Composite-coated ternary precursor and its preparation method and application

Abstract

The present invention discloses a composite-coated ternary precursor, its preparation method and application. The material includes a ternary precursor and a coating layer attached to the surface of the ternary precursor. The coating layer is obtained by a precipitation reaction of a first metal ion and a first polyanion. In the present invention, the metal ion and the polyanion can undergo a precipitation reaction to form a precipitate. Since there are a large number of active sites on the surface of the ternary precursor, with a relatively high specific surface energy, it is easy for the precipitate to attach and grow, and then a uniformly distributed coating layer is formed on the surface of the ternary precursor. After sintering the coated precursor into a cathode material, a part of the coating can form a protective layer on the material surface, reducing the dissolution of Ni and Co, inhibiting the side reaction between the cathode material and the electrolyte, and reducing the irreversible phase change on the material surface, thereby improving the stability of the ternary material; another part of the coating can penetrate into the material interior to form bulk doping.

Description

Technical Field

[0001] The present invention belongs to the technical field of cathode materials for lithium-ion batteries, and particularly relates to a composite-coated ternary precursor and a preparation method and application thereof. Background Art

[0002] Ternary lithium-ion cathode materials, including NCM materials and NCA materials, although having high specific capacity and cycling performance, their safety performance has been criticized. In recent years, electric vehicles using ternary lithium-ion batteries have caught fire many times, making people's demand for the safety of power batteries stronger and stronger. How to improve the safety performance of ternary batteries while ensuring the energy density has become one of the mainstream research directions for power batteries of electric vehicles.

[0003] The modification directions of ternary cathode materials include coating, doping, core-shell structure, concentration gradient structure, quaternary materials, etc., to improve the cycling performance and safety performance of batteries by enhancing the stability of the material structure. In terms of coating, the coating elements are mostly added in the sintering stage, which not only increases the number of sintering times, but also makes the coating materials uneven. Some methods are to coat on the surface of the precursor, but generally only single-property elements are coated, and the improvement effect is very limited, or multiple-stage coating is carried out, which increases the labor cost, and the operation difficulty increases, and the risk of material segregation increases. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. For this reason, the present invention provides a composite-coated ternary precursor and a preparation method and application thereof.

[0005] According to one aspect of the present invention, a composite-coated ternary precursor is provided, including a ternary precursor and a coating layer attached to the surface of the ternary precursor, wherein the coating layer is obtained by a precipitation reaction of a first metal ion and a first polyanion, and the first metal ion is Mg 2+ , Sc 3+ , Ti 3+ , V 2+ , Cr 2+ , Cu 2+ , Zn 2+ , Ge 2+ , Zr 4+ , Nb 5+ , In 3+ , Sb 3+ , Tb 4+ , Ta 4+ , Re 4+ , Ir 3+ , Pb 4+ or Bi 5+One or more of those, the first polyanion being SiO3 2- , AlO2 - , B4O7 2- , SO4 2- , PO4 3- , BO3 3- , MoO4 2- or WO4 2- One or more of those.

[0006] In some embodiments of the present invention, the content of the coating layer is 0.5 - 5% of the mass fraction of the ternary precursor.

[0007] In some embodiments of the present invention, the particle size of the ternary precursor is preferably 3 - 12 μm.

[0008] In some embodiments of the present invention, the ternary precursor is doped with a second metal ion and a second polyanion, the second metal ion being Mg 2+ , Sc 3+ , Ti 3+ , V 2+ , Cr 2+ , Cu 2+ , Zn 2+ , Ge 2+ , Zr 4+ , Nb 5+ , In 3+ , Sb 3+ , Tb 4+ , Ta 4+ , Re 4+ , Ir 3+ , Pb 4+ or Bi 5+ One or more of those, the second polyanion being SiO3 2- , PO4 3- , MoO4 2- or B4O7 2- One or more of those.

[0009] In some embodiments of the present invention, the total doping amount of the second metal ion and the second polyanion is 0.5 - 5% of the mass of the ternary precursor.

[0010] The present invention also provides a preparation method of the ternary precursor with composite coating, comprising the following steps:

[0011] S1: Prepare a first metal salt solution and a first polyanion salt solution respectively, the first metal salt solution being Mg 2 + , Sc 3+ , Ti 3+ , V2+ 、Cr 2+ 、Cu 2+ 、Zn 2+ 、Ge 2+ 、Zr 4+ 、Nb 5+ 、In 3+ 、Sb 3+ 、Tb 4+ 、Ta 4+ 、Re 4+ 、Ir 3+ 、Pb 4+ or Bi 5+ in one or more of the salt solutions, and the first polyanionic salt solution is SiO3 2- 、AlO2 - 、B4O7 2- 、SO4 2- 、PO4 3- 、BO3 3- 、MoO4 2- or WO4 2- in one or more of the salt solutions;

[0012] S2: At a certain stirring speed and temperature, add the first metal salt solution and the first polyanionic salt solution to the ternary precursor slurry to carry out a precipitation reaction, and maintain the reaction pH at 6.0 - 9.0 during the reaction. After the reaction is completed, a precipitate is obtained;

[0013] S3: Wash and dry the precipitate to obtain the composite-coated ternary precursor.

[0014] In some embodiments of the present invention, in step S1, the concentrations of the first metal salt solution and the first polyanionic salt solution are independently 0.5 - 2 mol / L.

[0015] In some embodiments of the present invention, in step S2, the time for adding the first metal salt solution and the first polyanionic salt solution is 0.5 - 1.5 h, and after the feeding is completed, aging is carried out for 0.5 - 1.5 h. The total volume of the first metal salt solution and the first polyanionic salt solution is 5 - 15 L.

[0016] In some embodiments of the present invention, when the ternary precursor is doped with a second metal ion and a second polyanion, the ternary precursor is prepared by the following method: dissolving soluble nickel salt, cobalt salt, manganese salt, and second metal salt in water in proportion to prepare a mixed metal salt solution; dissolving sodium hydroxide and second polyanion salt in water to prepare a doping precipitant; at a certain stirring speed and temperature, first adding ammonia water, then adjusting the pH to 9.5 - 12.5 with sodium hydroxide, and then adding the mixed metal salt solution, doping precipitant, and ammonia water for coprecipitation reaction to obtain the ternary precursor; the second metal salt is Mg 2+ , Sc 3+ , Ti 3+ , V 2+ , Cr 2+ , Cu 2+ , Zn 2+ , Ge 2+ , Zr 4+ , Nb 5+ , In 3+ , Sb 3+ , Tb 4+ , Ta 4+ , Re 4+ , Ir 3+ , Pb 4+ or Bi 5+ salt(s) of one or more of them, and the second polyanion salt is SiO3 2- , PO4 3- , MoO4 2- or B4O7 2- salt(s) of one or more of them. The second polyanion salt cannot be directly added to the mixed metal salt solution because the second polyanion salt will react with metal ions to form precipitation. Preferably, the stirring speed is 200 - 600 r / min, the reaction temperature of the coprecipitation reaction is 35 - 85 °C, and the concentration of ammonia water in the coprecipitation reaction is maintained at 0.5 - 12 g / L. The particle size of the ternary precursor is 3 - 12 μm. Doping metal elements in the mixed salt solution can achieve uniform mixing at the atomic scale and obtain a precursor with uniform element distribution; the radius of the metal cation is related to Li + and Ni 2+The radius is similar, which can effectively reduce the degree of lithium-nickel mixing and inhibit the capacity decay of the material; the doped polyanion in the precipitant needs to participate in the neutralization reaction first and then crystallize during the coprecipitation process, so it can be slowly released and evenly distributed in the precursor particles. The doped polyanion has a relatively large radius, which can increase the unit cell volume, play a role in supporting the three-dimensional framework structure of the material, expand the lithium-ion transmission channels, inhibit the phase change that occurs during the charge and discharge process of the material, and improve the electrochemical performance of the material. In addition, the polyanion can provide a part of oxygen atoms during the sintering process, reduce the oxygen defects inside the material, and the polyanion has a strong covalent bond network structure, which can inhibit the precipitation of oxygen during the charge and discharge process of the material and reduce the occurrence of side reactions. The synergistic effect of cations and anions can effectively improve the capacity and cycle performance of the ternary material.

[0017] In some embodiments of the present invention, the second metal salt in the mixed metal salt solution accounts for 0.1-2% of the total molar amount of the nickel salt, cobalt salt, and manganese salt.

[0018] In some embodiments of the present invention, the concentration of the mixed metal salt solution is 0.5-2.0 mol / L.

[0019] In some embodiments of the present invention, the concentration of the doped precipitant is 2-10 mol / L, and the molar ratio of sodium hydroxide to the second polyanion salt in the doped precipitant is (30-300):1.

[0020] The present invention also provides a ternary cathode material, which is prepared by sintering the composite-coated ternary precursor.

[0021] According to a preferred embodiment of the present invention, it has at least the following beneficial effects:

[0022] 1. The metal ions and polyanions of the present invention can undergo a precipitation reaction to form a precipitate. Since there are a large number of active sites on the surface of the ternary precursor, with a high specific surface energy, it is easy for the precipitate to attach and grow, and then a uniformly distributed coating layer is formed on the surface of the ternary precursor. After sintering the coated precursor into a cathode material, a part of the coating can form a protective layer on the surface of the material, reduce the dissolution of Ni and Co, inhibit the side reaction between the cathode material and the electrolyte, and reduce the irreversible phase change on the surface of the material, thereby improving the stability of the ternary material; another part of the coating can penetrate into the material interior to form bulk doping.

[0023] 2. The radius of the coated metal cation is similar to that of Li + and Ni 2+ which can effectively reduce the degree of lithium-nickel mixing and inhibit the capacity decay of the material.

[0024] 3. During the sintering process, a part of the coated polyanion penetrates into the interior of the material. Due to its relatively large radius, it can increase the unit cell volume, play a role in supporting the three-dimensional framework structure of the material, expand the lithium-ion transmission channels, inhibit the phase change that occurs during the charge and discharge process of the material, and improve the electrochemical performance of the material. Moreover, during the sintering process, the polyanion can provide a part of oxygen atoms, reduce the oxygen defects inside the material. The polyanion has a strong covalent bond network structure, which can inhibit the precipitation of oxygen during the charge and discharge process of the material and reduce the occurrence of side reactions.

[0025] 4. This solution adopts a one-step precipitation method, which can prepare a composite coating layer on the surface of the ternary precursor. The coating is evenly distributed, the process is simple, and it can be widely applied. The particles have a high sphericity, high capacity, and good cycle performance. Brief Description of the Drawings

[0026] The following further describes the present invention in conjunction with the drawings and embodiments, where:

[0027] Figure 1 is the SEM image of the composite-coated ternary precursor obtained in Example 1 of the present invention;

[0028] Figure 2 is the EDS image of the composite-coated ternary precursor obtained in Example 1 of the present invention;

[0029] Figure 3 is the SEM image of the precursor particles obtained in Comparative Example 1 of the present invention. Detailed Embodiments

[0030] The following will clearly and completely describe the concept of the present invention and the technical effects produced in conjunction with the embodiments to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present invention.

[0031] Example 1

[0032] In this example, a composite-coated ternary precursor was prepared. The specific process is as follows:

[0033] (1) Co-precipitation to prepare an undoped ternary precursor: A nickel-cobalt-manganese mixed solution prepared according to a molar ratio of 82:12:6, the nickel-cobalt-manganese mixed solution, a precipitant, and a complexing agent were simultaneously introduced into a reaction kettle, maintaining an inert gas atmosphere, a stirring speed of 300 r / min, a temperature of 70 °C, and a reaction pH of 11 - 12. The precursor Ni 0.82 Co 0.12 Mn 0.06(OH)2. After the particles grow to 10.5 μm, the pH value of the reaction system is adjusted to 7.0 - 8.0, the liquid addition is stopped, and the reaction materials are left in the autoclave;

[0034] (2) Prepare 1 mol / L magnesium sulfate solution and 1 mol / L sodium silicate solution;

[0035] (3) Prepare the precursor of the composite coating: Keep the stirring speed and temperature of the autoclave in step (1) unchanged. Simultaneously introduce 5 L of magnesium sulfate solution and 5 L of sodium silicate solution into the autoclave in step (1) at a flow rate of 5 L / h. Keep the reaction pH value at 7.0 - 8.0. Under the action of stirring, the anions and cations undergo a precipitation reaction, and a magnesium silicate coating film is uniformly formed on the surface of the precursor, with a coating reaction time of 1 h and the content of the coating being 1% of the mass fraction of the precursor;

[0036] (4) Material collection: Collect the precipitate in step (3) into the aging tank, and then obtain the ternary precursor with composite coating through filtration, washing, drying, screening, and packaging.

[0037] Figure 1 This is the SEM image of the ternary precursor with composite coating obtained in this example. It can be seen from the figure that although magnesium silicate is coated, the coating uniformly and densely forms a coating film, and hardly changes the original morphology of the precursor.

[0038] Figure 2 This is the EDS image of the ternary precursor with composite coating obtained in this example. It can be seen from the EDS image that the coated Mg and Si elements are uniformly distributed.

[0039] Example 2

[0040] This example prepares a ternary precursor with composite coating. The specific process is as follows:

[0041] (1) Preparation of doped ternary precursor by coprecipitation: Dissolve nickel sulfate, cobalt sulfate, manganese sulfate, and magnesium sulfate in deionized water at a molar ratio of 0.82:0.12:0.05:0.01, stir evenly, and prepare a mixed metal salt solution with a concentration of 1.6 mol / L; dissolve sodium hydroxide in deionized water, then add sodium silicate, stir evenly, and prepare a doped precipitant with a concentration of 5 mol / L, where the molar ratio of sodium hydroxide to sodium silicate is 200:1; add an appropriate amount of deionized water to the reaction kettle, start stirring and heating, with a stirring speed of 300 r / min and a reaction temperature of 65 °C, add ammonia water to the reaction kettle to make the ammonia water concentration in the kettle solution 6 g / L, then add a small amount of undoped sodium hydroxide solution to adjust the pH value in the kettle to 11.4 - 11.6, and continuously introduce nitrogen into the kettle to prevent oxidation. Then, simultaneously pump the mixed metal salt solution, doped precipitant, and ammonia water into the reaction kettle for coprecipitation reaction, keep the reaction temperature and ammonia water concentration unchanged, and control the nucleation and growth of the precursor particles by adjusting the reaction pH to obtain doped ternary precursor particles with a D50 particle size of 10 μm, and leave the reaction materials in the kettle;

[0042] (2) Prepare a 0.5 mol / L zirconium sulfate solution and a 1 mol / L ammonium dihydrogen phosphate solution;

[0043] (3) Preparation of the composite-coated precursor: Keep the stirring speed and temperature of the reaction kettle in step (1) unchanged, and simultaneously introduce 4.6 L of zirconium sulfate solution and 4.6 L of ammonium dihydrogen phosphate solution into the reaction kettle in step (1) at a flow rate of 3.8 L / h, keep the reaction pH value at 6.5 - 7.5. Under the action of stirring, the anions and cations undergo a precipitation reaction and are uniformly coated on the surface of the precursor to form a zirconium phosphate coating film. The coating reaction time is 1.2 h, and the content of the coating is 1.5% of the mass fraction of the precursor;

[0044] (4) Material collection: Collect the precipitate in step (3) into the aging tank, and then obtain the composite-coated ternary precursor through filtration, washing, drying, screening, and packaging.

[0045] Example 3

[0046] In this example, a composite-coated ternary precursor was prepared. The specific process is as follows:

[0047] (1) Preparation of undoped ternary precursor by coprecipitation: Simultaneously introduce a nickel-cobalt-manganese mixed solution, a precipitant, and a complexing agent prepared in a ratio of 5:2:3 into the reaction kettle, keep an inert gas atmosphere, a stirring speed of 350 r / min, a temperature of 55 °C, and a reaction pH of 11 - 12, and prepare the precursor Ni 0.5 Co 0.2 Mn 0.3(OH)2. After the particles grow to 5 μm, adjust the pH value of the reaction system to 7.0 - 8.0, stop adding liquid, and leave the reaction materials in the autoclave;

[0048] (2) Prepare 1.5 mol / L copper sulfate solution and 1 mol / L sodium molybdate solution;

[0049] (3) Prepare the precursor of composite coating: Keep the stirring speed and temperature of the autoclave in step (1) unchanged. Simultaneously introduce 3.9 L of copper sulfate solution and 5.9 L of sodium molybdate solution into the autoclave in step (1). The flow rate of the copper sulfate solution is 2.6 L / h, and the flow rate of the sodium molybdate solution is 3.9 L / h. Keep the reaction pH value at 7.0 - 8.0. Under the stirring action, anionic and cationic precipitation reactions occur, and a copper molybdate coating film is formed by uniform precipitation on the surface of the precursor. The coating reaction time is 1.5 h, and the content of the coating is 3% of the mass fraction of the precursor;

[0050] (4) Material collection: Collect the precipitate in step (3) into the aging tank, and then obtain the ternary precursor with composite coating through filtration, washing, drying, screening, and packaging.

[0051] Example 4

[0052] In this example, a ternary precursor with composite coating was prepared. The specific process is as follows:

[0053] (1) Prepare an undoped ternary precursor by coprecipitation: Simultaneously introduce the nickel-cobalt-manganese mixed solution, precipitant, and complexing agent prepared in a ratio of 6:2:2 into the autoclave. Keep an inert gas atmosphere, a stirring speed of 500 r / min, a temperature of 60 °C, and a reaction pH of 10 - 12. Prepare the precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2. After the particles grow to 4 μm, adjust the pH value of the reaction system to 7.0 - 8.0, stop adding liquid, and leave the reaction materials in the autoclave;

[0054] (2) Prepare 1.2 mol / L zinc sulfate solution and 1.5 mol / L sodium silicate solution;

[0055] (3) Prepare the precursor of composite coating: Keep the stirring speed and temperature of the autoclave in step (1) unchanged. Simultaneously introduce 5.9 L of zinc sulfate solution and 4.7 L of sodium silicate solution into the autoclave in step (1). The flow rate of the zinc sulfate solution is 4.5 L / h, and the flow rate of the sodium silicate solution is 3.6 L / h. Keep the reaction pH value at 7.5 - 8.5. Under the stirring action, anionic and cationic precipitation reactions occur, and a zinc silicate coating film is formed by uniform precipitation on the precursor. The coating reaction time is 1.3 h, and the content of the coating is 2% of the mass fraction of the precursor;

[0056] (4) Material collection: Collect the precipitate in step (3) into an aging tank, and then obtain the composite-coated ternary precursor through filtration, washing, drying, screening, and packaging.

[0057] Example 5

[0058] In this example, a composite-coated ternary precursor was prepared. The specific process is as follows:

[0059] (1) Co-precipitation to prepare an undoped ternary precursor: Simultaneously introduce a nickel-cobalt-manganese mixed solution, a precipitant, and a complexing agent prepared in a ratio of 70:5:25 into a reaction kettle, maintaining an inert gas atmosphere, a stirring speed of 550 r / min, a temperature of 62 °C, and a reaction pH of 10.5 - 11.5. Prepare the precursor Ni 0.70 Co 0.05 Mn 0.25 (OH)2. After the particles grow to 3 μm, adjust the pH value of the reaction system to 7.0 - 8.0, stop adding liquid, and leave the reaction materials in the kettle;

[0060] (2) Prepare a 0.8 mol / L zirconium sulfate solution and a 0.5 mol / L sodium tungstate solution;

[0061] (3) Prepare a composite-coated precursor: Keep the stirring speed and temperature in the reaction kettle in step (1) unchanged. Simultaneously introduce 1.6 L of zirconium sulfate solution and 5.1 L of sodium tungstate solution into the reaction kettle in step (1). The flow rate of the zirconium sulfate solution is 1.6 L / h, and the flow rate of the sodium tungstate solution is 5.1 L / h. Maintain the reaction pH value at 7.0 - 8.0. Under the action of stirring, anionic and cationic precipitation reactions occur, and a zirconium tungstate coating film is uniformly coated on the surface of the precursor. The coating reaction time is 1 h, and the content of the coating is 1.5% of the mass fraction of the precursor;

[0062] (4) Material collection: Collect the precipitate in step (3) into an aging tank, and then obtain the composite-coated ternary precursor through filtration, washing, drying, screening, and packaging.

[0063] Comparative Example 1

[0064] In this comparative example, an uncoated ternary precursor was prepared. The difference from Example 1 is that only steps (1) and (4) are carried out. The specific process is as follows:

[0065] (1) Co-precipitation to prepare an undoped ternary precursor: Simultaneously introduce a nickel-cobalt-manganese mixed solution, a precipitant, and a complexing agent prepared in a ratio of 82:12:6 into a reaction kettle, maintaining an inert gas atmosphere, a stirring speed of 300 r / min, a temperature of 70 °C, and a reaction pH of 11 - 12. Prepare the precursor Ni 0.82 Co0.12 Mn 0.06 (OH)2. After the particles grow to the desired particle size, adjust the pH value of the reaction system to 7.0 - 8.0 and stop adding liquid.

[0066] (2) Collect the precipitate in step (1) into an aging tank, and then obtain the uncoated ternary precursor through filtration, washing, drying, screening, and packaging.

[0067] Comparative Example 2

[0068] In this comparative example, a ternary precursor was prepared. The difference from Example 2 is that no coating and doping were carried out.

[0069] Comparative Example 3

[0070] In this comparative example, an uncoated ternary precursor Ni 0.5 Co 0.2 Mn 0.3 (OH)2 was prepared. The difference from Example 3 is that only steps (1) and (4) were carried out to obtain the uncoated ternary precursor.

[0071] Comparative Example 4

[0072] In this comparative example, an uncoated ternary precursor Ni 0.6 Co 0.2 Mn 0.2 (OH)2 was prepared. The difference from Example 4 is that only steps (1) and (4) were carried out to obtain the uncoated ternary precursor.

[0073] Comparative Example 5

[0074] In this comparative example, an uncoated ternary precursor Ni 0.70 Co 0.05 Mn 0.25 (OH)2 was prepared. The difference from Example 5 is that only steps (1) and (4) were carried out to obtain the uncoated ternary precursor.

[0075] Test Example

[0076] Mix the precursors of the examples and comparative examples with lithium salts, sinter at 500 - 800 °C to obtain the cathode material, make a coin-type half-cell, and conduct charge-discharge tests within a voltage range of 2.5 - 4.3 V and at a 1C rate. The results are shown in Table 1.

[0077] Table 1

[0078]

[0079] As can be seen from Table 1, the particle size, BET and TD of the precursor samples prepared in the examples and comparative examples are very close. The initial discharge specific capacities are almost the same, indicating that the coating does not significantly reduce the capacity of the material. After 100 cycles, the capacity retention rate of the examples is more than 10% higher than that of the undoped comparative examples, indicating that the coated anions and cations synergistically reduce lithium-nickel mixing, stabilize the material structure, reduce the occurrence of side reactions, and effectively improve the capacity and cycling performance of the ternary material.

[0080] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge scope of those of ordinary skill in the art. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. A composite-coated ternary precursor, characterized in that, It includes a ternary precursor and a coating layer attached to the surface of the ternary precursor. The coating layer is obtained by a precipitation reaction of a first metal ion and a first polyanion. The first metal ion is Cr 2+ , Cu 2+ , Zn 2+ , Ge 2+ , Sb 3+ , Tb 4+ , Re 4+ , Ir 3+ , Pb 4+ or Bi 5+ or one or more of them. The first polyanion is AlO 2- , B4O7 2- , SO4 2- , BO3 3- , MoO4 2- or WO4 2- or one or more of them; The ternary precursor is doped with a second metal ion and a second polyanion, and the second metal ion is Cr 2+ , Cu 2+ , Zn 2+ , Ge 2+ , Nb 5+ , Sb 3+ , Tb 4+ , Ta 4+ , Re 4+ , Ir 3+ , Pb 4+ or Bi 5+ or one or more of them, and the second polyanion is B4O7 2- .

2. The preparation method of the composite-coated ternary precursor according to claim 1, characterized in that, It includes the following steps: S1: Prepare a first metal salt solution and a first polyanion salt solution respectively. The first metal salt solution is one or more of the salt solutions of Cr 2+ 、Cu 2 + 、Zn 2+ 、Ge 2+ 、Sb 3+ 、Tb 4+ 、Re 4+ 、Ir 3+ 、Pb 4+ or Bi 5+ ; and the first polyanion salt solution is one or more of the salt solutions of AlO 2- 、B4O7 2- 、SO4 2- 、BO3 3- 、MoO4 2- or WO4 2- ; S2: Add the first metal salt solution and the first polyanionic salt solution to the ternary precursor slurry at a certain stirring speed and temperature, and carry out a precipitation reaction, while maintaining the reaction pH at 6.0 - 9.

0. After the reaction is completed, a precipitate is obtained; S3: Wash and dry the precipitate to obtain the ternary precursor with composite coating; The ternary precursor slurry is prepared by the following method: dissolving soluble nickel salt, cobalt salt, manganese salt, and second metal salt in water in proportion to prepare a mixed metal salt solution; dissolving sodium hydroxide and second polyanion salt in water to prepare a doping precipitant; at a certain stirring speed and temperature, first adding ammonia water, then adding sodium hydroxide to adjust the pH to 9.5 - 12.5, and then adding the mixed metal salt solution, doping precipitant, and ammonia water for coprecipitation reaction to obtain the ternary precursor slurry; the second metal salt is Cr 2+ , Cu 2+ , Zn 2+ , Ge 2+ , Nb 5+ , Sb 3+ , Tb 4+ , Ta 4+ , Re 4+ , Ir 3+ , Pb 4+ or Bi 5+ salt of one or more of them, and the second polyanion salt is B4O7 2- salt; The concentration of the doped precipitant is 2 - 10 mol / L, and the molar ratio of sodium hydroxide to the second polyanionic salt in the doped precipitant is (30 - 300):1; In the coprecipitation reaction, the concentration of ammonia water is maintained at 0.5 - 12 g / L.

3. The preparation method according to claim 2, characterized in that, In step S1, the concentrations of the first metal salt solution and the first polyanionic salt solution are independently 0.5 - 2 mol / L.

4. The preparation method according to claim 2, characterized in that, In step S2, the time for adding the first metal salt solution and the first polyanionic salt solution is 0.5 - 1.5 h, and aging is carried out for 0.5 - 1.5 h after the feeding is completed. The total volume of the first metal salt solution and the first polyanionic salt solution is 5 - 15 L.

5. The preparation method according to claim 2, wherein, The second metal salt in the mixed metal salt solution accounts for 0.1 - 2% of the total molar amount of the nickel salt, cobalt salt, and manganese salt.

6. The preparation method according to claim 2, wherein The concentration of the mixed metal salt solution is 0.5 - 2.0 mol / L.

7. A ternary cathode material, characterized in that, It is prepared by sintering the ternary precursor with composite coating according to claim 1.

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