Dual-gradient positive electrode precursor material, preparation method therefor, and use thereof

Abstract

The present application provides a dual-gradient positive electrode precursor material, a preparation method therefor, and a use thereof. The dual-gradient positive electrode precursor material comprises a gradient inner core and a gradient outer shell covering the gradient inner core. The gradient outer shell comprises an inner surface and an outer surface, wherein the inner surface is close to the gradient inner core, and the outer surface is away from the gradient inner core. The gradient inner core comprises a nickel element, a manganese element, and a doping element, and the gradient outer shell comprises a nickel element, a cobalt element, and a manganese element. From the core center of the gradient inner core to the outer surface of the gradient outer shell, the content of the nickel element gradually decreases, and the content of the manganese element gradually increases; from the core center of the gradient inner core to the surface of the gradient inner core, the content of the doping element gradually decreases; and from the inner surface of the gradient outer shell to the outer surface of the gradient outer shell, the content of the cobalt element gradually increases. The dual-gradient positive electrode precursor material of the present application allows the structural stability of the material to be significantly improved by means of a dual-gradient design in terms of composition and structure, thereby significantly improving the electrochemical performance of a battery.

Description

A dual-gradient cathode precursor material, its preparation method and application Technical Field

[0001] This application belongs to the field of battery technology and relates to a dual-gradient cathode precursor material, its preparation method and application. Background Technology

[0002] Lithium-ion batteries possess advantages such as high operating voltage, high energy density, good rate performance, high safety, long cycle life, low self-discharge, and no memory effect, making them widely used in electric vehicles and mobile devices. The cathode material significantly impacts the electrochemical performance and cost of lithium-ion batteries. High-nickel cathode materials, with their relatively high specific energy and operating voltage, have become the most commercially promising cathode materials. However, the excessively high Ni content in high-nickel materials, while increasing the specific capacity, can also compromise the material's structural stability. The highly active Ni generated during charging... 4+ The reaction with the electrolyte will generate a NiO-like rock salt phase, which will severely damage the structure of the layered material and cause the cathode material structure to collapse.

[0003] Since the precursor of the cathode material is used as the raw material for the preparation of the cathode material, the physicochemical properties and electrochemical performance of the cathode material mainly depend on the morphology, microstructure, particle size and tap density of the precursor. Therefore, it is necessary to improve the composition and structure of the precursor material to improve the problems caused by the excessive Ni content in high-nickel cathode materials. Summary of the Invention

[0004] This application provides a dual-gradient cathode precursor material, its preparation method, and its application. The dual-gradient cathode precursor material, through a dual-gradient design of composition and structure, can significantly improve the structural stability of the material, solve the problems caused by high nickel content, and thus significantly improve the electrochemical performance of the battery.

[0005] In a first aspect, this application provides a dual-gradient cathode precursor material, the dual-gradient cathode precursor material comprising a gradient core and a gradient shell covering the gradient core, the gradient shell comprising an inner surface and an outer surface, wherein the inner surface is close to the gradient core and the outer surface is far from the gradient core;

[0006] The gradient core includes nickel, manganese, and doping elements, and the gradient shell includes nickel, cobalt, and manganese. From the core of the gradient core to the outer surface of the gradient shell, the content of nickel gradually decreases and the content of manganese gradually increases.

[0007] From the core of the gradient kernel to its surface, the content of doped elements gradually decreases until it stops.

[0008] The cobalt content gradually increases from the inner surface of the gradient shell to the outer surface of the gradient shell.

[0009] The dual-gradient cathode precursor material described in this application contains nickel, manganese, cobalt, and doping elements. On the one hand, in the overall precursor material particles, the content of nickel gradually decreases from the inside to the outside, while the content of manganese gradually increases from the inside to the outside, so that nickel and manganese form a gradient distribution overall. On the other hand, the overall material particles of this application are divided into a gradient core and a gradient shell on the surface of the gradient core. The doping elements are only gradient-distributed in the gradient core, and the gradient distribution of the doping elements is the same as that of nickel, both of which have a gradually decreasing content. The gradient core forms a cobalt-free nickel-manganese precursor material with doped elements, thereby effectively improving the stability of the material, reducing lithium-nickel mixing, and solving the problem caused by the high nickel content in the gradient core. In this application, the cobalt element is only gradient-distributed in the gradient shell, making the gradient shell a gradient-distributed nickel-cobalt-manganese precursor material, further improving the structural stability of the material.

[0010] In one embodiment, the chemical formula of the dual-gradient cathode precursor material is Ni. x Co y Mn z M a (OH)₂, where 0.8 ≤ x < 1, for example, 0.8, 0.82, 0.84, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96 or 0.98; 0 < y ≤ 0.2, for example, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15, 0.17 or 0.2; 0 < z ≤ 0.2, for example, 0.05, 0.07, 0.09, 0.11, 0.13, 0.15, 0.17 or 0.2; 0 < a ≤ 0.1, for example, 0.01, 0.03, 0.05, 0.07, 0.09 or 0.1; x + y + z + a = 1; and M is a dopant element.

[0011] In one embodiment, M includes any one or a combination of at least two of Nb, Mo, or Ta.

[0012] The doping elements in the gradient kernel described in this application are selected from high-valence elements such as Nb, Mo, or Ta. After doping, high-valence elements may accumulate along the crystal boundary, which can play a role in fixing and protecting the crystal, thereby improving the crystal structure strength, strengthening the microstructure, and increasing the crystallinity of the material. Therefore, the performance of the precursor material can be maximized.

[0013] In one embodiment, the molar ratio of nickel in the gradient core to nickel in the gradient shell of the dual-gradient cathode precursor material is (0.7-0.95):(0.05-0.3), for example, it can be 0.7:0.3, 0.8:0.2, 0.9:0.1 or 0.95:0.05, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] In the dual-gradient cathode precursor material described in this application, the nickel content of the gradient core and the gradient shell is within a specific range, which can further enhance the synergistic effect of the gradient core and the gradient shell, promote the gradient distribution effect, and thus further improve the electrochemical performance of the material.

[0015] Secondly, this application provides a method for preparing a dual-gradient cathode precursor material as described in the first aspect, the method comprising the following steps:

[0016] A co-precipitation reaction is carried out on a high-nickel manganese solution, a medium-low nickel manganese solution, a dopant source solution, a precipitant solution, and a complexing agent solution to obtain a gradient core. Then, the dopant source solution is replaced with a cobalt source solution, and the co-precipitation reaction is continued to coat the surface of the gradient core with a gradient shell to obtain the dual-gradient cathode precursor material.

[0017] During the coprecipitation reaction, the flow rate of the high-nickel manganese solution gradually decreases, while the flow rate of the medium-low-nickel manganese solution gradually increases. When preparing the gradient core, the flow rate of the dopant source solution gradually decreases until the gradient core is obtained and then pauses. When preparing the gradient shell, the flow rate of the cobalt source solution gradually increases.

[0018] This application employs a high-nickel manganese solution and a medium-low nickel manganese solution as feedstocks, and controls the feed flow rate to gradually decrease the nickel content and gradually increase the manganese content in the particles. Furthermore, after obtaining a gradient core through the co-precipitation reaction, the dopant source solution is replaced with a cobalt source solution to continue the co-precipitation reaction, thereby obtaining a gradient shell on the surface of the gradient core. Therefore, this application can obtain the dual-gradient cathode precursor material through only one co-precipitation reaction.

[0019] In one embodiment, the molar ratio of manganese ions to nickel ions in the manganese-containing high-nickel solution is (0-0.2):(0.8-1), but does not include 0:(0.8-1). For example, it can be 0.02:0.98, 0.05:0.95, 0.1:0.9 or 0.2:0.8, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] In one embodiment, the total metal ion concentration in the manganese-containing high-nickel solution is 1.0-3.0 mol / L, for example, it can be 1.0 mol / L, 2.0 mol / L or 3.0 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] In one embodiment, the molar ratio of manganese ions to nickel ions in the manganese-containing low-nickel solution is (0.05-0.5):(0.5-0.85), for example, it can be 0.15:0.85, 0.25:0.75, 0.35:0.65 or 0.5:0.5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In one embodiment, the total metal ion concentration in the manganese-containing low-nickel solution is 1.0-3.0 mol / L, for example, it can be 1.0 mol / L, 2.0 mol / L or 3.0 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] In one embodiment, the pH of the coprecipitation reaction is 9-11.5, for example, 9, 10, 11 or 11.5, and the ammonia concentration is 0.1-10 g / L, for example, 0.1 g / L, 2 g / L, 4 g / L, 6 g / L, 8 g / L or 10 g / L, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0024] In one embodiment, the manganese-containing high-nickel solution, manganese-containing medium-low-nickel solution, dopant source solution, precipitant solution, and complexing agent solution are passed into the base liquid to carry out a co-precipitation reaction.

[0025] In one embodiment, the pH of the base solution is 9-12, for example, it can be 9, 10, 11 or 12, and the ammonia concentration is 0.1-5 g / L, for example, it can be 0.1 g / L, 1 g / L, 2 g / L, 3 g / L, 4 g / L or 5 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] In one embodiment, the temperature of the coprecipitation reaction is 30-80°C, for example, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] In one embodiment, the concentration of the precipitant solution is 9-12 mol / L, for example, it can be 9 mol / L, 10 mol / L, 11 mol / L or 12 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] In one embodiment, the precipitant solution comprises sodium hydroxide or potassium hydroxide.

[0029] In one embodiment, the concentration of the complexing agent solution is 6-10 mol / L, for example, it can be 6 mol / L, 8 mol / L or 10 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] In one embodiment, the complexing agent solution comprises ammonia.

[0031] In one embodiment, the coprecipitation reaction is carried out in a protective gas, which includes nitrogen and / or argon.

[0032] In one embodiment, after the coprecipitation reaction is completed, aging, solid-liquid separation, washing, and drying are also performed.

[0033] Thirdly, this application provides a cathode material obtained by mixing and sintering a lithium source with a dual-gradient cathode precursor material as described in the first aspect.

[0034] Fourthly, this application provides a lithium-ion battery, the lithium-ion battery comprising the positive electrode material as described in the third aspect.

[0035] Compared with the prior art, this application has the following advantages:

[0036] The dual-gradient cathode precursor material described in this application achieves a gradient distribution of nickel and manganese by gradually decreasing the nickel content from the inside out and gradually increasing the manganese content from the inside out. Furthermore, the material particles are divided into a gradient core and a gradient shell on the surface of the gradient core. Doping elements are only distributed in the gradient core, and their gradient distribution is the same as that of nickel, with both gradually decreasing content. This creates a gradient-distributed cobalt-free nickel-manganese precursor material containing doped elements within the gradient core, effectively improving material stability, reducing lithium-nickel mixing, and solving the problem caused by high nickel content in the gradient core. In this application, cobalt is only distributed in the gradient shell, making the gradient shell a gradient-distributed nickel-cobalt-manganese precursor material, further enhancing the structural stability of the material. Attached Figure Description

[0037] Figure 1 is a SEM image of the dual-gradient cathode precursor material described in Embodiment 1 of this application. Detailed Implementation

[0038] The technical solution of this application will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely to help understand this application and should not be regarded as specific limitations on this application.

[0039] Example 1

[0040] This embodiment provides a dual-gradient cathode precursor material, the chemical formula of which is Ni. 0.8 Co 0.05 Mn 0.1 Nb 0.05 (OH)2, the dual-gradient cathode precursor material includes a gradient core and a gradient shell with a nickel content molar ratio of 0.85:0.15, where the gradient core is coated with a gradient shell and the gradient shell is coated with a gradient shell.

[0041] The gradient shell includes an inner surface and an outer surface, wherein the inner surface is close to the gradient core and the outer surface is far from the gradient core; from the core of the gradient core to the outer surface of the gradient shell, the content of nickel gradually decreases and the content of manganese gradually increases; from the core of the gradient core to the surface of the gradient core, the content of Nb gradually decreases; from the inner surface of the gradient shell to the outer surface of the gradient shell, the content of cobalt gradually increases.

[0042] The preparation method of the dual-gradient cathode precursor material includes the following steps:

[0043] According to the formula, under a nitrogen atmosphere, a high-nickel manganese solution, a medium-low nickel manganese solution, an Nb source solution (sodium niobate solution), a sodium hydroxide solution, and ammonia water were introduced into a base solution (the pH of the base solution was 11, and the ammonia concentration was 2 g / L). A co-precipitation reaction was carried out at 50°C, a pH range of 9.8-10.5, and an ammonia concentration of 3-4 g / L. Then, the dopant source solution was replaced with a cobalt source solution (cobalt sulfate solution), and the co-precipitation reaction was continued. After aging, solid-liquid separation, washing, and drying, the dual-gradient cathode precursor material was obtained. The SEM image of the dual-gradient cathode precursor material is shown in Figure 1.

[0044] During the coprecipitation reaction, the flow rate of the high-nickel manganese solution gradually decreases, the flow rate of the medium-low nickel manganese solution gradually increases, the flow rate of the dopant source solution gradually decreases, and the flow rate of the cobalt source solution gradually increases.

[0045] The manganese-containing high-nickel solution has a manganese ion to nickel ion molar ratio of 0.05:0.95 and a total metal ion concentration of 2 mol / L; the manganese-containing medium-low-nickel solution has a nickel-manganese molar ratio of 0.7:0.3 and a total metal ion concentration of 2 mol / L; the sodium hydroxide solution has a concentration of 10 mol / L and the ammonia solution has a concentration of 5 mol / L.

[0046] Example 2

[0047] This embodiment provides a dual-gradient cathode precursor material, the chemical formula of which is Ni. 0.9 Co 0.02 Mn 0.05 Ta 0.03 (OH)2, the dual-gradient cathode precursor material includes a gradient core and a gradient shell with a nickel content molar ratio of 0.95:0.05, where the gradient core is coated with nickel and the gradient shell is coated with nickel.

[0048] The gradient shell includes an inner surface and an outer surface, wherein the inner surface is close to the gradient core and the outer surface is far from the gradient core; from the core of the gradient core to the outer surface of the gradient shell, the content of nickel gradually decreases and the content of manganese gradually increases; from the core of the gradient core to the surface of the gradient core, the content of Ta gradually decreases; from the inner surface of the gradient shell to the outer surface of the gradient shell, the content of cobalt gradually increases.

[0049] The preparation method of the dual-gradient cathode precursor material includes the following steps:

[0050] According to the formula, under a nitrogen atmosphere, a high-nickel manganese solution, a medium-low nickel manganese solution, a Ta source solution (sodium tantalate solution), a sodium hydroxide solution, and ammonia water are introduced into a base solution (the pH of the base solution is 12, and the ammonia concentration is 3 g / L). A co-precipitation reaction is carried out at 40°C, a pH of 10-10.8, and an ammonia concentration of 3.8-5.2 g / L. Then, the dopant source solution is replaced with a cobalt source solution (cobalt sulfate solution), and the co-precipitation reaction continues. After aging, solid-liquid separation, washing, and drying, the dual-gradient cathode precursor material is obtained.

[0051] During the coprecipitation reaction, the flow rate of the high-nickel manganese solution gradually decreases, the flow rate of the medium-low nickel manganese solution gradually increases, the flow rate of the dopant source solution gradually decreases, and the flow rate of the cobalt source solution gradually increases.

[0052] The manganese-containing high-nickel solution has a manganese ion to nickel ion molar ratio of 0.02:0.98 and a total metal ion concentration of 2.4 mol / L; the manganese-containing medium-low-nickel solution has a nickel-manganese molar ratio of 0.8:0.2 and a total metal ion concentration of 1.0 mol / L; the sodium hydroxide solution has a concentration of 12 mol / L and the ammonia solution has a concentration of 10 mol / L.

[0053] Example 3

[0054] This embodiment provides a dual-gradient cathode precursor material, the chemical formula of which is Ni. 0.8 Co 0.05 Mn 0.1 Nb 0.05 (OH)2, the dual-gradient cathode precursor material includes a gradient core and a gradient shell, wherein the molar ratio of nickel content in the gradient core to nickel content in the gradient shell is 0.80:0.20.

[0055] The gradient shell includes an inner surface and an outer surface, wherein the inner surface is close to the gradient core and the outer surface is far from the gradient core; from the core of the gradient core to the outer surface of the gradient shell, the content of nickel gradually decreases and the content of manganese gradually increases; from the core of the gradient core to the surface of the gradient core, the content of Nb gradually decreases; from the inner surface of the gradient shell to the outer surface of the gradient shell, the content of cobalt gradually increases.

[0056] The preparation method of the dual-gradient cathode precursor material includes the following steps:

[0057] According to the formula, under a nitrogen atmosphere, a high-nickel manganese solution, a medium-low nickel manganese solution, an Nb source solution (sodium niobate solution), a sodium hydroxide solution, and ammonia water are introduced into a base solution (the pH of the base solution is 11, and the ammonia concentration is 2 g / L). A co-precipitation reaction is carried out at 60°C, pH 11, and an ammonia concentration of 2 g / L. Then, the dopant source solution is replaced with a cobalt source solution (cobalt sulfate solution), and the co-precipitation reaction continues. After aging, solid-liquid separation, washing, and drying, the dual-gradient cathode precursor material is obtained.

[0058] During the coprecipitation reaction, the flow rate of the high-nickel manganese solution gradually decreases, the flow rate of the medium-low nickel manganese solution gradually increases, the flow rate of the dopant source solution gradually decreases, and the flow rate of the cobalt source solution gradually increases.

[0059] The manganese-containing high-nickel solution has a manganese ion to nickel ion molar ratio of 0.1:0.9 and a total metal ion concentration of 2.6 mol / L; the manganese-containing medium-low-nickel solution has a nickel-manganese molar ratio of 0.65:0.35 and a total metal ion concentration of 3.0 mol / L; the sodium hydroxide solution has a concentration of 9 mol / L and the ammonia solution has a concentration of 5 mol / L.

[0060] Example 4

[0061] This embodiment provides a dual-gradient cathode precursor material, which is the same as that in Embodiment 1 except that Nb is replaced with Al in equimolar amounts.

[0062] Example 5

[0063] This embodiment provides a dual-gradient cathode precursor material, which is the same as that in Example 1 except that Nb is replaced with Mg in equal molar amounts.

[0064] Example 6

[0065] This embodiment provides a dual-gradient cathode precursor material. Except for the molar ratio of nickel content in the gradient core to nickel content in the gradient shell being 0.75:0.25, which allows the molecular formula of the dual-gradient cathode precursor material to adapt to the gradient shell, the rest of the dual-gradient cathode precursor material is the same as in Embodiment 1.

[0066] Example 7

[0067] This embodiment provides a dual-gradient cathode precursor material. Except for the molar ratio of nickel content in the gradient core to nickel content in the gradient shell being 0.99:0.01, which allows the molecular formula of the dual-gradient cathode precursor material to adapt to the gradient shell, the rest of the dual-gradient cathode precursor material is the same as in Embodiment 1.

[0068] Comparative Example 1

[0069] This comparative example provides a cathode precursor material. The dual-gradient cathode precursor material is the same as in Example 1, except that the Nb source solution is not introduced in its preparation method, the cobalt source solution is continuously introduced during the co-precipitation reaction so that the obtained dual-gradient cathode precursor material does not contain Nb, and the cobalt content gradually increases from the particle core to the outer surface.

[0070] Comparative Example 2

[0071] This comparative example provides a cathode precursor material. The dual-gradient cathode precursor material is the same as in Example 1, except that the Nb source solution is not replaced with a cobalt source solution in its preparation method, so that the obtained dual-gradient cathode precursor material does not contain Co, and the Nb content gradually decreases from the particle core to the outer surface.

[0072] Comparative Example 3

[0073] This comparative example provides a cathode precursor material. Except for the fact that the contents of nickel, cobalt, manganese and Nb do not change in a gradient, and the flow rate of the solution does not change in the preparation method, the cathode precursor material is the same as that in Example 1.

[0074] The positive electrode precursor materials obtained in the above examples and comparative examples were mixed with lithium hydroxide, then heated at 400°C for 4 hours, and then heated at 800°C for 8 hours to obtain the positive electrode material, which was then used to prepare a positive electrode sheet. This positive electrode sheet was then used to prepare a battery with lithium sheet, polyethylene separator, and lithium hexafluorophosphate electrolyte. The 0.1C discharge specific capacity and the capacity retention rate after 100 cycles were then tested. The test results are shown in Table 1.

[0075] Table 1

[0076] As can be seen from the table above:

[0077] As shown in Example 1 and Comparative Examples 1-3, the cathode precursor material described in this application is a dual-gradient material. The doping elements and Co elements work together to achieve a dual gradient, effectively improving the material's stability, reducing lithium-nickel mixing, and enhancing the battery's electrochemical performance. As shown in Example 1 and Examples 4-5, the doping elements in the gradient core of this application can be high-valence elements such as Nb, Mo, or Ta, which can achieve crystal boundary accumulation. Unlike the doping mechanism of Al and Mg, this further enhances the electrochemical performance of the precursor material. As shown in Example 1 and Examples 6-7, in the dual-gradient doping of this application, the content of the gradient core and gradient shell needs to be matched to promote the effect of dual-gradient doping, thereby further improving the electrochemical performance of the precursor material.

[0078] In summary, this application provides a dual-gradient cathode precursor material, its preparation method, and its application. The dual-gradient cathode precursor material, through a dual-gradient design of composition and structure, can significantly improve the structural stability of the material, solve the problems caused by high nickel content, and thus significantly improve the electrochemical performance of the battery.

[0079] The above description is only a specific embodiment of this application, but the protection scope of this application is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application fall within the protection and disclosure scope of this application.

Claims

1. A dual-gradient cathode precursor material comprising a gradient core and a gradient shell that coats the gradient core, the gradient shell comprising an inner surface and an outer surface, wherein, The inner surface is close to the gradient kernel, and the outer surface is far from the gradient kernel; The gradient core includes nickel, manganese, and doping elements, and the gradient shell includes nickel, cobalt, and manganese. From the core of the gradient core to the outer surface of the gradient shell, the content of nickel gradually decreases and the content of manganese gradually increases. From the core of the gradient kernel to its surface, the content of doped elements gradually decreases until it stops. The cobalt content gradually increases from the inner surface of the gradient shell to the outer surface of the gradient shell.

2. The dual gradient cathode precursor material of claim 1, wherein, The chemical general formula of the double-gradient cathode precursor material is Ni x Co y Mn z M a (OH)2, wherein, 0.8≤x<1, 0 Optionally, M includes any one or a combination of at least two of Nb, Mo, or Ta.

3. The double gradient cathode precursor material of claim 1 or 2, wherein, In the dual-gradient cathode precursor material, the molar ratio of nickel in the gradient core to nickel in the gradient shell is (0.7-0.95):(0.05-0.3).

4. A method for preparing a dual-gradient cathode precursor material as described in any one of claims 1-3, comprising the following steps: A co-precipitation reaction is carried out on a high-nickel manganese solution, a medium-low nickel manganese solution, a dopant source solution, a precipitant solution, and a complexing agent solution to obtain a gradient core. Then, the dopant source solution is replaced with a cobalt source solution, and the co-precipitation reaction is continued to coat the surface of the gradient core with a gradient shell to obtain the dual-gradient cathode precursor material. During the coprecipitation reaction, the flow rate of the high-nickel manganese solution gradually decreases, while the flow rate of the medium-low-nickel manganese solution gradually increases. When preparing the gradient core, the flow rate of the dopant source solution gradually decreases until the gradient core is obtained and then pauses. When preparing the gradient shell, the flow rate of the cobalt source solution gradually increases.

5. The production method according to claim 4, wherein In the manganese-containing high-nickel solution, the molar ratio of manganese ions to nickel ions is (0-0.2):(0.8-1), but does not include 0:(0.8-1); Optionally, the total metal ion concentration in the manganese-containing high-nickel solution is 1.0-3.0 mol / L.

6. The production method according to claim 4 or 5, wherein In the manganese-containing low-nickel solution, the molar ratio of manganese ions to nickel ions is (0.05-0.5):(0.5-0.85); Optionally, the total metal ion concentration in the manganese-containing low-nickel solution is 1.0-3.0 mol / L.

7. The method of making according to any one of claims 4-6, wherein, The pH of the coprecipitation reaction is 9-11.5, and the ammonia concentration is 0.1-10 g / L; Optionally, the process involves passing a high-nickel manganese solution, a medium-low nickel manganese solution, a doped element source solution, a precipitant solution, and a complexing agent solution into the base solution to perform a co-precipitation reaction. Optionally, the pH of the substrate solution is 9-12, and the ammonia concentration is 0.1-5 g / L.

8. The method of making according to any one of claims 4-7, wherein, The temperature for the coprecipitation reaction is 30-80℃; Optionally, the concentration of the precipitant solution is 9-12 mol / L; Optionally, the concentration of the complexing agent solution is 6-10 mol / L.

9. The method of making according to any one of claims 4-8, wherein, The coprecipitation reaction is carried out in a protective gas, which includes nitrogen and / or argon. Optionally, after the coprecipitation reaction is completed, aging, solid-liquid separation, washing, and drying are also performed.

10. A cathode material obtained by mixing and sintering a lithium source and a dual-gradient cathode precursor material as described in any one of claims 1-3.

11. A lithium-ion battery comprising the positive electrode material as described in claim 10.

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