Lithium-rich manganese-based positive electrode material and multi-stage sintering preparation method and application thereof

Abstract

The invention provides a lithium-rich manganese-based positive electrode material and a multi-stage sintering preparation method and application thereof, and the multi-stage sintering preparation method comprises the following steps: mixing a lithium-rich manganese-based precursor material and a lithium source, and calcining in an inert atmosphere to obtain a calcined material; mixing and drying the calcined material, a residual alkali removal agent and a first solvent to obtain a residual alkali removal material; mixing and drying the residual alkali removal material, an organic coating and a second solvent to obtain a coating material; and carrying out at least three stages of sintering treatment on the coating material to obtain the lithium-rich manganese-based positive electrode material. According to the preparation method disclosed by the invention, multi-stage sintering treatment is combined with oxygen vacancy introduction, residual alkali treatment and coating treatment, so that the material structure can be regulated and controlled, residual alkali is eliminated, a coating layer is formed on the surface of the material, and the material has relatively high crystallinity, and thus the lithium-rich manganese-based positive electrode material with high performance is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a lithium-rich manganese-based cathode material, a multi-stage sintering preparation method thereof, and an application thereof. Background Art

[0002] The lithium-rich manganese-based cathode material has significant advantages such as high energy density, long cycle life, environmental friendliness, low cost, and good stability. Its chemical general formula is xLi2MnO3·(1-x)LiMO2 (where M = Ni, Co, or Mn, 0 < x < 1), showing a reversible capacity exceeding 250 mAh / g and an average working voltage higher than 3.5 V (versus Li / Li+), and has broad application prospects in the next-generation high-energy density (up to 400 Wh / kg) lithium batteries.

[0003] However, when preparing the lithium-rich manganese-based cathode material, adding a lithium source to sinter the precursor will cause residual alkali to accumulate on the surface of the obtained lithium-rich manganese-based cathode material. The surface residual alkali will reduce the ion mobility of the lithium-rich manganese-based cathode material, generate gas at high voltage, increase the interfacial impedance, resulting in performance degradation and potential safety hazards. In addition, the lithium-rich manganese-based cathode material has a serious Jahn-Teller effect, which will cause irreversible structural damage, thereby leading to a rapid decline in cycle performance.

[0004] Based on the above research, a preparation method of a lithium-rich manganese-based cathode material is needed. The preparation method can not only regulate the material structure, slow down the Jahn-Teller effect, but also improve the stability and rate performance of the material. Summary of the Invention

[0005] The purpose of the present invention is to provide a lithium-rich manganese-based cathode material, a multi-stage sintering preparation method thereof, and an application thereof. The preparation method can regulate the structure, eliminate residual alkali, form a coating layer on the material surface, and make the material have high crystallinity through multi-stage sintering treatment combined with the introduction of oxygen vacancies, residual alkali treatment, and coating treatment, thereby obtaining a lithium-rich manganese-based cathode material with high performance.

[0006] To achieve the purpose of this invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a multi-stage sintering preparation method of a lithium-rich manganese-based cathode material. The multi-stage sintering preparation method includes the following steps:

[0008] (1) Mix the lithium-rich manganese-based precursor material and the lithium source, and calcine in an inert atmosphere to obtain a calcined material;

[0009] (2) Mix and dry the calcined material obtained in step (1), a residual alkali removing agent, and a first solvent to obtain a residual alkali removing material;

[0010] (3) Mix and dry the residual alkali material, organic coating, and the second solvent described in step (2) to obtain a coating material.

[0011] (4) Perform at least three-stage sintering treatment on the coating material described in step (3) to obtain the lithium-rich manganese-based cathode material.

[0012] In the present invention, the lithium-rich manganese-based precursor material and the lithium source are first calcined in an inert atmosphere to introduce oxygen vacancies into the lithium-rich manganese-based material, regulate the structure of the material, slow down the Jahn-Teller effect, and improve the stability of the material. Then, surface residual alkali treatment is carried out to remove the surface residual alkali, and then an organic coating layer is coated to reduce the generation of gas in the material, reduce the safety risk of the battery under high voltage and high temperature operations, and improve the safety performance of the battery. Finally, multi-stage sintering treatment is carried out to improve the crystallinity of the material and remove the impurities introduced in the previous steps, thereby improving the thermal stability and structural stability of the material. Therefore, the lithium-rich manganese-based cathode material obtained by the preparation method of the present invention has excellent comprehensive electrochemical performance.

[0013] Preferably, the at least three-stage sintering treatment described in step (4) includes selecting three stages from the first-stage sintering, second-stage sintering, third-stage sintering, fourth-stage sintering, and fifth-stage sintering for sintering. Among them, the sintering temperature of each stage is not higher than 300 °C, for example, it can be 300 °C, 280 °C, 260 °C, 240 °C, or 220 °C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0014] The present invention performs multi-stage sintering at a low temperature, which can not only improve the stability of the coating layer but also further improve the crystallization performance of the material, thereby further improving the stability of the material. If the temperature of the multi-stage sintering treatment is too high, it will affect the crystallization of the material.

[0015] Preferably, the temperature of the first-stage sintering is 40-150 °C, for example, it can be 40 °C, 60 °C, 80 °C, 100 °C, 120 °C, 140 °C, or 150 °C, and the time is 0.5-3 h, for example, it can be 0.5 h, 1.5 h, 2.5 h, or 3 h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] Preferably, the temperature of the second-stage sintering is 80-220 °C, for example, it can be 80 °C, 120 °C, 160 °C, 200 °C, or 220 °C, and the time is 0.5-3 h, for example, it can be 0.5 h, 1.5 h, 2.5 h, or 3 h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0017] Preferably, the temperature of the third-stage sintering is 150 - 280 °C, for example, it can be 150 °C, 200 °C, 250 °C or 280 °C, and the time is 0.5 - 3 h, for example, it can be 0.5 h, 1.5 h, 2.5 h or 3 h. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] Preferably, the temperature of the fourth-stage sintering is 200 - 300 °C, for example, it can be 200 °C, 220 °C, 240 °C, 260 °C, 280 °C or 300 °C, and the time is 0.01 - 2 h, for example, it can be 0.01 h, 0.05 h, 1 h, 1.5 h or 2 h. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] Preferably, the temperature of the fifth-stage sintering is 250 - 300 °C, for example, it can be 250 °C, 260 °C, 270 °C, 280 °C, 290 °C or 300 °C, and the time is 0.01 - 2 h, for example, it can be 0.01 h, 0.05 h, 1 h, 1.5 h or 2 h. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0020] Preferably, under an inert atmosphere, the coating material in step (3) is first calcined at a temperature of 40 - 150 °C, for example, it can be 40 °C, 60 °C, 80 °C, 100 °C, 120 °C, 140 °C or 150 °C, for 0.5 - 3 h, for example, it can be 0.5 h, 1.5 h, 2.5 h or 3 h, then heated to 80 - 220 °C, for example, it can be 80 °C, 120 °C, 160 °C, 200 °C or 220 °C, and calcined for 0.5 - 3 h, for example, it can be 0.5 h, 1.5 h, 2.5 h or 3 h, then heated to 150 - 280 °C, for example, it can be 150 °C, 200 °C, 250 °C or 280 °C, and calcined for 0.5 - 3 h, for example, it can be 0.5 h, 1.5 h, 2.5 h or 3 h, then heated to 200 - 300 °C, for example, it can be 200 °C, 220 °C, 240 °C, 260 °C, 280 °C or 300 °C, and calcined for 0.01 - 2 h, for example, it can be 0.01 h, 0.05 h, 1 h, 1.5 h or 2 h, and finally heated to 250 - 300 °C, for example, it can be 250 °C, 260 °C, 270 °C, 280 °C, 290 °C or 300 °C, and calcined for 0.01 - 2 h, for example, it can be 0.01 h, 0.05 h, 1 h, 1.5 h or 2 h. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0021] Preferably, the organic coating in step (3) includes an amino-silane coupling agent, such as KH-550 (aminopropyltriethoxysilane).

[0022] The present invention can obtain a coating layer with strong bonding force and high density by using an amino-silane coupling agent for coating. Since the residual-alkali removing agent described in the present invention is preferably ammonium fluoride, lithium fluoride is obtained after the residual alkali is removed by ammonium fluoride. Lithium fluoride can form Si-O-F bonds with the amino-silane coupling agent through hydrogen bonding or condensation reactions, thereby realizing bonded coating. At the same time, the amino groups in the amino-silane coupling agent can further react with the residual alkali, which can not only further reduce the residual alkali, but also form a dense silicone oxide coating with strong bonding force. Finally, after multi-stage sintering, the silicone oxide coating is further crosslinked and cured, which can further improve the stability of the material.

[0023] Preferably, the mass ratio of the residual-alkali removing material, the organic coating material and the second solvent in step (2) is 1:(0.2-1):(2-5). For example, it can be 1:0.2:2, 1:0.4:3, 1:0.6:4 or 1:1:5, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0024] The present invention preferably sets the residual-alkali removing material and the organic coating material within a specific mass ratio range. If the amount of the organic coating material is too small, the coating effect cannot be preferably exerted. If the amount of the organic coating material is too large, it will not only affect the capacity of the material, but also affect the lithium ion transmission.

[0025] Preferably, the second solvent in step (3) includes ethanol and water.

[0026] Preferably, the temperature for mixing the residual-alkali removing material, the organic coating material and the second solvent in step (2) in step (3) is 50-70 °C. For example, it can be 50 °C, 60 °C or 70 °C, and the time is 3-5 h. For example, it can be 3 h, 4 h or 5 h, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0027] Preferably, the mass ratio of the calcined material and the residual-alkali removing agent in step (1) is 100:(2-8). For example, it can be 100:2, 100:4, 100:6 or 100:8, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0028] Preferably, the residual-alkali removing agent in step (2) includes fluorides, preferably ammonium fluoride.

[0029] Preferably, the first solvent in step (2) includes ethanol.

[0030] Preferably, the calcination in step (1) under an inert atmosphere includes sintering at 300 - 800 °C, such as 300 °C, 400 °C, 500 °C, 600 °C, 700 °C or 800 °C, for 6 - 15 h, such as 6 h, 8 h, 10 h, 12 h, 14 h or 15 h, in an inert atmosphere, and then heating to 600 - 1200 °C, such as 600 °C, 800 °C, 1000 °C or 1200 °C, and sintering for 8 - 16 h, such as 8 h, 10 h, 12 h, 14 h or 16 h. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0031] Preferably, the method for preparing the lithium-rich manganese-based precursor material described in step (1) includes the following steps:

[0032] Performing a coprecipitation reaction on the mixed metal salt solution, the precipitant solution and the complexing agent solution to obtain the lithium-rich manganese-based precursor material.

[0033] Preferably, the mixed metal salt solution contains nickel ions, cobalt ions, manganese ions and magnesium ions in a molar ratio of a:b:c:d, where a + b + c + d = 1, 0.1 < a < 0.5, such as 0.11, 0.2, 0.3, 0.4 or 0.49, 0 < b < 0.1, such as 0.01, 0.03, 0.05, 0.07 or 0.09, 0.5 < c < 0.8, such as 0.51, 0.6, 0.7 or 0.79, 0 ≤ d < 0.1, such as 0, 0.01, 0.03, 0.05, 0.07 or 0.09. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the total metal ion concentration in the mixed metal salt solution is 1.6 - 2.4 mol / L, such as 1.6 mol / L, 1.8 mol / L, 2.0 mol / L, 2.2 mol / L or 2.4 mol / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0035] Preferably, the concentration of the precipitant solution is 9 - 12 mol / L, such as 9 mol / L, 10 mol / L, 11 mol / L or 12 mol / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the concentration of the complexing agent solution is 5 - 10 mol / L, such as 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0037] Preferably, the pH of the coprecipitation reaction is 9-13. For example, it can be 9, 10, 11, 12 or 13, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0038] Preferably, the particle size D50 of the lithium-rich manganese-based precursor material is 1-15 μm. For example, it can be 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 11 μm, 13 μm or 15 μm, but is not limited to the listed values. Other unlisted values within the numerical range are equally applicable.

[0039] Preferably, the coprecipitation reaction is carried out in a protective gas.

[0040] In a second aspect, the present invention provides a lithium-rich manganese-based cathode material, which is prepared by the multi-stage sintering preparation method described in the second aspect.

[0041] In a third aspect, the present invention provides a lithium-ion battery, which includes the lithium-rich manganese-based cathode material described in the second aspect.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The lithium-rich manganese-based cathode material obtained by surface treatment, structure optimization and multi-stage sintering in the present invention can increase the capacity retention rate from 55.23% to more than 80.15% after 200 cycles, and can still maintain more than 91.9% of the capacity after 500 cycles. Moreover, it can still maintain a relatively high discharge specific capacity (such as 147.6 mAh / g) at a high rate (5C), which is significantly better than the untreated material. In addition, the surface organic coating layer reduces gas generation, reduces the safety risk of the battery under high voltage and high temperature operations, and effectively suppresses the voltage decay phenomenon and maintains the high working voltage of the material through structure optimization. Specific Embodiments

[0044] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0045] Example 1

[0046] This example provides a multi-stage sintering preparation method for a lithium-rich manganese-based cathode material, and the multi-stage sintering preparation method includes the following steps:

[0047] (1) Prepare a mixed salt solution A with a total ion concentration of 2 mol / L. In the mixed salt solution A, the molar ratio of nickel ions, cobalt ions, magnesium ions, and manganese ions is 30:5:3:62. Use an industrial liquid caustic soda with a concentration of 10 mol / L as the precipitant solution B, and use ammonia water with a concentration of 5 mol / L as the complexing agent solution C;

[0048] (2) Prepare a bottom solution E containing the precipitant solution and the complexing agent solution (ammonia water) in a reaction kettle. The pH of the bottom solution E is 11, the ammonia water concentration of the bottom solution E is 13 g / L, and the temperature of the bottom solution E is 50 °C;

[0049] (3) Introduce nitrogen into the reaction kettle as a protective gas, introduce oxygen, and add the mixed salt solution A, the precipitant solution B, and the complexing agent solution C into the above reaction kettle. Control the pH at 11.3 to 11.5, and carry out a coprecipitation reaction at 500 rpm for 20 hours. Then slowly and continuously reduce the pH to 9.5 (within 90 hours) to obtain precursor particles with a target particle size D50 of 6.5 μm;

[0050] (4) After centrifuging, washing, drying, removing magnetic foreign matters, etc. of the obtained spherical nickel-manganese precursor, spherical precursor particles are obtained;

[0051] (5) Structure regulation: Mix LiOH and the precursor evenly in proportion, and carry out staged sintering. The first stage is sintering at 550 °C for 10 h, and the second stage is sintering at 850 °C for 12 h under argon protection to obtain a calcined material;

[0052] (6) Surface residual alkali treatment: Mix the calcined material and ammonium fluoride in an ethanol solution in a mass ratio of 100:5, stir, and then dry to obtain a residual alkali removal material. Mix the residual alkali removal material, KH-550, ethanol, and water in a mass ratio of 1:0.5:2:1, mix at 60 °C for 4 h, and finally dry to remove the solvent to obtain a coated material;

[0053] (7) Re-calcination treatment: Calcinate the coated material obtained in step (6) under argon protection at 60 °C for 1.2 hours, then raise the temperature to 120 °C and calcine for 1 hour, then raise the temperature to 200 °C and calcine for 0.8 hour, then raise the temperature to 250 °C and calcine for 0.55 hour, and finally raise the temperature to 300 °C and calcine for 0.15 hour to obtain the lithium-rich manganese-based cathode material.

[0054] Example 2

[0055] This example provides a multi-stage sintering preparation method for a lithium-rich manganese-based cathode material. The multi-stage sintering preparation method includes the following steps:

[0056] (1) Prepare a mixed salt solution A with a total ion concentration of 1.6 mol / L. In the mixed salt solution A, the molar ratio of nickel ions, cobalt ions, magnesium ions, and manganese ions is 40:3:5:52. Use an industrial liquid caustic soda with a concentration of 9 mol / L as the precipitant solution B, and use ammonia water with a concentration of 5 mol / L as the complexing agent solution C;

[0057] (2) Prepare a bottom liquid E containing the precipitant solution and the complexing agent solution (ammonia water) in a reaction kettle. The pH of the bottom liquid E is 9, the ammonia water concentration of the bottom liquid E is 14 g / L, and the temperature of the bottom liquid E is 60 °C;

[0058] (3) Introduce nitrogen into the reaction kettle as a protective gas, and introduce oxygen. Then add the mixed salt solution A, the precipitant solution B, and the complexing agent solution C into the above reaction kettle. Control the pH at 11.5 to 12, and carry out a coprecipitation reaction at 500 rpm for 20 hours. Then slowly and continuously reduce the pH to 10 (within 100 hours) to obtain precursor particles with a target particle size D50 of 8 μm;

[0059] (4) After centrifuging, washing, drying, removing magnetic foreign substances, etc. of the obtained spherical nickel-manganese precursor, obtain spherical precursor particles;

[0060] (5) Structure regulation: Mix LiOH and the precursor evenly in proportion, and carry out staged sintering. The first stage is sintering at 800 °C for 6 h, and the second stage is sintering at 1200 °C for 8 h under argon protection to obtain a calcined material;

[0061] (6) Surface residual alkali treatment: Mix the calcined material and ammonium fluoride in an ethanol solution at a mass ratio of 100:8, stir, and then dry to obtain a material with residual alkali removed. Mix the material with residual alkali removed, KH-550, ethanol, and water at a mass ratio of 1:1:2.5:2.5, mix at 70 °C for 3 h, and finally dry to remove the solvent to obtain a coated material;

[0062] (7) Re-calcination treatment: Calcinate the coated material obtained in step (6) under argon protection at 40 °C for 3 hours, then raise the temperature to 80 °C and calcine for 3 hours, then raise the temperature to 150 °C and calcine for 3 hours, then raise the temperature to 200 °C and calcine for 2 hours, and finally raise the temperature to 250 °C and calcine for 2 hours to obtain the lithium-rich manganese-based cathode material.

[0063] Example 3

[0064] This example provides a multi-stage sintering preparation method for a lithium-rich manganese-based cathode material. The multi-stage sintering preparation method includes the following steps:

[0065] (1) Prepare a mixed salt solution A with a total ion concentration of 2.4 mol / L. In the mixed salt solution A, the molar ratio of nickel ions, cobalt ions, magnesium ions, and manganese ions is 30:5:3:62. Use industrial liquid caustic soda with a concentration of 12 mol / L as the precipitant solution B, and use ammonia water with a concentration of 10 mol / L as the complexing agent solution C;

[0066] (2) Prepare a bottom liquid E containing a precipitant solution and a complexing agent solution (ammonia water) in a reaction kettle. The pH of the bottom liquid E is 12, the ammonia water concentration of the bottom liquid E is 12 g / L, and the temperature of the bottom liquid E is 40 °C;

[0067] (3) Introduce nitrogen into the reaction kettle as a protective gas, introduce oxygen, and add the mixed salt solution A, the precipitant solution B, and the complexing agent solution C into the above reaction kettle. Control the pH at 11.3 to 11.5, and carry out a coprecipitation reaction at 500 rpm for 20 hours. Then slowly and continuously reduce the pH to 9.5 (within 80 hours) to obtain precursor particles with a target particle size D50 of 5.5 μm;

[0068] (4) After centrifuging, washing, drying, removing magnetic foreign matters, etc. of the obtained spherical nickel-manganese precursor, obtain spherical precursor particles;

[0069] (5) Structure regulation: Mix LiOH and the precursor in proportion and mix evenly, and carry out staged sintering. The first stage is sintering at 300 °C for 15 h, and the second stage is sintering at 600 °C for 8 h under argon protection to obtain a calcined material;

[0070] (6) Surface residual alkali treatment: Mix the calcined material and ammonium fluoride in an ethanol solution at a mass ratio of 100:2, stir, and then dry to obtain a residual alkali removal material. Mix the residual alkali removal material, KH-550, ethanol, and water at a mass ratio of 1:0.2:1:1, mix at 50 °C for 5 h, and finally dry to remove the solvent to obtain a coated material;

[0071] (7) Further calcination treatment: Calcinate the coated material obtained in step (6) under argon protection at 150 °C for 0.5 h, then raise the temperature to 220 °C and calcine for 0.5 h, then raise the temperature to 280 °C and calcine for 0.5 h, then raise the temperature to 290 °C and calcine for 0.5 h, and finally raise the temperature to 300 °C and calcine for 0.5 h to obtain the lithium-rich manganese-based cathode material.

[0072] Example 4

[0073] This embodiment provides a multi-stage sintering preparation method for a lithium-rich manganese-based cathode material. Except for calcining the coating material described in step (6) under argon protection at 60 °C for 1.2 hours, then heating to 120 °C and calcining for 1 hour, then heating to 200 °C and calcining for 0.8 hour, and then heating to 250 °C and calcining for 0.55 hour, the rest are the same as in Embodiment 1.

[0074] Example 5

[0075] This embodiment provides a multi-stage sintering preparation method for a lithium-rich manganese-based cathode material. Except for calcining the coating material described in step (6) under argon protection at 60 °C for 1.2 hours, then heating to 200 °C and calcining for 0.8 hour, and then heating to 300 °C and calcining for 0.55 hour, the rest are the same as in Embodiment 1.

[0076] Example 6

[0077] This embodiment provides a multi-stage sintering preparation method for a lithium-rich manganese-based cathode material. Except that the mass ratio of the residual alkali removing material and KH-550 described in step (6) is 1:1.5, the rest are the same as in Embodiment 1.

[0078] Example 7

[0079] This embodiment provides a multi-stage sintering preparation method for a lithium-rich manganese-based cathode material. Except that the mass ratio of the residual alkali removing material and KH-550 described in step (6) is 1:0.05, the rest are the same as in Embodiment 1.

[0080] Comparative Example 1

[0081] This comparative example provides a preparation method for a lithium-rich manganese-based cathode material. Except that the sintering in step (5) is carried out in an oxygen atmosphere, the rest are the same as in Embodiment 1.

[0082] Comparative Example 2

[0083] This comparative example provides a preparation method for a lithium-rich manganese-based cathode material. Except that in step (6), the residual alkali removal is not carried out and the calcined material is directly coated, the rest are the same as in Embodiment 1.

[0084] Comparative Example 3

[0085] This comparative example provides a preparation method for a lithium-rich manganese-based cathode material. Except that in step (6), the coating treatment is not carried out and the residual alkali removing material is directly subjected to multi-stage sintering in step (7), the rest are the same as in Embodiment 1.

[0086] Comparative Example 4

[0087] This comparative example provides a method for preparing a lithium-rich manganese-based cathode material. Except that the coating material in step (6) is calcined at a temperature of 300 °C for 3.7 hours under argon protection, the rest are the same as in Example 1.

[0088] Mix the lithium-rich manganese-based cathode materials, acetylene black, and polyvinylidene fluoride obtained in the above examples and comparative examples according to a mass ratio of 8:1:1, then drop N-methyl-2-pyrrolidone to prepare a slurry, and evenly coat it on an aluminum foil, dry it, and stamp it to make a battery electrode sheet. Assemble the battery electrode sheet, metallic lithium sheet, glass fiber separator, electrolyte (LiClO4), gasket, spring piece, and battery case into a button cell in an argon glove box; test the 0.2C discharge capacity, 1C discharge capacity, and capacity retention rate after 500 cycles at 0.2C of the button cell.

[0089] The test results are shown in Table 1:

[0090] Table 1

[0091]

[0092] As can be seen from Table 1:

[0093] From Example 1 and Comparative Example 1, it can be seen that by sintering the precursor and lithium source in an inert atmosphere, the present invention can optimize the material structure, introduce oxygen vacancies in the structure, thereby slowing down the Jahn-Teller effect of the material and improving the electrochemical performance of the material; from Example 1 and Comparative Example 2, it can be seen that by removing residual alkali, the present invention can improve the stability and rate performance of the material, etc.; from Example 1 and Comparative Example 3, it can be seen that by organic coating treatment, the present invention can improve the safety performance of the material, etc.; from Example 1 and Comparative Example 4, it can be seen that the multi-stage sintering treatment in the last step of the present invention can remove impurities introduced in the previous steps, improve the crystallinity of the material, and thereby improve the electrochemical performance of the material; from Example 1 and Examples 4-5, it can be seen that after coating, the present invention preferably adopts a five-stage low-temperature calcination treatment, which can further improve the crystallinity of the material, and thereby further improve the electrochemical performance of the material; from Example 1 and Examples 6-7, it can be seen that the present invention preferably controls the coating amount of the coating within a specific range, thereby improving the coating effect and the comprehensive electrochemical performance of the material.

[0094] The above are only specific embodiments 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 thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A multi-stage sintering method for preparing a lithium-rich manganese-based positive electrode material, characterized in that: The multi-stage sintering preparation method comprises the following steps: (1) mixing a lithium-rich manganese-based precursor material and a lithium source, and calcining the mixture under an inert atmosphere to obtain a calcined material; (2) mixing and drying the calcined material, the residual alkali removal agent and the first solvent described in step (1) to obtain a residual alkali removal material; (3) mixing and drying the residual alkali-removed material, the organic coating and the second solvent in step (2) to obtain a coating material; (4) The coating material of step (3) is subjected to at least three stages of sintering to obtain the lithium-rich manganese-based positive electrode material.

2. The multi-stage sintering preparation method according to claim 1, characterized in that: The at least three sintering processes in step (4) include selecting three stages from the first stage sintering, the second stage sintering, the third stage sintering, the fourth stage sintering and the fifth stage sintering for sintering, wherein the sintering temperature of each stage is not higher than 300°C.

3. The multi-stage sintering preparation method according to claim 2, characterized in that: The first stage sintering temperature is 40-150°C and the time is 0.5-3h; Preferably, the temperature of the second stage sintering is 80-220°C and the time is 0.5-3h; Preferably, the temperature of the third stage sintering is 150-280°C and the time is 0.5-3h; Preferably, the temperature of the fourth stage sintering is 200-300°C and the time is 0.01-2h; Preferably, the temperature of the fifth stage sintering is 250-300°C and the time is 0.01-2h; Preferably, under an inert atmosphere, the coating material in step (3) is first calcined at a temperature of 40-150°C for 0.5-3h, then heated to 80-220°C for 0.5-3h, then heated to 150-280°C for 0.5-3h, then heated to 200-300°C for 0.01-2h, and finally heated to 250-300°C for 0.01-2h.

4. The multi-stage sintering preparation method according to any one of claims 1 to 3, characterized in that: The organic coating in step (3) comprises an aminosilane coupling agent; Preferably, the mass ratio of the residual alkali removal material, the organic coating and the second solvent in step (2) is 1:(0.2-1):(2-5); Preferably, the second solvent in step (3) comprises ethanol and water; Preferably, in step (3), the temperature for mixing the residual alkali-removing material, the organic coating and the second solvent in step (2) is 50-70° C. and the time is 3-5 hours.

5. The multi-stage sintering preparation method according to any one of claims 1 to 4, characterized in that: The mass ratio of the calcined material to the residual alkali removal agent in step (1) is 100:(2-8); Preferably, the residual alkali removal agent in step (2) comprises fluoride, preferably ammonium fluoride; Preferably, in step (2), the first solvent comprises ethanol.

6. The multi-stage sintering preparation method according to any one of claims 1 to 5, characterized in that: The calcination under an inert atmosphere in step (1) includes sintering at 300-800° C. for 6-15 hours, and then heating to 600-1200° C. for 8-16 hours.

7. The multi-stage sintering preparation method according to any one of claims 1 to 6, characterized in that: The method for preparing the lithium-rich manganese-based precursor material in step (1) comprises the following steps: The mixed metal salt solution, the precipitant solution and the complexing agent solution are subjected to a coprecipitation reaction to obtain the lithium-rich manganese-based precursor material; Preferably, the mixed metal salt solution comprises nickel ions, cobalt ions, manganese ions and magnesium ions in a molar ratio of a:b:c:d, wherein a+b+c+d=1, 0.1 <a<0.5,0<b<0.1,0.5<c<0.8,0≤d<0.1。 8. The multi-stage sintering preparation method according to claim 7, characterized in that: The total metal ion concentration in the mixed metal salt solution is 1.6-2.4 mol / L; Preferably, the concentration of the precipitant solution is 9-12 mol / L; Preferably, the concentration of the complexing agent solution is 5-10 mol / L; Preferably, the pH of the coprecipitation reaction is 9-13; Preferably, the particle size D50 of the lithium-rich manganese-based precursor material is 1-15 μm; Preferably, the coprecipitation reaction is carried out in a protective gas.

9. A lithium-rich manganese-based positive electrode material, characterized in that: The lithium-rich manganese-based positive electrode material is prepared by the multi-stage sintering preparation method as described in any one of claims 1 to 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium-rich manganese-based positive electrode material as claimed in claim 9.

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