A positive electrode material, a preparation method and application thereof

Abstract

This invention provides a cathode material, its preparation method, and its application. The preparation method includes the following steps: mixing the high-nickel cathode material to be treated with potassium hexafluoronickelate, and performing heat treatment under an oxygen atmosphere to obtain the cathode material. This invention solves the problem of trivalent nickel decomposition to divalent nickel on the cathode material surface during oxidation sintering by using potassium hexafluoronickelate to oxidize the high-nickel cathode material, thus introducing nickel and fluorine into its surface layer. This reduces lithium-nickel mixing and avoids introducing electrochemically inert metal materials or difficult-to-remove impurities, thereby improving the capacity and cycle stability of the cathode material.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a cathode material, its preparation method and application. Background Technology

[0002] Battery materials are categorized into positive electrode materials, negative electrode materials, separators, and electrolytes. Positive electrode materials are one of the key materials in manufacturing lithium-ion batteries, accounting for over 25% of the battery cost. Their performance directly affects various battery performance indicators, making them central to lithium-ion batteries. Currently commercially available lithium battery positive electrode materials include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium iron phosphate, and ternary materials. Among these, ternary materials combine the advantages of all three materials, significantly reducing costs and exhibiting excellent cycle performance; their overall performance surpasses that of any single positive electrode material mentioned above.

[0003] High-nickel ternary lithium-ion battery cathode materials have become a research hotspot due to their advantages such as high specific capacity, low cost, and excellent safety, and are considered to be highly promising cathode materials for lithium-ion power batteries. However, high nickel content also brings problems such as structural instability and severe high-temperature gas expansion, especially nickel-lithium mixing. During the lithium-ion extraction process, divalent nickel ions embedded in the lithium layer are oxidized to trivalent nickel ions, leading to local structural collapse. Lithium ions then find it more difficult to embed into the collapsed sites, resulting in capacity loss. Therefore, research on pre-oxidation of ternary cathode material precursors to reduce nickel-lithium mixing is of great practical significance.

[0004] In the formation of high-nickel cathode materials (Ni > 0.6%), such as NCM and NCA, oxygen sintering is required to oxidize divalent nickel in the precursor to trivalent nickel. With increasing nickel content, it becomes difficult to oxidize divalent nickel to trivalent nickel using conventional oxidation sintering methods. Current technologies generally address this issue by extending the oxidation sintering time or increasing the oxidation sintering temperature; however, these methods are ineffective because trivalent nickel easily decomposes into divalent nickel at high temperatures, while prolonged low-temperature sintering leads to a significant increase in cost.

[0005] In the prior art, some researchers have improved the oxidation effect of divalent nickel by pre-oxidizing the precursor. For example, CN108511746A uses nitrate to oxidize the high-nickel precursor, which increases the amount of trivalent nickel in the precursor material. However, because the temperature of the cathode material surface is higher than that of the inner layer during oxidation sintering, it is easy to decompose and produce divalent nickel. Therefore, the divalent nickel on the surface of the cathode material obtained by this preparation method is still too high, which will affect its initial capacity and cycle performance, and will also introduce nitrogen elements that are difficult to remove.

[0006] For example, CN108461731A discloses a high-nickel ternary lithium battery cathode material and its preparation method. This method involves high-speed dispersion of nano-oxidant powder and paraffin wax, causing the paraffin wax to uniformly coat the surface of the nano-oxidant powder, forming a core-shell structure. Then, it is mixed with nickel, cobalt, and manganese sources, precipitated, further mixed with a lithium source, and sintered to remove organic matter, thus obtaining the high-nickel ternary lithium battery cathode material. This document also involves a pre-oxidation process on the precursor, and also suffers from the aforementioned problem of easy decomposition to obtain divalent nickel.

[0007] Therefore, how to reduce the decomposition of trivalent nickel during the oxidation sintering process of high-nickel cathode materials and improve their capacity and cycle performance is an urgent technical problem to be solved. Summary of the Invention

[0008] The purpose of this invention is to provide a cathode material, its preparation method, and its application. This invention uses potassium hexafluoronickelate to oxidize the high-nickel cathode material, incorporating nickel and fluorine into its surface layer. This solves the problem of trivalent nickel decomposition to divalent nickel on the cathode material surface during oxidation sintering, reduces lithium-nickel mixing, and avoids introducing electrochemically inert metal materials or difficult-to-remove impurities, thereby improving the capacity and cycle stability of the cathode material.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a cathode material, the method comprising the following steps:

[0011] The high-nickel cathode material to be treated is mixed with potassium hexafluoronickelate and heat-treated under an oxygen atmosphere to obtain the cathode material.

[0012] The high-nickel cathode material to be processed provided by the present invention is a cathode material obtained by oxidation sintering. It can be purchased directly or obtained by mixing the precursor with the lithium source and then sintering. The high-nickel cathode material in the present invention is a cathode material with a nickel stoichiometric ratio > 0.6.

[0013] This invention uses potassium hexafluoronickelate to oxidize the high-nickel cathode material to be treated, incorporating nickel and fluorine into its surface layer. This solves the problem of trivalent nickel decomposition to produce divalent nickel on the cathode material surface during oxidation sintering, reduces lithium-nickel mixing, and avoids introducing electrochemically inert metal materials or difficult-to-remove impurities, thereby improving the capacity and cycle stability of the cathode material.

[0014] In this invention, the high-nickel cathode material after oxidation and sintering is uniformly mixed with potassium hexafluoronickelate. Potassium hexafluoronickelate oxidizes the divalent nickel on the surface of the cathode material into trivalent nickel, while potassium hexafluoronickelate is reduced to nickel trifluoride and potassium fluoride. During the sintering process, trivalent nickel, fluorine and potassium are doped into the surface of the cathode material. Trivalent nickel can improve the capacity of the cathode material, fluorine can replace oxygen sites for doping, which can further improve the stability of the cathode material, and the potassium on the surface can be easily removed by a water washing step.

[0015] Therefore, the preparation method provided by the present invention can solve the problem of trivalent nickel decomposition to produce divalent nickel on the surface of the cathode material during oxidation sintering by introducing potassium hexafluoronickelate to oxidize and dope the cathode material. It does not require long-term low-temperature sintering, thus reducing costs and reducing lithium-nickel mixing. At the same time, it does not introduce electrochemically inert metal materials or impurities that are difficult to remove, thereby improving the capacity and cycle stability of the cathode material.

[0016] In this invention, if other types of oxidants are selected, such as strong oxidants like potassium permanganate, although the divalent nickel on the surface of the cathode material can be oxidized to trivalent nickel to a certain extent, manganese dioxide will be formed on the surface of the material, which will seriously affect the specific capacity and conductivity of the cathode material.

[0017] Preferably, the amount of potassium hexafluoronickelate added is 0.1% to 10% of the mass of the high-nickel cathode material to be treated, for example, 0.1%, 1%, 2%, 3%, 4%, 5%, 5.3%, 5.5%, 5.8%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 9.8%, or 10%, and more preferably 5% to 10%.

[0018] The potassium hexafluoronickelate provided by this invention can achieve better results when the addition amount is in the range of 5-10%. Within this range, the oxidation of divalent nickel will be more complete. At the same time, since it is nickel that is doped, it will not reduce the capacity of the material. However, if the addition amount is too high, exceeding 10%, it will lead to an excessively high surface nickel content and an excessively low manganese and cobalt content, thereby reducing cycle stability. If the addition amount is too low, less than 5%, although it can reduce the surface divalent nickel to some extent, there will still be some divalent nickel that is not completely oxidized.

[0019] Preferably, the heat treatment temperature is 200-500℃, such as 200℃, 205℃, 210℃, 220℃, 230℃, 240℃, 250℃, 260℃, 270℃, 280℃, 290℃, 300℃, 350℃, 400℃, 450℃ or 500℃, and more preferably 200-300℃.

[0020] In this invention, the heat treatment temperature is in the range of 200 to 300°C, which can oxidize the divalent nickel on the surface of the cathode material to trivalent nickel. However, if the temperature is too high, exceeding 300°C, it will increase unnecessary energy consumption and may promote the decomposition of trivalent nickel.

[0021] Preferably, the heat treatment time is 1 to 10 hours, such as 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, and preferably 1 to 3 hours.

[0022] The preparation method provided by this invention does not require an excessively long heat treatment time. The addition of potassium hexafluoronickelate can effectively reduce the heat treatment time to within 1 to 3 hours. It can also more effectively prevent the decomposition of trivalent nickel on the surface. However, if the heat treatment time is too long, exceeding 3 hours, the potassium hexafluoronickelate may be completely consumed, and the divalent nickel produced by the decomposition of trivalent nickel on the surface may not be oxidized.

[0023] Preferably, the method for preparing the high-nickel cathode material to be treated includes:

[0024] A high-nickel cathode precursor is mixed with a lithium source and sintered under an oxygen atmosphere to obtain the cathode material to be processed.

[0025] Preferably, the high-nickel cathode precursor has the general chemical formula Ni x Co y M 1-x-y (OH)2, x > 0.6, y ≥ 0, M includes Mn and / or Al, for example, x can be 0.63, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.93 or 0.95, etc., and y can be 0.05, 0.1, 0.13, 0.15, 0.2, 0.25, 0.3 or 0.33, etc.

[0026] Preferably, the high-nickel cathode precursor has the general chemical formula Ni x Co y M 1-x-y In (OH)2, x > 0.9, for example, 0.91, 0.92, 0.93, 0.94 or 0.95, etc.

[0027] Preferably, the lithium source includes lithium hydroxide.

[0028] In this invention, lithium hydroxide is selected as the lithium source, which makes the reaction more complete. If other lithium sources, such as lithium carbonate, are selected, incomplete decomposition may occur.

[0029] Preferably, the sintering temperature is 750–800°C, such as 750°C, 760°C, 770°C, 780°C, 790°C, or 800°C.

[0030] Preferably, the sintering time is 8 to 20 hours, such as 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours or 20 hours, with 8 to 12 hours being the most preferred.

[0031] In the preparation of the high-nickel cathode material to be treated, the present invention will carry out an oxidation heat treatment process. When potassium hexafluoronickelate is used as the oxidant, the oxidation sintering time can be shortened, thus saving sintering costs.

[0032] Preferably, the heat-treated material is sequentially washed with water and dried.

[0033] As a preferred technical solution, the preparation method includes the following steps:

[0034] (1) Mix the positive electrode precursor with lithium hydroxide and sinter at a sintering temperature of 750-800℃ for 8-12 hours in an oxygen atmosphere to obtain the positive electrode material to be modified.

[0035] (2) Mix the cathode material to be modified in step (1) with potassium hexafluoronickelate. The amount of potassium hexafluoronickelate added is 5-10% of the mass of the cathode material to be modified. Heat treat at 200-300°C for 1-3 hours in an oxygen atmosphere, wash with water, and dry to obtain the cathode material.

[0036] The general chemical formula of the positive electrode precursor is Ni. x Co y M 1-x-y (OH)2, x>0.9, y≥0, M includes Mn and / or Al.

[0037] In a second aspect, the present invention provides a cathode material, which is prepared by the cathode material preparation method described in the first aspect; the surface layer of the cathode material is doped with fluorine and nickel.

[0038] In the cathode material provided by this invention, fluorine and nickel will penetrate into the surface layer of the cathode material during the heat treatment process.

[0039] Thirdly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode material as described in the second aspect.

[0040] Compared with the prior art, the present invention has the following beneficial effects:

[0041] The preparation method provided by this invention solves the problem of trivalent nickel decomposition to divalent nickel on the surface of the cathode material during oxidation sintering by introducing potassium hexafluoronickelate for oxidation and doping. This eliminates the need for prolonged low-temperature sintering, thus reducing costs and minimizing lithium-nickel mixing. Furthermore, it avoids introducing electrochemically inert metal materials or difficult-to-remove impurities. The addition of fluorine and nickel to the surface layer of the high-nickel cathode material improves its capacity and cycle stability, achieving a comprehensive enhancement of the cathode material's electrochemical performance. The battery provided by this invention exhibits a discharge capacity of over 206.9 mAh / g at 0.1C, and retains over 85.3% of its capacity after 100 cycles. Attached Figure Description

[0042] Figure 1 The image shows a SEM image of the high-nickel cathode material provided in Example 1. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] Example 1

[0045] This embodiment provides a high-nickel cathode material, wherein the surface layer of the high-nickel cathode material is doped with fluorine and nickel.

[0046] The preparation method of the high-nickel cathode material is as follows:

[0047] (1) Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ and LiOH (Li to Ni molar ratio of 1:0.9) were mixed in a high-efficiency ball mill for 5 hours to obtain a homogeneous mixture. The mixture was then placed in an atmosphere furnace, oxygen was introduced at a rate of 3 L / min, and the temperature was increased to 800℃ at a rate of 5℃ / min. The mixture was then sintered at this temperature for 8 hours. After calcination, it was cooled to room temperature and passed through a 300-mesh sieve to remove excessively large particles, thus obtaining the high-nickel cathode material LiNi to be processed. 0.9 Co 0.05 Mn 0.05 O2;

[0048] (2) The high-nickel cathode material to be treated is mixed with potassium hexafluoronickelate (mass ratio of 100:5) in a high-efficiency mixer for 20 minutes to obtain a uniformly mixed material. Then the mixture is placed in an atmosphere furnace, oxygen is introduced at 3L / min, and heat-treated at 300℃ for 1 hour. After washing with water and drying, the high-nickel cathode material is obtained.

[0049] Figure 1The SEM image of the high-nickel cathode material provided in Example 1 is shown. Figure 1 It can be seen that the high-nickel cathode material in Example 1 has a polycrystalline structure, with a coating layer on its surface, obvious reaction traces, and intact particles.

[0050] Example 2

[0051] This embodiment provides a high-nickel cathode material, wherein the surface layer of the high-nickel cathode material is doped with fluorine and nickel.

[0052] The preparation method of the high-nickel cathode material is as follows:

[0053] (1) Ni 0.9 Co 0.05 Mn 0.05 (OH)₂ and LiOH (Li to Ni molar ratio 1:0.9) were mixed in a high-efficiency ball mill for 5 hours to obtain a homogeneous mixture. The mixture was then placed in an atmosphere furnace, oxygen was introduced at a rate of 3 L / min, and the temperature was increased to 780°C at a rate of 5°C / min. The mixture was then sintered at this temperature for 10 hours. After calcination, the mixture was cooled to room temperature and passed through a 300-mesh sieve to remove excessively large particles, thus obtaining the high-nickel cathode material LiNi to be processed. 0.9 Co 0.05 Mn 0.05 O2;

[0054] (2) The high-nickel cathode material to be treated is mixed with potassium hexafluoronickelate (mass ratio of 100:8) in a high-efficiency mixer for 20 minutes to obtain a uniformly mixed material. Then the mixture is placed in an atmosphere furnace, oxygen is introduced at 3L / min, and heat-treated at 250°C for 2 hours. After washing with water and drying, the high-nickel cathode material is obtained.

[0055] Example 3

[0056] This embodiment provides a high-nickel cathode material, wherein the surface layer of the high-nickel cathode material is doped with fluorine and nickel.

[0057] The preparation method of the high-nickel cathode material is as follows:

[0058] (1) Ni 0.8 Co 0.1 Mn 0.1 (OH)₂ and LiOH (Li to Ni molar ratio of 1:0.8) were mixed in a high-efficiency ball mill for 5 hours to obtain a homogeneous mixture. The mixture was then placed in an atmosphere furnace, oxygen was introduced at a rate of 3 L / min, and the temperature was increased to 780°C at a rate of 5°C / min. The mixture was then sintered at this temperature for 10 hours. After calcination, the mixture was cooled to room temperature and passed through a 300-mesh sieve to remove excessively large particles, thus obtaining the high-nickel cathode material LiNi to be processed. 0.8 Co0.1 Mn 0.1 O2;

[0059] (2) The high-nickel cathode material to be treated is mixed with potassium hexafluoronickelate (mass ratio of 100:10) in a high-efficiency mixer for 20 min to obtain a uniformly mixed material. Then the mixture is placed in an atmosphere furnace, oxygen is introduced at 3 L / min, and heat-treated at 200°C for 3 h. After washing with water and drying, the high-nickel cathode material is obtained.

[0060] Example 4

[0061] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the mass ratio of the high-nickel cathode material to be treated to potassium hexafluoronickelate is 100:3.

[0062] The remaining preparation methods and parameters are consistent with those in Example 1.

[0063] Example 5

[0064] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the mass ratio of the high-nickel cathode material to be treated to potassium hexafluoronickelate is 100:10.

[0065] The remaining preparation methods and parameters are consistent with those in Example 1.

[0066] Example 6

[0067] The difference between this embodiment and embodiment 1 is that in step (2) of this embodiment, the mass ratio of the high-nickel cathode material to be treated to potassium hexafluoronickelate is 100:15.

[0068] The remaining preparation methods and parameters are consistent with those in Example 1.

[0069] Example 7

[0070] The difference between this embodiment and embodiment 1 is that the heat treatment time in step (2) of this embodiment is 5 hours.

[0071] The remaining preparation methods and parameters are consistent with those in Example 1.

[0072] Example 8

[0073] The difference between this embodiment and embodiment 1 is that the heat treatment temperature in step (2) of this embodiment is 500℃.

[0074] The remaining preparation methods and parameters are consistent with those in Example 1.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is that potassium hexafluoronickelate is not added in step (2) of this comparative example.

[0077] The remaining preparation methods and parameters are consistent with those in Example 1.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is that this comparative example uses potassium permanganate for oxidation, and the preparation process is as follows:

[0080] Ni was oxidized using potassium permanganate (mass ratio 5:100). 0.9 Co 0.05 Mn 0.05 (OH)₂ was then mixed with LiOH (Li and Ni molar ratio 1:0.9) and milled in a high-efficiency ball mill for 5 hours to obtain a homogeneous mixture. The mixture was then placed in an atmosphere furnace, oxygen was introduced at a rate of 3 L / min, and the temperature was increased to 800°C at a rate of 5°C / min. The mixture was then sintered at this temperature for 8 hours. After calcination, the mixture was cooled to room temperature and passed through a 300-mesh sieve to remove excessively large particles, thus obtaining the high-nickel cathode material LiNi. 0.9 Co 0.05 Mn 0.05 O2.

[0081] Comparative Example 3

[0082] The difference between this comparative example and Example 3 is that potassium hexafluoronickelate is not added in step (2) of this comparative example.

[0083] The remaining preparation methods and parameters are consistent with those in Example 3.

[0084] The high-nickel cathode materials provided in Examples 1-8 and Comparative Examples 1-3 were used to prepare coin cells for lithium-ion battery electrochemical performance testing. The specific steps were as follows: Using N-methylpyrrolidone as a solvent, the positive electrode active material was mixed uniformly with acetylene black and PVDF in a mass ratio of 9.2:0.5:0.3, coated onto aluminum foil, and dried at 80°C for 8 hours under forced air, followed by vacuum drying at 120°C for 12 hours. The batteries were assembled in an argon-protected glove box, with a lithium metal sheet as the negative electrode, a polypropylene membrane as the separator, and 1M LiPF6-EC / DMC (1:1, v / v) as the electrolyte. A 2032-type coin cell case was used to assemble the coin cells in the argon-protected glove box, and then electrochemical performance testing was conducted at 25°C and 3.0-4.5V. The results are shown in Table 1 below.

[0085] Table 1

[0086]

[0087] The data from Examples 1 and 4-6 show that a mass percentage of potassium hexafluoronickelate of less than 5% is not conducive to improving specific capacity and cycle stability, while a mass percentage of more than 10% will lead to excessively high surface nickel content, thereby reducing cycle stability.

[0088] The data from Examples 1 and 7 show that adding potassium hexafluoronickelate results in an excessively long heat treatment time, which consumes more energy and causes the decomposition of trivalent nickel on the surface, reducing the specific capacity.

[0089] The data from Examples 1 and 8 show that when potassium hexafluoronickel is added, if the heat treatment temperature is too high, it will cause the trivalent nickel on the surface to decompose, reducing the specific capacity, while also increasing lithium-nickel mixing and reducing cycle stability.

[0090] The data from Example 1 and Comparative Example 1, and Example 3 and Comparative Example 3 show that without the addition of potassium hexafluoronickelate for oxidation, it is impossible to reduce the divalent nickel content on the surface of the cathode material, which leads to severe nickel-lithium mixing and a significant reduction in cycle stability and specific capacity.

[0091] The data from Example 1 and Comparative Example 2 show that while other types of oxidants can improve the cycle stability of cathode materials to some extent, it is difficult to achieve a dual improvement in capacity and cycle life. In other words, the improvement in one aspect of electrochemical performance comes at the expense of other performance aspects.

[0092] In summary, the preparation method provided by this invention, by introducing potassium hexafluoronickelate to oxidize and dope the cathode material, solves the problem of trivalent nickel decomposition to divalent nickel on the cathode material surface during oxidation sintering. It eliminates the need for prolonged low-temperature sintering, thus reducing costs and minimizing lithium-nickel mixing. Furthermore, it avoids introducing electrochemically inert metal materials or difficult-to-remove impurities. The addition of fluorine and nickel to the surface layer of the high-nickel cathode material improves its capacity and cycle stability, achieving a comprehensive enhancement of the cathode material's electrochemical performance. The battery provided by this invention exhibits a discharge capacity of over 206.9 mAh / g at 0.1C, and its capacity retention rate reaches over 85.3% after 100 cycles.

[0093] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a positive electrode material, characterized in that, The preparation method includes the following steps: High-nickel cathode material was mixed with potassium hexafluoronickelate and heat-treated under an oxygen atmosphere to obtain cathode material with fluorine and nickel doped on the surface. The amount of potassium hexafluoronickelate added is 5-10% of the mass of the high-nickel cathode material; The heat treatment temperature is 200~250℃; The heat treatment time is 1-3 hours; The stoichiometry of nickel in the high-nickel cathode material is >0.

8.

2. The method for preparing the cathode material according to claim 1, characterized in that, The preparation method of the high-nickel cathode material includes: A high-nickel cathode precursor is mixed with a lithium source and sintered in an oxygen atmosphere to obtain a high-nickel cathode material.

3. The method for preparing the cathode material according to claim 2, characterized in that, The chemical formula of the high-nickel cathode precursor is Ni x Co y M 1-x-y (OH)2, x>0.8, y≥0, M includes Mn and / or Al.

4. The method for preparing the cathode material according to claim 3, characterized in that, The high-nickel cathode precursor has the general chemical formula Ni x Co y M 1-x-y In (OH)2, x > 0.

9.

5. The method for preparing the cathode material according to claim 2, characterized in that, The lithium source includes lithium hydroxide.

6. The method for preparing the cathode material according to claim 2, characterized in that, The sintering temperature is 750~800℃.

7. The method for preparing the cathode material according to claim 2, characterized in that, The sintering time is 8~20h.

8. The method for preparing the cathode material according to claim 7, characterized in that, The sintering time is 8-12 hours.

9. The method for preparing the cathode material according to claim 2, characterized in that, The heat-treated material is then washed with water and dried sequentially.

10. The method for preparing the cathode material according to claim 1, characterized in that, The preparation method includes the following steps: (1) Mix the high-nickel cathode precursor with lithium hydroxide and sinter at a sintering temperature of 750~800℃ for 8~12h under an oxygen atmosphere to obtain the high-nickel cathode material; (2) Mix the high-nickel cathode material described in step (1) with potassium hexafluoronickelate, wherein the amount of potassium hexafluoronickelate added is 5-10% of the mass of the high-nickel cathode material, and heat-treat at a temperature of 200-250°C for 1-3 hours in an oxygen atmosphere, wash with water, and dry to obtain the cathode material. The chemical formula of the high-nickel cathode precursor is Ni. x Co y M 1-x-y (OH)2, x>0.9, y≥0, M includes Mn and / or Al.

11. A positive electrode material, characterized in that, The cathode material is prepared by the cathode material preparation method according to any one of claims 1-10; the surface layer of the cathode material is doped with fluorine and nickel.

12. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in claim 11.

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