Lithium battery positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a preparation method and application of a lithium ion positive electrode material. The method comprises the following steps: mixing and pelletizing a precursor, a lithium source and bentonite, and sequentially spraying a boric acid aqueous solution and an ammonium dihydrogen phosphate solution in the pelletizing process to form two-stage spherical raw material particles; and then sintering twice in an oxygen-rich first atmosphere and an oxygen-free second atmosphere respectively, so as to obtain the lithium ion positive electrode material with a stable structure. According to the method, integrated regulation and control are achieved in the pelletizing link, high-oxygen atmosphere lithiation and low-oxygen atmosphere structure stabilization sintering are combined, and the particle size uniformity and interface structure stability of the material are remarkably improved. The prepared positive electrode material has relatively high initial coulombic efficiency, excellent cycling stability and electrochemical performance, and can effectively improve the energy density and prolong the service life of the lithium ion battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a lithium-rich manganese-based cathode material, its preparation method, and its application in lithium-ion batteries. Background Technology With the increasing demand for high-energy-density lithium-ion batteries from electric vehicles, energy storage systems, and mobile devices, novel cathode materials with high specific capacity and high energy density have become a key research direction. Lithium-rich manganese-based cathode materials are widely considered to be one of the ideal cathode materials for next-generation high-energy-density batteries due to their high discharge specific capacity and relatively high operating voltage.

[0002] However, despite the significant capacity advantages of lithium-rich manganese-based materials, their commercial application still faces several key challenges. For example, during the preparation of battery cathode materials, poor control of reaction atmosphere uniformity and excessive oxidation or reduction environments in local areas lead to differential and uncontrollable reconstruction of the material surface structure, resulting in excessive sintering growth or the formation of a dense surface layer in some primary particles. This directly causes abnormal fluctuations in the material's specific surface area (either too high or too low), impaired bulk electronic / ionic conductivity, and reduced electrolyte wetting and interfacial charge transport efficiency, all of which contribute to a significantly lower-than-expected discharge specific capacity and poor cycle stability. Summary of the Invention

[0003] This invention provides a lithium-ion battery cathode material, a preparation method, and its application in lithium-ion batteries. The method aims to address the problems of poor discharge specific capacity and cycle stability in existing battery cathode materials.

[0004] In a first aspect, the present invention provides a method for preparing a lithium-ion cathode material, comprising the following steps: S1. Mix the precursor, lithium source and bentonite to obtain a mixed powder; S2. The mixed powder is pelletized by spraying boric acid aqueous solution during the pelletizing process to obtain the first spherical raw material particles; S3. The first spherical raw material particles are sintered for the first time in a first atmosphere to obtain a sintered material; S4. The primary sintered material is subjected to secondary pelletizing. During the secondary pelletizing process, ammonium dihydrogen phosphate solution is sprayed to form second spherical raw material particles. S5. The second spherical raw material particles are sintered for a second time in a second atmosphere to obtain the lithium-ion cathode material; the second atmosphere is an oxygen-free atmosphere.

[0005] In one optional embodiment, the precursor is a precursor for preparing lithium-rich manganese-based cathode materials, with the chemical formula Ni. x Co y Mn （1-x-y）(OH)₂, wherein 0.2≤x≤0.4, 0.03≤y≤0.08. The lithium source is selected from at least one of lithium hydroxide, lithium carbonate, and lithium oxalate. These lithium sources can provide suitable lithium-ion sources and react with the precursor during the preparation process. The mixed powder also contains metal oxides, which are selected from at least one of TiO₂, WO₃, and MoO₃, with a total content of 1000-4000 ppm. Controlling the content of metal oxides within an appropriate range can further improve the performance of the battery. The bentonite accounts for 1-5% of the mass of the mixed powder, thereby ensuring good structure and electrochemical performance of the battery material. The molar ratio of the lithium source to the precursor is 0.70-0.75:1. This molar ratio setting can precisely control the lithium-ion supply during the reaction process, ensuring that the sodium-ion battery cathode material obtains the desired ideal structure and performance during the synthesis process.

[0006] In one optional embodiment, the concentration of the boric acid aqueous solution is controlled within the range of 0.1-2.0 mol / L, which helps optimize the surface structure and conductivity of the battery material. The liquid-solid ratio of the mixed powder to the boric acid aqueous solution is precisely controlled to ensure sufficient reaction, further improving the stability and performance of the material. Furthermore, the particle size of the first spherical raw material particles is set to 1-3 cm, which helps ensure uniform raw material particles suitable for subsequent sintering processes.

[0007] In one optional embodiment, during a single sintering process, the oxygen volume concentration in the first atmosphere is controlled between 50% and 100%. This range effectively controls the oxidation reaction during sintering, improving the performance of the battery cathode material. The first sintering step includes sintering at 500-700°C for 4-8 hours, followed by sintering at 900-1000°C for 10-16 hours, thereby ensuring the structural stability of the sodium-ion battery material and optimizing its electrochemical performance.

[0008] In one optional embodiment, the concentration of the ammonium dihydrogen phosphate aqueous solution is 0.2-0.8 mol / L to ensure optimal material surface treatment during sintering. The particle size of the second spherical raw material particles is set to 1-3 cm to accommodate further sintering. The implementation also includes a step of mixing the primary sintering material with bentonite, with a bentonite-to-primary sintering material mass ratio of 1-5%, to ensure the quality and stability of the final product.

[0009] In one optional embodiment, during the second sintering, the second atmosphere is nitrogen at a flow rate of 10 L / min. This setting effectively avoids excessive oxidation and ensures the reducibility and electrical conductivity of the material. The temperature of the second sintering is 500-700°C, the heating rate is controlled at 1-5°C / min, and the holding time is 4-8 hours. By adjusting these conditions, the particle structure of the material can be optimized, and its cycle stability and electrochemical performance can be improved.

[0010] In one alternative implementation, the pelletizing process is completed by a pelletizing machine or a disc pelletizer. Selecting appropriate equipment can effectively shape the raw material particles into spherical shapes, which helps to improve the uniformity of the material during sintering, thereby improving the overall performance of the battery material.

[0011] In one alternative implementation, after the second sintering, the material is allowed to cool naturally to room temperature before being pulverized and sieved. This process helps ensure that the particle size of the material is appropriate for subsequent use and battery assembly, while also optimizing the quality and consistency of the battery cathode material.

[0012] Secondly, the present invention also provides a lithium battery cathode material prepared by the above preparation method.

[0013] Thirdly, the present invention also provides a lithium-ion battery comprising the lithium battery positive electrode material described in the present invention.

[0014] The technical solution of this invention has the following advantages: (1) This invention selects lithium-rich manganese-based precursors, lithium sources, and additionally added metal oxides (TiO2, WO3, MoO3) containing Al. 3+ Si 4+ Bentonite is premixed to obtain a blended powder. Due to the addition of boric acid aqueous solution (0.1-2.0 mol / L), pelletizing is performed simultaneously, transforming the powder material into uniform 1-3 cm green pellets. Sintering is then carried out under a high-oxygen atmosphere. After the powder is pelletized, the inter-material gaps increase, which facilitates sufficient contact between the blended powder and oxygen, improves the lithiation degree of the precursor, and reduces lattice distortion. 4+ Ti 4+ The support structure enhances the material's structural stability, while the high-strength BO bond energy and the synergistic effect of multiple elements effectively reduce oxygen evolution, thereby significantly improving the initial coulombic efficiency. The lithium-ion cathode material preparation method of this invention integrates key steps such as wet coating (phosphate) and pelletizing into a single pelletizing process, greatly simplifying the multi-step process of traditional methods and reducing production costs and equipment investment. This method can effectively control the particle size, morphology, and chemical composition of the material, improving the battery's conductivity, cycle stability, and energy density.

[0015] (2) By performing the first sintering under an oxygen atmosphere, the crystal structure of the material is effectively stabilized, reducing the capacity decay caused by phase transformation; the precise control of temperature and sintering time improves the sintering effect and further optimizes the cycling performance of the material.

[0016] (3) The present invention uses ammonium dihydrogen phosphate solution for wet coating, and after sintering, a coating layer such as fast ion conductor Li3PO4 is formed, which can effectively inhibit electrolyte corrosion and oxygen evolution, stabilize the interface structure, reduce residual alkali, stabilize surface lattice oxygen, inhibit oxygen release, improve cycle stability, and reduce capacity decay and voltage drop.

[0017] (4) The second sintering under nitrogen atmosphere helps stabilize the material, reduces defects and oxidation, ensures the performance stability of the material under high temperature environment, and improves the overall reliability of the battery.

[0018] (5) By using a pelletizer or a disc pelletizer, the present invention can effectively control the uniformity and particle size distribution of particles during the pelletizing process, thereby improving the consistency of the sintering process and the quality of the product.

[0019] (6) After the second sintering, the material is naturally cooled to room temperature, then pulverized and sieved to further optimize the particle size and morphology of the battery cathode material. This process helps improve the uniformity of the material, ensuring its consistency in the battery, and further improving the battery's electrochemical performance and cycle life. Pulverization and sieving also remove unacceptable coarse particles, ensuring stable material quality.

[0020] (7) The lithium battery cathode material of the present invention has excellent electrochemical performance, including high energy density, power density and cycle stability. Due to the use of optimized sintering and pelletizing processes, the material has good structural stability and conductivity, and is suitable for the cathode of high-performance lithium-ion batteries.

[0021] (8) The lithium-ion battery of the present invention has excellent charge and discharge performance, long cycle life and high energy density. The long-term stability and high power output of the battery can meet the needs of high-end electronic devices and electric vehicles. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the process flow of Embodiments 1-3 of the present invention. Detailed Implementation

[0024] The following embodiments are provided to better understand the present invention, but the following embodiments 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 scope of protection of the present invention.

[0025] Unless otherwise specified, the experimental steps or conditions in the examples were performed in accordance with conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0026] The bentonite used in this invention has the chemical formula Al2O3·4(SiO2)·H2O, sourced from Aladdin Reagent Network. It is a powder that becomes more viscous when it comes into contact with water and is used for pelletizing or granulation.

[0027] Example 1 This embodiment provides a method for preparing a lithium-ion cathode material, such as... Figure 1 As shown, it includes the following steps: S1: Weigh out lithium carbonate and precursor Ni 0.30 Co 0.05 Mn 0.65 The molar ratio of (OH)2 is 0.72:1. Then, 2% of bentonite based on the total mass of the precursor and lithium carbonate is weighed out, and 2000ppm TiO2, 1000ppm WoO3, and 1000ppm MoO3 are added. The mixture is then mixed in a high-speed mixer to obtain a mixed powder. S2: Place the mixed powder into a disc pelletizer. The disc pelletizer rotates at 250 r / min. Slowly spray a boric acid aqueous solution with a mass concentration of 1.0 mol / L along the edge of the disc pelletizer to form pellets. Sieve all the green pellets to obtain green pellets with a particle size of 2 cm. S3: The obtained green pellets are placed in a box furnace and heated to 600℃ at a heating rate of 2℃ / min for 5 hours, and then heated to 950℃ at a heating rate of 2℃ / min for 13 hours. The sintering atmosphere is oxygen with a flow rate of 10L / min and an oxygen concentration of 90%. The pellets are then allowed to cool naturally to room temperature, crushed, and sieved to obtain the primary sintered material. S4: The obtained primary sintering material is also placed in a disc pelletizer. The disc pelletizer rotates at 250 r / min. A 0.5 mol / L ammonium dihydrogen phosphate solution is slowly sprayed along the edge of the disc pelletizer. All green pellets are sieved to obtain green pellets with a particle size of 2 cm. S5: The obtained green pellets are placed in a box furnace and heated to 600°C at a heating rate of 2°C / min for sintering for 5 hours. The sintering atmosphere is nitrogen with a flow rate of 10L / min. The pellets are then allowed to cool naturally to room temperature. After crushing and sieving, the lithium-ion cathode material is obtained.

[0028] Example 2 S1: Weigh out lithium carbonate and precursor Ni 0.40 Co 0.08 Mn 0.52 The molar ratio of (OH)2 is 0.75:1. Then, 1% of bentonite based on the total mass of the precursor and lithium carbonate is weighed out, and 2000ppmTiO2, 1000ppmWoO3, and 1000ppmMoO3 are added. The mixture is then mixed in a high-speed mixer to obtain a mixed powder. S2: Place the mixed powder into a disc pelletizer at a rotation speed of 250 r / min. Slowly spray a boric acid aqueous solution with a mass concentration of 0.1 mol / L along the edge of the disc pelletizer to form pellets. Sieve all the green pellets to obtain green pellets with a particle size of 1 cm. S3: The obtained green pellets are placed in a box furnace and heated to 500℃ at a heating rate of 2℃ / min for 4 hours, and then heated to 900℃ at a heating rate of 2℃ / min for 10 hours. The sintering atmosphere is oxygen with a flow rate of 10L / min and an oxygen concentration of 50%. The mixture is then allowed to cool naturally to room temperature, crushed, and sieved to obtain the primary sintered material. S4: The obtained primary sintering material is also placed in a disc pelletizer. The disc pelletizer rotates at 250 r / min. A 0.2 mol / L ammonium dihydrogen phosphate solution is slowly sprayed along the edge of the disc pelletizer. All green pellets are sieved to obtain green pellets with a particle size of 1 cm. S5: The obtained green pellets are placed in a box furnace and heated to 500°C at a heating rate of 2°C / min for 4 hours. The sintering atmosphere is nitrogen with a flow rate of 10L / min. The pellets are then allowed to cool naturally to room temperature. After crushing and sieving, the lithium-ion cathode material is obtained.

[0029] Example 3 S1: Weigh out lithium carbonate and precursor Ni 0.20 Co 0.03 Mn 0.77 The molar ratio of (OH)2 is 0.7:1. Then, 5% of the total mass of the precursor and lithium carbonate, bentonite, is weighed out, and 2000ppm TiO2, 1000ppm WoO3, and 1000ppm MoO3 are added. The mixture is then mixed in a high-speed mixer to obtain a mixed powder. S2: Place the mixed powder into a disc pelletizer at a rotation speed of 250 r / min. Slowly spray a 2.0 mol / L boric acid aqueous solution along the edge of the disc pelletizer to pelletize the powder. Sieve all the green pellets to obtain green pellets with a particle size of 3 cm. S3: The obtained green pellets are placed in a box furnace and heated to 700℃ at a heating rate of 2℃ / min for 8 hours, and then heated to 1000℃ at a heating rate of 2℃ / min for 16 hours. The sintering atmosphere is oxygen with a flow rate of 10L / min and an oxygen concentration of 100%. The mixture is allowed to cool naturally to room temperature, crushed, and sieved to obtain the primary sintered material. S4: The obtained primary sintering material is also placed in a disc pelletizer. The disc pelletizer rotates at 250 r / min. A 0.8 mol / L ammonium dihydrogen phosphate solution is slowly sprayed along the edge of the disc pelletizer. All green pellets are sieved to obtain green pellets with a particle size of 3 cm. S5: The obtained green pellets are placed in a box furnace and heated to 700℃ at a heating rate of 2℃ / min for 8 hours. The sintering atmosphere is nitrogen with a flow rate of 10L / min. After natural cooling to room temperature, the pellets are crushed and sieved to obtain the lithium-ion cathode material.

[0030] Comparative Example 1 S1: Weigh out lithium carbonate and precursor Ni 0.30 Co 0.05 Mn 0.65 The molar ratio of (OH)2 is 0.72:1. 2000ppmTiO2, 1000ppmWoO3 and 1000ppmMoO3 are added separately and mixed in a high-speed mixer to obtain a mixed powder. S2: Heat to 600℃ at a heating rate of 2℃ / min and sinter for 5 hours, then heat to 950℃ at a heating rate of 2℃ / min and sinter for 13 hours. The sintering atmosphere is oxygen with a flow rate of 10L / min and an oxygen concentration of 90%. Allow to cool naturally to room temperature, then crush and sieve to obtain the primary sintered material. S3: Wet coating with 0.5 mol / L ammonium dihydrogen phosphate solution, and sieve all green pellets to obtain green pellets with a particle size of 2 cm; S4: The obtained green pellets are placed in a box furnace and heated to 600℃ at a heating rate of 2℃ / min for sintering for 5 hours. The sintering atmosphere is nitrogen with a flow rate of 10L / min. After natural cooling to room temperature, the pellets are crushed and sieved to obtain the lithium-ion cathode material.

[0031] Comparative Example 2 S1: Weigh out lithium carbonate and precursor Ni 0.30 Co 0.05 Mn 0.65The molar ratio of (OH)2 is 0.72:1. Then, 2% of bentonite based on the total mass of the precursor and lithium carbonate is weighed out, and 2000ppm TiO2, 1000ppm WoO3, and 1000ppm MoO3 are added. The mixture is then mixed in a high-speed mixer to obtain a mixed powder. S2: Place the mixed powder into a disc pelletizer. The disc pelletizer rotates at 250 r / min. Slowly spray the aqueous solution along the edge of the disc pelletizer to form pellets. Sieve all the green pellets to obtain green pellets with a particle size of 1 cm. S3: The obtained green pellets are placed in a box furnace and heated to 600℃ at a heating rate of 2℃ / min for 5 hours, and then heated to 950℃ at a heating rate of 2℃ / min for 13 hours. The sintering atmosphere is oxygen with a flow rate of 10L / min and an oxygen concentration of 90%. The pellets are then allowed to cool naturally to room temperature, crushed, and sieved to obtain the primary sintered material. S4: The obtained primary sintering material is also placed in a disc pelletizer. The disc pelletizer rotates at 250 r / min. A 0.5 mol / L ammonium dihydrogen phosphate solution is slowly sprayed along the edge of the disc pelletizer. All green pellets are sieved to obtain green pellets with a particle size of 3 cm. S5: The obtained green pellets are placed in a box furnace and heated to 600°C at a heating rate of 2°C / min for sintering for 5 hours. The sintering atmosphere is nitrogen with a flow rate of 10L / min. The pellets are then allowed to cool naturally to room temperature. After crushing and sieving, the lithium-ion cathode material is obtained.

[0032] Comparative Example 3 S1: Weigh out lithium carbonate and precursor Ni 0.30 Co 0.05 Mn 0.65 The molar ratio of (OH)2 is 0.72:1. Then, 2% of bentonite based on the total mass of the precursor and lithium carbonate is weighed out, and 2000ppm TiO2, 1000ppm WoO3, and 1000ppm MoO3 are added. The mixture is then mixed in a high-speed mixer to obtain a mixed powder. S2: Place the mixed powder into a disc pelletizer. The disc pelletizer rotates at 250 r / min. Slowly spray a boric acid aqueous solution with a mass concentration of 1.0 mol / L along the edge of the disc pelletizer to form pellets. Sieve all the green pellets to obtain green pellets with a particle size of 3 cm. S3: The obtained green pellets are placed in a box furnace and heated to 600℃ at a heating rate of 2℃ / min for 5 hours, and then heated to 950℃ at a heating rate of 2℃ / min for 13 hours. The sintering atmosphere is oxygen with a flow rate of 10L / min and an oxygen concentration of 90%. The pellets are then allowed to cool naturally to room temperature, crushed, and sieved to obtain the primary sintered material. S4: Place the obtained primary sintering material into a disc pelletizer. The disc pelletizer rotates at 250 r / min. Slowly spray an aqueous solution along the edge of the disc pelletizer. Sieve all the green pellets to obtain green pellets with a particle size of 1 cm. S5: The obtained green pellets are placed in a box furnace and heated to 600°C at a heating rate of 2°C / min for sintering for 5 hours. The sintering atmosphere is nitrogen with a flow rate of 10L / min. The pellets are then allowed to cool naturally to room temperature. After crushing and sieving, the lithium-ion cathode material is obtained.

[0033] Comparative Example 4 S1: Weigh out lithium carbonate and precursor Ni 0.30 Co 0.05 Mn 0.65 The molar ratio of (OH)2 is 0.72:1. Then, 2% of bentonite based on the total mass of the precursor and lithium carbonate is weighed out, and 2000ppm TiO2, 1000ppm WoO3, and 1000ppm MoO3 are added. The mixture is then mixed in a high-speed mixer to obtain a mixed powder. S2: Place the mixed powder into a disc pelletizer at a rotation speed of 250 r / min. Slowly spray a boric acid aqueous solution with a mass concentration of 1.0 mol / L along the edge of the disc pelletizer to form pellets. Sieve all the green pellets to obtain green pellets with a particle size of 1-3 cm. S3: The obtained green pellets are placed in a box furnace and heated to 600℃ at a heating rate of 2℃ / min for 5 hours, and then heated to 950℃ at a heating rate of 2℃ / min for 13 hours. The sintering atmosphere is oxygen with a flow rate of 10L / min and an oxygen concentration of 90%. The pellets are then allowed to cool naturally to room temperature, crushed, and sieved to obtain the primary sintered material. S4: Place the obtained primary sintering material into a disc pelletizer. The disc pelletizer rotates at 250 r / min. Slowly spray a 0.5 mol / L ammonium dihydrogen phosphate solution along the edge of the disc pelletizer. Sieve all the green pellets to obtain green pellets with a particle size of 1-3 cm. S5: The obtained green pellets are placed in a box furnace and heated to 600℃ at a heating rate of 2℃ / min for sintering for 5 hours. The sintering atmosphere is air with a flow rate of 10L / min. The pellets are then allowed to cool naturally to room temperature. After crushing and sieving, the lithium-ion cathode material is obtained.

[0034] Methods or standards for detecting effect data Button cell battery test The lithium-ion battery positive electrode materials in Examples 1-3 and Comparative Examples 1-4 were used as the main materials. Then, binders, conductive agents, and solvents were added, stirred and slurried, coated on aluminum foil, and dried and rolled to obtain positive electrode sheets. The binders used were polyvinylidene fluoride (PVDF) and acrylic acid, the conductive agents were conductive carbon black (SP) and conductive graphite (KS-6), and the solvent was N-methylpyrrolidone (NMP). The ratio of main materials, PVDF, acrylic acid, SP, KS-6, and NMP was 90g:5g:1g:1g:2g:220mL. The electrolyte was lithium hexafluorophosphate (LiPF6) as the electrolyte and a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:1 as the solvent, with an electrolyte concentration of 1mol / L. The negative electrode was a lithium sheet, and the separator was a polypropylene separator. The coin cells were assembled in an argon-filled glove box.

[0035] Electrochemical performance tests were conducted on the above-mentioned coin cells using a Blue Electric tester. The charge / discharge voltage range was 2.0V to 4.8V. The first charge / discharge cycle was performed at 0.1C, the second at 0.2C, the third at 0.5C, and the fourth to fifty-fourth cycles were performed at 1C (50 cycles of 1C / 1C). The cycle capacity retention rate was calculated as (discharge specific capacity of the fifty-fourth cycle / discharge specific capacity of the fourth cycle) * 100%. Rate performance was represented by the ratio of the 1C discharge specific capacity of the fourth cycle to the 0.1C discharge specific capacity of the first cycle * 100%. The test results are shown in Table 1.

[0036] Table 1. Test results of specific capacity, rate performance, and stability.

[0037] analyze: (1) As can be seen from the data in Table 1, the lithium-ion cathode materials prepared in Examples 1-3 all exhibit superior comprehensive performance in key performance indicators such as specific capacity, rate performance (1C / 0.1C), and cycle retention. Specifically, Example 1 has a specific capacity of 275 mAh / g, a rate performance of 90%, and a cycle retention of 95%; Examples 2 and 3 have specific capacities of 265 mAh / g and 260 mAh / g, respectively, rate performances of 87% and 85%, and cycle retention rates of 92% and 91%, respectively. These results demonstrate that the preparation method used in the examples of this application can effectively improve the capacity level, rate performance, and cycle stability of the cathode material.

[0038] (2) Compared with Example 1, the performance indicators of Comparative Examples 1-4 all decreased. Among them, the specific capacity of Comparative Example 1 was 250 mAh / g, the rate performance was 81%, and the cycle retention rate was 81%, which were significantly lower than those of Example 1. The main reason is that bentonite was not added as a pelletizing and structural auxiliary component during the preparation process of Comparative Example 1, and no pelletizing treatment was performed. This resulted in insufficient particle formability and structural density during sintering, which affected the structural stability and electrochemical performance of the material.

[0039] (3) Although Comparative Examples 2 and 3 added bentonite and underwent pelletizing treatment, they lacked the introduction of boric acid or ammonium dihydrogen phosphate in the corresponding pelletizing stages, respectively. Therefore, they could not achieve synergistic control of the main structure and surface interface of the material, and their specific capacity, rate performance, and cycle retention rate were still lower than those of the examples. Comparative Example 4 used an air atmosphere in the secondary sintering stage, which resulted in insufficient stability of the material surface structure, and its cycle retention rate was the lowest, at only 79%.

[0040] (4) As can be seen, the embodiments of this application introduce bentonite to assist in pelletizing, and introduce boric acid and ammonium dihydrogen phosphate in the primary pelletizing and secondary pelletizing stages respectively. With the addition of reasonable sintering atmosphere control, the synergistic optimization of the stability of the main structure and the surface interface of the cathode material is achieved, thereby significantly improving the specific capacity, rate performance and cycle retention rate.

[0041] In summary, the experimental data in Table 1 fully demonstrate that the preparation method used in the embodiments of this application has significant advantages in improving the overall electrochemical performance of lithium-ion cathode materials. Compared with the comparative examples that did not add bentonite, did not undergo a single pelletizing process, or lacked key control steps, the embodiments show superior technical effects in terms of specific capacity, rate performance, and cycle stability.

[0042] 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 lithium-ion cathode material, characterized in that, Includes the following steps: S1. Mix the precursor, lithium source and bentonite to obtain a mixed powder; S2. The mixed powder is pelletized by spraying boric acid aqueous solution during the pelletizing process to obtain the first spherical raw material particles; S3. The first spherical raw material particles are sintered for the first time in a first atmosphere to obtain a sintered material; S4. The primary sintered material is subjected to secondary pelletizing. During the secondary pelletizing process, ammonium dihydrogen phosphate solution is sprayed to form second spherical raw material particles. S5. The second spherical raw material particles are sintered for a second time in a second atmosphere to obtain the lithium-ion cathode material; the second atmosphere is an oxygen-free atmosphere.

2. The preparation method according to claim 1, characterized in that, The precursor mentioned in S1 is a precursor for preparing lithium-rich manganese-based cathode materials, with the chemical formula Ni. x Co y Mn （1-x-y） (OH)2, where 0.2≤x≤0.4, 0.03≤y≤0.08; And / or, the mixed powder described in S1 also contains metal oxides, wherein the metal oxides are selected from at least one of TiO2, WO3, and MoO3, and the total content of the metal oxides is 1000-4000 ppm; And / or, the bentonite accounts for 1-5% of the mass of the mixed powder; And / or, the molar ratio of lithium source to precursor is 0.70-0.75:

1.

3. The preparation method according to claim 1, characterized in that, The concentration of boric acid aqueous solution is 0.1-2.0 mol / L; And / or, the particle size of the first spherical raw material particle is 1-3 cm.

4. The preparation method according to claim 1, characterized in that, The oxygen volume concentration in the first atmosphere is 50-100%, and the gas flow rate is 10 L / min; And / or, the first sintering step includes sintering at 500-700°C for 4-8 hours, and then sintering at 900-1000°C for 10-16 hours.

5. The preparation method according to claim 1, characterized in that, The concentration of ammonium dihydrogen phosphate aqueous solution is 0.2-0.8 mol / L; And / or, the particle size of the second spherical raw material particle is 1-3 cm; And / or, it also includes the step of mixing the primary sintering material and bentonite, wherein the mass ratio of bentonite to primary sintering material is 1-5%.

6. The preparation method according to claim 1, characterized in that, The second atmosphere is nitrogen, and the gas flow rate is 10 L / min; And / or, the temperature of the second sintering is 500-700℃, and the holding time is 4-8 hours.

7. The preparation method according to claim 1, characterized in that, The pelletizing process is completed using a pelletizing machine or a disc granulator.

8. The preparation method according to any one of claims 1-7, characterized in that, The second sintering process also includes the steps of naturally cooling the material to room temperature, followed by crushing and sieving.

9. A lithium battery cathode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. A lithium-ion battery, characterized in that, Includes the cathode material as described in claim 9.

Images