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WO2023240598A1 - 改性正极材料、其制备方法、正极极片、二次电池、电池模块、电池包和用电装置 - Google Patents

改性正极材料、其制备方法、正极极片、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023240598A1
WO2023240598A1 PCT/CN2022/099464 CN2022099464W WO2023240598A1 WO 2023240598 A1 WO2023240598 A1 WO 2023240598A1 CN 2022099464 W CN2022099464 W CN 2022099464W WO 2023240598 A1 WO2023240598 A1 WO 2023240598A1
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Prior art keywords
positive electrode
cathode material
polymer electrolyte
battery
modified
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PCT/CN2022/099464
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English (en)
French (fr)
Inventor
王婧
陈强
吴奇
赵栋
范敬鹏
柳娜
Original Assignee
宁德时代新能源科技股份有限公司
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Priority to EP22930136.1A priority Critical patent/EP4322246A1/en
Priority to KR1020247000832A priority patent/KR20240019315A/ko
Priority to PCT/CN2022/099464 priority patent/WO2023240598A1/zh
Priority to CN202280059100.4A priority patent/CN117897826A/zh
Priority to JP2024517488A priority patent/JP2024534520A/ja
Priority to US18/384,665 priority patent/US20240079565A1/en
Publication of WO2023240598A1 publication Critical patent/WO2023240598A1/zh

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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
    • H01M4/366—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
    • 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
    • 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
    • H01M10/0565—Polymeric materials, e.g. gel-type or solid-type
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0065—Solid electrolytes
    • H01M2300/0082—Organic polymers
    • 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
    • H01M2300/0088—Composites
    • H01M2300/0091—Composites in the form of mixtures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to a modified cathode material, its preparation method, cathode plates, secondary batteries, battery modules, battery packs and electrical devices.
  • Lithium-ion batteries are the electrochemical energy storage systems with the highest energy density that have been applied. With the application of lithium-ion batteries in power vehicles and large-scale energy storage, the market has put forward higher requirements for their energy density and safety performance.
  • the positive electrode material accounts for a large proportion, about 3-4 times that of the negative electrode material. It can be seen that the performance of the cathode material directly affects the performance of the battery.
  • the development of higher energy density lithium-ion battery cathode materials is the only way for the development of lithium-ion batteries. Since the commercialization of lithium-ion batteries in the 1990s, the energy density of lithium-ion batteries has been improved almost by increasing the content of active materials and reducing the content of inactive materials in the slurry. However, in recent years, this direction It has reached a bottleneck period, and it is difficult to increase the content of active substances.
  • the first Coulombic efficiency of the battery refers to a layer of solid electrolyte film formed on the surface of the electrode material during the first charge and discharge process of the battery. A considerable portion of lithium ions will be lost during the electrolyte membrane process, resulting in a reduction in the capacity of the lithium battery, thereby reducing the energy density of the battery.
  • the main methods that people think of to improve the first Coulombic efficiency of lithium batteries include supplementing lithium in the negative electrode and coating the solid electrolyte membrane with electrode materials in advance. The process and operation of supplementing lithium in the negative electrode are relatively complicated.
  • the materials Advance coating is a more conventional material modification method and is easier to implement.
  • Coating the surface of the electrode material with a solid electrolyte membrane in advance can not only prevent the reaction of the electrolyte during the first charge and discharge, greatly improving the first Coulombic efficiency of the battery, but also utilize the strong controllability of the artificial solid electrolyte membrane to realize the structure.
  • the optimized design is a promising method to improve the first efficiency of batteries, and is also an important direction for the modification of electrode materials in the future.
  • the capacity retention rate of the battery during the cycle is the only way to achieve high energy density.
  • the material will continue to expand and shrink during the cycle, causing cracks, causing the electrolyte to further react through the artificial solid electrolyte membrane, thereby affecting the impedance and resistance of the battery. Capacity retention and other electrochemical properties.
  • the present application provides a modified cathode material, its preparation method, cathode plates, secondary batteries, battery modules, battery packs and electrical devices to improve the structural stability and rate performance of the cathode material.
  • the first aspect of the present application provides a modified cathode material.
  • the modified cathode material includes an inner core and a cladding layer.
  • the inner core is a cathode material.
  • the cladding layer includes a polymer electrolyte body and iron dispersed in the polymer electrolyte body. Electric ceramic materials.
  • the main body of the polymer electrolyte forms a film-like coating layer on the outer layer of the particles of the cathode material, which reduces the side reactions between the surface layer of the cathode material and the electrolyte, hinders the dissolution of the cathode material, and improves storage performance;
  • the flexible coating layer formed by the main body of the polymer electrolyte can inhibit the shrinkage and expansion of the cathode material during the charge and discharge process to a certain extent, thereby reducing cracks/powdering of the cathode material; at the same time, the composite coating layer including polymer electrolyte and ferroelectric ceramic material It has high ionic conductivity, provides more channels for ion transmission, and improves the rate performance of the synthesized cathode material.
  • the modified cathode material of this application has better structural stability, and the rate performance, material storage and cycle performance are all improved.
  • the mass of the above-mentioned coating layer is 0.5 wt% to 5 wt% of the mass of the modified cathode material, so as to achieve as complete and comprehensive coating of the cathode material as possible.
  • the mass content of the ferroelectric ceramic material in the coating layer is 2% to 10%, and further optionally 2% to 5%, thereby further utilizing the ferroelectric ceramic material to improve the ionic conductivity of the polymer electrolyte.
  • the ion diffusion coefficient of the modified cathode material is 10 - 11 ⁇ 10 -10 S/cm 2 to further optimize the rate performance of the modified cathode material.
  • the polymer electrolyte host is selected from polyethylene oxide (PEO), polyethylene glycol (PEG), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), vinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE copolymer), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP copolymer), vinylidene fluoride- One or more of the group consisting of chlorotrifluoroethylene copolymer (PVDF-CTFE copolymer).
  • PVDF-CTFE copolymer One or more of the group consisting of chlorotrifluoroethylene copolymer
  • the weight average molecular weight of the polymer electrolyte body is 1,500 to 80,000 to form a coating layer with better mechanical properties.
  • the above - mentioned ferroelectric ceramic material has the general formula : One or more of the group consisting of 2+ and La 2+ , Y is one or more of the group consisting of Ti 4+ , Zr 4+ , V 5+ , Nb 5+ and Ta 2+ ; optional Where, X is one or more of the group consisting of Li + , Sr 2+ , Pb 2+ and Ba 2+ , and Y is Ti 4+ and/or Nb 5+ .
  • the above-mentioned ferroelectric ceramic materials are all known materials in the art and have good chemical stability and good polarization properties.
  • the D V50 particle size of the ferroelectric ceramic material is 5 nm to 100 nm, and optionally the D V50 particle size of the ferroelectric ceramic material is 5 nm to 60 nm.
  • the use of nanoscale ferroelectric ceramic materials will, on the one hand, help the ferroelectric ceramic materials adhere to the surface of the cathode material; on the other hand, it will help the ferroelectric ceramic materials disperse in the segment gaps of the polymer electrolyte, thereby more effectively reducing polymerization.
  • the crystallinity of the electrolyte increases its ionic conductivity.
  • the thickness of the above-mentioned coating layer is 2 nm to 40 nm.
  • a coating layer within this thickness range can not only repeatedly protect the cathode material, effectively avoid surface side reactions, but also avoid Increased impedance caused by too thick cladding.
  • the D V50 particle size of the modified cathode material is 2 ⁇ m to 10 ⁇ m. It is beneficial for the material to exert a better gram capacity, and the cycle performance of the battery using this material is better.
  • the cathode material is any one or more of the group consisting of layered cathode materials, lithium-rich manganese-based cathode materials, spinel cathode materials, and conversion cathode materials.
  • cathode materials are all commonly used cathode materials in this field. After being coated with the above coating layer, the storage stability, structural stability and rate performance can be improved.
  • the phase state of the above-mentioned cathode material is O-3 phase, so that the modified cathode material has a higher capacity.
  • the second aspect of the application provides a method for preparing any of the above modified cathode materials.
  • the preparation method includes: step S1, preparing a polymer electrolyte solution; step S2, mixing the ferroelectric ceramic material and the cathode material. , to obtain a positive electrode material coated with ferroelectric ceramic material; step S3, mix and dry the solution of the polymer electrolyte and the positive electrode material coated with ferroelectric ceramic material, to obtain a modified positive electrode material.
  • the preparation method of this application first disperses the ferroelectric ceramic material on the surface of the cathode material to form a ferroelectric ceramic material-coated cathode material, and then uses a liquid polymer electrolyte to mix it. After drying, the polymer electrolytes are connected to form a film. A coating layer can be formed on the positive electrode material.
  • the above preparation method is simple and easy for industrial promotion and application.
  • the sum of the masses of the polymer electrolyte, cathode material and ferroelectric ceramic material is W1
  • the mass of the polymer electrolyte is W2
  • the mass of the ferroelectric ceramic material is W3, and W2/W1 is 0.5 wt% ⁇ 5wt% to achieve as complete and comprehensive coverage of the cathode material as possible; optionally, W3/(W2+W3) is between 2% ⁇ 10%, optionally between 2% ⁇ 5%
  • ferroelectric ceramic materials are further used to improve the ionic conductivity of polymer electrolytes.
  • the above-mentioned polymer electrolyte is selected from polyethylene oxide (PEO), polyethylene glycol (PEG), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF). ), vinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE copolymer), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP copolymer), vinylidene fluoride-chlorotrifluoroethylene copolymer (PVDF-CTFE One or more of the group consisting of copolymers.
  • PEO polyethylene oxide
  • PEG polyethylene glycol
  • PMMA polymethyl methacrylate
  • PAN polyacrylonitrile
  • PVDF polyvinylidene fluoride
  • PVDF-TrFE copolymer vinylidene fluoride-trifluoroethylene copolymer
  • the mass content of the polymer electrolyte in the above-mentioned polymer electrolyte solution is 0.5% to 10%, so as to facilitate the dispersion of the cathode material coated with the ferroelectric ceramic material therein, thereby achieving both ideal mixing effect.
  • the solvent used in the solution of the polymer electrolyte is selected from one or more of the group consisting of absolute ethanol, N-methylpyrrolidone (NMP), and N,N-dimethylformamide (DMF). Each of the above solvents has high solubility in the polymer electrolyte and is easy to remove during the drying process.
  • the drying in step S3 is spray drying.
  • the air inlet temperature of spray drying is 130°C to 220°C, and the air outlet temperature of spray drying is 60°C to 100°C.
  • a third aspect of the present application provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes any of the above.
  • Modified cathode materials Since the modified cathode material of the present application has better structural stability, the rate performance, material storage and cycle performance have been improved, so that the cathode plate containing it also has the above advantages.
  • the content of the modified positive electrode material in the positive electrode film layer is more than 90% by weight, optionally, 95% by weight to 98% by weight. weight%. In order to give full play to the advantages of the modified cathode material of the present application.
  • a fourth aspect of the present application provides a secondary battery, which includes any modified positive electrode material of the first aspect or the positive electrode sheet of the third aspect.
  • a fifth aspect of the present application provides a battery module including a secondary battery, wherein the secondary battery is the secondary battery of the fourth aspect.
  • a sixth aspect of the present application provides a battery pack, including a battery module, wherein the battery module is the battery module of the fifth aspect.
  • a seventh aspect of the present application provides an electrical device, including a secondary battery or a battery module or a battery pack, wherein the secondary battery is selected from the secondary battery of the fourth aspect, and the battery module is the battery module of the fifth aspect or The battery pack is a battery pack in the sixth aspect.
  • the characteristics of the modified cathode material of the present application enable the secondary batteries, battery modules, and battery packs with the same to have higher rate characteristics and cycle performance, thereby providing better electricity consumption for the secondary batteries, battery modules, or battery packs of the present application.
  • the device provides high power cycle stability.
  • Figure 1 is a scanning electron microscope image of the cathode material of Comparative Example 1.
  • Figure 2 is a scanning electron microscope image of the coated cathode material obtained in Comparative Example 3.
  • Figure 3 is a scanning electron microscope image of the coated cathode material obtained in Example 9.
  • Figure 4 is a scanning electron microscope image of the coated cathode material obtained in Example 1.
  • Figure 5 is a scanning electron microscope image of the coated cathode material obtained in Example 4.
  • FIG. 6 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 7 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 6 .
  • Figure 8 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 9 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 10 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 9 .
  • FIG. 11 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 ⁇ 4 and 2 ⁇ 5.
  • the numerical range “a ⁇ b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0 ⁇ 5" means that all real numbers between "0 ⁇ 5" have been listed in this article, and "0 ⁇ 5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • a secondary battery normally includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • active ions such as lithium ions
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • the electrolyte is between the positive electrode piece and the negative electrode piece and mainly plays the role of conducting active ions.
  • the modified cathode material includes an inner core and a cladding layer.
  • the inner core is a cathode material.
  • the cladding layer includes a polymer electrolyte body and iron dispersed in the polymer electrolyte body. Electric ceramic materials.
  • the main body of the polymer electrolyte forms a film-like coating layer on the outer layer of the particles of the cathode material, which reduces the side reactions between the surface layer of the cathode material and the electrolyte, hinders the dissolution of the cathode material, and improves the storage performance;
  • polymerization The flexible coating layer formed by the main body of the electrolyte can inhibit the shrinkage and expansion of the cathode material during the charge and discharge process to a certain extent, thereby reducing cracks/powdering of the cathode material; at the same time, the ferroelectric ceramic filler has permanent polarization and is incompatible with the electrolyte
  • the polymer electrolyte has a stronger Lewis acid-base effect, thereby reducing the crystallinity of the polymer electrolyte, improving its ionic conductivity, providing more channels for ion transmission, and improving the rate performance of the synthesized cathode material.
  • the mass of the above-mentioned coating layer is 0.5wt% to 5wt% of the mass of the modified cathode material, which not only prevents excessive content of the coating layer from affecting the performance of the cathode material itself, but also achieves the best possible use of the cathode material. Complete coverage possible.
  • Ferroelectric ceramic materials can reduce the crystallinity of polymer electrolytes, but too much ferroelectric ceramic material will lead to a decrease in the mechanical buffering capacity of the coating layer, thereby weakening the ability to reduce cracks/powdering of the cathode material; if too much ferroelectric ceramic material is used If it is too small, the effect on improving the ionic conductivity of the electrolyte polymer is not obvious.
  • the mass content of the ferroelectric ceramic material in the coating layer is 2% to 10%, and further optionally 2% to 7%, so as to further Ferroelectric ceramic materials are used to improve the ionic conductivity of the polymer electrolyte and to provide the coating with sufficient mechanical buffering capabilities.
  • the ionic conductivity of conventional polymer electrolytes is 10 -4 S/cm and below, for example, 10 -4 ⁇ 10 -8 S/cm.
  • the coating layer of this application is mainly composed of polymer electrolytes, it will After the ferroelectric ceramic material is modified, the ionic conductivity of the polymer electrolyte is improved, thereby increasing the ion diffusion coefficient of the modified cathode material. is 10 -11 ⁇ 10 -10 S/cm 2 , thereby further optimizing the rate performance of the modified cathode material.
  • the ion diffusion coefficient of the above modified cathode material can be detected using the following method:
  • the ion diffusion coefficient is detected by the AC impedance method.
  • the CHI604D impedance analyzer is used, the amplitude voltage is set to 5mV, the frequency range is 10 -2 ⁇ 10 5 Hz, the charge transfer impedance is tested after 300 cycles at room temperature, and the lithium ion is calculated by the following formula Diffusion coefficient Among them, Rct is the charge transfer resistance, F is the Faraday resistance constant, T is the absolute temperature, n is the number of electrons gained and lost, and R is the gas constant.
  • the polymer electrolyte used to form the polymer electrolyte main body of the present application can be a polymer that can be used as an electrolyte as conventionally defined in the art.
  • the polymer electrolyte main body is selected from polyethylene oxide, polyethylene glycol.
  • PVDF-TrFE copolymer vinylidene fluoride-trifluoroethylene copolymer
  • PVDF-HFP copolymer vinylidene fluoride-hexafluoropropylene copolymer
  • PVDF-CTFE copolymer vinylidene fluoride-chlorotrifluoroethylene copolymer
  • the weight average molecular weight of the polymer electrolyte body is 1,500 to 800,000.
  • the weight average molecular weight of the main body of the polymer electrolyte is lower than 1500, the coating layer formed on the cathode material has poor coating properties and is easily lost during the cycle; when the E weight average molecular weight of the polymer electrolyte is higher than 800000 When, the flexibility of the formed coating layer deviates.
  • the ferroelectric ceramic materials used in the present application can be selected from known ferroelectric ceramic materials.
  • the above-mentioned ferroelectric ceramic materials have the general formula: XYO 3 , X is Li + , Na + , K + , Mg 2+ , Ca 2+ , Sr 2+ , Pb 2+ , Ba 2+ and La 2+ , and Y is Ti 4+ , Zr 4+ , V 5+ , One or more of the group consisting of Nb 5+ and Ta 2+ ; optionally, X is one or more of the group consisting of Li + , Sr 2+ , Pb 2+ and Ba 2+ , Y is Ti 4+ and/or Nb 5+ .
  • the above-mentioned ferroelectric ceramic materials are all known materials in the art and have good chemical stability and good polarization properties.
  • the D V50 particle size of the ferroelectric ceramic material is 5 nm to 100 nm, and optionally the D V50 particle size of the ferroelectric ceramic material is 5 nm to 60 nm.
  • the use of nanoscale ferroelectric ceramic materials will, on the one hand, help the ferroelectric ceramic materials adhere to the surface of the cathode material; on the other hand, it will help the ferroelectric ceramic materials disperse in the segment gaps of the polymer electrolyte, thereby more effectively reducing polymerization.
  • the crystallinity of the electrolyte increases its ionic conductivity.
  • the coating layer of the present application can protect the cathode material while improving the rate performance.
  • the thickness of the above-mentioned coating layer is 2nm to 40nm.
  • the coating layer in this thickness range can repeatedly achieve the purpose of protecting the cathode material. protection, effectively avoiding surface side reactions, and also avoiding the increase in impedance caused by too thick a coating layer.
  • the D V50 particle size of the modified cathode material is 1 ⁇ m to 10 ⁇ m. It is beneficial for the material to exert a better gram capacity, and the cycle performance of the battery using this material is better.
  • the cathode material is any one or more of the group consisting of layered cathode materials, lithium-rich manganese-based cathode materials, spinel cathode materials, and conversion cathode materials.
  • the above types of cathode materials are all commonly used cathode materials in this field. After being coated with the above coating layer, the storage stability, structural stability and rate performance can be improved.
  • the above-mentioned layered cathode materials can be lithium cobalt oxide, nickel cobalt manganese ternary materials, etc., such as NCM111, NCM523, NCM622, NCM715, NCM811, NCM9655, NCM9631, NCA and corresponding various doping modifications and coating modifications.
  • the coating layer also plays a role in reducing the lithium content on the surface;
  • the above-mentioned lithium-rich manganese-based cathode materials can be lithium-rich lithium manganese oxide Li 2 MnO 3 , Li[Li 1/3 Mn 2/3 ]O 2 or xLiMO 2 ⁇ (1-x)Li[Li 1/3 Mn 2/3 ]O 2 (0 ⁇ x ⁇ 1), etc.
  • Each of the above positive electrode materials may be single crystal or polycrystalline, preferably polycrystalline.
  • the phase state of the above-mentioned cathode material is O-3 phase, so that the modified cathode material has a higher capacity.
  • the preparation method includes: step S1, preparing a polymer electrolyte solution; step S2, combining the ferroelectric ceramic material with the cathode material. The materials are mixed to obtain a ferroelectric ceramic material-coated cathode material; in step S3, the polymer electrolyte solution and the ferroelectric ceramic material-coated cathode material are mixed and dried to obtain a modified cathode material.
  • the preparation method of this application first disperses the ferroelectric ceramic material on the surface of the cathode material to form a ferroelectric ceramic material-coated cathode material, and then uses a liquid polymer electrolyte to mix it. After drying, the polymer electrolytes are connected to form a film. A coating layer can be formed on the positive electrode material.
  • the above preparation method is simple and easy for industrial promotion and application.
  • the loss of the polymer electrolyte, cathode material and ferroelectric ceramic material is not considered.
  • the sum of the masses of the above-mentioned polymer electrolyte, cathode material and ferroelectric ceramic material is W1
  • the mass of the polymer electrolyte is W2
  • the mass of the ferroelectric ceramic material is W3, (W2+W3)/W1 is between 0.5wt% and 5wt% to achieve as complete and comprehensive coverage of the cathode material as possible; optionally, W3/(W2+ W3) is between 2% and 10%, optionally between 2% and 7%
  • ferroelectric ceramic materials are further used to improve the ionic conductivity of the polymer electrolyte.
  • the above-mentioned polymer electrolyte can be a polymer that can be used as an electrolyte as defined conventionally in the art.
  • the main body of the polymer electrolyte is selected from the group consisting of polyethylene oxide, polyethylene glycol, polymethyl methacrylate, and polyethylene glycol.
  • PVDF-CTFE copolymers vinylidene fluoride-trifluoroethylene copolymer
  • PVDF-HFP copolymer vinylidene fluoride-hexafluoropropylene copolymer
  • PVDF-CTFE copolymers vinylidene fluoride-chlorotrifluoroethylene
  • the polymer electrolyte in order to fully mix the polymer electrolyte, cathode material and ferroelectric ceramic material evenly, the polymer electrolyte is dissolved in the solvent to form a solution.
  • the mass content of the polymer electrolyte in the above-mentioned polymer electrolyte solution is 0.5% to 10%, in order to facilitate the dispersion of the cathode material coated with ferroelectric ceramic materials, thereby achieving the ideal mixing effect of the two.
  • the solvent used in the solution of the polymer electrolyte is selected from the group consisting of absolute ethanol, N-methylpyrrolidone (NMP), N , one or more of the group consisting of N-dimethylformamide (DMF).
  • NMP N-methylpyrrolidone
  • DMF N-dimethylformamide
  • the drying in step S3 above can be vacuum drying, hot air drying or spray drying. When selected from vacuum drying or hot air drying, further crushing is performed after drying to control the particle size.
  • the drying in step S3 above is spray drying. dry.
  • the inlet air temperature of the spray drying is controlled to be 130°C to 220°C, and the air outlet temperature of the spray drying is controlled to be 60°C to 100°C. .
  • a micron-level modified cathode material with a relatively uniform particle size distribution and a D V50 particle size of 1 ⁇ m to 10 ⁇ m is obtained.
  • the positive electrode sheet usually includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes any of the above modified positive electrode materials. Since the modified cathode material of the present application has better structural stability, the rate performance, material storage and cycle performance have been improved, so that the cathode plate containing it also has the above advantages.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may also be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composites of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon.
  • At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder may be selected from polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA) , at least one of sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • PVDF polyvinylidene fluoride
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally also includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 6 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 8 shows the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any way.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG 11 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the sources and main properties of the polymer electrolytes used in the examples are as follows.
  • D V50 is about 9 ⁇ m.
  • BaTiO 3 was dry-mixed with the bare NCM811 cathode material at a concentration of 5000 ppm to obtain a BaTiO 3- coated NCM811 cathode material.
  • the mass ratio of the coating layer to the entire material was 0.5wt%.
  • Example 2 The difference from Example 1 is that the concentration of PVDF-HFP is adjusted to 0.5w/v%, BaTiO 3 is blended with the bare NCM811 cathode material at a concentration of 350 ppm to form a BaTiO 3- coated NCM811 material, so that the coating layer accounts for the material The overall mass ratio is reduced to 0.5wt%, and everything else remains unchanged.
  • Example 1 The difference from Example 1 is that the amount of BaTiO 3 is adjusted to 500 ppm, so that the mass content of BaTiO 3 in the coating layer is 5%, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that the amount of BaTiO 3 is adjusted to 200 ppm, so that the mass content of BaTiO 3 in the coating layer is 2%, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that the amount of BaTiO 3 is adjusted to 100 ppm, so that the mass content of BaTiO 3 in the coating layer is 1%, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that the amount of BaTiO 3 is adjusted to 1500 ppm, so that the mass content of BaTiO 3 in the coating layer is 15%, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that PEO is used to replace PVDF-HFP, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that PMMA is used to replace PVDF-HFP, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that PVDF-TrFE is used to replace PVDF-HFP, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that PVDF-CTFE is used to replace PVDF-HFP, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that SrTiO 3 is used to replace BaTiO 3 , and the others remain unchanged.
  • Example 1 The difference from Example 1 is that the dosage of PVDF-HFP is adjusted to 5wt%, the dosage of BaTiO 3 is 3500ppm, the content of the coating layer is 5%, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that the dosage of PVDF-HFP is adjusted to 7wt%, the dosage of BaTiO 3 is 4900ppm, so that the content of the coating layer is 7%, and the others remain unchanged.
  • Example 1 The difference from Example 1 is that the inlet air temperature of the spray drying was changed to 130°C, the outlet air temperature was changed to 60°C, and the others remained unchanged.
  • Example 1 The difference from Example 1 is that the inlet air temperature of the spray drying was changed to 220°C, the outlet air temperature was changed to 110°C, and the others remained unchanged.
  • Example 1 The difference from Example 1 is that the inlet air temperature of the spray drying is changed to 80°C, the outlet air temperature is changed to 30°C, and the others remain unchanged. Due to the low spray drying temperature, the resulting modified cathode material is slightly agglomerated.
  • Example 1 The difference from Example 1 is that the inlet air temperature of the spray drying was changed to 260°C, the outlet air temperature was changed to 160°C, and the others remained unchanged.
  • Example 2 The difference from Example 1 is that the D V50 of the bare NCM811 cathode material used is about 2 ⁇ m.
  • Example 1 The difference from Example 1 is that the D V50 of the BaTiO 3 used is about 5 nm.
  • Example 1 The difference from Example 1 is that the D V50 of the BaTiO 3 used is about 60 nm.
  • Example 1 The difference from Example 1 is that the D V50 of the BaTiO 3 used is about 100 nm.
  • Example 1 The difference from Example 1 is that the D V50 of the BaTiO 3 used is about 150 nm.
  • the field emission scanning electron microscope (Sigma300), transmission electron microscope (TECNAI G2 F20 STWIN), and laser particle size analyzer (GB/T 19077.1-2016/ISO 13320:2009 (particle size distribution laser diffraction method)) of the German ZEISS company were used to analyze the results obtained in the examples.
  • the materials were tested.
  • the morphology, thickness, D V50 particle size of the ferroelectric ceramic material, and the D V50 particle size of the obtained cathode material were tested.
  • the test results are recorded in Table 1. Comparative Example 1, Comparative Example 3, Example 9, Example 1.
  • the SEM images obtained in Example 4 are shown in Figures 1 to 5.
  • the polymer film was quantitatively analyzed using thermogravimetric analysis (PE TGA-7) with a heating rate of 10°C/min and air atmosphere.
  • the ferroelectric ceramic coating content can be obtained by using inductively coupled plasma emission spectrometry (Thermo Fisher Scientific) for elemental analysis.
  • [Positive electrode sheet] Add the positive active material obtained above, polyvinylidene fluoride (PVDF), and acetylene black to NMP in a weight ratio of 90:5:5, and stir in a drying room to form a slurry.
  • the above slurry is coated on aluminum foil, dried and cold pressed to form a positive electrode sheet.
  • the coating amount is 0.01g/cm 2 and the compacted density is 3.5g/cm 3 .
  • Electrode Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and then uniformly dissolve LiPF 6 in the above solution to obtain an electrolyte. , where the concentration of LiPF 6 is 1mol/L.
  • the isolation film was purchased from Cellgard Company, model number is cellgard 2400.
  • the positive electrode sheet, negative electrode sheet, isolation film and electrolyte prepared above are assembled into a CR2032 button battery (hereinafter also referred to as "charge battery”) in a battery charge box.
  • charge battery CR2032 button battery
  • [Positive electrode sheet] Mix the positive electrode active material obtained above with acetylene black and polyvinylidene fluoride (PVDF) in the N-methylpyrrolidone solvent system at a weight ratio of 94:3:3, and then coat it on the aluminum foil. It is dried and cold-pressed to obtain the positive electrode piece. The coating amount is 0.02g/cm 2 and the compacted density is 3.5g/cm 3 .
  • PVDF polyvinylidene fluoride
  • [Negative electrode sheet] Combine the negative active materials artificial graphite, hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) in a weight ratio of 90:5 :2:2:1 is mixed evenly in deionized water, then coated on copper foil, dried, and cold pressed to obtain a negative electrode piece. The coating amount is 0.015g/cm 2 and the compacted density is 1.6g/cm 3 .
  • Electrode Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and then uniformly dissolve LiPF 6 in the above solution to obtain an electrolyte. , where the concentration of LiPF 6 is 1mol/L.
  • PE porous polymer film is used as the isolation film.
  • the above-mentioned positive electrode pieces, isolation film, and negative electrode pieces are stacked in order, so that the isolation film is between the positive and negative electrodes to play an isolation role, and the bare battery core is obtained by winding.
  • the bare battery core is placed in the outer packaging, electrolyte is injected and packaged to obtain a full battery (hereinafter also referred to as "full battery”).
  • the length ⁇ width ⁇ height of the full battery 90mm ⁇ 30mm ⁇ 60mm, and the group margin of the battery is 91.0%.
  • 1/3C tests the full capacitance
  • 1C/1C tests its 25°C/45°C cycle
  • 70°C tests its gas production trend.
  • Full cells were stored at 100% state of charge (SOC) at 70°C. Measure the open circuit voltage (OCV) and AC internal resistance (IMP) of the battery cells before, after and during storage to monitor SOC, and measure the volume of the battery cells. After every 48 hours of storage, the full battery was taken out, OCV and IMP were tested after leaving it for 1 hour, and the cell volume was measured using the drainage method after cooling to room temperature.
  • the drainage method is to first separately measure the gravity F1 of the battery cell using a balance that automatically converts units using dial data, then completely places the battery core in deionized water (density is known to be 1g/cm 3 ), and measures the gravity of the battery core at this time.
  • the AC impedance method (CHI604D impedance analyzer, amplitude voltage 5mV, frequency range 10 -2 ⁇ 10 5 Hz) was used to test the charge transfer impedance after 300 cycles at room temperature, and the lithium ion diffusion coefficient was calculated by the following formula The test results are recorded in Table 2.
  • Rct is the charge transfer resistance
  • F is the Faraday resistance constant
  • T is the absolute temperature
  • n is the number of electrons gained and lost
  • R is the gas constant.
  • Comparative analysis of electron microscope scanning of samples prepared in Comparative Examples 1 and 3 and Examples 1, 4, and 9 shows that the ferroelectric ceramic coating alone can form an island-like coating on the surface of the cathode material, and the composite polymer electrolyte coating can form an island-like coating on the surface of the cathode material. A uniform film-like coating layer is formed, and as the amount of polymer coating increases, the continuity of the film becomes better.
  • Comparative analysis of the performance data of the samples prepared in Examples 1, 4, and 15 to 16 shows that a continuous and moderately thick composite polymer electrolyte coating is conducive to increasing circulation and inhibiting gas production. If the coating is discontinuous, the positive electrode The material is still exposed to the electrolyte. If the coating layer is too thick, electron transmission will be inhibited. With a reasonable coating amount, the prepared cathode material has a higher capacity, better cycle performance, and less gas production, indicating that the material has higher structural stability.
  • Example 25 By comparing the sample performance data of Example 1 and Examples 22 to 25, it can be seen that the particle size of BaTiO 3 also affects the capacity and cycle performance. When the particle size in Example 25 is too large, it will affect the crystallinity of the polymer electrolyte. The improvement effect is not obvious, resulting in insufficient improvement in the rate performance of the cathode material.

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Abstract

本申请提供了一种改性正极材料、其制备方法、正极极片、二次电池、电池模块、电池包和用电装置。该改性正极材料包括内核和包覆层，内核为正极材料，包覆层包括聚合物电解质主体和分散在聚合物电解质主体中的铁电陶瓷材料。聚合物电解质主体在正极材料的颗粒外层形成膜状包覆层，使正极材料表层与电解液的副反应降低，提升存储性能；其次，聚合物电解质主体形成的柔性包覆层能在一定程度上抑制充放电过程中正极材料的收缩膨胀，从而减少正极材料裂缝/粉化；同时复合包覆层具有较高的离子导电率，为离子传输提供更多通道，使合成的正极材料的倍率性能提高。因此上述改性正极材料，具有较好的结构稳定性，倍率性能、材料存储和循环性能均得到提升。

Description

改性正极材料、其制备方法、正极极片、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及电池技术领域，特别是涉及一种改性正极材料、其制备方法、正极极片、二次电池、电池模块、电池包和用电装置。
背景技术
锂离子电池是已经获得应用的能量密度最高的电化学储能体系。随着锂离子电池在动力汽车与大规模储能等方面的应用，市场对其能量密度以及安全性能提出了更高的要求。
从锂离子电池的构成出发，正极材料占很大比例，约为负极材料的3-4倍。可见，正极材料的性能直接影响着电池性能的好坏，发展更高能量密度锂离子电池正极材料是锂离子电池发展的必经之路。自从二十世纪九十年代锂离子电池商业化一来，几乎都是靠提高浆料中活性物质的含量、降低非活性物质的含量来实现锂离子电池能量密度的提高，但是近年来这一方向已经到了瓶颈期，活性物质的含量占比已经很难再提升。
于是人们又将目光瞄准到提高电池的首次库伦效率和循环容量保持率上，电池的首次库伦效率是指电池在首次充放电的过程中在电极材料表面形成的一层固体电解质膜，在形成固体电解质膜的过程中会损耗相当大一部分锂离子，造成锂电池的容量降低，进而降低电池的能量密度。目前人们想到的提升锂电池首次库伦效率的方法主要有负极补锂和电极材料提前包覆固体电解质膜层两种，负极补锂工艺和操作较为复杂，目前真正实现商业化的不是很多，而材料提前包覆是一种较为常规的材料改性方法，较易实现。将电极材料表面提前包覆上一层固体电解质膜，不仅可以阻止电解液在首次充放电时的反应，大大提升电池的首次库伦效率，还可以利用人造固体电解质膜较强的可控性实现结构的优化设计，是一种很有前景的提升电池首效的方法，也是未来电极材料改性的一个重要方向。而电池在循环过程中的容量保持率则是实现高能量密度的必由之路，材料在循环过程中会不断膨胀收缩导致出现裂纹，导致电解液透过人造固体电解质膜进一步反应，进而影响电池的阻抗、容量保持率等电化学性能。
发明内容
本申请提供了一种改性正极材料、其制备方法、正极极片、二次电池、电池模块、电池包和用电装置，以提高正极材料的结构稳定性和倍率性能。
本申请的第一方面提供了一种改性正极材料，该改性正极材料包括内核和包覆 层，内核为正极材料，包覆层包括聚合物电解质主体和分散在聚合物电解质主体中的铁电陶瓷材料。
该改性正极材料中，聚合物电解质主体在正极材料的颗粒外层形成膜状包覆层，使正极材料表层与电解液的副反应降低，阻碍正极材料的溶解，提升存储性能；其次，聚合物电解质主体形成的柔性包覆层能在一定程度上抑制充放电过程中正极材料的收缩膨胀，从而减少正极材料裂缝/粉化；同时，包括聚合物电解质和铁电陶瓷材料的复合包覆层具有较高的离子导电率，为离子传输提供更多通道，使合成的正极材料的倍率性能提高。综上，本申请的改性正极材料，具有较好的结构稳定性，倍率性能、材料存储和循环性能均得到提升。
在第一方面的任意实施方式中，上述包覆层的质量为改性正极材料质量的0.5wt％～5wt％，以实现对正极材料的尽可能完全全面的包覆。可选地，包覆层中铁电陶瓷材料的质量含量为2％～10％，进一步可选为2％～5％，从而进一步利用铁电陶瓷材料改善聚合物电解质的离子电导率。
在第一方面的任意实施方式中，上述改性正极材料的离子扩散系数
Figure PCTCN2022099464-appb-000001
为10 - 11～10 -10S/cm 2，以进一步优化改性正极材料的倍率性能。在第一方面的任意实施方式中，可选地，聚合物电解质主体选自聚环氧乙烷(PEO)、聚乙二醇(PEG)、聚甲基丙烯酸甲酯(PMMA)、聚丙烯腈(PAN)、聚偏氟乙烯(PVDF)、偏氟乙烯-三氟乙烯共聚物(PVDF-TrFE共聚物)、偏氟乙烯-六氟丙烯共聚物(PVDF-HFP共聚物)、偏氟乙烯-三氟氯乙烯共聚物(PVDF-CTFE共聚物)组成的组中的一种或多种。上述各材料均采用现有材料干燥而成，成本较低。
在第一方面的任意实施方式中，上述聚合物电解质主体的重均分子量为1500～80000，以形成机械性能更好的包覆层。
在第一方面的任意实施方式中，上述铁电陶瓷材料具有通式：XYO 3，X为Li +、Na +、K +、Mg 2+、Ca 2+、Sr 2+、Pb 2+、Ba 2+和La 2+组成的组中的一种或多种，Y为Ti 4+、Zr 4+、V 5+、Nb 5+和Ta 2+组成的组的一种或多种；可选地，X为Li +、Sr 2+、Pb 2+和Ba 2+组成的组中的一种或多种，Y为Ti 4+和/或Nb 5+。上述铁电陶瓷材料均为本领域已知材料，化学稳定性好，极化性能好。
在第一方面的任意实施方式中，铁电陶瓷材料的D V50粒径为5nm～100nm，可选地铁电陶瓷材料的D V50粒径为5nm～60nm。采用纳米级的铁电陶瓷材料，一方面有利于铁电陶瓷材料在正极材料的表面附着；另一方面有利于铁电陶瓷材料分散在聚合物电解质的链段间隙中，进而更有效地降低聚合物电解质的结晶度，提高其离子电导率。
在第一方面的任意实施方式中，上述包覆层的厚度为2nm～40nm，在该厚度范围的包覆层，既可以重复实现对正极材料的保护，有效避免表面副反应，而且还避免了包覆层太厚导致的阻抗增加。
在第一方面的任意实施方式中，可选地，改性正极材料的D V50粒径为2μm～10μm。有利于该材料发挥出更好的克容量，使用该材料电池的循环性能更优良。
在第一方面的任意实施方式中，正极材料为层状正极材料、富锂锰基正极材料、尖晶石正极材料、转化型正极材料组成的组中的任意一种或多种。
上述各类正极材料均为本领域常用的正极材料，在经过上述包覆层的包覆后，储存稳定性、结构稳定性和倍率性能均可得到改善。
在第一方面的任意实施方式中，上述正极材料的相态为O-3相，使得改性正极材料具有更高的容量。
本申请的第二方面提供了一种上述任一种的改性正极材料的制备方法，该制备方法包括：步骤S1，制备聚合物电解质的溶液；步骤S2，将铁电陶瓷材料与正极材料混合，得到铁电陶瓷材料包覆的正极材料；步骤S3，将聚合物电解质的溶液和铁电陶瓷材料包覆的正极材料混合、干燥，得到改性正极材料。
本申请的制备方法先将铁电陶瓷材料分散在正极材料的表面形成铁电陶瓷材料包覆的正极材料，然后再利用液态的聚合物电解质与其混合，通过干燥后，聚合物电解质连接成膜，即可在正极材料上形成包覆层。上述制备方法简单，易于工业推广应用。
在第二方面的任意实施方式中，上述聚合物电解质、正极材料和铁电陶瓷材料的质量和为W1，聚合物电解质的质量为W2，铁电陶瓷材料的质量为W3，W2/W1在0.5wt％～5wt％之间以实现对正极材料的尽可能完全全面的包覆；可选地，W3/(W2+W3)在2％～10％之间，可选地在2％～5％之间，进一步利用铁电陶瓷材料改善聚合物电解质的离子电导率。可选地，上述聚合物电解质选自聚环氧乙烷(PEO)、聚乙二醇(PEG)、聚甲基丙烯酸甲酯(PMMA)、聚丙烯腈(PAN)、聚偏氟乙烯(PVDF)、偏氟乙烯-三氟乙烯共聚物(PVDF-TrFE共聚物)、偏氟乙烯-六氟丙烯共聚物(PVDF-HFP共聚物)、偏氟乙烯-三氟氯乙烯共聚物(PVDF-CTFE共聚物)组成的组中的一种或多种。
在第二方面的任意实施方式中，上述聚合物电解质的溶液中聚合物电解质的质量含量为0.5％～10％，以便于铁电陶瓷材料包覆的正极材料在其中的分散，进而实现二者的理想混合效果。可选地，聚合物电解质的溶液所用溶剂选自无水乙醇、N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)组成的组中的一种或多种。上述各溶剂对聚合物电解质的溶解性较高，且在干燥过程中易于去除。
在第二方面的任意实施方式中，上述步骤S3的干燥为喷雾干燥，可选地，喷雾干燥的进风温度为130℃～220℃，喷雾干燥的出风温度为60℃～100℃。从而得到粒度分布较为均匀的微米级改性正极材料。
本申请的第三方面提供了一种正极极片，包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料，该正极活性材料包括上述 任一种的改性正极材料。由于本申请的改性正极材料具有较好的结构稳定性，倍率性能、材料存储和循环性能均得到提升，使具有其的正极极片也具有上述优势。
在第三方面的任意实施方式中，可选地，基于正极膜层的总重量计，改性正极材料在正极膜层中的含为90重量％以上，可选地，为95重量％至98重量％。以充分发挥本申请的改性正极材料的优势。
本申请的第四方面提供了一种二次电池，该二次电池包括上述第一方面的任意一种改性正极材料或第三方面的正极极片。
本申请的第五方面提供了一种电池模块，包括二次电池，其中，二次电池为第四方面的二次电池。
本申请的第六方面提供了一种电池包，包括电池模块，其中电池模块为第五方面的电池模块。
本申请的第七方面提供了一种用电装置，包括二次电池或电池模块或电池包，其中，二次电池选自第四方面的二次电池、电池模块为第五方面的电池模块或电池包为第六方面的电池包。
本申请的改性正极材料的特点，使得具有其的二次电池、电池模块、电池包具有较高的倍率特性和循环性能，进而为具有本申请二次电池、电池模块或电池包的用电装置提供了较高的动力循环稳定性。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1为对比例1的正极材料的扫描电镜图。
图2为对比例3所得的包覆后正极材料的扫描电镜图。
图3为实施例9所得的包覆后正极材料的扫描电镜图。
图4为实施例1所得的包覆后正极材料的扫描电镜图。
图5为实施例4所得的包覆后正极材料的扫描电镜图。
图6是本申请一实施方式的二次电池的示意图。
图7是图6所示的本申请一实施方式的二次电池的分解图。
图8是本申请一实施方式的电池模块的示意图。
图9是本申请一实施方式的电池包的示意图。
图10是图9所示的本申请一实施方式的电池包的分解图。
图11是本申请一实施方式的二次电池用作电源的用电装置的示意图。
在附图中，附图并未按照实际的比例绘制。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件。
具体实施方式
下面结合附图和实施例对本申请的实施方式作进一步详细描述。以下实施例的详细描述和附图用于示例性地说明本申请的原理，但不能用来限制本申请的范围，即本申请不限于所描述的实施例。
以下，适当地参照附图详细说明具体公开了本申请的改性正极材料及其制备方法、正极极片、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60～120和80～110的范围，理解为60～110和80～120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1～3、1～4、1～5、2～3、2～4和2～5。在本申请中，除非有其他说明，数值范围“a～b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0～5”表示本文中已经全部列出了“0～5”之间的全部实数，“0～5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的 步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
[二次电池]
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解液。在电池充放电过程中，活性离子(例如锂离子)在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
本申请的一个实施方式提供了一种改性正极材料，该改性正极材料包括内核和包覆层，内核为正极材料，包覆层包括聚合物电解质主体和分散在聚合物电解质主体中的铁电陶瓷材料。
上述改性正极材料中，聚合物电解质主体在正极材料的颗粒外层形成膜状包覆层，使正极材料表层与电解液的副反应降低，阻碍正极材料的溶解，提升存储性能；其次，聚合物电解质主体形成的柔性包覆层能在一定程度上抑制充放电过程中正极材料的收缩膨胀，从而减少正极材料裂缝/粉化；同时，铁电陶瓷填料因其具有永久性极化，与电解质聚合物电解质具有更强的路易斯酸碱效应，从而降低聚合物电解质的结晶度，提高其离子电导率，为离子传输提供更多通道，使合成的正极材料的倍率性能提高。综上，本申请的改性正极材料，具有较好的结构稳定性，倍率性能、材料存储和循环性能均得到提升。
在一些实施方式中，上述包覆层的质量为改性正极材料质量的0.5wt％～5wt％，既避免了包覆层含量过多影响正极材料本身的性能，又可以实现对正极材料的尽可能完全全面的包覆。
铁电陶瓷材料可以降低聚合物电解质的结晶度，但是铁电陶瓷材料用量过多导致包覆层的机械缓冲能力下降，进而减少正极材料裂缝/粉化的能力减弱；如果铁电陶瓷材料用量过少，对电解质聚合物的离子电导率提升效果不明显，在一些实施方式 中，包覆层中铁电陶瓷材料的质量含量为2％～10％，进一步可选为2％～7％，从而进一步利用铁电陶瓷材料改善聚合物电解质的离子电导率，而且使包覆层具有充分的机械缓冲能力。
常规的聚合物电解质的离子电导率在10 -4S/cm及以下，比如为10 -4～10 -8S/cm，本申请的包覆层，虽然以聚合物电解质为主体，但是在经过铁电陶瓷材料改性后，其聚合物电解质的离子电导率得到提升，从而使改性正极材料的离子扩散系数增加，改性正极材料的离子扩散系数
Figure PCTCN2022099464-appb-000002
为10 -11～10 -10S/cm 2，从而进一步优化改性正极材料的倍率性能。上述改性正极材料的离子扩散系数可以采用以下方法检测得到：
离子扩散系数通过交流阻抗法检测，比如采用CHI604D阻抗分析仪，设定振幅电压为5mV、频率范围10 -2～10 5Hz，测试常温循环300圈后的电荷传递阻抗，通过如下公式计算锂离子扩散系数
Figure PCTCN2022099464-appb-000003
Figure PCTCN2022099464-appb-000004
其中，Rct是电荷传递阻抗，F是法拉第电阻常数，T是绝对温度，n是得失电子数，R是气体常数。
用于形成本申请的聚合物电解质主体的聚合物电解质可以为本领域常规所定义的可作为电解质的聚合物，在一些实施方式中，聚合物电解质主体选自聚环氧乙烷、聚乙二醇、聚甲基丙烯酸甲酯、聚丙烯腈、聚偏氟乙烯、偏氟乙烯-三氟乙烯共聚物(PVDF-TrFE共聚物)、偏氟乙烯-六氟丙烯共聚物(PVDF-HFP共聚物)、偏氟乙烯-三氟氯乙烯共聚物(PVDF-CTFE共聚物)组成的组中的一种或多种。上述各材料均为现有材料，比如已知的改性或未改性的相应聚合物，具体物质本申请不再一一赘述。
为了形成机械性能更好的包覆层，在一些实施方式中，上述聚合物电解质主体的重均分子量为1500～800000。当聚合物电解质主体的重均分子量低于1500时，所形成的包覆层在正极材料上的包覆性较差，循环过程过程中容易流失；当聚合物电解质的E重均分子量高于800000时，所形成的包覆层的柔韧性偏差。
用于本申请的铁电陶瓷材料可以从已知的铁电陶瓷材料中进行选自，在一些实施方式中，上述铁电陶瓷材料具有通式：XYO 3，X为Li +、Na +、K +、Mg 2+、Ca 2+、Sr 2+、Pb 2+、Ba 2+和La 2+组成的组中的一种或多种，Y为Ti 4+、Zr 4+、V 5+、Nb 5+和Ta 2+组成的组的一种或多种；可选地，X为Li +、Sr 2+、Pb 2+和Ba 2+组成的组中的一种或多种，Y为Ti 4+和/或Nb 5+。上述铁电陶瓷材料均为本领域已知材料，化学稳定性好，极化性能好。
在一些实施方式中，铁电陶瓷材料的D V50粒径为5nm～100nm，可选地铁电陶瓷材料的D V50粒径为5nm～60nm。采用纳米级的铁电陶瓷材料，一方面有利于铁电陶瓷材料在正极材料的表面附着；另一方面有利于铁电陶瓷材料分散在聚合物电解质的链段间隙中，进而更有效地降低聚合物电解质的结晶度，提高其离子电导率。
本申请的包覆层可以起到保护正极材料同时提高倍率性能，在一些实施方式中，上述包覆层的厚度为2nm～40nm，在该厚度范围的包覆层，既可以重复实现对正 极材料的保护，有效避免表面副反应，而且还避免了包覆层太厚导致的阻抗增加。
在一些实施方式中，上述改性正极材料的D V50粒径为1μm～10μm。有利于该材料发挥出更好的克容量，使用该材料电池的循环性能更优良。
在第一方面的任意实施方式中，正极材料为层状正极材料、富锂锰基正极材料、尖晶石正极材料、转化型正极材料组成的组中的任意一种或多种。上述各类正极材料均为本领域常用的正极材料，在经过上述包覆层的包覆后，储存稳定性、结构稳定性和倍率性能均可得到改善。上述层状正极材料可以为钴酸锂、镍钴锰三元材料等，比如NCM111、NCM523、NCM622、NCM715、NCM811、NCM9655、NCM9631、NCA以及相应的各种掺杂改性、包覆改性后的材料，针对高镍三元材料，包覆层还起到降低其表面杂锂含量的作用；上述富锂锰基正极材料可以为富锂锰酸锂Li 2MnO 3、Li[Li 1/3Mn 2/3]O 2或xLiMO 2·(1-x)Li[Li 1/3Mn 2/3]O 2(0＜x＜1)等中的任意一种以及相应的各种掺杂改性、包覆改性后的材料；尖晶石正极材料可以为尖晶石结构的锰酸锂LiMn 2O 4、尖晶石结构的掺杂锰酸锂LiMn 2-xM xO 4(0＜x＜2，M为Ni、V、Cr、Cu、Co或Fe等)，转化型正极材料选自MX m，其中M＝Ti、V、Cr、Mn、Fe、Co、Ni、Cu等；X＝F、Cl、O、S、N、P等，m使MX m的化合价为0。上述各正极材料可以为单晶或多晶，优选为多晶。
在一些实施方式中，上述正极材料的相态为O-3相，使得改性正极材料具有更高的容量。
本申请的另一种实施方式提供了一种上述任一种的改性正极材料的制备方法，该制备方法包括：步骤S1，制备聚合物电解质的溶液；步骤S2，将铁电陶瓷材料与正极材料混合，得到铁电陶瓷材料包覆的正极材料；步骤S3，将聚合物电解质的溶液和铁电陶瓷材料包覆的正极材料混合、干燥，得到改性正极材料。
本申请的制备方法先将铁电陶瓷材料分散在正极材料的表面形成铁电陶瓷材料包覆的正极材料，然后再利用液态的聚合物电解质与其混合，通过干燥后，聚合物电解质连接成膜，即可在正极材料上形成包覆层。上述制备方法简单，易于工业推广应用。
在制备过程中，聚合物电解质、正极材料和铁电陶瓷材料不考虑损失，在一些实施方式中，上述聚合物电解质、正极材料和铁电陶瓷材料的质量和为W1，聚合物电解质的质量为W2，铁电陶瓷材料的质量为W3，(W2+W3)/W1在0.5wt％～5wt％之间以实现对正极材料的尽可能完全全面的包覆；可选地，W3/(W2+W3)在2％～10％之间，可选地在2％～7％之间，进一步利用铁电陶瓷材料改善聚合物电解质的离子电导率。
上述聚合物电解质可以为本领域常规所定义的可作为电解质的聚合物，在一些实施方式中，聚合物电解质主体选自聚环氧乙烷、聚乙二醇、聚甲基丙烯酸甲酯、聚丙烯腈、聚偏氟乙烯、偏氟乙烯-三氟乙烯共聚物(PVDF-TrFE共聚物)、偏氟乙烯- 六氟丙烯共聚物(PVDF-HFP共聚物)、偏氟乙烯-三氟氯乙烯共聚物(PVDF-CTFE共聚物)组成的组中的一种或多种。上述各材料均为现有材料，比如已知的改性或未改性的相应聚合物，具体物质本申请不再一一赘述。
本申请为了使聚合物电解质、正极材料和铁电陶瓷材料充分混合均匀，使聚合物电解质溶解在溶剂中形成溶液，在一些实施方式中，上述聚合物电解质的溶液中聚合物电解质的质量含量为0.5％～10％，以便于铁电陶瓷材料包覆的正极材料在其中的分散，进而实现二者的理想混合效果。为了尽可能减少溶解聚合物电解质所用溶剂的E用量，以利于该溶剂去除，在一些实施方式中，上述聚合物电解质的溶液所用溶剂选自无水乙醇、N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)组成的组中的一种或多种。上述各溶剂对聚合物电解质的溶解性较高，且在干燥过程中易于去除。
上述步骤S3中的干燥可以为真空干燥、热风干燥或者喷雾干燥，当选自真空干燥或热风干燥时，在干燥之后进行进一步破碎以控制其粒度，在一些实施方式中，上述步骤S3的干燥为喷雾干燥。为了提高喷雾干燥效率，并且控制喷雾干燥所得改性正极材料的粒度，在一些实施方式中，控制喷雾干燥的进风温度为130℃～220℃，喷雾干燥的出风温度为60℃～100℃。从而得到粒度分布较为均匀、且D V50粒径为1μm～10μm的微米级改性正极材料。
[正极极片]
正极极片通常包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料，该正极活性材料包括上述任一种的改性正极材料。由于本申请的改性正极材料具有较好的结构稳定性，倍率性能、材料存储和循环性能均得到提升，使具有其的正极极片也具有上述优势。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料还可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如 LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他 可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。作为示例，粘结剂可选自聚偏氟乙烯(PVDF)、丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，电解质为液态的，且包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，电解液还可选地包括添加剂。作为示例，添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构 隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图6是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图7，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图8是作为一个示例的电池模块4。参照图8，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图9和图10是作为一个示例的电池包1。参照图9和图10，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池 模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图11是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
[实施例]
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
其中实施例中所用聚合物电解质的来源和主要性能如下表。
Figure PCTCN2022099464-appb-000005
Figure PCTCN2022099464-appb-000006
对比例1
NCM811正极材料裸料，D V50为9μm左右。
对比例2
按照2w/v％的浓度配置PVDF-HFP/NMP溶液，将NCM811正极材料裸料加入到PVDF-HFP/NMP溶液中，固液质量体积比为1:1，搅拌均匀后采用喷雾干燥(进风温度180℃，出风温度80℃)得到PVDF-HFP包覆的正极材料，包覆层占比为2wt％。
对比例3
将BaTiO 3以5000ppm的浓度与NCM811正极材料裸料干法混合，得到BaTiO 3包覆NCM811正极材料，包覆层占材料整体的质量比为0.5wt％。
对比例4
按照1w/v％的浓度配置PVDF-HFP/NMP溶液，将Al 2O 3以700ppm的浓度与NCM811正极材料裸料共混形成Al 2O 3包覆的NCM811材料，将Al 2O 3包覆的NCM811材料加入到PVDF-HFP/NMP溶液中，固液比为1:1,搅拌均匀后经喷雾干燥(进风温度180℃，出风温度80℃)，得到Al 2O 3/PVDF-HFP包覆NCM811正极材料，包覆层占材料整体的质量比为1wt％，填料占包覆层整体的质量比为7wt％。
实施例1
按照1w/v％的浓度配置PVDF-HFP/NMP溶液，将BaTiO 3以700ppm的浓度与NCM811正极材料裸料共混形成BaTiO 3包覆的NCM811材料，将BaTiO 3包覆的NCM811材料加入到PVDF-HFP溶液中，固液质量体积比为1:1，搅拌均匀后经喷雾干燥(进风温度180℃，出风温度80℃)，得到BaTiO 3/PVDF-HFP包覆NCM811正极材料，包覆层占材料整体的质量比为1wt％，填料占包覆层整体的质量比为7wt％。
实施例2
按照2w/v％的浓度配置PEG/无水乙醇溶液，将LiNbO 3以500ppm的浓度与NCM9255正极材料裸料共混形成LiNbO 3包覆的NCM9255正极材料，将LiNbO 3包覆的NCM9255正极材料加入到PEG/无水乙醇溶液中，固液质量体积比为1:1，搅拌均匀后经喷雾干燥(进风温度180℃，出风温度80℃)，得到LiNbO 3/PEG包覆NCM9255正极材料，包覆层占材料整体的质量比为2wt％，填料占包覆层整体的质量比为2.5wt％。
实施例3
按照5w/v％的浓度配置PAN/DMF溶液，将SrTiO 3以5000ppm的浓度与NCM9255正极材料裸料共混形成SrTiO 3包覆的NCM9255正极材料，将SrTiO 3包覆的 高镍NCM正极材料加入到PAN/DMF溶液中，固液质量体积比为1:1，搅拌均匀后经喷雾干燥(进风温度180℃，出风温度80℃)，得到SrTiO 3/PAN包覆高镍NCM正极材料，包覆层占材料整体的质量比为5wt％，填料占包覆层整体的质量比为10wt％。
实施例4
与实施例1的区别在于，调整PVDF-HFP的浓度为0.5w/v％，BaTiO 3以350ppm的浓度与NCM811正极材料裸料共混形成BaTiO 3包覆的NCM811材料，使包覆层占材料整体的质量比降低为0.5wt％，其他保持不变。
实施例5
与实施例1的区别在于，调整BaTiO 3的用量为500ppm，使包覆层中BaTiO 3的质量含量为5％，其他保持不变。
实施例6
与实施例1的区别在于，调整BaTiO 3的用量为200ppm，使包覆层中BaTiO 3的质量含量为2％，其他保持不变。
实施例7
与实施例1的区别在于，调整BaTiO 3的用量为100ppm，使包覆层中BaTiO 3的质量含量为1％，其他保持不变。
实施例8
与实施例1的区别在于，调整BaTiO 3的用量为1500ppm，使包覆层中BaTiO 3的质量含量为15％，其他保持不变。
实施例9
按照1w/v％的浓度配置PVDF-HFP/NMP溶液，将BaTiO 3以700ppm的浓度与NCM811正极材料裸料共混形成BaTiO 3包覆的NCM811材料，将BaTiO 3包覆的NCM811材料加入到PVDF-HFP/NMP溶液中，固液质量体积比为1:1，搅拌均匀后在80℃下干燥24h，然后对干燥后物料进行粉碎，得到BaTiO 3/PVDF-HFP包覆高镍NCM正极材料。包覆层占BaTiO 3/PVDF-HFP包覆高镍NCM正极材料整体的质量比为1wt％，BaTiO 3占包覆层的质量比为7wt％。
实施例10
与实施例1的区别在于，采用PEO替换PVDF-HFP，其他保持不变。
实施例11
与实施例1的区别在于，采用PMMA替换PVDF-HFP，其他保持不变。
实施例12
与实施例1的区别在于，采用PVDF-TrFE替换PVDF-HFP，其他保持不变。
实施例13
与实施例1的区别在于，采用PVDF-CTFE替换PVDF-HFP，其他保持不变。
实施例14
与实施例1的区别在于，采用SrTiO 3替换BaTiO 3，其他保持不变。
实施例15
与实施例1的区别在于，调整PVDF-HFP的用量为5wt％，BaTiO 3的用量为3500ppm，使包覆层的含量为5％，其他保持不变。
实施例16
与实施例1的区别在于，调整PVDF-HFP的用量为7wt％，BaTiO 3的用量为4900ppm，使包覆层的含量为7％，其他保持不变。
实施例17
与实施例1的区别在于喷雾干燥进风温度改为130℃，出风温度改为60℃，其他保持不变。
实施例18
与实施例1的区别在于喷雾干燥进风温度改为220℃，出风温度改为110℃，其他保持不变。
实施例19
与实施例1的区别在于喷雾干燥进风温度改为80℃，出风温度改为30℃，其他保持不变。由于喷雾干燥温度较低，导致所得改性正极材料有轻微团聚。
实施例20
与实施例1的区别在于喷雾干燥进风温度改为260℃，出风温度改为160℃，其他保持不变。
实施例21
与实施例1的区别在于，所采用的NCM811正极材料裸料的D V50为2μm左右。
实施例22
与实施例1的区别在于，所采用的BaTiO 3的D V50为5nm左右。
实施例23
与实施例1的区别在于，所采用的BaTiO 3的D V50为60nm左右。
实施例24
与实施例1的区别在于，所采用的BaTiO 3的D V50为100nm左右。
实施例25
与实施例1的区别在于，所采用的BaTiO 3的D V50为150nm左右。
测试
1)杂锂含量
采用瑞士万通全自动电位滴定仪-905依照GB/T 9736-2008测试各实施例和对比例所得到的正极材料或改性正极材料的杂锂含量，结果记录在表1中。
2)包覆层形貌、厚度、包覆后正极料粒径
采用德国ZEISS公司的场发射扫描电子显微镜(Sigma300)、透射电镜(TECNAI G2 F20 STWIN)、激光粒度仪(GB/T 19077.1-2016/ISO 13320:2009(粒度分布激光衍射法))对实施例所得材料进行测试，包覆层形貌、厚度、铁电陶瓷材料D V50粒径、所得正极材料D V50粒径测试结果记录在表1中，对比例1、对比例3、实施例9、实施例1、实施例4所得SEM图依次为图1至5。
3)包覆层含量、铁电陶瓷材料含量
采用热重分析法(PE TGA-7)对聚合物膜进行定量分析，升温速率为10℃/min,空气氛围。采用电感耦合等离子体发射光谱法(Thermo Fisher Scientific)进行元素分析，可获得铁电陶瓷包覆含量。
4)扣电池制作及性能测试
【正极极片】将上述获得的正极活性材料、聚偏二氟乙烯(PVDF)、乙炔黑以90：5：5的重量比加入至NMP中，在干燥房中搅拌制成浆料。在铝箔上涂覆上述浆料，干燥、冷压制成正极极片。涂覆量为0.01g/cm 2，压实密度为3.5g/cm 3。
【负极极片】将0.5mm锂金属片作为负极极片。
【电解液】将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，其中LiPF 6的浓度为1mol/L。
【隔离膜】
隔离膜采购自Cellgard企业，型号为cellgard 2400。
将上述制备的正极极片、负极极片、隔离膜和电解液在扣电箱中组装成CR2032型扣式电池(下文也称“扣电”)。
扣式电池初始克容量及首效测试
在2.8～4.3V下，将扣式电池按照0.1C充电至4.3V，然后在4.3V下恒压充电至电流≤0.05mA，静置2min，此时的充电容量记为C0，然后按照0.1C放电至2.8V，此时的放电容量为初始克容量记为D0。首效按照D0/C0*100％计算得到。
结果参见表2。
5)全电池制作
【正极极片】将上述获得的正极活性材料与乙炔黑、聚偏二氟乙烯(PVDF)按重量比94:3:3在N-甲基吡咯烷酮溶剂体系中混合均匀后，涂覆于铝箔上并烘干、冷压，得到正极极片。涂覆量为0.02g/cm 2，压实密度为3.5g/cm 3。
【负极极片】将负极活性材料人造石墨、硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比90:5:2:2:1在去离子水中混合均匀后，涂覆于铜箔上烘干、冷压，得到负极极片。涂覆量为0.015g/cm 2，压实密度为1.6g/cm 3。
【电解液】将碳酸亚乙酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中得到电解液，其中LiPF 6的浓度为1mol/L。
【隔离膜】以PE多孔聚合薄膜作为隔离膜。
将上述正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入电解液并封装，得到全电池(下文也称“全电”)。全电池的长×宽×高＝90mm×30mm×60mm，电池的群裕度为91.0％。
1/3C测试全电容量，1C/1C测试其25℃/45℃循环，70℃测试其产气趋势。
全电初始克容量测试
在25℃恒温环境下，静置5min，按照1/3C放电至2.8V，静置5min，按照1/3C充电至4.25V，然后在4.25V下恒压充电至电流≤0.05C，静置5min，然后按照1/3C放电至2.8V，此时的放电容量为初始克容量，记为D0。结果参见表2。
25℃下全电池容量保持率
在25℃下，以1C的恒定电流充电至4.25V，后以4.25V恒压充电至电流降到0.05C，再以1C的恒定电流放电至2.8V，得首周放电比容量(Cd1)；如此反复充放电至第300周，得锂离子电池循环n周后的放电比容量记为Cdn。容量保持率＝循环n周后的放电比容量(Cdn)/首周放电比容量(Cd1)。结果参见表2。
45℃下全电池容量保持率
在45℃下，以1C的恒定电流充电至4.25V，后以4.25V恒压充电至电流降到0.05C，再以1C的恒定电流放电至2.8V，得首周放电比容量(Cd1)；如此反复充放电至第300周，得锂离子电池循环n周后的放电比容量记为Cdn。容量保持率＝循环n周后的放电比容量(Cdn)/首周放电比容量(Cd1)。结果参见表2。
全电池70℃胀气测试
在70℃下，存储100％充电状态(SOC)的全电池。在存储前后及过程中测量电芯的开路电压(OCV)和交流内阻(IMP)以监控SOC，并测量电芯的体积。其中在每存储48h后取出全电池，静置1h后测试OCV、IMP，并在冷却至室温后用排水法测量电芯体积。排水法即先用表盘数据自动进行单位转换的天平单独测量电芯的重力F1，然后将电芯完全置于去离子水(密度已知为1g/cm 3)中，测量此时的电芯的重力F2，电芯受到的浮力F浮即为F1-F2，然后根据阿基米德原理F浮＝ρgV_排，计算得到电芯体积V＝(F1-F2)/ρg。每次测试完体积后，对电芯进行补电，以1C的恒定电流充电至4.25V，后以4.25V恒压充电至电流降到0.05C，补电完成后入炉继续测试。存储30天后，测量电芯体积，并计算相对于存储前的电芯体积，存储后的电芯体积增加量，即产气量。测试结果记录在表2中。
6)离子扩散系数
采用交流阻抗法(CHI604D阻抗分析仪，振幅电压为5mV，频率范围10 -2～10 5Hz)测试常温循环300圈后的电荷传递阻抗，通过如下公式计算锂离子扩散系数
Figure PCTCN2022099464-appb-000007
测试结果记录在表2中。
Figure PCTCN2022099464-appb-000008
其中，Rct是电荷传递阻抗，F是法拉第电阻常数，T是绝对温度，n是得失电子数，R是气体常数。
表1
Figure PCTCN2022099464-appb-000009
Figure PCTCN2022099464-appb-000010
表2
Figure PCTCN2022099464-appb-000011
Figure PCTCN2022099464-appb-000012
通过对比例1和3与实施例1、4、9制备样品电镜扫描对比分析可知，单独铁电陶瓷包覆可在正极材料表面形成岛状包覆，复合聚合物电解质包覆能够在正极材料表面形成均匀的膜状包覆层，且随着聚合物包覆量的增加，膜的连续性变好。
通过对比例1～3与实施例制备样品杂锂数据对比分析可知，由于膜状包覆层的存在，一定程度上隔绝了H 2O和CO 2，从而降低NCM杂锂，且膜的连续性越好，杂锂量越低，进而可以提高容量，提高循环性能，减少产气。
通过对比例4与实施例1～4制备样品循环效果的对比，Al 2O 3与聚合物电解质相互作用较弱，对于改善包覆层离子传输作用有限，且Al 2O 3为非活性物质，是电子和离子的绝缘体，会导致容量下降。
通过实施例1、实施例4、15至16制备样品性能数据对比分析可知，连续且厚度适中的复合聚合物电解质包覆层，有利于增加循环与抑制产气，包覆层不连续，则正极材料依然暴露在电解液中，包覆层过厚，则抑制电子传输；在合理的包覆量下，制备的正极材料容量较高，循环性能较好，产气量较少，表明材料具有较高的结构稳定性。
通过对比实施例1、实施例22至25的样品性能数据可以看出，BaTiO 3的粒度大小对容量和循环性能也有影响，当实施例25中的粒度过大时，对聚合物电解质的结晶性改善效果不明显，导致正极材料的倍率性能提升不足。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本 申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (17)

  1. 一种改性正极材料，所述改性正极材料包括内核和包覆层，所述内核为正极材料，所述包覆层包括聚合物电解质主体和分散在所述聚合物电解质主体中的铁电陶瓷材料。
  2. 根据权利要求1所述的改性正极材料，其中，所述包覆层的质量为所述改性正极材料质量的0.5wt％～5wt％，可选地，所述包覆层中所述铁电陶瓷材料的质量含量为2％～10％，进一步可选为2％～7％。
  3. 根据权利要求1或2所述的改性正极材料，其中，所述改性正极材料的离子扩散系数为10 -11～10 -10S/cm 2，可选地，所述聚合物电解质主体选自聚环氧乙烷、聚乙二醇、聚甲基丙烯酸甲酯、聚丙烯腈、聚偏氟乙烯、偏氟乙烯-三氟乙烯共聚物、偏氟乙烯-六氟丙烯共聚物、偏氟乙烯-三氟氯乙烯共聚物组成的组中的一种或多种。
  4. 根据权利要求1至3中任一项所述的改性正极材料，其中，所述聚合物电解质主体的重均分子量为1500～800000。
  5. 根据权利要求1至4中任一项所述的改性正极材料，其中，所述铁电陶瓷材料具有通式：XYO 3，X为Li +、Na +、K +、Mg 2+、Ca 2+、Sr 2+、Pb 2+、Ba 2+和La 2+组成的组中的一种或多种，Y为Ti 4+、Zr 4+、V 5+、Nb 5+和Ta 2+组成的组的一种或多种；可选地，X为Li +、Sr 2+、Pb 2+和Ba 2+组成的组中的一种或多种，Y为Ti 4+和/或Nb 5+。
  6. 根据权利要求1至5中任一项所述的改性正极材料，其中，所述铁电陶瓷材料的D V50粒径为5nm～100nm，可选地所述铁电陶瓷材料的D V50粒径为5nm～60nm。
  7. 根据权利要求1至6中任一项所述的改性正极材料，其中，所述包覆层的厚度为2nm～40nm，可选地，所述改性正极材料的D V50粒径为2μm～10μm。
  8. 根据权利要求1至7中任一项所述的改性正极材料，其中，所述正极材料为层状正极材料、富锂锰基正极材料、尖晶石镍锰酸锂正极材料、转化型正极材料组成的组中的任意一种或多种；可选地，所述正极材料的相态为O-3相。
  9. 权利要求1至8中任一项所述的改性正极材料的制备方法，其中，所述制备方法包括：
    步骤S1，制备聚合物电解质的溶液；
    步骤S2，将铁电陶瓷材料与正极材料混合，得到铁电陶瓷材料包覆的正极材料；
    步骤S3，将所述聚合物电解质的溶液和所述铁电陶瓷材料包覆的正极材料混合、干燥，得到所述改性正极材料。
  10. 根据权利要求9所述的制备方法，其中，所述聚合物电解质、所述正极材料和所述铁电陶瓷材料的质量和为W1，所述聚合物电解质的质量为W2，所述铁电陶瓷材料的质量为W3，W2/W1在0.5wt％～5wt％之间；可选地，W3/(W2+W3)在2％～10％之间，可选地在2％～5％之间。
  11. 根据权利要求1所述的制备方法，其中，所述聚合物电解质的溶液中所述聚合 物电解质的质量含量为0.5％～10％，可选地，所述聚合物电解质的溶液所用溶剂选自无水乙醇、N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)组成的组中的一种或多种。
  12. 根据权利要求1所述的制备方法，其中，所述步骤S3的干燥为喷雾干燥，可选地，所述喷雾干燥的进风温度为130℃～220℃，所述喷雾干燥的出风温度为60℃～80℃。
  13. 一种正极极片，包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料，所述正极活性材料包括权利要求1至8中任一项所述的改性正极材料；可选地，基于所述正极膜层的总重量计，所述改性正极材料在所述正极膜层中的含量为70重量％以上，可选地，为80重量％至90重量％。
  14. 一种二次电池，其中，包括权利要求1至8中任一项所述的改性正极材料或权利要求13所述的正极极片。
  15. 一种电池模块，包括二次电池，其中，所述二次电池为权利要求14中任一项所述的二次电池。
  16. 一种电池包，包括电池模块，其中所述电池模块为权利要求15所述的电池模块。
  17. 一种用电装置，包括二次电池或电池模块或电池包，其中，所述二次电池选自权利要求14所述的二次电池、所述电池模块为权利要求15所述的电池模块或所述电池包为权利要求16所述的电池包。
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