Preparation method of vulcanized polyacrylonitrile fiber composite material for all-solid-state lithium-sulfur battery positive electrode

Abstract

The present invention provides a method for preparing a sulfurized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode, belonging to the technical field of all-solid-state lithium metal batteries. Specifically, the method comprises: mixing a small molecule organic compound containing a thiol functional group with polyacrylonitrile, sintering to obtain a powder A, dissolving the mixture in an organic solvent, heating and stirring to form a precursor solution B, spinning the mixture into a fiber shape through an electrospinning process, drying and pulverizing the mixture, and mixing it with sulfur powder to obtain a mixture D. The mixture is sintered to complete the sulfurization and removal of the crystalline sulfur element, and after cooling to room temperature, ball-milling the mixture into fiber particles to obtain a sulfurized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode. The present invention increases the proportion of bound sulfur in the positive electrode through a synthesis process of thiol modification, electrospinning, two-step sintering, and multiple ball millings, which helps to improve the electron and ion transport at the three-phase contact interface within the positive electrode, thereby improving the capacity release of the all-solid-state lithium-sulfur battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of all-solid-state lithium metal batteries, and in particular relates to a method for preparing a sulfurized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode. Background Art

[0002] Due to dwindling fossil fuel reserves, the uncertainty of future fossil fuel supplies, and humanity's growing energy demands, many countries are seeking alternative energy sources. The development of new energy industries is crucial for the adjustment, transformation, and upgrading of my country's energy structure. As a key component of this new energy industry chain, chemical power sources are garnering increasing attention. Lithium-ion batteries, as a new type of rechargeable battery, offer advantages such as high energy density, long cycle life, and low environmental impact, making them widely used in various areas of daily life and transportation. With the continued development of electronic devices and electric vehicles, the demand for chemical power sources will also continue to grow. Therefore, developing high-performance lithium-ion batteries with higher energy density and longer cycle life is essential for the development of the new energy industry.

[0003] Lithium-sulfur batteries (Li-S) rely on the phase change chemistry of sulfur Can accommodate more lithium ions. The theoretical specific capacity of lithium-sulfur batteries is as high as 1675mAh g -1 , the theoretical specific energy is as high as 2600Wh kg -1, which is 5 to 10 times higher than the most advanced lithium-ion batteries currently available, and has extremely broad application prospects in the field of energy storage equipment (Xu R, Lu J, Amine K. Progress in Mechanistic Understanding and Characterization Techniques of Li-S Batteries[J]. Advanced Energy Materials, 2015, 5(16)). In traditional liquid lithium-sulfur batteries, due to the high solubility and high mobility of polysulfides in liquid organic electrolytes, a shuttle effect occurs, which ultimately leads to effective mass loss, low coulombic efficiency and poor cycle stability of the battery. Therefore, the theoretical specific capacity and theoretical energy density of lithium-sulfur batteries have almost never been achieved (Ren W, Ma W, Zhang S, et al. Recent advances in shuttle effect inhibition for lithium sulfur batteries[J]. Energy Storage Materials, 2019, 23 707-732.). All-solid-state lithium-sulfur batteries use inorganic solid electrolytes, which can fundamentally avoid the shuttle effect caused by polysulfide dissolution and may also inhibit the growth of lithium dendrites to a certain extent (Liu Y, He P, Zhou H. Rechargeable Solid-State Li-Air and Li-S Batteries: Materials, Construction, and Challenges[J]. Advanced Energy Materials, 2018, 8(4)).

[0004] At present, all-solid-state lithium-sulfur batteries generally use sulfur as the positive electrode active material, but due to the extremely poor conductivity of sulfur, its capacity cannot be fully released. Therefore, polyacrylonitrile (PAN, (C3H3N) n ) conductive framework, the sulfur species are bound to the polyacrylonitrile conductive skeleton to obtain a sulfurized polyacrylonitrile (SPAN) positive electrode, which can improve the problem that the capacity cannot be fully released. However, the content of crystalline sulfur in sulfurized polyacrylonitrile is relatively large (>20%), and the conductivity of crystalline sulfur is very poor. Therefore, it is necessary to increase the content of bound sulfur (<20%), thereby improving the electronic conductivity of the positive electrode and ultimately improving the cycle stability of the all-solid-state lithium-sulfur battery. At the same time, in all-solid-state lithium-sulfur batteries, due to the poor solid-solid contact between the active material inside the positive electrode and the electrolyte, the ion transfer efficiency of sulfurized polyacrylonitrile also needs to be improved. Summary of the Invention

[0005] In response to the problems of poor electronic conductivity and ion transmission efficiency of existing sulfurized polyacrylonitrile positive electrodes, the present invention provides a method for preparing sulfurized polyacrylonitrile fiber composite materials for all-solid-state lithium-sulfur battery positive electrodes. Through the synthesis process of thiol modification, electrospinning, two-step sintering and multiple ball milling, the proportion of bound sulfur content in the positive electrode is increased, which helps to improve the electron and ion transmission at the three-phase contact interface inside the positive electrode, thereby improving the capacity release of the all-solid-state lithium-sulfur battery.

[0006] In order to achieve the above purpose, the technical methods adopted by the present invention are as follows:

[0007] A method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode comprises the following steps:

[0008] Step 1: mixing a small molecule organic compound containing a thiol functional group with polyacrylonitrile and sintering the mixture in a rare earth atmosphere or nitrogen to obtain powder A;

[0009] Step 2: dissolving powder A in an organic solvent, heating and stirring to form a precursor solution B;

[0010] Step 3: The precursor solution B is spun into fibers by an electrospinning process, and then dried to obtain a fiber film C;

[0011] Step 4: crush the fiber film C, and mix it with sulfur powder in a mass ratio of (3-5):1 to obtain a mixture D;

[0012] Step 5: Place the mixture D in a rare earth atmosphere or nitrogen, heat it to 250-450° C., and keep it warm for 5-8 hours to complete the vulcanization process; then cool it to 150-200° C. and keep it warm for 2-4 hours to remove the crystalline sulfur element, and cool it to room temperature to obtain a fiber sintered material E;

[0013] Step 6: ball-mill the fiber sintered material E into fiber particles to obtain a sulfurized polyacrylonitrile fiber composite material for the positive electrode of an all-solid-state lithium-sulfur battery.

[0014] Furthermore, the small molecule organic compound containing a thiol functional group in step 1 is tert-butyl mercaptan, trithiocyanate, cysteine, cysteamine, sodium methyl mercaptan, thioglycolic acid, naphthalene dithiol or mercaptoethylamine hydrochloride, and the mass ratio of the small molecule organic compound containing a thiol functional group to polyacrylonitrile is 1:1 to 5.

[0015] Furthermore, in step 1, the sintering temperature is 150-250° C. and the sintering time is 3-5 hours.

[0016] Furthermore, the organic solvent in step 2 is N,N-dimethylformamide, dimethyl sulfoxide, pyridine, propylene glycol, isopropyl acetate or tetrahydrofuran, and the mass ratio of powder A to the organic solvent is 1-3:15-20.

[0017] Furthermore, the heating and stirring in step 2 is carried out at a temperature of 40 to 60° C. for at least 10 hours.

[0018] Furthermore, the fiber film C obtained in step 3 has a thickness of 0.8 to 1.2 mm before drying, and a fiber diameter of 5 to 8 mm.

[0019] Furthermore, the process parameters of the electrospinning in step 3 are:

[0020] Transfer the precursor solution B to a 4-5 mL syringe, keep the distance between the syringe needle nozzle and the drum collector at 15-25 cm, apply a high voltage of 10-15 kV, and push the booster at a speed of 1-1.5 mm / min to electrospin the precursor solution B on a drum collector coated with aluminum foil. Peel the synthesized fibers off the aluminum foil every 6-8 hours to ensure that the fiber thickness is 0.8-1.2 mm.

[0021] Furthermore, the temperature was maintained at 45-50° C. during the electrospinning process to ensure that the precursor solution B had good fluidity.

[0022] Furthermore, the plane size of the fiber film C after crushing in step 4 is 0.2 to 0.5 cm.

[0023] Furthermore, the mixing in step 4 further includes a ball milling process, the ball milling speed is 200-500 rpm, and the ball milling time is 2-5 hours.

[0024] Furthermore, in step 6, fiber particles are obtained by ball milling multiple times.

[0025] Furthermore, the ball milling was performed at a rotation speed of 300 rpm for 3 to 5 minutes each time, and the ball milling was allowed to stand for 20 to 40 minutes to allow the temperature in the ball milling jar to drop to room temperature to prevent the temperature from accumulating too high and causing the bound sulfur to be separated from the fiber. The ball milling was repeated 30 to 40 times.

[0026] Furthermore, the length of the fiber particles is less than 10 μm.

[0027] An all-solid-state lithium-sulfur battery positive electrode material is obtained by mixing and ball-milling a sulfurized polyacrylonitrile fiber composite material, a sulfide solid electrolyte, and a conductive additive in a mass ratio of (2-4): (2-4): 1.

[0028] Furthermore, the sulfide solid electrolyte is Li 10 Sn2PS 12、Li3PS4、Li7P3S 11 , L 10 GP2S 12 or L6PS5C.

[0029] Furthermore, the conductive additive is conductive carbon black, carbon nanotubes, graphene or vapor-grown carbon fiber.

[0030] An all-solid-state lithium-sulfur battery is assembled based on an all-solid-state lithium-sulfur battery positive electrode material, a sulfide solid electrolyte and a Li-In alloy negative electrode; wherein the sulfide solid electrolyte is the same material as the sulfide solid electrolyte used to synthesize the all-solid-state lithium-sulfur battery positive electrode material.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention proposes a method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode. Through a synthesis process of thiol modification, electrospinning, two-step sintering, and multiple ball milling, the bound sulfur content of the all-solid-state lithium-sulfur battery positive electrode is increased, which helps to improve the electron and ion transmission at the three-phase contact interface inside the all-solid-state lithium-sulfur battery positive electrode, thereby improving the capacity release of the all-solid-state lithium-sulfur battery.

[0033] 2. Specifically, by modifying polyacrylonitrile with thiol groups, the polyacrylonitrile can capture more sulfur species during the thermal decomposition and cyclization process of the first high-temperature sintering step, thereby increasing the bound sulfur content in the vulcanized polyacrylonitrile fiber composite material. The crystalline sulfur is then removed through the second low-temperature sintering step, thereby improving the electronic conductivity of the positive electrode of the all-solid-state lithium-sulfur battery and ultimately improving the cycle stability of the all-solid-state lithium-sulfur battery.

[0034] 3. Preferably, short and fine fiber particles are constructed through multiple ball milling, and the fiber length is reduced to less than 10 μm without destroying the sulfur binding state, thereby further enhancing the effective contact area between the fiber particles and the sulfide solid electrolyte and the conductive additive, thereby increasing the three-phase contact interface for efficient transmission of electrons and ions, improving the capacity release of the all-solid-state lithium-sulfur battery, and thus improving the various performance indicators of the all-solid-state lithium-sulfur battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1This is a SEM (scanning electron microscope) image of the sulfurized polyacrylonitrile fiber composite material (denoted as S@SH-PAN) obtained in Example 1;

[0037] Figure 2 This is an enlarged SEM image of the vulcanized polyacrylonitrile fiber composite material obtained in Example 1;

[0038] Figure 3 This is a thermogravimetric analysis curve of the vulcanized polyacrylonitrile fiber composite material obtained in Example 1;

[0039] Figure 4 This is a thermogravimetric analysis curve of the vulcanized polyacrylonitrile fiber composite material obtained in Comparative Example 1;

[0040] Figure 5 This is the XRD (X-ray diffraction) pattern of the vulcanized polyacrylonitrile fiber composite material obtained in Example 1;

[0041] Figure 6 This is a CV scan of the all-solid-state lithium-sulfur battery using the vulcanized polyacrylonitrile fiber composite material as the positive electrode obtained in Example 2;

[0042] Figure 7 This is a comparison chart of the long cycle performance of the all-solid-state lithium-sulfur battery with the sulfurized polyacrylonitrile fiber composite material as the positive electrode obtained in Example 2 and Comparative Example 2. DETAILED DESCRIPTION

[0043] To further understand the present invention, preferred embodiments of the present invention are described below with reference to the following examples. However, it should be understood that these examples are intended only to further illustrate the features and advantages of the present invention and are not intended to limit the scope of the claims. All raw materials used in the present invention are not particularly limited in their sources and may be purchased commercially or prepared according to conventional methods known to those skilled in the art.

[0044] Example 1

[0045] This embodiment provides a method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode, comprising the following steps:

[0046] Step 1: ball-milling thiocyanate and polyacrylonitrile powders in a mass ratio of 1:1, transferring the resulting mixed powder to a refractory crucible, placing it in a tube furnace, and sintering it at 150°C in an argon atmosphere for 3 h to obtain powder A (denoted as SH-PAN).

[0047] Step 2: Powder A was dissolved in N,N-dimethylformamide at a mass ratio of 2:15, and the mixture was heated at 60° C. and stirred vigorously for 12 h to form a uniform precursor solution B.

[0048] Step 3: Transfer the precursor solution B to a 5 mL plastic syringe, keep the distance between the syringe needle nozzle and the drum collector at 15 cm, apply a high voltage of 15 kV to the prepared precursor solution B, and the booster push speed is 1 mm / min. The precursor solution B is electrospun on a drum collector coated with aluminum foil, and continuously heated during the electrospinning process, and the temperature is maintained at 45°C; every 6 hours, the synthesized fibers are peeled off from the aluminum foil, and the collected fibers are dried in a 60°C forced air oven to remove the remaining N,N-dimethylformamide to obtain a fiber film C.

[0049] Step 4: Place the fiber film C in a small fiber crusher for crushing. The crushed fiber pieces have a plane size of about 0.5 cm. Then, mix them with sulfur powder in a mass ratio of 4:1, transfer them to a planetary ball mill for ball milling, control the speed at 400 rpm, and ball mill for 3 hours to obtain a mixture D.

[0050] Step 5: Place mixture D into a refractory crucible, place it in a tube furnace, raise the temperature to 350°C under an argon environment, and keep it warm for 6 hours to complete the vulcanization process; then lower the temperature to 150°C and keep it warm for 3 hours to remove the crystalline sulfur element; wait for the tube furnace to cool naturally to room temperature, and take out the fiber sintered material E.

[0051] Step 6: Place the fiber sintered material E into a vibrating ball mill and mill it at a speed of 300 rpm for 3 minutes each time. Then let it stand for 20 minutes to allow the temperature in the ball mill to drop to room temperature, and then mill it again. Repeat this cycle 30 times to obtain the sulfurized polyacrylonitrile fiber composite material (denoted as S@SH-PAN).

[0052] Comparative Example 1

[0053] This comparative example provides a method for preparing a vulcanized polyacrylonitrile fiber composite material for use as a positive electrode in an all-solid-state lithium-sulfur battery. The steps differ from those in Example 1 only in that step 5 only involves maintaining the temperature at 350°C for 6 hours, excluding the step of cooling the temperature to 150°C for 3 hours to remove crystalline sulfur. The remaining steps remain unchanged. Finally, a vulcanized polyacrylonitrile fiber composite material (denoted as SPAN) is produced.

[0054] The vulcanized polyacrylonitrile fiber composite material synthesized in Example 1 was subjected to scanning electron microscopy observation, thermogravimetric analysis, organic element analysis test and X-ray diffraction analysis.

[0055] Figure 1 and Figure 2This is an SEM image of the vulcanized polyacrylonitrile fiber composite material obtained in Example 1. It can be seen that the fiber particles of the vulcanized polyacrylonitrile fiber composite material are short and thin, with a length of less than 10 μm. This makes the all-solid-state lithium-sulfur battery positive electrode material based on the vulcanized polyacrylonitrile fiber composite material have a larger surface area, and has more contact area with the sulfide solid electrolyte and conductive additive, which is beneficial to the transmission of ions and electrons inside the positive electrode of the all-solid-state lithium-sulfur battery.

[0056] Figure 3 This is a thermogravimetric analysis curve of the vulcanized polyacrylonitrile fiber composite material obtained in Example 1. It can be seen that the mass loss in the temperature range of 112 to 300°C (i.e., stage II) is only about 5%, and the mass loss in this stage mainly comes from elemental sulfur species. It can be seen that elemental sulfur only accounts for 5% of the total mass of the vulcanized polyacrylonitrile fiber composite material.

[0057] Figure 4 This is a thermogravimetric analysis curve of the vulcanized polyacrylonitrile fiber composite material obtained in Comparative Example 1. It can be seen that the mass loss in the temperature range of 112 to 300°C (i.e., stage II) is as high as 30%. It can be seen that elemental sulfur accounts for about 30% of the total mass of the vulcanized polyacrylonitrile fiber composite material, indicating that compared with Comparative Example 1, the electronic conductivity of the vulcanized polyacrylonitrile fiber composite material obtained in Example 1 is greatly improved.

[0058] Table 1 shows the organic element analysis test results of the vulcanized polyacrylonitrile fiber composite material obtained in Example 1. Two samples of vulcanized polyacrylonitrile fiber composite materials prepared in the same batch were used for testing. The total content of sulfur species was about 36%, and the elemental sulfur obtained by thermogravimetric analysis accounted for about 5%. It can be seen that the bound sulfur content in the vulcanized polyacrylonitrile fiber composite material is about 30%. The removal of crystalline elemental sulfur in step 5 can improve the electronic conductivity of the all-solid-state lithium-sulfur battery positive electrode material based on the vulcanized polyacrylonitrile fiber composite material.

[0059] Table 1

[0060] Sample number N(％) C(％) H(％) S(％) O(％) 1 18.194 37.212 1.529 36.011 / 2 18.722 37.175 1.57 35.884 /

[0061] Figure 5 This is the XRD pattern of the vulcanized polyacrylonitrile fiber composite material obtained in Example 1, in which the characteristic peaks of the sulfur crystal planes (100), (102) and (110) of the vulcanized polyacrylonitrile fiber composite material disappear, indicating that the synthesized vulcanized polyacrylonitrile fiber composite material is mainly composed of amorphous phase bound sulfur.

[0062] Example 2

[0063] In this embodiment, the vulcanized polyacrylonitrile fiber composite material obtained in Example 1 is used to synthesize an all-solid-state lithium-sulfur battery positive electrode material, and then an all-solid-state lithium-sulfur battery is assembled.

[0064] Specifically, the vulcanized polyacrylonitrile fiber composite material obtained in Example 1 was mixed with L 10 GP2S 12 , carbon nanotubes in a mass ratio of 4:2:1, ground in a glove box for 40 minutes, transferred to a planetary ball mill, and sealed with sealing glue; the ball mill was taken out of the glove box, placed in a planetary ball mill for ball milling and mixing, the speed was set to 200 rpm, and the ball milling time was 10 hours. After the ball milling, the ball mill was transferred to the glove box and the ball milled material was taken out, i.e., the positive electrode material of the all-solid-state lithium-sulfur battery.

[0065] The obtained all-solid-state lithium-sulfur battery cathode material is used as the cathode and the electrolyte L 10 GP2S 12 , Li-In alloy negative electrode is assembled into an all-solid-state lithium-sulfur battery.

[0066] Comparative Example 2

[0067] In this comparative example, an all-solid-state lithium-sulfur battery positive electrode material was synthesized from the vulcanized polyacrylonitrile fiber composite material obtained in Comparative Example 1, and then an all-solid-state lithium-sulfur battery was assembled. The process was different from that in Example 2 except that the vulcanized polyacrylonitrile fiber composite material obtained in Example 1 was replaced by the vulcanized polyacrylonitrile fiber composite material obtained in Comparative Example 1; the rest of the process was the same.

[0068] The all-solid-state lithium-sulfur battery obtained in Example 2 was subjected to constant current charge and discharge tests on a blue-electric test system with a voltage range of 0.5 to 2.5 V. The test results were as follows: Figure 6 The CV scan diagram shown in the figure shows that the all-solid-state lithium-sulfur battery with sulfurized polyacrylonitrile fiber composite material (S@SH-PAN) as the positive electrode active material does not introduce unnecessary redox reactions, the reversibility of the electrode reaction is good, and the battery has a high current response, a small polarization voltage, and good reaction kinetics.

[0069] The all-solid-state lithium-sulfur batteries obtained in Example 2 and Comparative Example 2 were subjected to cyclic voltammetry tests on an electrochemical workstation with a scan rate set to 0.1 mV / s. Figure 7 As shown in the long cycle performance comparison chart, it can be seen from the figure that compared with the all-solid-state lithium-sulfur battery with sulfurized polyacrylonitrile fiber composite material (SPAN) as the positive electrode material in Comparative Example 2, the all-solid-state lithium-sulfur battery with sulfurized polyacrylonitrile fiber composite material (S@SH-PAN) as the positive electrode material in Example 2 has a greater capacity release, and the initial capacity is as high as 928 mAh / g, which is much higher than 368 mAh / g in Comparative Example 2, indicating that the sulfurized polyacrylonitrile fiber composite material obtained in Example 1 helps to improve the electron and ion transport at the three-phase contact interface inside the positive electrode of the all-solid-state lithium-sulfur battery, thereby improving the capacity release.

[0070] Example 3

[0071] This embodiment provides a method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode. The steps are different from those in Example 1, except that the mass ratio of thiocyanuric acid and polyacrylonitrile powder in step 1 is adjusted from 1:1 to 1:5, and the sintering temperature is adjusted to 250°C; the remaining steps remain unchanged.

[0072] Example 4

[0073] This embodiment provides a method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode. The steps are different from those in Example 1, except that the mass ratio of 2:15 in step 2 is adjusted to 1:20; the remaining steps remain unchanged.

[0074] Example 5

[0075] This embodiment provides a method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode. The steps are different from those in Example 1, except that the step of "peeling the synthesized fiber off the aluminum foil every 6 hours" in step 3 is adjusted to "peeling the synthesized fiber off the aluminum foil every 8 hours" to increase the thickness of the fiber film C; the remaining steps remain unchanged.

[0076] Example 6

[0077] This embodiment provides a method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode. The steps are different from those in Example 1, except that the sintering temperature for removing crystalline sulfur in step 5 is adjusted to 200° C. and the holding time is adjusted to 2 h. The remaining steps remain unchanged.

[0078] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core ideas, including the best mode, and also enables any technician in the field to practice the present invention, including making and using any device or system, and implementing any combined method. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. The scope of patent protection of the present invention is defined by the claims and may include other embodiments that can be thought of by those skilled in the art. If these other embodiments have structural elements that are not different from the literal wording of the claims, or if they include equivalent structural elements that are not substantially different from the literal wording of the claims, then these other embodiments should also be included in the scope of the claims.

Claims

1. A method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode, characterized in that: The following steps are involved: Step 1: mixing a small molecule organic compound containing a thiol functional group with polyacrylonitrile and sintering the mixture in a rare earth atmosphere or nitrogen to obtain powder A; Step 2: dissolving powder A in an organic solvent, heating and stirring to form a precursor solution B; Step 3: The precursor solution B is spun into fibers by an electrospinning process, and then dried to obtain a fiber film C; Step 4: crush the fiber film C, and mix it with sulfur powder in a mass ratio of (3-5):1 to obtain a mixture D; Step 5: placing the mixture D in a rare earth atmosphere or nitrogen, heating it to 250-450° C., and keeping it warm for 5-8 hours; then cooling it to 150-200° C., keeping it warm for 2-4 hours, and cooling it to room temperature to obtain a fiber sintered material E; Step 6: ball-milling the fiber sintered material E into fiber particles to obtain a sulfurized polyacrylonitrile fiber composite material for the positive electrode of an all-solid-state lithium-sulfur battery.

2. The method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode according to claim 1, characterized in that: The small molecule organic compound containing a thiol functional group in step 1 is tert-butyl mercaptan, trithiocyanate, cysteine, cysteamine, sodium methyl mercaptan, thioglycolic acid, naphthalene dithiol or mercaptoethylamine hydrochloride, and the mass ratio of the small molecule organic compound containing a thiol functional group to polyacrylonitrile is 1:1 to 5.

3. The method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode according to claim 1, characterized in that: The sintering temperature in step 1 is 150-250° C. and the sintering time is 3-5 hours.

4. The method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode according to claim 1, characterized in that: The organic solvent in step 2 is N,N-dimethylformamide, dimethyl sulfoxide, pyridine, propylene glycol, isopropyl acetate or tetrahydrofuran, and the mass ratio of powder A to the organic solvent is 1-3:15-20.

5. The method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode according to claim 1, characterized in that: The heating and stirring in step 2 is performed at a temperature of 40 to 60° C. for at least 10 hours.

6. The method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode according to claim 1, characterized in that: The fiber film C obtained in step 3 has a thickness of 0.8 to 1.2 mm before drying, and a fiber diameter of 5 to 8 mm.

7. The method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode according to claim 1, characterized in that: In step 6, fiber particles are obtained by ball milling multiple times, specifically at a rotation speed of 300 rpm, each ball milling for 3 to 5 minutes, standing for 20 to 40 minutes to allow the temperature in the ball mill to drop to room temperature, and repeating the ball milling 30 to 40 times.

8. The method for preparing a vulcanized polyacrylonitrile fiber composite material for an all-solid-state lithium-sulfur battery positive electrode according to claim 7, characterized in that: The length of the fiber particles is less than 10 μm.

9. An all-solid-state lithium-sulfur battery cathode material, characterized in that: The method is obtained by mixing and ball-milling the vulcanized polyacrylonitrile fiber composite material for the positive electrode of an all-solid-state lithium-sulfur battery according to any one of claims 1 to 8, a sulfide solid electrolyte, and a conductive additive in a mass ratio of (2-4): (2-4):

1.

10. An all-solid-state lithium-sulfur battery, characterized in that: It is obtained by assembling the all-solid-state lithium-sulfur battery positive electrode material, sulfide solid electrolyte and Li-In alloy negative electrode according to claim 9; wherein the sulfide solid electrolyte and the sulfide solid electrolyte used in synthesizing the all-solid-state lithium-sulfur battery positive electrode material are the same material.

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