Preparation method of composite material for modifying lithium-sulfur battery diaphragm
By preparing tin disulfide-nitrogen-doped porous carbon composite materials, the problems of complex and high cost in the preparation of existing lithium-sulfur battery separators were solved, the capacity and initial efficiency of lithium-sulfur batteries were improved, and the adsorption effect of polysulfides was enhanced.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-24
- Publication Date
- 2026-03-24
AI Technical Summary
Existing methods for preparing lithium-sulfur battery separators are complex and costly, and their polysulfide shuttle effect is not sufficiently suppressed, which affects battery performance.
A modified separator with strong polysulfide adsorption capacity and high specific surface area is prepared by using tin disulfide-nitrogen doped porous carbon composite material through hydrothermal reaction and heat treatment, which alleviates volume expansion and improves battery capacity and first efficiency.
This study achieved a simple and low-cost modification of lithium-sulfur battery separators, which significantly improved battery capacity and initial efficiency.
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Figure CN121717364A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-sulfur battery separator modification technology, and more specifically to a method for preparing composite materials for modifying lithium-sulfur battery separators. Background Technology
[0002] The increasing popularity of electric vehicles and reliance on portable technologies have propelled battery technology innovation to the forefront. The rising production of electric vehicles demands significant advancements in lithium-ion battery technology, emphasizing energy density, charging rate, and safety. Lithium-ion batteries and their derivatives currently dominate the portable electronics and large-scale energy storage battery markets. However, the energy density of lithium-ion batteries is already approaching its theoretical value.
[0003] Compared to lithium-ion batteries, lithium-sulfur batteries (LSBs) offer higher theoretical capacity, lower cost, and are more environmentally friendly, making them one of the most promising next-generation energy storage systems. The theoretical energy density of LSBs is 2600 Wh / kg. -1 The specific capacity is 1675mAhg -1 It is about 5 times higher than LIBs.
[0004] CN116742277A discloses a covalent organic framework material, its preparation method, and a modified lithium-sulfur battery separator, along with its application. The method involves mixing a covalent organic framework material containing anions and abundant regular pore structures with a conductive agent, binder, and solvent, followed by mechanical ball milling to form a fine and uniform slurry. This slurry is then coated onto a commercially available separator to form a specially modified separator. This patent application uses a slurry coating method to prepare the functionalized separator. The patent application uses a covalent organic framework containing anions and abundant regular pore structures as a modified lithium-sulfur battery separator material, suppressing polysulfide shuttle through the special regular pore structure to improve the electrochemical performance of the lithium-sulfur battery. However, this method uses covalent organic frameworks, resulting in a complex synthesis process and high preparation cost.
[0005] CN116826304A discloses a porous micron-sized spherical MoS2 modified lithium-sulfur battery separator and its preparation method. The preparation method includes: (1) mixing thiourea, ammonium molybdate and DMF in a certain proportion; stirring and ultrasonically dispersing to obtain a uniform solution; (2) placing the above solution in an oven and keeping it at a certain temperature, and cooling to obtain a crude product, which is then washed and dried to obtain porous micron-sized spherical MoS2; (3) uniformly coating the porous micron-sized spherical MoS2, conductive material and PVDF on one side of the separator substrate to obtain the modified separator. The patent mentions the chemical adsorption of polysulfides. The patent application prepared porous micron-sized spherical MoS2 composed of multiple MoS2 sheets by a solvothermal method. Through the adsorption and catalytic effect of the interlayer defects of MoS2, the shuttle effect of polysulfides was suppressed. However, the synthesized porous micron-sized spherical MoS2 is large in size and easily aggregates. The catalytic effect of porous micron-sized spherical MoS2 on soluble polysulfides is not fully reflected.
[0006] CN116826300A discloses a modified lithium-sulfur battery separator, its preparation method, and its application. The method uses a polypropylene separator as a substrate, with the surface modified by a composite film formed by the self-assembly of a porous bimetallic phosphide derived from iron-nickel Prussian blue and carbon nanotubes. The porous bimetallic phosphide exposes more active sites, enhancing the adsorption of soluble polysulfides and effectively suppressing the shuttle effect. The patent application mentions that the porous structure can adsorb polysulfides and exhibits good wettability to the electrolyte. This patent application obtains the porous bimetallic phosphide through co-precipitation and phosphating; however, because the phosphating agent selected during phosphating is sodium hypophosphite, the highly toxic gas PH3 is generated during the phosphating process. Summary of the Invention
[0007] To address at least one deficiency in the existing technology, the present invention provides a method for preparing a composite material for modifying lithium-sulfur battery separators. The preparation method of the present invention is simple and can obtain a tin disulfide / nitrogen-doped porous carbon composite material with a large specific surface area. Furthermore, the obtained composite material can be used to modify lithium-sulfur battery separators to improve capacity and first-efficiency.
[0008] To achieve its objective, the present invention provides the following technical solution:
[0009] This invention provides a method for preparing a composite material for a modified lithium-sulfur battery separator, the method comprising the following steps:
[0010] (1) Preparation of nitrogen-doped porous carbon, including the following steps:
[0011] The pulverized activated carbon powder is washed with hydrochloric acid and then dried to obtain washed activated carbon; the washed activated carbon is activated in an alkaline solution to obtain activated activated carbon; then the activated activated carbon is annealed under inert gas protection at a temperature of 500-800℃.
[0012] The activated carbon powder is activated carbon without nitrogen, nitrogen-doped activated carbon, or activated carbon that carries nitrogen and can be formed into nitrogen-doped activated carbon after the annealing treatment.
[0013] If the activated carbon powder is activated carbon that does not carry nitrogen, after the annealing treatment, the annealed activated carbon will be doped with nitrogen.
[0014] (2) Tin disulfide is grown in situ on the nitrogen-doped porous carbon obtained in step (1) by hydrothermal reaction to obtain a nitrogen-doped porous carbon / tin disulfide substrate;
[0015] (3) The nitrogen-doped porous carbon / tin disulfide substrate is heat-treated in an inert gas atmosphere at a temperature of 300-600°C and a time of 2-5 hours.
[0016] In another aspect, the present invention provides the application of the composite material prepared by the above-described preparation method in the separator of a lithium-sulfur battery.
[0017] The technical solution provided by this invention has the following beneficial effects:
[0018] The composite material prepared by this invention is a tin disulfide-nitrogen-doped porous carbon composite material, which has strong polysulfide adsorption capacity and high specific surface area. It can be used to modify lithium-sulfur battery separators to improve capacity and first-time efficiency. Attached Figure Description
[0019] Figure 1 The XRD characterization results are for the composite material prepared in Example 1;
[0020] Figure 2 The morphology characterization results of the composite material obtained in Example 1 are shown below.
[0021] Figure 3-6 The results of elemental analysis of C, Sn, S and N in the composite material obtained in Example 1 are shown. Detailed Implementation
[0022] To facilitate understanding of the present invention, the following description, in conjunction with embodiments, will further illustrate the invention. It should be understood that the following embodiments are merely for a better understanding of the invention and do not imply that the invention is limited to these embodiments.
[0023] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
[0024] This invention provides a method for preparing a composite material for modified lithium-sulfur battery separators, the method comprising the following steps:
[0025] (1) Preparation of nitrogen-doped porous carbon, including the following steps:
[0026] The pulverized activated carbon powder is washed with hydrochloric acid and then dried to obtain washed activated carbon; the washed activated carbon is activated in an alkaline solution to obtain activated activated carbon; then the activated activated carbon is annealed under inert gas protection at a temperature of 500-800℃.
[0027] The activated carbon powder is activated carbon without nitrogen, nitrogen-doped activated carbon, or activated carbon that carries nitrogen and can be formed into nitrogen-doped activated carbon after the annealing treatment.
[0028] If the activated carbon powder is activated carbon that does not carry nitrogen, after the annealing treatment, the annealed activated carbon will be doped with nitrogen.
[0029] (2) Tin disulfide is grown in situ on the nitrogen-doped porous carbon obtained in step (1) by hydrothermal reaction to obtain a nitrogen-doped porous carbon / tin disulfide substrate;
[0030] (3) The nitrogen-doped porous carbon / tin disulfide substrate is heat-treated in an inert gas atmosphere at a temperature of 300-600°C and a time of 2-5 hours.
[0031] The composite material prepared by this invention is a tin disulfide-nitrogen-doped porous carbon composite material, in which nitrogen-doped amorphous carbon can alleviate volume expansion; the nitrogen-doped porous carbon prepared by the process of this invention, and tin disulfide grown in situ on its surface, followed by heat treatment, results in a composite material with strong polysulfide adsorption capacity and high specific surface area. The prepared composite material is used to modify lithium-sulfur battery separators, which can improve capacity and first-time efficiency.
[0032] In step (1), porous carbon can be cleaned and its specific surface area increased by washing with hydrochloric acid, activating with alkaline solution and annealing at 500-800℃, while nitrogen-doped porous carbon is obtained. Tin disulfide is grown on the surface of the nitrogen-doped porous carbon by hydrothermal reaction, followed by heat treatment. The resulting composite material is used in the modification of lithium-sulfur battery separators, which can effectively improve capacity and first-time efficiency.
[0033] Preferably, in step (1), the washing with hydrochloric acid involves mixing the activated carbon powder and hydrochloric acid at a mass ratio of 0.3-1:1, and preferably the washing time is 1.5-6 hours; followed by washing with deionized water; more preferably, the concentration of HCl in the hydrochloric acid is 5-10 wt%.
[0034] Preferably, the activation in step (1) involves soaking the washed activated carbon in an alkaline solution and then removing the solvent; more preferably, the alkaline solution is an aqueous sodium hydroxide solution with a concentration of 0.05-0.3 mol / L; more preferably, the soaking time is 0.5-3 h.
[0035] Preferably, in step (1), the annealing process is carried out at 500-800℃ for 1-8 hours, more preferably 2-6 hours. Preferably, the annealing process is carried out at a heating rate of 0.5-10℃ / min to the annealing temperature. Preferably, the annealing temperature is 600-700℃.
[0036] Nitrogen-doped porous carbon with the following specific surface area and particle size can be obtained through step (1): specific surface area of 350-2000 m² / g. 2 g -1 Preferred depth: 1000-1500m 2 g -1 Preferably, the nitrogen-doped porous carbon obtained in step (1) is ground to a particle size of 0.5 μm-10 μm before being used in step (2). Using nitrogen-doped porous carbon with this preferred characteristic for subsequent hydrothermal reaction and heat treatment results in a composite material with better application performance.
[0037] In some embodiments, in step (1), for activated carbon raw materials without nitrogen, after annealing, the nitrogen doping includes the following operation: mixing the annealed activated carbon with a nitrogen-containing dopant, and treating it at 500-850°C under inert gas protection, preferably holding it at 500-850°C for 1-5 hours. Preferably, the mass ratio of the annealed activated carbon to the nitrogen-containing dopant is 1:0.5-10. Preferably, the nitrogen-containing dopant is one or more of melamine, urea, and ammonium dihydrogen phosphate.
[0038] Preferably, the nitrogen doping amount in the composite material obtained in step (3) is 2-5% atomic percentage. In step (1), a corresponding activated carbon raw material that can achieve the desired nitrogen doping amount of the composite material can be selected, or the nitrogen doping amount in the nitrogen doping process can be adjusted so as to obtain a composite material with the target nitrogen doping amount.
[0039] Preferably, in step (2), the nitrogen-doped porous carbon is subjected to the hydrothermal reaction with a mixture of tin tetrachloride pentahydrate and thioacetamide; the mass ratio of the nitrogen-doped porous carbon to the mixture of tin tetrachloride pentahydrate and thioacetamide is 0.05-1:1, preferably 0.1-0.5:1. Performing the hydrothermal reaction at this preferred mass ratio allows for good control of the crystal structure and specific surface area of the final product, facilitating the acquisition of a composite material with better performance. The resulting composite material can significantly improve electrochemical performance when used in the modification of lithium-sulfur battery separators. The formed tin disulfide can adsorb polysulfides through chemical bonds, and its interplanar spacing d... 001 =0.591nm.
[0040] In some embodiments, the mass ratio of tin tetrachloride pentahydrate to thioacetamide is 0.5-1.5:1. Preferably, the hydrothermal reaction temperature is 100-200°C, and the reaction time is preferably 10-20 hours.
[0041] In a preferred embodiment, in step (1), the annealing temperature is 600-700℃; in step (2), when the nitrogen-doped porous carbon is subjected to the hydrothermal reaction with the mixture of tin tetrachloride pentahydrate and thioacetamide, the mass ratio of the nitrogen-doped porous carbon to the mixture of tin tetrachloride pentahydrate and thioacetamide is 0.1-0.5:1. Modifying the lithium-sulfur battery separator using the composite material obtained in the preferred manner is beneficial for obtaining better application performance, achieving both superior capacity and initial efficiency.
[0042] The activated carbon raw material used in this invention can be waste activated carbon. The inert gas mentioned in this article can be, but is not limited to, argon.
[0043] The composite material prepared by the method of this invention has a large specific surface area. The composite material prepared by this invention is a tin disulfide-nitrogen-doped porous carbon composite material prepared by a combination of hydrothermal and heat treatment. Nitrogen doping helps improve the electrical conductivity of porous carbon, and the nitrogen-doped porous carbon can bond with soluble polysulfides, forming chemisorption, which is beneficial to improving the adsorption effect. The formed amorphous porous carbon acts as a confinement material to alleviate volume expansion, and the tin disulfide grown in situ on the surface can chemisorb polysulfides. The composite material obtained by the method of this invention is particularly suitable for application in the modification of lithium-sulfur battery separators, which can promote the improvement of separator performance, increase capacity, and improve initial efficiency.
[0044] The present invention also provides the application of the composite material prepared by the above-described preparation method in the separator of a lithium-sulfur battery. For example, when the composite material is mixed with conductive carbon black Super P and a binder (e.g., polyvinylidene fluoride) and coated onto one side of a separator (e.g., a PP (polypropylene) separator) as a lithium-sulfur battery separator, it exhibits significantly improved capacity and first-pass efficiency.
[0045] The present invention will be further illustrated by the following embodiments, but it should not be construed as the present invention being limited to these embodiments.
[0046] Where specific experimental steps or conditions are not specified in the examples, the corresponding conventional experimental steps or conditions in this technical field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.
[0047] The test method is described below:
[0048] 1. Specific surface area test
[0049] BET and pore structure analysis were performed on a Micron Instruments TriStar II 3020 analyzer.
[0050] Test conditions: N2 was used as the adsorbate and adsorption was carried out at liquid nitrogen temperature (77K). The specific surface area was determined by the BET method, and the test range was P / P0 = 0.0096 to 0.9947.
[0051] Where P0 is the saturated vapor pressure of the adsorbate at the experimental temperature, and P is the equilibrium pressure during adsorption.
[0052] 2. The sample structure was characterized using a Bruker D8 Advance X-ray diffractometer (XRD) from Germany. The X-ray source was Cu Kα.
[0053] 3. Morphological characterization is performed using a FEI Nova Nano SEM 450 scanning electron microscope. The conductive tape is cut to an appropriate size and attached to the sample stage. An appropriate amount of powder sample is taken and evenly spread on the conductive tape. After blowing off any unadhesive powder with a bulb syringe, the test can be performed.
[0054] Example 1
[0055] A composite material for modifying lithium-sulfur battery separators, the preparation steps of which include:
[0056] (1) Preparation of nitrogen-doped porous carbon
[0057] Waste activated carbon was crushed to obtain activated carbon powder; the activated carbon powder was mixed with hydrochloric acid with a concentration of 10wt% at a mass ratio of 0.5:1, treated in air atmosphere for 3 hours, then washed with deionized water, and then dried to obtain washed activated carbon.
[0058] The washed activated carbon was soaked in a 0.1 mol / L sodium hydroxide aqueous solution for 2 hours, and then the water was evaporated to dryness to obtain activated carbon.
[0059] The activated carbon was annealed in an argon atmosphere by heating it to 600℃ (the annealing temperature) at a rate of 5℃ / min, holding it at 600℃ for 5 hours, and then automatically cooling it down. The annealed activated carbon was then mixed with melamine at a mass ratio of 1:8 and held at 800℃ for 3 hours to obtain nitrogen-doped porous carbon with a specific surface area of 358.8 m². 2 g -1 The particle size is 5μm;
[0060] (2) Nitrogen-doped porous carbon was mixed with a mixture of tin tetrachloride pentahydrate and thioacetamide at a mass ratio of 0.12:1, wherein the mass ratio of tin tetrachloride pentahydrate and thioacetamide was 1.18:1. The mixture was subjected to a hydrothermal reaction at 160°C for 12 hours and then automatically cooled to obtain a nitrogen-doped porous carbon / tin disulfide substrate.
[0061] (3) The doped porous carbon / tin disulfide substrate was heat-treated in an argon atmosphere at a temperature of 500°C for 3 hours to obtain the composite material.
[0062] The XRD characterization results of the obtained composite material are shown in [reference]. Figure 1 For morphological characterization results, please refer to Figure 2 The obtained composite material was analyzed using X-ray photoelectron spectroscopy. The analytical results for C, Sn, S, and N elements are shown in [reference needed]. Figure 3-6 .
[0063] The prepared composite material was used to modify the separator material of lithium-sulfur batteries, and the modified separator was assembled into lithium-sulfur batteries according to conventional methods. The preparation process of the coin cell is as follows: The composite material was mixed with conductive carbon black Super P and binder polyvinylidene fluoride (PVDF) at a mass ratio of 7:2:1. N-methylpyrrolidone (NMP) solvent was added and stirred into a uniform slurry. In this embodiment, the mass ratio of the composite material in the slurry was 70%. The slurry was uniformly coated onto a PP separator with a doctor blade and dried to obtain the modified separator. The obtained modified separator was punched into a sheet with a diameter of 12 mm and transferred to an MBraun 2000 glove box (Ar atmosphere, H2O and O2 concentration less than 0.1 × 10⁻⁶). -6 The battery (volume %) was assembled into a coin cell using lithium metal sheet as the reference electrode and sulfur / carbon composite material as the positive electrode. The battery capacity and initial efficiency were tested using the CT2001A battery tester from Wuhan Landian Electronics Co., Ltd., with a charge / discharge current of 0.1C (1C = 16750mAh / g) and a voltage of 1.7-2.8V.
[0064] Examples 2 and 3
[0065] Example 2 was carried out in accordance with Example 1, except that: in the preparation process of the button cell, the composite material was mixed uniformly with conductive carbon black Super P and binder polyvinylidene fluoride (PVDF) at a mass ratio of 8:2:1; the mass ratio of the composite material in the slurry was 80%.
[0066] Example 3 was carried out in accordance with Example 1, except that: in the preparation process of the button cell, the composite material was mixed uniformly with conductive carbon black Super P and binder polyvinylidene fluoride (PVDF) at a mass ratio of 6:2:1; the mass ratio of the composite material in the slurry was 60%.
[0067] Example 4
[0068] The procedure was carried out in accordance with Example 1, except that the annealing temperature in step (1) was 500°C.
[0069] Example 5
[0070] The process was carried out in accordance with Example 1, except that the annealing temperature in step (1) was 800°C.
[0071] Example 6
[0072] The procedure was carried out in accordance with Example 1, except that in step (2), the mass ratio of nitrogen-doped porous carbon to the mixture of tin tetrachloride pentahydrate and thioacetamide was 0.05:1.
[0073] Example 7
[0074] The procedure was carried out in accordance with Example 1, except that in step (2), the mass ratio of nitrogen-doped porous carbon to the mixture of tin tetrachloride pentahydrate and thioacetamide was 0.7:1.
[0075] Comparative Example 1
[0076] The modified diaphragm was prepared according to Example 1, except that the composite material was replaced with SnS2.
[0077] Comparative Example 2
[0078] The modified diaphragm was prepared according to Example 1, except that the composite material was replaced with N-AC.
[0079] The preparation steps of N-AC are as follows: refer to the preparation steps of the composite material in Example 1, except that steps (2) and (3) are not performed.
[0080] Comparative Example 3
[0081] The modified diaphragm was prepared according to Example 1, except that no composite material was added when preparing the slurry, and the mass ratio of Super P to the binder polyvinylidene fluoride (PVDF) in the slurry was 7:3.
[0082] Comparative Example 4
[0083] The procedure was carried out in accordance with Example 1, except that the annealing temperature in step (1) was 350°C.
[0084] Comparative Example 5
[0085] The procedure is carried out in accordance with Example 1, except that the heat treatment in step (3) is not performed.
[0086] Comparative Example 6
[0087] The procedure was carried out in accordance with Example 1, except that the hydrochloric acid washing step (1) was omitted, and the sodium hydroxide aqueous solution was used directly for activation.
[0088] The experimental results of each embodiment and comparative example are shown in Table 1.
[0089] Table 1
[0090]
[0091]
[0092] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A method for preparing a composite material for modified lithium-sulfur battery separators, characterized in that, The preparation method includes the following steps: (1) Preparation of nitrogen-doped porous carbon, including the following steps: The pulverized activated carbon powder is washed with hydrochloric acid and then dried to obtain washed activated carbon; the washed activated carbon is activated in an alkaline solution to obtain activated activated carbon; then the activated activated carbon is annealed under inert gas protection at a temperature of 500-800℃. The activated carbon powder is activated carbon without nitrogen, nitrogen-doped activated carbon, or activated carbon that carries nitrogen and can be formed into nitrogen-doped activated carbon after the annealing treatment. If the activated carbon powder is activated carbon that does not carry nitrogen, after the annealing treatment, the annealed activated carbon will be doped with nitrogen. (2) Tin disulfide is grown in situ on the nitrogen-doped porous carbon obtained in step (1) by hydrothermal reaction to obtain a nitrogen-doped porous carbon / tin disulfide substrate; (3) The nitrogen-doped porous carbon / tin disulfide substrate is heat-treated in an inert gas atmosphere at a temperature of 300-600°C and a time of 2-5 hours.
2. The preparation method according to claim 1, characterized in that, In step (1), the washing with hydrochloric acid involves mixing the activated carbon powder and hydrochloric acid at a mass ratio of 0.3-1:1, preferably for 1.5-6 hours; followed by washing with deionized water. Preferably, the concentration of HCl in the hydrochloric acid is 5-10 wt%.
3. The preparation method according to claim 1 or 2, characterized in that, The activation in step (1) involves soaking the washed activated carbon in an alkaline solution and then removing the solvent. Preferably, the alkaline solution is an aqueous solution of sodium hydroxide with a concentration of 0.05-0.3 mol / L; Preferably, the soaking time is 0.5-3 hours.
4. The preparation method according to any one of claims 1-3, characterized in that, In step (1), during the annealing process, the temperature is maintained at 500-800℃ for 1-8 hours, preferably 2-6 hours; And / or, when performing the annealing treatment, the temperature is increased to the annealing temperature at a heating rate of 0.5-10℃ / min; And / or, the annealing temperature is 600-700℃.
5. The preparation method according to any one of claims 1-4, characterized in that, The nitrogen-doped porous carbon obtained in step (1) satisfies the following condition: specific surface area of 350-2000 m². 2 g -1 Preferred depth: 1000-1500m 2 g -1 Preferably, the nitrogen-doped porous carbon obtained in step (1) is ground to a particle size of 0.5 μm-10 μm before being used in step (2).
6. The preparation method according to any one of claims 1-5, characterized in that, In step (1), the nitrogen doping includes the following operations: mixing the annealed activated carbon with a nitrogen-containing dopant and treating it at 500-850°C under inert gas protection, preferably holding it at 500-850°C for 1-5 hours; Preferably, the mass ratio of the activated carbon to the nitrogen-containing dopant is 1:0.5-10; Preferably, the nitrogen-containing dopant is one or more of melamine, urea, and ammonium dihydrogen phosphate.
7. The preparation method according to any one of claims 1-6, characterized in that, In the composite material obtained in step (3), the nitrogen doping amount is 2-5% atomic percentage.
8. The preparation method according to any one of claims 1-7, characterized in that, In step (2), the nitrogen-doped porous carbon is subjected to the hydrothermal reaction with a mixture of tin tetrachloride pentahydrate and thioacetamide.
9. The preparation method according to claim 8, characterized in that, The mass ratio of the nitrogen-doped porous carbon to the mixture of tin tetrachloride pentahydrate and thioacetamide is 0.05-1:1, preferably 0.1-0.5:1; Preferably, the mass ratio of tin tetrachloride pentahydrate to thioacetamide is 0.5-1.5:1; Preferably, the temperature of the hydrothermal reaction is 100-200℃, and the reaction time is preferably 10-20h.
10. The composite material prepared by the method according to any one of claims 1-9 is used in the separator of a lithium-sulfur battery.