WO2022133837A1 - 电化学装置以及电子装置 - Google Patents

电化学装置以及电子装置 Download PDF

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Publication number
WO2022133837A1
WO2022133837A1 PCT/CN2020/138743 CN2020138743W WO2022133837A1 WO 2022133837 A1 WO2022133837 A1 WO 2022133837A1 CN 2020138743 W CN2020138743 W CN 2020138743W WO 2022133837 A1 WO2022133837 A1 WO 2022133837A1
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lithium
powder
positive electrode
electrochemical device
cobalt oxide
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PCT/CN2020/138743
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English (en)
French (fr)
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吴霞
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东莞新能源科技有限公司
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Priority to EP20966411.9A priority Critical patent/EP4270545A1/en
Priority to PCT/CN2020/138743 priority patent/WO2022133837A1/zh
Priority to CN202080027584.5A priority patent/CN113748540B/zh
Publication of WO2022133837A1 publication Critical patent/WO2022133837A1/zh
Priority to US18/338,589 priority patent/US20230352661A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • 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
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application relates to the field of electrochemistry, and in particular, to an electrochemical device and an electronic device.
  • Lithium-ion batteries are widely used in portable electronic products, electric transportation, national defense aviation, energy storage and other fields due to their advantages of high energy density, good cycle performance, environmental protection, safety and no memory effect. In order to meet the needs of social development, it is an urgent problem to seek lithium-ion batteries with higher energy density and power density, which requires the cathode materials used to have higher specific capacity and higher voltage platform.
  • LiCoO 2 cathode material which has an R-3m phase structure and a theoretical capacity of 273.8mAh/g. It has good cycle and safety performance, high compaction density and simple preparation process. . Since its commercialization by Sony in 1991, LiCoO 2 cathode materials have dominated the lithium-ion battery materials market. In order to obtain higher specific energy, LiCoO 2 is developing towards high voltage (>4.6Vvs.Li/Li + ). However, when LiCoO 2 is charged to 4.5V, the capacity can only reach 190mAh/g.
  • metal cations such as Al, Mg, Ti, Zn, and Ni are generally used in the industry and scientific research community for bulk doping to improve the structural stability of R-3m phase LiCoO 2 .
  • the doping of most elements improves the structural stability of the material by delaying the irreversible phase transition, but the effect of this method on the structure stability is not obvious at voltages higher than 4.6V.
  • the doping amount increases, the theoretical capacity loss will increase. Therefore, there is an urgent need to find a cathode material for lithium-ion batteries with high specific capacity, high voltage platform, good structural reversibility, and interface stability at high voltage.
  • the present application provides an electrochemical device, which includes a positive electrode, the positive electrode includes a positive electrode active material layer, and after the electrochemical device is fully discharged, the positive electrode active material layer satisfies at least one of the following conditions:
  • the positive electrode active material layer includes a first powder and a second powder, the first powder includes a lithium cobalt oxide having a P6 3 mc structure, the second powder includes a lithium-containing metal oxide, and the lithium-containing metal oxide
  • the ratio of the molar content of Li element to the molar content of other metal elements is 0 ⁇ a ⁇ 0.5;
  • the positive electrode active material layer includes lithium cobalt oxide with a P6 3 mc structure, the surface of the lithium cobalt oxide has a lithium-containing metal oxide, and the ratio of the molar content of Li element in the lithium-containing metal oxide to the molar content of other metal elements is 0 ⁇ a ⁇ 0.5.
  • the lithium-containing metal oxide includes a compound represented by the general formula Li a NO 2+b , 0 ⁇ a ⁇ 0.5, 0 ⁇ b ⁇ 6, and N includes Al, Mg, Ti, Mn, Fe, Ni, At least one of Zn, Cu, Nb, Cr, Zr and Y; preferably, N includes at least one of Fe, Ni.
  • the lithium cobalt oxide includes the elements Li and Co, and optionally includes the element M, wherein the element M includes Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, Zr, and The sum of the molar contents of at least one of Y, Co and M elements is n Co+M .
  • the molar content of Li element in the lithium cobalt oxide is n Li
  • the ratio of n Li to n Co+M is x, wherein 0.6 ⁇ x ⁇ 0.95, preferably, 0.65 ⁇ x ⁇ 0.73;
  • the lithium cobalt oxide further includes Na element, the molar content of Na element is n Na , and the ratio of n Na to n Co+M is z, wherein 0 ⁇ z ⁇ 0.03;
  • the molar content of M element is n M
  • the ratio of n M to n Co+M is y, wherein 0 ⁇ y ⁇ 0.15
  • the molar content of Co element is n Co , n Co to n Co+M The ratio is 1-y.
  • the lithium cobalt oxide includes a compound represented by the general formula Li x Na z Co 1-y My O 2 , 0.6 ⁇ x ⁇ 0.95, 0 ⁇ y ⁇ 0.15, 0 ⁇ z ⁇ 0.03;
  • the XRD main peak of the lithium cobalt oxide (002) crystal plane lies between 17.5°-19°.
  • the average particle size D 0 of the second powder and the average particle size D 1 of the first powder satisfy: 0 ⁇ D 0 /D 1 ⁇ 0.05.
  • the average particle size D 1 of the first powder ranges from 15 ⁇ m to 30 ⁇ m.
  • the mass ratio of the second powder to the first powder is m, 0 ⁇ m ⁇ 0.3;
  • the average thickness of the lithium-containing metal oxide on the surface of the lithium cobalt oxide is h, and the average particle size of the lithium cobalt oxide is D, satisfying: 0 ⁇ h/D ⁇ 0.05.
  • the average particle size D of the lithium cobalt oxide ranges from 15 ⁇ m to 30 ⁇ m.
  • the first powder and the second powder are obtained by the following methods: after removing the binder and the conductive agent from the positive electrode active material layer, sieve with a 2000-mesh screen, and the second powder passes through the screen The powder that does not pass through the screen is the first powder.
  • the electrochemical device after the electrochemical device is fully discharged, its discharge capacity is not less than 210 mAh/g.
  • the electrochemical device charge cutoff voltage is 4.6V-4.8V.
  • the present application also provides an electronic device, including the aforementioned electrochemical device.
  • the electrochemical device provided by the present application has high specific capacity and high voltage cycling capacity stability.
  • full discharge means that the electrochemical device is subjected to constant current discharge until 0% state of charge (SOC).
  • SOC state of charge
  • all references to ratios are ratios under the same unit of measurement.
  • the "average particle size” means that the material powder is photographed and observed by a SEM scanning electron microscope, and then, 10 material particles are randomly selected from the SEM photograph using image analysis software, and these The respective areas of the material particles, and then, assuming that the material particles are spherical, the respective particle diameters R (diameter) are obtained by the following formula:
  • R 2 ⁇ (S/ ⁇ ) 1/2 ; wherein, S is the area of the material particle;
  • the process of obtaining the particle diameter R of the material particles was performed on 10 SEM images, and the particle diameters of the obtained 100 (10 ⁇ 10) material particles were arithmetically averaged to obtain the average particle diameter of the material particles.
  • the electrochemical device of the present application is, for example, a primary battery or a secondary battery.
  • the secondary battery is, for example, a lithium secondary battery, and the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
  • the electrochemical devices of the present application include a positive electrode sheet.
  • the positive electrode sheet is known in the art as a positive electrode sheet that can be used in electrochemical devices.
  • the positive electrode sheet includes a positive electrode active material layer.
  • the positive electrode active material layer includes a mixed-type composite positive electrode material formed by a lithium cobalt oxide having a P6 3 mc structure and a lithium-containing metal oxide and/or Coated composite cathode material.
  • the lithium cobalt oxide cathode material with P6 3 mc structure has a special HCP oxygen structure, and itself is a lithium-deficient material.
  • the charging process needs to extract lithium ions to open the channel, and the discharge process not only accommodates the self-extracted lithium ions, but also has electrochemical properties. Lithium intercalation ability to absorb extra lithium ions.
  • the cathode material When the cathode material is applied to lithium-ion batteries, its charge cut-off voltage can be as high as 4.8V, and it has excellent cycle performance and high-temperature storage performance.
  • the material itself is a lithium-deficient material and requires other components to provide lithium ions. While lithium-containing metal oxides release lithium ions during charging, but their own reversibility is poor, and most of the lithium ions are intercalated into the P6 3 mc cathode material, which is itself deficient in lithium ions, during discharge.
  • the P6 3 mc cathode material can accept this part of lithium ions well, and exhibits stable cycling characteristics, achieving high first-time charge-discharge efficiency and discharge capacity.
  • the positive electrode active material layer satisfies at least one of the following conditions:
  • the positive electrode active material layer includes a first powder and a second powder, the first powder includes a lithium cobalt oxide having a P6 3 mc structure, the second powder includes a lithium-containing metal oxide, and the lithium-containing metal oxide
  • the ratio of the molar content of Li element to the molar content of other metal elements is 0 ⁇ a ⁇ 0.5;
  • the positive electrode active material layer includes a lithium cobalt oxide having a P6 3 mc structure, the surface of the lithium cobalt oxide has a lithium-containing metal oxide, and the ratio of the molar content of the Li element in the lithium-containing metal oxide to the molar content of other metal elements is 0 ⁇ a ⁇ 0.5.
  • the first powder and the second powder are obtained by the following methods: after removing the binder and the conductive agent from the positive electrode active material layer, sieve with a 2000-mesh screen, and the second powder passes through the screen The powder that does not pass through the screen is the first powder.
  • the method of removing the binder and the conductive agent includes burning with a flame in an air atmosphere to burn off the binder and the conductive agent in the active material layer.
  • the positive electrode active material layer further satisfies at least one of the following conditions:
  • the mass ratio of the second powder to the first powder is m, 0 ⁇ m ⁇ 0.3;
  • the average thickness of the lithium-containing metal oxide on the surface of the lithium cobalt oxide is h, and the average particle size of the lithium cobalt oxide is D, which satisfies: 0 ⁇ h/D ⁇ 0.05.
  • the average particle size D of the lithium cobalt oxide ranges from 15 ⁇ m to 30 ⁇ m.
  • the average particle size D 0 of the second powder and the average particle size D 1 of the first powder satisfy: 0 ⁇ D 0 /D 1 ⁇ 0.05.
  • the average particle size D 1 of the first powder ranges from 15 ⁇ m to 30 ⁇ m.
  • the lithium cobalt oxide includes Li and Co elements, and optionally includes M element, wherein M element includes Al, Mg, Ti, Mn, Fe, Ni , at least one of Zn, Cu, Nb, Cr, Zr and Y, the sum of the molar contents of Co and M elements is n Co+M , and the lithium cobalt oxide satisfies at least one of the following conditions:
  • n Li The molar content of Li element is n Li , and the ratio of n Li to n Co+M is x, wherein 0.6 ⁇ x ⁇ 0.95, preferably, 0.65 ⁇ x ⁇ 0.73;
  • the lithium cobalt oxide further includes Na element, the molar content of Na element is n Na , the ratio of n Na to n Co+M is z, wherein 0 ⁇ z ⁇ 0.03;
  • the molar content of M element is n M
  • the ratio of n M to n Co+M is y, where 0 ⁇ y ⁇ 0.15
  • the molar content of Co element is n Co
  • the ratio of n Co to n Co+M is 1 -y.
  • the lithium cobalt oxide satisfies at least one of the following conditions:
  • the lithium cobalt oxide includes a compound represented by the general formula Li x Na z Co 1-y My O 2 , 0.6 ⁇ x ⁇ 0.95, 0 ⁇ y ⁇ 0.15, 0 ⁇ z ⁇ 0.03;
  • the XRD main peak of the lithium cobalt oxide (002) crystal plane is located between 17.5°-19°.
  • the method for confirming holes and cracks includes: using an ion polishing machine (Japan Electronics-IB-09010CP) to process the material to obtain a cross-section; using SEM to photograph the cross-section with a shooting magnification of not less than 5.0K to obtain Grain images, in which closed areas of a different color than the surrounding are holes and cracks.
  • the closed area refers to an area enclosed by closed lines in the image, and the line connecting any point inside the closed area and any point outside the area intersects the boundary of the area. In the image, connect any two points of a closed curve, the longest distance is the longest axis, and the shortest distance is the shortest axis.
  • the hole selection requirements may be: in a single particle in the image, the ratio of the longest axis of the closed area to the longest axis of the particle is not higher than 10%, and the difference between the longest axis and the shortest axis of the closed area is less than 0.5 microns;
  • the requirements for the selection of cracks can be as follows: the ratio of the longest axis of the closed region in a single particle to the longest axis of the particle is not less than 70%.
  • the lithium-containing metal oxide includes a compound represented by the general formula Li a NO 2+b , wherein 0 ⁇ a ⁇ 0.5, 0 ⁇ b ⁇ 6, N It includes at least one of Al, Mg, Ti, Mn, Fe, Ni, Zn, Cu, Nb, Cr, Zr and Y; preferably, N includes at least one of Fe and Ni.
  • the test steps of the discharge capacity include: charging and discharging in an environment of 25°C, charging at 0.5C Constant current charging is performed under the current until the upper limit voltage is 4.8V. Then, constant current discharge was performed at a discharge current of 0.5C until the final voltage was 3V, and the discharge capacity was obtained.
  • the electrochemical device charge cutoff voltage is 4.6V-4.8V.
  • the charge cut-off voltage is 4.6V-4.8V
  • the lithium cobalt oxide cathode material with P6 3 mc structure has a very stable interface due to its special oxygen structure, so that the electrochemical device can have good cycle performance.
  • the preparation method of the composite cathode material described above in the present application includes the following steps:
  • the precursor of M element doped (Co 1-y My ) 3 O 4 is synthesized by liquid-phase precipitation and sintering.
  • soluble cobalt salts for example, cobalt chloride, cobalt acetate, cobalt sulfate, nitric acid Cobalt, etc.
  • M salts eg, sulfate, etc.
  • a solvent eg, deionized water
  • a precipitant eg, sodium carbonate
  • complexing agent for example: ammonia water
  • lithium-containing molten salt for example, lithium nitrate, lithium chloride, lithium hydroxide, etc.
  • Lithium salts for example: lithium carbonate, lithium nitrate, lithium chloride, etc.
  • N salts or oxides for example: manganese acetate, nickel sulfate, manganese carbonate or manganese oxide, nickel oxide, etc.
  • Lithium salts for example: lithium carbonate, lithium nitrate, lithium chloride, etc.
  • N salts or oxides for example: manganese acetate, nickel sulfate, manganese carbonate or manganese oxide, nickel oxide, etc.
  • the structure of the positive electrode sheet is known in the art as the structure of the positive electrode sheet that can be used in an electrochemical device.
  • the preparation method of the positive electrode sheet is known in the art and can be used for the preparation of the positive electrode sheet of the electrochemical device.
  • a positive electrode active material, a binder, and a conductive material and a thickener are added as required, and then the positive electrode slurry is dissolved or dispersed in a solvent.
  • the solvent is evaporated and removed during the drying process.
  • the solvent is known in the art and can be used as the positive electrode active material layer, such as but not limited to N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • the electrochemical devices of the present application include a negative electrode sheet.
  • the negative electrode sheet is a negative electrode sheet known in the art that can be used in an electrochemical device.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector.
  • the anode active material layer includes an anode active material and an anode binder.
  • the negative electrode active material can be selected from various conventionally known materials that can be used as negative electrode active materials of electrochemical devices that can intercalate and deintercalate active ions or conventionally known materials capable of doping and dedoping active ions. substance.
  • the negative active material includes at least one of lithium metal, lithium metal alloy, transition metal oxide, carbon material, and silicon-based material.
  • the anode binder may include various polymeric binders.
  • the negative electrode active material layer further includes a negative electrode conductive agent.
  • the negative electrode conductive agent is used to provide conductivity for the negative electrode and can improve the conductivity of the negative electrode.
  • the negative electrode conductive agent is a conductive material known in the art that can be used as the negative electrode active material layer.
  • the negative electrode conductive agent may be selected from any conductive material as long as it does not cause chemical changes.
  • the structure of the negative electrode sheet is known in the art as the structure of the negative electrode sheet that can be used in an electrochemical device.
  • the preparation method of the negative electrode sheet is known in the art for the preparation method of the negative electrode sheet that can be used in an electrochemical device.
  • negative electrode active material and binder are usually added, and conductive material and thickener are added as required, and then dissolved or dispersed in a solvent to prepare negative electrode slurry.
  • the solvent is evaporated and removed during the drying process.
  • the solvent is known in the art and can be used as the negative electrode active material layer, and the solvent is, for example, but not limited to, water.
  • Thickeners are known in the art and can be used as a thickener for the negative active material layer, such as, but not limited to, sodium carboxymethylcellulose.
  • the electrochemical devices of the present application include a separator.
  • the separator is a separator known in the art that can be used in electrochemical devices, such as, but not limited to, a polyolefin-based porous membrane.
  • the polyolefin-based porous film comprises polyethylene (PE), ethylene-propylene copolymer, polypropylene (PP), ethylene-butene copolymer, ethylene-hexene copolymer, ethylene-methyl methacrylate Monolayer or multilayer film composed of one or more of ester copolymers.
  • the present application has no particular restrictions on the shape and thickness of the separator.
  • the preparation method of the separator is known in the art and can be used for the preparation of the separator of the electrochemical device.
  • the electrochemical devices of the present application comprise an electrolyte.
  • the electrolyte includes an electrolyte salt.
  • Electrolyte salts are those known to those skilled in the art that are suitable for use in electrochemical devices. Appropriate electrolyte salts can be selected for different electrochemical devices. For example, for lithium ion batteries, lithium salts are generally used as electrolyte salts.
  • the electrolyte further includes an organic solvent.
  • the organic solvent is an organic solvent known to those skilled in the art and suitable for electrochemical devices, for example, a non-aqueous organic solvent is generally used.
  • the non-aqueous organic solvent includes at least one of carbonate-based solvents, carboxylate-based solvents, ether-based solvents, sulfone-based solvents, or other aprotic solvents.
  • the electrolyte further includes additives.
  • the additives are known in the art and are suitable for electrochemical devices, and can be added according to the required performance of the electrochemical device.
  • the configuration of the electrolyte can be prepared by methods known to those skilled in the art, and its composition can be selected according to actual needs.
  • the electronic device of the present application can be any electronic device, such as but not limited to notebook computers, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headphone, VCRs, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, bicycles, Lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large storage batteries for household use, and lithium-ion capacitors.
  • the electrochemical device of the present application is not only applicable to the electronic devices listed above, but also applicable to energy storage power stations, marine vehicles, and air vehicles.
  • Airborne vehicles include airborne vehicles within the atmosphere and airborne vehicles outside the atmosphere.
  • the electronic device comprises an electrochemical device as described herein.
  • the lithium ion batteries of the examples and comparative examples were prepared according to the following methods.
  • the hybrid or coated composite positive electrode material is prepared.
  • the composite cathode material prepared above, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were fully stirred and mixed in an appropriate amount of N-methylpyrrolidone (NMP) in a weight ratio of 95:2:3. , to form a uniform positive electrode slurry; apply the positive electrode slurry on a 12 ⁇ m aluminum foil, dry, cold-press, and then cut and weld tabs to obtain a positive electrode sheet.
  • NMP N-methylpyrrolidone
  • the separator adopts polyethylene (PE) porous polymer film.
  • ethylene carbonate (EC), propylene carbonate (PC) and diethyl carbonate (DEC) were mixed in a weight ratio of 1:1:1, and LiPF 6 was added and mixed evenly to form an electrolytic solution.
  • the first cycle of discharge capacity and cycle performance test at 25°C, the lithium-ion batteries prepared in the examples and comparative examples were charged at a constant current of 0.5C to a voltage of 4.8V, then left for 5 minutes, and then discharged at a constant current of 0.5C To the voltage of 3.0V, let stand for 5min, this is a cycle charge and discharge process, the discharge capacity this time is recorded as the first cycle discharge capacity.
  • the lithium-ion battery was subjected to a 100-cycle charge-discharge test according to the above method, and the discharge capacity of the 100-cycle cycle was detected.
  • the capacity retention rate (%) of the lithium-ion battery after 100 cycles the discharge capacity of the 100th cycle/the discharge capacity of the first cycle x 100%.
  • Table 1 shows that after the lithium ion battery prepared using the hybrid composite cathode material/only using the lithium cobalt oxide with P6 3 mc structure as the cathode material is fully discharged, the cathode active material layer is burned in an air atmosphere to remove the stickiness.
  • the composition parameters and corresponding electrochemical properties of lithium cobalt oxides and lithium-containing metal oxides with P6 3 mc structure obtained after sieving with 2000 mesh screen after binding agent and conductive agent.
  • Table 2 shows the lithium cobalt oxide with P6 3 mc structure in the cathode active layer after full discharge of the lithium ion battery prepared using the coated composite cathode material/only using the lithium cobalt oxide with the P6 3 mc structure as the cathode material and the compositional parameters of the surface lithium-containing metal oxides and the corresponding electrochemical properties.
  • Table 3 shows the effect of the mass ratio of the lithium cobalt oxide with the P6 3 mc structure and the lithium-containing metal oxide in the hybrid composite cathode material on the performance of the lithium ion battery.
  • Table 4 shows the effect of the micro-morphology (holes and cracks) of Li-CoO with P6 3 mc structure in the hybrid composite cathode material on the performance of Li-ion batteries.
  • Comparative analysis of the data in Table 1 shows that, compared to Comparative Examples 1-5 to 1-8 using only lithium cobalt oxide having a P6 3 mc structure as the positive electrode material, Examples 1-1 using a hybrid composite positive electrode material Up to 1-14, the discharge capacity of the first cycle is significantly improved, and the capacity retention rate is also very good.
  • the examples with 0 ⁇ D 0 /D 1 ⁇ 0.05 have more excellent first-cycle discharge capacity and capacity retention, which is due to :
  • the particle size of the lithium-containing metal oxide is too large, which is not conducive to the full extraction of lithium ions in it, resulting in the first cycle of charge and discharge process, which cannot supplement the capacity of the lithium cobalt oxide with the P6 3 mc structure, resulting in The discharge capacity of the first cycle is reduced; on the other hand, the small particle size lithium-containing metal oxide will fill in the cracks between the large particle size lithium cobalt oxide particles with the P6 3 mc structure, and will not increase the lithium cobalt oxide.
  • the interfacial impedance between the active materials increases the interfacial impedance between the active materials, while the lithium-containing metal oxide with excessive particle size is blocked between the lithium-cobalt oxide particles with the P6 3 mc structure, which will increase the interfacial impedance between the active materials, resulting in the cycle performance. worse.
  • Example 4-1 using lithium cobalt oxide particles with both holes and cracks has the best discharge capacity and capacity retention rate in the first cycle. It is beneficial to the insertion and extraction of lithium ions inside the particles, thereby improving the discharge capacity. At the same time, the structure of pores and cracks is also conducive to the stress release during the cycle, thereby improving the cycle stability.

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Abstract

本申请提供了一种电化学装置，包括正极，正极包括正极活性材料层，电化学装置经满放后，正极活性材料层满足以下条件的至少一者：a)正极活性材料层包括第一粉体和第二粉体，第一粉体包括具有P63mc结构的锂钴氧化物，第二粉体包括含锂金属氧化物，含锂金属氧化物中Li元素的摩尔含量与其他金属元素的摩尔含量之比为0<a<0.5；b)正极活性材料层包括具有P63mc结构的锂钴氧化物，锂钴氧化物表面具有含锂金属氧化物，含锂金属氧化物中Li元素的摩尔含量与其他金属元素的摩尔含量之比为0<a<0.5。本申请的电化学装置具有高比容量和高电压循环稳定性。

Description

电化学装置以及电子装置 技术领域
本申请涉及电化学领域，具体涉及一种电化学装置以及电子装置。
背景技术
锂离子电池因其能量密度高、循环性能好、环保、安全且无记忆效应等优点，被广泛的应用于便携式电子产品、电动交通、国防航空、能源储备等领域。为了满足社会发展的需求，寻求具有更高能量密度和功率密度的锂离子电池是亟待解决的问题，这就要求所用正极材料具有更高比容量和更高电压平台。
目前在3C领域商业化用最多的正极材料是LiCoO 2正极材料，为R-3m相结构，理论容量为273.8mAh/g，其具有良好的循环及安全性能，高的压实密度且制备工艺简单。自1991年Sony公司实现商业化以来，LiCoO 2正极材料在锂离子电池材料市场一直占据着主要地位。为了获取更高比能量，LiCoO 2正朝着高电压(>4.6Vvs.Li/Li +)方向发展。然而LiCoO 2充电到4.5V，容量也仅能达到190mAh/g。人们试图通过从晶体结构中脱出更多的Li +来实现更高的比容量，但随着电压进一步升高，Li +大量脱出，晶体结构将发生一系列不可逆的相变(O3到H1-3，H1-3到O1)，使得材料循环性能和安全性能大大降低。加之，高电压下界面副反应加剧，Co金属溶出严重，而高电压电解液技术难以配套，常规电解液在高电压下分解加速、失效加快，因而容量衰减十分严重。
目前，产业界和科研界一般采用Al、Mg、Ti、Zn、Ni等金属阳离子进行体相掺杂，来提高R-3m相LiCoO 2的结构稳定性。大部分元素的掺杂都是通过推迟不可逆相变来提高材料的结构稳定性，但该方法在高于4.6V电压后对结构的稳定效果并不明显。此外，掺杂量增多，理论容量损失会增大。因此，急需寻求一种具有高比容量、高电压平台、结构可逆性好且在高电压下界面稳定的锂离子电池正极材料。
发明内容
在一些实施例中，本申请提供了一种电化学装置，其包括正极，正极包括正极活性材料层，电化学装置经满放后，正极活性材料层满足以下条件的至少一者：
a)正极活性材料层包括第一粉体和第二粉体，第一粉体包括具有P6 3mc结构的锂钴氧化物，第二粉体包括含锂金属氧化物，含锂金属氧化物中Li元素的摩尔含量与其他金属元素的摩尔含量之比为0<a<0.5；
b)正极活性材料层包括具有P6 3mc结构的锂钴氧化物，锂钴氧化物表面具有含锂金属氧化物，含锂金属氧化物中Li元素的摩尔含量与其他金属元素的摩尔含量之比为0<a<0.5。
在一些实施例中，含锂金属氧化物包括通式Li aNO 2+b表示的化合物，0<a<0.5，0<b<6，N包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Zr和Y中的至少一种；优选地，N包括Fe、Ni中的至少一种。
在一些实施例中，锂钴氧化物包括Li和Co元素，以及可选地包括M元素，其中M元素包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Zr和Y中的至少一种，Co和M元素的摩尔含量之和为n Co+M。
在一些实施例中，锂钴氧化物中Li元素的摩尔含量为n Li，n Li与n Co+M的比值为x，其中0.6<x<0.95，优选地，0.65<x<0.73；
在一些实施例中，锂钴氧化物进一步包括Na元素，Na元素的摩尔含量为n Na，n Na与n Co+M的比值为z，其中0≤z<0.03；
在一些实施例中，M元素的摩尔含量为n M，n M与n Co+M的比值为y，其中0≤y<0.15，Co元素的摩尔含量为n Co，n Co与n Co+M的比值为1-y。
在一些实施例中，锂钴氧化物包括通式Li xNa zCo 1-yM yO 2表示的化合物，0.6<x<0.95，0≤y<0.15，0≤z<0.03；
在一些实施例中，锂钴氧化物(002)晶面的XRD主峰位于17.5°-19°之间。
在一些实施例中，第二粉体的平均粒径D 0与第一粉体的平均粒径D 1满足：0<D 0/D 1<0.05。
在一些实施例中，第一粉体的平均粒径D 1范围为15μm至30μm。
在一些实施例中，第二粉体与第一粉体的质量比为m，0<m≤0.3；
在一些实施例中，锂钴氧化物表面的含锂金属氧化物的平均厚度为h，锂钴氧化物的平均粒径为D，满足：0<h/D≤0.05。
在一些实施例中，锂钴氧化物的平均粒径D范围为15μm至30μm。
在一些实施例中，具有P6 3mc结构的锂钴氧化物的颗粒内部存在孔洞或裂缝。
在一些实施例中，第一粉体和第二粉体通过如下方式获得：将正极活性材料层去除粘结剂和导电剂后，利用2000目筛网筛分，通过筛网的为第二粉体，未通过筛网的为第一粉体。
在一些实施例中，电化学装置经满放后，其放电容量不低于210mAh/g。
在一些实施例中，电化学装置充电截止电压为4.6V-4.8V。
进一步，本申请还提供了一种电子装置，包括前述的电化学装置。
本申请提供的电化学装置具有高比容量和高电压循环容量稳定性。
具体实施方式
应理解的是，所公开的实施例仅是本申请的示例，本申请可以以各种形式实施，因此，本文公开的具体细节不应被解释为限制，而是仅作为权利要求的基础且作为表示性的基础用于教导本领域普通技术人员以各种方式实施本申请。
在本申请的说明中，未明确说明的术语、专业用词均为本领域技术人员的公知常识，未明确说明的方法均为本领域技术人员公知的常规方法。
在本申请的说明中，“满放”是指将电化学装置进行恒流放电，直到0％荷电状态(SOC)。在本申请的说明中，涉及到比值的均为在同一计量单位下的比值。在本申请的说明中，“平均粒径”指的是通过SEM扫描电镜对材料粉体进行拍摄观察，然后，使用图像解析软件，从SEM照片中随机地选出10个材料颗粒，求出这些材料颗粒各自的面积，接着，假设材料颗粒是球形，通过以下公式求出各自的粒径R(直径)：
R＝2×(S/π) 1/2；其中，S为材料颗粒的面积；
对10张SEM图像进行求出上述材料颗粒粒径R的处理，并将所得100(10×10)个材料颗粒的粒径进行算数平均，从而求得所述材料颗粒的平均粒径。
下面详细说明本申请的电化学装置。
本申请的电化学装置例如为一次电池、二次电池。二次电池例如为锂二次电池，锂二次电池包含但不限于锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
[正极片]
在一些实施例中，本申请的电化学装置包含正极片。正极片是本领域技术公知的可被用于电化学装置的正极片。在一些实施例中，正极片包含正极活性材料层。
(正极活性材料层)
在一些实施例中，本申请的电化学装置经满放后，其中的正极活性材料层包括具有P6 3mc结构的锂钴氧化物和含锂金属氧化物形成的混合型复合正极材料和/或包覆型复合正极材料。具有P6 3mc结构的锂钴氧化物正极材料具有特殊的HCP氧结构，其本身为缺锂材料，充电过程需要脱出锂离子打开通道，而放电过程除容纳自身脱出锂离子外，还具有电化学嵌锂能力，吸收额外的锂离子。当该正极材料应用于锂离子电池时，其充电截止电压可高达4.8V，并具有优良的循环性能和高温存储性能。然而该材料本身为缺锂材料，需要其他组分提供锂离子。而含锂的金属氧化物在充电过程释放出锂离子，但其自身可逆性差，大部分锂离子在放电过程中嵌入到了本身缺锂离子的P6 3mc正极材料中。P6 3mc正极材料可以很好接收这部分锂离子，并呈现稳定的循环特性，实现高的首次充放电效率和放电容量。
在一些实施例中，本申请的电化学装置经满放后，正极活性材料层满足以下条件的至少一者：
a)正极活性材料层包括第一粉体和第二粉体，第一粉体包括具有P6 3mc结构的锂钴氧化物，第二粉体包括含锂金属氧化物，含锂金属氧化物中Li元素的摩尔含量与其他金属元素的摩尔含量之比为0<a<0.5；
b)正极活性材料层包括具有P6 3mc结构的锂钴氧化物，锂钴氧化物表面 具有含锂金属氧化物，含锂金属氧化物中Li元素的摩尔含量与其他金属元素的摩尔含量之比为0<a<0.5。
在一些实施例中，第一粉体和第二粉体通过如下方式获得：将正极活性材料层去除粘结剂和导电剂后，利用2000目筛网筛分，通过筛网的为第二粉体，未通过筛网的为第一粉体。其中，去除粘结剂和导电剂的方式包括在空气氛下利用火焰灼烧以将活性材料层中的粘结剂和导电剂烧除。
在一些实施例中，本申请的电化学装置经满放后，正极活性材料层还满足以下条件的至少一者：
c)第二粉体与第一粉体的质量比为m，0<m≤0.3；
d)锂钴氧化物表面的含锂金属氧化物的平均厚度为h，锂钴氧化物的平均粒径为D，满足：0<h/D≤0.05。
在一些实施例中，锂钴氧化物的平均粒径D范围为15μm至30μm。
在一些实施例中，本申请的电化学装置经满放后，第二粉体的平均粒径D 0与第一粉体的平均粒径D 1满足：0<D 0/D 1<0.05。在一些实施例中，第一粉体的平均粒径D 1范围为15μm至30μm。
<锂钴氧化物>
在一些实施例中，本申请的电化学装置经满放后，锂钴氧化物包括Li和Co元素，以及可选地包括M元素，其中M元素包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Zr和Y中的至少一种，Co和M元素的摩尔含量之和为n Co+M，并且锂钴氧化物满足以下条件的至少一者：
e)Li元素的摩尔含量为n Li，n Li与n Co+M的比值为x，其中0.6<x<0.95，优选地，0.65<x<0.73；
f)锂钴氧化物进一步包括Na元素，Na元素的摩尔含量为n Na，n Na与n Co+M的比值为z，其中0≤z<0.03；
g)M元素的摩尔含量为n M，n M与n Co+M的比值为y，其中0≤y<0.15，Co元素的摩尔含量为n Co，n Co与n Co+M的比值为1-y。
在一些实施例中，本申请的电化学装置经满放后，锂钴氧化物满足以下条件的至少一者：
h)所述锂钴氧化物包括通式Li xNa zCo 1-yM yO 2表示的化合物，0.6<x<0.95，0≤y<0.15，0≤z<0.03；
i)所述锂钴氧化物(002)晶面的XRD主峰位于17.5°-19°之间。
在一些实施例中，本申请的电化学装置经满放后，具有P6 3mc结构的锂钴氧化物的颗粒内部存在孔洞或裂缝。
在一些实施例中，孔洞和裂缝的确认方法包括：利用离子抛光机(日本电子-IB-09010CP)对材料进行加工，得到断面；利用SEM对断面进行拍摄，拍摄倍数不低于5.0K，获得颗粒图像，在图像中，与周围颜色不同的闭合区域即为孔洞和裂缝。其中，闭合区域是指图像中由封闭线条围成的一个区域，闭合区域内部任何一点与区域外任何一点的连线都和区域的边界相交。在图像中，连接闭合曲线任意两点，最长的距离即为最长轴，最短的距离即为最短轴。其中，孔洞选取要求可为：在图像的单个颗粒中闭合区域的最长轴与颗粒最长轴的比不高于10％，且闭合区域的最长轴与最短轴的差值小于0.5微米；裂缝的选取要求可为：单个颗粒中闭合区域的最长轴与颗粒最长轴的比不低于70％。
<含锂的金属氧化物>
在一些实施例中，本申请的电化学装置经满放后，含锂的金属氧化物包括通式Li aNO 2+b表示的化合物，其中0<a<0.5，0<b<6，N包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Zr和Y中的至少一种；优选地，N包括Fe、Ni中的至少一种。
在一些实施例中，电化学装置经满放后，其放电容量不低于210mAh/g，其中，放电容量的测试步骤包含：在25℃的环境中，进行充电和放电，在0.5C的充电电流下进行恒流充电，直到上限电压为4.8V。然后，在0.5C的放电电流下进行恒流放电，直到最终电压为3V，得到放电容量。
在一些实施例中，电化学装置充电截止电压为4.6V-4.8V。在充电截止电压在4.6V-4.8V时，具有P6 3mc结构的锂钴氧化物正极材料由于其特殊氧结构，其界面十分稳定，从而可使电化学装置具有良好的循环性能。
(复合正极材料的制备方法)
在一些实施例中，本申请前述的复合正极材料的制备方法，包括以下步骤：
(1)采用液相沉淀加烧结的方法合成M元素掺杂的(Co 1-yM y) 3O 4前躯 体，首先将可溶性钴盐(例如，氯化钴、醋酸钴、硫酸钴、硝酸钴等)和M盐(例如，硫酸盐等)按比例Co：M＝(1-y):y溶入溶剂(例如，去离子水)中，加入沉淀剂(例如：碳酸钠)和络合剂(例如：氨水)，调节PH(例如，将PH值调节5-9)，使之沉淀；然后将沉淀物进行烧结，研磨获得(Co 1-yM y) 3O 4粉体。最后，将(Co 1-yM y) 3O 4粉体与Na 2CO 3按化学计量比(例如：n：1-y)在700℃-900℃、空气气氛中反应36-48h，得到Na nCo 1-yM yO 2，0≤y<0.15，0.6≤n<1；
(2)采用Na nCo 1-yM yO 2作为前躯体，将其与含锂熔盐(例如，硝酸锂、氯化锂、氢氧化锂等)按比例优选Na：Li＝1：5，混合均匀，在200℃-400℃、空气气氛中反应2h-8h，反应物经去离子水多次洗涤，待熔盐清洗干净，烘干粉体得到具有HCP氧结构的Li xNa zCo 1-yM yO 2，0.6<x<0.95，0≤y<0.15，0≤z<0.03；
(3)将锂盐(例如：碳酸锂、硝酸锂、氯化锂等)和N盐或氧化物(例如：醋酸锰、硫酸镍、碳酸锰或氧化锰、氧化镍等)按照Li：N＝(2±h)：1比例，进行一步烧结合成得到Li hNO k，0<h<10，0<k<8；
(4)将步骤2与步骤3产物按照一定比例(例如：m＝0.1，m＝0.2，m＝0.25等)，混合均匀，得到混合型复合正极材料；
(5)将锂盐(例如：碳酸锂、硝酸锂、氯化锂等)和N盐或氧化物(例如：醋酸锰、硫酸镍、碳酸锰或氧化锰、氧化镍等)按照Li：N＝(2±h)：1比例加入到步骤2所得的粉体中，进行一步烧结得到包覆型复合正极材料。
在一些实施例中，正极片的结构为本领域技术公知的可被用于电化学装置的正极片的结构。
在一些实施例中，正极片的制备方法是本领域技术公知的可被用于电化学装置的正极片的制备方法。在一些实施例中，在正极浆料的制备中，通常加入正极活性物质、粘结剂，并根据需要加入导电材料和增稠剂后溶解或分散于溶剂中制成正极浆料。溶剂在干燥过程中挥发去除。溶剂是本领域公知的可被用作正极活性物质层的溶剂，溶剂例如但不限于N-甲基吡咯烷酮(NMP)。
[负极片]
在一些实施例中，本申请的电化学装置包含负极片。负极片是本领域技术公知的可被用于电化学装置的负极片。在一些实施例中，负极片包含负极集流体以及设置在负极集流体上的负极活性物质层。在一些实施例中，负极活性物质层包括负极活性物质以及负极粘结剂。
负极活性物质可选用本领域技术公知的各种可被用作电化学装置的负极活性物质的能够嵌入、脱嵌活性离子的传统公知的物质或能够掺杂、脱掺杂活性离子的传统公知的物质。
在一些实施例中，负极活性物质包含锂金属、锂金属合金、过渡金属氧化物、碳材料、硅基材料中的至少一种。
在一些实施例中，负极粘结剂可以包含各种聚合物粘合剂。
在一些实施例中，负极活性物质层还包含负极导电剂。负极导电剂用于为负极提供导电性，可改善负极导电率。负极导电剂是本领域公知的可被用作负极活性物质层的导电材料。负极导电剂可以选自任何导电的材料，只要它不引起化学变化即可。
在一些实施例中，负极片的结构为本领域技术公知的可被用于电化学装置的负极片的结构。
在一些实施例中，负极片的制备方法是本领域技术公知的可被用于电化学装置的负极片的制备方法。在一些实施例中，在负极浆料的制备中，通常加入负极活性物质、粘合剂，并根据需要加入导电材料和增稠剂后溶解或分散于溶剂中制成负极浆料。溶剂在干燥过程中挥发去除。溶剂是本领域公知的可被用作负极活性物质层的溶剂，溶剂例如但不限于水。增稠剂是本领域公知的可被用作负极活性物质层的增稠剂，增稠剂例如但不限于羧甲基纤维素钠。
[隔离膜]
在一些实施例中，本申请的电化学装置包含隔离膜。隔离膜是本领域技术公知的可被用于电化学装置的隔离膜，例如但不限于聚烯烃类多孔膜。在一些实施例中，聚烯烃类多孔膜包含聚乙烯(PE)、乙烯-丙烯共聚物、聚丙 烯(PP)、乙烯-丁烯共聚物、乙烯-己烯共聚物、乙烯-甲基丙烯酸甲酯共聚物中的一种或几种组成的单层或多层膜。
本申请对隔离膜的形态和厚度没有特别的限制。隔离膜的制备方法是本领域技术公知的可被用于电化学装置的隔离膜的制备方法。
[电解液]
在一些实施例中，本申请的电化学装置包含电解液。
在一些实施例中，电解液包含电解质盐。电解质盐是本领域技术公知的适用于电化学装置的电解质盐。针对不同的电化学装置，可以选用合适的电解质盐。例如对于锂离子电池，电解质盐通常使用锂盐。
在一些实施例中，电解液还包含有机溶剂。有机溶剂是本领域技术公知的适用于电化学装置的有机溶剂，例如通常使用非水有机溶剂。在一些实施例中，非水有机溶剂包含碳酸酯类溶剂、羧酸酯类溶剂、醚类溶剂、砜类溶剂或其他非质子溶剂中的至少一种。
在一些实施例中，电解液还包含添加剂。添加剂是本领域技术公知的适用于电化学装置的添加剂，可根据需要的电化学装置的性能进行添加。
电解液的配置可通过本领域技术人员公知的方法调配而成，其组成可根据实际需要进行选择。
其次说明本申请的电子装置。
本申请的电子装置可以是任何电子装置，例如但不限于笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池、锂离子电容器。注意的是，本申请的电化学装置除了适用于上述列举的电子装置外，还适用于储能电站、海运运载工具、空运运载工具。空运运载装置包含在大气层内的空运运载装置和大气层外的空运运载装置。
在一些实施例中，电子装置包含本申请所述的电化学装置。
下面结合实施例，进一步阐述本申请。应理解，这些实施例仅用于说明本申请而不用于限制本申请的范围。
在下述实施例、对比例中，所使用到的试剂、材料等如没有特殊的说明，均可商购获得或合成获得。
实施例和对比例的锂离子电池均按照下述方法制备。
1)正极片的制备
按照前述复合正极材料的制备方法制备混合型或包覆型复合正极材料。将上述制备的复合正极材料、导电炭黑(Super P)、粘结剂聚偏二氟乙烯(PVDF)按95：2：3重量比在适量的N-甲基吡咯烷酮(NMP)中充分搅拌混合，使其形成均匀的正极浆料；将该正极浆料涂布在12μm的铝箔上，干燥，冷压，再经过裁片、焊接极耳，得到正极片。
2)负极片的制备
将人造石墨、丁苯橡胶和羧甲基纤维素钠按照96:2:2的重量比与去离子水混合，搅拌均匀，得到负极浆料。将该负极浆料涂布在12μm的铜箔上。干燥，冷压，再经过裁片、焊接极耳，得到负极片。
3)隔离膜采用聚乙烯(PE)多孔聚合物薄膜。
4)电解液的制备
在干燥氩气环境下，将碳酸亚乙酯(EC)、碳酸亚丙酯(PC)和碳酸二乙酯(DEC)按照1:1:1的重量比混合，加入LiPF 6混合均匀，形成电解液，其中LiPF 6的浓度为1.15mol/L。
5)将上述正极片、隔离膜、负极片按次序叠放、卷绕、置于外包装箔中，留下注液口。从注液口灌注电解液，封装，再经过化成、容量等工序制得锂离子电池。
接下来说明锂离子电池的性能测试过程。
首圈放电容量及循环性能测试：在25℃下，将实施例和对比例制备得到的锂离子电池以0.5C恒流充电至电压为4.8V，之后静置5min，再以0.5C恒流放电至电压为3.0V，静置5min，此为一个循环充放电过程，此 次的放电容量记为首圈放电容量。将锂离子电池按照上述方法进行100圈循环充放电测试，检测得到第100圈循环的放电容量。锂离子电池循环100圈后的容量保持率(％)＝第100圈循环的放电容量/首圈放电容量×100％。
实施例和对比例的锂离子电池的相关参数以及锂离子电池的性能测试结果如表1-表4所示。
其中，表1展示了使用混合型复合正极材料/仅使用具有P6 3mc结构的锂钴氧化物作为正极材料制备的锂离子电池满放后，正极活性材料层在空气氛下火焰灼烧去除粘结剂和导电剂后，利用2000目筛网筛分后所得具有P6 3mc结构的锂钴氧化物和含锂金属氧化物的组成参数以及相应的电化学性能。
表2展示了使用包覆型复合正极材料/仅使用具有P6 3mc结构的锂钴氧化物作为正极材料制备的锂离子电池满放后，正极活性层中具有P6 3mc结构的锂钴氧化物和表面含锂金属氧化物的组成参数以及相应的电化学性能。
表3展示混合型复合正极材料中具有P6 3mc结构的锂钴氧化物和含锂金属氧化物的质量配比对锂离子电池性能的影响。
表4展示了混合型复合正极材料中具有P6 3mc结构的锂钴氧化物的微观形貌(孔洞和裂缝)对锂离子电池性能的影响。
Figure PCTCN2020138743-appb-000001
Figure PCTCN2020138743-appb-000002
表3
Figure PCTCN2020138743-appb-000003
表4
Figure PCTCN2020138743-appb-000004
对比分析表1中的数据可见，相较于仅使用具有P6 3mc结构的锂钴氧化物作为正极材料的对比例1-5至1-8，使用混合型复合正极材料的实施例1-1至1-14具有显著提升的首圈放电容量，且容量保持率同样非常优异。相较于D 0/D 1>0.05的对比例1-1至1-4，0<D 0/D 1<0.05的实施例具有更为优异的首圈放电容量和容量保持率，这是由于：一方面，含锂金属氧化物的粒径过大，不利于其内部的锂离子充分脱出，从而导致首圈充放电过程，其无法给具有P6 3mc结构的锂钴氧化物补充容量，造成首圈放电容量降低；另一方面，小粒径的含锂金属氧化物会填充在大粒径的具有P6 3mc结构的锂钴氧化物颗粒之间的裂缝中，不会增大锂钴氧化物颗粒之间的界面阻抗，而粒径过大的含锂金属氧化物阻隔在具有P6 3mc结构的锂钴氧化物颗粒之间，会增大活性材料之间的界面阻抗，从而导致循环性能变差。
对比分析表2中的数据可见，0<h/D≤0.05的实施例相较于仅使用具有P6 3mc结构的锂钴氧化物作为正极材料的对比例2-5至2-8，首圈放电容量同样显著提升，且容量保持率同样非常优异。而h/D>0.05的对比例2-1至2-4， 相较于对比例2-5至2-8，其首圈放电容量并未显著提升，而循环性能却大幅下降，这是由于过厚的含锂金属氧化物(本身电导偏低)增大了具有P6 3mc结构的锂钴氧化物颗粒之间的界面阻抗，从而导致循环性能大幅降低。
对比分析表3中的数据可见，混合型复合正极材料制得的锂离子电池中，筛下物的质量比m过大，其首圈放电容量和循环容量保持率均降低，这是由于，含锂金属氧化物过多，复合电极材料的整体电导偏低，充放电效率降低，因而容量降低；而脱锂后的含锂氧化物大量存在活性物质中，进一步恶化了循环过程电极材料的导电能力，因而循环衰减增大。
对比分析表4中的数据可见，使用同时具有孔洞和裂缝的锂钴氧化物颗粒的实施例4-1，其首圈放电容量和容量保持率均最优，这是由于，孔洞和裂缝结构有利于颗粒内部锂离子的嵌入和脱出，从而提高放电容量，同时，孔洞和裂缝结构也有利于循环过程中的应力释放，从而提升循环稳定性。
以上所述，仅是本申请的示例，并非对本申请做任何形式的限制，虽然本申请以较佳实施例揭示如上，然而并非用以限制本公开，任何熟悉本专业的技术人员，在不脱离本申请技术方案的范围内，利用上述揭示的技术内容做出些许的变动或修饰均等同于等效实施案例，均在本申请技术方案的范围内。

Claims (10)

  1. 一种电化学装置，包括正极，所述正极包括正极活性材料层，所述电化学装置经满放后，所述正极活性材料层满足以下条件的至少一者：
    a)所述正极活性材料层包括第一粉体和第二粉体，所述第一粉体包括具有P6 3mc结构的锂钴氧化物，所述第二粉体包括含锂金属氧化物，所述含锂金属氧化物中Li元素的摩尔含量与其他金属元素的摩尔含量之比为0<a<0.5；
    b)所述正极活性材料层包括具有P6 3mc结构的锂钴氧化物，所述锂钴氧化物表面具有含锂金属氧化物，所述含锂金属氧化物中Li元素的摩尔含量与其他金属元素的摩尔含量之比为0<a<0.5。
  2. 根据权利要求1所述的电化学装置，所述正极活性材料层满足以下条件的至少一者：
    c)所述第二粉体与所述第一粉体的质量比为m，0<m≤0.3；
    d)所述锂钴氧化物表面的含锂金属氧化物的平均厚度为h，所述锂钴氧化物的平均粒径为D，满足：0<h/D≤0.05。
  3. 根据权利要求1所述的电化学装置，所述含锂金属氧化物包括通式Li aNO 2+b表示的化合物，0<a<0.5，0<b<6，N包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Zr和Y中的至少一种。
  4. 根据权利要求1所述的电化学装置，所述锂钴氧化物包括Li和Co元素，以及可选地包括M元素，其中M元素包括Al、Mg、Ti、Mn、Fe、Ni、Zn、Cu、Nb、Cr、Zr和Y中的至少一种，所述Co和M元素的摩尔含量之和为n Co+M，其满足以下条件的至少一者：
    e)所述Li元素的摩尔含量为n Li，所述n Li与所述n Co+M的比值为x，其中0.6<x<0.95；
    f)所述锂钴氧化物进一步包括Na元素，所述Na元素的摩尔含量为n Na，所述n Na与所述n Co+M的比值为z，其中0≤z<0.03；
    g)所述M元素的摩尔含量为n M，所述n M与所述n Co+M的比值为y，其中0≤y<0.15，所述Co元素的摩尔含量为n Co，所述n Co与所述n Co+M的比值为1-y。
  5. 根据权利要求4所述的电化学装置，所述锂钴氧化物满足以下条件的至少一者：
    h)所述锂钴氧化物包括通式Li xNa zCo 1-yM yO 2表示的化合物，0.6<x<0.95，0≤y<0.15，0≤z<0.03；
    i)所述锂钴氧化物(002)晶面的XRD主峰位于17.5°-19°之间。
  6. 根据权利要求1所述的电化学装置，所述第二粉体的平均粒径D 0与所述第一粉体的平均粒径D 1满足：0<D 0/D 1<0.05；所述第一粉体的平均粒径D 1范围为15μm至30μm。
  7. 根据权利要求1所述的电化学装置，所述具有P6 3mc结构的锂钴氧化物的颗粒内部存在孔洞或裂缝。
  8. 根据权利要求1所述的电化学装置，所述第一粉体和所述第二粉体通过如下方式获得：将所述正极活性材料层去除粘结剂和导电剂后，利用2000目筛网筛分，通过所述筛网的为所述第二粉体，未通过所述筛网的为所述第一粉体。
  9. 根据权利要求1所述的电化学装置，所述电化学装置充电截止电压为4.6V-4.8V。
  10. 一种电子装置，包括根据权利要求1至9中任一项所述的电化学装置。
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