WO2024067407A1 - 电极材料及其制备方法，电极材料前驱体及其制备方法 - Google Patents

电极材料及其制备方法，电极材料前驱体及其制备方法 Download PDF

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Publication number
WO2024067407A1
WO2024067407A1 PCT/CN2023/120788 CN2023120788W WO2024067407A1 WO 2024067407 A1 WO2024067407 A1 WO 2024067407A1 CN 2023120788 W CN2023120788 W CN 2023120788W WO 2024067407 A1 WO2024067407 A1 WO 2024067407A1
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Prior art keywords
electrode material
precursor
layer
grain growth
positive electrode
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PCT/CN2023/120788
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English (en)
French (fr)
Inventor
许若愚
王博
陆宇阳
夏圣安
倪勇
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Huawei Technologies Co Ltd
University of Science and Technology of China USTC
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Huawei Technologies Co Ltd
University of Science and Technology of China USTC
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Priority to EP23870638.6A priority Critical patent/EP4571885A4/en
Publication of WO2024067407A1 publication Critical patent/WO2024067407A1/zh
Priority to US19/092,907 priority patent/US20250226400A1/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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/42—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2
    • C01G53/44—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2
    • C01G53/502—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt
    • C01G53/504—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5
    • C01G53/506—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing lithium and cobalt with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.5, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.5 with the molar ratio of nickel with respect to all the metals other than alkali metals higher than or equal to 0.8, e.g. Li(MzNixCoyMn1-x-y-z)O2 with x ≥ 0.8
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
    • C01G53/00—Compounds of nickel
    • C01G53/40—Complex oxides containing nickel and at least one other metal element
    • C01G53/42—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2
    • C01G53/44—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese
    • C01G53/50—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2
    • C01G53/51—Complex oxides containing nickel and at least one other metal element containing alkali metals, e.g. LiNiO2 containing manganese of the type (MnO2)n-, e.g. Li(NixMn1-x)O2 or Li(MyNixMn1-x-y)O2 containing sodium
    • 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
    • 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
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2002/00—Crystal-structural characteristics
    • C01P2002/50—Solid solutions
    • C01P2002/52—Solid solutions containing elements as dopants
    • C01P2002/54—Solid solutions containing elements as dopants one element only
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2004/00—Particle morphology
    • C01P2004/30—Particle morphology extending in three dimensions
    • C01P2004/32—Spheres
    • 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
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
    • 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
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the embodiments of the present application relate to the technical field of secondary batteries, and in particular to electrode materials and preparation methods thereof, and electrode material precursors and preparation methods thereof.
  • lithium-ion batteries are mainly composed of positive electrode materials, negative electrode materials, electrolytes and separators. Among them, the electrochemical properties of positive electrode materials and negative electrode materials directly affect the final performance of the battery.
  • Ternary polycrystalline positive electrode materials are considered to be one of the best choices for positive electrode materials for electric vehicles due to their high capacity, good cycle performance and moderate price.
  • the anisotropic lattice changes caused by the phase change of the material during the battery charging and discharging process make the internal stress distribution of the material uneven, and grain boundary cracking is prone to occur, resulting in the breakage of secondary particles, and the rapid increase of specific surface area and interface side reactions, which ultimately leads to an increase in battery impedance and a rapid decrease in performance. Therefore, it is necessary to provide a polycrystalline positive electrode material that can homogenize the stress distribution of polycrystalline positive electrode materials during the charging and discharging process, thereby inhibiting the grain boundary cracking phenomenon and improving battery performance.
  • an embodiment of the present application provides an electrode material, which can homogenize the stress distribution of secondary particles during the charge and discharge process, thereby suppressing the grain boundary cracking phenomenon to a certain extent, improving the cycle stability of the material, and improving the battery performance.
  • a first aspect of an embodiment of the present application provides an electrode material, which includes secondary particles formed by aggregation of multiple primary particles, and the secondary particles include an inner layer and an outer layer coated on the outer side of the inner layer, wherein the average particle size of the primary particles of the inner layer is greater than the average particle size of the primary particles of the outer layer.
  • the electrode material provided in the embodiment of the present application is structured such that the distribution of primary particles inside the secondary particles is arranged such that the average particle size of the primary particles in the inner layer is larger than the average particle size of the primary particles in the outer layer.
  • This structure can make the grain boundary density of the inner layer of the secondary particles smaller than the grain boundary density of the outer layer, thereby effectively dispersing the volume strain caused by the insertion and extraction of metal ions in the secondary particles, homogenizing the stress distribution inside the secondary particles, inhibiting grain boundary cracking, inhibiting the breakage of secondary particles, and improving the cyclic stability of the material.
  • this structure can make the metal ions in the secondary particles more evenly distributed in the charged state, thereby effectively improving the rate performance of the material.
  • the secondary particles are spherical or quasi-spherical particles.
  • the quasi-spherical shape is a shape that is close to a sphere.
  • the total radial distance between the center of the secondary particle and any point on the surface of the secondary particle is R
  • the outer layer is a region corresponding to a length of 20%-60% of R extending from the surface of the secondary particle toward the center
  • the inner layer is a region corresponding to a length of 40%-80% of R extending from the center of the secondary particle toward the surface.
  • the average particle size of the primary particles in the inner layer is 0.01R’ to 1.4R’, and R’ is half of the longest diameter of the secondary particles.
  • the average particle size of the primary particles in the outer layer is 0.001R’ to 0.3R’, and R’ is half of the longest diameter of the secondary particles.
  • the inner layer includes a doping element that promotes grain growth
  • the outer layer includes a doping element that inhibits grain growth
  • the doping elements that promote grain growth include one or more of strontium (Sr), cerium (Ce), bismuth (Bi), and magnesium (Mg); the doping elements that inhibit grain growth include one or more of boron (B), phosphorus (P), titanium (Ti), zirconium (Zr), niobium (Nb), antimony (Sb), tantalum (Ta), molybdenum (Mo), and tungsten (W).
  • the total molar content of the doping element that promotes grain growth and the doping element that inhibits grain growth is 0.1 mol%-1 mol%.
  • the average particle size of the primary particles is 10 nm-60 ⁇ m.
  • the average particle size of the secondary particles is 1 ⁇ m-200 ⁇ m.
  • the secondary particles include metal oxides for battery positive electrodes.
  • the metal oxide for the positive electrode of the battery is a metal oxide for the positive electrode of a lithium ion battery, a metal oxide for the positive electrode of a sodium ion battery, a metal oxide for the positive electrode of a potassium ion battery, or a metal oxide for the positive electrode of a magnesium ion battery.
  • the metal oxide for the positive electrode of the lithium-ion battery includes one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium titanium oxide, lithium iron phosphorus oxide, lithium nickel cobalt oxide, lithium nickel manganese oxide, and nickel cobalt multi-element oxide.
  • the outermost side of the outer layer contains an oxide of the doping element that inhibits grain growth.
  • the electrode material further includes a protective layer coated on the surface of the secondary particles.
  • a second aspect of the present application provides a method for preparing an electrode material, comprising:
  • An electrode material precursor is mixed with a metal salt and then calcined to obtain an electrode material, wherein the electrode material precursor includes an inner region and an outer region covering the inner region, the inner region includes a doping element that promotes grain growth, and/or the outer region includes a doping element that inhibits grain growth; the electrode material includes secondary particles formed by aggregation of multiple primary particles, the secondary particles include an inner layer and an outer layer covering the inner layer, wherein the average particle size of the primary particles in the inner layer is greater than the average particle size of the primary particles in the outer layer.
  • the calcination includes a first calcination and a second calcination performed sequentially, and the temperature of the first calcination is higher than the temperature of the second calcination.
  • the temperature (T1) of the first calcination is 600°C-1000°C
  • the temperature (T2) of the second calcination is 400°C-800°C.
  • the first calcination time is 2-4 hours, and the second calcination time is 6-14 hours.
  • the metal salt includes lithium salt, sodium salt, potassium salt or magnesium salt.
  • the electrode material precursor includes a metal oxide precursor for a positive electrode of a battery.
  • the metal oxide precursor for the battery positive electrode includes a hydroxide precursor of a metal oxide, an oxide precursor of a metal oxide, a carbonate precursor of a metal oxide, or a hydroxide oxide precursor of a metal oxide.
  • a third aspect of an embodiment of the present application provides an electrode material precursor, which includes a core layer and a shell layer covering the core layer, wherein the core layer includes a doping element that promotes grain growth, and/or the shell layer includes a doping element that inhibits grain growth.
  • the electrode material precursor includes a metal oxide precursor for a positive electrode of a battery.
  • the metal oxide precursor for the battery positive electrode includes a hydroxide precursor of a metal oxide, an oxide precursor of a metal oxide, a carbonate precursor of a metal oxide, or a hydroxide oxide precursor of a metal oxide.
  • the doping elements that promote grain growth include one or more of strontium (Sr), cerium (Ce), bismuth (Bi), and magnesium (Mg); the doping elements that inhibit grain growth include one or more of boron (B), phosphorus (P), titanium (Ti), zirconium (Zr), niobium (Nb), antimony (Sb), tantalum (Ta), molybdenum (Mo), and tungsten (W).
  • a fourth aspect of the present application provides a method for preparing an electrode material precursor, comprising:
  • the first raw material liquid further includes a doping element source that promotes grain growth, and/or the second raw material liquid further includes a doping element source that inhibits grain growth;
  • a second coprecipitation reaction is performed under an inert atmosphere to form a shell layer on the surface of the core layer of the electrode material precursor to obtain the electrode material precursor.
  • the doping element source that promotes grain growth includes a compound containing one or more doping elements selected from strontium (Sr), cerium (Ce), bismuth (Bi), and magnesium (Mg); the doping element source that inhibits grain growth includes a compound containing one or more doping elements selected from boron (B), phosphorus (P), titanium (Ti), zirconium (Zr), niobium (Nb), antimony (Sb), tantalum (Ta), molybdenum (Mo), and tungsten (W).
  • strontium Sr
  • Ce cerium
  • Bi bismuth
  • Mg magnesium
  • the doping element source that inhibits grain growth includes a compound containing one or more doping elements selected from boron (B), phosphorus (P), titanium (Ti), zirconium (Zr), niobium (Nb), antimony (Sb), tantalum (Ta), molybdenum (Mo), and tungsten (W).
  • a fifth aspect of the embodiments of the present application provides an electrode sheet, comprising a current collector and an electrode active layer arranged on the surface of the current collector, wherein the electrode active layer comprises the electrode material described in the first aspect of the embodiments of the present application.
  • a sixth aspect of the embodiments of the present application provides a battery, which includes the electrode material described in the first aspect of the embodiments of the present application, or includes the electrode sheet described in the fifth aspect of the embodiments of the present application.
  • An embodiment of the present application also provides a device, which includes the battery described in the sixth aspect of the embodiment of the present application.
  • the device includes an electronic device, an energy storage system or a vehicle.
  • FIG1 is a schematic diagram of the stacking structure of primary crystal grains of an existing polycrystalline positive electrode material 10;
  • FIG2 is a schematic diagram of the cross-sectional structure of an electrode material 100 provided in an embodiment of the present application.
  • FIG3 is a schematic diagram of the inner and outer layer distribution of a spherical electrode material 100 in one embodiment of the present application;
  • FIG4 is a schematic diagram showing the distribution of the inner layer and the outer layer of the quasi-spherical electrode material 100 in one embodiment of the present application;
  • FIG5 is a schematic diagram of a three-dimensional structure of an electrode material precursor 200 provided in an embodiment of the present application.
  • FIG6 is a schematic structural diagram of an electrode sheet 300 provided in an embodiment of the present application.
  • FIG. 7 is a schematic diagram of the structure of a battery 400 provided in an embodiment of the present application.
  • FIG8 is a schematic diagram of the structure of an apparatus 500 provided in an embodiment of the present application.
  • FIG9 is a schematic diagram of the structure of an apparatus 500 provided in another embodiment of the present application.
  • FIG10 is a schematic diagram of the structure of a device 500 provided in yet another embodiment of the present application.
  • FIG. 11 shows the results of crack extension lengths at different numbers of cycles for Example 1 of the present application and Comparative Example 1.
  • FIG. 1 is a schematic diagram of the stacking structure of the primary grains of the existing polycrystalline positive electrode material 10 .
  • the polycrystalline positive electrode material 10 is usually formed by the stacking and agglomeration of multiple primary grains 11 . Inside the polycrystalline positive electrode material 10 , there are grain boundaries 12 .
  • the grain boundaries 12 refer to the interfaces between the primary grains .
  • the change in the crystal structure of the material causes the volume of the lattice to change, resulting in the volume of the primary grains 11 constantly expanding and contracting during the charge and discharge process.
  • the volume strain caused by the insertion and removal of ions will accumulate at the grain boundaries 12 of the primary grains 11 , resulting in cracks in the secondary particles .
  • the secondary particles crack during the long cycle process, causing the material's cycle performance to decay and the internal resistance to increase.
  • a phase change occurs at the interface of the cracked secondary particles, resulting in an intensification of the electrolyte side reaction and a reduction in the material's cycle stability.
  • the present application provides an electrode material that can homogenize the stress distribution inside the secondary particles of the electrode material during the charge and discharge process, thereby suppressing the grain boundary cracking phenomenon to a certain extent, improving the material's cycle stability, and improving the battery performance.
  • FIG. 2 is a schematic diagram of the structure of the electrode material 100 provided in an embodiment of the present application, wherein the electrode material 100 includes secondary particles 100a formed by agglomerating a plurality of primary particles 101 (i.e., primary crystal grains), i.e., the electrode material 100 is a polycrystalline structure electrode material, and the secondary particles 100a include an inner layer 102 and an outer layer 103 coated on the outer side of the inner layer 102, wherein the average particle size of the primary particles 101a of the inner layer 102 is greater than the average particle size of the primary particles 101b of the outer layer 103.
  • the interface between the primary particles 101 constitutes a grain boundary 104.
  • the gray shaded area in FIG. 2 is used to indicate the area of the inner layer 102, and the area outside the gray shaded area is the area of the outer layer 103.
  • the electrode material 100 provided in the embodiment of the present application is structured such that the distribution of the primary particles 101 inside the secondary particles 100a is arranged such that the average particle size of the primary particles 101a in the inner layer 102 is greater than the average particle size of the primary particles 101b in the outer layer 103.
  • This structure can make the grain boundary density of the inner layer 102 of the secondary particles 100a smaller than the grain boundary density of the outer layer 103, thereby effectively dispersing the volume strain caused by the insertion and extraction of metal ions in the secondary particles 100a, homogenizing the stress distribution inside the secondary particles 100a, inhibiting the cracking of the grain boundaries 104, inhibiting the breakage of the secondary particles 100a, and improving the cyclic stability of the material.
  • this structure can make the metal ions more evenly distributed in the secondary particles 100a in the charged state, thereby effectively improving the rate performance of the material.
  • the secondary particles 100a are spherical or quasi-spherical particles.
  • the quasi-spherical shape is a shape close to a sphere, such as an ellipsoid.
  • the total radial distance between the center A of the secondary particle 100a and any point on the surface of the secondary particle 100a is defined as R, wherein the center A of the secondary particle 100a is the midpoint of the longest diameter (i.e., the longest diameter) of the secondary particle 100a, and the outer layer 103 refers to the area corresponding to the length extending from the surface of the secondary particle 100a to 20%-60%R toward the center A; and the inner layer 102 is the area corresponding to the length extending from the center A of the secondary particle 100a to 40%-80%R toward the surface.
  • the control of the inner layer 102 and the outer layer 103 regions of suitable size can make the area with a smaller grain boundary density inside the secondary particle controlled at a suitable proportion, thereby effectively inhibiting the grain boundary cracking of the secondary particle during the charge and discharge cycle, improving the structural stability, and at the same time ensuring that it has a better rate performance, thereby better balancing the rate performance and structural stability of the secondary particle.
  • the outer layer 103 may refer to the region corresponding to the length of 20%R, 25%R, 30%R, 35%R, 40%R, 45%R, 50%R, 55%R, 60%R extending from the surface of the secondary particle 100a to the center A; accordingly, the inner layer 102 is the region corresponding to the length of 80%R, 75%R, 70%R, 65%R, 60%R, 55%R, 50%R, 45%R, 40%R extending toward the surface.
  • the outer layer 103 refers to the region corresponding to the length of 30%R (i.e., 0.3R) extending from the surface of the secondary particle 100a to the center A (i.e., the region outside the dotted line in the figure); and the inner layer 102 is the region corresponding to the length of 70%R (i.e., 0.7R) extending from the center A of the secondary particle 100a to the surface (i.e., the region within the dotted line in the figure). area).
  • 30%R i.e., 0.3R
  • 70%R i.e., 0.7R
  • the total radial distance R between the center A of the secondary particle 100a and any point on the surface of the secondary particle 100a is equal to the value, R is the radius of the sphere, if the outer layer 103 refers to the area corresponding to the length from the surface of the secondary particle 100a to 30%R (i.e. 0.3R) extending toward the center A, and the inner layer 102 is the area corresponding to the length from the center A of the secondary particle 100a to 70%R (i.e.
  • the interface between the inner layer 102 and the outer layer 103 is a spherical surface corresponding to 0.7R proportionally reduced in each radial direction relative to the secondary particle 100a, the area from the interface to the surface of the secondary particle is the outer layer, and the area from the interface to the center of the secondary particle is the inner layer.
  • the total radial distance R between the center A of the secondary particle 100a and different points on the surface of the secondary particle 100a is not equal.
  • the interface between the inner layer 102 and the outer layer 103 is a spherical surface corresponding to 0.7R proportionally reduced in each radial direction of the secondary particle 100a.
  • interface I is the interface between the inner layer 102 and the outer layer 103.
  • the area from the interface to the surface of the secondary particle is the outer layer, and the area from the interface to the center of the secondary particle is the inner layer.
  • the interface between the inner layer 102 and the outer layer 103 may also be a non-spherical surface corresponding to the secondary particle 100a after being reduced in different proportions in each radial direction; for quasi-spherical secondary particles, the interface between the inner layer 102 and the outer layer 103 may also be a quasi-spherical surface corresponding to the secondary particle 100a after being reduced in different proportions in each radial direction.
  • the primary particles 101 constituting the secondary particles 100a may be spherical or quasi-spherical particles, or may be elongated particles, such as elongated particles with an aspect ratio of 1.1-4.
  • each primary particle 101 constituting the secondary particles 100a has a particle size, and the average particle size of the primary particles 101 is the average value of the particle sizes of the primary particles; wherein, when the aspect ratio of the primary particles 101 is less than 2:1, the particle size of the primary particles 101 refers to the longest diameter of the primary particles, and when the aspect ratio of the primary particles 101 is greater than or equal to 2:1, the particle size of the primary particles 101 refers to half of the sum of the longest diameter and the shortest diameter of the primary particles.
  • the particle size of the primary particle 101 can be specifically obtained by scanning electron microscopy characterization of the cross section of the secondary particle 100a.
  • the aspect ratio of the primary particle 101 in the cross section is less than 2:1, the longest diameter of the primary particle is recorded as the particle size of the primary particle 101.
  • the aspect ratio of the primary particle 101 in the cross section is greater than or equal to 2:1, half of the sum of the longest diameter and the shortest diameter of the primary particle is recorded as the particle size of the primary particle 101.
  • the average particle size of the primary particles 101a of the inner layer 102 is 0.01R’ to 1.4R’, that is, the average value of the particle size of each primary particle in the inner layer 102 is 0.01R’ to 1.4R’.
  • the average particle size of the primary particles 101b of the outer layer 103 is 0.001R’ to 0.3R’, that is, the average value of the particle size of each primary particle in the outer layer 103 is 0.001R’ to 0.3R’.
  • R’ is half of the longest diameter of the secondary particle 100a.
  • the average particle size of the primary particles 101 a of the inner layer 102 may be 50 nm to 7 ⁇ m, and the average particle size of the primary particles 101 b of the outer layer 103 may be 5 nm to 1.5 ⁇ m.
  • the average particle size of the primary particles 101a of the inner layer 102 can be 0.01R’, 0.02R’, 0.03R’, 0.05R’, 0.08R’, 0.1R’, 0.15R’, 0.2R’, 0.3R’, 0.4R’, 0.5R’, 0.6R’, 0.7R’, 0.8R’, 0.9R’, 1.0R’, 1.1R’, 1.2R’, 1.3R’, 1.4R’, and the average particle size of the primary particles 101b of the outer layer 103 can be 0.001R’, 0.002R’, 0.005R’, 0.0 1R’, 0.02R’, 0.03R’, 0.04R’, 0.05R’, 0.06R’, 0.07R’, 0.08R’, 0.1R’, 0.15R’, 0.2R’, 0.25R’, 0.3R’, and the average particle size of the primary particles in the inner layer 102 and the outer layer 103 is controlled
  • the average particle size of the primary particles 101a of the inner layer 102 is greater than the average particle size of the primary particles 101b of the outer layer 103, that is, the inner layer 102 is formed by the aggregation of multiple primary particles 101a with relatively large average particle sizes, and the outer layer 103 is formed by the aggregation of multiple primary particles 101b with relatively small average particle sizes.
  • the secondary particles 100a can form a structure with a grain boundary density gradient distribution. Through boundary scale simulation, such a structure can effectively disperse the volume strain caused by ion insertion and extraction in the secondary particles, thereby inhibiting the growth of cracks.
  • the average particle size of the primary particles 101a of the inner layer 102 can be 1.1 to 15 times the average particle size of the primary particles 101b of the outer layer 103.
  • the average particle size of the primary particles 101a of the inner layer 102 may be 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2 times, 3 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, 11 times, 12 times, 13 times, 14 times, 15 times the average particle size of the primary particles 101b of the outer layer 103.
  • the average particle size of the primary particles 101a of the inner layer 102 is 2 to 10 times the average particle size of the primary particles 101b of the outer layer 103. In some embodiments, the average particle size of the primary particles 101a of the inner layer 102 is 1.5 to 3 times the average particle size of the primary particles 101b of the outer layer 103.
  • the average particle size of the primary particles 101 is 10nm-60 ⁇ m.
  • the average particle size of the primary particles 101a of the inner layer 102 is 200nm-60 ⁇ m.
  • the average particle size of the primary particles in the inner layer may be in the range of 800nm-3 ⁇ m.
  • the average particle size of the primary particles 101b in the outer layer 103 is 10nm-20 ⁇ m.
  • the average particle size of the primary particles in the outer layer may be in the range of 100nm-1.5 ⁇ m.
  • the inner layer 102 includes a doping element that promotes grain growth
  • the outer layer 103 includes a doping element that inhibits grain growth.
  • the doping element that promotes grain growth may include but is not limited to one or more of strontium (Sr), cerium (Ce), bismuth (Bi), and magnesium (Mg); the doping element that inhibits grain growth may include but is not limited to one or more of boron (B), phosphorus (P), titanium (Ti), zirconium (Zr), niobium (Nb), antimony (Sb), tantalum (Ta), molybdenum (Mo), and tungsten (W).
  • the doping element that promotes grain growth refers to an element that can promote the growth of primary grains during the formation of secondary particles, which is different from the elements contained in the inner electrode material compound itself; and the doping element that inhibits grain growth refers to an element that can inhibit the growth of primary grains and refine the grain size during the formation of secondary particles, which is different from the elements contained in the outer electrode material compound itself.
  • the secondary particles include the electrode material compound lithium nickel cobalt manganese oxide, and the secondary particles also include strontium (Sr) element doped in the inner layer 102 and titanium (Ti) element doped in the outer layer 103.
  • the above-mentioned specific elements can be doped in different regions inside and outside the electrode material precursor to adjust the average particle size of the primary grains in the calcined electrode material polycrystalline structure to have an inner and outer gradient distribution.
  • the inner layer 102 includes a doping element that promotes grain growth, and the outer layer 103 does not include a doping element that inhibits grain growth; in this embodiment, during the formation of secondary particles, the inner layer 102 can obtain primary particles with a larger average particle size than the outer layer 103 under the action of the doping element that promotes grain growth, forming a gradient distribution structure of the average particle size of the inner and outer primary particles.
  • the outer layer 103 includes a doping element that inhibits grain growth, and the inner layer 102 does not include a doping element that promotes grain growth; in this embodiment, during the formation of secondary particles, the outer layer 103 will obtain primary particles with a smaller average particle size than the inner layer 102 under the action of the doping element that inhibits grain growth, forming a gradient distribution structure of the average particle size of the inner and outer primary particles.
  • the inner layer 102 includes a doping element that promotes grain growth
  • the outer layer 103 includes a doping element that inhibits grain growth; in this embodiment, during the formation of secondary particles, a gradient distribution structure of the average particle size of the inner and outer primary particles can be obtained, in which the average particle size of the primary particles of the inner layer 102 and the outer layer 103 differs more.
  • the inner layer 102 may include a small amount of doping elements that inhibit grain growth diffused from the outer layer 103 due to element diffusion; in some embodiments of the present application, the outer layer 103 may also include a small amount of doping elements that promote grain growth diffused from the inner layer 102 due to element diffusion.
  • the total molar content of the doping elements that promote grain growth and the doping elements that inhibit grain growth in the secondary particles 100a is 0.1mol%-1mol%.
  • the total molar content of the doping elements that promote grain growth and the doping elements that inhibit grain growth in the secondary particles 100a can be, for example, 0.1mol%, 0.2mol%, 0.3mol%, 0.4mol%, 0.5mol%, 0.6mol%, 0.7mol%, 0.8mol%, 0.9mol%, 1mol%.
  • the total molar content of the doping elements that promote grain growth and the doping elements that inhibit grain growth in the secondary particles 100a is 0.2mol%-0.5mol%.
  • the control of the content of the doping elements can not only enable the secondary particles to obtain a structure with a gradient distribution of the average particle size of the inner and outer primary particles, but also better avoid the negative impact of the doping elements on the performance of the electrode material such as the capacity.
  • the average particle size of the secondary particles 100a is 1 ⁇ m-200 ⁇ m.
  • the average particle size of the secondary particles 100a can be, for example, 1 ⁇ m, 5 ⁇ m, 10 ⁇ m, 15 ⁇ m, 20 ⁇ m, 25 ⁇ m, 30 ⁇ m, 35 ⁇ m, 40 ⁇ m, 45 ⁇ m, 50 ⁇ m, 55 ⁇ m, 60 ⁇ m, 65 ⁇ m, 70 ⁇ m, 75 ⁇ m, 80 ⁇ m, 90 ⁇ m, 100 ⁇ m, 110 ⁇ m, 120 ⁇ m, 130 ⁇ m, 140 ⁇ m, 150 ⁇ m, 160 ⁇ m, 170 ⁇ m, 180 ⁇ m, 190 ⁇ m, 200 ⁇ m.
  • the electrode material may be a positive electrode material for a battery or a negative electrode material for a battery.
  • the electrode material may be a lithium-ion battery electrode material, a sodium-ion battery electrode material, a potassium-ion battery electrode material or a magnesium-ion battery electrode material.
  • the secondary particle 100a includes a metal oxide for a positive electrode of a battery.
  • the metal oxide for the positive electrode of a battery may be a metal oxide for a positive electrode of a lithium-ion battery, a metal oxide for a positive electrode of a sodium-ion battery, a metal oxide for a positive electrode of a potassium-ion battery or a metal oxide for a positive electrode of a magnesium-ion battery.
  • the metal oxide for the positive electrode of a battery may be a composite oxide containing an alkali metal or an alkaline earth metal.
  • the inner layer 102 and the outer layer 103 of the secondary particle 100a may include the same metal oxide for the positive electrode of a battery or may include different metal oxides for the positive electrode of a battery.
  • the metal oxide for the positive electrode of the lithium ion battery includes a lithium-containing composite oxide
  • the lithium-containing composite oxide includes lithium cobalt oxide (such as lithium cobaltate LiCoO2 ), lithium nickel oxide (such as lithium nickelate LiNiO2 ), lithium manganese oxide (such as lithium manganate LiMnO2 , lithium permanganate), lithium titanium oxide (such as lithium titanate), lithium iron phosphorus oxide (such as lithium iron phosphate), lithium nickel cobalt oxide (such as lithium nickel cobaltate LiNi a Co 1-a O 2 ), lithium nickel manganese oxide (for example, lithium nickel manganeseate LiNi a Mn 1-a O 2 ), nickel cobalt multi-element oxide (such as lithium nickel cobalt manganeseate LiNi a Co b Mn 1-ab O 2 , lithium nickel cobalt aluminum oxide LiNi a Co b Al 1-ab O 2 , lithium nickel cobalt manganese aluminum oxide LiNi a Co
  • the lithium-containing composite oxide may be a stoichiometric lithium-containing oxide or a non-stoichiometric lithium-containing oxide.
  • ⁇ may be greater than 0 and less than or equal to 2. Any value of , 0 ⁇ a ⁇ 1, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1, 0 ⁇ 1-abc ⁇ 1.
  • the metal oxide for the positive electrode of the sodium ion battery includes a sodium-containing composite oxide
  • the sodium-containing composite oxide includes a sodium-containing transition metal oxide, which may be one or more of sodium manganese oxide, sodium copper iron manganese oxide, sodium nickel iron manganese oxide, and sodium copper nickel iron manganese oxide.
  • the metal oxide for the positive electrode of the potassium ion battery includes a composite oxide containing potassium, and the composite oxide containing potassium may be, for example, potassium cobalt oxide, potassium manganese oxide, potassium iron manganese oxide, etc.
  • the metal oxide for the positive electrode of the magnesium ion battery includes a composite oxide containing magnesium, and the composite oxide containing magnesium may be, for example, magnesium vanadium oxide, magnesium cobalt manganese oxide, magnesium nickel manganese oxide, magnesium manganese oxide, magnesium iron manganese oxide, etc.
  • the outermost side of the outer layer 103 (i.e., the periphery away from the center of the secondary particle) contains oxides of doping elements that inhibit grain growth. This is mainly because the doping elements in the outer layer 103 are segregated to the surface of the secondary particles and oxidized to form. The formation of oxides of doping elements in the outermost side of the outer layer 103 is beneficial to improving the cyclic performance of the secondary particles and reducing surface side reactions.
  • a protective layer may be provided on the surface of the secondary particle 100a of the electrode material of the embodiment of the present application as required.
  • the protective layer may include, for example, a metal oxide, etc.
  • the metal oxide may be, for example, magnesium oxide, aluminum oxide, titanium dioxide, etc.
  • the protective layer may reduce the side reactions on the surface of the secondary particles and improve the cycle performance of the secondary particles.
  • the present application also provides a method for preparing an electrode material, comprising:
  • An electrode material precursor is mixed with a metal salt and then calcined to obtain an electrode material, wherein the electrode material precursor includes a core layer and a shell layer surrounding the core layer, the core layer includes a doping element that promotes grain growth, and/or the shell layer includes a doping element that inhibits grain growth; the electrode material includes secondary particles formed by aggregation of multiple primary particles, the secondary particles include an inner layer and an outer layer covering the inner layer, wherein the average particle size of the primary particles in the inner layer is greater than the average particle size of the primary particles in the outer layer.
  • calcination includes a first calcination and a second calcination performed sequentially, and the temperature of the first calcination is higher than the temperature of the second calcination.
  • the first calcination is a high-temperature calcination
  • the temperature (T1) is 600°C-1000°C
  • the second calcination is a medium-temperature calcination
  • the temperature (T2) is 400°C-800°C.
  • the temperature of the first calcination is more than 100°C higher than the temperature of the second calcination.
  • the time of the second calcination is longer than the time of the first calcination.
  • the time of the first calcination can be 2-4 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours; the time of the second calcination can be 6-14 hours, such as 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours.
  • the crystals can be rapidly nucleated, and the long-term calcination in the medium-temperature calcination area can allow the primary grain size to grow slowly.
  • the two-stage calcination can increase the particle size of the primary grains while reducing the surface mixing of the material.
  • the metal salt includes a lithium salt, a sodium salt, a potassium salt or a magnesium salt.
  • the type of metal salt is determined according to the type of electrode material to be prepared in the end. For example, if the electrode material of a lithium-ion battery is pre-prepared, the metal salt is a lithium salt, which can be one or more of lithium nitrate, lithium hydroxide and lithium carbonate; the lithium salt can be added according to the molar ratio of non-lithium metal (such as transition metal Ni, Co, Mn, etc.) to lithium in the electrode material precursor of 1: (1 to 1.1), and the content of transition metal elements in the electrode material precursor can be obtained by ICP (Inductive Coupled Plasma Emission Spectrometer) characterization.
  • ICP Inductive Coupled Plasma Emission Spectrometer
  • the metal salt is a sodium salt, which can be one or more of sodium nitrate, sodium hydroxide, sodium carbonate and sodium supplement; if the electrode material of a potassium-ion battery is pre-prepared, the metal salt is a potassium salt, which can be one or more of potassium nitrate, potassium hydroxide and potassium carbonate; if the electrode material of a magnesium-ion battery is pre-prepared, the metal salt is a magnesium salt, which can be one or more of magnesium nitrate, magnesium hydroxide and magnesium carbonate.
  • the type of electrode material precursor is determined according to the type of electrode material that is ultimately desired to be prepared. For example, if a lithium-ion battery electrode material is pre-prepared, the electrode material precursor is a lithium-ion battery electrode material precursor; if a sodium-ion battery electrode material is pre-prepared, the electrode material precursor is a sodium-ion battery electrode material precursor; if a potassium-ion battery electrode material is pre-prepared, the electrode material precursor is a potassium-ion battery electrode material precursor; if a magnesium-ion battery electrode material is pre-prepared, the electrode material precursor is a magnesium-ion battery electrode material precursor.
  • the present application also provides an electrode material precursor 200, wherein the electrode material precursor 200 includes a core layer 201 and a shell layer 202 enclosing the core layer 201, that is, the core layer 201 is inside and the shell layer 202 is outside, wherein the core layer 201 includes a doping element that promotes grain growth, and/or the shell layer 202 includes a doping element that inhibits grain growth.
  • the electrode material precursor used in the above-mentioned method for preparing the electrode material may be the electrode material precursor 200.
  • the core layer 201 corresponds to the inner layer 102 of the secondary particle 100a of the aforementioned electrode material 100
  • the shell layer 202 corresponds to the outer layer 103 of the secondary particle 100a of the aforementioned electrode material 100.
  • the total radial distance between the center B of the electrode material precursor 200 and any point on the surface of the electrode material precursor 200 particle is defined as r, wherein the center B of the electrode material precursor 200 is the midpoint of the longest diameter (i.e., the longest diameter) of the electrode material precursor 200, and the shell layer 202 refers to the area corresponding to the length from the surface of the electrode material precursor 200 to the center B extending 20%-60% r; and the inner layer 102 is the area corresponding to the length from the center B of the electrode material precursor 200 to the surface extending 40%-80% r.
  • the specific division of the core layer 201 and the shell layer 202 can refer to the secondary particle of the electrode material 100 mentioned above. The division of the inner layer 102 and the outer layer 103 of the particle 100a will not be repeated here.
  • the core layer 201 includes a doping element that promotes grain growth
  • the shell layer 202 includes a doping element that inhibits grain growth.
  • the doping element that promotes grain growth may include but is not limited to one or more of strontium (Sr), cerium (Ce), bismuth (Bi), and magnesium (Mg); the doping element that inhibits grain growth may include but is not limited to one or more of boron (B), phosphorus (P), titanium (Ti), zirconium (Zr), niobium (Nb), antimony (Sb), tantalum (Ta), molybdenum (Mo), and tungsten (W).
  • the doping element that promotes grain growth refers to an element that can promote the growth of primary grains during the formation of secondary particles of the electrode material, which is different from the elements contained in the precursor compound of the core layer electrode material itself; and the doping element that inhibits grain growth refers to an element that can inhibit the growth of primary grains during the formation of secondary particles of the electrode material, which is different from the elements contained in the precursor compound of the shell layer electrode material itself.
  • the electrode material precursor includes the electrode material precursor compound itself, nickel cobalt manganese hydroxide, and also includes strontium (Sr) element doped in the core layer 201 , and titanium (Ti) element doped in the shell layer 202 .
  • the core layer 201 includes doping elements that promote grain growth, and the shell layer 202 does not include doping elements that inhibit grain growth. In other embodiments of the present application, the shell layer 202 includes doping elements that inhibit grain growth, and the core layer 201 does not include doping elements that promote grain growth. In other embodiments of the present application, the core layer 201 includes doping elements that promote grain growth, and the shell layer 202 includes doping elements that inhibit grain growth.
  • the total molar content of the doping elements that promote grain growth and the doping elements that inhibit grain growth in the electrode material precursor 200 is 0.1mol%-1mol%.
  • the total molar content of the doping elements that promote grain growth and the doping elements that inhibit grain growth in the electrode material precursor 200 can be, for example, 0.1mol%, 0.2mol%, 0.3mol%, 0.4mol%, 0.5mol%, 0.6mol%, 0.7mol%, 0.8mol%, 0.9mol%, 1mol%.
  • the total molar content of the doping elements that promote grain growth and the doping elements that inhibit grain growth in the electrode material precursor 200 is 0.2mol%-0.5mol%.
  • the embodiment of the present application dopes the above-mentioned specific elements in the preset inner and outer areas of the electrode material precursor to control the gradient distribution structure of the average particle size of the primary particles in the calcined polycrystalline structure of the electrode material to be large inside and small outside.
  • This can effectively improve the grain boundary cracking phenomenon of the electrode material during the charge and discharge cycle, enhance the cycle stability of the secondary particles of the electrode material, and at the same time, evenly distribute the concentration of cations (such as lithium ions) in the electrode material under the charging state, thereby improving the rate performance of the electrode material.
  • the electrode material precursor is used to prepare the electrode material having the above-mentioned characteristics, and the process is simple and controllable.
  • the electrode material precursor 200 may be a lithium ion battery electrode material precursor, a sodium ion battery electrode material precursor, a potassium ion battery electrode material precursor, or a magnesium ion battery electrode material precursor.
  • the electrode material precursor 200 includes a metal oxide precursor for a positive electrode of a battery.
  • the metal oxide precursor for a positive electrode of a battery may specifically include a hydroxide precursor of a metal oxide used in a positive electrode of a lithium ion battery, a sodium ion battery, a potassium ion battery, or a magnesium ion battery, an oxide precursor of a metal oxide, a carbonate precursor of a metal oxide, or a hydroxyl oxide precursor of a metal oxide.
  • the electrode material precursor may include Ni x Co y Mn 1-xy (OH) 2 , Ni x Co y Al 1-xy (OH) 2 , Ni x Co y Mn z Al 1-xyz (OH) 2 , etc.; wherein 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, 0 ⁇ 1-xy ⁇ 1, 0 ⁇ 1-xyz ⁇ 1.
  • the electrode material precursor 200 includes particles formed of the compound Ni x Co y Mn 1-xy (OH) 2 , the core layer of the particles contains a doping element strontium (Sr), and the shell layer contains a doping element titanium (Ti).
  • the present application also provides a method for preparing an electrode material precursor, comprising:
  • the first raw material liquid further includes a doping element source that promotes grain growth, and/or the second raw material liquid further includes a doping element source that inhibits grain growth;
  • a second coprecipitation reaction is performed under an inert atmosphere to form a shell layer on the surface of the core layer of the electrode material precursor to obtain the electrode material precursor.
  • the metal source solution of the core layer of the electrode material precursor is a solution containing the metal element of the core layer of the electrode material precursor.
  • the metal source solution of the shell layer of the electrode material precursor is a solution containing the metal element of the shell layer of the electrode material precursor.
  • the metal source solution is a solution containing a nickel source, a cobalt source, and a manganese source.
  • the metal source is a soluble metal salt, for example, the nickel source is a soluble nickel salt, specifically nickel sulfate, etc.; the cobalt source is a soluble cobalt salt, specifically cobalt sulfate, etc.; the manganese source is a soluble manganese salt, specifically manganese sulfate, etc.
  • a doping element source that promotes grain growth includes a compound containing one or more doping elements of strontium (Sr), cerium (Ce), bismuth (Bi), and magnesium (Mg); specifically, the doping element source that promotes grain growth may be a metal salt containing one or more doping elements of strontium (Sr), cerium (Ce), bismuth (Bi), and magnesium (Mg); for example, strontium salts, cerium salts, bismuth salts, and magnesium salts.
  • a doping element source that inhibits grain growth includes a compound containing one or more doping elements of boron (B), phosphorus (P), titanium (Ti), zirconium (Zr), niobium (Nb), antimony (Sb), tantalum (Ta), molybdenum (Mo), and tungsten (W).
  • the doping element source that inhibits grain growth may be a metal salt containing one or more doping elements of boron (B), phosphorus (P), titanium (Ti), Metal salts of one or more doping elements selected from zirconium (Zr), niobium (Nb), antimony (Sb), tantalum (Ta), molybdenum (Mo), and tungsten (W); for example, boron salts, phosphorus salts, titanium salts, zirconium salts, niobium salts, antimony salts, tantalum salts, molybdenum salts, and tungsten salts.
  • B boron
  • P phosphorus
  • Ti titanium
  • the first raw material liquid includes a doping element source that promotes grain growth, and the second raw material liquid does not include a doping element source that inhibits grain growth.
  • the second raw material liquid includes a doping element source that inhibits grain growth, and the first raw material liquid does not include a doping element source that promotes grain growth.
  • the first raw material liquid includes a doping element source that promotes grain growth, and at the same time, the second raw material liquid includes a doping element source that inhibits grain growth.
  • the precipitant may be a sodium hydroxide solution, and the molar concentration of the sodium hydroxide solution may be 2mol/L-4mol/L; the complexing agent may be an ammonia solution, and the mass concentration of the ammonia solution may be 8%-12%.
  • the pH of the first raw material liquid and the second raw material liquid may be controlled at 10.0-12.0 by ammonia water.
  • the inert atmosphere may be, for example, a nitrogen atmosphere.
  • an embodiment of the present application further provides an electrode sheet 300, the electrode sheet 300 includes a current collector 301 and an electrode active layer 302 disposed on the current collector 301, and the electrode active layer 302 includes the electrode material 100 described above in the present application.
  • the current collector 301 may be aluminum foil, etc.
  • the electrode active layer 302 may also include a conductive agent, a binder, etc.
  • the embodiment of the present application further provides a battery 400, and the battery 400 includes the electrode sheet provided in the embodiment of the present application, that is, includes the electrode material 100 provided in the embodiment of the present application.
  • the battery 400 may be a lithium ion secondary battery, a sodium ion secondary battery, a potassium ion secondary battery, a magnesium ion secondary battery, etc.
  • the battery 400 includes a positive electrode sheet 401, a negative electrode sheet 402, an electrolyte 403, and a separator 404.
  • lithium ions are released from the positive electrode active material, embedded in the negative electrode through the electrolyte separator, and at the same time, the positive electrode loses electrons and flows out from the external circuit through the current collector; the discharge process is the opposite, lithium ions are released from the negative electrode and return to the positive electrode, and at the same time, electrons move from the negative electrode to the positive electrode through the external circuit and do work externally.
  • the present application also provides a device 500, which includes the battery 400 provided in the embodiment of the present application.
  • the device 500 can select different electrochemical devices, such as batteries, battery modules or battery packs, according to actual use requirements.
  • the device 500 is an electronic device, which can be various consumer electronic products, such as mobile phones, tablet computers, mobile power supplies, portable computers, laptop computers and other wearable or movable electronic devices, televisions, DVD players, video recorders, camcorders, radios, recorders, combination audio systems, record players, laser record players, home office equipment, and home electronic health care equipment.
  • the electronic device includes the battery 400 provided in the embodiment of the present application, and the battery 400 is used to power the electronic device.
  • the device 500 is a vehicle, which includes the battery 400 provided in the embodiment of the present application, and the battery 400 is used to power the vehicle.
  • the vehicle can be a pure electric vehicle, a hybrid electric vehicle, an electric bicycle, an electric scooter, and other forms of electric vehicles.
  • the device 500 is an energy storage system, which includes a battery pack 501 and a battery management system 502 electrically connected to the battery pack 501 , and the battery pack 501 includes the battery 400 provided in the above-mentioned embodiment of the present application.
  • (1-1) preparing a nickel-cobalt-manganese metal salt solution: dissolving nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn of 82:12:6 to prepare a 2 mol/L uniformly mixed nickel-cobalt-manganese metal salt solution; preparing an ammonia solution with a mass concentration of 10 wt.% and a sodium hydroxide solution with a concentration of 4 mol/L; preparing a strontium salt solution with a molar concentration of 0.05 mol/L; preparing a titanium salt solution with a molar concentration of 0.05 mol/L;
  • a positive electrode material precursor Ni 0.82 Co 0.12 Mn 0.06 (OH) 2 which includes a core layer and a shell layer covering the outer side of the core layer, wherein the core layer is doped with elemental strontium (Sr) and the shell layer is doped with elemental titanium (Ti).
  • the polycrystalline positive electrode material, polyvinylidene fluoride (PVDF) and conductive agent super P are added to N-methylpyrrolidone (NMP) in a mass ratio of 90:5:5, and the mixture is fully stirred to obtain a slurry.
  • NMP N-methylpyrrolidone
  • the slurry is coated on an aluminum foil current collector, and the positive electrode sheets are obtained by drying, cold pressing and slitting.
  • the prepared positive electrode sheet, lithium sheet, electrolyte (1 mol/L LiPF 6 ) and separator were made into 2032 button cells.
  • the synthesis of the lithium-ion battery positive electrode material precursor Ni 0.82 Co 0.12 Mn 0.06 (OH) 2 the difference between comparative example 1 and example 1 is that, in comparative example 1, the strontium salt solution and the titanium salt solution in step (3) and step (4) are not added in stages, but the strontium salt solution and the titanium salt solution are evenly mixed and then added in one step, and other operations are the same.
  • the final precursor Ni 0.82 Co 0.12 Mn 0.06 (OH) 2 has uniform strontium and titanium doping in the entire particle.
  • the positive electrode material precursor Ni 0.82 Co 0.12 Mn 0.06 (OH) 2 of Comparative Example 1 was used to prepare the positive electrode material LiNi 0.82 Co 0.12 Mn 0.06 O 2 .
  • Example 1 According to the same method as in Example 1, a positive electrode sheet and a lithium ion battery were prepared using the positive electrode material LiNi 0.82 Co 0.12 Mn 0.06 O 2 of Comparative Example 1.
  • the positive electrode material precursor particles and polycrystalline positive electrode material particles prepared in Example 1 were cut by FIB (Focused Ion beam).
  • the cross-sections of the positive electrode material precursor particles and polycrystalline positive electrode material particles of Example 1 were observed by EDS energy-dispersive X-ray spectroscopy, and it can be observed that there are obvious signals of titanium elements on the outside of the cross-sections of the positive electrode material precursor particles and polycrystalline positive electrode material particles, and obvious signals of strontium elements on the inside of the cross-sections.
  • the cross-sectional morphological characteristics of the polycrystalline positive electrode material of Example 1 were observed by SEM (Scanning electron microscope), and it can be observed that the average particle size of the primary particles on the inside of the cross-section of the polycrystalline positive electrode material is significantly larger than the average particle size of the primary particles on the outside, and the grain boundary distribution on the outside of the cross-section is significantly denser than the grain boundary distribution on the inside of the cross-section.
  • the positive electrode material precursor particles and polycrystalline positive electrode material particles prepared in Comparative Example 1 were cut by FIB.
  • EDS By observing the cross-section of the positive electrode material precursor particles and polycrystalline positive electrode material particles of Comparative Example 1 by EDS, it can be observed that the signals of strontium and titanium are evenly distributed inside and outside the cross-section of the positive electrode material precursor particles and polycrystalline positive electrode material particles.
  • SEM By observing the cross-sectional morphology characteristics of the polycrystalline positive electrode material of Comparative Example 1 by SEM, it can be observed that the particle size of the primary grains inside and outside the cross-section of the polycrystalline positive electrode material is uniform.
  • Example 1 The batteries prepared in Example 1 and Comparative Example 1 were charged and discharged at 25 ⁇ 5°C at charge and discharge rates of 0.1C/0.1C and 1C/1C in the voltage range of 3.0V-4.3V, and the first cycle charge and discharge capacity and 100 cycle retention rate of the batteries were recorded. The results are shown in Table 1.
  • the embodiment of the present application uses step-by-step doping to dope the core layer and shell layer of the positive electrode material precursor material with different specific elements, so that in the process of forming the secondary particles of the polycrystalline positive electrode material, under the action of the above-mentioned specific doping elements, the average particle size of the primary particles of the inner layer of the finally obtained polycrystalline positive electrode material can be greater than the average particle size of the primary particles of the outer layer, that is, a structure with a gradient distribution of the average particle size of the inner and outer primary particles is formed.
  • the electrode material of the embodiment of the present application with a gradient distribution structure of the average particle size of the inner and outer primary particles can effectively improve the problem of deterioration of the cycle performance of the secondary particles of the electrode material caused by grain boundary cracking.
  • the positive electrode material of Example 1 of the present application has better rate performance and capacity retention rate than that of Comparative Example 1.
  • Example 1 and Comparative Example 1 were disassembled at different discharge states after 100 cycles, and the cross-sections of the positive electrode material particles were characterized by scanning electron microscopy (SEM), and the results are shown in Figure 11, which shows the results of crack extension lengths at different cycle numbers for Example 1 and Comparative Example 1. As shown in Figure 11, with the increase in the number of cycles, the cracks inside the secondary particles gradually increase, but the crack growth rate of Example 1 is much lower than that of Comparative Example 1.
  • (1-1) preparing a nickel-cobalt-manganese metal salt solution: dissolving nickel sulfate, iron sulfate and manganese sulfate in a molar ratio of Ni, Fe and Mn of 1:1:1 to prepare a 2 mol/L uniformly mixed nickel-cobalt-manganese metal salt solution;
  • a positive electrode material precursor Ni 0.33 Fe 0.33 Mn 0.33 (OH) 2 which includes a core layer and a shell layer covering the outer side of the core layer, wherein the core layer is doped with elemental magnesium (Mg) and the shell layer is doped with elemental tungsten (W).
  • the cathode material precursor Ni 0.33 Fe 0.33 Mn 0.33 (OH) 2 prepared above is fully mixed with sodium hydroxide to obtain a mixture, wherein the sodium hydroxide is added in a molar ratio of transition metals (including Ni, Fe, and Mn) in the precursor to sodium in the sodium hydroxide of 1:1.01;
  • the polycrystalline positive electrode material, polyvinylidene fluoride (PVDF) and conductive agent super P are added to N-methylpyrrolidone (NMP) in a mass ratio of 90:5:5, and the mixture is fully stirred to obtain a slurry.
  • NMP N-methylpyrrolidone
  • the slurry is coated on an aluminum foil current collector, and the positive electrode sheets are obtained by drying, cold pressing and slitting.
  • the prepared positive electrode sheet, sodium sheet, electrolyte (1 mol/L NaPF 6 ) and separator were made into 2032 button cells.
  • the synthesis of the sodium ion battery positive electrode material precursor Ni 0.33 Fe 0.33 Mn 0.33 (OH) 2 the difference between Comparative Example 2 and Example 2 is that, in Comparative Example 2, the magnesium salt solution and the tungsten salt solution in step (3) and step (4) are not added in stages, but the magnesium salt solution and the tungsten salt solution are evenly mixed and then added in one step, and other operations are the same.
  • the final precursor Ni 0.33 Fe 0.33 Mn 0.33 (OH) 2 has uniform magnesium and tungsten doping in the entire particle.
  • the cathode material precursor Ni 0.33 Fe 0.33 Mn 0.33 (OH) 2 of Comparative Example 2 was used to prepare the cathode material NaNi 0.33 Fe 0.33 Mn 0.33 O 2 .
  • Example 2 According to the same method as in Example 2, a positive electrode sheet and a sodium ion battery were prepared using the positive electrode material NaNi 0.33 Fe 0.33 Mn 0.33 O 2 of Comparative Example 2.
  • the positive electrode material precursor particles and polycrystalline positive electrode material particles prepared in Example 2 were cut by FIB. By observing the cross-section of the positive electrode material precursor particles and polycrystalline positive electrode material particles of Example 2 by EDS, it can be observed that there are obvious tungsten element signals on the outside of the cross-section of the positive electrode material precursor particles and the polycrystalline positive electrode material particles, and obvious magnesium element signals on the inside of the cross-section.
  • the average particle size of the primary particles on the inside of the cross-section of the polycrystalline positive electrode material is significantly larger than the average particle size of the primary particles on the outside, and the grain boundary distribution on the outside of the cross-section is significantly denser than the grain boundary distribution on the inside of the cross-section.
  • the positive electrode material precursor particles and polycrystalline positive electrode material particles prepared in Comparative Example 2 were cut by FIB.
  • EDS By observing the cross-section of the positive electrode material precursor particles and polycrystalline positive electrode material particles of Comparative Example 2 by EDS, it can be observed that the signals of tungsten and magnesium are evenly distributed inside and outside the cross-section of the positive electrode material precursor particles and polycrystalline positive electrode material particles.
  • SEM By observing the cross-sectional morphology characteristics of the polycrystalline positive electrode material of Comparative Example 2 by SEM, it can be observed that the particle size of the primary grains inside and outside the cross-section of the polycrystalline positive electrode material is uniform.
  • Example 2 The batteries prepared in Example 2 and Comparative Example 2 were charged and discharged at 25 ⁇ 5°C at charge and discharge rates of 0.1C/0.1C and 1C/1C in the voltage range of 3.0V-4.3V, and the first cycle charge and discharge capacity and 100 cycle retention rate of the batteries were recorded. The results are shown in Table 2.
  • the embodiment of the present application uses step-by-step doping to dope the core layer and shell layer of the positive electrode material precursor material with different specific elements, so that in the process of forming the secondary particles of the polycrystalline positive electrode material, under the action of the above-mentioned specific doping elements, the average particle size of the primary particles of the inner layer of the polycrystalline positive electrode material finally obtained can be greater than the average particle size of the primary particles of the outer layer, that is, a structure with a gradient distribution of the average particle size of the inner and outer primary particles is formed.
  • the electrode material of the embodiment of the present application with a gradient distribution structure of the average particle size of the inner and outer primary particles can effectively improve the problem of deterioration of the cycle performance of the secondary particles of the electrode material caused by grain boundary cracking.
  • the positive electrode material of Example 2 of the present application has better rate performance and capacity retention rate than that of Comparative Example 2.
  • (1-1) preparing a nickel-cobalt-manganese metal salt solution: dissolving nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of Ni:Co:Mn of 82:12:6 to prepare a 2 mol/L uniformly mixed nickel-cobalt-manganese metal salt solution; preparing an ammonia solution with a mass concentration of 10 wt.% and a sodium hydroxide solution with a concentration of 4 mol/L; preparing a strontium salt solution with a molar concentration of 0.05 mol/L;
  • a positive electrode material precursor Ni 0.82 Co 0.12 Mn 0.06 (OH) 2 which includes a core layer and a shell layer covering the outer side of the core layer.
  • the core layer is doped with element strontium (Sr), and the shell layer does not have any doping elements.
  • the polycrystalline positive electrode material, polyvinylidene fluoride (PVDF) and conductive agent super P are added to N-methylpyrrolidone (NMP) in a mass ratio of 90:5:5, and the mixture is fully stirred to obtain a slurry.
  • NMP N-methylpyrrolidone
  • the slurry is coated on an aluminum foil current collector, and the positive electrode sheets are obtained by drying, cold pressing and slitting.
  • the prepared positive electrode sheet, lithium sheet, electrolyte (1 mol/L LiPF 6 ) and separator were made into 2032 button cells.
  • the positive electrode material precursor Ni 0.82 Co 0.12 Mn 0.06 (OH) 2 of Comparative Example 3 was used to prepare the positive electrode material LiNi 0.82 Co 0.12 Mn 0.06 O 2 .
  • Example 3 According to the same method as in Example 3, a positive electrode sheet and a lithium ion battery were prepared using the positive electrode material LiNi 0.82 Co 0.12 Mn 0.06 O 2 of Comparative Example 3.
  • the positive electrode material precursor particles and polycrystalline positive electrode material particles prepared in Example 3 were cut by FIB.
  • the cross-sections of the positive electrode material precursor particles and polycrystalline positive electrode material particles in Example 3 were observed by EDS. It can be observed that there is obvious Sr element on the inner side of the cross-section.
  • SEM SEM
  • the positive electrode material precursor particles and polycrystalline positive electrode material particles prepared in Comparative Example 3 were cut by FIB.
  • EDS By observing the cross-section of the positive electrode material precursor particles and polycrystalline positive electrode material particles of Comparative Example 3 by EDS, it can be observed that the Sr signal is evenly distributed inside and outside the cross-section of the positive electrode material precursor particles and the polycrystalline positive electrode material particles.
  • SEM By observing the cross-sectional morphology of the polycrystalline positive electrode material of Comparative Example 3 by SEM, it can be observed that the particle size of the primary grains inside and outside the cross-section of the polycrystalline positive electrode material is uniform.
  • Example 3 The batteries prepared in Example 3 and Comparative Example 3 were charged and discharged at 25 ⁇ 5°C at charge and discharge rates of 0.1C/0.1C and 1C/1C in the voltage range of 3.0V-4.3V, and the first cycle charge and discharge capacity and 100 cycle retention rate of the batteries were recorded. The results are shown in Table 3.
  • the embodiment of the present application dopes the positive electrode material precursor material so that only the core layer is doped with the Sr element. Therefore, in the process of forming the secondary particles of the polycrystalline positive electrode material, under the action of the Sr element, the average particle size of the primary particles of the inner layer of the finally obtained polycrystalline positive electrode material can be greater than the average particle size of the primary particles of the outer layer, that is, a structure with a gradient distribution of the average particle sizes of the inner and outer primary particles is formed.
  • the electrode material of the embodiment of the present application with a gradient distribution structure of the average particle size of the inner and outer primary particles can effectively improve the problem of deterioration of the cycle performance of the secondary particles of the electrode material caused by grain boundary cracking.
  • the positive electrode material of Example 3 of the present application has better rate performance and capacity retention rate than that of Comparative Example 3.
  • At least one means one or more
  • plural means two or more.
  • At least one of the following” or similar expressions refers to any combination of these items, including any combination of single or plural items.
  • at least one of a, b, or c or “at least one of a, b, and c” can all mean: a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, where a, b, c can be single or multiple, respectively.
  • the size of the serial numbers of the above-mentioned processes does not limit the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

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Abstract

本申请实施例提供一种电极材料，所述电极材料包括由多个一次颗粒聚集而成的二次颗粒，所述二次颗粒包括内层和包覆于所述内层外侧的外层，其中，所述内层的一次颗粒的平均粒径大于所述外层的一次颗粒的平均粒径。该电极材料能够均匀化二次颗粒在充放电过程中的应力分布，从而一定程度抑制晶界开裂现象，提升材料的循环稳定性，改善电池性能。本申请实施例还提供了该电极材料的制备方法，以及电极材料前驱体及其制备方法。

Description

电极材料及其制备方法，电极材料前驱体及其制备方法
本申请要求于2022年9月27日提交中国专利局、申请号为202211183797.4、申请名称为“电极材料及其制备方法，电极材料前驱体及其制备方法”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请实施例涉及二次电池技术领域，特别是涉及电极材料及其制备方法，电极材料前驱体及其制备方法。
背景技术
随着智能手机和电动汽车的大量普及，电池性能的提升越来越受到业界关注。目前商业化锂离子电池主要由正极材料、负极材料、电解液和隔膜组成，其中，正极材料和负极材料的电化学性能直接影响到电池的最终性能。
三元多晶正极材料由于容量高，循环性能好，价格适中，被认为是电动汽车正极材料的最优选择之一。然而，相比钴酸锂和磷酸铁锂这两类正极材料，三元多晶正极材料在电池充放电过程中，由于材料相变导致的各向异性的晶格变化，使材料内部应力分布不均匀，容易出现晶界开裂，导致二次颗粒发生破碎，比表面积和界面副反应快速增加，最终导致电池阻抗上升，性能快速下降。因此，有必要提供一种多晶正极材料，能够均匀化多晶正极材料在充放电过程中的应力分布从而抑制晶界开裂现象，改善电池性能。
发明内容
鉴于此，本申请实施例提供一种电极材料，该电极材料能够均匀化二次颗粒在充放电过程中的应力分布，从而一定程度抑制晶界开裂现象，提升材料的循环稳定性，改善电池性能。
具体地，本申请实施例第一方面提供一种电极材料，所述电极材料包括由多个一次颗粒聚集而成的二次颗粒，所述二次颗粒包括内层和包覆于所述内层外侧的外层，其中，所述内层的一次颗粒的平均粒径大于所述外层的一次颗粒的平均粒径。
本申请实施例提供的电极材料通过将二次颗粒内部的一次颗粒分布设置为：内层的一次颗粒的平均粒径大于外层的一次颗粒的平均粒径，该结构可以使二次颗粒内层的晶界密度小于外层的晶界密度，从而可以有效地分散二次颗粒中由金属离子嵌入脱出造成的体积应变，均匀化二次颗粒内部的应力分布，抑制晶界开裂，抑制二次颗粒发生破碎，提升材料的循环稳定性能；同时，该结构可以使得充电状态下金属离子在二次颗粒中分布更均匀，从而有效提高材料的倍率性能。
本申请实施方式中，所述二次颗粒为球形或类球形颗粒。类球形即近似于球形的形状。
本申请实施方式中，所述二次颗粒的中心与所述二次颗粒的表面上任意一点之间的总径向距离为R，所述外层为从所述二次颗粒的表面至朝向中心延伸20％-60％所述R的长度所对应的区域；所述内层为从所述二次颗粒的中心至朝向表面延伸40％-80％所述R的长度所对应的区域。
本申请实施方式中，所述内层的一次颗粒的平均粒径为0.01R’至1.4R’，所述R’为所述二次颗粒的最长径的一半。
本申请实施方式中，所述外层的一次颗粒的平均粒径为0.001R’至0.3R’，所述R’为所述二次颗粒的最长径的一半。
本申请实施方式中，所述内层包括促进晶粒生长的掺杂元素，和/或所述外层包括抑制晶粒生长的掺杂元素。
本申请实施方式中，所述促进晶粒生长的掺杂元素包括锶(Sr)，铈(Ce)、铋(Bi)、镁(Mg)中的一种或多种；所述抑制晶粒生长的掺杂元素包括硼(B)、磷(P)、钛(Ti)、锆(Zr)、铌(Nb)、锑(Sb)、钽(Ta)、钼(Mo)、钨(W)中的一种或多种。
本申请实施方式中，所述二次颗粒中，所述促进晶粒生长的掺杂元素和所述抑制晶粒生长的掺杂元素的总摩尔含量为0.1mol％-1mol％。
本申请实施方式中，所述一次颗粒的平均粒径为10nm-60μm。
本申请实施方式中，所述二次颗粒的平均粒径为1μm-200μm。
本申请实施方式中，所述二次颗粒包括电池正极用金属氧化物。
本申请实施方式中，所述电池正极用金属氧化物为锂离子电池正极用金属氧化物、钠离子电池正极用金属氧化物、钾离子电池正极用金属氧化物或镁离子电池正极用金属氧化物。
本申请实施方式中，所述锂离子电池正极用金属氧化物包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂钛氧化物、锂铁磷氧化物、锂镍钴氧化物、锂镍锰氧化物、镍钴多元氧化物中的一种或多种。
本申请实施方式中，所述外层的最外侧含有所述抑制晶粒生长的掺杂元素的氧化物。
本申请实施方式中，所述电极材料还包括包覆在所述二次颗粒表面的保护层。
本申请实施例第二方面提供一种电极材料的制备方法，包括：
将电极材料前驱体与金属盐混合后经煅烧得到电极材料，所述电极材料前驱体包括内部区域和包覆所述内部区域的外部区域，所述内部区域包括促进晶粒生长的掺杂元素，和/或所述外部区域包括抑制晶粒生长的掺杂元素；所述电极材料包括由多个一次颗粒聚集而成的二次颗粒，所述二次颗粒包括内层和包覆所述内层的外层，其中，所述内层的一次颗粒的平均粒径大于所述外层的一次颗粒的平均粒径。
本申请实施方式中，所述煅烧包括依次进行的第一次煅烧和第二次煅烧，所述第一次煅烧的温度高于所述第二次煅烧的温度。
本申请实施方式中，所述第一次煅烧的温度(T1)为600℃-1000℃，所述第二次煅烧的温度(T2)为400℃-800℃。
本申请实施方式中，所述第一次煅烧的时间为2-4小时，所述第二次煅烧的时间为6-14小时。
本申请实施方式中，所述金属盐包括锂盐、钠盐、钾盐或镁盐。
本申请实施方式中，所述电极材料前驱体包括电池正极用金属氧化物前驱体。
本申请实施方式中，所述电池正极用金属氧化物前驱体包括金属氧化物的氢氧化物前驱体、金属氧化物的氧化物前驱体、金属氧化物的碳酸盐前驱体或金属氧化物的羟基氧化物前驱体。
本申请实施例第三方面提供一种电极材料前驱体，所述电极材料前驱体包括核层和包覆所述核层的壳层，所述核层包括促进晶粒生长的掺杂元素，和/或所述壳层包括抑制晶粒生长的掺杂元素。
本申请实施方式中，所述电极材料前驱体包括电池正极用金属氧化物前驱体。
本申请实施方式中，所述电池正极用金属氧化物前驱体包括金属氧化物的氢氧化物前驱体、金属氧化物的氧化物前驱体、金属氧化物的碳酸盐前驱体或金属氧化物的羟基氧化物前驱体。
本申请实施方式中，所述促进晶粒生长的掺杂元素包括锶(Sr)，铈(Ce)、铋(Bi)、镁(Mg)中的一种或多种；所述抑制晶粒生长的掺杂元素包括硼(B)、磷(P)、钛(Ti)、锆(Zr)、铌(Nb)、锑(Sb)、钽(Ta)、钼(Mo)、钨(W)中的一种或多种。
本申请实施例第四方面提供一种电极材料前驱体的制备方法，包括：
将电极材料前驱体的核层的金属源溶液与沉淀剂、络合剂混合，形成第一原料液；将第一原料液于惰性气氛下进行第一共沉淀反应，得到电极材料前驱体的核层；
将电极材料前驱体的壳层的金属源溶液与沉淀剂、络合剂混合，形成第二原料液；
其中，所述第一原料液还包括促进晶粒生长的掺杂元素源，和/或所述第二原料液还包括抑制晶粒生长的掺杂元素源；
将所述第二原料液与所述电极材料前驱体的核层混合后，于惰性气氛下进行第二共沉淀反应，在所述电极材料前驱体的核层表面形成壳层，得到电极材料前驱体。
本申请实施方式中，所述促进晶粒生长的掺杂元素源包括含锶(Sr)、铈(Ce)、铋(Bi)、镁(Mg)中的一种或多种掺杂元素的化合物；所述抑制晶粒生长的掺杂元素源包括含硼(B)、磷(P)、钛(Ti)、锆(Zr)、铌(Nb)、锑(Sb)、钽(Ta)、钼(Mo)、钨(W)中的一种或多种掺杂元素的化合物。
本申请实施例第五方面提供一种电极片，所述电极片包括集流体和设置在所述集流体表面的电极活性层，所述电极活性层包括本申请实施例第一方面所述的电极材料。
本申请实施例第六方面提供一种电池，所述电池包括本申请实施例第一方面所述的电极材料，或者包括本申请实施例第五方面所述的电极片。
本申请实施例还提供一种装置，所述装置包括本申请实施例第六方面所述的电池。
本申请实施方式中，所述装置包括电子设备、储能系统或车辆。
附图说明
图1是现有多晶正极材料10的一次晶粒的堆积结构示意图；
图2是本申请实施例提供的电极材料100的截面结构示意图；
图3是本申请一实施例中球形电极材料100的内层和外层分布示意图；
图4是本申请一实施例中类球形电极材料100的内层和外层分布示意图；
图5是本申请实施例提供的电极材料前驱体200的三维结构示意图；
图6是本申请实施例提供的电极片300的结构示意图；
图7是本申请实施例提供的电池400的结构示意图；
图8是本申请一实施例提供的装置500的结构示意图；
图9是本申请另一实施例提供的装置500的结构示意图；
图10是本申请又一实施例提供的装置500的结构示意图；
图11是本申请实施例1与对比例1的在不同循环圈数下裂纹扩展长度的结果。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例进行说明。
参见图1，图1是现有多晶正极材料10的一次晶粒的堆积结构示意图，多晶正极材料10通常是由多个一次晶粒11堆积团聚形成，在多晶正极材料10内部，分布有晶界12，晶界12是指一次晶粒之间的界面。多晶正极材料10在充放电的过程中，材料晶体结构的变化使其晶格体积发生变化，导致一次晶粒11的体积在充放电过程中不断地膨胀与收缩，这种由离子嵌入脱出造成的体积应变会在一次晶粒11的晶界12处累积，导致二次颗粒中产生裂纹，二次颗粒在长循环过程中开裂使得材料的循环性能衰减以及内阻增加；同时，开裂后的二次颗粒界面处发生相变，导致电解液副反应加剧，降低材料的循环稳定性。为了改善现有多晶正极材料在充放电循环过程中易开裂的问题，本申请提供了一种电极材料，该电极材料能够均匀化电极材料二次颗粒内部在充放电过程中的应力分布，从而一定程度抑制晶界开裂现象，提升材料的循环稳定性，改善电池性能。
参见图2，图2是本申请实施例提供的电极材料100的结构示意图，电极材料100包括由多个一次颗粒101(即一次晶粒)聚集而成的二次颗粒100a，即电极材料100为多晶结构电极材料，二次颗粒100a包括内层102和包覆于内层102外侧的外层103，其中，内层102的一次颗粒101a的平均粒径大于外层103的一次颗粒101b的平均粒径。一次颗粒101之间的界面构成晶界104。为便于理解，图2中采用灰色阴影区域示意内层102的区域，灰色阴影区域以外的区域为外层103区域。
本申请实施例提供的电极材料100通过将二次颗粒100a内部的一次颗粒101分布设置为：内层102的一次颗粒101a的平均粒径大于外层103的一次颗粒101b的平均粒径，该结构可以使二次颗粒100a内层102的晶界密度小于外层103的晶界密度，从而可以有效地分散二次颗粒100a中由金属离子嵌入脱出造成的体积应变，均匀化二次颗粒100a内部的应力分布，抑制晶界104开裂，抑制二次颗粒100a发生破碎，提升材料的循环稳定性能；同时，该结构可以使得充电状态下金属离子在二次颗粒100a中分布更均匀，从而有效提高材料的倍率性能。
本申请实施方式中，二次颗粒100a为球形或类球形颗粒。类球形即近似于球形的形状，例如椭球形等。
参见图3，本申请实施方式中，将二次颗粒100a的中心A与二次颗粒100a的表面上任意一点之间的总径向距离定义为R，其中，二次颗粒100a的中心A为二次颗粒100a的最长径(即最长直径)的中点，外层103是指从所述二次颗粒100a的表面至朝向中心A延伸20％-60％R的长度所对应的区域；而内层102为从所述二次颗粒100a的中心A至朝向表面延伸40％-80％R的长度所对应的区域。内层102一次颗粒粒径过大，倍率性能会变差，且裂纹是从二次颗粒内部一定范围内发生，并逐步延展，适合大小的内层102和外层103区域控制，可以使得二次颗粒内部晶界密度较小的区域控制在适合的占比，从而有效抑制二次颗粒在充放电循环过程中的晶界开裂，提升结构稳定性，同时又能保证其具有较优的倍率性能，从而较好平衡二次颗粒倍率性能和结构稳定性。具体地，外层103可以是指从所述二次颗粒100a的表面至朝向中心A延伸20％R、25％R、30％R、35％R、40％R、45％R、50％R、55％R、60％R的长度所对应的区域；相应地，内层102为从所述二次颗粒的中心A至朝向表面延伸80％R、75％R、70％R、65％R、60％R、55％R、50％R、45％R、40％R的长度所对应的区域。例如，图2中，外层103是指从所述二次颗粒100a的表面至朝向中心A延伸30％R(即0.3R)的长度所对应的区域(即图中虚线以外的区域)；而内层102为从所述二次颗粒100a的中心A至朝向表面延伸70％R(即0.7R)的长度所对应的区域(即图中虚线以内的区 域)。
可以理解地，对于规则的球形二次颗粒，二次颗粒100a的中心A与二次颗粒100a的表面上任意一点之间的总径向距离R为相等数值，R为球的半径，若外层103是指从所述二次颗粒100a的表面至朝向中心A延伸30％R(即0.3R)的长度所对应的区域，内层102为从所述二次颗粒100a的中心A至朝向表面延伸70％R(即0.7R)的长度所对应的区域，则内层102与外层103的分界面为相对二次颗粒100a各径向方向等比例缩小为0.7R所对应的球形面，分界面到二次颗粒表面的区域为外层，分界面到二次颗粒中心的区域为内层。而对于类球形二次颗粒，参见图4，二次颗粒100a的中心A与二次颗粒100a的表面上不同点之间的总径向距离R为不相等数值，若外层103是指从所述二次颗粒100a的表面至朝向中心A延伸30％R(即0.3R)的长度所对应的区域，内层102为从所述二次颗粒100a的中心A至朝向表面延伸70％R(即0.7R)的长度所对应的区域，则内层102与外层103的分界面为相对二次颗粒100a各径向方向等比例缩小为0.7R所对应的类球形面，如图4中界面I即为内层102与外层103的分界面，分界面到二次颗粒表面的区域为外层，分界面到二次颗粒中心的区域为内层。本申请一些实施方式中，对于球形二次颗粒，内层102与外层103的分界面也可以为二次颗粒100a在各径向方向进行不同比例缩小后所对应的非球形面；对于类球形二次颗粒，内层102与外层103的分界面也可以为二次颗粒100a在各径向方向进行不同比例缩小后所对应的类球形面。
本申请实施方式中，构成二次颗粒100a的一次颗粒101可以是球形或类球形颗粒，也可以是长条状颗粒，如长宽比为1.1-4的长条状颗粒。本申请实施方式中，构成二次颗粒100a的每一个一次颗粒101均具有一个粒径，一次颗粒101的平均粒径即为各个一次颗粒粒径的平均值；其中，当一次颗粒101的长宽比小于2:1时，一次颗粒101的粒径是指一次颗粒的最长径，当一次颗粒101的长宽比大于或等于2:1时，一次颗粒101的粒径是指一次颗粒的最长径与最短径之和的一半。一次颗粒101的粒径具体可以是对二次颗粒100a的截面进行扫描电镜表征获得，当截面中一次颗粒101的长宽比小于2:1时，记录一次颗粒的最长径为一次颗粒101的粒径，当截面中一次颗粒101的长宽比大于或等于2:1时，记录一次颗粒的最长径与最短径之和的一半为一次颗粒101的粒径。本申请实施方式中，内层102的一次颗粒101a的平均粒径为0.01R’至1.4R’，即内层102中各个一次颗粒粒径的平均值为0.01R’至1.4R’。本申请实施方式中，外层103的一次颗粒101b的平均粒径为0.001R’至0.3R’，即外层103中各个一次颗粒粒径的平均值为0.001R’至0.3R’。其中，R’为二次颗粒100a的最长径的一半。以粒径为10μm的球型二次颗粒为例，内层102的一次颗粒101a的平均粒径可以是50nm至7μm，外层103的一次颗粒101b的平均粒径可以是5nm至1.5μm。具体地，本申请实施方式中，内层102的一次颗粒101a的平均粒径可以是0.01R’、0.02R’、0.03R’、0.05R’、0.08R’、0.1R’、0.15R’、0.2R’、0.3R’、0.4R’、0.5R’、0.6R’、0.7R’、0.8R’、0.9R’、1.0R’、1.1R’、1.2R’、1.3R’、1.4R’，外层103的一次颗粒101b的平均粒径可以是0.001R’、0.002R’、0.005R’、0.01R’、0.02R’、0.03R’、0.04R’、0.05R’、0.06R’、0.07R’、0.08R’、0.1R’、0.15R’、0.2R’、0.25R’、0.3R’，将内层102和外层103中的一次颗粒的平均粒径相对R’控制在适合的比例，可以使构成整个二次颗粒100a的一次颗粒具有适合的数量，从而缓释二次颗粒在循环过程中由于碱金属离子嵌入脱出导致的一次颗粒间的应力积累，有效抑制了长循环后二次颗粒从内部开裂的现象。
本申请实施方式中，内层102的一次颗粒101a的平均粒径大于外层103的一次颗粒101b的平均粒径，即内层102是由多个平均粒径相对较大的一次颗粒101a聚集而成，外层103是由多个平均粒径相对较小的一次颗粒101b聚集而成。这样，二次颗粒100a可以形成具有晶界密度梯度分布的结构，通过界观尺度模拟，这样的结构可以有效的分散二次颗粒中由离子嵌入脱出造成的体积应变，从而抑制裂纹的增长。本申请实施方式中，内层102的一次颗粒101a的平均粒径可以是为外层103的一次颗粒101b的平均粒径的1.1倍至15倍。具体地，内层102的一次颗粒101a的平均粒径可以是外层103的一次颗粒101b的平均粒径的1.1倍、1.2倍、1.3倍、1.4倍、1.5倍、1.6倍、1.7倍、1.8倍、1.9倍、2倍、3倍、4倍、5倍、6倍、7倍、8倍、9倍、10倍、11倍、12倍、13倍、14倍、15倍。一些实施方式中，内层102的一次颗粒101a的平均粒径为外层103的一次颗粒101b的平均粒径的2倍至10倍。一些实施方式中，内层102的一次颗粒101a的平均粒径为外层103的一次颗粒101b的平均粒径的1.5倍至3倍。将内层102与外层103的一次颗粒平均粒径控制在适合的相对大小，可以获得适合的晶界密度梯度分布结构，从而更好地利用内层102的较大尺寸一次颗粒抑制二次颗粒在充放电长循环过程中从内部开裂，同时可以提升材料的倍率性能。过大的内层一次颗粒粒径会影响材料的倍率性能和容量发挥。
本申请实施方式中，二次颗粒100a中，一次颗粒101的平均粒径为10nm-60μm。本申请实施方式中，内层102的一次颗粒101a的平均粒径为200nm-60μm。对于10μm左右(例如7-13μm)大小的二次颗粒而 言，其内层一次颗粒平均粒径范围可以是800nm-3μm。本申请实施方式中，外层103的一次颗粒101b的平均粒径为10nm-20μm。对于10μm左右大小的二次颗粒而言，其外层一次颗粒平均粒径范围可以是100nm-1.5μm。
本申请实施方式中，内层102包括促进晶粒生长的掺杂元素，和/或外层103包括抑制晶粒生长的掺杂元素。本申请实施方式中，促进晶粒生长的掺杂元素可以是包括但不限于锶(Sr)，铈(Ce)、铋(Bi)、镁(Mg)中的一种或多种；抑制晶粒生长的掺杂元素可以是包括但不限于硼(B)、磷(P)、钛(Ti)、锆(Zr)、铌(Nb)、锑(Sb)、钽(Ta)、钼(Mo)、钨(W)中的一种或多种。其中，促进晶粒生长的掺杂元素是指能够在二次颗粒的形成过程中，促使一次晶粒长大的，与内层电极材料化合物本身所含元素不同的元素；而抑制晶粒生长的掺杂元素是指能够在二次颗粒的形成过程中，抑制一次晶粒长大，细化晶粒尺寸，与外层电极材料化合物本身所含元素不同的元素。例如，二次颗粒包括本身的电极材料化合物镍钴锰酸锂，二次颗粒还包括掺杂在内层102中的锶(Sr)元素，以及掺杂在外层103中的钛(Ti)元素。本申请实施例可以是通过在电极材料前驱体的内外不同区域掺杂上述特定的元素，以调控煅烧出的电极材料多晶结构中的一次晶粒的平均粒径呈内外梯度分布。
本申请一些实施方式中，内层102包括促进晶粒生长的掺杂元素，外层103不包括抑制晶粒生长的掺杂元素；该实施方式中，在二次颗粒的形成过程中，内层102在促进晶粒生长的掺杂元素的作用下可以获得相对外层103平均粒径更大的一次颗粒，形成内外一次颗粒平均粒径梯度分布结构。本申请另一些实施方式中，外层103包括抑制晶粒生长的掺杂元素，内层102不包括促进晶粒生长的掺杂元素；该实施方式中，在二次颗粒的形成过程中，外层103在抑制晶粒生长的掺杂元素的作用下将获得相对内层102平均粒径更小的一次颗粒，形成内外一次颗粒平均粒径梯度分布结构。本申请另一些实施方式中，内层102包括促进晶粒生长的掺杂元素，同时，外层103包括抑制晶粒生长的掺杂元素；该实施方式中，在二次颗粒的形成过程中，可以获得内层102与外层103的一次颗粒的平均粒径相差更大的内外一次颗粒平均粒径梯度分布结构。
本申请一些实施方式中，内层102中可能由于元素扩散包括少量由外层103扩散的抑制晶粒生长的掺杂元素；本申请一些实施方式中，外层103中也可能由于元素扩散包括少量由内层102扩散的促进晶粒生长的掺杂元素。
本申请实施方式中，二次颗粒100a中，促进晶粒生长的掺杂元素和抑制晶粒生长的掺杂元素的总摩尔含量为0.1mol％-1mol％。在具体实施例中，二次颗粒100a中，促进晶粒生长的掺杂元素和抑制晶粒生长的掺杂元素的总摩尔含量例如可以是0.1mol％、0.2mol％、0.3mol％、0.4mol％、0.5mol％、0.6mol％、0.7mol％、0.8mol％、0.9mol％、1mol％。一些实施例中，二次颗粒100a中，促进晶粒生长的掺杂元素和抑制晶粒生长的掺杂元素的总摩尔含量为0.2mol％-0.5mol％。适合掺杂元素含量的控制，既可以使二次颗粒获得内外一次颗粒平均粒径梯度分布的结构，又可以较好地避免掺杂元素对电极材料的容量等性能带来的负面影响。
本申请实施方式中，二次颗粒100a的平均粒径为1μm-200μm。一些实施例中，二次颗粒100a的平均粒径例如可以是1μm、5μm、10μm、15μm、20μm、25μm、30μm、35μm、40μm、45μm、50μm、55μm、60μm、65μm、70μm、75μm、80μm、90μm、100μm、110μm、120μm、130μm、140μm、150μm、160μm、170μm、180μm、190μm、200μm。
本申请实施方式中，电极材料可以是电池正极材料，也可以是电池负极材料。电极材料可以是锂离子电池电极材料、钠离子电池电极材料、钾离子电池电极材料或镁离子电池电极材料。本申请一些实施方式中，二次颗粒100a包括电池正极用金属氧化物。电池正极用金属氧化物可以是锂离子电池正极用金属氧化物、钠离子电池正极用金属氧化物、钾离子电池正极用金属氧化物或镁离子电池正极用金属氧化物。具体地，电池正极用金属氧化物可以是为含碱金属或碱土金属的复合氧化物。本申请实施方式中，二次颗粒100a的内层102和外层103可以是包括相同的电池正极用金属氧化物，也可以是包括不同的电池正极用金属氧化物。
本申请实施方式中，锂离子电池正极用金属氧化物包括含锂的复合氧化物，含锂的复合氧化物包括锂钴氧化物(如钴酸锂LiCoO2)、锂镍氧化物(如镍酸锂LiNiO2)、锂锰氧化物(如锰酸锂LiMnO2、高锰酸锂)、锂钛氧化物(如钛酸锂)、锂铁磷氧化物(如磷酸铁锂)、锂镍钴氧化物(如镍钴酸锂LiNiaCo1-aO2)、锂镍锰氧化物(例如镍锰酸锂LiNiaMn1-aO2)、镍钴多元氧化物(如镍钴锰酸锂LiNiaCobMn1-a-bO2、镍钴铝酸锂LiNiaCobAl1-a-bO2、镍钴锰铝酸锂LiNiaCobMncAl1-a-b-cO2)中的一种或多种，其中，0<a<1，0<b<1，0<c<1，0<1-a-b<1，0<1-a-b-c<1。含锂的复合氧化物可以是化学计量比的含锂氧化物，也可以是非化学计量比的含锂氧化物，例如锂离子电池电极材料LiηNiaCobMncAl1-a-b-cO2中，η可以是大于0小于或等于2 的任意值，0≤a≤1，0≤b≤1，0≤c≤1，0≤1-a-b-c≤1。
本申请实施方式中，钠离子电池正极用金属氧化物包括含钠的复合氧化物，含钠的复合氧化物包括含钠的过渡金属氧化物，可以是包括钠锰氧化物、钠铜铁锰氧化物、钠镍铁锰氧化物、钠铜镍铁锰氧化物中的一种或多种。
本申请实施方式中，钾离子电池正极用金属氧化物包括含钾的复合氧化物，含钾的复合氧化物例如可以是钾钴氧化物、钾锰氧化物、钾铁锰氧化物等。本申请实施方式中，镁离子电池正极用金属氧化物包括含镁的复合氧化物，含镁的复合氧化物例如可以是镁钒氧化物、镁钴锰氧化物、镁镍锰氧化物、镁锰氧化物、镁铁锰氧化物等。
本申请一些实施方式中，外层103的最外侧(即远离二次颗粒中心的外围)含有抑制晶粒生长的掺杂元素的氧化物，这主要是由于外层103的掺杂元素偏析至二次颗粒表面被氧化形成，外层103的最外侧中掺杂元素的氧化物的形成有利于提高二次颗粒循环性能，降低表面副反应。
考虑电极材料的结构稳定性和电化学性能，本申请实施例的电极材料的二次颗粒100a表面还可以根据需要设置保护层。保护层例如可以是包括金属氧化物等。金属氧化物例如可以是氧化镁、氧化铝、二氧化钛等。保护层可以降低二次颗粒表面副反应，提高二次颗粒循环性能。
本申请实施例还提供一种电极材料的制备方法，包括：
将电极材料前驱体与金属盐混合后经煅烧得到电极材料，电极材料前驱体包括核层和包述核层的壳层，核层包括促进晶粒生长的掺杂元素，和/或壳层包括抑制晶粒生长的掺杂元素；所述电极材料包括由多个一次颗粒聚集而成的二次颗粒，二次颗粒包括内层和包覆所述内层的外层，其中，内层的一次颗粒的平均粒径大于外层的一次颗粒的平均粒径。
本申请实施方式中，煅烧包括依次进行的第一次煅烧和第二次煅烧，第一次煅烧的温度高于第二次煅烧的温度。本申请一些实施方式中，第一次煅烧为高温煅烧，温度(T1)为600℃-1000℃，第二次煅烧为中温煅烧，温度(T2)为400℃-800℃。本申请实施方式中，第一次煅烧的温度高于第二次煅烧的温度100℃以上。第二次煅烧的时间比第一次煅烧的时间长，第一次煅烧的时间可以是2-4小时，例如2小时、2.5小时、3小时、3.5小时、4小时；第二次煅烧的时间可以是6-14小时，例如6小时、7小时、8小时、9小时、10小时、11小时、12小时、13小时、14小时。通过先在高温煅烧区域短时间煅烧可以让晶体快速成核，而在中温煅烧区域长时间煅烧可以让一次晶粒尺寸缓慢长大，对比常规煅烧工艺，两段煅烧可以在增大一次晶粒的粒径的同时降低材料的表面混排。
本申请实施方式中，金属盐包括锂盐、钠盐、钾盐或镁盐。金属盐的种类具体根据最终想要制备的电极材料的种类而定，例如，预制备锂离子电池电极材料则金属盐为锂盐，锂盐具体可以是硝酸锂、氢氧化锂、碳酸锂中的一种或多种；锂盐可以是按照电极材料前驱体中非锂的金属(如过渡金属Ni、Co、Mn等)与锂的摩尔比为1:(1～1.1)加入，电极材料前驱体中的过渡金属元素含量可以是通过ICP(Inductive Coupled Plasma Emission Spectrometer，电感耦合等离子光谱发生仪)表征获得。预制备钠离子电池电极材料则金属盐为钠盐，钠盐具体可以硝酸钠、氢氧化钠、碳酸钠和补钠剂中的一种或多种；预制备钾离子电池电极材料则金属盐为钾盐，钾盐具体可以是硝酸钾、氢氧化钾、碳酸钾中的一种或多种；预制备镁离子电池电极材料则金属盐为镁盐，镁盐具体可以是硝酸镁、氢氧化镁、碳酸镁中的一种或多种。
本申请实施方式中，电极材料前驱体的种类具体根据最终想要制备的电极材料的种类而定，例如，预制备锂离子电池电极材料则电极材料前驱体为锂离子电池电极材料前驱体；预制备钠离子电池电极材料则电极材料前驱体为钠离子电池电极材料前驱体；预制备钾离子电池电极材料则电极材料前驱体为钾离子电池电极材料前驱体；预制备镁离子电池电极材料则电极材料前驱体为镁离子电池电极材料前驱体。
参见图5，本申请实施例还提供一种电极材料前驱体200，电极材料前驱体200包括核层201和包述核层201的壳层202，即核层201在内，壳层202在外，其中，核层201包括促进晶粒生长的掺杂元素，和/或壳层202包括抑制晶粒生长的掺杂元素。上述电极材料的制备方法中采用的电极材料前驱体可以为该电极材料前驱体200。
本申请实施方式中，核层201对应生成前述电极材料100的二次颗粒100a的内层102，壳层202对应生成前述电极材料100的二次颗粒100a的外层103。相应地，将电极材料前驱体200的中心B与电极材料前驱体200颗粒表面上任意一点之间的总径向距离定义为r，其中，电极材料前驱体200的中心B为电极材料前驱体200的最长径(即最长直径)的中点，壳层202是指从电极材料前驱体200的表面至朝向中心B延伸20％-60％r的长度所对应的区域；而内层102为从电极材料前驱体200的中心B至朝向表面延伸40％-80％r的长度所对应的区域。具体核层201和壳层202的区域划分可参考前文电极材料100的二次颗 粒100a的内层102和外层103的划分，此处不再赘述。
本申请实施方式中，核层201包括促进晶粒生长的掺杂元素，和/或壳层202包括抑制晶粒生长的掺杂元素。本申请实施方式中，促进晶粒生长的掺杂元素可以是包括但不限于锶(Sr)，铈(Ce)、铋(Bi)、镁(Mg)中的一种或多种；抑制晶粒生长的掺杂元素可以是包括但不限于硼(B)、磷(P)、钛(Ti)、锆(Zr)、铌(Nb)、锑(Sb)、钽(Ta)、钼(Mo)、钨(W)中的一种或多种。其中，促进晶粒生长的掺杂元素是指能够在电极材料二次颗粒的形成过程中，促使一次晶粒长大的，与核层电极材料前驱体化合物本身所含元素不同的元素；而抑制晶粒生长的掺杂元素是指能够在电极材料二次颗粒的形成过程中，抑制一次晶粒长大，与壳层电极材料前驱体化合物本身所含元素不同的元素。例如，电极材料前驱体包括本身的电极材料前驱体化合物镍钴锰氢氧化物，还包括掺杂在核层201中的锶(Sr)元素，以及掺杂在壳层202中的钛(Ti)元素。
本申请一些实施方式中，核层201包括促进晶粒生长的掺杂元素，壳层202不包括抑制晶粒生长的掺杂元素。本申请另一些实施方式中，壳层202包括抑制晶粒生长的掺杂元素，核层201不包括促进晶粒生长的掺杂元素。本申请另一些实施方式中，核层201包括促进晶粒生长的掺杂元素，同时，壳层202包括抑制晶粒生长的掺杂元素。
本申请实施方式中，电极材料前驱体200中，促进晶粒生长的掺杂元素和抑制晶粒生长的掺杂元素的总摩尔含量为0.1mol％-1mol％。在具体实施例中，电极材料前驱体200中，促进晶粒生长的掺杂元素和抑制晶粒生长的掺杂元素的总摩尔含量例如可以是0.1mol％、0.2mol％、0.3mol％、0.4mol％、0.5mol％、0.6mol％、0.7mol％、0.8mol％、0.9mol％、1mol％。一些实施例中，电极材料前驱体200中，促进晶粒生长的掺杂元素和抑制晶粒生长的掺杂元素的总摩尔含量为0.2mol％-0.5mol％。
本申请实施例通过在电极材料前驱体的内外侧预设区域掺杂上述特定的元素，以调控煅烧出的电极材料多晶结构中一次颗粒平均粒径呈内大外小的梯度分布结构，可以有效改善电极材料在充放电循环过程中的晶界开裂现象，提升电极材料二次颗粒的循环稳定性，同时还能均匀化充电状态下电极材料中阳离子(如锂离子)的浓度，提高电极材料倍率性能；且采用该电极材料前驱体制备具有上述特征的电极材料，工艺简单可控。
本申请实施方式中，电极材料前驱体200可以是锂离子电池电极材料前驱体、钠离子电池电极材料前驱体、钾离子电池电极材料前驱体、镁离子电池电极材料前驱体。本申请一些实施方式中，电极材料前驱体200包括电池正极用金属氧化物前驱体。电池正极用金属氧化物前驱体具体可以是包括锂离子电池、钠离子电池、钾离子电池、镁离子电池正极中所用金属氧化物的氢氧化物前驱体、金属氧化物的氧化物前驱体、金属氧化物的碳酸盐前驱体或金属氧化物的羟基氧化物前驱体。例如，电极材料前驱体可以是包括NixCoyMn1-x-y(OH)2,NixCoyAl1-x-y(OH)2,NixCoyMnzAl1-x-y-z(OH)2等；其中0<x<1，0<y<1，0<z<1，0<1-x-y<1，0<1-x-y-z<1。一具体实施例中，电极材料前驱体200包括由化合物NixCoyMn1-x-y(OH)2形成的颗粒，颗粒的核层含有掺杂元素锶(Sr)，壳层含有掺杂元素钛(Ti)。
本申请实施例还提供一种电极材料前驱体的制备方法，包括：
将电极材料前驱体的核层的金属源溶液与沉淀剂、络合剂混合，形成第一原料液；将第一原料液于惰性气氛下进行第一共沉淀反应，得到电极材料前驱体的核层；
将电极材料前驱体的壳层的金属源溶液与沉淀剂、络合剂混合，形成第二原料液；
其中，所述第一原料液还包括促进晶粒生长的掺杂元素源，和/或所述第二原料液还包括抑制晶粒生长的掺杂元素源；
将所述第二原料液与所述电极材料前驱体的核层混合后，于惰性气氛下进行第二共沉淀反应，在所述电极材料前驱体的核层表面形成壳层，得到电极材料前驱体。
本申请实施方式中，电极材料前驱体的核层的金属源溶液即含有电极材料前驱体的核层金属元素的溶液，同样，电极材料前驱体的壳层的金属源溶液即含有电极材料前驱体的壳层金属元素的溶液。例如，电极材料前驱体的核层和壳层均包括化合物NixCoyMn1-x-y(OH)2，则金属源溶液为含有镍源、钴源、锰源的溶液。金属源为可溶性金属盐，例如镍源为可溶性镍盐，具体为硫酸镍等；钴源为可溶性钴盐，具体为硫酸钴等；锰源为可溶性锰盐，具体为硫酸锰等。
本申请实施方式中，促进晶粒生长的掺杂元素源包括含锶(Sr)、铈(Ce)、铋(Bi)、镁(Mg)中的一种或多种掺杂元素的化合物；具体地，促进晶粒生长的掺杂元素源可以是含锶(Sr)、铈(Ce)、铋(Bi)、镁(Mg)中的一种或多种掺杂元素的金属盐；例如锶盐、铈盐、铋盐、镁盐。本申请实施方式中，抑制晶粒生长的掺杂元素源包括含硼(B)、磷(P)、钛(Ti)、锆(Zr)、铌(Nb)、锑(Sb)、钽(Ta)、钼(Mo)、钨(W)中的一种或多种掺杂元素的化合物。具体地，抑制晶粒生长的掺杂元素源可以是含硼(B)、磷(P)、钛(Ti)、 锆(Zr)、铌(Nb)、锑(Sb)、钽(Ta)、钼(Mo)、钨(W)中的一种或多种掺杂元素的金属盐；例如硼盐、磷盐、钛盐、锆盐、铌盐、锑盐、钽盐、钼盐、钨盐。
本申请一些实施方式中，第一原料液包括促进晶粒生长的掺杂元素源，第二原料液不包括抑制晶粒生长的掺杂元素源。本申请另一些实施方式中，第二原料液包括抑制晶粒生长的掺杂元素源，第一原料液不包括促进晶粒生长的掺杂元素源。本申请另一些实施方式中，第一原料液包括促进晶粒生长的掺杂元素源，同时，第二原料液包括抑制晶粒生长的掺杂元素源。
本申请实施方式中，沉淀剂可以是氢氧化钠溶液，氢氧化钠溶液的摩尔浓度可以是2mol/L-4mol/L；络合剂可以是氨水溶液，氨水溶液的质量浓度可以是8％-12％。本申请实施方式中，可以通过氨水将第一原料液和第二原料液的pH控制在10.0-12.0。本申请实施方式中，惰性气氛例如可以是氮气气氛等。
参见图6，本申请实施例还提供一种电极片300，电极片300包括集流体301和设置在集流体301上的电极活性层302，电极活性层302中包括本申请前述的电极材料100。集流体301可以是铝箔等。电极活性层302还可以包括导电剂、粘结剂等。
参见图7，本申请实施例还提供一种电池400，电池400包括本申请实施例上述提供的电极片，即包括本申请实施例上述提供的电极材料100。电池400可以是锂离子二次电池、钠离子二次电池、钾离子二次电池、镁离子二次电池等。一些实施例中，电池400包括正极片401、负极片402、电解液403和隔膜404。以锂离子电池为例，在充电过程中，在外加电路的作用下，锂离子从正极活性物质脱出，经过电解液隔膜嵌入到负极，同时正极失去电子，经过集流体从外电路流出；放电的过程相反，锂离子从负极脱出回到正极，同时电子从负极经外电路移动到正极，并对外做功。
参见图8、图9和图10，本申请实施例还提供一种装置500，装置500包括本申请实施例上述提供的电池400。该装置500可以根据实际使用需求来选择不同的电化学装置，如电池、电池模块或电池包。本申请一些实施方式中，如图8所示，装置500为电子设备，该电子设备可以是各种消费类电子产品，如手机、平板电脑、移动电源、便携机、笔记本电脑以及其它可穿戴或可移动的电子设备、电视机、影碟机、录像机、摄录机、收音机、收录机、组合音响、电唱机、激光唱机、家庭办公设备、家用电子保健设备，电子设备包括本申请实施例上述提供的电池400，电池400为电子设备供电。本申请一些实施方式中，如图9所示，装置500为车辆，该车辆包括本申请实施例上述提供的电池400，电池400为车辆供电，该车辆可以是纯电动汽车、混合动力电动车、电动自行车、电动踏板车等各种形式的电动车辆。本申请一些实施方式中，如图10所示，装置500为储能系统，储能系统包括电池组501和与电池组501电连接的电池管理系统502，电池组501包括本申请实施例上述提供的电池400。
下面分多个实施例对本申请实施例进行进一步的说明。
实施例1
1、合成锂离子电池正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2，其包括核层和包覆于核层外侧的壳层，核层掺杂有元素锶(Sr)，壳层掺杂有元素钛(Ti)：
(1-1)配制镍钴锰金属盐溶液：将硫酸镍盐、硫酸钴盐和硫酸锰盐按照Ni、Co、Mn摩尔比为82:12:6溶解配制成2mol/L均匀混合的镍钴锰金属盐溶液；配制质量浓度为10wt.％氨水溶液和浓度为4mol/L氢氧化钠水溶液；配制摩尔浓度为0.05mol/L的锶盐溶液；配制摩尔浓度为0.05mol/L的钛盐溶液；
(1-2)配制质量浓度为10wt.％氨水溶液和浓度为4mol/L氢氧化钠水溶液；
(1-3)配制摩尔浓度为0.05mol/L的锶盐溶液；
(1-4)配制摩尔浓度为0.05mol/L的钛盐溶液；
(1-5)在反应釜中加入去离子水，再将配制好的氨水溶液和氢氧化钠水溶液加入到反应釜中，调节温度为70℃，pH值为11.0，搅拌转速为300rpm，然后缓慢加入(1-1)和(1-3)中上配制好的镍钴锰金属溶液以及锶盐溶液，并通过氨水把溶液pH控制在11.0；
(1-6)待前驱体颗粒生长到7μm粒径大小后，维持温度在70℃，pH值为11.0，搅拌转速为300rpm，重新缓慢注入上述配制好的氨水溶液和氢氧化钠水溶液，以及(1-1)和(1-4)中配制好的镍钴锰金属溶液和钛盐溶液；
(1-7)待前驱体颗粒生长到10μm粒径大小后，用弱碱液和去离子水洗涤烘干，得到正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2，其包括核层和包覆于核层外侧的壳层，核层掺杂有元素锶(Sr)，壳层掺杂有元素钛(Ti)。
2、合成多晶正极材料LiNi0.82Co0.12Mn0.06O2：
(2-1)将上述制备得到的正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2与氢氧化锂充分混合得到混合物，氢氧化锂按照前驱体中过渡金属(包括Ni、Co、Mn)与氢氧化锂中锂的摩尔比为1：1.01加入；
(2-2)将(2-1)中的混合物置于马弗炉中煅烧，高温煅烧温度为900℃，煅烧时间为6小时，随后降温至700℃煅烧10小时，煅烧气氛为纯氧气气氛，煅烧结束后自然冷却；
(2-3)将(2-2)中冷却后所得粉末破碎，过筛，除磁后真空封装，得到多晶正极材料LiNi0.82Co0.12Mn0.06O2。
3、正极片制备：
将多晶正极材料与聚偏氟乙烯(PVDF)、导电剂super P按照质量比90:5:5，加入到N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀得到浆料，将浆料涂布在铝箔集流体上，烘干、冷压、分切制得正极片。
4、锂离子电池制备：
将上述制备的正极片与锂片、电解液(1mol/L LiPF6)和隔膜制成2032扣式电池。
对比例1
锂离子电池正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2的合成，对比例1与实施例1的区别仅在于，对比例1没有分段加入步骤(3)和步骤(4)中的锶盐溶液和钛盐溶液，而是将锶盐溶液和钛盐溶液均匀混合后一步加入，其他操作相同，最终生成的前驱体Ni0.82Co0.12Mn0.06(OH)2整个颗粒中具有均匀的锶和钛掺杂。
按照实施例1相同的方法，采用对比例1的正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2制备得到正极材料LiNi0.82Co0.12Mn0.06O2。
按照实施例1相同的方法，采用对比例1的正极材料LiNi0.82Co0.12Mn0.06O2制备正极片和锂离子电池。
将实施例1中所制备得到的正极材料前驱体颗粒和多晶正极材料颗粒通过FIB(Focused Ion beam，聚焦离子束)切割。通过EDS能量散射X射线谱(Energy-dispersive X-ray spectroscopy)对实施例1的正极材料前驱体颗粒和多晶正极材料颗粒截面进行观察，可以观测到，正极材料前驱体颗粒和多晶正极材料颗粒截面外侧有明显的钛元素的信号，截面内侧有明显的锶元素的信号。通过SEM(Scanning electron microscope,扫描电子显微镜)观察实施例1多晶正极材料的截面形貌特征，可以观察到多晶正极材料的截面内侧的一次颗粒平均粒径明显大于外侧的一次颗粒平均粒径，截面外侧晶界分布明显比截面内侧晶界分布更密集。
将对比例1中所制备得到的正极材料前驱体颗粒和多晶正极材料颗粒通过FIB切割。通过EDS对对比例1的正极材料前驱体颗粒和多晶正极材料颗粒截面进行观察，可以观测到，锶和钛的信号在正极材料前驱体颗粒和多晶正极材料颗粒截面的内外侧均匀分布。通过SEM观察对比例1多晶正极材料的截面形貌特征，可以观察到多晶正极材料的截面上内外侧的一次晶粒的粒径大小均一。
将实施例1和对比例1制备的电池在25±5℃条件下，分别以0.1C/0.1C，1C/1C充放电倍率在3.0V-4.3V电压区间内对电池进行充放电测试，并记录电池的首圈充放电容量和100圈循环保持率，结果如表1所示。
表1：实施例1和对比例1电池的电化学性能
由表1的结果可知，本申请实施例通过分步掺杂使正极材料前驱体材料的核层和壳层分别掺杂不同的特定元素，从而在多晶正极材料二次颗粒的形成过程中，在上述特定掺杂元素的作用下，可以使得最终获得的多晶正极材料的内层的一次颗粒的平均粒径大于外层的一次颗粒的平均粒径，即形成内层和外层一次颗粒的平均粒径梯度分布的结构，相对于对比例1的均匀掺杂结构，本申请实施例的具有内外层一次颗粒的平均粒径梯度分布结构的电极材料，可以有效改善电极材料二次颗粒因晶界开裂导致的循环性能恶化的问题，本申请实施例1的正极材料相比对比例1具有更佳的倍率性能和容量保持率。
将实施例1和对比例1所制成的电池在循环100圈后在不同放电态下拆解，对其正极材料颗粒的截面进行扫描电子显微镜(SEM)表征，结果如图11所示，图11为实施例1和对比例1在不同循环圈数下裂纹扩展长度的结果。由图11可知，随着循环圈数的增加，二次颗粒内部的裂纹逐步增加，但是实施例1裂纹增长的速度远低于对比例1。
实施例2
1、合成钠离子电池正极材料前驱体Ni0.33Fe0.33Mn0.33(OH)2，其包括核层和包覆于核层外侧的壳层，核层掺杂有元素镁(Mg)，壳层掺杂有元素钨(W)：
(1-1)配制镍钴锰金属盐溶液：将硫酸镍盐、硫酸铁盐和硫酸锰盐按照Ni、Fe、Mn摩尔比为1:1:1溶解配制成2mol/L均匀混合的镍钴锰金属盐溶液；
(1-2)配制质量浓度为10wt.％氨水溶液和浓度为4mol/L氢氧化钠水溶液；
(1-3)配制摩尔浓度为0.05mol/L的镁盐溶液；
(1-4)配制摩尔浓度为0.05mol/L的钨盐溶液；
(1-5)在反应釜中加入去离子水，再将配制好的氨水溶液和氢氧化钠水溶液加入到反应釜中，调节温度为70℃，pH值为11.0，搅拌转速为300rpm，然后缓慢加入(1-1)和(1-3)中配制好的镍铁锰金属溶液以及镁盐溶液，并通过氨水把溶液pH控制在11.0；
(1-6)待前驱体颗粒生长到7μm粒径大小后，维持温度在70℃，pH值为11.0，搅拌转速为300rpm，重新缓慢注入配制好的氨水溶液和氢氧化钠水溶液，以及(1-1)和(1-4)中配制好的镍铁锰金属溶液和钨盐溶液；
(1-7)待前驱体颗粒生长到10μm粒径大小后，用弱碱液和去离子水洗涤烘干，得到正极材料前驱体Ni0.33Fe0.33Mn0.33(OH)2，其包括核层和包覆于核层外侧的壳层，核层掺杂有元素镁(Mg)，壳层掺杂有元素钨(W)。
2、合成多晶正极材料NaNi0.33Fe0.33Mn0.33O2：
(2-1)将上述制备得到的正极材料前驱体Ni0.33Fe0.33Mn0.33(OH)2与氢氧化钠充分混合得到混合物，氢氧化钠按照前驱体中过渡金属(包括Ni、Fe、Mn)与氢氧化钠中钠的摩尔比为1：1.01加入；
(2-2)将(2-1)中的混合物置于马弗炉中煅烧，高温煅烧温度为900℃，煅烧时间为6小时，随后降温至700度煅烧10小时，煅烧气氛为纯氧气气氛，煅烧结束后自然冷却；
(2-3)将(2-2)中冷却后所得粉末破碎，过筛，除磁后真空封装，得到多晶正极材料。
3、正极片制备：
将多晶正极材料与聚偏氟乙烯(PVDF)、导电剂super P按照质量比90:5:5，加入到N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀得到浆料，将浆料涂布在铝箔集流体上，烘干、冷压、分切制得正极片。
4、钠离子电池制备：
将上述制备的正极片与钠片、电解液(1mol/L NaPF6)和隔膜制成2032扣式电池。
对比例2
钠离子电池正极材料前驱体Ni0.33Fe0.33Mn0.33(OH)2的合成，对比例2与实施例2的区别仅在于，对比例2没有分段加入步骤(3)和步骤(4)中的镁盐溶液和钨盐溶液，而是将镁盐溶液和钨盐溶液均匀混合后一步加入，其他操作相同，最终生成的前驱体Ni0.33Fe0.33Mn0.33(OH)2整个颗粒中具有均匀的镁和钨掺杂。
按照实施例2相同的方法，采用对比例2的正极材料前驱体Ni0.33Fe0.33Mn0.33(OH)2制备得到正极材料NaNi0.33Fe0.33Mn0.33O2。
按照实施例2相同的方法，采用对比例2的正极材料NaNi0.33Fe0.33Mn0.33O2制备正极片和钠离子电池。
将实施例2中所制备得到的正极材料前驱体颗粒和多晶正极材料颗粒通过FIB切割。通过EDS对实施例2的正极材料前驱体颗粒和多晶正极材料颗粒截面进行观察，可以观测到，正极材料前驱体颗粒和多晶正极材料颗粒截面外侧有明显的钨元素的信号，截面内侧有明显的镁元素的信号。通过SEM观察实施例2多晶正极材料的截面形貌特征，可以观察到多晶正极材料的截面内侧的一次颗粒平均粒径明显大于外侧的一次颗粒平均粒径，截面外侧晶界分布明显比截面内侧晶界分布更密集。
将对比例2中所制备得到的正极材料前驱体颗粒和多晶正极材料颗粒通过FIB切割。通过EDS对对比例2的正极材料前驱体颗粒和多晶正极材料颗粒截面进行观察，可以观测到，钨和镁的信号在正极材料前驱体颗粒和多晶正极材料颗粒截面的内外侧均匀分布。通过SEM观察对比例2多晶正极材料的截面形貌特征，可以观察到多晶正极材料的截面上内外侧的一次晶粒的粒径大小均一。
将实施例2和对比例2制备的电池在25±5℃条件下，分别以0.1C/0.1C，1C/1C充放电倍率在3.0V-4.3V电压区间内对电池进行充放电测试，并记录电池的首圈充放电容量和100圈循环保持率，结果如表2所示。
表2：实施例2和对比例2电池的电化学性能
由表2的结果可知，本申请实施例通过分步掺杂使正极材料前驱体材料的核层和壳层分别掺杂不同的特定元素，从而在多晶正极材料二次颗粒的形成过程中，在上述特定掺杂元素的作用下，可以使得最终获得的多晶正极材料的内层的一次颗粒的平均粒径大于外层的一次颗粒的平均粒径，即形成内层和外层一次颗粒的平均粒径梯度分布的结构，相对于对比例2的均匀掺杂结构，本申请实施例的具有内外层一次颗粒的平均粒径梯度分布结构的电极材料，可以有效改善电极材料二次颗粒因晶界开裂导致的循环性能恶化的问题，本申请实施例2的正极材料相比对比例2具有更佳的倍率性能和容量保持率。
实施例3
1、合成锂离子电池正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2，其包括核层和包覆于核层外侧的壳层，核层掺杂有元素锶(Sr)：
(1-1)配制镍钴锰金属盐溶液：将硫酸镍盐、硫酸钴盐和硫酸锰盐按照Ni、Co、Mn摩尔比为82:12:6溶解配制成2mol/L均匀混合的镍钴锰金属盐溶液；配制质量浓度为10wt.％氨水溶液和浓度为4mol/L氢氧化钠水溶液；配制摩尔浓度为0.05mol/L的锶盐溶液；
(1-2)配制质量浓度为10wt.％氨水溶液和浓度为4mol/L氢氧化钠水溶液；
(1-3)配制摩尔浓度为0.05mol/L的锶盐溶液；
(1-4)在反应釜中加入去离子水，再将配制好的氨水溶液和氢氧化钠水溶液加入到反应釜中，调节温度为70℃，pH值为11.0，搅拌转速为300rpm，然后缓慢加入(1-1)和(1-3)中上配制好的镍钴锰金属溶液以及锶盐溶液，并通过氨水把溶液pH控制在11.0；
(1-5)待前驱体颗粒生长到7μm粒径大小后，维持温度在70℃，pH值为11.0，搅拌转速为300rpm，重新缓慢注入上述配制好的氨水溶液和氢氧化钠水溶液，以及(1-1)中配制好的镍钴锰金属溶液；
(1-6)待前驱体颗粒生长到10μm粒径大小后，用弱碱液和去离子水洗涤烘干，得到正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2，其包括核层和包覆于核层外侧的壳层，核层掺杂有元素锶(Sr)，壳层无任何掺杂元素。
2、合成多晶正极材料LiNi0.82Co0.12Mn0.06O2：
(2-1)将上述制备得到的正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2与氢氧化锂充分混合得到混合物，氢氧化锂按照前驱体中过渡金属(包括Ni、Co、Mn)与氢氧化锂中锂的摩尔比为1：1.01加入；
(2-2)将(2-1)中的混合物置于马弗炉中煅烧，高温煅烧温度为900℃，煅烧时间为6小时，随后降温至700℃煅烧10小时，煅烧气氛为纯氧气气氛，煅烧结束后自然冷却；
(2-3)将(2-2)中冷却后所得粉末破碎，过筛，除磁后真空封装，得到多晶正极材料LiNi0.82Co0.12Mn0.06O2。
3、正极片制备：
将多晶正极材料与聚偏氟乙烯(PVDF)、导电剂super P按照质量比90:5:5，加入到N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀得到浆料，将浆料涂布在铝箔集流体上，烘干、冷压、分切制得正极片。
4、锂离子电池制备：
将上述制备的正极片与锂片、电解液(1mol/L LiPF6)和隔膜制成2032扣式电池。
对比例3
锂离子电池正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2的合成，对比例3与实施例3的区别仅在于，对比例3没有分段加入步骤(3)的锶盐溶液，而是在合成前驱体的过程中持续将锶盐溶液一步加入，其他操作相同，最终生成的前驱体Ni0.82Co0.12Mn0.06(OH)2整个颗粒中具有均匀的锶掺杂。
按照实施例3相同的方法，采用对比例3的正极材料前驱体Ni0.82Co0.12Mn0.06(OH)2制备得到正极材料LiNi0.82Co0.12Mn0.06O2。
按照实施例3相同的方法，采用对比例3的正极材料LiNi0.82Co0.12Mn0.06O2制备正极片和锂离子电池。
将实施例3中所制备得到的正极材料前驱体颗粒和多晶正极材料颗粒通过FIB切割。通过EDS对实施例3的正极材料前驱体颗粒和多晶正极材料颗粒截面进行观察，可以观测到，截面内侧有明显的Sr元素 的信号。通过SEM观察实施例3多晶正极材料的截面形貌特征，可以观察到多晶正极材料的截面内侧的一次颗粒平均粒径明显大于外侧的一次颗粒平均粒径，截面外侧晶界分布明显比截面内侧晶界分布更密集。
将对比例3中所制备得到的正极材料前驱体颗粒和多晶正极材料颗粒通过FIB切割。通过EDS对对比例3的正极材料前驱体颗粒和多晶正极材料颗粒截面进行观察，可以观测到，Sr的信号在正极材料前驱体颗粒和多晶正极材料颗粒截面的内外侧均匀分布。通过SEM观察对比例3多晶正极材料的截面形貌特征，可以观察到多晶正极材料的截面上内外侧的一次晶粒的粒径大小均一。
将实施例3和对比例3制备的电池在25±5℃条件下，分别以0.1C/0.1C，1C/1C充放电倍率在3.0V-4.3V电压区间内对电池进行充放电测试，并记录电池的首圈充放电容量和100圈循环保持率，结果如表3所示。
表3：实施例3和对比例3电池的电化学性能
由表3的结果可知，本申请实施例通过掺杂使正极材料前驱体材料只有核层有Sr元素的掺杂，从而在多晶正极材料二次颗粒的形成过程中，在Sr元素的作用下，可以使得最终获得的多晶正极材料的内层的一次颗粒的平均粒径大于外层的一次颗粒的平均粒径，即形成内层和外层一次颗粒的平均粒径梯度分布的结构，相对于对比例3的均匀掺杂结构，本申请实施例的具有内外层一次颗粒的平均粒径梯度分布结构的电极材料，可以有效改善电极材料二次颗粒因晶界开裂导致的循环性能恶化的问题，本申请实施例3的正极材料相比对比例3具有更佳的倍率性能和容量保持率。
应理解，本文中涉及的第一、第二以及各种数字编号仅为描述方便进行的区分，并不用来限制本申请的范围。
本申请中，“和/或”，描述关联对象的关联关系，表示可以存在三种关系，例如，A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B的情况，其中A,B可以是单数或者复数。字符“/”一般表示前后关联对象是一种“或”的关系。
本申请中，“至少一个”是指一个或者多个，“多个”是指两个或两个以上。“以下至少一项(个)”或其类似表达，是指的这些项中的任意组合，包括单项(个)或复数项(个)的任意组合。例如，“a,b,或c中的至少一项(个)”，或，“a,b,和c中的至少一项(个)”，均可以表示：a,b,c,a-b(即a和b),a-c,b-c,或a-b-c，其中a,b,c分别可以是单个，也可以是多个。
应理解，在本申请的各种实施例中，上述各过程的序号的大小并不限定执行顺序的先后，部分或全部步骤可以并行执行或先后执行，各过程的执行顺序应以其功能和内在逻辑确定，而不应对本申请实施例的实施过程构成任何限定。

Claims (33)

  1. 一种电极材料，其特征在于，所述电极材料包括由多个一次颗粒聚集而成的二次颗粒，所述二次颗粒包括内层和包覆于所述内层外侧的外层，其中，所述内层的一次颗粒的平均粒径大于所述外层的一次颗粒的平均粒径。
  2. 如权利要求1所述的电极材料，其特征在于，所述二次颗粒为球形或类球形颗粒。
  3. 如权利要求2所述的电极材料，其特征在于，所述二次颗粒的中心与所述二次颗粒的表面上任意一点之间的总径向距离为R，所述外层为从所述二次颗粒的表面至朝向中心延伸20％-60％所述R的长度所对应的区域；所述内层为从所述二次颗粒的中心至朝向表面延伸40％-80％所述R的长度所对应的区域。
  4. 如权利要求3所述的电极材料，其特征在于，所述内层的一次颗粒的平均粒径为0.01R’至1.4R’，所述R’为所述二次颗粒的最长径的一半。
  5. 如权利要求3所述的电极材料，其特征在于，所述外层的一次颗粒的平均粒径为0.001R’至0.3R’，所述R’为所述二次颗粒的最长径的一半。
  6. 如权利要求1-5任一项所述的电极材料，其特征在于，所述内层的一次颗粒的平均粒径为外层的一次颗粒的平均粒径的1.1倍至15倍。
  7. 如权利要求1-6任一项所述的电极材料，其特征在于，所述内层包括促进晶粒生长的掺杂元素，和/或所述外层包括抑制晶粒生长的掺杂元素。
  8. 如权利要求7所述的电极材料，其特征在于，所述促进晶粒生长的掺杂元素包括锶，铈、铋、镁中的一种或多种；所述抑制晶粒生长的掺杂元素包括硼、磷、钛、锆、铌、锑、钽、钼、钨中的一种或多种。
  9. 如权利要求7-8任一项所述的电极材料，其特征在于，所述二次颗粒中，所述促进晶粒生长的掺杂元素和所述抑制晶粒生长的掺杂元素的总摩尔含量为0.1mol％-1mol％。
  10. 如权利要求1-9任一项所述的电极材料，其特征在于，所述一次颗粒的平均粒径为10nm-60μm。
  11. 如权利要求1-10任一项所述的电极材料，其特征在于，所述二次颗粒的平均粒径为1μm-200μm。
  12. 如权利要求1-11任一项所述的电极材料，其特征在于，所述电极材料包括锂离子电池电极材料、钠离子电池电极材料、钾离子电池电极材料或镁离子电池电极材料。
  13. 如权利要求1-12任一项所述的电极材料，其特征在于，所述二次颗粒包括电池正极用金属氧化物。
  14. 如权利要求13所述的电极材料，其特征在于，所述电池正极用金属氧化物为锂离子电池正极用金属氧化物、钠离子电池正极用金属氧化物、钾离子电池正极用金属氧化物或镁离子电池正极用金属氧化物。
  15. 如权利要求14所述的电极材料，其特征在于，所述锂离子电池正极用金属氧化物包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂钛氧化物、锂铁磷氧化物、锂镍钴氧化物、锂镍锰氧化物、镍钴多元氧化物中的一种或多种。
  16. 如权利要求7-9任一项所述的电极材料，其特征在于，所述外层的最外侧含有所述抑制晶粒生长的掺杂元素的氧化物。
  17. 如权利要求1-16所述的电极材料，其特征在于，所述电极材料还包括包覆在所述二次颗粒表面的保护层。
  18. 一种电极材料的制备方法，其特征在于，包括：
    将电极材料前驱体与金属盐混合后经煅烧得到电极材料，所述电极材料前驱体包括核层和包覆所述核层的壳层，所述核层包括促进晶粒生长的掺杂元素，和/或所述壳层包括抑制晶粒生长的掺杂元素；所述电极材料包括由多个一次颗粒聚集而成的二次颗粒，所述二次颗粒包括内层和包覆所述内层的外层，其中，所述内层的一次颗粒的平均粒径大于所述外层的一次颗粒的平均粒径。
  19. 如权利要求18所述的制备方法，其特征在于，所述煅烧包括依次进行的第一次煅烧和第二次煅烧，所述第一次煅烧的温度高于所述第二次煅烧的温度；所述第一次煅烧的时间为2-4小时，所述第二次煅烧的时间为6-14小时。
  20. 如权利要求19所述的制备方法，其特征在于，所述第一次煅烧的温度为600℃-1000℃，所述第二次煅烧的温度为400℃-800℃。
  21. 如权利要求18所述的制备方法，其特征在于，所述金属盐包括锂盐、钠盐、钾盐或镁盐。
  22. 如权利要求18所述的制备方法，其特征在于，所述电极材料前驱体包括电池正极用金属氧化物前驱体。
  23. 如权利要求22所述的制备方法，其特征在于，所述电池正极用金属氧化物前驱体包括金属氧化物的氢氧化物前驱体、金属氧化物的氧化物前驱体、金属氧化物的碳酸盐前驱体或金属氧化物的羟基氧化物前驱体。
  24. 一种电极材料前驱体，其特征在于，所述电极材料前驱体包括核层和包覆所述核层的壳层，所述核层包括促进晶粒生长的掺杂元素，和/或所述壳层包括抑制晶粒生长的掺杂元素。
  25. 如权利要求24所述的电极材料前驱体，其特征在于，所述电极材料前驱体包括电池正极用金属氧化物前驱体。
  26. 如权利要求25所述的电极材料前驱体，其特征在于，所述电池正极用金属氧化物前驱体包括金属氧化物的氢氧化物前驱体、金属氧化物的氧化物前驱体、金属氧化物的碳酸盐前驱体或金属氧化物的羟基氧化物前驱体。
  27. 如权利要求24-26任一项所述的电极材料前驱体，其特征在于，所述促进晶粒生长的掺杂元素包括锶、铈、铋、镁中的一种或多种；所述抑制晶粒生长的掺杂元素包括硼、磷、钛、锆、铌、锑、钽、钼、钨中的一种或多种。
  28. 一种电极材料前驱体的制备方法，其特征在于，包括：
    将电极材料前驱体的核层的金属源溶液与沉淀剂、络合剂混合，形成第一原料液；将第一原料液于惰性气氛下进行第一共沉淀反应，得到电极材料前驱体的核层；
    将电极材料前驱体的壳层的金属源溶液与沉淀剂、络合剂混合，形成第二原料液；
    其中，所述第一原料液还包括促进晶粒生长的掺杂元素源，和/或所述第二原料液还包括抑制晶粒生长的掺杂元素源；
    将所述第二原料液与所述电极材料前驱体的核层混合后，于惰性气氛下进行第二共沉淀反应，在所述电极材料前驱体的核层表面形成壳层，得到电极材料前驱体。
  29. 如权利要求28所述的制备方法，其特征在于，所述促进晶粒生长的掺杂元素源包括含锶、铈、铋、镁中的一种或多种掺杂元素的化合物；所述抑制晶粒生长的掺杂元素源包括含硼、磷、钛、锆、铌、锑、钽、钼、钨中的一种或多种掺杂元素的化合物。
  30. 一种电极片，其特征在于，所述电极片包括集流体和设置在所述集流体表面的电极活性层，所述电极活性层包括权利要求1-17任一项所述的电极材料。
  31. 一种电池，其特征在于，所述电池包括权利要求1-17任一项所述的电极材料，或者包括权利要求30所述的电极片。
  32. 一种装置，其特征在于，所述装置包括权利要求31所述的电池。
  33. 如权利要求32所述的装置，其特性在于，所述装置包括电子设备、储能系统或车辆。
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