A method for preparing a bimetallic sulfide heterojunction material

Abstract

The application is a preparation method of a bimetallic sulfide heterojunction material. The method comprises the following steps: (1) taking urea and cobalt chloride hexahydrate and dissolving them in deionized water to obtain a precursor material by heating reaction; then the precursor material is dissolved in deionized water with sodium sulfide nonahydrate to obtain Co9S8 powder by heating reaction; (2) adding Co9S8 into a mixed solution of an organic solvent and deionized water, then adding metal oxyacid salt and sulfur source in sequence, and obtaining the bimetallic sulfide heterojunction material by heating reaction. The lithium-sulfur battery assembled by the modified positive electrode of the bimetallic sulfide heterojunction material has an initial discharge specific capacity as high as 1426 mA h g ‑1 , and the average capacity attenuation of each cycle is only 0.008% after 2000 cycles under the condition of 4 C.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials, specifically relating to a method for preparing bimetallic sulfide heterojunction materials and their application in the field of lithium-sulfur batteries. Background Technology

[0002] With the ever-increasing demand for energy and the growing severity of environmental pollution, developing alternative green and clean energy storage systems to reduce the massive consumption of fossil fuels has become particularly important. Lithium-sulfur batteries, using elemental sulfur as the positive electrode and metallic lithium as the negative electrode, are considered a promising next-generation energy storage system due to their high theoretical specific capacity and energy density, low cost, and environmental friendliness. However, the charging and discharging process, involving multiple steps, phases, and electrons, generates a large amount of soluble polysulfides, which undergo a shuttle effect driven by the concentration gradient. This leads to side reactions between polysulfides and the lithium negative electrode, resulting in rapid capacity decay, reduced coulombic efficiency, and poor cycle stability in lithium-sulfur batteries. Therefore, modifying the positive electrode with a highly catalytically active sulfur support can significantly improve the reaction kinetics of polysulfide conversion, accelerate the liquid-solid conversion rate, and thus suppress the polysulfide shuttle effect, thereby improving the battery's rate performance and cycle stability.

[0003] Two-dimensional transition metal sulfides (TMDs) have shown promising application prospects in lithium-sulfur batteries due to their tunable electronic structure, strong catalytic activity, and excellent chemical stability. Wang et al. (Z. Cheng, Y. Chen, Y. Yang, L. Zhang, H. Pan, X. Fan, S. Xiang, and Z. Zhang, Metallic MoS2 nanoflowers decorated graphene nanosheet catalytically boosts the volumetric capacity and cycle life of lithium-sulfur batteries, Adv. Energy Mater. 2021, 11 (2003718.) reported a 1T-MoS2 nanoflower composite graphene nanomaterial with sulfur defects, and applied it as a cathode and separator system modifier in lithium-sulfur batteries. After 500 cycles, the capacity retention remained at 71.7%. Furthermore, at 4.27 mA cm⁻¹... -2 At high current density and 5.1 mg cm -2 Under ultra-high sulfur loading conditions, the battery can still exhibit 1360 mA h cm⁻¹ -3High volumetric capacity is a significant challenge for lithium-sulfur batteries. However, the electrochemical process of sulfur reduction involves not only multiple conversion reactions but also overcoming the energy barrier in the liquid-solid phase conversion between soluble long-chain polysulfides and insoluble short-chain polysulfides in the electrolyte. Therefore, single-component transition metal sulfides cannot accelerate all steps in the sulfur reduction process to the same degree, thus failing to completely reduce polysulfides to solid sulfides and causing a shuttle effect, hindering further improvement in the overall performance of lithium-sulfur batteries. Heterojunction engineering can effectively integrate the catalytic properties of different components, thereby synergistically regulating the complex polysulfide conversion process. Therefore, designing and synthesizing bimetallic sulfide heterojunction materials is crucial for effectively improving sulfur reduction kinetics, promoting complete solid sulfide deposition, suppressing the polysulfide shuttle effect, and enhancing the performance of lithium-sulfur batteries.

[0004] Currently, research on using bimetallic sulfide heterojunction materials as sulfur carriers to modify lithium-sulfur batteries is still relatively limited. Therefore, developing stable, simple to prepare, and low-cost bimetallic sulfide heterojunction materials for modifying lithium-sulfur battery cathodes is crucial for expanding the applications of lithium-sulfur batteries. Summary of the Invention

[0005] The purpose of this invention is to address the problems existing in the sulfur reduction process in lithium-sulfur batteries by providing a method for preparing bimetallic sulfide heterojunction materials and using them as sulfur carriers to modify cathodes for application in lithium-sulfur batteries. This method mainly uses Co9S8 as a precursor, first uniformly introducing metal oxyacid salts of molybdenum, tungsten, and vanadium, along with a sulfur source, into its dispersion, and then synthesizing bimetallic sulfide heterojunction materials through a hydrothermal secondary sulfidation reaction. The bimetallic sulfide heterojunction material obtained by this invention not only synergistically regulates the conversion of long-chain and short-chain reactions, but also the built-in electric field at the heterojunction interface accelerates the migration of polysulfide intermediates, achieving rapid deposition of solid sulfides and improving electrochemical performance. This solves the problem that single-component materials, due to limited catalytic centers, cannot gradually reduce polysulfides to achieve complete and uniform deposition, leading to polysulfide shuttle. The lithium-sulfur battery assembled with a cathode modified by the obtained bimetallic sulfide heterojunction material has an initial discharge specific capacity as high as 1426 mA hg. -1 Furthermore, after 2000 cycles under 4C conditions, the average capacity decay per cycle is only 0.008%.

[0006] The technical solution of this invention is as follows: A method for preparing a bimetallic sulfide heterojunction material, the method comprising the following steps: (1) Synthesis of Co9S8 Urea and cobalt chloride hexahydrate were dissolved in deionized water and stirred for 10-30 minutes. The resulting dispersion was then heated at 90-100 °C for 6-10 hours, allowed to cool naturally to room temperature, centrifuged, washed, and then dried under vacuum at 50-70 °C for 10-14 hours to obtain the precursor material. The prepared precursor material and sodium sulfide nonahydrate were then dissolved in deionized water and stirred for 10-30 minutes. The mixture was then heated at 150-180 °C for 6-10 hours, allowed to cool naturally to room temperature, centrifuged, washed, and then dried under vacuum to obtain Co9S8 powder. The mass ratio of urea to cobalt chloride hexahydrate is 1:2~4, and 0.2~0.5 g of urea is added to every 50 mL of deionized water; the mass ratio of precursor to sodium sulfide nonahydrate is 1:5~7, and 0.1~0.2 g of precursor is added to every 80 mL of deionized water. (2) Synthesis of bimetallic sulfide heterojunction materials The Co9S8 obtained in step (1) was added to a mixed solution of organic solvent and deionized water and sonicated for 10 to 30 minutes. Then, metal oxyacid salt and sulfur source were added in sequence, stirred for 10 to 30 minutes, and heated at 160 to 200 °C for 6 to 10 hours. After cooling naturally to room temperature, the mixture was centrifuged, washed, and vacuum dried to obtain a bimetallic sulfide heterojunction material. For every 0.05 g of Co9S8, add 10 to 20 mL of organic solvent and 0.05 to 0.15 g of metal oxyacid salt; the volume ratio of organic solvent to deionized water is 1:2 to 5. The mass ratio of the metal oxyacid salt to the sulfur source is 1:1 to 5; the metal oxyacid salt is sodium molybdate, sodium tungstate, or sodium vanadate. The centrifugation in steps (1) and (2) is performed at a speed of 4000-8000 for 3-6 minutes; the washing is performed by washing with deionized water and ethanol 3-5 times in sequence. The organic solvent mentioned in step (2) is formic acid, propionic acid, or acetic acid. The vacuum drying described in steps (1) and (2) is drying at 50-70 °C under vacuum for 10-14 hours.

[0007] The sulfur source mentioned in step (2) is thiourea, thioacetamide, or sodium thiosulfate; The bimetallic sulfide heterojunction material prepared by the method is used for the modification of the cathode of lithium-sulfur batteries and serves as the cathode of lithium-sulfur batteries.

[0008] The lithium-sulfur battery described above has a positive electrode made of a bimetallic sulfide heterojunction material-sulfur composite material; a negative electrode made of lithium sheet; a separator made of polypropylene; and an electrolyte containing a mixed solution of 1.0 M lithium bis(trifluoromethanesulfonate)imide; the solvent of the mixed solution is 1,3-dioxolane and dimethyl ether in a volume ratio of 1:1. The method for preparing the positive electrode includes the following steps: (1) Mix bimetallic sulfide heterojunction material with sulfur powder at a mass ratio of 1:3 to 4, add carbon disulfide, stir for 15 to 45 minutes, and after the carbon disulfide has completely volatilized, keep it at 155 to 160 °C for 8 to 12 hours to obtain bimetallic sulfide heterojunction material-sulfur composite material. In this process, 0.05 to 0.2 g of heterojunction is added for every 10 to 20 mL of carbon disulfide; (2) Grind the obtained bimetallic sulfide heterojunction material-sulfur composite material, conductive carbon black, and binder polyvinylidene fluoride (mass ratio 8:1:1) for 30-60 minutes, then add N-methylpyrrolidone dropwise and stir for 40-80 minutes. Coat the resulting slurry onto aluminum foil and dry it at 50-70 °C for 10-14 hours. Cut the foil to obtain a sulfur loading of approximately 1-1.5 mgcm³. -2 The positive electrode of a lithium-sulfur battery; In this process, 0.1 to 0.3 g of bimetallic sulfide heterojunction material-sulfur composite material is added to every 3 to 5 mL of N-methylpyrrolidone.

[0009] The essential features of this invention are: In bimetallic sulfide heterojunction materials prepared using Co9S8 as a precursor, the bimetallic centers can synergistically regulate the conversion between long-chain and short-chain reactions. Furthermore, when metal sulfides with different work functions form a heterojunction, electrons spontaneously transfer from the metal center with the lower work function to the metal center with the higher work function until the system reaches equilibrium. This creates a built-in electric field at the interface that accelerates the migration of polysulfide intermediates, enabling rapid deposition of solid sulfides and improving electrochemical performance.

[0010] The beneficial effects of this invention are as follows: (1) This invention provides a method for preparing bimetallic sulfide heterojunction materials, and the bimetallic sites provide an ideal platform for regulating the conversion of long-chain and short-chain reactions.

[0011] (2) The bimetallic sulfide heterojunction material prepared by this invention establishes a complete pathway for the electrochemical process of sulfur reduction. The built-in electric field between the bimetallic sulfides can effectively accelerate the rapid migration of polysulfide intermediates in different catalytic centers, realize the complete deposition of solid sulfides, and thus effectively suppress the shuttle effect.

[0012] (3) The lithium-sulfur battery assembled with the modified cathode material obtained by the bimetallic sulfide heterojunction material of the present invention exhibits 1426 mA hg at a 0.1 C rate. -1 The initial discharge specific capacity is high, and even after 2000 cycles at 4 C, the average capacity decay per cycle is only 0.008%, indicating that it can maintain good cycle stability under high current density and effectively improve the electrochemical performance of lithium-sulfur batteries. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the preparation of Co3S4@MoS2 material in Example 1.

[0014] Figure 2 The images show the ultraviolet photoelectron spectra of MoS2 and Co3S4 in Comparative Examples 1 and 2.

[0015] Figure 3 This is a schematic diagram of the electron flow of the Co3S4@MoS2 material before and after contact in Example 1.

[0016] Figure 4 The graph shows the rate performance of the Co3S4@MoS2 modified cathode in Example 1 and the Co3S4 modified cathode in Comparative Example 1.

[0017] Figure 5 This is a cyclic test diagram of the Co3S4@MoS2 modified cathode in Example 1 under high current density. Detailed Implementation

[0018] To further illustrate the method of the present invention, specific embodiments are described below with reference to the accompanying drawings. The following embodiments are merely specific preparation methods of the present invention and do not limit the scope of the invention.

[0019] Comparative Example 1: (1) Synthesis of MoS2 0.1 g sodium molybdate and 0.15 g thiourea were added to a mixture of 10 mL propionic acid and 20 mL deionized water. After stirring for 30 minutes, the mixture was heated at 180 °C for 8 hours. After naturally cooling to room temperature, the product was collected by centrifugation at 6000 rpm for 3 minutes. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain MoS2 material. Comparative Example 2: (1) Synthesis of Co9S8 0.3 g of urea and 1.19 g of cobalt chloride hexahydrate were dissolved in 50 mL of deionized water and stirred for 30 minutes. The resulting dispersion was then heated at 95 °C for 8 hours, allowed to cool naturally to room temperature, and centrifuged at 4000 rpm for 3 minutes to collect the product. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain the precursor material. Then, 0.1 g of the prepared precursor and 0.6 g of sodium sulfide nonahydrate were dissolved in 80 mL of deionized water and stirred for 30 minutes. The mixture was then heated at 160 °C for 8 hours, allowed to cool naturally to room temperature, and centrifuged at 8000 rpm for 5 minutes to collect the product. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain the Co9S8 material. (2) Synthesis of Co3S4 0.05 g Co9S8 was added to a mixture of 10 mL propionic acid and 20 mL deionized water and sonicated for 20 minutes. Then, 0.15 g thiourea was added to the solution and stirred for 30 minutes. The mixture was then heated at 180 °C for 8 hours and allowed to cool naturally to room temperature. The product was collected after centrifugation at 6000 rpm for 3 minutes. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain Co3S4 material. (3) Co3S4-S 0.15 g of sulfur powder and 0.05 g of Co3S4 were ground and mixed, 15 mL of carbon disulfide was added, and the mixture was stirred for 30 minutes. After the carbon disulfide was completely volatilized, the mixture was kept at 155 °C for 12 hours to obtain the Co3S4-S composite material.

[0020] Example 1: (1) Synthesis of Co9S8 0.3 g of urea and 1.19 g of cobalt chloride hexahydrate were dissolved in 50 mL of deionized water and stirred for 30 minutes. The resulting dispersion was then heated at 95 °C for 8 hours, allowed to cool naturally to room temperature, and centrifuged at 4000 rpm for 3 minutes to collect the product. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain the precursor material. Then, 0.1 g of the prepared precursor and 0.6 g of sodium sulfide nonahydrate were dissolved in 80 mL of deionized water and stirred for 30 minutes. The mixture was then heated at 160 °C for 8 hours, allowed to cool naturally to room temperature, and centrifuged at 8000 rpm for 5 minutes to collect the product. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain the Co9S8 material. (2) Synthesis of Co3S4@MoS2 0.05 g Co9S8 was added to a mixture of 10 mL propionic acid and 20 mL deionized water and sonicated for 20 minutes. Then, 0.1 g sodium molybdate and 0.15 g thiourea were added to the solution in sequence and stirred for 30 minutes. The mixture was then heated at 180 °C for 8 hours and allowed to cool naturally to room temperature. The product was collected after centrifugation at 6000 rpm for 3 minutes. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain Co3S4@MoS2 material. Figure 1 The diagram below shows the preparation of the Co3S4@MoS2 bimetallic sulfide heterojunction material in Example 1 of this invention.

[0021] Figure 2 The ultraviolet photoelectron spectra of MoS2 and Co3S4 in Comparative Examples 1 and 2 of this invention are shown in the figure. As shown, the work function of MoS2 is 6.13 eV, while that of Co3S4 is 5.27. Therefore, when MoS2 and Co3S4 are directly contacted to synthesize Co3S4@MoS2 material, electrons will spontaneously transfer from Co3S4 to MoS2 until the system reaches equilibrium; indicating that the Co3S4@MoS2 material obtained by this invention is a Mott-Schottky heterojunction material.

[0022] Figure 3 The figure shows a schematic diagram of the electron flow of the Co3S4@MoS2 material before and after contact in Embodiment 1 of the present invention. As shown in the figure, in the Co3S4@MoS2 material, the electron band of Co3S4 bends upward at the interface and forms an internal electric field from Co3S4 to MoS2 at its heterojunction interface, thereby accelerating the migration of polysulfide intermediates.

[0023] Example 2: Step (1) is the same as in Example 1; (2) Synthesis of Co3S4@WS2 0.05 g Co9S8 was added to a mixture of 10 mL formic acid and 20 mL deionized water and sonicated for 20 minutes. Then, 0.13 g sodium tungstate and 0.15 g thioacetamide were added to the solution and stirred for 30 minutes. The mixture was then heated at 180 °C for 8 hours and allowed to cool naturally to room temperature. The product was collected after centrifugation at 6000 rpm for 3 minutes. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain Co3S4@WS2 material. Example 3: Step (1) is the same as in Example 1; (2) Synthesis of Co3S4@VS2 0.05 g Co9S8 was added to a mixed solution of 10 mL acetic acid and 20 mL deionized water and sonicated for 20 minutes. Then, 0.07 g sodium vanadate and 0.32 g sodium thiosulfate were added to the solution in sequence and stirred for 30 minutes. The mixed solution was then heated at 180 °C for 8 hours and allowed to cool naturally to room temperature. The product was collected after centrifugation at 6000 rpm for 3 minutes. The product was then washed three times with deionized water and ethanol, respectively, and vacuum dried at 60 °C for 12 hours to obtain Co3S4@VS2 material. Example 4: The Co3S4@MoS2 prepared in Example 1 was used as a cathode modification material in lithium-sulfur batteries.

[0024] (1) Preparation of Co3S4@MoS2-S cathode: 0.15 g of sulfur powder and 0.05 g of Co3S4@MoS2 were ground and mixed, and 15 mL of carbon disulfide was added. The mixture was stirred for 30 minutes, and after the carbon disulfide had completely volatilized, it was kept at 155 °C for 12 hours to obtain the Co3S4@MoS2-S composite material. 0.16 mg of the Co3S4@MoS2-S composite material, 0.02 g of conductive carbon black, and 0.02 g of polyvinylidene fluoride binder were ground for 45 minutes to ensure thorough mixing. 3 mL of N-methylpyrrolidone was added dropwise, and the mixture was stirred for 60 minutes. The resulting slurry was coated onto aluminum foil and dried at 60 °C for 12 hours. The resulting piece, with a diameter of 14 mm and a sulfur loading of approximately 1.2 mg cm, was then cut. -2 Positive electrode for a Co3S4@MoS2-S lithium-sulfur battery.

[0025] (2) Battery assembly: The assembled lithium-sulfur battery has a positive electrode made of Co3S4@MoS2-S composite material; a negative electrode made of lithium sheet; a polypropylene separator; and an electrolyte solution containing 1.0 M lithium bis(trifluoromethanesulfonate)imide, 1,3-dioxolane, and dimethyl ether (volume ratio 1:1). A button-type lithium-sulfur battery was then assembled in an argon-filled glove box. The battery's rate performance and cycle test results were obtained using a Newway battery testing cabinet BST-5 V 20 mA. (See attached graphs for battery rate performance and cycle test results.) Figure 2 and Figure 3 It achieves excellent initial discharge specific capacity at a current density of 0.1C and still exhibits excellent cycle stability at a high current density of 4C.

[0026] Example 5: The other steps are the same as in Example 4, except that Co3S4-S composite material is used as the positive electrode to assemble the battery.

[0027] Figure 4In this invention, both the lithium-sulfur battery assembled with the Co3S4@MoS2-S cathode and the battery assembled with the Co3S4-S cathode in Embodiment 1 were tested using a Xinwei battery test cabinet BST-5 V 20 mA. The lithium-sulfur battery assembled with the Co3S4@MoS2-S cathode achieved 1426 mA hg at 0.1 C. -1 Initial discharge specific capacity, and still achieves 570 mA hg at 6 C. -1 The high specific capacity. In contrast, the initial discharge specific capacity of the Co3S4-S cathode in Comparative Example 1 is only 1200 mA hg under 0.1 C conditions. -1 Moreover, it only showed 351 mA hg at 6 C. -1 The specific capacity indicates that the cathode modification material of this invention effectively promotes the catalytic conversion of polysulfides and inhibits the shuttle effect of polysulfides, thereby improving the performance of lithium-sulfur batteries.

[0028] Figure 5 In Example 1 of this invention, the lithium-sulfur battery assembled with the Co3S4@MoS2-S cathode exhibited an average capacity decay of only 0.008% per cycle after 2000 cycles at a high current density of 4 C. This demonstrates that the cathode modification material of this invention has a significant effect on improving the cycle stability of lithium-sulfur batteries during fast charging and discharging, providing effective guidance for the next step of commercial application of lithium-sulfur batteries.

[0029] Matters not covered in this invention are common knowledge.

Claims

1. A method for preparing a bimetallic sulfide heterojunction material, characterized in that, The method includes the following steps: (1) Synthesis of Co9S8 Urea and cobalt chloride hexahydrate were dissolved in deionized water and stirred for 10-30 minutes. The resulting dispersion was then heated at 90-100 °C for 6-10 hours, allowed to cool naturally to room temperature, centrifuged, washed, and then dried under vacuum at 50-70 °C for 10-14 hours to obtain the precursor material. The prepared precursor material and sodium sulfide nonahydrate were then dissolved in deionized water and stirred for 10-30 minutes. The mixture was then heated at 150-180 °C for 6-10 hours, allowed to cool naturally to room temperature, centrifuged, washed, and then dried under vacuum to obtain Co9S8 powder. The mass ratio of urea to cobalt chloride hexahydrate is 1:2~4, and 0.2~0.5 g of urea is added to every 50 mL of deionized water; the mass ratio of precursor to sodium sulfide nonahydrate is 1:5~7, and 0.1~0.2 g of precursor is added to every 80 mL of deionized water. (2) Synthesis of bimetallic sulfide heterojunction materials The Co9S8 obtained in step (1) was added to a mixed solution of organic solvent and deionized water and sonicated for 10 to 30 minutes. Then, metal oxyacid salt and sulfur source were added in sequence, stirred for 10 to 30 minutes, and heated at 160 to 200 °C for 6 to 10 hours. After naturally cooling to room temperature, the mixture was centrifuged, washed, and vacuum dried to obtain a bimetallic sulfide heterojunction material. For every 0.05 g of Co9S8, add 10-20 mL of organic solvent and 0.05-0.15 g of metal oxyacid salt; the volume ratio of organic solvent to deionized water is 1:2-5. The mass ratio of the metal oxyacid salt to the sulfur source is 1:1 to 5; the metal oxyacid salt is sodium molybdate, sodium tungstate, or sodium vanadate.

2. The method for preparing the bimetallic sulfide heterojunction material as described in claim 1, characterized in that, The centrifugation in steps (1) and (2) is performed at a speed of 4000-8000 for 3-6 minutes; the washing is performed by washing with deionized water and ethanol 3-5 times respectively; the vacuum drying in steps (1) and (2) is performed at 50-70 ℃ under vacuum for 10-14 hours.

3. The method for preparing the bimetallic sulfide heterojunction material as described in claim 1, characterized in that, The organic solvent mentioned in step (2) is formic acid, propionic acid or acetic acid.

4. The method for preparing the bimetallic sulfide heterojunction material as described in claim 1, characterized in that, The sulfur source mentioned in step (2) is thiourea, thioacetamide or sodium thiosulfate.

5. The application of the bimetallic sulfide heterojunction material prepared by the method described in claim 1, characterized in that, Used for cathode modification in lithium-sulfur batteries, and as the cathode of lithium-sulfur batteries.

6. The application as described in claim 5, characterized in that, The lithium-sulfur battery described herein has a positive electrode consisting of a bimetallic sulfide heterojunction material-sulfur composite material and a negative electrode consisting of a lithium sheet. The diaphragm is a polypropylene diaphragm; the electrolyte is a mixed solution containing 1.0 M lithium bis(trifluoromethanesulfonate)imide; the solvent of the mixed solution is 1,3-dioxolane and dimethyl ether in a volume ratio of 1:

1. The method for preparing the positive electrode includes the following steps: (1) Mix bimetallic sulfide heterojunction material with sulfur powder at a mass ratio of 1:3 to 4, add carbon disulfide, stir for 15 to 45 minutes, and after the carbon disulfide has completely volatilized, keep it at 155 to 160 °C for 8 to 12 hours to obtain bimetallic sulfide heterojunction material-sulfur composite material. In this process, 0.05 to 0.2 g of heterojunction is added for every 10 to 20 mL of carbon disulfide; (2) Grind the obtained bimetallic sulfide heterojunction material-sulfur composite material, conductive carbon black, and binder polyvinylidene fluoride (mass ratio 8:1:1) for 30-60 minutes, then add N-methylpyrrolidone dropwise and stir for 40-80 minutes. Coat the resulting slurry onto aluminum foil and dry it at 50-70 °C for 10-14 hours. Cut the foil to obtain a sulfur loading of approximately 1-1.5 mgcm³. -2 The positive electrode of a lithium-sulfur battery; In this process, 0.1 to 0.3 g of bimetallic sulfide heterojunction material-sulfur composite material is added to every 3 to 5 mL of N-methylpyrrolidone.

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