Lithium battery positive electrode material of doped core-shell structure, preparation method therefor and use thereof

Abstract

A lithium battery positive electrode material of a doped core-shell structure, a preparation method therefor and the use thereof. The lithium battery positive electrode material comprises a high-nickel lithium battery inner core and a low-nickel lithium battery shell, the chemical formulas of the high-nickel lithium battery inner core and the low-nickel lithium battery shell each individually being: LiNixCoyMnzM(1-x-y-z)O2, 0<x<1, 0≤y<1, 0<z<1, and M being a doping element and comprising any one or a combination of at least two of Al, Zr, W, Mg, Ti, Cr, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge. The lithium battery positive electrode material keeps a good specific discharge capacity and rate capability while increasing the energy density of batteries, and controls the structure phase transition of materials during charging-discharging cycle processes, so as to improve the electrochemical stability, thus aiding in large-scale popularization and application.

Description

A doped core-shell structured lithium battery positive electrode material and its preparation method and application Technical Field

[0001] The present application belongs to the technical field of lithium-ion batteries and relates to a lithium-ion battery positive electrode material, and in particular to a lithium-ion battery positive electrode material with a doped core-shell structure and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries, due to their high energy density, excellent rate performance, and low self-discharge, have become a widely used power and energy storage device in our lives. In recent years, with the widespread use of rechargeable batteries in electric vehicles, the market has placed high demands on their energy density, safety, rate performance, and manufacturing costs.

[0003] Ni in ternary materials can mainly increase the capacity and improve the energy density of the battery. However, as the Ni content increases, the nickel-lithium mixed discharge phenomenon becomes serious, which hinders the Li + Diffusion reduces the discharge capacity and rate performance, but high-nickel materials will undergo phase change during the charging and discharging process, resulting in reduced thermal stability and cycle performance, thereby affecting the service life and safety of power lithium batteries for new energy vehicles.

[0004] In addition, the synthesis of existing positive electrode material precursors basically adopts a one-step co-precipitation method. The ternary ratio is fixed throughout the reaction stage, and the reaction system is stable and simple, but this limits the role of different elements to a certain extent.

[0005] It can be seen from this that how to provide a lithium battery positive electrode material and its preparation method to improve the battery energy density while maintaining good discharge specific capacity and rate performance, and control the structural phase change of the material during the charge and discharge cycle, thereby improving the electrochemical stability, has become an urgent problem that technical personnel in this field need to solve.

[0006] Summary of the Invention

[0007] 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.

[0008] In response to the shortcomings of the existing technology, the purpose of this application is to provide a doped core-shell structured lithium battery positive electrode material and its preparation method and application. The lithium battery positive electrode material improves the battery energy density while maintaining good discharge specific capacity and rate performance, controls the structural phase change of the material during the charge and discharge cycle, thereby improving the electrochemical stability, and is conducive to large-scale promotion and application.

[0009] To achieve this goal, this application adopts the following technical solutions:

[0010] In a first aspect, the present application provides a doped core-shell structured lithium battery positive electrode material, wherein the lithium battery positive electrode material comprises a high-nickel lithium battery core and a low-nickel lithium battery shell.

[0011] The chemical formulas of the high nickel lithium battery core and the low nickel lithium battery shell are independently: LiNi x Co y Mn z M (1-x-y-z) O2.

[0012] Wherein: 0<x<1, 0≤y<1, 0<z<1, for example, x=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, y=0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, z=0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0013] M is a doping element, including any one or a combination of at least two of Al, Zr, W, Mg, Ti, Cr, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge. Typical but non-limiting combinations include the combination of Al and Zr, the combination of Zr and W, the combination of W and Mg, the combination of Mg and Ti, the combination of Ti and Cr, the combination of Cr and Ca, the combination of Ca and Mo, the combination of Mo and Y, the combination of Y and Fe, the combination of Fe and Cu, the combination of Cu and Zn, the combination of Zn and V, the combination of V and Nb, the combination of Nb and La, the combination of La and Ce, the combination of Ce and Sn, or the combination of Sn and Ge.

[0014] The Ni content in the high-nickel lithium battery core is higher than the Ni content in the low-nickel lithium battery shell.

[0015] The lithium battery positive electrode material provided in this application designs the distribution of Ni content in the core and the shell, and structurally regulates the precursor and the positive electrode material, so that the high-nickel lithium battery core exerts energy characteristics and the low-nickel lithium battery shell plays a stabilizing role, thereby giving the lithium battery positive electrode material the advantages of high capacity and high stability.

[0016] In addition, the present application adds specific types of doping elements to the core and shell of the lithium battery positive electrode material, thereby controlling the structural phase change of the material during the charge and discharge cycle, further improving the electrochemical stability, and facilitating large-scale promotion and application.

[0017] In one embodiment, the number of layers of the low-nickel lithium battery shell is at least 1 layer, for example, it can be 1 layer, 2 layers, 3 layers, 4 layers or 5 layers, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] In one embodiment, the average particle size of the lithium battery positive electrode material is 2-20 μm, for example, it can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0019] In a second aspect, the present application provides a method for preparing the lithium battery positive electrode material as described in the first aspect, the preparation method comprising the following steps:

[0020] (1) independently preparing a high-nickel metal salt solution, a low-nickel metal salt solution, a doping metal salt solution, a precipitant solution, and a complexing agent solution;

[0021] (2) mixing a high-nickel metal salt solution, a doping metal salt solution, a precipitant solution, and a complexing agent solution to perform a first coprecipitation reaction to obtain a high-nickel core;

[0022] (3) mixing the high-nickel core, the low-nickel metal salt solution, the doping metal salt solution, the precipitant solution, and the complexing agent solution to perform a second coprecipitation reaction to obtain a core-shell structure precursor;

[0023] (4) Mixing the precursor and the lithium source and sintering them to obtain a lithium battery positive electrode material.

[0024] Wherein, the metal elements in the high-nickel metal salt solution and the low-nickel metal salt solution include Ni, Co and Mn, and the Ni content in the high-nickel metal salt solution is higher than the Ni content in the low-nickel metal salt solution; the metal elements in the doped metal salt solution include any one or a combination of at least two of Al, Zr, W, Mg, Ti, Cr, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge, typical but non-limiting combinations include the combination of Al and Zr, the combination of Zr and W, the combination of W and Mg, the combination of Mg and Ti, the combination of Ti and Cr, the combination of Cr and Ca, the combination of Ca and Mo, the combination of Mo and Y, the combination of Y and Fe, the combination of Fe and Cu, the combination of Cu and Zn, the combination of Zn and V, the combination of V and Nb, the combination of Nb and La, the combination of La and Ce, the combination of Ce and Sn, or the combination of Sn and Ge.

[0025] The present application regulates the elemental composition of the core and the shell during the step-by-step co-precipitation reaction to obtain a high-nickel core to provide high capacity for the battery, while simultaneously obtaining a low-nickel shell to improve the cycle stability of the battery. The resulting core-shell structured positive electrode material has a consistent morphology, good particle sphericity and uniformity, and no core-shell separation occurs after sintering, thereby improving the structural stability of the positive electrode material and achieving a good balance between high energy density and high safety of the battery at both the structural and compositional levels.

[0026] In addition, the present application adds specific types of doping elements during the step-by-step co-precipitation reaction process. By controlling the conditions of the reaction system, the doping elements can be uniformly co-precipitated during the reaction process of the core and the shell, and are not affected by the core-shell element composition, thereby further improving the stability of the material during the charge and discharge cycle.

[0027] The preparation method provided in this application has a simple process, low energy consumption, and consistent stability of products in the same batch, and is suitable for industrial large-scale production.

[0028] In one embodiment, the metal salts in the high-nickel metal salt solution and the low-nickel metal salt solution in step (1) independently include any one of sulfate, nitrate or chloride, or a combination of at least two of them. Typical but non-limiting combinations include a combination of sulfate and nitrate, a combination of nitrate and chloride, a combination of sulfate and chloride, or a combination of sulfate, nitrate and chloride.

[0029] In one embodiment, the total concentration of metal ions in the high-nickel metal salt solution in step (1) is 1-5 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0030] In one embodiment, the total concentration of metal ions in the low-nickel metal salt solution in step (1) is 1-5 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] In one embodiment, the total concentration of metal ions in the doped metal salt solution in step (1) is 1-3 mol / L, for example, it can be 1 mol / L, 1.2 mol / L, 1.4 mol / L, 1.6 mol / L, 1.8 mol / L, 2 mol / L, 2.2 mol / L, 2.4 mol / L, 2.6 mol / L, 2.8 mol / L or 3 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0032] In one embodiment, the precipitant solution in step (1) comprises any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution, or a combination of at least two thereof. Typical but non-limiting combinations include a combination of sodium hydroxide solution and potassium hydroxide solution, a combination of potassium hydroxide solution and sodium carbonate solution, a combination of sodium hydroxide solution and sodium carbonate solution, or a combination of sodium hydroxide solution, potassium hydroxide solution and sodium carbonate solution.

[0033] In one embodiment, the concentration of the precipitant solution in step (1) is 1-15 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L or 15 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0034] In one embodiment, the complexing agent solution in step (1) comprises any one of ammonia water, oxalic acid solution or sodium pyrophosphate solution, or a combination of at least two of them. Typical but non-limiting combinations include a combination of ammonia water and oxalic acid solution, a combination of oxalic acid solution and sodium pyrophosphate solution, a combination of ammonia water and sodium pyrophosphate solution, or a combination of ammonia water, oxalic acid solution and sodium pyrophosphate solution.

[0035] In one embodiment, the concentration of the complexing agent solution in step (1) is 1-10 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0036] In one embodiment, the temperature of the first coprecipitation reaction in step (2) is 35-80°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0037] In one embodiment, the pH of the solution in the first coprecipitation reaction in step (2) is 8-13, for example, it can be 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5 or 13, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0038] In one embodiment, the first coprecipitation reaction in step (2) is accompanied by stirring at a rate of 150-500 rpm, for example, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0039] In one embodiment, the average particle size of the high nickel core in step (2) is 2-18 μm, for example, it can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm or 18 μm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0040] In one embodiment, the temperature of the second coprecipitation reaction in step (3) is 35-80°C, for example, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0041] In one embodiment, the pH of the solution of the second coprecipitation reaction in step (3) is 8-12, for example, it can be 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5 or 12, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0042] In one embodiment, the second coprecipitation reaction in step (3) is accompanied by stirring at a rate of 100-400 rpm, for example, 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm or 400 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] In one embodiment, the average particle size of the precursor in step (3) is 2.5-20 μm, for example, it can be 2.5 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm or 20 μm, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0044] In one embodiment, the lithium source in step (4) includes lithium hydroxide and / or lithium carbonate.

[0045] In one embodiment, the mixing molar ratio of the precursor and the lithium source in step (4) is 1:(1-2), for example, it can be 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8 or 1:2, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0046] In one embodiment, the temperature of the sintering treatment in step (4) is 500-1000°C, for example, it can be 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C or 1000°C, but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0047] In one embodiment, the sintering treatment time in step (4) is 6-20 hours, for example, it can be 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours or 20 hours, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] In one embodiment, the sintering treatment in step (4) is followed by crushing and screening.

[0049] As an optional technical solution of the second aspect of the present application, the preparation method comprises the following steps:

[0050] (1) independently preparing a high nickel metal salt solution with a total metal ion concentration of 1-5 mol / L, a low nickel metal salt solution with a total metal ion concentration of 1-5 mol / L, a doped metal salt solution with a total metal ion concentration of 1-3 mol / L, a precipitant solution of 1-15 mol / L, and a complexing agent solution of 1-10 mol / L;

[0051] (2) mixing a high-nickel metal salt solution, a doping metal salt solution, a precipitant solution, and a complexing agent solution, and performing a first coprecipitation reaction at 35-80° C. and a solution pH of 8-13, accompanied by stirring at a rate of 150-500 rpm, to obtain a high-nickel core with an average particle size of 2-18 μm;

[0052] (3) mixing the high-nickel core, the low-nickel metal salt solution, the doping metal salt solution, the precipitant solution, and the complexing agent solution, and performing a second coprecipitation reaction at 35-80° C. and a solution pH of 8-12, accompanied by stirring at a rate of 100-400 rpm to obtain a core-shell structure precursor with an average particle size of 2.5-20 μm;

[0053] (4) The precursor and the lithium source are mixed in a molar ratio of 1:(1-2), sintered at 500-1000° C. for 6-20 h, and crushed and sieved to obtain a doped core-shell structured lithium battery positive electrode material.

[0054] In which, the metal elements in the high-nickel metal salt solution and the low-nickel metal salt solution include Ni, Co and Mn, and the Ni content in the high-nickel metal salt solution is higher than the Ni content in the low-nickel metal salt solution; the metal salts in the high-nickel metal salt solution and the low-nickel metal salt solution independently include any one of sulfate, nitrate or chloride, or a combination of at least two; the metal elements in the doped metal salt solution include any one of Al, Zr, W, Mg, Ti, Cr, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge, or a combination of at least two; the precipitant solution includes any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution, or a combination of at least two; the complexing agent solution includes any one of ammonia water, oxalic acid solution or sodium pyrophosphate solution, or a combination of at least two.

[0055] In a third aspect, the present application provides a lithium-ion battery, which comprises the lithium-ion positive electrode material as described in the first aspect.

[0056] The numerical range described in this application includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, this application no longer exhaustively lists the specific point values ​​included in the range.

[0057] Compared with the prior art, the present invention has the following advantages:

[0058] (1) The lithium battery positive electrode material provided in this application designs the distribution of Ni content in the core and shell, and structurally regulates the precursor and the positive electrode material, so that the high-nickel lithium battery core plays an energy characteristic and the low-nickel lithium battery shell plays a stability role, thereby making the lithium battery positive electrode material have the advantages of high capacity and high stability;

[0059] (2) The present application adds specific types of doping elements to the core and shell of the lithium battery positive electrode material, thereby controlling the structural phase change of the material during the charge and discharge cycle, further improving the electrochemical stability, and facilitating large-scale promotion and application.

[0060] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0061] The technical solution of this application is further explained below through specific implementation methods.

[0062] Example 1

[0063] This embodiment provides a doped core-shell structure lithium battery positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0064] (1) nickel sulfate, cobalt sulfate and manganese sulfate were dissolved in deionized water at a molar ratio of Ni, Co and Mn of 98:1:1 to prepare a high-nickel metal salt solution with a total metal ion concentration of 1.5 mol / L; nickel sulfate, cobalt sulfate and manganese sulfate were dissolved in deionized water at a molar ratio of Ni, Co and Mn of 1:1:1 to prepare a low-nickel metal salt solution with a total metal ion concentration of 1.5 mol / L; and zirconium sulfate solution with a metal ion concentration of 1.5 mol / L, 2 mol / L sodium hydroxide solution and 2 mol / L ammonia water were prepared at the same time;

[0065] (2) High nickel metal salt solution, zirconium sulfate solution, sodium hydroxide solution and ammonia water are introduced into a reactor, and a first coprecipitation reaction is carried out at 45° C. and a solution pH of 12±1, and the concentration of ammonia water is controlled to be 4.5±1.5 g / L, accompanied by stirring at a rate of 400±100 rpm. When the particle size of the material reaches 2.5 μm, the reaction is stopped to obtain a high nickel core Ni 0.97 Co 0.01 Mn 0.01 Zr 0.01 (OH)2;

[0066] (3) The low nickel metal salt solution, zirconium sulfate solution, sodium hydroxide solution and ammonia water are continuously introduced into the reactor, and a second coprecipitation reaction is carried out at 45°C and a solution pH of 11±1. The concentration of ammonia water is controlled to be 5±2 g / L, and the stirring process is carried out at a rate of 250±50 rpm. When the particle size of the material reaches 4.5 μm, the reaction is stopped to obtain a core-shell structure precursor Ni 0.86 Co 0.05 Mn 0.07 Zr 0.02 (OH)2;

[0067] (4) The precursor and lithium carbonate were mixed in a molar ratio of 1:1.5, sintered at 600 ° C for 20 h, cooled to room temperature, crushed and sieved to obtain a doped core-shell structure lithium battery positive electrode material LiNi 0.86 Co 0.05 Mn 0.07Zr 0.02 O2.

[0068] Example 2

[0069] This embodiment provides a doped core-shell structure lithium battery positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0070] (1) nickel nitrate, cobalt nitrate and manganese nitrate are dissolved in deionized water at a molar ratio of Ni, Co and Mn of 8:1:1 to prepare a high-nickel metal salt solution with a total metal ion concentration of 2 mol / L; nickel nitrate, cobalt nitrate and manganese nitrate are dissolved in deionized water at a molar ratio of Ni, Co and Mn of 4:2:4 to prepare a low-nickel metal salt solution with a total metal ion concentration of 2 mol / L; and simultaneously prepare an aluminum nitrate solution with a metal ion concentration of 2 mol / L, a potassium hydroxide solution of 3 mol / L and an ammonia solution of 3 mol / L;

[0071] (2) High nickel metal salt solution, aluminum nitrate solution, potassium hydroxide solution and ammonia water are introduced into a reactor, and a first coprecipitation reaction is carried out at 60° C. and a solution pH of 11±1, and the concentration of ammonia water is controlled to be 7±3 g / L, accompanied by a stirring process at a rate of 350±50 pm. When the particle size of the material reaches 10 μm, the reaction is stopped to obtain a high nickel core Ni 0.78 Co 0.1 Mn 0.1 Al 0.02 (OH)2;

[0072] (3) The low nickel metal salt solution, aluminum nitrate solution, potassium hydroxide solution and ammonia water were continuously introduced into the reactor, and a second coprecipitation reaction was carried out at 60°C and a solution pH of 10±1. The concentration of ammonia water was controlled to be 8±4 g / L, and the stirring process was carried out at a rate of 250±50 rpm. When the particle size of the material reached 14 μm, the reaction was stopped to obtain a core-shell structure precursor Ni 0.6 Co 0.15 Mn 0.23 Al 0.02 (OH)2;

[0073] (4) The precursor and lithium hydroxide were mixed in a molar ratio of 1:1.5, sintered at 700 ° C for 15 h, cooled to room temperature, crushed and sieved to obtain a doped core-shell structure lithium battery positive electrode material LiNi 0.6 Co 0.15 Mn 0.23 Al 0.02 O2.

[0074] Example 3

[0075] This embodiment provides a doped core-shell structure lithium battery positive electrode material and a preparation method thereof, the preparation method comprising the following steps:

[0076] (1) nickel chloride, cobalt chloride and manganese chloride are dissolved in deionized water at a molar ratio of Ni, Co and Mn of 7:1:2 to prepare a high-nickel metal salt solution with a total metal ion concentration of 5 mol / L; nickel chloride, cobalt chloride and manganese chloride are dissolved in deionized water at a molar ratio of Ni, Co and Mn of 4:3:3 to prepare a low-nickel metal salt solution with a total metal ion concentration of 5 mol / L; and simultaneously prepare a magnesium chloride solution with a metal ion concentration of 5 mol / L, a sodium carbonate solution with a 10 mol / L solution and a sodium pyrophosphate solution with a metal ion concentration of 10 mol / L;

[0077] (2) High nickel metal salt solution, magnesium chloride solution, sodium carbonate solution and sodium pyrophosphate solution are introduced into a reactor, and a first coprecipitation reaction is carried out at 70° C. and a solution pH of 11±1. The concentration of the sodium pyrophosphate solution is controlled to be 7±3 g / L, accompanied by a stirring process at a rate of 250±50 rpm. When the particle size of the material reaches 15 μm, the reaction is stopped to obtain a high nickel core Ni 0.68 Co 0.1 Mn 0.2 Mg 0.02 (OH)2;

[0078] (3) The low nickel metal salt solution, magnesium chloride solution, sodium carbonate solution and sodium pyrophosphate solution were continuously introduced into the reactor, and a second coprecipitation reaction was carried out at 70°C and a solution pH of 10±1. The concentration of the sodium pyrophosphate solution was controlled to be 9±3 g / L, accompanied by a stirring process at a rate of 150±50 rpm. When the particle size of the material reached 18 μm, the reaction was stopped to obtain a core-shell structure precursor Ni 0.50 Co 0.20 Mn 0.25 Mg 0.05 (OH)2;

[0079] (4) The precursor and lithium carbonate were mixed in a molar ratio of 1:1.8, sintered at 800 ° C for 10 h, cooled to room temperature, crushed and sieved to obtain a doped core-shell structure lithium battery positive electrode material LiNi 0.50 Co 0.20 Mn 0.25 Mg 0.05 O2.

[0080] Example 4

[0081] This embodiment provides a doped core-shell structure lithium battery positive electrode material and a preparation method thereof. Except that cobalt sulfate is not added to the high-nickel metal salt solution and the low-nickel metal salt solution, the remaining steps and conditions are the same as those in Example 1, and therefore are not described here.

[0082] Example 5

[0083] This embodiment provides a doped core-shell structured lithium battery positive electrode material and a preparation method thereof. The preparation method comprises the following steps: except that step (3) is repeated twice, i.e., two layers of low-nickel shell are coated on the surface of the high-nickel core; the remaining steps and conditions are the same as those in Example 1, and therefore are not described in detail here.

[0084] Comparative Example 1

[0085] This comparative example provides a lithium battery positive electrode material and a preparation method thereof. The preparation method does not perform step (3), that is, directly sintering the high-nickel core as a precursor with lithium carbonate. The remaining steps and conditions are the same as those in Example 1, so they are not described here.

[0086] Comparative Example 2

[0087] This comparative example provides a lithium battery positive electrode material and a preparation method thereof. Except that no zirconium sulfate solution is added in the two coprecipitation reactions, the remaining steps and conditions of the preparation method are the same as those in Example 1, and therefore are not described in detail here.

[0088] Performance testing:

[0089] Button-type lithium-ion batteries were prepared using the lithium-ion positive electrode materials obtained in Examples 1-5 and Comparative Examples 1-2. The specific preparation method includes: adding the lithium-ion positive electrode material, acetylene black and polyvinylidene fluoride to N-methyl-2-pyridine in a mass ratio of 8:1:1 to prepare a solution, which was then evenly applied on aluminum foil, dried, and stamped into thin sheets; and assembling the battery pole piece, the elemental lithium sheet, the glass fiber diaphragm, the electrolyte (LiClO4), the gasket, the shrapnel and the battery shell in an argon glove box to form a button-type battery.

[0090] Table 1 below shows the electrochemical performance test data of button batteries prepared using the lithium battery positive electrode materials obtained in Examples 1-5 and Comparative Examples 1-2, respectively.

[0091] Table 1

[0092] As can be seen from Table 1, the positive electrode material obtained in Example 1 exhibits higher specific capacity and cycle stability after being prepared into a battery; Examples 2, 3 and 5 also exhibit relatively high cycle stability; Example 4 has a slight decrease in cycle performance due to the removal of Co; the Ni content of Comparative Examples 1 and 2 is the same as that of Example 1, so the specific capacity is not much different, but their cycle performance is significantly worse.

[0093] It can be seen that the lithium battery positive electrode material provided in this application structurally regulates the precursor and positive electrode material by designing the Ni content distribution in the core and the shell, so that the high-nickel lithium battery core plays an energy characteristic and the low-nickel lithium battery shell plays a stability role, thereby making the lithium battery positive electrode material have the advantages of high capacity and high stability.

[0094] In addition, the present application adds specific types of doping elements to the core and shell of the lithium battery positive electrode material, thereby controlling the structural phase change of the material during the charge and discharge cycle, further improving the electrochemical stability, and facilitating large-scale promotion and application.

[0095] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of this application. It should be understood that the above is only a specific embodiment of this application and is not intended to limit this application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application should be included in the scope of protection of this application.

Claims

1. A doped core-shell lithium battery positive electrode material, comprising a high-nickel lithium battery core and a low-nickel lithium battery shell; The chemical formulas of the high-nickel lithium battery core and the low-nickel lithium battery shell are independently: LiNi x Co y Mn z M (1-x-y-z) O2; in: 0<x<1, 0≤y<1, 0<z<1; M is a doping element, including any one or a combination of at least two of Al, Zr, W, Mg, Ti, Cr, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge; The Ni content in the high-nickel lithium battery core is higher than the Ni content in the low-nickel lithium battery shell.

2. The lithium battery positive electrode material according to claim 1, wherein The number of layers of the low-nickel lithium battery shell is at least 1; Optionally, the average particle size of the lithium battery positive electrode material is 2-20 μm.

3. A method for preparing a lithium battery positive electrode material as claimed in claim 1 or 2, comprising the following steps: (1) independently preparing a high-nickel metal salt solution, a low-nickel metal salt solution, a doping metal salt solution, a precipitant solution and a complexing agent solution; (2) mixing a high-nickel metal salt solution, a doping metal salt solution, a precipitant solution and a complexing agent solution to perform a first coprecipitation reaction to obtain a high-nickel core; (3) mixing the high-nickel core, the low-nickel metal salt solution, the doping metal salt solution, the precipitant solution and the complexing agent solution to perform a second coprecipitation reaction to obtain a core-shell structure precursor; (4) mixing the precursor and the lithium source and performing sintering treatment to obtain a lithium battery positive electrode material; Among them, the metal elements in the high-nickel metal salt solution and the low-nickel metal salt solution include Ni, Co and Mn, and the Ni content in the high-nickel metal salt solution is higher than the Ni content in the low-nickel metal salt solution; the metal elements in the doped metal salt solution include any one of Al, Zr, W, Mg, Ti, Cr, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge, or a combination of at least two of them.

4. The preparation method according to claim 3, wherein The metal salts in the high-nickel metal salt solution and the low-nickel metal salt solution in step (1) independently include any one of sulfate, nitrate or chloride, or a combination of at least two thereof; Optionally, the total concentration of metal ions in the high-nickel metal salt solution in step (1) is 1-5 mol / L; Optionally, the total concentration of metal ions in the low-nickel metal salt solution in step (1) is 1-5 mol / L; Optionally, the total concentration of metal ions in the doped metal salt solution in step (1) is 1-3 mol / L.

5. The preparation method according to claim 3 or 4, wherein The precipitant solution in step (1) comprises any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution or a combination of at least two thereof; Optionally, the concentration of the precipitant solution in step (1) is 1-15 mol / L; Optionally, the complexing agent solution in step (1) includes any one of ammonia water, oxalic acid solution or sodium pyrophosphate solution, or a combination of at least two thereof; Optionally, the concentration of the complexing agent solution in step (1) is 1-10 mol / L.

6. The preparation method according to any one of claims 3 to 5, wherein: Step (2) the temperature of the first coprecipitation reaction is 35-80° C.; Optionally, the pH of the solution in the first coprecipitation reaction in step (2) is 8-13; Optionally, the first coprecipitation reaction in step (2) is accompanied by stirring at a rate of 150-500 rpm; Optionally, the average particle size of the high nickel core in step (2) is 2-18 μm.

7. The preparation method according to any one of claims 3 to 6, wherein: Step (3) the temperature of the second coprecipitation reaction is 35-80° C.; Optionally, the pH of the solution of the second coprecipitation reaction in step (3) is 8-12; Optionally, the second coprecipitation reaction in step (3) is accompanied by stirring at a rate of 100-400 rpm. deal with; Optionally, the average particle size of the precursor in step (3) is 2.5-20 μm.

8. The preparation method according to any one of claims 3 to 7, wherein: The lithium source in step (4) includes lithium hydroxide and / or lithium carbonate; Optionally, the mixing molar ratio of the precursor to the lithium source in step (4) is 1:(1-2); Optionally, the sintering temperature in step (4) is 500-1000° C. Optionally, the sintering time in step (4) is 6-20 hours; Optionally, the sintering treatment in step (4) is followed by crushing and screening.

9. The preparation method according to any one of claims 3 to 8, wherein: The preparation method comprises the following steps: (1) independently preparing a high nickel metal salt solution with a total metal ion concentration of 1-5 mol / L, a low nickel metal salt solution with a total metal ion concentration of 1-5 mol / L, a doped metal salt solution with a total metal ion concentration of 1-3 mol / L, a precipitant solution of 1-15 mol / L, and a complexing agent solution of 1-10 mol / L; (2) mixing a high-nickel metal salt solution, a doping metal salt solution, a precipitant solution and a complexing agent solution, and performing a first coprecipitation reaction at 35-80° C. and a solution pH of 8-13, accompanied by a stirring process at a rate of 150-500 rpm, to obtain a high-nickel core with an average particle size of 2-18 μm; (3) mixing the high-nickel core, the low-nickel metal salt solution, the doping metal salt solution, the precipitant solution and the complexing agent solution, and performing a second coprecipitation reaction at 35-80° C. and a solution pH of 8-12, accompanied by a stirring process at a rate of 100-400 rpm, to obtain a core-shell structure precursor with an average particle size of 2.5-20 μm; (4) mixing the precursor and the lithium source in a molar ratio of 1:(1-2), sintering at 500-1000° C. for 6-20 h, and crushing and sieving to obtain a doped core-shell structured lithium battery positive electrode material; Wherein, the metal elements in the high nickel metal salt solution and the low nickel metal salt solution include Ni, Co and Mn, and the Ni content in the high-nickel metal salt solution is higher than the Ni content in the low-nickel metal salt solution; the metal salts in the high-nickel metal salt solution and the low-nickel metal salt solution respectively and independently include any one of sulfate, nitrate or chloride or a combination of at least two; the metal element in the doped metal salt solution includes any one of Al, Zr, W, Mg, Ti, Cr, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge or a combination of at least two; the precipitant solution includes any one of sodium hydroxide solution, potassium hydroxide solution or sodium carbonate solution or a combination of at least two; the complexing agent solution includes any one of ammonia water, oxalic acid solution or sodium pyrophosphate solution or a combination of at least two.

10. A lithium ion battery comprising the lithium battery positive electrode material as claimed in claim 1 or 2.

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