positive electrode active material 10 using GD-MS, ICP-MS, etc., or may be based on the value of the composition of raw materials in the process of producing the positive electrode active material 10.
  • fluorine which is one of the additive elements X
  • fluorine is a monovalent anion
  • fluorine when part of the oxygen in the surface layer 10a is replaced by fluorine, the lithium desorption energy is reduced.
  • the valence of the cobalt ion accompanying lithium desorption changes from trivalent to tetravalent in the absence of fluorine, and from divalent to trivalent in the presence of fluorine, resulting in different oxidation-reduction potentials. Therefore, when part of the oxygen in the surface layer 10a of the positive electrode active material 10 is replaced by fluorine, it can be said that desorption and insertion of lithium ions near the fluorine can occur smoothly.
  • the melting point of a fluoride such as lithium fluoride when used in a lithium ion battery, it is possible to improve the charge/discharge characteristics, large current characteristics, etc. Furthermore, the presence of fluorine in the surface layer 10a having the surface that is in contact with the electrolyte can effectively improve corrosion resistance against hydrofluoric acid. As will be described in a later embodiment, when the melting point of a fluoride such as lithium fluoride is lower than the melting point of other additive element sources, it can function as a flux (also called a flux agent) that lowers the melting point of other additive element sources.
  • divalent magnesium may be more stable near divalent nickel. Therefore, even when x in Li x CoO 2 is small, the elution of magnesium may be suppressed. Therefore, it may contribute to the stabilization of the surface layer 10a.
  • additive elements with different distributions such as additive element X and additive element Y
  • additive element X and additive element Y additive elements with different distributions
  • additive element Y additive element Y
  • additive element Y such as aluminum
  • each additive element When multiple additive elements are included as described above, the effects of each additive element are synergistic and can contribute to further stabilization of the surface layer 10a.
  • the inclusion of magnesium, nickel, and aluminum is highly effective in providing a stable composition and crystal structure, and is therefore preferable.
  • the surface layer 10a is occupied only by a compound of the added element and oxygen, it is not preferable because it makes it difficult to insert and remove lithium.
  • the surface layer 10a it is not preferable for the surface layer 10a to be occupied only by MgO, a structure in which MgO and NiO(II) are solid-solved, and/or a structure in which MgO and CoO(II) are solid-solved. Therefore, it is preferable that the surface layer 10a contains at least cobalt and also contains lithium in the discharged state, so that a path for the insertion and removal of lithium is secured.
  • the surface layer 10a has a higher cobalt concentration than magnesium. It is also preferable that the surface layer 10a has a higher cobalt concentration than nickel. It is also preferable that the surface layer 10a has a higher cobalt concentration than aluminum. It is also preferable that the surface layer 10a has a higher cobalt concentration than fluorine.
  • the surface layer 10a has a higher concentration of magnesium than nickel.
  • some of the additive elements especially magnesium and nickel, have a higher concentration in the surface layer portion 10a than in the bulk portion 10b, and are also present randomly and dilutely in the bulk portion 10b.
  • aluminum which is one of the additive elements, is also present randomly and dilutely in the bulk portion 10b.
  • magnesium and aluminum are present at appropriate concentrations in the lithium site of the bulk portion 10b, it has the effect of making it easier to maintain the layered rock salt type crystal structure as described above.
  • nickel is present at an appropriate concentration in the bulk portion 10b, it is possible to suppress the shift of the layered structure consisting of octahedra of cobalt and oxygen as described above.
  • magnesium and nickel are present together, a synergistic effect of suppressing the elution of magnesium can be expected as described above.
  • the crystal structure of the lithium cobalt oxide changes continuously from the bulk portion 10b toward the surface portion 10a.
  • the surface portion 10a has a composition and crystal structure that are more stable at room temperature (25°C) than the bulk portion 10b.
  • at least a part of the surface portion 10a of the positive electrode active material 10 that can be used as one embodiment of the present invention has a rock salt type crystal structure.
  • the surface portion 10a has both a layered rock salt type crystal structure and a rock salt type crystal structure.
  • the surface portion 10a has the characteristics of both a layered rock salt type crystal structure and a rock salt type crystal structure.
  • the crystal orientation of the surface layer portion 10a and the bulk portion 10b roughly coincide.
  • the surface layer portion 10a and the bulk portion 10b are topotaxy.
  • topotaxis refers to a three-dimensional structural similarity in which the crystal orientations roughly match, or to a crystallographically identical orientation.
  • Epitaxy refers to a structural similarity at a two-dimensional interface.
  • the topotaxis relationship between the surface layer 10a and the bulk layer 10b can reduce distortion of the crystal structure and/or deviations in the atomic arrangement. This can suppress the causes of pits.
  • pits refer to holes that are formed as defects progress in the positive electrode active material.
  • the positive electrode active material 10 usable as one embodiment of the present invention has a crystal structure different from that of conventional positive electrode active materials in a charged state, that is, in a state where x in Li x CoO 2 is small, due to the distribution of the added elements and/or the crystal structure as described above.
  • small x means 0.1 ⁇ x ⁇ 0.24.
  • This structure has one CoO 2 layer in the unit cell. Therefore, it is sometimes called monoclinic O1 type or O1 type.
  • P-3m1 trigonal O1
  • lithium cobalt oxide has a crystal structure of space group R-3m as shown in FIG. 5.
  • This structure can be said to be a structure in which a trigonal O1 type CoO 2 structure and an R-3m(O3) LiCoO 2 structure are alternately stacked. Therefore, this crystal structure may be called an H1-3 type crystal structure.
  • the number of cobalt atoms per unit cell in the H1-3 type crystal structure is twice that of other structures.
  • the c-axis of the H1-3 type crystal structure is shown as 1/2 of the unit cell in order to make it easier to compare with other crystal structures.
  • the coordinates of cobalt and oxygen in the unit cell of the H1-3 type crystal structure can be expressed as Co (0, 0, 0.42150 ⁇ 0.00016), O1 (0, 0, 0.27671 ⁇ 0.00045), and O2 (0, 0, 0.11535 ⁇ 0.00045).
  • O1 and O2 are oxygen atoms.
  • Which unit cell should be used to express a certain crystal structure can be determined, for example, by Rietveld analysis using X-ray diffraction (XRD). In the Rietveld analysis, the unit cell with the smallest GOF (goodness of fit) value is adopted.
  • the two crystal structures that produce more dynamic structural changes also have a large difference in volume.
  • the difference in volume between the H1-3 crystal structure and the R-3m(O3) crystal structure in a discharged state is greater than 3.5%, typically 3.9% or more.
  • the H1-3 type crystal structure has a structure in which two CoO layers are continuous, such as the trigonal O1 type, and is therefore highly likely to be unstable.
  • the crystal structure of conventional lithium cobalt oxide collapses.
  • the collapse of the crystal structure causes deterioration of cycle characteristics. This is because the collapse of the crystal structure reduces the number of sites where lithium can exist stably and makes it difficult to insert and remove lithium. Note that not only when charging and discharging are repeated so that x is 0.12 or less, but even when x is 0.24 or less, the collapse of the crystal structure often occurs, causing deterioration of cycle characteristics. For this reason, in practical use, conventional lithium cobalt oxide is repeatedly charged and discharged in lithium-ion batteries while controlling x to a value greater than 0.24.
  • the positive electrode active material 10 usable as one embodiment of the present invention shown in FIG. 4 has a smaller change in crystal structure between a discharge state in which x in Li x CoO 2 is 1 and a state in which x is 0.24 or less, or a state in which x is 0.15, than a conventional positive electrode active material.
  • the positive electrode active material 10 can reduce the deviation of the CoO 2 layer between a state in which x is 1 and a state in which x is 0.24 or less.
  • the positive electrode active material 10 can also reduce the change in volume compared per cobalt atom.
  • the positive electrode active material 10 is less likely to collapse in crystal structure even when charging and discharging such that x is 0.24 or less are repeated, and excellent cycle characteristics can be realized.
  • the positive electrode active material 10 can have a more stable crystal structure than a conventional positive electrode active material in a state in which x in Li x CoO 2 is 0.24 or less. Therefore, when the positive electrode active material 10 maintains a state in which x in Li x CoO 2 is 0.24 or less, a short circuit is unlikely to occur, and the safety of the lithium ion battery is improved.
  • the positive electrode active material 10 has a crystal structure different from the H1-3 type crystal structure of conventional lithium cobalt oxide.
  • the positive electrode active material 10 has a crystal structure belonging to the trigonal space group R-3m.
  • the symmetry of the CoO 2 layer is the same as that of O3. Therefore, in this specification and the like, this crystal structure is referred to as an "O3' type crystal structure".
  • the coordinates of cobalt and oxygen in the unit cell can be expressed in the range of Co(0,0,0.5), O(0,0,x), 0.20 ⁇ x ⁇ 0.25.
  • P2/m monoclinic O1(15)
  • x of about 0.15 can be expressed as 0.13 ⁇ x ⁇ 0.24, typically 0.13 ⁇ x ⁇ 0.18.
  • the monoclinic O1(15) type crystal structure can be expressed by the following ranges of the coordinates of cobalt and oxygen in the unit cell: Co1(0.5,0,0.5), Co2(0,0.5,0.5), O1( XO1,0 , ZO1 ), 0.23 ⁇ XO1 ⁇ 0.24, 0.61 ⁇ ZO1 ⁇ 0.65, O2(XO2,0.5, ZO2 ), 0.75 ⁇ XO2 ⁇ 0.78, 0.68 ⁇ ZO2 ⁇ 0.71.
  • c 0.484 ⁇ 0.001 (nm).
  • This crystal structure can also be fitted to the space group R-3m if a certain degree of error is allowed.
  • the coordinates of the oxygen of cobalt in the unit cell can be expressed in the range of Co(0,0,0.5), O(0,0,Z O ), 0.21 ⁇ Z O ⁇ 0.23.
  • the change in the crystal structure of the positive electrode active material 10 when x in Li x CoO 2 is small, that is, when a large amount of lithium is released, is suppressed more than in the conventional positive electrode active material.
  • the change in volume is also suppressed when compared per the same number of cobalt atoms. Therefore, it can be seen that the crystal structure of the positive electrode active material 10 is not easily broken even when charging and discharging are repeated such that x is 0.24 or less, and the decrease in the charge and discharge capacity in the charge and discharge cycle is suppressed.
  • the positive electrode active material 10 since more lithium can be stably used than in the conventional positive electrode active material, the positive electrode active material 10 has a large discharge capacity per weight and per volume. Therefore, by using the positive electrode active material 10, a lithium ion battery with a high discharge capacity per weight and per volume can be produced.
  • the positive electrode active material 10 may have an O3' type crystal structure when x in Li x CoO 2 is 0.15 or more and 0.24 or less, and it is estimated that the positive electrode active material 10 has an O3' type crystal structure even when x is higher than 0.24 and 0.27 or less. It has also been confirmed that the positive electrode active material 10 may have a monoclinic O1 (15) type crystal structure when x in Li x CoO 2 is higher than 0.1 and 0.2 or less, typically when x is 0.13 or more and 0.18 or less.
  • the crystal structure is not necessarily limited to the above range of x because it is affected not only by x in Li x CoO 2 but also by the number of charge/discharge cycles, charge/discharge current, temperature, electrolyte, etc.
  • the positive electrode active material 10 may have only the O3' type crystal structure, may have only the monoclinic O1(15) type, or may have both crystal structures.
  • the bulk portion 10b of the positive electrode active material 10 does not have to have the O3' type and/or the monoclinic O1(15) type crystal structure. It may contain other crystal structures, or may be partially amorphous.
  • the state in which x in Li x CoO 2 is small can be rephrased as a state in which it is charged at a high charging voltage.
  • the positive electrode active material 10 is preferable because it can maintain the crystal structure of R-3m (O3) even when charged at a high charging voltage, for example, a voltage of 4.6 V or more at 25 ° C.
  • the positive electrode active material 10 can be preferable because it can take an O3' type crystal structure when charged at a higher charging voltage, for example, a voltage of 4.65 V or more and 4.7 V or less at 25 ° C.
  • the positive electrode active material 10 can be preferable because it can take a monoclinic O1 (15) type crystal structure when charged at an even higher charging voltage, for example, a voltage higher than 4.7 V and 4.8 V or less at 25 ° C.
  • the positive electrode active material 10 when the charging voltage is further increased, H1-3 type crystals may finally be observed.
  • the crystal structure is affected by the number of charge/discharge cycles, the charge/discharge current, the electrolyte, etc., so when the charging voltage is lower, for example, even when the charging voltage is 4.5 V or more and less than 4.6 V at 25°C, the positive electrode active material 10 usable as one embodiment of the present invention may be able to have an O3' type crystal structure.
  • the monoclinic O1(15) type crystal structure when charging at a voltage of 4.65 V or more and 4.7 V or less at 25°C, the monoclinic O1(15) type crystal structure may be able to be formed.
  • the voltage of the lithium ion battery drops by the amount of the graphite potential compared to the above.
  • the potential of graphite is about 0.01 V to 0.7 V based on the potential of lithium metal. Therefore, in the case of a lithium ion battery using graphite as the negative electrode active material, the battery has a similar crystal structure at the voltage obtained by subtracting the graphite potential from the above voltage.
  • lithium is shown to exist with equal probability at all lithium sites, but this is not limited to the above. Lithium may exist disproportionately at some of the lithium sites. The distribution of lithium can be analyzed, for example, by neutron diffraction.
  • the O3' type crystal structure and the monoclinic O1(15) type crystal structure have random lithium between the layers, but are similar to the CdCl2 type crystal structure.
  • This CdCl2 type-like crystal structure is close to the crystal structure of lithium nickel oxide when it is charged to Li0.06NiO2 , but it is known that pure lithium cobalt oxide or layered rock salt type positive electrode active materials containing a large amount of cobalt do not usually have a CdCl2 type crystal structure.
  • the concentration gradient of the additive element is the same in multiple locations on the surface layer 10a of the positive electrode active material 10.
  • the reinforcement resulting from the additive element is present homogeneously in the surface layer 10a. Even if a portion of the surface layer 10a is reinforced, if there is a portion without reinforcement, stress may be concentrated in the portion without reinforcement. If stress is concentrated in a portion of the positive electrode active material 10, defects such as cracks may occur there, which may lead to cracking of the positive electrode active material and a decrease in discharge capacity. However, it is not necessary that the additive element has the same concentration gradient in all of the surface layer 10a of the positive electrode active material 10.
  • the additive element contained in the positive electrode active material 10 that can be used as one embodiment of the present invention is distributed as described above, and at least a part of the additive element is unevenly distributed in and near the crystal grain boundaries 11 as shown in FIG. 3B.
  • the magnesium concentration at and near the grain boundaries 11 of the positive electrode active material 10 is preferably higher than that in other regions of the bulk portion 10b.
  • the fluorine concentration at and near the grain boundaries 11 is preferably higher than that in other regions of the bulk portion 10b.
  • the nickel concentration at and near the grain boundaries 11 is preferably higher than that in other regions of the bulk portion 10b.
  • the aluminum concentration at and near the grain boundaries 11 is preferably higher than that in other regions of the bulk portion 10b.
  • the grain boundaries 11 are one type of planar defect, they are prone to become unstable like the surface, and changes in the crystal structure are likely to begin. Therefore, by increasing the concentration of the added element at and near the grain boundaries 11, such changes in the crystal structure can be more effectively suppressed.
  • the magnesium concentration and fluorine concentration are high at and near the grain boundaries 11, even if cracks occur along the grain boundaries 11 of the positive electrode active material 10 that can be used as one embodiment of the present invention, the magnesium concentration and fluorine concentration are high near the surface created by the cracks. Therefore, the corrosion resistance to hydrofluoric acid can be improved even in the positive electrode active material after cracks have occurred.
  • x in Li x CoO 2 is small in a certain positive electrode active material
  • whether or not it is a positive electrode active material 10 that can be used as one embodiment of the present invention having an O3' type and/or monoclinic O1(15) type crystal structure can be determined by analyzing a positive electrode having a positive electrode active material in a charged state in which x in Li x CoO 2 is small using XRD, electron beam diffraction, neutron diffraction, electron spin resonance (ESR), nuclear magnetic resonance (NMR), or the like.
  • XRD is particularly preferred because it can analyze the symmetry of transition metals such as cobalt contained in the positive electrode active material with high resolution, can compare the degree of crystallinity and the orientation of the crystals, can analyze the periodic distortion of the lattice and the crystallite size, and can provide sufficient accuracy even when measuring the positive electrode obtained by disassembling a lithium-ion battery as is.
  • powder XRD can provide diffraction peaks that reflect the crystal structure of the bulk portion 10b of the positive electrode active material 10, which occupies the majority of the volume of the positive electrode active material 10.
  • the measurement sample is a powder
  • this is sometimes called the powder XRD measurement described above, and the powder can be set up by placing it in a glass sample holder, sprinkling the sample on a greased silicone anti-reflective plate, etc.
  • the measurement sample is a positive electrode
  • the positive electrode can be attached to the substrate with double-sided tape, and the positive electrode active material layer can be set to match the measurement surface required by the device.
  • the positive electrode active material 10 can be used as one aspect 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, an H1-3 type or trigonal O1 type crystal structure may be produced. Therefore, to determine whether the positive electrode active material 10 can be used as one aspect of the present invention, analysis of the crystal structure, such as XRD, and information such as the charging capacity or charging voltage are required.
  • the crystal structure may change when exposed to air.
  • the crystal structure may change from O3' type and monoclinic O1(15) type to H1-3 type. Therefore, it is preferable to handle all samples used for crystal structure analysis in an inert atmosphere such as an argon atmosphere.
  • whether the distribution of the added elements in a certain positive electrode active material is in the state described above can be determined by analysis using, for example, XPS, energy dispersive X-ray spectroscopy (EDX), electron probe microanalysis (EPMA), etc.
  • the crystal structure of the surface layer 10a, the grain boundaries 11, etc. can be analyzed by electron beam diffraction of a cross section of the positive electrode active material 10.
  • An example of an evaluation condition for determining whether a certain composite oxide is a positive electrode active material 10 that can be used as an embodiment of the present invention is a method of preparing a coin cell (e.g., CR2032 type, diameter 20 mm, height 3.2 mm) having lithium metal as a counter electrode and charging it under predetermined conditions. Also, an example of an evaluation condition for determining whether a certain electrolyte is an electrolyte that can be used as an embodiment of the present invention is a method of preparing a coin cell (e.g., CR2032 type, diameter 20 mm, height 3.2 mm) having lithium metal as a counter electrode and charging it under predetermined conditions.
  • the procedure 1 described below is an example for confirming the physical properties of the positive electrode active material 10 that can be used as one embodiment of the present invention. Therefore, the electrolyte is different from the configuration of the lithium ion battery, which is one embodiment of the present invention.
  • a lithium-ion battery is disassembled, the electrolyte-impregnated positive electrode is removed, and the positive electrode is punched out to a size that fits into a prepared coin cell.
  • the positive electrode contains a conductive material and a binder in addition to the positive electrode active material.
  • the electrolyte and the like are removed before punching out the positive electrode. For example, after removing the positive electrode, the positive electrode can be washed using an organic solvent or the like.
  • the coin cell has lithium metal as the counter electrode.
  • a material other than lithium metal can be used as the counter electrode.
  • the potential in this specification is the potential of the positive electrode when the counter electrode is lithium metal.
  • the coin cell has a 25 ⁇ m thick porous polypropylene film as a separator.
  • the coin cell uses stainless steel (SUS) for the positive electrode can and stainless steel (SUS) for the negative electrode can.
  • SUS stainless steel
  • the coin cell A for evaluation prepared under the above conditions is charged at a constant current (also called CC charging) of 10 mA/g (equivalent to 0.05 C when 1 C is 200 mA/g per weight of positive electrode active material) to any voltage (e.g., 4.5 V, 4.55 V, 4.6 V, or 4.65 V, 4.7 V, 4.75 V, 4.8 V).
  • CC charging constant current
  • any voltage e.g., 4.5 V, 4.55 V, 4.6 V, or 4.65 V, 4.7 V, 4.75 V, 4.8 V.
  • the temperature during charging of the evaluation coin cell A can be 25°C.
  • the temperature during charging can be the temperature of the thermostatic bath in which the coin cell A is placed.
  • coin cell A is disassembled in a glove box with an argon atmosphere to remove the positive electrode, thereby obtaining a positive electrode active material with a desired charging capacity.
  • seal the cell in an argon atmosphere to suppress reactions with external components.
  • XRD can be performed by sealing the cell in a sealed container with an argon atmosphere. It is also preferable to remove and analyze the positive electrode promptly after charging is completed. Specifically, it is preferable to do so within one hour after charging is completed, and more preferably within 30 minutes.
  • Evaluation Procedure 2 A lithium ion battery is disassembled, the positive electrode impregnated with the electrolyte is taken out, and the electrolyte is measured by nuclear magnetic resonance (e.g., 1 H NMR) to identify at least the organic solvent.
  • nuclear magnetic resonance e.g., 1 H NMR
  • the mixing ratio (volume ratio) of the organic solvent can also be identified.
  • the lithium salt and additives contained in the electrolyte can be added if it is a material that does not form a coating on the positive electrode active material, for example, a material for adjusting viscosity.
  • the electrolyte may contain an additive.
  • the positive electrode is punched out to a size that will fit into a coin cell.
  • the positive electrode contains a conductive material and a binder.
  • the electrolyte and other materials are removed after the nuclear magnetic resonance measurement and before the positive electrode is punched out. For example, after removing the positive electrode, it can be washed using an organic solvent or the like.
  • the coin cell has lithium metal as the counter electrode.
  • materials other than lithium metal can also be used for the counter electrode.
  • the coin cell is prepared with an electrolyte that has been identified using nuclear magnetic resonance spectroscopy.
  • This electrolyte is an embodiment of the electrolyte of the present invention.
  • the coin cell has a 25 ⁇ m thick porous polypropylene film as a separator.
  • the coin cell uses stainless steel (SUS) for the positive electrode can and stainless steel (SUS) for the negative electrode can.
  • SUS stainless steel
  • the evaluation coin cell B prepared under the above conditions is charged to a desired voltage (e.g., 4.5 V, 4.55 V, 4.6 V, or 4.65 V, 4.7 V, 4.75 V, 4.8 V) and then discharged.
  • a desired voltage e.g., 4.5 V, 4.55 V, 4.6 V, or 4.65 V, 4.7 V, 4.75 V, 4.8 V.
  • the charging conditions can be seen in the examples below.
  • the discharging conditions can be seen in the examples below.
  • the charging temperature of the evaluation coin cell B can be set to 25°C and below freezing, and it can be confirmed how the charge/discharge capacity at below freezing is compared to the charge/discharge capacity at 25°C.
  • XRD measurement of the coin cell A and the like can be performed using the following apparatus and conditions. Note that the XRD measurement apparatus and conditions are not limited to those described below.
  • XRD device Bruker AXS, D8 ADVANCE
  • X-ray source CuK ⁇ 1 line Output: 40KV, 40mA
  • Figures 8A and 8B show the XRD patterns of O3' type, monoclinic O1(15) type, and H1-3 type, with Figure 8A showing an enlarged view of the region where 2 ⁇ (degree) is in the range of 18° to 21°, and Figure 8B showing an enlarged view of the region where 2 ⁇ (degree) is in the range of 42° to 46°.
  • the patterns of LiCoO2 (O3) and CoO2 (O1) were created using Reflex Powder Diffraction, one of the modules of Materials Studio (BIOVIA), from crystal structure information obtained from ICSD (Inorganic Crystal Structure Database).
  • the pattern of H1-3 type crystal structure was similarly created from the crystal structure information described in Non-Patent Document 2.
  • the crystal structure patterns of the O3′ type and monoclinic O1(15) type were estimated from the XRD pattern of the positive electrode active material usable as one embodiment of the present invention, and fitted using TOPAS ver. 3 (crystal structure analysis software manufactured by Bruker), to create XRD patterns in the same manner as the others.
  • the positive electrode active material 10 usable as one embodiment of the present invention has an O3' type and/or monoclinic O1 (15) type crystal structure when x in Li x CoO 2 is small, but not all of them may be O3' type and/or monoclinic O1 (15) type crystal structures. It may contain other crystal structures, or may be partially amorphous. However, when Rietveld analysis is performed on the XRD pattern, it is preferable that the O3' type and/or monoclinic O1 (15) type crystal structure is 50% or more, more preferably 60% or more, and even more preferably 66% or more. If the O3' type and/or monoclinic O1 (15) type crystal structure is 50% or more, more preferably 60% or more, and even more preferably 66% or more, it can be a positive electrode active material with sufficiently excellent cycle characteristics.
  • the O3' type and/or monoclinic O1(15) type crystal structure is 35% or more, more preferably 40% or more, and even more preferably 43% or more.
  • each diffraction peak after charging is sharp, i.e., the half-width is narrow.
  • the half-width varies depending on the XRD measurement conditions or the value of 2 ⁇ (degree), even for peaks arising from the same crystal phase.
  • the half-width is preferably 0.2° or less, more preferably 0.15° or less, and even more preferably 0.12° or less. Note that not all peaks necessarily meet this requirement. If some peaks meet this requirement, it can be said that the crystallinity of the crystal phase is high. Therefore, it contributes to stabilizing the crystal structure after charging sufficiently.
  • the crystallite size of the O3' type and monoclinic O1 (15) crystal structures of the positive electrode active material 10 is reduced to only about 1/20 of LiCoO 2 (O3) in the discharged state. Therefore, even under the same XRD measurement conditions as the positive electrode before charging and discharging, a clear O3' type crystal structure peak can be confirmed when x in Li x CoO 2 is small.
  • the crystallite size becomes small and the peak becomes broad and small. The crystallite size can be determined from the half-width of the XRD peak.
  • the positive electrode includes a positive electrode active material layer and a positive electrode current collector.
  • the positive electrode active material layer includes a positive electrode active material, and may further include at least one of a conductive additive and a binder.
  • the positive electrode active material described in the first embodiment can be used.
  • Figure 9A shows an example of a schematic diagram of a cross section of a positive electrode.
  • the current collector 550 can be, for example, a metal foil.
  • the positive electrode can be formed by applying a slurry onto the metal foil and drying it. It is also possible to press the metal foil after drying.
  • the positive electrode is formed by forming an active material layer on the current collector 550.
  • the slurry is a material liquid used to form an active material layer on the current collector 550, and contains an active material, a binder, and a solvent, and preferably also contains a conductive assistant.
  • the slurry is also called an electrode slurry or an active material slurry.
  • a positive electrode slurry is used when forming a positive electrode active material layer, and a negative electrode slurry is used when forming a negative electrode active material layer.
  • the positive electrode active material 561 has the function of taking in and/or releasing lithium ions during charging and discharging.
  • the positive electrode active material 561 used in one embodiment of the present invention can be a material that is less susceptible to deterioration during charging and discharging even at high charging voltages.
  • the charging voltage is expressed based on the potential of lithium metal.
  • a high charging voltage is, for example, a charging voltage of 4.6 V or more, preferably 4.65 V or more, more preferably 4.7 V or more, even more preferably 4.75 V or more, and most preferably 4.8 V or more.
  • the positive electrode active material 561 used in one embodiment of the present invention can be any material that does not deteriorate much due to charging and discharging even at a high charging voltage, and can be one described in embodiment 1 or embodiment 2. Note that the positive electrode active material 561 can be two or more materials with different particle sizes as long as the material does not deteriorate much due to charging and discharging even at a high charging voltage.
  • the conductive assistant is also called a conductive agent or conductive material, and may be a carbon material.
  • attaching the conductive assistant between multiple active materials the multiple active materials are electrically connected to each other, increasing the conductivity.
  • the term "attachment” does not only refer to the active material and the conductive assistant being in physical contact with each other, but also includes the concept of covalent bonding, bonding due to van der Waals forces, covering part of the surface of the active material with the conductive assistant, fitting the conductive assistant into the surface irregularities of the active material, and electrically connecting even when not in contact with each other.
  • Figure 9A illustrates carbon black 553 as a conductive additive.
  • a binder can be mixed to bond the current collector 550, such as a metal foil, and the active material to form the positive electrode of the lithium-ion battery.
  • the binder is also called a binding agent.
  • the binder is a polymeric material, and if a large amount of binder is added, the ratio of active material in the positive electrode decreases, and the discharge capacity of the lithium-ion battery decreases. Therefore, it is preferable to mix the minimum amount of binder.
  • the areas not filled with the positive electrode active material 561, the second active material 562, and the carbon black 553 indicate voids or binders.
  • FIG. 9A illustrates an example in which the positive electrode active material 561 is illustrated as being spherical, this is not particularly limited.
  • the cross-sectional shape of the positive electrode active material 561 may be an ellipse, a rectangle, a trapezoid, a pyramid, a polygon with rounded corners, or an asymmetric shape.
  • FIG. 9B illustrates an example in which the positive electrode active material 561 has a polygonal shape with rounded corners.
  • graphene 554 is used as a carbon material used as a conductive additive.
  • a positive electrode active material layer having a positive electrode active material 561, graphene 554, and carbon black 553 is formed on a current collector 550.
  • the weight of the carbon black to be mixed is preferably 1.5 to 20 times, and more preferably 2 to 9.5 times, the weight of graphene.
  • the dispersion stability of carbon black 553 is excellent during slurry preparation, and agglomerations are unlikely to occur.
  • a higher electrode density can be achieved than a positive electrode using only carbon black 553 as a conductive additive.
  • the capacity per unit weight can be increased.
  • the density of the positive electrode active material layer measured by weight can be 3.5 g/cc or more.
  • the electrode density is lower than that of a positive electrode that uses only graphene as a conductive additive, by mixing the first carbon material (graphene) and the second carbon material (acetylene black) within the above range, it can be used for rapid charging. For this reason, it is particularly effective when used as an in-vehicle lithium-ion battery.
  • Figure 9C illustrates an example of a positive electrode that uses carbon fiber 555 instead of graphene.
  • Figure 9C shows an example different from Figure 9B.
  • Using carbon fiber 555 can prevent the carbon black 553 from agglomerating and improve dispersibility.
  • the areas not filled with the positive electrode active material 561, the carbon fiber 555, or the carbon black 553 indicate voids or binders.
  • FIG. 9D shows another example of a positive electrode.
  • FIG. 9C shows an example in which carbon fiber 555 is used in addition to graphene 554. Using both graphene 554 and carbon fiber 555 can prevent aggregation of carbon black such as carbon black 553, and can further improve dispersibility.
  • the areas that are not filled with the positive electrode active material 561, the carbon fiber 555, the graphene 554, and the carbon black 553 indicate voids or binders.
  • a lithium ion battery can be produced by using any one of the positive electrodes shown in Figures 9A to 9D, stacking a separator on the positive electrode, placing the stack of the separator and the negative electrode on top of a container (exterior body, metal can, etc.) that houses the stack, and filling the container with the electrolyte from the vesicles.
  • ⁇ Binder> As the binder, it is preferable to use a rubber material such as styrene-butadiene rubber (SBR), styrene-isoprene-styrene rubber, acrylonitrile-butadiene rubber, butadiene rubber, ethylene-propylene-diene copolymer, etc. Furthermore, as the binder, fluororubber can be used.
  • SBR styrene-butadiene rubber
  • fluororubber can be used as the binder.
  • ⁇ Positive electrode current collector> As the current collector, a material having high electrical conductivity, such as metals such as stainless steel, gold, platinum, aluminum, and titanium, and alloys thereof, can be used. In addition, it is preferable that the material used for the positive electrode current collector does not dissolve at the potential of the positive electrode. In addition, an aluminum alloy to which an element that improves heat resistance, such as silicon, titanium, neodymium, scandium, and molybdenum, is added can be used. In addition, it can be formed of a metal element that reacts with silicon to form a silicide.
  • Examples of metal elements that react with silicon to form a silicide include zirconium, titanium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, and nickel.
  • the current collector can be appropriately shaped in a foil, plate, sheet, mesh, punched metal, expanded metal, or other form.
  • the current collector has a thickness of 5 ⁇ m to 30 ⁇ m.
  • the negative electrode includes a negative electrode active material layer and a negative electrode current collector.
  • the negative electrode active material layer may include a negative electrode active material, and may further include a conductive additive and a binder.
  • Niobium Electrode Active Material for example, an alloy material and/or a carbon material can be used.
  • the negative electrode active material can be an element capable of performing a charge/discharge reaction by alloying/dealloying reaction with lithium.
  • the negative electrode active material can be an element capable of performing a charge/discharge reaction by alloying/dealloying reaction with lithium.
  • one or more materials selected from silicon, tin, gallium, aluminum, germanium, lead, antimony, bismuth, silver, zinc, cadmium, indium, etc. can be used.
  • Such 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.
  • compounds having these elements can be used.
  • Examples include SiO , Mg2Si , Mg2Ge , SnO, SnO2 , Mg2Sn , SnS2 , V2Sn3 , FeSn2, CoSn2 , Ni3Sn2 , Cu6Sn5, Ag3Sn , Ag3Sb, Ni2MnSb, CeSb3, LaSn3, La3Co2Sn7 , CoSb3 , InSb , SbSn , etc.
  • elements capable of carrying out charge/discharge reactions by alloying/dealloying reactions with lithium, and compounds containing such elements may be referred to as alloy - based materials.
  • SiO refers to, for example, silicon monoxide.
  • SiO can be expressed as SiO x .
  • x preferably has a value of 1 or close to 1.
  • x is preferably 0.2 or more and 1.5 or less, and more preferably 0.3 or more and 1.2 or less.
  • the carbon material may be one or more selected from graphite, easily graphitizable carbon (soft carbon), non-graphitizable carbon (hard carbon), carbon fiber (carbon nanotube), graphene, carbon black, etc.
  • the graphite may be artificial graphite or natural graphite.
  • artificial graphite include mesocarbon microbeads (MCMB), coke-based artificial graphite, and pitch-based artificial graphite.
  • MCMB mesocarbon microbeads
  • pitch-based artificial graphite spherical graphite having a spherical shape
  • MCMB may have a spherical shape, which is preferable.
  • it is relatively easy to reduce the surface area of MCMB which may be preferable.
  • natural graphite include flake graphite and spheroidized natural graphite.
  • graphite When lithium ions are inserted into graphite (when a lithium-graphite intercalation compound is formed), graphite exhibits a low potential (0.05 V to 0.3 V vs. Li/Li + ) similar to that of lithium metal. This allows lithium ion batteries using graphite to exhibit a high operating voltage. Furthermore, graphite is preferred because it has the advantages of a relatively high capacity per unit volume, a relatively small volume expansion, low cost, and higher safety than lithium metal.
  • one or more oxides selected from titanium dioxide ( TiO2 ), lithium titanium oxide ( Li4Ti5O12 ), lithium- graphite intercalation compound (LixC6 ) , niobium pentoxide ( Nb2O5 ), tungsten oxide ( WO2 ), molybdenum oxide ( MoO2 ) , etc. can be used as the negative electrode active material.
  • Li2.6Co0.4N3 is preferable because it shows a large discharge capacity (900mAh/g, 1890mAh/ cm3 ).
  • the composite nitride of lithium and a transition metal When a composite nitride of lithium and a transition metal is used, lithium ions are contained in the negative electrode active material, and therefore it is preferable that the composite nitride of lithium and a transition metal is combined with a material that does not contain lithium ions as a positive electrode active material, such as V 2 O 5 or Cr 3 O 8. Even when a material that contains lithium ions is used as the positive electrode active material, the composite nitride of lithium and a transition metal can be used as the negative electrode active material by desorbing the lithium ions contained in the positive electrode active material in advance.
  • materials that undergo conversion reactions can be used as negative electrode active materials.
  • transition metal oxides that do not form an alloy with lithium such as cobalt oxide (CoO), nickel oxide (NiO ) , and iron oxide (FeO)
  • CoO cobalt oxide
  • NiO nickel oxide
  • FeO iron oxide
  • Materials that undergo conversion reactions include oxides such as Fe2O3 , CuO, Cu2O , RuO2 , and Cr2O3 , sulfides such as CoS0.89 , NiS , and CuS, nitrides such as Zn3N2 , Cu3N , and Ge3N4 , phosphides such as NiP2 , FeP2 , and CoP3 , and fluorides such as FeF3 and BiF3 .
  • the conductive additive and binder that the negative electrode active material layer can have can be the same materials as the conductive additive and binder that the positive electrode active material layer can have.
  • the negative electrode current collector may be made of the same material as the positive electrode current collector, or may be made of copper, etc. 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 The electrolyte described in the first embodiment can be used.
  • a separator is disposed between the positive electrode and the negative electrode.
  • a separator formed of fibers having cellulose such as paper, nonwoven fabric, glass fiber, ceramics, or synthetic fibers using nylon (polyamide), vinylon (polyvinyl alcohol fiber), polypropylene (referred to as PP), polyimide (referred to as PI), polyester, acrylic, polyolefin, polyurethane, etc.
  • the porosity of the separator can be 35% to 90%, preferably 60% to 85%.
  • the porosity of the separator using polypropylene can be 35% to 45%.
  • the porosity of the separator using polyimide can be 75% to 85%.
  • the thickness of the separator is preferably 10 ⁇ m to 80 ⁇ m, more preferably 20 ⁇ m to 60 ⁇ m.
  • the separator using polyimide can have a high porosity and can be made thick (typically, the thickness is 50 ⁇ m to 60 ⁇ m).
  • the separator into a bag shape and place it so that it wraps around either the positive or negative electrode.
  • the separator may have a multi-layer structure.
  • an organic material film such as polypropylene or polyethylene may be coated with a ceramic material, a fluorine material, a polyamide material, or a mixture of these.
  • the ceramic material for example, aluminum oxide particles or silicon oxide particles may be used.
  • the fluorine material for example, PVDF or polytetrafluoroethylene may be used.
  • the polyamide material for example, nylon or aramid (meta-aramid or para-aramid) may be used.
  • the safety of the lithium-ion battery can be maintained even if the overall thickness of the separator is thin, allowing the capacity per volume of the lithium-ion battery to be increased.
  • the exterior body of the lithium ion battery can be made of a metal material such as aluminum or a resin material.
  • a film-shaped exterior body can also be used.
  • As the film a three-layer structure film can be used in which a thin metal film having excellent flexibility such as aluminum, stainless steel, copper, nickel, etc. is provided on a film made of a material such as polyethylene, polypropylene, polycarbonate, ionomer, polyamide, etc., and an insulating synthetic resin film such as a polyamide-based resin or polyester-based resin is further provided on the thin metal film as the outer surface of the exterior body.
  • This embodiment can be used in combination with other embodiments.
  • FIG. 10A and Fig. 10B An example of the laminated lithium ion battery 100 is shown in Fig. 10A and Fig. 10B.
  • Fig. 10A and Fig. 10B are external views, and the lithium ion battery 100 has the electrolyte and separator (not shown in Fig. 10) described in the above embodiment, the negative electrode 106, and the positive electrode 107.
  • the negative electrode 106 preferably has a larger area than the positive electrode 107.
  • the lithium ion battery 100 further has a negative electrode lead electrode 510 electrically connected to the negative electrode 106, and a positive electrode lead electrode 511 electrically connected to the positive electrode 107.
  • the electrolyte layer, the negative electrode 106, and the positive electrode 107 are housed in an exterior body 509, and a part of the negative electrode lead electrode 510 and a part of the positive electrode lead electrode 511 protrude from the exterior body 509.
  • a bonding area 508 is provided on a part of the outer periphery of the exterior body 509.
  • Fig. 10A shows an example in which the negative lead electrode 510 and the positive lead electrode 511 protrude from the same side of the exterior body 509, and the adhesive region 508 is located at least on the side from which each lead electrode protrudes and two sides adjacent to that side.
  • FIG. 10B shows an example in which the side from which the negative lead electrode 510 protrudes from the exterior body 509 and the side from which the positive lead electrode 511 protrudes from the exterior body 509 face each other, and the adhesive region 508 is located at least on the two sides from which each lead electrode protrudes and one side sandwiched between the two sides.
  • the sides on which the adhesive region 508 is not located correspond to the sides on which the exterior body 509 is folded.
  • organic solvent and positive electrode active material of the present invention are used in a laminated lithium ion battery 100, excellent charge/discharge characteristics are expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • Fig. 11A is an exploded perspective view of a coin-type (single-layer flat) lithium ion battery
  • Fig. 11B is an external view
  • Fig. 11C is a cross-sectional view thereof.
  • Coin-type lithium ion batteries are mainly used in small electronic devices. In this specification and the like, coin-type lithium ion batteries include button-type lithium ion batteries.
  • FIG. 11A is a schematic diagram showing the overlapping of components (vertical relationship and positional relationship). Therefore, Fig. 11A and Fig. 11B are not completely corresponding views.
  • Figure 11A shows how the positive electrode 304, negative electrode 307, spacer 342, and washer 332 are stacked and sealed with the negative electrode can 302 and positive electrode can 301. Note that the electrolyte and separator described in the above embodiment are not shown in Figure 11A.
  • the spacer 342 and washer 332 are used to protect the inside or to fix the position inside the can when the positive electrode can 301 and the negative electrode can 302 are crimped together.
  • the spacer 342 or washer 332 is made of stainless steel or an insulating material.
  • the positive electrode 304 is a laminated structure in which a positive electrode active material layer 306 is formed on a positive electrode current collector 305.
  • Figure 11B is an oblique view of the completed coin-type lithium-ion battery 100.
  • the coin-type lithium-ion battery 100 may have a positive electrode can 301, which also serves as a positive electrode terminal, and a negative electrode can 302, which also serves as a negative electrode terminal, which are insulated and sealed with a gasket 303 made of polypropylene or the like.
  • the positive electrode 304 is formed of a positive electrode current collector 305 and a positive electrode active material layer 306 provided in contact with the positive electrode current collector.
  • 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.
  • the positive electrode can 301 is electrically connected to the positive electrode 304
  • the negative electrode can 302 is electrically connected to the negative electrode 307.
  • the positive electrode 304 and the negative electrode 307 used in the coin-type lithium-ion battery 100 each have an active material layer formed on only one side.
  • the positive electrode can 301 is placed on the bottom, and the positive electrode can 304, negative electrode 307, and negative electrode can 302 are stacked in this order, and the positive electrode can 301 and the negative electrode can 302 are crimped together via a gasket 303 to produce a coin-shaped lithium-ion battery 100.
  • organic solvent and positive electrode active material of the present invention are used in a coin-type lithium-ion battery 100, excellent charge/discharge characteristics are expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • a cylindrical lithium ion battery 616 has a positive electrode cap (battery lid) 601 on the top surface, and a battery can (external can) 602 on the side and bottom surfaces.
  • the positive electrode cap 601 and the battery can (external can) 602 are insulated by a gasket (insulating packing) 610.
  • FIG 12B is a schematic diagram showing the cross section of a cylindrical lithium ion battery.
  • the cylindrical lithium ion battery shown in Figure 12B has a positive electrode cap (battery lid) 601 on the top surface, and a battery can (external can) 602 on the side and bottom surfaces.
  • the positive electrode cap and battery can (external can) 602 are insulated by a gasket (insulating packing) 610.
  • a battery element is provided, in which a strip-shaped positive electrode 604 and a negative electrode 606 are wound with an electrolyte layer 605 sandwiched between them.
  • the battery element is wound around a central axis. One end of the battery can 602 is closed and the other end is open.
  • the battery element, in which the positive electrode, negative electrode, and separator are wound is sandwiched between a pair of opposing insulating plates 608 and 609.
  • the inside of the battery can 602 in which the battery element is provided is filled with an electrolyte (not shown) according to one embodiment of the present invention.
  • the positive and negative electrodes used in a cylindrical storage battery are wound, it is preferable to form active material on both sides of the current collector.
  • a lithium ion battery 616 in which the height of the cylinder is greater than the diameter of the cylinder is illustrated in Figures 12A to 12D, this is not limited to this.
  • a lithium ion battery in which the diameter of the cylinder is greater than the height of the cylinder may also be used. With this configuration, for example, it is possible to miniaturize the lithium ion battery.
  • 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 electrode terminal 603 is resistance-welded to a safety valve mechanism 613, and the negative electrode terminal 607 is resistance-welded to the bottom of the battery can 602.
  • 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 cuts off 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 thermosensitive resistor whose resistance increases when the temperature increases, and prevents abnormal heat generation by limiting the amount of current due to the increase in resistance.
  • the PTC element may be made of a barium titanate (BaTiO 3 ) based ceramic material or the like.
  • FIG 12C shows an example of a power storage system 615.
  • the power storage system 615 has multiple lithium ion batteries 616 and is sometimes called a battery pack.
  • the positive electrode of each lithium ion battery is in contact with and electrically connected to a conductor 624 separated by an insulator 625.
  • the conductor 624 is electrically connected to a control circuit 620 via wiring 623.
  • the negative electrode of each lithium ion battery is electrically connected to the control circuit 620 via wiring 626.
  • a protection circuit that prevents overcharging or overdischarging can be applied as the control circuit 620.
  • FIG 12D shows an example of a power storage system 615.
  • the power storage system 615 has multiple lithium ion batteries 616, which are sandwiched between a conductive plate 628 and a conductive plate 614.
  • the multiple lithium ion batteries 616 are electrically connected to the conductive plate 628 and the conductive plate 614 by wiring 627.
  • the multiple lithium ion batteries 616 may be connected in parallel, in series, or in parallel and then further connected in series.
  • lithium ion batteries 616 may be connected in parallel and then further connected in series.
  • the lithium ion batteries 616 When the lithium ion batteries 616 are overheated, they can be cooled by the temperature control device, and when the lithium ion batteries 616 are too cold, they can be heated by the temperature control device. This makes the performance of the power storage system 615 less susceptible to the outside air temperature.
  • the power storage system 615 is electrically connected to the control circuit 620 via wiring 621 and wiring 622.
  • Wiring 621 is electrically connected to the positive electrodes of the multiple lithium ion batteries 616 via conductive plate 628
  • wiring 622 is electrically connected to the negative electrodes of the multiple lithium ion batteries 616 via conductive plate 614.
  • organic solvent and positive electrode active material of the present invention are used in a cylindrical lithium-ion battery 100, excellent charge/discharge characteristics are expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • the lithium ion battery 913 shown in FIG. 13A has a wound body 950 in which terminals 951 and 952 are provided inside the housing 930.
  • the wound body 950 is impregnated with an electrolyte of one embodiment of the present invention inside the housing 930.
  • the terminal 952 is in contact with the housing 930, and the terminal 951 is not in contact with the housing 930 by using an insulating material or the like.
  • the housing 930 is shown separated for convenience, but in reality, the wound body 950 is covered by the housing 930, and the terminals 951 and 952 extend outside the housing 930.
  • a metal material e.g., aluminum, etc.
  • a resin material can be used for the housing 930.
  • the housing 930 shown in FIG. 13A may be formed from a plurality of materials.
  • the lithium ion battery 913 shown in FIG. 13B has a housing 930a and a housing 930b bonded together, and a wound body 950 is provided in the area surrounded by the housings 930a and 930b.
  • the housing 930a can be made of an insulating material such as organic resin.
  • an insulating material such as organic resin.
  • the antenna may be provided inside the housing 930a.
  • the housing 930b can be made of, for example, a metal material.
  • the wound body 950 has a negative electrode 931, a positive electrode 932, and an electrolyte layer 933.
  • the wound body 950 is a wound body in which the negative electrode 931 and the positive electrode 932 are stacked on top of each other with the electrolyte layer 933 in between, and the laminated sheet is wound. Note that the stack of the negative electrode 931, the positive electrode 932, and the electrolyte layer 933 may be stacked multiple times.
  • a lithium ion battery 913 having a wound body 950a as shown in Figures 14A to 14C can be used.
  • the wound body 950a shown in Figure 14A has a negative electrode 931, a positive electrode 932, and an electrolyte layer 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 electrolyte layer 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 the negative electrode active material layer 931a and the positive electrode active material layer 932a. From the standpoint of safety, it is preferable that the negative electrode active material layer 931a is wider than the positive electrode active material layer 932a. Furthermore, a wound body 950a having such a shape is preferable because of its good safety and productivity.
  • the negative electrode 931 is electrically connected to terminal 951.
  • Terminal 951 is electrically connected to terminal 911a.
  • the positive electrode 932 is electrically connected to terminal 952.
  • Terminal 952 is electrically connected to terminal 911b.
  • the wound body 950a is covered by the housing 930 to form the lithium ion battery 913. It is preferable to provide the housing 930 with a safety valve, an overcurrent protection element, etc.
  • the safety valve is a valve that opens when the inside of the housing 930 reaches a certain internal pressure to prevent the battery from exploding.
  • the lithium ion battery 913 can be configured to have multiple wound bodies 950a. By using multiple wound bodies 950a, the lithium ion battery 913 can have a larger charge/discharge capacity.
  • the description of the lithium ion battery 913 shown in FIGS. 13A to 13C can be referred to.
  • organic solvent and positive electrode active material of the present invention are used in a lithium ion battery 913 having a wound body, excellent charge and discharge characteristics are expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • an electric vehicle is equipped with first batteries 1301a and 1301b as main driving lithium ion batteries, and a second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304.
  • first batteries 1301a and 1301b as main driving lithium ion batteries
  • second battery 1311 that supplies power to an inverter 1312 that starts a motor 1304.
  • the organic solvent and positive electrode active material of the present invention are used for the first batteries 1301a and 1301b, excellent charge and discharge characteristics are expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • the second battery 1311 is also called a cranking battery (also called a starter battery).
  • the second battery 1311 only needs to have high output, and does not need to have a large capacity.
  • 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 or a stacked type.
  • the first battery 1301a may use the secondary battery of embodiment 4.
  • By using the secondary battery of embodiment 4 for the first battery 1301a it is possible to achieve a high capacity, improve safety, and reduce the size and weight.
  • first batteries 1301a and 1301b are connected in parallel, but three or more batteries may be connected in parallel. Also, if the first battery 1301a can store sufficient power, the first battery 1301b may not be necessary.
  • a battery pack having multiple lithium ion batteries it is possible to extract large amounts of power.
  • the multiple lithium ion batteries may be connected in parallel, in series, or in parallel and then further in series. Multiple lithium ion batteries are also called a battery pack.
  • a service plug or circuit breaker that can cut off high voltage without using tools is provided in the first battery 1301a in order to cut off power from multiple lithium-ion batteries.
  • the power of the first batteries 1301a and 1301b is mainly used to rotate the motor 1304, but also supplies power to 42V in-vehicle components (such as the electric power steering 1307, heater 1308, and defogger 1309) via the DCDC circuit 1306. If the vehicle has a rear motor 1317 on the rear wheels, the first battery 1301a is also used to rotate the rear motor 1317.
  • the second battery 1311 also supplies power to 14V in-vehicle components (audio 1313, power windows 1314, lamps 1315, etc.) via the DCDC circuit 1310.
  • the first battery 1301a will be described with reference to Figure 15B.
  • FIG. 15B nine rectangular lithium ion batteries 1300 are connected in series, one electrode is fixed by a fixing part 1413 made of an insulator, and the other electrode is fixed by a fixing part 1414 made of an insulator.
  • the batteries are fixed by the fixing parts 1413 and 1414, but the batteries can be stored in a battery storage box (also called a housing). Since it is assumed that the vehicle is subjected to vibration or shaking from the outside (such as the road surface), it is preferable to fix multiple lithium ion batteries by the fixing parts 1413 and 1414 and the battery storage box.
  • One electrode is electrically connected to the control circuit part 1320 by a wiring 1421.
  • the other electrode is electrically connected to the control circuit part 1320 by a wiring 1422.
  • the control circuit unit 1320 can use a memory circuit including a transistor using an oxide semiconductor.
  • a charge control circuit or a battery control system having a memory circuit including a transistor using an oxide semiconductor may be called 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 such as In-M-Zn oxide (wherein element M is one or more selected from aluminum, gallium, yttrium, copper, vanadium, beryllium, boron, titanium, iron, nickel, germanium, zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum, tungsten, or magnesium) as the oxide.
  • the In-M-Zn oxide that can be used as the oxide is CAAC-OS (C-Axis Aligned Crystal Oxide Semiconductor) or CAC-OS (Cloud-Aligned Composite Oxide Semiconductor).
  • CAAC-OS has multiple crystalline regions, and the multiple crystalline regions are oxide semiconductors whose c-axes are aligned in a specific direction.
  • the specific direction is the thickness direction of the CAAC-OS film, the normal direction of the surface on which the CAAC-OS film is formed, or the normal direction of the surface of the CAAC-OS film.
  • the crystalline regions are regions in which the atomic arrangement has periodicity.
  • CAAC-OS has a region in which multiple crystalline regions are connected in the a-b plane direction, and the region may have distortion.
  • the distortion refers to a portion in which the direction of the lattice arrangement changes between a region in which the lattice arrangement is uniform and another region in which the lattice arrangement is uniform in the region in which multiple crystalline regions are connected.
  • CAAC-OS is an oxide semiconductor that is c-axis aligned and does not have a clear orientation in the a-b plane direction.
  • the control circuit unit 1320 uses a transistor using an oxide semiconductor.
  • the control circuit unit 1320 can also be formed using a unipolar transistor.
  • a transistor using an oxide semiconductor in the semiconductor layer has a wider operating ambient temperature range than single-crystal Si, from -40°C to 150°C, and the characteristic change is smaller than that of a single crystal even when the lithium-ion battery is heated.
  • the off-current of a transistor using an oxide semiconductor is below the lower measurement limit regardless of temperature even at 150°C, but the off-current characteristic of a single-crystal Si transistor is highly temperature-dependent. For example, at 150°C, the off-current of a single-crystal Si transistor increases, and the current on/off ratio does not become sufficiently large.
  • the control circuit unit 1320 can improve safety.
  • the control circuit unit 1320 which uses a memory circuit including transistors using oxide semiconductors, can also function as an automatic control device for lithium-ion batteries against 10 causes of instability, such as micro-shorts.
  • Functions for eliminating the 10 causes of instability include overcharging prevention, overcurrent prevention, overheating control during charging, cell balancing in a battery pack, over-discharging prevention, a fuel gauge, automatic control of charging voltage and current according to temperature, control of charging current according to degree of deterioration, detection of abnormal behavior of micro-shorts, and prediction of abnormalities related to micro-shorts, and at least one of these functions is provided by the control circuit unit 1320.
  • a micro-short circuit refers to a tiny short circuit inside a lithium-ion battery.
  • One of the causes of a micro-short circuit is said to be localized current concentration in parts of the positive electrode and negative electrode due to uneven distribution of the positive electrode active material caused by multiple charge and discharge cycles, or the generation of by-products due to side reactions, resulting in a micro-short circuit.
  • control circuit unit 1320 can also be said to detect the terminal voltage of the lithium-ion battery and manage the charge/discharge state of the lithium-ion battery. For example, to prevent overcharging, it can turn off both the output transistor and the cutoff switch of the charging circuit almost simultaneously.
  • FIG. 15C An example of a block diagram of the battery pack 1415 shown in FIG. 15B is shown in FIG. 15C.
  • the control circuit unit 1320 has at least a switch unit 1324 including a switch for preventing overcharging and a switch for preventing overdischarging, a control circuit 1322 for controlling the switch unit 1324, and a voltage measurement unit for the first battery 1301a.
  • the control circuit unit 1320 has an upper limit voltage and a lower limit voltage for the lithium ion battery used, and limits the upper limit of the current from the outside and the upper limit of the output current to the outside.
  • the range between the lower limit voltage and the upper limit voltage of the lithium ion battery is within the voltage range recommended for use, and when it is outside that range, the switch unit 1324 operates and functions as a protection circuit.
  • control circuit unit 1320 can also be called a protection circuit because it controls the switch unit 1324 to prevent overcharging and overdischarging. For example, when the control circuit 1322 detects a voltage that is likely to cause overcharging, the switch unit 1324 is turned off to cut off the current. Furthermore, a PTC element can be provided in the charge/discharge path to provide a function of cutting off the current in response to an increase in temperature. In addition, the control circuit section 1320 has an external terminal 1325 (+IN) and an external terminal 1326 (-IN).
  • the switch portion 1324 can be configured by combining an n-channel transistor and a p-channel transistor.
  • the switch portion 1324 is not limited to a switch having a Si transistor using single crystal silicon, and can be formed of a power transistor having, for example, Ge (germanium), SiGe (silicon germanium), GaAs (gallium arsenide), GaAlAs (gallium aluminum arsenide), InP (indium phosphide), SiC (silicon carbide), ZnSe (zinc selenide), GaN (gallium nitride), GaO x (gallium oxide; x is a real number greater than 0), or the like.
  • a memory element using an OS transistor can be freely arranged by stacking it on a circuit using a Si transistor, integration can be easily performed.
  • the control circuit portion 1320 using an OS transistor can be stacked on the switch portion 1324 and integrated into one chip, which enables miniaturization.
  • the first batteries 1301a and 1301b mainly supply power to 42V (high voltage) in-vehicle devices, and the second battery 1311 supplies power to 14V (low voltage) in-vehicle devices.
  • Lead-acid batteries are often used as the second battery 1311 because of their cost advantage.
  • the advantage of using a lithium-ion battery as the second battery 1311 is that it is maintenance-free, but if it is used for a long period of time, for example, for more than three years, there is a risk of abnormalities occurring that cannot be detected at the time of manufacture.
  • the second battery 1311 that starts the inverter becomes inoperable, even if the first batteries 1301a and 1301b have remaining capacity, in order to prevent the motor from being unable to start, if the second battery 1311 is a lead-acid battery, power is supplied from the first battery to the second battery, and the battery is charged to always maintain a fully charged state.
  • lithium ion batteries are used for both the first battery 1301a and the second battery 1311, but the second battery 1311 can also be a lead acid battery, an all-solid-state battery, or an electric double layer capacitor.
  • the organic solvent and positive electrode active material of the present invention are used in the above-mentioned lithium ion battery, excellent charge and discharge characteristics are expected in a wide temperature range including temperatures from below freezing to high temperatures.
  • regenerative energy generated by the rotation of the tire 1316 is sent to the motor 1304 via the gear 1305, and is then sent from the motor controller 1303 and the battery controller 1302 via the control circuit unit 1321 to charge the second battery 1311.
  • 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 regenerative energy, it is desirable that the first batteries 1301a and 1301b are capable of being rapidly charged.
  • the battery controller 1302 can set the charging voltage and charging current of the first batteries 1301a and 1301b.
  • the battery controller 1302 can set charging conditions according to the charging characteristics of the lithium ion battery used and can perform rapid charging.
  • the charger outlet or the charger connection cable is electrically connected to the battery controller 1302.
  • the power supplied from the external charger is charged to the first batteries 1301a and 1301b via the battery controller 1302.
  • some chargers are provided with a control circuit, and although the function of the battery controller 1302 may not be used, it is preferable to charge the first batteries 1301a and 1301b via the control circuit section 1320 to prevent overcharging.
  • the connection cable or the charger connection cable may be provided with a control circuit.
  • the control circuit section 1320 may also be called an ECU (Electronic Control Unit).
  • the ECU is connected to a CAN (Controller Area Network) provided in the electric vehicle.
  • the CAN is one of the serial communication standards used as an in-vehicle LAN.
  • the ECU includes a microcomputer.
  • the ECU also uses a CPU or GPU.
  • External chargers installed at charging stations and the like come in a variety of types, including 100V outlets, 200V outlets, and 3-phase 200V and 50kW outlets.
  • charging can also be performed by receiving power from external charging equipment using a contactless power supply system, etc.
  • Lithium-ion batteries can also be installed in transportation vehicles such as agricultural machinery, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing aircraft and rotary-wing aircraft, rockets, artificial satellites, space probes, planetary probes, and spacecraft.
  • transportation vehicles such as agricultural machinery, mopeds including electrically assisted bicycles, motorcycles, electric wheelchairs, electric carts, small or large ships, submarines, aircraft such as fixed-wing aircraft and rotary-wing aircraft, rockets, artificial satellites, space probes, planetary probes, and spacecraft.
  • Figures 16A to 16D show an example of a transportation vehicle using one embodiment of the present invention.
  • the automobile 2001 shown in Figure 16A is an electric automobile that uses an electric motor as a power source for running. Or, it is a hybrid automobile that can appropriately select and use an electric motor and an engine as a power source for running.
  • a lithium ion battery is mounted on a vehicle
  • an example of the lithium ion battery shown in the above embodiment is installed in one or more locations.
  • the organic solvent and positive electrode active material of the present invention are used in the lithium ion battery mounted on the vehicle, excellent charge and discharge characteristics are expected in a wide temperature range including temperatures from below freezing to high temperatures.
  • the automobile 2001 shown in FIG. 16A has a battery pack 2200, which has a battery module to which multiple lithium ion batteries are connected. It is preferable that the battery pack 2200 further has a charge control device electrically connected to the battery module.
  • automobile 2001 can charge the lithium ion battery of automobile 2001 by receiving power supply from an external charging facility using a plug-in method, a contactless power supply method, or the like. Charging can be performed appropriately using a predetermined method such as CHAdeMO (registered trademark) or Combo for the charging method and connector standard.
  • the lithium ion battery can be used in charging stations installed in commercial facilities, and can also be used as a home power source.
  • plug-in technology can be used to charge a power storage device installed in automobile 2001 using power supply from an external source.
  • Charging can be performed by converting AC power to DC power via a conversion device such as an AC-DC converter.
  • a power receiving device can be mounted on the vehicle and power can be supplied contactlessly from a power transmitting device on the ground for charging.
  • this contactless power supply method by incorporating a power transmitting device into the road or an exterior wall, charging can be performed not only when the vehicle is stopped but also while it is moving.
  • This contactless power supply method can also be used to transmit and receive power between two vehicles.
  • solar cells can be installed on the exterior of the vehicle to charge the lithium-ion battery when the vehicle is stopped and when it is moving.
  • An electromagnetic induction method or a magnetic field resonance method can be used for such contactless power supply.
  • Figure 16B shows a large transport vehicle 2002 with an electrically controlled motor as an example of a transport vehicle.
  • the battery module of the transport vehicle 2002 is, for example, a four-cell unit of lithium ion batteries with a nominal voltage of 3.0 V to 5.0 V, with 48 cells connected in series to achieve a maximum voltage of 170 V.
  • the number of lithium ion batteries in the battery pack 2201 it has the same functions as Figure 15B, so a description will be omitted. If the organic solvent and positive electrode active material of the present invention are used in the lithium ion batteries of the battery pack 2201, excellent charge and discharge characteristics can be expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • FIG 16C shows, as an example, a large transport vehicle 2003 having an electrically controlled motor.
  • the battery module of the transport vehicle 2003 has, for example, 100 or more lithium ion batteries with a nominal voltage of 3.0 V to 5.0 V connected in series to produce a maximum voltage of 600 V. Furthermore, except for the number of lithium ion batteries constituting the battery module of the battery pack 2202, it has the same functions as those in Figure 15B, so a description will be omitted. If the organic solvent and positive electrode active material of the present invention are used in the lithium ion battery of the module, excellent charge and discharge characteristics can be expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • FIG. 16D shows an aircraft 2004 having an engine that burns fuel.
  • the aircraft 2004 shown in FIG. 16D has wheels for takeoff and landing, and can therefore be considered part of a transportation vehicle. It has a battery module formed by connecting multiple lithium-ion batteries, and has a battery pack 2203 that includes the battery module and a charging control device.
  • the battery module of the aircraft 2004 has a maximum voltage of 32 V, for example, with eight 4 V lithium ion batteries connected in series. Other than the number of lithium ion batteries constituting the battery module of the battery pack 2203, it has the same functions as those in FIG. 15B, so a description thereof will be omitted.
  • FIG. 17A is an example of an electric bicycle using a lithium-ion battery of one embodiment of the present invention.
  • the lithium-ion battery of one embodiment of the present invention can be applied to the electric bicycle 8700 shown in FIG. 17A.
  • the lithium-ion battery of one embodiment of the present invention can also have a protection circuit.
  • the electric bicycle 8700 includes a power storage device 8702.
  • the power storage device 8702 can supply electricity to a motor that assists the rider.
  • the power storage device 8702 is portable, and FIG. 17B shows the power storage device 8702 removed from the bicycle.
  • the power storage device 8702 includes a plurality of lithium-ion batteries 8701 of one embodiment of the present invention, and the remaining battery charge and the like can be displayed on a display unit 8703.
  • the organic solvent and positive electrode active material of the present invention are used for the lithium-ion battery 8701, excellent charge and discharge characteristics can be expected in a wide temperature range, including temperatures from below freezing to high temperatures.
  • the power storage device 8702 also has a control circuit 8704 capable of controlling charging or detecting an abnormality of the lithium ion battery, an example of which is shown in embodiment 7.
  • the control circuit 8704 is electrically connected to the positive and negative electrodes of the lithium ion battery 8701. This can greatly contribute to the elimination of accidents such as fires caused by lithium ion batteries.
  • FIG 17C is an example of a two-wheeled vehicle using a lithium-ion battery of one embodiment of the present invention.
  • a scooter 8600 shown in Figure 17C includes a power storage device 8602, a side mirror 8601, and a turn signal light 8603.
  • the power storage device 8602 can supply electricity to the turn signal light 8603.
  • excellent charge and discharge characteristics can be expected in a wide temperature range, including temperatures from below freezing to high temperatures.
  • the scooter 8600 shown in FIG. 17C can store the power storage device 8602 in the 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.
  • FIG. 1 An example of mounting a lithium ion battery according to one embodiment of the present invention in an electronic device will be described.
  • Examples of electronic devices mounting a lithium ion battery include television devices (also called televisions or television receivers), monitors for computers, digital cameras, digital video cameras, digital photo frames, mobile phones (also called mobile phones or mobile phone devices), portable game machines, portable information terminals, audio playback devices, and large game machines such as pachinko machines.
  • portable information terminals include notebook personal computers, tablet terminals, e-book terminals, and mobile phones.
  • FIG 18A shows an example of a mobile phone.
  • the mobile phone 2100 includes a display unit 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 also includes a lithium ion battery 2107.
  • the organic solvent and positive electrode active material of the present invention are used in a lithium ion battery, excellent charge and discharge characteristics are expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • the mobile phone 2100 can execute various applications such as mobile phone calls, e-mail, text browsing and creation, music playback, Internet communication, and computer games.
  • the operation button 2103 can have various functions, such as time setting, power on/off operation, wireless communication on/off operation, silent mode and power saving mode.
  • the functions of the operation button 2103 can be freely set by an operating system built into the mobile phone 2100.
  • the mobile phone 2100 is also capable of performing standardized short-range wireless communication. For example, it can communicate with a wireless headset to enable hands-free calling.
  • the mobile phone 2100 also has 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 charging can also be performed by wireless power supply without using the external connection port 2104.
  • the mobile phone 2100 preferably has a sensor.
  • the mobile phone 2100 is equipped with a fingerprint sensor, a pulse sensor, a body temperature sensor or other human body sensor, a touch sensor, a pressure sensor, an acceleration sensor, etc.
  • Figure 18B shows an unmanned aerial vehicle 2300 having multiple rotors 2302.
  • the unmanned aerial vehicle 2300 is sometimes called a drone.
  • the unmanned aerial vehicle 2300 has a lithium ion battery 2301, which is one embodiment of the present invention, a camera 2303, and an antenna (not shown).
  • the unmanned aerial vehicle 2300 can be remotely controlled via the antenna.
  • excellent charge and discharge characteristics are expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • the microphone 6402 has a function of detecting the user's voice and environmental sounds.
  • the speaker 6404 has a function of emitting sound.
  • the robot 6400 can communicate with the user using the microphone 6402 and the 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 unit 6405.
  • the display unit 6405 can also be equipped with a touch panel.
  • the display unit 6405 may also be a removable information terminal, and by installing it in a fixed position on the robot 6400, charging and data transfer are possible.
  • the robot 6400 includes a lithium ion battery 6409 according to one embodiment of the present invention and a semiconductor device or electronic component in its internal area.
  • a lithium ion battery 6409 according to one embodiment of the present invention
  • a semiconductor device or electronic component in its internal area.
  • the cleaning robot 6300 can analyze an image captured by the camera 6303 and determine whether or not there is an obstacle such as a wall, furniture, or a step. Furthermore, if an object that may become entangled in the brush 6304, such as a wire, is detected by image analysis, the rotation of the brush 6304 can be stopped.
  • the cleaning robot 6300 includes a lithium ion battery 6306 according to one embodiment of the present invention and a semiconductor device or electronic component in its internal area. When the organic solvent and positive electrode active material of the present invention are used in the lithium ion battery, excellent charge and discharge characteristics are expected in a wide temperature range, including temperatures from below freezing to high temperatures.
  • FIG 19A shows an artificial satellite 6800 as an example of space equipment.
  • the artificial satellite 6800 has a body 6801, a solar panel 6802, an antenna 6803, and a lithium-ion battery 6805.
  • the solar panel may be called a solar cell module.
  • the satellite 6800 can generate a signal.
  • the signal is transmitted via the antenna 6803, and can be received, for example, by a receiver installed on the ground or by another satellite.
  • a receiver installed on the ground or by another satellite.
  • the position of the receiver that received the signal can be measured.
  • the satellite 6800 can constitute, for example, a satellite positioning system.
  • the artificial satellite 6800 can be configured to have a sensor.
  • the artificial satellite 6800 can have the function of detecting sunlight reflected off an object on the ground.
  • the artificial satellite 6800 can have a thermal infrared sensor, the artificial satellite 6800 can have the function of detecting thermal infrared rays emitted from the earth's surface. From the above, the artificial satellite 6800 can have the function of, for example, an earth observation satellite.
  • the solar sail 6902 can also be designed to be folded up small until it leaves the atmosphere, and then deployed into a large sheet outside the Earth's atmosphere (outer space) as shown in Figure 19B.
  • FIG 19C shows a spacecraft 6910 as an example of space equipment.
  • the spacecraft 6910 has a body 6911, a solar panel 6912, and a lithium ion battery 6913.
  • the body 6911 can have, for example, a pressurized compartment and a non-pressurized compartment.
  • the pressurized compartment can also be designed to accommodate a crew member. Electricity generated by irradiating the solar panel 6912 with sunlight can be charged into the lithium ion battery 6913.
  • Figure 19D shows a rover 6920 as an example of space equipment.
  • the rover 6920 has a body 6921 and a lithium ion battery 6923.
  • the organic solvent and positive electrode active material of the present invention are used in the lithium ion battery, excellent charge and discharge characteristics are expected over a wide temperature range, including temperatures from below freezing to high temperatures.
  • the rover 6920 can also be configured to have a solar panel 6922.
  • the rover 6920 can also be designed to accommodate a crew member.
  • the electricity generated by sunlight irradiating the solar panel 6912 can be used to charge the lithium ion battery 6923, and the lithium ion battery 6923 can also be charged with electricity generated by other power sources, such as a fuel cell, a radioisotope thermoelectric converter, etc.
  • the procedure for preparing a sample evaluation cell using a positive electrode active material is as follows.
  • Air compressed air, thoroughly dried was flowed through the furnace at 10 L/min. Specifically, the opening width of the exhaust port was adjusted so that the furnace differential pressure gauge indicated 5 Pa. When cooling the furnace, it was cooled at a rate of 200°C/hour, and the air flow was not stopped until it reached 200°C.
  • step S22_1 LiF and MgF2 were mixed in dehydrated acetone at a rotation speed of 500 rpm for 20 hours to prepare an additive element source (A1 source).
  • A1 source additive element source
  • step S31 of FIG. 2A the A1 source was mixed with the lithium cobalt oxide after the initial heating in a dry state.
  • a Picobond manufactured by Hosokawa Micron
  • the mixture was stirred at a rotation speed of 3000 rpm for 10 minutes and sieved with an automatic sieve to obtain mixture 903 (step S32).
  • step S33 the mixture 903 was heated.
  • the heating conditions were 900°C and 20 hours.
  • a lid was placed on the scabbard containing the mixture 903.
  • the inside of the scabbard was made into an oxygen-containing atmosphere, and the inflow and outflow of the oxygen could be blocked ( O2 purge).
  • a roller hearth kiln simulator furnace manufactured by Noritake Company, Ltd.
  • Oxygen was flowed into the furnace at 10 L/min ( O2 flow). Specifically, the opening width of the exhaust port was adjusted so that the differential pressure gauge of the furnace was 5 Pa (positive pressure inside the furnace).
  • the inside of the furnace was cooled, it was cooled at a rate of 200°C/hour, and the flow of oxygen was not stopped until it reached 200°C. In this way, a composite oxide containing Mg and F was obtained.
  • step S20_2 the A2 source of step S20_2 was prepared.
  • Ni(OH) 2 and Al(OH) 3 shown in step S21_2 of FIG. 2C were weighed out so that each was 0.5 mol% relative to lithium cobalt oxide, and mixed while grinding in dehydrated acetone as in step S22_2 to obtain a mixture A2, that is, the A2 source.
  • a Picobond manufactured by Hosokawa Micron was used as the mixing means, and the mixture was stirred at a rotation speed of 3000 rpm for 10 minutes to obtain a mixture A2 (step S23_2).
  • step S34 the mixture 904 was mixed as in step S34 of FIG. 2A, and the mixture 904 was obtained as in step S35.
  • step S36 the mixture 904 was heated at 850° C. for 10 hours in a furnace into which oxygen was introduced. During heating, a lid was placed on the scabbard containing the mixture 904.
  • a roller hearth kiln simulator furnace manufactured by Noritake Co., Ltd. was used as a firing furnace, and the scabbard was placed in the furnace and heated at the above heating temperature. Oxygen was flowed in the furnace at 10 L/min ( O2 flow). The opening width of the exhaust port was adjusted so that the differential pressure gauge of the furnace was 5 Pa.
  • lithium cobalt oxide having Mg, F, Ni, and Al was obtained (step S37).
  • the positive electrode active material 10 of sample 1 is an LCO containing Mg, F, Ni, and Al, and the change in crystal structure of this positive electrode active material between the discharged state where x in the above-mentioned Li x CoO 2 is 1 and the state where x is 0.24 or less, or the state where x is 0.15, is smaller than that of conventional LCO.
  • the above sample 1 was prepared as the positive electrode active material 10, acetylene black (AB) was prepared as the conductive material, and polyvinylidene fluoride (PVDF) was prepared as the binder. PVDF was prepared by dissolving it in N-methyl-2-pyrrolidone (NMP) at a weight ratio of 5% in advance.
  • NMP N-methyl-2-pyrrolidone
  • the positive electrode active material: AB: PVDF was mixed to be 95: 3: 2 (weight ratio) to prepare a slurry.
  • NMP was used as the solvent for the slurry.
  • the slurry was applied to an aluminum positive electrode current collector, and then the solvent was volatilized.
  • the thickness of the aluminum positive electrode current collector was 20 ⁇ m.
  • a pressing process was performed using a roll press machine after the solvent was evaporated.
  • the pressing process was performed under the condition of a linear pressure of 210 kN/m.
  • the upper and lower rolls of the roll press machine were both set at 120°C. 120°C is the temperature at which PVDF melts.
  • the thickness of the positive electrode active material layer was 76 ⁇ m or more and 77 ⁇ m or less.
  • the amount of the positive electrode supported was about 6 mg/ cm2 .
  • a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) was assembled using sample 1 as the positive electrode.
  • the coin cell used lithium metal as the counter electrode.
  • Stainless steel (SUS) was used for the positive and negative electrode cans of the coin cell.
  • Such coin cells are sometimes called half cells or test batteries.
  • the coin cell of sample 1 used PP as the separator. Furthermore, the coin cell of sample 1 was not subjected to aging treatment. In this example, the secondary battery was completed without aging.
  • the positive electrode active material 10 of Example 1 was used for the positive electrode, and the cycle characteristics were evaluated for a half cell of Sample 1 of Example 1 using an electrolyte according to one embodiment of the present invention, and a half cell of a comparative example.
  • the environmental temperatures in which Sample 1 was placed were 25°C and 45°C, and the cycle characteristics were measured. In this cycle test, 45°C is considered a high temperature.
  • the charging in the cycle test was CC charging at a charge rate of 0.5C until the final voltage reached 4.7V, and then CV charging was performed until the current reached 0.05C. A 10-minute rest period was held after CV charging, and then discharging was started. CC discharging was performed at a discharge rate of 0.5C until the final voltage reached 2.5V.
  • 1C 200mA/g (current per weight of positive electrode active material is 200mA/g).
  • the results at an environmental temperature of 25°C are shown in Figure 20A, and the results at 45°C are shown in Figure 20B.
  • discharge capacity retention rate capacity retention
  • the current is actually measured, and it is preferable to measure the current by the four-terminal method.
  • charging electrons flow from the positive terminal through the charge/discharge meter to the negative terminal, so the charging current flows from the negative terminal through the charge/discharge meter to the positive terminal.
  • discharging electrons flow from the negative terminal through the charge/discharge meter to the positive terminal, so the discharging current flows from the positive terminal through the charge/discharge meter to the negative terminal.
  • the charging current and discharging current are measured by an ammeter in the charge/discharge meter, and the accumulated amounts of current flowing in one charge and one discharge correspond to the charging capacity and discharging capacity, respectively.
  • the accumulated amount of discharge current flowing in the first cycle discharge can be called the first cycle discharge capacity
  • the accumulated amount of discharge current flowing in the 50th cycle discharge can be called the 50th cycle discharge capacity.
  • the comparative example was the same as sample 1 except for the electrolyte. The results of the cycle test for the comparative example are shown in Figures 20A, 20B, and 21.
  • the discharge capacity at the first cycle, the maximum discharge capacity, and the rate of increase from the discharge capacity at the first cycle were also calculated and are shown in Table 1 below.
  • sample 1 has a high first cycle discharge capacity, and the rate of increase from the first cycle discharge capacity, i.e., the capacity increase at the beginning of the cycle, is suppressed.
  • the F-substituted electrolyte of sample 1 has an increase in capacity at the beginning of the cycle even without aging, but the increase in capacity at the beginning of the cycle is suppressed more than in the comparative example.
  • the F-substituted electrolyte has significantly lower charge transfer resistance, such as that associated with solvation/desolvation of lithium ions or the insertion/removal of lithium ions into the positive electrode active material, than other electrolytes, based on the results of the impedance measurement.
  • Figure 22 shows the charge/discharge characteristics of sample 1, with the vertical axis representing voltage and the horizontal axis representing capacity.
  • Figure 22 shows data from the first and tenth cycles. As shown in Figure 22, sample 1 has a high charge/discharge capacity from the beginning of the cycle.
  • Figure 23A shows a graph of sample 1 with the capacity on the vertical axis and the number of cycles on the horizontal axis
  • Figure 23B shows a graph of sample 1 with the charge/discharge efficiency on the vertical axis and the number of cycles on the horizontal axis.
  • cycle numbers 1 to 10 in Figure 23A are the same data as cycle numbers 1 to 10 in Figure 20A
  • Figure 23A corresponds to a partial enlargement of Figure 20A.
  • Sample 1_P and Reference Example 1 were prepared to measure AC impedance and evaluate charge/discharge characteristics. The preparation conditions for each sample are explained below.
  • step S15 the lithium cobalt oxide is heated at 850° C. for 2 hours in a furnace into which oxygen is introduced. During heating, oxygen is not supplied to the furnace.
  • step S31 of FIG. 2A the lithium cobalt oxide that had been heat-treated in step S15 was mixed with A1 to obtain a mixture 903 as in step S32, and in step S33, the mixture 903 was heated at 900°C for 20 hours in a furnace into which oxygen had been introduced.
  • step S20_2 Ni(OH) 2 and Al(OH) 3 shown in step S21_2 of FIG. 2C were weighed out to be 0.5 mol% relative to lithium cobalt oxide, and mixed while grinding in dehydrated acetone as in step S22_2 to obtain a mixture A2, that is, an A2 source. Then, as in step S34 of FIG. 2A, the mixture 903 and the mixture A2 were mixed to obtain a mixture 904 as in step S35. Next, in step S36, the mixture 904 was heated at 850° C. for 10 hours in a furnace into which oxygen was introduced. During heating, oxygen was not supplied to the furnace. In this way, the positive electrode active material of sample 1_P was obtained.
  • the positive electrode active material of sample 1_P is an LCO containing Mg, F, Ni, and Al, and the change in the crystal structure of this positive electrode active material between the discharged state where x in the above-mentioned Li x CoO 2 is 1 and the state where x is 0.24 or less, or the state where x is 0.15, is smaller than that of conventional LCO.
  • the above positive electrode active material was prepared as the positive electrode of sample 1_P, acetylene black (AB) as a conductive additive, and polyvinylidene fluoride (PVDF) as a binder.
  • the PVDF was prepared by dissolving it in N-methyl-2-pyrrolidone (NMP) as a solvent at a weight ratio of 5%.
  • NMP N-methyl-2-pyrrolidone
  • a slurry was prepared in which the positive electrode active material:AB:PVDF ratio was 95:3:2 (weight ratio), and the slurry was applied to an aluminum positive electrode current collector. After that, pressing was performed at a linear pressure of 210 kN/m and 120°C.
  • a coin cell (CR2032 type, diameter 20 mm, height 3.2 mm) was assembled using Sample 1_P as the positive electrode.
  • the coin cell used lithium metal as the counter electrode.
  • Stainless steel (SUS) was used for the positive and negative electrode cans of the coin cell.
  • sample 1_P the conditions for preparing an evaluation cell for AC impedance measurement will be described.
  • An aging treatment was performed on a half cell having sample 1_P.
  • charging under the following conditions and discharging under the following conditions were repeated for two cycles.
  • the environmental temperature in which sample 1_P was placed was set to 25°C, and constant current charging (hereinafter referred to as CC charging) was performed at a rate of 0.1C until the end voltage reached 4.6V, and then constant voltage charging (hereinafter referred to as CV charging) was performed at 4.6V until the current reached 0.01C.
  • CC charging constant current charging
  • CV charging constant voltage charging
  • CC discharging constant current discharging
  • the charging conditions were: CC charging at an ambient temperature of 25°C at a rate of 0.1 C until the final voltage reached 4.5 V, and then CV charging until the current reached 0.01 C.
  • the ambient temperature was the temperature of the thermostatic chamber (manufactured by Espec Corporation) in which each sample was placed, and will hereafter be referred to simply as the ambient temperature.
  • 1 C 200 mA/g (current per weight of positive electrode active material is 200 mA/g).
  • the half cell containing sample 1_P was left in a thermostatic chamber for 6 hours. Then, under an argon atmosphere, the positive electrode of sample 1_P was removed from the half cell. The removed positive electrode was impregnated with electrolyte.
  • a symmetrical cell was also assembled for Reference Example 1 in the same manner as Sample 1_P. In this manner, an evaluation cell for Sample 1 and an evaluation cell for Reference Example 1 were prepared.
  • FIG. 24A and FIG. 24B the Nyquist diagram and the equivalent circuit diagram used for fitting are shown in FIG. 24A and FIG. 24B, respectively.
  • Z' on the horizontal axis indicates resistance [ ⁇ ]
  • -Z" on the vertical axis indicates reactance [ ⁇ ].
  • CPE HF and CPE LF correspond to double layer capacitance.
  • the resistance marked with R S corresponds to the resistance of the electrolyte
  • the resistance marked with R HF corresponds to the resistance related to electronic conduction in the electrode or the adsorption and desorption of lithium ions on the electrode surface
  • the resistance marked with R LF corresponds to the charge transfer resistance corresponding to the solvation and desolvation of lithium ions, the insertion and desorption of lithium ions, and the surface coating resistance.
  • the surface coating can be formed by the decomposition of the organic solvent and deposition on the active material. Note that W in FIG. 24A and FIG. 24B is a diffusion coefficient corresponding to the diffusion of lithium ions in a solid.
  • the AC impedance measurements were performed using a measuring device combining a potentio/galvanostat (hereinafter referred to as "P/G”) and a frequency response analyzer (hereinafter referred to as "FRA"), while controlling the environmental temperature in which the symmetrical cell was placed to 25°C, 0°C, -20°C, -40°C, and 25°C, respectively.
  • the alternating current amplitude (AC amplitude) in the FRA was set to 10 mV, and the frequency applied to the symmetrical cell was varied within a range of 0.3 mHz to 100 kHz. Specifically, when the environmental temperatures were 25°C and 0°C, the frequency was changed from 1 mHz to 100 kHz, respectively.
  • FIG. 25A shows the results of AC impedance measurement of Sample 1_P and Reference Example 1 when the environmental temperature is 25° C.
  • the frequency of the apex of the arc corresponding to R LF was 3.8 Hz, and the resistance was 76 ( ⁇ ).
  • the frequency of the apex of the arc corresponding to R LF was 1.7 Hz, and the resistance was 126 ( ⁇ ).
  • FIG. 25B shows an enlarged view of a region in FIG. 25A where Z′ is near 50 ( ⁇ ) and is marked with a square.
  • the frequency of the apex of the arc corresponding to R HF was 14094 Hz, and the resistance was 3.6 ( ⁇ ).
  • FIG. 25C shows R S , R HF , and R LF of Sample 1_P and Reference Example 1 together.
  • the measurement conditions for the AC impedance measurement were an amplitude voltage of 10 mV and a frequency sweep in the range from 200 kHz to 10 mHz, and then an AC impedance value of 1001.6 Hz (sometimes called 1 kHz) was extracted. When sweeping, 74 points per digit were measured. The measurement environment temperature was 25°C. After charging the lithium ion secondary battery to a voltage of 4.5 V, the AC impedance measurement was performed within 2 hours. From the results of the AC impedance measurement, it was found that it is preferable that the impedance value at a frequency of 1 kHz after charging the lithium ion secondary battery to a voltage of 4.5 V is less than 90 m ⁇ .
  • the AC impedance measurement is performed immediately after charging the lithium ion secondary battery to a voltage of 4.5 V, and immediately refers to the period from the end of charging the lithium ion secondary battery to the AC impedance measurement being within 24 hours, preferably within 12 hours, and more preferably within 6 hours.

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017208246A (ja) * 2016-05-19 2017-11-24 株式会社Ｇｓユアサ 非水電解液二次電池用非水電解液、非水電解液二次電池、及び非水電解液二次電池の製造方法
WO2018123238A1 (ja) * 2016-12-26 2018-07-05 パナソニックＩｐマネジメント株式会社 非水電解質二次電池
WO2022229776A1 (ja) * 2021-04-29 2022-11-03 株式会社半導体エネルギー研究所 二次電池、および電子機器
JP2022180183A (ja) * 2021-05-24 2022-12-06 株式会社Ｇｓユアサ 非水電解質蓄電素子用の負極、非水電解質蓄電素子、及びそれらの製造方法
JP2023033572A (ja) * 2018-08-03 2023-03-10 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の作製方法

Family Cites Families (2)

* Cited by examiner, † Cited by third party
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CN112201844A (zh) 2017-06-26 2021-01-08 株式会社半导体能源研究所 正极活性物质的制造方法及二次电池
US20220131146A1 (en) 2020-10-26 2022-04-28 Semiconductor Energy Laboratory Co., Ltd. Secondary battery and electronic device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2017208246A (ja) * 2016-05-19 2017-11-24 株式会社Ｇｓユアサ 非水電解液二次電池用非水電解液、非水電解液二次電池、及び非水電解液二次電池の製造方法
WO2018123238A1 (ja) * 2016-12-26 2018-07-05 パナソニックＩｐマネジメント株式会社 非水電解質二次電池
JP2023033572A (ja) * 2018-08-03 2023-03-10 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の作製方法
WO2022229776A1 (ja) * 2021-04-29 2022-11-03 株式会社半導体エネルギー研究所 二次電池、および電子機器
JP2022180183A (ja) * 2021-05-24 2022-12-06 株式会社Ｇｓユアサ 非水電解質蓄電素子用の負極、非水電解質蓄電素子、及びそれらの製造方法

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