Sulfur-containing polymer battery material, positive plate, preparation method of positive plate and lithium-sulfur battery

Abstract

The invention relates to the technical field of battery materials, and discloses a sulfur-containing polymer battery material, a positive plate, a preparation method of the positive plate and a lithium-sulfur battery. The preparation method of the sulfur-containing polymer battery material comprises the step of carrying out cross-linking curing on molten sulfur and trimethylolpropane trimethacrylate according to a mass ratio of (1-4): 1. An O atom in a C = O functional group in the polymer S-TMPTMA prepared by the method is used as an electron-rich active site and can effectively perform chemical adsorption on relatively electron-poor lithium in a lithium polysulfide intermediate in a lithium-sulfur electrochemical reaction process, so that the dissolution of lithium polysulfide in an ether-based electrolyte is relieved, and the influence of a shuttle effect is weakened. In a preferred embodiment, the polymer is prepared as printing ink to manufacture an electrode through three-dimensional printing, and the electrode has excellent electrochemical performance.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to a sulfur-containing polymer battery material, a positive electrode sheet and a preparation method thereof, and a lithium-sulfur battery. Background Art

[0002] Lithium-ion batteries, as a new clean energy source, have been widely used in various industries. However, they still face the bottleneck of 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 positive electrode material of lithium-sulfur batteries, has a theoretical capacity of up to 1675 mAh / g. However, pure sulfur powder as the positive electrode active material has a significant disadvantage, namely the "shuttle effect" of lithium-sulfur batteries. This effect is mainly attributed to the fact that lithium polysulfide intermediates produced during the electrochemical reaction between lithium and sulfur can dissolve in ether electrolytes. Due to the concentration gradient effect, the lithium polysulfide diffuses toward the negative electrode, where it is ultimately reduced to inactive sulfur, ultimately leading to rapid capacity decay in lithium-sulfur batteries. Therefore, the functional design of sulfur-based positive electrode materials is particularly important.

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

[0004] The object of the present invention is to provide a sulfur-containing polymer battery material, a positive electrode sheet and a preparation method thereof, and a lithium-sulfur battery, aiming to improve at least one problem mentioned in the background art.

[0005] The present invention is achieved in that: In a first aspect, an embodiment of the present invention provides a method for preparing a sulfur-containing polymer battery material, comprising: Molten sulfur and trimethylolpropane trimethacrylate are cross-linked and cured in a mass ratio of 1 to 4:1.

[0006] In an optional embodiment, the cross-linking and curing method includes: Trimethylolpropane trimethacrylate and molten sulfur are uniformly mixed under an inert gas protective atmosphere, and fully reacted at a temperature of 165-180° C. to obtain a viscous liquid; the viscous liquid is then placed in an environment of 120-130° C. to solidify to obtain a solid.

[0007] In an optional embodiment, 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) Fully react at a temperature of 165-180°C for 10-15 minutes to obtain a viscous liquid; (3) The curing time is 20~28h.

[0008] In an alternative embodiment, after crosslinking and curing to obtain a solid, the following steps are further included: Crushing the solid into a powder with an average particle size of 8 - 12 μm; Optionally, the crushing method is ball milling.

[0009] In a second aspect, an embodiment of the present invention provides a sulfur-containing polymer battery material prepared by using the preparation method provided in the embodiment of the present invention.

[0010] In a third aspect, an embodiment of the present invention provides a method for preparing a positive electrode sheet for a lithium-sulfur battery, using the sulfur-containing polymer battery material provided in the embodiment of the present invention to prepare the positive electrode sheet.

[0011] In an alternative embodiment, the preparation method includes: Providing printing ink with a solid content of 18 - 25%, which includes a sulfur-containing polymer battery material; Using the printing ink as a raw material for three-dimensional printing to obtain a primary product, Drying the primary product to obtain a grid-shaped positive electrode sheet.

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

[0013] In a fourth aspect, the present invention provides a positive electrode sheet prepared by using the preparation method according to any one of the foregoing embodiments.

[0014] In a fifth aspect, the present invention provides a lithium-sulfur battery including the positive electrode sheet according to the foregoing embodiment.

[0015] The present invention has the following beneficial effects: The preparation method provided by the present invention uses the inverse vulcanization method to crosslink and polymerize molten sulfur with trimethylolpropane trimethacrylate (TMPTMA) as a crosslinking agent to generate a polymer S-TMPTMA mainly composed of sulfur chains. TMPTMA introduces C=O functional groups as a crosslinking agent, and the O atom in the C=O functional group can effectively chemically adsorb the relatively electron-deficient lithium in the polysulfide intermediate during the lithium-sulfur electrochemical reaction process, thereby alleviating the dissolution of polysulfide in the ether-based electrolyte and weakening the influence of the "shuttle effect". Compared with pure sulfur powder, it can significantly improve the specific capacity utilization and cycle capacity retention rate of lithium-sulfur batteries; in addition to the above-mentioned advantages of using TMPTMA as a crosslinking agent, its non-linear and poly-unsaturated bond molecular structure can ensure the rigidity of the prepared polymer S-TMPTMA, making the product S-TMPTMA present a hard solid state, which is beneficial for crushing into powder for use in manufacturing the positive electrode sheet.

[0016] In some preferred embodiments, S-TMPTMA is made into a positive electrode printing ink. Through 3D printing, a self-supporting lithium-sulfur battery positive electrode with a three-dimensional spatial structure and a high sulfur loading can be prepared, which has good electrical performance as the positive electrode of a lithium-sulfur battery. The 3D printing preparation of the lithium-sulfur battery positive electrode can carry out pattern design, making the positive electrode have a good spatial structure and pores, giving sufficient infiltration space for the electrolyte. The electrode prepared by 3D printing has better electrochemical performance than the electrode prepared by the conventional slurry coating method. Brief Description of the Drawings

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use 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 therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0018] Figure 1 It is the reaction schematic diagram of the synthesis of S-TMPTMA; Figure 2 It is the schematic diagram of the operation mode during the synthesis of S-TMPTMA; Figure 3 It is the SEM image of S-TMPTMA powder; Figure 4 It is the appearance diagram of the self-supporting electrode prepared in Example 1; Figure 5 It is the partial SEM image of the self-supporting electrode prepared in Example 1; Figure 6 It is the cycle performance curve diagram of Example 1; Figure 7 It is the cyclic performance curve graph of Example 6; Figure 8 It is the cyclic performance curve graph of Comparative Example 3; Figure 9 It is the cyclic performance curve graph of Comparative Example 4. Specific Embodiments

[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. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0020] Based on the problems existing in the prior art, the inventors have the following considerations: The sulfur-containing polymer prepared by the inverse vulcanization (retrograde vulcanization) method is a potential cathode material for lithium-sulfur batteries. The organic framework it contains can effectively physically and chemically adsorb polysulfide through functional design, thereby achieving the function of alleviating the "shuttle effect". In addition, due to the intrinsically slow reaction kinetics of the sulfur reduction reaction in lithium-sulfur batteries, the sulfur loading of the cathode sheet of lithium-sulfur batteries is generally low. If the sulfur loading is too high, the thickness of the electrode sheet increases, which may lead to insufficient infiltration of the electrolyte, thereby affecting the electrochemistry reaction kinetics and the battery capacity, and ultimately affecting the overall energy density of the battery, causing a great obstacle to the commercialization of lithium-sulfur batteries. Therefore, the preparation of cathode sheets with high sulfur loading needs to be optimized in order to achieve a higher specific capacity.

[0021] The sulfur-containing polymer battery materials, cathode sheets, their preparation methods, and lithium-sulfur batteries provided by the embodiments of the present invention will be specifically described below.

[0022] The preparation method of the sulfur-containing polymer battery material provided by the embodiment of the present invention includes: Crosslinking and curing molten sulfur and trimethylolpropane trimethacrylate in a mass ratio of 3.5 - 4.5:1.

[0023] In the preparation method provided by the embodiment of the present invention, trimethylolpropane trimethacrylate (TMPTMA) is used as a crosslinking agent to crosslink and polymerize molten sulfur to generate a polymer S-TMPTMA mainly composed of sulfur chains. TMPTMA introduces the C=O functional group as a crosslinking agent. The O atom in the C=O functional group can effectively chemically adsorb the relatively electron-deficient lithium in the polysulfide intermediate during the lithium-sulfur electrochemical reaction process as an electron-rich active site, thereby alleviating the dissolution of polysulfide in the ether-based electrolyte and weakening the influence of the "shuttle effect". Compared with pure sulfur powder, the specific capacity and cycle capacity retention rate of the lithium-sulfur battery can be significantly improved; in addition to the above-mentioned advantages of using TMPTMA as a crosslinking agent, its non-linear and multi-unsaturated bond molecular structure can ensure the rigidity of the prepared polymer S-TMPTMA, making the product S-TMPTMA present a hard solid state, which is beneficial to being crushed into powder for use in the manufacture of the positive electrode sheet.

[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 the present invention. If there is too much molten sulfur, unreacted elemental sulfur will exist in the product, forming a mixture, which does not meet the requirements of the positive electrode active material of the lithium-sulfur battery; if there is too little molten sulfur, the content of active sulfur in the product will be too low, and the subsequent electrical performance will not be good.

[0025] Specifically, the preparation method includes: S1. Provide molten sulfur Place sulfur powder in a container, protect it with an inert gas, raise the temperature of the container to 115 - 140 °C (such as 115 °C, 120 °C, 125 °C, 130 °C or 140 °C), and use a magnetic stirrer and a magnetic stirrer to slowly stir and disperse (the rotation speed can be, for example, 250 - 350 rpm) until it can be observed that the sulfur powder has completely melted and is a bright yellow liquid, and there is no obvious powdery object in the glass bottle.

[0026] S2. Crosslinking and curing The first-step reaction: The reaction principle is as Figure 1 shown. While maintaining the protection of the inert gas, quickly drop TMPTMA into the container filled with molten sulfur, increase the stirring speed (for example, 650 - 750 rpm), raise the temperature of the container to 165 - 180 °C (such as 165 °C, 170 °C, 175 °C or 185 °C), and react for 10 - 15 minutes. At this time, the reactant presents as a brown viscous liquid; The second-step reaction: Pour the brown viscous liquid into a high-temperature resistant silicone mold, and then place it in an oven at 120 - 130 °C (such as 120 °C, 125 °C or 130 °C) for curing for 20 - 28 hours (such as 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] The molten sulfur has a cyclic structure of S8. In the first step of the reaction, the temperature is raised to 165 - 180 °C to open the sulfur ring to form sulfur chains, and sulfur free radicals are formed at both ends of the sulfur chains. At this time, the sulfur chains containing sulfur free radicals will also polymerize with each other to form long sulfur chains, and the free radicals are still carried at the ends; by adding the small molecule reaction crosslinking agent TMPTMA, the sulfur free radicals will attack and open the double bond of TMPTMA, and graft sulfur chains at both ends of the double bond respectively to form a polymer. However, the polymer product obtained directly by cooling is not stable, because there are a large number of long sulfur chains in the structure, and backbite behavior may occur during the cooling process, that is, the sulfur ring structure is formed again and precipitated, resulting in the final product being a mixture rather than a pure polymer, and the repeatability of the product is poor. In the second step of the reaction, the mixture obtained in the first step of the reaction is cured at 120 - 130 °C, so that the sulfur chains can still be slowly reconstructed during this process, and finally a stable polymer structure is formed without the precipitation of elemental sulfur, ensuring the consistency of the final product.

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

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

[0031] The preparation method for the positive electrode applied to a lithium-sulfur battery provided by the embodiment of the present invention uses the sulfur-containing polymer battery material provided by the embodiment of the present invention to prepare the positive electrode. Since the positive electrode obtained by this method is prepared by using the sulfur-containing polymer battery material provided by the embodiment of the present invention, the battery has better electrochemical performance after being applied in the lithium-sulfur battery.

[0032] Specifically, the preparation method includes: S1. Providing printing ink The printing ink includes a solvent and a sulfur-containing polymer battery material. Optionally, in order to ensure the full dispersion of the sulfur-containing polymer battery material, the printing ink may further include a dispersant.

[0033] Optionally, the solvent can be water or other organic solvents.

[0034] When the solvent is water, the printing ink is an aqueous system. In order to ensure the full dispersion of the conductive carbon material, the dispersant can be selected from graphene oxide, and graphene oxide can not only act as a dispersant but also play the role of a conductive agent.

[0035] When the solvent is other organic solvents, the printing ink is an oily system, and other conventional dispersants can be added to the components to help the components in the ink disperse evenly with each other.

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

[0037] Taking GO as the dispersant as an example, the specific preparation method is as follows: Shear and grind the GO layered material to obtain small-particle-size GO powder with an average particle size of 3 μm; Slowly add the small-particle-size GO powder into deionized water, and with high-speed stirring (such as 1500 - 2500 rpm), form a stable GO dispersion. Then, gradually and slowly add the S-TMPTMA powder into the above GO dispersion, and quickly cool it to room temperature after stirring to form a stable printing ink. Seal the prepared printing ink in a cavity made of PTFE material for subsequent printing.

[0038] S2. Three-dimensional printing Add the printing ink into a syringe dedicated for three-dimensional printing. Then, install the syringe into a three-dimensional printing device (Aerotech). Then, use CAD software to design the printing pattern, which is generally preferably designed as a grid shape.

[0039] Optionally, the thickness of the grid-shaped positive electrode is 0.5 - 0.75 mm (such as 0.5 mm, 0.6 mm or 0.75 mm), and the thickness of the positive electrode can be controlled by the number of printing layers. After designing the shape and size, the electrode can be printed on a Teflon substrate. Immediately after printing, cool the electrode with liquid nitrogen and transfer it to a freeze-drying oven for freeze-drying for 36 - 48 h to completely remove the solvent brought in by the printing ink and ensure the self-supportability of the electrode. Then, heat-treat the dried electrode at 40 - 160 °C for 25 - 35 min to achieve closer contact between the sulfur active material and the conductive framework.

[0040] Aiming at the problem that the electrochemical performance of a high-loading lithium-sulfur positive electrode manufactured by the existing homogenization coating method is relatively poor, a printing ink is prepared based on a sulfur-rich polymer, and then a high-loading self-supporting lithium-sulfur positive electrode with a good spatial structure is printed by using 3D printing technology. This positive electrode is conducive to the full infiltration of the electrolyte, thereby building a better lithium-ion transmission channel and ultimately significantly improving the specific capacity performance of the lithium-sulfur positive electrode.

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

[0042] The lithium-sulfur battery provided by the embodiment of the present invention includes the positive electrode provided by the embodiment of the present invention.

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

[0044] Example 1 As Figure 2 shown, first, 4 g of sulfur powder was added to a 14 mL high-temperature-resistant cylindrical glass sample bottle, and an atmosphere protection was carried out using a nitrogen balloon. The temperature was raised to 135 °C, and slow stirring and dispersion were carried out using a magnetic stirrer and a magnetic stirrer (rotation speed 300 rpm) until it could be observed that the sulfur powder had completely melted and was a bright yellow liquid, and there was no obvious powdery substance in the glass bottle.

[0045] 1 g of the TMPTMA liquid sample was quickly dropped into the glass bottle, the nitrogen atmosphere was maintained, the stirring speed was increased to 700 rpm, and the reaction temperature was increased to 165 °C. The reaction was carried out for 15 min. At this time, the reactants had become a brown viscous liquid. The sample was poured into a high-temperature-resistant silicone mold and cured in an oven at 130 °C for 24 h to obtain a black hard solid, which was the S-TMPTMA polymer. The solid was ball-milled to make the particle size ground to an average particle size of about 10 μm, and the preparation of the S-TMPTMA polymer powder was completed. The scanning electron microscope (SEM) photograph of the product is as Figure 3 shown.

[0046] The GO layered material was sheared and ground and separated to obtain particles with an average particle size of 3 μm, which were small in size and relatively uniform. Then, 0.5 g of the ground GO sheet material was slowly added to 10 g of deionized water, and high-speed stirring (2000 rpm) was carried out to form a stable GO dispersion liquid. Then, 1.5 g of the S-TMPTMA polymer powder was slowly added to the above GO dispersion liquid, and after stirring, it was quickly cooled to room temperature to form a stable printing ink. The mass ratio of S-TMPTMA to GO was 3:1. The prepared printing ink was sealed in a PTFE material cavity and prepared for subsequent printing.

[0047] The printing ink was added to a 10 mL three-dimensional printing special syringe with a needle diameter of 0.25 mm. Then, the syringe was installed in a three-dimensional printing device (Aerotech). Then, the printing pattern was designed using CAD software, and the designed pattern was an 8*8 mm square grid pattern with an electrode thickness of 0.5 mm (the number of electrode printing layers was two). The electrode was printed on a Teflon material substrate according to the above dimensions. After printing, the electrode was immediately cooled with liquid nitrogen and transferred to a freeze-drying oven for freeze-drying for 48 hours to completely remove water. Then, the electrode was heated in an oven at 150 °C for 30 min to achieve closer contact between the sulfur active material and the conductive framework, and finally, the prepared S-TMPTMA polymer-based self-supporting electrode ( Figure 4), the sulfur loading of the electrode is about 12.5 mg s / cm 2 , scanning electron microscope (SEM) photos such as Figure 5 shown.

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

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

[0050] Example 4 This embodiment is basically the same as the first embodiment, except that: During the reaction, 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 170°C. The reaction was allowed to proceed for 13 minutes, at which point the reactant became a tan, viscous liquid. This sample was then poured into a high-temperature-resistant silicone mold and cured in a 125°C oven for 24 hours to yield a black, hard solid, S-TMPTMA polymer.

[0051] Example 5 This embodiment is basically the same as the first embodiment, except that: During the reaction, 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 180°C. The reaction was allowed to proceed for 10 minutes, at which point the reactant became a tan, viscous liquid. This sample was then poured into a high-temperature-resistant silicone mold and cured in a 120°C oven for 24 hours to yield a black, hard solid, 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 is different from that in embodiment 1, specifically: S-TMPTMA, carbon black conductive agent and PVDF binder were ground and mixed in a mass ratio of 7:2:1. The ground mixed powder was evenly dispersed in NMP solvent to make a slurry. The slurry was then evenly coated on the surface of aluminum foil and then placed in a vacuum drying oven at 60°C for drying. After drying, the positive electrode was obtained by cutting. A high sulfur loading (about 10.2 mg) was achieved by controlling the coating thickness to 700 μm. s / cm 2 ).

[0053] Note: Due to the limitations of the conventional process for manufacturing the positive electrode sheet by loading the slurry on the current collector, it is difficult to further increase the proportion of S-TMPTMA in the slurry based on this embodiment. If further increased, obvious material dropping will occur. If the coating thickness of the slurry is increased, the electrochemical performance of the prepared electrode sheet will decrease. Therefore, compared with Example 1, this embodiment cannot maintain the same amount of S-TMPTMA used in the positive electrode sheet.

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

[0055] Under these conditions, a small amount of yellow fine powder, i.e., elemental sulfur, can be observed after ball milling the final product. Therefore, too high a sulfur ratio will result in a relatively low content of cross-linking monomers and cannot completely react sulfur. The final product is a mixture with poor product consistency, which does not meet the requirements of lithium-sulfur positive electrode materials. Therefore, electrodes were not 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 2 g, and the amount of TMPTMA used is 3 g.

[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 prepared in Example 1 was 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 was replaced with an equal amount of sulfur powder with the same particle size.

[0059] Experimental Example The positive electrode sheets prepared in each example and comparative example were assembled into batteries to measure the electrochemical performance. Specifically as follows: The above positive electrode, separator, lithium sheet, and electrolyte were assembled into a CR2032 coin cell. The cycling performance of each assembled battery at 0.2C was measured. The test results are shown in Table 1 and Figures 6 to 9 as shown Figures 6 to 9 are the cycling performance statistical graphs of Example 1, Example 6, Comparative Example 3, and Comparative Example 4 respectively.

[0060] Table 1 Statistical data of the electrochemical performance of the batteries assembled in each example and comparative example

[0061] From Table 1 and Figure 6 and 8It can be seen that the cathodes prepared in the various embodiments of the present invention have excellent electrochemical performance when assembled into batteries.

[0062] Comparing Example 1 ( Figure 6 ), with Example 6 ( Figure 8 ), the results show that under high-load conditions, the performance of the 3D-printed cathode is significantly better than that of the thick electrode manufactured by the conventional slurry coating process. The specific capacity of the S-TMPTMA-based (sulfur loading of about 12.5 mg s / cm 2 ) is higher than 650 mAh / g s , while the specific capacity of the conventional S-TMPTMA thick electrode (sulfur loading of about 10.2 mg s / cm 2 ) is only 450 mAh / g s . Thus, it can be seen that the cathode prepared by 3D printing has better electrochemical performance than the cathode prepared by the conventional method.

[0063] Comparing Example 1 ( Figure 6 ) with Comparative Example 3 ( Figure 7 ), and Example 6 ( Figure 8 ) with Comparative Example 4 ( Figure 9 ), the results show that for the cathode active material, the specific capacity and the cyclic capacity decay rate of the S-TMPTMA-based printed electrode (776 mAh / g s , 0.195%) are also significantly better than those of the pure sulfur powder-based printed electrode (678 mAh / g s , 0.327%). The specific capacity and the capacity decay rate of the thick electrode prepared by the conventional process based on S-TMPTMA are also better than those of the thick electrode 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, further improving the electrochemical performance of the cathode of high-load lithium-sulfur batteries.

[0064] In summary, the preparation method provided by the present invention uses the inverse vulcanization method to crosslink and polymerize molten sulfur with trimethylolpropane trimethacrylate (TMPTMA) as the crosslinking agent, generating a polymer S-TMPTMA mainly composed of sulfur chains. TMPTMA as the crosslinking agent introduces the C=O functional group, and the O atom in the C=O functional group can effectively chemically adsorb the relatively electron-deficient lithium in the polysulfide intermediate during the lithium-sulfur electrochemical reaction process as an electron-rich active site, thereby alleviating the dissolution of polysulfide in the ether-based electrolyte and weakening the influence of the "shuttle effect". Compared with pure sulfur powder, it can significantly improve the gravimetric capacity and cycle capacity retention rate of the lithium-sulfur battery; in addition to the above-mentioned advantages of using TMPTMA as the crosslinking agent, its non-linear and multi-unsaturated bond molecular structure can ensure the rigidity of the prepared polymer S-TMPTMA, making the product S-TMPTMA present a hard solid state, which is beneficial for crushing into powder for use in manufacturing the positive electrode sheet.

[0065] In a preferred embodiment, S-TMPTMA is made into a positive electrode printing ink. Through 3D printing, a self-supporting lithium-sulfur battery positive electrode with a three-dimensional spatial structure and a high sulfur loading can be prepared, which has good electrical performance as the positive electrode of a lithium-sulfur battery. The 3D printing preparation of the lithium-sulfur battery positive electrode can be pattern-designed, enabling the positive electrode to have a good spatial structure and pores, giving sufficient wetting space for the electrolyte. The electrode prepared by 3D printing has better electrochemical performance than the electrode prepared by the conventional slurry coating method.

[0066] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a sulfur-containing polymer battery material, characterized in that Comprising: Crosslinking and curing molten sulfur and trimethylolpropane trimethacrylate in a mass ratio of 1 - 4:

1.

2. The preparation method according to claim 1, wherein The methods of crosslinking and curing include: Mixing trimethylolpropane trimethacrylate and molten sulfur evenly under an inert gas protection atmosphere, and fully reacting at a temperature of 165 - 180 °C to obtain a viscous liquid; then curing the viscous liquid in an environment of 120 - 130 °C to obtain a solid.

3. The preparation method according to claim 2, characterized in that, Comprising at least one of the following technical features (1) - (3): (1) The inert gas is at least one of nitrogen and argon; (2) Reacting fully for 10 - 15 min at a temperature of 165 - 180 °C to obtain the viscous liquid; (3) The curing time is 20 - 28 h.

4. The preparation method according to claim 1, wherein After crosslinking and curing to obtain a solid, it further includes: Crushing the solid into a powder with an average particle size of 8 - 12 μm; Optionally, the crushing method is ball milling.

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

6. A preparation method of a positive electrode sheet applied to a lithium-sulfur battery, characterized in that, Using the sulfur-containing polymer battery material described in claim 5 to prepare a positive electrode sheet.

7. The preparation method according to claim 6, wherein Comprising: Providing printing ink, the solid content of the printing ink is 18 - 25%, and it includes the sulfur-containing polymer battery material; Performing three-dimensional printing with the printing ink as a raw material to obtain a primary product; Drying the primary product to obtain a grid-shaped positive electrode sheet.

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

9. A positive electrode sheet, characterized in that, Prepared by the preparation method described in any one of claims 6 - 8.

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

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