Monocrystal lithium-rich manganese-based positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a single-crystal lithium-rich manganese-based positive electrode material as well as a preparation method and application thereof. The preparation method of the single-crystal lithium-rich manganese-based material comprises the following steps: synthesizing a nickel-cobalt-manganese hydroxide as a precursor by using a coprecipitation method, then fully mixing the precursor with a lithium source, and then preparing the single-crystal lithium-rich manganese-based positive electrode material by adopting a stepped sintering schedule in combination with a high-temperature-section short-time low-oxygen-partial-pressure mixed atmosphere. According to the method, a stepped sintering schedule is adopted, the conditions such as the temperature, the heating and cooling rate and the atmosphere during sintering are reasonably regulated and controlled, the stepped sintering schedule is beneficial to optimizing the processes such as crystal crystallization, crystal growth and crystal defect repair, the short-time low-oxygen-partial-pressure mixed atmosphere in the high-temperature section is beneficial to achieving better crystal domain dispersion, the staggered structure of the Li2MnO3 phase is improved, and the performance of the lithium ion battery is improved. And finally, the micron-sized single-crystal lithium-rich manganese-based positive electrode material with good grain size consistency is obtained.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of chemical energy storage batteries, and particularly relates to a single-crystal lithium-rich manganese-based positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] The lithium-rich manganese-based (xLiMO2·(1-x)Li2MnO3) positive electrode material is considered as a potential next-generation positive electrode material due to its high discharge specific capacity (>250 mAh g -1 ), high energy density (~1000 Wh kg -1 ), low cost and environmental friendliness. However, due to the inherent characteristics of the structure, the lithium-rich manganese-based material has some unavoidable problems during the cycle, such as loss of lattice oxygen, dissolution of transition metal ions, serious surface phase transition and interface side reaction, which cause performance defects, such as low first-cycle coulombic efficiency, poor rate performance, rapid capacity / voltage attenuation, and performance and safety hazards caused by gas production. Therefore, it is urgent to develop a new process to prepare a lithium-rich manganese-based positive electrode material with high energy density, high power density, excellent cycle performance and good thermal stability.

[0003] At present, the lithium-rich manganese-based positive electrode material mainly has a polycrystalline structure, and has problems such as uneven mass transfer inside and outside the secondary particles, accumulation of internal stress to easily produce cracks, poor structural / chemical stability and serious interface side reaction. Compared with the polycrystalline material, the single-crystal material has the advantages of improved particle integrity, consistent lattice orientation, reduced internal interface / specific surface area, enhanced mechanical strength / thermal stability and higher tap density, and has attracted widespread attention from researchers.

[0004] The existing method for preparing the single-crystal lithium-rich manganese-based positive electrode material is mainly a molten salt method, but a large amount of molten salt is needed as a reaction medium, and in addition, complex post-processing steps such as additional water washing and drying are also needed, which is not conducive to its industrial application. SUMMARY

[0005] In view of the above problems in the prior art, the purpose of the present application is to provide a single-crystal lithium-rich manganese-based positive electrode material and a preparation method thereof, which can meet the application requirements of industrialization of the single-crystal lithium-rich manganese-based positive electrode material and high-energy-density lithium ion batteries.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows: The preparation method of the single-crystal lithium-rich manganese-based positive electrode material comprises the following steps: uniformly mixing a nickel-cobalt-manganese hydroxide precursor and a lithium source, and then sintering by using a step-by-step sintering method combined with a high-temperature short-time low-oxygen partial pressure mixed atmosphere to prepare a single-crystal lithium-rich manganese-based positive electrode material with micron size and good grain size uniformity.

[0007] The step-by-step sintering system is beneficial to optimize the processes of crystal crystallization, crystal growth and crystal defect repair, and the short-time low-oxygen partial pressure mixed atmosphere in the high-temperature section helps to achieve better domain dispersion and improve the layer structure of the Li2MnO3 phase.

[0008] Further, the nickel-cobalt-manganese hydroxide precursor has a chemical formula of Ni x Co y Mn 1-x-y (OH)2, wherein 0.1<=x<=0.2 and 0.1<=y<=0.2.

[0009] Further, the nickel-cobalt-manganese hydroxide precursor can be prepared by a method comprising the following steps: MnSO4.H2O, NiSO4.H2O and CoSO4.H2O are dissolved in deionized water in a certain stoichiometric ratio, then NaOH aqueous solution and NH3.H2O are slowly added into the continuously stirred water bath (60℃) solution, and the process is carried out under nitrogen protection, and the solution pH is kept in the range of 10.5-11 during the whole precipitation process; after the reaction is completed, the obtained precipitate is filtered and repeatedly washed with deionized water and ethanol; and the precipitate is dried at 100℃ to obtain the nickel-cobalt-manganese oxide precursor.

[0010] Further, the lithium source can be lithium carbonate and / or lithium hydroxide.

[0011] Further, the molar ratio of lithium in the lithium source to transition metals (Ni+Co+Mn) in the nickel-cobalt-manganese hydroxide precursor can be (0.9-1.25):(0.8-1).

[0012] Further, the step-by-step sintering method is as follows: the mixture is heated from room temperature to a first temperature platform (500-650)℃, the sintering time is (4-6)h, then heated from the first temperature platform to a second temperature platform (900-950)℃, the sintering time is (6-10)h, then heated from the second temperature platform to a third temperature platform (1000-1100)℃, the sintering time is (1-3)h, then cooled from the third temperature platform to a fourth temperature platform (800-850)℃, the sintering time is (1-3)h, and finally naturally cooled to room temperature. The heating and cooling rates of the above heating and cooling processes are all (2-5)℃ / min.

[0013] Further, the sintering atmosphere of the third temperature platform is a low-oxygen partial pressure mixed atmosphere, the oxygen partial pressure p(O2) / p θ =0.05-0.2%, the atmosphere is a mixed gas of Ar (or N2) and O2, and the sintering atmosphere of the remaining sections is air, and the gas volume is 0.6-1.

[0014] The single-crystal lithium-rich manganese-based positive electrode material prepared by the method also belongs to the protection scope of the present application.

[0015] The single-crystal lithium-rich manganese-based positive electrode material as a lithium ion battery positive electrode material or in the preparation of a lithium ion battery positive electrode material also belongs to the protection scope of the present application. The present application also provides a lithium ion battery.

[0016] The lithium ion battery provided by the present application comprises the single-crystal lithium-rich manganese-based positive electrode material.

[0017] The present application also provides an electric device comprising the lithium ion battery.

[0018] Compared with the prior art, the present application has the following beneficial effects: 1. The present application adopts a ladder-type sintering system and reasonably controls the temperature, temperature rising and falling rate and atmosphere and other conditions during sintering, the ladder-type sintering system is beneficial to optimizing the processes of crystal crystallization, crystal growth and crystal defect repair, the short-time low-oxygen partial pressure mixed atmosphere at a high temperature section helps to realize better crystal domain dispersion and improve the layer structure of the Li2MnO3 phase, and finally the single-crystal lithium-rich manganese-based positive electrode material with micron level and good grain size consistency is obtained.

[0019] 2. The single-crystal lithium-rich manganese-based positive electrode material prepared by the present application can be applied to large-scale production and high-energy density lithium ion batteries. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 SEM image of the single-crystal lithium-rich manganese-based positive electrode material prepared for Example 1; Figure 2 Charge-discharge curve diagram of the single-crystal lithium-rich manganese-based positive electrode material prepared for Example 1 at 0.1C; Figure 3 Cycle performance diagram of the single-crystal lithium-rich manganese-based positive electrode material prepared for Example 1 and the positive electrode materials prepared for Comparative Examples 1 and 2 at 1C; Figure 4 Rate performance diagram of the single-crystal lithium-rich manganese-based positive electrode material prepared for Example 1 at different current densities. DETAILED DESCRIPTION

[0021] The present application will be further described in detail below in combination with specific embodiments, and the embodiments given are only for illustrating the present application, rather than limiting the scope of the present application. The embodiments provided below can be used as a guide for further improvement by those skilled in the art, and do not constitute any limitation on the present application in any way.

[0022] The experimental methods in the following examples are all conventional methods, and are carried out according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents, etc. used in the following examples can be obtained commercially, unless otherwise specified.

[0023] Example 1, A preparation method of a single-crystal lithium-rich manganese-based positive electrode material, comprising the following steps: (1) The preparation process of the nickel-cobalt-manganese hydroxide precursor is as follows: MnSO4·H2O, NiSO4·H2O, and CoSO4·H2O with a molar ratio of Mn:Ni:Co of 7:2:1 are dissolved in deionized water, and the total concentration of metal ions is 2.0 mol / L -1 . Subsequently, 4M aqueous NaOH and 1.6M NH3·H2O are slowly added dropwise into the continuously stirred water bath (60°C) solution, and the process is carried out under nitrogen protection, and the pH of the solution is maintained in the range of 10.5-11 during the entire precipitation process. After the reaction is completed, the obtained precipitate is filtered and repeatedly washed with deionized water and ethanol. The precipitate is dried at 100°C to obtain the nickel-cobalt-manganese oxide precursor Ni 0.2 Co 0.1 Mn 0.7 (OH)2.

[0024] (2) The nickel-cobalt-manganese hydroxide precursor prepared in (1) and lithium carbonate are fully mixed using a mixing device, and the molar ratio of lithium carbonate to lithium and transition metals in the nickel-cobalt-manganese hydroxide precursor is 1.2:0.8.

[0025] (3) Subsequently, a stepwise sintering schedule is used for sintering, and the specific sintering schedule is as follows: from room temperature to a first temperature platform of 500°C, the sintering time is 4h, then from the first temperature platform to a second temperature platform of 950°C, the sintering time is 10h, then from the second temperature platform to a third temperature platform of 1000°C, the sintering time is 1h, and the atmosphere at this temperature platform is a low oxygen partial pressure O2 / Ar mixed atmosphere, the oxygen partial pressure p(O2) / p θ =0.05%, then from the third temperature platform to a fourth temperature platform of 850°C, the sintering time is 2h, and finally naturally cooled to room temperature. The heating and cooling rates of the above heating and cooling process are both 5°C / min. The obtained sample is a single-crystal lithium-rich manganese-based positive electrode material, and the appearance is as shown in Figure 1 . As can be seen from Figure 1 , the material presents a clear single-crystal morphology, and the particle size distribution is relatively uniform.

[0026] (4) The prepared single crystal lithium-rich manganese-based cathode material was assembled into a half-cell for electrochemical performance testing. When preparing the electrode slurry, PVDF was used as the binder and conductive carbon black was used as the conductive agent. The cathode material: binder: conductive agent = 9:0.5:0.5, and the above materials were uniformly dispersed in the organic solvent NMP. The obtained electrode slurry was coated onto the current collector aluminum foil, then dried, rolled and sliced, and then assembled into a half-cell. The entire assembly process was carried out in a glove box with low water and oxygen content (<0.1 ppm). Lithium sheets were used as the counter electrode, Celgard polypropylene film was used as the separator, and the electrolyte used was 1 M LiPF6 (the solvent was a mixed solvent of ethylene carbonate / diethyl carbonate in a volume ratio of 1:1).

[0027] Figure 2 The first week charge and discharge curve of single crystal lithium-rich manganese-based cathode material at 0.1C. Figure 2 It can be seen that the charge specific capacity is 292.3 mAh / g and the discharge specific capacity is 242.6 mAh / g.

[0028] Figure 3 This is the cycle performance diagram of single crystal lithium-rich manganese-based cathode material at 1C. Figure 3 It can be seen that the capacity retention rate after 100 cycles is 95.6% of the initial capacity. Compared with Comparative Examples 1 and 2, this step-by-step sintering method combined with the preparation strategy of a high-temperature, short-term, low-oxygen partial pressure mixed atmosphere helps improve the cycling performance of the material.

[0029] Figure 4 The figure shows the rate performance of single crystal lithium-rich manganese-based cathode materials at different current densities. Figure 4 It can be seen that the capacity retention rate is 62% at 0.1C-5C. After charging and discharging at 0.1C again, the discharge specific capacity can be restored to 241 mAh / g.

[0030] Example 2 A method for preparing a single-crystal lithium-rich manganese-based positive electrode material comprises the following steps: (1) The preparation process of nickel cobalt manganese hydroxide precursor is as follows: MnSO4·H2O, NiSO4·H2O, and CoSO4·H2O with a Mn:Ni:Co molar ratio of 7:2:1 were dissolved in deionized water. The total metal ion concentration was 2.0 mol L -1 . Subsequently, 4M NaOH aqueous solution and 1.6M NH3·H2O were slowly added dropwise to the solution in a continuously stirred water bath (60°C) under nitrogen protection, and the pH of the solution was kept in the range of 10.5-11 during the entire precipitation process. After the reaction was complete, the obtained precipitate was filtered and repeatedly washed with deionized water and ethanol. The precipitate was dried at 100°C to obtain nickel cobalt manganese oxide precursor Ni 0.2 Co0.1 Mn 0.7 (OH)2.

[0031] (2) The nickel-cobalt-manganese hydroxide precursor prepared in (1) and lithium carbonate are fully mixed using a mixing device, and the molar ratio of lithium carbonate to lithium and transition metals in the nickel-cobalt-manganese hydroxide precursor is 0.9:0.8.

[0032] (3) Then, sintering is performed using a step sintering schedule, and the specific sintering schedule is as follows: from room temperature to a first temperature platform of 650°C, the sintering time is 4h, then from the first temperature platform to a second temperature platform of 950°C, the sintering time is 8h, then from the second temperature platform to a third temperature platform of 1100°C, the sintering time is 2h, and the atmosphere at this temperature platform is a low oxygen partial pressure O2 / N2 mixed atmosphere, the oxygen partial pressure p(O2) / p θ =0.1%, then from the third temperature platform to a fourth temperature platform of 800°C, the sintering time is 3h, and finally, natural cooling to room temperature. The heating and cooling rates of the above heating and cooling processes are both 5°C / min.

[0033] Example 3 A preparation method of a single-crystal lithium-rich manganese-based positive electrode material, comprising the following steps: (1) The preparation process of the nickel-cobalt-manganese hydroxide precursor is as follows: MnSO4·H2O, NiSO4·H2O, and CoSO4·H2O with a molar ratio of Mn:Ni:Co of 7:2:1 are dissolved in deionized water, and the total concentration of metal ions is 2.0 mol / L -1 . Then, 4M NaOH aqueous solution and 1.6M NH3·H2O are slowly added dropwise into the continuously stirred water bath (60°C) solution, and the process is carried out under nitrogen protection, and the solution pH is maintained in the range of 10.5-11 during the entire precipitation process. After the reaction is complete, the obtained precipitate is filtered and repeatedly washed with deionized water and ethanol. The precipitate is dried at 100°C to obtain a nickel-cobalt-manganese oxide precursor Ni 0.2 Co 0.1 Mn 0.7 (OH)2.

[0034] (2) The nickel-cobalt-manganese hydroxide precursor prepared in (1) and lithium hydroxide are fully mixed using a mixing device, and the molar ratio of lithium hydroxide to lithium and transition metals in the nickel-cobalt-manganese hydroxide precursor is 1.2:0.8.

[0035] (3) then sintering using a step sintering schedule, the specific sintering schedule is as follows, from room temperature to a first temperature platform 650℃, the sintering time is 5h, then from the first temperature platform to a second temperature platform 950℃, the sintering time is 10h, then from the second temperature platform to a third temperature platform 1000℃, the sintering time is 1h, the atmosphere at this temperature platform is a low oxygen partial pressure O2 / Ar mixed atmosphere, the oxygen partial pressure p(O2) / p θ =0.1%, then from the third temperature platform to a fourth temperature platform 850℃, the sintering time is 2h, and finally naturally cooled to room temperature. The heating and cooling rates of the above heating and cooling processes are both 2℃ / min.

[0036] Example 4 A preparation method of a single crystal lithium-rich manganese-based positive electrode material, comprising the following steps: (1) The preparation process of the nickel-cobalt-manganese hydroxide precursor is as follows: MnSO4·H2O, NiSO4·H2O and CoSO4·H2O with a molar ratio of Mn:Ni:Co being 7:2:1 are dissolved in deionized water, and the total concentration of metal ions is 2.0 mol / L -1 . Then, 4M aqueous NaOH and 1.6M NH3·H2O are slowly added dropwise into the continuously stirred water bath (60℃) solution, and the process is carried out under nitrogen protection, and the solution pH is kept in the range of 10.5-11 during the whole precipitation process. After the reaction is completed, the obtained precipitate is filtered and repeatedly washed with deionized water and ethanol. The precipitate is dried at 100℃ to obtain a nickel-cobalt-manganese oxide precursor Ni 0.2 Co 0.1 Mn 0.7 (OH)2.

[0037] (2) The nickel-cobalt-manganese hydroxide precursor prepared in (1) and lithium carbonate are fully mixed using a mixing device, and the molar ratio of lithium carbonate to lithium and transition metals in the nickel-cobalt-manganese hydroxide precursor is 1.25:0.8.

[0038] (3) then sintering using a step sintering schedule, the specific sintering schedule is as follows, from room temperature to a first temperature platform 650℃, the sintering time is 5h, then from the first temperature platform to a second temperature platform 900℃, the sintering time is 10h, then from the second temperature platform to a third temperature platform 1000℃, the sintering time is 3h, the atmosphere at this temperature platform is a low oxygen partial pressure O2 / Ar mixed atmosphere, the oxygen partial pressure p(O2) / p θ =0.05%, then from the third temperature platform to a fourth temperature platform 800℃, the sintering time is 3h, and finally naturally cooled to room temperature. The heating and cooling rates of the above heating and cooling processes are both 2℃ / min.

[0039] Example 5 A preparation method of a single-crystal lithium-rich manganese-based positive electrode material, comprising the following steps: (1) The preparation process of the nickel-cobalt-manganese hydroxide precursor is as follows: MnSO4·H2O, NiSO4·H2O, and CoSO4·H2O with a molar ratio of Mn:Ni:Co of 7:2:1 are dissolved in deionized water, and the total concentration of metal ions is 2.0 mol / L. -1 Then, 4M aqueous NaOH and 1.6M NH3·H2O are slowly added dropwise into the continuously stirred water bath (60°C) solution, and the process is carried out under nitrogen protection, and the pH of the solution is kept in the range of 10.5-11 during the whole precipitation process. After the reaction is completed, the obtained precipitate is filtered and repeatedly washed with deionized water and ethanol. The precipitate is dried at 100°C to obtain a nickel-cobalt-manganese oxide precursor Ni 0.2 Co 0.1 Mn 0.7 (OH)2(0.1 < x < 0.2, 0.1 < y < 0.2).

[0040] (2) The nickel-cobalt-manganese hydroxide precursor prepared in (1) and lithium carbonate are uniformly mixed by using a mixing device, and the molar ratio of lithium carbonate to lithium and transition metals in the hydroxide precursor is 1.2:0.9.

[0041] (3) Then, a stepwise sintering system is used for sintering, and the specific sintering system is as follows: from room temperature to a first temperature platform of 650°C, the sintering time is 6h, then from the first temperature platform to a second temperature platform of 950°C, the sintering time is 8h, then from the second temperature platform to a third temperature platform of 1000°C, the sintering time is 2h, and the atmosphere at this temperature platform is a low oxygen partial pressure O2 / Ar mixed atmosphere, the oxygen partial pressure p(O2) / p θ =0.2%, then from the third temperature platform to a fourth temperature platform of 850°C, the sintering time is 3h, and finally naturally cooled to room temperature. The heating and cooling rates of the above heating and cooling processes are all 5°C / min.

[0042] Comparative Example 1 A preparation method of a lithium-rich manganese-based positive electrode material, comprising the following steps: (1) The preparation process of the nickel-cobalt-manganese hydroxide precursor is as follows: MnSO4·H2O, NiSO4·H2O, and CoSO4·H2O with a molar ratio of Mn:Ni:Co of 7:2:1 are dissolved in deionized water, and the total concentration of metal ions is 2.0 mol / L. -1The 4M aqueous NaOH solution and 1.6M NH3·H2O are slowly added dropwise into the continuously stirred water bath (60°C) solution, and the process is carried out under nitrogen protection, with the solution pH maintained in the range of 10.5-11 throughout the precipitation process. After the reaction is complete, the obtained precipitate is filtered and repeatedly washed with deionized water and ethanol. The precipitate is dried at 100°C to obtain a nickel-cobalt-manganese oxide precursor Ni 0.2 Co 0.1 Mn 0.7 (OH)2.

[0043] (2) The nickel-cobalt-manganese hydroxide precursor prepared in (1) and lithium carbonate are uniformly mixed using a mixing device, and the molar ratio of lithium carbonate to lithium and transition metals in the hydroxide precursor is 1.2:0.8.

[0044] (3) Then, sintering is carried out using a constant-temperature sintering system, and the specific sintering system is as follows: from room temperature to a first temperature platform of 650°C, the sintering time is 6h, then from the first temperature platform to 900°C, the sintering time is 15h, and the atmosphere at this temperature platform is a low oxygen partial pressure O2 / Ar mixed atmosphere, the oxygen partial pressure p(O2) / p θ =0.2%, and finally naturally cooled to room temperature. The heating rate of the above heating process is 5°C / min.

[0045] Figure 3 The comparison chart of the cycle performance curves of the prepared lithium-rich manganese-based positive electrode material at 1C. It can be seen from Figure 3 that the capacity retention rate of Comparative Example 1 after 100 cycles at 1C is 85.4%, and the cycle performance is poorer than that of Example 1 (the capacity retention rate after 100 cycles is 95.6%).

[0046] Comparative Example 2 A preparation method of a lithium-rich manganese-based positive electrode material, comprising the following steps: (1) The preparation process of the nickel-cobalt-manganese hydroxide precursor is as follows: MnSO4·H2O, NiSO4·H2O, and CoSO4·H2O with a molar ratio of Mn:Ni:Co of 7:2:1 are dissolved in deionized water, and the total concentration of metal ions is 2.0 mol / L. -1 The 4M aqueous NaOH solution and 1.6M NH3·H2O are slowly added dropwise into the continuously stirred water bath (60°C) solution, and the process is carried out under nitrogen protection, with the solution pH maintained in the range of 10.5-11 throughout the precipitation process. After the reaction is complete, the obtained precipitate is filtered and repeatedly washed with deionized water and ethanol. The precipitate is dried at 100°C to obtain a nickel-cobalt-manganese oxide precursor Ni 0.2 Co 0.1 Mn 0.7 (OH)2.

[0047] (2) The nickel-cobalt-manganese hydroxide precursor prepared in (1) and lithium carbonate are mixed well using a mixing device, and the molar ratio of lithium hydroxide to lithium and transition metals in the nickel-cobalt-manganese hydroxide precursor is 1.2:0.9.

[0048] (3) Then, a step sintering schedule is used for sintering, and the specific sintering schedule is as follows: from room temperature to a first temperature platform of 650℃, the sintering time is 6h, then from the first temperature platform to a second temperature platform of 950℃, the sintering time is 8h, then from the second temperature platform to a third temperature platform of 1000℃, the sintering time is 2h, then from the third temperature platform to a fourth temperature platform of 850℃, the sintering time is 3h, and finally, natural cooling to room temperature. The temperature rising and falling rates in the above temperature rising and falling process are both 5℃ / min, and air is used as the sintering atmosphere throughout the process.

[0049] Figure 3 The cycle performance curve of the prepared lithium-rich manganese-based positive electrode material at 1C is shown in Figure 2. It can be seen that the capacity retention rate of Comparative Example 2 after 100 cycles at 1C is 89.6%, and the cycle performance is poorer than that of Example 1 (the capacity retention rate after 100 cycles is 95.6%). Figure 3

[0050] The above has described the present application in detail. For those skilled in the art, without departing from the purpose and scope of the present application, and without unnecessary experiments, the present application can be implemented in a wide range of equivalent parameters, concentrations and conditions. Although the present application gives a special example, it should be understood that further improvements can be made to the present application. In general, according to the principle of the present application, the present application intends to include any changes, uses or improvements of the present application, including changes made by conventional techniques known in the art, which are outside the scope disclosed in the present application. Some basic features can be applied within the scope of the following attached claims.​

Claims

1. A method for preparing a single-crystalline lithium-rich manganese-based cathode material, comprising the steps of thoroughly mixing a nickel-cobalt-manganese hydroxide precursor and a lithium source, and then sintering the mixture using a stepped sintering method combined with a high-temperature, short-term, low-oxygen partial pressure mixed atmosphere to prepare a single-crystalline lithium-rich manganese-based cathode material; The step-wise sintering method is as follows: the mixed material is heated from room temperature to a first temperature platform of (500-650)°C for a sintering time of (4-6) hours, then heated from the first temperature platform to a second temperature platform of (900-950)°C for a sintering time of (6-10) hours, then heated from the second temperature platform to a third temperature platform of (1000-1100)°C for a sintering time of (1-3) hours, then cooled from the third temperature platform to a fourth temperature platform of (800-850)°C for a sintering time of (1-3) hours, and finally cooled naturally to room temperature; The sintering atmosphere of the third temperature platform is a low oxygen partial pressure mixed atmosphere.

2. The preparation method according to claim 1, wherein: The chemical formula of the nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn 1-x-y (OH)2, where 0.1≤x≤0.2, 0.1≤y≤0.

2.

3. The preparation method according to claim 2, wherein: The nickel-cobalt-manganese hydroxide precursor is prepared according to a method comprising the following steps: dissolving MnSO4·H2O, NiSO4·H2O, and CoSO4·H2O in deionized water at a certain stoichiometric ratio; then slowly adding a NaOH aqueous solution and NH3·H2O dropwise to the continuously stirred water bath solution under nitrogen protection, maintaining the solution pH within the range of 10.5-11 during the entire precipitation process; after the reaction is complete, filtering the obtained precipitate and repeatedly washing it with deionized water and ethanol; and drying the precipitate to obtain the nickel-cobalt-manganese oxide precursor.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The lithium source is lithium carbonate and / or lithium hydroxide.

5. The preparation method according to claim 1, wherein: The molar ratio of lithium in the lithium source to the transition metal (Ni+Co+Mn) in the nickel-cobalt-manganese hydroxide precursor is (0.9-1.25): (0.8-1).

6. The preparation method according to claim 1, wherein: The heating and cooling rates of the step-by-step sintering process are (2-5)°C / min; The sintering atmosphere of the third temperature platform is a mixed gas of O2 and Ar or N2, and the sintering atmosphere of the remaining sections is air with an aeration volume of 0.6-1.

7. A single crystal lithium-rich manganese-based positive electrode material prepared according to the method according to any one of claims 1 to 6.

8. Use of the single crystal lithium-rich manganese-based positive electrode material according to claim 7 as a positive electrode material for lithium-ion batteries or in the preparation of a positive electrode material for lithium-ion batteries.

9. A lithium-ion battery, characterized in that: The lithium-ion battery contains the single-crystal lithium-rich manganese-based positive electrode material according to claim 7.

10. An electrical device, characterized in that: The electrical equipment contains the lithium-ion battery according to claim 9.

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