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

Abstract

A modified lithium-rich manganese-based positive electrode material, and a preparation method therefor and the use thereof. The preparation method comprises the following steps: (1) injecting a mixed metal salt solution, a precipitant, a complexing agent, a cationic dopant and an anionic dopant into a reaction device in a parallel flow manner, and subjecting same to a co-precipitation reaction; (2) washing the product of the co-precipitation reaction, so as to obtain a modified lithium-rich manganese-based precursor; and (3) mixing the modified lithium-rich manganese-based precursor with a lithium source, and sintering same, so as to obtain a modified lithium-rich manganese-based positive electrode material. By means of the co-precipitation reaction, uniform atom-scale co-doping of anions and cations is achieved, the content of doping atoms is precise and controllable, and the problems of introduction of impurities, element segregation and even component deviation caused by traditional solid-phase reactions are avoided.

Description

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

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

[0002] With the rapid development of the green economy and the growing demand for green energy, higher requirements are placed on the energy density of lithium-ion batteries. The improvement of energy density is mainly restricted by the energy density of the positive electrode material. At present, commercial positive electrode materials mainly include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium iron phosphate (LiFePO4) and ternary materials (LiNi x Co y Mn z O2 or LiNi x Co y Al z O2). Among these, ternary materials have the highest energy density, but their specific capacity is still less than 200 mAh / g. Furthermore, ternary materials require the use of expensive cobalt and nickel, metals with low strategic reserves. Therefore, developing high-energy-density and low-cost cathode materials is a key research priority.

[0003] Layered lithium-rich manganese-based materials greatly reduce the use of expensive cobalt and nickel, significantly reducing material costs. Furthermore, due to their unique crystal structure and elemental composition, they exhibit special transition metal redox and anion redox mechanisms, resulting in extremely high theoretical specific capacity and a high voltage platform. However, anion redox is a double-edged sword: while providing high capacity, it can also lead to oxidation of oxygen atoms and even oxygen evolution, severely reducing cycle stability.

[0004] CN108557905A discloses a lithium-rich manganese-based material precursor, which is a lithium-rich manganese-based material carbonate precursor with a flaky morphology. The preparation process of the lithium-rich manganese-based material precursor includes: simultaneously pumping a mixed salt solution, a precipitant, and a complexing agent into a reactor at a rate of 0.12L / h to 0.9L / h, controlling the reaction temperature to 35 to 65°C, the pH value to 7.5 to 8.5, and the stirring speed to 400 to 1000rpm. After the reaction is completed, aging is carried out for 5 to 20 hours, and the precipitate is separated, washed, and dried to obtain the flaky lithium-rich manganese-based material carbonate precursor.

[0005] CN104466162A discloses a method for preparing a gradient lithium-rich manganese-based precursor and a gradient lithium-rich manganese-based positive electrode material. A mixed solution A, a mixed solution B, and a solution C with different manganese ion contents are prepared, and are added to a first reactor, a second reactor, and a third reactor in sequence for reaction. The first reactor, the second reactor, and the third reactor are connected in series for a cyclic reaction to obtain a gradient lithium-rich manganese-based precursor.

[0006] In the lithium-rich manganese-based positive electrode material prepared by the precursor described in the above scheme, some transition metals will migrate into the tetrahedral gaps during the cycle, so the material structure will change to spinel, resulting in voltage decay and greatly reduced cycle performance, which hinders the further commercial application of lithium-rich manganese-based materials.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of this application is to provide a modified lithium-rich manganese-based positive electrode material and its preparation method and application. This application realizes uniform co-doping of anions and cations at the atomic level through a co-precipitation reaction, and the doping atom content is precisely controllable, avoiding the problems of impurities, element segregation and even component deviation introduced by traditional solid-phase reactions.

[0010] To achieve this goal, this application adopts the following technical solutions:

[0011] In a first aspect, the present application provides a method for preparing a modified lithium-rich manganese-based positive electrode material, the preparation method comprising the following steps:

[0012] (1) injecting a mixed metal salt solution, a precipitant, a complexing agent, a cationic dopant, and an anionic dopant into a reaction device in parallel to perform a coprecipitation reaction;

[0013] (2) washing the product of the coprecipitation reaction to obtain a modified lithium-rich manganese-based precursor;

[0014] (3) The modified lithium-rich manganese-based precursor and a lithium source are mixed, and the modified lithium-rich manganese-based positive electrode material is obtained by sintering.

[0015] During the preparation of the modified lithium-rich manganese-based cathode material described herein, coprecipitation of anionic and cationic dopants achieves metal cation doping in the transition metal layer and anionic doping in the oxygen sites, creating a unique synergistic effect and achieving complementary advantages, effectively stabilizing lattice oxygen and mitigating lattice oxygen loss. Furthermore, precise selection and controlled optimization of the complexing agent prevent element enrichment and the formation of impurity phases. This effectively inhibits the migration of transition metal ions into the lithium layer during the cycling of the layered lithium-rich manganese oxide cathode material, suppressing the formation of the spinel phase.

[0016] In one embodiment, the solute of the mixed metal salt solution in step (1) includes nickel salt, cobalt salt and manganese salt.

[0017] In one embodiment, the total metal concentration in the mixed metal salt solution is 1 to 2.5 mol / L, for example, 1 mol / L, 1.5 mol / L, 1.8 mol / L, 2 mol / L or 2.5 mol / L.

[0018] In one embodiment, the precipitant includes any one of Na2CO3 solution, NH4HCO3 solution or carbonic acid, or a combination of at least two thereof.

[0019] In one embodiment, the concentration of the precipitant is 0.4 to 3 mol / L, for example, 0.4 mol / L, 1 mol / L, 1.2 mol / L, 1.5 mol / L or 3 mol / L.

[0020] In one embodiment, the complexing agent comprises sodium citrate solution and / or disodium EDTA solution.

[0021] In one embodiment, the concentration of the complexing agent is 0.1 to 0.3 mol / L, for example, 0.1 mol / L, 0.15 mol / L, 0.2 mol / L, 0.25 mol / L or 0.3 mol / L.

[0022] In one embodiment, the cationic dopant in step (1) comprises any one of zinc salt solution, magnesium salt solution, aluminum salt solution or cerium salt solution, or a combination of at least two thereof.

[0023] In one embodiment, the concentration of the cationic dopant is 0.008 to 0.012 mol / L, for example, 0.008 mol / L, 0.009 mol / L, 0.01 mol / L, 0.011 mol / L or 0.012 mol / L.

[0024] In one embodiment, the anion dopant includes any one of ammonium fluoride solution, sodium fluoride solution, or potassium fluoride solution, or a combination of at least two thereof.

[0025] In one embodiment, the concentration of the anion dopant is 0.008 to 0.012 mol / L, for example, 0.008 mol / L, 0.009 mol / L, 0.01 mol / L, 0.011 mol / L or 0.012 mol / L.

[0026] In one embodiment, the temperature of the coprecipitation reaction in step (1) is 45-85°C, for example, 45°C, 50°C, 60°C, 70°C or 85°C.

[0027] In one embodiment, the atmosphere of the co-precipitation reaction comprises nitrogen.

[0028] In one embodiment, the stirring speed of the coprecipitation reaction is 250-400 rpm, for example, 250 rpm, 280 rpm, 300 rpm, 350 rpm or 400 rpm.

[0029] In one embodiment, the pH of the coprecipitation reaction is 7.5 to 10.5, for example, 7.5, 8, 9, 10 or 10.5.

[0030] In one embodiment, the endpoint of the coprecipitation reaction is that the particle size of the particles in the system is 1 to 20 μm, for example, 1 μm, 5 μm, 10 μm, 15 μm or 20 μm.

[0031] In one embodiment, the detergent used in the washing process of step (2) comprises a sodium carbonate solution.

[0032] In one embodiment, the concentration of the sodium carbonate solution is 2 to 6 mol / L, for example, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L or 6 mol / L.

[0033] In one embodiment, the washing treatment is performed at a temperature of 60-100°C, for example, 60°C, 70°C, 80°C, 90°C or 100°C.

[0034] In one embodiment, the washing treatment in step (2) is followed by a drying treatment.

[0035] In one embodiment, the drying temperature is 40-200°C, for example, 40°C, 80°C, 100°C, 150°C or 200°C.

[0036] In one embodiment, the lithium source in step (3) includes lithium hydroxide and / or lithium carbonate.

[0037] In one embodiment, the sintering temperature is 600-1000°C, for example, 600°C, 700°C, 800°C, 900°C or 1000°C.

[0038] In one embodiment, the sintering treatment time is 10 to 50 hours, for example, 10 hours, 20 hours, 30 hours, 40 hours or 50 hours.

[0039] In a second aspect, the present application provides a modified lithium-rich manganese-based positive electrode material, wherein the modified lithium-rich manganese-based positive electrode material is prepared by the method described in the first aspect;

[0040] In one embodiment, the doping amount of cations in the modified lithium-rich manganese-based positive electrode material is 2500-3000 ppm, for example, 2500 ppm, 2600 ppm, 2700 ppm, 2800 ppm or 3000 ppm.

[0041] In one embodiment, the doping amount of anions in the modified lithium-rich manganese-based positive electrode material is 2400-2700 ppm, for example, 2400 ppm, 2450 ppm, 2500 ppm, 2600 ppm or 2700 ppm.

[0042] In a third aspect, the present application provides a positive electrode plate, which comprises the modified lithium-rich manganese-based positive electrode material as described in the second aspect.

[0043] In a fourth aspect, the present application provides a lithium-ion battery, wherein the lithium-ion battery comprises the positive electrode sheet as described in the third aspect.

[0044] Compared with the prior art, this application has the following beneficial effects:

[0045] (1) This application uses soluble metal salt solutions and fluorine-containing compounds as dopants to achieve uniform atomic-level co-doping of anions and cations during wet co-precipitation. The content of doped atoms is precisely controllable, avoiding the problems of impurities, element segregation, and even component deviation introduced by traditional solid-phase reactions.

[0046] (2) The method described in this application has a simple process flow, mild and controllable conditions, and low cost, and can be prepared in large quantities and industrially, and has good application prospects.

[0047] (3) The discharge capacity of the anion-cation co-doped lithium-rich manganese positive electrode material described in this application can reach up to 236.5 mAh / g, and the capacity retention rate can reach more than 91.8% after 100 cycles, while the capacity retention rate of the undoped material is only 45.6%, indicating that an appropriate amount of anion-cation doping can significantly improve the structural stability and cycle performance.

[0048] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0050] FIG1 is an electron probe scanning image of the doped element zinc in the modified lithium-rich manganese-based positive electrode material described in Example 1 of the present application.

[0051] FIG2 is an electron probe scanning image of the doped element fluorine in the modified lithium-rich manganese-based positive electrode material described in Example 1 of the present application. DETAILED DESCRIPTION

[0052] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0053] Example 1

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

[0055] (1) 2 mol / L ternary sulfate solution with a metal molar ratio of Ni:Co:Mn = 0.30:0.05:0.65, 3 mol / L Na2CO3 solution, 0.3 mol / L complexing agent sodium citrate solution, 0.01 mol / L zinc sulfate solution, 0.01 mol / L sodium fluoride solution and 99.99% purity nitrogen were injected into a 1000 L continuously stirred reactor, the reaction temperature was maintained at 50 ° C, the pH was 8.8, the stirring rate was 400 rpm, and the reaction was stopped after the target particle size reached 10 μm;

[0056] (2) After centrifuging the reaction slurry using a tripod centrifuge, the slurry was washed with a 4 mol / L Na2CO3 solution and pure water in sequence, with the temperature of the washing medium being 80°C, and dried at 150°C to obtain a lithium-rich manganese-based precursor of the carbonate system;

[0057] (3) The lithium-rich manganese-based precursor is mixed evenly with Li2CO3, and sintered at a high temperature of 900°C for 10 hours to obtain the modified lithium-rich manganese-based positive electrode material.

[0058] The electron probe scanning diagram of the doping elements zinc and fluorine of the modified lithium-rich manganese-based positive electrode material is shown in Figure 1-2. It can be seen from Figure 1-2 that the doping elements zinc and fluorine described in this application are uniformly distributed in the modified lithium-rich manganese-based positive electrode material.

[0059] Example 2

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

[0061] (1) 1 mol / L ternary sulfate solution with a metal molar ratio of Ni:Co:Mn = 0.30:0.05:0.65, 0.4 mol / L Na2CO3 solution, 0.1 mol / L complexing agent sodium citrate solution, 0.008 mol / L cerium sulfate solution, 0.008 mol / L sodium fluoride solution and 99.99% purity nitrogen were injected into a 1000 L continuously stirred reactor, the reaction temperature was maintained at 45 ° C, the pH was 10.5, the stirring rate was 250 rpm, and the reaction was stopped after the target particle size reached 1 μm;

[0062] (2) After centrifuging the reaction slurry using a tripod centrifuge, the slurry was washed with a 2 mol / L Na2CO3 solution and pure water in sequence, with the temperature of the washing medium being 60°C, and dried at 50°C to obtain a lithium-rich manganese-based precursor of the carbonate system;

[0063] (3) The lithium-rich manganese-based precursor is mixed evenly with Li2CO3, and sintered at a high temperature of 600°C for 50 hours to obtain the modified lithium-rich manganese-based positive electrode material.

[0064] Example 3

[0065] This embodiment provides a modified lithium-rich manganese-based positive electrode material. The preparation method of the modified lithium-rich manganese-based positive electrode material is as follows:

[0066] (1) 2.5 mol / L ternary sulfate solution with a metal molar ratio of Ni:Co:Mn=0.30:0.05:0.65, 3 mol / L Na2CO3 solution, 0.3 mol / L complexing agent sodium citrate solution, 0.012 mol / L magnesium sulfate solution, 0.012 mol / L potassium fluoride solution and 99.99% purity nitrogen were injected into a 1000 L continuously stirred reactor, the reaction temperature was maintained at 85°C, the pH was 7.5, the stirring rate was 400 rpm, and the reaction was stopped after the target particle size reached 20 μm;

[0067] (2) After centrifuging the reaction slurry using a tripod centrifuge, the slurry was washed with a 6 mol / L Na2CO3 solution and pure water in sequence, with the temperature of the washing medium being 100°C, and dried at 200°C to obtain a carbonate system lithium-rich manganese-based precursor;

[0068] (3) The lithium-rich manganese-based precursor is mixed evenly with Li2CO3, and sintered at a high temperature of 1000°C for 10 hours to obtain the modified lithium-rich manganese-based positive electrode material.

[0069] Example 4

[0070] The only difference between this embodiment and embodiment 1 is that the concentration of the zinc sulfate solution is 0.005 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0071] Example 5

[0072] The only difference between this embodiment and embodiment 1 is that the concentration of the zinc sulfate solution is 0.015 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0073] Example 6

[0074] The only difference between this embodiment and embodiment 1 is that the concentration of the sodium fluoride solution is 0.005 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0075] Example 7

[0076] The only difference between this embodiment and embodiment 1 is that the concentration of the sodium fluoride solution is 0.015 mol / L, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0077] Comparative Example 1

[0078] The only difference between this comparative example and Example 1 is that zinc sulfate and sodium fluoride solution are not added, and other conditions and parameters are exactly the same as those in Example 1.

[0079] Comparative Example 2

[0080] The only difference between this comparative example and Example 1 is that no zinc sulfate solution is added, and other conditions and parameters are exactly the same as those in Example 1.

[0081] Comparative Example 3

[0082] The only difference between this comparative example and Example 1 is that no sodium fluoride solution is added, and other conditions and parameters are exactly the same as those in Example 1.

[0083] Performance testing:

[0084] Ion doping concentration test: Weigh 0.1000g of sample and moisten it with a small amount of water in a Teflon crucible. Add 2mL of nitric acid and heat to digest. Remove the acid, dilute to 20mL, and dilute 5-fold before testing. Prepare a standard solution of the corresponding element and directly measure the doping element content using ICP-AES.

[0085] The positive electrode materials obtained in the above examples and comparative examples are prepared into lithium-ion batteries by the following method:

[0086] The positive electrode material, binder polyvinylidene fluoride, and conductive agent Super P were added to N-methylpyrrolidone at a mass ratio of 97:1.5:1.5 and stirred to form a first positive electrode slurry; the first positive electrode slurry was then evenly coated on the positive electrode current collector aluminum foil, dried and roll-pressed to obtain a positive electrode sheet;

[0087] Graphite, conductive agent acetylene black, thickener CMC and binder SBR are mixed in a mass ratio of 96:1:1.5:1.5, and deionized water is added as a solvent and stirred thoroughly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained after drying, cold pressing and slitting;

[0088] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1, and then fully dried lithium salt LiPF6 was dissolved in the mixed solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0089] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, then wrapped with aluminum-plastic film. After drying, the electrolyte is injected. After packaging, standing and formation processes, a lithium-ion battery is obtained. The separator is a PE porous film with a thickness of 11μm, an air permeability of 280s / 100mL, and a porosity of 40%.

[0090] The specific capacity and cycle capacity retention rate of the obtained lithium-ion battery were tested, and the results are shown in Table 1.

[0091] The specific capacity test method is as follows: using the Blue Electric Battery Test System, at 25°C, the lithium-ion battery is charged and discharged three times in the voltage range of 2.5V to 4.5V at a charge and discharge rate of 0.04A / g (calculated based on the mass of the positive electrode material) to measure the battery specific capacity;

[0092] The test method for the cycle capacity retention rate is: at 25°C, cycle at a charge and discharge rate of 0.19A / g (calculated based on the mass of the positive electrode material). After 100 cycles, the discharge capacity of the battery at this time is divided by the discharge capacity of the second cycle, which is the battery's 100-cycle cycle capacity retention rate.

[0093] The test results are shown in Table 1:

[0094] Table 1

[0095] As can be seen from Table 1, it can be obtained from Examples 1-3 that the discharge capacity of the anion-cation co-doped lithium-rich manganese positive electrode material described in this application can reach up to 236.5mAh / g, and the capacity retention rate can reach more than 91.8% after 100 cycles, while the capacity retention rate of the undoped material is only 45.6%, indicating that an appropriate amount of anion-cation doping can significantly improve the structural stability and cycle performance. This application can significantly improve the cycle stability of lithium-rich manganese-based materials by doping with specific metal elements zinc, cerium and magnesium with high bonding strength with oxygen elements. Among them, the zinc element has the most obvious improvement effect.

[0096] By comparing Example 1 with Examples 4-5, it can be seen that in the preparation process of the modified lithium-rich manganese-based positive electrode material described in the present application, the concentration of the cationic dopant will affect the doping amount of the cations, and thus affect the performance of the obtained positive electrode material. The cation doping concentration is controlled at 0.008~0.012mol / L, and the cation doping amount in the modified lithium-rich manganese-based positive electrode material is 2500~3000ppm, and the obtained positive electrode material has better performance. If the concentration of the cationic dopant is too high, the doping amount of cations in the modified lithium-rich manganese-based positive electrode material will be too high, thereby reducing the discharge specific capacity; if the concentration of the cationic dopant is too low, the doping amount of cations in the modified lithium-rich manganese-based positive electrode material will be too low, which has limited effect on improving the lattice stability, resulting in the cycle performance not reaching the ideal state.

[0097] By comparison of Example 1 and Examples 6-7, it can be seen that in the preparation process of the modified lithium-rich manganese-based positive electrode material described in the present application, the concentration of the anion dopant will affect its performance, and thus affect the performance of the obtained positive electrode material. The anion doping concentration is controlled at 0.008~0.012mol / L, and the anion doping amount in the modified lithium-rich manganese-based positive electrode material is 2400~2700ppm, and the obtained positive electrode material has better performance. If the concentration of the anion dopant is too high or too low, the anion doping amount in the modified lithium-rich manganese-based positive electrode material will be too high or too low, thereby reducing the discharge specific capacity and significantly reducing the cycle performance of the lithium-rich manganese positive electrode material.

[0098] By comparing Example 1 and Comparative Examples 1-3, it can be seen that in the preparation process of the modified lithium-rich manganese-based positive electrode material described in the present application, the doping of metal cations in the transition metal layer and the doping of anions in the oxygen position are achieved by co-precipitation of anion dopants and cationic dopants, which produces a unique synergistic effect and achieves complementary advantages, effectively stabilizes lattice oxygen, and alleviates lattice oxygen loss.

[0099] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A method for preparing a modified lithium-rich manganese-based positive electrode material, comprising the following steps: (1) injecting a mixed metal salt solution, a precipitant, a complexing agent, a cationic dopant, and an anionic dopant into a reaction device in parallel to perform a coprecipitation reaction; (2) washing the product of the coprecipitation reaction to obtain a modified lithium-rich manganese-based precursor; (3) The modified lithium-rich manganese-based precursor and a lithium source are mixed, and the modified lithium-rich manganese-based positive electrode material is obtained by sintering.

2. The preparation method according to claim 1, wherein The solute of the mixed metal salt solution in step (1) includes nickel salt, cobalt salt and manganese salt; Optionally, the total metal concentration in the mixed metal salt solution is 1 to 2.5 mol / L; Optionally, the precipitant includes any one or a combination of at least two of Na2CO3 solution, NH4HCO3 solution or carbonic acid; Optionally, the concentration of the precipitant is 0.4 to 3 mol / L; Optionally, the complexing agent includes sodium citrate solution and / or disodium ethylenediaminetetraacetic acid solution; Optionally, the concentration of the complexing agent is 0.1-0.3 mol / L.

3. The preparation method according to claim 1 or 2, wherein: The cationic dopant in step (1) comprises any one of a zinc salt solution, a magnesium salt solution, an aluminum salt solution or a cerium salt solution, or a combination of at least two thereof; Optionally, the concentration of the cationic dopant is 0.008 to 0.012 mol / L; Optionally, the anion dopant includes any one of ammonium fluoride solution, sodium fluoride solution or potassium fluoride solution, or a combination of at least two thereof; Optionally, the concentration of the anion dopant is 0.008-0.012 mol / L.

4. The preparation method according to any one of claims 1 to 3, wherein The temperature of the coprecipitation reaction in step (1) is 45-85° C. Optionally, the atmosphere of the coprecipitation reaction includes nitrogen; Optionally, the stirring speed of the coprecipitation reaction is 250 to 400 rpm; Optionally, the pH of the coprecipitation reaction is 7.5 to 10.5; Optionally, the end point of the coprecipitation reaction is that the particle size of particles in the system is 1 to 20 μm.

5. The preparation method according to any one of claims 1 to 3, wherein: The detergent for the washing treatment in step (2) comprises a sodium carbonate solution; Optionally, the concentration of the sodium carbonate solution is 2 to 6 mol / L; Optionally, the washing treatment is performed at a temperature of 60-100°C.

6. The preparation method according to any one of claims 1 to 5, wherein: After the washing process in step (2), a drying process is performed; Optionally, the drying process is performed at a temperature of 40 to 200°C.

7. The preparation method according to any one of claims 1 to 6, wherein: The lithium source in step (3) includes lithium hydroxide and / or lithium carbonate; Optionally, the sintering temperature is 600-1000°C; Optionally, the sintering treatment time is 10 to 50 hours.

8. A modified lithium-rich manganese-based positive electrode material prepared by the method according to any one of claims 1 to 7; Optionally, the doping amount of cations in the modified lithium-rich manganese-based positive electrode material is 2500 to 3000 ppm; Optionally, the doping amount of anions in the modified lithium-rich manganese-based positive electrode material is 2400 to 2700 ppm.

9. A positive electrode sheet comprising the modified lithium-rich manganese-based positive electrode material according to claim 8.

10. A lithium ion battery comprising the positive electrode sheet according to claim 9.

Images