Surface treatment method for positive electrode material of lithium battery

Abstract

The invention relates to the technical field of lithium battery positive electrode material surface treatment, and discloses a lithium battery positive electrode material surface treatment method which comprises the following steps: firstly, selecting a high-purity lithium battery positive electrode material precursor, and performing surface activation treatment on the positive electrode material; according to the surface treatment method for the positive electrode material of the lithium battery, through construction of a nanoscale metal oxide coating layer, reaction of the positive electrode material and an electrolyte under high voltage is effectively inhibited, electrolyte decomposition and gas generation are reduced, and the battery can stably work under higher voltage, so that the energy density of the battery is improved; meanwhile, an efficient conductive network formed by coating of the carbon nano tube-graphene composite conductive material improves the transmission efficiency of electrons and ions, further improves the charge and discharge performance of the battery, facilitates the realization of higher energy density output, and improves the charge and discharge performance of the battery through the synergistic effect of a coating layer and final surface treatment. The violent reaction between the positive electrode material and the electrolyte is effectively prevented, and the risk of thermal runaway of the battery is reduced.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology for lithium battery cathode materials, specifically a method for surface treatment of lithium battery cathode materials. Background Technology

[0002] With the increasing global demand for clean energy, lithium batteries, as a highly efficient and clean energy storage device, have been widely used in numerous fields. Among these, the cathode material, as a core component of lithium batteries, directly determines key indicators such as energy density, charge / discharge efficiency, cycle life, and safety performance. However, existing lithium battery cathode materials face many challenges in practical applications, necessitating effective surface treatment technologies for improvement.

[0003] In high-voltage applications, cathode materials are prone to serious problems such as crystal structure breakage, electrolyte decomposition, internal gas generation, and volume expansion. For example, when the charging cut-off voltage increases, the valence states of transition metal ions (such as cobalt, nickel, and manganese) in the cathode material change. These higher-valence transition metal ions have strong oxidizing properties and react with the electrolyte, leading to electrolyte decomposition, the generation of large amounts of gas, and damage to the crystal structure of the cathode material. This causes rapid capacity decay and a sharp deterioration in cycle performance. Furthermore, interfacial side reactions between the cathode material and the electrolyte also increase the battery's internal resistance, further reducing the battery's charge / discharge efficiency and energy density.

[0004] From a cycle life perspective, traditional cathode materials gradually deteriorate during long-term charge-discharge processes due to factors such as internal stress changes, lattice distortion, and the dissolution of active materials, leading to a reduction in active sites and a continuous decrease in battery capacity. These problems are particularly pronounced under high-rate charge-discharge conditions, limiting the application of lithium batteries in scenarios requiring rapid charging and discharging (such as the fast-charging requirements of electric vehicles). Regarding safety, the unstable structure and chemical reactions on the cathode material surface can easily trigger safety accidents such as battery thermal runaway. When the internal temperature of the battery rises, the reaction between the cathode material and the electrolyte intensifies, generating more heat and gas. If heat dissipation and reaction control are not timely, it may lead to battery fire or even explosion, seriously threatening personal and property safety.

[0005] Currently, although some surface treatment methods have been proposed, such as simple metal oxide coating and carbon coating, these methods have many shortcomings. Metal oxide coatings are often insulating materials, which reduces the conductivity of the material to some extent and affects the power performance of the battery. Traditional carbon coating methods are prone to metal ion reduction at high temperatures, and organic carbon sources are difficult to carbonize at low temperatures. Furthermore, achieving uniform coating during the process is difficult, failing to fully utilize the advantages of carbon coating. Therefore, developing a novel and efficient surface treatment method for lithium-ion battery cathode materials is of paramount importance for solving these problems and improving the overall performance of lithium-ion batteries. Summary of the Invention

[0006] (a) Technical problems to be solved

[0007] To address the shortcomings of existing technologies, this invention provides a method for surface treatment of lithium battery cathode materials. This method has the advantages of improving the performance of lithium batteries in terms of energy density, cycle life, and safety through precise control of the cathode material surface, thereby meeting the demand for high-performance lithium batteries in fields such as electric vehicles and energy storage systems, and solving the aforementioned problems.

[0008] (II) Technical Solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a surface treatment method for lithium battery cathode materials, comprising the following steps:

[0010] Step 1: First, select a high-purity lithium battery cathode material precursor, put the selected cathode material precursor into deionized water, ultrasonically clean it for 15-30 minutes to remove surface impurities and adsorbed gases, and then dry it in a vacuum drying oven at 80-100℃ for 6-8 hours to obtain a dry and clean cathode material, and then perform surface activation treatment on the cathode material.

[0011] Step 2: Preparation of nanoscale alumina sol and carbon nanotube-graphene composite conductive materials;

[0012] Step 3: Add the surface-activated cathode material to the nano-sized alumina sol and ultrasonically disperse for 30-60 minutes to uniformly coat the material surface with the sol. Then, slowly evaporate the solvent in the mixture at 60-80℃ to form a uniform gel layer on the surface of the cathode material. Next, place the sample in a muffle furnace and calcine at 400-500℃ for 2-3 hours to transform the gel layer into a nano-sized alumina coating layer.

[0013] Step 4: Next, the calcined positive electrode material and the carbon nanotube-graphene composite conductive material are mixed at a mass ratio of 100:(3-5), and anhydrous ethanol is added as a dispersant. The mixture is then ball-milled in a planetary ball mill for 2-3 hours at a speed of 300-500 rpm, so that the carbon nanotube-graphene composite conductive material is uniformly attached to the surface of the positive electrode material to form a conductive network coating layer.

[0014] Step 5: Then, place the coated positive electrode material into a tube furnace and heat it to 800-900℃ at a heating rate of 5-10℃ / min under an argon protective atmosphere. Hold it at this temperature for 1-2 hours and then allow it to cool naturally to room temperature.

[0015] Step Six: Finally, immerse the annealed cathode material in a solution containing organic additives for 1-2 hours. Remove the material and dry it in a vacuum drying oven to obtain the final surface-treated lithium battery cathode material.

[0016] Preferably, the lithium battery cathode material precursor in step one is either lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

[0017] Preferably, the positive electrode material surface activation treatment step in step one includes:

[0018] First, the dried cathode material is immersed in a dilute hydrochloric acid solution with a concentration of 0.1-0.3 mol / L and stirred at room temperature for 30-60 minutes to dissolve some of the metal ions on the surface of the cathode material, forming tiny pores and defects, and increasing the surface active sites.

[0019] Then rinse the positive electrode material repeatedly with deionized water until the pH value of the rinsing solution is between 6.5 and 7, and dry it again in a vacuum drying oven to complete the surface activation treatment.

[0020] Preferably, the preparation step of the nano-scale alumina sol in step two is as follows:

[0021] Dissolve an appropriate amount of aluminum isopropoxide in anhydrous ethanol to form a solution with a concentration of 0.5-1 mol / L. While stirring continuously, slowly add deionized water at a rate of 1-2 drops / second. At the same time, add glacial acetic acid as a catalyst and adjust the pH of the solution to 4-5.

[0022] Then continue stirring the reaction for 2-3 hours to obtain a transparent nano-sized alumina sol.

[0023] Preferably, the carbon nanotube-graphene composite conductive material synthesis step in step two is as follows:

[0024] Carbon nanotubes were prepared by chemical vapor deposition, using methane as the carbon source and ferrocene as the catalyst. The mixed gas was introduced into the reactor at a high temperature of 700-800℃ to grow carbon nanotubes on the substrate.

[0025] The prepared carbon nanotubes were then mixed with a graphene oxide dispersion and ultrasonically treated to ensure uniform dispersion. Sodium borohydride was then added as a reducing agent and reacted at 60-80°C for 2-4 hours to reduce the graphene oxide to graphene, which then combined with the carbon nanotubes. After centrifugation, washing, and drying, the carbon nanotube-graphene composite conductive material was obtained.

[0026] Preferably, the thickness of the nano-alumina coating layer in step three is controlled at 5-10 nm.

[0027] Preferably, the organic additive in step six is ​​either trimethyl phosphate or vinylene carbonate.

[0028] (III) Beneficial Effects

[0029] Compared with the prior art, the present invention provides a surface treatment method for lithium battery cathode materials, which has the following beneficial effects:

[0030] 1. This lithium battery cathode material surface treatment method effectively suppresses the reaction between the cathode material and the electrolyte under high voltage by constructing a nanoscale metal oxide coating layer, reducing electrolyte decomposition and gas generation, enabling the battery to operate stably at higher voltages, thereby improving the battery's energy density. At the same time, the highly efficient conductive network formed by the carbon nanotube-graphene composite conductive material coating reduces the material's internal resistance, improves the electron and ion transport efficiency, further enhances the battery's charge and discharge performance, and helps to achieve higher energy density output.

[0031] 2. This lithium battery cathode material surface treatment method effectively prevents violent reactions between the cathode material and the electrolyte through the synergistic effect of the coating layer and the final surface treatment, reducing the risk of battery thermal runaway. Under extreme conditions such as high temperature and overcharge, the treated cathode material can maintain structural stability, reduce the generation of heat and gas, improve the safety performance of the battery, and provide strong protection for the application of lithium batteries in fields with high safety requirements such as electric vehicles and energy storage systems. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1:

[0034] A method for surface treatment of lithium battery cathode material includes the following steps:

[0035] Step 1: First, select a high-purity lithium battery cathode material precursor, put the selected cathode material precursor into deionized water, ultrasonically clean it for 15 minutes to remove surface impurities and adsorbed gases, and then dry it in a vacuum drying oven at 80℃ for 6 hours to obtain a dry and clean cathode material. Then, perform surface activation treatment on the cathode material. The lithium battery cathode material precursor is lithium nickel cobalt manganese oxide.

[0036] The surface activation treatment steps for positive electrode materials include:

[0037] First, the dried cathode material is immersed in a 0.1 mol / L dilute hydrochloric acid solution and stirred at room temperature for 30 minutes to dissolve some of the metal ions on the surface of the cathode material, forming tiny pores and defects, and increasing the surface active sites.

[0038] Then rinse the positive electrode material repeatedly with deionized water until the pH value of the rinsing solution is 6.5, and dry it again in a vacuum drying oven to complete the surface activation treatment;

[0039] Step 2: Preparation of nanoscale alumina sol and carbon nanotube-graphene composite conductive materials;

[0040] The preparation steps for nano-sized alumina sol are as follows:

[0041] Dissolve an appropriate amount of aluminum isopropoxide in anhydrous ethanol to form a solution with a concentration of 0.5 mol / L. While stirring continuously, slowly add deionized water at a rate of 1 drop / second. At the same time, add glacial acetic acid as a catalyst and adjust the pH of the solution to 4.

[0042] Then, the reaction was continued for 2 hours to obtain a transparent nano-sized alumina sol;

[0043] The synthesis steps of carbon nanotube-graphene composite conductive materials are as follows:

[0044] Carbon nanotubes were prepared by chemical vapor deposition, using methane as the carbon source and ferrocene as the catalyst. The mixed gas was introduced into the reactor at a high temperature of 700℃ to grow carbon nanotubes on the substrate.

[0045] Then, the prepared carbon nanotubes were mixed with graphene oxide dispersion and ultrasonically treated to make them uniformly dispersed. Sodium borohydride was added as a reducing agent and reacted at 60°C for 2 hours to reduce graphene oxide to graphene and combine it with carbon nanotubes. After centrifugation, washing and drying, carbon nanotube-graphene composite conductive material was obtained.

[0046] Step 3: The surface-activated cathode material is added to the nano-sized alumina sol and ultrasonically dispersed for 30 minutes to ensure that the sol uniformly coats the material surface. Then, the solvent is slowly evaporated at 60°C to form a uniform gel layer on the cathode material surface. Next, the sample is placed in a muffle furnace and calcined at 400°C for 2 hours to transform the gel layer into a nano-sized alumina coating layer with a thickness controlled at 5 nm.

[0047] Step 4: Next, the calcined cathode material and carbon nanotube-graphene composite conductive material are mixed at a mass ratio of 100:3, and anhydrous ethanol is added as a dispersant. The mixture is then ball-milled in a planetary ball mill for 2 hours at a speed of 300 rpm, so that the carbon nanotube-graphene composite conductive material is uniformly attached to the surface of the cathode material to form a conductive network coating layer.

[0048] Step 5: Then, place the coated positive electrode material into a tube furnace, heat it to 800°C at a heating rate of 5°C / min under an argon protective atmosphere, hold it at that temperature for 1 hour, and then allow it to cool naturally to room temperature.

[0049] Step Six: Finally, immerse the annealed cathode material in a solution containing organic additives for 1 hour. Remove the material and dry it in a vacuum drying oven to obtain the final surface-treated lithium battery cathode material. The organic additive is trimethyl phosphate.

[0050] Example 2:

[0051] A method for surface treatment of lithium battery cathode material includes the following steps:

[0052] Step 1: First, select a high-purity lithium battery cathode material precursor, place the selected cathode material precursor in deionized water, ultrasonically clean it for 30 minutes to remove surface impurities and adsorbed gases, and then dry it in a vacuum drying oven at 100℃ for 8 hours to obtain a dry and clean cathode material. Then, perform surface activation treatment on the cathode material. The lithium battery cathode material precursor is lithium nickel cobalt aluminum oxide.

[0053] The surface activation treatment steps for positive electrode materials include:

[0054] First, the dried cathode material is immersed in a 0.3 mol / L dilute hydrochloric acid solution and stirred at room temperature for 60 minutes to dissolve some of the metal ions on the surface of the cathode material, forming tiny pores and defects, and increasing the surface active sites.

[0055] Then rinse the positive electrode material repeatedly with deionized water until the pH value of the rinsing solution is at 7, and dry it again in a vacuum drying oven to complete the surface activation treatment.

[0056] Step 2: Preparation of nanoscale alumina sol and carbon nanotube-graphene composite conductive materials;

[0057] The preparation steps for nano-sized alumina sol are as follows:

[0058] Dissolve an appropriate amount of aluminum isopropoxide in anhydrous ethanol to form a solution with a concentration of 1 mol / L. While stirring continuously, slowly add deionized water at a rate of 2 drops / second. At the same time, add glacial acetic acid as a catalyst and adjust the pH of the solution to 5.

[0059] Then, the reaction was stirred for another 3 hours to obtain a transparent nano-sized alumina sol.

[0060] The synthesis steps of carbon nanotube-graphene composite conductive materials are as follows:

[0061] Carbon nanotubes were prepared by chemical vapor deposition, using methane as the carbon source and ferrocene as the catalyst. The mixed gas was introduced into the reactor at a high temperature of 800℃ to grow carbon nanotubes on the substrate.

[0062] Then, the prepared carbon nanotubes were mixed with graphene oxide dispersion and ultrasonically treated to make them uniformly dispersed. Sodium borohydride was added as a reducing agent and reacted at 80°C for 4 hours to reduce graphene oxide to graphene and combine it with carbon nanotubes. After centrifugation, washing and drying, carbon nanotube-graphene composite conductive material was obtained.

[0063] Step 3: The surface-activated cathode material is added to the nano-sized alumina sol and ultrasonically dispersed for 60 minutes to ensure that the sol uniformly coats the material surface. Then, the solvent is slowly evaporated at 80°C to form a uniform gel layer on the cathode material surface. Next, the sample is placed in a muffle furnace and calcined at 500°C for 3 hours to transform the gel layer into a nano-sized alumina coating layer with a thickness controlled at 10 nm.

[0064] Step 4: Next, the calcined cathode material and carbon nanotube-graphene composite conductive material are mixed at a mass ratio of 100:5, anhydrous ethanol is added as a dispersant, and the mixture is ball-milled in a planetary ball mill for 3 hours at a speed of 500 rpm, so that the carbon nanotube-graphene composite conductive material is uniformly attached to the surface of the cathode material to form a conductive network coating layer.

[0065] Step 5: Then, place the coated positive electrode material into a tube furnace and heat it to 900°C at a heating rate of 10°C / min under an argon protective atmosphere. Hold it at that temperature for 2 hours and then allow it to cool naturally to room temperature.

[0066] Step Six: Finally, immerse the annealed cathode material in a solution containing organic additives for 2 hours. Remove the material and dry it in a vacuum drying oven to obtain the final surface-treated lithium battery cathode material. The organic additive is vinylene carbonate.

[0067] Example 3:

[0068] A method for surface treatment of lithium battery cathode material includes the following steps:

[0069] Step 1: First, select a high-purity lithium battery cathode material precursor, place the selected cathode material precursor in deionized water, ultrasonically clean it for 20 minutes to remove surface impurities and adsorbed gases, and then dry it in a vacuum drying oven at 80℃ for 7 hours to obtain a dry and clean cathode material. Then, perform surface activation treatment on the cathode material. The lithium battery cathode material precursor is lithium nickel cobalt manganese oxide.

[0070] The surface activation treatment steps for positive electrode materials include:

[0071] First, the dried cathode material is immersed in a 0.2 mol / L dilute hydrochloric acid solution and stirred at room temperature for 40 minutes to dissolve some of the metal ions on the surface of the cathode material, forming tiny pores and defects, and increasing the surface active sites.

[0072] Then rinse the positive electrode material repeatedly with deionized water until the pH value of the rinsing solution is 6.5, and dry it again in a vacuum drying oven to complete the surface activation treatment;

[0073] Step 2: Preparation of nanoscale alumina sol and carbon nanotube-graphene composite conductive materials;

[0074] The preparation steps for nano-sized alumina sol are as follows:

[0075] Dissolve an appropriate amount of aluminum isopropoxide in anhydrous ethanol to form a solution with a concentration of 0.5 mol / L. While stirring continuously, slowly add deionized water at a rate of 1 drop / second. At the same time, add glacial acetic acid as a catalyst and adjust the pH of the solution to 5.

[0076] Then, the reaction was stirred for another 3 hours to obtain a transparent nano-sized alumina sol.

[0077] The synthesis steps of carbon nanotube-graphene composite conductive materials are as follows:

[0078] Carbon nanotubes were prepared by chemical vapor deposition, using methane as the carbon source and ferrocene as the catalyst. The mixed gas was introduced into the reactor at a high temperature of 700℃ to grow carbon nanotubes on the substrate.

[0079] Then, the prepared carbon nanotubes were mixed with graphene oxide dispersion and ultrasonically treated to make them uniformly dispersed. Sodium borohydride was added as a reducing agent and reacted at 80°C for 4 hours to reduce graphene oxide to graphene and combine it with carbon nanotubes. After centrifugation, washing and drying, carbon nanotube-graphene composite conductive material was obtained.

[0080] Step 3: The surface-activated cathode material is added to the nano-sized alumina sol and ultrasonically dispersed for 40 minutes to ensure that the sol uniformly coats the material surface. Then, the solvent is slowly evaporated at 60-80℃ to form a uniform gel layer on the surface of the cathode material. Next, the sample is placed in a muffle furnace and calcined at 400℃ for 2 hours to transform the gel layer into a nano-sized alumina coating layer with a thickness controlled at 8nm.

[0081] Step 4: Next, the calcined cathode material and carbon nanotube-graphene composite conductive material are mixed at a mass ratio of 100:4. Anhydrous ethanol is added as a dispersant. The mixture is then ball-milled in a planetary ball mill for 2 hours at a speed of 400 rpm. This allows the carbon nanotube-graphene composite conductive material to adhere evenly to the surface of the cathode material, forming a conductive network coating layer.

[0082] Step 5: Then, place the coated positive electrode material into a tube furnace, heat it to 900°C at a heating rate of 8°C / min under an argon protective atmosphere, hold it at that temperature for 2 hours, and then allow it to cool naturally to room temperature.

[0083] Step Six: Finally, immerse the annealed cathode material in a solution containing organic additives for 1 hour. Remove the material and dry it in a vacuum drying oven to obtain the final surface-treated lithium battery cathode material. The organic additive is vinylene carbonate.

[0084] The beneficial effects of this invention are as follows: This surface treatment method for lithium battery cathode materials effectively suppresses the reaction between the cathode material and the electrolyte under high voltage by constructing a nanoscale metal oxide coating layer, reducing electrolyte decomposition and gas generation, enabling the battery to operate stably at higher voltages, thereby improving the battery's energy density. Simultaneously, the highly efficient conductive network formed by the carbon nanotube-graphene composite conductive material coating reduces the material's internal resistance, improves electron and ion transport efficiency, further enhancing the battery's charge and discharge performance, and contributing to higher energy density output. Through the synergistic effect of the coating layer and the final surface treatment, it effectively prevents violent reactions between the cathode material and the electrolyte, reducing the risk of battery thermal runaway. Under extreme conditions such as high temperature and overcharge, the treated cathode material maintains structural stability, reduces heat and gas generation, and improves battery safety performance, providing strong protection for the application of lithium batteries in electric vehicles, energy storage systems, and other fields with high safety requirements.

[0085] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for surface treatment of lithium battery cathode material, characterized in that, Includes the following steps: Step 1: First, select a high-purity lithium battery cathode material precursor, put the selected cathode material precursor into deionized water, ultrasonically clean it for 15-30 minutes to remove surface impurities and adsorbed gases, and then dry it in a vacuum drying oven at 80-100℃ for 6-8 hours to obtain a dry and clean cathode material, and then perform surface activation treatment on the cathode material. Step 2: Preparation of nanoscale alumina sol and carbon nanotube-graphene composite conductive materials; Step 3: Add the surface-activated cathode material to the nano-sized alumina sol and ultrasonically disperse for 30-60 minutes to uniformly coat the material surface with the sol. Then, slowly evaporate the solvent in the mixture at 60-80℃ to form a uniform gel layer on the surface of the cathode material. Next, place the sample in a muffle furnace and calcine at 400-500℃ for 2-3 hours to transform the gel layer into a nano-sized alumina coating layer. Step 4: Next, the calcined positive electrode material and the carbon nanotube-graphene composite conductive material are mixed at a mass ratio of 100:(3-5), and anhydrous ethanol is added as a dispersant. The mixture is then ball-milled in a planetary ball mill for 2-3 hours at a speed of 300-500 rpm, so that the carbon nanotube-graphene composite conductive material is uniformly attached to the surface of the positive electrode material to form a conductive network coating layer. Step 5: Then, place the coated positive electrode material into a tube furnace and heat it to 800-900℃ at a heating rate of 5-10℃ / min under an argon protective atmosphere. Hold it at this temperature for 1-2 hours and then allow it to cool naturally to room temperature. Step Six: Finally, immerse the annealed cathode material in a solution containing organic additives for 1-2 hours. Remove the material and dry it in a vacuum drying oven to obtain the final surface-treated lithium battery cathode material.

2. The surface treatment method for lithium battery cathode material according to claim 1, characterized in that, In step one, the lithium battery cathode material precursor is either lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide.

3. The surface treatment method for lithium battery cathode material according to claim 1, characterized in that, The positive electrode material surface activation treatment step in step one includes: First, the dried cathode material is immersed in a dilute hydrochloric acid solution with a concentration of 0.1-0.3 mol / L and stirred at room temperature for 30-60 minutes to dissolve some of the metal ions on the surface of the cathode material, forming tiny pores and defects, and increasing the surface active sites. Then rinse the positive electrode material repeatedly with deionized water until the pH value of the rinsing solution is between 6.5 and 7, and dry it again in a vacuum drying oven to complete the surface activation treatment.

4. The surface treatment method for lithium battery cathode material according to claim 1, characterized in that, The preparation steps for the nano-scale alumina sol in step two are as follows: Dissolve an appropriate amount of aluminum isopropoxide in anhydrous ethanol to form a solution with a concentration of 0.5-1 mol / L. While stirring continuously, slowly add deionized water at a rate of 1-2 drops / second. At the same time, add glacial acetic acid as a catalyst and adjust the pH of the solution to 4-5. Then continue stirring the reaction for 2-3 hours to obtain a transparent nano-sized alumina sol.

5. The surface treatment method for lithium battery cathode material according to claim 1, characterized in that, The synthesis steps of the carbon nanotube-graphene composite conductive material in step two are as follows: Carbon nanotubes were prepared by chemical vapor deposition, using methane as the carbon source and ferrocene as the catalyst. The mixed gas was introduced into the reactor at a high temperature of 700-800℃ to grow carbon nanotubes on the substrate. The prepared carbon nanotubes were then mixed with a graphene oxide dispersion and ultrasonically treated to ensure uniform dispersion. Sodium borohydride was then added as a reducing agent and reacted at 60-80°C for 2-4 hours to reduce the graphene oxide to graphene, which then combined with the carbon nanotubes. After centrifugation, washing, and drying, the carbon nanotube-graphene composite conductive material was obtained.

6. The surface treatment method for lithium battery cathode material according to claim 1, characterized in that, In step three, the thickness of the nano-alumina coating layer is controlled at 5-10 nm.

7. The surface treatment method for lithium battery cathode material according to claim 1, characterized in that, The organic additive in step six is ​​either trimethyl phosphate or vinylene carbonate.