Coated modified ternary positive electrode material, and preparation method and application thereof

Abstract

The present application relates to the technical field of lithium ion batteries, in particular to a coated modified ternary positive electrode material and a preparation method and application thereof. The preparation method of the coated modified ternary positive electrode material comprises the following steps: mixing a nickel-cobalt-manganese hydroxide precursor and a lithium source, and sequentially performing pre-calcination treatment and primary calcination treatment to obtain a primary calcination product; obtaining mesoporous Al2O3 material and WO3 quantum dot powder; mixing the primary calcination product, the mesoporous Al2O3 material and the WO3 quantum dot powder to obtain a mixture, and performing secondary calcination treatment to obtain the coated modified ternary positive electrode material. The present application simultaneously coats the mesoporous Al2O3 material and the WO3 quantum dot powder on the surface of the ternary material matrix, both of which are nanomaterials, so that the coating effect is more compact and thinner, and the mesoporous Al2O3 material can adsorb the WO3 quantum dot powder, release the WO3 quantum dot powder in a high-temperature environment, and make the WO3 more uniformly distributed.

Description

Technical Field

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

[0002] Lithium-ion batteries possess advantages such as high operating voltage, high energy density, long cycle life, and low environmental pollution, and have been widely used in various consumer electronics and power battery fields. Reducing size, lightening weight, and extending the lifespan of lithium-ion batteries are current trends and requirements in the electronics industry. Therefore, developing high-energy-density, lightweight rechargeable batteries is an urgent need for industry development.

[0003] Methods to improve the energy density of lithium-ion batteries include: using higher energy density positive and negative electrode material systems, increasing the charging cut-off voltage, and improving the compaction density of the positive and negative electrodes. Among these, the idea of ​​increasing the charging cut-off voltage has opened up the research and development of high-voltage positive electrode materials. Currently, high-voltage positive electrode materials are mainly prepared by doping or coating the material surface with additives. However, existing coated and modified positive electrode materials not only have poor coating effects, but also poor electronic and ionic conductivity, which hinders the diffusion of lithium during the insertion and extraction process, thereby reducing the rate performance of lithium batteries. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of poor coating effect and poor conductivity of existing coated modified cathode materials, thereby providing a coated modified ternary cathode material, its preparation method and application to solve the above problems.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A method for preparing a coated and modified ternary cathode material includes:

[0007] A nickel-cobalt-manganese hydroxide precursor was mixed with a lithium source and subjected to pre-calcination and primary calcination treatments to obtain a calcined product.

[0008] Obtain mesoporous Al2O3 materials and WO3 quantum dot powder;

[0009] A mixture is prepared by mixing a calcined product with mesoporous Al2O3 material and WO3 quantum dot powder to obtain a mixture, which is then subjected to a second calcination treatment to obtain a coated and modified ternary cathode material.

[0010] Preferably, the chemical formula of the nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn 1-x-y (OH)2, of which 0.5 <x≤1,0<y≤0.5,x+y<1;

[0011] And / or, the lithium source is at least one of lithium carbonate, lithium hydroxide, and lithium acetate;

[0012] And / or, the specific surface area of ​​the nickel-cobalt-manganese hydroxide precursor is 8-20 m². 2 / g;

[0013] And / or, the tap density of the nickel-cobalt-manganese hydroxide precursor is 1.0-2.0 g / cm³. 3 ;

[0014] And / or, the median particle size D50 of the nickel-cobalt-manganese hydroxide precursor is 3-7 μm.

[0015] Preferably, the molar ratio of lithium element in the lithium source to metal element in the nickel-cobalt-manganese hydroxide precursor is (0.9-1.2):1;

[0016] And / or, in the mixture, the Al doping amount is 1000-4000ppm, and the W doping amount is 1-2 times that of the Al doping amount.

[0017] Preferably, the temperature of the pre-calcination treatment is 650-850℃, and the duration of the pre-calcination treatment is 4-8 hours;

[0018] And / or, the temperature of the first calcination treatment is 800-950℃, and the duration of the first calcination treatment is 8-12h;

[0019] And / or, the temperature of the secondary calcination treatment is 250-650℃, and the duration of the secondary calcination treatment is 4-6h;

[0020] And / or, the pre-calcination treatment, primary calcination treatment and secondary calcination treatment are carried out in an air or oxygen atmosphere;

[0021] And / or, after the primary calcination treatment and the secondary calcination treatment, cooling, crushing, and sieving are also performed.

[0022] Preferably, the process for obtaining the mesoporous Al2O3 material is as follows: urea and hexadecyltrimethylammonium bromide are dissolved in ammonia water, aluminum nitrate solution is added to carry out a hydrothermal synthesis reaction, and then aging, solid-liquid separation and drying are performed to obtain the mesoporous Al2O3 material.

[0023] Preferably, the concentration of the ammonia solution is 2-4 mol / L;

[0024] And / or, the concentration of the aluminum nitrate solution is 0.1-0.5 mol / L;

[0025] And / or, the mass ratio of the urea to hexadecyltrimethylammonium bromide is 1:(0.2-5);

[0026] And / or, based on a total mass of urea and cetyltrimethylammonium bromide of 1g, the amount of ammonia water used is 2.5-25mL;

[0027] And / or, based on a total mass of urea and cetyltrimethylammonium bromide of 1g, the amount of aluminum nitrate solution used is 2.5-25mL;

[0028] And / or, the temperature of the hydrothermal synthesis reaction is 65-95℃, and the duration of the hydrothermal synthesis reaction is 3-5h;

[0029] And / or, the aging treatment temperature is 25-50℃, and the aging treatment duration is 2-4 hours;

[0030] And / or, the drying temperature is 50-65℃, and the drying time is 3-5h.

[0031] Preferably, the process of obtaining the WO3 quantum dot powder is as follows: tungsten disulfide is dispersed in a solvent to obtain a dispersion, hydrogen peroxide is added to the dispersion to obtain a mixture, the mixture is transferred to a reactor for hydrothermal reaction, solid-liquid separation is performed to obtain a filtrate, and finally the filtrate is dialyzed and freeze-dried to obtain WO3 quantum dot powder.

[0032] Preferably, the solvent is anhydrous ethanol;

[0033] And / or, based on 1 g of tungsten disulfide, the amount of solvent used is 20-200 mL;

[0034] And / or, based on 1g of tungsten disulfide, the amount of hydrogen peroxide used is 4-60mL;

[0035] And / or, the temperature of the hydrothermal reaction is 40-80℃, and the duration of the hydrothermal reaction is 3-8h;

[0036] And / or, the solid-liquid separation is performed by vacuum filtration using a filter membrane with a pore size of 0.22 μm;

[0037] And / or, the dialysis is performed using a dialysis bag with a molecular weight cutoff of 1000D, and the duration of the dialysis is 2-3 days;

[0038] And / or, the freeze-drying temperature is -40℃ to 0℃, and the freeze-drying pressure is 20Pa.

[0039] The present invention also provides a coated modified ternary cathode material, which is prepared by the above-described method for preparing coated modified ternary cathode materials.

[0040] The present invention also provides the application of the above-mentioned coated modified ternary cathode material in lithium-ion batteries.

[0041] In this invention, the heating rate of the pre-calcination treatment, the first calcination treatment, and the second calcination treatment is 2-5℃ / min.

[0042] The technical solution of this invention has the following advantages:

[0043] 1. A method for preparing a coated modified ternary cathode material, comprising: mixing a nickel-cobalt-manganese hydroxide precursor with a lithium source and sequentially performing a pre-calcination treatment and a first calcination treatment to obtain a calcined product; obtaining mesoporous Al2O3 material and WO3 quantum dot powder; mixing the calcined product with the mesoporous Al2O3 material and WO3 quantum dot powder to obtain a mixture, and performing a second calcination treatment to obtain the coated modified ternary cathode material. This invention simultaneously coats the surface of a ternary material matrix with WO3 quantum dot powder and mesoporous Al2O3 material, both of which are nanomaterials. This not only makes the coating effect denser and thinner, but also allows the mesoporous Al2O3 material to adsorb WO3 quantum dot powder and release it under high-temperature conditions, thereby making the WO3 distribution more uniform.

[0044] In addition, the porous structure of mesoporous Al2O3 materials can effectively reduce the direct contact between the electrolyte and the cathode material, thus reducing the dissolution of the cathode material. Quantum dot WO3 has higher electronic and ionic conductivity than bulk WO3, and can not only coat the surface of the ternary material matrix, but also fill the interparticle gaps in the ternary material matrix, thereby further improving the conductivity of the ternary cathode material, slowing down the capacity decay of the cathode material, and greatly improving the cycle life of the cathode material.

[0045] 2. In a method for preparing a coated modified ternary cathode material according to the present invention, the cathode material is coated to ensure that only Li... + Only by allowing the cathode metal to pass freely through the coating layer can the electrolyte pass through it. This reduces the dissolution of the cathode metal, resists the erosion of the electrolyte, thereby reducing the capacity decay of the material and improving the conductivity and rate performance of the ternary cathode material. Detailed Implementation

[0046] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0047] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0048] Example 1

[0049] This embodiment provides a method for preparing a coated and modified ternary cathode material, including the following steps:

[0050] 1) Weigh out Ni according to the molar ratio of lithium to nickel, cobalt, and manganese in the nickel-cobalt-manganese hydroxide precursor of 1.06:1. 0.6 Co 0.1 Mn 0.3 (OH)2 precursor and lithium carbonate, wherein Ni 0.6 Co 0.1 Mn 0.3 The specific surface area of ​​the (OH)2 precursor is 11 m². 2 / g, tap density is 1.83g / cm³ 3 The median particle size D50 is 3.8 μm, and Ni 0.6 Co 0.1 Mn 0.3 (OH)2 precursor and lithium carbonate are mixed evenly in a high-speed mixer to obtain a mixed powder;

[0051] 2) Place the mixed powder from step 1) into a box furnace, heat it to 800℃ at a heating rate of 2℃ / min for pre-calcination treatment for 8 hours, then heat it to 940℃ at a high temperature for calcination for 10 hours at a heating rate of 2℃ / min. The calcination atmosphere is compressed air with an air flow rate of 10L / min. Finally, let it cool naturally to room temperature, pulverize it, and pass it through a 300-mesh sieve to obtain a calcined product.

[0052] 3) Weigh 3g of urea and 3g of cetyltrimethylammonium bromide (CTAB) and dissolve them in 30mL of ammonia water with a concentration of 2mol / L. While stirring, heat the mixture to 80℃ and add 30mL of aluminum nitrate solution with a concentration of 0.2mol / L to carry out hydrothermal synthesis reaction for 4h. Then, age the mixture at 40℃ for 3h, filter it, and then dry it at 60℃ for 4h to obtain mesoporous Al2O3 material.

[0053] 4) Weigh 3g of tungsten disulfide and disperse it in 150mL of anhydrous ethanol. Add 40mL of hydrogen peroxide to the dispersion to obtain a mixture. Transfer the mixture to a 500mL reactor and perform hydrothermal reaction at 60℃ for 6h. Allow it to cool naturally to room temperature. Then, use a 0.22μm pore size filter membrane for vacuum filtration to collect the filtrate. Pack the filtrate into a dialysis bag with a molecular weight cutoff of 1000D and dialyze it for 2d. Finally, freeze the dialysate obtained from the dialysis and freeze-dry it at -30℃ and 20Pa to obtain WO3 quantum dot powder (particle size 2-20nm).

[0054] 5) Mix the calcined product from step 2) with the mesoporous Al2O3 material from step 3) and the WO3 quantum dot powder from step 4) to obtain a mixture. In the mixture, the doping amount of Al is 1000ppm and the doping amount of W is 2000ppm.

[0055] 6) Place the mixture from step 5) into a box furnace, heat it to 400℃ at a heating rate of 2℃ / min and calcine it for 5 hours. Then, let it cool naturally to room temperature, pulverize it, and pass it through a 300-mesh sieve to obtain the coated modified ternary cathode material.

[0056] Example 2

[0057] This embodiment provides a method for preparing a coated and modified ternary cathode material, including the following steps:

[0058] 1) Weigh out Ni according to the ratio of lithium element to nickel, cobalt, and manganese elements in the nickel-cobalt-manganese hydroxide precursor, which is 0.9:1. 0.6 Co 0.1 Mn 0.3 (OH)₂ precursor and lithium hydroxide, wherein Ni 0.6 Co 0.1 Mn 0.3 The specific surface area of ​​the (OH)2 precursor is 11 m². 2 / g, tap density is 1.83g / cm³ 3 The median particle size D50 is 3.8 μm, and Ni 0.6 Co 0.1 Mn 0.3 (OH)2 precursor and lithium carbonate are mixed evenly in a high-speed mixer to obtain a mixed powder;

[0059] 2) Place the mixed powder from step 1) into a box furnace, heat it to 650℃ at a heating rate of 3℃ / min for pre-calcination treatment for 8 hours, then heat it to 800℃ at a high temperature for calcination for 12 hours at a heating rate of 3℃ / min. The calcination atmosphere is compressed air with an air flow rate of 10L / min. Finally, cool it naturally to room temperature, pulverize it, and pass it through a 300-mesh sieve to obtain a calcined product.

[0060] 3) Weigh 5g of urea and 1g of cetyltrimethylammonium bromide (CTAB) and dissolve them in 15mL of ammonia water with a concentration of 4mol / L. While stirring, heat the mixture to 65℃ and add 15mL of aluminum nitrate solution with a concentration of 0.5mol / L to carry out hydrothermal synthesis reaction for 5h. Then, age the mixture at 25℃ for 4h, filter it, and then dry it at 50℃ for 3h to obtain mesoporous Al2O3 material.

[0061] 4) Weigh 3g of tungsten disulfide and disperse it in 60mL of anhydrous ethanol. Add 12mL of hydrogen peroxide to the dispersion to obtain a mixture. Transfer the mixture to a 500mL reactor and perform hydrothermal reaction at 40℃ for 3h. Allow it to cool naturally to room temperature. Then, use a 0.22μm pore size filter membrane for vacuum filtration to collect the filtrate. Pack the filtrate into a dialysis bag with a molecular weight cutoff of 1000D and dialyze it for 2d. Finally, freeze the dialysate obtained from the dialysis and freeze-dry it at 0℃ and 20Pa to obtain WO3 quantum dot powder (particle size 2-20nm).

[0062] 5) Mix the calcined product from step 2) with the mesoporous Al2O3 material from step 3) and the WO3 quantum dot powder from step 4) to obtain a mixture. In the mixture, the doping amount of Al is 2000ppm and the doping amount of W is 4000ppm.

[0063] 6) Place the mixture from step 5) into a box furnace, heat it to 250°C at a heating rate of 3°C / min and calcine it for 6 hours. Then, let it cool naturally to room temperature, pulverize it, and pass it through a 300-mesh sieve to obtain the coated modified ternary cathode material.

[0064] Example 3

[0065] This embodiment provides a method for preparing a coated and modified ternary cathode material, including the following steps:

[0066] 1) Weigh out Ni according to the molar ratio of lithium to nickel, cobalt, and manganese in the nickel-cobalt-manganese hydroxide precursor of 1.2:1. 0.6 Co 0.1 Mn 0.3 (OH)2 precursor and lithium acetate, wherein Ni 0.6 Co 0.1 Mn 0.3 The specific surface area of ​​the (OH)2 precursor is 11 m². 2 / g, tap density is 1.83g / cm³ 3 The median particle size D50 is 3.8 μm, and Ni 0.6 Co 0.1 Mn 0.3 (OH)2 precursor and lithium carbonate are mixed evenly in a high-speed mixer to obtain a mixed powder;

[0067] 2) Place the mixed powder from step 1) into a box furnace, heat it to 850℃ at a heating rate of 5℃ / min for pre-calcination treatment for 4 hours, then heat it to 950℃ at a high temperature for calcination for 8 hours at a heating rate of 5℃ / min. The calcination atmosphere is compressed air with an air flow rate of 10L / min. Finally, cool it naturally to room temperature, pulverize it, and pass it through a 300-mesh sieve to obtain a calcined product.

[0068] 3) Weigh 1g of urea and 5g of cetyltrimethylammonium bromide (CTAB) and dissolve them in 150mL of ammonia water with a concentration of 3mol / L. While stirring, heat the solution to 95℃ and add 150mL of aluminum nitrate solution with a concentration of 0.1mol / L for hydrothermal synthesis reaction for 3h. Then, age the solution at 50℃ for 2h, filter it, and then dry it at 65℃ for 5h to obtain mesoporous Al2O3 material.

[0069] 4) Weigh 1g of tungsten disulfide and disperse it in 200mL of anhydrous ethanol. Add 60mL of hydrogen peroxide to the dispersion to obtain a mixture. Transfer the mixture to a 500mL reactor and perform hydrothermal reaction at 80℃ for 8h. Allow it to cool naturally to room temperature. Then, use a 0.22μm pore size filter membrane for vacuum filtration to collect the filtrate. Pack the filtrate into a dialysis bag with a molecular weight cutoff of 1000D and dialyze it for 3 days. Finally, freeze the dialysate obtained from the dialysis and freeze-dry it at a temperature of -40℃ and a pressure of 20Pa to obtain WO3 quantum dot powder (particle size 2-20nm).

[0070] 5) The calcined product in step 2) is mixed with the mesoporous Al2O3 material in step 3) and the WO3 quantum dot powder in step 4) to obtain a mixture. In the mixture, the doping amount of Al is 4000ppm and the doping amount of W is 4000ppm.

[0071] 6) Place the mixture from step 5) into a box furnace, heat it to 650°C at a heating rate of 5°C / min and calcine it for 4 hours. Then, let it cool naturally to room temperature, pulverize it, and pass it through a 300-mesh sieve to obtain the coated modified ternary cathode material.

[0072] Example 4

[0073] The difference between this embodiment and Embodiment 1 is that Ni is used. 0.6 Co 0.1 Mn 0.3 (OH)2 precursor replaced with Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor, other conditions are the same as in Example 1.

[0074] Comparative Example 1

[0075] The difference between this comparative example and Example 1 is that the mesoporous Al2O3 material and WO3 quantum dot powder coating is not performed, and the secondary calcination treatment is performed directly. Other conditions are the same as in Example 1.

[0076] Comparative Example 2

[0077] The difference between this comparative example and Example 1 is that only conventional WO3 powder (particle size of 10 μm) was used for coating, while other conditions were the same as in Example 1.

[0078] Comparative Example 3

[0079] The difference between this comparative example and Example 1 is that only WO3 quantum dot powder is used for coating, while other conditions are the same as in Example 1.

[0080] Comparative Example 4

[0081] The difference between this comparative example and Example 1 is that only mesoporous Al2O3 material is used for coating, while other conditions are the same as in Example 1.

[0082] Comparative Example 5

[0083] The difference between this comparative example and Example 1 is that conventional WO3 powder (particle size 10 μm) was used for coating, and mesoporous Al2O3 material was added at the same time. Other conditions are the same as in Example 1.

[0084] Test Example 1

[0085] The ternary cathode materials prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to capacity testing, and the results are shown in Table 1. The conductivity of the ternary cathode materials was tested using a coin cell at the same discharge rate, with a test standard of 3.0-4.25V@0.1C@25℃ and a test compaction density of 3.3 g / cm³. 3 The nominal specific capacity is 190mAh / g; the cycle performance test method is: capacity retention rate of coin cell after 100 discharge cycles, the test standard is: 3.0-4.25V@0.1C@25℃, and the test compaction density is 3.3g / cm³. 3 The nominal specific capacity is 190mAh / g; the rate performance test method is: the ratio of the first discharge capacity at high rate to the first discharge capacity at low rate for coin cells, with the test standard being: 3.0-4.25V@0.1C / 0.5C / 1C@25℃, and the test compaction density being 3.3g / cm³. 3 The nominal specific capacity is 190mAh / g.

[0086] Table 1

[0087]

[0088]

[0089] According to the test results in Table 1, compared with Comparative Examples 1-5, the conductivity, cycle performance and rate performance of Examples 1-4 of the present invention are significantly improved.

[0090] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a coated and modified ternary cathode material, characterized in that, include: A nickel-cobalt-manganese hydroxide precursor was mixed with a lithium source and subjected to pre-calcination and primary calcination treatments to obtain a calcined product. Obtain mesoporous Al2O3 materials and WO3 quantum dot powder; A mixture is prepared by mixing a calcined product with mesoporous Al2O3 material and WO3 quantum dot powder to obtain a mixture, which is then subjected to a second calcination treatment to obtain a coated and modified ternary cathode material.

2. The preparation method according to claim 1, characterized in that, The chemical formula of the nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn 1-x-y (OH)2, of which 0.5 <x≤1,0<y≤0.5,x+y<1; And / or, the lithium source is at least one of lithium carbonate, lithium hydroxide, and lithium acetate; And / or, the specific surface area of ​​the nickel-cobalt-manganese hydroxide precursor is 8-20 m². 2 / g; And / or, the tap density of the nickel-cobalt-manganese hydroxide precursor is 1.0-2.0 g / cm³. 3 ; And / or, the median particle size D50 of the nickel-cobalt-manganese hydroxide precursor is 3-7 μm.

3. The preparation method according to claim 1 or 2, characterized in that, The molar ratio of lithium in the lithium source to the metal element in the nickel-cobalt-manganese hydroxide precursor is (0.9-1.2):1; And / or, in the mixture, the Al doping amount is 1000-4000ppm, and the W doping amount is 1-2 times that of the Al doping amount.

4. The preparation method according to any one of claims 1-3, characterized in that, The temperature of the pre-calcination treatment is 650-850℃, and the duration of the pre-calcination treatment is 4-8h; And / or, the temperature of the first calcination treatment is 800-950℃, and the duration of the first calcination treatment is 8-12h; And / or, the temperature of the secondary calcination treatment is 250-650℃, and the duration of the secondary calcination treatment is 4-6h; And / or, the pre-calcination treatment, primary calcination treatment and secondary calcination treatment are carried out in an air or oxygen atmosphere; And / or, after the primary calcination treatment and the secondary calcination treatment, cooling, crushing, and sieving are also performed.

5. The preparation method according to any one of claims 1-4, characterized in that, The process for obtaining the mesoporous Al2O3 material is as follows: urea and hexadecyltrimethylammonium bromide are dissolved in ammonia water, aluminum nitrate solution is added to carry out a hydrothermal synthesis reaction, and then aging, solid-liquid separation and drying are performed to obtain the mesoporous Al2O3 material.

6. The preparation method according to claim 5, characterized in that, The concentration of the ammonia solution is 2-4 mol / L; And / or, the concentration of the aluminum nitrate solution is 0.1-0.5 mol / L; And / or, the mass ratio of the urea to hexadecyltrimethylammonium bromide is 1:(0.2-5); And / or, based on a total mass of urea and cetyltrimethylammonium bromide of 1g, the amount of ammonia water used is 2.5-25mL; And / or, based on a total mass of urea and cetyltrimethylammonium bromide of 1g, the amount of aluminum nitrate solution used is 2.5-25mL; And / or, the temperature of the hydrothermal synthesis reaction is 65-95℃, and the duration of the hydrothermal synthesis reaction is 3-5h; And / or, the aging treatment temperature is 25-50℃, and the aging treatment duration is 2-4 hours; And / or, the drying temperature is 50-65℃, and the drying time is 3-5h.

7. The preparation method according to any one of claims 1-6, characterized in that, The process of obtaining WO3 quantum dot powder is as follows: tungsten disulfide is dispersed in a solvent to obtain a dispersion, hydrogen peroxide is added to the dispersion to obtain a mixture, the mixture is transferred to a reactor for hydrothermal reaction, solid-liquid separation is performed to obtain a filtrate, and finally the filtrate is dialyzed and freeze-dried to obtain WO3 quantum dot powder.

8. The preparation method according to claim 7, characterized in that, The solvent is anhydrous ethanol; And / or, based on 1 g of tungsten disulfide, the amount of solvent used is 20-200 mL; And / or, based on 1g of tungsten disulfide, the amount of hydrogen peroxide used is 4-60mL; And / or, the temperature of the hydrothermal reaction is 40-80℃, and the duration of the hydrothermal reaction is 3-8h; And / or, the solid-liquid separation is performed by vacuum filtration using a filter membrane with a pore size of 0.22 μm; And / or, the dialysis is performed using a dialysis bag with a molecular weight cutoff of 1000D, and the duration of the dialysis is 2-3 days; And / or, the freeze-drying temperature is -40℃ to 0℃, and the freeze-drying pressure is 20Pa.

9. A coated and modified ternary cathode material, characterized in that, It is prepared by the method for preparing the coated modified ternary cathode material according to any one of claims 1-8.

10. The application of the coated modified ternary cathode material according to claim 9 in lithium-ion batteries.

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