Doped coated lithium-rich manganese-based positive electrode material, preparation method therefor and use thereof

Abstract

The present application provides a doped coated lithium-rich manganese-based positive electrode material, a preparation method therefor, and a use thereof. The preparation method comprises the following steps: (1) concurrently injecting a metal salt solution, a precipitant, and a complexing agent into a base solution, starting stirring, then concurrently injecting a molybdenum source solution, and carrying out a one-step coprecipitation reaction; (2) replacing the molybdenum source solution with a lanthanum source solution and carrying out a two-step coprecipitation reaction to obtain a modified lithium-rich manganese-based precursor; (3) mixing the modified lithium-rich manganese-based precursor with a lithium source and carrying out a one-step sintering treatment to obtain a primary sintered material; and (4) mixing the primary sintered material with an aluminum source and a calcium source and carrying out a two-step sintering treatment to obtain the doped coated lithium-rich manganese-based positive electrode material. The doped coated lithium-rich manganese-based positive electrode material prepared by the method of the present application has relatively high conductivity, exhibits good coulombic efficiency, and has excellent cycling stability and voltage decay resistance effect.

Description

A doped and coated lithium-rich manganese-based positive electrode material and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of lithium-ion batteries and relates to a doped and coated lithium-rich manganese-based positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-rich manganese-based cathode materials have attracted widespread attention due to their high energy density and discharge capacity, which is twice that of current cathode materials. However, they have low electrical conductivity, and the contact resistance between the electrode and the electrolyte increases during high-rate charge and discharge. Combined with concentration polarization and side reactions, these materials exhibit poor performance at high-rate charge and discharge in actual power battery applications, resulting in low initial charge and discharge coulombic efficiency and poor cycling performance. This leads to a series of problems, making them far from practical application.

[0003] CN108557905A discloses a lithium-rich manganese-based material precursor, which is a lithium-rich manganese-based material carbonate precursor with a flaky morphology. The preparation process of the lithium-rich manganese-based material precursor includes: simultaneously pumping a mixed salt solution, a precipitant, and a complexing agent into a reactor at a rate of 0.12L / h to 0.9L / h, controlling the reaction temperature to 35 to 65°C, the pH value to 7.5 to 8.5, and the stirring speed to 400 to 1000rpm. After the reaction is completed, aging for 5 to 20 hours, separating, washing, and drying the precipitate to obtain the flaky lithium-rich manganese-based material carbonate precursor. In the process of preparing the lithium-rich manganese-based material precursor, the particle size of the lithium-rich manganese-based material precursor is difficult to control, and fine particles are easily obtained, and the reaction cycle is long.

[0004] CN104466162A discloses a method for preparing a gradient lithium-rich manganese-based precursor and a gradient lithium-rich manganese-based positive electrode material. The method comprises preparing a mixed solution A, a mixed solution B, and a solution C with different manganese ion contents, and sequentially adding them to a first reactor, a second reactor, and a third reactor for reaction. The first reactor, the second reactor, and the third reactor are connected in series for a cyclic reaction to obtain a gradient lithium-rich manganese-based precursor. The preparation process of the gradient lithium-rich manganese-based precursor is complex, the reaction cycle is long, and it is difficult to industrialize.

[0005] The preparation process of the above-mentioned lithium-rich manganese-based positive electrode material is complicated, and the cycle performance of the obtained material is poor and the coulombic efficiency is low, making it difficult to apply in practice.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] The present application provides a doped and coated lithium-rich manganese-based positive electrode material, a preparation method and application thereof. The doped and coated lithium-rich manganese-based positive electrode material prepared by the method described in the present application has high electrical conductivity, exhibits good coulombic efficiency, and has excellent cycle stability and anti-voltage decay effect.

[0009] In a first aspect, the present application provides a method for preparing a doped and coated lithium-rich manganese-based positive electrode material, the preparation method comprising the following steps:

[0010] (1) injecting a metal salt solution, a precipitant, and a complexing agent into a bottom solution in parallel, and then stirring the solution and injecting a molybdenum source solution into the bottom solution in parallel to perform a one-step coprecipitation reaction;

[0011] (2) replacing the molybdenum source solution with a lanthanum source solution, and performing a two-step coprecipitation reaction to obtain a modified lithium-rich manganese-based precursor;

[0012] (3) mixing the modified lithium-rich manganese-based precursor with a lithium source and performing a one-step sintering treatment to obtain a sintered material;

[0013] (4) The single-sintered material is mixed with an aluminum source and a calcium source, and subjected to a two-step sintering treatment to obtain the doped and coated lithium-rich manganese-based positive electrode material.

[0014] The present application sequentially dopes molybdenum and lanthanum into a lithium-rich manganese-based precursor. The molybdenum element is doped at the center of the precursor. Its presence minimizes the primary particle size and maintains the grain structure of the precursor within a wide range of lithiation (calcination) temperatures. In addition, it affects the crystallinity of the layered nickel-rich positive electrode material, increases the calcination (lithiation) temperature for forming the optimal crystal structure, and significantly improves its cycle stability. The lanthanum element precursor is doped on the outer side, and the La element supports the spatial structure of the precursor and stabilizes the precursor structure. The synergistic effect of the two can better improve the electrochemical properties of its lithium-rich layered oxide. Coating a composite coating of aluminum and calcium on the surface of the positive electrode material can greatly increase the energy barrier for oxygen release from the lithium-rich material to stabilize the surface oxygen of the Li-rich material. The lithium-rich electrode prepared from the doped and coated lithium-rich manganese-based positive electrode material described in the present application exhibits excellent cycle performance and reduces the voltage decay of the lithium-rich material.

[0015] In one embodiment, the molar ratio of manganese, nickel and cobalt in the metal salt solution of step (1) is x:y:z, x>0.5, 0≥y>0.5, 0≥z>0.5, x+y+z=1.

[0016] In one embodiment, the precipitating agent comprises an alkali solution.

[0017] In one embodiment, the complexing agent comprises aqueous ammonia.

[0018] In one embodiment, the base liquid includes alkali solution and ammonia water.

[0019] In one embodiment, the molybdenum source solution comprises an ammonium molybdate solution.

[0020] In one embodiment, the pH of the one-step coprecipitation reaction in step (1) is 8 to 9, for example, 8, 8.2, 8.5, 8.8 or 9.

[0021] In one embodiment, the temperature of the one-step coprecipitation reaction is 70-80°C, for example, 70°C, 72°C, 75°C, 78°C or 80°C.

[0022] In one embodiment, the endpoint of the one-step coprecipitation reaction is that the particle size D501 in the system is 2 to 4 μm, for example, 2 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm.

[0023] In one embodiment, the lanthanum source solution in step (2) comprises a lanthanum sulfate solution.

[0024] In one embodiment, the endpoint of the two-step coprecipitation reaction is that the particle size D502-D501 in the system is 1.5 to 3 μm, for example, 1.5 μm, 2.5 μm, 3 μm, 3.5 μm or 4 μm.

[0025] In one embodiment, the doping amount of molybdenum element in the modified lithium-rich manganese-based precursor in step (2) is 2000-4000 ppm, for example: 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm or 4000 ppm.

[0026] In one embodiment, the doping amount of lanthanum in the modified lithium-rich manganese-based precursor is 2000-4000 ppm, for example, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm or 4000 ppm.

[0027] In one embodiment, the lithium source in step (3) includes lithium hydroxide and / or lithium carbonate.

[0028] In one embodiment, the one-step sintering process includes one-stage sintering and two-stage sintering.

[0029] In one embodiment, the temperature of the first stage sintering is 400-600°C, for example, 400°C, 450°C, 500°C, 550°C or 600°C.

[0030] In one embodiment, the holding time of the sintering stage is 6 to 10 hours, for example, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours.

[0031] In one embodiment, the temperature of the second stage sintering is 800-1200°C, for example, 800°C, 900°C, 1000°C, 1100°C or 1200°C.

[0032] In one embodiment, the second-stage sintering time is 20 to 30 hours, for example, 20 hours, 22 hours, 24 hours, 27 hours or 30 hours.

[0033] In one embodiment, the aluminum source in step (4) comprises aluminum oxide.

[0034] In one embodiment, the mass ratio of the aluminum source to the sintered material is 1:(95-100), for example, 1:95, 1:96, 1:98, 1:99 or 1:100.

[0035] In one embodiment, the calcium source comprises calcium fluoride.

[0036] In one embodiment, the mass ratio of the calcium source to the calcined material is 1:(95-100), for example: 1:95, 1:96, 1:98, 1:99 or 1:100, etc.

[0037] In one embodiment, the temperature of the two-step sintering treatment is 800-1200°C, for example, 800°C, 900°C, 1000°C, 1100°C or 1200°C.

[0038] In one embodiment, the two-step sintering treatment takes 8 to 12 hours, for example, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours.

[0039] In a second aspect, the present application provides a doped and coated lithium-rich manganese-based positive electrode material, which is prepared by the method described in the first aspect.

[0040] In a third aspect, the present application provides a positive electrode plate, which comprises the doped and coated lithium-rich manganese-based positive electrode material as described in the second aspect.

[0041] In a fourth aspect, the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode sheet as described in the third aspect.

[0042] Compared with the related art, this application has the following beneficial effects:

[0043] (1) The doped and coated lithium-rich manganese-based positive electrode material prepared by the method described in the present application has high electrical conductivity, exhibits good coulombic efficiency, and has excellent cycle stability and resistance to voltage decay.

[0044] (2) The battery made of the doped and coated lithium-rich manganese-based positive electrode material described in this application can achieve an initial efficiency of more than 86.9%, an initial discharge capacity of more than 268.6 mAh / g, and a 50-week capacity retention rate of more than 95.3%.

[0045] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0046] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0047] Example 1

[0048] This embodiment provides a doped and coated lithium-rich manganese-based positive electrode material. The preparation method of the doped and coated lithium-rich manganese-based positive electrode material is as follows:

[0049] (1) According to the molar ratio of Ni:Co:Mn=2:2:6, a sulfate solution, 40% NaOH solution and 22% ammonia water were prepared. 800L of pure water was added to the reactor, and then ammonia water was added to make the pH value of the bottom liquid reach about 8.5. The temperature of the reactor was maintained at 80°C. N2 was introduced throughout the reaction to prevent oxidation. The sulfate solution was uniformly added to the reactor at a feeding rate of 70L / h. At the same time, a mixed solution of ammonia water and alkali solution was added to control the pH value of the reaction environment between 8.5 and 8.8. The stirring was turned on at a speed of 500rpm. After the reaction started, the ammonium molybdate solution was injected. When the particle size reached 3μm, the ammonium molybdate solution pump was turned off. The molybdenum doping amount was 3000ppm.

[0050] (2) Turn on the lanthanum sulfate solution pump, and when the precursor grows to 5 μm, turn off the metering pump to stop the reaction. The lanthanum doping amount is 3000 ppm. The reaction material is filtered, washed, dried at 160 ° C, and sieved to obtain a modified lithium-rich manganese-based precursor;

[0051] (3) The modified lithium-rich manganese-based precursor and the lithium source are mixed according to Li / M=1.02, placed in a roller kiln, first heated to 500°C and kept warm for 8 hours, then continued to heat to about 1000°C and kept warm for 24 hours, and then slowly cooled to obtain a fired material;

[0052] (4) The calcined material and the ground Al2O3 (the mass ratio of Al2O3 to the calcined material is 1:96) and CaF2 (the mass ratio of CaF2 to the calcined material is 1:95) are fully mixed in a ball mill, and then placed in a roller kiln and heat-treated at 1000°C in an air atmosphere for 10 hours to obtain the doped coated lithium-rich manganese-based positive electrode material.

[0053] Example 2

[0054] This embodiment provides a doped and coated lithium-rich manganese-based positive electrode material. The preparation method of the doped and coated lithium-rich manganese-based positive electrode material is as follows:

[0055] (1) According to the molar ratio of Ni:Co:Mn=2:1:7, a sulfate solution, a 40% NaOH solution and a 22% ammonia solution were prepared. 800L of pure water was added to the reactor, and then ammonia solution was added to make the pH value of the bottom liquid reach about 8.5. The temperature of the reactor was maintained at 75°C. N2 was introduced throughout the reaction to prevent oxidation. The sulfate solution was uniformly added to the reactor at a feeding rate of 70L / h. At the same time, a mixed solution of ammonia solution and alkali solution was added to control the pH value of the reaction environment between 8.5 and 8.8. The stirring was turned on at a speed of 500rpm. After the reaction started, the ammonium molybdate solution was injected. When the particle size reached 3.5μm, the ammonium molybdate solution pump was turned off. The molybdenum doping amount was 2000ppm.

[0056] (2) Turn on the lanthanum sulfate solution pump, and when the precursor grows to 5.2 μm, turn off the metering pump to stop the reaction. The lanthanum doping amount is 2500 ppm. The reaction material is filtered, washed, dried at 160° C., and sieved to obtain a modified lithium-rich manganese-based precursor;

[0057] (3) The modified lithium-rich manganese-based precursor and the lithium source are mixed according to Li / M=1.02, placed in a roller kiln, first heated to 400°C and kept warm for 10 hours, then continued to heat to about 800°C and kept warm for 30 hours, and then slowly cooled to obtain a fired material;

[0058] (4) The calcined material and the ground Al2O3 (the mass ratio of Al2O3 to the calcined material is 1:100) and CaF2 (the mass ratio of CaF2 to the calcined material is 1:99) are fully mixed in a ball mill, and then placed in a roller kiln and heat-treated at 800°C in an air atmosphere for 12 hours to obtain the doped and coated lithium-rich manganese-based positive electrode material.

[0059] Example 3

[0060] This embodiment provides a doped and coated lithium-rich manganese-based positive electrode material. The preparation method of the doped and coated lithium-rich manganese-based positive electrode material is as follows:

[0061] (1) According to the molar ratio of Ni:Co:Mn=1:2:7, a sulfate solution, a 40% NaOH solution and a 22% ammonia solution were prepared. 800L of pure water was added to the reactor, and then ammonia solution was added to make the pH value of the bottom liquid reach about 8.5. The temperature of the reactor was maintained at 70°C. N2 was introduced throughout the reaction to prevent oxidation. The sulfate solution was uniformly added to the reactor at a feeding rate of 70L / h. At the same time, a mixed solution of ammonia solution and alkali solution was added to control the pH value of the reaction environment between 8.2 and 8.5. The stirring was turned on at a speed of 500rpm. After the reaction started, the ammonium molybdate solution was injected. When the particle size reached 4μm, the ammonium molybdate solution pump was turned off. The molybdenum doping amount was 4000ppm.

[0062] (2) Turn on the lanthanum sulfate solution pump, and when the precursor grows to 5.8 μm, turn off the metering pump to stop the reaction. The lanthanum doping amount is 3500 ppm. The reaction material is filtered, washed, dried at 160 ° C, and sieved to obtain a modified lithium-rich manganese-based precursor;

[0063] (3) The modified lithium-rich manganese-based precursor and the lithium source were mixed according to Li / M=1.02, placed in a roller kiln, first heated to 600°C and kept warm for 8 hours, then continued to heat to about 1200°C and kept warm for 20 hours, and then slowly cooled to obtain a fired material;

[0064] (4) The calcined material and the ground Al2O3 (the mass ratio of Al2O3 to the calcined material is 1:95) and CaF2 (the mass ratio of CaF2 to the calcined material is 1:95) are fully mixed in a ball mill, and then placed in a roller kiln and heat-treated at 1200°C in an air atmosphere for 8 hours to obtain the doped and coated lithium-rich manganese-based positive electrode material.

[0065] Example 4

[0066] The only difference between this embodiment and embodiment 1 is that the doping amount of molybdenum is 1000 ppm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0067] Example 5

[0068] The only difference between this embodiment and embodiment 1 is that the doping amount of molybdenum is 5000 ppm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0069] Example 6

[0070] The only difference between this embodiment and embodiment 1 is that the doping amount of lanthanum is 1000 ppm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0071] Example 7

[0072] The only difference between this embodiment and embodiment 1 is that the doping amount of lanthanum is 5000 ppm, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0073] Example 8

[0074] The only difference between this embodiment and embodiment 1 is that the one-step sintering is performed at 1000° C., and the other conditions and parameters are exactly the same as those in embodiment 1.

[0075] Comparative Example 1

[0076] The only difference between this comparative example and Example 1 is that no molybdenum source solution is added, and other conditions and parameters are exactly the same as those in Example 1.

[0077] Comparative Example 2

[0078] The only difference between this comparative example and Example 1 is that no lanthanum source solution is added, and other conditions and parameters are exactly the same as those in Example 1.

[0079] Comparative Example 3

[0080] The only difference from Example 1 is that the lanthanum source solution is added first and then the molybdenum source solution is added. Other conditions and parameters are exactly the same as those in Example 1.

[0081] Comparative Example 4

[0082] The only difference from Example 1 is that no calcium source and aluminum source are added for coating, and other conditions and parameters are exactly the same as those in Example 1.

[0083] Performance testing:

[0084] The positive electrode materials obtained in the examples and comparative examples were used to prepare button batteries. The specific preparation method was as follows: a slurry was applied at a ratio of 90 (main material): 5 (polyvinylidene fluoride PVDF): 5 (conductive agent acetylene black) to form a pole piece, a metal lithium sheet was used as a counter electrode, the diaphragm model was Celgard 2500, and a 1 mol / L lithium hexafluorophosphate solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) (the volume ratio of EC to DMC was 1:1) was used as the electrolyte. CR2032 button batteries were assembled in an argon glove box (wherein water <0.01 ppm and oxygen <0.01 ppm). Finally, the batteries were placed in a blue electric test system for electrical performance testing.

[0085] The electrical performance test conditions are as follows: charge and discharge voltage range 2.0V-4.8V, test temperature 25℃, 0.1C / 0.1C cycle for 1 week to test the initial charge and discharge capacity of the battery, and use this to calculate the first efficiency, and 1C / 1C cycle for 50 weeks to test the cycle performance of the battery. The test results are shown in Table 1:

[0086] Table 1

[0087] As can be seen from Table 1, from Examples 1-3, the battery prepared by the doped and coated lithium-rich manganese-based positive electrode material described in this application can achieve an initial efficiency of more than 86.9%, an initial discharge capacity of more than 268.6 mAh / g, and a 50-week capacity retention rate of more than 95.3%.

[0088] By comparing Example 1 with Examples 4-5, it can be seen that during the preparation process of the doped coated lithium-rich manganese-based positive electrode material described in the present application, the doping amount of molybdenum will affect its performance. When the doping amount of molybdenum is controlled at 2000-4000 ppm, the performance of the doped coated lithium-rich manganese-based positive electrode material is better. If the doping amount of molybdenum is too high, the crystallinity of the Ni-rich layered positive electrode material will be damaged; if the doping amount of molybdenum is too low, the fine-grained structure of the precursor cannot be maintained within a wide temperature range.

[0089] By comparing Example 1 with Examples 6-7, it can be seen that during the preparation process of the doped coated lithium-rich manganese-based positive electrode material described in the present application, the doping amount of lanthanum will affect its performance. The doping amount of lanthanum is controlled at 2000-4000ppm, and the performance of the doped coated lithium-rich manganese-based positive electrode material is better. If the lanthanum doping amount is too high, the discharge capacity and rate performance of the material will not be greatly improved. If the lanthanum doping amount is too low, the Li + The hindrance of transfer at the electrode-electrode interface has little effect on improving the electrode kinetics.

[0090] As can be seen from the comparison between Example 1 and Example 8, the present application produces a single-fired material through two-stage sintering. The mixed coating layer structure formed during the high-temperature calcination of the outer layer of the precursor and doped with the same elements as the inner part of the precursor can make the outer oxide and the inner precursor structure more tightly combined, significantly reducing the problem of shedding of the nano-oxide layer, so that the co-coating method can exert a synergistic effect and comprehensively improve the structural stability of the lithium-ion battery ternary precursor.

[0091] From the comparison between Example 1 and Comparative Examples 1-2, it can be seen that the present application doped molybdenum and lanthanum into the lithium-rich manganese-based positive electrode material, and the synergistic effect of the two can better improve the electrochemical performance of its lithium-rich layered oxide.

[0092] By comparing Example 1 and Comparative Example 3, it can be seen that the present application sequentially dopes molybdenum and lanthanum into the lithium-rich manganese-based precursor. Molybdenum is doped at the center of the precursor. Its presence minimizes the primary particle size and maintains the grain structure of the precursor within a wide lithiation (calcination) temperature range. In addition, it affects the crystallinity of the layered nickel-rich positive electrode material, increases the calcination (lithiation) temperature for forming the optimal crystal structure, and significantly improves its cycle stability. The lanthanum precursor is doped on the outer side. The La element supports the spatial structure of the precursor and stabilizes the precursor structure. The two can play a better synergistic role. Otherwise, the synergistic effect is significantly reduced.

[0093] From the comparison between Example 1 and Comparative Example 4, it can be seen that the composite coating layer of aluminum and calcium coated on the surface of the positive electrode material in the present application can greatly increase the energy barrier for oxygen release of the lithium-rich material and thus stabilize the surface oxygen of the Li-rich material.

[0094] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for preparing a doped and coated lithium-rich manganese-based positive electrode material, comprising the following steps: (1) injecting a metal salt solution, a precipitant and a complexing agent into a bottom solution in parallel, and then injecting a molybdenum source solution into the bottom solution in parallel after stirring to perform a one-step coprecipitation reaction; (2) replacing the molybdenum source solution with a lanthanum source solution, performing a two-step coprecipitation reaction, and obtaining a modified lithium-rich manganese-based precursor; (3) mixing the modified lithium-rich manganese-based precursor with a lithium source and performing a one-step sintering treatment to obtain a sintered material; (4) The one-sintered material is mixed with an aluminum source and a calcium source, and subjected to a two-step sintering treatment to obtain the doped and coated lithium-rich manganese-based positive electrode material.

2. The preparation method according to claim 1, wherein The molar ratio of manganese, nickel and cobalt in the metal salt solution of step (1) is x:y:z, x>0.5, 0≥y>0.5, 0≥z>0.5, x+y+z=1; Optionally, the precipitant comprises alkali solution; Optionally, the complexing agent includes aqueous ammonia; Optionally, the base liquid includes alkali solution and ammonia water; Optionally, the molybdenum source solution includes ammonium molybdate solution.

3. The preparation method according to claim 1 or 2, wherein: The pH of the one-step coprecipitation reaction in step (1) is 8 to 9; Optionally, the temperature of the one-step coprecipitation reaction is 70-80°C; Optionally, the endpoint of the one-step coprecipitation reaction is that the particle size D501 in the system is 2 to 4 μm.

4. The preparation method according to any one of claims 1 to 3, wherein The lanthanum source solution in step (2) comprises a lanthanum sulfate solution; Optionally, the endpoint of the two-step coprecipitation reaction is that the particle size D502-D501 in the system is 1.5-3 μm.

5. The preparation method according to any one of claims 1 to 4, wherein: The doping amount of molybdenum element in the modified lithium-rich manganese-based precursor in step (2) is 2000-4000 ppm; Optionally, the doping amount of lanthanum element in the modified lithium-rich manganese-based precursor is 2000-4000 ppm.

6. The preparation method according to any one of claims 1 to 5, wherein: The lithium source in step (3) includes lithium hydroxide and / or lithium carbonate; Optionally, the one-step sintering process includes one-stage sintering and two-stage sintering; Optionally, the temperature of the first stage sintering is 400-600°C; Optionally, the heat preservation time of the sintering stage is 6 to 10 hours; Optionally, the temperature of the second stage sintering is 800-1200°C; Optionally, the second-stage sintering time is 20 to 30 hours.

7. The preparation method according to any one of claims 1 to 6, wherein: The aluminum source in step (4) comprises aluminum oxide; Optionally, the mass ratio of the aluminum source to the sintered material is 1:(95-100); Optionally, the calcium source comprises calcium fluoride; Optionally, the mass ratio of the calcium source to the calcined material is 1:(95-100); Optionally, the temperature of the two-step sintering treatment is 800-1200°C; Optionally, the two-step sintering process takes 8 to 12 hours.

8. A doped and coated lithium-rich manganese-based positive electrode material, wherein: The doped and coated lithium-rich manganese-based positive electrode material is prepared by the method as described in any one of claims 1 to 7.

9. A positive electrode sheet, wherein: The positive electrode plate comprises the doped and coated lithium-rich manganese-based positive electrode material as described in claim 8.

10. A lithium ion battery, wherein: The lithium-ion battery comprises the positive electrode sheet as claimed in claim 9.

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