CuS composite material, and preparation method and application thereof

Abstract

The application discloses a CuS composite material and a preparation method and application thereof. The CuS composite material has the following structural general formula: Y-S CuS@C1@C2, wherein C1 represents an inner carbon shell layer, C2 represents an outer carbon shell layer, CuS represents a CuS compound, and Y-S represents a core-shell structure with a rattle shape. The CuS compound is the inner core, and the outer surface of the inner core is coated with an inner carbon shell layer. The inner carbon shell layer is in close contact with the outer surface of the inner core. The outer surface of the inner carbon shell layer is provided with an outer carbon shell layer. The outer carbon shell layer is an outer hollow carbon shell layer. A hollow gap is left between the inner carbon shell layer and the outer carbon shell layer. The CuS compound is a CuS nanoparticle. The size of the CuS nanoparticle is 300-350 nm. The application has good structural stability, an adjustable internal interface and the like. In a secondary potassium ion battery, the application has a high capacity, good cycle retention and excellent rate performance.

Description

Technical Field

[0001] This invention belongs to the field of new energy, and specifically relates to a CuS composite material, its preparation method, and its application. Background Technology

[0002] In potassium-ion batteries, transition metal sulfides have attracted widespread attention due to their moderate theoretical potassium storage capacity and excellent redox reversibility. Among them, copper-based sulfides (such as CuS and Cu2S) have high theoretical capacity, low cost, and are environmentally friendly, making them promising anode materials for potassium-ion batteries. However, due to the large radius of potassium ions, the significant volume changes during potassium insertion / extraction can damage the electrode material structure, leading to a rapid decline in the potassium storage performance of the anode material. Meanwhile, K... + The slow reaction kinetics also limit the potassium storage performance of the anode material. Therefore, designing a suitable potassium-ion battery anode material with high potassium storage performance is an extremely challenging task.

[0003] Lifang Jiao et al. designed CuS-C@Nb2O5-C nanofibers with a core-shell structure. (Adv.Funct.Mater., doi.org / 10.1002 / adfm.202007712) In this structure, copper sulfide nanoparticles are distributed in the core layer of carbon nanofibers, while Nb2O5 is distributed on the surface of the carbon nanofiber shell. At 0.1A g... -1 After 100 cycles at a current density, the reversible capacity remains at 259.2 mA hg. -1 ; 2.0A g -1 After 2000 cycles at a current density, the reversible capacity remains at 95.1 mA hg. -1 However, the limited contact sites and uncontrollable buffer volume during potassium insertion / extraction lead to poor electron / ion transport efficiency and material structure degradation. Therefore, a combination of good structural integrity and superior charge transport is crucial for designing high-performance potassium-ion battery anodes. Summary of the Invention

[0004] To address the existing technical problems, the purpose of this invention is to provide CuS composite materials, their preparation methods, and applications.

[0005] The objective of this invention is achieved as follows: a CuS composite material, wherein the CuS composite material has the following general structural formula: YS CuS@C1@C2, where C1 represents the inner carbon shell layer, C2 represents the outer carbon shell layer, CuS represents a CuS compound, and YS represents a core-shell structure with a bell-shaped shape; characterized in that the CuS compound is the core, the outer surface of the CuS compound is covered by an inner carbon shell layer, the inner carbon shell layer and the outer surface of the core CuS compound are in close contact, an outer carbon shell layer is provided outside the inner carbon shell layer, the outer carbon shell layer is an outer hollow carbon shell layer, and a hollow gap is left between the inner carbon shell layer and the outer carbon shell layer; the CuS compound is CuS nanoparticles, the size of which is 300-350 nm.

[0006] Furthermore, the outer carbon shell is a hollow carbon shell, and the volume of the hollow carbon shell is more than 1.5 times the volume of the CuS nanoparticles, and more preferably 1.5 to 3 times.

[0007] Furthermore, the outer hollow carbon shell has a morphology similar to a rhombic dodecahedron; the inner and outer surfaces of the outer hollow carbon shell have a porous structure; and the outer hollow spherical carbon shell contains carbon.

[0008] Furthermore, the carbon atoms of the outer hollow carbon shell are doped with S and N atoms; S and N are uniformly distributed inside and on the surface of the outer hollow carbon shell.

[0009] Furthermore, the mass content of the CuS nanoparticles in the CuS composite material is 48 wt% or more, and more preferably 48-86 wt%.

[0010] The method for preparing a CuS composite material according to the present invention includes the following steps:

[0011] 1) Copper metal ions and organic ligands self-assemble in solution to form copper-organic framework compounds Cu-MOF;

[0012] 2) Cu-MOF was coated with 2-methylimidazolium zinc salt ZIF-8 to obtain the ZIF-8-encapsulated Cu-MOF complex Cu-MOF@ZIF-8;

[0013] 3) Pre-annealing and carbonizing Cu-MOF@ZIF-8 under an inert atmosphere to obtain Cu@C1@ZIF-8; the pre-annealing and carbonization step includes: holding at an inert atmosphere and at a temperature of 350℃, 400℃ or 450℃ for 1-3 hours to obtain Cu@C1@ZIF-8.

[0014] 4) Selectively etch the internal components of ZIF-8 in Cu@C1@ZIF-8 with tannic acid solution to obtain a rattle-shaped composite YS Cu@C1@ZIF-8 with internal pores; the solvent used in the tannic acid solution is a water-alcohol mixed solvent.

[0015] 5) YS Cu@C1@ZIF-8 was annealed and carbonized in an Ar / H2 atmosphere while Zn was removed to obtain YS Cu@C1@C2;

[0016] 6) YS Cu@C1@C2 is vulcanized under a sulfur vapor atmosphere to obtain YS CuS@C1@C2 composite material, which is the CuS composite material.

[0017] Further, the preparation method of the copper-organic framework compound Cu-MOF in step 1 above is as follows: copper salt and tricresyl peroxide are dissolved in dimethyl sulfoxide (DMSO) and reacted fully. Then, the solution is added dropwise to polyvinylpyrrolidone (PVP) solution. After the reaction is fully completed, the reaction solution is centrifuged to remove the mother liquor. The precipitate is washed with methanol to obtain a methanol dispersion of Cu-MOF. The copper salt is selected from one or more of copper sulfate, copper chloride, copper nitrate or copper acetate.

[0018] Further, the preparation method of Cu-MOF@ZIF-8 in step 2 above is as follows: the Cu-MOF methanol dispersion is uniformly dispersed in the methanol solution of zinc salt, and then the methanol solution of dimethylimidazole is added. After the reaction is complete, the mixture is filtered, washed, and dried to obtain the Cu-MOF complex Cu-MOF@ZIF-8 encapsulated by ZIF-8; the zinc salt is selected from one or more of zinc nitrate, zinc chloride, and zinc sulfate.

[0019] Furthermore, the preparation method of Y-SCuS@C1@C2 composite material obtained by vulcanizing YS Cu@C1@C2 in step 6 above is as follows:

[0020] YS Cu@C1@C2 and sulfur powder were sealed in a vacuum quartz tube in a certain proportion. The entire quartz tube was annealed and vulcanized at high temperature, and after removing excess sulfur powder, the product obtained was the YS CuS@C1@C2 composite material.

[0021] The ratio of YS Cu@C1@C2 to sulfur powder is such that the amount of sulfur in the sulfur powder is greater than the amount in YS Cu@C1@C2, preferably a mass ratio of 1:1.

[0022] The CuS composite material prepared by the above-described method of the present invention is applied to a potassium-ion battery. The potassium-ion battery includes a positive electrode, a negative electrode, and an electrolyte. The negative electrode includes a current collector and a negative electrode material loaded on the current collector. The negative electrode material contains the CuS composite material described above.

[0023] Specifically, the technical solution of the present invention is:

[0024] A CuS composite material, having the following general structural formula: Y-SCuS@C1@C2, where C1 represents the inner carbon shell, C2 represents the outer carbon shell, CuS represents a CuS compound, and YS represents a core-shell structure with a bell-shaped shape. It includes the following characteristics:

[0025] It has a bell-shaped core-shell structure. The core is CuS, and the outer surface of CuS is covered with a carbon layer, which is the inner carbon shell layer. The inner carbon shell layer is in close contact with the outer surface of the core CuS. The outermost carbon shell layer is a hollow carbon shell, and there is a hollow gap between the inner carbon shell layer and the outer carbon shell layer.

[0026] The CuS is in nanoparticle form with a particle size of 300-350 nm;

[0027] The outermost carbon shell (outermost hollow carbon shell) has a volume that is more than 1.5 times the volume of CuS nanoparticles, and more preferably 1.5 to 3 times.

[0028] The outermost hollow carbon shell has a morphology of a rhombic dodecahedron.

[0029] The outermost hollow spherical carbon shell has a porous structure on both its inner and outer surfaces;

[0030] The outermost hollow spherical carbon shell is composed of carbon.

[0031] The carbon atoms of the outermost hollow carbon shell are doped with S and N atoms; S and N are uniformly distributed inside and on the surface of the carbon shell.

[0032] The CuS content relative to the composite material is 48 wt%, more preferably 48-86 wt%.

[0033] This invention provides CuS composite materials for use in potassium-ion batteries.

[0034] This invention provides a secondary battery containing CuS composite material, the secondary battery including a potassium-ion battery, the potassium-ion battery including a positive electrode, a negative electrode and an electrolyte; the negative electrode including a current collector and a negative electrode material loaded on the current collector; wherein, the negative electrode material contains the CuS composite material.

[0035] A method for preparing CuS composite materials includes the following steps:

[0036] 1. Copper metal ions and organic ligands self-assemble in solution to form copper-organic framework compounds (Cu-MOF);

[0037] 2. Cu-MOF was coated with 2-methylimidazolium zinc salt (ZIF-8) to obtain ZIF-8-encapsulated Cu-MOF complex (Cu-MOF@ZIF-8);

[0038] 3. Cu-MOF@ZIF-8 is pre-annealed and carbonized under an inert atmosphere to obtain Cu@C1@ZIF-8; the pre-annealing and carbonization step includes: holding at an inert atmosphere and at a temperature of 350℃ or 400℃ or 450℃ for 1-3 hours.

[0039] 4. Selectively etch the internal components of ZIF-8 in Cu@C1@ZIF-8 with a tannic acid solution to obtain a rattle-shaped composite YS Cu@C1@ZIF-8 with internal pores; the solvent in the tannic acid solution is a water-alcohol mixture.

[0040] 5. Annealing and carbonization in an Ar / H2 atmosphere while removing Zn simultaneously yields YS Cu@C1@C2;

[0041] 6. YS Cu@C1@C2 is vulcanized under a sulfur vapor atmosphere to obtain YS CuS@C1@C2 composite material, which is the CuS composite material.

[0042] Optionally, step 1 includes: dissolving copper salt and tricresyl peroxide in dimethyl sulfoxide (DMSO) and reacting them fully, then adding the mixture dropwise to a polyvinylpyrrolidone (PVP) solution. After the reaction is fully completed, the reaction solution is centrifuged to remove the mother liquor, and the precipitate is washed with methanol to obtain a methanol dispersion of Cu-MOF. The copper salt includes one or more of copper sulfate, copper chloride, copper nitrate, or copper acetate.

[0043] Optionally, step 2 includes: uniformly dispersing the Cu-MOF methanol dispersion into a zinc salt methanol solution, then adding a dimethylimidazole methanol solution, reacting fully, filtering, washing, and drying to obtain the ZIF-8-encapsulated Cu-MOF complex (Cu-MOF@ZIF-8); the zinc salt includes one or more of zinc nitrate, zinc chloride, and zinc sulfate.

[0044] Optionally, step 6 includes:

[0045] YS Cu@C1@C2 and sulfur powder are sealed in a vacuum quartz tube in a certain proportion. The entire quartz tube is annealed and vulcanized at high temperature, and then excess sulfur powder is removed to obtain the product, which is the YS CuS@C1@C2 composite material.

[0046] The ratio of YS Cu@C1@C2 to sulfur powder is such that the amount of sulfur in the sulfur powder is greater than the amount in YS Cu@C1@C2, preferably a mass ratio of 1:1.

[0047] The beneficial effects of this invention are as follows: This invention modulates the internal interface of the material to a certain extent, designing a CuS / carbon interface. In this invention, Cu-MOF is used as a precursor. After carbonizing the MOF, an internal carbon layer can be directly introduced into the material, shortening the diffusion path of electrons and ions in the CuS core and enhancing electron / ion transport from the outer carbon shell to the CuS core. The abundant porosity and large specific surface area of ​​the MOF itself also contribute to improved reaction kinetics. Furthermore, the CuS@C1 core is confined within a ZIF-8 derived hollow carbon shell, providing sufficient internal void space to buffer the volume expansion during potassium ion insertion / extraction, resulting in a unique bell-shaped structure. The outer carbon shell structure, to some extent, reduces the aggregation between active materials. The Y-SCuS@C1@C2 composite material exhibits good structural stability and tunable internal interface properties, demonstrating high capacity, good cycle retention, and excellent rate performance in secondary potassium-ion batteries. (1 A g) -1 At a current density, the capacity remains at 190 mA hg after 1000 cycles. -1 Meanwhile, the charging and discharging current changes from 0.1A g -1 Increased to 20A g -1 Rate performance testing was conducted at 20A g. -1 Its capacity remains at 195 mA hg -1 .

[0048] The preparation method of the present invention is simple to operate, has a short cycle, and is easy to scale up for production. Attached Figure Description

[0049] Figure 1 Scanning electron microscope (SEM) image of the bell-shaped carbon-based CuS composite material (Y-SCuS@C1@C2) prepared in Example 1.

[0050] Figure 2 X-ray diffraction pattern of the bell-shaped carbon-based CuS composite material (Y-SCuS@C1@C2) prepared in Example 1.

[0051] Figure 3Thermogravimetric analysis (TGA) of the bell-shaped carbon-based CuS composite material (Y-SCuS@C1@C2) prepared in Example 1.

[0052] Figure 4 The diagram shows the charge-discharge cycle performance of a potassium-ion battery using the bell-shaped carbon-based CuS composite material (Y-SCuS@C1@C2) prepared in Example 1 as the negative electrode material.

[0053] Figure 5 The diagram shows the charge / discharge rate performance of a potassium-ion battery using the bell-shaped carbon-based CuS composite material (Y-SCuS@C1@C2) prepared in Example 1 as the negative electrode material.

[0054] Figure 6 Scanning electron microscope image of the CuS composite material (CuS / Cl) prepared in Example 2.

[0055] Figure 7 The image shows the X-ray diffraction pattern of the CuS composite material (CuS / Cl) prepared in Example 2.

[0056] Figure 8 Thermogravimetric analysis (TGA) of the CuS composite material (CuS / C1) prepared in Example 2.

[0057] Figure 9 The battery charge-discharge cycle performance diagram of the CuS composite material (CuS / Cl) prepared in Example 2 as the negative electrode material of potassium-ion battery.

[0058] Figure 10 The battery charge / discharge rate performance diagram of the CuS composite material (CuS / Cl) prepared in Example 2 is a potassium-ion battery anode material.

[0059] Figure 11 A schematic diagram of the preparation process in Example 1. Detailed Implementation

[0060] Example 1:

[0061] 1) Dissolve 2.44 g of copper nitrate trihydrate and 0.58 g of trimesic acid in 5.0 g of dimethyl sulfoxide (DMSO), sonicate for 30 min, and then place in a 65 °C oven overnight. Then, add 1.0 ml of the above liquid dropwise to 10 ml of methanol containing 100 mg of polyvinylpyrrolidone (PVP) (Mw = 40000), and stir vigorously in an oil bath at 55 °C for 90 min. Wash the product three times by centrifugation with methanol, dry to obtain Cu-MOF nanoparticles, and then disperse in 10 ml of methanol for later use.

[0062] 2) The dispersion containing 20 mg of Cu-MOF nanoparticles was added to 20 ml of methanol solution containing 100 mM zinc nitrate hexahydrate, stirred for 20 s, and immediately poured into 20 ml of methanol solution containing 200 mM dimethylimidazole, stirred for 20 s, and allowed to stand for 24 h. After filtration and washing with methanol and drying, Cu-MOF@ZIF-8 was obtained.

[0063] 3) Place Cu-MOF@ZIF-8 in a tube furnace under an argon atmosphere for pre-annealing and carbonization. The pre-annealing temperature is 400℃ and the annealing time is 1h.

[0064] 4) Disperse the annealed sample in a mixed solution of 0.47 ml anhydrous ethanol and 8.05 ml water. While stirring, quickly pour in 8.75 ml of an aqueous solution containing 87.5 mg tannic acid, stop stirring, let stand for 10 min, wash with ethanol and water by centrifugation, and dry to obtain Y-SCu@C1@ZIF-8.

[0065] 5) The obtained YS Cu@C1@ZIF-8 was placed in a tube furnace under an Ar / H2 atmosphere for annealing and carbonization while removing Zn. The annealing temperature was 650℃ and held for 5 hours. After natural cooling, YS Cu@C1@C2 was obtained.

[0066] 6) The obtained YS Cu@C1@C2 was sealed in a tube with sulfur powder at a mass ratio of 1:1 and placed in a muffle furnace. It was first kept at 155℃ for 6 hours, and then heated to 250℃ and kept for 3 hours. After natural cooling, the product was placed in a tube furnace under an argon atmosphere and kept at 200℃ for 6 hours to remove excess sulfur powder, thus obtaining YS CuS@C1@C2.

[0067] In step 3), the pre-annealing and carbonization temperature should not exceed 450°C. Excessive temperature will cause excessive damage to the structure of the outer ZIF-8 layer, thereby causing the failure of subsequent selective corrosion of the internal components of ZIF-8 by tannin acid.

[0068] In step 5), the annealing and carbonization temperature needs to be above 600℃, otherwise Zn will not be completely removed.

[0069] Figure 1 The image shows a scanning electron microscope (SEM) image of the bell-shaped carbon-based CuS composite material (Y-SCuS@C1@C2) prepared in Example 1. It can be seen that the composite material has a bell-shaped structure (with a bell-shaped core-shell structure). The core is a CuS compound and is well confined within the inner carbon shell. The inner carbon shell is in close contact with the outer surface of the core CuS. The outer carbon shell is a hollow carbon shell, and there is a hollow gap between the inner and outer carbon shells. The outer carbon shell is a ZIF-8 derived hollow carbon shell.

[0070] Figure 2The X-ray diffraction pattern of the YS CuS@C1@C2 composite material prepared in this embodiment can determine the phase of CuS.

[0071] Figure 3 Thermogravimetric analysis of the YS CuS@C1@C2 composite material prepared in this embodiment, with a content of 48 wt%.

[0072] 7) The product from step 6), YS CuS@C1@C2 composite material (70wt%), conductive carbon black (15wt%), and carboxymethyl cellulose (CMC 15wt%), were thoroughly ground in an agate mortar, with deionized water used as a dispersant. The resulting slurry was coated onto a prepared nickel foam current collector and vacuum-dried at 80°C for 12 hours. The electrode was then weighed. The mass of the slurry on each current collector was determined based on the mass difference before and after drying. After weighing, the electrode was again dried in a vacuum drying oven at 80°C for 2 hours and then placed in a glove box in preparation for coin cell assembly.

[0073] 8) The button cell was assembled in an argon-filled glove box, with a potassium metal sheet as the negative electrode, glass fiber as the separator, and the electrode sheet made as the positive electrode.

[0074] 9) The constant current charge-discharge test mainly examines the charge-discharge specific capacity, cycle performance, and rate performance of potassium-ion half-cells under different currents. Initially, the positive electrode material in the potassium-ion half-cell lacks potassium ions; therefore, constant current discharge is required at the beginning to allow potassium ions to embed into the positive electrode. After discharge, the positive electrode material is in a potassium-rich state, and the charging test begins. This cycle is repeated. The test voltage range for the potassium-ion half-cell is 0.05-2.8V, and the charge-discharge current density is set to 100mA g based on experimental conditions. -1 ~20A g -1 Not equal.

[0075] Figure 4 The image shows the charge-discharge cycle performance of the YS CuS@C1@C2 nanocomposite material prepared in this embodiment in a potassium-ion battery. Its performance at 1 A g... -1 At the specified current density, the capacity remained at 190 mA hg after 1000 cycles. -1 ;

[0076] Figure 5 The image shows the charge-discharge rate performance of the YS CuS@C1@C2 nanocomposite material prepared in this embodiment in a potassium-ion battery. Rate performance testing was performed by starting the charge-discharge current from 0.1 A g / g. -1 Increased to 20A g -1 In 20A g -1Its capacitance is 195 mA hg at a current density. -1 When the current density increases from 20 A g -1 Return to 0.1A g -1 At that time, its reversible capacity remained at 399 mA hg -1 It exhibits excellent rate performance.

[0077] Figure 11 The diagram illustrates the synthesis process in this embodiment. First, a ZIF-8 layer is coated onto the surface of Cu-MOF to construct a Cu-MOF@ZIF-8 structure. Due to the difference in stability between the two MOFs, HKUST-1 is first converted to Cu / Cl during the pre-carbonization process, while ZIF-8 retains its crystalline structure. Then, ZIF-8 is etched with tannic acid to form a hollow structure, yielding Y-SCu / Cl@ZIF-8. Subsequently, the sample is calcined at high temperature in a reducing atmosphere to carbonize ZIF-8 and remove metallic Zn. Finally, after sulfidation treatment, the YS CuS@Cl@C2 composite material is obtained.

[0078] Example 2 (Comparative Example):

[0079] 1) Dissolve 2.44 g of copper nitrate trihydrate and 0.58 g of trimesic acid in 5.0 g of dimethyl sulfoxide (DMSO), sonicate for 30 min, and then place in a 65 °C oven overnight. Then, add 1.0 ml of the above liquid dropwise to 10 ml of methanol containing 100 mg PVP (Mw = 40000), and stir vigorously in an oil bath at 55 °C for 90 min. Wash the product three times by centrifugation with methanol and dry to obtain Cu-MOF.

[0080] 2) The obtained Cu-MOF was placed in a tube furnace under an argon atmosphere and annealed at 400℃ for 1 h, and then heated to 650℃ and held for 5 h to obtain Cu / Cl.

[0081] 3) After sealing the obtained Cu / Cl with sulfur powder at a mass ratio of 1:1, place it in a muffle furnace and maintain it at 155℃ for 6 hours, then raise the temperature to 250℃ and maintain it for 3 hours. After natural cooling, place the product in a tube furnace under an argon atmosphere and maintain it at 200℃ for 6 hours to remove excess sulfur powder, thus obtaining CuS / Cl. Figure 6 The image shown is a scanning electron microscope image of the CuS composite material (CuS / Cl) prepared in Example 2. It can be seen that the composite material has a bell-shaped structure with a core of CuS and an outermost carbon shell derived from Cu-MOF.

[0082] Figure 7 The X-ray diffraction pattern of the CuS composite material (CuS / Cl) prepared in Example 2 can be used to determine the phase of CuS.

[0083] Figure 8Thermogravimetric analysis of the CuS composite material (CuS / Cl) prepared in Example 2, with a content of 86 wt%.

[0084] Figure 9 Example 2 shows the charge-discharge cycle performance of the CuS composite material (CuS / Cl) prepared as a potassium-ion battery anode material. Its performance at 1 A g... -1 At the given current density, the capacity after 100 cycles is 33 mA hg. -1 ;

[0085] Figure 10 Example 2 shows the charge / discharge rate performance of the CuS composite material (CuS / Cl) prepared as a potassium-ion battery anode material. Rate performance testing was performed on it, with the charge / discharge current starting from 0.1 A g / g. -1 Increased to 20A g -1 In 20A g -1 Its capacity is 100 mA hg at the current density. -1 .

Claims

1. A method for preparing a CuS composite material, comprising the following steps: 1) Copper metal ions and organic ligands self-assemble in solution to obtain copper-organic framework compound Cu-MOF; the preparation method of copper-organic framework compound Cu-MOF is as follows: copper salt and tricresyl acid are dissolved in dimethyl sulfoxide and reacted fully, then added dropwise to polyvinylpyrrolidone solution. After the reaction is fully completed, the reaction solution is centrifuged to remove the mother liquor, and the precipitate is washed with methanol to obtain a methanol dispersion of Cu-MOF; the copper salt is selected from one or more of copper sulfate, copper chloride, copper nitrate or copper acetate; 2) Cu-MOF was coated with 2-methylimidazolium zinc salt ZIF-8 to obtain the ZIF-8-encapsulated Cu-MOF complex Cu-MOF@ZIF-8; 3) Pre-annealing and carbonizing Cu-MOF@ZIF-8 under an inert atmosphere to obtain Cu@C1@ZIF-8; the pre-annealing and carbonization step includes: under an inert atmosphere and at 350°C o C or 400 o C or 450 o Cu@C1@ZIF-8 was obtained by maintaining the temperature at C for 1-3 h. 4) Selectively etch the internal components of ZIF-8 in Cu@C1@ZIF-8 with tannic acid solution to obtain a rattle-shaped composite YS Cu@C1@ZIF-8 with internal pores; the solvent used in the tannic acid solution is a water-alcohol mixture. 5) YS Cu@C1@ZIF-8 was annealed and carbonized in an Ar / H2 atmosphere while Zn was removed to obtain YS Cu@C1@C2; 6) YS Cu@C1@C2 is sulfurized under a sulfur vapor atmosphere to obtain the YS CuS@C1@C2 composite material, which is the CuS composite material mentioned above. The CuS composite material has the following general structural formula: YS CuS@C1@C2, where C1 represents the inner carbon shell layer, C2 represents the outer carbon shell layer, CuS represents the CuS compound, and YS represents a core-shell structure with a bell-shaped shape. The CuS compound is the core, and the outer surface of the CuS compound is covered with an inner carbon shell layer. The inner carbon shell layer and the outer surface of the core CuS compound are in close contact. An outer carbon shell layer is provided outside the inner carbon shell layer. The outer carbon shell layer is a hollow carbon shell layer, and there is a hollow gap between the inner carbon shell layer and the outer carbon shell layer. The CuS compound is CuS nanoparticles with a size of 300-350 nm.

2. The method for preparing a CuS composite material according to claim 1, characterized in that, The preparation method of Cu-MOF@ZIF-8 in step 2) is as follows: the Cu-MOF methanol dispersion is uniformly dispersed in the methanol solution of zinc salt, and then the methanol solution of dimethylimidazole is added. After the reaction is complete, the mixture is filtered, washed, and dried to obtain the Cu-MOF complex Cu-MOF@ZIF-8 encapsulated by ZIF-8. The zinc salt is selected from one or more of zinc nitrate, zinc chloride, and zinc sulfate.

3. The method for preparing a CuS composite material according to claim 1, characterized in that, The preparation method of YS CuS@C1@C2 composite material obtained by vulcanizing YS Cu@C1@C2 in step 6) is as follows: YS Cu@C1@C2 and sulfur powder were sealed in a vacuum quartz tube in a certain proportion. The entire quartz tube was annealed and vulcanized at high temperature, and after removing excess sulfur powder, the product obtained was the YS CuS@C1@C2 composite material. The ratio of YS Cu@C1@C2 to sulfur powder is such that the amount of sulfur in the sulfur powder is greater than the amount in YS Cu@C1@C2.

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