Hollow ZnS-CatMoS2 composite material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of battery materials, and relates to a hollow ZnS-CatMoS2 composite material as well as a preparation method and application thereof. The preparation method comprises the following steps: mixing and stirring 2-methylimidazole and zinc acetate dihydrate, aging to prepare a Zn-C precursor, carbonizing and vulcanizing to prepare ZnS-C, and growing MoS2 on the surface of the ZnS-C by using a hydrothermal method to obtain the hollow ZnS-CatMoS2 composite material. Wherein the flaky MoS2 wrapped on the surface has a high specific surface area and a large number of active sites and has strong adsorption performance on polysulfide, the ZnS inside has excellent bidirectional catalytic performance and accelerates conversion of the polysulfide, and a carbon skeleton provides a high-speed channel for electron ion transfer in reaction. Under the synergistic effect of adsorption, catalysis and electric conduction, the polysulfide is subjected to efficient catalytic conversion, so that the effect of inhibiting the shuttle effect of the polysulfide is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery material preparation, and particularly relates to a hollow ZnS-C@MoS2 composite material, a preparation method thereof, and an application thereof. Background Art

[0002] Although the maximum energy density of existing commercial lithium-ion batteries has approached the limit, it still cannot meet the requirements of green industries such as electrical energy storage. Therefore, it is urgent to establish a green new lithium battery system with high capacity and good cycle stability. The theoretical energy density of lithium-sulfur batteries is much higher than that of lithium cobalt oxide batteries widely used commercially. In addition, sulfur, which is rich in reserves on Earth, has the advantages of high yield, low price, and low environmental pollution, making lithium-sulfur batteries have a broader development prospect. However, lithium-sulfur batteries still have some inevitable challenges, and the "shuttle effect" of polysulfides is considered to be the main reason for the low capacity and poor cycle stability of lithium-sulfur batteries.

[0003] By modifying and optimizing the separator of lithium-sulfur batteries, polysulfides can be effectively intercepted between the separator and the positive electrode, enabling them to continue to participate in the electrochemical reaction, which can improve the performance of lithium-sulfur batteries. General methods for modifying conventional polypropylene separators include: uniformly mixing nano-carbon and / or non-polar nano-materials as functional layer materials, and tightly covering the original separator by coating, suction filtration, etc.; this is one of the effective ways to develop low-cost, high-energy-density lithium-sulfur batteries.

[0004] Commonly used separator modification materials include carbon materials, metal compounds, etc. Although carbon materials have good electrical conductivity, they lack the ability to adsorb and catalytically convert polysulfides. Due to their unique lattice structure and adjustable electronic structure, metal sulfides have been widely studied in the field of lithium-sulfur batteries. There are sulfurophilic sites on their surfaces, which can promote electron transfer and accelerate redox reactions, and promote the catalytic conversion of polysulfides. Among them, layered molybdenum disulfide (MoS2), as a two-dimensional material, has attracted extensive attention due to its large exposed active surface, strong chemical polarity, and excellent intrinsic catalytic activity. However, the "shuttle effect" of polysulfides in a single MoS2 material has limited improvement on battery performance. Summary of the Invention

[0005] The purpose of the present invention is to provide a hollow ZnS-C@MoS2 composite material, a preparation method thereof, and an application thereof, so as to provide a composite material integrating conductivity-catalysis-adsorption for the capacity attenuation of lithium-sulfur batteries, and solve the problem that it is difficult for existing separator materials to inhibit the shuttle effect of polysulfides in lithium-sulfur batteries.

[0006] The present invention is realized through the following technical solutions:

[0007] A preparation method of a hollow ZnS-C@MoS2 composite material, comprising the following steps:

[0008] S1. Dissolve 2-methylimidazole and zinc acetate dihydrate in a methanol solution, stir well, let stand, centrifuge, and dry to obtain a Zn-C precursor;

[0009] S2. Carbonize the Zn-C precursor under a protective atmosphere to obtain a Zn-C material;

[0010] S3. Add the Zn-C material to an aqueous solution containing thiourea, and hydrothermally sulfurize the Zn-C to obtain a ZnS-C composite material;

[0011] S4. Add the ZnS-C composite material to a solution containing ammonium molybdate and thiourea, and hydrothermally prepare a hollow ZnS-C@MoS2 composite material.

[0012] Further, in S1, the mass ratio of the 2-methylimidazole to the zinc acetate dihydrate is (1-1.5):(0.75-1).

[0013] Further, in S1, the standing time of the solution is 20-30 h;

[0014] The drying temperature is 60-80 °C, and the drying duration is 12-24 h.

[0015] Further, in S2, the carbonization temperature is 550-650 °C, the heating rate is 2-5 °C / min, the protective atmosphere is argon, and the heat preservation duration of the carbonization is 2-5 h.

[0016] Further, in S3, the hydrothermal temperature of the ZnS-C is 150 °C-180 °C, and the hydrothermal duration is 12-24 h.

[0017] Further, in S3, the mass ratio of the Zn-C to the thiourea is (0.075-0.152):1.

[0018] Further, in S4, the preparation process of the solution containing ammonium molybdate and thiourea is as follows:

[0019] Add ammonium molybdate and thiourea to a water and ethylene glycol solution, and mix to obtain a solution containing ammonium molybdate and thiourea;

[0020] The volume ratio of water to the ethylene glycol solution is (0.25-1):1; the mass ratio of ammonium molybdate to thiourea is (0.2-0.33):1.

[0021] Further, in S4, the hydrothermal temperature is 150-200 °C, and the hydrothermal duration is 12-24 h.

[0022] The present invention also discloses a hollow ZnS-C@MoS2 composite material prepared by the preparation method. The hollow ZnS-C@MoS2 composite material has a hollow rhombic dodecahedron structure, and the particle size is 600-700 nm.

[0023] A layer of nano-sheet MoS2 is uniformly grown on the outer surface of ZnS-C.

[0024] The height of the nano-sheet MoS2 is 30-50 nm, and the thickness is 2-3 nm.

[0025] The C material has N doping.

[0026] The present invention also discloses the application of the hollow ZnS-C@MoS2 composite material in a lithium-sulfur battery. The hollow ZnS-C@MoS2 composite material is used to modify the separator to assemble a lithium-sulfur battery. When the lithium-sulfur battery is in the voltage range of 1.7-2.8 V and at a 2C rate, after 500 cycles, the reversible specific capacity reaches 523-565 Ah·g. -1 .

[0027] Compared with the prior art, the present invention has the following beneficial technical effects:

[0028] The present invention discloses a preparation method of a hollow ZnS-C@MoS2 composite material. First, a Zn-C precursor is prepared from 2-methylimidazole and zinc acetate. After carbonization, a porous carbon structure is obtained, which contains Zn components and can also form nitrogen-doped carbon to improve the conductivity of the carbon material. After sulfidation, Zn is converted into ZnS while the carbon structure is retained. Then, the ZnS-C composite material is added to an ammonium molybdate and thiourea solution, and MoS2 is formed by hydrothermal method to wrap around the outside of ZnS-C, forming a hollow structure.

[0029] Flaky MoS2 has a high specific surface area and abundant active sites, which can strongly adsorb polysulfides, reduce their dissolution and migration. The internal ZnS exhibits bidirectional catalytic performance (promoting the reduction and oxidation reactions of polysulfides), accelerating its conversion kinetics and reducing the accumulation of intermediate products. The carbon skeleton provides a continuous electron / ion transport channel, reduces the reaction impedance, and improves the reaction efficiency. The three work together to significantly inhibit the "shuttle effect" of polysulfides.

[0030] MoS2 focuses on adsorption, and ZnS focuses on catalysis. The two work together to optimize the reaction path. The carbon skeleton not only enhances the conductivity but also prevents the aggregation of active components (ZnS, MoS2) and maintains the high activity of the material.

[0031] Furthermore, the carbonization temperature is 550-650 °C and the duration is 2-5 h, which can not only fully carbonize the precursor but also prevent zinc volatilization caused by too high temperature.

[0032] Furthermore, in step S3, the hydrothermal temperature of ZnS-C is 150 °C to 180 °C, and the duration is 12 to 24 h; this condition can ensure that Zn-C is completely sulfided to form ZnS-C. Excessive temperature and too long time will waste energy.

[0033] Furthermore, the height of the nanosheet MoS2 is 30 to 50 nm, and the thickness is 2 to 3 nm; this can utilize its large surface area to fully adsorb polysulfides.

[0034] The present invention discloses a hollow ZnS-C@MoS2 composite material. In the hollow ZnS-C@MoS2 composite material, ZnS has good reduction / oxidation catalytic ability, and nitrogen-doped carbon has excellent electrical conductivity, providing a high-speed channel for the conduction of electrons and ions, and ensuring the efficiency of the electrochemical reaction. In order to enhance the adsorption ability of this composite material for polysulfides, a layer of nanosheet MoS2 is uniformly grown on the outer surface of ZnS-C, and its large specific surface area is used to enhance the adsorption ability for polysulfides. Its action process is that first, the large specific surface area of MoS2 is used to adsorb polysulfides around the heterojunction, and then under the action of the concentration difference, the polysulfides will move towards the inside of the material. The internal ZnS has good catalytic conversion ability, which can accelerate the catalytic conversion of polysulfides, thereby inhibiting the shuttle of polysulfides. And this material is a hollow structure, which can provide a accommodation space for the volume change caused by the conversion of lithium polysulfide during the charge and discharge process of polysulfides, improve the structural stability of the material, and endow the material with excellent long-cycle performance and rate performance.

[0035] The present invention also discloses the application of the hollow ZnS-C@MoS2 composite material in lithium-sulfur batteries. Through these comprehensive designs, the Li-S battery containing the ZnS-C@MoS2 modified PP separator exhibits excellent rate performance and long-term cycle stability, with an initial discharge capacity of 1573.4 mAh g -1 at 0.1C, and after 500 cycles at 2C, the decay rate per cycle is 0.048%. The ZnS-C@MoS2 composite material prepared in the present invention can significantly accelerate the conversion of polysulfides and inhibit the shuttle effect of polysulfides in Li-S batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. 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.

[0037] Figure 1XRD pattern of the hollow ZnS-C@MoS2 composite material prepared in Example 1 of the present invention;

[0038] Figure 2 SEM characterization diagram of the hollow ZnS-C@MoS2 composite material prepared in Example 1 of the present invention;

[0039] Figure 3 TEM characterization diagram of the hollow ZnS-C@MoS2 composite material prepared in Example 1 of the present invention;

[0040] Figure 4 Mapping characterization diagram of the hollow ZnS-C@MoS2 composite material prepared in Example 1 of the present invention;

[0041] Figure 5 Front and back comparison diagrams of the PP separator modified with the hollow ZnS-C@MoS2 composite material prepared in Example 1 of the present invention. The upper part shows the front and back of the unmodified PP separator, and the lower part shows the front and back of the modified PP separator;

[0042] Figure 6 Cycling performance diagram of the hollow ZnS-C@MoS2 composite material prepared in Example 1 of the present invention. Detailed implementation manners

[0043] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0044] Conventional instrument equipment in the art is used in the following embodiments. For the experimental methods without specific conditions noted in the following embodiments, they are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. Various raw materials are used in the following embodiments. Unless otherwise stated, commercially available products are used, and their specifications are conventional specifications in the art.

[0045] Example 1

[0046] (1) Dissolve 2.63 g of 2-methylimidazole and 1.75 g of zinc acetate dihydrate in 400 mL of methanol solution, stir well at room temperature for 5 minutes, then let it stand for 24 h, then centrifuge at a speed of 4000 r / min, wash with methanol solution 3 times, and then keep it warm at 70 °C in a vacuum drying oven for 12 h. The precursor powder is obtained.

[0047] (2) Place 200 mg of the precursor in a porcelain boat and put it in a tube furnace. Under an argon atmosphere, heat it to 600 °C at a heating rate of 5 °C / min and hold for 2 h to carbonize the precursor into Zn-C.

[0048] (3) First, dissolve 300 mg of thiourea in 50 ml of aqueous solution and stir for 1 h to form solution A. Then add 30 mg of Zn-C to solution A and stir well for 1 h to form solution B. Put solution B into a 100 ml autoclave, hold at 180 °C for 12 h, then centrifuge 3 times with deionized water and dry at 60 °C to obtain ZnS-C.

[0049] (4) First, dissolve 220 mg of ammonium molybdate and 800 mg of thiourea in a solution of 10 ml of water and 40 ml of ethylene glycol, stir for 1 h to form solution A. Then add 30 mg of ZnS-C to solution A and stir well for 1 h to form solution B. Put solution B into a 100 ml autoclave, hold at 180 °C for 24 h, then centrifuge 3 times with anhydrous ethanol and deionized water respectively and dry at 60 °C to obtain ZnS-C@MoS2.

[0050] When performing electrical tests, use sulfur-carbon nanotubes as the cathode material of the lithium-sulfur battery, use metallic lithium as the anode, use a CR2032 type battery case, and modulate the ZnS-C@MoS2 prepared by the above method into a slurry and coat it on a Celgard 2500 separator. The electrolyte consists of 1.0 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), the mixed solvent is DME / DOL (volume ratio 1:1) and 1.0% LiNO3 additive. Thus, assemble a lithium-sulfur battery for electrical tests.

[0051] The XRD characterization of the ZnS-C@MoS2 composite material prepared in this example is shown in Figure 1 . It can be seen from Figure 1 that the composite material is highly consistent with the standard cards of ZnS (PDF#05-0566) and MoS2 (PDF#37-1492). This indicates that the ZnS-C@MoS2 composite material is successfully prepared.

[0052] The SEM photo of the ZnS-C@MoS2 composite material prepared in this example is shown in Figure 2 , and the TEM photo is shown in Figure 3 . It can be seen that the size of the ZnS-C@MoS2 dodecahedron is 650 nm, and ZnS-C@MoS2 has a hollow structure, the height of the MoS2 on the surface is 40 nm, and the thickness is 2 nm.

[0053] In addition, the elemental mapping test results of the ZnS-C@MoS2 composite material prepared by the present invention are shown in Figure 4As can be seen from the figure, C, Mo, S, Zn, and N are uniformly distributed in the composite, and it can be seen that the distribution of Mo and S elements is a bit wider than that of Zn, C, and N elements, indicating that MoS2 grows uniformly on the outer surface of ZnS-NC.

[0054] Figure 5 This is a macroscopic view of the separator modified with the ZnS-C@MoS2 composite material. It can be seen from the figure that ZnS-C@MoS2 forms a uniform black coating on the PP membrane, and the separator is modified to assemble a battery.

[0055] The obtained materials were subjected to performance tests. The cycling performance results of the lithium-sulfur battery assembled with the separator modified by the ZnS-C@MoS2 composite material are as Figure 6 shown. As Figure 6 can be seen, in the voltage range of 1.7 - 2.8 V, at a 2C rate, after 500 cycles, the reversible specific capacity can still reach 565 mAh·g -1 .

[0056] Example 2

[0057] (1) Dissolve 2.63 g of 2-methylimidazole and 1.5 g of zinc acetate dihydrate in 400 mL of methanol solution, stir well at room temperature for 5 minutes, then let it stand for 22 h, then centrifuge at a speed of 4000 r / min, and wash with methanol solution 3 times, and then keep it warm at 65 °C in a vacuum drying oven for 20 h. The precursor powder is prepared.

[0058] (2) Place 200 mg of the precursor in S1 in a porcelain boat, place it in a tubular furnace, and under an argon atmosphere, heat it to 570 °C at a heating rate of 4 °C / min and keep it warm for 2 h to carbonize the precursor into Zn-C.

[0059] (3) First, dissolve 250 mg of thiourea in 50 ml of aqueous solution, stir for 1 h to form solution A. Then add 30 mg of Zn-C to solution A and stir well for 1 h to form solution B. Put solution B into a 100 ml reaction kettle, keep it warm at 170 °C for 15 h, then centrifuge with deionized water 3 times and dry at 60 °C to obtain ZnS-C.

[0060] (4) First, dissolve 200 mg of ammonium molybdate and 800 mg of thiourea in a solution of 20 ml of water and 30 ml of ethylene glycol, stir for 1 h to form solution A. Then add 30 mg of ZnS-C to solution A and stir well for 1 h to form solution B. Put solution B into a 100 ml reaction kettle, keep it warm at 170 °C for 18 h, then centrifuge with anhydrous ethanol and deionized water 3 times each and dry at 50 °C to obtain ZnS-C@MoS2.

[0061] The size of the ZnS-C@MoS2 dodecahedron prepared in this example is approximately 600 nm, and ZnS-C@MoS2 has a hollow structure. The height of MoS2 on the surface is 30 nm, and the thickness is 3 nm.

[0062] The lithium-sulfur battery assembled by modifying the separator with the ZnS-C@MoS2 composite material prepared in this example has a reversible specific capacity of 533 mAh·g after 500 cycles at a rate of 2C in the voltage range of 1.7 - 2.8 V. -1 。

[0063] Example 3

[0064] (1) Dissolve 2.0 g of 2-methylimidazole and 2.0 g of zinc acetate dihydrate in 400 mL of methanol solution, stir well at room temperature for 5 minutes, then let it stand for 20 h, then centrifuge at a speed of 4000 r / min, wash with methanol solution 3 times, and then keep it warm at 60 °C in a vacuum drying oven for 24 h. The precursor powder is obtained.

[0065] (2) Place 200 mg of the precursor in S1 in a porcelain boat, put it in a tube furnace, and under an argon atmosphere, heat it to 550 °C at a heating rate of 3 °C / min and keep it warm for 5 h to carbonize the precursor into Zn-C.

[0066] (3) First, dissolve 200 mg of thiourea in 50 ml of aqueous solution, stir for 1 h to form solution A. Then add 30 mg of Zn-C to solution A and stir well for 1 h to form solution B. Put solution B into a 100 ml autoclave, keep it warm at 160 °C for 18 h, then centrifuge with deionized water 3 times and dry at 60 °C to obtain ZnS-C.

[0067] (4) First, dissolve 170 mg of ammonium molybdate and 800 mg of thiourea in a solution of 25 ml of water and 25 ml of ethylene glycol, stir for 1 h to form solution A. Then add 30 mg of ZnS-C to solution A and stir well for 1 h to form solution B. Put solution B into a 100 ml autoclave, keep it warm at 150 °C for 24 h, then centrifuge with anhydrous ethanol and deionized water 3 times each and dry at 60 °C to obtain ZnS-C@MoS2.

[0068] The size of the ZnS-C@MoS2 dodecahedron prepared in this example is 650 nm, and ZnS-C@MoS2 has a hollow structure. The height of MoS2 on the surface is 40 nm, and the thickness is 2 nm. The lithium-sulfur battery assembled by modifying the separator with the ZnS-C@MoS2 composite material prepared in this example has a reversible specific capacity of 523 mAh·g after 500 cycles at a rate of 2C in the voltage range of 1.7 - 2.8 V. -1 。

[0069] Example 4

[0070] (1) Dissolve 3.0 g of 2-methylimidazole and 2.0 g of zinc acetate dihydrate in 400 mL of methanol solution, stir well at room temperature for 5 minutes, then let it stand for 28 h, then centrifuge at a speed of 4000 r / min, and wash with methanol solution 3 times, and then keep it warm at 75 °C in a vacuum drying oven for 11 h. The precursor powder is prepared.

[0071] (2) Place 200 mg of the precursor in S1 in a porcelain boat, place it in a tubular furnace, and under an argon atmosphere, heat it to 620 °C at a heating rate of 2 °C / min and keep it warm for 2 h to carbonize the precursor into Zn-C.

[0072] (3) First, dissolve 350 mg of thiourea in 50 ml of aqueous solution and stir for 1 h to form solution A. Then add 30 mg of Zn-C to solution A and stir well for 1 h to form solution B. Put solution B into a 100 ml autoclave, keep it warm at 155 °C for 21 h, and then centrifuge with deionized water 3 times and dry at 60 °C to obtain ZnS-C.

[0073] (4) First, dissolve 250 mg of ammonium molybdate and 800 mg of thiourea in a solution of 30 ml of water and 20 ml of ethylene glycol, stir for 1 h to form solution A. Then add 30 mg of ZnS-C to solution A and stir well for 1 h to form solution B. Put solution B into a 100 ml autoclave, keep it warm at 190 °C for 11 h, and then centrifuge with absolute ethanol and deionized water 3 times each and dry at 60 °C to obtain ZnS-C@MoS2.

[0074] The size of the ZnS-C@MoS2 dodecahedron prepared in this example is 700 nm, and ZnS-C@MoS2 has a hollow structure, the height of MoS2 on the surface is 50 nm, and the thickness is 2 nm. The lithium-sulfur battery assembled by modifying the separator with the ZnS-C@MoS2 composite material prepared in this example has a reversible specific capacity of 541 mAh·g after 500 cycles at a 2C rate in the voltage range of 1.7 - 2.8 V. -1 。

[0075] In order to better combine the excellent electrical conductivity of carbon materials with the adsorption and catalytic properties of metal compounds, metal compound / carbon composites can be prepared. The difficulty is to prevent particle agglomeration during the preparation process and ensure a high specific surface area of the material to achieve effective adsorption and efficient catalysis of polysulfides.

[0076] In summary, the present invention aims at efficiently adsorbing and catalytically converting polysulfides, designs and prepares a hollow ZnS-C@MoS2 polyhedral composite material, combines the excellent properties of each material. The large specific surface area of the ultrathin molybdenum disulfide nanosheets provides a large number of anchoring sites for the rapid adsorption of polysulfides. ZnS has high bidirectional electrocatalytic activity. The nitrogen-doped carbon skeleton provides a high-speed channel for charge transfer in the electrochemical reaction and a channel for the efficient catalytic conversion of polysulfides. The hollow structure can provide a buffer space for the volume change during the reaction process, which is beneficial to the stability of the electrode structure. The ZnS-C@MoS2 composite material combining the advantages of these several materials performs excellently in inhibiting the shuttle effect of polysulfides and improving the battery performance. This work provides a strategy for realizing high-activity metal sulfide composite materials for advanced lithium-sulfur batteries.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a hollow ZnS-C@MoS2 composite material, characterized in that: The following steps are involved: S1. Dissolve 2-methylimidazole and zinc acetate dihydrate in a methanol solution, stir thoroughly, let stand, centrifuge, and dry to obtain a Zn-C precursor; S2, carbonizing the Zn-C precursor into a Zn-C material under a protective atmosphere; S3, adding the Zn-C material into an aqueous solution containing thiourea, and vulcanizing the Zn-C into a ZnS-C composite material by a hydrothermal method; S4. Add the ZnS-C composite material into a solution containing ammonium molybdate and thiourea, and prepare a hollow ZnS-C@MoS2 composite material by a hydrothermal method.

2. The method for preparing the hollow ZnS-C@MoS2 composite material according to claim 1, characterized in that: In S1, the mass ratio of the 2-methylimidazole to zinc acetate dihydrate is (1-1.5): (0.75-1).

3. The method for preparing the hollow ZnS-C@MoS2 composite material according to claim 1, characterized in that: In S1, the solution is allowed to stand for 20 to 30 h; The drying temperature is 60-80°C and the drying time is 12-24 hours.

4. The method for preparing the hollow ZnS-C@MoS2 composite material according to claim 1, characterized in that: In S2, the carbonization temperature is 550-650°C, the heating rate is 2-5°C / min, the protective atmosphere is argon, and the carbonization insulation time is 2-5h.

5. The method for preparing the hollow ZnS-C@MoS2 composite material according to claim 1, characterized in that: In S3, the hydrothermal temperature of ZnS-C is 150°C to 180°C, and the hydrothermal time is 12 to 24 h.

6. The method for preparing the hollow ZnS-C@MoS2 composite material according to claim 1, characterized in that: In S3, the mass ratio of Zn-C to thiourea is (0.075-0.152):

1.

7. The method for preparing the hollow ZnS-C@MoS2 composite material according to claim 1, characterized in that: In S4, the preparation process of the solution containing ammonium molybdate and thiourea is: adding ammonium molybdate and thiourea into water and ethylene glycol solution, and mixing to obtain a solution containing ammonium molybdate and thiourea; The volume ratio of water to ethylene glycol solution is (0.25-1):1; the mass ratio of ammonium molybdate to thiourea is (0.2-0.33):

1.

8. The method for preparing a ZnS-C@MoS2 composite material according to claim 1, characterized in that: In S4, the hydrothermal temperature is 150-200°C, and the hydrothermal time is 12-24h.

9. A hollow ZnS-C@MoS2 composite material prepared by the preparation method according to any one of claims 1 to 8, characterized in that: The hollow ZnS-C@MoS2 composite material has a hollow rhombic dodecahedron structure and a particle size of 600 to 700 nm; A layer of nanosheet MoS2 grows uniformly on the outer surface of ZnS-C; The height of the nano-sheet MoS2 is 30-50nm and the thickness is 2-3nm; The C material has N doping.

10. The hollow ZnS-C@MoS2 composite material according to claim 9 has application in lithium-sulfur batteries, characterized in that: The hollow ZnS-C@MoS2 composite modified diaphragm is assembled into a lithium-sulfur battery. The lithium-sulfur battery has a reversible specific capacity of 523m-565Ah·g after 500 cycles at a voltage range of 1.7-2.8V and a rate of 2C. -1 .

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