Disordered phase structure lithium-rich manganese-based positive electrode material, preparation method and battery

Abstract

The embodiment of the invention provides a lithium-rich manganese-based positive electrode material with a disordered phase structure, a preparation method and a battery, a manganese source, a sodium source and a lithium source are mixed in proportion, the ratio of the amount of substance of the sodium source to the amount of substance of the lithium source is 1: 9-9: 1, and the ratio of the total amount of substance of the sodium source and the lithium source to the amount of substance of the manganese source is 0.8-1.2: 1; placing the mixed raw material in a porcelain boat, and heating and preserving heat in a heating furnace to obtain a precursor material with a strip-shaped superstructure; mixing the precursor material with molten salt according to the mass ratio of 1: (1-20), and uniformly grinding; placing the mixture in a porcelain boat, and heating and preserving heat in the atmosphere of air, oxygen or argon; and washing the treated sample with deionized water and drying to obtain the lithium-rich manganese-based positive electrode material with the disordered phase structure. Therefore, through precursor structure regulation and control and molten salt treatment, a lithium-deficient state structure with disordered Li-coated Mn6 honeycomb distribution is obtained, the cycling stability and the voltage holding ratio of the material are remarkably improved, and meanwhile, the advantages of low cost and high specific capacity are maintained.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode material technology, specifically to a disordered phase structure lithium-rich manganese-based cathode material, its preparation method, and a battery, which is suitable for high-energy-density, low-cost, and environmentally friendly lithium-ion battery systems. Background Technology

[0002] Lithium-rich manganese-based cathode materials are considered an important candidate for next-generation lithium-ion battery cathode materials due to their advantages such as low cost, high theoretical capacity, and environmental friendliness. However, traditional lithium-rich manganese-based materials suffer from severe voltage and capacity decay during cycling, which limits their commercial application.

[0003] Currently, common improvement methods include transition metal doping, surface coating, and structure control, but these methods often introduce additional metal elements or complex processes, increasing costs and preparation difficulty. Summary of the Invention

[0004] In view of this, the present invention provides a disordered phase structure lithium-rich manganese-based cathode material, a preparation method and a battery. By controlling the precursor structure and molten salt treatment, a lithium-deficient structure with disordered Li@Mn6 honeycomb distribution is obtained, which significantly improves the cycle stability and voltage retention of the material, while maintaining the advantages of low cost and high specific capacity.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a method for preparing a disordered phase structure lithium-rich manganese-based cathode material, comprising the following steps: (1) Mix manganese source, sodium source and lithium source in proportion, wherein the molar ratio of sodium source to lithium source is 1:9 to 9:1, and the molar ratio of total sodium source and lithium source to manganese source is 0.8 to 1.2:1. (2) Place the mixed raw materials in a ceramic boat and heat them in a heating furnace at a heating rate of 1~5℃ / min to 500~700℃, and keep them at that temperature for 10~30 hours to obtain a precursor material with a ribbon-like superstructure. (3) Mix the precursor material and molten salt at a molar ratio of 1:1 to 20 and grind them evenly; (4) Place the mixture in a porcelain boat and heat it to 200-400°C at a heating rate of 1-5°C / min under air, oxygen or argon atmosphere, and keep it at that temperature for 5-8 hours; (5) The treated sample was washed with deionized water and dried to obtain a lithium-rich manganese-based cathode material with a disordered phase structure.

[0006] Preferably, the manganese source is selected from one or more of MnCl2, MnCO3, MnNO3, and (CH3COO)2Mn.

[0007] Preferably, the sodium source is selected from one or more of NaCl, Na2CO3, NaNO3, and CH3COONa.

[0008] Preferably, the lithium source is selected from one or more of LiCl, Li2CO3, LiNO3, and CH3COOLi.

[0009] Preferably, the molten salt is selected from one or more of LiNO3, LiCl, NaCl, and NaNO3.

[0010] Preferably, the molar ratio of the sodium source to the lithium source is 7:3.

[0011] Preferably, the heat preservation time in step (2) is 15 to 25 hours.

[0012] Preferably, the heat preservation time in step (4) is 6 to 7 hours; the atmosphere of the heating furnace is oxygen.

[0013] Secondly, the present invention provides a lithium-rich manganese-based cathode material with a disordered phase structure, which is prepared by the above method and has a lithium-deficient structure with disordered Li@Mn6 honeycomb distribution.

[0014] Thirdly, the present invention provides a lithium-ion battery comprising the aforementioned disordered phase structure lithium-rich manganese-based cathode material.

[0015] Compared to existing technologies, it has the following beneficial effects: 1) A precursor with a banded superstructure was prepared by controlling the sodium-lithium ratio, which dispersed the Li@Mn6 superstructure. In subsequent preparations, a material with disordered Li@Mn6 distribution was obtained. The disordered Li@Mn6 distribution was achieved by controlling the structure, thereby improving the structural stability. 2) It does not introduce other transition metal ions, thus maintaining the material's low cost and environmental friendliness; 3) The preparation process is simple and suitable for large-scale production; 4) The material exhibits high specific capacity, excellent cycle stability and voltage retention, making it suitable for high energy density lithium-ion batteries. Attached Figure Description

[0016] Figure 1 This is an HADDF-STEM image of a precursor with a banded superstructure provided in an embodiment of the present invention; Figure 2 These are the rate performance diagrams for Embodiment 1 and Comparative Example 1 of the present invention; Figure 3 These are 1C long-cycle performance graphs of Embodiment 1 and Comparative Example 1 of the present invention; Figure 4These are in-situ electrochemical differential mass spectrometry test graphs of oxygen and carbon dioxide production during the first charge-discharge cycle of Embodiment 1 and Comparative Example 1 of the present invention. Figure 5 These are X-ray diffraction peak diagrams of the superlattice diffraction peaks of Embodiment 1 and Comparative Example 1 of the present invention; Figure 6 These are the distribution diagrams of the disordered Li@Mn6 superstructure in Embodiment 1 and the ordered Li@Mn6 superstructure in Comparative Example 1 of the present invention. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0018] Before providing a further detailed description of the present invention, the nouns and terms used in the embodiments of the present invention will be explained, and the nouns and terms used in the embodiments of the present invention shall be interpreted as follows.

[0019] This invention provides a disordered phase structure lithium-rich manganese-based cathode material and its preparation method. For the raw materials, the manganese source can be selected from one or more of MnCO3, MnNO3, and (CH3COO)2Mn. The sodium source can be selected from one or more of NaCl, Na2CO3, NaNO3, and CH3COONa. The lithium source can be selected from one or more of LiCl, Li2CO3, LiNO3, and CH3COOLi.

[0020] Here, the raw material ratio is as follows: the molar ratio of sodium source to lithium source is 1:9 to 9:1, preferably 2:8 to 8:2. The molar ratio of the total molar amount of sodium source and lithium source to the molar amount of manganese source is 0.8 to 1.2:1.

[0021] Here, the precursor preparation is as follows: the uniformly mixed raw materials are placed in a ceramic boat, and the temperature is increased to 500-700℃ at 1-5℃ / min under an air, oxygen or argon atmosphere, and held for 10-30 hours to obtain a precursor material with a banded superstructure.

[0022] Here, molten salt treatment is performed: the precursor and molten salt (such as LiNO3, LiCl, NaCl, NaNO3, etc.) are mixed at a molar ratio of 1:1 to 20 and ground evenly. The mixture is then heated to 200 to 400°C at a rate of 1 to 5°C / min under the same atmosphere and held at that temperature for 5 to 8 hours.

[0023] Here, post-processing: the reaction product is washed with deionized water and dried to obtain a disordered phase structure lithium-rich manganese-based cathode material.

[0024] Example 1 Example 1 Raw material ratio: The molar ratio of sodium source to lithium source is 7:3; the molar ratio of total sodium source and lithium source to manganese source is 1:1. Preparation process: Manganese source (MnCO) 3） Sodium source (Na2CO3) and lithium source (Li2CO3) were mixed evenly in the above proportions; the mixture was loaded into a ceramic boat and heated to 700℃ at 5℃ / min in an air atmosphere, and held for 20 hours to obtain a precursor material with a banded superstructure; the precursor was mixed with LiNO3 and LiCl molten salt at a molar ratio of 1:10 and ground for 10 minutes; the mixture was heated to 280℃ at 5℃ / min in an oxygen atmosphere and held for 6 hours; after the reaction was completed, the sample was washed with deionized water and dried at 80℃ for 12 hours to obtain a disordered phase structure lithium-rich manganese-based cathode material.

[0025] Performance results: The discharge specific capacity after activation at 0.1C rate is 275 mAh / g; the capacity retention rate reaches 71.1% after 200 cycles at 1C; the voltage decay rate is significantly reduced, and the structural stability is excellent.

[0026] Comparative Example 1 Raw material ratio: The molar ratio of sodium source to lithium source is 6:4; the molar ratio of total sodium and lithium source to manganese source is 1:1. Preparation process: The raw material mixing ratio was the same as in Example 1; the precursor preparation conditions were the same as in Example 1; no molten salt ion exchange treatment was performed; the precursor was directly washed and dried to obtain a conventional structure lithium-rich manganese-based cathode material.

[0027] Performance results: Please see Figures 1 to 3 The discharge specific capacity after activation at 0.1C is 244 mAh / g; after 200 cycles at 1C, the capacity retention is only 60.5%; and the structural stability is poor. Please refer to [link / reference]. Figure 4 Compared to Comparative Example 1, Example 1 can suppress oxygen production and improve the safety of the material. Please refer to [link / reference]. Figure 5 Example 1 has a disordered structure, while Comparative Example 1 has an ordered structure and exhibits superlattice diffraction peaks. Please refer to [link / reference]. Figure 6 Example 1 has a disordered Li@Mn6 superstructure, while Comparative Example 1 has an ordered Li@Mn6 superstructure.

[0028] Comparative analysis A comparison of Example 1 and Comparative Example 1 shows that the molten salt ion exchange treatment described in this invention, combined with a specific sodium-lithium ratio (7:3), can effectively construct a disordered Li@Mn6 superstructure distribution, significantly improving the rate performance and long-cycle stability of the material. In contrast, the comparative example material, despite having a similar ratio, showed a significant decrease in electrochemical performance without structural regulation, indicating that the construction of the disordered phase structure plays a crucial role in the material's performance.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for preparing a disordered phase structure lithium-rich manganese-based cathode material, characterized in that, Includes the following steps: (1) Mix manganese source, sodium source and lithium source in proportion, wherein the molar ratio of sodium source to lithium source is 1:9 to 9:1, and the molar ratio of total sodium source and lithium source to manganese source is 0.8 to 1.2:

1. (2) Place the mixed raw materials in a ceramic boat and heat them in a heating furnace at a heating rate of 1~5℃ / min to 500~700℃, and keep them at that temperature for 10~30 hours to obtain a precursor material with a ribbon-like superstructure. (3) Mix the precursor material and molten salt at a molar ratio of 1:1 to 20 and grind them evenly; (4) Place the mixture in a porcelain boat and heat it to 200-400°C at a heating rate of 1-5°C / min under air, oxygen or argon atmosphere, and keep it at that temperature for 5-8 hours; (5) The treated sample was washed with deionized water and dried to obtain a lithium-rich manganese-based cathode material with a disordered phase structure.

2. The preparation method according to claim 1, characterized in that, The manganese source is selected from one or more of MnCl2, MnCO3, MnNO3, and (CH3COO)2Mn.

3. The preparation method according to claim 1, characterized in that, The sodium source is selected from one or more of NaCl, Na2CO3, NaNO3, and CH3COONa.

4. The preparation method according to claim 1, characterized in that, The lithium source is selected from one or more of LiCl, Li2CO3, LiNO3, and CH3COOLi.

5. The preparation method according to claim 1, characterized in that, The molten salt is selected from one or more of LiNO3, LiCl, NaCl, and NaNO3.

6. The preparation method according to claim 1, characterized in that, The molar ratio of the sodium source to the lithium source is 7:

3.

7. The preparation method according to claim 1, characterized in that, The heat preservation time mentioned in step (2) is 15 to 25 hours.

8. The preparation method according to claim 1, characterized in that, The heat preservation time in step (4) is 6 to 7 hours; the atmosphere of the heating furnace is oxygen.

9. A lithium-rich manganese-based cathode material with a disordered phase structure, characterized in that, It is prepared by the method described in any one of claims 1 to 8 and has a lithium-deficient structure with disordered Li@Mn6 honeycomb distribution.

10. A lithium-ion battery, characterized in that, It includes the lithium-rich manganese-based cathode material with a disordered phase structure as described in claim 9.

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