Preparation method of graphene / lithium iron phosphate composite positive electrode material

Abstract

This invention provides a method for preparing a graphene / lithium iron phosphate composite cathode material, comprising: S1: Weighing ferric sulfate, phosphoric acid, and lithium hydroxide in a molar ratio of (1-3):1:3, mixing them evenly to obtain a mixed solution with a pH of 6-7; S2: Transferring the mixed solution to a reaction vessel, maintaining a temperature of 110-150℃, heating and reacting for 6-8 hours, and after the reaction is complete, cooling to room temperature and filtering to obtain a light green filter cake; S3: Washing the light green filter cake with deionized water, collecting the filter cake, drying it in a vacuum drying oven at 50-80℃ for 4-6 hours, and after drying, grinding the filter cake for 30 minutes to obtain lithium iron phosphate powder; S4: Preparing composite fibers of polyacrylonitrile organic polymer, lithium iron phosphate, and graphene with an average diameter of approximately 100 nm using electrospinning; S5: Curing the composite fibers of polyacrylonitrile organic polymer, lithium iron phosphate, and graphene. This invention saves preparation time, reduces costs, and improves the charge-discharge performance, cycle stability, and safety of lithium-ion batteries.

Description

Technical Field

[0001] This disclosure relates to the field of lithium-ion batteries, and more specifically to a method for preparing a graphene / lithium iron phosphate composite cathode material. Background Technology

[0002] Lithium iron phosphate (LFP) is considered an ideal cathode material for electric vehicles due to its advantages such as low cost, high reliability of lithium insertion / extraction, and good thermal stability. Graphene, with its excellent electronic conductivity, large specific surface area, and good mechanical properties, contributes to lithium storage capacity over a wide voltage range and is widely used to improve the conductivity of materials, often referred to as an industrial additive. Graphene-modified LFP has also attracted widespread attention from researchers.

[0003] Although there are many research reports on graphene / lithium iron phosphate composites, they are all based on coating or composite graphene or graphene oxide onto lithium iron phosphate or its precursors, followed by heat treatment to obtain the composite material. The complex and cumbersome process of synthesizing graphene leads to a long and inefficient preparation process for the composite material. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing graphene / lithium iron phosphate composite cathode materials, which solves the problem of long and inefficient preparation processes for composite materials due to the complex and cumbersome process of synthesizing graphene, thereby saving time and reducing costs.

[0005] This invention provides a method for preparing a graphene / lithium iron phosphate composite cathode material, comprising:

[0006] S1: Weigh out ferric sulfate, phosphoric acid, and lithium hydroxide according to a molar ratio of (1-3):1:3, mix them thoroughly to obtain a mixed solution with a pH of 6-7;

[0007] S2: Transfer the mixed solution to the reaction vessel, maintain the temperature at 110-150℃, heat the reaction for 6-8 hours, and after the reaction is complete, cool to room temperature, filter, and obtain a light green filter cake.

[0008] S3: Wash the light green filter cake with deionized water, collect the filter cake, and dry it in a vacuum drying oven at 50-80℃ for 4-6 hours. After drying, grind the filter cake for 30 minutes to obtain lithium iron phosphate powder.

[0009] S4: Composite fibers of polyacrylonitrile organic polymers, lithium iron phosphate, and graphene with an average diameter of approximately 100 nm were prepared by electrospinning.

[0010] S5: Curing of polyacrylonitrile organic polymers, lithium iron phosphate, and graphene composite fibers yields a graphene / lithium iron phosphate composite cathode material.

[0011] Furthermore, the molar ratio of ferric sulfate, phosphoric acid, and lithium hydroxide is 2:1:3.

[0012] Furthermore, in step S1, the pH of the mixed solution is 6; in step S2, the heating time is 8 hours, and the temperature is maintained at 130°C.

[0013] Furthermore, the temperature inside the vacuum drying oven is 80℃, and the drying time is 6 hours.

[0014] Furthermore, step S4 includes the following steps:

[0015] S41: Mix dry polyacrylonitrile organic polymer, graphene powder and lithium iron phosphate powder;

[0016] S42: The mixture obtained in step S41 is dissolved in dimethylformamide (DMF) solvent, and polyacrylonitrile organic polymer, lithium iron phosphate and graphene composite fiber are prepared by electrospinning at a concentration of 18 wt%. The electrospinning conditions are as follows: spinning temperature is 25-30℃, spinning voltage is 10-20kV, feed speed is 6-10μL / min, and spinning distance is 15-28cm.

[0017] Furthermore, the polyacrylonitrile organic polymer can be one or more of the following: carbonized polyacrylonitrile (pPAN), oxidized polyacrylonitrile (O@PAN), vulcanized polyacrylonitrile (S@PAN), selenized polyacrylonitrile (Se@PAN), tellurized polyacrylonitrile (Te@PAN), selenium-doped vulcanized polyacrylonitrile (SeS@PAN), tellurium-doped vulcanized polyacrylonitrile (TeS@PAN), and selenium-tellurium-doped vulcanized polyacrylonitrile (SeTeS@PAN).

[0018] Furthermore, the spinning voltage is 10kV and the spinning distance is 15cm, or the spinning voltage is 20kV and the spinning distance is 28cm.

[0019] Furthermore, step S5 includes the following steps:

[0020] S51: Using sodium carboxymethyl cellulose adhesive of 0.5-0.9 Pa·s, polyacrylonitrile organic polymer, lithium iron phosphate and graphene composite fiber are bonded layer by layer and then rolled and compacted.

[0021] S52: The solid material obtained after bonding and compacting in step S51 is placed in a muffle furnace and heat-treated in a nitrogen atmosphere at a temperature of 80-100°C at a heating rate of 5-10°C / min for 1.5 hours to obtain the product.

[0022] S53: The product is naturally cooled at room temperature of 20-27°C to obtain graphene / lithium iron phosphate composite cathode material.

[0023] Furthermore, in step S52, the temperature is raised to 90°C for heat treatment.

[0024] Furthermore, the thickness of the sodium carboxymethyl cellulose adhesive is within 4 μm.

[0025] Compared with the prior art, this disclosure has the following beneficial effects: This disclosure solves the problem that the process of preparing composite materials is long and inefficient due to the complex and cumbersome process of synthesizing graphene, saves time, reduces costs, and greatly improves the high-current charge and discharge performance, cycle stability and safety of lithium-ion batteries.

[0026] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of this disclosure, nor is it intended to restrict the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0027] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein:

[0028] Figure 1 A flowchart illustrating a method for preparing a graphene / lithium iron phosphate composite cathode material according to an embodiment of the present disclosure is shown. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments of this disclosure, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this disclosure.

[0030] Furthermore, the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0031] A method for preparing a graphene / lithium iron phosphate composite cathode material includes:

[0032] S1: Weigh out ferric sulfate, phosphoric acid, and lithium hydroxide according to a molar ratio of (1-3):1:3, mix them thoroughly to obtain a mixed solution with a pH of 6-7;

[0033] S2: Transfer the mixed solution to the reaction vessel, maintain the temperature at 110-150℃, heat the reaction for 6-8 hours, and after the reaction is complete, cool to room temperature, filter, and obtain a light green filter cake.

[0034] S3: Wash the light green filter cake with deionized water, collect the filter cake, and dry it in a vacuum drying oven at 50-80℃ for 4-6 hours. After drying, grind the filter cake for 30 minutes to obtain lithium iron phosphate powder.

[0035] S4: Composite fibers of polyacrylonitrile organic polymers, lithium iron phosphate, and graphene with an average diameter of approximately 100 nm were prepared by electrospinning.

[0036] S5: Curing of polyacrylonitrile organic polymers, lithium iron phosphate, and graphene composite fibers yields a graphene / lithium iron phosphate composite cathode material.

[0037] This embodiment prepares graphene / lithium iron phosphate composite cathode material by electrospinning, which reduces the preparation time, improves the preparation efficiency, reduces the cost, and greatly improves the high-current charge-discharge performance, cycle stability and safety of lithium-ion batteries.

[0038] Furthermore, the molar ratio of ferric sulfate, phosphoric acid, and lithium hydroxide is 2:1:3.

[0039] Furthermore, in step S1, the pH of the mixed solution is 6; in step S2, the heating time is 8 hours, and the temperature is maintained at 130°C.

[0040] Furthermore, the temperature inside the vacuum drying oven is 80℃, and the drying time is 6 hours.

[0041] Furthermore, step S4 includes the following steps:

[0042] S41: Mix dry polyacrylonitrile organic polymer, graphene powder and lithium iron phosphate powder;

[0043] S42: The mixture obtained in step S41 is dissolved in dimethylformamide (DMF) solvent, and polyacrylonitrile organic polymer, lithium iron phosphate and graphene composite fiber are prepared by electrospinning at a concentration of 18 wt%. The electrospinning conditions are as follows: spinning temperature is 25-30℃, spinning voltage is 10-20kV, feed speed is 6-10μL / min, and spinning distance is 15-28cm.

[0044] Furthermore, the polyacrylonitrile organic polymer can be one or more of the following: carbonized polyacrylonitrile (pPAN), oxidized polyacrylonitrile (O@PAN), vulcanized polyacrylonitrile (S@PAN), selenized polyacrylonitrile (Se@PAN), tellurized polyacrylonitrile (Te@PAN), selenium-doped vulcanized polyacrylonitrile (SeS@PAN), tellurium-doped vulcanized polyacrylonitrile (TeS@PAN), and selenium-tellurium-doped vulcanized polyacrylonitrile (SeTeS@PAN).

[0045] Furthermore, the spinning voltage is 10kV and the spinning distance is 15cm, or the spinning voltage is 20kV and the spinning distance is 28cm.

[0046] Furthermore, step S5 includes the following steps:

[0047] S51: Using sodium carboxymethyl cellulose adhesive of 0.5-0.9 Pa·s, polyacrylonitrile organic polymer, lithium iron phosphate and graphene composite fiber are bonded layer by layer and then rolled and compacted.

[0048] S52: The solid material obtained after bonding and compacting in step S51 is placed in a muffle furnace and heat-treated in a nitrogen atmosphere at a temperature of 80-100°C at a heating rate of 5-10°C / min for 1.5 hours to obtain the product.

[0049] S53: The product is naturally cooled at room temperature of 20-27°C to obtain graphene / lithium iron phosphate composite cathode material.

[0050] Furthermore, in step S52, the temperature is raised to 90°C for heat treatment.

[0051] Furthermore, the thickness of the sodium carboxymethyl cellulose adhesive is within 4 μm.

[0052] Example 1

[0053] A method for preparing a graphene / lithium iron phosphate composite cathode material includes the following steps:

[0054] S1: Weigh out ferric sulfate, phosphoric acid, and lithium hydroxide in a molar ratio of 2:1:3, mix them thoroughly to obtain a mixed solution with a pH of 6.

[0055] S2: Transfer the mixed solution obtained in step S1 to the reaction vessel, maintain the temperature at 130℃, and carry out the heating reaction for 8 hours. After the reaction is completed, cool to room temperature, filter, and obtain a light green filter cake.

[0056] S3: Wash the light green filter cake obtained in step S2 with deionized water, then collect the filter cake and dry it in a vacuum drying oven at 80°C for 6 hours. After drying, grind the filter cake thoroughly for 30 minutes to obtain lithium iron phosphate powder.

[0057] S4: Composite fibers of polyacrylonitrile oxide (O@PAN), lithium iron phosphate, and graphene with an average diameter of approximately 100 nm were prepared by electrospinning. First, dried polyacrylonitrile oxide (O@PAN), graphene powder, and lithium iron phosphate powder were mixed to obtain a mixture. Then, the mixture was dissolved in dimethylformamide (DMF) solvent, and composite fibers of polyacrylonitrile oxide (O@PAN), lithium iron phosphate, and graphene were prepared by electrospinning at a concentration of 18 wt%. The electrospinning conditions were: spinning temperature of 25℃, spinning voltage of 10 kV, feed rate of 6 μL / min, and spinning distance of 15 cm.

[0058] S5: The polyacrylonitrile oxide (O@PAN), lithium iron phosphate, and graphene composite fibers obtained in step S4 are cured to obtain a graphene / lithium iron phosphate composite cathode material. First, the polyacrylonitrile oxide (O@PAN), lithium iron phosphate, and graphene composite fibers obtained in this example are bonded layer by layer using sodium carboxymethyl cellulose binder at 0.5-0.9 Pa·s and then rolled and compacted to obtain a solid material, wherein the thickness of the sodium carboxymethyl cellulose binder is less than 4 μm; then, the solid material obtained after bonding and compaction is placed in a muffle furnace and heat-treated to 90°C for 1.5 h in a nitrogen atmosphere at a heating rate of 5-10°C / min to obtain the product; finally, the product is naturally cooled at room temperature of 20-27°C to obtain the graphene / lithium iron phosphate composite cathode material.

[0059] The lithium-ion battery using the graphene / lithium iron phosphate composite cathode material prepared in this embodiment achieved ultra-high rate performance and cycle performance. At a discharge rate of 1C, the discharge specific capacity was 155 mA·h / g, and after 100 cycles, the capacity retention rate was 95.3% and the peak potential was 400 mV. At a discharge rate of 5C, the discharge specific capacity was 152 mA·h / g, and after 100 cycles, the capacity retention rate was 90.7% and the peak potential was 420 mV.

[0060] Example 2

[0061] A method for preparing a graphene / lithium iron phosphate composite cathode material includes the following steps:

[0062] S1: Weigh out ferric sulfate, phosphoric acid, and lithium hydroxide in a molar ratio of 2:1:3, mix them thoroughly to obtain a mixed solution with a pH of 6.

[0063] S2: Transfer the mixed solution obtained in step S1 to the reaction vessel, maintain the temperature at 130℃, and carry out the heating reaction for 8 hours. After the reaction is completed, cool to room temperature, filter, and obtain a light green filter cake.

[0064] S3: Wash the light green filter cake obtained in step S2 with deionized water, then collect the filter cake and dry it in a vacuum drying oven at 80°C for 6 hours. After drying, grind the filter cake thoroughly for 30 minutes to obtain lithium iron phosphate powder.

[0065] S4: Composite fibers of polyacrylonitrile oxide (O@PAN), lithium iron phosphate, and graphene with an average diameter of approximately 100 nm were prepared by electrospinning. First, dried polyacrylonitrile oxide (O@PAN), graphene powder, and lithium iron phosphate powder were mixed to obtain a mixture. Then, the mixture was dissolved in dimethylformamide (DMF) solvent, and composite fibers of polyacrylonitrile oxide (O@PAN), lithium iron phosphate, and graphene were prepared by electrospinning at a concentration of 18 wt%. The electrospinning conditions were: spinning temperature of 30℃, spinning voltage of 20 kV, feed speed of 10 μL / min, and spinning distance of 28 cm.

[0066] S5: The polyacrylonitrile oxide (O@PAN), lithium iron phosphate, and graphene composite fibers obtained in step S4 are cured to obtain a graphene / lithium iron phosphate composite cathode material. First, the polyacrylonitrile oxide (O@PAN), lithium iron phosphate, and graphene composite fibers obtained in this example are bonded layer by layer using sodium carboxymethyl cellulose binder at 0.5-0.9 Pa·s and then rolled and compacted to obtain a solid material, wherein the thickness of the sodium carboxymethyl cellulose binder is less than 4 μm; then, the solid material obtained after bonding and compaction is placed in a muffle furnace and heat-treated to 90°C for 1.5 h in a nitrogen atmosphere at a heating rate of 5-10°C / min to obtain the product; finally, the product is naturally cooled at room temperature of 20-27°C to obtain the graphene / lithium iron phosphate composite cathode material.

[0067] The lithium-ion battery using the graphene / lithium iron phosphate composite cathode material prepared in this embodiment achieved ultra-high rate performance and cycle performance. At a discharge rate of 1C, the discharge specific capacity was 154.6 mA·h / g, and after 100 cycles, the capacity retention rate was 94.8% and the peak potential was 410 mV. At a discharge rate of 5C, the discharge specific capacity was 151.2 mA·h / g, and after 100 cycles, the capacity retention rate was 90.4% and the peak potential was 430 mV.

[0068] Compare with Example 1

[0069] A method for preparing a lithium iron phosphate composite cathode material includes the following steps:

[0070] S1: Weigh out ferric sulfate, phosphoric acid, and lithium hydroxide in a molar ratio of 2:1:3, mix them thoroughly to obtain a mixed solution with a pH of 6.

[0071] S2: Transfer the mixed solution obtained in step S1 to the reaction vessel, maintain the temperature at 130℃, and carry out the heating reaction for 8 hours. After the reaction is completed, cool to room temperature, filter, and obtain a light green filter cake.

[0072] S3: The light green filter cake obtained in step S2 is first washed with deionized water, then the filter cake is collected and placed in a vacuum drying oven at 80°C for 6 hours. After drying, the filter cake is thoroughly ground for 30 minutes to obtain lithium iron phosphate composite cathode material.

[0073] The lithium iron phosphate composite cathode material prepared in step S3 was used in a lithium-ion battery. At a discharge rate of 1C, the discharge specific capacity was 145 mA·h / g, and after 100 cycles, the capacity retention rate was 62%, and the peak potential was 450 mV. At a discharge rate of 5C, the discharge specific capacity was 144.3 mA·h / g, and after 100 cycles, the capacity retention rate was 56.7%, and the peak potential was 460 mV.

[0074] In the above embodiments and comparative examples, the composite cathode material was prepared in the same environment. The specific operation process and discharge specific capacity, capacity retention rate and peak potential are detailed in Table 1 below: discharge specific capacity, capacity retention rate and peak potential of different embodiments and comparative examples at a discharge rate of 1C.

[0075] Table 1

[0076]

[0077] As can be clearly seen from the table above, compared to the lithium iron phosphate composite cathode material without graphene, the graphene / lithium iron phosphate composite cathode material prepared by electrospinning in this invention exhibits a significantly increased discharge specific capacity from 145 mA·h / g to over 154.6 mA·h / g at a 1C discharge rate; after 100 cycles, the capacity retention rate significantly increases from 62% to over 94.8%; and the peak potential difference is at least 40 mV lower than that of the material without graphene, further enhancing the energy density and power density of the lithium-ion battery. Table 2 shows the discharge specific capacity, capacity retention rate, and peak potential of different embodiments and control examples at a 5C discharge rate.

[0078] Table 2

[0079]

[0080] As can be clearly seen from the table above, compared with the lithium iron phosphate composite cathode material without graphene, the graphene / lithium iron phosphate composite cathode material prepared by electrospinning in this invention significantly increases the discharge specific capacity from 144.3 mA·h / g to over 151.2 mA·h / g at a discharge rate of 5C; after 100 cycles, the capacity retention rate significantly increases from 56.7% to over 90.4%; and the peak potential difference is at least 30 mV lower than that of the material without graphene, further enhancing the energy density and power density of the lithium-ion battery.

[0081] According to embodiments of the present invention, the following technical effects are achieved:

[0082] This invention prepares graphene / lithium iron phosphate composite cathode materials via electrospinning, reducing preparation time, improving efficiency, and lowering costs. Furthermore, the composite fibers obtained by electrospinning, containing polyacrylonitrile organic polymers, lithium iron phosphate, and graphene, have a large specific surface area. After curing, the resulting graphene / lithium iron phosphate composite cathode material is used in lithium-ion batteries, further enhancing their energy and power density. At a 1C discharge rate, the discharge specific capacity significantly increases from 145 mA·h / g to over 154.6 mA·h / g; after 100 cycles, the capacity retention rate significantly increases from 62% to over 94.8%; and the peak potential difference is at least 40 mV lower than that of materials without graphene, further enhancing the energy and power density of lithium-ion batteries. At a discharge rate of 5C, the discharge specific capacity increased significantly from 144.3 mA·h / g to over 151.2 mA·h / g; after 100 cycles, the capacity retention increased significantly from 56.7% to over 90.4%; the peak potential difference was at least 30 mV lower than that of materials without graphene, further enhancing the energy density and power density of lithium-ion batteries. The addition of graphene conductive additives to lithium iron phosphate cathode materials greatly improves the high-current charge-discharge performance, cycle stability, and safety of lithium-ion batteries.

[0083] In the description of this specification, the terms "one embodiment," "some embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0084] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing a graphene / lithium iron phosphate composite cathode material, characterized in that, include: S1: Weigh out ferric sulfate, phosphoric acid, and lithium hydroxide according to a molar ratio of (1~3):1:3, mix them thoroughly to obtain a mixed solution with a pH of 6~7; S2: Transfer the mixed solution to a reaction vessel, maintain the temperature at 110~150℃, heat the reaction for 6~8 hours, and after the reaction is complete, cool to room temperature, filter, and obtain a light green filter cake. S3: Wash the light green filter cake with deionized water, collect the filter cake, and dry it in a vacuum drying oven at 50~80℃ for 4~6 hours. After drying, grind the filter cake for 30 minutes to obtain lithium iron phosphate powder. S4: A composite fiber of polyacrylonitrile organic polymer, lithium iron phosphate and graphene with an average diameter of 100 nm was prepared by electrospinning. S5: The polyacrylonitrile organic polymer, lithium iron phosphate, and graphene composite fiber are cured to obtain a graphene / lithium iron phosphate composite cathode material. in, Step S4 includes the following steps: S41: Mix dry polyacrylonitrile organic polymer, graphene powder and lithium iron phosphate powder; S42: The mixture obtained in step S41 is dissolved in dimethylformamide (DMF) solvent, and the composite fiber of polyacrylonitrile organic polymer, lithium iron phosphate, and graphene is prepared by electrospinning at a concentration of 18 wt%. The electrospinning conditions are as follows: spinning temperature 25-30℃, spinning voltage 10-20 kV, feed speed 6-10 μL / min, and spinning distance 15-28 cm. Step S5 includes the following steps: S51: Using sodium carboxymethyl cellulose adhesive with a viscosity of 0.5~0.9 Pa·s, the polyacrylonitrile organic polymer, lithium iron phosphate and graphene composite fiber are bonded layer by layer and then rolled and compacted. S52: The solid material obtained after bonding and compacting in step S51 is placed in a muffle furnace and heated to 80-100°C in a nitrogen atmosphere at a heating rate of 5-10°C / min for 1.5 hours to obtain the product. S53: The product is naturally cooled at room temperature of 20~27℃ to obtain the graphene / lithium iron phosphate composite cathode material.

2. The method according to claim 1, characterized in that, The molar ratio of ferric sulfate, phosphoric acid, and lithium hydroxide is 2:1:

3.

3. The method according to claim 1, characterized in that, in, In step S1, the pH of the mixed solution is 6; in step S2, the heating time is 8 hours, and the temperature is maintained at 130°C.

4. The method of claim 1, wherein, In step S3, The temperature inside the vacuum drying oven is 80℃, and the drying time is 6 hours.

5. The method according to claim 1, characterized in that, The polyacrylonitrile organic polymer is one or more of the following: carbonized polyacrylonitrile (cPAN), oxidized polyacrylonitrile (O@PAN), vulcanized polyacrylonitrile (S@PAN), selenized polyacrylonitrile (Se@PAN), tellurized polyacrylonitrile (Te@PAN), selenium-doped vulcanized polyacrylonitrile (SeS@PAN), tellurium-doped vulcanized polyacrylonitrile (TeS@PAN), and selenium-tellurium-doped vulcanized polyacrylonitrile (SeTeS@PAN).

6. The method of claim 1, wherein, in, The spinning voltage is 10kV and the spinning distance is 15cm, or the spinning voltage is 20kV and the spinning distance is 28cm.

7. The method according to claim 1, characterized in that, wherein, In step S52, the temperature is raised to 90°C for heat treatment.

8. The method according to claim 1, characterized in that, The thickness of the sodium carboxymethyl cellulose adhesive is within 4 μm.

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