High-nickel precursor material doped with carbon nano tube as well as preparation method and application of high-nickel precursor material

Abstract

The invention provides a carbon nanotube-doped high-nickel precursor material and a preparation method and application thereof, and the preparation method comprises the following steps: introducing a high-nickel mixed metal salt solution, a carbon nanotube dispersion liquid, a complexing agent solution and a precipitant solution into a base solution, and carrying out a co-precipitation reaction to obtain the carbon nanotube-doped high-nickel precursor material. The high-nickel precursor material doped with the carbon nano tube is obtained; the carbon nanotube dispersion liquid comprises carbon nanotubes, a dispersing agent and a solvent. According to the preparation method disclosed by the invention, the carbon nano tube is introduced when the high-nickel precursor is prepared by coprecipitation, so that the subsequently prepared positive electrode material can form a carbon nano tube reinforced high-nickel material, and the positive electrode has good conductivity while the stability of the positive electrode is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and relates to a high-nickel precursor material doped with carbon nanotubes, a preparation method and an application thereof. Background Art

[0002] Solid-state batteries have higher safety compared to liquid batteries and have extremely high energy density. High-nickel ternary cathode materials (such as NCM811, NCM922, etc.) are considered ideal choices for high-energy-density lithium-ion battery systems due to their high voltage, high specific capacity and cost-effectiveness. Moreover, high-nickel ternary cathode materials are more suitable for solid-state battery systems and can further improve the energy density of solid-state batteries.

[0003] However, the current high-nickel material system is difficult to further improve the capacity, and its stability problem still exists, such as the essential problem of cracking after the material is cycled; CN111908517A discloses a method for preventing cracking during the synthesis of high-nickel ternary precursors. By means of a segmented intermittent process, small-particle-size and medium-particle-size precursor particles are mechanically mixed during the synthesis of high-nickel precursors, so that the collision between particles plays a buffering role and avoids cracking of particles during the synthesis process. However, it cannot effectively avoid the cracking of large particles during the growth process and can only reduce the probability of cracking.

[0004] Based on the above research, a preparation method of a high-nickel precursor material is needed, and the high-nickel precursor obtained by the preparation method has high stability and conductivity. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-nickel precursor material doped with carbon nanotubes, a preparation method and an application thereof. By introducing carbon nanotubes during the coprecipitation to prepare the high-nickel precursor, the cathode material prepared subsequently can form a high-nickel material enhanced by carbon nanotubes, which has good conductivity while improving the stability of the cathode.

[0006] To achieve the purpose of the present invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a preparation method of a high-nickel precursor material doped with carbon nanotubes, and the preparation method includes the following steps:

[0008] A high-nickel mixed metal salt solution, a carbon nanotube dispersion, a complexing agent solution and a precipitant solution are introduced into a bottom liquid for coprecipitation reaction to obtain the high-nickel precursor material doped with carbon nanotubes;

[0009] The carbon nanotube dispersion includes carbon nanotubes, a dispersant and a solvent.

[0010] In the coprecipitation reaction process of the high-nickel precursor material, the present invention adds a carbon nanotube dispersion liquid, so that carbon nanotubes are doped in the precursor material, and a three-dimensional conductive network can also be formed between the high-nickel precursor material particles. When preparing the subsequent cathode material, a high-nickel cathode material enhanced by carbon nanotubes is formed, thereby improving the stability and conductivity of the high-nickel cathode material.

[0011] Preferably, the carbon nanotubes are acid-modified carbon nanotubes.

[0012] The present invention uses acid-modified carbon nanotubes, and carboxyl groups are introduced into the carbon nanotubes. It can undergo an in-situ grafting reaction with a dispersant containing hydroxyl groups, which can not only construct a continuous and stable conductive network in the high-nickel precursor material, but also improve the dispersibility of the precursor particles, thereby further improving the stability and conductivity of the high-nickel cathode material.

[0013] Preferably, the method for preparing the acid-modified carbon nanotubes includes:

[0014] Mix, wash, and dry the acid solution and carbon nanotubes to obtain the acid-modified carbon nanotubes.

[0015] Preferably, the temperature for mixing the acid solution and carbon nanotubes is 80 - 100 °C, such as 80 °C, 85 °C, 90 °C, 95 °C, or 100 °C, and the time is 4 - 8 h, such as 4 h, 5 h, 6 h, 7 h, or 8 h, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0016] Preferably, the washing includes washing with deionized water until the washing liquid is neutral.

[0017] Preferably, the acid solution includes nitric acid and / or sulfuric acid with a concentration of 65 - 98 wt%, such as 65 wt%, 68 wt%, 90 wt%, or 98 wt%, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0018] Preferably, in the mixed solution obtained by mixing the acid solution and carbon nanotubes, the content of carbon nanotubes is 1 - 10 mg / mL, such as 1 mg / mL, 3 mg / mL, 5 mg / mL, 7 mg / mL, 9 mg / mL, or 10 mg / mL, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0019] Preferably, the length of the carbon nanotubes is 1 μm - 5 μm, such as 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm, but not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0020] The present invention uses shorter carbon nanotubes in combination with a precursor material, making it easier for the carbon nanotubes to be incorporated into the precursor material.

[0021] Preferably, the dispersant includes a dispersant containing hydroxyl groups, preferably polyethylene glycol.

[0022] The present invention uses polyethylene glycol containing hydroxyl groups as a dispersant, and it can also graft carbon nanotubes in-situ during the coprecipitation reaction process, further improving the performance of the high-nickel precursor material.

[0023] Preferably, the carbon nanotube dispersion also includes an initiator to promote the grafting reaction between the acid-modified carbon nanotubes and polyethylene glycol.

[0024] Preferably, the initiator includes azobisisobutyronitrile.

[0025] Preferably, in the carbon nanotube dispersion, the content of the initiator is 0.5 - 3 wt%, for example, it can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt% or 3 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0026] Preferably, in the carbon nanotube dispersion, the content of the carbon nanotubes is 2 - 10 wt%, for example, it can be 2 wt%, 4 wt%, 6 wt%, 8 wt% or 10 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0027] In the carbon nanotube dispersion of the present invention, the content of the carbon nanotubes will affect the stability and conductivity of the material. If the content of the carbon nanotubes is too low, the improvement effect will be poor. If the content of the carbon nanotubes is too high, it is easy for the carbon nanotubes to agglomerate, affecting their subsequent performance.

[0028] Preferably, in the carbon nanotube dispersion, the content of the dispersant is 0.5 - 3 wt%, for example, it can be 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt% or 3 wt%, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0029] The content of the dispersant in the present invention not only affects the dispersion of the carbon nanotubes but also affects the in-situ grafting effect between the carbon nanotubes and the dispersant, thus affecting the performance of the material. If the content of the dispersant is too low, the dispersion of the carbon nanotubes will become poor, and it is easy for the carbon nanotubes to agglomerate. If the content of the dispersant is too high, it will cause an increase in cost and is also not conducive to performance improvement.

[0030] Preferably, the flow rate of the high-nickel mixed metal salt solution is 2-8 L / h, for example, it can be 2 L / h, 4 L / h, 6 L / h or 8 L / h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable, preferably 4-8 L / h.

[0031] Preferably, the flow rate of the carbon nanotube dispersion is 0.3-5 L / h, for example, it can be 0.3 L / h, 1 L / h, 2 L / h, 3 L / h, 4 L / h or 5 L / h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable, preferably 0.6-3 L / h.

[0032] Preferably, the pH of the coprecipitation reaction is 10.5-11.5, for example, it can be 10.5, 10.7, 10.9, 11.1, 11.3 or 11.5, and the temperature is 40-80 °C, for example, it can be 40 °C, 50 °C, 60 °C, 70 °C or 80 °C, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0033] Preferably, the stirring rate of the coprecipitation reaction is 200-400 r / min, for example, it can be 200 r / min, 250 r / min, 300 r / min, 350 r / min or 400 r / min, and the time is 60-100 h, for example, it can be 60 h, 70 h, 80 h, 90 h or 100 h, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0034] Preferably, the coprecipitation reaction is carried out in a protective atmosphere, such as in a nitrogen atmosphere.

[0035] Preferably, the pH of the bottom liquid is 11.0-12.0, for example, it can be 11.0, 11.2, 11.4, 11.6, 11.8 or 12.0, and the concentration of the complexing agent is 0.2-0.5 mol / L, for example, it can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0036] Preferably, the high-nickel mixed metal salt solution includes nickel ions, cobalt ions and manganese ions.

[0037] Preferably, the molar ratio of the nickel ions, cobalt ions and manganese ions is x:y:(1-x-y), where x≥0.9 (preferably 0.9≤x<1), for example, it can be 0.9, 0.92, 0.94, 0.96 or 0.98, 0≤y≤0.1, for example, it can be 0.01, 0.03, 0.05, 0.07, 0.09 or 0.1, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0038] Preferably, the total metal ion concentration of the high-nickel mixed metal salt solution is 2-4 mol / L, for example, it can be 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L or 4 mol / L, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0039] Preferably, a nickel source, a cobalt source and a manganese source are formulated into the high-nickel mixed metal salt solution. The nickel source includes any one or a combination of at least two of nickel nitrate, nickel sulfate or nickel chloride; the cobalt source includes any one or a combination of at least two of cobalt nitrate, cobalt sulfate or cobalt chloride; the manganese source includes any one or a combination of at least two of manganese nitrate, manganese sulfate or manganese chloride.

[0040] Preferably, the complexing agent solution includes any one or a combination of at least two of an ammonia water solution, a citric acid solution or a sodium citrate solution.

[0041] Preferably, the concentration of the complexing agent solution is 0.1-0.5 mol / L, for example, it can be 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L or 0.5 mol / L, but is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0042] Preferably, the precipitating agent solution includes a sodium hydroxide solution.

[0043] In a second aspect, the present invention provides a high-nickel precursor material doped with carbon nanotubes, and the high-nickel precursor material doped with carbon nanotubes is prepared by the preparation method described in the first aspect.

[0044] In a third aspect, the present invention provides a high-nickel cathode material, and the high-nickel cathode material is obtained by mixing and sintering a lithium source and the high-nickel precursor material doped with carbon nanotubes described in the second aspect.

[0045] Preferably, the sintering includes first maintaining the temperature at 450 - 550 °C, such as 450 °C, 500 °C or 550 °C, for 4.5 - 5.5 h, such as 4.5 h, 5.0 h or 5.5 h, then heating up to 700 - 900 °C, such as 700 °C, 800 °C or 900 °C, and maintaining the temperature for 10 - 16 h, such as 10 h, 11 h, 12 h, 13 h, 14 h, 15 h or 16 h. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0046] Preferably, the lithium source includes LiOH or Li2CO3.

[0047] Preferably, the carbon nanotube-doped high-nickel precursor material and the lithium source are mixed in a stoichiometric ratio of 1:(1.02 - 1.05), such as 1:1.02, 1:1.03, 1:1.04 or 1:1.05. However, it is not limited to the listed values, and other unlisted values within the numerical range are equally applicable.

[0048] In a fourth aspect, the present invention provides a lithium-ion battery, which includes the high-nickel cathode material as described in the third aspect.

[0049] Compared with the prior art, the present invention has the following beneficial effects:

[0050] During the coprecipitation reaction process of the high-nickel precursor material, the present invention adds a carbon nanotube dispersion liquid, enabling the carbon nanotubes to be doped in the precursor material and forming a three-dimensional conductive network among the high-nickel precursor material particles. When preparing the subsequent cathode material, a carbon nanotube-reinforced high-nickel cathode material is formed, thereby improving the stability and conductivity of the high-nickel cathode material. Detailed Embodiments

[0051] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0052] Example 1

[0053] This example provides a preparation method for a carbon nanotube-doped high-nickel precursor material, and the preparation method includes the following steps:

[0054] (1) Weigh nickel sulfate, cobalt sulfate and manganese sulfate according to a molar ratio of 0.9:0.05:0.05, and prepare a high-nickel mixed metal salt solution with a total metal ion concentration of 2 mol / L;

[0055] A mixed solution of sulfuric acid and nitric acid is mixed with carbon nanotubes with a length of 3 μm at 90 °C for 6 h. Among them, the concentration of sulfuric acid is 98 wt%, the concentration of nitric acid is 68 wt%, the volume ratio of sulfuric acid to nitric acid is 3:1, and the concentration of carbon nanotubes in the mixed acid solution is 5 mg / mL. Then, it is washed with deionized water until the washing liquid is neutral, and finally dried to obtain the acid-modified carbon nanotubes;

[0056] The acid-modified carbon nanotubes, water, azobisisobutyronitrile, and polyethylene glycol are configured into a carbon nanotube dispersion. In the carbon nanotube dispersion, the content of the acid-modified carbon nanotubes is 5 wt%, the content of polyethylene glycol is 0.2 wt%, and the content of azobisisobutyronitrile is 0.2 wt%;

[0057] (2) Adjust the temperature of the reaction kettle to 60 °C, adjust the pH of the bottom liquid in the range of 11.0 - 11.5, the concentration of ammonia water is 0.3 mol / L. Nitrogen is introduced into the bottom liquid and continuously stirred at a speed of 380 r / min. Then, the high-nickel mixed metal salt solution, carbon nanotube dispersion, sodium hydroxide solution, and ammonia water solution described in step (1) are introduced into the bottom liquid in parallel. Under the conditions of a pH range of 10.5 - 11.0 and an ammonia water concentration of 0.3 mol / L, the coprecipitation reaction is carried out for 80 h and then the reaction is stopped. After washing, drying, and sieving, the high-nickel precursor material doped with carbon nanotubes is obtained;

[0058] Among them, the feeding flow rate of the high-nickel mixed metal salt solution is 4 L / h, and the feeding flow rate of the carbon nanotube dispersion is 1.5 L / h.

[0059] Example 2

[0060] This example provides a preparation method of a high-nickel precursor material doped with carbon nanotubes. The preparation method includes the following steps:

[0061] (1) Weigh nickel sulfate, cobalt sulfate, and manganese sulfate according to a molar ratio of 0.92:0.05:0.03, and prepare a high-nickel mixed metal salt solution with a total metal ion concentration of 2 mol / L;

[0062] A mixed solution of sulfuric acid and nitric acid is mixed with carbon nanotubes with a length of 1 μm at 100 °C for 4 h. Among them, the concentration of sulfuric acid is 98 wt%, the concentration of nitric acid is 68 wt%, the volume ratio of sulfuric acid to nitric acid is 2:1, and the concentration of carbon nanotubes in the mixed acid solution is 1 mg / mL. Then, it is washed with deionized water until the washing liquid is neutral, and finally dried to obtain the acid-modified carbon nanotubes;

[0063] Prepare a carbon nanotube dispersion by mixing the acid-modified carbon nanotubes, water, azobisisobutyronitrile, and polyethylene glycol. In the carbon nanotube dispersion, the content of the acid-modified carbon nanotubes is 10 wt%, the content of polyethylene glycol is 3 wt%, and the content of azobisisobutyronitrile is 3 wt%.

[0064] (2) Adjust the temperature of the reaction kettle to 40 °C, adjust the pH of the bottom liquid to the range of 11.5 - 12.0, the concentration of ammonia water is 0.5 mol / L. Introduce nitrogen into the bottom liquid and continuously stir at a speed of 350 r / min. Then, simultaneously introduce the high-nickel mixed metal salt solution, carbon nanotube dispersion, sodium hydroxide solution, and ammonia water described in step (1) into the bottom liquid. Carry out a coprecipitation reaction for 60 h under the conditions of a pH in the range of 11.0 - 11.5 and an ammonia water concentration of 0.3 mol / L, and then stop the reaction. After washing, drying, and sieving, obtain the high-nickel precursor material doped with carbon nanotubes;

[0065] Among them, the feeding flow rate of the high-nickel mixed metal salt solution is 6 L / h, and the feeding flow rate of the carbon nanotube dispersion is 1.2 L / h.

[0066] Example 3

[0067] This example provides a preparation method of a high-nickel precursor material doped with carbon nanotubes. The preparation method includes the following steps:

[0068] (1) Weigh nickel sulfate, cobalt sulfate, and manganese sulfate according to a molar ratio of 0.9:0.05:0.05, and prepare a high-nickel mixed metal salt solution with a total metal ion concentration of 4 mol / L;

[0069] Mix a mixed solution of sulfuric acid and nitric acid with carbon nanotubes having a length of 5 μm at 80 °C for 8 h. Among them, the concentration of sulfuric acid is 98 wt%, the concentration of nitric acid is 68 wt%, the volume ratio of sulfuric acid to nitric acid is 1:1, the concentration of carbon nanotubes in the mixed acid solution is 10 mg / mL. Then, wash with deionized water until the washing liquid is neutral, and finally dry to obtain the acid-modified carbon nanotubes;

[0070] Prepare a carbon nanotube dispersion by mixing the acid-modified carbon nanotubes, water, azobisisobutyronitrile, and polyethylene glycol. In the carbon nanotube dispersion, the content of the acid-modified carbon nanotubes is 2 wt%, the content of polyethylene glycol is 0.5 wt%, and the content of azobisisobutyronitrile is 0.5 wt%;

[0071] (2) Adjust the temperature of the reaction kettle to 80 °C, adjust the pH of the bottom liquid to 11.0 - 11.5, the concentration of ammonia water is 0.2 mol / L, introduce nitrogen into the bottom liquid and continuously stir at a speed of 400 r / min, then introduce the high-nickel mixed metal salt solution, carbon nanotube dispersion, sodium hydroxide solution and ammonia water described in step (1) into the bottom liquid in a flowing manner, and carry out a coprecipitation reaction for 100 h under the conditions of pH 10.5 - 11.0 and ammonia water concentration of 0.3 mol / L, then stop the reaction. After washing, drying and sieving, the high-nickel precursor material doped with carbon nanotubes is obtained;

[0072] Among them, the flow rate of the high-nickel mixed metal salt solution introduced is 8 L / h, and the flow rate of the carbon nanotube dispersion introduced is 7.5 L / h.

[0073] Example 4

[0074] This example provides a preparation method of a high-nickel precursor material doped with carbon nanotubes. Except that the content of acid-modified carbon nanotubes in the carbon nanotube dispersion is 0.5 wt%, the rest are the same as in Example 1.

[0075] Example 5

[0076] This example provides a preparation method of a high-nickel precursor material doped with carbon nanotubes. Except that the content of acid-modified carbon nanotubes in the carbon nanotube dispersion is 12 wt%, the rest are the same as in Example 1.

[0077] Example 6

[0078] This example provides a preparation method of a high-nickel precursor material doped with carbon nanotubes. Except that the content of polyethylene glycol in the carbon nanotube dispersion is 0.1 wt%, the rest are the same as in Example 1.

[0079] Example 7

[0080] This example provides a preparation method of a high-nickel precursor material doped with carbon nanotubes. Except that the content of polyethylene glycol in the carbon nanotube dispersion is 5 wt%, the rest are the same as in Example 1.

[0081] Example 8

[0082] This example provides a preparation method of a high-nickel precursor material doped with carbon nanotubes. Except that the length of the carbon nanotubes is 0.5 μm, the rest are the same as in Example 1.

[0083] Example 9

[0084] This embodiment provides a method for preparing a high-nickel precursor material doped with carbon nanotubes. The preparation method is the same as that of Example 1 except that the length of the carbon nanotubes is 7 μm.

[0085] Example 10

[0086] This embodiment provides a method for preparing a high-nickel precursor material doped with carbon nanotubes. The preparation method is the same as that of Example 1 except that the step of preparing acid-modified carbon nanotubes is not carried out, and unmodified carbon nanotubes are directly used to prepare a carbon nanotube dispersion.

[0087] Comparative Example 1

[0088] This comparative example provides a method for preparing a high-nickel precursor material. The preparation method is the same as that of Example 1 except that the carbon nanotube dispersion is not introduced during the coprecipitation reaction in step (2).

[0089] The high-nickel precursor materials obtained in the above examples and comparative examples are mixed with LiOH at a stoichiometric ratio of 1:1.02, heated to 500 °C, held for 5 h, then continuously heated to 800 °C, held for 12 h, and then cooled with the furnace to obtain a high-nickel ternary cathode material. The cathode material, polyvinylidene fluoride, and acetylene black are mixed in a mass ratio of 80:10:10, NMP (N-methylpyrrolidone) is added, and the mixture is stirred to form a slurry, which is coated on an aluminum foil, dried to form a cathode, a lithium sheet is used as the anode, assembled into a CR2025 coin cell, and its electrochemical performance is tested at 2.8 - 4.3 V. The test results are shown in Table 1:

[0090] Table 1

[0091]

[0092]

[0093] It can be seen from Table 1 that:

[0094] As can be seen from Example 1 and Comparative Example 1, by introducing carbon nanotubes during coprecipitation, the present invention can improve the stability and conductivity of the material, thereby improving the cycle performance and rate performance of the battery; as can be seen from Example 1 and Examples 4-5, the content of carbon nanotubes introduced during coprecipitation in the present invention affects the performance of the material; as can be seen from Example 1 and Examples 6-7, the content of the dispersant in the carbon nanotube dispersion of the present invention not only affects the dispersibility of carbon nanotubes, but also affects the grafting reaction between carbon nanotubes and the dispersant, thereby affecting the performance of the material; as can be seen from Example 1 and Examples 8-9, the length of the carbon nanotubes in the present invention affects the doping of carbon nanotubes and the construction of the conductive network. Preferably within a specific range, the performance of the material can be further improved; as can be seen from Example 1 and Example 10, the present invention preferably uses acid-modified carbon nanotubes, which can enable the grafting reaction between carbon nanotubes and the dispersant during coprecipitation, improve the dispersibility of the precursor material and the construction of the conductive network, and improve the stability and conductivity of the material.

[0095] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and disclosure scope of the present invention.

Claims

1. A preparation method of a doped carbon nanotube high-nickel precursor material, characterized in that The preparation method comprises the following steps: A high-nickel mixed metal salt solution, a carbon nanotube dispersion, a complexing agent solution and a precipitant solution are introduced into a bottom solution to carry out a coprecipitation reaction, thereby obtaining the high-nickel precursor material doped with carbon nanotubes; The carbon nanotube dispersion comprises carbon nanotubes, a dispersant and a solvent.

2. The preparation method according to claim 1, characterized in that, The carbon nanotubes are acid-modified carbon nanotubes; Preferably, the method for preparing the acid-modified carbon nanotubes comprises: Mixing an acid solution with carbon nanotubes, washing and drying them to obtain the acid-modified carbon nanotubes; Preferably, the temperature for mixing the acid solution with the carbon nanotubes is 80-100 °C and the time is 4-8 h; Preferably, the washing includes washing with deionized water until the washing liquid is neutral.

3. The preparation method according to claim 1 or 2, characterized in that The length of the carbon nanotubes is 1 μm - 5 μm; Preferably, the dispersant comprises a dispersant containing hydroxyl groups, preferably polyethylene glycol; Preferably, an initiator is further included in the carbon nanotube dispersion; Preferably, in the carbon nanotube dispersion, the content of the initiator is 0.5-3 wt%.

4. The preparation method according to any one of claims 1-3, characterized in that, In the carbon nanotube dispersion, the content of the carbon nanotubes is 2-10 wt%; Preferably, in the carbon nanotube dispersion, the content of the dispersant is 0.5-3 wt%.

5. The preparation method according to any one of claims 1-4, characterized in that, The feeding flow rate of the high-nickel mixed metal salt solution is 2-8 L / h; Preferably, the feeding flow rate of the carbon nanotube dispersion is 0.3-5 L / h; Preferably, the pH of the coprecipitation reaction is 10.5-11.5 and the temperature is 40-80 °C; Preferably, the stirring rate of the coprecipitation reaction is 200-400 r / min and the time is 60-100 h; Preferably, the coprecipitation reaction is carried out in a protective atmosphere.

6. The preparation method according to any one of claims 1-5, characterized in that, The pH of the bottom solution is 11.0-12.0 and the complexing agent concentration is 0.2-0.5 mol / L; Preferably, the high-nickel mixed metal salt solution comprises nickel ions, cobalt ions and manganese ions; Preferably, the molar ratio of the nickel ions, cobalt ions and manganese ions is x:y:(1-x-y), wherein x≥0.9 and 0≤y≤0.1; Preferably, the total metal ion concentration of the high-nickel mixed metal salt solution is 2-4 mol / L.

7. A high-nickel precursor material doped with carbon nanotubes, characterized in that, The high-nickel precursor material doped with carbon nanotubes is prepared by the preparation method according to any one of claims 1-6.

8. A high-nickel cathode material, characterized in that, The high-nickel cathode material is obtained by mixing and sintering a lithium source and the high-nickel precursor material doped with carbon nanotubes according to claim 7.

9. The high-nickel cathode material according to claim 8, characterized in that, The sintering includes first keeping the temperature at 450-550 °C for 4.5-5.5 h, and then raising the temperature to 700-900 °C and keeping the temperature for 10-16 h.

10. A lithium-ion battery, characterized in that, The lithium ion battery comprises the high-nickel cathode material according to claim 8 or 9.

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