CN117174876A - A kind of cathode precursor material and its preparation method and application - Google Patents

Abstract

The invention provides a positive electrode precursor material, and a preparation method and application thereof. The positive electrode precursor material sequentially coats the inner core, the middle layer and the outer shell layer from inside to outside; the inner core comprises a first hydroxide precursor material; the intermediate layer comprises a hydroxide material of a doping element, and the shell comprises a second hydroxide precursor; the molar content of nickel in the second hydroxide precursor material is less than the molar content of nickel in the first hydroxide precursor. According to the invention, the intermediate layer doped with elements is added into the precursor material, so that the transition effect of the inner core and the outer shell layer is achieved, the combination between the inner core and the outer shell is enhanced, the outer shell is effectively prevented from being separated, and the structural stability is improved, thereby improving the structural stability of the positive electrode material and obtaining the positive electrode material with excellent cycle performance and multiplying power performance.

Description

A kind of cathode precursor material and its preparation method and application

Technical field

The invention belongs to the technical field of lithium ion batteries and relates to a positive electrode precursor material and its preparation method and application.

Background technique

As energy demand continues to increase, lithium-ion batteries have become the main power source for electric vehicles, smartphones, laptops, etc., and are also widely used in the field of energy storage. As the core component of lithium-ion batteries, the performance of cathode materials directly affects key indicators such as energy density, cycle life and safety performance of the battery.

In order to increase the capacity of the ternary nickel cobalt lithium manganate cathode material, the proportion of nickel element has been continuously increased, from the initial 33% to more than 80%. In recent years, it has even increased to more than 90%, forming an ultra-high nickel cathode material. . Ultra-high nickel cathode materials are considered to be the most promising cathode materials. Research shows that they have high capacity, but poor cycle stability and low material conductivity. At present, surface coating of lithium-ion battery cathode materials is one of the most effective modification methods. However, the traditional coating process is complex, the coating is uneven, and the conductivity of the material is reduced. The coating effect is poor, and the cathode material is easily Side reactions occur when in contact with the electrolyte, seriously affecting the service life of the material and reducing the conductivity of the material.

CN112310389A discloses a method for preparing an ultra-high nickel single crystal cathode material, which includes the following steps: S1. Mix the ternary precursor and lithium hydroxide at a lithium to metal molar ratio of 1.01 to 1.10:1, and add doping Agent, calcined in an oxygen atmosphere to obtain primary calcined material; S2. Pass the primary calcined material through coarse crushing, fine crushing, sieving, and demagnetization to obtain pulverized material; S3. Combine the pulverized material with water at a water-to-material ratio of 0.5:1 ~5:1 is added to the reaction kettle, the temperature of the reaction kettle is controlled, and then the reagent is added for reaction. After the reaction is completed, dry it to obtain a mixture; S4. Mix the mixture with the modified coating agent and place it in an atmosphere furnace for secondary Calcined once, and then subjected to coarse crushing, fine crushing, sieving, and demagnetization, the ternary cathode material is obtained. In this document, conventional metal coating is used, but the coating effect is poor, and the ultra-high nickel cathode material is a single crystal material.

CN113809320A A quaternary polycrystalline cathode material, its preparation method and use. The chemical formula of the quaternary polycrystalline cathode material is LiNi _a Co _b Mn _c Al _d Ta _(1-abcd) O ₂ , where 0.9≤a< 1.0 The quaternary polycrystalline cathode material is then prepared. In this document, there is no coating and it is a single crystal cathode material.

At the same time, the core-shell ultra-high nickel cathode materials obtained after coating still have many problems in terms of cycle performance, so the commercial application process is slow.

Therefore, how to improve the electrochemical performance of cathode materials with high nickel content is an urgent technical problem that needs to be solved.

Contents of the invention

In view of the shortcomings of the existing technology, the purpose of the present invention is to provide a cathode precursor material and its preparation method and application. In the present invention, an intermediate layer of doped elements is added to the precursor material, which serves as a transition between the core and the outer shell layer, enhances the bonding between the core and the outer shell, effectively prevents the outer shell from detaching, and improves the stability of the structure, thus The structural stability of the cathode material is improved, and a cathode material with excellent cycle performance and rate performance is obtained.

To achieve this goal, the present invention adopts the following technical solutions:

In a first aspect, the present invention provides a cathode precursor material, which sequentially covers an inner core, an intermediate layer and an outer shell layer from the inside to the outside; the inner core includes a first hydroxide precursor material; the The middle layer includes a hydroxide material doped with elements, the shell includes a second hydroxide precursor; the molar content of nickel in the second hydroxide precursor material is less than that of the first hydroxide precursor. The molar content of nickel in .

In addition to nickel, the precursor material provided by the present invention may also include cobalt and/or manganese, which can be adjusted appropriately according to actual needs.

In the cathode material provided by the invention, the nickel content of the core is higher than that of the outer shell, realizing the gradient distribution of nickel and improving the battery capacity; at the same time, the middle layer of the doped element is coordinated with the middle layer, the inner core and the outer shell. The tight connection between them serves as a transition between the core and the outer shell layer, strengthens the bond between the core and the outer shell, effectively prevents the outer shell from detaching, and improves the structural stability, thereby improving the structural stability of the cathode material. A cathode material with excellent cycle performance and rate performance was obtained.

In the present invention, if an intermediate layer is not provided, it is impossible to isolate the cracks in the outer casing from gradually eroding into the interior due to cycles, affecting the cycle performance of the battery; and if the nickel content between the core and the outer casing remains consistent, the battery capacity will be low.

Preferably, the general chemical formula of the first hydroxide precursor material is _Nix Co _y Mn _1-xy (OH) ₂ , where 0.8<x≤0.99 and 0≤y≤0.2.

For example, the x can be 0.8, 0.83, 0.85, 0.9, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98 or 0.99, etc., and the y can be 0, 0.001, 0.002, 0.003, 0.004, 0.005 , 0.006, 0.007, 0.008, 0.009, 0.01, 0.13, 0.15, 0.18 or 0.2, etc.

In the present invention, the core is made of high-nickel positive electrode material, which increases the battery capacity.

Preferably, the molar amount of the doping element is 0.01 to 0.1% of the total molar amount of the total metal elements in the cathode precursor material, such as 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06% , 0.07%, 0.08%, 0.09% or 0.1%, etc.

In the present invention, if the molar amount of the doping element is too small, the function of the intermediate layer cannot be achieved, while if too much, the battery performance will be affected.

Preferably, the doping element includes any one or a combination of at least two of Al, Mg, Zn, Ti, Na, Li, Sn or Nb.

Preferably, the general chemical formula of the second hydroxide precursor material is Ni _a Co _b Mn _1-ab (OH) ₂ , where 0.2<a≤0.6, 0≤b≤0.2.

For example, the a can be 0.21, 0.23, 0.25, 0.28, 0.3, 0.33, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, 0.5, 0.53, 0.55, 0.58 or 0.6, etc., and the b can be 0, 0.03 , 0.05, 0.08, 0.1, 0.13, 0.15, 0.18 or 0.2, etc.

In the present invention, the core is made of a high-nickel precursor material, and the outer shell is made of a medium-low nickel precursor material, which allows the outer shell to maintain high cycle performance and the core to provide higher capacity, achieving synergistic improvement in capacity and cycle performance.

In a second aspect, the present invention provides a method for preparing the cathode precursor material as described in the first aspect, the preparation method comprising the following steps:

The first main metal mixed salt solution, the precipitant solution and the complexing agent solvent are added to the bottom liquid in parallel flow to perform the first stage of co-precipitation reaction. After reaching the first target particle size, the first main metal mixed salt solution is replaced. For the dopant solution, perform the second stage of co-precipitation reaction;

After the second stage co-precipitation reaction is completed, the dopant solution is replaced with the second main metal mixed salt solution, and the third stage co-precipitation reaction is continued. After reaching the final target particle size, the reaction is completed and the cathode precursor is obtained. Material;

The molar content of nickel in the second main metal mixed salt solution is less than the molar content of the first main metal mixed salt solution.

The preparation method provided by the invention obtains a cathode precursor material with a stable structure through a three-stage co-precipitation reaction. The preparation method is simple, easy to operate, and is suitable for large-scale production.

Preferably, the molar concentration of the main metal element in the first main metal mixed salt solution and the molar concentration of the main metal element in the second main metal mixed salt solution are each independently 1.6 to 2.4 mol/L, such as 1.6 mol/L. , 1.7mol/L, 1.8mol/L, 1.9mol/L, 2mol/L, 2.1mol/L, 2.2mol/L, 2.3mol/L or 2.4mol/L, etc.

Preferably, the concentration of the precipitant solution is 9 to 12 mol/L, such as 9 mol/L, 10 mol/L, 11 mol/L or 12 mol/L, etc.

Preferably, the precipitant solution includes an alkaline solution.

Preferably, the concentration of the complexing agent solution is 7 to 10 mol/L, such as 7 mol/L, 8 mol/L, 9 mol/L or 10 mol/L, etc.

Preferably, the complexing agent solution includes an ammonia solution.

Preferably, the first target particle size is 3 to 9 μm, such as 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 8 μm, 9 μm, etc.

In the present invention, if the first target particle size is too large, it is not conducive to the coating of the intermediate layer; if it is too small, it will affect the overall nickel content of the precursor material.

Preferably, when the molar amount of the doping element in the dopant is 0.05 to 0.1% of the total molar amount of the total metal elements in the cathode precursor material, for example, 0.05%, 0.06%, 0.07%, 0.08 %, 0.09% or 0.1%, etc., the second stage of co-precipitation reaction ends.

In the present invention, during the co-precipitation process in the first stage, if the doping amount of the doping element is too much, it will affect the battery capacity; if the doping amount is too little, the connection between the core and the outer shell cannot be realized.

Preferably, the final target particle size is 9 to 14 μm, such as 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm or 14 μm, etc.

Preferably, the pH value during the coprecipitation reaction is 9 to 13, such as 9, 9.3, 9.5, 9.8, 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8, 12, 12.3, 12.5, 12.8 Or 13 etc.

As a preferred technical solution, the preparation method includes the following steps:

Add the first main metal mixed salt solution, liquid alkali solution and ammonia solution into the bottom liquid in parallel flow to perform the first stage of co-precipitation reaction. After reaching the first target particle size of 3 to 9 μm, add the first main metal mixed salt solution Replace it with a dopant solution and perform the second stage co-precipitation reaction. When the molar amount of the doping element in the dopant is 0.05 to 0.1% of the total molar amount of the total metal elements in the cathode precursor material. , the second stage of co-precipitation reaction ends;

After the second-stage co-precipitation reaction is completed, the dopant solution is replaced with the second main metal mixed salt solution, and the third-stage co-precipitation reaction is continued. After reaching the final target particle size of 9 to 14 μm, the reaction is completed and the above-mentioned Cathode precursor materials;

The molar content of nickel in the second main metal mixed salt solution is less than the molar content in the first main metal mixed salt solution; the pH value during the coprecipitation reaction is 9-13.

It should be noted that the entire co-precipitation reaction provided by the present invention is performed under a protective atmosphere, and the preparation of the bottom liquid in the present invention and the parameters of the co-precipitation reaction process at each stage are all conventional technical choices.

Optionally, water, precipitant solution and complexing agent solution are adjusted and mixed to obtain a bottom liquid, wherein the pH in the bottom liquid is controlled at 9 to 13, and the concentration of the complexing agent solution in the bottom liquid is 1 to 8 g/L. The temperature in it is 30~80℃;

Optionally, the reaction temperature during the co-precipitation reaction is 30-80°C, and the stirring rate is 200-500 rpm; and the pH value of each stage can be adaptively adjusted within the optional range.

In a third aspect, the present invention provides a cathode material, which is obtained by mixing and sintering the cathode precursor material as described in the first aspect and a lithium source.

In the present invention, the selection of lithium source, the number of sintering times, the sintering time and the sintering temperature are all routine choices for those skilled in the art; those skilled in the art can choose one sintering or multiple sinterings according to actual needs, and at the same time perform adaptive doping and cladding.

Preferably, the sintered material is carbon coated.

In the present invention, carbon coating is performed on the surface of the cathode material obtained by sintering, which can improve the cycle performance and rate performance of the cathode material.

In a fourth aspect, the present invention also provides a lithium ion battery, which includes the cathode material as described in the third aspect.

Compared with the prior art, the present invention has the following beneficial effects:

In the cathode material provided by the present invention, the nickel content of the core is higher than that of the outer shell, achieving a gradient distribution of nickel. At the same time, the middle layer of the doped element is synergistically matched, and the middle layer is closely combined with the core and the outer shell. The transition between the core and the shell layer strengthens the bond between the core and the shell, effectively prevents the shell from detaching, and improves the structural stability, thus improving the structural stability of the cathode material and obtaining excellent cycle performance. and rate performance cathode materials.

Detailed ways

The technical solution of the present invention will be further described below through specific examples. Those skilled in the art should understand that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

Example 1

This embodiment provides a cathode precursor material that sequentially covers the core, the middle layer and the outer shell layer from the inside to the outside; the chemical formula of the core is Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ and the middle layer is Aluminum hydroxide, the chemical formula of the outer shell is Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ ; where the molar amount of aluminum is 0.05% of the total molar amount of the total metal elements in the cathode precursor material.

The preparation method of the positive electrode precursor material is as follows:

Step 1: Configure sulfate solution A with a total ion concentration of 2mol/L, in which the molar ratio of nickel ions, cobalt ions, and manganese ions is 96:3:1, and configure sulfate solution B with a total ion concentration of 2mol/L. The molar ratio of nickel ions, cobalt ions, and manganese ions is 5:2:3. Industrial liquid alkali with a concentration of 10 mol/L is used as the precipitant solution C, and 9 mol/L ammonia water is used as the complexing agent solution D. The configuration is 2 mol/L. L aluminum sulfate solution E;

Step 2: Configure the bottom liquid F containing a certain precipitant solution and complexing agent solution in the reaction kettle. The pH of F is controlled at 10. The ammonia concentration in F is 2g/L. The temperature of F is 40°C; and nitrogen gas is introduced. As a protective gas, add mixed salt solution A, precipitant solution B and complexing agent solution C into the bottom liquid F of the above reaction kettle in parallel to ensure a pH value of 10. Use an ordinary stirring paddle at a rotation speed of 300 rpm. In the first stage of the co-precipitation reaction, seed particles with a first target particle size D50 of 7.5 μm are obtained. Stop injecting mixed solution A; then add solution E to perform the second stage of co-precipitation reaction, and stop when the molar amount of aluminum reaches 0.05%. Add solution E; add solution B to carry out the third stage of co-precipitation reaction. When the particle size D50 grows to 12 μm, the co-precipitation reaction ends;

Step 3: The obtained product is centrifuged, washed, dried, and magnetic foreign matter removed to obtain the positive electrode precursor material.

Example 2

This embodiment provides a cathode precursor material that sequentially covers the core, the middle layer and the outer shell layer from the inside to the outside; the chemical formula of the core is Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ and the middle layer is The chemical formula of the hydroxide of aluminum is Ni _0.5 Co _0.2 Mn _0.3 (OH) ₂ ; where the molar amount of aluminum is 0.1% of the total molar amount of the total metal elements in the cathode precursor material.

The preparation method of the positive electrode precursor material is as follows:

Step 1: Configure A with a total ion concentration of 2.4mol/L sulfate solution, in which the molar ratio of nickel ions, cobalt ions, and manganese ions is 96:3:1, and configure a sulfate solution with a total ion concentration of 2.4mol/L. B, where the molar ratio of nickel ions, cobalt ions, and manganese ions is 5:2:3, industrial liquid alkali with a concentration of 10 mol/L is used as the precipitant solution C, and 9 mol/L ammonia water is used as the complexing agent solution D. Configuration 2mol/L aluminum sulfate solution E;

Step 2: Configure the bottom liquid F containing a certain precipitant solution and complexing agent solution in the reaction kettle. The pH of F is controlled at 10. The ammonia concentration in F is 2g/L. The temperature of F is 40°C; and nitrogen gas is introduced. As a protective gas, add mixed salt solution A, precipitant solution B and complexing agent solution C into the bottom liquid F of the above reaction kettle in parallel to ensure a pH value of 10. Use an ordinary stirring paddle at a rotation speed of 300 rpm. In the first stage of the co-precipitation reaction, seed particles with a first target particle size D50 of 3 μm are obtained. Stop injecting mixed solution A; then add solution E to perform the second stage of co-precipitation reaction. Stop adding when the molar amount of aluminum reaches 0.1%. Solution E; add solution B to carry out the third stage of co-precipitation reaction. When the particle size D50 grows to 9 μm, the co-precipitation reaction ends;

Step 3: The obtained product is centrifuged, washed, dried, and magnetic foreign matter removed to obtain the positive electrode precursor material.

Example 3

This embodiment provides a cathode precursor material that sequentially covers the core, the middle layer and the outer shell layer from the inside to the outside; the chemical formula of the core is Ni _0.91 Co _0.05 Mn _0.04 (OH) ₂ , and the middle layer is The chemical formula of the shell of a mixed hydroxide of magnesium and zirconium is Ni _0.6 Co _0.2 Mn _0.2 (OH) ₂ ; where the sum of the molar amounts of magnesium and zirconium is 0.08% of the total molar amount of the total metal elements in the cathode precursor material .

The preparation method of the positive electrode precursor material is as follows:

Step 1: Configure A with a total ion concentration of 1.6 mol/L sulfate solution, in which the molar ratio of nickel ions, cobalt ions, and manganese ions is 91:5:4, and configure a sulfate solution with a total ion concentration of 1.6 mol/L. B, where the molar ratio of nickel ions, cobalt ions, and manganese ions is 6:2:2, industrial liquid alkali with a concentration of 9mol/L is used as the precipitant solution C, and 7mol/L ammonia water is used as the complexing agent solution D. Configuration 1.6 mol/L solution E of magnesium sulfate and zirconium (the molar ratio of magnesium and zirconium is 1:1);

Step 2: Configure the bottom liquid F containing a certain precipitant solution and complexing agent solution in the reaction kettle. The pH of F is controlled at 10.8. The ammonia concentration in F is 2g/L. The temperature of F is 50°C; and nitrogen gas is introduced. As a protective gas, add the mixed salt solution A, precipitant solution B and complexing agent solution C into the bottom liquid F of the above reaction kettle in parallel to ensure a pH value of 11. Use an ordinary stirring paddle at a speed of 380 rpm. In the first stage of the co-precipitation reaction, seed particles with a first target particle size D50 of 8.5 μm are obtained. Stop injecting mixed solution A; then add solution E to perform the second stage of co-precipitation reaction, and stop when the molar amount of aluminum reaches 0.08%. Add solution E; add solution B to carry out the third stage of co-precipitation reaction. When the particle size D50 grows to 12 μm, the co-precipitation reaction ends;

Step 3: The obtained product is centrifuged, washed, dried, and magnetic foreign matter removed to obtain the positive electrode precursor material.

Example 4

The difference between this embodiment and Example 1 is that the D50 of the first target particle size in step 2 of this embodiment is 2 μm.

The remaining preparation methods and parameters are consistent with Example 1.

Example 5

The difference between this embodiment and Example 1 is that the D50 of the first target particle size in step 2 of this embodiment is 10 μm.

The remaining preparation methods and parameters are consistent with Example 1.

Example 6

The difference between this embodiment and Embodiment 1 is that in step 2 of this embodiment, when the molar amount of aluminum is 1.5% of the total molar amount of the total metal elements in the cathode precursor material, the second stage co-precipitation reaction ends.

The remaining preparation methods and parameters are consistent with Example 1.

Example 7

The difference between this embodiment and Example 1 is that in step 2 of this embodiment, when the molar amount of aluminum is 0.03% of the total molar amount of the total metal elements in the cathode precursor material, the second stage co-precipitation reaction ends.

The remaining preparation methods and parameters are consistent with Example 1.

Comparative example 1

The difference between this comparative example and Example 1 is that the positive electrode precursor material provided in this comparative example does not contain an intermediate layer, that is, the core is directly followed by the outer shell.

In the preparation method, solution E is not prepared, and the second-stage co-precipitation reaction is not performed. After the first-stage co-precipitation reaction is completed, the third-stage co-precipitation reaction is directly performed.

The remaining preparation methods and parameters are consistent with Example 1.

Comparative example 2

The difference between this comparative example and Example 1 is that the chemical formula of the cathode precursor material in this comparative example is Ni _0.96 Co _0.03 Mn _0.01 (OH) ₂ (that is, it is the core material from the inside to the outside).

In the preparation method, the co-precipitation reaction in the second stage and the third stage is not performed, and the co-precipitation reaction in the first stage is carried out until the target particle size of 12 μm is reached.

The remaining preparation methods and parameters are consistent with Example 1.

The cathode precursor materials and Li ₂ CO ₃ powder provided in Examples 1-7 and Comparative Examples 1-2 were evenly mixed according to the element ratio (the molar ratio of Li:Me (metal element) is 1.05:1.0), and the mixture was heated at 800°C. The first-burning material is calcined in an air atmosphere, and then the first-burning material is mixed with a glucose solution and coated with liquid carbon to obtain a positive electrode material.

Mix the cathode material, acetylene black, and polyvinylidene fluoride at a mass ratio of 8:1:1, add NMP, and obtain the cathode slurry. Apply it evenly on the aluminum foil, dry it, and stamp it into thin sheets (cathode sheets). . Assemble battery pole pieces, metal lithium sheets, and polyethylene separators into button batteries.

The obtained battery was subjected to a performance test. The test conditions were: 25°C: voltage range 2.5V to 3.65V, charge and discharge rate 0.1C/0.1C, capacity and cycle performance were measured, and a rate of 0.1C/1C was also carried out. Performance test, the results are shown in Table 1.

Table 1

It can be concluded from Table 1:

It can be seen from the data results of Example 1 and Examples 4 and 5 that if the first target particle size is too small, it will affect the battery capacity, and if it is too large, it will lead to a low cycle retention rate.

It can be seen from the data results of Example 1 and Examples 6 and 7 that during the second stage of coprecipitation reaction, if the molar amount of doping elements is too large, it will affect the battery capacity, while if it is too small, it will lead to a lower cycle retention rate. Low.

From the data results of Example 1 and Comparative Examples 1 and 2, it can be seen that in the present invention, the gradient distribution of nickel and the addition of the intermediate layer work together to improve the stability of the core-shell structure. The outer shell is not easy to detach, thereby improving the stability of the core-shell structure. Improved cycle performance and rate performance.

In summary, in the cathode material provided by the present invention, the nickel content of the core is higher than that of the outer shell, achieving a gradient distribution of nickel. At the same time, the intermediate layer of the doping element is synergistically matched, and the intermediate layer is between the core and the outer shell. The tight combination plays a transitional role between the core and the shell layer, strengthens the bond between the core and the shell, effectively prevents the shell from detaching, improves the structural stability, thereby improving the structural stability of the cathode material, and obtains Cathode material with excellent cycle performance and rate capability.

The applicant declares that the present invention illustrates the detailed methods of the present invention through the above embodiments, but the present invention is not limited to the above detailed methods, that is, it does not mean that the present invention must rely on the above detailed methods to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent replacement of raw materials of the product of the present invention, addition of auxiliary ingredients, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims (10)

1. A positive electrode precursor material, characterized in that the positive electrode precursor material sequentially covers an inner core, an intermediate layer and an outer shell layer from the inside to the outside; the inner core includes a first hydroxide precursor material; the middle The layer includes a hydroxide material doped with an element, the shell includes a second hydroxide precursor; the molar content of nickel in the second hydroxide precursor material is less than that in the first hydroxide precursor. The molar content of nickel. 2. The cathode precursor material according to claim 1, wherein the general chemical formula of the first hydroxide precursor material is _Nix Co _y Mn _1-xy (OH) ₂ , wherein 0.8< x≤0.99, 0≤y≤0.2; Preferably, the molar amount of the doping element is 0.01 to 0.1% of the total molar amount of the total metal elements in the cathode precursor material; Preferably, the doping element includes any one or a combination of at least two of Al, Mg, Zn, Ti, Na, Li, Sn or Nb. 3. The cathode precursor material according to claim 1 or 2, wherein the general chemical formula of the second hydroxide precursor material is Ni _a Co _b Mn _1-ab (OH) ₂ , wherein, 0.2<a≤0.6, 0≤b≤0.2. 4. A method for preparing the cathode precursor material according to any one of claims 1 to 3, characterized in that the preparation method includes the following steps: The first main metal mixed salt solution, the precipitant solution and the complexing agent solvent are added to the bottom liquid in parallel flow to perform the first stage of co-precipitation reaction. After reaching the first target particle size, the first main metal mixed salt solution is replaced. For the dopant solution, perform the second stage of co-precipitation reaction; After the second stage co-precipitation reaction is completed, the dopant solution is replaced with the second main metal mixed salt solution, and the third stage co-precipitation reaction is continued. After reaching the final target particle size, the reaction is completed and the cathode precursor is obtained. Material; The molar content of nickel in the second main metal mixed salt solution is less than the molar content of the first main metal mixed salt solution. 5. The preparation method of the cathode precursor material according to claim 4, characterized in that the molar concentration of the main metal element in the first main metal mixed salt solution is equal to the molar concentration of the main metal element in the second main metal mixed salt solution. The molar concentration is independently 1.6~2.4mol/L; Preferably, the concentration of the precipitant solution is 9 to 12 mol/L; Preferably, the precipitant solution includes an alkaline solution; Preferably, the concentration of the complexing agent solution is 7 to 10 mol/L; Preferably, the complexing agent solution includes an ammonia solution. 6. The preparation method of cathode precursor material according to claim 4 or 5, characterized in that the first target particle size is 3 to 9 μm; Preferably, when the molar amount of the doping element in the dopant is 0.05% to 0.1% of the total molar amount of the total metal elements in the cathode precursor material, the second stage coprecipitation reaction ends; Preferably, the final target particle size is 9 to 14 μm; Preferably, the pH value during the coprecipitation reaction is 9-13. 7. The preparation method of the cathode precursor material according to any one of claims 4 to 6, characterized in that the preparation method includes the following steps: Add the first main metal mixed salt solution, liquid alkali solution and ammonia solution into the bottom liquid in parallel flow to perform the first stage of co-precipitation reaction. After reaching the first target particle size of 3 to 9 μm, add the first main metal mixed salt solution Replace it with a dopant solution and perform the second stage co-precipitation reaction. When the molar amount of the doping element in the dopant is 0.05 to 0.1% of the total molar amount of the total metal elements in the cathode precursor material. , the second stage of co-precipitation reaction ends; After the second-stage co-precipitation reaction is completed, the dopant solution is replaced with the second main metal mixed salt solution, and the third-stage co-precipitation reaction is continued. After reaching the final target particle size of 9 to 14 μm, the reaction is completed and the above-mentioned Cathode precursor materials; The molar content of nickel in the second main metal mixed salt solution is less than the molar content in the first main metal mixed salt solution; the pH value during the coprecipitation reaction is 9-13. 8. A positive electrode material, characterized in that the positive electrode is obtained by mixing and sintering the positive electrode precursor material according to any one of claims 1 to 3 and a lithium source. 9. The cathode material according to claim 8, wherein the sintered material is carbon-coated. 10. A lithium ion battery, characterized in that the lithium ion battery includes the cathode material according to claim 8 or 9.