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

Abstract

The invention provides a lithium-rich manganese-based positive electrode material and a preparation method and application thereof, and belongs to the technical field of positive electrode materials. According to the lithium-rich manganese-based positive electrode material provided by the invention, the lithium-rich manganese-based positive electrode material is of a core-shell structure; the chemical formula of the shell layer is Li [NiaMnbWc] O2, a is greater than 0 and less than or equal to 0.65, c is 0.005-0.03, and a + b + c is equal to 1; the chemical formula of the core layer is Li [NixMnyWz] O2, x is more than or equal to 0.65 and less than or equal to 0.95, z is 0.005-0.03, and x + y + z = 1; a is less than x. According to the invention, the concentrations of nickel and manganese elements in the shell layer and the core layer are distributed in a gradient manner, so that lithium ions are diffused from a high-concentration region to a low-concentration region in the charging and discharging process, slow and ordered release and embedding are realized, and the cycling stability of the battery is improved; the shell layer plays a role of a coating layer, the transmission rate of lithium ions is adjusted, slow release of the lithium ions is realized, and the cycling stability of the battery is improved.

Description

Technical Field

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

[0002] Lithium-ion batteries have seen rapid development in consumer electronics, electric vehicles, and grid energy storage. Rechargeable lithium-ion batteries are a key technology that can accelerate the transition of traditional industries toward sustainable and intelligent mobility, helping to provide clean, affordable, and safe energy and enabling traditional industries to achieve a cleaner, circular economy.

[0003] At present, the cathode materials for lithium-ion batteries mainly include spinel structure lithium manganese oxide (LiMn2O4), olivine structure lithium iron phosphate (LiFePO4) and lithium iron manganese phosphate (LiMn x Fe 1-x PO4) and layered lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-y O2), however, due to their inherent single crystal domain properties, these cathode materials release reversible lithium ions to the maximum extent during the first cycle activation process, and generally have problems such as metal element dissolution, irreversible phase change and structural collapse in the subsequent cycle process, resulting in the attenuation of cycle stability.

[0004] Therefore, how to improve the positive electrode material to enhance the cycle stability of the battery has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The present invention aims to provide a lithium-rich manganese-based cathode material and its preparation method and application. Batteries prepared using the lithium-rich manganese-based cathode material provided by the present invention have excellent cycle stability.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a lithium-rich manganese-based positive electrode material, wherein the lithium-rich manganese-based positive electrode material is a core-shell structure;

[0008] The chemical formula of the shell is Li[Ni a Mn b W c ]O2, 0<a≤0.65, c=0.005~0.03, a+b+c=1;

[0009] The chemical formula of the core layer is Li[Ni x Mn y W z]O2, 0.65≤x≤0.95, z=0.005~0.03, x+y+z=1;

[0010] Said a<x.

[0011] Preferably, c and z are independently 0.005, 0.01, 0.02 or 0.03.

[0012] Preferably, a is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 or 0.65.

[0013] Preferably, x is 0.7, 0.8, 0.9 or 0.95.

[0014] The present invention also provides a method for preparing the lithium-rich manganese-based positive electrode material described in the above technical solution, comprising the following steps:

[0015] (1) mixing a first nickel salt solution, a first manganese salt solution, a first tungsten salt solution, a first precipitant solution, and a first complexing agent solution to perform a first coprecipitation reaction to obtain a core layer precursor solution;

[0016] (2) mixing the core layer precursor solution obtained in step (1), the second nickel salt solution, the second manganese salt solution, the second tungsten salt solution, the second precipitant solution, and the second complexing agent solution, and performing a second coprecipitation reaction to obtain a ternary concentration gradient precursor;

[0017] (3) Mixing the ternary concentration gradient precursor obtained in step (2) with a lithium source and calcining the mixture to obtain a lithium-rich manganese-based positive electrode material.

[0018] Preferably, the first precipitant in step (1) is at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate and potassium bicarbonate.

[0019] Preferably, the first complexing agent in step (1) is aqueous ammonia.

[0020] Preferably, the temperature of the first coprecipitation reaction in step (1) is 40 to 80° C., and the time of the first coprecipitation reaction is 20 to 35 hours.

[0021] Preferably, the roasting in step (3) includes a first roasting and a second roasting performed sequentially; the temperature of the first roasting is 250-600°C, and the time of the first roasting is 1-6 hours; the temperature of the second roasting is 700-1000°C, and the time of the second roasting is 5-30 hours.

[0022] The present invention also provides the use of the lithium-rich manganese-based positive electrode material described in the above technical solution or the lithium-rich manganese-based positive electrode material prepared by the preparation method described in the above technical solution in lithium-ion batteries.

[0023] The present invention provides a lithium-rich manganese-based cathode material, wherein the lithium-rich manganese-based cathode material is a core-shell structure; the chemical formula of the shell is Li[Ni a Mn b W c ]O2, 0<a≤0.65, c=0.005~0.03, a+b+c=1; the chemical formula of the core layer is Li[Ni x Mn y W z ]O2, 0.65≤x≤0.95, z=0.005~0.03, x+y+z=1; the a<x. The concentration difference between nickel and manganese elements in the shell layer and the core layer of the present invention causes lithium ions to diffuse from the high-concentration area to the low-concentration area during the charge and discharge process. During charging, lithium ions are released from the lattice of the lithium-rich manganese-based positive electrode material. Due to the concentration difference between the core layer and the shell layer, the lithium ions will preferentially diffuse from the core layer with a higher concentration to the shell layer with a lower concentration, and then enter the electrolyte. During discharge, lithium ions are embedded in the lithium-rich manganese-based positive electrode material from the electrolyte, first entering the shell layer, and then gradually diffusing and embedding into the core layer. The existence of this concentration difference provides a driving force for the diffusion of lithium ions, enabling them to be released and embedded slowly and orderly, thereby improving the cycle stability of the battery. The shell layer has a surface coating layer, which can adjust the transmission rate of lithium ions, prevent excessive reaction between the electrolyte and the lithium-rich manganese-based positive electrode material, and control the diffusion rate of lithium ions at the interface, so that lithium ions can only enter or leave the lithium-rich manganese-based positive electrode material through the coating layer at a certain rate, further realizing the slow release of lithium ions and improving the cycle stability of the battery. Experimental results show that the battery assembled with the lithium-rich manganese-based positive electrode material provided by the present invention has a first-cycle discharge capacity of 180.4-188.6 mAh / g at a 1C rate, and a capacity retention rate of 81.8-90.3% after 50 charge and discharge cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the XRD pattern of the lithium-rich manganese-based positive electrode material prepared in Example 1;

[0025] Figure 2 This is a SEM image of the lithium-rich manganese-based positive electrode material prepared in Example 1;

[0026] Figure 3 This is a cycle performance diagram of a battery assembled with the lithium-rich manganese-based positive electrode material prepared in Example 1 within a voltage range of 2.5 to 4.4 V and at a rate of 1C. DETAILED DESCRIPTION

[0027] The present invention provides a lithium-rich manganese-based positive electrode material, wherein the lithium-rich manganese-based positive electrode material is a core-shell structure;

[0028] The chemical formula of the shell is Li[Ni a Mn b W c ]O2, 0<a≤0.65, c=0.005~0.03, a+b+c=1;

[0029] The chemical formula of the core layer is Li[Ni x Mn y W z ]O2, 0.65≤x≤0.95, z=0.005~0.03, x+y+z=1;

[0030] Said a<x.

[0031] In the present invention, a is preferably 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 or 0.65; and c is preferably 0.005, 0.01, 0.02 or 0.03.

[0032] In the present invention, the x is preferably 0.7, 0.8, 0.9 or 0.95; the z is preferably 0.005, 0.01, 0.02 or 0.03.

[0033] The concentration gradient distribution of nickel and manganese elements in the shell and core layers of the present invention allows lithium ions to diffuse from areas with high concentration to areas with low concentration during the charge and discharge process. During charging, lithium ions are released from the lattice of the lithium-rich manganese-based positive electrode material. Due to the concentration difference between the core layer and the shell layer, the lithium ions will preferentially diffuse from the core layer with higher concentration to the shell layer with lower concentration, and then enter the electrolyte. During discharge, lithium ions are embedded in the lithium-rich manganese-based positive electrode material from the electrolyte, first entering the shell layer, and then gradually diffusing and embedding into the core layer. The existence of this concentration gradient provides a driving force for the diffusion of lithium ions, enabling them to be released and embedded slowly and orderly, thereby improving the cycle stability of the battery. The shell layer has a surface coating layer, which can adjust the transmission rate of lithium ions, prevent excessive reaction between the electrolyte and the lithium-rich manganese-based positive electrode material, and control the diffusion rate of lithium ions at the interface, so that lithium ions can only enter or leave the lithium-rich manganese-based positive electrode material through the coating layer at a certain rate, further realizing the slow release of lithium ions and improving the cycle stability of the battery.

[0034] The lithium-rich manganese-based positive electrode material provided by the present invention has the characteristic of continuously and slowly releasing lithium ions during the cycle process, so that the cycle retention rate of the material shows a trend of first increasing and then decreasing, which significantly improves the cycle stability of the battery.

[0035] The present invention also provides a method for preparing the lithium-rich manganese-based positive electrode material described in the above technical solution, comprising the following steps:

[0036] (1) mixing a first nickel salt solution, a first manganese salt solution, a first tungsten salt solution, a first precipitant solution, and a first complexing agent solution to perform a first coprecipitation reaction to obtain a core layer precursor solution;

[0037] (2) mixing the core layer precursor solution obtained in step (1), the second nickel salt solution, the second manganese salt solution, the second tungsten salt solution, the second precipitant solution, and the second complexing agent solution, and performing a second coprecipitation reaction to obtain a ternary concentration gradient precursor;

[0038] (3) Mixing the ternary concentration gradient precursor obtained in step (2) with a lithium source and calcining the mixture to obtain a lithium-rich manganese-based positive electrode material.

[0039] The present invention mixes a first nickel salt solution, a first manganese salt solution, a first tungsten salt solution, a first precipitant solution and a first complexing agent solution, performs a first coprecipitation reaction, and obtains a core layer precursor solution.

[0040] In the present invention, the first nickel salt is preferably at least one of nickel sulfate, nickel nitrate and nickel chloride; the first manganese salt is preferably at least one of manganese sulfate, manganese nitrate and manganese chloride; the first tungsten salt is preferably at least one of tungsten sulfate, tungsten nitrate and tungsten chloride; the molar ratio of nickel ions in the first nickel salt, manganese ions in the first manganese salt and tungsten ions in the first tungsten salt is preferably 95: (3 to 4.5): (0.5 to 2).

[0041] As an embodiment, the molar ratio of nickel ions in the first nickel salt, manganese ions in the first manganese salt, and tungsten ions in the first tungsten salt may be 95:(3.4-4.0):(1-1.5).

[0042] The present invention has no particular limitation on the preparation method of the first nickel salt solution, the first manganese salt solution, and the first tungsten salt solution; they can be prepared using water.

[0043] In the present invention, the first precipitant is preferably at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate; the concentration of the first precipitant solution is preferably 5 to 7 mol / L. In one embodiment, the concentration of the first precipitant solution can be 5.5 mol / L, 6 mol / L, or 6.5 mol / L. The present invention does not particularly limit the preparation method of the first precipitant solution; it can be prepared using water.

[0044] In the present invention, the first complexing agent is preferably aqueous ammonia; the concentration of the first complexing agent solution is preferably 1.5 to 4 mol / L. In one embodiment, the concentration of the first complexing agent solution can be 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, or 3 mol / L. The present invention does not particularly limit the preparation method of the first complexing agent solution; it can be prepared using water.

[0045] In the present invention, the mixing of the first nickel salt solution, the first manganese salt solution, the first tungsten salt solution, the first precipitant solution and the first complexing agent solution is preferably performed by mixing the first nickel salt solution, the first manganese salt solution and the first tungsten salt solution to obtain a first salt solution, and then adding the first precipitant solution and the first complexing agent solution.

[0046] The present invention has no special limitation on the operation of mixing the first nickel salt solution, the first manganese salt solution and the first tungsten salt solution, and a technical solution for preparing a mixed material well known to those skilled in the art can be used.

[0047] In the present invention, the sum of the concentrations of nickel ions, manganese ions, and tungsten ions in the first salt solution is preferably 1.5 to 2.5 mol / L, more preferably 2 mol / L. In the present invention, if the sum of the concentrations of nickel ions, manganese ions, and tungsten ions in the first salt solution is lower than 1.5 mol / L, the rate of the first coprecipitation reaction will be too slow, affecting production efficiency, and may not be able to form an ideal core layer precursor solution, ultimately affecting the structure and performance of the positive electrode material; if the concentration is too high, higher than 2.5 mol / L, the ion concentration in the system will be too high, resulting in the first coprecipitation reaction being too intense and difficult to control, generating uneven precipitation, affecting the purity and morphology of the product, and having a negative impact on the performance of the positive electrode material.

[0048] The present invention has no special limitation on the operation of adding the first precipitant solution and the first complexing agent solution, and the technical scheme for preparing the mixed material well known to those skilled in the art can be adopted.

[0049] In the present invention, the temperature of the first coprecipitation reaction is preferably 40 to 80°C; and the time of the first coprecipitation reaction is preferably 25 to 30 hours. By limiting the temperature and time of the first coprecipitation reaction to the above ranges, the degree of the first coprecipitation reaction can be improved.

[0050] As an embodiment, the temperature of the first coprecipitation reaction can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or 75°C; the time of the first coprecipitation reaction can be 26h, 27h, 28h or 29h.

[0051] In the present invention, the pH value during the first coprecipitation reaction is preferably 11.2-12; the ammonium concentration during the first coprecipitation reaction is preferably 7-8 g / L.

[0052] The present invention has no particular limitation on the amount of the first precipitant solution, as long as the pH value during the first coprecipitation reaction is within the range of 11.2 to 12.

[0053] The present invention has no particular limitation on the amount of the first complexing agent solution, as long as the ammonium concentration during the first coprecipitation reaction is within the range of 7 to 8 g / L.

[0054] In the present invention, the first coprecipitation reaction is preferably carried out under stirring conditions; the stirring speed is preferably 200 to 500 rpm. As an embodiment, the stirring speed can be 300 rpm or 400 rpm.

[0055] In the present invention, the first coprecipitation reaction is preferably carried out in a nitrogen atmosphere.

[0056] After obtaining the core layer precursor solution, the present invention mixes the core layer precursor solution, a second nickel salt solution, a second manganese salt solution, a second tungsten salt solution, a second precipitant solution and a second complexing agent solution to perform a second coprecipitation reaction to obtain a ternary concentration gradient precursor.

[0057] In the present invention, the second nickel salt is preferably at least one of nickel sulfate, nickel nitrate and nickel chloride; the second manganese salt is preferably at least one of manganese sulfate, manganese nitrate and manganese chloride; the second tungsten salt is preferably at least one of tungsten sulfate, tungsten nitrate and tungsten chloride; the molar ratio of nickel ions in the second nickel salt, manganese ions in the second manganese salt and tungsten ions in the second tungsten salt is preferably 65: (32 to 34.5): (0.5 to 3).

[0058] As an embodiment, the molar ratio of nickel ions in the second nickel salt, manganese ions in the second manganese salt, and tungsten ions in the second tungsten salt may be 65:(33-34):(1-2).

[0059] The present invention has no particular limitation on the preparation method of the second nickel salt solution, the second manganese salt solution, and the second tungsten salt solution; they can be prepared using water.

[0060] In the present invention, the second precipitant is preferably at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate, and potassium bicarbonate; the concentration of the second precipitant solution is preferably 5 to 7 mol / L. In one embodiment, the concentration of the second precipitant solution can be 5.5 mol / L, 6 mol / L, or 6.5 mol / L. The present invention does not specifically limit the preparation method of the second precipitant solution; it can be prepared using water.

[0061] In the present invention, the second complexing agent is preferably aqueous ammonia; the concentration of the second complexing agent solution is preferably 1.5 to 4 mol / L. In one embodiment, the concentration of the second complexing agent solution can be 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L, or 3 mol / L. The present invention does not particularly limit the preparation method of the second complexing agent solution; it can be prepared using water.

[0062] In the present invention, the mixing of the core layer precursor solution, the second nickel salt solution, the second manganese salt solution, the second tungsten salt solution, the second precipitant solution and the second complexing agent solution is preferably performed by mixing the second nickel salt solution, the second manganese salt solution and the second tungsten salt solution to obtain a second salt solution, which is then added to the core layer precursor solution, and finally the second precipitant solution and the second complexing agent solution are added.

[0063] In the present invention, the sum of the concentrations of nickel ions, manganese ions, and tungsten ions in the second salt solution is preferably 1.5 to 2.5 mol / L, more preferably 2 mol / L. In the present invention, if the sum of the concentrations of nickel ions, manganese ions, and tungsten ions in the second salt solution is lower than 1.5 mol / L, the rate of the second coprecipitation reaction will be too slow, affecting production efficiency, and may not be able to form an ideal shell precursor solution, ultimately affecting the structure and performance of the positive electrode material; if the concentration is too high, higher than 2.5 mol / L, the ion concentration in the system will be too high, resulting in the second coprecipitation reaction being too intense and difficult to control, generating uneven precipitation, affecting the purity and morphology of the product, and having a negative impact on the performance of the positive electrode material.

[0064] The present invention has no special limitation on the operation of mixing the second nickel salt solution, the second manganese salt solution and the second tungsten salt solution, and a technical solution for preparing a mixed material well known to those skilled in the art can be used.

[0065] In the present invention, the volume ratio of the core layer precursor solution to the second salt solution is preferably (0.5-2): 1. As an embodiment, the volume ratio of the core layer precursor solution to the second salt solution can be (1-1.5):1.

[0066] The present invention has no particular limitation on the operation of adding the precursor to the core layer solution, and any operation well known to those skilled in the art may be used.

[0067] The present invention has no special limitation on the operation of adding the second precipitant solution and the second complexing agent solution, and the technical scheme for preparing the mixed material well known to those skilled in the art can be adopted.

[0068] In the present invention, the temperature of the second coprecipitation reaction is preferably 40-80°C; the time of the second coprecipitation reaction is preferably 45-50 hours. In the present invention, limiting the temperature and time of the second coprecipitation reaction to the above ranges can improve the degree of the second coprecipitation reaction.

[0069] As an embodiment, the temperature of the second coprecipitation reaction can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C or 75°C; the time of the second coprecipitation reaction can be 46h, 47h, 48h or 49h.

[0070] In the present invention, the pH value during the second coprecipitation reaction is preferably 11 to 11.8; the ammonium concentration during the second coprecipitation reaction is preferably 7.5 to 8.5 g / L. As an embodiment, the pH value during the second coprecipitation reaction can be 11.5; and the ammonium concentration during the second coprecipitation reaction can be 8 g / L.

[0071] The present invention has no particular limitation on the amount of the second precipitant solution, as long as the pH value during the second coprecipitation reaction is within the range of 11 to 11.8.

[0072] The present invention has no particular limitation on the amount of the second complexing agent solution, as long as the ammonium concentration during the second coprecipitation reaction is within the range of 7.5 to 8.5 g / L.

[0073] In the present invention, the second coprecipitation reaction is preferably carried out under stirring conditions; the stirring speed is preferably 200 to 500 rpm. As an embodiment, the stirring speed can be 300 rpm, 380 rpm or 400 rpm.

[0074] In the present invention, the second coprecipitation reaction is preferably carried out in a nitrogen atmosphere.

[0075] After the second coprecipitation reaction is completed, the present invention preferably filters, washes, dries, and sieves the product obtained from the second coprecipitation reaction in sequence to remove iron, thereby obtaining a ternary concentration gradient precursor.

[0076] The present invention has no particular limitation on the filtering operation, and any operation well known to those skilled in the art may be used to obtain filter residue.

[0077] The present invention has no particular limitation on the washing operation, and washing until neutrality is achieved can be performed using operations well known to those skilled in the art.

[0078] The present invention has no particular limitation on the drying operation, and the drying can be performed until constant weight is reached. As an embodiment, the drying temperature can be 130° C. or 140° C.; and the drying time can be 8 hours or 10 hours.

[0079] The present invention has no special limitation on the operation of screening and iron removal, and operations well known to those skilled in the art may be used.

[0080] After obtaining the ternary concentration gradient precursor, the present invention mixes the ternary concentration gradient precursor with a lithium source and calcines the mixture to obtain a lithium-rich manganese-based positive electrode material.

[0081] In the present invention, the lithium source is preferably at least one of lithium carbonate, lithium hydroxide, lithium hydroxide monohydrate, lithium nitrate, lithium chloride and lithium sulfate.

[0082] In the present invention, the molar ratio of the metal in the ternary concentration gradient precursor to the lithium in the lithium source is preferably (1.05-1.35): 1. As an embodiment, the molar ratio of the metal in the ternary concentration gradient precursor to the lithium in the lithium source may be (1.10-1.30): 1, or may be 1.15: 1, 1.18: 1, 1.20: 1, or 1.25: 1.

[0083] The present invention has no special limitation on the operation of mixing the ternary concentration gradient precursor and the lithium source, and the technical scheme for preparing the mixed material well known to those skilled in the art can be adopted.

[0084] In the present invention, the calcination preferably includes a first calcination and a second calcination performed sequentially; the temperature of the first calcination is preferably 250-600°C; the time of the first calcination is preferably 1-6 hours; the temperature of the second calcination is preferably 700-1000°C; and the time of the second calcination is preferably 5-30 hours. By limiting the calcination process parameters within the above ranges, the present invention can form a specific layered crystal structure, providing channels for the insertion and extraction of lithium ions. During the charge and discharge cycle, the lattice structure undergoes slight expansion and contraction. This structural change is relatively slow and reversible, allowing lithium ions to gradually move and release within the lattice, rather than being instantly extracted or inserted in large quantities. This achieves a slow release of lithium ions, thereby improving the cycle stability of the battery.

[0085] As an embodiment, the temperature of the first calcination may be 300°C, 350°C, 400°C, 450°C, 500°C or 550°C; the time of the first calcination may be 2h, 3h, 4h or 5h; the temperature of the second calcination may be 750°C, 800°C, 850°C, 900°C or 950°C; the time of the second calcination may be 10h, 12h, 15h, 20h, 25h or 28h.

[0086] In the present invention, the rate of heating to the first calcination temperature is preferably 2 to 10°C / min; the rate of heating to the second calcination temperature is preferably 2 to 10°C / min. As an embodiment, the rate of heating to the first calcination temperature may be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, or 9°C / min; the rate of heating to the second calcination temperature may be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, or 9°C / min.

[0087] In the present invention, the calcination is preferably carried out in an oxygen atmosphere. The calcination in an oxygen atmosphere can improve the degree of calcination.

[0088] After the calcination is completed, the present invention preferably cools, crushes and sieves the calcined product in sequence to obtain a lithium-rich manganese-based positive electrode material.

[0089] In the present invention, the cooling rate is preferably 2 to 20°C / min. As an embodiment, the cooling rate can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min, 16°C / min, 17°C / min, 18°C / min or 19°C / min.

[0090] The present invention has no particular limitation on the crushing operation, and any operation well known to those skilled in the art may be used.

[0091] The present invention has no special limitation on the sieving operation, and the sieving operation can be adjusted according to the required particle size.

[0092] In the present invention, the particle size of the lithium-rich manganese-based positive electrode material is preferably 1 to 20 μm. The present invention limits the particle size of the lithium-rich manganese-based positive electrode material to the above range, while ensuring a reasonable reaction between the lithium-rich manganese-based positive electrode material and the electrolyte, it can maintain a good compaction density and lithium ion transmission efficiency, so that the battery achieves a good balance in terms of cycle stability, energy density and charge-discharge performance, etc., and avoids the situation where the particle size is too small, the specific surface area of ​​the lithium-rich manganese-based positive electrode material increases, which may lead to excessive reactivity with the electrolyte, increase side reactions, and reduce the cycle stability and safety of the battery. It can also avoid the situation where the particle size is too large, which affects the compaction density of the lithium-rich manganese-based positive electrode material, reduces the energy density of the battery, and may also hinder the transmission of lithium ions and affect the charge-discharge performance of the battery.

[0093] The preparation method provided by the present invention has a simple and easy-to-control process, removes the Co element with large price fluctuations, is low-cost and environmentally friendly, is suitable for large-scale industrialization, and has good application prospects.

[0094] The present invention also provides the use of the lithium-rich manganese-based positive electrode material described in the above technical solution or the lithium-rich manganese-based positive electrode material prepared by the preparation method described in the above technical solution in lithium-ion batteries.

[0095] The battery assembled using the lithium-rich manganese-based positive electrode material provided by the present invention has good electrochemical performance.

[0096] The present invention has no special limitation on the operation of applying the lithium-rich manganese-based positive electrode material in a lithium-ion battery, and operations well known to those skilled in the art can be used.

[0097] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0098] Example 1

[0099] The lithium-rich manganese-based cathode material has a core-shell structure;

[0100] The chemical formula of the shell is Li[Ni a Mn b W c ]O2, a is 0.65, b is 0.345, c is 0.005, a+b+c=1;

[0101] The chemical formula of the core layer is Li[Ni x Mn y W z]O2, x is 0.95, y is 0.045, z is 0.005, x+y+z=1;

[0102] The preparation method of the lithium-rich manganese-based positive electrode material comprises the following steps:

[0103] (1) A first nickel salt solution, a first manganese salt solution and a first tungsten salt solution are mixed to obtain a first salt solution, and then 150 L of the first salt solution is added to a reactor in a nitrogen atmosphere at a rate of 5 L / h, and then a first precipitant solution and a first complexing agent solution are added, and a first coprecipitation reaction is carried out at 60°C for 30 hours under stirring at 400 rpm to obtain a core layer precursor solution; wherein the first nickel salt is nickel sulfate, the first manganese salt is manganese sulfate, and the first tungsten salt is tungsten sulfate, and the molar ratio of nickel ions in the first nickel salt, manganese ions in the first manganese salt and tungsten ions in the first tungsten salt is 95:4.5:0.5; the sum of the concentrations of nickel ions, manganese ions and tungsten ions in the first salt solution is 2 mol / L; the first precipitant is sodium hydroxide; the concentration of the first precipitant solution is 6 mol / L; the first complexing agent is ammonia water; the concentration of the first complexing agent solution is 4 mol / L; the pH value during the first coprecipitation reaction is 11.6; and the ammonium concentration during the first coprecipitation reaction is 7.5 g / L;

[0104] (2) The second nickel salt solution, the second manganese salt solution and the second tungsten salt solution are mixed to obtain a second salt solution, and then 150L of the second salt solution is pumped into the reactor at a rate of 3L / h, and then the second precipitant solution and the second complexing agent solution are added, and a second coprecipitation reaction is carried out at 60°C for 50h under stirring at 380rpm, and then filtered, washed, dried and sieved to remove iron to obtain a ternary concentration gradient precursor; wherein the second nickel salt is nickel sulfate, the second manganese salt is manganese sulfate, the second tungsten salt is tungsten sulfate, the nickel ions in the second nickel salt, the manganese ions in the second manganese salt and The molar ratio of tungsten ions in the second tungsten salt is 65:34.5:0.5; the sum of the concentrations of nickel ions, manganese ions, and tungsten ions in the second salt solution is 2 mol / L; the second precipitant is sodium hydroxide; the concentration of the second precipitant solution is 6 mol / L; the second complexing agent is aqueous ammonia; the concentration of the second complexing agent solution is 4 mol / L; the volume ratio of the core layer precursor solution to the second salt solution is 1:1; the pH value during the second coprecipitation reaction is 11.5; the ammonium concentration during the second coprecipitation reaction is 8 g / L; the drying temperature is 130°C, and the drying time is 10 hours.

[0105] (3) The ternary concentration gradient precursor obtained in step (2) is mixed with lithium hydroxide, and then calcined in a muffle furnace in an oxygen atmosphere, followed by cooling, crushing and sieving to obtain a lithium-rich manganese-based positive electrode material with a particle size of 1 to 20 μm; wherein the molar ratio of the metal in the ternary concentration gradient precursor to the lithium in the lithium hydroxide is 1.18:1; the calcination is a first calcination and a second calcination performed in sequence, the first calcination temperature is 500°C, the time is 2 hours; the second calcination temperature is 800°C, the time is 12 hours; the heating rate to the first calcination temperature is 5°C / min; the heating rate to the second calcination temperature is 10°C / min; and the cooling rate is 10°C / min.

[0106] Example 2

[0107] The lithium-rich manganese-based cathode material has a core-shell structure;

[0108] The chemical formula of the shell is Li[Ni a Mn b W c ]O2, a is 0.65, b is 0.34, c is 0.01, a+b+c=1;

[0109] The chemical formula of the core layer is Li[Ni x Mn y W z ]O2, x is 0.95, y is 0.04, z is 0.01, x+y+z=1;

[0110] The preparation method of the lithium-rich manganese-based positive electrode material comprises the following steps:

[0111] (1) A first nickel salt solution, a first manganese salt solution and a first tungsten salt solution are mixed to obtain a first salt solution, and then 150 L of the first salt solution is added to a reactor in a nitrogen atmosphere at a rate of 5 L / h, and then a first precipitant solution and a first complexing agent solution are added, and a first coprecipitation reaction is carried out at 60°C for 30 h under stirring at 400 rpm to obtain a core layer precursor solution; wherein the first nickel salt is nickel sulfate, the first manganese salt is manganese sulfate, and the first tungsten salt is tungsten sulfate, and the molar ratio of nickel ions in the first nickel salt, manganese ions in the first manganese salt and tungsten ions in the first tungsten salt is 95:4:1; the sum of the concentrations of nickel ions, manganese ions and tungsten ions in the first salt solution is 2 mol / L; the first precipitant is sodium hydroxide; the concentration of the first precipitant solution is 5 mol / L; the first complexing agent is ammonia water; the concentration of the first complexing agent solution is 4 mol / L; the pH value during the first coprecipitation reaction is 11.5; and the ammonium concentration during the first coprecipitation reaction is 7.5 g / L;

[0112] (2) The second nickel salt solution, the second manganese salt solution and the second tungsten salt solution are mixed to obtain a second salt solution, and then 150L of the second salt solution is pumped into the reactor at a rate of 3L / h, and then the second precipitant solution and the second complexing agent solution are added, and a second coprecipitation reaction is carried out at 60°C for 50h under stirring at 380rpm, and then filtered, washed, dried and sieved to remove iron in sequence to obtain a ternary concentration gradient precursor; wherein the second nickel salt is nickel sulfate, the second manganese salt is manganese sulfate, the second tungsten salt is tungsten sulfate, the nickel ions in the second nickel salt and the manganese ions in the second manganese salt are tungsten sulfate, and the nickel ions in the second nickel salt and the manganese ions in the second manganese salt are tungsten sulfate. The molar ratio of nickel ions and tungsten ions in the second tungsten salt is 65:34:1; the sum of the concentrations of nickel ions, manganese ions and tungsten ions in the second salt solution is 2 mol / L; the second precipitant is sodium hydroxide; the concentration of the second precipitant solution is 5 mol / L; the second complexing agent is ammonia water; the concentration of the first complexing agent solution is 4 mol / L; the volume ratio of the core layer precursor solution to the second salt solution is 1:1; the pH value during the second coprecipitation reaction is 11.5; the ammonium concentration during the second coprecipitation reaction is 8 g / L; the drying temperature is 140°C and the drying time is 8 hours;

[0113] (3) The ternary concentration gradient precursor obtained in step (2) is mixed with lithium hydroxide, and then calcined in a muffle furnace in an oxygen atmosphere, followed by cooling, crushing and sieving to obtain a lithium-rich manganese-based positive electrode material with a particle size of 1 to 20 μm; wherein the molar ratio of the metal in the ternary concentration gradient precursor to the lithium in the lithium hydroxide is 1.18:1; the calcination is a first calcination and a second calcination performed in sequence, the first calcination temperature is 500°C, the time is 2 hours; the second calcination temperature is 800°C, the time is 12 hours; the temperature is increased to the first calcination temperature at a rate of 5°C / min; the temperature is increased to the second calcination temperature at a rate of 5°C / min; the cooling rate is 10°C / min.

[0114] Example 3

[0115] The lithium-rich manganese-based cathode material has a core-shell structure;

[0116] The chemical formula of the shell is Li[Ni a Mn b W c ]O2, a is 0.65, b is 0.33, c is 0.02, a+b+c=1;

[0117] The chemical formula of the core layer is Li[Ni x Mn y W z ]O2, x is 0.95, y is 0.03, z is 0.02, x+y+z=1;

[0118] The preparation method of the lithium-rich manganese-based positive electrode material comprises the following steps:

[0119] (1) A first nickel salt solution, a first manganese salt solution and a first tungsten salt solution are mixed to obtain a first salt solution, and then 150 L of the first salt solution is added to a reactor in a nitrogen atmosphere at a rate of 5 L / h, and then a first precipitant solution and a first complexing agent solution are added, and a first coprecipitation reaction is carried out at 60°C for 30 h under stirring at 400 rpm to obtain a core layer precursor solution; wherein the first nickel salt is nickel sulfate, the first manganese salt is manganese sulfate, and the first tungsten salt is tungsten sulfate, and the molar ratio of nickel ions in the first nickel salt, manganese ions in the first manganese salt and tungsten ions in the first tungsten salt is 95:3:2; the sum of the concentrations of nickel ions, manganese ions and tungsten ions in the first salt solution is 2 mol / L; the first precipitant is sodium hydroxide; the concentration of the first precipitant solution is 7 mol / L; the first complexing agent is ammonia water; the concentration of the first complexing agent solution is 4 mol / L; the pH value during the first coprecipitation reaction is 11.5; and the ammonium concentration during the first coprecipitation reaction is 7.5 g / L;

[0120] (2) The second nickel salt solution, the second manganese salt solution and the second tungsten salt solution are mixed to obtain a second salt solution, and then 150L of the second salt solution is pumped into the reactor at a rate of 3L / h, and then the second precipitant solution and the second complexing agent solution are added, and a second coprecipitation reaction is carried out at 60°C for 50h under stirring at 380rpm, and then filtered, washed, dried and sieved to remove iron in sequence to obtain a ternary concentration gradient precursor; wherein the second nickel salt is nickel sulfate, the second manganese salt is manganese sulfate, the second tungsten salt is tungsten sulfate, the nickel ions in the second nickel salt and the manganese ions in the second manganese salt are tungsten sulfate, and the nickel ions in the second nickel salt and the manganese ions in the second manganese salt are tungsten sulfate. The molar ratio of the nickel ion and the tungsten ion in the second tungsten salt is 65:33:2; the sum of the concentrations of the nickel ion, manganese ion and tungsten ion in the second salt solution is 2 mol / L; the second precipitant is sodium hydroxide; the concentration of the second precipitant solution is 7 mol / L; the second complexing agent is ammonia water; the concentration of the second complexing agent solution is 4 mol / L; the volume ratio of the core layer precursor solution to the second salt solution is 1:1; the pH value during the second coprecipitation reaction is 11.5; the ammonium concentration during the second coprecipitation reaction is 8 g / L; the drying temperature is 140° C., and the drying time is 8 hours;

[0121] (3) The ternary concentration gradient precursor obtained in step (2) is mixed with lithium hydroxide, and then calcined in a muffle furnace in an oxygen atmosphere, followed by cooling, crushing and sieving to obtain a lithium-rich manganese-based positive electrode material with a particle size of 1 to 20 μm; wherein the molar ratio of the metal in the ternary concentration gradient precursor to the lithium in the lithium hydroxide is 1.18:1; the calcination is a first calcination and a second calcination performed in sequence, the first calcination temperature is 500°C, the time is 2 hours; the second calcination temperature is 800°C, the time is 12 hours; the temperature is increased to the first calcination temperature at a rate of 5°C / min; the temperature is increased to the second calcination temperature at a rate of 5°C / min; the cooling rate is 10°C / min.

[0122] Example 4

[0123] The lithium-rich manganese-based cathode material has a core-shell structure;

[0124] The chemical formula of the shell is Li[Ni a Mn b W c ]O2, a is 0.65, b is 0.32, c is 0.03, a+b+c=1;

[0125] The chemical formula of the core layer is Li[Ni x Mn y W z ]O2, x is 0.95, y is 0.02, z is 0.03, x+y+z=1;

[0126] The preparation method of the lithium-rich manganese-based positive electrode material comprises the following steps:

[0127] (1) A first nickel salt solution, a first manganese salt solution and a first tungsten salt solution are mixed to obtain a first salt solution, and then 150 L of the first salt solution is added to a reactor in a nitrogen atmosphere at a rate of 5 L / h, and then a first precipitant solution and a first complexing agent solution are added, and a first coprecipitation reaction is carried out at 60°C for 30 h under stirring at 400 rpm to obtain a core layer precursor solution; wherein the first nickel salt is nickel sulfate, the first manganese salt is manganese sulfate, and the first tungsten salt is tungsten sulfate, and the molar ratio of nickel ions in the first nickel salt, manganese ions in the first manganese salt and tungsten ions in the first tungsten salt is 95:2:3; the sum of the concentrations of nickel ions, manganese ions and tungsten ions in the first salt solution is 2 mol / L; the first precipitant is sodium hydroxide; the concentration of the first precipitant solution is 5.5 mol / L; the first complexing agent is ammonia water; the concentration of the first complexing agent solution is 4 mol / L; the pH value during the first coprecipitation reaction is 11.5; and the ammonium concentration during the first coprecipitation reaction is 7.5 g / L;

[0128] (2) The second nickel salt solution, the second manganese salt solution and the second tungsten salt solution are mixed to obtain a second salt solution, and then 150L of the second salt solution is pumped into the reactor at a rate of 3L / h, and then the second precipitant solution and the second complexing agent solution are added, and a second coprecipitation reaction is carried out at 60°C for 50h under stirring at 380rpm, and then filtered, washed, dried and sieved to remove iron to obtain a ternary concentration gradient precursor; wherein the second nickel salt is nickel sulfate, the second manganese salt is manganese sulfate, the second tungsten salt is tungsten sulfate, the nickel ions in the second nickel salt and the manganese ions in the second manganese salt are tungsten sulfate, and the nickel ions in the second nickel salt and the manganese ions in the second manganese salt are tungsten sulfate. The molar ratio of the nickel ion and the tungsten ion in the second tungsten salt is 65:32:3; the sum of the concentrations of nickel ions, manganese ions, and tungsten ions in the second salt solution is 2 mol / L; the second precipitant is sodium hydroxide; the concentration of the second precipitant solution is 5.5 mol / L; the second complexing agent is ammonia water; the concentration of the second complexing agent solution is 4 mol / L; the volume ratio of the core layer precursor solution to the second salt solution is 1:1; the pH value during the second coprecipitation reaction is 11.5; the ammonium concentration during the second coprecipitation reaction is 8 g / L; the drying temperature is 140°C and the drying time is 8 hours;

[0129] (3) The ternary concentration gradient precursor obtained in step (2) is mixed with lithium hydroxide, and then calcined in a muffle furnace in an oxygen atmosphere, followed by cooling, crushing and sieving to obtain a lithium-rich manganese-based positive electrode material with a particle size of 1 to 20 μm; wherein the molar ratio of the metal in the ternary concentration gradient precursor to the lithium in the lithium hydroxide is 1.18:1; the calcination is a first calcination and a second calcination performed in sequence, the first calcination temperature is 500°C, the time is 2 hours; the second calcination temperature is 800°C, the time is 12 hours; the temperature is increased to the first calcination temperature at a rate of 5°C / min; the temperature is increased to the second calcination temperature at a rate of 5°C / min; the cooling rate is 10°C / min.

[0130] Comparative Example 1

[0131] The chemical formula of lithium-rich manganese-based positive electrode material is LiNi 0.8 Mn 0.2 O2;

[0132] The preparation method of the lithium-rich manganese-based positive electrode material is:

[0133] (1) preparing a salt solution containing nickel sulfate and manganese sulfate, wherein the molar ratio of nickel ions to manganese ions in the salt solution is 8:2, and the sum of the concentrations of nickel ions and manganese ions in the salt solution is 2 mol / L;

[0134] (2) 400 L of salt solution was added to a reactor at a rate of 10 L / h in a nitrogen atmosphere and a rotation speed of 350 rpm. 4 mol / L of ammonia water was added to the reactor as a complexing agent. At the same time, 4 mol / L of NaOH solution was pumped into the reactor to maintain the pH value at 11.8. The coprecipitation reaction was carried out for 40 h, and then filtered and washed to neutrality, and dried at 130 ° C for 11 h to obtain a precursor;

[0135] (3) The precursor and lithium hydroxide were mixed in a molar ratio of 1:1.1 and calcined in a muffle furnace at 800°C for 12 hours, and then crushed and sieved to obtain a lithium-rich manganese-based positive electrode material.

[0136] The pH value, specific surface area, moisture content and tap density of the lithium-rich manganese-based positive electrode materials prepared in Examples 1 to 4 and Comparative Example 1 were tested, and the results are shown in Table 1.

[0137] The test method for pH value is:

[0138] Accurately weigh a certain amount of powder sample, add the sample to deionized water, and stir until it is completely dissolved to form a uniform suspension;

[0139] Standard buffer solutions of pH 7.00 and pH 10.01 were used.

[0140] Calibrate according to the pH meter instructions, first using pH 7.00 buffer, then using pH 10.01 buffer for a second point calibration;

[0141] Rinse the electrode with deionized water and wipe it dry, immerse the electrode in the sample solution, and record the pH value after the reading stabilizes.

[0142] The test method for specific surface area is:

[0143] Principle: Based on the Brunauer-Emmett-Teller theory, the specific surface area is calculated by the amount of gas adsorption.

[0144] Degassing was performed to remove adsorbed substances, nitrogen was adsorbed at liquid nitrogen temperature, and the specific surface area was calculated based on the adsorption isotherm.

[0145] Determination of water content by Karl Fischer method:

[0146] Principle: Water determination by titration based on a chemical reaction.

[0147] Procedure: Dissolve the sample in anhydrous methanol and titrate to the endpoint using Karl Fischer reagent. Calculate the water content based on the titrated volume.

[0148] Tap density meter to measure tap density:

[0149] Prepare the sample: Select an appropriate amount of powder sample (50 g) and accurately weigh its mass using a balance;

[0150] Gently pour the weighed powder into the measuring cylinder and record the initial volume of the powder, that is, the volume before vibration treatment;

[0151] Place the graduated cylinder filled with powder into the tap density meter and set the vibration frequency and number of vibrations to 2 times / second and 1500 times;

[0152] Start the tap density instrument, vibrate the powder according to the set parameters, and observe and record the final volume (Vf) after tapping;

[0153] Calculate the tap density according to the formula: ρ = m / Vf

[0154] Table 1 Physical properties of lithium-rich manganese-based positive electrode materials prepared in Examples 1 to 4 and Comparative Example 1

[0155] project pH <![CDATA[BETm 2 / g]]> Moisture / ppm <![CDATA[Tap density g / cm 3 > Example 1 11.5 0.45 232.5 2.18 Example 2 11.3 0.48 220.4 2.21 Example 3 11.6 0.42 237.3 2.24 Example 4 11.5 0.46 228.5 2.14 Comparative Example 1 10.9 0.52 248.3 1.90

[0156] It can be seen from Table 1 that the water content of the lithium-rich manganese-based positive electrode materials of Examples 1 to 4 is lower than that of Comparative Example 1, and the pH value is higher than that of Comparative Example 1, and the tap density is higher than 2 g / cm 3 , compared with Comparative Example 1, the tap density is higher, indicating that the battery capacity is higher.

[0157] The lithium-rich manganese-based positive electrode materials prepared in Examples 1 to 4 and Comparative Example 1 were used as positive electrodes and metal lithium sheets were used as negative electrodes to assemble button-type half-cells for charge and discharge comparison tests. The results are shown in Table 2 below, where the test method is:

[0158] The active material (i.e., positive electrode material), conductive agent (acetylene black) and binder (polyvinylidene fluoride) are mixed in a mass ratio of 8:1:1, and an appropriate amount of NMP is added and stirred evenly to make a slurry. The slurry is then evenly coated on aluminum foil. After drying in a vacuum drying oven, it is punched into positive electrode sheets of the required size. Metal lithium sheets are used as negative electrodes, and glass fiber separators are used to separate the positive and negative electrodes to assemble them into button-type half-cells.

[0159] Electrolyte selection: Lithium-ion battery positive electrode material system, organic electrolyte containing lithium salt (LiPF6), solvent is ethylene carbonate.

[0160] Charge and discharge test: Use the battery testing system to perform charge and discharge tests on button half-cell batteries.

[0161] Reference standard: GB / T37201-2018

[0162] Table 2 Performance data of batteries assembled with lithium-rich manganese-based positive electrode materials prepared in Examples 1 to 4 and Comparative Example 1

[0163] project First cycle discharge capacity at 1C rate / mAh / g Capacity retention after 50 charge and discharge cycles / % Example 1 180.4 81.8 Example 2 188.6 90.3 Example 3 185.4 85.4 Example 4 182.3 82.9 Comparative Example 1 174.1 76.9

[0164] It can be concluded from Table 2 that the battery composed of the lithium-rich manganese-based positive electrode material prepared in Examples 1 to 4 can achieve a maximum initial discharge capacity of 188.6 mAh / g at a rate of 1C, and a capacity retention rate of up to 90.3% after 50 charge and discharge cycles, while the initial discharge capacity of the ordinary cobalt-free binary high-nickel positive electrode material in Comparative Example 1 is 174.1 mAh / g, and the capacity retention rate after 50 charge and discharge cycles is 76.9%. It can be seen that the discharge capacity of the battery prepared using the lithium-rich manganese-based positive electrode material provided by the present invention is better than the discharge capacity of the battery prepared using the ordinary cobalt-free binary high-nickel positive electrode material; and the optimal tungsten doping amount in the present invention is 1%.

[0165] Figure 1 This is the XRD pattern of the lithium-rich manganese-based positive electrode material prepared in Example 1;

[0166] Figure 2 This is a SEM image of the lithium-rich manganese-based positive electrode material prepared in Example 1;

[0167] Figure 3 This is a cycle performance diagram of a battery assembled with the lithium-rich manganese-based positive electrode material prepared in Example 1 within a voltage range of 2.5 to 4.4 V and at a rate of 1C.

[0168] from Figure 1 It can be seen that the lithium-rich manganese-based positive electrode material prepared in Example 1 has specific crystal structure characteristic peaks, which match the crystal structure of the target lithium-rich manganese-based positive electrode material, proving that the lithium-rich manganese-based positive electrode material with the expected crystal structure has been successfully prepared, and no obvious impurity peaks appear, indicating that the prepared material has high purity and a relatively complete crystal structure.

[0169] from Figure 2 It can be seen that the lithium-rich manganese-based positive electrode material prepared in Example 1 exhibits a clear core-shell structure, the boundary between the core and the shell is relatively clear, and the particle size is relatively uniform, and the particle size is within the expected range of 1 to 20 μm. The surface morphology of the material is good, and there is no obvious agglomeration or defects.

[0170] from Figure 3 It can be seen that the battery made of the lithium-rich manganese-based positive electrode material prepared in Example 1 has excellent cycle stability.

[0171] It can be seen from the above examples and comparative examples that the battery prepared using the lithium-rich manganese-based positive electrode material provided by the present invention has excellent cycle stability.

[0172] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A lithium-rich manganese-based positive electrode material, characterized in that The lithium-rich manganese-based positive electrode material is a core-shell structure; The chemical formula of the shell is Li[Ni a Mn b W c ]O2, 0<a≤0.65, c=0.005~0.03, a+b+c=1; The chemical formula of the core layer is Li[Ni x Mn y W z ]O2, 0.65≤x≤0.95, z=0.005~0.03, x+y+z=1; Said a<x.

2. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that The c and z are independently 0.005, 0.01, 0.02 or 0.

03.

3. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that The a is 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 or 0.

65.

4. The lithium-rich manganese-based positive electrode material according to claim 1, characterized in that The x is 0.7, 0.8, 0.9 or 0.

95.

5. The method for preparing the lithium-rich manganese-based positive electrode material according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) mixing a first nickel salt solution, a first manganese salt solution, a first tungsten salt solution, a first precipitant solution, and a first complexing agent solution to perform a first coprecipitation reaction to obtain a core layer precursor solution; (2) mixing the core layer precursor solution obtained in step (1), the second nickel salt solution, the second manganese salt solution, the second tungsten salt solution, the second precipitant solution, and the second complexing agent solution, and performing a second coprecipitation reaction to obtain a ternary concentration gradient precursor; (3) Mixing the ternary concentration gradient precursor obtained in step (2) with a lithium source and calcining the mixture to obtain a lithium-rich manganese-based positive electrode material.

6. The preparation method according to claim 5, characterized in that The first precipitant in step (1) is at least one of sodium hydroxide, sodium carbonate, sodium bicarbonate, potassium hydroxide, potassium carbonate and potassium bicarbonate.

7. The preparation method according to claim 5, characterized in that The first complexing agent in step (1) is aqueous ammonia.

8. The preparation method according to claim 5, characterized in that The temperature of the first coprecipitation reaction in step (1) is 40-80° C., and the time of the first coprecipitation reaction is 20-35 hours.

9. The preparation method according to claim 5, characterized in that The calcination in step (3) includes a first calcination and a second calcination performed sequentially; the temperature of the first calcination is 250-600°C, and the time of the first calcination is 1-6 hours; the temperature of the second calcination is 700-1000°C, and the time of the second calcination is 5-30 hours.

10. Use of the lithium-rich manganese-based positive electrode material according to any one of claims 1 to 4 or the lithium-rich manganese-based positive electrode material prepared by the preparation method according to any one of claims 5 to 9 in lithium-ion batteries.

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