WO2024041531A1 - 正极活性材料及其制备方法、正极极片、二次电池和电子设备 - Google Patents

正极活性材料及其制备方法、正极极片、二次电池和电子设备 Download PDF

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WO2024041531A1
WO2024041531A1 PCT/CN2023/114239 CN2023114239W WO2024041531A1 WO 2024041531 A1 WO2024041531 A1 WO 2024041531A1 CN 2023114239 W CN2023114239 W CN 2023114239W WO 2024041531 A1 WO2024041531 A1 WO 2024041531A1
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fluorine
active material
doped
preparation
ternary
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PCT/CN2023/114239
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English (en)
French (fr)
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陈德贤
王慧敏
李琪
吕菲
徐宁
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天津巴莫科技有限责任公司
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Priority to EP23798327.5A priority Critical patent/EP4350814A1/en
Publication of WO2024041531A1 publication Critical patent/WO2024041531A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • 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
    • 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 present application relates to the field of electrochemistry technology, and in particular to a positive active material and its preparation method, positive electrode sheet, secondary battery and electronic equipment.
  • Secondary batteries represented by lithium-ion batteries have the advantages of high operating voltage, high energy density, good safety and no memory effect, and have achieved great success in the fields of portable electronic devices, electric vehicles and hybrid vehicles.
  • ternary materials such as nickel, cobalt and manganese are widely used as cathode materials due to their advantages such as higher capacity and energy density.
  • secondary batteries containing ternary cathode materials such as nickel, cobalt and manganese The structural stability is poor during deep charge and discharge, resulting in poor cycle performance.
  • this application provides a cathode active material and a preparation method thereof, a cathode plate, a secondary battery and an electronic device, aiming to improve the structural stability and cycle performance of the secondary battery.
  • a first aspect of the application provides a cathode active material including:
  • a coating structure covering at least part of the surface of a fluorine-doped ternary cathode material substrate wherein the coating structure includes an aluminum-rich inner coating layer relatively close to the surface of the fluorine-doped ternary cathode material substrate and a coating layer relatively far away from the fluorine-doped ternary cathode material substrate.
  • the cathode active material satisfies at least one of the following conditions (1) to (2):
  • the fluorine-doped ternary cathode material matrix includes a transition region, which is distributed in a shallow layer of the fluorine-doped ternary cathode material matrix close to the coating structure, and the transition region Contains AlF 3 ;
  • the cladding structure also includes a transition layer located between the aluminum-rich inner cladding layer and the titanium-rich outer cladding layer, with Li-Al-O distributed in the transition layer. -Ti solid solution structure.
  • the cathode active material satisfies at least one of the following conditions (1) to (4):
  • the average particle size of the particles of the positive electrode active material is 3 ⁇ m to 15 ⁇ m;
  • the average particle size of the particles of the fluorine-doped ternary cathode material matrix is 3 ⁇ m to 15 ⁇ m;
  • the thickness of the aluminum-rich inner cladding layer is 5nm ⁇ 100nm;
  • the thickness of the titanium-rich outer cladding layer is 5nm to 100nm.
  • the cathode active material satisfies at least one of the following conditions (1) to (3):
  • the mass percentage of aluminum element in the aluminum-rich inner cladding layer is 0.002% to 20%;
  • the mass percentage of titanium element in the titanium-rich outer cladding layer is 0.002% to 20%.
  • the second aspect of the application provides a method for preparing a positive active material, including:
  • a secondary sintering process is performed to form a coating structure covering at least part of the surface of the fluorine-doped ternary cathode material matrix,
  • the coating structure includes an aluminum-rich inner coating layer relatively close to the surface of the fluorine-doped ternary cathode material base and a titanium-rich outer coating layer relatively far away from the surface of the fluorine-doped ternary cathode material base.
  • mixing the sol of the fluorine-containing ternary precursor and the lithium salt, and performing a sintering process includes:
  • the pre-dopant is subjected to a primary sintering treatment at 300°C to 1000°C, preferably 350°C to 950°C, for 10h to 30h, preferably 15h to 25h.
  • the preparation method satisfies at least one of the following conditions (1) to (3):
  • Lithium salts include one or more of lithium carbonate, lithium hydroxide, lithium nitrate or lithium acetate;
  • the secondary sintering process includes:
  • the fluorine-doped ternary cathode material matrix and the MAX compound-containing coating agent are evenly mixed and then ball-milled to obtain a pre-coating material;
  • the pre-coating material is subjected to a segmented sintering process to form a coating structure covering at least part of the surface of the fluorine-doped ternary cathode material matrix to obtain a cathode active material.
  • performing segmented sintering treatment on the pre-cladding material includes:
  • the first sintered material is subjected to a sintering treatment at 400°C to 700°C, preferably 450°C to 650°C, for 5h to 30h, preferably 10h to 25h, to obtain a positive electrode active material.
  • the preparation method satisfies at least one of the following conditions (1) to (3):
  • the molecular formula of the coating agent containing MAX type compound is Ti m AlC n , where 0 ⁇ m ⁇ 5, 0 ⁇ n ⁇ 5;
  • the coating agent containing MAX type compound includes nanoparticles of MAX type compound, and the average particle size of the nanoparticles is 10nm ⁇ 2000nm;
  • providing a sol containing a fluorine-containing ternary precursor includes:
  • the mixture is ball milled to provide a sol containing the fluorine-containing ternary precursor.
  • the preparation method satisfies at least one of the following conditions (1) to (3):
  • the solid content of the sol containing the fluorine-containing ternary precursor is 5% to 50%;
  • the concentration of the aqueous solution containing fluoride salt is 0.05mol/L ⁇ 5mol/L;
  • the preparation method satisfies at least one of the following conditions (1) to (4):
  • the molecular formula of the ternary precursor is Ni a Co b Mn 1-ab (OH) 2 , where 0.33 ⁇ a ⁇ 0.95, 0.05 ⁇ b ⁇ 0.77;
  • the ternary precursor contains micron particles, and the average particle size of the micron particles is 4 ⁇ m to 20 ⁇ m;
  • the dispersant includes one or more of cetyltrimethylammonium chloride, dodecyltrimethylammonium chloride, cetylpyridinium chloride and sodium benzenesulfonate;
  • the fluoride salt includes one or more of ammonium fluoride, sodium fluoride, magnesium fluoride and aluminum fluoride, preferably ammonium fluoride.
  • a third aspect of the application provides a cathode electrode sheet, including the cathode active material provided in the first aspect of the application or the cathode active material prepared according to the preparation method provided in the second aspect of the application.
  • a fourth aspect of the present application provides a secondary battery, including the positive electrode plate provided in the third aspect of the present application.
  • the fifth aspect of the present application provides an electronic device, including the secondary battery provided by the fourth aspect of the present application.
  • the electronic device of the present application includes the secondary battery provided by the present application, and thus has at least the same advantages as the secondary battery.
  • the cathode active material provided by this application is doped with fluorine element.
  • the doped fluorine element can enter the crystal lattice of the cathode active material bulk phase and suppress the lattice distortion caused by the migration of oxygen element during the cycle, thereby Improve the stability of the crystal structure, reduce grain boundary cracks and structural collapse caused by the deintercalation of active ions (such as lithium ions) in the crystal structure, improve the structural stability of the cathode active material, and thereby improve the cycle performance of the secondary battery.
  • the coating structure composed of an aluminum-rich inner coating layer and a titanium-rich outer coating layer in the cathode active material is uniform, dense, and has high mechanical strength. It can effectively stabilize the electrode/electrolyte interface of the secondary battery cathode and isolate the cathode.
  • the reaction path between the highly oxidized transition metal elements in the active material and the electrolyte can reduce the formation of hydrofluoric acid, reduce the dissolution of transition metal elements caused by hydrofluoric acid corroding the surface of the cathode active material, and weaken the dissolution of transition metal elements.
  • the resulting distortion of the surface structure of the cathode active material further improves the interface stability of the ternary cathode of the secondary battery and further improves the cycle performance of the secondary battery.
  • Figure 1 is an XRD pattern of the cathode active materials of Examples 1 to 2 and Comparative Example 1.
  • Figure 2 is an SEM image and an EDS image of the cathode active material of Example 1.
  • Figure 3 is a comparison chart of the cycle performance of the cathode active materials of Examples 1 to 2 and Comparative Examples 1 to 2. .
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • every point or individual value between the endpoints of a range is included in the range.
  • each point or single value may serve as a lower or upper limit on its own in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • secondary batteries containing ternary cathode materials such as nickel, cobalt and manganese have two main problems during the cycle: (1) During the cycle, the secondary battery contains active ions (such as lithium ions) The continuous embedding and detachment will cause the expansion and contraction of the crystal lattice in the ternary cathode material, which can easily lead to grain boundary cracks and the collapse of the crystal structure in the ternary cathode material, reducing the cycle performance of the battery; (2) Secondary There is an electrode/electrolyte interface reaction in the positive electrode of the secondary battery.
  • active ions such as lithium ions
  • the electrolyte easily reacts with the highly oxidized Ni 4+ in the ternary positive electrode material at the electrode interface to produce hydrofluoric acid, which corrodes the electrode interface, resulting in The massive dissolution of transition metal elements causes further decline in the cycle performance of secondary batteries.
  • the traditional method is to perform solid-phase doping modification of elements on ternary materials, such as doping a single nano-oxide or co-doping multiple elements, which can improve the crystal structure of ternary materials to a certain extent. stability, thereby improving its cycle performance; and using inorganic metal oxides, such as alumina, magnesium oxide, titanium oxide and boron oxide, as coating agents to coat and modify ternary materials, to a certain extent avoid
  • ternary material and the electrolyte reduces the dissolution of transition metal ions and improves the cycle performance of the secondary battery.
  • a first aspect of the embodiment of the present application provides a cathode active material, including: a fluorine-doped ternary cathode material matrix; and a coating structure covering at least part of the surface of the fluorine-doped ternary cathode material matrix, wherein , the cladding structure includes an aluminum-rich inner cladding layer relatively close to the surface of the fluorine-doped ternary cathode material base and relatively far away from the fluorine-doped ternary cathode material.
  • a titanium-rich outer cladding layer on the surface of the material substrate.
  • the cathode active material provided by this application is doped with fluorine element.
  • the doped fluorine element can enter the bulk phase lattice of the cathode active material and replace part of the oxygen atoms to form a bond energy higher than that of MO chemical bonds.
  • Strong MF chemical bonds M is Ni, Co or Mn
  • the grain boundary cracks and the collapse of the crystal structure caused by the deintercalation of active ions (such as lithium ions) improve the structural stability of the cathode active material, thereby improving the cycle performance of the secondary battery.
  • part of the doped fluorine element will remain in the superficial layer of the cathode active material, forming fluorides such as AlF 3 and TiF 3 in the interface layer of the cathode. This part of fluoride can better isolate the secondary battery.
  • the electrode/electrolyte interface is conducive to enhancing interface stability and improving cycle performance.
  • the fluorine-doped ternary cathode material matrix includes a transition region.
  • the transition region is distributed in a shallow layer of the fluorine-doped ternary cathode material matrix close to the cladding structure, and the transition region contains AlF 3 .
  • the radius of the fluorine atom doped into the bulk phase of the cathode active material is smaller than the radius of the oxygen atom, doping with fluorine element will increase the tetrahedral space volume of the crystal lattice of the cathode active material.
  • This can increase the interlayer spacing to a certain extent, broaden the diffusion channels of active ions (such as lithium ions), accelerate the deintercalation rate of active ions in the crystal lattice, and reduce the risk of active ions staying or even accumulating during the deintercalation process.
  • the grain boundary cracks and crystal structure collapse further improve the structural stability of the cathode active material and the cycle performance of the secondary battery.
  • the Ni-F bond with stronger bond energy formed after doping with fluorine element can reduce the degree of mixing of Li + /Ni 2+ and make the layered structure of the cathode active material more orderly and complete, thus improving its Structural stability further improves the cycle performance of secondary batteries.
  • the cladding structure further includes a transition layer located between the aluminum-rich inner cladding layer and the titanium-rich outer cladding layer, and a Li-Al-O-Ti solid solution structure is distributed in the transition layer.
  • the coating structure composed of an aluminum-rich inner cladding layer and a titanium-rich outer cladding layer in the cathode active material has high uniformity and density, high mechanical strength, and can effectively stabilize the secondary battery cathode.
  • the electrode/electrolyte interface isolates the reaction path between the highly oxidized transition metal elements in the cathode active material and the electrolyte, thereby reducing the formation of hydrofluoric acid and reducing the dissolution of transition metal elements caused by hydrofluoric acid corroding the surface of the cathode active material.
  • the particles of the cathode active material have an average particle diameter of 3 ⁇ m to 15 ⁇ m.
  • the average particle size of the positive active material is within a suitable range, which is conducive to more uniform mixing between particles, reduces the gap between particles when mixing, increases the compaction density of the positive electrode, and improves the rate performance of the secondary battery.
  • the average particle size of the particles of the fluorine-doped ternary cathode material matrix is 3 ⁇ m to 15 ⁇ m.
  • the average particle size of the particles of the fluorine-doped ternary cathode material matrix is controlled within the above range, which is beneficial to improving the uniformity of contact and mixing with the MAX compound-containing coating agent, and improving the effectiveness of the MAX compound-containing coating agent. The uniformity of coating, thereby improving the uniformity and density of the coating structure.
  • the thickness of the aluminum-rich inner cladding layer is 5 nm to 100 nm.
  • the thickness of the aluminum-rich inner cladding layer is 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100nm or within the range of any of the above values.
  • the thickness of the titanium-rich outer cladding layer is 5 nm to 100 nm.
  • the thickness of the titanium-rich outer cladding layer is 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100nm or within the range of any of the above values.
  • the thickness of the aluminum-rich inner cladding layer and the titanium-rich outer cladding layer is lower than 5nm, the coating effect will be poor and the coating will not be in place; if the thickness of the coating layer is higher than 100nm, the secondary battery will be damaged. The capacity and cycle performance are reduced, so the thickness of the coating layer needs to be controlled within the above range.
  • the mass percentage of aluminum element in the aluminum-rich inner cladding layer is 0.002% to 20% based on the total mass of the cathode active material.
  • the mass percentage of titanium element in the titanium-rich outer coating layer is 0.002% to 20% based on the total mass of the cathode active material.
  • a second aspect of the embodiment of the present application provides a method for preparing a cathode active material, including the following steps:
  • a secondary sintering process is performed to form a coating covering at least part of the surface of the fluorine-doped ternary cathode material matrix.
  • the structure, wherein the coating structure includes an aluminum-rich inner coating layer relatively close to the surface of the fluorine-doped ternary cathode material base and a titanium-rich outer coating layer relatively far away from the surface of the fluorine-doped ternary cathode material base.
  • the sol of the fluorine-containing ternary precursor and the lithium salt are used to perform liquid phase mixing and sintering to realize the doping of the fluorine element (wet doping), which can increase the amount of the fluorine element.
  • the covering contact area of the ternary precursor makes it easier for the fluorine element to enter the lattice of the ternary material during a sintering process, and achieves an orderly doping distribution inside the material lattice, forming a
  • M-F chemical bond with strong bond energy weakens the migration of oxygen element during deep charge and discharge cycles and inhibits the lattice distortion caused by the migration of oxygen element, thereby improving the stability of the crystal structure and reducing Grain boundary cracks and the collapse of the crystal structure caused by the deintercalation of active ions (such as lithium ions) in the crystal structure improve the structural stability of the cathode active material, thereby improving the cycle performance of the secondary battery.
  • the secondary sintering treatment can form a coating structure composed of an aluminum-rich inner cladding layer and a titanium-rich outer cladding layer.
  • This coating structure has high uniformity and density, high mechanical strength, and can effectively stabilize the secondary
  • the electrode/electrolyte interface of the secondary battery cathode isolates the reaction path between the highly oxidized transition metal elements in the cathode active material and the electrolyte, thereby reducing the formation of hydrofluoric acid and reducing the transition caused by hydrofluoric acid corroding the surface of the cathode active material.
  • the dissolution of metal elements weakens the distortion of the surface structure of the cathode active material caused by the dissolution of transition metal elements, thereby improving the interface stability of the ternary cathode of secondary batteries and improving its cycle performance.
  • providing a sol containing a fluorine-containing ternary precursor in step S10 includes the following steps:
  • the solid content of the sol containing the fluorine-containing ternary precursor is 5% to 50%.
  • the solid content can be 5%, 10%, 15%, 20%, 25%, 30%, 35%. , 40%, 45%, 50% or within the range of any of the above values. Controlling the solid content within an appropriate range will help improve the utilization rate of the fluorine-containing ternary precursor, and at the same time avoid more agglomeration and precipitation.
  • the solid content after mixing the ternary precursor, dispersant and fluoride salt-containing aqueous solution is exactly within the range of 5 to 50%, evaporated water does not need to be used; if the obtained mixed solution is relatively dilute, or the target solid content is to be obtained.
  • the mixed solution can be placed in a rotary evaporator to evaporate the solvent to obtain the sol with the target solid content.
  • the molecular formula of the ternary precursor is Ni a Co b Mn 1-ab (OH) 2 , where 0.33 ⁇ a ⁇ 0.95 and 0.05 ⁇ b ⁇ 0.77.
  • the ternary precursor includes microparticles, and the average particle diameter of the microparticles is 4 ⁇ m to 20 ⁇ m.
  • the average particle diameter of the microparticles is 4 ⁇ m, 7 ⁇ m, 10 ⁇ m, 13 ⁇ m, 16 ⁇ m, 19 ⁇ m, 20 ⁇ m or above. Any range of values.
  • the average particle size of the microparticles contained in the ternary precursor has a meaning known in the art and can be measured using instruments and methods known in the art. For example, you can refer to the GB/T 19077-2016 particle size distribution laser diffraction method and use a laser particle size analyzer to conveniently measure it, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the United Kingdom.
  • the concentration of the aqueous solution containing fluoride salt is 0.05 mol/L ⁇ 5 mol/L.
  • the concentration can be 0.05mol/L, 0.1mol/L, 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, 2.5mol/L, 3mol/L, 3.5mol/L, 4mol/L, 4.5mol/L , 5mol/L or within the range of any of the above values. Controlling the concentration of the fluoride salt aqueous solution within an appropriate range is beneficial to obtaining a fluorine-containing ternary precursor with an appropriate fluorine element concentration, thereby achieving better fluorine element doping effect in the subsequent primary sintering process.
  • the type of fluoride salt is not specifically limited and can be selected according to actual needs.
  • the fluoride salt may include one or more of ammonium fluoride, sodium fluoride, magnesium fluoride and aluminum fluoride, preferably ammonium fluoride.
  • the functions of using fluoride salt as a dopant in this application include: on the one hand, the electronegativity of fluorine doping is higher than that of oxygen atoms, so doping can strengthen the bond between metal atoms and anions in the ternary material. can help stabilize the structure; more importantly, after fluorine atoms are doped, the fluorine atoms doped in the shallow layer can react with the aluminum-rich layer to form AlF 3 with better stability, effectively stabilizing the structure of the shallow layer. Suppresses the structural reconstruction phenomenon that occurs during the circulation process.
  • the mass ratio of the ternary precursor, the dispersant and the fluoride salt is 1:(0.001 ⁇ 1.0):(0.001 ⁇ 0.1).
  • the type of dispersant is not specifically limited and can be selected according to actual needs.
  • the dispersant may include one or more of cetyltrimethylammonium chloride, dodecyltrimethylammonium chloride, cetylpyridinium chloride, and sodium benzenesulfonate.
  • step S20 the sol of the fluorine-containing ternary precursor and the lithium salt are mixed, and performing a sintering process includes the following steps:
  • the molecular formula of the fluorine-doped ternary cathode material matrix is LiNix Co y Mn 1-xy O 2-z F z , where 0.33 ⁇ x ⁇ 0.95, 0.05 ⁇ y ⁇ 0.77, 0 ⁇ z ⁇ 1.
  • the molar ratio of the lithium element in the lithium salt to all transition metal elements in the fluorine-doped ternary cathode material matrix is (1.0 ⁇ 1.1):1.
  • the type of lithium salt is not specifically limited and can be selected according to actual needs.
  • the lithium salt may include one or more of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.
  • the temperature of the first sintering process is 300°C to 1000°C, for example, it can be 300°C, 400°C, 500°C, 600°C, 700°C, 800°C, 900°C, 1000°C or above. Any range of values.
  • the temperature of the first sintering treatment is 350°C to 950°C.
  • the time of the first sintering process is 10h to 30h, for example, it can be 10h, 15h, 20h, 25h, 30h or within the range of any of the above values.
  • the time of the first sintering treatment is 15h to 25h.
  • the sintering atmosphere for the first sintering process is not particularly limited and can be selected according to actual needs.
  • the sintering atmosphere may be air, oxygen, or a mixed atmosphere of air and oxygen.
  • the temperature and time of the first sintering treatment are controlled within an appropriate range.
  • M is Ni, Co or Mn
  • MO chemical bonds which weakens the migration of oxygen elements during deep charge and discharge cycles and inhibits crystallization caused by the migration of oxygen elements.
  • Lattice distortion thereby improving the stability of the crystal structure, reducing grain boundary cracks and the collapse of the crystal structure caused by the deintercalation of active ions (such as lithium ions) in the crystal structure, improving the structural stability of the cathode active material, and thereby improving the secondary Secondary battery cycle performance.
  • active ions such as lithium ions
  • some fluorine elements will remain in the superficial layer of the cathode active material, forming fluorides such as AlF 3 and TiF 3 in the interface layer of the cathode. This part of fluoride can better isolate the electrode of the secondary battery/ The electrolyte interface is conducive to enhancing the stability of the interface and improving its cycle performance.
  • the secondary sintering process includes the following steps:
  • the molecular formula of the MAX compound-containing coating agent is Tim AlC n , where 0 ⁇ m ⁇ 5, 0 ⁇ n ⁇ 5.
  • the MAX compound-containing coating agent is Ti 3 AlC 2 .
  • MAX compounds as coating agents for the following reasons: (1) M and X in MAX compounds form a layered structure, and A is an interlayer element. Its structural characteristics determine the composition of There will be differences in activity; (2) MAX compounds have a layered structure, which is very similar to ternary materials. In addition, their electronic conductivity is high, which is much higher than that of conventional oxide coatings (conventional oxide coatings). The electronic conductivity of the coating is about 10 -4 cm/s). After coating, it can not only suppress the interface reaction, but also improve the electrochemical activity of the coated material such as rate; (3) MAX type compounds are simple to prepare and are made of Composed of common elements, the cost is controllable and easy to industrialize.
  • the MAX compound-containing coating agent includes nanoparticles of the MAX compound, and the average particle size of the nanoparticles is 10 nm to 2000 nm.
  • the average particle diameter of the nanoparticles is 100nm, 400nm, 700nm, 1000nm, 1300nm, 1600nm, 1900nm or within the range of any of the above values.
  • the average particle size of the nanoparticles of the MAX type compound is within a suitable range, which can achieve uniform coating and is conducive to the compactness of the subsequently formed coating layer.
  • the mass ratio of the fluorine-doped ternary cathode material matrix to the MAX-type compound-containing coating agent is 1: (0.0005-0.1).
  • the pre-dopant needs to be sintered step by step in steps S3100 and S3110 as follows. processing, and it is necessary to control the heating rate during the segmented sintering process.
  • performing segmented sintering on the pre-cladding material in step S310 includes the following steps:
  • S3110 Perform a sintering treatment on the first sintered material at 400°C to 700°C, preferably 450°C to 650°C, for 5h to 30h, preferably 10h to 25h, to obtain a positive electrode active material.
  • step S3100 first performs a low-temperature sintering process.
  • the temperature of the low-temperature sintering process needs to be controlled between 5°C and 400°C, for example, 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C or within the range of any of the above values; the time needs to be Control it between 1h and 10h, for example, 2h, 4h, 8h or within the range of any of the above values; the heating rate is ⁇ 3°C/min.
  • the highly active Al element in the coating agent containing the MAX compound can be migrated Al 2 O 3 nanoparticles are formed on the surface, and are first coated on the surface of the ternary material to form an aluminum-rich inner cladding layer.
  • the coating layer presents an island-like structure and the structure is relatively loose.
  • step S3110 performs a high-temperature section sintering process.
  • the temperature of the high-temperature sintering treatment needs to be controlled between 400°C and 700°C, for example, 450°C, 500°C, 550°C, 600°C, 650°C or within the range of any of the above values; the time needs to be controlled between 5h and 30h. For example, 10h, 15h, 20h, 25h or within the range of any of the above values; heating rate ⁇ 5°C/min.
  • the MAX compound dopant can be decomposed to completely form TiO 2 , and the TiO 2 can be formed in a rich atmosphere.
  • the aluminum inner cladding layer is cladded to form a titanium-rich outer cladding layer, resulting in a double-layer cladding structure composed of an aluminum-rich inner cladding layer and a titanium-rich outer cladding layer. Since the obtained coating structure forms an Al 2 O 3 -TiO 2 solid solution, its structure is dense and uniform, and it has high mechanical strength.
  • the sintering atmospheres of the low-temperature section sintering process and the high-temperature section sintering process are not particularly limited and can be selected according to actual needs.
  • the sintering atmosphere may be air, oxygen, or a mixed atmosphere of air and oxygen.
  • a cladding structure composed of an aluminum-rich inner cladding layer and a titanium-rich outer cladding layer can be formed.
  • This cladding structure has high uniformity and density, and high mechanical strength. It can effectively stabilize the electrode/electrolyte interface of the positive electrode of the secondary battery and isolate the reaction path between the highly oxidized transition metal elements in the positive active material and the electrolyte, thereby reducing the formation of hydrofluoric acid and reducing the corrosion of the surface of the positive active material due to hydrofluoric acid.
  • the resulting dissolution of transition metal elements weakens the distortion of the surface structure of the cathode active material caused by the dissolution of transition metal elements, thereby improving the interface stability of the ternary cathode of secondary batteries and improving its cycle performance.
  • the third aspect of the embodiment of the present application provides a positive electrode sheet, including the positive active material provided in the first aspect of the present application or the positive active material prepared by the preparation method provided in the second aspect of the present application.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the second aspect of the present application.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • Composite current collectors can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • a fourth aspect of the embodiment of the present application provides a secondary battery, including the positive electrode plate provided in the third aspect of the present application.
  • the type of secondary battery is not specifically limited and may include any battery in which an electrochemical reaction occurs to convert chemical energy into electrical energy.
  • it may be a lithium-ion battery or a sodium-ion battery.
  • the secondary battery further includes a negative electrode plate, an electrolyte, and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • a fifth aspect of the embodiment of the present application provides an electronic device, including the secondary battery provided in the fourth aspect of the present application.
  • the secondary battery can be used as a power source in the electronic device.
  • the type of electronic device is not particularly limited and may be used in any electronic device known in the art.
  • electronic devices may include, but are not limited to, notebook computers, pen computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, headsets, etc.
  • Stereo headphones video recorders, LCD TVs, portable cleaners, portable CD players, mini discs, transceivers, electronic notepads, calculators, memory cards, portable recorders, radios, backup power supplies, motors, cars, motorcycles, boosters Bicycles, bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the preparation method of Comparative Example 1 is similar to the preparation method of Example 1, except that the positive electrode active material is not doped and coated, that is, Ni 0.6 Co 0.1 Mn 0.3 (OH) 2 ternary precursor and hydrogen
  • the temperature was 960°C
  • the sintering time was 12 hours
  • the undoped and coated cathode active material LiNi 0.6 Co 0.1 Mn 0.3 O 2 was obtained after jaw crushing, roller crushing and airflow pulverization.
  • Comparative Example 2 The preparation method of Comparative Example 2 is similar to the preparation method of Example 2. The difference is that the positive electrode active material is not doped with fluorine element, but the segmented sintering in this application is used to form an aluminum-rich inner layer and a titanium-rich inner layer.
  • the double-layer coating treatment of the outer layer is implemented as follows:
  • Comparative Example 3 The preparation method of Comparative Example 3 is similar to the preparation method of Example 1. The difference is that the positive electrode active material is only subjected to the liquid phase doping treatment of fluorine element in this application, but no coating treatment is performed, that is, the implementation is omitted. Step (3) in Example 1.
  • the specific implementation is as follows:
  • the preparation method of Comparative Example 4 is similar to the preparation method of Example 1, except that the positive electrode active material is first doped with fluorine element using a traditional dry method, and then coated with inorganic metal oxide.
  • the preparation method of Comparative Example 5 is similar to the preparation method of Example 1, except that only one sintering process is performed in step (3), the sintering temperature is 650°C, the sintering time is 10h, and the heating rate is 10°C/min.
  • the cathode active materials prepared in Examples 1 to 4 and Comparative Examples 1 to 5 or the further prepared lithium ions were subjected to relevant performance tests.
  • the test results are shown in Table 1-3 below.
  • test conditions or test standards for each performance test item are as follows:
  • the cathode active materials in Examples 1 to 2 and Comparative Example 1 were cycled for 200 cycles at a voltage of 2.8V-4.4V and a rate of 0.1C/0.1C, and then the cycled cathode active material powder was placed in an XRD testing instrument ( Model Bruker D8) sample stage, using a scanning rate of 2°/min and a scanning angle range of 10° to 90°, the XRD diffraction pattern shown in Figure 1 is obtained.
  • the samples of Examples 1 to 2 and Comparative Example 1 were subjected to XRD refinement to obtain the refinement data in Table 1 below; XRD refinement refers to the use of the Rietveld method to refine the XRD data.
  • the positive active material was tested with a ZEISS sigma 300 scanning electron microscope, and the morphology of the sample was observed with reference to the standard JY/T010-1996, and the morphology and EDS energy spectrum were obtained as shown in Figure 2.
  • the metal dissolution amounts of the three elements Ni, Co, and Mn were compared after storage at 80°C for 30 days and 60 days respectively when the battery was fully charged.
  • the test method is as follows: Assemble the prepared ternary positive electrode material into a button battery. When the battery is fully charged (4.4V), the battery is disassembled after storage at 80°C for 30 days and 60 days respectively. The positive electrode plates are cleaned with DMC and scraped. Remove the active material layer of the positive electrode sheet, and then heat it in aqua regia for 15min-30min to dissolve it. The solution is subjected to ICP testing for Ni, Co, and Mn content, and the data in Table 1 is obtained. The metal dissolution amounts of three elements: Ni, Co, and Mn were tested. The test results are shown in Table 2 below.
  • the lithium-ion battery is charged at 45°C with a constant current of 1C to 4.4V, then charged with a constant voltage until the current is 0.1C, left to stand for 5 minutes, and then discharged with a constant current of 1C to 2.8V.
  • This is a charge-discharge cycle, and tested Record the discharge capacity at this time as D01; perform 200 cycles of the lithium-ion battery according to the above charging and discharging process, and record the discharge capacity of the 200th cycle as D1. Record the test data in Table 3 below.
  • the values of the unit cell parameters c, a, c/a and the unit cell volume have increased, because the F atomic ratio
  • the radius of O atoms is small.
  • F doping can increase the volume of the tetrahedral space of the crystal lattice, thereby increasing the interlayer spacing to a certain extent, broadening the diffusion channels of active ions (such as lithium ions), and accelerating the diffusion of active ions in the crystal.
  • the deintercalation rate in the lattice further improves the stability of the cathode active material structure.
  • F doping enhances the stability of the unit cell structure and suppresses structural distortion during cycling. This is directly reflected in the fact that the half-peak width of the (104) crystal plane of Examples 1 to 2 is significantly higher than that of Comparative Example 1. ;
  • the synergistic effect of the surface aluminum-rich and titanium-rich coating layers forms a dense Li-Al-Ti-O solid solution structure, which reduces the "apparent volume” or "apparent size” of the material and further enhances the electrode/electrolyte interface
  • the stability is directly reflected in the fact that the peak position of the (003) crystal plane of Examples 1 to 2 is smaller than that of Comparative Example 1.
  • the dissolution amount of metal elements is significantly lower than that in Comparative Examples 1 to 5. It shows that F doping can better stabilize the crystal structure and improve the first efficiency of the material.
  • the coated fluorine doped and Al and Ti coated ternary cathode materials obtained by the preparation method provided in this application can be used in lithium ion batteries.
  • the cathode active material prepared in this application has good dispersion, the single crystal has a rounded morphology, and a uniform coating layer can be seen on the surface of the material.
  • Al, Ti and F elements can be detected on the surface of the material, and the coating layer includes a solid solution formed by the oxides of Al and Ti.
  • Examples 1 to 4 and Comparative Examples 1 to 5 have differentiated electrochemical properties.
  • the ternary cathode material prepared using the method provided by this application has charge and discharge capacity, first efficiency and cycle performance. It is better. It shows that by comparing Examples 1, 2 and Comparative Example 4, it can be seen that the charge and discharge capacity, first time efficiency and cycle performance of the ternary cathode material obtained by the preparation method provided in this application are higher than those of the blank sample, which only performs fluorine doping. Product performance obtained by hybrid or only aluminum-rich and titanium-rich coating processes.

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Abstract

一种正极活性材料及其制备方法、正极极片、二次电池和电子设备，正极活性材料包括：氟掺杂的三元正极材料基体；和覆于氟掺杂的三元正极材料基体的至少部分表面的包覆结构，其中，包覆结构包括靠近氟掺杂的三元正极材料基体表面的富铝内包覆层和远离氟掺杂的三元正极材料基体表面的富钛外包覆层。该正极活性材料能够提升二次电池的结构稳定性及循环性能。

Description

正极活性材料及其制备方法、正极极片、二次电池和电子设备
相关申请的交叉引用
本申请要求于2022年08月26日提交中国国家知识产权局的申请号为202211035114.0、名称为“正极活性材料及其制备方法、正极极片、二次电池和电子设备”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
本申请涉及电化学技术领域，特别是涉及一种正极活性材料及其制备方法、正极极片、二次电池和电子设备。
背景技术
以锂离子电池为代表的二次电池具有工作电压高、能量密度高、安全性好和无记忆效应等优点，已在便携式电子设备、电动汽车和混合动力汽车等领域获得了巨大的成功。目前，在传统的二次电池中，镍钴锰等三元材料因具有较高的容量和能量密度等优势而被广泛应用于正极材料，但是包含镍钴锰等三元正极材料的二次电池在进行深度充放电时的结构稳定性较差，导致其循环性能不佳。
发明内容
基于此，本申请提供一种正极活性材料及其制备方法、正极极片、二次电池和电子设备，旨在提升二次电池的结构稳定性及循环性能。
本申请的第一个方面提供了一种正极活性材料，包括：
氟掺杂的三元正极材料基体；和
覆于氟掺杂的三元正极材料基体的至少部分表面的包覆结构，其中，包覆结构包括相对靠近氟掺杂的三元正极材料基体表面的富铝内包覆层和相对远离氟掺杂的三元正极材料基体表面的富钛外包覆层。
根据本申请第一方面的任一实施方式，所述正极活性材料满足如下条件(1)至(2)中的至少一个：
(1)所述氟掺杂的三元正极材料基体包括过渡区，所述过渡区分布于所述氟掺杂的三元正极材料基体的靠近所述包覆结构的浅表层，所述过渡区内包含AlF3；
(2)所述包覆结构还包括过渡层，所述过渡层位于所述富铝内包覆层和所述富钛外包覆层之间，所述过渡层内分布有Li-Al-O-Ti固溶体结构。
根据本申请第一方面的任一实施方式，正极活性材料满足如下条件(1)至(4)中的至少一个：
(1)正极活性材料的粒子的平均粒径为3μm～15μm；
(2)氟掺杂的三元正极材料基体的粒子的平均粒径为3μm～15μm；
(3)富铝内包覆层的厚度为5nm～100nm；
(4)富钛外包覆层的厚度为5nm～100nm。
根据本申请第一方面的任一实施方式，所述正极活性材料满足如下条件(1)至(3)中的至少一个：
(1)氟掺杂的三元正极材料基体的分子式为LiwNixCoyMn1-x-yO2-zFz，其中，0.95≤w≤1.05，0.33≤x<0.95，0.05<y≤0.77，0＜z<1，当w＝1时，所述氟掺杂的三元正极材料基体的分子式为LiNixCoyMn1-x-yO2-zFz；
(2)基于正极活性材料的总质量，富铝内包覆层中铝元素的质量百分含量为0.002％～20％；
(3)基于正极活性材料的总质量，富钛外包覆层中钛元素的质量百分含量为0.002％～20％。
本申请的第二方面提供了一种正极活性材料的制备方法，包括：
提供含氟三元前驱体的溶胶；
对含氟三元前驱体的溶胶与锂盐进行混合处理，进行一次烧结处理，得到氟掺杂的三元正极材料基体；
对氟掺杂的三元正极材料基体与含MAX型化合物包覆剂混合处理后，进行二次烧结处理，以形成覆于氟掺杂的三元正极材料基体的至少部分表面的包覆结构，其中，包覆结构包括相对靠近氟掺杂的三元正极材料基体表面的富铝内包覆层和相对远离氟掺杂的三元正极材料基体表面的富钛外包覆层。
根据本申请第二方面的任一实施方式，对含氟三元前驱体的溶胶与锂盐进行混合处理，进行一次烧结处理包括：
将含氟三元前驱体的溶胶与锂盐混合均匀后进行球磨处理，得到预掺杂料；
在300℃～1000℃、优选为350℃～950℃下，对预掺杂料进行10h～30h、优选为15h～25h的一次烧结处理。
根据本申请第二方面的任一实施方式，制备方法满足如下条件(1)至(3)中的至少一者：
(1)氟掺杂的三元正极材料基体的分子式为LiwNixCoyMn1-x-yO2-zFz，其中，0.95≤w≤1.05，0.33≤x<0.95，0.05<y≤0.77，0＜z<1，当w＝1时，所述氟掺杂的三元正极材料基体的分子式为LiNixCoyMn1-x-yO2-zFz；
(2)锂盐包括碳酸锂、氢氧化锂、硝酸锂或醋酸锂中的一种或多种；
(3)锂盐中的锂元素与氟掺杂的三元正极材料基体中的所有过渡金属元素的摩尔比为 (1.0～1.1):1。
根据本申请第二方面的任一实施方式，对氟掺杂的三元正极材料基体与含MAX型化合物包覆剂混合处理后，进行二次烧结处理包括：
对氟掺杂的三元正极材料基体与含MAX型化合物包覆剂混合均匀后进行球磨处理，得到预包覆料；
对预包覆料进行分段烧结处理，以形成覆于氟掺杂的三元正极材料基体的至少部分表面的包覆结构，得到正极活性材料。
根据本申请第二方面的任一实施方式，对预包覆料进行分段烧结处理包括：
在5℃～400℃、优选为50℃～350℃下，对预包覆料进行1h～10h、优选为2h～8h的烧结处理，得到第一烧结料；
在400℃～700℃、优选为450℃～650℃下，对第一烧结料进行5h～30h、优选为10h～25h的烧结处理，得到正极活性材料。
根据本申请第二方面的任一实施方式，所述制备方法满足如下条件(1)至(3)中的至少一者：
(1)含MAX型化合物包覆剂的分子式为TimAlCn，其中，0<m<5，0<n<5；
(2)含MAX型化合物包覆剂包括MAX型化合物的纳米粒子，纳米粒子的平均粒径为10nm～2000nm；
(3)氟掺杂的三元正极材料基体与含MAX型化合物包覆剂的质量比为1:(0.0005～0.1)。
根据本申请第二方面的任一实施方式，提供含氟三元前驱体的溶胶包括：
使三元前驱体、分散剂与含氟化盐的水溶液接触并混合，得到混合液；
对混合液进行球磨处理，以提供含氟三元前驱体的溶胶。
根据本申请第二方面的任一实施方式，制备方法满足如下条件(1)至(3)中的至少一者：
(1)含氟三元前驱体的溶胶的固含量为5％～50％；
(2)含氟化盐的水溶液的浓度为0.05mol/L～5mol/L；
(3)三元前驱体、所述分散剂及所述氟化盐的质量比为1:(0.001～1.0):(0.001～0.1)。
根据本申请第二方面的任一实施方式，制备方法满足如下条件(1)至(4)中的至少一者：
(1)三元前驱体的分子式为NiaCobMn1-a-b(OH)2，其中，0.33≤a<0.95，0.05<b≤0.77；
(2)三元前驱体包含微米粒子，微米粒子的平均粒径为4μm～20μm；
(3)分散剂包括十六烷基三甲基氯化铵、十二烷基三甲基氯化铵、十六烷基氯化吡啶和苯磺酸钠中的一种或几种；
(4)氟化盐包括氟化铵、氟化钠、氟化镁和氟化铝中的一种或几种，优选为氟化铵。
本申请的第三方面提供了一种正极极片，包括本申请第一方面提供的正极活性材料或采用根据本申请第二方面提供的制备方法制得的正极活性材料。
本申请的第四方面提供了一种二次电池，包括本申请第三方面提供的正极极片。
本申请的第五方面提供了一种电子设备，包括本申请第四方面提供的二次电池。
本申请的电子设备包括本申请提供的二次电池，因而至少具有与所述二次电池相同的优势。
本申请提供的正极活性材料中进行了氟元素的掺杂，掺杂的氟元素能够进入正极活性材料体相的晶格内，抑制循环过程中因氧元素的迁移而导致的晶格畸变，从而提升晶体结构的稳定性，减少晶体结构中由于活性离子(如锂离子)的脱嵌而造成的晶界裂纹和结构坍塌，提升正极活性材料的结构稳定性，进而提升二次电池的循环性能。
此外，正极活性材料中由富铝内包覆层和富钛外包覆层组成的包覆结构均匀且致密、机械强度较高，能够有效稳定二次电池正极的电极/电解液界面，隔绝正极活性材料中高氧化态的过渡金属元素与电解液的反应通路，从而减少氢氟酸的形成，降低因氢氟酸腐蚀正极活性材料表面而产生的过渡金属元素的溶出，减弱因过渡金属元素溶出而导致的正极活性材料表面结构的畸变，从而进提升二次电池三元正极的界面稳定性，进一步提升二次电池的循环性能。
附图说明
图1为实施例1～2和对比例1的正极活性材料的XRD图。
图2为实施例1的正极活性材料的SEM图和EDS图。
图3为实施例1～2和对比例1～2的正极活性材料的循环性能对比图。。
具体实施方式
为了便于理解本申请，下面将参照相关附图对本申请进行更全面的描述。附图中给出了本申请的较佳实施例。但是，本申请可以以许多不同的形式来实现，并不限于本文所描述的实施例。相反地，提供这些实施例的目的是使对本申请的公开内容的理解更加透彻全面。
为了简便，本申请仅明确地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，尽管未明确记载，但是范围端点间的每个点或单个数值都包含在该范围内。因而，每个点或单个数值可以作为自身的下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。需要说明的是，除非另有说明，本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合，“以上”、“以下”为包含本数，“一种或多种”中的“多种”的含义是两种以上。
本申请的上述申请内容并不意欲描述本申请中的每个公开的实施方式或每种实现方式。如下描述更具体地举例说明示例性实施方式。在整篇申请中的多处，通过一系列实施例提供了指导，这些实施例可以以各种组合形式使用。在各个实例中，列举仅作为代表性组，不应解释为穷举。
发明人在研究过程中发现，包含镍钴锰等三元正极材料的二次电池在循环过程中存在两个主要的问题：(1)二次电池在循环过程中由于活性离子(如锂离子)的不断嵌入和脱出，会使得三元正极材料内产生晶格的膨胀和收缩，由此易导致三元正极材料内出现晶界裂纹和晶体结构的坍塌，降低电池的循环性能；(2)二次电池的正极存在电极/电解液界面反应，特别是在高温环境下，电解液易与电极界面处的三元正极材料中高氧化态的Ni4+反应产生氢氟酸，从而腐蚀电极界面，导致过渡金属元素的大量溶出，造成二次电池循环性能的进一步下降。
为了解决前述技术问题，传统的方法是对三元材料进行元素的固相掺杂改性，例如掺杂单一纳米氧化物或共掺杂多种元素，可以在一定程度上改善三元材料晶体结构的稳定性，从而提升其循环性能；以及利用无机金属氧化物，如氧化铝、氧化镁、氧化钛和氧化硼等为包覆剂，对三元材料进行包覆改性，在一定程度上避免三元材料与电解液的直接接触，减少过渡金属离子的溶出，提升二次电池的循环性能。
但发明人经过进一步的研究发现，常规的固相掺杂法在高温时大部分掺杂元素会分布在三元材料的浅表层和表面，无法进入到材料的晶格内部，而且掺杂元素的分布不均匀，无法有效抑制循环过程中锂离子脱嵌造成的晶界裂纹和晶体结构的坍塌，导致二次电池循环性能的下降。此外，利用常规的无机金属氧化物对三元材料进行包覆改性时，也存在包覆层强度低且不均匀、呈现岛状分布的问题，继而在电极制作碾压和循环过程中，容易出现包覆层的开裂和溶解问题，导致形成新的暴露界面，引起界面持续发生结构的劣化和性能的衰减，最终也会导致二次电池循环性能的下降。为至少在一定程度上解决前述技术问题，发明人提出了如下的技术方案。
本申请实施方式的第一方面提供了一种正极活性材料，包括：氟掺杂的三元正极材料基体；和覆于氟掺杂的三元正极材料基体的至少部分表面的包覆结构，其中，包覆结构包括相对靠近氟掺杂的三元正极材料基体表面的富铝内包覆层和相对远离氟掺杂的三元正极 材料基体表面的富钛外包覆层。
本申请提供的正极活性材料中进行了氟元素的掺杂，掺杂的氟元素一方面能够进入正极活性材料的体相晶格内，代替部分氧原子形成相较于M-O化学键而言键能更强的M-F化学键(M为Ni，Co或Mn)，减弱深度充放电循环过程中氧元素的迁移，并抑制因氧元素迁移而导致的晶格畸变，从而提升晶体结构的稳定性，减少晶体结构中由于活性离子(如锂离子)的脱嵌而造成的晶界裂纹和晶体结构的坍塌，提升正极活性材料的结构稳定性，进而提升二次电池的循环性能。另一方面，掺杂的氟元素还会有部分残留在正极活性材料的浅表层，在正极的界面层中形成AlF3和TiF3等氟化物，这部分氟化物能够更好的隔绝二次电池的电极/电解液界面，有利于增强界面稳定性，提升循环性能。
在一些实施方式中，氟掺杂的三元正极材料基体包括过渡区，过渡区分布于氟掺杂的三元正极材料基体的靠近包覆结构的浅表层，过渡区内包含AlF3。
本申请中，由于进入正极活性材料体相内掺杂的氟原子的半径小于氧原子的半径，因此，氟元素掺杂后一方面会使正极活性材料的晶格的四面体空间体积增加，由此可在一定程度上增大层间距，拓宽活性离子(如锂离子)的扩散通道，加快活性离子在晶格中的脱嵌速率，减少活性离子由于在脱嵌过程中的停留甚至累积而造成的晶界裂纹和晶体结构坍塌，进一步提升正极活性材料结构的稳定性及二次电池的循环性能。另一方面，氟元素掺杂后形成的键能更强的Ni-F键可以降低Li+/Ni2+的混排程度，使正极活性材料的层状结构更加有序和完整，从而提升其结构稳定性，进一步提升二次电池的循环性能。更为重要的是，氟掺杂与包覆结构之间存在协同效应，这归因于在晶体浅表层的F原子能够与富铝内包覆层内的氧化铝发生反应，生产耐HF腐蚀的AlF3，进一步增强电极/电解液界面的稳定性，同时也在一定程度上抑制了浅表层在循环过程的结构劣化(形成岩盐相和氧缺陷等)，增强晶体结构稳定性。
在一些实施方式中，包覆结构还包括过渡层，过渡层位于富铝内包覆层和富钛外包覆层之间，过渡层内分布有Li-Al-O-Ti固溶体结构。
本申请中，正极活性材料中由富铝内包覆层和富钛外包覆层组成的包覆结构具备较高的均匀性和致密性，机械强度较高，能够有效稳定二次电池正极的电极/电解液界面，隔绝正极活性材料中高氧化态的过渡金属元素与电解液的反应通路，从而减少氢氟酸的形成，降低因氢氟酸腐蚀正极活性材料表面而产生的过渡金属元素的溶出，减弱因过渡金属元素溶出而导致的正极活性材料表面结构的畸变，从而提升二次电池三元正极的界面稳定性，提升其循环性能。另一方面，在富铝内包覆层和富钛外包覆层间存在一层类似固体电解质的Li-Al-O-Ti的固溶体结构(如图1-2所示)，相比于相对“松散”的常规氧化物包覆层结构，Al和Ti元素形成的固溶体具有更为致密，其具有更高的锂离子和电子电导率，能够更好抑 制材料表面过渡金属的溶出，以及提升材料的倍率性能。
在一些实施方式中，正极活性材料的粒子的平均粒径为3μm～15μm。正极活性材料的平均粒径在合适范围内，有利于粒子之间混合更均匀，减小粒子间进行混合时的间隙，提升正极的压实密度，提升二次电池的倍率性能。
在一些实施方式中，氟掺杂的三元正极材料基体的粒子的平均粒径为3μm～15μm。氟掺杂的三元正极材料基体的粒子的平均粒径控制在上述范围内，有利于提升其与含MAX型化合物包覆剂接触混合的均匀性，并提升含MAX型化合物包覆剂对其包覆的均匀性，进而提升包覆结构的均匀性及致密性。
在一些实施方式中，富铝内包覆层的厚度为5nm～100nm，例如，富铝内包覆层的厚度为5nm，10nm，20nm，30nm，40nm，50nm，60nm，70nm，80nm，90nm、100nm或处于以上任何数值所组成的范围内。
在一些实施方式中，富钛外包覆层的厚度为5nm～100nm，例如，富钛外包覆层的厚度为5nm、10nm，20nm，30nm，40nm，50nm，60nm，70nm，80nm，90nm、100nm或处于以上任何数值所组成的范围内。
本申请实施方式中，富铝内包覆层和富钛外包覆层的厚度低于5nm会使得包覆效果不佳，包覆不到位；包覆层的厚度高于100nm会导致二次电池的容量和循环性能下降，因而需将包覆层厚度控制在上述范围内。
在一些实施方式中，氟掺杂的三元正极材料基体的分子式为LiwNixCoyMn1-x-yO2-zFz，其中，0.95≤w≤1.05，0.33≤x<0.95，0.05<y≤0.77，0<z<1，当w＝1时，所述氟掺杂的三元正极材料基体的分子式为LiNixCoyMn1-x-yO2-zFz。
在一些实施方式中，基于正极活性材料的总质量，富铝内包覆层中铝元素的质量百分含量为0.002％～20％。
在一些实施方式中，基于正极活性材料的总质量，富钛外包覆层中钛元素的质量百分含量为0.002％～20％。
本申请实施方式的第二方面提供了一种正极活性材料的制备方法，包括如下步骤：
S10、提供含氟三元前驱体的溶胶；
S20、对含氟三元前驱体的溶胶与锂盐进行混合处理，进行一次烧结处理，得到氟掺杂的三元正极材料基体；
S30、对氟掺杂的三元正极材料基体与含MAX型化合物包覆剂混合处理后，进行二次烧结处理，以形成覆于氟掺杂的三元正极材料基体的至少部分表面的包覆结构，其中，包覆结构包括相对靠近氟掺杂的三元正极材料基体表面的富铝内包覆层和相对远离氟掺杂的三元正极材料基体表面的富钛外包覆层。
本申请提供的正极活性材料的制备方法中，通过利用含氟三元前驱体的溶胶与锂盐进行液相混合及烧结后实现氟元素的掺杂(湿法掺杂)，能够增大氟元素对三元前驱体的包覆接触面积，使得在一次烧结处理的过程中氟元素更易进入三元材料的晶格内，并实现在材料晶格内部的有序掺杂分布，在晶格内形成强键能的M-F化学键(M为Ni，Co或Mn)，减弱深度充放电循环过程中氧元素的迁移，并抑制因氧元素迁移而导致的晶格畸变，从而提升晶体结构的稳定性，减少晶体结构中由于活性离子(如锂离子)的脱嵌而造成的晶界裂纹和晶体结构的坍塌，提升正极活性材料的结构稳定性，进而提升二次电池的循环性能。
此外，二次烧结处理能够形成富铝内包覆层和富钛外包覆层组成的包覆结构，该包覆结构具备较高的均匀性和致密性，机械强度较高，能够有效稳定二次电池正极的电极/电解液界面，隔绝正极活性材料中高氧化态的过渡金属元素与电解液的反应通路，从而减少氢氟酸的形成，降低因氢氟酸腐蚀正极活性材料表面而产生的过渡金属元素的溶出，减弱因过渡金属元素溶出而导致的正极活性材料表面结构的畸变，从而提升二次电池三元正极的界面稳定性，提升其循环性能。
在一些实施方式中，步骤S10中提供含氟三元前驱体的溶胶包括如下步骤：
S100、使三元前驱体、分散剂与含氟化盐的水溶液接触并混合，得到混合液；
S110、对混合液进行球磨处理，以提供含氟三元前驱体的溶胶。
在一些实施例中，含氟三元前驱体的溶胶的固含量为5％～50％，例如，固含量可以为5％，10％，15％，20％，25％，30％，35％，40％，45％，50％或处于以上任何数值所组成的范围内。将固含量控制在合适范围内，有利于提高含氟三元前驱体的利用率，同时可以避免出现较多的团聚和沉淀。
具体地，若三元前驱体、分散剂和含氟化盐的水溶液混合后的固含量正好在5～50％范围内则可不用蒸发水；若得到的混合液较稀，或者要获得目标固含量的溶胶，可将混合液置于旋转蒸发仪中蒸发溶剂得到目标固含量的溶胶。
在一些实施例中，三元前驱体的分子式为NiaCobMn1-a-b(OH)2，其中，0.33≤a<0.95，0.05<b≤0.77。
在一些实施例中，三元前驱体包含微米粒子，微米粒子的平均粒径为4μm～20μm，例如，微米粒子的平均粒径为4μm，7μm，10μm，13μm，16μm，19μm，20μm或处于以上任何数值所组成的范围内。
三元前驱体包含的微米粒子的平均粒径为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在一些实施例中，含氟化盐的水溶液的浓度为0.05mol/L～5mol/L，例如，浓度可以为 0.05mol/L，0.1mol/L，0.5mol/L，1mol/L，1.5mol/L，2mol/L，2.5mol/L，3mol/L，3.5mol/L，4mol/L，4.5mol/L，5mol/L或处于以上任何数值所组成的范围内。氟化盐的水溶液的浓度控制在合适范围内，有利于获得氟元素浓度适宜的含氟三元前驱体，从而在后续的一次烧结过程中实现更好的氟元素掺杂效果。
在一些实施例中，氟化盐的种类没有具体的限定，可根据实际需求进行选择。例如，氟化盐可以包括氟化铵、氟化钠、氟化镁和氟化铝中的一种或几种，优选为氟化铵。
本申请中选用氟化盐作为掺杂剂可以起到的作用包括：一方面，氟掺杂的电负性要高于氧原子，因此掺杂后能够增强三元材料中金属原子与阴离子的键能，有利于稳定结构；更为重要的是，氟原子掺杂后，在浅层掺杂的氟原子能够与富铝层发生反应形成稳定性更佳的AlF3，有效稳定浅表层的结构，抑制了其在循环过程中出现的结构重构现象。
在一些实施例中，三元前驱体、分散剂及氟化盐的质量比为1:(0.001～1.0):(0.001～0.1)。
在一些实施例中，分散剂的种类没有具体的限定，可根据实际需求进行选择。例如，分散剂可以包括十六烷基三甲基氯化铵、十二烷基三甲基氯化铵、十六烷基氯化吡啶和苯磺酸钠中的一种或几种。
在一些实施方式中，步骤S20中对含氟三元前驱体的溶胶与锂盐进行混合处理，进行一次烧结处理包括如下步骤：
S200、将含氟三元前驱体的溶胶与锂盐混合均匀后进行球磨处理，得到预掺杂料；
S210、在300℃～1000℃、优选为350℃～950℃下，对预掺杂料进行10h～30h、优选为15h～25h的一次烧结处理，得到氟掺杂的三元正极材料基体。
在一些实施例中，氟掺杂的三元正极材料基体的分子式为LiNixCoyMn1-x-yO2-zFz，其中，0.33≤x<0.95，0.05<y≤0.77，0＜z<1。
在一些实施例中，锂盐中的锂元素与氟掺杂的三元正极材料基体中的所有过渡金属元素的摩尔比为(1.0～1.1):1。
在一些实施例中，锂盐的种类没有具体的限定，可根据实际需求进行选择。例如，锂盐可以包括碳酸锂、氢氧化锂、硝酸锂和醋酸锂中的一种或几种。
在一些实施例中，第一次烧结处理的温度为300℃～1000℃，例如，可以为300℃，400℃，500℃，600℃，700℃，800℃，900℃，1000℃或处于以上任何数值所组成的范围内。优选的，第一次烧结处理的温度为350℃～950℃。
在一些实施例中，第一次烧结处理的时间为10h～30h，例如，可以为10h，15h，20h，25h，30h或处于以上任何数值所组成的范围内。优选的，第一次烧结处理的时间为15h～25h。
在一些实施例中，第一次烧结处理的烧结气氛没有特别的限制，可根据实际需求进行选择。例如，烧结气氛可以为空气、氧气或空气与氧气的混合气氛。
本申请实施例中，第一次烧结处理的温度和时间均控制在合适范围内，通过温度与时间的配合，一方面能使大部分的氟元素进入正极活性材料的体相晶格内，代替部分氧原子形成相较于M-O化学键而言键能更强的M-F化学键(M为Ni，Co或Mn)，减弱深度充放电循环过程中氧元素的迁移，并抑制因氧元素迁移而导致的晶格畸变，从而提升晶体结构的稳定性，减少晶体结构中由于活性离子(如锂离子)的脱嵌而造成的晶界裂纹和晶体结构的坍塌，提升正极活性材料的结构稳定性，进而提升二次电池的循环性能。另一方面，还有部分氟元素会残留在正极活性材料的浅表层，在正极的界面层中形成AlF3和TiF3等氟化物，这部分氟化物能够更好的隔绝二次电池的电极/电解液界面，有利于增强界面稳定性，提升其循环性能。
在一些实施方式中，步骤S30中对氟掺杂的三元正极材料基体与含MAX型化合物包覆剂混合处理后，进行二次烧结处理包括如下步骤：
S300、对氟掺杂的三元正极材料基体与含MAX型化合物包覆剂混合均匀后进行球磨处理，得到预包覆料；
S310、对预包覆料进行分段烧结处理，以形成覆于氟掺杂的三元正极材料基体的至少部分表面的包覆结构，得到正极活性材料。
在一些实施例中，含MAX型化合物包覆剂的分子式为TimAlCn，其中，0<m<5，0<n<5。优选的，含MAX型化合物包覆剂为Ti3AlC2。
本申请选择MAX型化合物作为包覆剂主要包括以下原因：(1)MAX型化合物中M和X形成层状结构，A为层间插层元素，其结构上的特点决定了M和A元素的活性上会有区别；(2)MAX型化合物为层状结构，与三元材料结构上相似性较大，另外其电子电导率高，远高于常规的氧化物包覆层(常规氧化物包覆层的电子电导率约为10-4cm/s)，包覆后既能够抑制界面反应，又能够提升包覆后材料的电化学活性如倍率等；(3)MAX型化合物制备简单，由常见的元素组成，成本可控易于工业化。
在一些实施例中，含MAX型化合物包覆剂包括MAX型化合物的纳米粒子，纳米粒子的平均粒径为10nm～2000nm。例如，纳米粒子的平均粒径为100nm，400nm，700nm，1000nm，1300nm，1600nm，1900nm或处于以上任何数值所组成的范围内。MAX型化合物的纳米粒子的平均粒径在合适范围内，能够实现均匀包覆，有利于后续形成的包覆层的致密性。
在一些实施例中，氟掺杂的三元正极材料基体与含MAX型化合物包覆剂的质量比为1:(0.0005～0.1)。
需要说明的是，为了使正极活性材料中形成由富铝内包覆层和富钛外包覆层组成的包覆结构，需要对预掺杂料进行如下步骤S3100和步骤S3110中的分段烧结处理，并且需要控制分段烧结处理过程中的升温速率。
在一些实施方式中，步骤S310中对预包覆料进行分段烧结处理包括如下步骤：
S3100、在5℃～400℃、优选为50℃～350℃下，对预掺杂料进行1h～10h、优选为2h～8h的烧结处理，得到第一烧结料；
S3110、在400℃～700℃、优选为450℃～650℃下，对第一烧结料进行5h～30h、优选为10h～25h的烧结处理，得到正极活性材料。
在一些实施例中，步骤S3100先进行低温段烧结处理。低温段烧结处理的温度需控制在5℃～400℃，例如，50℃，100℃，150℃，200℃，250℃，300℃，350℃或处于以上任何数值所组成的范围内；时间需控制在1h～10h，例如，2h，4h，8h或处于以上任何数值所组成的范围内；升温速率≤3℃/min。
在低温段烧结处理时，通过将温度、时间和升温速率均控制在合适范围内，即通过温度、时间和升温速率的配合，能够使含MAX型化合物包覆剂中活性较高的Al元素迁移至表面形成Al2O3纳米颗粒，并首先实现在三元材料表面的包覆，形成富铝内包覆层，此时包覆层呈现岛状结构，结构较为疏松。
在一些实施例中，步骤S3110进行高温段烧结处理。高温段烧结处理的温度需控制在400℃～700℃，例如，450℃，500℃，550℃，600℃，650℃或处于以上任何数值所组成的范围内；时间需控制在5h～30h，例如，10h，15h，20h，25h或处于以上任何数值所组成的范围内；升温速率≤5℃/min。
在高温段烧结处理时，通过将温度、时间和升温速率均控制在合适范围内，即通过温度、时间和升温速率的配合，能够使MAX型化合物掺杂剂分解完全形成TiO2，并在富铝内包覆层基础上进行包覆，形成富钛外包覆层，得到由富铝内包覆层和富钛外包覆层组成的双层包覆结构。由于得到的包覆结构形成了Al2O3-TiO2固溶体，因此其结构致密且均匀，具有较高机械的强度。
在一些实施例中，低温段烧结处理和高温段烧结处理的烧结气氛没有特别的限制，可根据实际需求进行选择。例如，烧结气氛可以为空气、氧气或空气与氧气的混合气氛。
由此，通过进行分段烧结处理，能够形成富铝内包覆层和富钛外包覆层组成的包覆结构，该包覆结构具备较高的均匀性和致密性，机械强度较高，能够有效稳定二次电池正极的电极/电解液界面，隔绝正极活性材料中高氧化态的过渡金属元素与电解液的反应通路，从而减少氢氟酸的形成，降低因氢氟酸腐蚀正极活性材料表面而产生的过渡金属元素的溶出，减弱因过渡金属元素溶出而导致的正极活性材料表面结构的畸变，从而提升二次电池三元正极的界面稳定性，提升其循环性能。
本申请实施方式的第三方面提供了一种正极极片，包括本申请第一方面提供的正极活性材料或采用根据本申请第二方面提供的制备方法制得的正极活性材料。
在一些实施方式中，正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括本申请第二方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
本申请实施方式的第四方面提供了一种二次电池，包括本申请第三方面提供的正极极片。
在一些实施方式中，二次电池的种类不做具体的限定，可以包括其中发生电化学反应以将化学能与电能互相转化的任何电池，例如可以为锂离子电池或钠离子电池。
在一些实施方式中，二次电池还包括负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
本申请实施方式的第五方面提供了一种电子设备，包括本申请第四方面提供的二次电池。其中，二次电池可在所述电子设备中作为电源使用。
在一些实施方式中，电子设备的种类没有特别限定，其可以是用于现有技术中已知的任何电子设备。例如，电子设备可以包括但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴 式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
实施例
以下为具体实施例，下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
(1)将2.5kg 4.0μm Ni0.6Co0.1Mn0.3(OH)2三元前驱体、50g十六烷基三甲基氯化铵加入到6L 0.005mol/L氟化铵水溶液中球磨2h，形成一定固含量的溶胶，混合均匀后控制固含量为40％，得到含氟三元前驱体的溶胶；
(2)取2.0kg含氟三元前驱体的溶胶与0.958kg碳酸锂混合，球磨2h后进行烧结，其中，碳酸锂中的锂元素与三元前驱体中的过渡金属元素的摩尔比为Li/(Ni+Co+Mn)＝1.053，控制烧结温度为960℃，烧结时间为12h，烧结气氛为空气，烧结后得到氟掺杂的三元正极材料基体；
(3)取2.0kg氟掺杂的三元正极材料基体与12.5g 30nm的Ti3AlC2混合，球磨2h后进行分段烧结，低温段烧结温度为400℃，烧结时间为4h，升温速率为1.5℃/min；高温段烧结温度为650℃，烧结时间为8h，升温速率为4℃/min，烧结气氛为空气，烧结后得到氟掺杂以及富铝内层、富钛外层双层包覆的正极活性材料。
实施例2
(1)将2.5kg 4.0μm Ni0.6Co0.1Mn0.3(OH)2三元前驱体、50g十六烷基三甲基氯化铵加入到6L 0.005mol/L氟化铵水溶液中球磨2h，形成一定固含量的溶胶，混合均匀后控制固含量为40％，得到含氟三元前驱体的溶胶；
(2)取2.0kg含氟三元前驱体的溶胶与0.958kg碳酸锂混合，球磨2h后进行烧结，其中，碳酸锂中的锂元素与三元前驱体中的过渡金属元素的摩尔比为Li/(Ni+Co+Mn)＝1.053，控制烧结温度为960℃，烧结时间为12h，烧结气氛为空气，烧结后得到氟掺杂的三元正极材料基体；
(3)取2.0kg氟掺杂的三元正极材料基体与25g 30nm的Ti3AlC2混合，球磨2h后进行分段烧结，低温段烧结温度为400℃，烧结时间为4h，升温速率为1.5℃/min；高温段烧 结温度为650℃，烧结时间为8h，升温速率为4℃/min，烧结气氛为空气，烧结后得到氟掺杂以及富铝内层、富钛外层双层包覆的正极活性材料。
实施例3
(1)将2.5kg 4.0μm Ni0.60Co0.1Mn0.28(OH)2三元前驱体、50g十六烷基三甲基氯化铵加入到6L 0.005mol/L氟化铵水溶液中球磨2h，形成一定固含量的溶胶，混合均匀后控制固含量为40％，得到含氟三元前驱体的溶胶；
(2)取2.0kg含氟三元前驱体的溶胶与0.970kg碳酸锂混合，球磨2h后进行烧结，其中，碳酸锂中的锂元素与三元前驱体中的过渡金属元素的摩尔比为Li/(Ni+Co+Mn)＝1.060，控制烧结温度为960℃，烧结时间为12h，烧结气氛为空气，烧结后得到氟掺杂的三元正极材料基体；
(3)取2.0kg氟掺杂的三元正极材料基体与25g 30nm的Ti3AlC2混合，球磨2h后进行分段烧结，低温段烧结温度为400℃，烧结时间为4h，升温速率为1.0℃/min；高温段烧结温度为650℃，烧结时间为8h，升温速率为10℃/min，烧结气氛为空气，烧结后得到氟掺杂以及富铝内层、富钛外层双层包覆的正极活性材料。
实施例4
(1)将2.5kg 15μm Ni0.6Co0.1Mn0.3(OH)2三元前驱体、50g十六烷基三甲基氯化铵加入到12L 0.005mol/L氟化铵水溶液中球磨2h，形成一定固含量的溶胶，混合均匀后控制固含量为20％，得到含氟三元前驱体的溶胶；
(2)取2.0kg含氟三元前驱体的溶胶与0.998kg碳酸锂混合，球磨2h后进行烧结，其中，碳酸锂中的锂元素与三元前驱体中的过渡金属元素的摩尔比为Li/(Ni+Co+Mn)＝1.070，烧结温度为750℃，烧结时间为15h，烧结气氛为空气，烧结后得到氟掺杂的三元正极材料基体；
(3)取2.0kg氟掺杂的三元正极材料基体与125g 30nm的Ti3AlC2混合，球磨2h后进行分段烧结，低温段烧结温度为350℃，烧结时间为3h，升温速率为2.5℃/min；高温段烧结温度为680℃，烧结时间为10h，升温速率为5℃/min，烧结气氛为空气，烧结后得到氟掺杂以及富铝内层、富钛外层双层包覆的正极活性材料。
对比例1
对比例1的制备方法与实施例1的制备方法相似，不同之处在于：对正极活性材料不做掺杂和包覆处理，即将Ni0.6Co0.1Mn0.3(OH)2三元前驱体与氢氧化锂按照锂元素与过渡金属元素的摩尔比为Li/(Ni+Co+Mn)＝1.053的比例混合均匀后，在箱式炉氧气气氛下进行烧结，升温速率为10℃/min，烧结温度为960℃，烧结时间为12h，经鄂破、对辊和气流粉碎后得到未掺杂和包覆的正极活性材料LiNi0.6Co0.1Mn0.3O2。
对比例2
对比例2的制备方法与实施例2的制备方法相似，不同之处在于：对正极活性材料不做氟元素的掺杂处理，但利用本申请中的分段烧结进行富铝内层、富钛外层的双层包覆处理，具体实现方式如下：
(1)取2.0kg三元前驱体的溶胶与0.958kg碳酸锂混合，球磨2h后进行烧结，其中，碳酸锂中的锂元素与三元前驱体中的过渡金属元素的摩尔比为Li/(Ni+Co+Mn)＝1.053，控制烧结温度为960℃，烧结时间为12h，烧结气氛为空气，烧结后得到三元正极材料基体；
(2)取2.0kg三元正极材料基体与12.5g 30nm的Ti3AlC2混合，球磨2h后进行分段烧结，低温段烧结温度为400℃，烧结时间为4h，升温速率为1.5℃/min；高温段烧结温度为650℃，烧结时间为8h，升温速率为4℃/min，烧结气氛为空气，烧结后得到富铝内层、富钛外层双层包覆的正极活性材料。
对比例3
对比例3的制备方法与实施例1的制备方法相似，不同之处在于：对正极活性材料只做本申请中的氟元素的液相掺杂处理，但不进行包覆处理，即省略了实施例1中的步骤(3)。具体实现方式如下：
(1)将2.5kg 4.0μm Ni0.6Co0.1Mn0.3(OH)2三元前驱体、50g十六烷基三甲基氯化铵加入到6L 0.005mol/L氟化铵水溶液中球磨2h，形成一定固含量的溶胶，混合均匀后控制固含量为40％，得到含氟三元前驱体的溶胶；
(2)取2.0kg含氟三元前驱体的溶胶与0.958kg碳酸锂混合，球磨2h后进行烧结，其中，碳酸锂中的锂元素与三元前驱体中的过渡金属元素的摩尔比为Li/(Ni+Co+Mn)＝1.053，控制烧结温度为960℃，烧结时间为12h，烧结气氛为空气，烧结后得到氟掺杂的三元正极材料；
对比例4
对比例4的制备方法与实施例1的制备方法相似，不同之处在于：先利用传统干法对正极活性材料进行氟元素的掺杂处理，然后包覆无机金属氧化物。
(1)将2.5kg 4.0μm Ni0.6Co0.1Mn0.3(OH)2三元前驱体、0.958kg碳酸锂、2.2g氟化铵混合后干法球磨2h后，碳酸锂中的锂元素与三元前驱体中的过渡金属元素的摩尔比为Li/(Ni+Co+Mn)＝1.053，控制烧结温度为960℃，烧结时间为12h，烧结气氛为空气，烧结后得到氟掺杂的三元正极材料基体；
(3)取2.0kg氟掺杂的三元正极材料基体与12.5g纳米氧化铝和10g纳米氧化钛混合，球磨2h后进行分段烧结，烧结温度为600℃烧结时间为8h，升温速率为10℃/min，烧结气氛为空气，烧结后得到氟掺杂以及铝钛包覆的正极活性材料。
对比例5
对比例5的制备方法与实施例1的制备方法相似，不同之处在于：步骤(3)中只进行一次烧结处理，烧结温度为650℃，烧结时间为10h，升温速率为10℃/min。
将实施例1～4及对比例1～5制得的正极活性材料或进一步制成的锂离子进行相关性能测试，测试结果如下表1-3所示。
其中，各项性能测试项目的测试条件或测试标准如下：
(1)正极活性材料XRD测试
先将实施例1～2和对比例1中的正极活性材料在2.8V-4.4V电压、0.1C/0.1C倍率下循环200圈，然后将循环后的正极活性材料粉末放置在XRD测试仪器(型号布鲁克D8)样品台中，使用2°/min的扫描速率，扫描角度范围10°至90°，得到如附图1所示的XRD衍射图。并将实施例1～2和对比例1的样品进行XRD精修，得到如下表1中的精修数据；XRD精修是指采用Rietveld方法对XRD数据进行精修。
(2)正极活性材料SEM及EDS测试
将正极活性材料用ZEISS sigma 300扫描电子显微镜进行测试，参照标准JY/T010-1996对样品形貌进行观测，得到如附图2所示的形貌图及EDS能谱图。
(3)锂离子电池的金属溶出量测试
针对实施例1-4和对比例1-5制得的正极材料，考察在电池满电状态下，于80℃分别存储30天、60天后，Ni、Co、Mn三种元素的金属溶出量对比。测试方法如下：将制得的三元正极材料组装成扣式电池，在电池满电(4.4V)时，在80℃下存储30天和60天后分别拆开电池，DMC清洗正极极片，刮下正极极片活性物质层，然后将其在王水中加热15min-30min溶解，溶液进行ICP测试Ni、Co、Mn含量，得到表1的数据。对Ni、Co、Mn三种元素的金属溶出量进行测试，测试结果如下表2所示。
(4)锂离子电池的高温循环性能测试
锂离子电池在45℃下以1C恒流充电至4.4V，然后恒压充电至电流为0.1C，静置5min，然后以1C恒流放电至2.8V，此为一圈充放电循环，并测试记录此时的放电容量为D01；按照上述充放电过程使锂离子电池进行200圈循环，测试记录第200圈循环的放电容量为D1，将测试数据记录在如下表3中。
表1
从附图1可以看出，与对比例1相比，实施例1～2中的样品经循环后并无杂峰出现， 说明氟元素掺杂和富铝、富钛层包覆后并未改变正极活性材料的晶体结构，同时材料的结构有较好的稳定性，没有出现结构异变。
此外，从上表1中的XRD精修结果可以看出，实施例1～2的样品经循环后I003/104强度比要大于对比例1，这是因为正极活性材料经F掺杂后形成的M-F键的键能要高于原来的M-O键(M为Ni，Co或Mn)，键能更强的M-F化学键能够增强晶体结构的稳定性，并且降低Li+/Ni2+混排程度，使材料的层状结构更加有序和完整，进而提升正极活性材料的结构稳定性；另外晶胞参数c、a、c/a和晶胞体积的值都增大了，这是因为F原子比O原子的半径小，F掺杂后能够增大晶格的四面体空间的体积，从而可在一定程度上增大层间距，拓宽活性离子(如锂离子)的扩散通道，加快活性离子在晶格中的脱嵌速率，由此进一步提升正极活性材料结构的稳定性。更为重要的是，F掺杂增强了晶胞结构稳定性，抑制了循环过程中结构畸变，直接体现是实施例1～2的(104)晶面的半峰宽要明显高于对比例1；而表面富铝和富钛包覆层的协同作用形成致密的Li-Al-Ti-O固溶体结构，减少了材料的“表观体积”或“表观大小”，进一步增强电极/电解液界面的稳定性，直接体现是实施例1～2的(003)晶面的峰位置向小于对比例1。
表2
从表2可以看出，实施例1～4中利用本申请提供的制备方法得到的三元正极材料经长时间的高温存储后，金属元素的溶出量明显低于对比例1～5。表明通F掺杂能够更好的稳定晶体结构，提高材料的首次效率，同时本申请提供的制备方法获得的包覆的氟掺杂和Al和Ti包覆的三元正极材料在锂离子电池中能够形成有效稳定的界面，可以显著降低电极/电解液的界面反应，减少氢氟酸的形成，从而减少氢氟酸对三元正极材料表面的腐蚀导致的过渡金属Ni/Co/Mn元素的溶出，有利于提升锂离子电池的高温存储性能。
从附图2中的左图可以看出，本申请制备的正极活性材料具有良好的分散性，单晶形貌圆润，在材料表面可以看到有一层均匀的包覆层。从附图2中的右图可以看出，在材料表面可以检测到Al、Ti和F元素，包覆层包括Al和Ti的氧化物形成的固溶体。
表3
从表3可以看出，实施例1～4与对比例1～5具有差异化的电化学性能，利用本申请提供的方法制备得到的三元正极材料，其充放电容量、首次效率和循环性能更优，说明通过对比实施例1、2和对比例4可知，本申请提供的制备方法得到的三元正极材料，其充放电容量、首次效率和循环性能均高于空白样品、只进行氟掺杂或只进行富铝和富钛包覆工艺获得的产品性能。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本申请书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请专利的保护范围应以所附权利要求为准。

Claims (16)

  1. 一种正极活性材料，其特征在于，包括：
    氟掺杂的三元正极材料基体；和
    覆于所述氟掺杂的三元正极材料基体的至少部分表面的包覆结构，其中，所述包覆结构包括相对靠近所述氟掺杂的三元正极材料基体表面的富铝内包覆层和相对远离所述氟掺杂的三元正极材料基体表面的富钛外包覆层。
  2. 根据权利要求1所述的正极活性材料，其特征在于，所述正极活性材料满足如下条件(1)至(2)中的至少一个：
    (1)所述氟掺杂的三元正极材料基体包括过渡区，所述过渡区分布于所述氟掺杂的三元正极材料基体的靠近所述包覆结构的浅表层，所述过渡区内包含AlF3；
    (2)所述包覆结构还包括过渡层，所述过渡层位于所述富铝内包覆层和所述富钛外包覆层之间，所述过渡层内分布有Li-Al-O-Ti固溶体结构。
  3. 根据权利要求1所述的正极活性材料，其特征在于，所述正极活性材料满足如下条件(1)至(4)中的至少一个：
    (1)所述正极活性材料的粒子的平均粒径为3μm～15μm；
    (2)所述氟掺杂的三元正极材料基体的粒子的平均粒径为3μm～15μm；
    (3)所述富铝内包覆层的厚度为5nm～100nm；
    (4)所述富钛外包覆层的厚度为5nm～100nm。
  4. 根据权利要求1-3任一项所述的正极活性材料，其特征在于，所述正极活性材料满足如下条件(1)至(3)中的至少一个：
    (1)所述氟掺杂的三元正极材料基体的分子式为LiwNixCoyMn1-x-yO2-zFz，其中，0.95≤w≤1.05，0.33≤x<0.95，0.05<y≤0.77，0＜z<1，当w＝1时，所述氟掺杂的三元正极材料基体的分子式为LiNixCoyMn1-x-yO2-zFz；
    (2)基于所述正极活性材料的总质量，所述富铝内包覆层中铝元素的质量百分含量为0.002％～20％；
    (3)基于所述正极活性材料的总质量，所述富钛外包覆层中钛元素的质量百分含量为0.002％～20％。
  5. 一种正极活性材料的制备方法，其特征在于，包括：
    提供含氟三元前驱体的溶胶；
    对所述含氟三元前驱体的溶胶与锂盐进行混合处理，进行一次烧结处理，得到氟掺杂的三元正极材料基体；
    对所述氟掺杂的三元正极材料基体与含MAX型化合物包覆剂混合处理后，进行二次烧结处理，以形成覆于所述氟掺杂的三元正极材料基体的至少部分表面的包覆结构，其中，所述包覆结构包括相对靠近所述氟掺杂的三元正极材料基体表面的富铝内包覆层和相对远离所述氟掺杂的三元正极材料基体表面的富钛外包覆层。
  6. 根据权利要求5所述的制备方法，其特征在于，对所述含氟三元前驱体的溶胶与锂盐进行混合处理，进行一次烧结处理包括：
    将所述含氟三元前驱体的溶胶与锂盐混合均匀后进行球磨处理，得到预掺杂料；
    在300℃～1000℃、优选为350℃～950℃下，对所述预掺杂料进行10h～30h、优选为15h～25h的一次烧结处理。
  7. 根据权利要求5或6所述的制备方法，其特征在于，所述制备方法满足如下条件(1)至(3)中的至少一者：
    (1)所述氟掺杂的三元正极材料基体的分子式为LiwNixCoyMn1-x-yO2-zFz，其中，0.95≤w≤1.05，0.33≤x<0.95，0.05<y≤0.77，0<z<1，当w＝1时，所述氟掺杂的三元正极材料基体的分子式为LiNixCoyMn1-x-yO2-zFz；
    (2)所述锂盐包括碳酸锂、氢氧化锂、硝酸锂或醋酸锂中的一种或多种；
    (3)所述锂盐中的锂元素与所述氟掺杂的三元正极材料基体中的所有过渡元素的摩尔比为(1.0～1.1):1。
  8. 根据权利要求5所述的制备方法，其特征在于，对所述氟掺杂的三元正极材料基体与含MAX型化合物包覆剂混合处理后，进行二次烧结处理包括：
    对所述氟掺杂的三元正极材料基体与所述含MAX型化合物包覆剂混合均匀后进行球磨处理，得到预包覆料；
    对所述预包覆料进行分段烧结处理，以形成所述覆于所述氟掺杂的三元正极材料基体的至少部分表面的包覆结构，得到所述正极活性材料。
  9. 根据权利要求8所述的制备方法，其特征在于，对所述预包覆料进行分段烧结处理包括：
    在5℃～400℃、优选为50℃～350℃下，对所述预包覆料进行1h～10h、优选为2h～8h的烧结处理，得到第一烧结料；
    在400℃～700℃、优选为450℃～650℃下，对所述第一烧结料进行5h～30h、优选为10h～25h的烧结处理，得到所述正极活性材料。
  10. 根据权利要求5或8所述的制备方法，其特征在于，所述制备方法满足如下条件(1)至(3)中的至少一者：
    (1)所述含MAX型化合物包覆剂的分子式为TimAlCn，其中，0<m<5，0<n<5；
    (2)所述含MAX型化合物包覆剂包括MAX型化合物的纳米粒子，所述纳米粒子的平均粒径为10nm～2000nm；
    (3)所述氟掺杂的三元正极材料基体与所述含MAX型化合物包覆剂的质量比为1:(0.0005～0.1)。
  11. 根据权利要求5所述的制备方法，其特征在于，所述提供含氟三元前驱体的溶胶包括：
    使三元前驱体、分散剂与含氟化盐的水溶液接触并混合，得到混合液；
    对所述混合液进行球磨处理，以提供所述含氟三元前驱体的溶胶。
  12. 根据权利要求11所述的制备方法，其特征在于，所述制备方法满足如下条件(1)至(3)中的至少一者：
    (1)所述含氟三元前驱体的溶胶的固含量为5％～50％；
    (2)所述含氟化盐的水溶液的浓度为0.05mol/L～5mol/L；
    (3)所述三元前驱体、所述分散剂及所述氟化盐的质量比为1:(0.001～1.0):(0.001～0.1)。
  13. 根据权利要求11或12所述的制备方法，其特征在于，所述制备方法满足如下条件(1)至(4)中的至少一者：
    (1)所述三元前驱体的分子式为NiaCobMn1-a-b(OH)2，其中，0.33≤a<0.95，0.05<b≤0.77；
    (2)所述三元前驱体包含微米粒子，所述微米粒子的平均粒径为4μm～20μm；
    (3)所述分散剂包括十六烷基三甲基氯化铵、十二烷基三甲基氯化铵、十六烷基氯化吡啶或苯磺酸钠中的一种或多种；
    (4)所述氟化盐包括氟化铵、氟化钠、氟化镁或氟化铝中的一种或多种，优选为氟化铵。
  14. 一种正极极片，其特征在于，包括权利要求1-4任一项所述的正极活性材料或采用根据权利要求5-13任一项所述的制备方法制得的正极活性材料：
  15. 一种二次电池，其特征在于，包括权利要求14所述的正极极片。
  16. 一种电子设备，其特征在于，包括权利要求15所述的二次电池。
PCT/CN2023/114239 2022-08-26 2023-08-22 正极活性材料及其制备方法、正极极片、二次电池和电子设备 WO2024041531A1 (zh)

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