Lithium-sulfur battery cathode with intercalated bilayer structure and method of making same

Abstract

The present application relates to a kind of mutual embedding type double-layer structure lithium-sulfur battery anode: on the surface of sulfur anode from top to bottom is the catalyst layer consisting of nanoscale catalyst and the mixed layer consisting of catalyst, binder, conductive agent and sulfur carbon composite;Preparation method: by adjusting the viscosity of coating slurry, the particle size ratio of catalyst and active material and coating drying rate, use buoyancy competition mechanism to form lithium-sulfur battery anode with mutual embedding type double-layer structure in one step.Catalyst layer uses physical blocking effect and chemical adsorption effect to alleviate or prevent the capacity loss caused by "shuttle effect" of polysulfide, improve the capacity retention rate and coulomb efficiency of lithium-sulfur battery;Catalyst in mixed layer improves the utilization rate and conversion efficiency of active sulfur by chemical adsorption effect and catalytic conversion mechanism, thereby improving the specific capacity and rate performance of lithium-sulfur battery.This method is simple and easy to operate, suitable for industrial production.

Description

Technical Field

[0001] This invention relates to a lithium-sulfur battery cathode with an intercalated bilayer structure that can improve the specific capacity, coulombic efficiency, and cycle life of lithium-sulfur batteries. The invention also relates to a method for preparing the aforementioned lithium-sulfur battery cathode, applicable to new energy fields such as lithium-sulfur batteries. Background Technology

[0002] With the rapid development of the new energy vehicle industry, the increasing number of electric vehicles and the extreme mismatch between the corresponding charging infrastructure have led to a growing demand for high-energy-density batteries. The energy density of traditional lithium-ion battery cathode materials is already close to its theoretical value and will be unable to meet the requirements of future market applications. In particular, with the proposed ultimate goals of "carbon peaking" and "carbon neutrality," the new energy vehicle market will expand rapidly, making the search for new battery systems with higher energy density imperative. Sulfur, due to its abundant reserves, low price, environmental friendliness, ease of recycling, and high theoretical specific capacity (1675 mAh / g) and theoretical specific energy (2600 Wh / kg), is considered one of the most promising battery systems to achieve an energy density of over 500 Wh / kg. However, the poor conductivity of sulfur and its tendency to produce a "shuttle effect" during charging and discharging have hindered the further application and development of lithium-sulfur batteries. Currently, many research institutions and companies both domestically and internationally are dedicated to the research and development of lithium-sulfur batteries. Common methods include improving sulfur utilization through conductive materials; using porous materials to immobilize and adsorb polysulfides; utilizing the coordination of chemical bonds with polysulfides; and employing the physicochemical barrier effects of coatings and functional membranes to reduce the "shuttle effect" in lithium-sulfur batteries, thereby improving their discharge specific capacity and cycle life. While these methods have yielded promising results, their complexity or high cost make large-scale production difficult and hinder industrial application.

[0003] Therefore, it is particularly important to develop a lithium-sulfur battery cathode that is simple to operate, highly feasible, and has excellent performance, as well as its preparation method. The large-scale preparation of lithium-sulfur battery cathodes is of great significance to the industrial development of lithium-sulfur batteries and even to promoting the industrialization of new energy vehicles. Summary of the Invention

[0004] The first technical problem to be solved by this invention is to provide an intercalated double-layer structure lithium-sulfur battery cathode.

[0005] The second technical problem to be solved by the present invention is to provide a method for preparing the above-mentioned intercalated bilayer structure lithium-sulfur battery cathode.

[0006] The intercalated bilayer lithium-sulfur battery cathode prepared by the method of the present invention is simple in process, convenient in operation, low in cost, has excellent performance and is easy to industrialize.

[0007] To solve the first technical problem mentioned above, the technical solution adopted by the present invention is as follows:

[0008] A lithium-sulfur battery cathode with an intercalated double-layer structure is characterized by having a catalyst layer composed of nanoscale catalysts and a mixed layer composed of catalysts, binders, conductive agents and sulfur-carbon composites covering the surface of the sulfur cathode from the outside to the inside.

[0009] The catalyst layer has a thickness of 0.1 micrometers to 2 micrometers, and the catalyst is one of cobalt sulfide, molybdenum sulfide, nickel sulfide or selenium sulfide. Its particle size ratio to the particle size of the sulfur-carbon composite is 1:100 to 1:1000, and its mass percentage in the sulfur cathode (excluding the substrate) is 2% to 5%.

[0010] The catalyst layer on the surface of the sulfur cathode uses physical barrier and chemical adsorption effects to alleviate or block the capacity loss caused by the "shuttle effect" of polysulfides, thereby improving the capacity retention rate and coulombic efficiency of the battery. The catalyst dispersed in the mixed layer improves the utilization rate and conversion efficiency of active sulfur through chemical adsorption and catalytic conversion mechanisms, thereby improving the discharge specific capacity and rate performance of lithium-sulfur batteries.

[0011] To solve the second technical problem mentioned above, the technical solution adopted by the present invention is as follows:

[0012] A method for preparing the above-mentioned lithium-sulfur battery cathode is characterized in that: the preparation of an intercalated bilayer sulfur cathode is achieved by using a conventional coating process and a buoyancy competition mechanism.

[0013] Preferably, the preparation method specifically includes the following steps:

[0014] Step 1. Put the conductive carbon material and elemental sulfur into a ball mill jar for physical mixing in a certain mass ratio. After ball milling, pour the mixture into a hydrothermal reactor and place it in a constant temperature drying oven at 160°C to 180°C for 10 to 15 hours. After natural cooling, the sulfur-carbon composite can be obtained.

[0015] Step 2. Add the catalyst and binder to the water solvent in a certain proportion and stir to mix. After stirring evenly, add the conductive agent and sulfur-carbon complex in sequence and stir thoroughly. Set aside for use. The viscosity of the slurry is controlled by adjusting the content of the water solvent.

[0016] Step 3. Using the prepared slurry, a coating machine is used to coat it onto the surface of the positive electrode foil, and then vacuum drying is performed to finally obtain the lithium-sulfur battery positive electrode; the thickness of the catalyst layer and the distribution of the catalyst inside the mixed layer are achieved by adjusting the drying rate during the coating process.

[0017] The sulfur-carbon composite is a composite of elemental sulfur and conductive carbon material, with a sulfur content of 60% to 70%, and the sulfur-carbon composite accounts for 75% to 90% of the mass of the sulfur cathode (excluding the substrate).

[0018] The conductive carbon material is one of acetylene black, conductive carbon black, Ketjen black, carbon nanotubes, carbon nanofibers, graphene oxide, and graphene.

[0019] The binder is one or two of lithium carboxymethyl cellulose, carboxymethyl cellulose, sodium alginate, polyacrylic acid, lithium polyacrylate, chitosan, glucose and polyacrylate, and the total mass of the binder accounts for 4% to 10% of the mass of the sulfur cathode (excluding the substrate).

[0020] The conductive agent is one of carbon nanotubes, carbon nanofibers, graphene oxide, and graphene, and its mass percentage in the sulfur cathode (excluding the substrate) is 3% to 10%.

[0021] The principle of this invention: Using a conventional coating process, a buoyancy competition mechanism is employed to control the ascent rate of particles with significantly different particle sizes by adjusting the slurry viscosity and drying rate. Ultimately, the smaller particles are suspended on the surface of the sulfur cathode, while excess small particles mix with larger particles in the lower layer, forming a lithium-sulfur battery cathode with an interlocking double-layer structure. This application utilizes nano-catalysts with a particle size ratio of 1:100 to 1:1000, sulfur-carbon composites, and large-sized one-dimensional or two-dimensional conductive agents. By adjusting the slurry viscosity and the drying rate during coating, the smallest catalyst particles are allowed to accumulate most quickly and abundantly on the surface of the sulfur cathode through buoyancy, forming a sulfur cathode with an interlocking structure consisting of a catalyst layer and a mixed layer composed of catalyst, conductive agent, sulfur-carbon composite, and binder. The surface catalyst layer utilizes physical barriers and chemisorption effects to mitigate capacity loss caused by the "shuttle effect" of polysulfides, thereby improving the battery's capacity retention and coulombic efficiency. The catalyst dispersed in the mixed layer improves the utilization and conversion efficiency of active sulfur through chemisorption and catalytic conversion mechanisms, thus enhancing the discharge specific capacity and rate performance of the lithium-sulfur battery. Furthermore, the preparation method of the described intercalated bilayer lithium-sulfur battery cathode is simple and easy for industrial production, promoting the industrial application of high-energy-density lithium batteries.

[0022] Compared with the prior art, the advantages of the present invention are: (1) The preparation method is simple. By combining a simple coating process with a buoyancy competition mechanism, the desired intercalated double-layer lithium-sulfur battery cathode can be obtained in one step; (2) The effect is significant. Through the synergistic effect of physical barrier, chemical adsorption and catalytic conversion of the catalyst layer, the specific capacity, coulombic efficiency, rate performance and cycle life of the lithium-sulfur battery can be effectively improved; (3) The operation is convenient and the cost is low, making it easy to industrialize. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the positive electrode structure of the lithium-sulfur battery of the present invention;

[0024] Figure 2 The graph shows the cycle performance of the pouch cell prepared by the sulfur cathode without the buoyancy competition mechanism in Comparative Example 1 under a 0.2C rate condition.

[0025] Figure 3 This is a graph showing the cycle performance of a pouch cell prepared using a sulfur cathode coated with a buoyancy competition mechanism in Example 1 under a 0.2C rate condition.

[0026] The reference numerals in the figure refer to: 1-catalyst layer; 2-mixture layer; 3-aluminum foil. Detailed Implementation

[0027] The present invention will now be described in detail through exemplary embodiments.

[0028] Figure 1 The diagram shows the structure of a lithium-sulfur battery cathode with an intercalated double-layer structure according to the present invention. The surface of the sulfur cathode is covered from the outside to the inside with a catalyst layer composed of nano-scale catalysts and a mixed layer composed of catalysts, binders, conductive agents and sulfur-carbon composites. The thickness of the catalyst layer ranges from 0.1 micrometers to 2 micrometers, the particle size ratio of the catalyst to the sulfur-carbon composite is 1:100 to 1:1000, and the mass percentage of the catalyst in the sulfur cathode (excluding the substrate) is 2% to 5%.

[0029] The above-mentioned method for preparing sulfur cathode combines conventional coating processes with a buoyancy competition mechanism, and specifically includes the following steps:

[0030] Step 1. Put the conductive carbon material and elemental sulfur into a ball mill jar for physical mixing in a certain mass ratio. After ball milling, pour the mixture into a hydrothermal reactor and place it in a constant temperature drying oven at 160°C to 180°C for 10 to 15 hours. After natural cooling, the sulfur-carbon composite can be obtained.

[0031] Step 2. Add the catalyst and binder to the water-based solvent in a certain proportion and stir until homogeneous. Then, add the conductive agent and sulfur-carbon composite in sequence and stir thoroughly until homogeneous. Set aside for use. The viscosity of the slurry is controlled by adjusting the content of the water-based solvent.

[0032] Step 3. Using the prepared slurry, coat it onto the surface of the positive electrode foil using a coating machine, and then dry it under vacuum to obtain the final lithium-sulfur battery positive electrode. The thickness of the catalyst layer and the distribution of the catalyst within the mixed layer are controlled by adjusting the drying rate during the coating process.

[0033] Examples of the preparation method are as follows.

[0034] Example 1

[0035] Step 1. Put 350g of activated carbon and 650g of elemental sulfur into a ball mill jar, and then ball mill at a speed of 600 rpm for 2 hours. After that, pour it into a hydrothermal reactor, place it in a constant temperature drying oven at 180 degrees Celsius, and let it stand for 15 hours. Then let it cool naturally to room temperature to obtain the carbon-sulfur complex.

[0036] Step 2. Add 40g of polyacrylic acid to 2160g of high-purity water and stir. After stirring for 6 hours, add 20g of molybdenum sulfide, 40g of carbon nanotubes and 900g of sulfur-carbon composite to the polyacrylic acid aqueous solution in sequence, with an interval of 4 hours between each addition. After adding the sulfur-carbon composite, add another 540g of high-purity water. Continue stirring the slurry under vacuum for 4 hours to obtain a sulfur cathode slurry with a viscosity of 2050mPa.s. The particle size ratio of molybdenum sulfide to carbon-sulfur composite is 1:100. The self-rotation speed of the slurry mixer is 2000 rpm and the revolution speed is 40 rpm.

[0037] Step 3. Pour the prepared slurry into a coating tank and coat it onto the surface of the positive electrode foil using a transfer coating machine. After coating, place the electrode material in a vacuum drying oven to remove trace amounts of water, thus completing the preparation of the sulfur positive electrode. The drying rate of the coating is 1.44 kg / hm. 2 The temperature of the vacuum drying oven is 60 degrees Celsius, the vacuum drying time is 24 hours, and the thickness of the catalyst layer is about 0.2 micrometers.

[0038] Preparation of the soft-pack battery: Commercial lithium foil was used as the negative electrode; a commercial lithium-sulfur electrolyte was used, the lithium salt was lithium bis(trifluoromethanesulfonyl)imide with a concentration of 1 mol / L, the solvent was ethylene glycol dimethyl ether and 1,3-dioxolane with a volume ratio of 1:1, and the additive was lithium nitrate with a concentration of 0.1 mol / L; a commercial Celgard battery separator (PE) was used, the sulfur positive electrode had an electrode size of 8 cm x 4 cm, and the sulfur content of the electrode was 238 mg.

[0039] The activation rate of the soft-pack battery is 0.1C / 0.1C (1C = 1600mAh / g), the charge / discharge rate of the battery cycle is 0.2C / 0.2C, and the test voltage range is 1.6V-2.6V.

[0040] Comparative Example 1

[0041] A pouch cell was prepared using a sulfur cathode that was not prepared with a buoyancy competition mechanism, the same lithium anode, electrolyte, and separator as in Example 1, and the test parameters were exactly the same as in Example 1.

[0042] Example 2

[0043] The only difference between this embodiment and Embodiment 1 is that:

[0044] Step 2. Add 40g of polyacrylic acid to 2400g of high-purity water and stir for 6 hours. Then, add 30g of molybdenum sulfide, 40g of carbon nanotubes, and 890g of sulfur-carbon composite to the polyacrylic acid aqueous solution in sequence. After adding the sulfur-carbon composite, add another 600g of high-purity water. Stir the slurry under vacuum for another 4 hours to obtain a sulfur cathode slurry with a viscosity of 2130 mPa·s. The particle size ratio of molybdenum sulfide to carbon-sulfur composite is 1:210.

[0045] Step 3. The thickness of the catalyst layer is approximately 0.4 micrometers.

[0046] Example 3

[0047] The only difference between this embodiment and Embodiment 1 is that:

[0048] Step 2. Add 50g of polyacrylic acid to 2400g of high-purity water and stir for 6 hours. Then, add 30g of molybdenum sulfide, 45g of carbon nanotubes, and 875g of sulfur-carbon composite to the polyacrylic acid aqueous solution in sequence, with an interval of 4 hours between each addition. After adding the sulfur-carbon composite, add another 600g of high-purity water. Stir the slurry under vacuum for another 4 hours to obtain a sulfur cathode slurry with a viscosity of 2250mPa·s. The particle size ratio of molybdenum sulfide to carbon-sulfur composite is 1:350.

[0049] Step 3. The drying rate of the coating is 1.47 kg / hm. 2 The catalyst layer is approximately 0.5 micrometers thick.

[0050] Example 4

[0051] The only difference between this embodiment and Embodiment 1 is that:

[0052] Step 2. Add 60g of polyacrylic acid to 2400g of high-purity water and stir. After stirring for 6 hours, add 30g of molybdenum sulfide, 50g of carbon nanotubes and 860g of sulfur-carbon composite to the polyacrylic acid aqueous solution in sequence, with an interval of 4 hours between each addition. After adding the sulfur-carbon composite, add another 600g of high-purity water. Stir the slurry under vacuum for another 4 hours to obtain a sulfur cathode slurry with a viscosity of 2380mPa.s. The particle size ratio of molybdenum sulfide to carbon-sulfur composite is 1:400.

[0053] Step 3. The coating drying rate is 1.52 kg / hm. 2 The thickness of the catalyst layer is approximately 1.0 micrometers.

[0054] Example 5

[0055] The only difference between this embodiment and Embodiment 1 is that:

[0056] Step 1. Put 400g of activated carbon and 600g of elemental sulfur into a ball mill jar.

[0057] Step 2. Add 40g of sodium alginate to 2400g of high-purity water and stir. After stirring for 6 hours, add 30g of molybdenum sulfide, 40g of carbon nanofibers and 890g of sulfur-carbon composite to the sodium alginate aqueous solution in sequence, with an interval of 4 hours between each addition. After adding the sulfur-carbon composite, add another 600g of high-purity water. Stir the slurry under vacuum for another 4 hours to obtain a sulfur cathode slurry with a viscosity of 2160mPa.s. The particle size ratio of molybdenum sulfide to carbon-sulfur composite is 1:500.

[0058] Step 3. The drying rate of the coating is 1.68 kg / hm. 2 The thickness of the catalyst layer is approximately 1.3 micrometers.

[0059] Example 6

[0060] Step 1. Put 400g of Ketjen black and 600g of elemental sulfur into a ball mill jar.

[0061] Step 2. Add 100g of polyacrylic acid to 3200g of high-purity water and stir. After stirring for 6 hours, add 50g of molybdenum sulfide, 50g of carbon nanofibers and 800g of sulfur-carbon composite to the polyacrylic acid aqueous solution in sequence, with an interval of 4 hours between each addition. After adding the sulfur-carbon composite, add another 800g of high-purity water. Stir the slurry under vacuum for another 4 hours to obtain a sulfur cathode slurry with a viscosity of 2000mPa.s. The particle size ratio of molybdenum sulfide to carbon-sulfur composite is 1:1000.

[0062] Step 3. The drying rate of the coating is 1.71 kg / hm. 2The thickness of the catalyst layer is approximately 2.0 micrometers.

[0063] Example 7

[0064] Step 1. Put 300g of Ketjen black and 700g of elemental sulfur into a ball mill jar.

[0065] Step 2. Add 50g of polyacrylic acid to 2836g of high-purity water and stir. After stirring for 6 hours, add 40g of nickel sulfide, 40g of carbon nanofibers and 870g of sulfur-carbon composite to the polyacrylic acid aqueous solution in sequence, with an interval of 4 hours between each addition. After adding the sulfur-carbon composite, add another 709g of high-purity water. Stir the slurry under vacuum for another 4 hours to obtain a sulfur cathode slurry with a viscosity of 1910mPa.s. The particle size ratio of molybdenum sulfide to carbon-sulfur composite is 1:300.

[0066] Step 3. The drying rate of the coating is 1.62 kg / hm. 2 The thickness of the catalyst layer is approximately 1.4 micrometers.

[0067] Table 1 Examples 1-7 and Comparative Example 1

[0068] Initial capacity (0.2C) Capacity retention (40 weeks) Coulomb efficiency Example 1 233mAh 96.7％ 97.4％ Example 2 230mAh 97.9％ 98.0％ Example 3 245mAh 98.3％ 98.6％ Example 4 252mAh 98.5％ 98.7％ Example 5 246mAh 99.1％ 98.8％ Example 6 267mAh 99.8％ 99.1％ Example 7 259mAh 98.6％ 98.3％ Comparative Example 1 268mAh 79.9％ 95.6％

[0069] As shown in Table 1, from the results of Examples 1 to 7 and Comparative Example 1, it can be seen that Comparative Example 1 (e.g.

[0070] Figure 2 (As shown) Activated at a rate of 0.1C, the first discharge capacity was 304mAh, which is converted to specific capacitance.

[0071] The capacity is as high as 1277mAh; Example 1 (e.g.) Figure 3(As shown) Activated at 0.1C, the first-cycle discharge capacity was 301mAh, equivalent to a specific capacity of 1265mAh. Comparative Example 1, at a discharge rate of 0.2C, had a first-cycle discharge specific capacity of 268mAh, which is 1-38mAh higher than that of Examples 1-7 at 0.2C. This indicates that Comparative Example 1 did not utilize a buoyancy competition mechanism, resulting in a relatively uniform distribution of the catalyst throughout the sulfur cathode. The catalytic conversion and chemisorption effects improved the overall utilization rate of active sulfur, leading to a relatively high discharge capacity and specific capacity. Comparative Example 1 maintained a capacity retention of 79.9% after 40 cycles at 0.2C, which is 16.8%-19.9% ​​lower than that of Examples 1-7. The coulombic efficiency of Comparative Example 1 after 40 cycles at 0.2C was 95.6%, which is 1.8%-3.5% lower than that of Examples 1-7. It is evident that the sulfur cathode, employing a buoyancy competition mechanism, forms a catalyst layer on the electrode surface. This layer effectively mitigates the "shuttle effect" of polysulfides by utilizing physical barriers and chemical adsorption effects, thereby improving the battery's capacity retention and coulombic efficiency. The catalyst dispersed within the mixed layer can further enhance the utilization rate of active sulfur through catalytic conversion and chemical adsorption effects, thereby increasing the battery's specific capacity and rate performance. The effect becomes increasingly pronounced with increasing cycle count.

[0072] By comparing the performance of the examples and comparative soft-pack batteries, it can be seen that by introducing a buoyancy competition mechanism to prepare a sulfur cathode with an intercalated bilayer structure based on the traditional coating process, the catalyst layer can alleviate the "shuttle effect" of polysulfides through physical barrier and chemical adsorption, thereby improving the battery's capacity retention and coulombic efficiency. The catalyst mixed inside the sulfur cathode improves the utilization rate of active sulfur through chemical adsorption and catalytic conversion mechanisms, thereby increasing the battery's specific capacity and rate performance. Through the synergistic effect of physical barrier, chemical adsorption, and catalytic conversion of the catalyst, the specific capacity, coulombic efficiency, rate performance, and cycle life of lithium-sulfur batteries can be effectively improved.

Claims

1. A lithium-sulfur battery cathode having an intercalation bilayer structure, characterized by: To cover the surface of the sulfur cathode with a catalyst layer composed of nanoscale catalysts and a mixed layer composed of catalysts, conductive agents, sulfur-carbon composites, and binders from the surface to the inside; By using nanoscale catalysts and sulfur-carbon composites with a particle size ratio of 1:100-1:1000 and large-size one-dimensional or two-dimensional conductive agents, and by adjusting the viscosity of the slurry and the drying rate during coating, the smallest catalysts are gathered in the surface layer of the sulfur cathode by buoyancy, forming a sulfur cathode with a catalyst layer and a mixed layer composed of catalysts, conductive agents, sulfur-carbon composites, and binders in an interpenetrating structure.

2. The lithium-sulfur battery cathode with intercalated bilayer structure according to claim 1, characterized in that: The catalyst is one of cobalt sulfide, molybdenum sulfide, nickel sulfide, or selenium sulfide, with a particle size ratio of 1:100-1:1000 to the sulfur-carbon composite, and its mass percentage in the sulfur cathode is 2%-5% without a substrate, and the thickness of the catalyst layer is 0.1-2 microns.

3. The lithium-sulfur battery cathode with intercalated bilayer structure according to claim 1, characterized in that: The sulfur-carbon composite is a composite of elemental sulfur and conductive carbon materials, with a sulfur content of 60%-70%, and its mass percentage in the sulfur cathode is 75%-90% without a substrate.

4. The lithium-sulfur battery cathode having a dual intercalation structure according to claim 1, characterized in that: The binder in the mixed layer is one or two of lithium carboxymethyl cellulose, carboxymethyl cellulose, sodium alginate, polyacrylic acid, lithium polyacrylate, chitosan, glucose, and polyacrylate, and the total mass percentage of the binder in the sulfur cathode is 4%-10% without a substrate.

5. The lithium-sulfur battery cathode of claim 1, wherein: The conductive agent in the mixed layer is one of carbon nanotubes, carbon nanofibers, graphene oxide, and graphene, and its mass percentage in the sulfur cathode is 3%-10% without a substrate.

6. A method for preparing a lithium-sulfur battery cathode having a self- intercalating double-layer structure according to any one of claims 1 to 5, characterized in that: In sequence through the coating process and the buoyancy competition mechanism process; By using nanoscale catalysts and sulfur-carbon composites with a particle size ratio of 1:100-1:1000 and large-size one-dimensional or two-dimensional conductive agents, and by adjusting the viscosity of the slurry and the drying rate during coating, the smallest catalysts are gathered in the surface layer of the sulfur cathode by buoyancy, forming a sulfur cathode with a catalyst layer and a mixed layer composed of catalysts, conductive agents, sulfur-carbon composites, and binders in an interpenetrating structure.

7. The method of claim 6, wherein the lithium-sulfur cathode is prepared by , specifically comprising the following steps: Step 1. Put the conductive carbon material and elemental sulfur into a ball mill jar according to a certain mass ratio for physical mixing, pour the mixture into a hydrothermal reaction kettle after ball milling, and place it in a constant-temperature drying box at a temperature of 160-180 degrees for 10-15 hours, and then obtain the sulfur-carbon composite after natural cooling; Step 2. Put the catalyst and the binder into the water solvent according to a certain proportion for stirring and mixing, then add the conductive agent and the sulfur-carbon composite in sequence for sufficient stirring, and then wait for use after uniform stirring; Step 3. Use the prepared slurry to complete the coating on the surface of the positive electrode foil using a coating machine, and then perform vacuum drying treatment to finally obtain a lithium-sulfur battery cathode.

8. The method of claim 7, wherein: The conductive carbon material is one of acetylene black, ketjen black, carbon nanotubes, carbon nanofibers, graphene oxide, and graphene.

9. The method of claim 7, wherein: The viscosity of the slurry is controlled by adjusting the content of the water solvent in Step 2.

10. The method of claim 7, wherein: The thickness of the catalyst layer and the distribution of the catalyst inside the mixed layer are achieved in Step 3 by adjusting the drying rate during the coating process.

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