WO2025035609A1 - 正极活性材料及其制备方法、正极极片、电池和用电装置 - Google Patents

正极活性材料及其制备方法、正极极片、电池和用电装置 Download PDF

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Publication number
WO2025035609A1
WO2025035609A1 PCT/CN2023/128568 CN2023128568W WO2025035609A1 WO 2025035609 A1 WO2025035609 A1 WO 2025035609A1 CN 2023128568 W CN2023128568 W CN 2023128568W WO 2025035609 A1 WO2025035609 A1 WO 2025035609A1
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Prior art keywords
positive electrode
electrode active
active material
coating layer
battery
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PCT/CN2023/128568
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English (en)
French (fr)
Inventor
许跃
杨惠玲
秦猛
官英杰
温严
黄起森
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to EP23949028.7A priority Critical patent/EP4723239A1/en
Publication of WO2025035609A1 publication Critical patent/WO2025035609A1/zh
Priority to US19/305,021 priority patent/US20250372649A1/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • 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
    • 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
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
    • C01P2002/85—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by XPS, EDX or EDAX data
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/60—Particles characterised by their size
    • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/11—Powder tap density
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/12—Surface area
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/40—Electric properties
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the field of batteries, and specifically relates to a positive electrode active material and a preparation method thereof, a positive electrode sheet, a battery and an electrical device.
  • Lithium-ion batteries are facing great challenges due to the increasing shortage of lithium resources, the rising prices of upstream materials, the lagging development of recycling technology, and the low recycling rate of old batteries.
  • Sodium-ion batteries can use the sodium ion deintercalation process between the positive and negative electrodes to achieve charging and discharging.
  • the reserves of sodium resources are far more abundant than lithium, the distribution is more extensive, and the cost is far lower than lithium. Therefore, sodium-ion batteries have become a new generation of electrochemical systems with great potential to replace lithium secondary batteries.
  • sodium-ion batteries have the problem of low cycle performance.
  • the present application provides a positive electrode active material, aiming to improve the cycle performance of a battery containing the positive electrode active material.
  • the present application provides a positive electrode active material in one aspect, wherein the positive electrode active material comprises:
  • a core comprising Na x R y (PO 4 ) z (P 2 O 7 ) k , wherein 1 ⁇ x ⁇ 7, 1 ⁇ y ⁇ 4, 1 ⁇ z ⁇ 4, 1 ⁇ k ⁇ 4, and R comprises at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, or Pb;
  • a first coating layer is formed on at least a portion of the core, the first coating layer comprises MaOb , M comprises at least one of Ca , Bi, Ba, Ti, Al, Nb, Mg, Fe, Cu, Zn, Mn, Ni or Co, 1 ⁇ a ⁇ 7, 1 ⁇ b ⁇ 12.
  • the present application includes at least the following beneficial effects: the present application forms a first coating layer including MaOb on at least a portion of a core including NaxRy ( PO4 ) z ( P2O7 ) k , wherein M includes at least one of Ca , Bi , Ba, Ti, Al, Mg, Fe, Cu, Zn, Mn, Ni or Co.
  • the first coating layer of this composition can reduce the contact between the core and H2O , CO2 and the like in the air, thereby improving the environmental stability and moisture resistance of the material, and further improving the cycle performance of the battery.
  • the first coating layer can reduce the side reaction between the core surface and the electrolyte, stabilize the interface between the positive electrode active material and the electrolyte, improve the stability of the material, and further improve the cycle performance of the battery containing it.
  • the first coating layer of this composition will not reduce The first-cycle coulombic efficiency of the positive electrode active material is improved, so that the battery maintains a high first-cycle coulombic efficiency.
  • the inner core includes at least one of Na 4 R 3 (PO 4 ) 2 P 2 O 7 or Na 7 V 4 (PO 4 ) 4 P 2 O 7 , wherein R includes at least one of Fe, Ni, Co or Mn.
  • MaOb includes at least one of TiO2 , Al2O3 , Nb2O5 , MgO, Co3O4 , CaTiO3 , Bi4Ti3O12 or BaTiO3 .
  • the cycle performance of the battery containing the MaOb can be improved and the battery can maintain a high first cycle coulombic efficiency.
  • the content of the first coating layer is w%
  • the residual alkali content of the core is z%, 0.06 ⁇ z/w ⁇ 3, and can be optionally 0.06 ⁇ z/w ⁇ 1.
  • the cycle performance of the battery containing the core can be improved and the battery can maintain a high first-cycle coulombic efficiency.
  • 1% ⁇ w% ⁇ 3%, and optionally 1.5% ⁇ w% ⁇ 2.5% are examples of the cycle performance of the battery containing the same.
  • the thickness of the first coating layer is 1 nm-10 nm, and can be 2 nm-8 nm, thereby improving the cycle performance of the battery containing the first coating layer and maintaining a high first cycle coulombic efficiency of the battery.
  • the positive electrode active material further includes a second coating layer, the second coating layer is formed on at least a portion of the core, the first coating layer is formed on at least a portion of the second coating layer, and the second coating layer includes carbon.
  • the environmental stability, moisture resistance and conductivity of the positive electrode active material can be improved, thereby improving the kinetic performance and cycle performance of the battery containing the positive electrode active material.
  • the carbon content in the second coating layer is n%, 0.16 ⁇ n/w ⁇ 1.5, and optionally 0.32 ⁇ n/w ⁇ 0.8.
  • the environmental stability, moisture resistance and conductivity of the positive electrode active material can be improved, thereby improving the kinetic performance and cycle performance of the battery containing the same.
  • the environmental stability, moisture resistance and conductivity of the positive electrode active material can be improved, thereby improving the kinetic performance and cycle performance of the battery containing the positive electrode active material.
  • the positive electrode active material satisfies at least one of the following conditions:
  • the volume average particle size Dv50 of the positive electrode active material is 2 ⁇ m-8 ⁇ m, and can be 2 ⁇ m-5 ⁇ m;
  • the Dv99 of the positive electrode active material is 10 ⁇ m-40 ⁇ m, and can be optionally 15 ⁇ m-30 ⁇ m;
  • the BET specific surface area of the positive electrode active material is 3m 2 /g-11m 2 /g, and can be 7m 2 /g-10m 2 /g;
  • the compaction density of the positive electrode active material at a pressure of 100 MPa is 1.3 g/cm 3 -2.1 g/cm 3 , and can be 1.7 g/cm 3 -1.9 g/cm 3 .
  • the second aspect of the present application provides a method for preparing a positive electrode active material, comprising:
  • the core material comprising NaxRy ( PO4 ) z ( P2O7 ) k , wherein 1 ⁇ x ⁇ 7, 1 ⁇ y ⁇ 4, 1 ⁇ z ⁇ 2, 1 ⁇ k ⁇ 4, and R comprises at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W, or Pb;
  • the core material is mixed with MaOb and sintered, where M includes at least one of Ti, Al, Mg, Fe, Cu, Zn, Mn, Ni or Co, 1 ⁇ a ⁇ 7, 1 ⁇ b ⁇ 12, to obtain a positive electrode active material.
  • a first coating layer comprising MaOb (M comprises at least one of Ti, Al, Mg, Fe, Cu, Zn, Mn , Ni or Co, 1 ⁇ a ⁇ 7 , 1 ⁇ b ⁇ 12) can be formed on a core comprising NaxRy( PO4 )z( P2O7 ) k .
  • the first coating layer of this composition can reduce the contact of the core with H2O , CO2, etc. in the air, thereby improving the environmental stability and moisture resistance of the material, and further improving the cycle performance of the battery containing the same.
  • the first coating layer of this composition will not deteriorate the first-cycle coulomb efficiency of the positive electrode active material, thereby allowing the battery to maintain a higher first-cycle coulomb efficiency.
  • the sintering temperature is 250° C.-550° C.
  • the holding time is 2 h-8 h.
  • the core material before the core material is mixed and sintered with MaOb , the core material is mixed and sintered with a carbon source in advance.
  • a second carbon-containing coating layer can be formed on the surface of the core material, thereby improving the environmental stability, moisture resistance and conductivity of the positive electrode active material, thereby improving the cycle performance and kinetic performance of the battery containing the same.
  • the third aspect of the present application provides a positive electrode plate, which includes the positive electrode active material described in the first aspect of the present application or the positive electrode active material obtained by the method described in the second aspect of the present application.
  • the fourth aspect of the present application provides a battery, which includes the positive electrode plate described in the third aspect of the present application.
  • the battery comprises a sodium ion battery.
  • the fifth aspect of the present application provides an electrical device, which includes the battery described in the fourth aspect of the present application.
  • FIG. 1 is a schematic diagram of a positive electrode active material according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a positive electrode active material according to another embodiment of the present application.
  • FIG. 3 is a schematic diagram of a battery according to an embodiment of the present application.
  • FIG. 4 is an exploded view of the battery shown in FIG. 3 according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 7 is an exploded view of the battery pack shown in FIG. 6 according to an embodiment of the present application.
  • FIG. 8 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.
  • FIG. 9 is an XRD comparison diagram of the positive electrode active materials of Example 1 and Comparative Example 1 of the present application.
  • FIG. 10 is a distribution diagram of the Ti element in the EDS spectrum of the positive electrode active material of Example 1 of the present application.
  • “Scope” disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope limited in this way can be including end values or not including end values, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • 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.
  • the method may also include step (c), which means that step (c) can be added to the method in any order.
  • the method can include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.
  • Polyanion phosphate cathode materials have become one of the most popular cathode active materials for sodium ion batteries due to their abundant resources, environmental friendliness, ease of large-scale production, open sodium ion diffusion channels, and good thermal stability.
  • polyanion phosphate cathode materials have residual alkali on their surface (residual alkali includes sodium bicarbonate and sodium carbonate, etc.), which easily reacts with H2O , CO2 , etc. in the air, resulting in poor environmental stability and moisture resistance of the materials, thereby reducing battery cycle performance.
  • the present application forms a first coating layer including MaOb on at least part of the inner core including NaxRy ( PO4 ) z ( P2O7 ) k , wherein M includes at least one of Ca, Bi, Ba, Ti, Al , Nb, Mg, Fe, Cu, Zn, Mn, Ni or Co.
  • the first coating layer of this composition can reduce the contact between the inner core and H2O , CO2 and the like in the air, thereby improving the environmental stability and moisture resistance of the material, and further improving the cycle performance of the battery.
  • the first coating layer can reduce the side reaction between the inner core surface and the electrolyte, stabilize the interface between the positive electrode active material and the electrolyte, improve the stability of the material, and further improve the cycle performance of the battery containing it.
  • the first coating layer of this composition will not reduce the first-cycle coulomb efficiency of the positive electrode active material, thereby allowing the battery to maintain a relatively high first-cycle coulomb efficiency.
  • the positive electrode active material disclosed in the embodiment of the present application is suitable for sodium ion batteries, and the battery disclosed in the embodiment of the present application can be used in various energy storage systems that use batteries as power sources or use batteries as energy storage elements.
  • Electrical equipment may include, but is not limited to, mobile phones, tablets, laptops, electric toys, electric tools, battery cars, electric cars, ships, spacecraft, etc.
  • electric toys may include fixed or mobile electric toys, for example, game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.
  • spacecraft may include airplanes, rockets, space shuttles, and spacecraft, etc.
  • the present application proposes a positive electrode active material.
  • the positive electrode active material 20 includes a core 21 and a first coating layer 22, wherein the core includes NaxRy ( PO4 ) z ( P2O7 ) k , wherein 1 ⁇ x ⁇ 7 , 1 ⁇ y ⁇ 4, 1 ⁇ z ⁇ 4 , 1 ⁇ k ⁇ 4, R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W or Pb, and the first coating layer 22 is formed on at least a portion of the core 21, and the first coating layer 22 includes MaOb , M includes at least one of Ca, Bi, Ba, Ti, Al, Nb, Mg, Fe, Cu, Zn, Mn, Ni or Co , 1 ⁇ a ⁇ 7, 1 ⁇ b ⁇ 12.
  • the present invention forms a first coating layer 22 including MaOb on at least a portion of a core 21 including NaxRy ( PO4 ) z ( P2O7 ) k , wherein M includes at least one of Ca , Bi, Ba, Ti, Al, Nb, Mg, Fe, Cu, Zn, Mn, Ni or Co, and the first coating layer 22 of the composition can reduce the contact between the core 21 and the air.
  • the first coating layer 22 can reduce the side reaction between the surface of the core 21 and the electrolyte , stabilize the interface between the positive electrode active material 20 and the electrolyte, improve the stability of the material, and thus improve the cycle performance of the battery containing it.
  • the first coating layer 22 of this composition will not reduce the first cycle coulomb efficiency of the positive electrode active material 20, so that the battery maintains a high first cycle coulomb efficiency.
  • the core 21 includes this content of sodium ions, which can increase the gram capacity of the battery, so that the battery has a higher capacity.
  • R in the NaxRy ( PO4 ) z ( P2O7 ) k includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W or Pb, and 1 ⁇ y ⁇ 4, for example, 2 ⁇ x ⁇ 4, 3 ⁇ x ⁇ 4, etc. Therefore, the positive electrode active material composed of the present application has the advantages of high chemical stability, thermal stability, electrochemical stability and specific capacity.
  • the Na x R y (PO 4 ) z (P 2 O 7 ) k may include Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 , Na 4 Ni 3 (PO 4 ) 2 P 2 O 7 , Na 4 Co 3 (PO 4 ) 2 P 2 O 7 , Na 4 Mn 3 (PO 4 ) 2 P 2 O 7 , Na 7 V 4 (PO 4 ) 4 P 2 O 7 , Na 4.02 Fe 2.85 (PO 4 ) 2 P 2 O 7 , Na 4 Fe 2.9 Mg 0.1 (PO 4 ) 2 P 2 O 7 , Na 4 Fe 2.95 Al 0.05 (PO 4 ) 2 P 2 O 7 or Na 4 Fe 2.99 Cu 0.01 (PO 4 ) 2 P 2 O 7 .
  • the core 21 includes at least one of Na 4 R 3 (PO 4 ) 2 P 2 O 7 or Na 7 V 4 (PO 4 ) 4 P 2 O 7 , wherein R includes at least one of Fe, Ni, Co or Mn, such as Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 , Na 4 Ni 3 (PO 4 ) 2 P 2 O 7 , Na 4 Co 3 (PO 4 ) 2 P 2 O 7 , and Na 4 Mn 3 (PO 4 ) 2 P 2 O 7.
  • R includes at least one of Fe, Ni, Co or Mn, such as Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 , Na 4 Ni 3 (PO 4 ) 2 P 2 O 7 , Na 4 Co 3 (PO 4 ) 2 P 2 O 7 , and Na 4 Mn 3 (PO 4 ) 2 P 2 O 7.
  • the battery will be accompanied by Na deintercalation and consumption during the charge and discharge process, and the molar content of Na is different when the battery is discharged to different states.
  • the molar content of Na is the initial state of the material, that is, the state before feeding.
  • the positive electrode active material is used in the battery system, and after the charge and discharge cycle, the molar content of Na will change.
  • the molar content of O is only a theoretical value.
  • the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.
  • the first coating layer 22 is formed on at least a portion of the core 21, and the first coating layer 22 includes MaOb , M includes at least one of Ca, Bi, Ba, Ti, Al, Nb, Mg, Fe, Cu, Zn, Mn, Ni or Co, 1 ⁇ a ⁇ 7 , 1 ⁇ b ⁇ 12, for example, a is 2 ⁇ a ⁇ 6, 3 ⁇ a ⁇ 5, 3 ⁇ a ⁇ 4, etc. Therefore, the present application forms the first coating layer 22 including the above composition on at least a portion of the core 21 including NaxRy ( PO4 ) z ( P2O7 ) k.
  • the first coating layer 22 of Ma O b can reduce the contact between the core 21 and H 2 O, CO 2 , etc.
  • the first coating layer 22 can reduce the side reaction between the surface of the core 21 and the electrolyte, stabilize the interface between the positive electrode active material 20 and the electrolyte, improve the stability of the material, and further improve the cycle performance of the battery containing it.
  • the first coating layer 22 of the composition will not reduce the first cycle coulomb efficiency of the positive electrode active material 20, so that the battery maintains a high first cycle coulomb efficiency.
  • MaOb may include at least one of CaO, Bi2O3, BaO, TiO2, Al2O3, Nb2O5 , MgO , FeO , CuO , ZnO, MnO2 , NiO, or Co3O4 .
  • the MaOb may include at least one of TiO2, Al2O3, Nb2O5 , MgO , Co3O4 , CaTiO3 , Bi4Ti3O12 or BaTiO3 .
  • the present application forms the first coating layer 22 of the above composition on the core 21.
  • the first coating layer 22 of the composition can reduce the contact between the core 21 and H2O , CO2 and the like in the air, thereby improving the environmental stability and moisture resistance of the material, and further improving the cycle performance of the battery.
  • the first coating layer 22 can reduce the side reaction between the surface of the core 21 and the electrolyte, stabilize the interface between the positive electrode active material 20 and the electrolyte, improve the stability of the material, and further improve the cycle performance of the battery containing it.
  • the first coating layer 22 of the composition will not reduce the first cycle coulomb efficiency of the positive electrode active material 20, so that the battery maintains a high first cycle coulomb efficiency.
  • the content of the first coating layer 22 is w%; based on the total mass of the inner core 21, the residual alkali content of the inner core 21 is z%, 0.06 ⁇ z/w ⁇ 3, for example, 0.08 ⁇ z/w ⁇ 3, 0.1 ⁇ z/w ⁇ 3, 0.2 ⁇ z/w ⁇ 2.8, 0.5 ⁇ z/w ⁇ 2.5, 0.7 ⁇ z/w ⁇ 2.2, 1 ⁇ z/w ⁇ 2, 1.2 ⁇ z/w ⁇ 1.8, 1.5 ⁇ z/w ⁇ 1.7, etc.
  • residual alkali residual alkali includes sodium bicarbonate and sodium carbonate, etc.
  • the residual alkali on the surface is easy to react with H2O , CO2 and the like in the air, resulting in poor environmental stability and moisture resistance of the material.
  • the content w% of the first coating layer 22 and the residual alkali amount z% of the core 21 are controlled to meet the above ratio, which can significantly improve the environmental stability and moisture resistance of the material, thereby improving the cycle performance of the battery.
  • the content w% of the first coating layer 22 and the residual alkali amount z% of the core 21 meet 0.06 ⁇ z/w ⁇ 1.
  • the test of the residual alkali content z% of the inner core 21 can be measured by instruments and methods known in the art.
  • the free sodium in the inner core of the positive electrode active material of the sodium ion battery can be tested with reference to GB/T9725-2007 "General Rules for Potentiometric Titration of Chemical Reagents" for the test of free lithium, and the test results are converted according to the ratio of the molecular weights of residual sodium and residual lithium.
  • the molecular weight of NaHCO 3 is 84
  • the molecular weight of LiHCO 3 is 68.
  • the free lithium content obtained by the test result is 0.1%.
  • the free sodium content of the positive electrode material is converted to 0.124%.
  • the method for testing the free lithium content of the positive electrode material in GB/T9725-2007 "General Rules for Potentiometric Titration of Chemical Reagents" is: take samples and prepare the test solution according to the provisions of the product standard. Insert the specified electrode, start the electromagnetic stirrer, and titrate with the specified standard titration solution. Drip about 90% of the required titration volume from the burette. Add a standard titration solution to measure the potential or pH value of the solution. After that, measure the potential or pH value once for each 1mL or appropriate amount of standard titration solution added.
  • the content w% of the first coating layer 22 satisfies 1% ⁇ w% ⁇ 3%, for example, 1.2% ⁇ w% ⁇ 2.8%, 1.5% ⁇ w% ⁇ 2.5%, 1.7% ⁇ w% ⁇ 2.2%, 1.8% ⁇ w% ⁇ 2%, etc. Therefore, the content w% of the first coating layer 22 of the present application satisfies the above conditions, which can improve the environmental stability and moisture resistance of the material, thereby improving the cycle performance of the battery.
  • the first coating layer 22 of this content can reduce the side reaction between the surface of the core 21 and the electrolyte, stabilize the interface between the positive electrode active material 20 and the electrolyte, improve the stability of the material, and thereby improve the cycle performance of the battery containing it.
  • the first coating layer 22 of this content will not reduce the first cycle coulomb efficiency of the positive electrode active material 20, so that the battery maintains a high first cycle coulomb efficiency.
  • the content w% of the first coating layer 22 satisfies 1.5% ⁇ w% ⁇ 2.5%.
  • the residual alkali content z% of the core 21 satisfies 0.2% ⁇ z% ⁇ 3%, for example, 0.5% ⁇ z% ⁇ 2.8%, 0.8% ⁇ z% ⁇ 2.5%, 1% ⁇ z% ⁇ 2.2%, 1.2% ⁇ z% ⁇ 2%, 1.5% ⁇ z% ⁇ 1.8%, etc.
  • the residual alkali content z% of the core 21 of the present application satisfies the above conditions, which can reduce the decomposition and gas production of residual alkali during the battery cycle, reduce battery flatulence, and thus improve the battery cycle performance.
  • the residual alkali content z% of the core 21 satisfies 0.2% ⁇ z% ⁇ 0.6%.
  • the thickness of the first coating layer 22 can be 1nm-10nm, such as 2nm-9nm, 3nm-8nm, 4nm-7nm, 5nm-6nm, etc. Therefore, the thickness of the first coating layer 22 of the present application meets the above conditions, which can improve the environmental stability and moisture resistance of the material, thereby improving the cycle performance of the battery. At the same time, the first coating layer 22 of this thickness can reduce the side reaction between the surface of the core 21 and the electrolyte, stabilize the interface between the positive electrode active material 20 and the electrolyte, improve the stability of the material, and thereby improve the cycle performance of the battery containing it.
  • the first coating layer 22 of this thickness will not reduce the first cycle coulomb efficiency of the positive electrode active material, so that the battery maintains a higher first cycle coulomb efficiency.
  • the thickness of the first coating layer 22 is 2nm-8nm.
  • the positive electrode active material 20 further includes a second coating layer 23, the second coating layer 23 is formed on at least a portion of the core 21, the first coating layer 22 is formed on at least a portion of the second coating layer 23, and the second coating layer 23 includes carbon.
  • the second coating layer 23 can not only improve the environmental stability and moisture resistance of the core 21, but also improve the conductivity of the core 21, thereby improving the kinetic performance and cycle performance of the battery containing the same.
  • the second coating layer 23 The carbon content in the medium is n%, 0.16 ⁇ n/w ⁇ 1.5, for example, 0.18 ⁇ n/w ⁇ 1.5, 0.2 ⁇ n/w ⁇ 1.5, 0.25 ⁇ n/w ⁇ 1.5, 0.3 ⁇ n/w ⁇ 1.5, 0.35 ⁇ n/w ⁇ 1.45, 0.4 ⁇ n/w ⁇ 1.4, 0.45 ⁇ n/w ⁇ 1.35, 0.5 ⁇ n/w ⁇ 1.3, 0.55 ⁇ n/w ⁇ 1.25, 0.6 ⁇ n/w ⁇ 1.2, 0.65 ⁇ n/w ⁇ 1.1, 0.7 ⁇ n/w ⁇ 1, 0.8 ⁇ n/w ⁇ 0.9, 0.85 ⁇ n/w ⁇ 0.9, etc.
  • the carbon content n% in the second coating layer 23 of the present application and the content w% of the first coating layer 22 are controlled within the above range, which can significantly improve the environmental stability, moisture resistance and conductivity of the positive electrode active material 20, thereby improving the kinetic performance and cycle performance of the battery containing the positive electrode active material 20.
  • the carbon content n% in the second coating layer 23 satisfies 0.32 ⁇ n/w ⁇ 0.8.
  • the carbon content in the second coating layer 23 is n%, 0.5% ⁇ n% ⁇ 1.5%, for example, 0.6% ⁇ n% ⁇ 1.4%, 0.7% ⁇ n% ⁇ 1.3%, 0.8% ⁇ n% ⁇ 1.3%, 0.9% ⁇ n% ⁇ 1.2%, 1% ⁇ n% ⁇ 1.1%, etc. Therefore, the carbon content n% in the second coating layer 23 of the present application is controlled within the above range, which can significantly improve the environmental stability, moisture resistance and conductivity of the positive electrode active material 20, thereby improving the kinetic performance and cycle performance of the battery containing it. In other embodiments of the present application, based on the total mass of the positive electrode active material 20, the carbon content n% in the second coating layer 23 satisfies 0.8% ⁇ n% ⁇ 1.2%.
  • the volume average particle size Dv50 of the positive electrode active material 20 is 2 ⁇ m-8 ⁇ m, for example, the Dv50 of the positive electrode active material can be 2.5 ⁇ m-7.5 ⁇ m, 3 ⁇ m-7 ⁇ m, 3.5 ⁇ m-6.5 ⁇ m, 4 ⁇ m-6 ⁇ m, 4.5 ⁇ m-5.5 ⁇ m, 4.8 ⁇ m-5 ⁇ m, etc. In other embodiments of the present application, the volume average particle size Dv50 of the positive electrode active material 20 is 2 ⁇ m-5 ⁇ m.
  • the Dv99 of the positive electrode active material 20 is 10 ⁇ m-40 ⁇ m, for example, the Dv99 of the positive electrode active material can be 12 ⁇ m-37 ⁇ m, 15 ⁇ m-35 ⁇ m, 18 ⁇ m-32 ⁇ m, 20 ⁇ m-30 ⁇ m, 22 ⁇ m-28 ⁇ m, 23 ⁇ m-25 ⁇ m, etc. In other embodiments of the present application, the Dv99 of the positive electrode active material 20 is 15 ⁇ m-30 ⁇ m.
  • the volume average particle size Dv50 refers to the particle size corresponding to the cumulative volume distribution percentage of 50%
  • Dv99 refers to the particle size corresponding to the cumulative volume distribution percentage of 99%.
  • the test method of the volume average particle size Dv50 and Dv99 can refer to the standard GB/T 19077-2016 and be measured using a laser particle size analyzer (such as Malvern Master Size3000).
  • the BET specific surface area of the positive electrode active material 20 is 3m 2 /g-11m 2 /g, for example, the BET specific surface area of the positive electrode active material 20 may be 4m 2 /g-10m 2 /g, 5m 2 /g-9m 2 /g, 6m 2 /g-8m 2 /g, 7m 2 /g-7.5m 2 /g, etc. In other embodiments of the present application, the BET specific surface area of the positive electrode active material 20 is 7m 2 /g-10m 2 /g.
  • the BET specific surface area of the positive electrode active material 20 has a well-known meaning in the art and can be measured using instruments and methods well-known in the art. For example, it can be tested by referring to the following method: using the American Micromeritics multi-station fully automatic specific surface area and pore analyzer GeminiVII2390, take about 7g of the sample and put it into a 9cc long tube with a bulb, degas at 200°C for 2h, and then put it into the main machine for testing to obtain the BET specific surface area data of the positive electrode active material 20.
  • the compaction density of the positive electrode active material 20 under a pressure of 100 MPa is 1.3 g/cm 3 -2.1 g/cm 3 , for example, the compaction density of the positive electrode active material 20 under a pressure of 100 MPa may be 1.4 g/cm 3 -2 g/cm 3 , 1.5 g/cm 3 -1.9 g/cm 3 , 1.6 g/cm 3 -1.8 g/cm 3 , 1.7 g/cm 3 -1.8 g/cm 3 , etc. In some embodiments of the present application, the compaction density of the positive electrode active material 20 under a pressure of 100 MPa is 1.7 g/cm 3 -1.9 g/cm 3 .
  • compacted density has a well-known meaning in the art and can be measured by instruments and methods well-known in the art.
  • the following test method can be used: a certain amount of powder m is placed in a special compaction mold, the mold is placed on a compaction density instrument, a pressure of 100 MPa is set, and the thickness and volume v of the powder under a pressure of 300 MPa is measured on the equipment.
  • the conduction distance within the positive electrode active material 20 is small and the surface side reactions are small, which promotes the positive electrode active material 20 to exert its gram capacity and improves the capacity retention rate of the battery containing it.
  • the second aspect of the present application provides a method for preparing the positive electrode active material according to the first aspect, comprising:
  • the core material includes NaxRy ( PO4 ) z ( P2O7 ) k , wherein 1 ⁇ x ⁇ 7, 1 ⁇ y ⁇ 4 , 1 ⁇ z ⁇ 2 , 1 ⁇ k ⁇ 4, and R includes at least one of Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Sn, Hf, Ta, W or Pb.
  • the core material of step S100 is mixed with Ma O b and sintered, and a first coating layer including Ma O b is coated on the surface of the core material, where M includes at least one of Ti, Al, Mg, Fe, Cu, Zn, Mn, Ni or Co, 1 ⁇ a ⁇ 7, 1 ⁇ b ⁇ 12, to obtain a positive electrode active material.
  • M includes at least one of Ti, Al, Mg, Fe, Cu, Zn, Mn, Ni or Co, 1 ⁇ a ⁇ 7, 1 ⁇ b ⁇ 12, to obtain a positive electrode active material.
  • free sodium ions (residual alkali) on the surface of the core material will enter the crystal structure of the core material, thereby increasing the sodium ions in the core material, so the first coating layer including Ma O b formed during the sintering process will not deteriorate the first cycle coulomb efficiency of the positive electrode active material.
  • the core material is uniformly mixed with a solvent such as anhydrous ethanol, and then Ma O b is added and mixed uniformly, and then the solvent is evaporated by vacuum evaporation (70°C-100°C, such as 70°C, 80°C, 90°C or 100°C) using a rotary evaporator, and then the filter cake is washed several times using a suction filtration device, and the filter cake is dried in a vacuum oven, and then the powder material is calcined at 250°C-550°C under a nitrogen atmosphere for 2h-8h to form a first coating layer including Ma O b on the surface of the core material.
  • a solvent such as anhydrous ethanol
  • the sintering temperature can be 300°C-500°C, 350°C-450°C, 350°C-400°C, etc.
  • the calcination time can be 3h-7h, 4h-6h, 5h-6h, etc.
  • a dense first coating layer can be formed on the surface of the core, thereby improving the environmental stability and moisture resistance of the material, and then improving the cycle performance of the battery containing it.
  • the core material before the core material is mixed with Ma O b and sintered, the core material is mixed with a carbon source and sintered in advance, so that a second coating layer containing carbon can be formed on the surface of the core material to improve the positive electrode active material.
  • the environmental stability, moisture resistance and conductivity of the battery can be improved, thereby improving the cycle performance and kinetic performance of the battery containing it.
  • the core material is mixed with a carbon source and sintered under nitrogen as a protective gas, the temperature is raised to 500°C-600°C, for example, 520°C-580°C, 540°C-560°C, and the sintering is carried out for 6h-14h, for example, 7h-13h, 8h-12h, 9h-11h, 10h-11h.
  • a second carbon-containing coating layer is formed on the surface of the core material.
  • the carbon source may include at least one of sucrose, tannic acid, polyethylene glycol, polyvinyl pyrrolidone, glucose, ascorbic acid, or citric acid.
  • the third aspect of the present application provides a positive electrode plate, which includes the positive electrode active material described in the first aspect of the present application or the positive electrode active material obtained by the method described in the second aspect of the present application.
  • the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode active material mentioned above or the positive electrode active material obtained by the method described above.
  • the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite negative electrode current collector.
  • the metal foil aluminum foil may be used.
  • the composite negative electrode current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite negative electrode current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.) on a substrate.
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material layer may further optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode active material layer may further optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N-methylpyrrolidone
  • a fourth aspect of the present application provides a battery, which includes the positive electrode plate described in the third aspect of the present application.
  • the battery comprises a sodium ion battery.
  • a battery includes a positive electrode, a negative electrode, an electrolyte, and a separator.
  • active ions are embedded and released back and forth between the positive electrode and the negative electrode. It plays the role of conducting ions.
  • the isolation membrane is set between the positive electrode and the negative electrode, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes the polymer described in the first aspect of the present application.
  • the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.) on a substrate.
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may adopt the negative electrode active material for the battery known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate, etc.
  • the silicon-based material may include at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites or silicon alloys.
  • the tin-based material may include at least one of elemental tin, tin oxide compounds or tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.
  • the negative electrode active material layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.
  • a conductive agent which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.
  • the negative electrode active material layer may further optionally include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent and the binder are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.
  • the solvent may include ethylene carbonate, propylene carbonate, ethyl methyl carbonate, At least one of diethyl ester, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, ethylene glycol dimethyl ether, methyl ethyl sulfone or diethyl sulfone.
  • the electrolyte may further include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride.
  • the isolation membrane may be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer may be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the 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 package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG3 is a battery cell 1 of a square structure as an example.
  • the outer package may include a shell 11 and a cover plate 13.
  • the shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 12 through a winding process or a lamination process.
  • the electrode assembly 12 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 12.
  • the number of electrode assemblies 12 contained in the battery cell 1 can be one or more, and those skilled in the art can select according to specific actual needs.
  • batteries may be assembled into a battery module.
  • the number of batteries contained in the battery module may be one or more. The specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG5 is a battery module 2 as an example.
  • a plurality of battery cells 1 may be arranged in sequence along the length direction of the battery module 2. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 1 may be fixed by fasteners.
  • the battery module 2 may further include a housing having a receiving space, and the plurality of battery cells 1 are received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG6 and FIG7 are battery packs 3 as an example.
  • the battery pack 1 may include a battery box and a plurality of battery modules 2 disposed in the battery box.
  • the battery box includes an upper box body 31 and a lower box body 32, and the upper box body 31 can be covered on the lower box body 32 to form a closed space for accommodating the battery modules 2.
  • the plurality of battery modules 2 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • FIG8 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the device is usually required to be light and thin, and a battery may be used as a power source.
  • Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 material is evenly mixed in an anhydrous ethanol solvent, and titanium dioxide sol is added, wherein the mass ratio of Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 material to solvent is 80:200, and the solvent is evaporated out in vacuum (80°C) by a rotary evaporator, and then the material is washed by a suction filtration device, and the filter cake is dried in a vacuum oven, and then the powder material is calcined at 300°C for 6h in a nitrogen atmosphere, and a first coating layer including titanium dioxide is formed on the surface of the Na 4 Fe 3 (PO 4 ) 2 P 2 O 7 material after natural cooling, i.e., the positive electrode active material.
  • the polyvinylidene fluoride binder is fully dissolved in N-methylpyrrolidone, and a carbon black conductive agent and a positive electrode active material are added to prepare a uniformly dispersed slurry, wherein the mass ratio of the polyvinylidene fluoride binder to the carbon black conductive agent and the positive electrode active material is 10:20:70.
  • the slurry is evenly coated on both sides of the aluminum foil, and then transferred to a vacuum drying oven for complete drying.
  • the obtained electrode sheet is rolled and then punched to obtain a positive electrode sheet.
  • the negative electrode active material hard carbon, conductive agent carbon black (Super P), binder styrene-butadiene rubber (SBR), and sodium carboxymethyl cellulose (CMC-Na) are uniformly mixed in a proper amount of solvent deionized water at a mass ratio of 96:1.5:1.5:1 to obtain a negative electrode slurry.
  • the negative electrode slurry is coated on both sides of the negative electrode collector copper foil, and a negative electrode active material layer is formed on both sides of the negative electrode collector through drying and cold pressing. Finally, the negative electrode sheet is obtained through striping and cutting processes.
  • Polypropylene film is used as the isolation film.
  • the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then they are wound to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the prepared electrolyte is injected into the dried sodium ion battery. After vacuum packaging, standing, forming, and shaping processes, a sodium ion battery is obtained.
  • Example 2 The preparation methods of the sodium ion batteries of Examples 2-35 and Comparative Example 1 are the same as that of Example 1, except that the compositions of the prepared positive electrode active materials are different, as shown in Table 1.
  • Conductive agent carbon black (Super P) and binder styrene-butadiene rubber (SBR) were mixed uniformly in a proper amount of deionized water as a solvent at a mass ratio of 1.5:1.5 to obtain a negative electrode slurry.
  • the negative electrode slurry was coated on both sides of the negative electrode collector copper foil, and a negative electrode active material layer was formed on both sides of the negative electrode collector through drying and cold pressing. Finally, the negative electrode was obtained through striping and cutting processes. The remaining steps such as the preparation of the positive electrode, electrolyte, isolation membrane and sodium ion battery were the same as those in Example 1.
  • the XRD comparison diagram of the positive electrode active materials of Example 1 and Comparative Example 1 is shown in Figure 9.
  • the peak positions of the XRD diagrams of the positive electrode active materials of Example 1 and Comparative Example 1 are the same as those of the XRD diagram of the positive electrode active material of Comparative Example 1, indicating that coating the first coating layer on the outer surface of the inner core of Example 1 does not destroy the lattice structure of the inner core material, and because the amount of the first coating is small, the characteristic peak of the coating layer material does not appear in the XRD diffraction peak.
  • Na 4 R 3 (PO 4 ) 2 P 2 O 7 material is mixed with glucose and sintered. The temperature is raised to 550°C in nitrogen as a protective gas and kept warm for 4 hours. As non-carbon elements in glucose are removed, a second carbon-containing coating layer is formed on the surface of the core material. The core forming the second coating layer is placed in anhydrous ethanol solvent and mixed evenly. Titanium dioxide sol is added, wherein the mass ratio of Na 4 R 3 (PO 4 ) 2 P 2 O 7 material to the solvent is 80:200. A rotary evaporator is used to vacuum evaporate the solvent (80°C).
  • the material is then washed with a suction filtration device, the filter cake is dried in a vacuum oven, and the powder material is then calcined at 300°C in a nitrogen atmosphere for 6 hours. After natural cooling, a first coating layer including titanium dioxide is formed on the surface of the second coating layer, i.e., the positive electrode active material.
  • Example 38-44 and Comparative Example 2 The preparation methods of the sodium ion batteries of Examples 38-44 and Comparative Example 2 are the same as that of Example 37, except that the compositions of the prepared positive electrode active materials are different, as shown in Table 2.
  • Conductive agent carbon black (Super P) and binder styrene-butadiene rubber (SBR) are mixed evenly in a proper amount of solvent deionized water at a mass ratio of 1.5:1.5 to obtain a negative electrode slurry.
  • the negative electrode slurry is coated on both sides of the negative electrode collector copper foil.
  • a negative electrode active material layer is formed on both sides of the negative electrode collector through drying and cold pressing.
  • the negative electrode sheet is obtained through striping and cutting processes. The remaining steps such as the preparation of the positive electrode sheet, electrolyte, isolation membrane and sodium ion battery are the same as those in Example 37.
  • the positive electrode active material was exposed to room temperature (humidity was about 10%), and the water content of the positive electrode active material was tested at 0 min and 60 min respectively.
  • the specific test method can refer to the GB/T 11133-2015 test method.
  • the ambient temperature was controlled at 25°C.
  • the battery was charged to 3.65V at 1C, then charged to 0.05C at a constant voltage, left to stand for 10 minutes, and then discharged to 1.5V at 1C.
  • the discharge capacity was recorded as C 0 .
  • 300 cycles were performed according to the above charge and discharge process.
  • the discharge capacity at the 300th cycle was C 1 .
  • the cycle capacity retention rate of the battery cell C 1 /C 0 *100%.

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Abstract

一种正极活性材料及其制备方法、正极极片、电池和用电装置，所述正极活性材料包括内核和第一包覆层，所述内核包括Na xR y(PO 4) z(P 2O 7) k，其中，1≤x≤7，1≤y≤4，1≤z≤4，1≤k≤4，R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W或Pb中的至少一种；所述第一包覆层形成在所述内核的至少部分上，所述第一包覆层包括MaOb，M包括Ca、Bi、Ba、Ti、Al、Nb、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12。

Description

正极活性材料及其制备方法、正极极片、电池和用电装置 技术领域
本申请属于电池领域，具体涉及一种正极活性材料及其制备方法、正极极片、电池和用电装置。
背景技术
锂资源的日益紧缺、上游材料价格不断攀升、循环回收技术开发滞后、老旧电池循环回收利用率低下等问题使得锂离子电池面临着极大的挑战。钠离子电池能够利用钠离子在正负极之间的脱嵌过程实现充放电，而且钠资源的储量远比锂丰富、分布更为广泛、成本远比锂低，因此钠离子电池成为很有潜能替代锂二次电池的新一代电化学体系。然而，由于现有正极活性材料稳定性较差，导致钠离子电池存在循环性能低的问题。
发明内容
鉴于背景技术中存在的技术问题，本申请提供一种正极活性材料，旨在提高含有其的电池的循环性能。
为了实现上述目的，本申请一个方面提出了一种正极活性材料，所述正极活性材料包括：
内核，所述内核包括NaxRy(PO4)z(P2O7)k，其中，1≤x≤7，1≤y≤4，1≤z≤4，1≤k≤4，R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W或Pb中的至少一种；
第一包覆层，所述第一包覆层形成在所述内核的至少部分上，所述第一包覆层包括MaOb，M包括Ca、Bi、Ba、Ti、Al、Nb、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12。
本申请至少包括如下所述的有益效果：本申请通过在包括NaxRy(PO4)z(P2O7)k的内核的至少部分上形成包括MaOb的第一包覆层，M包括Ca、Bi、Ba、Ti、Al、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，该组成的第一包覆层可以降低内核与空气中的H2O、CO2等接触，从而提高材料的环境稳定性和抗湿能力，进而提高电池的循环性能。同时该第一包覆层可以减少内核表面与电解液之间的副反应，稳定正极活性材料与电解液之间的界面，提高材料的稳定性，进而提高含有其电池的循环性能。另外该组成的第一包覆层不会降低 正极活性材料的首圈库伦效率，从而使得电池保持较高的首圈库伦效率。
在本申请一些实施方式中，所述内核包括Na4R3(PO4)2P2O7或Na7V4(PO4)4P2O7中的至少之一，其中R包括Fe、Ni、Co或Mn中的至少之一。
在本申请一些实施方式中，MaOb包括TiO2、Al2O3、Nb2O5、MgO、Co3O4、CaTiO3、Bi4Ti3O12或BaTiO3中的至少之一。由此，可以提高含有其电池的循环性能且使得电池保持较高的首圈库伦效率。
在本申请一些实施方式中，基于所述正极活性材料的总质量，所述第一包覆层的含量为w％，
基于所述内核的总质量，所述内核的残碱量为z％，0.06≤z/w≤3，可选为0.06≤z/w≤1。由此，可以提高含有其电池的循环性能且使得电池保持较高的首圈库伦效率。
在本申请一些实施方式中，1％≤w％≤3％，可选为1.5％≤w％≤2.5％。由此，可以提高含有其电池的循环性能且使得电池保持较高的首圈库伦效率。
在本申请一些实施方式中，0.2％≤z％≤3％，可选为0.2％≤z％≤0.6％。
在本申请一些实施方式中，所述第一包覆层的厚度为1nm-10nm，可选为2nm-8nm。由此，可以提高含有其电池的循环性能且使得电池保持较高的首圈库伦效率。
在本申请一些实施方式中，所述正极活性材料还包括第二包覆层，所述第二包覆层形成在所述内核的至少部分上，所述第一包覆层形成在所述第二包覆层的至少部分上，所述第二包覆层包括碳。由此，可以提高正极活性材料的环境稳定性、抗湿能力和导电性，从而提高含有其电池的动力学性能和循环性能。
在本申请一些实施方式中，基于所述正极活性材料的总质量，所述第二包覆层中碳的含量为n％，0.16≤n/w≤1.5，可选地0.32≤n/w≤0.8。由此，可以提高正极活性材料的环境稳定性、抗湿能力和导电性，从而提高含有其电池的动力学性能和循环性能。
在本申请一些实施方式中，0.5％≤n％≤1.5％，可选地0.8％≤n％≤1.2％。由此，可以提高正极活性材料的环境稳定性、抗湿能力和导电性，从而提高含有其电池的动力学性能和循环性能。
在本申请一些实施方式中，所述正极活性材料满足下述条件中的至少之一：
所述正极活性材料的体积平均粒径Dv50为2μm-8μm，可选为2μm-5μm；
所述正极活性材料的Dv99为10μm-40μm，可选为15μm-30μm；
所述正极活性材料的BET比表面积为3m2/g-11m2/g，可选为7m2/g-10m2/g；
所述正极活性材料在100MPa压力下的压实密度为1.3g/cm3-2.1g/cm3，可选为1.7g/cm3-1.9g/cm3。
本申请第二方面提出了一种制备正极活性材料的方法，包括：
提供内核材料，所述内核材料包括NaxRy(PO4)z(P2O7)k，其中，1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W或Pb中的至少一种；
将所述内核材料与MaOb混合烧结，M包括Ti、Al、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12，得到正极活性材料。
由此，采用本申请的方法可以在包括NaxRy(PO4)z(P2O7)k的内核上形成包括MaOb的第一包覆层(M包括Ti、Al、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12)，该组成的第一包覆层可以降低内核与空气中的H2O、CO2等接触，从而提高材料的环境稳定性和抗湿能力，进而提高含有其电池的循环性能，并且该组成的第一包覆层不会恶化正极活性材料的首圈库伦效率，从而使得电池保持较高的首圈库伦效率。
在本申请一些实施方式中，所述烧结的温度为250℃-550℃，保温时间为2h-8h。
在本申请一些实施方式中，在将所述内核材料与MaOb混合烧结前，预先将所述内核材料与碳源混合烧结。由此，可以在内核材料表面形成含碳的第二包覆层，提高正极活性材料的环境稳定性、抗湿能力和导电性，从而提高含有其电池的循环性能和动力学性能。
本申请第三方面提出了一种正极极片，所述正极极片包括本申请第一方面所述的正极活性材料或采用本申请第二方面所述的方法得到的正极活性材料。
本申请第四方面提出了一种电池，所述电池包括本申请第三方面所述的正极极片。
在本申请一些实施方式中，所述电池包括钠离子电池。
本申请第五方面提出了一种用电装置，所述用电装置包括本申请第四方面所述的电池。
本申请的附加方面和优点将在下面的描述中部分给出，部分将从下面的描述中变得明显，或通过本申请的实践了解到。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是本申请一实施方式的正极活性材料的示意图。
图2是本申请另一实施方式的正极活性材料的示意图。
图3是本申请一实施方式的电池的示意图。
图4是图3所示的本申请一实施方式的电池的分解图。
图5是本申请一实施方式的电池模块的示意图。
图6是本申请一实施方式的电池包的示意图。
图7是图6所示的本申请一实施方式的电池包的分解图。
图8是本申请一实施方式的电池用作电源的用电装置的示意图。
图9是本申请实施例1和对比例1的正极活性材料的XRD对比图。
图10是本申请实施例1的正极活性材料的EDS能谱中Ti元素的分布图。
附图标记说明：
1电池；11壳体；12电极组件；13盖板；2电池模块；3电池包；31上箱体；32下箱
体；20正极活性材料；21内核；22第一包覆层；23第二包覆层。
具体实施方式
下面对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤 (c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
随着电动汽车与可充电移动设备的技术发展和需求提升，二次电池作为新能源领域的代表，与其相关的研究工作也迅猛发展。钠离子电池相比于传统的锂离子电池具有强劲的价格优势，在大规模储电系统中具有广泛的应用前景。
聚阴离子磷酸盐正极材料由于资源充足，环境友好，易于规模化生产且具有开放的钠离子扩散通道，热稳定性较好，所以成为热门的钠离子电池正极活性材料之一。然而由于工艺、配方等原因，导致聚阴离子磷酸盐正极材料表面残碱(残碱包括碳酸氢钠和碳酸钠等)，表面残碱易与空气中的H2O、CO2等反应而导致材料环境稳定性和抗湿能力较差，进而降低电池循环性能。
本申请通过在包括NaxRy(PO4)z(P2O7)k的内核的至少部分上形成包括MaOb的第一包覆层，M包括Ca、Bi、Ba、Ti、Al、Nb、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，该组成的第一包覆层可以降低内核与空气中的H2O、CO2等接触，从而提高材料的环境稳定性和抗湿能力，进而提高电池的循环性能。同时该第一包覆层可以减少内核表面与电解液之间的副反应，稳定正极活性材料与电解液之间的界面，提高材料的稳定性，进而提高含有其电池的循环性能。另外该组成的第一包覆层不会降低正极活性材料的首圈库伦效率，从而使得电池保持较高的首圈库伦效率。
本申请实施例公开的正极活性材料适用于钠离子电池，并且本申请实施例公开的电池可以用于使用电池作为电源的用电设备或者使用电池作为储能元件的各种储能系统。用电设备可以包括但不限于手机、平板、笔记本电脑、电动玩具、电动工具、电瓶车、电动汽车、轮船、航天器等等。其中，电动玩具可以包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等，航天器可以包括飞机、火箭、航天飞机和宇宙飞船等等。
本申请第一方面提出了一种正极活性材料，参考图1，所述正极活性材料20包括内核21和第一包覆层22，其中，所述内核包括NaxRy(PO4)z(P2O7)k，其中，1≤x≤7，1≤y≤4，1≤z≤4，1≤k≤4，R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W或Pb中的至少一种，所述第一包覆层22形成在所述内核21的至少部分上，所述第一包覆层22包括MaOb，M包括Ca、Bi、Ba、Ti、Al、Nb、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12。
本申请至少包括如下所述的有益效果：本申请通过在包括NaxRy(PO4)z(P2O7)k的内核21的至少部分上形成包括MaOb的第一包覆层22，M包括Ca、Bi、Ba、Ti、Al、Nb、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，该组成的第一包覆层22可以降低内核21与空 气中的H2O、CO2等接触，从而提高材料的环境稳定性和抗湿能力，进而提高电池的循环性能。同时该第一包覆层22可以减少内核21表面与电解液之间的副反应，稳定正极活性材料20与电解液之间的界面，提高材料的稳定性，进而提高含有其电池的循环性能。另外该组成的第一包覆层22不会降低正极活性材料20的首圈库伦效率，从而使得电池保持较高的首圈库伦效率。
在本申请一些实施方式中，所述NaxRy(PO4)z(P2O7)k中，1≤x≤7，例如x取值为2≤x≤6，3≤x≤5，3≤x≤4等。由此，该内核21中包括该含量的钠离子，可以提高电池的克容量，从而使得电池具有较高的容量。
在本申请一些实施方式中，所述NaxRy(PO4)z(P2O7)k中R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W或Pb中的至少一种，并且1≤y≤4，例如2≤x≤4，3≤x≤4等。由此，本申请组成的正极活性材料具有化学稳定性、热稳定性、电化学稳定性和比容量高的优势。
在本申请一些实施方式中，所述NaxRy(PO4)z(P2O7)k中，1≤z≤4，1≤k≤4，例如2≤z≤4，3≤z≤4等，2≤k≤4，3≤k≤4等。
作为示例，所述NaxRy(PO4)z(P2O7)k可以包括Na4Fe3(PO4)2P2O7、Na4Ni3(PO4)2P2O7、Na4Co3(PO4)2P2O7、Na4Mn3(PO4)2P2O7、Na7V4(PO4)4P2O7、Na4.02Fe2.85(PO4)2P2O7、Na4Fe2.9Mg0.1(PO4)2P2O7、Na4Fe2.95Al0.05(PO4)2P2O7或Na4Fe2.99Cu0.01(PO4)2P2O7中的至少之一。
在本申请另一些实施方式中，所述内核21包括Na4R3(PO4)2P2O7或Na7V4(PO4)4P2O7中的至少之一，其中R包括Fe、Ni、Co或Mn中的至少之一，例如Na4Fe3(PO4)2P2O7、Na4Ni3(PO4)2P2O7、Na4Co3(PO4)2P2O7、Na4Mn3(PO4)2P2O7。由此，采用该组成的内核21，可以提高正极活性材料20的克容量，从而提高含有电池的容量。
需要说明的是，电池在充放电过程中会伴随Na的脱嵌及消耗，电池在放电到不同状态时Na的摩尔含量不同。本申请中关于内核21的列举中，Na的摩尔含量为材料初始状态，即投料前状态，正极活性材料应用于电池体系中，经过充放电循环，Na的摩尔含量会发生变化。
本申请中关于内核21的列举中，O的摩尔含量仅为理论状态值，晶格释氧会导致氧的摩尔含量发生变化，实际O的摩尔含量会出现浮动。
在本申请一些实施方式中，所述第一包覆层22形成在所述内核21的至少部分上，所述第一包覆层22包括MaOb，M包括Ca、Bi、Ba、Ti、Al、Nb、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12，例如a取值为2≤a≤6，3≤a≤5，3≤a≤4等。由此，本申请通过在包括NaxRy(PO4)z(P2O7)k的内核21的至少部分上形成包括上述组 成的MaOb的第一包覆层22，该组成的第一包覆层22可以降低内核21与空气中的H2O、CO2等接触，从而提高材料的环境稳定性和抗湿能力，进而提高电池的循环性能。同时该第一包覆层22可以减少内核21表面与电解液之间的副反应，稳定正极活性材料20与电解液之间的界面，提高材料的稳定性，进而提高含有其电池的循环性能。另外该组成的第一包覆层22不会降低正极活性材料20的首圈库伦效率，从而使得电池保持较高的首圈库伦效率。
作为示例，MaOb可以包括CaO、Bi2O3、BaO、TiO2、Al2O3、Nb2O5、MgO、FeO、CuO、ZnO、MnO2、NiO或Co3O4中的至少之一。
在本申请一些实施方式中，所述MaOb可以包括TiO2、Al2O3、Nb2O5、MgO、Co3O4、CaTiO3、Bi4Ti3O12或BaTiO3中的至少之一。由此，本申请通过在内核21上形成上述组成的第一包覆层22，该组成的第一包覆层22可以降低内核21与空气中的H2O、CO2等接触，从而提高材料的环境稳定性和抗湿能力，进而提高电池的循环性能。同时该第一包覆层22可以减少内核21表面与电解液之间的副反应，稳定正极活性材料20与电解液之间的界面，提高材料的稳定性，进而进一步提高含有其电池的循环性能。另外该组成的第一包覆层22不会降低正极活性材料20的首圈库伦效率，从而使得电池保持较高的首圈库伦效率。
在本申请一些实施方式中，基于所述正极活性材料20的总质量，所述第一包覆层22的含量为w％；基于所述内核21的总质量，所述内核21的残碱量为z％，0.06≤z/w≤3，例如0.08≤z/w≤3，0.1≤z/w≤3，0.2≤z/w≤2.8，0.5≤z/w≤2.5，0.7≤z/w≤2.2，1≤z/w≤2，1.2≤z/w≤1.8，1.5≤z/w≤1.7等。具体的，由于工艺、配方等原因，导致内核21表面残碱(残碱包括碳酸氢钠和碳酸钠等)，表面残碱易与空气中的H2O、CO2等反应而导致材料环境稳定性和抗湿能力较差，而本申请控制所述第一包覆层22的含量w％与所述内核21的残碱量z％满足上述比例，可以显著提高材料的环境稳定性和抗湿能力，进而提高电池的循环性能。在本申请另一些实施方式中，所述第一包覆层22的含量w％与所述内核21的残碱量z％满足0.06≤z/w≤1。
本申请中，所述内核21的残碱量z％的测试可以采用本领域公知的仪器及方法进行测定，例如可以参照GB/T9725-2007《化学试剂电位滴定法通则》对于游离锂的测试，对钠离子电池正极活性材料中内核的游离钠进行测试，所得测试结果根据残余钠和残余锂的分子量的比例换算而得。例如，NaHCO3分子量为84，LiHCO3分子量为68，测试结果得到的游离锂的含量为0.1％，按照NaHCO3与LiHCO3的分子量的比例，换算得到正极材料的游离钠的含量为0.124％。GB/T9725-2007《化学试剂电位滴定法通则》测试正极材料的游离锂的含量的方法为：按产品标准的规定取样并制备试液。插入规定的电极，开动电磁搅拌器，用规定的标准滴定溶液进行滴定。从滴定管中滴入约为所需滴定体积的百分之九十 的标准滴定溶液，测量溶液的电位或pH值。以后每滴加1mL或适量标准滴定溶液测量一次电位或pH值，化学计量点前后，每滴加0.1mL标准滴定溶液，测量一次。继续滴定至电位或pH值变化不大为止。记录每次滴加标准滴定溶液后滴定管的读数以及测得的电位或pH值，用作图法或二级微商法确定滴定终点。
在本申请一些实施方式中，基于所述正极活性材料20的总质量，所述第一包覆层22的含量w％满足1％≤w％≤3％，例如1.2％≤w％≤2.8％，1.5％≤w％≤2.5％，1.7％≤w％≤2.2％，1.8％≤w％≤2％等。由此，本申请的第一包覆层22的含量w％满足上述条件，可以提高材料的环境稳定性和抗湿能力，进而提高电池的循环性能，同时该含量的第一包覆层22可以减少内核21表面与电解液之间的副反应，稳定正极活性材料20与电解液之间的界面，提高材料的稳定性，进而提高含有其电池的循环性能。另外该含量的第一包覆层22不会降低正极活性材料20的首圈库伦效率，从而使得电池保持较高的首圈库伦效率。在本申请另一些实施方式中，基于所述正极活性材料20的总质量，所述第一包覆层22的含量w％满足1.5％≤w％≤2.5％。
在本申请一些实施方式中，基于所述内核21的总质量，所述内核21的残碱量z％满足0.2％≤z％≤3％，例如0.5％≤z％≤2.8％，0.8％≤z％≤2.5％，1％≤z％≤2.2％，1.2％≤z％≤2％，1.5％≤z％≤1.8％等。由此，本申请的所述内核21的残碱的含量z％满足上述条件，可以降低电池循环过程中残碱的分解产气，降低电池胀气，从而提高电池的循环性能。在本申请一些实施方式中，基于所述正极活性材料20的总质量，所述内核21的残碱量z％满足0.2％≤z％≤0.6％。
在本申请一些实施方式中，所述第一包覆层22的厚度可以为1nm-10nm，例如2nm-9nm，3nm-8nm，4nm-7nm，5nm-6nm等。由此，本申请的第一包覆层22的厚度满足上述条件，可以提高材料的环境稳定性和抗湿能力，进而提高电池的循环性能，同时该厚度的第一包覆层22可以减少内核21表面与电解液之间的副反应，稳定正极活性材料20与电解液之间的界面，提高材料的稳定性，进而提高含有其电池的循环性能。另外该厚度的第一包覆层22不会降低正极活性材料的首圈库伦效率，从而使得电池保持较高的首圈库伦效率。在本申请另一些实施方式中，所述第一包覆层22的厚度为2nm-8nm。
在本申请一些实施方式中，参考图2，所述正极活性材料20还包括第二包覆层23，所述第二包覆层23形成在所述内核21的至少部分上，所述第一包覆层22形成在所述第二包覆层23的至少部分上，所述第二包覆层23包括碳。由此，通过在内核21的外表面包覆包括碳的第二包覆层23，该第二包覆层23不仅可以提高内核21的环境稳定性和抗湿能力，而且可以提高内核21的导电性，从而提高含有其电池的动力学性能和循环性能。
在本申请一些实施方式中，基于所述正极活性材料20的总质量，所述第二包覆层23 中碳的含量为n％，0.16≤n/w≤1.5，例如0.18≤n/w≤1.5，0.2≤n/w≤1.5，0.25≤n/w≤1.5，0.3≤n/w≤1.5，0.35≤n/w≤1.45，0.4≤n/w≤1.4，0.45≤n/w≤1.35，0.5≤n/w≤1.3，0.55≤n/w≤1.25，0.6≤n/w≤1.2，0.65≤n/w≤1.1，0.7≤n/w≤1，0.8≤n/w≤0.9，0.85≤n/w≤0.9等。由此，本申请的第二包覆层23中碳含量n％和所述第一包覆层22的含量w％控制在上述范围内，可以显著提高正极活性材料20的环境稳定性、抗湿能力和导电性，从而提高含有其电池的动力学性能和循环性能。在本申请另一些实施方式中，基于所述正极活性材料20的总质量，所述第二包覆层23中碳的含量n％满足0.32≤n/w≤0.8。
在本申请一些实施方式中，基于所述正极活性材料20的总质量，所述第二包覆层23中碳的含量为n％，0.5％≤n％≤1.5％，例如0.6％≤n％≤1.4％，0.7％≤n％≤1.3％，0.8％≤n％≤1.3％，0.9％≤n％≤1.2％，1％≤n％≤1.1％等。由此，本申请的第二包覆层23中碳含量n％控制在上述范围内，可以显著提高正极活性材料20的环境稳定性、抗湿能力和导电性，从而提高含有其电池的动力学性能和循环性能。在本申请另一些实施方式中，基于所述正极活性材料20的总质量，所述第二包覆层23中碳的含量n％满足0.8％≤n％≤1.2％。
在本申请一些实施方式中，所述正极活性材料20的体积平均粒径Dv50为2μm-8μm，例如，正极活性材料的Dv50可以为2.5μm-7.5μm，3μm-7μm，3.5μm-6.5μm，4μm-6μm，4.5μm-5.5μm，4.8μm-5μm等。在本申请另一些实施方式中，所述正极活性材料20的体积平均粒径Dv50为2μm-5μm。
在本申请一些实施方式中，所述正极活性材料20的Dv99为10μm-40μm，例如，正极活性材料的Dv99可以为12μm-37μm，15μm-35μm，18μm-32μm，20μm-30μm，22μm-28μm，23μm-25μm等。在本申请另一些实施方式中，所述正极活性材料20的Dv99为15μm-30μm。
本申请中，体积平均粒径Dv50是指累计体积分布百分数达到50％时所对应的粒径，Dv99是指累计体积分布百分数达到99％时所对应的粒径，例如体积平均粒径Dv50和Dv99的测试方法可以参照标准GB/T 19077-2016，使用激光粒度分析仪(例如Malvern Master Size3000)进行测定。
在本申请一些实施方式中，所述正极活性材料20的BET比表面积为3m2/g-11m2/g，例如正极活性材料20的BET比表面积可以是4m2/g-10m2/g，5m2/g-9m2/g，6m2/g-8m2/g，7m2/g-7.5m2/g等。在本申请另一些实施方式中，所述正极活性材料20的BET比表面积为7m2/g-10m2/g。
本申请中，正极活性材料20的BET比表面积为本领域公知的含义，可以采用本领域公知的仪器及方法进行测定，例如可以参照如下方法测试得到：使用美国麦克多站式全自动比表面积与孔隙分析仪GeminiVII2390，取约7g左右的样品放入9cc带球泡的长管中，200℃脱气2h，随后放入主机测试得到正极活性材料20的BET比表面积数据。
在本申请一些实施方式中，所述正极活性材料20在100MPa压力下的压实密度为1.3g/cm3-2.1g/cm3，例如正极活性材料20在100MPa压力下的压实密度可以是1.4g/cm3-2g/cm3，1.5g/cm3-1.9g/cm3，1.6g/cm3-1.8g/cm3，1.7g/cm3-1.8g/cm3等。在本申请一些实施方式中，所述正极活性材料20在100MPa压力下的压实密度为1.7g/cm3-1.9g/cm3。
本申请中，“压实密度”为本领域公知的含义，可以采用本领域公知的仪器和方法测定，例如可以采用下列测试方法：定量m的粉末放于压实专用模具中，将模具放在压实密度仪器上，设置100MPa压力，在设备上测出300MPa压力下粉末的厚度体积v，通过密度＝质量m/体积v，计算出压实密度；(具体参考GB/T24533-2009)。
具体的，当本申请的正极活性材料20的体积平均粒径Dv50、体积平均粒径Dv99、比表面积和100MPa压力下的压实密度中的至少之一在上述范围时，正极活性材料20内的传导距离小、表面副反应少，促进了正极活性材料20发挥其克容量，提升了含有其的电池的容量保持率。
本申请第二方面提供了一种制备第一方面所述的正极活性材料的方法，包括：
S100：提供内核材料
在本申请一些实施方式中，所述内核材料包括NaxRy(PO4)z(P2O7)k，其中，1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W或Pb中的至少一种。
S200：将所述内核材料与MaOb混合烧结
在本申请一些实施方式中，将步骤S100的所述内核材料与MaOb混合烧结，在所述内核材料表面包覆包括MaOb的第一包覆层，M包括Ti、Al、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12，得到正极活性材料。具体的，烧结过程中，内核材料表面游离的钠离子(残碱)，会进入内核材料的晶体结构中，从而增加内核材料中钠离子，因此烧结过程形成的包括MaOb的第一包覆层不会恶化正极活性材料的首圈库伦效率。
作为示例，将内核材料与溶剂例如无水乙醇均匀混合，然后加入MaOb混合均匀后，采用旋转蒸发仪真空蒸发(70℃-100℃，例如70℃、80℃、90℃或100℃)出溶剂，随后采用抽滤装置将滤饼洗涤几遍，将滤饼在真空烘箱中烘干，随后将粉体材料在氮气氛围下250℃-550℃下焙烧2h-8h，在内核材料表面形成包括MaOb的第一包覆层。例如，烧结温度可以为300℃-500℃，350℃-450℃，350℃-400℃等。焙烧时间可以为3h-7h，4h-6h，5h-6h等。该烧结温度下可以在内核表面形成致密的第一包覆层，从而提高材料的环境稳定性和抗湿能力，进而提高含有其电池的循环性能。
在本申请一些实施方式中，在将所述内核材料与MaOb混合烧结前，预先将所述内核材料与碳源混合烧结，从而可以在内核材料表面形成含碳的第二包覆层，提高正极活性材料 的环境稳定性、抗湿能力和导电性，从而提高含有其电池的循环性能和动力学性能。
在本申请一些实施方式中，所述内核材料与碳源混合烧结，在氮气作保护气体，升温至500℃-600℃，例如520℃-580℃，540℃-560℃，保温6h-14h，例如7h-13h，8h-12h，9h-11h，10h-11h进行烧结，随着碳源中非碳元素的脱出，在内核材料表面形成含碳的第二包覆层。
作为示例，碳源可以包括蔗糖、单宁酸、聚乙二醇、聚乙烯吡咯烷酮、葡萄糖、抗坏血酸或柠檬酸中的至少一种。
本申请第三方面提出了一种正极极片，所述正极极片包括本申请第一方面所述的正极活性材料或采用本申请第二方面所述的方法得到的正极活性材料。
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极活性材料层，所述正极活性材料层包括上述的正极活性材料或采用所述的方法得到的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极活性材料层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在本申请一些实施方式中，所述正极集流体可采用金属箔片或复合负极集流体。例如，作为金属箔片，可采用铝箔。复合负极集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合负极集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)，聚对苯二甲酸乙二醇酯(PET)，聚对苯二甲酸丁二醇酯(PBT)，聚苯乙烯(PS)，聚乙烯(PE)等的基材)上而形成。
在本申请一些实施方式中，正极活性材料层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物或含氟丙烯酸酯树脂中的至少一种。
在本申请一些实施方式中，正极活性材料层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯或碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
本申请第四方面提供了一种电池，所述电池包括本申请第三方面所述的正极极片。
在本申请一些实施方式中，所述电池包括钠离子电池。
通常情况下，电池包括正极极片、负极极片、电解质和隔离膜。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。电解质在正极极片和负极极片之间 起到传导离子的作用。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，同时可以使离子通过。
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极活性物质层，所述负极活性物质层包括本申请第一方面所述的聚合物。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极活性物质层设置在负极集流体相对的两个表面中的任意一者或两者上。
在本申请一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)，聚对苯二甲酸乙二醇酯(PET)，聚对苯二甲酸丁二醇酯(PBT)，聚苯乙烯(PS)，聚乙烯(PE)等的基材)上而形成。
在本申请一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种:人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可包括单质硅、硅氧化合物、硅碳复合物、硅氮复合物或硅合金中的至少一种。所述锡基材料可包括单质锡、锡氧化合物或锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在本申请一些实施方式中，负极活性物质层还可选地包括导电剂。导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯或碳纳米纤维中的至少一种。
在本申请一些实施方式中，负极活性物质层还可选地包括其他助剂，例如增稠剂(如梭甲基纤维素钠(CMC-Na))等。
在本申请一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂和粘接剂分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在本申请一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在本申请一些实施方式中，所述电解质钠盐可以包括六氟磷酸钠、二氟草酸硼酸钠、四氟硼酸钠、双草酸硼酸钠、高氯酸钠、六氟砷酸钠、双(氟磺酰)亚胺钠、三氟甲基磺酸钠或双(三氟甲基磺酰)亚胺钠中的至少之一。
在本申请一些实施方式中，溶剂可包括碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸 二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、乙二醇二甲醚、甲乙砜或二乙砜中的至少一种。
在本申请一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可包括玻璃纤维、无纺布、聚乙烯、聚丙烯或聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图3是作为一个示例的方形结构的电池单体1。
在一些实施方式中，参照图4，外包装可包括壳体11和盖板13。其中，壳体11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11具有与容纳腔连通的开口，盖板13能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件12。电极组件12封装于所述容纳腔内。电解液浸润于电极组件12中。电池单体1所含电极组件12的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，电池可以组装成电池模块，电池模块所含电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图5是作为一个示例的电池模块2。参照图5，在电池模块2中，多个电池单体1可以是沿电池模块2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电池单体1进行固定。
可选地，电池模块2还可以包括具有容纳空间的外壳，多个电池单体1容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图6和图7是作为一个示例的电池包3。参照图6和图7，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2。电池箱包括上箱体31和下箱体32，上箱体31能够盖设于下箱体32，并形成用于容纳电池模块2的封闭空间。多个电池模块2可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图8是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用电池作为电源。
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
1、正极极片的制备
(1)正极活性材料的制备
将Na4Fe3(PO4)2P2O7材料放在无水乙醇溶剂均匀混合，加入二氧化钛溶胶，其中，Na4Fe3(PO4)2P2O7材料与溶剂的质量比为80：200，采用旋转蒸发仪真空蒸发(80℃)出溶剂，随后采用抽滤装置对材料进行洗涤，将滤饼在真空烘箱中烘干，随后将粉体材料在氮气氛围下300℃下焙烧6h，自然降温后在Na4Fe3(PO4)2P2O7的材料表面形成包括二氧化钛的第一包覆层，即正极活性材料。
(2)正极极片的制备
将聚偏氟乙烯粘结剂充分溶解于N甲基吡咯烷酮中，加入炭黑导电剂与正极活性材料制成分散均匀的浆料，其中聚偏氟乙烯粘结剂与炭黑导电剂和正极活性材料的质量比为10：20:70，将浆料均匀涂敷在铝箔两侧表面，然后转移到真空干燥箱中完全干燥，将得到的极片进行辊压，然后进行冲切，得到正极极片。
2、负极极片的制备
将负极活性材料硬碳、导电剂炭黑(Super P)、粘结剂丁苯橡胶(SBR)、羧甲基纤维素钠(CMC-Na)按质量比96：1.5：1.5：1在适量的溶剂去离子水中混合均匀，得到负极浆料，将负极浆料涂布于负极集流体铜箔双侧表面上，通过烘干、冷压，在负极集流体双侧表面上形成负极活性材料层，最后经分条、裁切工序，得到负极极片。
3、电解液的制备
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将充分干燥的电解质盐NaPF6溶解于乙二醇二甲醚中，混合均匀后获得浓度为0.5mol/L的电解液。
4、隔离膜
以聚丙烯膜作为隔离膜。
5、二次电池的制备
将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件；将电极组件置于外包装中，将上述制备好的电解液注入到干燥后的钠离子电池中，经过真空封装、静置、化成、整形工序，获得钠离子电池。
实施例2-35以及对比例1的钠离子电池的制备方法同于实施例1，区别在于制备正极活性材料的组成不同，具体如表1所示。
实施例36
负极极片的制备
将导电剂炭黑(Super P)、粘结剂丁苯橡胶(SBR)按质量比1.5：1.5在适量的溶剂去离子水中混合均匀，得到负极浆料，将负极浆料涂布于负极集流体铜箔双侧表面上，通过烘干、冷压，在负极集流体双侧表面上形成负极活性材料层，最后经分条、裁切工序，得到负极极片，其余步骤如正极极片、电解液、隔离膜和钠离子电池的制备同于实施例1。
实施例1和对比例1的正极活性材料的XRD对比图如图9所示，由图9可知，实施例1和对比例1的正极活性材料的XRD图与对比例1的正极活性材料的XRD图的出峰位置相同，表明实施例1的在内核外表面包覆第一包覆层不会破坏内核材料的晶格结构，并且因第一包覆量较少，XRD衍射峰中并未出现包覆层物质的特征峰。
实施例1的正极活性材料的EDS能谱中Ti元素的分布图(参考GB/T 17359-2012测试 方法)如图10所示，显示正极活性材料表面第一包覆层中Ti元素分布均匀。

实施例37
正极活性材料的制备
将Na4R3(PO4)2P2O7材料与葡萄糖混合烧结，在氮气作保护气体，升温至550℃，保温4h，随着葡萄糖中非碳元素的脱出，在内核材料表面形成含碳的第二包覆层，将形成第二包覆层的内核放在无水乙醇溶剂均匀混合，加入二氧化钛溶胶，其中，Na4R3(PO4)2P2O7材料与溶剂的质量比为80：200，采用旋转蒸发仪真空蒸发(80℃)出溶剂，随后采用抽滤装置对材料进行洗涤，将滤饼在真空烘箱中烘干，随后将粉体材料在氮气氛围下300℃下焙烧6h，自然降温后在第二包覆层表面形成包括二氧化钛的第一包覆层，即正极活性材料。
其余步骤如正极极片、负极极片、电解液、隔离膜和钠离子电池的制备同于实施例1。
实施例38-44以及对比例2的钠离子电池的制备方法同于实施例37，区别在于制备正极活性材料的组成不同，具体如表2所示。
实施例45
负极极片的制备
将导电剂炭黑(Super P)、粘结剂丁苯橡胶(SBR)按质量比1.5：1.5在适量的溶剂去离子水中混合均匀，得到负极浆料，将负极浆料涂布于负极集流体铜箔双侧表面上，通过烘干、冷压，在负极集流体双侧表面上形成负极活性材料层，最后经分条、裁切工序，得到负极极片，其余步骤如正极极片、电解液、隔离膜和钠离子电池的制备同于实施例37。
对实施例1-45和对比例1-2正极活性材料的环境稳定性以及所得钠离子电池首圈库伦效率和循环性能进行表征，表征结果如表3所示。
(1)正极活性材料的环境稳定性
将正极活性材料暴露在室温下(湿度约为10％)的环境下，分别在0min和60min测试正极活性材料的水含量，具体测试方法可以参考GB/T 11133-2015测试方法。
(2)钠离子电池的首圈库伦效率
将钠离子二次电池在0℃下以1/3C的恒定电流充电至3.75V，之后以3.75V恒压充电至电流降到0.05C，得到首次充电容量(Cc1)；再以1/3C的恒定电流放电至1.5V，得到首次放电容量(Cd1)，并计算钠离子电池首圈库伦效率＝首次放电容量(Cd1)/首次充电容量(Cc1)*100％。
(3)循环性能测试：
控制环境温度为25℃，电池以1C充电到3.65V，随后恒压充电到0.05C，静置10min，然后1C放电到1.5V，记录放电容量为C0，按照上述充放电流程进行300个循环，第300圈的放电容量为C1，电芯的循环容量保持率＝C1/C0*100％。
表3

结论：对比实施例1-36和对比例1，实施例1-36的正极活性材料相较于对比例1的正极活性材料在60min后的含水量明显较低，表明实施例1-36的正极活性材料具有较高的抗湿能力，并且实施例1-36对应电池的首圈库伦效率和容量保持率均高于对比例1。对比实施例37-45和对比例2，实施例37-45的正极活性材料相较于对比例1的正极活性材料在60min后的含水量明显较低，表明实施例37-45的正极活性材料具有较高的抗湿能力，并且实施例37-45对应电池的首圈库伦效率和容量保持率均高于对比例2。由此表明采用本申请的正极活性材料具有优异的抗湿能力，并且提高含有其电池的首圈库伦效率和循环性能。
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 (18)

  1. 一种正极活性材料，其中，包括：
    内核，所述内核包括NaxRy(PO4)z(P2O7)k，其中，1≤x≤7，1≤y≤4，1≤z≤4，1≤k≤4，R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W或Pb中的至少一种；
    第一包覆层，所述第一包覆层形成在所述内核的至少部分上，所述第一包覆层包括MaOb，M包括Ca、Bi、Ba、Ti、Al、Nb、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12。
  2. 根据权利要求1所述的正极活性材料，其中，所述内核包括Na4R3(PO4)2P2O7或Na7V4(PO4)4P2O7中的至少之一，其中R包括Fe、Ni、Co或Mn中的至少之一。
  3. 根据权利要求1或2所述的正极活性材料，其中，MaOb包括TiO2、Al2O3、Nb2O5、MgO、Co3O4、CaTiO3、Bi4Ti3O12或BaTiO3中的至少之一。
  4. 根据权利要求1-3中任一项所述的正极活性材料，其中，基于所述正极活性材料的总质量，所述第一包覆层的含量为w％，
    基于所述内核的总质量，所述内核的残碱量为z％，0.06≤z/w≤3，可选为0.06≤z/w≤1。
  5. 根据权利要求4所述的正极活性材料，其中，1％≤w％≤3％，可选为1.5％≤w％≤2.5％。
  6. 根据权利要求4或5所述的正极活性材料，其中，0.2％≤z％≤3％，可选为0.2％≤z％≤0.6％。
  7. 根据权利要求1-6中任一项所述的正极活性材料，其中，所述第一包覆层的厚度为1nm-10nm，可选为2nm-8nm。
  8. 根据权利要求4-6中任一项所述的正极活性材料，其中，所述正极活性材料还包括第二包覆层，所述第二包覆层形成在所述内核的至少部分上，所述第一包覆层形成在所述第二包覆层的至少部分上，所述第二包覆层包括碳。
  9. 根据权利要求8所述的正极活性材料，其中，基于所述正极活性材料的总质量，所述第二包覆层中碳的含量为n％，0.16≤n/w≤1.5，可选地0.32≤n/w≤0.8。
  10. 根据权利要求9所述的正极活性材料，其中，0.5％≤n％≤1.5％，可选地0.8％≤n％≤1.2％。
  11. 根据权利要求1-10中任一项所述的正极活性材料，其中，所述正极活性材料满足下述条件中的至少之一：
    所述正极活性材料的体积平均粒径Dv50为2μm-8μm，可选为2μm-5μm；
    所述正极活性材料的Dv99为10μm-40μm，可选为15μm-30μm；
    所述正极活性材料的BET比表面积为3m2/g-11m2/g，可选为7m2/g-10m2/g；
    所述正极活性材料在100MPa压力下的压实密度为1.3g/cm3-2.1g/cm3，可选为1.7g/cm3-1.9g/cm3。
  12. 一种制备正极活性材料的方法，其中，包括：
    提供内核材料，所述内核材料包括NaxRy(PO4)z(P2O7)k，其中，1≤x≤7，1≤y≤4，1≤z≤2，1≤k≤4，R包括Mg、Al、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Zr、Nb、Mo、Sn、Hf、Ta、W或Pb中的至少一种；
    将所述内核材料与MaOb混合烧结，M包括Ti、Al、Mg、Fe、Cu、Zn、Mn、Ni或Co中的至少之一，1≤a≤7，1≤b≤12，得到正极活性材料。
  13. 根据权利要求12所述的方法，其中，所述烧结的温度为250℃-550℃，保温时间为2h-8h。
  14. 根据权利要求12或13所述的方法，其中，在将所述内核材料与MaOb混合烧结前，预先将所述内核材料与碳源混合烧结。
  15. 一种正极极片，其中，包括权利要求1-11中任一项所述的正极活性材料或采用权利要求12-14中任一项所述的方法得到的正极活性材料。
  16. 一种电池，其中，包括权利要求15所述的正极极片。
  17. 根据权利要求16所述的电池，其中，所述电池包括钠离子电池。
  18. 一种用电装置，其中，包括权利要求16或17所述的电池。
PCT/CN2023/128568 2023-08-17 2023-10-31 正极活性材料及其制备方法、正极极片、电池和用电装置 Ceased WO2025035609A1 (zh)

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