High-nickel ternary positive electrode material coated with fast ion conductor in situ

Abstract

The invention discloses a surface modification method of a high-nickel ternary positive electrode material, relates to a surface in-situ coating technology based on a fast ion conductor, and aims to solve the key problems of interface failure and structure recession in a high-nickel material circulation process. According to the method, a functionalized interface layer with a three-dimensional lithium ion conduction network is constructed on the surface of a positive electrode through a nanoscale in-situ coating technology, and the method is characterized in that a fast ion conductor material is adopted as a coating medium, and interface lithium ion transmission kinetics is remarkably improved by means of the high lithium ion diffusion coefficient of the fast ion conductor material; a continuous coating layer with controllable thickness is formed through a sol-gel method preparation process, and the lithium ion superconducting characteristic is realized while the electron tunneling effect is maintained; the composite structure layer has both a physical barrier function and a mechanical buffer function, and can effectively inhibit electrolyte interface side reaction and particle crack propagation induced by electrochemical cycle stress strain.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery positive electrode materials, and specifically relates to a high-nickel ternary positive electrode material in situ coated with a fast ion conductor, and further discloses a preparation method and application thereof. Background Art

[0002] As an important innovation direction of the modern transportation system, electric vehicles have shown significant advantages in reducing dependence on traditional energy and promoting environmental sustainability. However, problems such as high cost of power batteries and range anxiety are still restricting the improvement of their market penetration. Among them, high-nickel ternary positive electrode materials have become one of the most promising core positive electrode materials in the field of power batteries due to their high energy density and relatively low cost. The micron-sized secondary spherical structure formed by the aggregation of nano-sized primary particles can effectively improve the material's tap density and structural stability, and is an effective way to obtain an ideal high energy density.

[0003] Although high-nickel ternary layered cathode materials have significant advantages, their structural evolution under high delithiation conditions still faces key challenges. When the material is in a state of deep delithiation, the anisotropic volume deformation along the c-axis direction will induce lattice stress accumulation, resulting in microcracks inside the secondary particles. It is worth noting that the stress and strain generated by this lattice distortion not only destroys the structural integrity of the particles, but also exposes new interfaces to contact the electrolyte, further catalyzing the irreversible transformation of the lattice structure from a layered structure to a rock salt phase structure. In particular, when the nickel content exceeds 80%, the crack propagation dynamics during the cycle are significantly intensified, forming a through-type channel to promote electrolyte penetration, triggering continuous interfacial side reactions, and causing irreversible consumption of active lithium. This will significantly increase the lithium ion diffusion energy barrier, leading to an increase in the electrode polarization voltage, and ultimately causing accelerated capacity decay. Further analysis shows that this multi-scale structural failure mechanism (microcracks-irreversible phase change-accelerated capacity decay) forms a joint effect: crack propagation increases the active surface → phase change intensifies structural stress → interface reconstruction accelerates capacity decay, which constitutes the core scientific problem that restricts the cyclic stability of high-nickel materials. These phenomena lead to a serious decline in the performance of high-nickel ternary layered cathode materials, limiting their practical application in the field of electric vehicles. Summary of the invention

[0004] In view of the above problems of interface failure and structural degradation of high-nickel ternary positive electrode materials, and in order to obtain excellent electrochemical performance and cycle stability, the present invention provides an in-situ fast ion conductor coating method for the surface of high-nickel ternary positive electrode materials. Through fine in-situ coating of the surface of nanoscale fast ion conductors, a three-dimensional lithium ion channel is constructed at the positive electrode interface. Due to its high lithium ion diffusion coefficient, the reaction kinetics of lithium ions are accelerated, so that it has both electron tunneling characteristics and lithium ion superconducting characteristics. Not only that, while improving the ionic and electronic conductivity of the material, it can also serve as a physical isolation layer to isolate the contact and side reactions with the electrolyte of the positive electrode particles, and due to the stress buffering mechanism of the coating layer, the lattice distortion stress caused by the phase change under the deep delithiation state is alleviated, and the generation of microcracks in the positive electrode particles is suppressed, thereby ensuring the cycle stability of the high-nickel ternary positive electrode material.

[0005] In order to achieve the above-mentioned purpose of the invention, the technical scheme and steps adopted by the present invention are as follows:

[0006] A preparation method for in-situ coating of inorganic fast ion conductor on the surface of high-nickel ternary positive electrode material, characterized in that: a continuous and dense inorganic fast ion conductor nano coating is constructed on the surface of single crystal positive electrode particles by using a sol-gel method combined with a solid-phase sintering coating technology, wherein the general structural formula of the ternary positive electrode material is LiNi x Co y M z O 2 (M=Al, Mn, 0.80≤x<1.00, 0<y≤0.10, 0<z≤0.10, x+y+z=1), its D50 particle size is 3-20 μm, and the particle size of the inorganic fast ion conductor coating layer is controlled at 5-50 nm. The specific preparation process includes the following steps: Step 1: dissolving a compound containing the target inorganic fast ion conductor coating material element in an organic solvent according to a certain stoichiometric ratio to prepare a mixed metal salt coating solution; Step 2: adding citric acid and high-nickel ternary positive electrode material matrix to the above coating solution for mixed coating, heating and stirring in a constant temperature water bath until the solution is completely evaporated to obtain a solid gel coating material; Step 3: Fully dry and sinter the solid gel-like coating material to obtain a high-nickel ternary positive electrode material in situ coated with an inorganic fast ion conductor.

[0007] In one or more technical solutions, the inorganic fast ion conductor in step 1 is Li 10 G 2 S 12 (LGPS), Li 1.3 Al 0.3 Ti 1.7 P 3 O 12 (LATP)、Li1.3 In 0.3 Ti 1.7 P 3 O 12 (LITP)、Li 1.5 Al 0.5 Ge 1.5 P 3 O 12 (LAGP), Li 7 La 3 Zr 2 O 12 LLZO, Li 0.33 La 0.56 TiO 3 (LLTO), Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO). The compound containing the target coating element is easily soluble in organic solvents and can easily react with water to generate compounds with higher boiling points. It can react with water vapor in the air under high humidity to avoid volatilization of the coating agent during the sintering process. Preferably, the compound containing the target coating element is one or more of tetrabutyl titanate, aluminum isopropoxide, zirconium isopropoxide, indium nitrate, vanadium chloride, vanadium acetylacetonate, lanthanum acetylacetonate, tantalum pentachloride, germanium acetate, and lithium dihydrogen phosphate.

[0008] In one or more technical schemes, the organic solvent in step 1 is any one or more of anhydrous ethanol, methanol, tetrahydrofuran, N,N-dimethylformamide, N-methylpyrrolidone, dioxane, toluene, ether, acetone, chloroform, carbon tetrachloride, etc.

[0009] In one or more technical solutions, the molar concentration of the mixed metal salt coating solution in step 1 is 1-5 mol L -1 Preferably, the molar concentration of the coating solution is 1-3 mol L -1 .

[0010] In one or more technical solutions, the amount of citric acid added in step 2 is 1-3 mol L -1 , to ensure the uniformity of sol-gel coating.

[0011] In one or more technical solutions, the high-nickel ternary positive electrode material matrix in step 2 is a primary sintered product or a secondary sintered product of a single crystal material of lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminum oxide (NCA), and its general chemical formula is LiNi x Co y M zO 2 (M=Al, Mn, 0.80≤x<1.00, 0<y≤0.10, 0<z≤0.10, x+y+z=1), its D50 particle size is 3-20 μm. As a preferred structure, its formula is LiNi 0.83 Co 0.11 Mn 0.06 O 2 .

[0012] In one or more technical solutions, the speed of heating and stirring in step 2 is 200-500 rpm. Preferably, the stirring speed is 200-300 rpm.

[0013] In one or more technical solutions, the process of heating and stirring in a constant temperature water bath in step 2 is: stirring at a temperature of 50-90° C. for 0.5-8 h. Preferably, the process of heating and stirring is stirring at a temperature of 70-90° C. for 1-5 h.

[0014] In one or more technical solutions, the drying process in step 3 is: drying in a vacuum oven at 60-120° C. for 8-20 h. Preferably, the drying process is drying in a vacuum oven at 60-80° C. for 12-14 h.

[0015] In one or more technical solutions, the sintering process in step 3 is: calcining at 400-650° C. for 4-10 h in a single atmosphere. Preferably, the sintering process is calcining at 400-650° C. for 5-8 h in a single atmosphere.

[0016] In one or more technical solutions, the atmosphere environment of the atmosphere sintering in step three is an inert atmosphere or an oxygen-rich atmosphere, wherein the inert atmosphere is nitrogen or argon.

[0017] In one or more technical solutions, the coating concentration of the inorganic fast ion conductor in the high nickel ternary positive electrode material in the in-situ coating of the inorganic fast ion conductor in step 3 is 1-5wt%, preferably 1wt%.

[0018] In addition, the present invention assembles batteries with the high nickel ternary positive electrode material (Coating sample) coated with the inorganic fast ion conductor in situ and the high nickel ternary positive electrode material (Pure sample) not subjected to coating treatment, and conducts comparative analysis of electrochemical performance. The CR2016 button half-cell system is used for testing, with the prepared material pole piece as the positive electrode, a metal lithium sheet with a diameter of 1 mm selected as the negative electrode, a Celgard polyethylene diaphragm (PE) as the diaphragm, and a commercial LB-002 electrolyte (1.0M LiPF6 dissolved in a mixed solution of EC:DMC:EMC=1:1:1 vol%) selected as the electrolyte. The thickness and morphology of the coating layer are characterized and analyzed by high-resolution transmission electron microscopy (HR-TEM), and the 1C long-cycle electrochemical test proves that the inorganic fast ion conductor in situ coating layer not only effectively inhibits the interface side reaction between the surface of the positive electrode material and the electrolyte, but also alleviates the lattice distortion stress caused by the irreversible phase change under the deep delithiation state through mechanical buffering, so that it has better structural stability and electrochemical stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only part of the embodiments of the present invention. For ordinary technicians in this field, they can also obtain drawings of other parts of the embodiments based on these drawings without creative work.

[0020] Figure 1 This is a schematic diagram of high-resolution transmission electron microscopy (HR-TEM) characterization of the high-nickel ternary cathode material treated with in-situ inorganic fast ion conductor coating in Example 1 of the present invention. Through high-resolution transmission electron microscopy (HR-TEM) structural characterization, it can be clearly observed that a uniform and dense fast ion conductor interface layer is formed on the surface of the high-nickel ternary cathode material treated with in-situ coating, and its thickness is precisely controlled within the range of 10±3nm.

[0021] Figure 2 The figure is a schematic diagram comparing the charge-discharge cycle curves of the high-nickel ternary positive electrode material treated with in-situ inorganic fast ion conductor coating in Example 1 of the present invention and the conventional high-nickel ternary positive electrode material in the comparative example. The electrochemical performance test further verified the significant improvement of the material stability by the surface coating technology. The voltage range was set at 3-4.3V, and a 1C charge-discharge cycle was performed at room temperature (25°C). The first-cycle discharge capacity of the two samples at 0.1C remained slightly different (Pure sample: 208.6 mAh g -1 ; Coating sample: 208.7 mAh g -1), after 100 1C charge-discharge cycles, compared with the traditional high-nickel ternary cathode material 157.3 mAh g -1 The discharge specific capacity and capacity retention rate of 82.1% are achieved. The high nickel ternary cathode material treated by in-situ coating of inorganic fast ion conductor has better electrochemical performance and cycle capacity retention rate (173.2 mAh g -1 ; 89.8%). DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0023] In order to further understand the present invention, the preferred embodiments of the present invention are described below. However, it should be understood that these descriptions exist only to further illustrate the features and advantages of the present invention and are not intended to limit the claims of the present invention. The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification.

[0024] The theories or mechanisms described and disclosed in this article, whether right or wrong, should not limit the scope of the present invention in any way. The present invention can also be implemented or applied through other different specific implementation methods. The details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0025] Herein, when describing embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all substitutes, improvements and equivalents of the methods and materials described in the present invention can be included in the scope limited by the claims.

[0026] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0027] Example

[0028] A high nickel ternary positive electrode material with an inorganic fast ion conductor in-situ coated on the surface and a preparation method thereof, characterized in that a continuous and dense inorganic fast ion conductor nano coating is constructed on the surface of single crystal positive electrode particles by using a sol-gel method combined with a solid phase sintering coating technology, and the structural formula of the ternary positive electrode material is LiNi x Co y M z O 2 (M=Al, Mn, 0.80≤x<1.00, 0<y≤0.10, 0<z≤0.10, x+y+z=1), its D50 particle size is 3-20 μm, and the particle size of the inorganic fast ion conductor coating layer is controlled at 5-50 nm. The specific preparation process includes the following steps: Step 1: dissolving a compound containing the target inorganic fast ion conductor coating material element in an organic solvent according to a certain stoichiometric ratio to prepare a mixed metal salt coating solution; Step 2: adding citric acid and high-nickel ternary positive electrode material matrix to the above coating solution for mixed coating, heating and stirring in a constant temperature water bath until the solution is completely evaporated to obtain a coated gel powder; Step 3: Fully dry and sinter the coated gel powder to obtain a high-nickel ternary positive electrode material with an inorganic fast ion conductor in-situ coated thereon.

[0029] In an embodiment, the inorganic fast ion conductor in step 1 is Li 10 G 2 S 12 (LGPS), Li 1.3 Al 0.3 Ti 1.7 P 3 O 12 (LATP)、Li 1.3 In 0.3 Ti 1.7 P 3 O 12 (LITP)、Li 1.5 Al 0.5 Ge 1.5 P 3 O 12 (LAGP), Li 7 La 3 Zr 2 O 12 LLZO, Li 0.33 La 0.56 TiO 3 (LLTO), Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12(LLZTO). The compound containing the target coating element is easily soluble in organic solvents and can easily react with water to generate compounds with higher boiling points. It can react with water vapor in the air under high humidity to avoid volatilization of the coating agent during the sintering process. Preferably, the compound containing the target coating element is one or more of tetrabutyl titanate, aluminum isopropoxide, zirconium isopropoxide, indium nitrate, vanadium chloride, vanadium acetylacetonate, lanthanum acetylacetonate, tantalum pentachloride, germanium acetate, and lithium dihydrogen phosphate.

[0030] In an embodiment, the organic solvent in step 1 is any one or more of anhydrous ethanol, methanol, tetrahydrofuran, N, N-dimethylformamide, N-methylpyrrolidone, dioxane, toluene, ether, acetone, chloroform, carbon tetrachloride, etc.

[0031] In an embodiment, the molar concentration of the mixed metal salt coating solution in step 1 is 1-5 mol L -1 Preferably, the molar concentration of the coating solution is 1-3 mol L -1 .

[0032] In the embodiment, the amount of citric acid added in step 2 is 1-3 mol L -1 , to ensure the uniformity of sol-gel coating.

[0033] In an embodiment, the high-nickel ternary positive electrode material matrix in step 2 is a primary sintered product or a secondary sintered product of a single crystal material of lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminum oxide (NCA), and its general chemical formula is LiNi x Co y M z O 2 (M=Al, Mn, 0.80≤x<1.00, 0<y≤0.10, 0<z≤0.10, x+y+z=1), its D50 particle size is 3-20 μm. As a preferred structure, its formula is LiNi 0.83 Co 0.11 Mn 0.06 O 2 .

[0034] In an embodiment, the heating and stirring speed in step 2 is 200-500 rpm. Preferably, the stirring speed is 200-300 rpm.

[0035] In an embodiment, the heating and stirring process in the constant temperature water bath in step 2 is: stirring at a temperature of 50-90° C. for 0.5-8 h. Preferably, the heating and stirring process is stirring at a temperature of 70-90° C. for 1-5 h.

[0036] In an embodiment, the drying process in step 3 is: drying in a vacuum oven at 60-120° C. for 8-20 h. Preferably, the drying process is drying in a vacuum oven at 60-80° C. for 12-14 h.

[0037] In an embodiment, the sintering process in step 3 is: calcining at 400-650° C. for 4-10 h in a single atmosphere. Preferably, the sintering process is calcining at 400-650° C. for 5-8 h in a single atmosphere.

[0038] In an embodiment, the atmosphere environment of the atmosphere sintering in step three is an inert atmosphere or an oxygen-rich atmosphere, wherein the inert atmosphere is nitrogen or argon.

[0039] In an embodiment, the coating concentration of the inorganic fast ion conductor in the high nickel ternary positive electrode material in the in-situ coating of the inorganic fast ion conductor in step 3 is 1-5 wt %, preferably 1 wt %.

[0040] Example 1

[0041] A high nickel ternary positive electrode material with an inorganic fast ion conductor in-situ coated on the surface, the general structural formula of which is Li 1.3 In 0.3 Ti 1.7 (PO 4 ) 3 @LiNi 0.83 Co 0.11 Mn 0.06 O 2 (LITP@SCNCM, Coating sample). The ternary cathode material is a single crystal particle with a particle size D50 of 5-15 μm. The specific preparation process of the material includes the following steps: Step 1: Indium nitrate nonahydrate (In(NO 3 ) 3 9H 2 O) dispersed in anhydrous ethanol, and subjected to magnetic stirring for 0.5-1 h to obtain solution A; Step 2: Add the corresponding amount of lithium dihydrogen phosphate (LiH 2 PO 4 ) and tetrabutyl titanate (C 16 H 36 O 4 Ti) was added dropwise into solution A, and solution B was obtained after magnetic stirring for 0.5-1 h; Step 3: Evenly mix the B solution with the initial SCNCM and citric acid, and heat and stir at 60-80°C to obtain black LITP-coated SCNCM gel powder; Step 4: The obtained coated gel powder is fully dried and calcined in a pure oxygen atmosphere at 500-650 °C with a heating rate of 2-3 °C / min. Finally, after sintering for 6-12 h, the surface in-situ coated inorganic fast ion conductor Li 1.3 In 0.3 Ti 1.7 (PO 4 ) 3 @LiNi 0.83 Co 0.11 Mn 0.06 O 2 (LITP@SCNCM) materials.

[0042] Example 2

[0043] A high nickel ternary positive electrode material with an inorganic fast ion conductor in-situ coated on the surface, the general structural formula of which is Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 @LiNi 0.8 Co 0.15 Al 0.05 O 2 (LATP@NCA). The ternary cathode material is a single crystal particle with a particle size D50 of 5-15 μm. The specific preparation process of the material includes the following steps: Step 1: Aluminum nitrate nonahydrate (Al(NO 3 ) 3 9H 2 O) dispersed in anhydrous ethanol, and subjected to magnetic stirring for 0.5-1 h to obtain solution A; Step 2: Add the corresponding amount of lithium dihydrogen phosphate (LiH 2 PO 4 ) and tetrabutyl titanate (C 16 H 36 O 4 Ti) was added dropwise into solution A, and solution B was obtained after magnetic stirring for 0.5-1 h; Step 3: Evenly mix the B solution with the ternary cathode material NCA and citric acid, and heat and stir at 60-80°C to obtain a black LATP-coated NCA gel powder; Step 4: The obtained coated gel powder is fully dried and calcined in a pure oxygen atmosphere at 500-650 °C with a heating rate of 2-3 °C / min. Finally, after sintering for 6-12 h, the surface in-situ coated inorganic fast ion conductor Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3@LiNi 0.8 Co 0.15 Al 0.05 O 2 (LATP@NCA) materials.

[0044] Comparative Example

[0045] This comparative example uses the same method to process the traditional NCM high-nickel ternary positive electrode material as a comparison with Example 1.

[0046] A high-nickel ternary positive electrode material, the general structural formula of which is LiNi 0.83 Co 0.11 Mn 0.06 O 2 (SCNCM, Puresample). The ternary cathode material is a single crystal particle with a particle size D50 of 5-15 μm. Similar to Example 1, the specific preparation process of the material includes the following steps: Step 1: LiNi ternary cathode material 0.83 Co 0.11 Mn 0.06 O 2 Dispersed in anhydrous ethanol, solution A was obtained after magnetic stirring for 0.5-1 h; Step 2: Evenly mix solution A and citric acid, and obtain solution B after magnetic stirring for 0.5-1 h; Step 3: Heat and stir the B solution at 60-80°C to obtain a gel powder of a high-nickel ternary positive electrode NCM; Step 4: The obtained gel powder is fully dried and calcined in a pure oxygen atmosphere at 500-650 °C for 6-12 h to obtain a single crystal NCM material LiNi 0.83 Co 0.11 Mn 0.06 O 2 Particles.

Claims

1. A high-nickel ternary positive electrode material with an inorganic fast ion conductor in-situ coated on the surface and a preparation method thereof, characterized in that: A continuous and dense inorganic fast ion conductor nano-coating is constructed on the surface of single crystal positive electrode particles by using a sol-gel method combined with a solid phase sintering coating technology. The structural formula of the ternary positive electrode material is LiNi x Co y M z O2 (M=Al, Mn, 0.80≤x<1.00, 0<y≤0.10, 0<z≤0.10, x+y+z=1), its D50 particle size is 3-20 μm, and the particle size of the inorganic fast ion conductor coating layer is controlled at 5-50 nm. The specific preparation process comprises the following steps: Step 1: dissolving a compound containing the target inorganic fast ion conductor coating material element in an organic solvent according to a certain stoichiometric ratio to prepare a mixed metal salt coating solution; Step 2: adding citric acid and high-nickel ternary positive electrode material matrix to the above coating solution for mixed coating, heating and stirring in a constant temperature water bath until the solution is completely evaporated to obtain a coated gel powder; Step 3: Fully dry and sinter the coated gel powder to obtain a high-nickel ternary positive electrode material with an inorganic fast ion conductor in-situ coated thereon.

2. The preparation method according to claim 1, wherein the inorganic fast ion conductor in step 1 is Li 10 GeP2S 12 (LGPS), Li 1.3 Al 0.3 Ti 1.7 P3O 12 (LATP)、Li 1.3 In 0.3 Ti 1.7 P3O 12 (LITP)、Li 1.5 Al 0.5 Ge 1.5 P3O 12 (LAGP), Li7La3Zr2O 12 LLZO, Li 0.33 La 0.56 TiO3 (LLTO), Li 6.4 Ln3Z 1.4 Ta 0.6 O 12 (LLZTO). The compound containing the target coating element is easily soluble in organic solvents and can easily react with water to generate compounds with higher boiling points. It can react with water vapor in the air under high humidity to avoid volatilization of the coating agent during the sintering process. Preferably, the compound containing the target coating element is one or more of tetrabutyl titanate, aluminum isopropoxide, zirconium isopropoxide, indium nitrate, vanadium chloride, vanadium acetylacetonate, lanthanum acetylacetonate, tantalum pentachloride, germanium acetate, and lithium dihydrogen phosphate.

3. The preparation method according to claim 1, wherein the organic solvent in step 1 is any one or more of anhydrous ethanol, methanol, tetrahydrofuran, N, N-dimethylformamide, N-methylpyrrolidone, dioxane, toluene, ether, acetone, chloroform, carbon tetrachloride, etc.

4. The preparation method according to claim 1, wherein the high-nickel ternary positive electrode material matrix in step 2 is a primary sintered product or a secondary sintered product of a single crystal material of lithium nickel cobalt manganese oxide (NCM) or lithium nickel cobalt aluminum oxide (NCA), and its general chemical formula is LiNi x Co y M z O2 (M=Al, Mn, 0.80≤x<1.00, 0<y≤0.10, 0<z≤0.10, x+y+z=1), its D50 particle size is 3-20 μm.

5. The preparation method according to claim 1, wherein the heating and stirring speed in step 2 is 200-500 rpm. Preferably, the stirring speed is 200-300 rpm.

6. The preparation method according to claim 1, wherein the heating and stirring process in the constant temperature water bath in step 2 is: stirring at a temperature of 50-90°C for 0.5-8 h. Preferably, the heating and stirring process is stirring at a temperature of 70-90°C for 1-5 h.

7. The preparation method according to claim 1, wherein the drying process in step 3 is: drying in a vacuum oven at 60-120°C for 8-20 h. Preferably, the drying process is drying in a vacuum oven at 60-80°C for 12-14 h.

8. The preparation method according to claim 1, wherein the sintering process in step 3 is: calcining at 400-650°C for 4-10 h in a single atmosphere. Preferably, the sintering process is calcining at 400-650°C for 5-8 h in a single atmosphere.

9. The preparation method according to claim 1, wherein the atmosphere environment of the atmosphere sintering in step 3 is an inert atmosphere or an oxygen-rich atmosphere sintering, wherein the inert atmosphere is nitrogen or argon.

10. The preparation method according to claim 1, wherein the coating concentration of the inorganic fast ion conductor in the high nickel ternary positive electrode material in the in-situ coating of the inorganic fast ion conductor in step 3 is 1-5wt%, preferably 1wt%.

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