Modified lithium-rich manganese-based positive electrode material and preparation method and application thereof

Abstract

The application provides a modified lithium-rich manganese-based positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: (1) mixing manganese salt, doped metal salt and terephthalic acid solution, and obtaining a doped Mn-MOF material through a solvothermal reaction; (2) mixing the doped Mn-MOF material with an oxidizing agent and a solvent, adjusting pH, and performing a high-pressure hydrothermal reaction to obtain a doped MnO2 material; (3) mixing the doped MnO2 material with a nickel source, a cobalt source and a lithium source, and performing a calcination treatment to obtain the modified lithium-rich manganese-based positive electrode material. The doped manganese dioxide is prepared in the manner of pre-preparing the doped Mn-MOF, which can ensure that the doped elements can be accurately doped into the target position, the elements doped in the bulk phase can stabilize the adjacent Mn-O, Co-O and Ni-O bonds, the migration energy barrier of Mn, Co and Ni is improved, and therefore the structural stability of the lithium-rich positive electrode material is greatly improved.

Description

Technical Field

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

[0002] High energy density remains a perpetual development trend for lithium-ion batteries. In lithium-ion batteries, the cathode material is crucial for improving energy density. Currently, commercially available cathode materials for power batteries mainly include olivine-structured LiFePO4 and layered LiNi. x Co y Mn 1-x-y O2, the electron transfer of these materials during the electrode reaction process is all through the metal cation pair (Fe). 2+ / Fe 3+ Ni 2+ / Ni 3+ / Ni 4+ Co 3+ / Co 4+ The charge compensation through redox reactions inherent in lithium-rich manganese-based cathode materials essentially limits their specific capacity. However, LRMO, due to its unique anionic redox reaction mechanism, achieves a high specific capacity exceeding 280 mAh / g within a voltage range of 2-4.8 V, paving the way for higher energy densities.

[0003] However, lithium-rich manganese-based cathode materials suffer from low intrinsic conductivity, irreversible loss of lattice oxygen, and the transformation from layered phase to spinel phase during cycling, resulting in poor rate performance, low initial coulombic efficiency, and rapid capacity and voltage decay, which limits their practical applications.

[0004] CN116639733A obtained a boron-cerium co-doped lithium-rich manganese-based cathode material by calcining a mixture of manganese cobalt hydroxide precursor, lithium source, cerium nitrate and sodium borohydride. The co-doping synergistic effect of cerium and boron ions can effectively reduce the increased transfer resistance of the cathode material during cycling, reduce the phase transition rate of the material, and maintain a high median voltage.

[0005] CN116605921A discloses a method for preparing tungsten-doped lithium-rich manganese-based cathode materials. Tungsten doping can alleviate the structural collapse caused by material phase transition, reduce impedance, improve charge transfer capability, and improve the thermal stability of the material, ultimately showing good cycle performance and rate performance.

[0006] Although the doping method described above can improve performance to some extent, it cannot prevent the discharge voltage from continuously decreasing due to phase transition. Furthermore, the added dopant elements tend to accumulate on the material surface and cannot regulate the crystal structure of the material. Summary of the Invention

[0007] The purpose of this invention is to provide a modified lithium-rich manganese-based cathode material, its preparation method, and its application. This invention prepares doped manganese dioxide by pre-preparing a doped Mn-MOF, which can ensure that the doped elements can be accurately incorporated into the target positions. The bulk doped elements can stabilize the adjacent Mn-O, Co-O, and Ni-O bonds, and enhance the migration energy barriers of Mn, Co, and Ni, thereby greatly improving the structural stability of the lithium-rich cathode material.

[0008] To achieve this objective, the present invention employs the following technical solution:

[0009] In a first aspect, the present invention provides a method for preparing a modified lithium-rich manganese-based cathode material, the method comprising the following steps:

[0010] (1) Manganese salt, doped metal salt and terephthalic acid solution are mixed and then subjected to solvothermal reaction to obtain doped Mn-MOF material;

[0011] (2) The doped Mn-MOF material is mixed with an oxidant and a solvent, and the pH is adjusted to carry out a high-pressure hydrothermal reaction to obtain a doped MnO2 material.

[0012] (3) The doped MnO2 material is mixed with a nickel source, a cobalt source and a lithium source, and then calcined to obtain the modified lithium-rich manganese-based cathode material.

[0013] This invention first synthesizes a cation-doped Mn-based bimetallic MOF via a solvothermal method, then converts it into element-doped MnO2 (M = Ru, Mg, Al, Fe) via hydrothermal conversion. Finally, it is mechanically mixed with nickel, cobalt, and lithium sources and calcined at high temperature to obtain an in-situ bulk-phase lithium-rich manganese-based cathode material doped with elements such as Ru, Mg, Al, and Fe. This invention, by doping Mn-MOF with metal elements before preparing doped MnO2 material, can alleviate phase transitions, thereby improving the structural stability of the crystal; simultaneously, it suppresses irreversible oxygen evolution, improves the first coulombic efficiency of the lithium-rich manganese-based cathode material (LRMO), and enhances the electrochemical performance of the LRMO cathode material.

[0014] Preferably, the manganese salt in step (1) includes any one or a combination of at least two of manganese sulfate, manganese nitrate, or manganese chloride.

[0015] Preferably, the doped metal salt includes any one or a combination of at least two of the following: chloride, nitrate or sulfate containing Ru, Mg, Al or Fe.

[0016] Preferably, the mass ratio of the manganese salt to the doped metal salt is (3-8):1, for example: 3:1, 4:1, 5:1, 6:1 or 8:1, etc.

[0017] Preferably, the solvent of the terephthalic acid solution includes any one or a combination of at least two of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, or methanol.

[0018] Preferably, the concentration of the terephthalic acid solution is 10-50 g / L, for example: 10 g / L, 20 g / L, 30 g / L, 40 g / L or 50 g / L.

[0019] Preferably, an alkaline solution is added and stirred before the solvothermal reaction in step (1).

[0020] Preferably, the concentration of the alkaline solution is 0.2 to 0.8 mol / L, for example: 0.2 mol / L, 0.3 mol / L, 0.5 mol / L, 0.6 mol / L or 0.8 mol / L, etc.

[0021] Preferably, the temperature of the solvothermal reaction is 90 to 120°C, for example: 90°C, 95°C, 100°C, 110°C or 120°C.

[0022] Preferably, the solvothermal reaction time is 8 to 12 hours, for example: 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0023] Preferably, the solvothermal reaction is followed by washing and drying.

[0024] Preferably, the detergent used for washing includes deionized water and / or ethanol.

[0025] Preferably, the oxidant in step (2) includes potassium permanganate.

[0026] Preferably, the mass ratio of the doped Mn-MOF material to the oxidant is (1.5 to 2.5):1, for example: 1.5:1, 1.8:1, 2:1, 2.2:1 or 2.5:1, etc.

[0027] Preferably, the solvent includes deionized water.

[0028] Preferably, the pH in step (2) is 0.5 to 1.5, for example: 0.5, 0.8, 1, 1.2 or 1.5, etc.

[0029] Preferably, the apparatus for the high-pressure hydrothermal reaction includes a high-pressure reactor.

[0030] Preferably, the temperature of the high-pressure hydrothermal reaction is 120-180°C, for example: 120°C, 130°C, 150°C, 160°C or 180°C.

[0031] Preferably, the high-pressure hydrothermal reaction time is 20 to 30 hours, for example: 20 hours, 22 hours, 25 hours, 28 hours or 30 hours.

[0032] Preferably, the high-pressure hydrothermal reaction is followed by centrifugation, washing, and drying.

[0033] Preferably, the detergent used for washing includes deionized water and / or ethanol.

[0034] Preferably, the nickel source in step (3) includes any one or a combination of at least two of nickel nitrate, nickel chloride, or nickel sulfate.

[0035] Preferably, the cobalt source includes any one or a combination of at least two of cobalt nitrate, cobalt chloride, or cobalt sulfate.

[0036] Preferably, the lithium source includes lithium hydroxide and / or lithium carbonate.

[0037] Preferably, the atmosphere for the roasting process in step (3) includes oxygen and / or air.

[0038] Preferably, the roasting process includes one-step roasting and two-step roasting.

[0039] Preferably, the temperature of the first-step calcination is 300-600℃, for example: 300℃, 350℃, 400℃, 500℃ or 600℃.

[0040] Preferably, the roasting time for the first step is 3 to 10 hours, for example: 3 hours, 5 hours, 6 hours, 8 hours or 10 hours.

[0041] Preferably, the temperature of the two-step roasting is 600-1000℃, for example: 600℃, 700℃, 800℃, 900℃ or 1000℃.

[0042] Preferably, the two-step roasting time is 10 to 20 hours, for example: 10 hours, 12 hours, 15 hours, 18 hours or 20 hours.

[0043] In a second aspect, the present invention provides a modified lithium-rich manganese-based cathode material, which is prepared by the method described in the first aspect.

[0044] Thirdly, the present invention provides a positive electrode sheet comprising the modified lithium-rich manganese-based positive electrode material as described in the second aspect.

[0045] Fourthly, the present invention provides a lithium-ion battery comprising a positive electrode as described in the third aspect.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) The present invention prepares doped manganese dioxide by pre-preparing doped Mn-MOF, which can ensure that the doped elements can be accurately doped into the target position and will not accumulate on the material surface. The bond energy between the doped metal and oxygen is higher than that between nickel, cobalt and manganese and oxygen, and has a stronger binding force on O, which can effectively slow down O loss and vacancy generation.

[0048] (2) This invention performs bulk doping on lithium-rich manganese-based cathode materials. The bulk doped elements can stabilize the adjacent Mn-O, Co-O, and Ni-O bonds, and increase the migration energy barriers of Mn, Co, and Ni, thereby greatly improving the structural stability of lithium-rich cathode materials. At the same time, the bulk doping of elements can increase the average valence state of the internal electronic structure, suppress the transformation of the material's cell structure from layered to spinel-like, and alleviate the Jahn-Teller effect.

[0049] (3) The modified lithium-rich manganese-based cathode material prepared by the method of the present invention has good performance, with a first-cycle capacity of more than 286.9 mAh / g and a capacity retention rate of more than 89.1% after 100 cycles. Detailed Implementation

[0050] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0051] Example 1

[0052] This embodiment provides a modified lithium-rich manganese-based cathode material, and the preparation method of the modified lithium-rich manganese-based cathode material is as follows:

[0053] (1) Weigh 3g of terephthalic acid (TPA) and dissolve it in 100mL of N,N-dimethylformamide (DMF). Then weigh 2g of manganese chloride and 0.57g of ruthenium trichloride and add them to the above solution. Stir well at room temperature, then add 10mL of 0.4mol / L NaOH dropwise. After stirring for 30min, transfer the solution to a high-pressure reactor and solvothermal react at 100℃ for 10h. After the reaction is complete and cooled to room temperature, collect the precipitate by centrifugation, wash it twice with deionized water and ethanol alternately, and then dry it to obtain Ru-doped Mn-MOF material.

[0054] (2) Add 1g of Ru-doped Mn-MOF material and 0.5g of potassium permanganate to 20mL of deionized water, adjust the pH to 1 by adding sulfuric acid dropwise, transfer to a high-pressure reactor, and hydrothermally react at 150℃ for 24h. After the reaction is completed and cooled to room temperature, collect the precipitate by centrifugation, wash twice with deionized water and ethanol alternately, and then dry to obtain Ru-doped MnO2 material;

[0055] (3) According to Li1.2 Mn 0.54 Co 0.13 Ni 0.13 The elemental ratios in O2 were determined by weighing Ru-doped MnO2 material, nickel nitrate, cobalt nitrate, and lithium hydroxide (with a slight excess of lithium hydroxide at 1.05 times the ratio of 1.2) and mixing them in a mortar. An appropriate amount of ethanol was added as a grinding aid. After thorough grinding, the mortar was placed in an oven and allowed to evaporate completely before further dry grinding. The uniformly ground powder was then calcined at 500°C in air for 5 hours, ground again, and then calcined at 900°C in air for 12 hours to obtain the modified lithium-rich manganese-based cathode material.

[0056] Example 2

[0057] This embodiment provides a modified lithium-rich manganese-based cathode material, and the preparation method of the modified lithium-rich manganese-based cathode material is as follows:

[0058] (1) Weigh 3g of terephthalic acid (TPA) and dissolve it in 100mL of N,N-dimethylformamide (DMF). Then weigh 2g of manganese chloride and 0.26g of magnesium chloride and add them to the above solution. Stir well at room temperature, then add 15mL of 0.2mol / L NaOH dropwise. After stirring for 30min, transfer the solution to a high-pressure reactor and solvothermal react at 90℃ for 12h. After the reaction is complete and cooled to room temperature, collect the precipitate by centrifugation, wash it twice with deionized water and ethanol alternately, and then dry it to obtain Mg-doped Mn-MOF material.

[0059] (2) Add 1.5g of Mg-doped Mn-MOF material and 1g of potassium permanganate to 30mL of deionized water, adjust the pH to 1.2 by adding sulfuric acid dropwise, transfer to a high-pressure reactor, and hydrothermally react at 120℃ for 30h. After the reaction is completed and cooled to room temperature, collect the precipitate by centrifugation, wash twice with deionized water and ethanol alternately, and then dry to obtain Mg-doped MnO2 material;

[0060] (3) According to Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 The elemental ratios in O2 were determined by weighing Mg-doped MnO2 material, nickel nitrate, cobalt nitrate, and lithium hydroxide (with a slight excess of lithium hydroxide at 1.05 times the ratio of 1.2) and mixing them in a mortar. An appropriate amount of ethanol was added as a grinding aid. After thorough grinding, the mortar was placed in an oven and allowed to evaporate completely before further dry grinding. The uniformly ground powder was then calcined at 400°C in air for 10 hours, ground again, and then calcined at 800°C in air for 15 hours to obtain the modified lithium-rich manganese-based cathode material.

[0061] Example 3

[0062] This embodiment provides a modified lithium-rich manganese-based cathode material, and the preparation method of the modified lithium-rich manganese-based cathode material is as follows:

[0063] (1) Weigh 3g of terephthalic acid (TPA) and dissolve it in 100mL of N,N-dimethylformamide (DMF). Then weigh 2.4g of manganese chloride and 0.37g of aluminum chloride and add them to the above solution. Stir well at room temperature, then add 5mL of 0.8mol / L NaOH dropwise. After stirring for 30min, transfer the solution to a high-pressure reactor and solvothermal react at 120℃ for 8h. After the reaction is complete and cooled to room temperature, collect the precipitate by centrifugation, wash it twice with deionized water and ethanol alternately, and then dry it to obtain Al-doped Mn-MOF material.

[0064] (2) Add 2.5g of Al-doped Mn-MOF material and 1g of potassium permanganate to 30mL of deionized water, adjust the pH to 1 by adding sulfuric acid dropwise, transfer to a high-pressure reactor, and hydrothermally react at 180℃ for 20h. After the reaction is completed and cooled to room temperature, collect the precipitate by centrifugation, wash twice with deionized water and ethanol alternately, and then dry to obtain Al-doped MnO2 material;

[0065] (3) According to Li 1.2 Mn 0.54 Co 0.13 Ni 0.13 The elemental ratios in O2 were determined by weighing Al-doped MnO2 material, nickel nitrate, cobalt nitrate, and lithium hydroxide (with a slight excess of lithium hydroxide at 1.05 times the ratio of 1.2) and mixing them in a mortar. An appropriate amount of ethanol was added as a grinding aid. After thorough grinding, the mortar was placed in an oven and allowed to evaporate completely before further dry grinding. The uniformly ground powder was then calcined at 600°C in air for 3 hours, ground again, and then calcined at 800°C in air for 15 hours to obtain the modified lithium-rich manganese-based cathode material.

[0066] Example 4

[0067] The only difference between this embodiment and Embodiment 1 is that the mass ratio of manganese salt (manganese chloride) to doped metal salt (ruthenium trichloride) is 2:1. All other conditions and parameters are exactly the same as in Embodiment 1.

[0068] Example 5

[0069] The only difference between this embodiment and Embodiment 1 is that the mass ratio of manganese salt (manganese chloride) to doped metal salt (ruthenium trichloride) is 10:1. All other conditions and parameters are exactly the same as in Embodiment 1.

[0070] Example 6

[0071] The only difference between this embodiment and Embodiment 1 is that the mass ratio of the doped Mn-MOF material to the oxidant (potassium permanganate) is 1:1. All other conditions and parameters are exactly the same as in Embodiment 1.

[0072] Example 7

[0073] The only difference between this embodiment and Embodiment 1 is that the mass ratio of the doped Mn-MOF material to the oxidant (potassium permanganate) is 3:1. All other conditions and parameters are exactly the same as in Embodiment 1.

[0074] Comparative Example 1

[0075] The only difference between this comparative example and Example 1 is that no doping element is added; all other conditions and parameters are exactly the same as in Example 1.

[0076] Performance testing:

[0077] Using the materials prepared in the examples and comparative examples as positive electrodes, the active material, Super P, and polyvinylidene fluoride (PVDF) were mixed and dispersed in N-methylpyrrolidone (NMP) at a weight ratio of 90:5:5 to form a uniform slurry. The slurry was then cast onto aluminum foil using a doctor blade method and vacuum dried at 60°C for 12 hours to obtain LRMO positive electrode sheets. CR-2025 coin cells were assembled in a glove box, with lithium metal sheets as the negative electrode, a PP / PE / PP microporous membrane as the separator, and 1M LiPF6 (DMC:DEC = 1:1) as the electrolyte. To ensure sufficient internal electrolyte wetting of the electrodes, the assembled coin cells were allowed to stand at room temperature for 24 hours before testing. The assembled coin half-cells were subjected to constant current charge-discharge testing using a Blue Battery testing system, with a voltage range of 2.0–4.8V (vs. Li). + / Li), at room temperature, after two weeks of activation at 0.1C, the battery was subjected to performance tests for different cycles at 1C. The test results are shown in Table 1:

[0078] Table 1

[0079] Capacity (mAh / g) First-efficacy (%) Capacity retention rate (%) after 100 cycles Example 1 287.8 84.9 89.7 Example 2 286.9 84.3 89.5 Example 3 287.1 84.4 89.1 Example 4 265.5 84.7 90.1 Example 5 245.3 76.8 75.9 Example 6 262.5 82.5 88.4 Example 7 271.4 81.9 86.3 Comparative Example 1 235.2 73.8 56.7

[0080] As can be seen from Table 1, the modified lithium-rich manganese-based cathode material prepared by the method of the present invention, as obtained from Examples 1-3, has good performance, with an initial capacity of over 286.9 mAh / g and a capacity retention rate of over 89.1% after 100 cycles.

[0081] A comparison of Examples 1 and 4-5 shows that the mass ratio of manganese salt to doped metal salt affects the performance of the modified lithium-rich manganese-based cathode material described in this invention. Controlling the mass ratio of manganese salt to doped metal salt to 3-8:1 results in a better performance of the lithium-rich manganese-based cathode material. If the amount of doped metal salt added is too small, the improvement effect on the structure and electrochemical performance of the material is limited. If the amount of doped metal salt added is too large, the doping element does not completely enter the material lattice, resulting in an increase in the inactive phase and a decrease in the capacity of the material.

[0082] A comparison of Examples 1 and 6-7 shows that the mass ratio of doped Mn-MOF material to oxidant affects the performance of the modified lithium-rich manganese-based cathode material described in this invention. Controlling the mass ratio of doped Mn-MOF material to oxidant to 1.5–2.5:1 yields a better-performing lithium-rich manganese-based cathode material. If the amount of oxidant added is too small, the resulting particles are smaller, side reactions are aggravated, and the cycle life deteriorates. If the amount of oxidant added is too large, the resulting particles have a larger particle size, a longer ion-electron transport distance, and lower capacity.

[0083] As can be seen from the comparison between Example 1 and Comparative Example 1, the present invention performs bulk doping on lithium-rich manganese-based cathode materials. The bulk-doped elements can stabilize the adjacent Mn-O, Co-O, and Ni-O bonds, and enhance the migration energy barriers of Mn, Co, and Ni, thereby greatly improving the structural stability of lithium-rich cathode materials. At the same time, the bulk doping of elements can increase the average valence state of the internal electronic structure, suppress the transformation of the material's cell structure from layered to spinel-like, and alleviate the Jahn-Teller effect.

[0084] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a modified lithium-rich manganese-based cathode material, characterized in that, The preparation method includes the following steps: (1) Manganese salt, doped metal salt and terephthalic acid solution are mixed and subjected to solvothermal reaction to obtain doped Mn-MOF material; (2) The doped Mn-MOF material is mixed with an oxidant and a solvent, and the pH is adjusted to carry out a high-pressure hydrothermal reaction to obtain a doped MnO2 material; (3) The doped MnO2 material is mixed with a nickel source, a cobalt source and a lithium source, and then calcined to obtain the modified lithium-rich manganese-based cathode material; The mass ratio of the manganese salt to the doped metal salt is (3~8):

1.

2. The preparation method according to claim 1, characterized in that, The manganese salt in step (1) includes any one or a combination of at least two of manganese sulfate, manganese nitrate, or manganese chloride.

3. The preparation method according to claim 1, characterized in that, The doped metal salt includes any one or a combination of at least two of the following: chlorides, nitrates, or sulfates containing Ru, Mg, Al, or Fe.

4. The preparation method according to claim 1, characterized in that, The solvent for the terephthalic acid solution includes any one or a combination of at least two of N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, or methanol.

5. The preparation method according to claim 1, characterized in that, The concentration of the terephthalic acid solution is 10~50 g / L.

6. The preparation method according to claim 1, characterized in that, Before the solvothermal reaction in step (1), add alkali solution and stir.

7. The preparation method according to claim 6, characterized in that, The concentration of the alkaline solution is 0.2~0.8 mol / L.

8. The preparation method according to claim 1, characterized in that, The temperature of the solvothermal reaction is 90~120℃.

9. The preparation method according to claim 1, characterized in that, The solvothermal reaction takes 8 to 12 hours.

10. The preparation method according to claim 1, characterized in that, The solvent thermal reaction is followed by washing and drying.

11. The preparation method according to claim 10, characterized in that, The detergent used for washing includes deionized water and / or ethanol.

12. The preparation method according to claim 1, characterized in that, The oxidant in step (2) includes potassium permanganate.

13. The preparation method according to claim 1, characterized in that, The mass ratio of the doped Mn-MOF material to the oxidant is (1.5~2.5):

1.

14. The preparation method according to claim 1, characterized in that, The solvent in step (2) includes deionized water.

15. The preparation method according to claim 1, characterized in that, The pH value in step (2) is 0.5 to 1.

5.

16. The preparation method according to claim 1, characterized in that, The apparatus for the high-pressure hydrothermal reaction includes a high-pressure reactor.

17. The preparation method according to claim 1, characterized in that, The temperature of the high-pressure hydrothermal reaction is 120~180℃.

18. The preparation method according to claim 1, characterized in that, The high-pressure hydrothermal reaction takes 20-30 hours.

19. The preparation method according to claim 1, characterized in that, The high-pressure hydrothermal reaction is followed by centrifugation, washing, and drying.

20. The preparation method according to claim 19, characterized in that, The detergent used for washing includes deionized water and / or ethanol.

21. The preparation method according to claim 1, characterized in that, The nickel source in step (3) includes any one or a combination of at least two of nickel nitrate, nickel chloride, or nickel sulfate.

22. The preparation method according to claim 1, characterized in that, The cobalt source includes any one or a combination of at least two of cobalt nitrate, cobalt chloride, or cobalt sulfate.

23. The preparation method according to claim 1, characterized in that, The lithium source includes lithium hydroxide and / or lithium carbonate.

24. The preparation method according to claim 1, characterized in that, The atmosphere for the roasting process in step (3) includes oxygen and / or air.

25. The preparation method according to claim 1, characterized in that, The roasting process includes one-step roasting and two-step roasting.

26. The preparation method according to claim 25, characterized in that, The roasting temperature in the first step is 300~600℃.

27. The preparation method according to claim 25, characterized in that, The roasting time for the first step is 3 to 10 hours.

28. The preparation method according to claim 25, characterized in that, The temperature for the two-step roasting is 600~1000℃.

29. The preparation method according to claim 25, characterized in that, The two-step roasting time is 10~20 hours.

30. A modified lithium-rich manganese-based cathode material, characterized in that, The modified lithium-rich manganese-based cathode material is prepared by the method described in any one of claims 1-29.

31. A positive electrode plate, characterized in that, The positive electrode comprises the modified lithium-rich manganese-based positive electrode material as described in claim 30.

32. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode as described in claim 31.