Full-concentration gradient precursor material, preparation method therefor and use thereof

Abstract

A full-concentration gradient precursor material, a preparation method therefor, and a use thereof. The full-concentration gradient precursor material comprises an inner core and an outer shell, wherein the inner core comprises a nickel-cobalt-manganese precursor material containing a doping element, and the outer shell comprises a nickel-cobalt-manganese precursor material free of a doping element; and from the center of the inner core to an outer surface of the outer shell in the full-concentration gradient precursor material, the content of the element nickel has a decreasing gradient, and the contents of the elements cobalt and manganese have increasing gradients. By means of a combination of a doped core-shell structure and a full-concentration gradient structure, the full-concentration gradient precursor material solves the problem of interface compatibility between the inner core and the outer shell and improves the power performance and cycle performance of the material.

Description

A full concentration gradient precursor material and its preparation method and application Technical Field

[0001] The present application belongs to the field of battery technology and relates to a full concentration gradient precursor material and a preparation method and application thereof. Background Art

[0002] For ternary materials commonly used in lithium-ion batteries, the capacity of the material gradually increases with increasing nickel content. However, as nickel content increases, the thermal stability and cycling performance of the ternary material decrease dramatically. Moreover, within a certain range, the battery's energy density and cycling performance show a negative correlation. Core-shell structures with high nickel content inside and high manganese content outside can provide high capacity as well as structural and thermal stability.

[0003] For example, CN 114649521A discloses a hollow porous concentration gradient positive electrode material, in which the concentrations of nickel ions, cobalt ions, and manganese ions contained in the positive electrode material are distributed in a gradient from the center to the surface. The concentration gradient of the nickel ions contained in the positive electrode material decreases from the center to the surface of the positive electrode material, and the concentration of nickel ions at the center of the positive electrode material is 90%-100%, and the concentration of nickel ions at the surface of the positive electrode material is 60%-70%; the concentration gradients of the cobalt ions and manganese ions contained in the positive electrode material both increase from the center to the surface of the positive electrode material, and the concentrations of cobalt ions and manganese ions at the center of the positive electrode material are 0%-5%, and the concentrations of cobalt ions and manganese ions at the surface of the positive electrode material are 15%-20%; the hollow porous concentration gradient positive electrode material has a concentration gradient structure and higher material surface structure stability. Compared with ordinary homogeneous high-nickel positive electrode materials, it has obvious advantages in terms of cycle performance, rate and safety performance.

[0004] However, the above-mentioned prior art is a concentration gradient material with a core-shell structure. When the composition and structure of the core material and the shell material are greatly different, gaps will be generated between the core and the shell after long-term charging and discharging, and the core will gradually lose the channel for lithium ion migration, resulting in a sharp decrease in the specific capacity of the material.

[0005] Based on the above research, there is a need to provide a full concentration gradient precursor material, which is easy to industrialize and can improve the power performance and cycle performance of the material.

[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] The purpose of this application is to provide a full-concentration-gradient precursor material, its preparation method and application. By combining the core-shell structure and the full-concentration-gradient structure, the compatibility problem at the interface between the inner core and the outer shell is solved, and the power performance and cycling performance of the material are improved.

[0009] To achieve this purpose, the following technical solutions are adopted in this application:

[0010] In the first aspect, this application provides a full-concentration-gradient precursor material, which includes an inner core and an outer shell. The inner core includes a nickel-cobalt-manganese precursor material containing doping elements, and the outer shell includes a nickel-cobalt-manganese precursor material without doping elements;

[0011] From the core of the inner core to the outer surface of the outer shell of the full-concentration-gradient precursor material, the content gradient of nickel element decreases, and the content gradients of cobalt element and manganese element increase.

[0012] The precursor material in this application is a full-concentration-gradient material. From the inside to the outside, the content gradient of nickel element decreases, and the content gradients of cobalt element and manganese element increase. At the same time, it is a core-shell structure. The inner core is doped with elements, and the outer shell is not doped. The doped elements in the inner core can diffuse into the outer shell during lithium doping sintering and can form an internal porous structure through sintering, overcoming the problem of excessive difference between the inner core and the outer shell and the interface compatibility between the inner core and the outer shell, and improving the power performance and cycling performance of the material.

[0013] In one embodiment, the matrix chemical formula of the full-concentration-gradient precursor material is Ni

[0016] ,

[0015] , ,

[0014] , , Co y Mn z (OH)2, where 0.5 < x ≤ 1, for example, it can be 0.55, 0.7, 0.9 or 1, 0 < y ≤ 0.5, for example, it can be 0.05, 0.1, 0.3 or 0.5, 0 < z ≤ 0.5, for example, it can be 0.05, 0.1, 0.3 or 0.5, and x + y + z = 1.

[0014] In one embodiment, the doping elements include any one or a combination of at least two of Zr, Al, W, Ti, Mg, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge.

[0015] The doping elements in this application are derived from laterite nickel ore.

[0016] In one embodiment, in the full concentration gradient precursor material, the doping amount of the doping element is 1000-5000 ppm, for example, it can be 1000 ppm, 2000 ppm, 3000 ppm, 4000 ppm or 5000 ppm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] In a second aspect, the present application provides a method for preparing the full concentration gradient precursor material as described in the first aspect, the preparation method comprising the following steps:

[0018] The nickel solution, the cobalt solution, the manganese solution, the doping solution, the precipitant solution and the complexing agent solution are subjected to a coprecipitation reaction;

[0019] During the coprecipitation reaction, the flow rate of the nickel solution gradually decreases, the flow rates of the cobalt solution and the manganese solution gradually increase, and the feeding of the doping solution is stopped after nucleation is completed.

[0020] The preparation method of the present application is simple and can be produced on a large scale. It only requires the nickel solution, cobalt solution, manganese solution, doping solution, etc. to be fed separately and in parallel, and the feed flow rate and the feeding time of the doping solution are controlled. This can achieve the one-step preparation of doped core-shell structures and full concentration gradient structures, solving the problem of industrialization of full concentration gradient materials.

[0021] In one embodiment, during the coprecipitation reaction, the total flow rate of the nickel solution, the cobalt solution and the manganese solution remains unchanged.

[0022] In one embodiment, the flow rates of the nickel solution, the cobalt solution, and the manganese solution are independently varied at uniform speeds.

[0023] In one embodiment, when the coprecipitation reaction starts, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is (92-98):(2-9):(2-9), for example, it can be 92:4:4, 95:2:3 or 98:1:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] At the beginning of the co-precipitation described in this application, the above flow ratio can be selected for feeding to ensure that the core of the material is high in nickel. However, if the flow rate of the nickel solution is too large, the nickel content inside the core is too high, which will affect the overall stability of the material.

[0025] In one embodiment, at the end of the coprecipitation reaction, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is (40-50): (10-40): (10-40), for example, it can be 40:20:40, 45:30:25 or 50:40:10, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] In the precursor material of the present application, the nickel content gradually decreases, but cannot be reduced to too low. Therefore, when the above coprecipitation reaction is completed, the flow rate of the nickel solution should not be too low. If the flow rate of the nickel solution is too low, it will affect the capacity of the material.

[0027] In one embodiment, the total coprecipitation reaction time is 30-100h, but does not include 30h. For example, it can be 35h, 50h, 60h, 80h or 100h, but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable.

[0028] In one embodiment, the coprecipitation reaction lasts for 5-30 hours, for example, 5 hours, 10 hours, 15 hours, 20 hours, 25 hours or 30 hours, and the feeding of the doping solution is stopped.

[0029] In one embodiment, the ratio of the flow rate of the doping solution to the sum of the flow rates of the nickel solution, the cobalt solution and the manganese solution is 1:(10-20), for example, it can be 1:10, 1:12.5, 1:15, 1:17.5 or 1:20, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0030] The ratio of the flow rate of the doping solution described in the present application to the total flow rate of the nickel-cobalt-manganese solution will affect the amount of doping in the precursor material.

[0031] In one embodiment, the pH of the coprecipitation reaction is 10-13, for example, 10, 11, 12 or 13, and the stirring speed is 100-500 rpm, for example, 100 rpm, 300 rpm or 500 rpm, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] In one embodiment, the concentration of the complexing agent solution is 0.1-0.5 mol / L, for example, 0.1 mol / L, 0.3 mol / L or 0.5 mol / L, but is not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0033] In one embodiment, the complexing agent solution includes any one of ammonia, citric acid, oxalic acid, acetic acid, EDTA or ammonium carbonate, or a combination of at least two thereof.

[0034] In one embodiment, the precipitant solution comprises NaOH solution and / or KOH solution.

[0035] As an optional technical solution of the preparation method described in this application, the preparation method comprises the following steps:

[0036] Perform a coprecipitation reaction on a nickel solution, a cobalt solution, a manganese solution, a doping solution, a precipitant solution, and a complexing agent solution. The coprecipitation reaction lasts for 5 - 30 h, then stop the feeding of the doping solution. The total time of the coprecipitation reaction is 30 - 100 h (excluding 30 h), the pH is 10 - 13, and the stirring speed is 100 - 500 rpm. After the coprecipitation reaction ends, the full-concentration-gradient precursor material is obtained.

[0037] At the start of the coprecipitation reaction, the flow rate ratio of the nickel solution, the cobalt solution, and the manganese solution is (92 - 98):(2 - 9):(2 - 9). Then, the flow rate of the nickel solution decreases uniformly, and the flow rates of the cobalt solution and the manganese solution increase uniformly, and the total flow rate of the nickel solution, the cobalt solution, and the manganese solution remains unchanged.

[0038] At the end of the coprecipitation reaction, the flow rate ratio of the nickel solution, the cobalt solution, and the manganese solution is (40 - 50):(10 - 40):(10 - 40); the ratio of the flow rate of the doping solution to the total flow rate of the nickel solution, the cobalt solution, and the manganese solution is 1:(10 - 20).

[0039] In a third aspect, the present application provides a cathode material, which is obtained by mixing a lithium source with the full-concentration-gradient precursor material as described in the first aspect and calcining.

[0040] In one embodiment, the cathode material includes a core and a shell. The doping elements in the core diffuse into the shell, and the nickel, cobalt, and manganese elements are distributed in a gradient manner.

[0041] In the present application, doping elements are added during the nucleation process of the precursor material. On the one hand, it can generate pores during later sintering to improve the power performance of the material. On the other hand, the doping elements diffuse during high-temperature sintering and the distribution gradually becomes uniform, further improving the cycling performance of the material, so as to obtain the porous and concentration-gradient cathode material.

[0042] In one embodiment, the matrix chemical formula of the cathode material is Li(Ni a Co b X c )O2, where 0.5 < a ≤ 1, for example, it can be 0.55, 0.7, 0.9, or 1, 0 < b ≤ 0.5, for example, it can be 0.05, 0.1, 0.3, or 0.5, 0 < c ≤ 0.5, for example, it can be 0.05, 0.1, 0.3, or 0.5, and a + b + c = 1.

[0043] In one embodiment, the molar ratio of lithium ions in the lithium source to the total metal ions in the full concentration gradient precursor material is (1-1.08):1, for example, it can be 1:1, 1.05:1 or 1.08:1, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In one embodiment, the calcination temperature is 600-800°C, such as 600°C, 700°C or 800°C, the calcination time is 10-20h, such as 10h, 15h or 20h, and the atmosphere includes an oxygen atmosphere.

[0045] In a fourth aspect, the present application provides a battery, comprising the positive electrode material as described in the third aspect.

[0046] Compared with the prior art, this application has the following beneficial effects:

[0047] The precursor material described in the present application is a full concentration gradient material and at the same time a core-shell structure, with the core doped with elements. The doped elements in the core can, on the one hand, produce pores during later sintering, thereby improving the power performance of the material; on the other hand, they can diffuse during high-temperature sintering, thereby becoming gradually evenly distributed, further improving the cycle performance of the material. Therefore, the porous positive electrode material with an element concentration gradient distribution can be obtained; at the same time, the preparation method described in the present application can be industrialized.

[0048] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0049] The technical solution of the present application is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present application and should not be regarded as specific limitations of the present application.

[0050] Example 1

[0051] This embodiment provides a full concentration gradient precursor material, the full concentration gradient precursor material comprising a core and a shell, the core comprising a nickel-cobalt-manganese precursor material containing a doping element, and the shell comprising a nickel-cobalt-manganese precursor material not containing a doping element;

[0052] The full concentration gradient precursor material has a nickel content gradient decreasing from the core to the outer surface of the shell, and a cobalt and manganese content gradient increasing; the matrix chemical formula of the full concentration gradient precursor material is Ni 0.74 Co 0.1 Mn 0.16 (OH)2, the doping element is Zr, and the doping amount of the doping element is 1500ppm;

[0053] The preparation method comprises the following steps:

[0054] Under nitrogen atmosphere protection, nickel solution, cobalt solution, manganese solution, doping solution, precipitant solution and complexing agent solution are added to the reactor in parallel to carry out coprecipitation reaction. When the coprecipitation reaction reaches 10 hours, the feeding of the doping solution is stopped. The total time of the coprecipitation reaction is 60 hours. The pH during the coprecipitation reaction is maintained between 11.8 and 12.0, the stirring speed is 500 rpm, and the ammonia concentration is 0.1 mol / L. After the reaction is completed, the product is washed and dried to obtain the full concentration gradient precursor material.

[0055] The nickel solution is a nickel sulfate solution with a concentration of 2 mol / L, the cobalt solution is a cobalt sulfate solution with a concentration of 2 mol / L, the manganese solution is a manganese sulfate solution with a concentration of 2 mol / L, the doping solution is a zirconium sulfate solution with a concentration of 0.5 mol / L, the precipitant solution is a 10 mol / L NaOH solution, and the complexing agent solution is a 5 mol / L ammonia solution;

[0056] At the beginning of the coprecipitation reaction, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is 98:1:1, then the flow rate of the nickel solution decreases at a uniform rate, the flow rates of the cobalt solution and the manganese solution increase at a uniform rate, and the total flow rate of the nickel solution, the cobalt solution and the manganese solution remains unchanged;

[0057] When the coprecipitation reaction is completed, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is 50:20:30; the ratio of the flow of the doping solution to the total flow of the nickel solution, the cobalt solution and the manganese solution is 1:20.

[0058] Example 2

[0059] This embodiment provides a full concentration gradient precursor material, the full concentration gradient precursor material comprising a core and a shell, the core comprising a nickel-cobalt-manganese precursor material containing a doping element, and the shell comprising a nickel-cobalt-manganese precursor material not containing a doping element;

[0060] The full concentration gradient precursor material has a nickel content gradient decreasing from the core to the outer surface of the shell, and a cobalt and manganese content gradient increasing; the matrix chemical formula of the full concentration gradient precursor material is Ni 0.8 Co 0.1 Mn 0.1 (OH)2, the doping element is Mg, and the doping amount of the doping element is 1600ppm;

[0061] The preparation method comprises the following steps:

[0062] Under nitrogen atmosphere protection, nickel solution, cobalt solution, manganese solution, doping solution, precipitant solution and complexing agent solution are added to the reactor in parallel to carry out coprecipitation reaction. The coprecipitation reaction is continued for 5 hours, and the feeding of the doping solution is stopped. The total time of the coprecipitation reaction is 30 hours. The pH during the coprecipitation reaction is maintained between 12.0 and 12.2. The stirring speed is 300 rpm and the ammonia concentration is 0.3 mol / L. After the reaction is completed, the mixture is washed and dried to obtain the full concentration gradient precursor material.

[0063] The nickel solution is a nickel sulfate solution with a concentration of 1.5 mol / L, the cobalt solution is a cobalt sulfate solution with a concentration of 1.5 mol / L, the manganese solution is a manganese sulfate solution with a concentration of 1.5 mol / L, the doping solution is a magnesium sulfate solution with a concentration of 1 mol / L, the precipitant solution is a 10 mol / L NaOH solution, and the complexing agent solution is a 5 mol / L ammonia solution;

[0064] At the beginning of the coprecipitation reaction, the flow ratio of the nickel solution, the cobalt solution, and the manganese solution is 96:2:2, then the flow rate of the nickel solution decreases at a uniform rate, the flow rates of the cobalt solution and the manganese solution increase at a uniform rate, and the total flow rate of the nickel solution, the cobalt solution, and the manganese solution remains unchanged;

[0065] At the end of the coprecipitation reaction, the flow ratio of the nickel solution, cobalt solution and manganese solution was 60:20:20; the ratio of the flow of the doping solution to the total flow of the nickel solution, cobalt solution and manganese solution was 1:15.

[0066] Example 3

[0067] This embodiment provides a full concentration gradient precursor material, the full concentration gradient precursor material comprising a core and a shell, the core comprising a nickel-cobalt-manganese precursor material containing a doping element, and the shell comprising a nickel-cobalt-manganese precursor material not containing a doping element;

[0068] The full concentration gradient precursor material has a nickel content gradient decreasing from the core to the outer surface of the shell, and a cobalt and manganese content gradient increasing; the matrix chemical formula of the full concentration gradient precursor material is Ni 0.66 Co 0.17 Mn 0.17 (OH)2, the doping element is Ca, and the doping amount of the doping element is 5000ppm;

[0069] The preparation method comprises the following steps:

[0070] Under nitrogen atmosphere protection, nickel solution, cobalt solution, manganese solution, doping solution, precipitant solution and complexing agent solution are added to the reactor in parallel to carry out coprecipitation reaction. The coprecipitation reaction is continued for 30 hours, and the feeding of the doping solution is stopped. The total time of the coprecipitation reaction is 100 hours. The pH during the coprecipitation reaction is maintained in the range of 11.4-11.6, the stirring speed is 200 rpm, and the ammonia concentration is 0.5 mol / L. After the reaction is completed, the material is washed and dried to obtain the full concentration gradient precursor material.

[0071] The nickel solution is a nickel sulfate solution with a concentration of 1 mol / L, the cobalt solution is a cobalt sulfate solution with a concentration of 1 mol / L, the manganese solution is a manganese sulfate solution with a concentration of 1 mol / L, the doping solution is a calcium sulfate solution with a concentration of 0.4 mol / L, the precipitant solution is a 10 mol / L NaOH solution, and the complexing agent solution is a 5 mol / L ammonia solution;

[0072] At the beginning of the coprecipitation reaction, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is 92:4:4, then the flow rate of the nickel solution decreases at a uniform rate, the flow rates of the cobalt solution and the manganese solution increase at a uniform rate, and the total flow rate of the nickel solution, the cobalt solution and the manganese solution remains unchanged;

[0073] At the end of the coprecipitation reaction, the flow ratio of the nickel solution, cobalt solution and manganese solution is 40:30:30; the ratio of the flow of the doping solution to the total flow of the nickel solution, cobalt solution and manganese solution is 1:10.

[0074] Example 4

[0075] This embodiment provides a full concentration gradient precursor material. The full concentration gradient precursor material is the same as Example 1 except that in its preparation method, the feeding of the doping solution is stopped when the coprecipitation reaction reaches 3 hours to make the full concentration gradient precursor material adaptive.

[0076] Example 5

[0077] This embodiment provides a full concentration gradient precursor material. The full concentration gradient precursor material is the same as Example 1 except that in its preparation method, the feeding of the doping solution is stopped when the coprecipitation reaction reaches 35 hours to make the full concentration gradient precursor material adaptive.

[0078] Example 6

[0079] This embodiment provides a full concentration gradient precursor material. The full concentration gradient precursor material is the same as Example 1 except that in its preparation method, the ratio of the flow rate of the doping solution to the sum of the flow rates of the nickel solution, cobalt solution and manganese solution is 1:5, so that the full concentration gradient precursor material can be adaptively changed.

[0080] Example 7

[0081] This embodiment provides a full concentration gradient precursor material. The full concentration gradient precursor material is the same as Example 1 except that in its preparation method, the ratio of the flow rate of the doping solution to the sum of the flow rates of the nickel solution, cobalt solution and manganese solution is 1:30, so that the full concentration gradient precursor material can be adaptively changed.

[0082] Example 8

[0083] This embodiment provides a full concentration gradient precursor material. The full concentration gradient precursor material is the same as Example 1 except that in its preparation method, at the beginning of the coprecipitation reaction, the flow ratio of the nickel solution, cobalt solution and manganese solution is 99.5:0.25:0.25, so that the full concentration gradient precursor material can adapt to changes.

[0084] Example 9

[0085] This embodiment provides a full concentration gradient precursor material. The full concentration gradient precursor material is the same as Example 1 except that in its preparation method, at the end of the co-precipitation reaction, the flow ratio of the nickel solution, cobalt solution and manganese solution is 30:45:45, so that the full concentration gradient precursor material can adapt to changes.

[0086] Comparative Example 1

[0087] This comparative example provides a full concentration gradient precursor material, which is the same as Example 1 except that no doping solution is added in the preparation method to adapt the full concentration gradient precursor material.

[0088] Comparative Example 2

[0089] This comparative example provides a precursor material. The precursor material is the same as Example 1 except that in its preparation method, the flow rates of the nickel solution, cobalt solution and manganese solution remain unchanged, and the flow ratio of the three is 70:15:15, so that the precursor material adapts to the change.

[0090] The precursor materials obtained in the above embodiments and comparative examples were uniformly mixed with LiOH·H2O at a lithium ratio of 1.02, and calcined at 800°C for 10 h in an oxygen atmosphere to obtain a positive electrode material. A positive electrode sheet was prepared using the obtained positive electrode material, and a battery was prepared with a lithium sheet, a lithium hexafluorophosphate electrolyte, and a polyethylene separator. The power performance and cycle performance of the battery were tested under the following test conditions: at 25°C, a voltage range of 2.8 to 4.3 V, a power performance of 8C / 0.2C discharge ratio, and a cycle performance of 1000 charge and discharge cycles at 1C.

[0091] The test results are shown in the following table:

[0092] Table 1

[0093] From the above table we can see that:

[0094] It can be seen from Example 1 and Comparative Examples 1-2 that the precursor material described in the present application has a doped core-shell structure and is a full concentration gradient material, which can significantly improve the power and cycle performance of the battery; it can be seen from Example 1 and Examples 4-7 that the introduction time and introduction flow rate of the doping solution will affect the content of the doping element in the material, thereby affecting the battery performance; it can be seen from Example 1 and Examples 8-9 that the amount of nickel solution introduced in the initial stage of co-precipitation of the present application is large, but it should not be too large. As the co-precipitation reaction proceeds, the amount of nickel solution introduced gradually decreases, but it is not easy to drop to too low, otherwise it will also affect the material performance, and it is impossible to obtain a material with excellent comprehensive performance.

[0095] In summary, the present application provides a full concentration gradient precursor material, a preparation method and an application thereof. The full concentration gradient precursor material solves the compatibility problem of the core and shell interface by combining a doped core-shell structure and a full concentration gradient structure, thereby improving the power performance and cycle performance of the material.

[0096] The above description is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Those skilled in the art should understand that any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application fall within the protection scope and disclosure scope of the present application.

Claims

1. A full concentration gradient precursor material, comprising a core and a shell, wherein the core comprises a nickel-cobalt-manganese precursor material containing a doping element, and the shell comprises a nickel-cobalt-manganese precursor material not containing a doping element; The full concentration gradient precursor material has a nickel content gradient decreasing from the core to the outer surface of the shell, and a cobalt content and a manganese content gradient increasing.

2. The full concentration gradient precursor material according to claim 1, wherein The matrix chemical formula of the full-concentration-gradient precursor material is Ni x Co y Mn z (OH)2, where 0.5 < x ≤ 1, 0 < y ≤ 0.5, 0 < z ≤ 0.5 and x + y + z = 1; Optionally, the doping element includes any one or a combination of at least two of Zr, Al, W, Ti, Mg, Ca, Mo, Y, Fe, Cu, Zn, V, Nb, La, Ce, Sn or Ge; Optionally, in the full concentration gradient precursor material, the doping amount of the doping element is 1000-5000ppm.

3. A method for preparing a full concentration gradient precursor material as claimed in claim 1 or 2, the preparation method comprising the following steps: The nickel solution, the cobalt solution, the manganese solution, the doping solution, the precipitant solution and the complexing agent solution are subjected to a coprecipitation reaction; During the coprecipitation reaction, the flow rate of the nickel solution gradually decreases, the flow rates of the cobalt solution and the manganese solution gradually increase, and the feeding of the doping solution is stopped after nucleation is completed.

4. The preparation method according to claim 3, wherein During the coprecipitation reaction, the total flow rate of the nickel solution, the cobalt solution and the manganese solution remains unchanged; Optionally, the flow rates of the nickel solution, the cobalt solution and the manganese solution are changed independently and at a uniform rate; Optionally, when the coprecipitation reaction starts, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is (92-98):(2-9):(2-9); Optionally, at the end of the coprecipitation reaction, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is (40-50):(10-40):(10-40).

5. The preparation method according to claim 3 or 4, wherein The total time of the coprecipitation reaction is 30-100h, but excluding 30h; Optionally, when the coprecipitation reaction lasts for 5-30 hours, the feeding of the doping solution is stopped; Optionally, the ratio of the flow rate of the doping solution to the total flow rate of the nickel solution, the cobalt solution and the manganese solution is 1:(10-20).

6. The preparation method according to any one of claims 3 to 5, wherein: The pH of the coprecipitation reaction is 10-13, and the stirring speed is 100-500 rpm; Optionally, the complexing agent solution includes any one or a combination of at least two of ammonia water, citric acid, oxalic acid, acetic acid, EDTA or ammonium carbonate; Optionally, the precipitant solution includes NaOH solution and / or KOH solution.

7. The preparation method according to any one of claims 3 to 6, wherein: The preparation method comprises the following steps: A nickel solution, a cobalt solution, a manganese solution, a doping solution, a precipitant solution and a complexing agent solution are subjected to a coprecipitation reaction. When the coprecipitation reaction lasts for 5-30 hours, the feeding of the doping solution is stopped. The total time of the coprecipitation reaction is 30-100 hours, but excluding 30 hours. The pH is 10-13, and the stirring speed is 100-500 rpm. After the coprecipitation reaction is completed, the full concentration gradient precursor material is obtained; At the beginning of the coprecipitation reaction, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is (92-98):(2-9):(2-9), then the flow rate of the nickel solution decreases at a uniform rate, the flow rates of the cobalt solution and the manganese solution increase at a uniform rate, and the total flow rate of the nickel solution, the cobalt solution and the manganese solution remains unchanged; At the end of the coprecipitation reaction, the flow ratio of the nickel solution, the cobalt solution and the manganese solution is (40-50):(10-40):(10-40); the flow rate of the doping solution is the same as the flow rate of the nickel solution, the cobalt solution and the manganese solution. The total ratio is 1:(10-20).

8. A positive electrode material obtained by mixing and calcining a lithium source with the full concentration gradient precursor material as claimed in claim 1 or 2.

9. The positive electrode material according to claim 8, wherein The positive electrode material comprises a core and an outer shell, the doping element in the core diffuses from the core to the outer shell, and the nickel element, the cobalt element and the manganese element are distributed in a gradient; Optionally, the matrix chemical formula of the positive electrode material is Li(Ni a Co b X c )O2, where 0.5 < a ≤ 1, 0 < b ≤ 0.5, 0 < c ≤ 0.5 and a + b + c = 1.

10. A battery comprising the positive electrode material according to claim 8 or 9.

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