Titanium-doped carbon fiber negative electrode material and preparation method thereof

Abstract

This invention discloses a method for preparing titanium-doped carbon fiber anode material. The method involves intercalating graphite and then combining it with carbon fiber, followed by sequential carbon coating, carbonization, and pulverization to obtain the anode material. Physical adsorption is used to combine the intercalated graphite with carbon fiber, improving conductivity and reducing the amount of carbon fiber used, thus lowering costs. Furthermore, the very small particle size of graphite allows it to fill defects in the carbon fiber through adsorption, providing volume support during charge and discharge, dispersing stress generated during carbon fiber deformation, and further limiting the expansion and contraction of the core structure by forming a core-shell structure, thereby improving cycle performance. Additionally, titanium dioxide is uniformly dispersed in the coating solution, resulting in a uniform distribution of titanium dioxide particles on the shell structure. Titanium dioxide has a large interlayer spacing structure, which can serve as a lithium-ion transport interface, improving the initial coulombic efficiency of the material and increasing the lithium intercalation capacity of the shell material, thereby improving the specific capacity and energy density of the anode.

Description

Technical Field

[0001] This invention relates to the field of anode materials, and in particular to a titanium-doped carbon fiber anode material and its preparation method. Background Technology

[0002] The primary reason for the volume change of the negative electrode in lithium-ion batteries is the insertion and extraction of lithium ions during charging and discharging. During charging, lithium ions insert from the positive electrode into the negative electrode, causing the negative electrode material to expand in volume; conversely, during discharging, lithium ions extract from the negative electrode and return to the positive electrode, causing the negative electrode material to shrink in volume. This volume change is due to changes in the crystal structure caused by the insertion and extraction of lithium ions, and it affects the battery's capacity and cycle stability, leading to a gradual decline in battery performance. To improve battery performance, some manufacturers use carbon fiber anode materials to manufacture the negative electrodes of lithium-ion batteries. During charging and discharging, carbon fiber anode materials exhibit smaller volume changes, significantly extending the battery's cycle life.

[0003] However, carbon fiber has relatively weak conductivity and high cost, making it difficult to promote its application in various fields. Therefore, it is necessary to improve existing carbon fiber anode materials. Summary of the Invention

[0004] In view of this, the present invention addresses the deficiencies of the existing technology, and its main objective is to provide a titanium-doped carbon fiber anode material and its preparation method, which can effectively solve the problems that the existing carbon fiber anode materials have relatively weak conductivity and high cost, making it difficult to promote and apply them in various fields.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing a titanium-doped carbon fiber anode material includes the following steps:

[0007] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:(1-5):(0.05-0.5). The reaction temperature is 40℃ and the reaction time is 10-40min to obtain intercalated graphite powder.

[0008] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and hold it for 10-60s to obtain expanded graphite.

[0009] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an inert gas atmosphere and heat it to 2500℃ at a heating rate of 50-90℃ / h, and keep it at that temperature for 1-3h to obtain conductive graphite.

[0010] (4) Place the conductive graphite and carbon fiber obtained in step (3) in acetone, with a mass ratio of conductive graphite to carbon fiber of (1-3):1, sonicate for 1-5 hours, and dry to obtain graphite-carbon fiber composite material.

[0011] (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is (10-100):(1-5):(1-10). The stirring speed is 50-150 rpm and the stirring temperature is 30-50℃. Stir until the ethanol evaporates completely to obtain the coating material.

[0012] (6) Place the coating obtained in step (5) in a reactor and carbonize it in an inert gas atmosphere at a carbonization temperature of 800-1000℃ for 4-6 hours. After cooling, crush it to obtain the negative electrode material.

[0013] As a preferred option, the intercalating agent in step (1) is a mixture of concentrated sulfuric acid and concentrated nitric acid.

[0014] As a preferred embodiment, the oxidant in step (1) is ammonium persulfate.

[0015] As a preferred embodiment, the ultrafine graphite in step (1) is ultrafine flake graphite with D10 = 0.05 μm, D50 = 0.16 μm, and D90 = 0.5 μm.

[0016] As a preferred embodiment, the inert gas in steps (3) and (6) is argon.

[0017] As a preferred option, the asphalt in step (5) is petroleum asphalt or coal tar pitch.

[0018] As a preferred embodiment, the titanium dioxide in step (5) is nano-sized titanium dioxide (B).

[0019] A titanium-doped carbon fiber anode material is prepared by the aforementioned method for preparing titanium-doped carbon fiber anode materials.

[0020] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution:

[0021] By combining intercalated graphite with carbon fiber through physical adsorption, conductivity is improved, and the amount of carbon fiber used is reduced, thus lowering costs. Furthermore, the very small particle size of graphite allows it to fill defects in the carbon fiber. During charge and discharge, graphite provides resistance to the volume reduction of the carbon fiber and disperses the stress generated during carbon fiber deformation. Combined with carbon coating to form a core-shell structure, this further restricts the expansion and contraction of the core structure, improving cycle performance. Additionally, the coating solution contains uniformly dispersed titanium dioxide, resulting in a uniform distribution of titanium dioxide particles on the shell structure. The large interlayer spacing of titanium dioxide effectively increases the lithium intercalation space, improving the lithium intercalation capacity of the shell material, thereby increasing the specific capacity and energy density of the anode.

[0022] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to specific embodiments. Detailed Implementation

[0023] This invention discloses a method for preparing titanium-doped carbon fiber anode material, comprising the following steps:

[0024] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:(1-5):(0.05-0.5). The reaction temperature is 40℃ and the reaction time is 10-40min to obtain intercalated graphite powder. The ultrafine graphite is ultrafine flake graphite with D10=0.05μm, D50=0.16μm, and D90=0.5μm. The intercalating agent is a mixture of concentrated sulfuric acid and concentrated nitric acid, and the oxidizing agent is ammonium persulfate.

[0025] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and hold it for 10-60s to obtain expanded graphite.

[0026] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an argon atmosphere and heat it to 2500℃ at a heating rate of 50-90℃ / h, and keep it at that temperature for 1-3h to obtain conductive graphite.

[0027] (4) The conductive graphite and carbon fiber obtained in step (3) are placed in acetone with a mass ratio of (1-3):1. The mixture is sonicated for 1-5 hours and then dried to obtain a graphite-carbon fiber composite material.

[0028] (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is (10-100):(1-5):(1-10). The stirring speed is 50-150 rpm and the stirring temperature is 30-50℃. Stir until the ethanol evaporates completely to obtain the coating. The asphalt is petroleum asphalt or coal tar pitch and the titanium dioxide is nano-sized titanium dioxide (B).

[0029] (6) Place the coating obtained in step (5) in a reactor and carbonize it in an argon atmosphere at a carbonization temperature of 800-1000℃ for 4-6 hours. After cooling, crush it to obtain the negative electrode material.

[0030] The present invention also discloses a titanium-doped carbon fiber anode material, which is prepared by the aforementioned method for preparing titanium-doped carbon fiber anode materials.

[0031] The following analysis will be conducted in conjunction with specific embodiments.

[0032] Example 1

[0033] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:1:0.3. The reaction temperature is 40℃ and the reaction time is 30min to obtain intercalated graphite powder. The ultrafine graphite is ultrafine flake graphite with D10 = 0.05μm, D50 = 0.16μm and D90 = 0.5μm. The intercalating agent is a mixture of concentrated sulfuric acid and concentrated nitric acid. The oxidizing agent is ammonium persulfate.

[0034] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and keep it warm for 30s to obtain expanded graphite.

[0035] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an argon atmosphere and heat it to 2500℃ at a heating rate of 50℃ / h, and keep it at that temperature for 2h to obtain conductive graphite.

[0036] (4) The conductive graphite and carbon fiber obtained in step (3) are placed in acetone with a mass ratio of 2:1. After ultrasonication for 3 hours and drying, a graphite-carbon fiber composite material is obtained.

[0037] (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is 50:2:10. The stirring speed is 100 rpm and the stirring temperature is 30°C. Stir until the ethanol evaporates completely to obtain the coating. The asphalt is coal tar pitch and the titanium dioxide is nano-sized titanium dioxide (B).

[0038] (6) The coating obtained in step (5) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 800°C for 4.5 hours. After cooling, it is crushed to obtain the negative electrode material.

[0039] Example 2

[0040] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:3:0.05. The reaction temperature is 40℃ and the reaction time is 10-40min to obtain intercalated graphite powder. The ultrafine graphite is ultrafine flake graphite with D10 = 0.05μm, D50 = 0.16μm and D90 = 0.5μm. The intercalating agent is a mixture of concentrated sulfuric acid and concentrated nitric acid. The oxidizing agent is ammonium persulfate.

[0041] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and hold it for 60s to obtain expanded graphite.

[0042] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an argon atmosphere and heat it to 2500℃ at a heating rate of 60℃ / h, and keep it at that temperature for 3h to obtain conductive graphite.

[0043] (4) The conductive graphite and carbon fiber obtained in step (3) are placed in acetone with a mass ratio of 2.5:1. The mixture is sonicated for 1.5 hours and dried to obtain a graphite-carbon fiber composite material.

[0044] (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is 10:5:1. The stirring speed is 50 rpm and the stirring temperature is 50℃. Stir until the ethanol is completely evaporated to obtain the coating. The asphalt is petroleum asphalt and the titanium dioxide is nano-sized titanium dioxide (B).

[0045] (6) The coating obtained in step (5) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 900°C for 5 hours. After cooling, it is crushed to obtain the negative electrode material.

[0046] Example 3

[0047] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:5:0.2. The reaction temperature is 40℃ and the reaction time is 10min to obtain intercalated graphite powder. The ultrafine graphite is ultrafine flake graphite with D10 = 0.05μm, D50 = 0.16μm and D90 = 0.5μm. The intercalating agent is a mixture of concentrated sulfuric acid and concentrated nitric acid. The oxidizing agent is ammonium persulfate.

[0048] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and hold it for 10s to obtain expanded graphite.

[0049] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an argon atmosphere and heat it to 2500℃ at a heating rate of 90℃ / h, and keep it at that temperature for 3h to obtain conductive graphite.

[0050] (4) The conductive graphite and carbon fiber obtained in step (3) are placed in acetone with a mass ratio of 1:1. After ultrasonication for 4 hours and drying, a graphite-carbon fiber composite material is obtained.

[0051] (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is 100:4:8. The stirring speed is 100 rpm and the stirring temperature is 45°C. Stir until the ethanol is completely evaporated to obtain the coating. The asphalt is petroleum asphalt and the titanium dioxide is nano-sized titanium dioxide (B).

[0052] (6) The coating obtained in step (5) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 850°C for 6 hours. After cooling, it is crushed to obtain the negative electrode material.

[0053] Example 4

[0054] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to an oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:5:0.5. The reaction temperature is 40℃ and the reaction time is 25min to obtain intercalated graphite powder. The ultrafine graphite is ultrafine flake graphite with D10 = 0.05μm, D50 = 0.16μm and D90 = 0.5μm. The intercalating agent is a mixture of concentrated sulfuric acid and concentrated nitric acid. The oxidizing agent is ammonium persulfate.

[0055] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and hold it for 50s to obtain expanded graphite.

[0056] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an argon atmosphere and heat it to 2500℃ at a heating rate of 55℃ / h, and keep it at that temperature for 1h to obtain conductive graphite.

[0057] (4) The conductive graphite and carbon fiber obtained in step (3) are placed in acetone with a mass ratio of 2:1. After ultrasonication for 5 hours and drying, a graphite-carbon fiber composite material is obtained.

[0058] (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is 25:1:1. The stirring speed is 80 rpm and the stirring temperature is 35°C. Stir until the ethanol is completely evaporated to obtain the coating. The asphalt is petroleum asphalt and the titanium dioxide is nano-sized titanium dioxide (B).

[0059] (6) The coating obtained in step (5) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 900°C for 4 hours. After cooling, it is crushed to obtain the negative electrode material.

[0060] Example 5

[0061] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:3:0.3. The reaction temperature is 40℃ and the reaction time is 40min to obtain intercalated graphite powder. The ultrafine graphite is ultrafine flake graphite with D10 = 0.05μm, D50 = 0.16μm and D90 = 0.5μm. The intercalating agent is a mixture of concentrated sulfuric acid and concentrated nitric acid. The oxidizing agent is ammonium persulfate.

[0062] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and hold it for 35s to obtain expanded graphite.

[0063] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an argon atmosphere and heat it to 2500℃ at a heating rate of 70℃ / h, and keep it at that temperature for 2.5h to obtain conductive graphite.

[0064] (4) The conductive graphite and carbon fiber obtained in step (3) are placed in acetone with a mass ratio of 3:1. After ultrasonication for 5 hours and drying, a graphite-carbon fiber composite material is obtained.

[0065] (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is 100:4:7. The stirring speed is 150 rpm and the stirring temperature is 45°C. Stir until the ethanol is completely evaporated to obtain the coating. The asphalt is coal tar pitch and the titanium dioxide is nano-sized titanium dioxide (B).

[0066] (6) The coating obtained in step (5) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 880°C for 4.5 hours. After cooling, it is crushed to obtain the negative electrode material.

[0067] Example 6

[0068] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:3:0.35. The reaction temperature is 40℃ and the reaction time is 30min to obtain intercalated graphite powder. The ultrafine graphite is ultrafine flake graphite with D10 = 0.05μm, D50 = 0.16μm and D90 = 0.5μm. The intercalating agent is a mixture of concentrated sulfuric acid and concentrated nitric acid. The oxidizing agent is ammonium persulfate.

[0069] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and hold it for 60s to obtain expanded graphite.

[0070] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an argon atmosphere and heat it to 2500℃ at a heating rate of 90℃ / h, and keep it at that temperature for 3h to obtain conductive graphite.

[0071] (4) The conductive graphite and carbon fiber obtained in step (3) are placed in acetone with a mass ratio of 2.6:1. After sonication for 1 hour and drying, a graphite-carbon fiber composite material is obtained.

[0072] (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is 30:3:2. The stirring speed is 70 rpm and the stirring temperature is 30°C. Stir until the ethanol is completely evaporated to obtain the coating. The asphalt is petroleum asphalt or coal tar pitch and the titanium dioxide is nano-sized titanium dioxide (B).

[0073] (6) The coating obtained in step (5) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 1000℃ for 4.5h. After cooling, it is crushed to obtain the negative electrode material.

[0074] Comparative Example 1

[0075] (1) Titanium dioxide and asphalt are dispersed evenly in ethanol to obtain a coating liquid. Then, carbon fiber is placed in the coating liquid and heated and stirred. The mass ratio of carbon fiber to titanium dioxide and asphalt is 50:2:10. The stirring speed is 100 rpm and the stirring temperature is 30°C. Stirring is carried out until the ethanol is completely evaporated to obtain the coating. The asphalt is coal tar pitch and the titanium dioxide is nano-sized titanium dioxide (B).

[0076] (2) The coating obtained in step (1) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 800°C for 4.5 hours. After cooling, it is crushed to obtain the negative electrode material.

[0077] Comparative Example 2

[0078] (1) The carbon fiber is placed in asphalt and heated and stirred. The mass ratio of carbon fiber to asphalt is 50:12, the stirring speed is 100 rpm, the stirring temperature is 30°C, and the stirring is continued until the ethanol is completely evaporated to obtain the coating. The asphalt is coal tar pitch.

[0079] (2) The coating obtained in step (1) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 800°C for 4.5 hours. After cooling, it is crushed to obtain the negative electrode material.

[0080] Comparative Example 3

[0081] (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:1:0.3. The reaction temperature is 40℃ and the reaction time is 30min to obtain intercalated graphite powder. The ultrafine graphite is ultrafine flake graphite with D10 = 0.05μm, D50 = 0.16μm and D90 = 0.5μm. The intercalating agent is a mixture of concentrated sulfuric acid and concentrated nitric acid. The oxidizing agent is ammonium persulfate.

[0082] (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and keep it warm for 30s to obtain expanded graphite.

[0083] (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an argon atmosphere and heat it to 2500℃ at a heating rate of 50℃ / h, and keep it at that temperature for 2h to obtain conductive graphite.

[0084] (4) The conductive graphite and carbon fiber obtained in step (3) are placed in acetone with a mass ratio of 2:1. After ultrasonication for 3 hours and drying, a graphite-carbon fiber composite material is obtained.

[0085] (5) The graphite-carbon fiber composite material obtained in step (4) is placed in asphalt and heated and stirred. The mass ratio of graphite-carbon fiber composite material to asphalt is 50:12, the stirring speed is 100 rpm, the stirring temperature is 30°C, and the stirring is continued until the ethanol is completely evaporated to obtain the coating. The asphalt is coal tar pitch.

[0086] (6) The coating obtained in step (5) is placed in a reactor and carbonized in an argon atmosphere at a carbonization temperature of 800°C for 4.5 hours. After cooling, it is crushed to obtain the negative electrode material.

[0087] Performance tests were conducted on the above-mentioned embodiments and comparative examples, and the test results are shown in Table 1. The data were obtained through testing with coin cells.

[0088]

[0089] Table 1

[0090] The above data clearly demonstrate that the anode material prepared using the method of this invention exhibits excellent specific capacity, initial efficiency, and capacity retention. Compared to Comparative Example 1, Comparative Example 1 shows slightly lower specific capacity and initial efficiency, but after 300 cycles, its capacity retention is significantly worse. This is because Comparative Example 1 lacks the use of ultra-small particle size graphite to fill the carbon fiber, which fails to effectively suppress electrode volume changes during charge and discharge, resulting in relatively poor capacity retention. Compared to Comparative Example 2, Comparative Example 2 shows lower initial efficiency and significantly worse cycle performance, mainly due to the lack of graphite to maintain structural stability and the absence of a stable ion transport interface provided by titanium dioxide. After 300 cycles, its capacity retention is only 88.5%. Compared with Comparative Example 3, Comparative Example 3 lacks titanium dioxide doping, resulting in a significant decrease in initial efficiency. Although the capacity can still maintain a good level, the shell structure lacks a stable ion transport interface provided by titanium dioxide, causing the capacity retention rate of Comparative Example 3 to decrease more significantly after 300 cycles compared with Comparative Example 1.

[0091] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a titanium-doped carbon fiber anode material, characterized in that: It includes the following steps: (1) Graphite powder is mixed with intercalating agent and oxidizing agent and subjected to oxidative intercalation reaction. The graphite powder is ultrafine graphite. The mass ratio of graphite powder to intercalating agent and oxidizing agent is 1:(1-5):(0.05-0.5). The reaction temperature is 40℃ and the reaction time is 10-40min to obtain intercalated graphite powder. (2) Dry the intercalated graphite powder obtained in step (1), then heat it rapidly to 1000℃ and hold it for 10-60s to obtain expanded graphite; (3) After cooling the expanded graphite obtained in step (2) to room temperature, transfer it to an inert gas atmosphere and heat it to 2500℃ at a heating rate of 50-90℃ / h, and keep it at that temperature for 1-3h to obtain conductive graphite. (4) Place the conductive graphite and carbon fiber obtained in step (3) in acetone, with a mass ratio of conductive graphite to carbon fiber of (1-3):1, sonicate for 1-5 hours, and dry to obtain graphite-carbon fiber composite material. (5) Disperse titanium dioxide and asphalt evenly in ethanol to obtain a coating liquid. Then, place the graphite-carbon fiber composite material obtained in step (4) into the coating liquid and heat and stir. The mass ratio of graphite-carbon fiber composite material to titanium dioxide and asphalt is (10-100):(1-5):(1-10). The stirring speed is 50-150 rpm and the stirring temperature is 30-50℃. Stir until the ethanol evaporates completely to obtain the coating. (6) Place the coating obtained in step (5) in a reactor and carbonize it in an inert gas atmosphere. The carbonization temperature is 800-1000℃ and the carbonization time is 4-6h. After cooling, crush it to obtain the negative electrode material.

2. The method for preparing titanium-doped carbon fiber anode material according to claim 1, characterized in that: The intercalating agent in step (1) is a mixture of concentrated sulfuric acid and concentrated nitric acid.

3. The method for preparing titanium-doped carbon fiber anode material according to claim 1, characterized in that: The oxidant in step (1) is ammonium persulfate.

4. The method for preparing titanium-doped carbon fiber anode material according to claim 1, characterized in that: The ultrafine graphite in step (1) is ultrafine flake graphite with D10=0.05μm, D50=0.16μm, and D90=0.5μm.

5. The method for preparing titanium-doped carbon fiber anode material according to claim 1, characterized in that: The inert gas used in steps (3) and (6) is argon.

6. The method for preparing titanium-doped carbon fiber anode material according to claim 1, characterized in that: The asphalt used in step (5) is petroleum asphalt or coal tar pitch.

7. The method for preparing titanium-doped carbon fiber anode material according to claim 1, characterized in that: The titanium dioxide in step (5) is nano-sized B-phase titanium dioxide.

8. A titanium-doped carbon fiber anode material, characterized in that: It is prepared by the method for preparing titanium-doped carbon fiber anode material according to any one of claims 1-7.

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