Composite material, preparation method thereof and aluminum-sulfur battery

Abstract

The invention provides a composite material, a preparation method thereof and an aluminum-sulfur battery, and belongs to the technical field of battery materials. The composite material comprises a composite carrier and elemental sulfur loaded on the composite carrier, the composite carrier comprises a carbon carrier and a PMo12-based metal organic framework growing on the carbon carrier, and the PMo12-based metal organic framework comprises a metal organic framework with a pore structure and phosphomolybdic acid encapsulated in the pore structure. The composite material provided by the invention has excellent conductivity, high sulfur loading capacity, strong polysulfide anchoring capability and efficient sulfur conversion catalytic activity, and is beneficial to improving the cycle performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, specifically to a composite material, its preparation method, and an aluminum-sulfur battery. Background Technology

[0002] Since the 1980s, aluminum-sulfur batteries have been developed due to the high energy density and +3 valence of aluminum. Aluminum and sulfur have high theoretical volumetric capacity, making them potential candidates for next-generation green energy storage devices.

[0003] However, sulfur produces polysulfides during discharge, and these polysulfides dissolve in the electrolyte, which can easily cause problems such as shuttle effect and poor sulfur utilization, resulting in poor cycle performance of aluminum-sulfur batteries. Summary of the Invention

[0004] In view of the technical problems existing in the background art, this application provides a composite material, a method for preparing the same, and an aluminum-sulfur battery, aiming to solve the technical problem of poor cycle performance of existing aluminum-sulfur batteries due to the generation of polysulfides.

[0005] In a first aspect, embodiments of this application provide a composite material comprising a composite support and elemental sulfur loaded on the composite support, wherein the composite support comprises a carbon support and PMo grown on the carbon support. 12 The base metal-organic framework, the PMo 12 The base metal-organic framework includes a metal-organic framework with a porous structure and phosphomolybdic acid encapsulated within the porous structure.

[0006] Optionally, in some embodiments of this application, the carbon support includes one or more of one-dimensional carbon materials, two-dimensional carbon materials, and three-dimensional porous carbon frameworks.

[0007] Optionally, in some embodiments of this application, the metal-organic framework has a metal element and an organic ligand, wherein the metal element includes one or more of copper, cobalt, iron, and zinc, and the organic ligand is derived from one or more of pyromellitic acid and 2-methylimidazole.

[0008] Optionally, in some embodiments of this application, the carbon support in the composite material has a mass percentage content of 5-10%, the elemental sulfur has a mass percentage content of 50-80%, and the balance is PMo. 12 Metal-organic frameworks.

[0009] Optionally, in some embodiments of this application, the one-dimensional carbon material includes one or more of carbon nanotubes and carbon nanofibers; the two-dimensional carbon material includes one or more of reduced graphene oxide and graphene sheets; and the three-dimensional porous carbon framework includes one or more of carbon nanofiber sponges, carbon nanofoams, and hierarchical porous carbon materials.

[0010] Secondly, embodiments of this application propose a method for preparing the composite material as described above, comprising the following steps: Construct a carbon support and load PMo onto the carbon support. 12 Based on metal-organic frameworks, composite supports were obtained; The composite carrier is mixed with elemental sulfur to form a sulfur composite, thus obtaining a composite material.

[0011] Optionally, in some embodiments of this application, the mass ratio of the composite carrier to the elemental sulfur is 1:1.1~4.

[0012] Optionally, in some embodiments of this application, the step of mixing the composite carrier with elemental sulfur to obtain a composite material includes: mixing the composite carrier with elemental sulfur and heat-treating it at 155~250℃ for 2~12h in an inert atmosphere to obtain the composite material; or, mixing the composite carrier, elemental sulfur and an organic solvent, stirring at 25~50℃ for 6~24h, then washing with the organic solvent and drying at 60~100℃ for 8~12h to obtain the composite material.

[0013] Optionally, in some embodiments of this application, a carbon support is constructed and PMo is loaded onto the carbon support. 12 The steps for obtaining a composite support from a metal-organic framework include: Metal salt, organic ligand, phosphomolybdic acid and water are mixed to obtain a precursor mixture. Then, a carbon support is mixed with the precursor mixture and reacted at 80~180℃ for 6~72h to obtain a composite support. The carbon support is a two-dimensional carbon material or a three-dimensional porous carbon framework. or, A composite carrier is obtained by mixing a one-dimensional carbon material precursor, a metal salt, an organic ligand, phosphomolybdic acid, and a solvent, and reacting the mixture. The one-dimensional carbon material precursor includes one or more of polyvinylidene fluoride, polyacrylonitrile, and biomass polymers.

[0014] Optionally, in some embodiments of this application, the metal salt includes one or more of copper salt, cobalt salt, iron salt, and zinc salt.

[0015] Optionally, in some embodiments of this application, the organic ligand includes one or more of pyromellitic acid and 2-methylimidazole.

[0016] Optionally, in some embodiments of this application, the mass ratio of the metal salt, the organic ligand, and the phosphomolybdic acid is 1:2~3:3~6.

[0017] Optionally, in some embodiments of this application, in the step of mixing a metal salt, an organic ligand, phosphomolybdic acid and water to obtain a precursor mixture, and then mixing a carbon support with the precursor mixture and reacting at 80~180°C for 6~72h to obtain a composite support, the mass ratio of phosphomolybdic acid to the carbon support is 1:1~3.

[0018] Optionally, in some embodiments of this application, in the step of mixing a one-dimensional carbon material precursor, a metal salt, an organic ligand, phosphomolybdic acid, and a solvent to react and obtain a composite support: The mass ratio of the phosphomolybdic acid to the one-dimensional carbon material precursor is 1:6~8.

[0019] Optionally, in some embodiments of this application, in the step of mixing a one-dimensional carbon material precursor, a metal salt, an organic ligand, phosphomolybdic acid, and a solvent to react and obtain a composite support: The reaction is carried out by electrospinning in an electric field environment with an electric field strength of 0.5~3kV / cm.

[0020] Optionally, in some embodiments of this application, the solvent includes one or more of dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0021] Thirdly, embodiments of this application propose an aluminum-sulfur battery comprising the composite material described above.

[0022] The technical solution proposed in this application has the following beneficial effects: This application provides a composite material that combines excellent conductivity, high sulfur loading, strong polysulfide anchoring ability, and efficient sulfur conversion catalytic activity, which helps to improve the cycle performance of the battery. Specifically, it combines a carbon support with a high specific surface area and a PMo composite material with a high specific surface area and abundant pore structure. 12 The combination of metal-organic frameworks to construct a composite carrier not only effectively enhances the multi-level electron transport pathway and improves the conductivity of the composite material, but also provides abundant sulfur adsorption sites and buffers the volume change space of sulfur. This allows the composite material to load more sulfur and improve the volume change problem of the battery. At the same time, it provides abundant Lewis acid sites, which can strongly adsorb sulfides generated during the discharge of aluminum-sulfur batteries, thereby suppressing the shuttle effect. In addition, the multi-acid structure also provides abundant redox sites, which helps to catalyze the conversion reaction of sulfur and accelerate the reaction kinetics.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0025] Figure 1 TEM image of the composite material obtained in Example 1; Figure 2 The nitrogen adsorption-desorption isotherm and pore size distribution of the composite material prepared in Example 1 are shown. Figure 3 The graph shows the cycle performance test results of the aluminum-sulfur battery based on the composite material of Example 1. Figure 4 TEM image of the composite material obtained in Example 2; Figure 5 The nitrogen adsorption-desorption isotherm and pore size distribution of the composite material prepared in Example 3 are shown. Figure 6 TEM image of the composite material prepared in Comparative Example 1; Figure 7 The graph shows the cycle performance test results of the aluminum-sulfur battery based on the composite material of Comparative Example 1. Figure 8 TEM image of the composite material prepared in Comparative Example 2; Figure 9 The graph shows the cycle performance test results of the aluminum-sulfur battery based on the composite material of Comparative Example 2. Detailed Implementation

[0026] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0028] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0029] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0030] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0031] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0032] In the description of the embodiments of this application, the term "at least one" refers to one or more, "more than one" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces). "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0033] During operation, sulfur in aluminum-sulfur batteries forms polysulfide intermediates in the electrodes. These polysulfides dissolve in the electrolyte, which not only easily causes a shuttle effect, reducing sulfur utilization, but also increases the electrolyte concentration. These issues result in low coulombic efficiency and poor cycle performance in aluminum-sulfur batteries.

[0034] In view of this, in a first aspect, embodiments of this application provide a composite material, comprising a composite support and elemental sulfur loaded on the composite support, wherein the composite support comprises a carbon support and PMo grown on the carbon support. 12 The base metal-organic framework, the PMo 12 The basic metal-organic framework includes a metal-organic framework with a porous structure and phosphomolybdic acid (i.e., Keggin-type H3PMo) encapsulated within the porous structure. 12 O 40 abbreviated as PMo 12 ).

[0035] This composite material combines a carbon support with a high specific surface area and PMo with a high specific surface area and abundant pore structure. 12 A composite support was constructed by combining a metal-organic framework, and then elemental sulfur was loaded onto the composite support. The carbon support provides an electron transport pathway, buffers the volume change space of sulfur, and acts as a PMo (phosphorus oxide). 12 Substrates for metal-organic framework growth; PMo 12 Metal-organic frameworks (MOFs) possess high specific surface area and abundant pore structures. These pore structures can confine sulfur, thereby fixing it within the pores and reducing its dissolution. Their polyacid components also provide abundant Lewis acid sites and redox sites. The former strongly adsorbs sulfides generated during aluminum-sulfur battery discharge, reducing sulfide dissolution and thus suppressing the shuttle effect and mitigating the problem of high electrolyte concentration. The latter helps catalyze sulfur conversion reactions and accelerates reaction kinetics. PMo 12 The combination of a metal-organic framework (MOF) and a carbon support creates a larger specific surface area, allowing for the loading of more elemental sulfur and effectively enhancing multi-level electron transport pathways, thereby improving the conductivity of the composite material. In summary, this application provides a composite material that combines excellent conductivity, high sulfur loading, strong polysulfide anchoring ability, and efficient sulfur conversion catalytic activity, contributing to improved battery cycle performance.

[0036] In some embodiments of this application, the carbon support can refer to a multidimensional carbon material, such as one or more of one-dimensional carbon materials, two-dimensional carbon materials, and three-dimensional porous carbon frameworks. It is understood that when the carbon support is multiple of the carbon materials listed above, it can be a mixture of multiple carbon materials or a composite of multiple carbon materials, which helps to construct a multi-level conductive network and provide abundant sulfur adsorption sites. In some specific embodiments, the one-dimensional carbon material can include, but is not limited to, one or more of carbon nanotubes (CNTs) and carbon nanofibers (CNFs); the two-dimensional carbon material can include, but is not limited to, one or more of reduced graphene oxide (rGO) and graphene sheets; the three-dimensional porous carbon framework can include, but is not limited to, one or more of carbon nanosponges, carbon nanofoams, and hierarchical porous carbon materials.

[0037] The metal-organic framework refers to a crystalline porous material with a periodic network structure, formed by the self-assembly of metal ions or metal clusters and organic ligands through coordination bonds. It contains a metal element and an organic ligand. In some embodiments, the metal element may include, but is not limited to, one or more of copper, cobalt, iron, and zinc, and the organic ligand may be derived from, but is not limited to, one or more of trimesic acid and 2-methylimidazole.

[0038] In some embodiments of this application, the carbon support in the composite material has a mass percentage of 5-10%, the elemental sulfur has a mass percentage of 50-80%, and the balance is PMo. 12 Metal-organic frameworks. By controlling the proportions of the three components within the aforementioned range, the conductivity, sulfur loading, sulfide anchoring ability, and sulfur conversion catalytic activity of the composite material can be improved in a balanced manner.

[0039] Furthermore, in a second aspect, embodiments of this application provide a method for preparing a composite material, which can obtain the composite material described above. The preparation method includes the following steps: S10, Construct a carbon support and load PMo onto the carbon support. 12 Based on metal-organic frameworks, composite supports were obtained; S20, the composite carrier is mixed with elemental sulfur to perform sulfur composite, thereby obtaining a composite material.

[0040] This preparation method has simple and easy-to-control process steps, and can effectively prepare carbon-supported PMo. 12 The product obtained by the metal-organic framework is a composite carrier, and the composite material is loaded with elemental sulfur in its pores or on its surface.

[0041] Step S10 is mainly used to construct the composite support. Specifically, depending on the type of carbon support, one can choose to first form or provide a carbon support and then grow PMo on its surface.12 The metal-organic framework can then be used to obtain a composite support, or alternatively, a carbon support precursor and PMo can be combined. 12 Precursors for metal-organic frameworks are mixed, and carbon supports and PMo are constructed simultaneously. 12 Based on metal-organic frameworks, composite supports are obtained. For example: In some embodiments, when the carbon support is a two-dimensional carbon material or a three-dimensional porous carbon framework, step S10 may specifically include: S10a, mixing a metal salt, an organic ligand, phosphomolybdic acid and water to obtain a precursor mixture, then mixing the carbon support with the precursor mixture and reacting at 80~180°C for 6~72h to obtain a composite support.

[0042] The metal salt may include, but is not limited to, one or more of copper salts, cobalt salts, iron salts, and zinc salts. The organic ligand may include, but is not limited to, one or more of trimesic acid and 2-methylimidazole.

[0043] The amounts of metal salt, organic ligand, phosphomolybdic acid, and carbon support fed in the experiment can satisfy the following: the mass ratio of the metal salt, the organic ligand, and the phosphomolybdic acid is 1:2~3:3~6; and the mass ratio of the phosphomolybdic acid to the carbon support is 1:1~3.

[0044] In other embodiments, when the carbon support is a one-dimensional carbon material, step S10 may specifically include: S10b, mixing the one-dimensional carbon material precursor, metal salt, organic ligand, phosphomolybdic acid, and solvent to react and obtain a composite support. The one-dimensional carbon material precursor refers to a precursor capable of forming a one-dimensional carbon material, and may include, but is not limited to, one or more of polyvinylidene fluoride, polyacrylonitrile, and biomass polymers. The biomass polymers may include, but are not limited to, one or more of cellulose, lignin, and chitosan.

[0045] The metal salt may include, but is not limited to, one or more of copper, cobalt, iron, and zinc salts. The anion in the metal salt may be acetate, nitrate, chloride, sulfate, etc. Specifically, the metal salt may be copper acetate, cobalt acetate, ferric acetate, zinc acetate, copper nitrate, cobalt nitrate, ferric nitrate, zinc nitrate, copper chloride, cobalt chloride, ferric chloride, zinc chloride, copper sulfate, cobalt sulfate, ferric sulfate, zinc sulfate, etc. The organic ligand may include, but is not limited to, one or more of trimesic acid and 2-methylimidazole. The solvent may include, but is not limited to, one or more of dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

[0046] The amounts of metal salt, organic ligand, phosphomolybdic acid, and one-dimensional carbon material precursor can satisfy the following: the mass ratio of the metal salt, the organic ligand, and the phosphomolybdic acid is 1:2~3:3~6; and the mass ratio of the phosphomolybdic acid to the one-dimensional carbon material precursor is 1:6~8.

[0047] In step S10b, the reaction can be electrospinning, that is, mixing a one-dimensional carbon material precursor, a metal salt, an organic ligand, phosphomolybdic acid, and a solvent, and then carrying out the reaction by electrospinning in an electric field environment with an electric field strength of 0.5~3kV / cm.

[0048] In some embodiments of this application, after constructing the composite carrier (e.g., after completing the solvothermal reaction of step S10a, or the electrospinning reaction of step S10b), the reaction product can be cooled, washed with DMF, ethanol, etc., and then vacuum dried at 60°C to 120°C.

[0049] In addition, in some embodiments, the carbon support may be pretreated, for example, by cleaning the carbon support with water or alcohol solvent.

[0050] Step S20 is used to load elemental sulfur onto the composite support. Specifically, this can be achieved using a melt-diffusion method. For example: In some embodiments, step S20 can be implemented by the following steps: S20a, mixing the composite carrier with elemental sulfur, and heat-treating it at 155~250°C for 2~12 hours in an inert atmosphere to obtain the composite material. By performing heat treatment at a specific temperature, the molten sulfur is allowed to fully diffuse, penetrate, and fill the pores of the composite carrier.

[0051] The inert atmosphere may include nitrogen, argon, etc.; the mass ratio of the composite carrier to the elemental sulfur is 1:1.1~4.

[0052] In other embodiments, step S20 can be implemented as follows: S20b, the composite carrier, elemental sulfur, and organic solvent are mixed and stirred at 25-50°C for 6-24 hours, then washed with the organic solvent, and dried at 60-100°C for 8-12 hours to obtain the composite material. Through solution impregnation, sulfur is uniformly deposited in the pores of the composite carrier. In actual preparation, the above steps can be repeated multiple times for repeated impregnation to increase the sulfur loading.

[0053] The organic solvent can be any organic solvent capable of dissolving sulfur, such as carbon disulfide, toluene, etc. The mass ratio of the composite carrier to the elemental sulfur is 1:1.1~4. During washing, the aforementioned organic solvent can be used to wash away the unembedded sulfur on the surface of the composite material.

[0054] Thirdly, embodiments of this application also propose an aluminum-sulfur battery, comprising the composite material described above.

[0055] Specifically, the aluminum-sulfur battery includes a positive electrode and a negative electrode. The positive electrode includes a positive active material, which includes the composite material, thus giving the aluminum-sulfur battery better cycle performance.

[0056] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0057] Example 1 Using rGO as the carbon framework, Keggin-type H3PMo 12 O 40 As a polyacid, pyromellitic acid was used as a ligand to prepare the composite material S@rGO / NENU-5 via in-situ growth. The preparation steps are as follows: Step 1, Preparation of the rGO / NENU-5 composite support: Graphene oxide washed with ethanol was dispersed in water to obtain a GO solution with a concentration of 0.8 mg / mL. The rGO solution containing 0.3 g of reduced graphene oxide was then mixed with 0.3 g of H3PMo. 12 O 40 The mixture was homogenized by ultrasonication to obtain rGO-PMo. 12 Solution. Dissolve 0.05 g of copper acetate and 0.1 g of 1,3,5-benztricarboxylic acid in water and add to rGO-PMo. 12 The solution was mixed to obtain a final product. The mixture was transferred to a reaction vessel and reacted at 150°C for 24 h. After cooling to room temperature, the mixture was centrifuged, the solid phase was collected and washed several times with ethanol, and then dried under vacuum at 60°C to obtain rGO / NENU-5.

[0058] Step 2, preparation of composite material S@rGO / NENU-5: The rGO / NENU-5 prepared above was mixed with elemental sulfur at a mass ratio of 3:7, and heat-treated at 155℃ for 8 hours under an argon atmosphere to obtain the S@rGO / NENU-5 composite material.

[0059] Example 2 Using one-dimensional carbon nanofibers as the carbon framework, Keggin-type H3PMo 12 O 40As a polyacid, pyromellitic acid was used as a ligand to prepare the composite material S@CNFs / NENU-5 via in-situ growth. The preparation steps are as follows: Step 1, Preparation of CNFs / NENU-5 Composite Carrier: 0.9 g of polyvinylidene fluoride, 0.05 g of copper acetate, 0.3 g of phosphomolybdic acid, and 0.1 g of 1,3,5-benzyltricarboxylic acid were dispersed in 50 mL of dimethylformamide and stirred for 12 h to obtain a mixture. The mixture was electrospun under an electric field of 2 kV / cm and then vacuum dried at 60 °C to obtain the CNFs / NENU-5 composite membrane.

[0060] Step 2, preparation of composite material S@CNFs / NENU-5: The CNFs / NENU-5 prepared above is mixed with elemental sulfur at a mass ratio of 3:7 and heat-treated at 155℃ for 8 hours under an argon atmosphere to obtain the S@CNFs / NENU-5 composite material.

[0061] Example 3 Using three-dimensional porous carbon sponge as a carbon support, Keggin-type H3PMo 12 O 40 As a polyacid, pyromellitic acid was used as a ligand to synthesize NENU-5 in situ, followed by sulfur complexation to obtain S@NC / NENU-5.

[0062] Step 1: In-situ growth of NENU-5 on carbon sponge: 0.5 g of three-dimensional porous carbon sponge, cleaned with ethanol, was immersed in a solution containing 0.05 g of copper acetate, 0.1 g of 1,3,5-benztricarboxylic acid, and 0.3 g of H3PMo. 12 O 40 The mixture was reacted at 150°C for 24 hours in 40 mL of aqueous solution, washed and dried to obtain the composite carrier NC / NENU-5.

[0063] Step 2, preparation of composite material S@NC / NENU-5: The composite carrier NC / NENU-5, elemental sulfur and CS2 are mixed and stirred at 40°C for 10 h, then washed with CS2 and dried at 80°C for 10 h. The above steps are repeated multiple times until the mass ratio of NC / NENU-5 to elemental sulfur reaches 3:7 (which can be calculated based on the weight gain of the dried product relative to the composite carrier), thus obtaining composite material S@NC / NENU-5.

[0064] Comparative Example 1 This comparative example scheme is basically the same as that of Example 1, except that in this comparative example, S@rGO is used, and correspondingly, step one is removed, and rGO / NENU-5 in step two is replaced with rGO. All other parameters and conditions remain unchanged.

[0065] Comparative Example 2 This comparative example is basically the same as Example 1, except that this comparative example uses S@rGO / PMo. 12 In the ZIF-67 composite material, correspondingly, in step one, copper acetate and 1,3,5-pyromellitic acid were replaced with cobalt hexahydrate and 2-methylimidazole to synthesize the ZIF-67 metal-organic framework. Otherwise, all other parameters and conditions remained unchanged.

[0066] I. Testing Methods 1. Morphology Test: The morphology of the composite material was tested using transmission electron microscopy (TEM), and the results are as follows: Figure 1 , Figure 4 , Figure 6 and Figure 8 As shown.

[0067] 2. Specific surface area test: The specific surface area of ​​the solid material was determined using a Quadrasorb EVO fully automated specific surface area and porosity analyzer. The results are as follows: Figure 2 and Figure 5 As shown in the figure, the vertical axis "absorption volume" represents the adsorption volume.

[0068] 3. Battery Performance Testing: A composite material was used as the positive electrode active material, mixed with conductive carbon black and a binder (PVDF) at a mass ratio of 8:1:1. The PVDF was dissolved in N-methylpyrrolidone (NMP) to form a slurry. The slurry was coated onto a 12mm thick molybdenum foil and dried to obtain the positive electrode sheet. An aluminum sheet was used as the negative electrode, and AlCl3 and 1-ethyl-3-methylimidazolium salt were used as the electrolyte. A glass fiber separator was employed, and coin-type aluminum-sulfur batteries were assembled in an argon-filled glove box.

[0069] The coin-type aluminum-sulfur battery was tested using an electrochemical workstation at a temperature of 25±1℃ and a voltage range of 0.1-2V. The test results are as follows: Figure 3 , Figure 7 and Figure 9 As shown in the figure, the vertical axis represents specific capacity, the vertical axis represents coulombic efficiency, and the horizontal axis represents cycle number. The two curves in the figure, from top to bottom, are the coulombic efficiency change curve and the specific capacity change curve, respectively.

[0070] II. Analysis of Test Results for Each Embodiment and Comparative Example See Figure 2 and Figure 5 As can be seen, the specific surface area of ​​the composite material prepared in Example 1 is 480 m². 2 / g, the specific surface area of ​​the composite material prepared in Example 3 reached 330 m². 2 / g indicates that the composite material prepared in the embodiments of this application has a high specific surface area, which is due to the carbon support and porous PMo 12 The hierarchical porous structure constructed using MOFs not only provides ample loading space for elemental sulfur, achieving a sulfur loading of over 80 wt.%, but more importantly, its abundant micropores and mesopores effectively confine sulfur and its discharge products, polysulfides, physically inhibiting their dissolution into the electrolyte. Furthermore, Figure 3 The results show that the battery in Example 1 has a specific capacity of 703 mAh / g at 500 mA / g and a high capacity retention rate after cycling, indicating that the composite material prepared in this application has high specific capacity and high capacity retention rate, which fully demonstrates that the composite material of the present invention has both high sulfur utilization rate and excellent cycle stability.

[0071] Further, see Figure 3 , Figure 7 and Figure 9 It can be seen that Example 1 has a higher specific capacity and capacity retention than Comparative Examples 1 and 2. Comparing the performance data and morphology of Example 1 and Comparative Example 1, it can be concluded that PMo 12 The introduction of a metal-organic framework is key to improving performance. Comparative Example 1 uses only rGO as a support, which has limited specific surface area and pore volume, and lacks strong chemisorption sites for polysulfides; therefore, its capacity and cycling stability are significantly lower than those of Example 1. This comparison strongly demonstrates that the PMo grown on rGO in this invention... 12 The metal-organic framework plays multiple synergistic roles: PMo 12 The high specific surface area and porous structure of metal-organic frameworks enhance their physical confinement capabilities, while PMo in their framework... 12 Its abundant Lewis acid sites enable strong chemisorption of polysulfides, thus synergistically suppressing the shuttle effect at both physical and chemical levels. Encapsulated PMo 12 As a highly efficient redox mediator, it can significantly accelerate the conversion kinetics of polysulfides (i.e., "liquid-solid" conversion) and reduce reaction polarization. This not only improves rate performance but also reduces the residence time of polysulfides in the electrolyte, further enhancing cycle stability. Example 1 exhibits higher specific capacity and capacity retention than Comparative Example 2, despite both using a metal center and carbon support; Example 1 demonstrates significantly superior performance. This highlights the unique advantages of constructing POMOFs using phosphomolybdic acid as the structural unit compared to traditional ZIF series MOFs: while ZIF-67 possesses some adsorption capacity, its catalytic activity is limited. In contrast, the Keggin-structured PMo... 12It is a polyacid anion with clear redox activity. After being encapsulated in the channels of MOF, it can act as a built-in, non-leaking "electron pump" to continuously catalyze the redox reaction of polysulfides, a function that ordinary MOFs do not possess.

[0072] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A composite material, characterized in that, The composite support includes a composite support and elemental sulfur supported on the composite support, wherein the composite support includes a carbon support and PMo grown on the carbon support. 12 The base metal-organic framework, the PMo 12 The base metal-organic framework includes a metal-organic framework with a porous structure and phosphomolybdic acid encapsulated within the porous structure.

2. The composite material according to claim 1, characterized in that, The carbon support includes one or more of one-dimensional carbon materials, two-dimensional carbon materials, and three-dimensional porous carbon frameworks; and / or, The metal-organic framework comprises a metal element and an organic ligand, wherein the metal element includes one or more of copper, cobalt, iron, and zinc, and the organic ligand is derived from one or more of trimesic acid and 2-methylimidazole; and / or, In the composite material, the carbon support has a mass percentage of 5-10%, the elemental sulfur has a mass percentage of 50-80%, and the balance is PMo. 12 Metal-organic frameworks.

3. The composite material according to claim 2, characterized in that, The one-dimensional carbon material includes one or more of carbon nanotubes and carbon nanofibers; the two-dimensional carbon material includes one or more of reduced graphene oxide and graphene sheets; the three-dimensional porous carbon framework includes one or more of carbon nanofiber sponges, carbon nanofoams, and hierarchical porous carbon materials.

4. A method for preparing the composite material according to any one of claims 1 to 3, characterized in that, Includes the following steps: Construct a carbon support and load PMo onto the carbon support. 12 Based on metal-organic frameworks, composite supports were obtained; The composite carrier is mixed with elemental sulfur to form a sulfur composite, thus obtaining a composite material.

5. The preparation method according to claim 4, characterized in that, The mass ratio of the composite carrier to the elemental sulfur is 1:1.1~4; and / or, The steps of mixing the composite carrier with elemental sulfur to obtain a composite material include: mixing the composite carrier with elemental sulfur and heat-treating it at 155~250℃ for 2~12h in an inert atmosphere to obtain the composite material; or, mixing the composite carrier, elemental sulfur and an organic solvent, stirring at 25~50℃ for 6~24h, washing with the organic solvent, and drying at 60~100℃ for 8~12h to obtain the composite material.

6. The preparation method according to claim 4, characterized in that, Construct a carbon support and load PMo onto the carbon support. 12 The steps for obtaining a composite support from a metal-organic framework include: Metal salt, organic ligand, phosphomolybdic acid and water are mixed to obtain a precursor mixture. Then, a carbon support is mixed with the precursor mixture and reacted at 80~180℃ for 6~72h to obtain a composite support. The carbon support is a two-dimensional carbon material or a three-dimensional porous carbon framework. or, A composite carrier is obtained by mixing a one-dimensional carbon material precursor, a metal salt, an organic ligand, phosphomolybdic acid, and a solvent, and reacting the mixture. The one-dimensional carbon material precursor includes one or more of polyvinylidene fluoride, polyacrylonitrile, and biomass polymers.

7. The preparation method according to claim 6, characterized in that, The metal salt includes one or more of copper, cobalt, iron, and zinc salts; and / or, The organic ligand includes one or more of pyromellitic acid and 2-methylimidazole; and / or The mass ratio of the metal salt, the organic ligand, and the phosphomolybdic acid is 1:2~3:3~6.

8. The preparation method according to claim 6, characterized in that, In the step of mixing a metal salt, an organic ligand, phosphomolybdic acid, and water to obtain a precursor mixture, and then mixing a carbon support with the precursor mixture and reacting at 80-180°C for 6-72 hours to obtain a composite support, the mass ratio of phosphomolybdic acid to the carbon support is 1:1-3.

9. The preparation method according to claim 6, characterized in that, In the step of mixing a one-dimensional carbon material precursor, a metal salt, an organic ligand, phosphomolybdic acid, and a solvent to obtain a composite support: The mass ratio of the phosphomolybdic acid to the one-dimensional carbon material precursor is 1:6~8; and / or, The reaction is carried out by electrospinning in an electric field environment with an electric field strength of 0.5~3kV / cm; and / or, The solvent includes one or more of dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

10. An aluminum-sulfur battery, characterized in that, Includes the composite material as described in any one of claims 1 to 3.

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