High-uniformity lithium rare earth oxide coated lithium-rich manganese-based positive electrode material and solid-phase preparation method thereof

Abstract

The invention belongs to the technical field of lithium ion battery positive electrode materials, and discloses a surface coating modification method of a lithium-rich manganese-based positive electrode material, which comprises the following steps: uniformly mixing lithium carbonate and a rare earth oxide according to a molar ratio, and calcining at 900-1000 DEG C to form a high-crystallinity lithium rare earth oxide; grinding, stirring and uniformly mixing the ground, screened and refined lithium rare earth oxide and the lithium-rich manganese-based positive electrode material, and finally, carrying out gradient heating and sintering on the mixed material to obtain the lithium-rich manganese-based positive electrode material coated with the lithium rare earth oxide. The preparation method disclosed by the invention is simple in process and good in repeatability, the obtained product is uniform in morphology and consistent in size, and shows stability and cycle life higher than those of a traditional method in a lithium ion battery as a positive electrode material, the lithium-rich manganese-based positive electrode material coated with LiDyO2 with the mass fraction of 3% circulates for 200 circles at the multiplying power of 0.5 C, and the capacity retention rate can reach 93%. And the voltage attenuation is only 0.19 V. And the capacity retention ratio of the uncoated positive electrode material after 200 cycles is only 86%, and the voltage attenuation is 0.26 V.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode material technology, specifically relating to a surface coating modification method and application of lithium-rich manganese-based cathode material. Background Technology

[0002] Building a modern, safe, efficient, and green clean energy system is of paramount importance. Within this system, lithium-ion batteries, as a key component of energy storage, are increasingly becoming closely intertwined with human production and daily life.

[0003] Currently, cathode materials, as a core component of lithium-ion batteries, determine the overall performance of the battery. Among various cathode materials, lithium-rich manganese-based cathode materials have attracted widespread attention from researchers due to their advantages such as high specific capacity and low cost. However, lithium-rich manganese-based cathode materials suffer from problems such as rapid capacity decay and poor structural stability during actual cycling applications, which limits their further industrial application in the lithium battery field.

[0004] To address these issues, researchers have employed a series of methods, including coating, doping, and morphology control, to improve the electrochemical performance of lithium-rich manganese cathode materials. Among these, coating structures, as an important method in modification systems, have attracted widespread market attention. Coating materials are mainly divided into three categories: oxides, such as Al2O3, TiO2, LiAlO2, and ZnO, which can suppress electrolyte side reactions but have low lithium-ion conductivity; phosphates, such as AlPO4, Li3V2(PO4)3, and LiMnPO4, which possess lithium-ion conductivity but generally have limited structural stability; in addition, sulfides and graphene are also commonly used as coating materials, but these materials also suffer from slightly poor chemical stability or complex coating processes. Currently, the main methods for industrially constructing coated structures include: 1. Wet chemical methods, which suffer from complex processes, the need for solvents, high costs, and potential damage to the substrate; 2. Solid-state methods, which suffer from limitations such as uneven coating, discontinuous coating layers, and poor performance. Therefore, finding a solid-phase coating method that is simple to process, provides uniform and stable coating, and can significantly improve the electrochemical performance of materials has become an urgent technical problem to be solved. Summary of the Invention

[0005] In view of the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a highly uniform lithium rare earth oxide coated lithium-rich manganese-based cathode material and its solid-phase preparation method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing lithium rare earth oxide-coated lithium-rich manganese-based cathode material includes the following steps: (1) Lithium carbonate and Dy2O3 are uniformly mixed at a fixed molar ratio and then sintered at a high temperature of 900℃-1000℃. Subsequently, lithium rare earth oxides with good crystallinity are selected by XRD diffraction and finally lithium rare earth oxides with microscale particle size LiDyO2 are obtained by high-energy grinding and sieving. (2) Mix the carbonates with a ratio of Ni, Co and Mn of 1:1:4 with an appropriate amount of lithium carbonate, then add alcohol to a mortar and grind them evenly, and finally calcine at 820°C for 10 hours to obtain lithium-rich manganese-based cathode material. (3) Grind and mix the materials obtained in step (1) and step (2) with alcohol in a mortar, dry and take them out, then stir and sonicate them with alcohol in a beaker, finally evaporate the alcohol, scrape out the powder and calcine it at 405℃ for 2 hours to obtain LiDyO2 coated lithium-rich manganese-based cathode material.

[0007] Preferably, in step (1), the molar ratio of lithium carbonate to Dy2O3 is 1 / 1, 1.5 / 1, or 2 / 1.

[0008] Preferably, in step (1), the heating rate of the tubular furnace is 5°C / min.

[0009] Preferably, in step (1), the high-energy grinding and sieving process is a 200-mesh sieve.

[0010] Preferably, in step (2), the mass ratio of carbonate to lithium carbonate is 0.692:0.308.

[0011] Preferably, in step (2), the heating and cooling program of the tubular furnace is as follows: the heating gradient is 5℃ / min from 25℃ to 350℃; the heating gradient is 0.3℃ / min from 350℃ to 450℃, and the temperature is held for 5 hours; the heating gradient is 1.5℃ / min from 450℃ to 820℃, and the temperature is held for 10 hours; the cooling gradient is 0.5℃ / min from 820℃ to 600℃, and the temperature is finally allowed to drop naturally.

[0012] Preferably, in step (3), the alcohol is stirred and ultrasonically alternated for 15 minutes.

[0013] Preferably, in step (3), the heating and cooling program of the tubular furnace is as follows: the heating gradient from 25℃ to 280℃ is 30℃ / min, and the temperature is held for 1h; the heating gradient from 280℃ to 405℃ is 0.4℃ / min, and the temperature is held for 2.5h; the cooling gradient from 405℃ to 350℃ is 0.4℃ / min, and finally the temperature is naturally cooled.

[0014] The principle of this invention is as follows: using a high-energy grinding and high-temperature sintering method, LiDyO2 is coupled with lithium-rich manganese-based cathode material to synthesize lithium rare earth oxide-coated lithium-rich manganese-based cathode material with uniform size and morphology.

[0015] The lithium rare earth oxide-coated lithium-rich manganese-based cathode material synthesized in this invention exhibits stable charge-discharge performance in the field of lithium-ion batteries.

[0016] Compared with existing technologies, the beneficial effects of this invention are reflected in: 1. This invention uses a high-energy grinding-high-temperature sintering method to prepare LiDyO2-coated lithium-rich manganese-based cathode materials. This preparation method is simple, low-cost, has a yield of nearly 100%, and good reproducibility. 2. The product prepared by this invention has a uniform particle structure and consistent size; 3. The lithium rare earth oxide LiDyO2-coated lithium-rich manganese-based cathode material prepared by this invention exhibits higher stability and cycle life than traditional methods in the field of lithium-ion batteries. Specifically, the lithium-rich manganese-based cathode material coated with 3% mass fraction LiDyO2 retains 93% of its capacity and has a voltage decay of 0.19V after 200 cycles at a rate of 0.5C, while the uncoated cathode material retains only 86% of its capacity and has a voltage decay of 0.26V after 200 cycles. Attached Figure Description

[0017] Figure 1 The images shown are high-resolution scanning electron microscope (SEM) images of the lithium rare earth oxide-coated lithium-rich manganese-based cathode material obtained in Example 1 of this invention; where images a, b, and c correspond to different magnifications, and image dj shows the area captured by Mapping.

[0018] Figure 2 The image shows the X-ray diffraction (XRD) pattern of the LiDyO2-coated lithium-rich manganese-based cathode material obtained in Example 1 of this invention.

[0019] Figure 3 The EIS curve of the LiDyO2-coated lithium-rich manganese-based cathode material obtained in Example 1 of this invention in the battery pack is shown. Figure 3 a) Chemical cycle curve ( Figure 3 b), Ratio characteristic curve ( Figure 3 c), Charge-discharge current curve ( Figure 3 d). The uncoated lithium-rich manganese-based cathode material is the standard cathode material.

[0020] Figure 4This is a flowchart of the synthesis experiment of the LiDyO2-coated lithium-rich manganese-based cathode material obtained in Example 1 of the present invention. Detailed Implementation

[0021] The embodiments of the present invention are described in detail below. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0022] Example 1 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 925℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 2 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0023] The SEM image of the lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this embodiment is shown below. Figure 1 As shown (a, b, and c represent different magnifications). From Figure 1 As can be seen from AC, the product obtained in this embodiment has a uniform particle structure and consistent size, with a particle size of approximately 10 μm. Figure 1 The mapping spectrum in EJ confirms the coexistence of Ni, Mn, Co, and Dy elements, and that lithium dysprosium oxide is uniformly coated on the surface of the lithium-rich manganese-based cathode material. Figure 2 In the XRD pattern, the diffraction peaks of the prepared lithium dysprosium oxide-coated lithium-rich manganese-based cathode material correspond well with the diffraction peaks of the LiDyO2 standard card in the full spectrum, indicating that lithium dysprosium oxide can be effectively coupled with lithium-rich manganese-based cathode material. Figure 3 The electrochemical test data effectively demonstrate the improved electrochemical performance of lithium-rich manganese-based cathode materials coated with lithium dysprosium oxide. Figure 3 In a, the EIS results clearly show that the coating structure can effectively enhance the kinetic performance of the charging and discharging process; Figure 3In section b, the cycling experiment effectively confirmed that the coating structure can enhance the stability of the material, laying a solid foundation for industrial application. The material with the best performance was coated with 3wt.% LiDyO2. After 200 cycles at 0.5C, the capacity retention rate reached 93% and the voltage drop was only 0.19V. In contrast, the uncoated cathode material had a capacity retention rate of only 86% and a voltage drop of 0.26V after 200 cycles. Figure 3 In c, the rate characteristic test results show that the coated material still maintains good discharge capacity, proving that it has excellent reversibility; Figure 3 In d, the discharge specific capacity first increases and then decreases with the increase of the coating ratio. This is attributed to the good conductivity of the coating layer, which can contribute part of the capacity during the reaction process.

[0024] Example 2 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 2 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0025] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0026] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0027] Example 3 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 900℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 2 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0028] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0029] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0030] Example 4 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 850℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 2 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0031] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0032] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0033] Example 5 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 8h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 2 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0034] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0035] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0036] Example 6 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 500 °C for 2 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0037] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0038] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0039] Example 7 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.057g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 2 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0040] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0041] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0042] Example 8 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 30 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 2 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0043] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0044] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0045] Example 9 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 3 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0046] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0047] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0048] Example 10 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 820℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 1 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0049] Characterization showed that the product obtained in this embodiment has a homogeneous core-shell structure and uniform size.

[0050] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example still exhibits excellent electrochemical stability when tested using the same method as in Example 1.

[0051] Comparative Example 1 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 1000℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 18 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 1 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0052] Characterization revealed that the core-shell structure of the product obtained in this embodiment was blurred or even destroyed.

[0053] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example was tested using the same method as in Example 1. The material had extremely low initial efficiency, severe voltage decay, and a sharp decline in cycle performance in a short period of time.

[0054] Comparative Example 2 (1) 0.298g of lithium carbonate and 1g of dysprosium oxide were uniformly mixed and then calcined at 1000℃ for 12h. Subsequently, lithium dysprosium oxide with good crystallinity was selected by XRD diffraction and finally lithium dysprosium oxide with microscale particle size was obtained by high-energy grinding and sieving. (2) Mix 2.5g of carbonate precursor with 1.113g of lithium carbonate evenly, then add 5mL of alcohol to a mortar and grind them evenly, and finally calcine at 1000℃ for 10h to obtain lithium-rich manganese-based cathode material. (3) Mix 60 mg of lithium dysprosium oxide and 600 mg of lithium-rich manganese-based cathode material in a mortar with 5 mL of alcohol, dry and remove. Then stir and sonicate alternately with 20 mL of alcohol in a beaker for 15 min. Finally, evaporate the alcohol, scrape off the powder and calcine at 405 °C for 1 h to obtain lithium dysprosium oxide coated lithium-rich manganese-based cathode material.

[0055] Characterization revealed that the core-shell structure of the product obtained in this embodiment was excessively thick.

[0056] The lithium dysprosium oxide-coated lithium-rich manganese-based cathode material prepared in this example was tested using the same method as in Example 1. The initial efficiency and rate performance of the material were severely degraded.

[0057] The above description is merely an exemplary embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for surface coating modification of lithium-rich manganese-based cathode materials, characterized in that, Includes the following steps: (1) Lithium carbonate and dysprosium trioxide are uniformly mixed at a fixed molar ratio and then sintered at a high temperature of 900℃-1000℃. Subsequently, the well-crystallized lithium rare earth oxide LiDyO2 is selected by XRD diffraction and finally the lithium rare earth oxide with microscale particle size is obtained by high-energy grinding and sieving. (2) Mix the carbonates with a ratio of Ni, Co and Mn of 1:1:4 with an appropriate amount of lithium carbonate, then add alcohol to a mortar and grind them evenly, and finally calcine at 820°C for 10 hours to obtain lithium-rich manganese-based cathode material. (3) The materials obtained in step (1) and step (2) are mixed with alcohol in a mortar and dried. Then, they are stirred and sonicated with alcohol in a beaker. Finally, the alcohol is evaporated, the powder is scraped off, and calcined at 405°C for 2 hours to obtain lithium rare earth oxide coated lithium-rich manganese-based cathode material.

2. The surface coating modification method for a lithium-rich manganese-based cathode material according to claim 1, characterized in that: In step (1), the molar ratio of lithium carbonate to dysprosium trioxide is 1 / 1, 1.5 / 1, or 2 / 1.

3. The surface coating modification method for a lithium-rich manganese-based cathode material according to claim 1, characterized in that: In step (1), the heating rate of the tube furnace is 5℃ / min.

4. The surface coating modification method for a lithium-rich manganese-based cathode material according to claim 1, characterized in that: In step (1), the grinding and sieving process is 200 mesh sieving.

5. The surface coating modification method for a lithium-rich manganese-based cathode material according to claim 1, characterized in that: In step (2), the mass ratio of carbonate to lithium carbonate is 0.692:0.

308.

6. The surface coating modification method for a lithium-rich manganese-based cathode material according to claim 1, characterized in that: In step (2), the heating and cooling program of the tubular furnace is as follows: the heating gradient is 5℃ / min from 25℃ to 350℃; the heating gradient is 0.3℃ / min from 350℃ to 450℃, and the temperature is held for 5 hours; the heating gradient is 1.5℃ / min from 450℃ to 820℃, and the temperature is held for 10 hours; the cooling gradient is 0.5℃ / min from 820℃ to 600℃, and the temperature is finally cooled naturally.

7. The surface coating modification method for a lithium-rich manganese-based cathode material according to claim 1, characterized in that: In step (3), alcohol is stirred and sonicated alternately for 15 minutes.

8. The surface coating modification method for a lithium-rich manganese-based cathode material according to claim 1, characterized in that: In step (3), the heating and cooling program of the tubular furnace is as follows: the heating gradient from 25℃ to 280℃ is 30℃ / min, and the temperature is held for 1 hour; the heating gradient from 280℃ to 405℃ is 0.4℃ / min, and the temperature is held for 2.5 hours; the cooling gradient from 405℃ to 350℃ is 0.4℃ / min, and the temperature is finally cooled naturally.

9. A lithium rare earth oxide-coated lithium-rich manganese-based cathode material with uniform morphology and consistent size prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the lithium rare earth oxide-coated lithium-rich manganese-based cathode material with uniform morphology and consistent size as described in claim 9 is as a cathode material in the field of lithium-ion batteries.

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