Sulfur support materials for lithium-sulfur batteries, composite sulfur cathodes, and methods of making the same

Abstract

The present application relates to the technical field of lithium-sulfur batteries, and particularly relates to a sulfur carrier material for lithium-sulfur batteries, a composite sulfur positive electrode and a preparation method thereof. The present application adopts a unique liquid metal-organic precursor and ordered mesoporous silica template, and synthesizes a single-atom-based sulfur carrier material with a full-confined channel structure and rich Fe-N-C sites by a grinding processing method (channel-Fe SAC ), and further uses the same to prepare a composite sulfur positive electrode material and a composite sulfur positive electrode for lithium-sulfur batteries. Benefited from the spatial geometry optimization of the material, including a confined channel for local LiPSs, an active center, a conductive carbon, and a three-phase interface of the three-phase interface, the channel-Fe SAC can effectively accelerate the conversion of polysulfides, thereby preventing the polysulfide shuttling and the formation of inert polysulfides.

Description

Technical Field

[0001] This invention relates to the field of lithium-sulfur battery technology, specifically to sulfur carrier materials, composite sulfur cathodes, and their preparation methods for lithium-sulfur batteries. Background Technology

[0002] Due to their ultra-high theoretical specific capacity (~1675 mAh / g) and energy density (~2600 Wh / Kg), as well as their environmentally friendly and abundant sulfur resources, lithium-sulfur batteries have been considered one of the most promising next-generation rechargeable energy storage devices. However, the practical application of lithium-sulfur batteries is still hindered by several challenges: the high activation energy of the conversion process from soluble LiPS to insoluble Li₂S₂ / Li₂S; the insulation properties of S and Li₂S; and the shuttle effect. A severe shuttle effect leads to reduced sulfur utilization and corrosion of Li metal, resulting in rapid capacity decay of lithium-sulfur batteries. To overcome these difficulties, numerous electrocatalysts have been developed and introduced into sulfur cathodes to accelerate the conversion of polysulfides, which is considered an effective strategy to mitigate the shuttle effect. Among these, metal sulfides, oxides, nitrides, and their heterojunctions have been identified as highly efficient catalysts that accelerate LiPS conversion through polar-polar interactions with LiPS, thereby achieving remarkable lithium-sulfur battery performance. Nevertheless, in order to ensure the overall energy density of the battery, it is necessary to reduce the amount of these inactive materials added, which poses a greater challenge to LiPS electrocatalysts.

[0003] Carbon-based single-atom catalysts (SACs) consist of monodisperse sites, providing an atomically dense catalytic interface to accelerate polysulfide conversion. Simultaneously, SACs exhibit other advantages as sulfur supports, such as high conductivity, low cost, high specific surface area, and light weight. These advantages make them promising candidates for achieving efficient, stable, and high-energy-density lithium-sulfur batteries. Among various carbon-based SACs, Fe-N4-based cathodes, in particular, have demonstrated excellent polysulfide catalytic conversion capabilities. However, most carbon-based SAC cathodes possess open sites or mesoporous structures with current-voltage openness, leading to rapid escape of polysulfides around the active sites, limiting polysulfide capture and catalytic efficiency (especially in liquid-solid conversion). Therefore, rationally optimizing the capture and conversion of polysulfide intermediates around the atomically catalytic sites of the cathode material is both necessary and challenging. Summary of the Invention

[0004] The purpose of this invention is to provide a sulfur support material with a fully confined pore structure and loaded with single Fe atoms (hereinafter referred to as channel-Fe). SAC It has a microenvironment for local capture and catalysis, thereby enabling the rapid conversion of polysulfide intermediates.

[0005] Specifically, the present invention provides a method for preparing a sulfur carrier material for lithium-sulfur batteries, comprising the following steps:

[0006] (1) Dopamine or its derivatives are mixed with FeCl3·6H2O at a mass ratio of 1:7-14 and ground thoroughly until the yellow powder is completely converted into a flowable black liquid to obtain a liquid organic-inorganic hybrid precursor.

[0007] (2) The liquid organic-inorganic hybrid precursor and ordered mesoporous silica are mixed and ground in a mass ratio of 10-3:1 (preferably 5:1), and then pyrolyzed under the protection of an inert gas to obtain a black powder.

[0008] (3) After washing and drying the black powder, it is subjected to secondary heat treatment at 800-1000℃ under the protection of inert gas to obtain sulfur carrier material for lithium-sulfur batteries.

[0009] Furthermore, the dopamine derivative is dopamine hydrochloride.

[0010] Further, in step (1), the mass ratio of dopamine or its derivative to FeCl3·6H2O is 1:10.

[0011] Further, in step (1), the grinding includes ball milling in a ball mill.

[0012] Further, in step (2), the pyrolysis includes heating at 700-900°C for 1-3 hours, preferably at 800°C for 2 hours, with a heating rate of 5°C / min.

[0013] Furthermore, the ordered mesoporous silica has a particle size of 7–9 nm.

[0014] Furthermore, the inert gas includes argon.

[0015] Further, in step (3), the washing is performed using HCl and NH4HF2 or HF, for example, using 1M HCl and 4M NH4HF2.

[0016] Further, in step (3), the drying includes drying in a vacuum oven at 50-80°C for 6-15 hours, for example, drying in a vacuum oven at 60°C for 12 hours.

[0017] The present invention also provides a sulfur carrier material for lithium-sulfur batteries, which is prepared by the method described above.

[0018] This invention also provides a method for preparing a composite sulfur cathode material for lithium-sulfur batteries, comprising the following steps:

[0019] Sublimed sulfur in a weight ratio of 7:3 and sulfur carrier material as described herein were mixed and ground uniformly. The mixture was then heated at 155°C for 12 hours and cooled to room temperature to obtain sulfur composite cathode material.

[0020] The present invention also provides a composite sulfur cathode material for lithium-sulfur batteries, which is prepared by the method described above.

[0021] This invention also provides a method for preparing a composite sulfur cathode for lithium-sulfur batteries, comprising the following steps:

[0022] Using N-methylpyrrolidone (NMP) as a solution, the composite sulfur cathode material described herein is mixed with carbon nanotubes (CNTs) and polyvinylidene fluoride (PVDF) at a mass ratio of 8:1:1 to obtain a slurry. The slurry is then coated onto aluminum foil and vacuum dried at 60°C for 12 hours to obtain the composite sulfur cathode for lithium-sulfur batteries.

[0023] The present invention also provides a composite sulfur cathode for lithium-sulfur batteries, which is prepared by the method described above.

[0024] Beneficial effects of the invention

[0025] The present invention provides a sulfur support material with a fully confined pore structure and loaded with single Fe atoms (channel-Fe). SAC Thanks to the optimized spatial geometry of the material, including ordered channels for in-situ capture and confined migration of polysulfides, and a fully confined three-phase boundary between atomic-level sites, conductive carbon, and electrolyte, channel-FeSAC can efficiently capture and accelerate LiPS conversion, avoiding shuttle effects and the generation of inactive LiPS. Theoretical calculations and experimental observations demonstrate that, compared to bowl-FeSAC and flat-FeSAC, channel-FeSAC exhibits exceptional polysulfide localization capture capabilities and the ability to accelerate Li2S deposition and conversion kinetics during cycling. As a result, a battery assembled with a channel-FeSAC-based cathode exhibited an efficiency of 845 mAh g⁻¹ at 1.0C rate. -1 High initial capacity and 532mAh g after 400 cycles -1 High capacity retention. Furthermore, lithium-sulfur batteries assembled with channel-FeSAC-based cathodes exhibit high sulfur loading (8.62 mg / cm³). -2 ) and low electrolyte / sulfur ratio (5 μL mg) -1 At 0.2C, it exhibited a capacity of 7.24 mAh cm⁻¹. -2 The high areal capacity. This invention provides important insights into the role of fully confined channels and locally trapped catalytic microenvironments in polysulfide catalysts in lithium-sulfur batteries and offers new avenues for the creation of high-performance lithium-sulfur battery cathodes. Attached image description:

[0026] Figure 1 The channel-Fe of the present invention is shown SAC An exemplary schematic diagram of the preparation process.

[0027] Figure 2 The channel-Fe prepared according to the present invention is shown using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SAC bowl-Fe SAC and flat-Fe SAC The results were characterized by the morphology and nanostructure of the material.

[0028] Figure 3 This invention demonstrates the channel-Fe prepared according to the present invention. SAC bowl-Fe SAC and flat-Fe SAC The X-ray diffraction (XRD) characterization results.

[0029] Figure 4 This invention demonstrates the channel-Fe prepared according to the present invention. SAC bowl-Fe SAC and flat-Fe SAC The catalytic performance test results.

[0030] Figure 5 This invention demonstrates the channel-Fe prepared according to the present invention. SAC bowl-Fe SAC and flat-Fe SAC The battery performance test results. Detailed Implementation

[0031] The present invention will be further illustrated below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in this technical field.

[0032] This invention utilizes a unique liquid metal-organic precursor and SBA-15 ordered mesoporous silica template to synthesize a single-atom-based cathode material with abundant Fe-NC sites and a fully confined pore structure (channel-Fe) via ball milling. SAC In short, FeCl3·6H2O inorganic crystals act as an active salt template and also as a metal species to coordinate with dopamine hydrochloride (DA). After ball milling, the unique Fe... 3+-DA complexes can be transformed into liquid metal-organic hybrid precursors. Subsequently, a certain amount of ordered mesoporous silica (SBA-15) is continuously ball-milled with this liquid precursor until a homogeneous mixture is observed. Good flowability ensures complete injection into the mesopores of the template. Figure 1 ). Prepared Fe 3+ The -DA-silica mixture was pyrolyzed under an Ar atmosphere to obtain Fe-NC-doped porous carbon. Residual metal salts and the SBA-15 template were then removed with hydrochloric acid and hydrofluoric acid or NH4HF2, followed by a secondary heat treatment to obtain the final product, named channel-Fe. SAC Simultaneously, Bowe-Fe was synthesized using the same method, both with and without silica nanospheres. SAC (semi-confined three-phase boundary) and flat-Fe SAC By comparing (unconfined three-phase boundaries), the influence of spatial geometric confinement on polysulfide capture and catalytic conversion is revealed.

[0033] Example 1: channel-Fe SAC Preparation

[0034] Dopamine hydrochloride and FeCl3·6H2O were thoroughly ground in a ball mill at a mass ratio of 1:10. After continuous ball milling for 30 minutes, the yellow powder was completely transformed into a flowable black liquid, indicating that the complexation reaction between dopamine hydrochloride and FeCl3·6H2O was completed, yielding a liquid organic-inorganic hybrid precursor.

[0035] The prepared liquid organic-inorganic hybrid precursor was further ground with 2g of ordered mesoporous silica SBA-15 powder (Su zhan) with a particle size of 7-9nm at a mass ratio of 5:1. The resulting mixture was then transferred to an argon tube furnace and heated at 800℃ for 2h at a heating rate of 5℃ / min. The resulting black powder was continuously washed with 1M HCl and 4M NH4HF2 to remove metal salts and templates, and then dried in a vacuum oven at 60℃ for 12h to obtain channel-Fe. SAC Sulfur carrier.

[0036] Comparative Example 1: flat-Fe SAC Preparation

[0037] The liquid organic-inorganic hybrid precursor prepared as described in Example 1 was transferred to an argon tube furnace and heated at 700°C for 2 hours at a heating rate of 5°C / min. The resulting black powder was continuously washed with 1M HCl to remove metal salts, and then dried in a vacuum oven at 60°C for 12 hours to obtain flat-Fe with a planar structure. SAC Sulfur carrier.

[0038] Comparative Example 2: bowl-Fe SAC Preparation

[0039] The liquid organic-inorganic hybrid precursor prepared as described in Example 1 was further ground with 2g of silica nanospheres (SiO2 powder, Ludox Sm-30) with a particle size of 7-9nm at a mass ratio of 5:1. The resulting mixture was then transferred to an argon tube furnace and heated at 800°C for 2h at a heating rate of 5°C / min. The resulting black powder was continuously washed with 1M HCl and 4M NH4HF2 to remove metal salts and templates, and then dried in a vacuum oven at 60°C for 12h to obtain bowl-shaped Fe. SAC Sulfur carrier.

[0040] Application Example 1: Preparation of Composite Sulfur Cathode

[0041] Sublimed sulfur and the prepared sulfur support were ground uniformly in a mortar in a weight ratio of 7:3. Then, the mixture was heated at 155°C for 12 hours and cooled to room temperature to obtain the composite sulfur cathode material.

[0042] Using NMP as a solution, the composite sulfur cathode material was mixed with CNTs and PVDF at a mass ratio of 8:1:1 to obtain a slurry. The slurry was coated onto carbon-coated aluminum foil and vacuum-dried at 60°C for 12 hours. The dried cathode was cut into 12 mm diameter discs for use as the working electrode. The sulfur loading of a conventional electrode is approximately 1.0 mg / cm³. -2 .

[0043] Application Example 2: Assembly and Electrochemical Testing of Li-S Batteries

[0044] Using a composite sulfur cathode, Celgard 2500 diaphragm, and lithium foil as the anode, CR2032 coin cells were assembled in an Ar-filled glove box. The electrolyte composition was 1.0M LiTFSI, DOL:DME = 1:1 Vol%, with 1.0% LiNO3 added. The Land 2001A battery testing system was used for 1.6-2.8V (vs. Li + Cyclic and rate performance between / Li). In the cycling tests, the maximum capacity after activation was used as the initial capacity. Cyclic voltammetry (CV) measurements were performed on a Garmmy electrochemical workstation at voltages of 1.6 and 2.8 V.

[0045] Application Example 3: Li2S Nucleation Test

[0046] A Li₂S₈ solution was prepared by dissolving sublimed sulfur and Li₂S in a tetraenamine solution at a mass ratio of 7:1. A sulfur-free sample cathode was used as the working electrode, and lithium foil was used as the counter electrode to assemble the battery. 20 μL of the Li₂S₈ solution was used as the cathode-side electrolyte, and 20 μL of the Li₂S₈-free solution was used as the anode-side electrolyte. First, the battery was discharged at a constant current of 0.112 mA to 2.06 V. Then, the battery was maintained at a constant potential of 2.05 V to allow Li₂S nucleation until the current dropped below 10 μA. -5 A.

[0047] Application Example 4: Symmetrical Cell Testing

[0048] The symmetrical battery was assembled from two identical electrodes. The prepared sample, carbon nanotubes, and PVDF were mixed in NMP at a mass ratio of 8:1:1 to prepare the electrode, which was then coated onto carbon-coated aluminum foil. A Celgard 2500 was used as the separator. The 0.5M Li₂S₆ electrolyte was prepared by dissolving appropriate amounts of sulfur and Li₂S in a blank electrolyte (1M LiTFSI in DOL / DME (volume ratio 1:1)) and stirring overnight at 70°C in an Ar-filled glove box. 40 μL of the 0.5M Li₂S₆ electrolyte was added dropwise to a CR2032 coin cell. Electrochemical tests were performed on a Garmmy 1010 electrochemical workstation at 2 mV s between -0.8 and 0.8 V. -1 Next, test CV.

[0049] Performance test results:

[0050] 1. Morphological and structural characterization

[0051] The morphology and nanostructure of the sulfur supports prepared in Example 1 and Comparative Examples 1-2 were investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). (channel-Fe) SAC The SEM images show a clear structure from SBA-15, bowl-Fe SAC It exhibits a mesoporous structure derived from silica nanoparticles, while flat-Fe... SAC It exhibits a smooth two-dimensional nanosheet structure. Figure 2 ac). channel-Fe SAC It exhibits a fully confined and ordered channel structure, while the bowl-shaped Fe... SAC and flat-Fe SAC Then there are randomly distributed mesopores and micropores respectively. Figure 2 df). The corresponding energy-dispersive X-ray spectroscopy (EDS) elemental map shows that channel-Fe SAC The C, N, and Fe were uniformly distributed, and no obvious metal nanoparticles were observed. Figure 2 g). Nitrogen adsorption tests were then performed to demonstrate channel-Fe. SAC bowl-Fe SAC and flat-Fe SAC The porous nature of channel-Fe. SAC bowl-Fe SAC and flat-Fe SAC The specific surface areas of BET were 1063, 1314 and 1497 m², respectively. 2 g -1 flat-Fe SAC The N2 adsorption / desorption isotherms are related to the type I isotherms of the microporous structure, while channel-Fe SAC and bowl-Fe SAC It exhibits typical type IV isotherms, indicating the successful introduction of additional micropores. Figure 2 h). The pore size distribution indicates that the channel-Fe SAC and bowl-Fe SAC They have similar mesopore sizes in the range of 5–10 nm. Figure 2 i).

[0052] channel-Fe SAC and bowl-Fe SAC X-ray diffraction (XRD) showed similar diffraction peaks to graphitic carbon, while flat-Fe... SAC It exhibits low graphitization due to its numerous microporous structures. Figure 3 a) This can be further confirmed by the lower ID / IG in the Raman spectrum. Figure 3 b). X-ray photoelectron spectroscopy (XPS) was used to analyze the prepared channel-Fe SAC bowl-Fe SAC and flat-Fe SAC Detailed atomic structure characterization and quantitative elemental analysis were performed. Figure 3 Fe signals can be observed in the high-resolution region scan shown in c, where the Fe 2p region scan can assemble Fe. 2+ and Fe 3+ Price, no Fe 0 This suggests the formation of atomic Fe-NC catalytic sites. Based on XPS results, channel-Fe was calculated. SAC The iron content is 0.83 wt.%, bowl-Fe SAC The iron content is 0.70 wt.%, flat-Fe SACThe iron content was 1.15 wt.%, indicating the consistency of the catalytic sites. N1s spectra showed that the three samples contained similar nitrogen species: pyridine N (~397.8 eV), pyridine N (~398.5 eV), graphitic N (~400.9 eV), and N oxide (~405.2 eV). Figure 3 d).

[0053] 2. Catalytic performance test

[0054] After verifying that these sulfur supports possess similar Fe-NC catalytic sites but exhibit varying degrees of spatial confinement effects, the kinetics of polysulfide catalytic conversion were further investigated. Generally, the high nucleation barrier of Li₂S during discharge is accompanied by a soluble-insoluble phase, typically leading to prolonged accumulation time of liquid polysulfide intermediates in the cathode, further resulting in a frustrating "shuttle effect." To verify the channel-Fe... SAC To evaluate the promoting effect of Li₂S on liquid-solid transformation, a potentiostatic precipitation experiment of Li₂S was specifically designed. For example... Figure 4 As shown in ab, channel-Fe based on the fully confined three-phase boundary SAC The Li₂S precipitation capacity of the electrode is 292.93 mAh g⁻¹. -1 (Calculated based on Faraday's law), higher than bowl-Fe SAC (228.86mAh g -1 ) and flat-Fe SAC (164.23mAh g -1 As can be seen from SEM, Li2S almost completely covers the channel-Fe. SAC The surface of the electrode. To further investigate its promoting effect on polysulfide conversion, the electrochemical reaction kinetics of the cathode in a coin cell were systematically studied. First, CV curves were plotted at a scan rate of 0.1 mV / s for a voltage range of 1.6–2.8 V. Figure 4 c). At around 2.0V and 2.3V, two consecutive cathode peaks can be observed, which are due to Li₂S. n (4≤n≤8)(A1) is reduced to Li2S2 / Li2S (A2). The anodic peak at around 2.4V corresponds to the reverse conversion of Li2S to S8 (A3). It is worth noting that, with bowl-Fe... SAC and flat-Fe SAC In comparison, channel-Fe SAC The cathode exhibited the highest peak current in the sulfur reduction reaction, indicating its role in promoting kinetics. The determination of the Tafel slope provided kinetic parameters for further elucidating the catalytic activity of different sulfur supports; the fitting results are shown below. Figure 4As shown in d. Based on channel-Fe SAC bowl-Fe SAC and flat-Fe SAC The Tafel slopes for the reduction of sulfur from soluble LiPS to solid Li₂S₂ / Li₂S were 25.6, 65.7, and 117.8 mV dec, respectively. -1 This indicates that the liquid-solid transformation kinetics are consistent with the degree of spatial confinement; during the oxidation process, channel-Fe SAC It also shows advantages in the reversible dissolution of Li2S, which may be due to optimized interfacial contact. Figure 4 e).

[0055] 3. Battery performance testing

[0056] In button cells, for channel-Fe SAC bowl-Fe SAC and flat-Fe SAC The lithium-ion battery performance of the prepared cathode was evaluated. Charge-discharge curves at different current densities showed that the channel-Fe... SAC The cathode has a capacity of 1330 mAh g at 0.1C. -1 Much higher than bowl-Fe SAC (1060mAh g -1 ) and flat-Fe SAC (870mAh g -1 ()( Figure 5 a). Figure 5 b summarizes the overpotential and conversion efficiency (Q2 / Q1, where Q1 is S8) for the conversion of soluble solids. 2- →S4 2- Capacity contribution of each stage, Q2 is S4 2- →Capacity contribution of the Li2S2 / Li2S stage). Compared with other cathodes, channel-Fe SAC The cathode exhibits the lowest nucleation overpotential and the highest conversion efficiency. Rate performance indicates that channel-Fe... SAC The rate capacities of the cathode at 0.1, 0.2, 0.5, 1.0, and 2.0 °C were 1324, 931, 838, 789, and 704 mAh g, respectively. -1 It is significantly better than bowl-Fe SAC and flat-Fe SAC cathode( Figure 5 c). At a charge / discharge rate of 1.0C, channel-Fe SAC The reversible capacity after 400 cycles was 532 mAh g⁻¹, significantly better than bowl-Fe. SACBattery (402mAh g) -1 ) and flat-Fe SAC Battery (380mAh g) -1 It exhibits excellent long-term stability. Figure 5 d). To further confirm channel-Fe SAC Potential applications in lithium-sulfur batteries were investigated, focusing on the electrochemical performance of the cathode under high sulfur loading and low electrolyte conditions. For example... Figure 5 As shown in d, the sulfur loading is 8.62 mg cm⁻¹. -2 channel-Fe SAC With an E / S ratio of 8 μL mg⁻¹, it has a capacity of 6.35 mAh / cm³. -2 High areal capacity and a single-turn attenuation rate as low as 0.25% ( Figure 5 All electrochemical results indicate that, based on channel-Fe SAC The cathode has ordered channels and fully constrained three-phase boundaries that enable local capture and migration suppression of LiPS, which can effectively improve the cycle performance of Li-S cells.

[0057] In summary, this invention has created a novel carbon cathode material for SAC with fully confined channels for the localized capture and catalytic conversion of LiPS intermediates, thereby enabling high-performance Li-S batteries. This is achieved thanks to the channel-Fe... SAC The spatial geometry optimization of the cathode, including ordered channels for local trapping and migration inhibition of LiPS, and a fully constrained three-phase boundary between the atomic catalytic center, conductive carbon, and electrolyte, demonstrates in our research that channel-Fe SAC Polysulfide intermediates can be effectively captured and converted through sulfur redox reactions, thereby eliminating the shuttle effect and the generation of inert LiPS. Therefore, using chennel-Fe... SAC The Li-S cell with cathode assembly exhibits a 7.24 mAh / cm³ at 0.2C. -2 High initial area capacity, 8.62 mg / cm³ -2 Its high sulfur loading and low E / S ratio of 5 μL mg⁻¹ suggest that it has potential for practical applications in high-energy and long-life Li-S batteries.

[0058] It should be noted that while the preferred embodiments of the present invention are given in the specification and accompanying drawings, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are not intended to impose additional limitations on the content of the present invention; their purpose is to provide a more thorough and comprehensive understanding of the disclosure of the present invention. Furthermore, the above-described technical features can be combined with each other to form various embodiments not listed above, all of which are considered to be within the scope of the present invention specification. Moreover, those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a sulfur carrier material for lithium-sulfur batteries, characterized in that, Includes the following steps: (1) Dopamine or its derivatives are mixed with FeCl3·6H2O at a mass ratio of 1:7-14 and ground thoroughly until the yellow powder is completely converted into a flowable black liquid to obtain a liquid organic-inorganic hybrid precursor. (2) The liquid organic-inorganic hybrid precursor and ordered mesoporous silica were mixed and ground in a mass ratio of 10-3:1, and then pyrolyzed under the protection of an inert gas to obtain a black powder. (3) After washing and drying the black powder, it is subjected to secondary heat treatment at 800-1000℃ under the protection of inert gas to obtain sulfur carrier material for lithium-sulfur batteries.

2. The preparation method according to claim 1, characterized in that, The dopamine derivative is dopamine hydrochloride.

3. The preparation method according to claim 1, characterized in that, In step (2), the pyrolysis includes heating at 700-900°C for 1-3 hours.

4. The preparation method according to claim 1, characterized in that, The ordered mesoporous silica has a particle size of 7-9 nm.

5. The preparation method according to claim 1, characterized in that, In step (3), the washing is performed using HCl and NH4HF2, and the drying includes drying in a vacuum oven at 50-80°C for 6-15 hours.

6. A sulfur carrier material for lithium-sulfur batteries, characterized in that, The sulfur carrier material is prepared by the method described in any one of claims 1-5.

7. A method for preparing a composite sulfur cathode material for lithium-sulfur batteries, characterized in that, Includes the following steps: Sublimed sulfur in a weight ratio of 7:3 and the sulfur carrier material according to claim 6 were mixed and ground uniformly. The mixture was then heated at 155°C for 12 h under the protection of an inert gas and cooled to room temperature to obtain a sulfur composite cathode material.

8. A composite sulfur cathode material for lithium-sulfur batteries, characterized in that, The composite sulfur cathode material is prepared by the method described in claim 7.

9. A method for preparing a composite sulfur cathode for lithium-sulfur batteries, characterized in that, Includes the following steps: Using N-methylpyrrolidone as a solution, the composite sulfur cathode material according to claim 8 is mixed with carbon nanotubes and polyvinylidene fluoride at a mass ratio of 8:1:1 to obtain a slurry. The slurry is coated on aluminum foil and vacuum dried at 60°C for 12 h to obtain the composite sulfur cathode for lithium-sulfur batteries.

10. A composite sulfur cathode for lithium-sulfur batteries, characterized in that, The composite sulfur cathode material is prepared by the method described in claim 9.

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