Cathode materials and their preparation methods, lithium-ion batteries

Abstract

This invention discloses a positive electrode material and its preparation method, as well as a lithium-ion battery, relating to the field of lithium-ion battery electrode materials. The preparation method of the positive electrode material includes: (1) mixing positive electrode raw materials, binder, and dispersant uniformly in a weight ratio of 10:(0.2-2):(10-50) to obtain a slurry; (2) spray-drying the slurry to obtain a powder; and (3) sintering the powder using a fluidized bed. The binder is selected from one or more of starch, PVP, PEG, PVA, and PAN, and the dispersant is selected from one or more of ethanol, isopropanol, and water. Implementing this invention can reduce the sintering temperature of the positive electrode material, shorten its sintering reaction time, and improve its sintering quality. Specifically, the sintering time of the positive electrode material of this invention can be shortened to 2-60 min.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery electrode materials, and more particularly to a positive electrode material and its preparation method. Background Technology

[0002] Lithium-ion batteries are mainly composed of positive electrode materials, electrolytes, and negative electrode materials. Among these, the positive electrode material is the decisive factor in the electrochemical performance of lithium-ion batteries. The rational selection of positive electrode materials and the improvement of their synthesis processes can significantly enhance the performance and lifespan of lithium-ion batteries. Furthermore, the material and time costs required for synthesizing positive electrode materials are often higher in the production process of lithium-ion batteries. Therefore, improving the synthesis rate and consistency of positive electrode materials and addressing the energy consumption issues in the synthesis process are urgently needed.

[0003] Current technologies primarily employ static sintering to synthesize lithium-ion battery cathode materials. Static sintering equipment mainly consists of tunnel kilns and roller furnaces. Because tunnel kilns and roller furnaces place the material to be sintered on rollers and continuously blown a sintering atmosphere into the heating and isothermal zones, the atmosphere slowly permeates the material under natural flow, reacting with it. This results in problems such as long sintering times and poor material consistency after sintering. For example, the current sintering time for ternary cathode material NCM523 is 8-24 hours. Dynamic sintering equipment mainly uses rotary kilns. Compared to tunnel kilns and roller furnaces, although rotary kilns improve the contact between the material and the reaction atmosphere by tumbling the material back and forth, the reaction time is still long (approximately 6-20 hours for NCM523), resulting in significant heat loss. Problems such as insufficient contact between the reactant gas and solid components and poor material consistency remain unresolved. In addition, rotary kilns also pose certain safety risks and environmental pollution, such as wear of rotary joints, heat loss, and dust removal issues. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a cathode material that can significantly shorten the preparation process (sintering time), reduce the sintering temperature, and produce a cathode material with excellent performance.

[0005] Another technical problem that this invention aims to solve is to provide a cathode material.

[0006] Another technical problem that the present invention needs to solve is to provide a lithium-ion battery.

[0007] To address the above problems, this invention discloses a method for preparing a cathode material, comprising:

[0008] (1) The positive electrode material, binder and dispersant are mixed evenly in a weight ratio of 10:(0.2-2):(10-50) to obtain a slurry;

[0009] (2) The slurry is spray-dried to obtain powder;

[0010] (3) The powder is sintered in a fluidized bed;

[0011] The binder is selected from one or more of starch, PVP, PEG, PVA, and PAN, and the dispersant is selected from one or more of ethanol, isopropanol, and water.

[0012] As an improvement to the above technical solution, the adhesive is a mixture of PVA and PEG200 with a weight ratio of 1:(0.3-0.5).

[0013] As an improvement to the above technical solution, in step (2), the inlet air temperature of the spray drying tower is 150-200℃.

[0014] As an improvement to the above technical solution, in step (3), the heating rate of the fluidized bed is 10-20℃ / min, the sintering temperature is 600-1100℃, and the sintering time is 2-60min.

[0015] The sintering atmosphere is selected from one or more of the following: oxidizing atmosphere, inert atmosphere, neutral atmosphere, reducing atmosphere, carburizing atmosphere, and nitriding atmosphere.

[0016] As an improvement to the above technical solution, the cathode material includes a mixture of a ternary cathode material precursor and a lithium source; or

[0017] The cathode material includes a mixture of lithium and cobalt sources; or

[0018] The cathode material includes a mixture of lithium and nickel sources; or

[0019] The cathode material includes a mixture of lithium and manganese sources; or

[0020] The cathode material includes a mixture of lithium source, phosphorus source and iron source; or

[0021] The cathode material includes a mixture of lithium source, phosphorus source and manganese source.

[0022] As an improvement to the above technical solution, the cathode material also includes a doping modifier and / or a coating agent.

[0023] As an improvement to the above technical solution, the particle size of the powder is larger than the particle size of the cathode material.

[0024] As an improvement to the above technical solution, the powder has a core-shell structure, and the particle size of the powder is 1.5-5 times that of the cathode material.

[0025] Accordingly, the present invention also discloses a positive electrode material prepared by the above-described preparation method.

[0026] Accordingly, the present invention also discloses a lithium-ion battery comprising the above-mentioned cathode material.

[0027] Implementing this invention has the following beneficial effects:

[0028] The method for preparing the cathode material of this invention involves spray drying a slurry obtained by mixing cathode raw materials, binders, and dispersants to form a single-phase material with a core-shell structure. This single-phase material is tightly bonded and will not be dispersed by the atmosphere gas during fluidized bed sintering, maintaining the consistency of the cathode material. Simultaneously, fluidized bed sintering ensures that the cathode material is fully enveloped by the atmosphere during the sintering process, thereby reducing the sintering temperature, significantly shortening the sintering reaction time, and improving the sintering quality of the cathode material. Specifically, the sintering time of the cathode material of this invention can be shortened to 2-60 minutes, and the cycle performance of the resulting cathode material is not inferior to that of conventional sintering, and may even be slightly improved. Attached Figure Description

[0029] Figure 1 This is an electron microscope image of the powder obtained in Example 1 of the present invention;

[0030] Figure 2 This is an electron microscope image of the powder obtained in Example 2 of the present invention;

[0031] Figure 3 This is an electron microscope image of the powder obtained in Example 3 of the present invention;

[0032] Figure 4 This is an electron microscope image of the powder obtained in Example 4 of the present invention;

[0033] Figure 5 This is an electron microscope image of the powder obtained in Example 5 of the present invention;

[0034] Figure 6 These are electron microscope images of the nickel-cobalt-manganese ternary precursors used in Examples 1-5 of this invention;

[0035] Figure 7 This is the X-ray diffraction (XRD) pattern of the cathode material obtained in Example 1 of this invention;

[0036] Figure 8 This is the X-ray diffraction (XRD) pattern of the cathode material obtained in Example 2 of this invention;

[0037] Figure 9 These are the X-ray diffraction (XRD) patterns of the nickel-cobalt-manganese ternary precursors used in Embodiments 1 and 2 of this invention.

[0038] Figure 10 This is a long-cycle curve of the positive electrode material obtained in Embodiment 2 of the present invention after being prepared into a coin cell.

[0039] Figure 11 This is a stepped cycle curve of the positive electrode material obtained in Embodiment 2 of the present invention after being prepared into a coin cell. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It is hereby declared that the directional terms such as up, down, left, right, front, back, inside, and outside used in this text are based solely on the accompanying drawings and are not intended to specifically limit the invention.

[0041] This invention provides a method for preparing a cathode material, comprising the following steps:

[0042] (1) The positive electrode material, binder and dispersant are mixed evenly in a weight ratio of 10:(0.2-2):(10-50) to obtain a slurry;

[0043] The cathode material is any raw material that can be used to prepare common cathode materials. Common cathode materials in this field include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, ternary materials, lithium iron phosphate, and lithium manganese phosphate, but are not limited to these. Correspondingly, the cathode material includes a mixture of cobalt source (e.g., cobalt oxide, cobalt carbonate, but not limited to these) and lithium source (e.g., lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium chloride, but not limited to these); or the cathode material includes a mixture of manganese source (e.g., manganese oxide, manganese tetroxide, manganese nitrate, but not limited to these) and lithium source (e.g., lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium chloride, but not limited to these); or the cathode material includes a mixture of nickel source (e.g., nickel hydroxide, nickel oxide, nickel carbonate, but not limited to these) and lithium source (e.g., lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium chloride, but not limited to these); or the cathode material includes a precursor of ternary cathode material (e.g., ... The cathode material comprises a mixture of lithium source (e.g., NCM523, NCM811, NCA, etc., but not limited to) and lithium source (e.g., lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium chloride, but not limited to); or the cathode material comprises a mixture of lithium source (e.g., lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium chloride, but not limited to), phosphorus source (e.g., ammonium hydrogen phosphate, but not limited to), and iron source (e.g., ferric oxalate, ferric acetate, but not limited to); or the cathode material comprises a mixture of lithium source (e.g., lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium chloride, but not limited to), phosphorus source (e.g., ammonium hydrogen phosphate, but not limited to), and manganese source (e.g., manganese oxide, manganese tetroxide, manganese nitrate, but not limited to).

[0044] Furthermore, the cathode material also includes doping modifiers and / or coating agents. The doping modifiers can be commonly used doping modifiers in cathode materials, such as metal oxides, for example, iron oxide, magnesium oxide, titanium oxide, cerium oxide, and zirconium oxide, but are not limited to these. The coating agent can be carbon, but is not limited to this.

[0045] Furthermore, the proportions of each component in the cathode material are readily available to those skilled in the art based on existing technology, and will not be elaborated upon here.

[0046] The binder is selected from starch, PVP, PEG, PVA, and PAN, and the dispersant is selected from one or more of ethanol, isopropanol, and water. The inventors unexpectedly discovered that by using the above combination, the cathode material, binder, and dispersant can be formed into a homogeneous single-phase material with a lithium source as the shell and other cathode materials (metal precursors) as the core through a spray drying process, providing a good foundation for subsequent fluidized bed sintering.

[0047] Preferably, the binder is a mixture of at least two of PVA, PVP, or PEG. Using these solvents avoids the problems of exposed metal precursors and empty shells of the lithium source caused by excessively fast drying rates during spray drying, resulting in a more stable core-shell structure. The PEG can be PEG10, PEG50, PEG100, PEG200, or PEG250, but is not limited to these.

[0048] More preferably, in one embodiment of the present invention, the binder is a mixture of PVA and PEG200, with a weight ratio of 1:(0.3-0.5), exemplarily 1:0.32, 1:0.35, 1:0.4, 1:0.44, or 1:0.48, but not limited thereto. Based on the above binder, firstly, the coating is tight, and the particle size of the obtained powder can reach 4-5 times the particle size of the positive electrode raw material; secondly, it effectively promotes the uniformity and sphericity of the powder particle size; and thirdly, it can not only form a stable core-shell structure, but also increase the spray drying speed, further improving production efficiency.

[0049] It should be noted that there are various raw materials for battery cathode materials, and the composition, particle size, and quality of these raw materials differ, making them difficult to mix effectively in a fluidized bed atmosphere, thus hindering fluidized bed sintering. However, this application, by selecting specific binders and dispersants, enables the various raw materials to form a single-phase substance with a large, uniform particle size and a core-shell structure, providing a good foundation for fluidized bed sintering. This avoids the need for pre-sintering or other pretreatment methods and significantly shortens the sintering time. Furthermore, due to the use of fluidized bed sintering, the powder particles have more sufficient contact with the atmosphere, improving the various properties of the sintered cathode material.

[0050] The weight ratio of the cathode material, binder, and dispersant is 10:(0.2-2):(10-50), with examples including 10:1:20, 10:0.5:24, 10:0.8:35, 10:0.3:26, and 10:0.7:43, but not limited to these. Based on this controlled weight ratio, firstly, a slurry with good flowability can be formed, which in turn forms a powder with concentrated particle distribution during subsequent spray drying, improving the performance of the cathode material after sintering; secondly, increasing the proportion of cathode material improves the performance of the cathode material after sintering.

[0051] Specifically, based on the control in the above embodiments, the particle size of the subsequently obtained powder is 1.5-5 times the particle size of the cathode material.

[0052] Preferably, in one embodiment of the present invention, water is used as the dispersant, as water does not react with the raw materials and has high safety for large-scale production.

[0053] Preferably, in one embodiment of the present invention, in this step, the positive electrode raw material, binder, and dispersant are mixed uniformly using a ball mill; wherein, the ball milling media are zirconium oxide balls to prevent contamination of the positive electrode raw material.

[0054] (2) The slurry is spray-dried to obtain powder;

[0055] Specifically, the inlet air temperature of the spray drying tower is 150-200℃. When the inlet air temperature is <150℃, the slurry will be heated unevenly, and leakage will occur at the nozzle. For example, the inlet air temperature of the spray drying tower is 155℃, 165℃, 175℃, 185℃, 192℃, or 197℃, but is not limited to these.

[0056] (3) The powder is sintered in a fluidized bed;

[0057] Specifically, the powder is added to a fluidized bed, and the atmosphere required for the sintering reaction is introduced from the bottom for sintering. The sintering atmosphere can be one or more of the following: oxidizing atmosphere, inert atmosphere, neutral atmosphere, reducing atmosphere, carburizing atmosphere, and nitriding atmosphere, but is not limited to these. During sintering, the heating rate of the fluidized bed is controlled at 10-20℃ / min, the sintering temperature at 600-1100℃, and the sintering time at 2-60min.

[0058] Accordingly, the present invention also discloses a cathode material prepared by the above-described preparation method. The present invention further discloses a lithium-ion battery comprising the above-described cathode material.

[0059] The present invention will now be described with reference to specific embodiments:

[0060] Example 1

[0061] This embodiment discloses a method for preparing a cathode material, which includes the following steps:

[0062] (1) Add the cathode material, binder and dispersant to a ball mill in a weight ratio of 10:0.5:15 and mix them evenly to obtain a slurry; wherein, the cathode material is a mixture of nickel-cobalt-manganese ternary precursor (Ni:Co:Mn=5:2:3) and lithium hydroxide, and the molar ratio of the two is 1:1.04; the binder is PAN and the dispersant is water.

[0063] (2) The slurry is spray-dried to obtain powder;

[0064] The intake air temperature is 180℃;

[0065] (3) The powder is sintered in a fluidized bed; wherein the heating rate is 10℃ / min, the atmosphere is an oxidizing atmosphere, the sintering temperature is 800℃, and the sintering time is 10min.

[0066] Example 2

[0067] This embodiment discloses a method for preparing a cathode material, which includes the following steps:

[0068] (1) The cathode material, binder and dispersant are added to a ball mill in a weight ratio of 10:1:20 and mixed evenly to obtain a slurry. The cathode material is a mixture of nickel-cobalt-manganese ternary precursor (Ni:Co:Mn=5:2:3) and lithium hydroxide, with a molar ratio of 1:1.04. The binder is a mixture of PVA and PEG200, with a weight ratio of 1:0.35. The dispersant is water.

[0069] (2) The slurry is spray-dried to obtain powder;

[0070] The intake air temperature is 190℃;

[0071] (3) The powder is sintered in a fluidized bed; wherein the heating rate is 15℃ / min, the atmosphere is an oxidizing atmosphere, the sintering temperature is 800℃, and the sintering time is 20min.

[0072] Example 3

[0073] This embodiment discloses a method for preparing a cathode material, which includes the following steps:

[0074] (1) Add the cathode material, binder and dispersant to a ball mill in a weight ratio of 10:1:20 and mix them evenly to obtain a slurry; wherein, the cathode material is a mixture of nickel-cobalt-manganese ternary precursor (Ni:Co:Mn=5:2:3) and lithium hydroxide, and the molar ratio of the two is 1:1.02; the binder is PEG200 and the dispersant is water.

[0075] (2) The slurry is spray-dried to obtain powder;

[0076] The intake air temperature is 180℃;

[0077] (3) The powder is sintered in a fluidized bed; wherein the heating rate is 15℃ / min, the atmosphere is an oxidizing atmosphere, the sintering temperature is 800℃, and the sintering time is 20min.

[0078] Example 4

[0079] This embodiment discloses a method for preparing a cathode material, which includes the following steps:

[0080] (1) Add the cathode material, binder and dispersant to a ball mill in a weight ratio of 10:1:20 and mix them evenly to obtain a slurry; wherein, the cathode material is a mixture of nickel-cobalt-manganese ternary precursor (Ni:Co:Mn=5:2:3) and lithium hydroxide, and the molar ratio of the two is 1:1.04; the binder is PVA.

[0081] (2) The slurry is spray-dried to obtain powder;

[0082] The intake air temperature is 180℃;

[0083] (3) The powder is sintered in a fluidized bed; wherein the heating rate is 15℃ / min, the atmosphere is an oxidizing atmosphere, the sintering temperature is 800℃, and the sintering time is 20min.

[0084] Example 5

[0085] This embodiment discloses a method for preparing a cathode material, which includes the following steps:

[0086] (1) The cathode material, binder and dispersant are added to a ball mill in a weight ratio of 10:0.5:15 and mixed evenly to obtain a slurry. The cathode material is a mixture of nickel-cobalt-manganese ternary precursor (Ni:Co:Mn=5:2:3) and lithium hydroxide, with a molar ratio of 1:1.04. The binder is a mixture of PVA and PEG200, with a weight ratio of 1:2. The dispersant is water.

[0087] (2) The slurry is spray-dried to obtain powder;

[0088] The intake air temperature is 180℃;

[0089] (3) The powder is sintered in a fluidized bed; wherein the heating rate is 15℃ / min, the atmosphere is an oxidizing atmosphere, the sintering temperature is 800℃, and the sintering time is 20min.

[0090] Comparative Example

[0091] This comparative example provides a method for preparing a cathode material, which includes:

[0092] 1. The nickel-cobalt-manganese ternary precursor (Ni:Co:Mn=5:2:3) and lithium hydroxide were mixed evenly in a ball mill at a ratio of 1:1.04 to obtain powder;

[0093] 2. Place the powder into a roller furnace and react at 800℃ for 8 hours to obtain the final product.

[0094] Experimental Example 1

[0095] The powders obtained in Examples 1-6 were tested, as follows:

[0096] (1) Flowability test: Place a glass cylinder with a diameter of 30 mm and a height of 50 mm on a glass plate, fill it with ceramic powder and level it, then lift the glass cylinder. Record the maximum height H of the material pile after the powder naturally flows out. s Liquidity is then calculated using the following formula:

[0097] f = 50 - H s

[0098] Where f is the flowability of the powder, H s This represents the maximum height of the material pile formed during the flowability test.

[0099] (2) Ratio of powder particle size to cathode material particle size: The particle size of the powder and the cathode material used were analyzed using electron microscopy, and the ratio was calculated according to the following formula:

[0100]

[0101] In the formula, D min d represents the minimum particle size of the powder (measured by electron microscopy). max This represents the maximum particle size of the cathode material (measured by electron microscopy).

[0102] (3) Particle size distribution determination: The powder was sieved using 1600 mesh (10μm) and 2000 mesh (6μm) sieves. The weights of the material passing through and under the sieves were recorded, and the particle size distribution was calculated using the following formula:

[0103]

[0104] In the formula, w1 is the weight ratio of powder with a mesh size of 1600 or larger, w2 is the weight ratio of powder with a mesh size of 2000 or smaller, and w 12 The weight ratio of powder with a mesh size of less than 1600 and a mesh size of more than 2000.

[0105] The specific test results are shown in the table below:

[0106] f / mm α β Example 1 31.2 2.98 0.28 Example 2 36.8 4.87 0.11 Example 3 34.3 4.15 0.13 Example 4 32.6 4.23 0.15 Example 5 37.3 3.51 0.22

[0107] As can be seen from the table, the spray drying process of this invention effectively increases the particle size of the powder. Further details can be found at [link to table]. Figures 1-5 ,in Figure 1 This is an electron microscope image of the powder obtained in Example 1. Figure 2 Here is an electron microscope image of the powder obtained in Example 2. Figure 3 Here is an electron microscope image of the powder obtained in Example 3. Figure 4 This is an electron microscope image of the powder obtained in Example 4. Figure 5 This is an electron microscope image of the powder obtained in Example 5. Figure 6 The images show electron microscope (EM) images of the nickel-cobalt-manganese ternary precursors used in Examples 1-5. As can be seen from the images, the preparation method of this invention forms a distinct shell structure on the surface of the nickel-cobalt-manganese ternary precursors. Furthermore, through… Figure 1 , Figure 2 The comparison shows that using a mixture of PVA and PEG200 in a specific ratio as a binder results in powder particles that are more spherical and have a higher particle size uniformity. Figures 2-4 The comparison shows that when only PEG200 or PVA is used, uncoated empty shells are easily formed. Figure 3 , Figure 4 B) and a small amount of ternary precursors that were not fully encapsulated ( Figure 3 , Figure 4 A in the middle). Through Figure 2 , Figure 5 The comparison shows that when the ratio of PVA to PEG200 changes, although the core-shell structure of the coating is good, the particle size uniformity is poor.

[0108] Further, see Figures 7-9 , Figure 7 , Figure 8 The XRD patterns of the cathode materials obtained in Examples 1 and 2 are as follows: Figure 9 The figures show the XRD patterns of the nickel-cobalt-manganese ternary precursors used in Examples 1 and 2. As can be seen from the figures, the cathode material generated by the rapid sintering of the present invention can still ensure the formation of the ternary material NCM523 phase while significantly shortening the reaction time.

[0109] Experimental Example 2

[0110] The cathode materials obtained in Example 2 and Comparative Example 1 were used to prepare coin cells, and the following tests were performed:

[0111] (1) Long cycle performance test: At 30℃, the battery is charged and discharged at 1C for 500 cycles to compare the degree of capacity decay.

[0112] (2) Stepped cycle performance test: At 30℃, the battery is discharged at 0.5C / 0.5C, 1C / 1C, 5C / 5C, and 0.5C / 0.5C, and the capacity decay is compared.

[0113] For details, see Figure 10 The figure shows the long-cycle curves of the cathode materials obtained in Example 2 and the comparative example after they were prepared into coin cells. As can be seen from the figure, the cathode material of Example 2 exhibits excellent long-cycle performance. At the 500th cycle, the capacity retention rate of Example 2 is still 69%, while the capacity retention rate of the comparative example is 60% at the 500th cycle.

[0114] For details, see Figure 11 The figure shows the step cycle curves of the cathode materials obtained in Example 2 and the comparative example after they were prepared into coin cells. As can be seen from the figure, the cathode material of Example 2 exhibits excellent high-rate performance. After 10 charge-discharge cycles from 5C back to 0.5C, the capacity retention rate of Example 2 is still 80%, while the capacity retention rate of the comparative example is only 77%.

[0115] The above description is a preferred embodiment of the invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the invention, and these improvements and modifications are also considered to be within the scope of protection of the invention.

Claims

1. A method for preparing a positive electrode material, characterized in that, include: (1) The cathode material, binder and dispersant are mixed evenly in a weight ratio of 10:(0.2-2):(10-50) to obtain a slurry; wherein the cathode material includes a ternary cathode material precursor and lithium hydroxide; (2) The slurry is spray-dried to obtain powder; (3) The powder is sintered in a fluidized bed; wherein the sintering temperature is 600-1100℃ and the sintering time is 20min; The binder is a mixture of PVA and PEG200 in a weight ratio of 1:(0.3-0.5), and the dispersant is one or more of ethanol, isopropanol, and water.

2. The method for preparing the cathode material as described in claim 1, characterized in that, In step (2), the inlet air temperature of the spray drying tower is 150-200℃.

3. The method for preparing the cathode material as described in claim 1, characterized in that, In step (3), the heating rate of the fluidized bed is 10-20℃ / min; The sintering atmosphere may be selected from one or more of the following: oxidizing atmosphere, inert atmosphere, neutral atmosphere, reducing atmosphere, carburizing atmosphere, or nitriding atmosphere.

4. The method for preparing the cathode material as described in claim 1, characterized in that, The cathode material also includes doping modifiers and / or coating agents.

5. The method for preparing the cathode material as described in claim 1, characterized in that, The particle size of the powder is larger than that of the cathode material.

6. The method for preparing the cathode material as described in claim 1, characterized in that, The powder has a core-shell structure, and the particle size of the powder is 1.5-5 times that of the cathode material.

7. A positive electrode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.

8. A lithium-ion battery, characterized in that, Including the cathode material as described in claim 7.

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