Sulfur-containing polymer battery material, positive electrode sheet, preparation method thereof and lithium-sulfur battery

Abstract

This invention relates to the field of battery materials technology, disclosing sulfur-containing polymer battery materials, positive electrode sheets, their preparation methods, and lithium-sulfur batteries. The preparation method of the sulfur-containing polymer battery material includes: crosslinking and curing molten sulfur with trimethylolpropane trimethacrylate at a mass ratio of 1-4:1. In the polymer S-TMPTMA obtained by this method, the O atoms in the C=O functional groups act as electron-rich active sites, effectively chemically adsorbing relatively electron-poor lithium from the lithium polysulfide intermediate during the lithium-sulfur electrochemical reaction, thereby alleviating the dissolution of lithium polysulfides in ether-based electrolytes and reducing the influence of the "shuttle effect." In a preferred embodiment, this polymer is used as a printing ink to manufacture electrodes via 3D printing, and these electrodes exhibit excellent electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to sulfur-containing polymer battery materials, positive electrode sheets and their preparation methods, and lithium-sulfur batteries. Background Technology

[0002] Currently, lithium-ion batteries, as a clean and novel energy source, have been widely used in various industries. However, they still face the bottleneck of relatively low energy density. Lithium-sulfur batteries, as a branch of lithium-ion batteries, have a theoretical energy density of up to 2600 Wh / kg, which is significantly superior to conventional lithium-ion batteries. Sulfur, as the cathode material in lithium-sulfur batteries, has a theoretical specific capacity as high as 1675 mAh / g. However, using sulfur powder alone as the cathode active material has a significant disadvantage: the "shuttle effect" in lithium-sulfur batteries. This effect is mainly attributed to the fact that the lithium polysulfide intermediates produced during the electrochemical reaction between lithium and sulfur can dissolve in ether-based electrolytes. Due to the concentration gradient effect, the lithium polysulfides diffuse towards the negative electrode and are eventually reduced to form deactivated sulfur, ultimately leading to rapid capacity decay in lithium-sulfur batteries. Therefore, the functional design of sulfur-based cathode materials is particularly important.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide sulfur-containing polymer battery materials, positive electrode sheets, methods for preparing the same, and lithium-sulfur batteries, aiming to improve at least one of the problems mentioned in the background art.

[0005] This invention is implemented as follows: In a first aspect, embodiments of the present invention provide a method for preparing a sulfur-containing polymer battery material, comprising: Molten sulfur and trimethylolpropane trimethacrylate are crosslinked and cured at a mass ratio of 1 to 4:1.

[0006] In optional embodiments, the cross-linking curing process includes: Trimethylolpropane trimethacrylate was mixed with molten sulfur under an inert gas atmosphere and reacted thoroughly at a temperature of 165-180°C to obtain a viscous liquid; then the viscous liquid was placed in an environment of 120-130°C to solidify and obtain a solid.

[0007] In an optional implementation, the method further includes at least one of the following technical features (1) to (3): (1) The inert gas is at least one of nitrogen and argon; (2) React at 165~180℃ for 10~15 min to obtain a viscous liquid; (3) The curing time is 20~28h.

[0008] In an optional embodiment, crosslinking and curing are performed to obtain a solid, and the process further includes: The solid is pulverized into powder with an average particle size of 8~12μm; Optionally, the pulverizing method is ball milling.

[0009] Secondly, embodiments of the present invention provide a sulfur-containing polymer battery material, which is prepared using the preparation method provided in embodiments of the present invention.

[0010] Thirdly, embodiments of the present invention provide a method for preparing a positive electrode sheet for lithium-sulfur batteries, wherein the positive electrode sheet is prepared using sulfur-containing polymer battery materials provided in embodiments of the present invention.

[0011] In an optional embodiment, the preparation method includes: Provide printing inks with a solid content of 18-25%, which include sulfur-containing polymer battery materials; A preliminary product is obtained by 3D printing using printing ink as the raw material. The initial product is dried to obtain a grid-shaped positive electrode sheet.

[0012] In an optional embodiment, the preparation method further includes at least one of the following features (1) to (5): (1) The printing ink also includes a dispersant, and the mass ratio of sulfur-containing polymer battery material to dispersant is 2~4:1; Optionally, the dispersant is graphene oxide; (2) The thickness of the positive electrode sheet is 0.5~0.75mm; (3) The solvent in the printing ink is water; (4) The method of drying the initial product includes: first freeze drying to remove the solvent, and then heat treatment at 140~160℃ for 25~35min; (5) Before drying the initial product, the initial product is also rapidly cooled using liquid nitrogen.

[0013] Fourthly, the present invention provides a positive electrode sheet, which is prepared by any of the preparation methods described in the foregoing embodiments.

[0014] Fifthly, the present invention provides a lithium-sulfur battery, including a positive electrode as described in the foregoing embodiments.

[0015] The present invention has the following beneficial effects: The preparation method provided by this invention utilizes a reverse sulfurization method with trimethylolpropane trimethacrylate (TMPTMA) as a crosslinking agent to crosslink and polymerize molten sulfur, generating a sulfur-chain-dominated polymer S-TMPTMA. TMPTMA, as a crosslinking agent, introduces C=O functional groups. The O atoms in the C=O functional groups, as electron-rich active sites, can effectively chemically adsorb the relatively electron-poor lithium in the lithium polysulfide intermediate during the lithium-sulfur electrochemical reaction, thereby alleviating the dissolution of lithium polysulfides in ether-based electrolytes and reducing the influence of the "shuttle effect." Compared with pure sulfur powder, it can significantly improve the specific capacity and cycle capacity retention of lithium-sulfur batteries. In addition to the advantages mentioned above, the nonlinear and multi-unsaturated molecular structure of TMPTMA as a crosslinking agent ensures the rigidity of the obtained polymer S-TMPTMA, making the product S-TMPTMA a hard solid, which is beneficial for pulverizing into powder for use in the manufacture of positive electrode sheets.

[0016] In some preferred embodiments, S-TMPTMA is used to fabricate the cathode printing ink. 3D printing enables the fabrication of high-sulfur-loading, self-supporting lithium-sulfur battery cathodes with a three-dimensional spatial structure, exhibiting excellent electrochemical performance as lithium-sulfur battery cathodes. 3D printing allows for patterned design of the lithium-sulfur battery cathode, resulting in a well-defined spatial structure and pores that provide ample space for electrolyte wetting. Electrodes fabricated using 3D printing exhibit superior electrochemical performance compared to electrodes prepared using conventional slurry coating methods. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram illustrating the reaction principle of S-TMPTMA synthesis. Figure 2 This is a schematic diagram illustrating the operation method during S-TMPTMA synthesis; Figure 3 SEM image of S-TMPTMA powder; Figure 4 This is an external view of the self-supporting electrode prepared in Example 1; Figure 5 This is a partial SEM image of the self-supporting electrode obtained in Example 1; Figure 6 This is a graph showing the cycle performance of Example 1; Figure 7 This is a graph showing the cycle performance of Example 6; Figure 8 The circuit performance curves for Comparative Example 3 are shown. Figure 9 The graph shows the cycle performance of Comparative Example 4. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0020] Based on the problems existing in the current technology, the inventors considered the following: Sulfur-containing polymers prepared by desulfurization are promising cathode materials for lithium-sulfur batteries. Their organic frameworks can be functionalized to effectively physically and chemically adsorb lithium polysulfides, thereby mitigating the "shuttle effect." Furthermore, due to the inherently slow reaction kinetics of the sulfur reduction reaction in lithium-sulfur batteries, the sulfur loading of the cathode is generally low. Excessive sulfur loading leads to electrode thickness, potentially causing insufficient electrolyte wetting, which in turn affects electrochemical reaction kinetics and battery capacity, ultimately impacting the overall energy density and significantly hindering the commercialization of lithium-sulfur batteries. Therefore, the preparation of high-sulfur-loading cathodes requires further optimization to achieve higher specific capacity.

[0021] The following is a detailed description of the sulfur-containing polymer battery material, positive electrode sheet, its preparation method, and lithium-sulfur battery provided in the embodiments of the present invention.

[0022] The method for preparing sulfur-containing polymer battery materials provided in this invention includes: Molten sulfur and trimethylolpropane trimethacrylate were crosslinked and cured at a mass ratio of 3.5 to 4.5:1.

[0023] The preparation method provided in this invention uses trimethylolpropane trimethacrylate (TMPTMA) as a crosslinking agent to crosslink and polymerize molten sulfur, generating a sulfur-chain-dominated polymer S-TMPTMA. TMPTMA, as a crosslinking agent, introduces C=O functional groups. The O atoms in the C=O functional groups, as electron-rich active sites, can effectively chemically adsorb the relatively electron-poor lithium in the lithium polysulfide intermediate during the lithium-sulfur electrochemical reaction, thereby alleviating the dissolution of lithium polysulfides in ether-based electrolytes and reducing the influence of the "shuttle effect." Compared with pure sulfur powder, it can significantly improve the specific capacity and cycle capacity retention of lithium-sulfur batteries. In addition to the advantages mentioned above, the nonlinear and multi-unsaturated molecular structure of TMPTMA as a crosslinking agent ensures the rigidity of the obtained polymer S-TMPTMA, making the product S-TMPTMA a hard solid, which is beneficial for pulverizing into powder for use in manufacturing positive electrode sheets.

[0024] It should be noted that the mass ratio of molten sulfur to trimethylolpropane trimethacrylate participating in the reaction should be within the range required by this invention. If there is too much molten sulfur, unreacted elemental sulfur will be present in the product, forming a mixture, which does not meet the requirements of the positive electrode active material of lithium-sulfur batteries. If there is too little molten sulfur, the active sulfur content in the product will be too low, resulting in poor subsequent electrical performance.

[0025] Specifically, the preparation method includes: S1, providing molten sulfur Place the sulfur powder in a container and protect it with an inert gas. Raise the container temperature to 115-140°C (e.g., 115°C, 120°C, 125°C, 130°C, or 140°C). Use a magnetic stirrer and a magnetic stir bar to slowly disperse the sulfur powder (e.g., 250-350 rpm) until the sulfur powder is completely melted and appears as a bright yellow liquid, with no obvious powdery particles in the glass bottle.

[0026] S2, Crosslinking Curing First step reaction: The reaction principle is as follows Figure 1 As shown, under inert gas protection, TMPTMA is rapidly added dropwise to a container containing molten sulfur. The stirring speed is increased (e.g., 650~750 rpm), and the container temperature is raised to 165~180℃ (e.g., 165℃, 170℃, 175℃ or 185℃). The reaction is carried out for 10~15 minutes. At this time, the reactant is a brownish-black viscous liquid. The second step of the reaction involves pouring a brown, viscous liquid into a high-temperature resistant silicone mold and then placing it in an oven at 120-130°C (e.g., 120°C, 125°C, or 130°C) to cure for 20-28 hours (e.g., 20 hours, 24 hours, or 28 hours) to obtain a black, hard solid, which is S-TMPTMA.

[0027] Optionally, the inert gas is at least one of nitrogen and argon.

[0028] Molten sulfur has an S8 cyclic structure. In the first step of the reaction, the temperature is raised to 165-180℃, causing the sulfur ring to open and form sulfur chains. Sulfur free radicals are formed at the two ends of the sulfur chains. At this time, the sulfur chains containing sulfur free radicals also polymerize to form long sulfur chains, with the ends still carrying free radicals. The addition of the small molecule crosslinking agent TMPTMA allows the sulfur free radicals to attack and open the double bonds of TMPTMA, grafting sulfur chains onto both ends of the double bonds to form a polymer. However, the polymer product is unstable when cooled directly because of the large number of long sulfur chains in the structure. During cooling, backbite behavior may occur, i.e., the sulfur ring structure is reformed and precipitated, resulting in a mixture rather than a pure polymer in the final product, with poor reproducibility. The second step solidifies the mixture obtained in the first step at 120-130℃, allowing the sulfur chains to slowly reconstruct during this process, ultimately forming a stable polymer structure without the precipitation of elemental sulfur, ensuring the consistency of the final product.

[0029] S3, Crushing The black, hard solid obtained in step S2 was ball-milled into powder with an average particle size of 10 μm.

[0030] The sulfur-containing polymer battery material provided in this embodiment of the invention is prepared using the preparation method provided in this embodiment of the invention.

[0031] The method for preparing a positive electrode for lithium-sulfur batteries provided in this invention uses a sulfur-containing polymer battery material provided in this invention to prepare the positive electrode. Because the positive electrode prepared by this method is made using the sulfur-containing polymer battery material provided in this invention, it enables the battery to exhibit better electrochemical performance when applied to lithium-sulfur batteries.

[0032] Specifically, the preparation method includes: S1, Provide printing ink The printing ink comprises solvents and sulfur-containing polymer battery materials. Optionally, to ensure adequate dispersion of the sulfur-containing polymer battery materials, the printing ink may also include a dispersant.

[0033] Alternatively, the solvent may be water or other organic solvents.

[0034] When the solvent is water, the printing ink is an aqueous system. In order to ensure that the conductive carbon material can be fully dispersed, the dispersant can be selected from graphene oxide. Graphene oxide not only acts as a dispersant but also as a conductive agent.

[0035] When the solvent is other organic solvent, the printing ink is an oil-based system. Other conventional dispersants can also be added to the components to help the components in the ink disperse evenly.

[0036] The solid content of the printing ink is 18-25% (e.g., 18%, 20%, 23% or 25%). The mass ratio of sulfur-containing polymer battery material to dispersant is 3-4:1 (e.g., 3:1, 3.5:1 or 4:1).

[0037] Taking GO as a dispersant as an example, the specific preparation method is as follows: The GO layered material was sheared and ground to separate it, resulting in small-particle-size GO powder with an average particle size of 3 μm. Small-particle-size GO powder is slowly added to deionized water while being stirred at high speed (e.g., 1500~2500 rpm) to form a stable GO dispersion. Then, S-TMPTMA powder is gradually and slowly added to the GO dispersion, and the mixture is rapidly cooled to room temperature after stirring to form a stable printing ink. The resulting printing ink is sealed in a PTFE cavity, ready for subsequent printing.

[0038] S2, 3D Printing Printing ink is added to a 3D printing syringe. The syringe is then installed into the 3D printing equipment (Aerotech). The print pattern is then designed using CAD software, typically a grid pattern.

[0039] Optionally, the thickness of the mesh-shaped positive electrode is 0.5~0.75mm (e.g., 0.5mm, 0.6mm, or 0.75mm), and the thickness of the positive electrode can be controlled by the number of printing layers. After the shape and size are designed, the electrode can be printed on a Teflon substrate. Immediately after printing, the electrode is cooled with liquid nitrogen and transferred to a freeze-drying oven for 36~48 hours to completely remove the solvent introduced by the printing ink, ensuring the self-support of the electrode. Afterward, the dried electrode is heat-treated at 40~160℃ for 25~35 minutes to achieve a tighter contact between the sulfur active material and the conductive framework.

[0040] To address the issue of poor electrochemical performance in high-load lithium-sulfur cathodes fabricated using existing slurry coating methods, a printing ink based on a sulfur-rich polymer was prepared. Then, 3D printing technology was used to print a high-load self-supporting lithium-sulfur cathode with a well-defined spatial structure. This cathode facilitates thorough electrolyte wetting, thereby establishing better lithium-ion transport channels and ultimately significantly improving the specific capacity of the lithium-sulfur cathode.

[0041] The electrode sheet provided in this embodiment of the invention is prepared using the preparation method provided in this embodiment of the invention.

[0042] The lithium-sulfur battery provided in this embodiment of the invention includes a positive electrode provided in this embodiment of the invention.

[0043] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0044] Example 1 like Figure 2 As shown, 4g of sulfur powder was first added to a 14mL high-temperature resistant cylindrical glass sample vial, and a nitrogen balloon was used for atmosphere protection. The temperature was raised to 135℃, and the sample was slowly stirred and dispersed using a magnetic stirrer (300rpm) until the sulfur powder was observed to be completely melted and turned into a bright yellow liquid, with no obvious powdery matter present in the glass vial.

[0045] 1g of TMPTMA liquid sample was rapidly added dropwise to a glass bottle under a nitrogen atmosphere. The stirring speed was increased to 700 rpm, and the reaction temperature was raised to 165℃. The reaction was allowed to proceed for 15 minutes, at which point the reactant had become a brownish-red viscous liquid. The sample was poured into a high-temperature resistant silicone mold and cured in a 130℃ oven for 24 hours, yielding a black, hard solid, which is the S-TMPTMA polymer. This solid was then ball-milled to an average particle size of approximately 10μm, completing the preparation of the S-TMPTMA polymer powder. A scanning electron microscope (SEM) image of the product is shown below. Figure 3 As shown.

[0046] GO layered material was sheared and ground to obtain relatively uniform particles with an average particle size of 3 μm. 0.5 g of the ground GO sheet material was then slowly added to 10 g of deionized water while stirring at high speed (2000 rpm) to form a stable GO dispersion. Next, 1.5 g of S-TMPTMA polymer powder was slowly added to the GO dispersion, and the mixture was rapidly cooled to room temperature after stirring to form a stable printing ink. The mass ratio of S-TMPTMA to GO was 3:1. The resulting printing ink was sealed in a PTFE cavity, ready for subsequent printing.

[0047] Printing ink was added to a 10 mL syringe specifically designed for 3D printing, with a needle diameter of 0.25 mm. The syringe was then installed into a 3D printing machine (Aerotech). Next, the printing pattern was designed using CAD software, resulting in an 8*8 mm square grid pattern with an electrode thickness of 0.5 mm (two electrode layers). The electrode was printed on a Teflon substrate according to these dimensions. Immediately after printing, the electrode was cooled with liquid nitrogen and transferred to a freeze-drying oven for 48 hours to completely remove moisture. Subsequently, the electrode was heated in a 150°C oven for 30 minutes to achieve a tighter contact between the sulfur-active material and the conductive framework, ultimately yielding the prepared S-TMPTMA polymer-based self-supporting electrode. Figure 4The sulfur loading of this electrode is approximately 12.5 mg. s / cm 2 Scanning electron microscope (SEM) images such as Figure 5 As shown.

[0048] Example 2 This embodiment is basically the same as Embodiment 1, except that the amount of molten sulfur used is 2.5g and the amount of TMPTMA used is 2.5g.

[0049] Example 3 This embodiment is basically the same as Embodiment 1, except that the amount of molten sulfur used is 3g and the amount of TMPTMA used is 2g.

[0050] Example 4 This embodiment is basically the same as Embodiment 1, except that: During the reaction, 1g of TMPTMA liquid sample was rapidly added dropwise to a glass bottle while maintaining a nitrogen atmosphere. The stirring speed was increased to 700 rpm, and the reaction temperature was raised to 170℃. The reaction was allowed to proceed for 13 minutes, at which point the reactant had become a brownish-brown viscous liquid. The sample was then poured into a high-temperature resistant silicone mold and cured in a 125℃ oven for 24 hours to obtain a black, hard solid, which is the S-TMPTMA polymer.

[0051] Example 5 This embodiment is basically the same as Embodiment 1, except that: During the reaction, 1g of TMPTMA liquid sample was rapidly added dropwise to a glass bottle while maintaining a nitrogen atmosphere. The stirring speed was increased to 700 rpm, and the reaction temperature was raised to 180℃. The reaction was allowed to proceed for 10 minutes, at which point the reactant had become a brownish-brown viscous liquid. The sample was then poured into a high-temperature resistant silicone mold and cured in a 120℃ oven for 24 hours to obtain a black, hard solid, which is the S-TMPTMA polymer.

[0052] Example 6 This embodiment is basically the same as embodiment 1, except that: The method for preparing the positive electrode in this embodiment differs from that in Example 1, specifically as follows: S-TMPTMA, carbon black conductive agent, and PVDF binder were ground and mixed in a 7:2:1 mass ratio. The resulting powder was then uniformly dispersed in NMP solvent to prepare a slurry. The slurry was then uniformly coated onto the surface of aluminum foil and dried in a vacuum oven at 60°C. After drying, the cathode was cut to obtain the cathode material. A high sulfur loading (approximately 10.2 mg) was achieved by controlling the coating thickness to 700 μm. s / cm 2 ).

[0053] Note: Due to the limitations of conventional slurry loading processes for manufacturing positive electrode sheets on current collectors, the proportion of S-TMPTMA in the slurry cannot be further increased in this embodiment. If it is further increased, there will be significant material loss. If the coating thickness of the slurry is increased, the electrochemical performance of the resulting electrode sheet will be reduced. Therefore, this embodiment cannot maintain the same amount of S-TMPTMA in the positive electrode sheet as in Example 1.

[0054] Comparative Example 1 This comparative example is basically the same as Example 1, except that the amount of molten sulfur used is 4.5g and the amount of TMPTMA used is 0.5g.

[0055] Under these conditions, a small amount of yellow powder, which is elemental sulfur, can be observed after ball milling the final product. Therefore, an excessively high sulfur ratio will lead to a relatively low content of crosslinking monomers, preventing the sulfur reaction from being complete. The final product is a mixture with poor consistency, which does not meet the requirements for lithium-sulfur cathode materials. Therefore, no electrode was fabricated for testing.

[0056] Comparative Example 2 This comparative example is basically the same as Example 1, except that the amount of molten sulfur used is 2g and the amount of TMPTMA used is 3g.

[0057] Comparative Example 3 This comparative example is basically the same as Example 1, except that when preparing the printing ink, the S-TMPTMA powder obtained in Example 1 is replaced with an equal amount of sulfur powder with the same particle size.

[0058] Comparative Example 4 This comparative example is basically the same as Example 6, except that the S-TMPTMA powder is replaced with an equal amount of sulfur powder with the same particle size.

[0059] Experimental Example The positive electrode sheets prepared in each embodiment and comparative example were assembled into batteries, and their electrochemical performance was measured. Details are as follows: The above-mentioned positive electrode, separator, lithium sheet, and electrolyte were assembled into a CR2032 button cell. The cycle performance of each assembled cell at 0.2C was measured. The test results are shown in Table 1 and... Figures 6 to 9 As shown, Figures 6 to 9 The graphs show the cyclic performance statistics of Examples 1 and 6 and Comparative Examples 3 and 4, respectively.

[0060] Table 1. Statistical analysis of the electrochemical performance of batteries assembled in various embodiments and comparative examples.

[0061] From Table 1 and Figure 6 , 8It can be seen that the positive electrode assembly of the various embodiments of the present invention has better electrochemical performance.

[0062] Example 1 ( Figure 6 ) and Example 6 ( Figure 8 In comparison, the results showed that under high load conditions, the performance of the 3D printed cathode was significantly better than that of the thick electrode manufactured by the conventional slurry coating process, with an S-TMPTMA-based cathode (sulfur loading of approximately 12.5 mg). s / cm 2 The gram capacity is higher than 650 mAh / g s While conventional S-TMPTMA thick electrodes (sulfur loading approximately 10.2 mg) s / cm 2 Its capacity is only 450 mAh / g s Therefore, it is evident that the cathode fabricated by 3D printing exhibits better electrochemical performance compared to cathodes fabricated by conventional methods.

[0063] Example 1 ( Figure 6 ) and Comparative Example 3 ( Figure 7 In comparison, Example 6 ( Figure 8 ) and Comparative Example 4 ( Figure 9 The comparison results show that, for the positive electrode active material, the S-TMPTMA-based printed electrode has a higher specific capacity and a lower cycle capacity decay rate (776 mAh / g). s The 0.195% concentration is also significantly better than that of pure sulfur powder-based printing electrodes (678 mAh / g). s (0.327%). The specific capacity and capacity decay rate of the thick electrode prepared by the conventional process based on S-TMPTMA are also better than those prepared by the conventional process based on pure sulfur powder. This confirms that the introduction of TMPTMA (C=O functional group) has a certain inhibitory effect on the shuttle effect of lithium-sulfur batteries, and further improves the electrochemical performance of the cathode of high-load lithium-sulfur batteries.

[0064] In summary, the preparation method provided by this invention utilizes reverse sulfurization with trimethylolpropane trimethacrylate (TMPTMA) as a crosslinking agent to crosslink and polymerize molten sulfur, generating a sulfur-chain-dominated polymer S-TMPTMA. TMPTMA, as a crosslinking agent, introduces C=O functional groups. The O atoms in the C=O functional groups, as electron-rich active sites, can effectively chemically adsorb the relatively electron-poor lithium in the lithium polysulfide intermediate during the lithium-sulfur electrochemical reaction, thereby alleviating the dissolution of lithium polysulfides in ether-based electrolytes and reducing the influence of the "shuttle effect." Compared with pure sulfur powder, it can significantly improve the specific capacity and cycle capacity retention of lithium-sulfur batteries. In addition to the advantages mentioned above, the nonlinear and multi-unsaturated molecular structure of TMPTMA as a crosslinking agent ensures the rigidity of the obtained polymer S-TMPTMA, making the product S-TMPTMA a hard solid, which is beneficial for pulverizing into powder for use in the manufacture of positive electrode sheets.

[0065] In a preferred embodiment, S-TMPTMA is used to fabricate the positive electrode printing ink. Through 3D printing, a high-sulfur-loading, self-supporting lithium-sulfur battery positive electrode with a three-dimensional spatial structure can be prepared, exhibiting excellent electrical performance as a lithium-sulfur battery positive electrode. 3D printing allows for patterned design of the lithium-sulfur battery positive electrode, resulting in a well-defined spatial structure and channels that provide ample space for electrolyte wetting. Electrodes fabricated using 3D printing exhibit better electrochemical performance compared to electrodes prepared using conventional slurry coating methods.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a sulfur-containing polymer battery material, characterized in that, include: Molten sulfur and trimethylolpropane trimethacrylate were crosslinked and cured at a mass ratio of 1 to 4:

1. Methods for cross-linking and curing include: Trimethylolpropane trimethacrylate was mixed with molten sulfur under an inert gas atmosphere and reacted thoroughly at 165-180°C for 10-15 minutes to obtain a viscous liquid; then the viscous liquid was placed in an environment of 120-130°C for 20-28 hours to obtain a solid. The viscous liquid is obtained by reacting fully at a temperature of 165~180℃. The sulfur-containing polymer battery material is used to prepare the positive electrode sheet by 3D printing.

2. The preparation method according to claim 1, characterized in that, The inert gas is at least one of nitrogen and argon.

3. The preparation method according to claim 1, characterized in that, Crosslinking and curing to obtain a solid, followed by: The solid is pulverized into powder with an average particle size of 8~12μm.

4. The preparation method according to claim 1, characterized in that, The pulverizing method is ball milling.

5. A sulfur-containing polymer battery material, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 4.

6. A method for preparing a positive electrode sheet for lithium-sulfur batteries, characterized in that, A positive electrode sheet is prepared by three-dimensional printing using sulfur-containing polymer battery materials as described in claim 5.

7. The preparation method according to claim 6, characterized in that, include: A printing ink is provided, the printing ink having a solid content of 18-25%, and comprising the sulfur-containing polymer battery material; A preliminary product is obtained by 3D printing using the aforementioned printing ink as the raw material; The initial product is dried to obtain a grid-shaped positive electrode sheet.

8. The preparation method according to claim 7, characterized in that, It also includes at least one of the following features (1) to (5): (1) The printing ink also includes a dispersant, and the mass ratio of the sulfur-containing polymer battery material to the dispersant is 2~4:1; The dispersant is graphene oxide; (2) The thickness of the positive electrode sheet is 0.5~0.75mm; (3) The solvent in the printing ink is water; (4) The method of drying the initial product includes: first performing freeze drying to remove the solvent, and then heat treating it at 140~160℃ for 25~35min; (5) Before drying the primary product, the primary product is rapidly cooled using liquid nitrogen.

9. A positive electrode plate, characterized in that, It is prepared by the preparation method described in any one of claims 6 to 8.

10. A lithium-sulfur battery, characterized in that, Includes the positive electrode as described in claim 9.

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