Lithium-rich manganese-based positive electrode material and preparation method thereof

Abstract

The invention discloses a lithium-rich manganese-based positive electrode material and a preparation method, and relates to the technical field of lithium ion battery positive electrode materials, and the preparation method comprises the following steps: jointly dropwise adding a lithium acetate aqueous solution and a transition metal salt aqueous solution into a citric acid aqueous solution, maintaining the reaction temperature, and continuously stirring to form gel; and carrying out secondary calcination on the gel to obtain a lithium-rich manganese-based positive electrode material precursor, carrying out high shear stress and heat treatment combined treatment on the lithium-rich manganese-based positive electrode material precursor, washing, and drying to finally obtain the lithium-rich manganese-based positive electrode material. The lithium-rich manganese-based positive electrode material is prepared by adopting a sol-gel method, a two-step calcination method and a high shear stress and heat treatment combined mode, lattice oxygen can be stabilized by introducing oxygen vacancies, and the cycling stability is improved; by introducing the lithium vacancy, the migration energy of lithium ions can be reduced, the migration of the lithium ions is accelerated, and the rate capability is improved; the generation of the disordered layer hinders the contact between the electrolyte and the internal material, the reaction between the material and the electrolyte is reduced, the stress caused by lattice distortion is relieved by the internal local disorder, and the stability of the material is enhanced. The lithium-rich manganese-based positive electrode material prepared by the invention is applied to a lithium ion battery and shows excellent electrochemical performance, and the preparation method hardly generates waste liquid and shows the characteristic of environmental friendliness.

Description

Technical Field

[0001] The present invention relates to the technical field of cathode materials for lithium-ion batteries, and particularly to a modification method for lithium-rich manganese-based cathode materials. Background Art

[0002] Lithium-ion batteries play a crucial role in the energy storage field due to their excellent voltage platform, high energy density, long service life, low self-discharge rate, and significant green environmental protection characteristics. The capacity of lithium-ion batteries is limited by the cathode material, which prompts people to seek cathode materials with higher energy density. Lithium-rich manganese-based cathode materials (xLiMnO·(1-x)LiMO (M = transition metals such as Ni, Co, Mn, 0 < x < 1, LLO)) stand out under this demand for improving battery performance.

[0003] LLO is considered one of the hot materials for the next-generation lithium-ion batteries for electric vehicles because of its high capacity (>200 mAh / g) and low cost. However, LLO materials also have characteristics such as poor cycle stability and poor rate performance, which hinder the wide application of LLO cathode materials and the process of China's transition to clean energy.

[0004] In previous studies, it was found that actively introducing oxygen vacancies is beneficial to stabilizing lattice oxygen, inhibiting the migration of transition metal ions, and improving cycle stability; the introduction of lithium vacancies can reduce the migration barrier of lithium ions, accelerate the migration speed of lithium ions, and improve rate performance. However, the methods for introducing lithium vacancies and oxygen vacancies before were cumbersome and complex in operation, increasing the cost. For example, using the high-temperature synthesis method, the material is calcined at high temperature in an inert atmosphere, and the calcination temperature and time need to be precisely controlled; using the reduction method, reducing gases such as hydrogen and carbon monoxide are used to reduce the lithium-rich manganese-based material to introduce oxygen vacancies and lithium vacancies. The reduction method needs to be carried out at a certain temperature and pressure, and at the same time, attention should be paid to the safety of the reducing gas; the doping method, by doping other elements such as transition metal elements and rare earth elements in the lithium-rich manganese-based material, can change the electronic structure and crystal structure of the material, thereby introducing oxygen vacancies. The doping method needs to select appropriate doping elements and doping amounts to achieve the best effect; the surface treatment method, by treating the surface of the lithium-rich manganese-based material, such as acid treatment, alkali treatment, plasma treatment, etc., can generate oxygen vacancies on its surface. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method for lithium-rich manganese-based materials. The method provided by the present invention is simple in operation; the lithium-rich manganese-based cathode material prepared by the method has excellent electrochemical performance. The purpose of the present invention is achieved through the following technical solutions:

[0006] A preparation method of a lithium-rich manganese-based cathode material, characterized by comprising the following steps:

[0007] Drop the aqueous solution of lithium acetate and the aqueous solution of transition metal salt into the aqueous solution of citric acid together, maintain the reaction temperature at 0-90 °C, react for 2-10 h under the stirring speed of 200-1000 rpm to form a gel, subject the gel to secondary calcination to obtain a precursor of the lithium-rich manganese-based cathode material, then put the precursor of the lithium-rich manganese-based cathode material heated to the heat treatment temperature into a cooling medium stirred at a high speed for cooling, after being treated by the combined use of high shear stress + heat treatment, wash and dry to finally obtain the lithium-rich manganese-based cathode material.

[0008] Further, the concentrations of the aqueous solution of lithium acetate, the aqueous solution of transition metal salt and the aqueous solution of citric acid are 0.3-2 mol / L.

[0009] Further, the molar ratio of lithium acetate, transition metal salt and sodium citrate is 1-2:1:1-2.

[0010] Further, the transition metal element in the transition metal salt is one or more of Fe, Mn, Co, Ni, Cu and Zn.

[0011] Further, the transition metal salt is one or more of transition metal nitrate, transition metal acetate and transition metal sulfate.

[0012] Further, the secondary calcination process adopts the "two-stage uniform temperature control-insulation method", the first-stage calcination temperature is 450-600 °C, the insulation time is 4-8 h, the second-stage calcination temperature is 750-950 °C, the insulation time is twice that of the first stage, and the whole process heating rate is 2-10 °C / min, in an air atmosphere.

[0013] Further, the heat treatment temperature is 750-950 °C, and the high shear stress rotation speed is 500-15000 rpm.

[0014] Further, the cooling medium is one or more of air, oil, aqueous solution, ethanol solution and liquid nitrogen.

[0015] Further, the dropping rates of the aqueous solution of lithium acetate and the aqueous solution of transition metal salt are 1-50 mL / min.

[0016] Further, the lithium-rich manganese-based cathode material is an irregular polyhedron with a particle size of 0.05-2 μm.

[0017] The beneficial effects of the above technical solutions are:

[0018] The lithium-rich manganese-based material prepared by the sol-gel method - two-step calcination method and the combination of high shear stress + heat treatment in the present invention has good structural stability; the electrochemical performance of the cathode material with introduced vacancies is improved, and an amorphous layer is formed on the material surface while introducing vacancies, and a locally amorphous structure is formed inside the material, which can slow down lattice distortion, release the stress generated by lattice strain, and improve the stability of the material; the preparation process provided by the present invention is simple, reduces the errors caused by cumbersome steps, and is conducive to promoting commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 XRD images of the materials described in Example 1 and Comparative Example 1;

[0020] Figure 2 SEM image of the material described in Example 1;

[0021] Figure 3 SEM image of the material described in Comparative Example 1;

[0022] Figure 4 First charge-discharge curves of the button battery prepared from the material described in Example 1 at room temperature, 0.1C rate, and voltage window in the range of 2.8 - 4.8V;

[0023] Figure 5 First charge-discharge curves of the button battery prepared from the material described in Comparative Example 1 at room temperature, 0.1C rate, and voltage window in the range of 2.8 - 4.8V;

[0024] Figure 6 Cycling stability curves of the button batteries prepared from the materials described in Example 1 and Comparative Example 1 at room temperature, 3C rate, and voltage window in the range of 2.8 - 4.8V. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention provides a modification method for rapidly cooling a lithium-rich manganese-based material, comprising the following steps:

[0026] An aqueous solution of lithium acetate and an aqueous solution of transition metal salt are jointly dropped into an aqueous solution of citric acid, maintaining the reaction temperature at 0 - 90°C, reacting for 2 - 10h under a stirring speed of 200 - 1000rpm to form a gel, subjecting the gel to secondary calcination to obtain a precursor of the lithium-rich manganese-based cathode material, and then placing the precursor of the lithium-rich manganese-based cathode material heated to the heat treatment temperature into a cooling medium stirred at a high speed for cooling. After treatment by the combination of high shear stress + heat treatment, washing and drying are carried out to finally obtain the lithium-rich manganese-based cathode material.

[0027] In the present invention, an aqueous solution of lithium acetate and an aqueous solution of a transition metal salt are jointly dropped into an aqueous solution of citric acid for reaction to form a gel. In the present invention, the concentration of the aqueous solution of the transition metal salt is preferably 0.3-2 mol / L, more preferably 0.5-1 mol / L. In a specific embodiment of the present invention, the concentration of the aqueous solution of the transition metal salt is preferably controlled to be more than 35% of the saturated concentration; the saturated concentration is based on the saturated concentration of the solution at the reaction temperature. In the present invention, the transition metal element in the transition metal salt is preferably one or more of Fe, Mn, Co, Ni, Cu, and Zn; the transition metal salt is preferably one or more of a transition metal nitrate, a transition metal acetate, and a transition metal sulfate. Specifically, the transition metal salt is preferably one or more of cobalt sulfate heptahydrate, manganese acetate tetrahydrate, and nickel nitrate hexahydrate, or a mixture of cobalt sulfate heptahydrate, manganese acetate tetrahydrate, and nickel nitrate hexahydrate. When the transition metal salt is a mixture of multiple transition metal salts, the molar amounts of the individual metal salts in the mixture are preferably equal; the aqueous solution of the transition metal salt is preferably prepared from a transition metal salt and deionized water.

[0028] In the present invention, the molar ratio of lithium acetate to the transition metal salt is preferably 1-2:1, more preferably 1.2-1.6:1; the molar ratio of the transition metal salt to citric acid is preferably 1:1-2, more preferably 1:1-1.6.

[0029] In the present invention, the dropping rates of the aqueous solution of lithium acetate and the aqueous solution of the transition metal salt are independently preferably 1-50 mL min-1, more preferably 2-30 mL min-1. The device used for dropping is preferably a peristaltic pump or a constant pressure funnel. In a specific embodiment of the present invention, the dropping rates of the aqueous solution of lithium acetate and the aqueous solution of the transition metal salt are preferably the same.

[0030] In the present invention, the reaction temperature during the gel formation process is preferably 0-90 °C, more preferably 40-80 °C. The stirring speed is preferably 200-1000 rpm, more preferably 300-500 rpm. The reaction time is preferably 2-10 h, more preferably 2-6 h. In an embodiment of the present invention, specifically, the temperature of the aqueous solution of citric acid is controlled within the reaction temperature range, and then an aqueous solution of lithium acetate and an aqueous solution of the transition metal salt (the temperatures of the two solutions are controlled to be the same as that of the aqueous solution of citric acid) are dropped into it. The temperature is kept constant during the dropping process, and after the dropping is completed, it is kept warm until the reaction ends. During the period from the start of dropping to the end of the reaction, stirring is always carried out at a certain speed.

[0031] In the present invention, the secondary calcination process adopts the "two-stage uniform temperature control - heat preservation method", specifically: the first-stage calcination temperature is preferably 450 - 600 °C, more preferably 500 °C, the heat preservation time is preferably 4 - 8 h, more preferably 5 - 6 h, the second-stage calcination temperature is preferably 750 - 950 °C, more preferably 850 °C, the heat preservation time is preferably 8 - 16 h, more preferably 10 - 12 h, the whole-process heating rate is preferably 2 - 10 °C / min, more preferably 5 - 8 °C / min, in an air atmosphere. Any process of this two-stage uniform temperature control - heat preservation program cannot be changed.

[0032] In the present invention, the obtained lithium-rich manganese-based material precursor is treated by combining high shear stress and heat treatment to introduce vacancies and form a defective layer, and then washed and dried. The washing solvent is preferably one or more of deionized water and absolute ethanol, more preferably deionized water, the drying temperature is preferably 80 - 120 °C, more preferably 120 °C, the heat treatment temperature is preferably 750 - 950 °C, more preferably 800 - 900 °C, the high shear stress rotation speed is preferably 500 - 15000 rpm, more preferably 10000 rpm, and the cooling medium is preferably one or more of air, oil, aqueous solution, ethanol solution, and liquid nitrogen.

[0033] The lithium-rich manganese-based cathode material prepared by the present invention has an irregular polyhedral morphology, and the particle size is 0.05 - 2 μm, specifically it can be 0.5 - 1.0 μm, 1.5 μm, or 1.5 - 2.0 μm.

[0034] In the present invention, the chemical formula of the lithium-rich manganese-based cathode material is expressed as xLiMnO·(1 - x)LiMO, where the value range of x is 0 - 1, preferably 0.1 - 0.3; M is a transition metal element, specifically one or more of Fe, Mn, Co, Ni, Cu, and Zn. The lithium-rich manganese-based cathode material prepared by the present invention has excellent electrochemical performance and good lithium storage performance, and has broad application prospects in lithium-ion batteries.

[0035] The present invention has no special requirements for the application of the lithium-rich manganese-based cathode material in lithium-ion batteries, and it can be applied by using methods well-known to those skilled in the art. In a specific embodiment of the present invention, preferably, the lithium-rich manganese-based cathode material is mixed with a conductive agent and a binder according to a mass ratio of 8:1:1, and then added to an organic solvent to obtain a cathode slurry, and then the cathode slurry is coated on a current collector to obtain a cathode; using the cathode, a lithium-ion battery can be assembled according to methods well-known to those skilled in the art.

[0036] The following describes the solutions in the specific embodiments of the present invention in a complete manner, but they are not all the embodiments of the present invention; all other embodiments obtained by other technical personnel within the scope of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0037] Example 1

[0038] Weigh 2.29 mmol of cobalt acetate, 2.29 mmol of nickel acetate tetrahydrate, 9.5 mmol of manganese acetate tetrahydrate and 22.2 mmol of lithium acetate and dissolve them in 50 mL of deionized water respectively, denoted as solution A (transition metal salt solution) and solution B (aqueous lithium acetate solution); weigh 16.9 mmol of citric acid powder and dissolve it in 100 mL of deionized water, denoted as solution C. Heat solution A and solution B to 80 °C and drip them into solution C at 80 °C at a rate of 2 mL min⁻¹ through a peristaltic pump, while stirring with a magnetic stirrer at a speed of 500 rpm. After stirring for 4 h, dry it in a vacuum oven at 120 °C for 12 h, then grind it evenly in an agate mortar, put it into a muffle furnace, and calcine it using the "two-stage uniform temperature control - heat preservation method". The first-stage sintering temperature is 500 °C and the heat preservation time is 6 h. The second-stage sintering temperature is 350 °C higher than the first stage and the heat preservation time is twice that of the first stage. The whole process heating rate is 5 °C / min. Under an air atmosphere, cool it to room temperature to obtain the product Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 .

[0039] Then heat 1 g of the obtained Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 to 850 °C and keep it at this temperature for 30 min. After taking it out, put it into 100 mL of continuously stirred deionized water and stir for 5 min. The stirring speed is 10,000 rpm. Then filter and dry it to obtain the lithium-rich manganese-based cathode material.

[0040] Comparative Example 1

[0041] The difference from Example 1 is that the lithium-rich manganese-based material in Comparative Example 1 is not subjected to rapid cooling treatment, that is, after two-stage calcination, it is not reheated to 850 °C again, but directly put into 100 mL of continuously stirred deionized water and stirred for 5 min, and then filtered and dried to obtain the lithium-rich manganese-based cathode material.

[0042] Figure 1 XRD patterns of the lithium-rich manganese-based cathode materials prepared in Example 1 and Comparative Example 1 are shown in Figure 1 It can be seen that both materials prepared in Example 1 and Comparative Example 1 are a mixed phase of R-3m and C2 / m. Therefore, the above results show that the rapid cooling treatment does not change the phase state of the material.

[0043] The lithium-rich manganese-based cathode materials obtained in Example 1 and Comparative Example 1 were subjected to SEM testing, asFigures 2 - 3 As shown, both materials are irregular polyhedra with a particle size of 0.05 - 2 μm. The results show that the surface morphology of the materials has not changed after the modification treatment.

[0044] Electrochemical tests:

[0045] Weigh the cathode materials, conductive carbon black, and polyvinylidene fluoride described in Example 1 and Comparative Example 1 according to a mass ratio of 8:1:1, mix them, use N-methylpyrrolidone as the solvent, stir for 10 h to obtain uniform slurries respectively, uniformly coat them on the carbon-coated aluminum foil current collector, and dry at 80 °C for 10 h; punch the dried electrode sheets, select flat and smooth electrode sheets for weighing and calculate the mass of the active material; use a lithium sheet as the anode, and assemble button cells in a glove box with an argon atmosphere (requiring the water and oxygen content to be below 0.01 ppm). The electrolyte used is: 1.2 M lithium hexafluorophosphate dissolved in ethylene carbonate (EC) and diethyl carbonate (EMC) with a volume ratio of 3:7, and containing 2% wt of vinylene carbonate (VC) as an additive. Use a BlueTEC test system to conduct the first charge-discharge test on the button cells obtained in Example 1 and Comparative Example 1, and the voltage window is 2.0 - 4.8 V.

[0046] Figure 4 When the lithium-rich manganese-based cathode material prepared in Example 1 is used as an electrode of a lithium-ion battery, at a current density of 20 mA g -1 The first charge-discharge data at the current density. According to Figure 4 It can be seen that for the lithium-ion battery assembled with the lithium-rich manganese-based cathode material prepared in Example 1, at a current density of 20 mA g -1 The first cycle can provide a reversible capacity of 252.33 mAh g -1

[0047] Figure 5 When the lithium-rich manganese-based cathode material prepared in Comparative Example 1 is used as an electrode of a lithium-ion battery, at a current density of 20 mA g -1 The first charge-discharge data at the current density. According to Figure 5 It can be seen that for the lithium-ion battery assembled with the lithium-rich manganese-based cathode material prepared in Comparative Example 1, at a current density of 20 mA g -1 The first cycle can provide a reversible capacity of 240.14 mAh g -1

[0048] Figure 6 When the lithium-rich manganese-based cathode materials prepared in Example 1 and Comparative Example 1 are used as electrodes of a lithium-ion battery, at a current density of 200 mA g -1 The cycle data at the current density. According to Figure 6 It can be seen that for the lithium-ion battery assembled with the lithium-rich manganese-based cathode material prepared in Example 1, at a current density of 200 mA g -1 ​​The capacity retention rate is about 88.01% after 500 cycles at a current density of; while for the lithium-rich manganese-based cathode material prepared in Comparative Example 1 and assembled into a lithium-ion battery, the capacity retention rate is about 83.9% after 500 cycles at a current density of 200 mA g -1 The capacity retention rate is about 83.9% after 500 cycles at a current density of 200 mA g

[0049] The better electrochemical performance of Example 1 compared to Comparative Example 1 is attributed to the introduction of vacancies, which stabilizes the lattice oxygen, accelerates the lithium-ion transport, and thus improves the electrochemical performance of the lithium-rich manganese-based cathode material. An amorphous layer is formed on the material surface, and a locally disordered structure is formed inside the material, which can slow down the lattice distortion, release the stress generated by the lattice strain, and improve the stability of the material;

[0050] Example 2

[0051] Referring to Example 1, the difference is that the cooling medium is changed to air. Accordingly, after obtaining the product Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 After that, 1 g of the obtained Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 The product is heated to 850 °C and held for 30 min, then taken out and cooled in air. After cooling to room temperature, it is put into 100 mL of continuously stirred deionized water for washing, and the stirring speed is 10,000 rpm. The remaining steps all refer to Example 1.

[0052] According to the above method, the lithium-rich manganese-based cathode material prepared in Example 2 is assembled into a lithium-ion battery, and the electrochemical performance is tested. The results show that the obtained lithium-ion battery can provide a reversible capacity of 231.3 mAh·g -1 at the first cycle at a current density of 20 mA·g -1 and the capacity retention rate is about 87.3% after 200 cycles at a current density of 200 mA·g -1 The capacity retention rate is about 87.3% after 200 cycles at a current density of 200 mA·g

[0053] Example 3

[0054] Referring to Example 1, the difference is that the calcination temperature in the second stage is 900 °C. Accordingly, after obtaining the primary product Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 After that, 1 g of the obtained Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 The product was heated to 900 °C and held for 30 min, then taken out and put into 100 mL of continuously stirred deionized water. The stirring speed was 10,000 rpm, and then it was filtered and dried. The remaining steps all refer to Example 1.

[0055] According to the above method, the lithium-rich manganese-based cathode material prepared in Example 3 was assembled into a lithium-ion battery, and its electrochemical performance was tested. The results show that the obtained lithium-ion battery can provide a reversible capacity of 249.06 mAh·g -1 at a current density of 20 mA·g -1 and a capacity retention rate of about 92.8% after 200 cycles at a current density of 200 mA·g -1 .

[0056] Example 4

[0057] Referring to Example 1, the difference is that the second calcination temperature is 900 °C. After obtaining the primary product Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 After that, 1 g of the obtained Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 product was heated to 900 °C and held for 30 min, taken out and cooled to room temperature in air, then put into 100 mL of continuously stirred deionized water. The stirring speed was 10,000 rpm, and then it was filtered and dried. The remaining steps all refer to Example 1.

[0058] According to the above method, the lithium-rich manganese-based cathode material prepared in Example 3 was assembled into a lithium-ion battery, and its electrochemical performance was tested. The results show that the obtained lithium-ion battery can provide a reversible capacity of 226.85 mAh·g -1 at a current density of 20 mA·g -1 and a capacity retention rate of about 86.5% after 200 cycles at a current density of 200 mA·g -1 .

[0059] Comparative Example 2

[0060] Different from Example 4, the lithium-rich manganese-based material in Comparative Example 2 was not subjected to the combined treatment of high shear stress + heat treatment. That is, after two-stage calcination, it was not reheated to 900 °C, but directly put into 100 mL of continuously stirred deionized water and stirred for 5 min. The stirring speed was 500 rpm, and then it was filtered and dried to obtain the lithium-rich manganese-based cathode material.

[0061] According to the above method, the lithium-rich manganese-based cathode material prepared in Comparative Example 2 was assembled into a lithium-ion battery, and the electrochemical performance was tested. The results show that the obtained lithium-ion battery can provide a reversible capacity of 241.74 mAh·g -1 at the current density of -1 20 mA·g -1 in the first cycle, and the capacity retention rate is about 90.1% after 200 cycles at the current density of 200 mA·g

[0062] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a lithium-rich manganese-based positive electrode material, characterized in that: The following steps are involved: A lithium acetate aqueous solution and a transition metal salt aqueous solution are added dropwise to a citric acid aqueous solution, the reaction temperature is maintained at 0-90°C, and the reaction is carried out for 2-10 hours at a stirring speed of 200-1000 rpm to form a gel, and the gel is subjected to secondary calcination to obtain a lithium-rich manganese-based positive electrode material precursor, and then the lithium-rich manganese-based positive electrode material precursor heated to a heat treatment temperature is placed in a cooling medium stirred at a high speed for cooling, and after a combined treatment of high shear stress + heat treatment, it is washed and dried to finally obtain a lithium-rich manganese-based positive electrode material.

2. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The concentrations of the lithium acetate aqueous solution, the transition metal salt aqueous solution and the citric acid aqueous solution are 0.3-2 mol / L.

3. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The molar ratio of the lithium acetate, the transition metal salt and the sodium citrate is 1-2:1:1-2.

4. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The transition metal element in the transition metal salt is one or more of Fe, Mn, Co, Ni, Cu and Zn.

5. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The transition metal salt is one or more of transition metal nitrate, transition metal acetate and transition metal sulfate.

6. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The secondary calcination procedure adopts a "two-stage uniform temperature control-insulation method". The first stage calcination temperature is 450-600°C, and the insulation time is 4-8 hours. The second stage calcination temperature is 750-950°C, and the insulation time is twice that of the first stage. The heating rate of the whole process is 2-10°C / min under air atmosphere.

7. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The heat treatment temperature is 750-950° C., and the high shear stress rotation speed is 500-15000 rpm.

8. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The cooling medium is one or more of air, oil, aqueous solution, ethanol solution and liquid nitrogen.

9. The method for preparing a lithium-rich manganese-based positive electrode material according to claim 1, characterized in that: The dropping rate of the lithium acetate aqueous solution and the transition metal salt aqueous solution is 1-50 mL / min.

10. A lithium-rich manganese-based positive electrode material and preparation method according to claim 1, characterized in that: The lithium-rich manganese-based positive electrode material is an irregular polyhedron with a particle size of 0.05 to 2 μm.

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