WO2023173413A1 - 二次电池以及包含其的电池模块、电池包及用电装置 - Google Patents

二次电池以及包含其的电池模块、电池包及用电装置 Download PDF

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WO2023173413A1
WO2023173413A1 PCT/CN2022/081725 CN2022081725W WO2023173413A1 WO 2023173413 A1 WO2023173413 A1 WO 2023173413A1 CN 2022081725 W CN2022081725 W CN 2022081725W WO 2023173413 A1 WO2023173413 A1 WO 2023173413A1
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secondary battery
optionally
central core
active material
core material
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PCT/CN2022/081725
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English (en)
French (fr)
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张振国
彭畅
王嗣慧
柳娜
范敬鹏
赵栋
姚志杰
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宁德时代新能源科技股份有限公司
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Priority to EP22929233.9A priority Critical patent/EP4290612A1/en
Priority to PCT/CN2022/081725 priority patent/WO2023173413A1/zh
Priority to CN202280027066.2A priority patent/CN117121232A/zh
Priority to US18/466,815 priority patent/US20230420751A1/en
Publication of WO2023173413A1 publication Critical patent/WO2023173413A1/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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/485—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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • 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
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • H01M2300/004—Three solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the field of battery technology, and specifically relates to a secondary battery, a battery module, a battery pack and an electrical device containing the same.
  • the purpose of this application is to provide a secondary battery and a battery module, a battery pack and an electrical device containing the same.
  • the secondary battery has significantly improved electrochemical performance under high voltage, and at the same time, the secondary battery can also Taking into account high energy density.
  • a first aspect of the present application provides a secondary battery, including a positive electrode sheet containing a positive active material and a non-aqueous electrolyte, wherein the positive active material includes a central core material and a modification layer located on the surface of the central core material,
  • the modification layer includes an orthophosphate with a molecular formula of A a+ x [PO 4 ] 3- y
  • the non-aqueous electrolyte includes a molecular formula of B b+ m [PO 1+c F 3-c ]
  • c- n is a fluorine-containing phosphate
  • B represents one or more of Li, Na, K, Rb, Cs, Mg, Ca, and Ba, 1 ⁇ b ⁇ 2, c represents 1 or 2
  • the secondary battery of the present application simultaneously satisfies the requirement that the positive active material has a modified layer containing orthophosphate A a+ x [PO 4 ] 3- y and the non-aqueous electrolyte contains fluorine-containing phosphate B b+ m [PO 1+c F 3 -c ] c- n , the elution amount of transition metals in the positive active material is reduced, the damage to the SEI film on the surface of the negative active material is reduced, and the irreversible consumption of active ions is reduced, and the secondary battery of the present application has significant improvement under high voltage.
  • the electrochemical performance, for example, the cycle life and storage life of the secondary battery are significantly increased.
  • the secondary battery of the present application can also take into account high energy density.
  • the mass percentage of the orthophosphate is C%, and C is 0.2-20, optionally 1-6.
  • the mass percentage of orthophosphate is within a suitable range, it can better and more comprehensively protect the central core material without affecting the energy density of the secondary battery, and further improve the cycle life of the secondary battery under high voltage. and storage life.
  • the mass percentage content of the fluorine-containing phosphate is D%, and D is 0.1-3, optionally 0.5-2.
  • the mass percentage of fluorine-containing phosphate is within a suitable range, it can significantly reduce the dissolution of orthophosphate, thereby better protecting the central core material without affecting the kinetic performance and energy density of the secondary battery. , further improving the cycle life and storage life of secondary batteries under high voltage.
  • C ⁇ D is 0.1-15, optionally 1-5.
  • the central core material can be better and more comprehensively protected, and the secondary battery can also take into account high energy density and good kinetic performance.
  • the ratio of the mass of P element in the modification layer to the total mass of the cathode active material is E%, and E is 0.05-6, optionally 0.2-3.
  • the mass percentage of the P element is within an appropriate range, the central core material can be better and more comprehensively protected without affecting the energy density of the secondary battery, and the cycle life and cycle life of the secondary battery under high voltage can be further improved. Storage life.
  • the voltage platform of the cathode active material is ⁇ 3.8V vsLi + /Li, optionally, the voltage platform is ⁇ 4.0Vvs Li + /Li.
  • the central core material includes Mn element.
  • the mass percentage of the Mn element is F%, F ⁇ 25.
  • the central core material of this application can be a manganese-rich material, which has the advantages of high gram capacity and high voltage platform, and can significantly increase the energy density of secondary batteries.
  • the central core material includes spinel-type lithium manganate LiM p Mn 2-p O 4 , lithium manganese phosphate LiN q Mn 1-q PO 4 , and layered manganese-rich material Li 1 +t Mn 1-w L w O 2+t , one or more of them, 0 ⁇ p ⁇ 1, 0 ⁇ q ⁇ 0.5, 0 ⁇ t ⁇ 1, 0 ⁇ w ⁇ 0.5, each of M, N and L Independently represents one or more of Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, and Si.
  • the central core material includes one of spinel-type lithium manganate LiM p Mn 2-p O 4 , layered manganese-rich material Li 1+t Mn 1-w L w O 2+t or Various.
  • These central core materials have the advantages of high gram capacity and high voltage platform. At the same time, these central core materials are low-cost, environmentally friendly and have stable body structure.
  • the central core material has a single crystal or quasi-single crystal morphology. Particles with single crystal or single crystal-like morphology are not easily broken and can reduce the probability of new surfaces being exposed; at the same time, central core materials with single crystal or single crystal-like morphology have better dispersion and are easier to achieve full coverage.
  • the modification layer is located on 50%-100% of the surface of the central core material, optionally 85%-100% of the surface.
  • A represents one or more of Li, Na, K, Mg, Ni, Co, Ti, Al, Nb, W, optionally represents Na, K, Ni, Co, One or more of Al, Nb, and W.
  • Orthophosphate containing the above elements is itself a fast ion conductor, so coating it in the central core material will not significantly reduce the overall capacity of the cathode active material. Therefore, the secondary battery of the present application can take into account the advantages of high energy density. In addition, orthophosphates containing the above elements have lower melting points, helping to protect the central core material more completely.
  • the orthophosphate includes Li 3 PO 4 , Na 3 PO 4 , K 3 PO 4 , Mg 3 (PO 4 ) 2 , AlPO 4 , Nb 3 (PO 4 ) 5 , LiNiPO 4.
  • TiLi 2 (PO 4 ) 2 LiNi 0.8 Co 0.2 PO 4
  • LiNi 0.8 Co 0.2 PO 4 optionally including Na 3 PO 4 , K 3 PO 4 , AlPO 4 , Nb 3 (PO 4 ) 5
  • LiNiPO 4 One or more of LiNi 0.8 Co 0.2 PO 4 .
  • B represents one or more of Li, Na, K, Mg, optionally represents Na, K, or a combination thereof.
  • Fluorine-containing phosphates containing the above elements are slightly soluble in the non-aqueous electrolyte, so when they reach saturation in the non-aqueous electrolyte, they will precipitate and deposit on the surfaces of the positive and negative electrodes, protecting the positive and negative electrodes.
  • c represents 2.
  • c- n represents monofluorophosphate B b+ m [PO 3 F] 2- n .
  • difluorophosphate B b+ m [PO 2 F 2 ] - n (c represents 1)
  • monofluorophosphate B b+ m [PO 3 F] 2- n is a solvent in a non-aqueous electrolyte (such as carbonic acid The solubility in ester solvents, etc.) is lower.
  • the monofluorophosphate B b+ m [PO 3 F] 2- n itself also has the function of capturing HF, so it can further improve the stability of the secondary battery and improve the cycle life and storage life of the secondary battery under high voltage.
  • the fluorine-containing phosphate includes LiPO 2 F 2 , NaPO 2 F 2 , KPO 2 F 2 , Li 2 PO 3 F, Na 2 PO 3 F, and K 2 PO 3 F.
  • LiPO 2 F 2 , NaPO 2 F 2 , KPO 2 F 2 , Li 2 PO 3 F, Na 2 PO 3 F, and K 2 PO 3 F includes LiPO 2 F 2 , NaPO 2 F 2 , KPO 2 F 2 , Li 2 PO 3 F, Na 2 PO 3 F, and K 2 PO 3 F.
  • the specific surface area of the cathode active material is less than 1.5m 2 /g, optionally 0.1m 2 /g-1m 2 /g.
  • the volume particle size Dv50 of the positive active material is 1 ⁇ m-20 ⁇ m, optionally 3 ⁇ m-15 ⁇ m.
  • a second aspect of the present application provides a battery module, which includes the secondary battery of the first aspect of the present application.
  • a third aspect of the present application provides a battery pack, which includes one of the secondary battery of the first aspect of the present application and the battery module of the second aspect of the present application.
  • a fourth aspect of the present application provides an electrical device, which includes at least one of the secondary battery of the first aspect of the present application, the battery module of the second aspect, and the battery pack of the third aspect of the present application.
  • the battery modules, battery packs and electrical devices of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of a power consumption device including the secondary battery of the present application as a power source.
  • 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. Furthermore, 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: 1-3, 1-4, 1-5, 2- 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 includes an electrode assembly and a non-aqueous electrolyte.
  • the electrode assembly includes a positive electrode piece, a negative electrode piece and a separator.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer.
  • the positive electrode film layer is coated on the surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer.
  • the negative electrode film layer is coated on the surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • 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 non-aqueous electrolyte plays a role in conducting active ions between the positive electrode piece and the negative electrode piece.
  • cathode active materials with a high voltage platform and increasing the operating voltage of secondary batteries are effective ways to increase the energy density of secondary batteries.
  • the non-aqueous electrolyte is more likely to oxidize, decompose and generate A large amount of HF will corrode the surface of the cathode active material and cause a large amount of transition metals (such as Mn, etc.) to dissolve. After the transition metal dissolves, the crystal structure of the cathode active material is destroyed, thereby reducing the capacity of the cathode.
  • the transition metal also migrates and deposits on the surface of the anode after dissolution, thereby destroying the solid non-aqueous electrolyte interface on the surface of the anode active material.
  • membrane SEI membrane
  • the dissolution of transition metals will significantly deteriorate the electrochemical performance of the secondary battery and cause the capacity of the secondary battery to rapidly decay.
  • the higher the operating voltage of the secondary battery the more serious the dissolution of transition metals will be, which will affect the electrochemical performance of the secondary battery. The deterioration is getting more serious.
  • the first aspect of the embodiment of the present application provides a secondary battery that can maintain good electrochemical performance under high voltage.
  • A represents Li
  • Orthophosphates such as Li 3 PO 4 , etc.
  • fluorine-containing phosphates such as monofluorophosphate, difluorophosphate, etc.
  • the non-aqueous electrolyte contains fluorine-containing phosphate B b+ m [PO 1+c F 3-c ] c- n . Since B b+ m [PO 1+c F 3-c ] c - n is slightly soluble in non-aqueous electrolyte and will ionize [PO 2 F 2 ] - , [PO 3 F 1 ] 2- , which reacts with orthophosphate A a+ x [PO 4 ] 3- y to capture HF. The products have the same anionic part.
  • the non-aqueous electrolyte contains fluorine-containing phosphate B b+ m [PO 1+c F 3-c ] c- n , the dissolution of orthophosphate in the modified layer can be reduced, the modified layer can be stabilized, and the modified layer can be stabilized through the principle of precipitation-dissolution equilibrium. Reduce damage to the modified layer, thereby better protecting the core core material.
  • the properties of fluorine-containing phosphate B b+ m [PO 1+c F 3-c ] c- n are relatively stable and are not sensitive to HF, trace amounts of water and other components in the non-aqueous electrolyte. Therefore, with the development of non-aqueous electrolysis Liquid consumption and the precipitation of fluorine-containing phosphate on the surface of the positive active material.
  • the fluorine-containing phosphate in the non-aqueous electrolyte reaches saturation, it will precipitate and deposit on the surface of the positive and negative electrodes, playing a role in protecting the positive and negative electrodes, such as reducing the activity of the negative electrodes. Destroy the SEI film on the surface of the material, repair the SEI film, reduce the erosion of the central core material by HF, etc.
  • A represents Li, Na, K, Rb, Cs, Mg, Ca, Ba, Ni, Fe, Co, Ti, Al, Cr, V, Nb, One or more of W.
  • Orthophosphate containing the above elements is itself a fast ion conductor, so coating it in the central core material will not significantly reduce the overall capacity of the cathode active material. Therefore, the secondary battery of the present application can take into account the advantages of high energy density.
  • orthophosphates containing the above elements have lower melting points, helping to protect the central core material more completely.
  • A represents one or more of Li, Na, K, Mg, Ni, Co, Ti, Al, Nb, and W.
  • A represents one or more of Na, K, Ni, Co, Al, Nb, and W.
  • B represents one or more of Li, Na, K, Rb, Cs, Mg, Ca, and Ba.
  • the fluorine-containing phosphate containing the above elements is slightly soluble in the non-aqueous electrolyte, so when it reaches saturation in the non-aqueous electrolyte, it will precipitate and deposit on the surfaces of the positive and negative electrodes, protecting the positive and negative electrodes.
  • B represents one or more of Li, Na, K, and Mg.
  • B represents Na, K, or a combination thereof.
  • the secondary battery of the present application simultaneously satisfies the requirements that the positive active material has a modified layer containing orthophosphate A a+ x [PO 4 ] 3- y and the non-aqueous electrolyte contains fluorine-containing phosphate B b+ m [PO 1+c
  • F 3-c ] c- n the elution amount of the transition metal in the positive active material is reduced, the damage of the SEI film on the surface of the negative active material is reduced, and the irreversible consumption of active ions is reduced.
  • the secondary battery of the present application has Significantly improved electrochemical performance, for example, the cycle life and storage life of the secondary battery are significantly increased.
  • the secondary battery of the present application can also take into account high energy density.
  • the orthophosphate includes Li 3 PO 4 , Na 3 PO 4 , K 3 PO 4 , Mg 3 (PO 4 ) 2 , AlPO 4 , Nb 3 (PO 4 ) 5 , LiNiPO 4 , TiLi One or more of 2 (PO 4 ) 2 and LiNi 0.8 Co 0.2 PO 4 .
  • the orthophosphate includes one or more of Na 3 PO 4 , K 3 PO 4 , AlPO 4 , Nb 3 (PO 4 ) 5 , LiNiPO 4 , and LiNi 0.8 Co 0.2 PO 4 .
  • the secondary battery has further improved electrochemical performance under high voltage, and for example, the cycle life and storage life of the secondary battery are further increased.
  • b, c, m, and n can all represent 1, that is, B b+ m [PO 1+c F 3-c ] c- n can be B + [PO 2 F 2 ] - , in which case B represents one or more of Li, Na, K, Rb, Cs, optionally, B represents one or more of Li, Na, K, further, B represents Na, K, or a combination thereof.
  • c and m can both represent 1, and b and n can both represent 2, that is, B b+ m [PO 1+c F 3- c ] c- n can be B 2+ [PO 2 F 2 ] - 2 , in this case, B represents one or more of Mg, Ca, and Ba.
  • B represents Mg, Ca, or a combination thereof. Further, B represents Mg.
  • c and m can both represent 2, and b and n can both represent 1, that is, B b+ m [PO 1+c F 3-c ] c- n can be B + 2 [PO 3 F] 2 - , at this time B represents one or more of Li, Na, K, Rb, Cs, optionally, B represents one or more of Li, Na, K, further, B represents Na, K , or a combination thereof.
  • b and c can both represent 2, and m and n can both represent 1, that is, B b+ m [PO 1+c F 3-c ] c- n can be B 2+ [PO 3 F] 2 - , in this case, B represents one or more of Mg, Ca, and Ba.
  • B represents Mg, Ca, or a combination thereof. Further, B represents Mg.
  • B may represent a combination of one or more of Li, Na, K, Rb, and Cs and one or more of Mg, Ca, and Ba.
  • c represents 2.
  • fluorine-containing phosphate B b+ m [PO 1+c F 3-c ] c- n represents monofluorophosphate B b+ m [PO 3 F] 2- n .
  • difluorophosphate B b+ m [PO 2 F 2 ] - n (c represents 1), monofluorophosphate B b+ m [PO 3 F] 2- n is a solvent in a non-aqueous electrolyte (such as carbonic acid The solubility in ester solvents, etc.) is lower.
  • the monofluorophosphate B b+ m [PO 3 F] 2- n itself also has the function of capturing HF, so it can further improve the stability of the secondary battery and improve the cycle life and storage life of the secondary battery under high voltage.
  • the fluorine-containing phosphate includes one of LiPO 2 F 2 , NaPO 2 F 2 , KPO 2 F 2 , Li 2 PO 3 F, Na 2 PO 3 F, K 2 PO 3 F, or Various.
  • the fluorine-containing phosphate includes one or more of Li 2 PO 3 F, Na 2 PO 3 F, and K 2 PO 3 F.
  • the mass percentage of the orthophosphate is C%, and C is 20 or less.
  • the mass percentage of orthophosphate should not be too high, as this may significantly reduce the energy density of the secondary battery.
  • C can be a range of 0.2, 0.3, 0.5, 1, 2, 3, 4, 5, 6, 8, 10, 12, 14, 16, 18, 20 or any of the above values.
  • C is 0.2-20, 0.2-16, 0.2-12, 0.2-10, 0.2-8, 0.2-6, 0.2-4, 0.5-20, 0.5-16, 0.5-12, 0.5-10, 0.5-8, 0.5-6, 0.5-4, 1-20, 1-16, 1-12, 1-10, 1-8, 1-6, 1-4, 2-20, 2-16, 2- 12, 2-10, 2-8, 2-6, or 2-4.
  • the mass percentage of orthophosphate is within a suitable range, it can better and more comprehensively protect the central core material without affecting the energy density of the secondary battery, and further improve the cycle life of the secondary battery under high voltage. and storage life.
  • the mass percentage content of the fluorine-containing phosphate is D%, and D is less than 3.
  • the mass percentage of fluorine-containing phosphate should not be too low. At this time, it may not be able to reduce the dissolution of orthophosphate, nor can it protect the surfaces of the positive and negative electrodes, which will affect the cycle of secondary batteries under high voltage. Improvements in longevity and storage life may not be significant.
  • the mass percentage of fluorine-containing phosphate should not be too high. At this time, too much fluorine-containing phosphate may precipitate and deposit on the surface of the negative electrode, which may reduce the kinetic performance and energy density of the secondary battery.
  • D may be a range of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0 or any above values.
  • D is 0.1-3, 0.1-2.5, 0.1-2, 0.1-1.5, 0.1-1, 0.2-3, 0.2-2.5, 0.2-2, 0.2-1.5, 0.2-1, 0.5-3, 0.5-2.5, 0.5-2, 0.5-1.5, or 0.5-1.
  • the mass percentage of fluorine-containing phosphate is within a suitable range, it can significantly reduce the dissolution of orthophosphate, thereby better protecting the central core material without affecting the kinetic performance and energy density of the secondary battery. , further improving the cycle life and storage life of secondary batteries under high voltage.
  • C ⁇ D is 0.1-15.
  • C ⁇ D can be 0.1, 0.2, 0.3, 0.5, 0.8, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or any of the above values The range it consists of.
  • C ⁇ D is 0.5-15, 0.5-12, 0.5-10, 0.5-8, 0.5-6, 0.5-5, 0.5-4, 1-15, 1-12, 1-10, 1- 8, 1-6, 1-5, or 1-4.
  • the central core material can be better and more comprehensively protected, and the secondary battery can also take into account high energy density and good kinetic performance.
  • the content of orthophosphate is small, it is easy to capture HF and dissolve it into the non-aqueous electrolyte, quickly exposing the central core material. Therefore, at this time, the concentration of fluorine-containing phosphate in the non-aqueous electrolyte can be appropriately increased, or even It can reach or approach the saturation concentration. On the one hand, it can inhibit the dissolution of orthophosphate after capturing HF to the greatest extent.
  • the fluorine-containing phosphate in the non-aqueous electrolyte can also help to dissolve the fluorine-containing phosphate in the non-aqueous electrolyte before exposing the central core material. It quickly saturates and deposits on the surface of the cathode active material to form a protective layer, reducing the impact of HF on the cathode active material and reducing the dissolution of transition metal ions. When the content of orthophosphate is greater, it has a better protective effect on the central core material and less transition metal ions are dissolved. Therefore, the content of fluorine-containing phosphate in the non-aqueous electrolyte can be appropriately reduced at this time to avoid excessive The fluorine-containing phosphate is deposited on the surface of the negative electrode, affecting the energy density and kinetic performance of the secondary battery.
  • the ratio of the mass of P element in the modification layer to the total mass of the cathode active material is E%, and E is 0.05-6.
  • E can be a range of 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.8, 1, 2, 3, 4, 5, 6 or any of the above values.
  • E is 0.1-6, 0.1-5, 0.1-4, 0.1-3, 0.1-2, 0.1-1, 0.2-6, 0.2-5, 0.2-4, 0.2-3, 0.2-2, Or 0.2-1.
  • the mass percentage of the P element is within an appropriate range, the central core material can be better and more comprehensively protected without affecting the energy density of the secondary battery, and the cycle life and cycle life of the secondary battery under high voltage can be further improved. Storage life.
  • the central core material includes Mn element.
  • the mass percentage of the Mn element is F%, F ⁇ 25.
  • the central core material of this application can be a manganese-rich material, which has the advantages of high gram capacity and high voltage platform, and can significantly increase the energy density of secondary batteries.
  • the central core material includes but is not limited to spinel lithium manganate LiM p Mn 2-p O 4 , lithium manganese phosphate LiN q Mn 1-q PO 4 , and layered manganese-rich material Li 1+t
  • Mn 1-w L w O 2+t 0 ⁇ p ⁇ 1, 0 ⁇ q ⁇ 0.5, 0 ⁇ t ⁇ 1, 0 ⁇ w ⁇ 0.5, M, N, L independently Represents one or more of Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, and Si.
  • the central core material includes one or more of spinel-type lithium manganate LiM p Mn 2-p O 4 and layered manganese-rich material Li 1+t Mn 1-w L w O 2+t kind.
  • central core materials have the advantages of high gram capacity and high voltage platform. At the same time, these central core materials are low-cost, environmentally friendly and have stable body structure. However, these central core materials are easily corroded by HF in the non-aqueous electrolyte, causing a large number of Mn dissolves.
  • a modified layer containing orthophosphate A a + - n can reduce the erosion of the central core material by HF and reduce the dissolution of transition metals such as Mn, thus helping to give full play to the advantages of the central core material with high gram capacity and high voltage platform, and the secondary battery of the present application can have Taking into account both high energy density and excellent electrochemical performance.
  • p 0.
  • q 0.
  • M represents Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, Si of one or more.
  • N represents Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, B, Al, Si of one or more.
  • L represents Ni, Co, Fe, Cr, V, Ti, Zr, La, Ce, Rb, P, W, Nb, Mo, Sb, One or more of B, Al, and Si.
  • the bonding strength between the central core material and the modified layer can be improved.
  • these doping elements can further stabilize the bulk structure of the central core material and reduce the negative impact of HF erosion.
  • the content of doping elements in the central core material should not be too high, which may significantly reduce the overall gram capacity of the cathode active material. At the same time, when the content of doping elements is too high, it is difficult to ensure the uniformity of doping. Therefore, It may affect the overall positive active material and the electrochemical performance of the secondary battery.
  • the spinel type lithium manganate LiM p Mn 2-p O 4 may include but is not limited to LiMn 2 O 4 , LiCr 0.1 Mn 1.9 O 4 , LiAl 0.1 Mn 1.9 O 4 , LiNi 0.4 Mn 1.6 O 4 , LiNi 0.5 Mn 1.5 O 4 , LiNi 0.6 Mn 1.4 O 4 , LiNi 0.4 Cr 0.2 Mn 1.4 O 4 , LiNi 0.5 Ti 0.1 Mn 1.4 O 4 , LiNi 0.5 Ti 0.1 Mn 1.4 O 4 , LiNi 0.5 Ti 0.1 Mn 1.4 O 4 , LiNi 0.5 Ti 0.5 Mn 1.0 O 4 one or more.
  • lithium manganese phosphate LiN q Mn 1-q PO 4 may include but is not limited to LiMnPO 4 , LiFe 0.5 Mn 0.5 PO 4 , LiCo 0.5 Mn 0.5 PO 4 , LiNi 0.5 Mn 0.5 PO 4 , LiNi 0.4 Mn 0.6 PO 4 , One or more of LiNi 0.3 Mn 0.7 PO 4 , LiNi 0.2 Mn 0.8 PO 4 , LiNi 0.1 Mn 0.9 PO 4 .
  • the layered manganese-rich material Li 1+t Mn 1-w L w O 2+t may include but is not limited to LiMnO 2 , Li 1.5 MnO 2.5 , Li 2 MnO 3 , Li 1.5 Co 0.5 Mn 0.5 O 2.5 , Li One or more of 1.2 Ni 0.3 Mn 0.7 O 2.2 , Li 1.3 Ni 0.1 Co 0.1 Fe 0.1 Mn 0.7 O 2.3 , Li 1.3 Ni 0.1 Co 0.1 Mn 0.8 O 2.3 , Li 1.1 Ni 0.4 Co 0.05 Al 0.05 Mn 0.5 O 2.1 kind.
  • the central core material has a single crystal or quasi-single crystal morphology. Particles with single crystal or single crystal-like morphology are not easily broken and can reduce the probability of new surfaces being exposed; at the same time, central core materials with single crystal or single crystal-like morphology have better dispersion and are easier to achieve full coverage.
  • the modification layer is located on 50%-100% of the surface of the central core material.
  • the modification layer is located on 85%-100% of the surface of the central core material.
  • the modification layer is located on 95%-100% of the surface of the central core material.
  • the modification layer is located on 100% of the surface of the central core material.
  • the voltage platform of the cathode active material is ⁇ 3.8V vs Li + /Li.
  • the voltage platform of the cathode active material is ⁇ 4.0V vs Li + /Li.
  • the voltage platform of the positive active material has a meaning well known in the art, and can be measured using instruments and methods well known in the art.
  • the cathode active material has a specific surface area of less than 1.5 m 2 /g.
  • the specific surface area of the positive active material is 0.1m 2 /g-1m 2 /g.
  • the specific surface area of a material has a well-known meaning in the art, and can be measured using instruments and methods well-known in the art.
  • the nitrogen adsorption specific surface area analysis test can pass the Tri-Star3020 type specific surface area of the American Micromeritics company. Pore size analysis tester.
  • the volume particle size Dv50 of the cathode active material is 1 ⁇ m-20 ⁇ m.
  • the volume particle size Dv50 of the positive active material is 3 ⁇ m-15 ⁇ m.
  • the specific surface area of the positive electrode active material is smaller, which helps the modification layer to fully protect the central core material at a smaller content.
  • the transmission speed of active ions is faster, so the positive electrode active material can also take into account good dynamic properties.
  • the volume particle size Dv50 of the positive electrode active material is within a suitable range, the uniformity of the positive electrode slurry and the positive electrode film layer is better, and the processing performance of the positive electrode sheet is also better.
  • the volume particle size Dv50 of the material has a well-known meaning in the art. It represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%. It can be measured using instruments and methods known in the art. For example, you can refer to the GB/T 19077-2016 particle size distribution laser diffraction method and use a laser particle size analyzer to conveniently measure it, such as the Mastersizer2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the United Kingdom.
  • the central core material can be obtained by using preparation methods known in the art, such as solid-phase heat treatment.
  • the solid-phase heat treatment process is currently the most mature preparation process and has the advantages of high efficiency, excellent product performance, and highly controllable product microstructure.
  • the preparation method of the central core material includes the steps of: mixing various raw materials required to prepare the central core material, such as lithium sources, manganese sources, doping element precursors, etc., and then heating them to T1 temperature for insulation. After heat treatment and cooling, the central core material is obtained.
  • the product obtained after high-temperature sintering can be processed through crushing, grinding, ball milling and other processes to open up the soft agglomeration between particles and improve the particle size. of dispersion.
  • T1 may be 900-1100°C.
  • the heat treatment time is 5-40 hours.
  • a secondary insulation heat treatment can be performed at 500-800°C. This will help reduce oxygen defects formed during high-temperature sintering, thereby further improving the stability of the bulk structure of the central core material and the surface structure.
  • This application has no special restrictions on the secondary insulation heat treatment time and can be adjusted according to the actual situation. For example, the heat treatment time is 5-50 hours.
  • the positive electrode active material can be obtained using preparation methods known in the art, such as direct coating method, in-situ coating method, etc.
  • the direct coating method refers to directly mixing the orthophosphate A a + layer.
  • the in-situ coating method refers to mixing the raw materials used to form orthophosphate A a+ x [PO 4 ] 3- y with the central core material evenly, and then converting each raw material into orthophosphate A a+ x [PO 4 ] 3- y reacts in situ on the surface of the central core material to form a modified layer.
  • the in-situ coating method can achieve a more uniform and comprehensive coating of the central core material by the modification layer, and can flexibly select each raw material to reduce dependence on specific modification layer materials.
  • the mixing method of each raw material can be dry mixing or liquid phase mixing.
  • Heat treatment can also be performed during or after coating. Heat treatment is conducive to further diffusion of the modification layer material, thereby helping to form a modification layer that is evenly dispersed and has high bonding strength with the central core material.
  • the heat treatment temperature is 500-1000°C.
  • the heat treatment time is 1-50h.
  • the preparation method of the positive active material includes the steps: S101, mix the central core material (which can be a finished product or a semi-finished product) with pure water and stir evenly to form a suspension; S102, mix the orthophosphate A a+ x [PO 4 ] 3- y is added to the suspension obtained in S101 and stirred thoroughly, then filtered and dried to obtain a solid powder; in S103, the solid powder obtained in S102 is heat treated at 500-1000°C to obtain a surface coated with positive Phosphate A a+ x [PO 4 ] 3- y modifies the central core material of the layer, which completes the preparation of the cathode active material.
  • the heat treatment process of S103 can also be omitted.
  • the preparation method of the positive active material includes the steps: S201, combine the central core material (which can be a finished product or a semi-finished product) and orthophosphate A a+ x [PO 4 ] 3- y through ball milling, high-energy ball milling, etc. The process is mixed uniformly to obtain a solid powder; S202, the solid powder obtained in S201 is heat-treated at 500-1000°C to obtain a central core material whose surface is coated with an orthophosphate A a+ x [PO 4 ] 3- y modification layer, namely The preparation of cathode active material is completed.
  • the heat treatment process of S202 can also be omitted.
  • the preparation method of the positive active material includes the steps: S301, mix the central core material (which can be a finished product or semi-finished product) with pure water and stir evenly to form a suspension; S302, add the soluble A source to S301 The obtained suspension is evenly dispersed; S303, dissolve the soluble phosphate in pure water to obtain a phosphate solution; S304, add the phosphate solution obtained in S303 to the suspension obtained in S302 and stir continuously until the target orthophosphate is obtained.
  • Products A a + _ The central core material coated with the orthophosphate A a+ x [PO 4 ] 3- y modification layer completes the preparation of the positive active material.
  • the heat treatment process of S306 can also be omitted.
  • the soluble A source is one or more of hydroxides, oxides, halides, carbonates, sulfates, nitrates, oxalates, etc. containing element A, for example, it can be lithium hydroxide , sodium chloride, potassium nitrate, nickel sulfate, etc.
  • the soluble phosphate may include one or more of ammonium phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and the like.
  • the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and including a positive active material.
  • the positive electrode current collector has two surfaces opposite in its 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 cathode film layer of the present application does not exclude other cathode active materials other than the above-mentioned cathode active materials.
  • the other cathode active materials can be cathode active materials known in the art for secondary batteries, such as lithium cobalt oxide, Lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium iron phosphate and Carbon composite materials, etc.
  • the positive electrode film layer optionally further includes a positive electrode conductive agent.
  • a positive electrode conductive agent includes superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, and graphene. , one or more types of carbon nanofibers.
  • the mass percentage of the cathode conductive agent is ⁇ 5%.
  • the positive electrode film layer optionally further includes a positive electrode binder.
  • the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene - One or more of propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • tetrafluoroethylene-hexafluoropropylene copolymer tetrafluoroethylene-hexafluoropropylene copolymer
  • fluorine-containing acrylate resin based on the total mass of the cathode
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying, and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the non-aqueous electrolyte solution further includes a lithium salt and a non-aqueous solvent.
  • the types and contents of the lithium salt and the non-aqueous solvent are not specifically limited and can be selected according to actual needs.
  • the lithium salt may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonimide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium difluorodioxalate borate (LiBOB), lithium difluorodioxalate phosphate (LiDFOP), lithium tetrafluorooxalate phosphate (LiTFOP) or one or more.
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • the solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropylene carbonate Ester (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA) ), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), butyric acid
  • ethyl ester EB
  • 1,4-butyrolactone GBL
  • sulfolane SF
  • MSM dimethyl sulfone
  • EMS methyl ethyl sulfone
  • additives may optionally be included in the non-aqueous electrolyte solution.
  • the 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 performance, and additives that improve battery performance. Additives for low temperature power performance, etc.
  • the secondary battery of the present application also includes a negative electrode plate and a separator.
  • 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 and including a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite in its 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 active material may be a negative active material known in the art for secondary batteries.
  • the negative active material includes but is not limited to one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials.
  • the tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries 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 active material includes but is not limited to one or more of natural graphite, artificial graphite, soft carbon, and hard carbon.
  • These negative active materials have the advantage of high gram capacity, which helps to improve the open circuit voltage and energy density of secondary batteries; at the same time, these negative active materials have high structural stability, so they also help to improve the dynamic performance and long-term performance of secondary batteries. Cycling stability.
  • the negative electrode film layer optionally further includes a negative electrode conductive agent.
  • a negative electrode conductive agent may include superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite One or more of ene and carbon nanofibers.
  • the mass percentage of the negative electrode conductive agent is ⁇ 5%.
  • the negative electrode film layer optionally further includes a negative electrode binder.
  • the negative electrode binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, One of polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylic acid sodium PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) or more.
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • acrylic resin for example, One of polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylic acid sodium PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) or more.
  • the mass percentage of the negative electrode binder is ⁇ 5%.
  • the negative electrode film layer optionally includes other additives.
  • other auxiliaries may include thickeners, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • CMC-Na sodium carboxymethylcellulose
  • PTC thermistor materials such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • the mass percentage content of the other additives is ⁇ 2%.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying, and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode sheet described in the present application further includes a conductive undercoat layer (for example, made of Conductive agent and adhesive).
  • the negative electrode sheet described in this application further includes a protective layer covering the surface of the negative electrode film layer.
  • the isolation film is disposed between the positive electrode piece and the negative electrode piece, and mainly functions to prevent the positive and negative electrodes from short-circuiting, and at the same time, allows active ions to pass through.
  • isolation membrane There is no particular restriction on the type of isolation membrane in this application, and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane may include one or more of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.
  • the isolation film may be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different.
  • the positive electrode piece, the isolation film and the negative electrode piece 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 non-aqueous 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 soft bag may be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
  • This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. As shown in FIG. 1 , a square-structured secondary battery 5 is shown 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 is used to 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 non-aqueous electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to needs.
  • the positive electrode sheet, the separator, the negative electrode sheet, and the non-aqueous electrolyte may be assembled to form a secondary battery.
  • the positive electrode sheet, isolation film, and negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is placed in an outer package, dried, and then injected with non-aqueous electrolyte. After vacuum packaging, static Through processes such as placement, formation, and shaping, secondary batteries are obtained.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a schematic diagram of 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, and the number of battery modules contained in the battery pack can be adjusted 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 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover 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 manner.
  • Embodiments of the present application also provide an electrical device, which includes at least one of a secondary battery, a battery module, and a battery pack of the present application.
  • the secondary battery, battery module or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electrical device may be, but is not limited to, 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, electric Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the power-consuming device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 6 is a schematic diagram of 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.
  • battery packs or battery modules can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • the loading amount of the negative active material on one side of the negative current collector is 0.008g/cm 2 .
  • Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a volume ratio of 1:1:1 to obtain an organic solvent.
  • the fully dried lithium salt LiPF 6 and fluorine-containing Phosphate LiPO 2 F 2 is dissolved in the above-mentioned organic solvent to obtain a non-aqueous electrolyte solution.
  • the concentration of LiPF 6 is 1 mol/L; the mass percentage of LiPO 2 F 2 is 1%, based on the total mass of the non-aqueous electrolyte.
  • a porous polypropylene membrane is used as the isolation membrane.
  • the positive electrode sheet, isolation film, and negative electrode sheet are stacked and wound in order to obtain the electrode assembly; the electrode assembly is placed in the outer packaging, dried and injected with non-aqueous electrolyte, followed by vacuum packaging, standing, forming, shaping, etc. process to obtain a secondary battery.
  • the preparation method of the secondary battery is similar to Example 1, except that the preparation parameters of the positive active material and the non-aqueous electrolyte are different. See Table 1 for details.
  • the preparation method of the secondary battery is similar to Example 1, except that LiNi 0.5 Mn 1.5 O 4 is directly used as the positive active material.
  • the preparation method of the secondary battery is similar to Example 1, except that the fluorine-containing phosphate LiPO 2 F 2 is not added to the non-aqueous electrolyte.
  • the preparation method of the secondary battery is similar to Example 31, except that Li 1.2 Ni 0.3 Mn 0.7 O 2.2 is directly used as the positive electrode active material, and the fluorine-containing phosphate LiPO 2 F 2 is not added to the non-aqueous electrolyte.
  • the secondary battery At 25°C, charge the secondary battery with a constant current of 0.3C to the upper limit cut-off voltage, and then charge it with a constant voltage of this cut-off voltage until the current is 0.05C; after leaving it standing for 5 minutes, discharge the secondary battery with a constant current of 0.33C to The lower limit cut-off voltage, the discharge capacity obtained at this time is the initial discharge capacity of the secondary battery.
  • the secondary battery At 25°C, charge the secondary battery with a constant current of 0.3C to the upper limit cut-off voltage, and then charge it with a constant voltage of this cut-off voltage until the current is 0.05C. At this time, the secondary battery is in a fully charged state. Store the fully charged secondary battery in an environment of 45°C, take it out every 5 days, and discharge it to the lower limit cut-off voltage at a constant current of 0.33C to obtain the discharge capacity after storage for a period of time; then, the secondary battery is stored according to the After the battery is fully charged in the above method, it is stored in a 45°C environment again until the discharge capacity of the secondary battery attenuates to 80% of the initial discharge capacity. The test ends and the total storage days of the secondary battery are recorded. The longer the storage days of the secondary battery, the longer the expected life of the secondary battery in high-temperature storage.
  • the upper limit cut-off voltage of Example 1-30 and Comparative Example 1-2 is 4.9V and the lower limit cut-off voltage is 3.5V; the upper limit cut-off voltage of Example 31 and Comparative Example 3 is 4.5V and the lower limit cut-off voltage is 4.5V.
  • the voltage is 2.8V.
  • Table 2 shows the performance test results of Examples 1-31 and Comparative Examples 1-3. Table 2
  • Example 1 132 516 158 Example 2 131 534 163 Example 3 130 396 124 Example 4 128 413 135 Example 5 132 459 146 Example 6 127 563 174 Example 7 125 617 202 Example 8 123 652 220 Example 9 112 733 247 Example 10 107 769 289 Example 11 98 758 283 Example 12 133 307 98 Example 13 132 367 129 Example 14 132 396 144 Example 15 131 431 152 Example 16 130 523 172 Example 17 126 539 189 Example 18 121 541 196 Example 19 113 529 181 Example 20 131 315 94 Example 21 113 672 235 Example 22 128 224 79 Example 23 133 631 194 Example 24 130 679 221 Example 25 127 498 144 Example 26 129 542 188 Example 27 128 793 304 Example 28 133 733 260 Example 29 135 439 124 Example 30 134 688 2

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Abstract

本申请提供一种二次电池以及包含其的电池模块、电池包及用电装置，所述二次电池包括含有正极活性材料的正极极片以及非水电解液，其中，所述正极活性材料包括中心核材料以及位于所述中心核材料表面的修饰层，所述修饰层包括分子式为A a+ x[PO 4] 3- y的正磷酸盐，A表示Li、Na、K、Rb、Cs、Mg、Ca、Ba、Ni、Fe、Co、Ti、Al、Cr、V、Nb、W中的一种或多种，1≤a≤6，并且ax＝3y；所述非水电解液包括分子式为B b+ m[PO 1+cF 3-c] c- n的含氟磷酸盐，B表示Li、Na、K、Rb、Cs、Mg、Ca、Ba中的一种或多种，1≤b≤2，c表示1或2，并且bm＝cn。本申请的二次电池在高电压下具有明显改善的电化学性能，同时还可以兼顾高能量密度。

Description

二次电池以及包含其的电池模块、电池包及用电装置 技术领域
本申请属于电池技术领域，具体涉及一种二次电池以及包含其的电池模块、电池包及用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着二次电池的应用及推广，其能量密度受到越来越多的关注。采用具有高电压平台的正极活性材料能够有效提高二次电池的能量密度，但是高工作电压下正极活性材料表面的腐蚀和过渡金属的溶出加剧。因此，如何增强高电压平台正极活性材料的稳定性，是目前亟待解决的技术问题。
发明内容
本申请的目的在于提供一种二次电池以及包含其的电池模块、电池包及用电装置，所述二次电池在高电压下具有明显改善的电化学性能，同时所述二次电池还可以兼顾高能量密度。
本申请第一方面提供一种二次电池，包括含有正极活性材料的正极极片以及非水电解液，其中，所述正极活性材料包括中心核材料以及位于所述中心核材料表面的修饰层，所述修饰层包括分子式为A a+ x[PO 4] 3- y的正磷酸盐，A表示Li、Na、K、Rb、Cs、Mg、Ca、Ba、Ni、Fe、Co、Ti、Al、Cr、V、Nb、W中的一种或多种，1≤a≤6，并且ax＝3y；所述非水电解液包括分子式为B b+ m[PO 1+cF 3-c] c- n的含氟磷酸盐，B表示Li、Na、K、Rb、Cs、Mg、Ca、Ba中的一种或多种，1≤b≤2，c表示1或2，并且bm＝cn。
当本申请的二次电池同时满足正极活性材料具有包含正磷酸盐A a+ x[PO 4] 3- y的修饰层并且非水电解液含有含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n时，正极活性材料中过渡金属的溶出量减少、负极活性材料表面SEI膜的破坏减少、活性离子的不可逆消耗降低，进而本申请的二次电池在高电压下具有明显改善的电化学性能，例如，二次电池的循环寿命和存储寿命明显增加，同时本申请的二次电池还可以兼顾高能量密度。
在本申请的任意实施方式中，基于所述正极活性材料的总质量，所述正磷酸盐的质量百分含量为C％，C为0.2-20，可选地为1-6。正磷酸盐的质量百分含量在合适的范围内时，可以在不影响二次电池能量密度的前提下，更好、更全面地保护中心核材料，进一步提高二次电池高电压下的循环寿命和存储寿命。
在本申请的任意实施方式中，基于所述非水电解液的总质量，所述含氟磷酸盐的质量百分含量为D％，D为0.1-3，可选地为0.5-2。含氟磷酸盐的质量百分含量在合适的 范围内时，能明显减少正磷酸盐的溶解，从而可以在不影响二次电池动力学性能和能量密度的前提下，更好地保护中心核材料，进一步提高二次电池高电压下的循环寿命和存储寿命。
在本申请的任意实施方式中，C×D为0.1-15，可选地为1-5。当正磷酸盐和含氟磷酸盐的含量满足上述关系式时，能够更好、更全面地保护中心核材料，同时二次电池还能兼顾高能量密度和良好的动力学性能。
在本申请的任意实施方式中，所述修饰层中P元素的质量与所述正极活性材料总质量的比值为E％，E为0.05-6，可选地为0.2-3。P元素的质量百分含量在合适的范围内时，可以在不影响二次电池能量密度的前提下，更好、更全面地保护中心核材料，进一步提高二次电池高电压下的循环寿命和存储寿命。
在本申请的任意实施方式中，所述正极活性材料的电压平台≥3.8V vsLi +/Li，可选地，所述电压平台≥4.0Vvs Li +/Li。
在本申请的任意实施方式中，所述中心核材料包括Mn元素，可选地，基于所述中心核材料的总质量，所述Mn元素的质量百分含量为F％，F≥25。本申请的中心核材料可以为富锰材料，其具有克容量高、电压平台高的优势，可以明显提升二次电池的能量密度。
在本申请的任意实施方式中，所述中心核材料包括尖晶石型锰酸锂LiM pMn 2-pO 4、磷酸锰锂LiN qMn 1-qPO 4、层状富锰材料Li 1+tMn 1-wL wO 2+t中的一种或多种，0≤p≤1，0≤q≤0.5，0≤t≤1，0≤w≤0.5，M、N、L各自独立地表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种。可选地，所述中心核材料包括尖晶石型锰酸锂LiM pMn 2-pO 4、层状富锰材料Li 1+tMn 1-wL wO 2+t中的一种或多种。这些中心核材料具有克容量高、电压平台高的优势，同时这些中心核材料的制造成本低、环保且本体结构稳定。
在本申请的任意实施方式中，所述中心核材料具有单晶或类单晶形貌。具有单晶或类单晶形貌的颗粒不易破碎，可以减少新表面被暴露的概率；同时，具有单晶或类单晶形貌的中心核材料的分散性更好，更易实现全面包覆。
在本申请的任意实施方式中，所述修饰层位于所述中心核材料50％-100％的表面，可选地为85％-100％的表面。
在本申请的任意实施方式中，A表示Li、Na、K、Mg、Ni、Co、Ti、Al、Nb、W中的一种或多种，可选地表示Na、K、Ni、Co、Al、Nb、W中的一种或多种。含有上述元素的正磷酸盐自身也是快离子导体，因此将其包覆在中心核材料后不会明显降低正极活性材料整体的容量，进而本申请的二次电池可以同时兼顾高能量密度优势。此外，含有上述元素的正磷酸盐的熔点较低，有助于更全面地保护中心核材料。
在本申请的任意实施方式中，所述正磷酸盐包括Li 3PO 4、Na 3PO 4、K 3PO 4、Mg 3(PO 4) 2、AlPO 4、Nb 3(PO 4) 5、LiNiPO 4、TiLi 2(PO 4) 2、LiNi 0.8Co 0.2PO 4中的一种或多种，可选地包括Na 3PO 4、K 3PO 4、AlPO 4、Nb 3(PO 4) 5、LiNiPO 4、LiNi 0.8Co 0.2PO 4中的一种或多种。
在本申请的任意实施方式中，B表示Li、Na、K、Mg中的一种或多种，可选地表示Na、K、或其组合。含有上述元素的含氟磷酸盐微溶于非水电解液，因此当其在非水 电解液中达到饱和后会析出并沉积在正负极表面，起到保护正负极的作用。
在本申请的任意实施方式中，c表示2。此时含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n表示一氟磷酸盐B b+ m[PO 3F] 2- n。与二氟磷酸盐B b+ m[PO 2F 2] - n(c表示1)相比，一氟磷酸盐B b+ m[PO 3F] 2- n在非水电解液中的溶剂(例如碳酸酯溶剂等)中的溶解度更低，一方面可以更好地通过沉淀溶解平衡的原理减少修饰层中正磷酸盐的溶解、稳定修饰层并减少修饰层的破坏，更好地保护中心核材料；另一方面其更容易在非水电解液中达到饱和并析出，从而能够更好地起到保护正负极的作用，例如进一步减少负极活性材料表面SEI膜的破坏、修复SEI膜、减少HF对中心核材料的侵蚀等。此外，一氟磷酸盐B b+ m[PO 3F] 2- n本身也具有捕获HF的作用，因此可以进一步提高二次电池的稳定性，提高二次电池高电压下的循环寿命和存储寿命。
在本申请的任意实施方式中，所述含氟磷酸盐包括LiPO 2F 2、NaPO 2F 2、KPO 2F 2、Li 2PO 3F、Na 2PO 3F、K 2PO 3F中的一种或多种，可选地包括Li 2PO 3F、Na 2PO 3F、K 2PO 3F中的一种或多种。
在本申请的任意实施方式中，所述正极活性材料的比表面积在1.5m 2/g以下，可选地为0.1m 2/g-1m 2/g。
在本申请的任意实施方式中，所述正极活性材料的体积粒径Dv50为1μm-20μm，可选地为3μm-15μm。
本申请第二方面提供一种电池模块，其包括本申请第一方面的二次电池。
本申请第三方面提供一种电池包，其包括本申请第一方面的二次电池、第二方面的电池模块中的一种。
本申请第四方面提供一种用电装置，其包括本申请第一方面的二次电池、第二方面的电池模块、第三方面的电池包中的至少一种。
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
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方式，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是本申请的二次电池的一实施方式的示意图。
图2是图1的二次电池的实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
在附图中，附图未必按照实际的比例绘制。其中，附图标记说明如下：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盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池以及包含其的电池模块、电池包及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，并且这样的技术方案应被认为包含在本申请的公开内容中。
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，并且这样的技术方案应被认为包含在本申请的公开内容中。
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，二次电池包括电极组件和非水电解液，电极组件包括正极极片、负极极片和隔离膜。正极极片包括正极集流体和正极膜层，正极膜层涂布于正极集流体的表面，并且正极膜层包括正极活性材料。负极极片包括负极集流 体和负极膜层，负极膜层涂布于负极集流体的表面，并且负极膜层包括负极活性材料。在电池充放电过程中，活性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。非水电解液在正极极片和负极极片之间起到传导活性离子的作用。
随着二次电池的应用及推广，人们对其能量密度的要求越来越高。采用具有高电压平台的正极活性材料、提高二次电池的工作电压是提高二次电池能量密度的有效途径，但是，当二次电池的工作电压提高后，非水电解液更容易氧化分解并生成大量HF，HF会腐蚀正极活性材料表面、导致大量过渡金属(例如Mn等)溶出。过渡金属溶出后，正极活性材料的晶体结构被破坏，由此降低了正极容量发挥；此外，过渡金属溶出后还会迁移并沉积至负极表面，从而破坏负极活性材料表面的固体非水电解液界面膜(SEI膜)、影响SEI膜的离子传导，进而还降低了负极容量发挥。因此，过渡金属溶出后会明显恶化二次电池的电化学性能、导致二次电池的容量快速衰减，并且二次电池的工作电压越高，过渡金属溶出越严重，其对二次电池电化学性能的恶化也越严重。
为了改善正极活性材料的高电压性能，目前的研究工作主要几种在以下几个方面：(1)提供耐高电压氧化的非水电解液体系；(2)提供正极活性材料的掺杂或包覆改性方案。但是，现有的非水电解液体系在高电压下生成HF几乎是无法避免的，而常规的包覆层会受到HF侵蚀而不断溶解、或者无法进行全面包覆，因此，上述方案虽然可在一定程度上改善二次电池的电化学性能，但是改善效果有限。
鉴于此，本申请实施方式第一方面提供了一种二次电池，其能在高电压下保持良好的电化学性能。
二次电池
本申请实施方式第一方面的二次电池包括含有正极活性材料的正极极片以及非水电解液，其中，所述正极活性材料包括中心核材料以及位于所述中心核材料表面的修饰层，所述修饰层包括分子式为A a+ x[PO 4] 3- y的正磷酸盐，A表示Li、Na、K、Rb、Cs、Mg、Ca、Ba、Ni、Fe、Co、Ti、Al、Cr、V、Nb、W中的一种或多种，1≤a≤6，并且ax＝3y；所述非水电解液包括分子式为B b+ m[PO 1+cF 3-c] c- n的含氟磷酸盐，B表示Li、Na、K、Rb、Cs、Mg、Ca、Ba中的一种或多种，1≤b≤2，c表示1或2，并且bm＝cn。
正磷酸盐(例如Li 3PO 4等)可以捕获非水电解液中产生的HF，从而减少HF对中心核材料的侵蚀、减少过渡金属的溶出。但是，本申请的发明人在研究过程中意外发现，正磷酸盐捕获HF后会生成含氟磷酸盐(例如一氟磷酸盐、二氟磷酸盐等)，由于这种含氟磷酸盐微溶于非水电解液中的溶剂(例如碳酸酯溶剂等)，因此，作为修饰层的正磷酸盐会不断地被消耗直至完全溶解至非水电解液中而丧失包覆改性效果。
在本申请的二次电池中，非水电解液含有含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n，由于B b+ m[PO 1+cF 3-c] c- n微溶于非水电解液中后会电离出[PO 2F 2] -、[PO 3F 1] 2-，其与正磷酸盐A a+ x[PO 4] 3- y捕获HF后反应产物具有相同的阴离子部分。因此，当非水电解液含有含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n时，可以通过沉淀溶解平衡的原理减少修饰层中正磷酸盐的溶解、稳定修饰层并减少修饰层的破坏，从而更好地保护中心核材料。
同时，含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n自身的性质比较稳定，对非水电解液中的HF、微量水等成分不敏感，因此随着非水电解液消耗及正极活性材料表面含氟磷酸盐的析出， 非水电解液中的含氟磷酸盐达到饱和后会析出并沉积在正负极表面，起到保护正负极的作用，例如减少负极活性材料表面SEI膜的破坏、修复SEI膜、减少HF对中心核材料的侵蚀等。
在正磷酸盐A a+ x[PO 4] 3- y中，A表示Li、Na、K、Rb、Cs、Mg、Ca、Ba、Ni、Fe、Co、Ti、Al、Cr、V、Nb、W中的一种或多种。含有上述元素的正磷酸盐自身也是快离子导体，因此将其包覆在中心核材料后不会明显降低正极活性材料整体的容量，进而本申请的二次电池可以同时兼顾高能量密度优势。此外，含有上述元素的正磷酸盐的熔点较低，有助于更全面地保护中心核材料。在一些实施例中，A表示Li、Na、K、Mg、Ni、Co、Ti、Al、Nb、W中的一种或多种。可选地，A表示Na、K、Ni、Co、Al、Nb、W中的一种或多种。
在含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n中，B表示Li、Na、K、Rb、Cs、Mg、Ca、Ba中的一种或多种。含有上述元素的含氟磷酸盐微溶于非水电解液，因此当其在非水电解液中达到饱和后会析出并沉积在正负极表面，起到保护正负极的作用。在一些实施例中，B表示Li、Na、K、Mg中的一种或多种。可选地，B表示Na、K、或其组合。
因此，当本申请的二次电池同时满足正极活性材料具有包含正磷酸盐A a+ x[PO 4] 3- y的修饰层并且非水电解液含有含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n时，正极活性材料中过渡金属的溶出量减少、负极活性材料表面SEI膜的破坏减少、活性离子的不可逆消耗降低，进而本申请的二次电池在高电压下具有明显改善的电化学性能，例如，二次电池的循环寿命和存储寿命明显增加，同时本申请的二次电池还可以兼顾高能量密度。
在正磷酸盐A a+ x[PO 4] 3- y中，a表示元素A的平均化合价，1≤a≤6，并且ax＝3y，以使正磷酸盐A a+ x[PO 4] 3- y呈电中性。
在一些实施例中，所述正磷酸盐包括Li 3PO 4、Na 3PO 4、K 3PO 4、Mg 3(PO 4) 2、AlPO 4、Nb 3(PO 4) 5、LiNiPO 4、TiLi 2(PO 4) 2、LiNi 0.8Co 0.2PO 4中的一种或多种。可选地，所述正磷酸盐包括Na 3PO 4、K 3PO 4、AlPO 4、Nb 3(PO 4) 5、LiNiPO 4、LiNi 0.8Co 0.2PO 4中的一种或多种。
此时，二次电池在高电压下具有进一步改善的电化学性能，例如，二次电池的循环寿命和存储寿命进一步增加。
在含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n中，b表示元素B的平均化合价，c表示阴离子[PO 1+cF 3-c]的化合价，1≤b≤2，c表示1或2，并且bm＝cn，以使含氟磷酸盐B b+ m[PO 1+cF 3- c] c- n呈电中性。
在一些实施例中，b、c、m、n可以均表示1，即B b+ m[PO 1+cF 3-c] c- n可以为B +[PO 2F 2] -，此时B表示Li、Na、K、Rb、Cs中的一种或多种，可选地，B表示Li、Na、K中的一种或多种，进一步地，B表示Na、K、或其组合。
在一些实施例中，c、m可以均表示1，并且b、n可以均表示2，即B b+ m[PO 1+cF 3- c] c- n可以为B 2+[PO 2F 2] - 2，此时B表示Mg、Ca、Ba中的一种或多种，可选地，B表示Mg、Ca、或其组合，进一步地，B表示Mg。
在一些实施例中，c、m可以均表示2，b、n可以均表示1，即B b+ m[PO 1+cF 3-c] c- n可以为B + 2[PO 3F] 2-，此时B表示Li、Na、K、Rb、Cs中的一种或多种，可选地，B表示Li、Na、K中的一种或多种，进一步地，B表示Na、K、或其组合。
在一些实施例中，b、c可以均表示2，m、n可以均表示1，即B b+ m[PO 1+cF 3-c] c- n可以为B 2+[PO 3F] 2-，此时B表示Mg、Ca、Ba中的一种或多种，可选地，B表示Mg、Ca、或其组合，进一步地，B表示Mg。
当然，b、m、n也可以不为整数，例如，B可以表示Li、Na、K、Rb、Cs中的一种或多种与Mg、Ca、Ba中的一种或多种的组合。
在一些实施例中，c表示2。此时含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n表示一氟磷酸盐B b+ m[PO 3F] 2- n。与二氟磷酸盐B b+ m[PO 2F 2] - n(c表示1)相比，一氟磷酸盐B b+ m[PO 3F] 2- n在非水电解液中的溶剂(例如碳酸酯溶剂等)中的溶解度更低，一方面可以更好地通过沉淀溶解平衡的原理减少修饰层中正磷酸盐的溶解、稳定修饰层并减少修饰层的破坏，更好地保护中心核材料；另一方面其更容易在非水电解液中达到饱和并析出，从而更容易沉积到正负极表面，更好地起到保护正负极的作用，例如进一步减少负极活性材料表面SEI膜的破坏、修复SEI膜、减少HF对中心核材料的侵蚀等。此外，一氟磷酸盐B b+ m[PO 3F] 2- n本身也具有捕获HF的作用，因此可以进一步提高二次电池的稳定性，提高二次电池高电压下的循环寿命和存储寿命。
在一些实施例中，所述含氟磷酸盐包括LiPO 2F 2、NaPO 2F 2、KPO 2F 2、Li 2PO 3F、Na 2PO 3F、K 2PO 3F中的一种或多种。可选地，所述含氟磷酸盐包括Li 2PO 3F、Na 2PO 3F、K 2PO 3F中的一种或多种。
在一些实施例中，基于所述正极活性材料的总质量，所述正磷酸盐的质量百分含量为C％，C为20以下。正磷酸盐的质量百分含量不宜过高，此时可能会明显降低二次电池的能量密度。
例如，在一些实施例中，C可以为0.2，0.3，0.5，1，2，3，4，5，6，8，10，12，14，16，18，20或以上任何数值所组成的范围。可选地，C为0.2-20，0.2-16，0.2-12，0.2-10，0.2-8，0.2-6，0.2-4，0.5-20，0.5-16，0.5-12，0.5-10，0.5-8，0.5-6，0.5-4，1-20，1-16，1-12，1-10，1-8，1-6，1-4，2-20，2-16，2-12，2-10，2-8，2-6，或2-4。正磷酸盐的质量百分含量在合适的范围内时，可以在不影响二次电池能量密度的前提下，更好、更全面地保护中心核材料，进一步提高二次电池高电压下的循环寿命和存储寿命。
在一些实施例中，基于所述非水电解液的总质量，所述含氟磷酸盐的质量百分含量为D％，D在3以下。含氟磷酸盐的质量百分含量不宜太低，此时可能无法起到减少正磷酸盐溶解的作用，也无法起到保护正负极表面的作用，进而其对二次电池高电压下的循环寿命和存储寿命的改善效果可能不明显。含氟磷酸盐的质量百分含量也不宜太高，此时可能出现过多的含氟磷酸盐析出并沉积到负极表面，由此可能降低二次电池的动力学性能和能量密度。
例如，在一些实施例中，D可以为0.1，0.2，0.3，0.4，0.5，0.6，0.8，1.0，1.5，2.0，2.5，3.0或以上任何数值所组成的范围。可选地，D为0.1-3，0.1-2.5，0.1-2，0.1-1.5，0.1-1，0.2-3，0.2-2.5，0.2-2，0.2-1.5，0.2-1，0.5-3，0.5-2.5，0.5-2，0.5-1.5，或0.5-1。含氟磷酸盐的质量百分含量在合适的范围内时，能明显减少正磷酸盐的溶解，从而可以在不影响二次电池动力学性能和能量密度的前提下，更好地保护中心核材料，进一步提高二次电池高电压下的循环寿命和存储寿命。
在一些实施例中，C×D为0.1-15。例如，C×D可以为0.1，0.2，0.3，0.5，0.8， 1，2，3，4，5，6，7，8，9，10，11，12，13，14，15或以上任何数值所组成的范围。可选地，C×D为0.5-15，0.5-12，0.5-10，0.5-8，0.5-6，0.5-5，0.5-4，1-15，1-12，1-10，1-8，1-6，1-5，或1-4。
当正磷酸盐和含氟磷酸盐的含量满足上述关系式时，能够更好、更全面地保护中心核材料，同时二次电池还能兼顾高能量密度和良好的动力学性能。当正磷酸盐的含量较少时，其容易因捕获HF溶解至非水电解液中而很快暴露中心核材料，因此，此时可以适当提高非水电解液中含氟磷酸盐的浓度，甚至可以使其达到或接近饱和浓度，一方面能够最大程度地抑制正磷酸盐捕获HF后的溶解，另一方面还有助于在暴露中心核材料之前，使非水电解液中的含氟磷酸盐快速饱和并沉积在正极活性材料表面形成保护层，减少HF对正极活性材料的影响、减少过渡金属离子溶出。当正磷酸盐的含量较多时，其对中心核材料的保护作用较好，过渡金属离子溶出较少，因此，此时可以适当降低非水电解液中含氟磷酸盐的含量，从而避免过多的含氟磷酸盐沉积到负极表面，影响二次电池的能量密度和动力学性能。
在一些实施例中，所述修饰层中P元素的质量与所述正极活性材料总质量的比值为E％，E为0.05-6。例如，E可以为0.05，0.1，0.2，0.3，0.4，0.5，0.6，0.8，1，2，3，4，5，6或以上任何数值所组成的范围。可选地，E为0.1-6，0.1-5，0.1-4，0.1-3，0.1-2，0.1-1，0.2-6，0.2-5，0.2-4，0.2-3，0.2-2，或0.2-1。P元素的质量百分含量在合适的范围内时，可以在不影响二次电池能量密度的前提下，更好、更全面地保护中心核材料，进一步提高二次电池高电压下的循环寿命和存储寿命。
在一些实施例中，所述中心核材料包括Mn元素，可选地，基于所述中心核材料的总质量，所述Mn元素的质量百分含量为F％，F≥25。本申请的中心核材料可以为富锰材料，其具有克容量高、电压平台高的优势，可以明显提升二次电池的能量密度。
可选地，所述中心核材料包括但不限于尖晶石型锰酸锂LiM pMn 2-pO 4、磷酸锰锂LiN qMn 1-qPO 4、层状富锰材料Li 1+tMn 1-wL wO 2+t中的一种或多种，0≤p≤1，0≤q≤0.5，0≤t≤1，0≤w≤0.5，M、N、L各自独立地表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种。进一步地，所述中心核材料包括尖晶石型锰酸锂LiM pMn 2-pO 4、层状富锰材料Li 1+tMn 1-wL wO 2+t中的一种或多种。
这些中心核材料具有克容量高、电压平台高的优势，同时这些中心核材料的制造成本低、环保且本体结构稳定，但是，这些中心核材料容易受到非水电解液中HF的侵蚀，造成大量Mn溶出。通过在中心核材料表面设置包含正磷酸盐A a+ x[PO 4] 3- y的修饰层以及在非水电解液中使用含氟磷酸盐B b+ m[PO 1+cF 3-c] c- n，可以减少HF对中心核材料的侵蚀、减少Mn等的过渡金属的溶出，从而有助于充分发挥中心核材料克容量高、电压平台高的优势，进而本申请的二次电池可以具有同时兼顾高能量密度和优异的电化学性能。
在一些实施例中，p＝0。
在一些实施例中，q＝0。
在一些实施例中，t＝0，并且w＝0。
在一些实施例中，0＜p≤1，M表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种。
在一些实施例中，0＜q≤0.5，N表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、 P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种。
在一些实施例中，0＜t≤1，0＜w≤0.5，L表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种。
当中心核材料中掺杂有与修饰层相同或具有相似性质的元素时，可以提高中心核材料与修饰层之间的结合强度。同时，这些掺杂元素还可以进一步稳定中心核材料的体相结构，减少HF侵蚀的负面影响。
此外，中心核材料中掺杂元素的含量不宜太高，此时可能会明显降低正极活性材料整体的克容量；同时，掺杂元素的含量太高时，掺杂的均匀程度难以保证，由此可能影响正极活性材料整体以及二次电池的电化学性能。
作为示例，尖晶石型锰酸锂LiM pMn 2-pO 4可以包括但不限于LiMn 2O 4、LiCr 0.1Mn 1.9O 4、LiAl 0.1Mn 1.9O 4、LiNi 0.4Mn 1.6O 4、LiNi 0.5Mn 1.5O 4、LiNi 0.6Mn 1.4O 4、LiNi 0.4Cr 0.2Mn 1.4O 4、LiNi 0.5Ti 0.1Mn 1.4O 4、LiNi 0.5Ti 0.1Mn 1.4O 4、LiNi 0.5Ti 0.5Mn 1.0O 4中的一种或多种。
作为示例，磷酸锰锂LiN qMn 1-qPO 4可以包括但不限于LiMnPO 4、LiFe 0.5Mn 0.5PO 4、LiCo 0.5Mn 0.5PO 4、LiNi 0.5Mn 0.5PO 4、LiNi 0.4Mn 0.6PO 4、LiNi 0.3Mn 0.7PO 4、LiNi 0.2Mn 0.8PO 4、LiNi 0.1Mn 0.9PO 4中的一种或多种。
作为示例，层状富锰材料Li 1+tMn 1-wL wO 2+t可以包括但不限于LiMnO 2、Li 1.5MnO 2.5、Li 2MnO 3、Li 1.5Co 0.5Mn 0.5O 2.5、Li 1.2Ni 0.3Mn 0.7O 2.2、Li 1.3Ni 0.1Co 0.1Fe 0.1Mn 0.7O 2.3、Li 1.3Ni 0.1Co 0.1Mn 0.8O 2.3、Li 1.1Ni 0.4Co 0.05Al 0.05Mn 0.5O 2.1中的一种或多种。
在一些实施例中，所述中心核材料具有单晶或类单晶形貌。具有单晶或类单晶形貌的颗粒不易破碎，可以减少新表面被暴露的概率；同时，具有单晶或类单晶形貌的中心核材料的分散性更好，更易实现全面包覆。
在一些实施例中，所述修饰层位于所述中心核材料50％-100％的表面。可选地，所述修饰层位于所述中心核材料85％-100％的表面。进一步地，所述修饰层位于所述中心核材料95％-100％的表面。特别地，所述修饰层位于所述中心核材料100％的表面。
在一些实施例中，所述正极活性材料的电压平台≥3.8Vvs Li +/Li。可选地，所述正极活性材料的电压平台≥4.0Vvs Li +/Li。
在本申请中，正极活性材料的电压平台为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。
在一些实施例中，所述正极活性材料的比表面积在1.5m 2/g以下。可选地，所述正极活性材料的比表面积为0.1m 2/g-1m 2/g。正极活性材料的比表面积较小时，有助于实现修饰层在较小含量下全面地保护中心核材料，从而避免采用过厚的修饰层而降低二次电池的动力学性能和能量密度。
在本申请中，材料的比表面积为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19587-2017，采用氮气吸附比表面积分析测试方法测试，并用BET(BrunauerEmmett Teller)法计算得出，其中氮气吸附比表面积分析测试可以通过美国Micromeritics公司的Tri-Star3020型比表面积孔径分析测试仪进行。
在一些实施例中，所述正极活性材料的体积粒径Dv50为1μm-20μm。可选地，所 述正极活性材料的体积粒径Dv50为3μm-15μm。正极活性材料的体积粒径Dv50在合适的范围内时，正极活性材料的比表面积较小，从而有助于实现修饰层在较小含量下全面地保护中心核材料。同时，正极活性材料的体积粒径Dv50在合适的范围内时，活性离子的传输速度较快，从而正极活性材料还可以同时兼顾良好的动力学性能。此外，正极活性材料的体积粒径Dv50在合适的范围内时，正极浆料和正极膜层的均一性更好，正极极片的加工性能也更好。
在本申请中，材料的体积粒径Dv50为本领域公知的含义，其表示材料累计体积分布百分数达到50％时所对应的粒径，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer2000E型激光粒度分析仪。
在本申请中，所述中心核材料可以采用本领域公知的制备方法得到，例如采用固相热处理法得到。固相热处理工艺是当前最成熟的制备工艺，具有效率高、产品性能优异、产品微观形貌结构可控程度高等优点。
在一些实施例中，所述中心核材料的制备方法包括步骤：将制备中心核材料所需的各原料，例如锂源、锰源、掺杂元素前驱体等，混合后升温至T1温度进行保温热处理，降温后即得到中心核材料。
为了获得所需粒径分布以及晶粒形貌的中心核材料，可以在高温烧结结束后通过破碎、研磨、球磨等工艺处理高温烧结后所得到的产物，以打开颗粒间的软团聚、提高颗粒的分散性。
可选地，为了获得所需粒径分布的单晶或类单晶形貌的中心核材料，T1可以为900-1100℃。本申请对热处理时间没有特别的限制，可以根据实际情况进行调整，例如，热处理时间5-40h。
为了进一步获得氧缺陷更少的单晶或类单晶形貌的中心核材料，在T1温度保温热处理后，还可以在500-800℃进行二次保温热处理。此时有利于减少高温烧结时形成的氧缺陷，从而进一步提高中心核材料体相结构以及表面结构的稳定性。本申请对二次保温热处理时间没有特别的限制，可以根据实际情况进行调整，例如，热处理时间为5-50h。
在本申请中，所述正极活性材料可以采用本领域公知的制备方法得到，例如采用直接包覆法、原位包覆法等。直接包覆法是指将正磷酸盐A a+ x[PO 4] 3- y与中心核材料直接混合均匀，使正磷酸盐A a+ x[PO 4] 3- y直接在中心核材料表面形成修饰层。原位包覆法是指将用于形成正磷酸盐A a+ x[PO 4] 3- y的各原料与中心核材料混合均匀，各原料经过化学反应后转变为正磷酸盐A a+ x[PO 4] 3- y并在中心核材料表面原位反应形成修饰层。原位包覆法可以实现修饰层更均匀、更全面地包覆中心核材料，并且可以灵活选择各原料，降低对特定修饰层材料的依赖性。
包覆时，各原料的混合方式可以为干法混合，也可以为液相混合。
包覆时或包覆后还可以进行热处理，热处理有利于修饰层材料的进一步扩散，从而有利于形成分散均匀且与中心核材料结合强度高的修饰层。可选地，所述热处理温度为500-1000℃。可选地，热处理时间为1-50h。
在一些实施例中，所述正极活性材料的制备方法包括步骤：S101，将中心核材料(可以为成品或半成品)与纯水混合并搅拌均匀形成悬浊液；S102，将正磷酸盐 A a+ x[PO 4] 3- y加入S101得到的悬浊液中充分搅拌均匀后，过滤、干燥得到固体粉末；S103，将S102得到的固体粉末在500-1000℃下热处理，得到表面包覆有正磷酸盐A a+ x[PO 4] 3- y修饰层的中心核材料，即完成正极活性材料的制备。
可选地，S103的热处理工艺也可以省略。
在一些实施例中，所述正极活性材料的制备方法包括步骤：S201，将中心核材料(可以为成品或半成品)与正磷酸盐A a+ x[PO 4] 3- y通过球磨、高能球磨等工艺混合均匀，得到固体粉末；S202，将S201得到的固体粉末在500-1000℃下热处理，得到表面包覆有正磷酸盐A a+ x[PO 4] 3- y修饰层的中心核材料，即完成正极活性材料的制备。
可选地，S202的热处理工艺也可以省略。
在一些实施例中，所述正极活性材料的制备方法包括步骤：S301，将中心核材料(可以为成品或半成品)与纯水混合并搅拌均匀形成悬浊液；S302，将可溶性A源加入S301得到的悬浊液中分散均匀；S303，将可溶性磷酸盐溶于纯水中得到磷酸盐溶液；S304，将S303得到的磷酸盐溶液加入S302得到的悬浊液中不停搅拌直至目标正磷酸盐产物A a+ x[PO 4] 3- y沉淀在中心核材料表面；S305，过滤S304的悬浊液，干燥得到固体粉末；S306，将S305得到的固体粉末在500-1000℃下热处理，得到表面包覆有正磷酸盐A a+ x[PO 4] 3- y修饰层的中心核材料，即完成正极活性材料的制备。
可选地，S306的热处理工艺也可以省略。
可选地，可溶性A源为含有元素A的氢氧化物、氧化物、卤化物、碳酸盐、硫酸盐、硝酸盐、草酸盐等中的一种或多种，例如可以为氢氧化锂、氯化纳、硝酸钾、硫酸镍等。
可选地，可溶性磷酸盐可以包括磷酸铵、磷酸氢铵、磷酸二氢铵等中的一种或多种。
在一些实施例中，所述正极极片包括正极集流体以及设置在所述正极集流体至少一个表面且包括正极活性材料的正极膜层。例如，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极膜层设置于所述正极集流体的两个相对表面中的任意一者或两者上。
本申请的正极膜层并不排除除了上述正极活性材料以外的其他正极活性材料，所述其他正极活性材料可采用本领域公知的用于二次电池的正极活性材料，例如，锂钴氧化物、锂镍氧化物、锂锰氧化物、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、锂镍钴铝氧化物、磷酸铁锂、磷酸铁锂与碳的复合材料等。
在一些实施例中，所述正极膜层还可选地包括正极导电剂。本申请对所述正极导电剂的种类没有特别的限制，作为示例，所述正极导电剂包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或多种。在一些实施例中，基于所述正极膜层的总质量，所述正极导电剂的质量百分含量≤5％。
在一些实施例中，所述正极膜层还可选地包括正极粘结剂。本申请对所述正极粘结剂的种类没有特别的限制，作为示例，所述正极粘结剂可包括聚偏氟乙烯(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、含氟丙烯酸酯类树脂中的一种或多种。在一些实施例中，基于所述正极膜层的总质量，所述正极粘结剂的质量百分含量≤5％。
在一些实施例中，所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或多种。作为示例，高分子材料基层可选自聚丙烯(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。
所述正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
在一些实施例中，所述非水电解液还包括锂盐和非水溶剂。所述锂盐和所述非水溶剂的种类以及含量不受具体的限制，可根据实际需求进行选择。
作为示例，所述锂盐可包括六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二草酸硼酸锂(LiBOB)、二氟二草酸磷酸锂(LiDFOP)、四氟草酸磷酸锂(LiTFOP)中的一种或多种。
作为示例，所述溶剂可包括碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或多种。
在一些实施例中，所述非水电解液中还可选地包括添加剂。例如，所述添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，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、改善电池高温性能的添加剂、改善电池低温功率性能的添加剂等。
本申请的二次电池还包括负极极片以及隔离膜。
[负极极片]
在一些实施例中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面且包括负极活性材料的负极膜层。例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层设置在所述负极集流体的两个相对表面中的任意一者或两者上。
所述负极活性材料可采用本领域公知的用于二次电池的负极活性材料。作为示例，所述负极活性材料包括但不限于天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或多种。所述硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的一种或多种。所述锡基材料可包括单质锡、锡氧化物、锡合金材料中的一种或多种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的传统公知的材料。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。
可选地，所述负极活性材料包括但不限于天然石墨、人造石墨、软炭、硬炭中的一种或多种。这些负极活性材料具有克容量高的优势，有助于提升二次电池的开路电压和能量密度；同时这些负极活性材料结构稳定性高，因此还有助于提升二次电池的动力学性能和长期循环稳定性。
在一些实施例中，所述负极膜层还可选地包括负极导电剂。本申请对所述负极导电剂的种类没有特别的限制，作为示例，所述负极导电剂可包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的一种或多种。在一些实施例中，基于所述负极膜层的总质量，所述负极导电剂的质量百分含量≤5％。
在一些实施例中，所述负极膜层还可选地包括负极粘结剂。本申请对所述负极粘结剂的种类没有特别的限制，作为示例，所述负极粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、羧甲基壳聚糖(CMCS)中的一种或多种。在一些实施例中，基于所述负极膜层的总质量，所述负极粘结剂的质量百分含量≤5％。
在一些实施例中，所述负极膜层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC-Na)、PTC热敏电阻材料等。在一些实施例中，基于所述负极膜层的总质量，所述其他助剂的质量百分含量≤2％。
在一些实施例中，所述负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铜、铜合金、镍、镍合金、钛、钛合金、银、银合金中的一种或多种。作为示例，高分子材料基层可选自聚丙烯(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。
所述负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。所述负极浆料通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
所述负极极片并不排除除了所述负极膜层之外的其他附加功能层。例如在某些实施例中，本申请所述的负极极片还包括夹在所述负极集流体和所述负极膜层之间、设置于所述负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施例中，本申请所述的负极极片还包括覆盖在所述负极膜层表面的保护层。
[隔离膜]
所述隔离膜设置在所述正极极片和所述负极极片之间，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。本申请对所述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。
在一些实施例中，所述隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或多种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。当所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施例中，所述正极极片、所述隔离膜和所述负极极片可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施例中，所述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非水电解液。
在一些实施例中，所述二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。所述二次电池的外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或多种。
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。如图1是作为一个示例的方形结构的二次电池5。
在一些实施例中，如图2所示，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用于盖设所述开口，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。非水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几个，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和非水电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入非水电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
电池模块及电池包
在本申请的一些实施例中，根据本申请的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多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4的示意图。如图3所示，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。
在一些实施例中，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根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，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用于盖设下箱体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。
用电装置
本申请实施方式还提供一种用电装置，所述用电装置包括本申请的二次电池、电池模块、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。所述用电装置可以但不限于是移动设备(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。
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6是作为一个示例的用电装置的示意图。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高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
正极活性材料的制备
将中心核材料LiNi 0.5Mn 1.5O 4单晶颗粒与纯水混合并搅拌均匀形成悬浊液；将正磷酸盐Li 3PO 4加入悬浊液中，充分搅拌均匀后，过滤、干燥得到固体粉末；将固体粉末在600℃下热处理10h，得到表面包覆有Li 3PO 4修饰层的LiNi 0.5Mn 1.5O 4。基于正极活性材料的总质量，Li 3PO 4的质量百分含量为2％，修饰层中P元素的质量与正极活性材料总质量的比值为0.54％。
正极极片的制备
将上述正极活性材料、导电剂炭黑(SuperP)、粘结剂聚偏氟乙烯(PVDF)按照质量比96:2.5:1.5在适量的溶剂NMP中充分搅拌混合，形成均匀的正极浆料；将正极浆料均匀涂覆于正极集流体铝箔的表面上，经干燥、冷压后，得到正极极片。正极集流体单侧上正极活性材料的负载量为0.02g/cm 2。
负极极片的制备
将负极活性材料人造石墨、导电剂炭黑(Super P)、粘结剂丁苯橡胶、增稠剂羧甲基纤维素钠按照质量比96:1:1:2在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。负极集流体单侧上负极活性材料的负载量为0.008g/cm 2。
非水电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按照按体积比1:1:1进行混合得到有机溶剂，接着将充分干燥的锂盐LiPF 6、含氟磷酸盐LiPO 2F 2溶解于上述有机溶剂中，得到非水电解液。LiPF 6浓度为1mol/L；LiPO 2F 2的质量百分含量为1％，基于非水电解液的总质量计。
隔离膜的制备
采用多孔聚丙烯膜作为隔离膜。
二次电池的制备
将正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件置于外包装中，干燥后注入非水电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
实施例2至实施例31
二次电池的制备方法与实施例1类似，不同之处在于正极活性材料和非水电解液的制备参数不同，具体详见表1。
对比例1
二次电池的制备方法与实施例1类似，不同之处在于正极活性材料直接采用LiNi 0.5Mn 1.5O 4。
对比例2
二次电池的制备方法与实施例1类似，不同之处在于非水电解液中未加入含氟磷酸盐LiPO 2F 2。
对比例3
二次电池的制备方法与实施例31类似，不同之处在于正极活性材料直接采用Li 1.2Ni 0.3Mn 0.7O 2.2，并且非水电解液中未加入含氟磷酸盐LiPO 2F 2。
表1
Figure PCTCN2022081725-appb-000001
Figure PCTCN2022081725-appb-000002
测试部分
(1)正极活性材料初始放电克容量测试
在25℃下，将二次电池以0.3C恒流充电至上限截止电压，然后以该截止电压恒压充电至电流为0.05C；静置5min之后，将二次电池以0.33C恒流放电至下限截止电压，此时得到的放电容量即为二次电池的初始放电容量。
正极活性材料的初始克容量(mAh/g)＝二次电池的初始放电容量/正极活性材料的总质量。
(2)二次电池高温循环性能测试
在45℃下，将二次电池以0.3C恒流充电至上限截止电压，然后以该截止电压恒压充电至电流为0.05C；静置5min之后，将二次电池以0.33C恒流放电至下限截止电压，此为一个充放电循环过程，此次的放电容量为二次电池的初始放电容量。将二次电池按上述方法循环充放电，直至循环后的放电容量衰减为初始放电容量的80％，结束测试，记录此时二次电池的循环圈数。二次电池的循环圈数越高，表明二次电池的高温循环预期寿命越长。
(3)二次电池高温存储性能测试
在25℃下，将二次电池以0.3C恒流充电至上限截止电压，然后以该截止电压恒压充电至电流为0.05C，此时二次电池处于满充状态。将满充状态的二次电池置于45℃环境中存储，每隔5天取出一次，并以0.33C恒流放电至下限截止电压，得到存储一段时间后的放电容量；之后将二次电池按照上述方式满充后再次置于45℃环境中存储，直至二次电池存储后的放电容量衰减为初始放电容量的80％，结束测试，记录二次电池总的存储天数。二次电池的存储天数越多，表明二次电池的高温存储预期寿命越长。
在上述各性能测试中，实施例1-30和对比例1-2的上限截止电压为4.9V，下限截止电压为3.5V；实施例31和对比例3的上限截止电压为4.5V，下限截止电压为2.8V。
表2示出实施例1-31和对比例1-3的性能测试结果。 表2
序号 初始克容量(mAh/g) 高温循环圈数 高温存储天数
实施例1 132 516 158
实施例2 131 534 163
实施例3 130 396 124
实施例4 128 413 135
实施例5 132 459 146
实施例6 127 563 174
实施例7 125 617 202
实施例8 123 652 220
实施例9 112 733 247
实施例10 107 769 289
实施例11 98 758 283
实施例12 133 307 98
实施例13 132 367 129
实施例14 132 396 144
实施例15 131 431 152
实施例16 130 523 172
实施例17 126 539 189
实施例18 121 541 196
实施例19 113 529 181
实施例20 131 315 94
实施例21 113 672 235
实施例22 128 224 79
实施例23 133 631 194
实施例24 130 679 221
实施例25 127 498 144
实施例26 129 542 188
实施例27 128 793 304
实施例28 133 733 260
实施例29 135 439 124
实施例30 134 688 238
实施例31 217 544 178
对比例1 133 189 61
对比例2 132 220 79
对比例3 214 159 98
从实施例1-30和对比例1-2、实施例31和对比例3的测试结果可以看出，当二次电池同时满足正极活性材料具有包含正磷酸盐的修饰层并且非水电解液含有含氟磷酸盐时，其高电压下的循环寿命和存储寿命明显增加，同时其还可以兼顾高能量密度。可能的原因在于，当二次电池同时满足正极活性材料具有包含正磷酸盐的修饰层并且非水电解液含有含氟磷酸盐时，正极活性材料中过渡金属的溶出量减少、负极活性材料表面SEI膜的破坏减少、活性离子的不可逆消耗降低，从而可以更好地发挥正极活性材料克容量高、电压平台高的优势。
从实施例1-12的测试结果可以看出，正磷酸盐的质量百分含量在合适的范围内时，可以在不影响二次电池能量密度的前提下，更好、更全面地保护中心核材料，从而进一步提高二次电池高电压下的循环寿命和存储寿命。
从实施例13-20的测试结果可以看出，含氟磷酸盐的质量百分含量在合适的范围内时，能明显减少正磷酸盐的溶解，从而可以在不影响二次电池能量密度的前提下，更好地保护中心核材料，进一步提高二次电池高电压下的循环寿命和存储寿命。
从实施例1-22的测试结果还可以看出，当正磷酸盐和含氟磷酸盐的含量进一步满足C×D在0.1至15之间时，能进一步减少正磷酸盐的溶解，从而更好、更全面地保护中心核材料，进而二次电池能在具有高能量密度的前提下，具有进一步提高的循环寿命和存储寿命。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (15)

  1. 一种二次电池，包括含有正极活性材料的正极极片以及非水电解液，其中，
    所述正极活性材料包括中心核材料以及位于所述中心核材料表面的修饰层，所述修饰层包括分子式为A a+ x[PO 4] 3- y的正磷酸盐，A表示Li、Na、K、Rb、Cs、Mg、Ca、Ba、Ni、Fe、Co、Ti、Al、Cr、V、Nb、W中的一种或多种，1≤a≤6，并且ax＝3y；
    所述非水电解液包括分子式为B b+ m[PO 1+cF 3-c] c- n的含氟磷酸盐，B表示Li、Na、K、Rb、Cs、Mg、Ca、Ba中的一种或多种，1≤b≤2，c表示1或2，并且bm＝cn。
  2. 根据权利要求1所述的二次电池，其中，基于所述正极活性材料的总质量，所述正磷酸盐的质量百分含量为C％，基于所述非水电解液的总质量，所述含氟磷酸盐的质量百分含量为D％，并且所述二次电池满足如下条件(1)至(3)中的至少一者：
    (1)C为0.2-20，可选地为1-6；
    (2)D为0.1-3，可选地为0.5-2；
    (3)C×D为0.1-15，可选地为1-5。
  3. 根据权利要求1或2所述的二次电池，所述修饰层中P元素的质量与所述正极活性材料总质量的比值为E％，E为0.05-6，可选地为0.2-3。
  4. 根据权利要求1-3中任一项所述的二次电池，其中，所述正极活性材料的电压平台≥3.8Vvs Li +/Li，可选地，所述电压平台≥4.0Vvs Li +/Li。
  5. 根据权利要求1-4中任一项所述的二次电池，其中，所述中心核材料包括Mn元素，可选地，基于所述中心核材料的总质量，所述Mn元素的质量百分含量为F％，F≥25。
  6. 根据权利要求1-5中任一项所述的二次电池，其中，所述中心核材料包括尖晶石型锰酸锂LiM pMn 2-pO 4、磷酸锰锂LiN qMn 1-qPO 4、层状富锰材料Li 1+tMn 1-wL wO 2+t中的一种或多种，0≤p≤1，0≤q≤0.5，0≤t≤1，0≤w≤0.5，M、N、L各自独立地表示Ni、Co、Fe、Cr、V、Ti、Zr、La、Ce、Rb、P、W、Nb、Mo、Sb、B、Al、Si中的一种或多种，
    可选地，所述中心核材料包括尖晶石型锰酸锂LiM pMn 2-pO 4、层状富锰材料Li 1+tMn 1- wL wO 2+t中的一种或多种。
  7. 根据权利要求1-6中任一项所述的二次电池，其中，所述中心核材料具有单晶或类单晶形貌。
  8. 根据权利要求1-7中任一项所述的二次电池，其中，
    A表示Li、Na、K、Mg、Ni、Co、Ti、Al、Nb、W中的一种或多种，可选地表示Na、K、Ni、Co、Al、Nb、W中的一种或多种；和/或，
    B表示Li、Na、K、Mg中的一种或多种，可选地表示Na、K、或其组合。
  9. 根据权利要求1-8中任一项所述的二次电池，其中，c表示2。
  10. 根据权利要求1-9中任一项所述的二次电池，其中，
    所述正磷酸盐包括Li 3PO 4、Na 3PO 4、K 3PO 4、Mg 3(PO 4) 2、AlPO 4、Nb 3(PO 4) 5、LiNiPO 4、TiLi 2(PO 4) 2、LiNi 0.8Co 0.2PO 4中的一种或多种，可选地包括Na 3PO 4、K 3PO 4、AlPO 4、Nb 3(PO 4) 5、LiNiPO 4、LiNi 0.8Co 0.2PO 4中的一种或多种；和/或，
    所述含氟磷酸盐包括LiPO 2F 2、NaPO 2F 2、KPO 2F 2、Li 2PO 3F、Na 2PO 3F、K 2PO 3F中的一种或多种，可选地包括Li 2PO 3F、Na 2PO 3F、K 2PO 3F中的一种或多种。
  11. 根据权利要求1-10中任一项所述的二次电池，其中，所述修饰层位于所述中心核材料50％-100％的表面，可选地为85％-100％的表面。
  12. 根据权利要求1-11中任一项所述的二次电池，其中，
    所述正极活性材料的比表面积在1.5m 2/g以下，可选地为0.1m 2/g-1m 2/g；和/或，
    所述正极活性材料的体积粒径Dv50为1μm-20μm，可选地为3μm-15μm。
  13. 一种电池模块，包括根据权利要求1-12中任一项所述的二次电池。
  14. 一种电池包，包括根据权利要求1-12中任一项所述的二次电池、根据权利要求13所述的电池模块中的一种。
  15. 一种用电装置，包括根据权利要求1-12中任一项所述的二次电池、根据权利要求13所述的电池模块、根据权利要求14所述的电池包中的至少一种。
PCT/CN2022/081725 2022-03-18 2022-03-18 二次电池以及包含其的电池模块、电池包及用电装置 WO2023173413A1 (zh)

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JP2014022294A (ja) * 2012-07-20 2014-02-03 Sumitomo Metal Mining Co Ltd 非水電解質二次電池用正極活物質およびその製造方法
JP2014192069A (ja) * 2013-03-28 2014-10-06 Sanyo Electric Co Ltd リチウムイオン電池
CN107251303A (zh) * 2015-02-27 2017-10-13 三洋电机株式会社 非水电解质二次电池
CN107408722A (zh) * 2015-04-22 2017-11-28 松下知识产权经营株式会社 非水电解质二次电池
CN113519078A (zh) * 2019-03-12 2021-10-19 本田技研工业株式会社 锂离子电池用正极及锂离子电池

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JP2014022294A (ja) * 2012-07-20 2014-02-03 Sumitomo Metal Mining Co Ltd 非水電解質二次電池用正極活物質およびその製造方法
JP2014192069A (ja) * 2013-03-28 2014-10-06 Sanyo Electric Co Ltd リチウムイオン電池
CN107251303A (zh) * 2015-02-27 2017-10-13 三洋电机株式会社 非水电解质二次电池
CN107408722A (zh) * 2015-04-22 2017-11-28 松下知识产权经营株式会社 非水电解质二次电池
CN113519078A (zh) * 2019-03-12 2021-10-19 本田技研工业株式会社 锂离子电池用正极及锂离子电池

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