Bimetallic sulfide, its preparation method, composite, its preparation method, lithium-sulfur cathode material and lithium-sulfur battery

Abstract

The present invention provides a bimetallic sulfide, a preparation method thereof, a composite and a preparation method thereof, a lithium-sulfur cathode material and a lithium-sulfur battery. The chemical formula of the bimetallic sulfide is M x Co 3‑x S4, where M is selected from any one of Ni, Cu, Mn, V, Fe, Zn, Mo. The morphology of the bimetallic sulfide is a hollow porous nanocube structure, where 0.5 ≤ x ≤ 1.5. The M of the hollow porous nanocube x Co 3‑x S4 has a high specific surface area (more active sites). If it is used for the loading of S, it greatly improves the sulfur fixation effect of M x Co 3‑x S4 and alleviates the volume expansion caused by charge and discharge; furthermore, the bimetals with multiple valences (M and Co) play a synergistic role in the catalytic conversion of polysulfides, improving the theoretical capacity of the lithium-sulfur cathode material and the rate performance and cycle performance of the lithium-sulfur battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-sulfur batteries, and in particular, to a bimetallic sulfide and a preparation method thereof, a composite and a preparation method thereof, a lithium-sulfur cathode material, and a lithium-sulfur battery. Background Art

[0002] Due to the economic development, population growth, and the change of traditional lifestyles, the modern society has an increasing demand for energy. However, with the sharp increase in the use of chemical fuels, the resulting environmental pollution problems have become increasingly serious, and people are becoming more and more worried about this. To solve this problem, while reducing people's dependence on fossil fuels and finding renewable new energy sources have become the top priorities of research work. Lithium-ion batteries have been widely used in the past 20 years due to their high energy density, low cost, and easy portability. However, the current technology of lithium-ion batteries mainly focuses on the research of insertion-type composite anode and cathode materials, which severely limits their charge storage capacity and energy density. The capacity of the insertion-type oxide cathode is currently difficult to reach 250 mAh·g -1 . On the other hand, the capacity of the graphite anode is also limited to 370 mAh·g -1 . In order to overcome the charge storage limitation brought by the insertion / extraction mode of lithium-ion batteries, in recent years, lithium-sulfur batteries based on the conversion reaction mechanism have received more and more attention. Sulfur is one of the most abundant elements in the earth's crust, and elemental sulfur mainly exists in the form of S8 on the earth. For a lithium-sulfur battery using sulfur as the cathode material, its theoretical specific capacity is as high as 1672 mAh·g -1 , which is much higher than that of current commercial lithium-ion batteries and is currently considered to be one of the most promising lithium secondary battery systems for research and application.

[0003] Although lithium-sulfur batteries have the advantages of high capacity, high specific capacity, low production cost, and environmental friendliness, there are still problems such as low active material utilization rate, short cycle life, and poor safety, which severely restrict the commercial application of lithium-sulfur batteries. The main reasons for the above problems are as follows: (1) The insulation problem of S: The room-temperature conductivity of elemental sulfur is only 5×10 -30 S·cm -1 ; (2) The shuttle effect: The polysulfide intermediate Li2S x (6 < x ≤ 8) generated in the electrode reaction is extremely soluble in solvents DME and DOL and passes through the separator to react with metallic lithium, generating solid Li2S, resulting in irreversible loss of active material S and reduction of Coulomb efficiency. Severe shuttle effect also leads to phenomena such as infinite charging and poor charging. (4) Volume expansion: Due to sulfur (2.07 g·cm -3 ) and the final product Li2S (1.66 g·cm -3) have different densities, and the volume expansion during the charge and discharge process of the battery is about 80%. During long-term cycling, the continuous shrinkage and expansion of the volume can easily lead to the pulverization of the cathode material, thus seriously affecting the capacity of the lithium-sulfur battery.

[0004] In recent years, researchers have prepared sulfur-based composite cathode materials by combining active sulfur with non-polar materials such as carbon materials (such as activated carbon, mesoporous carbon, graphene, carbon nanotubes, carbon nanofibers), polymers (such as polyacrylonitrile, polyaniline, polypyrrole), or with polar materials such as metal oxides, metal sulfides, or matrix materials with specific structures such as metal carbides / nitrides, which can significantly improve the cycling performance and rate performance of lithium-sulfur batteries.

[0005] However, in the current lithium-sulfur battery cathodes, there are problems with the uniform distribution of single metal sulfides or multiple metal sulfide dopants prepared as active sites, and at the same time, it depends on the pore structure and surface area of the substrate material; graphene and carbon nanotube materials have poor dispersibility, and the substrate materials are prone to aggregation during the preparation process, which may lead to uneven dispersion of active substances, thereby reducing the utilization rate of active substances, increasing electrode polarization, and further affecting the capacity performance and rate performance of the battery. Summary of the Invention

[0006] The main object of the present invention is to provide a bimetallic sulfide, its preparation method, a composite, its preparation method, a lithium-sulfur cathode material and a lithium-sulfur battery to solve the problems of poor capacity performance and cycling performance of lithium-sulfur batteries in the prior art.

[0007] To achieve the above object, according to one aspect of the present invention, a bimetallic sulfide is provided. The chemical formula of the bimetallic sulfide is M x Co 3-x S4, M is selected from any one of Ni, Cu, Mn, V, Fe, Zn, Mo, and the morphology of the bimetallic sulfide is a hollow porous nanocube structure, where 0.5 ≤ x ≤ 1.5.

[0008] Furthermore, the edge length of the above porous nanocube is 450 - 550 nm. Preferably, the pore diameter of the bimetallic sulfide is 2 - 6 nm, and preferably the specific surface area of the bimetallic sulfide is 25 - 40 m 2 / g.

[0009] According to another aspect of the present invention, a preparation method of a bimetallic sulfide is provided. The preparation method includes step S1, etching the M x Co 3-x [Co(CN)6]2 precursor with an acid solution to obtain hollow M x Co 3-x [Co(CN)6]2; step S2, hollowing out M xCo 3-x Calcine [Co(CN)₆]₂ to obtain a bimetallic sulfide. The calcination is carried out in a gas containing H₂S. Preferably, the gas containing H₂S is a mixture of H₂S and N₂ or a mixture of H₂S and an inert gas.

[0010] Further, the process of the above etching treatment includes mixing an acid solution, a surfactant, and M x Co 3-x Mix the [Co(CN)₆]₂ precursor and then carry out etching treatment. Preferably, the surfactant is selected from polyvinylpyrrolidone or cetyltrimethylammonium bromide. The hydrogen ion concentration in the acid solution is 1 - 5 mol / L. Preferably, the acid solution is selected from any one or more of hydrochloric acid, aqueous nitric acid, and aqueous sulfuric acid. Preferably, the mass ratio of the [Co(CN)₆]₂ precursor to the surfactant is 1:5 - 1:7. Preferably, the temperature of the etching treatment is 140 - 200 °C. x Co 3-x Further, based on hydrogen ions, the molar ratio of the [Co(CN)₆]₂ precursor to the acid solution is 1:2×10

[0011] ~1:10×10 x Co 3-x 4 4 .

[0012] Further, the molar ratio of the above H₂S to the hollow [Co(CN)₆]₂ is 4:1 - 8:1. Preferably, the volume fraction of H₂S in the mixed gas is 5 - 15%. x Co 3-x

[0013] Further, the process of the above calcination includes heating the hollow [Co(CN)₆]₂ in the mixed gas at a rate of 2 - 5 °C / min to 350 - 400 °C to obtain a calcined intermediate. Preferably, the calcination time is 3 - 5 h; cooling the calcined intermediate in the mixed gas at a rate of 2 - 5 °C / min to 20 - 25 °C to obtain the bimetallic sulfide. x Co 3-x

[0014] According to another aspect of the present invention, a composite is provided. The composite is an M x Co 3-x S₄ - S composite. In the M x Co 3-x S₄ - S composite, the mass ratio of M x Co 3-x S₄ to S is 1:4 - 5.

[0015] ​​​​According to another aspect of the present invention, a method for preparing a composite is provided. The preparation method includes mixing an M x Co 3-x S4 suspension with an S8 solution to obtain a mixture; adjusting the pH value of the mixture to 6-7, then stirring, washing, and drying to obtain the composite. Preferably, the stirring time is 8-10 h.

[0016] Furthermore, the solid content of the above-mentioned M x Co 3-x S4 suspension is 0.25-0.3 mg / mL. Preferably, the S8 solution is obtained by dissolving S8 elemental sulfur in an aqueous sulfide solution. Preferably, the mass ratio of S8 elemental sulfur to the sulfide is 1:12.5-15. Preferably, the concentration of the aqueous sulfide solution is 1.6-1.8 mol / L. Preferably, the aqueous sulfide solution is selected from any one or more of an aqueous sodium sulfide solution, an aqueous potassium sulfide solution, and an aqueous ammonium sulfide solution.

[0017] According to another aspect of the present invention, a lithium-sulfur cathode material is provided. The lithium-sulfur cathode material includes a sulfur-containing composite, and the sulfur-containing composite is the above-mentioned composite.

[0018] According to another aspect of the present invention, a lithium-sulfur battery is provided. The lithium-sulfur battery includes a positive electrode and a negative electrode, and the positive electrode is the above-mentioned lithium-sulfur cathode material.

[0019] Applying the technical solution of the present invention, since M x Co 3-x S4 is a sulfide material with a spinel structure, its delocalized electronic structure gives it high ionic and electronic conductivity; the hollow porous nanocube M x Co 3-x S4 has a high specific surface area (more active sites). If M x Co 3-x S4 is used for the loading of S, on the one hand, based on a large amount of S entering the cavity inside the hollow porous nanocube through the pores on the surface of the hollow porous nanocube, a part of S will also be adsorbed on the surface of the hollow porous nanocube, thereby greatly improving the sulfur fixation effect of M x Co 3-x S4 to obtain an M x Co 3-x S4-S composite containing more S, on the other hand, can relieve the volume expansion caused by charge and discharge; at the same time, the strongly polar M x Co 3-xS4 is beneficial for its combination with polysulfide ions to form TM-S covalent bonds. This TM-S covalent bond has a strong binding energy and electron transfer ability, thus facilitating the effective chemical adsorption and conversion of polysulfides. Moreover, the dual metals (M and Co) with multiple valences play a synergistic role in the catalytic conversion of polysulfides, greatly alleviating the shuttle effect of polysulfide ions. As a result, the theoretical capacity of the cathode material for lithium-sulfur batteries is improved, and the rate performance and cycling performance of lithium-sulfur batteries are enhanced. Brief Description of the Drawings

[0020] The accompanying drawings forming a part of this application are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0021] Figure 1 Shows the Cu obtained in Example 1 5 / 3 Co 4 / 3 Scanning electron microscope image of the [Co(CN)6]2 precursor;

[0022] Figure 2 Shows Figure 1 The Cu shown 5 / 3 Co 4 / 3 Partial enlarged view of the [Co(CN)6]2 precursor;

[0023] Figure 3 Shows the scanning electron microscope image of the hollow CuCo2S4 obtained in Example 1;

[0024] Figure 4 Shows Figure 1 Partial enlarged view of the broken structure in the shown hollow CuCo2S4;

[0025] Figure 5 Shows the transmission electron microscope image of the hollow CuCo2S4 obtained in Example 1;

[0026] Figure 6 Shows the XRD spectrum of the hollow CuCo2S4 obtained in Example 1; and

[0027] Figure 7 Shows the cycling performance curve of the lithium-sulfur battery obtained in Example 1 at a rate of 0.2C. Detailed Description of the Embodiments

[0028] It should be noted that, without conflict, the embodiments in this application and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0029] As analyzed in the background art, there are problems with poor capacity performance and cycling performance of lithium-sulfur batteries in the prior art. To solve this problem, the present invention provides a bimetallic sulfide, a preparation method thereof, a composite, a preparation method thereof, a lithium-sulfur cathode material, and a lithium-sulfur battery.

[0030] In a typical embodiment of the present application, a bimetallic sulfide is provided, and the chemical formula of the bimetallic sulfide is M x Co 3-x S4, M is selected from any one of Ni, Cu, Mn, V, Fe, Zn, Mo, and the morphology of the bimetallic sulfide is a hollow porous nanocube structure, where 0.5 ≤ x ≤ 1.5.

[0031] Since M x Co 3-x S4 is a sulfide material with a spinel structure, and its delocalized electronic structure gives it high ionic and electronic conductivity; the hollow porous nanocube of M x Co 3-x S4 has a high specific surface area (more active sites). If M x Co 3-x S4 is used for the loading of S, on the one hand, on the basis that a large amount of S enters the cavity inside the hollow porous nanocube through the pores on the surface of the hollow porous nanocube, a part of S will also be adsorbed on the surface of the hollow porous nanocube, thus greatly improving the sulfur fixation effect of M x Co 3-x S4, and obtaining an M x Co 3-x S4-S composite containing more S. On the other hand, it can relieve the volume expansion caused by charge and discharge; at the same time, the strongly polar M x Co 3-x S4 is conducive to its combination with polysulfide ions to form TM-S covalent bonds. The TM-S covalent bond has a strong binding energy and electron transfer ability, which is conducive to the effective chemical adsorption and conversion of polysulfides. Then, through the synergistic effect of the dual metals (M and Co) with multiple valences on the catalytic conversion of polysulfides, the shuttle effect of polysulfide ions is greatly alleviated, thereby improving the theoretical capacity of the lithium-sulfur battery cathode material and improving the rate performance and cycling performance of the lithium-sulfur battery.

[0032] In an embodiment of the present application, the edge length of the above-mentioned porous nanocube is 450 - 550 nm, preferably the pore diameter of the bimetallic sulfide is 2 - 6 nm, and preferably the specific surface area of the bimetallic sulfide is 25 - 40 m 2 / g.

[0033] When applying the bimetallic sulfide of the present application to the cathode material of a lithium-sulfur battery, the porous nanocube of the above size of Mx Co 3-x S4 has a larger specific surface area, which is more conducive to the solidification of sulfur, obtaining as much sulfur-loaded cathode material as possible, and alleviating the volume expansion caused by charge and discharge, thereby improving the performance of lithium-sulfur batteries.

[0034] In another typical embodiment of the present application, a method for preparing the above-mentioned bimetallic sulfide is provided. The preparation method includes step S1 of etching the M x Co 3-x [Co(CN)6]2 precursor with an acid solution to obtain hollow M x Co 3-x [Co(CN)6]2; step S2 of calcining the hollow M x Co 3-x [Co(CN)6]2 to obtain the bimetallic sulfide. The calcination is carried out in a gas containing H2S. Preferably, the gas containing H2S is a mixture of H2S and N2 or a mixture of H2S and an inert gas.

[0035] By etching the M x Co 3-x [Co(CN)6]2 precursor with an acid solution, a surface-porous and hollow M x Co 3-x [Co(CN)6]2 is obtained. After the porous and hollow M x Co 3-x [Co(CN)6]2 is calcined in a gas containing H2S, a spinel-type, surface-porous and hollow bimetallic sulfide is obtained. The preparation method is simple and easy to industrialize.

[0036] In an embodiment of the present application, the process of the above etching treatment includes mixing an acid solution, a surfactant, and the M x Co 3-x [Co(CN)6]2 precursor and then carrying out the etching treatment. Preferably, the surfactant is selected from polyvinylpyrrolidone or cetyltrimethylammonium bromide. The hydrogen ion concentration in the acid solution is 1-5 mol / L. Preferably, the acid solution is selected from any one or more of hydrochloric acid, nitric acid aqueous solution, and sulfuric acid aqueous solution. Preferably, the mass ratio of the M x Co 3-x [Co(CN)6]2 precursor to the surfactant is 1:5-1:7. Preferably, the temperature of the etching treatment is 140-200 °C.

[0037] The above-mentioned surfactant (organic macromolecule) is coated on the surface of the cube of the M x Co 3-x [Co(CN)6]2 precursor, so that on the M x Co3-x A certain protective layer is formed on the surface of the cube of the [[Co(CN)6]]2 precursor. At the etching temperature of 140-200 °C, a large amount of the solute in the acid solution is converted into acidic gaseous solutes, and water is converted into water vapor. As the acidic gaseous solutes and water vapor increase, a large amount of acidic gaseous solutes and water vapor penetrate through the protective layer and seep into the M x Co 3-x inside the cube of the [[Co(CN)6]]2 precursor and react with the internal complex therein. On the one hand, the dissolution of M and Co causes M x Co 3-x to form a certain cavity inside the cube of the [[Co(CN)6]]2 precursor. At the same time, CN - reacts with the acidic gaseous solutes and water vapor to generate HCN and CO2. As time goes by, HCN and CO2 escape from the inside of the cube of the M x Co 3-x cube of the [[Co(CN)6]]2 precursor, thereby further enriching the surface pores of the cube of the M x Co 3-x cube of the [[Co(CN)6]]2 precursor. Meanwhile, the protective layer reduces the corrosiveness of the acidic gas to the surface of the cube of the M x Co 3-x cube of the [[Co(CN)6]]2 precursor, and then a porous and hollow bimetallic sulfide is formed. If the concentration of the acid solution is too low, the required volume of the acid solution is too large, increasing the workload of post-treatment. If the concentration of the acid solution is too high, on the one hand, its corrosiveness is too strong, resulting in partial damage to the cubic structure of the [[Co(CN)6]]2 precursor of M x Co 3-x cube, making the obtained bimetallic sulfide unfavorable for the fixation of more sulfur. Therefore, in order to balance the above two aspects, the acid solution with the above concentration and the surfactant with the above ratio are beneficial to forming sufficient protection on the surface of the cube of the [[Co(CN)6]]2 precursor of M x Co 3-x cube while not affecting the performance of the remaining active ingredients due to excessive addition thereof.

[0038] To improve the etching effect of the acid solution and obtain a bimetallic sulfide with as rich pores as possible, thereby improving the sulfur fixation ability of the bimetallic sulfide, it is preferably that, in terms of hydrogen ions, the molar ratio of the [[Co(CN)6]]2 precursor of M x Co 3-x to the acid solution is 1:2×10 4 ~1:10×10 4 .

[0039] To ensure a hollow M x Co 3-x[Co(CN)6]2 is converted into the bimetallic sulfide as much as possible, preferably the above-mentioned H2S and hollow M x Co 3-x The molar ratio of [Co(CN)6]2 is 4:1 to 8:1, and preferably the volume fraction of H2S in the mixed gas is 5 to 15%.

[0040] In an embodiment of the present application, the above-mentioned calcination process includes hollow M x Co 3-x [Co(CN)6]2 is heated to 350 - 400 °C at a rate of 2 - 5 °C / min in the mixed gas to obtain a calcined intermediate, and preferably the calcination time is 3 - 5 h; the calcined intermediate is cooled to 20 - 25 °C at a rate of 2 - 5 °C / min in the mixed gas to obtain the bimetallic sulfide.

[0041] The control of the above-mentioned heating and cooling rates is beneficial to reducing the fragmentation of the bimetallic sulfide particles, and the control of the calcination temperature and time helps to completely convert M x Co 3-x [Co(CN)6]2 into M x Co 3-x S4.

[0042] In another typical embodiment of the present application, a composite is provided, and the composite is an M x Co 3-x S4 - S composite. In the M x Co 3-x S4 - S composite, the mass ratio of M x Co 3-x S4 to S is 1:4 to 5.

[0043] The M x Co 3-x S4 - S composite with the above mass ratio loads more sulfur. Using the M x Co 3-x S4 - S composite as the positive electrode material of the lithium - sulfur battery can significantly improve the electrical performance of the lithium - sulfur battery.

[0044] In another typical embodiment of the present application, a preparation method of the aforementioned composite is provided. The preparation method includes mixing an M x Co 3-x S4 suspension with an S8 solution to obtain a mixture; adjusting the pH value of the mixture to 6 - 7, then stirring, washing and drying to obtain the composite, and preferably the stirring time is 8 - 10 h.

[0045] The control of the above pH value and stirring conditions helps M x Co 3-xThe sufficient mixing of the S4 suspension and the S8 solution to improve M x Co 3-x The contact probability between S4 and S8, and then fix S8 on M x Co 3-x On S4, to obtain M with high sulfur loading x Co 3-x S4-S composite.

[0046] In one embodiment of the present application, the above-mentioned M x Co 3-x The solid content of the S4 suspension is 0.25 - 0.3 mg / mL. Preferably, the S8 solution is obtained by dissolving S8 elemental sulfur in an aqueous sulfide solution. Preferably, the mass ratio of S8 elemental sulfur to sulfide is 1:12.5 - 15. Preferably, the concentration of the aqueous sulfide solution is 1.6 - 1.8 mol / L. Preferably, the aqueous sulfide solution is selected from any one or more of aqueous sodium sulfide solution, aqueous potassium sulfide solution, and aqueous ammonium sulfide solution.

[0047] Since S8 is insoluble in water, dissolving S8 elemental sulfur in an aqueous sulfide solution gives polysulfide ions that are soluble in water, so that it can contact with M x Co 3-x S4 suspension of M x Co 3-x S4 sufficiently, and then the polysulfide ions enter the pores and surface of M x Co 3-x S4. Controlling the mass ratio of S8 elemental sulfur to sulfide and the concentration of the aqueous sulfide solution within the above ranges is beneficial to the temporary conversion of S8 elemental sulfur into soluble polysulfide ions. The M x Co 3-x S4 suspension is more conducive to reacting with the polysulfide ions in the S8 solution to obtain M x Co 3-x S4-S composite with sufficient sulfur loading.

[0048] In another typical embodiment of the present application, a lithium-sulfur cathode material is provided. The lithium-sulfur cathode material includes a sulfur-containing composite, and the sulfur-containing composite is the aforementioned composite.

[0049] Using M x Co 3-x The lithium-sulfur cathode material obtained from the S4-S composite improves the theoretical capacity of the lithium-sulfur battery cathode material and improves the rate performance and cycle performance of the lithium-sulfur battery.

[0050] In another typical embodiment of the present application, a lithium-sulfur battery is provided. The lithium-sulfur battery includes a positive electrode and a negative electrode, and the positive electrode is the aforementioned lithium-sulfur cathode material.

[0051] Using a lithium-sulfur cathode material with improved rate performance and cycling performance as the cathode material of a lithium-sulfur battery can significantly improve the performance and service life of the lithium-sulfur battery.

[0052] The following will illustrate the beneficial technical effects of this application in combination with specific examples and comparative examples.

[0053] Examples 1 to 29 are the preparation examples of M x Co 3-x S4

[0054] Example 1

[0055] Cu 5 / 3 Co 4 / 3 Preparation of the [Co(CN)6]2 precursor:

[0056] Dissolve CuSO4·5H2O (0.25 mmol) and CoCl2·6H2O (0.2 mmol) in 200 mL of ethanol, and then add sodium citrate (2.25 mmol) to prepare solution A. Subsequently, dissolve K3[Co(CN)6] (0.3 mmol) in 100 mL of ethanol to prepare solution B. Drop solution B into solution A under magnetic stirring, and fully mix the two solutions under magnetic stirring. At room temperature, let it stand for 24 hours, centrifuge, and wash with ethanol 3 - 4 times to obtain a precipitate, and dry it at 60 °C for 12 h to obtain hollow Cu 5 / 3 Co 4 / 3 [Co(CN)6]2, as Figure 1 and Figure 2 shown, the morphology of the Cu 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor is cubic.

[0057] Hollow Cu 5 / 3 Co 4 / 3 Preparation of [Co(CN)6]2:

[0058] Add the obtained precipitate Cu 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor (20 mg) and polyvinylpyrrolidone (PVP, K30) (100 mg) into the hydrochloric acid solution (20 mL, concentration 5 mol / L) in a Teflon container, stir for 2 h, transfer the container to a stainless steel autoclave, and then heat it at 150 °C in an electric furnace for 3 hours. After standing for 24 h, centrifuge, wash with ethanol 3 - 4 times, and dry at 60 °C for 12 h to obtain hollow Cu 5 / 3 Co 4 / 3 [Co(CN)6]2, where Cu 5 / 3 Co 4 / 3The molar ratio of the [Co(CN)6]2 precursor to hydrochloric acid is 1:6×10 4 , Cu 5 / 3 Co 4 / 3 The mass ratio of the [Co(CN)6]2 precursor to polyvinylpyrrolidone is 1:5.

[0059] Preparation of CuCo2S4:

[0060] 100 mg of hollow Cu 5 / 3 Co 4 / 3 [Co(CN)6]2 was placed in a H2S / Ar mixed gas (5% H2S by volume fraction, and the molar ratio of H2S to hollow Cu 5 / 3 Co 4 / 3 [Co(CN)6]2 is 6:1), and calcined at 350 °C (heating rate is 2 °C / min) for 3 h, and cooled to room temperature at a rate of 2 °C / min to obtain the bimetallic sulfide CuCo2S4. It can be seen from Figure 3 that the structure of part of the Cu 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor has been broken after being etched by the acid solution. From Figure 4 the broken porous nanocube structure, it can be determined that the morphology of the bimetallic sulfide obtained after being etched by the acid solution is a hollow porous nanocube structure with a cavity in the center. Figure 5 The distance between the lattices of the bimetallic sulfide shown in Figure 6 and the XRD pattern of the bimetallic sulfide shown in Figure 7 further prove that the bimetallic sulfide is CuCo2S4. 2 / g.

[0061] Example 2

[0062] The difference between Example 2 and Example 1 is that

[0063] Cu 5 / 3 Co 4 / 3 The molar ratio of the [Co(CN)6]2 precursor to hydrochloric acid is 1:2×10 4 , and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 480 nm, the pore diameter is 2 - 5 nm, and the specific surface area is 25 m 2 / g.

[0064] Example 3

[0065] Example 3 is different from Example 1 in that

[0066] Cu 5 / 3 Co 4 / 3 The molar ratio of the [Co(CN)6]2 precursor to hydrochloric acid is 1:10×10 4 , and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 530 nm, the pore diameter is 2 - 6 nm, and the specific surface area is 40 m 2 / g.

[0067] Example 4

[0068] Example 4 is different from Example 1 in that

[0069] Cu 5 / 3 Co 4 / 3 The molar ratio of the [Co(CN)6]2 precursor to hydrochloric acid is 1:10 4 , and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 450 nm, the pore diameter is 2 - 3 nm, and the specific surface area is 20 m 2 / g.

[0070] Example 5

[0071] Example 5 is different from Example 1 in that

[0072] Cu 5 / 3 Co 4 / 3 The mass ratio of the [Co(CN)6]2 precursor to polyvinylpyrrolidone is 1:6, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 550 nm, the pore diameter is 2 - 4 nm, and the specific surface area is 32 m 2 / g.

[0073] Example 6

[0074] Example 6 is different from Example 1 in that

[0075] Cu 5 / 3 Co 4 / 3 The mass ratio of the [Co(CN)6]2 precursor to polyvinylpyrrolidone is 1:7, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 450 nm, the pore diameter is 3 - 5 nm, and the specific surface area is 30 m 2 / g.

[0076] Example 7

[0077] Example 7 is different from Example 1 in that

[0078] Cu 5 / 3 Co4 / 3 The mass ratio of the [Co(CN)6]2 precursor to polyvinylpyrrolidone is 1:3, and the bimetallic sulfide CuCo2S4 is finally obtained. The edge length of its nanocube structure is 700 nm, the pore size is 2 - 3 nm, and the specific surface area is 22 m 2 / g.

[0079] Example 8

[0080] The difference between Example 8 and Example 1 is that

[0081] The concentration of hydrochloric acid is 3 mol / L, and the bimetallic sulfide CuCo2S4 is finally obtained. The edge length of its nanocube structure is 480 nm, the pore size is 2 - 4 nm, and the specific surface area is 30 m 2 / g.

[0082] Example 9

[0083] The difference between Example 9 and Example 1 is that

[0084] The concentration of hydrochloric acid is 1 mol / L, and the bimetallic sulfide CuCo2S4 is finally obtained. The edge length of its nanocube structure is 520 nm, the pore size is 2 - 3 nm, and the specific surface area is 27 m 2 / g.

[0085] Example 10

[0086] The difference between Example 10 and Example 1 is that

[0087] The concentration of hydrochloric acid is 0.5 mol / L, and the bimetallic sulfide CuCo2S4 is finally obtained. The edge length of its nanocube structure is 500 nm, the pore size is 1 - 3 nm, and the specific surface area is 20 m 2 / g.

[0088] Example 11

[0089] The difference between Example 11 and Example 1 is that

[0090] The molar ratio of H2S to hollow Cu 5 / 3 Co 4 / 3 [Co(CN)6]2 is 8:1, and the bimetallic sulfide CuCo2S4 is finally obtained. The edge length of its nanocube structure is 540 nm, the pore size is 2 - 5 nm, and the specific surface area is 37 m 2 / g.

[0091] Example 12

[0092] The difference between Example 12 and Example 1 is that

[0093] The molar ratio of H2S to hollow Cu 5 / 3 Co4 / 3 The molar ratio of [Co(CN)6]2 is 4:1, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nano-cube structure is 520 nm, the pore diameter is 2 - 4 nm, and the specific surface area is 30 m 2 / g.

[0094] Example 13

[0095] The difference between Example 13 and Example 1 is that

[0096] The molar ratio of H2S to hollow Cu 5 / 3 Co 4 / 3 [Co(CN)6]2 is 2:1, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nano-cube structure is 600 nm, the pore diameter is 2 - 3 nm, and the specific surface area is 23 m 2 / g.

[0097] Example 14

[0098] The difference between Example 14 and Example 1 is that

[0099] The volume fraction of H2S in the mixed gas is 10%, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nano-cube structure is 480 nm, the pore diameter is 2 - 4 nm, and the specific surface area of the bimetallic sulfide is 38 m 2 / g.

[0100] Example 15

[0101] The difference between Example 15 and Example 1 is that

[0102] The volume fraction of H2S in the mixed gas is 15%, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nano-cube structure is 500 nm, the pore diameter is 2 - 6 nm, and the specific surface area is 40 m 2 / g.

[0103] Example 16

[0104] The difference between Example 16 and Example 1 is that

[0105] The volume fraction of H2S in the mixed gas is 3%, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nano-cube structure is 550 nm, the pore diameter is 2 - 4 nm, and the specific surface area is 25 m 2 / g.

[0106] Example 17

[0107] The difference between Example 17 and Example 1 is that

[0108] At a temperature of 370 °C (heating rate: 2 °C / min), calcine for 4 h, and cool to room temperature at a rate of 2 °C / min to finally obtain the bimetallic sulfide CuCo2S4. The edge length of its nanocube structure is 500 nm, the pore diameter is 3 - 6 nm, and the specific surface area is 38 m 2 / g.

[0109] Example 18

[0110] The difference between Example 18 and Example 1 is that

[0111] At a temperature of 400 °C (heating rate: 2 °C / min), calcine for 5 h, and cool to room temperature at a rate of 2 °C / min to finally obtain the bimetallic sulfide CuCo2S4. The edge length of its nanocube structure is 550 nm, the pore diameter is 4 - 6 nm, and the specific surface area is 40 m 2 / g.

[0112] Example 19

[0113] The difference between Example 19 and Example 1 is that

[0114] At a temperature of 300 °C (heating rate: 2 °C / min), calcine for 3 h, and cool to room temperature at a rate of 2 °C / min to finally obtain the bimetallic sulfide CuCo2S4. The edge length of its nanocube structure is 520 nm, the pore diameter is 2 - 4 nm, and the specific surface area is 28 m 2 / g.

[0115] Example 20

[0116] The difference between Example 20 and Example 1 is that

[0117] The heating rate is 3 °C / min, calcine for 3 h, and cool to room temperature at a rate of 3 °C / min to finally obtain the bimetallic sulfide CuCo2S4. The edge length of its nanocube structure is 480 nm, the pore diameter is 2 - 5 nm, and the specific surface area is 34 m 2 / g.

[0118] Example 21

[0119] The difference between Example 21 and Example 1 is that

[0120] The heating rate is 5 °C / min, calcine for 3 h, and cool to room temperature at a rate of 5 °C / min to finally obtain the bimetallic sulfide CuCo2S4. The edge length of its nanocube structure is 450 nm, the pore diameter is 3 - 6 nm, and the specific surface area is 38 m 2 / g.

[0121] Example 22

[0122] Example 22 is different from Example 1 in that,

[0123] The heating rate is 1 °C / min, calcined for 3 h, cooled to room temperature at a rate of 1 °C / min, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 500 nm, the pore size is 2 - 4 nm, and the specific surface area is 30 m 2 / g.

[0124] Example 23

[0125] Example 23 is different from Example 1 in that,

[0126] The surfactant is cetyltrimethylammonium bromide, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 400 nm, the pore size is 3 - 6 nm, and the specific surface area is 35 m 2 / g.

[0127] Example 24

[0128] Example 24 is different from Example 1 in that,

[0129] The acid solution is an aqueous nitric acid solution, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 480 nm, the pore size is 2 - 4 nm, and the specific surface area is 35 m 2 / g.

[0130] Example 25

[0131] Example 25 is different from Example 1 in that,

[0132] The temperature of the etching treatment is 140 °C, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 550 nm, the pore size is 2 - 4 nm, and the specific surface area is 30 m 2 / g.

[0133] Example 26

[0134] Example 26 is different from Example 1 in that,

[0135] The temperature of the etching treatment is 200 °C, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 450 nm, the pore size is 3 - 6 nm, and the specific surface area is 40 m 2 / g.

[0136] Example 27

[0137] Example 27 is different from Example 1 in that,

[0138] The temperature of the etching treatment is 130 °C, and finally the bimetallic sulfide CuCo2S4 is obtained. The edge length of its nanocube structure is 550 nm, the pore size is 2 - 3 nm, and the specific surface area is 28 m 2 / g.

[0139] Example 28

[0140] Ni 5 / 3 Co 4 / 3 Preparation of the [Co(CN)6]2 precursor:

[0141] Dissolve Ni(NO3)2·6H2O (0.25 mmol) and CoCl2·6H2O (0.2 mmol) in 200 mL of ethanol, and then add sodium citrate (2.25 mmol) to prepare solution A. Subsequently, dissolve K3[Co(CN)6] (0.3 mmol) in 100 mL of ethanol to prepare solution B. Drop solution B into solution A under magnetic stirring, and fully mix the two solutions under magnetic stirring. At room temperature, let it stand for 24 hours, centrifuge, and wash with ethanol 3 - 4 times to obtain a precipitate, which is dried at 60 °C for 12 h to obtain the Ni 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor.

[0142] Hollow Ni 5 / 3 Co 4 / 3 Preparation of hollow Ni

[0143] Add the obtained precipitate Ni 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor (20 mg) and polyvinylpyrrolidone (PVP, K30) (100 mg) to the hydrochloric acid solution (20 mL, concentration 5 mol / L) in a Teflon container, stir for 2 h, transfer the container to a stainless steel autoclave, and then heat at 150 °C in an electric furnace for 3 hours. After standing for 24 h, centrifuge, wash with ethanol 3 - 4 times, and dry at 60 °C for 12 h to obtain hollow Ni 5 / 3 Co 4 / 3 [Co(CN)6]2, where the molar ratio of the Ni 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor to hydrochloric acid is 1:6×10 4 , and the mass ratio of the Ni 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor to polyvinylpyrrolidone is 1:6.

[0144] Preparation of NiCo2S4:

[0145] Add 100 mg of hollow Ni 5 / 3 Co4 / 3 [Co(CN)6]2 was placed in a mixed gas of H2S / Ar (H2S with a volume fraction of 5%, and the molar ratio of H2S to hollow Ni 5 / 3 Co 4 / 3 [Co(CN)6]2 was 6:1), and calcined at a temperature of 350 °C (heating rate of 2 °C / min) for 3 h, and then cooled to room temperature at a rate of 2 °C / min to obtain the bimetallic sulfide NiCo2S4, whose nanocube structure had an edge length of 450 nm, a pore size of 2 - 6 nm, and a specific surface area of 40 m 2 / g.

[0146] Example 29

[0147] Mn 5 / 3 Co 4 / 3 Preparation of the [Co(CN)6]2 precursor:

[0148] Mn(CH3COO)2·4H2O (0.25 mmol) and CoCl2·6H2O (0.2 mmol) were dissolved in 200 mL of ethanol, and then sodium citrate (2.25 mmol) was added to prepare solution A. Subsequently, K3[Co(CN)6] (0.3 mmol) was dissolved in 100 mL of ethanol to prepare solution B. Solution B was dropped into solution A under magnetic stirring, and the two solutions were fully mixed under magnetic stirring. At room temperature, it was left standing for 24 hours, centrifuged, and washed with ethanol 3 - 4 times to obtain a precipitate, which was dried at 60 °C for 12 h to obtain the Mn 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor.

[0149] Hollow Mn 5 / 3 Co 4 / 3 Preparation of the hollow [Co(CN)6]2:

[0150] The obtained precipitate Mn 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor (20 mg) and polyvinylpyrrolidone (PVP, K30) (100 mg) were added to a hydrochloric acid solution (20 mL, concentration of 5 mol / L) in a Teflon container. Stir for 2 h, transfer the container to a stainless steel autoclave, and then heat it in an electric furnace at 150 °C for 3 hours. After standing for 24 h, centrifuge, wash with ethanol 3 - 4 times, and dry at 60 °C for 12 h to obtain the hollow Mn 5 / 3 Co 4 / 3 [Co(CN)6]2, where the molar ratio of the Mn 5 / 3 Co 4 / 3 [Co(CN)6]2 precursor to hydrochloric acid was 1:6×10 4 , Mn 5 / 3Co 4 / 3 The mass ratio of the [Co(CN)6]2 precursor to polyvinylpyrrolidone is 1:6.

[0151] Preparation of MnCo2S4:

[0152] Put the hollow Mn 5 / 3 Co 4 / 3 [Co(CN)6]2 into a H2S / Ar mixed gas (containing 5% by volume of H2S, and the molar ratio of H2S to hollow Mn 5 / 3 Co 4 / 3 [Co(CN)6]2 is 6:1), and calcine it at a temperature of 350 °C (heating rate is 2 °C / min) for 3 h, and then cool it to room temperature at a rate of 2 °C / min to obtain the bimetallic sulfide MnCo2S4, whose edge length of the nanocube structure is 550 nm, pore diameter is 2 - 5 nm, and specific surface area is 30 m 2 / g.

[0153] Examples 30 to 35 are preparation examples of the composite (M x Co 3-x S4 - S composite).

[0154] In the following preparation examples of the M x Co 3-x S4 - S composite, the M x Co 3-x S4 used is the M x Co 3-x S4 prepared in any one of Examples 1 to 29 above.

[0155] Example 30

[0156] Dissolve the S8 element in an aqueous sodium sulfide solution to obtain an S8 solution, and then mix the CuCo2S4 suspension with a solid content of 0.3 mg / mL and the S8 solution to obtain a mixture; adjust the pH value of the mixture to 6 - 7 and stir for 8 h, then wash and dry it to obtain the CuCo2S4 - S composite, where the mass ratio of the S8 element to sodium sulfide is 1:12.5, the concentration of the aqueous sodium sulfide solution is 1.6 mol / L, and the mass ratio of CuCo2S4 to S in the CuCo2S4 - S composite is 1:4.

[0157] Example 31

[0158] The difference between Example 31 and Example 30 is that

[0159] The mass ratio of S8 elemental substance to sodium sulfide is 1:15, the concentration of the sodium sulfide aqueous solution is 1.8 mol / L, and finally a CuCo2S4-S composite is obtained. The mass ratio of CuCo2S4 to S in the CuCo2S4-S composite is 1:4.5.

[0160] Example 32

[0161] The difference between Example 32 and Example 30 is that

[0162] The mass ratio of S8 elemental substance to sodium sulfide is 1:13, the concentration of the sodium sulfide aqueous solution is 1.7 mol / L, and finally a CuCo2S4-S composite is obtained. The mass ratio of CuCo2S4 to S in the CuCo2S4-S composite is 1:5.

[0163] Example 33

[0164] The difference between Example 33 and Example 30 is that

[0165] The solid content of the CuCo2S4 suspension is 0.25 mg / mL, the sulfide aqueous solution is an ammonium sulfide aqueous solution, the mass ratio of S8 elemental substance to sodium sulfide is 1:13, the concentration of the sodium sulfide aqueous solution is 1.7 mol / L, and finally a CuCo2S4-S composite is obtained. The mass ratio of CuCo2S4 to S in the CuCo2S4-S composite is 1:4.

[0166] Example 34

[0167] The difference between Example 34 and Example 30 is that

[0168] Dissolve the S8 elemental substance in the sodium sulfide aqueous solution to obtain an S8 solution, and then mix the NiCo2S4 suspension with a solid content of 0.3 mg / mL with the S8 solution to obtain a mixture; adjust the pH value of the mixture to 6-7, stir for 8 h, wash and dry to obtain a NiCo2S4-S composite, wherein the mass ratio of S8 elemental substance to sodium sulfide is 1:12.5, the concentration of the sodium sulfide aqueous solution is 1.6 mol / L, and the mass ratio of NiCo2S4 to S in the NiCo2S4-S composite is 1:4.

[0169] Example 35

[0170] The difference between Example 35 and Example 30 is that

[0171] Dissolve S8 elemental substance in an aqueous solution of sodium sulfide to obtain an S8 solution, and then mix a MnCo2S4 suspension with a solid content of 0.3 mg / mL with the S8 solution to obtain a mixture; adjust the pH value of the mixture to 6-7, stir for 8 h, then wash and dry to obtain a MnCo2S4-S composite. Among them, the mass ratio of S8 elemental substance to sodium sulfide is 1:12.5, the concentration of the aqueous solution of sodium sulfide is 1.6 mol / L, and the mass ratio of MnCo2S4 to S in the MnCo2S4-S composite is 1:4.

[0172] Preparation Example of Lithium-Sulfur Battery Positive Electrode

[0173] The MnCo2S4-S composite used in the following examples was prepared by any one of Examples 30 to 35.

[0174] Dissolve the prepared MnCo2S4-S composite, acetylene black, and polyvinylidene fluoride (PVDF) in N-methyl-2-pyrrolidone (NMP) liquid in a ratio of 8:1:1 to obtain a slurry. Coat the slurry evenly on an Al foil and place it in a vacuum drying oven at 50 °C. After drying for 24 h, take out the Al foil and roll it under a pressure of 18 MPa. Subsequently, punch it into a lithium-sulfur battery positive electrode with a diameter of 12 mm, use a 14 mm lithium sheet as the negative electrode of the battery, Celgard 2400 as the separator, and assemble a CR-2025 type button battery in a glove box filled with Ar. The electrolyte is prepared from a mixed solvent of ethylene glycol diethyl ether (DME) and 1,3-dioxolane (DOL) (the volume ratio of the two is 1:1) / 1.0 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.2 mol·L -1 of LiNO3.

[0175] Comparative Example

[0176] Positive Electrode Preparation:

[0177] Mix the active substance sublimed sulfur powder, conductive agent Super-P, and binder polyvinylidene fluoride (PVDF) in a mass ratio of 8:1:1. First, grind and mix the sulfur powder and Super-P evenly in a mortar, add a 5% PVDF solution by mass, drop an appropriate amount of NMP as a solvent, and stir magnetically for 8 h. Then, coat the paste-like positive electrode slurry evenly on the aluminum foil current collector, and then place it in a vacuum drying oven at 50 °C and dry for 24 h.

[0178] Battery Assembly:

[0179] The Al foil was rolled under a pressure of 18 MPa. Subsequently, it was punched into an electrode sheet with a diameter of 12 mm. A 14 mm lithium sheet was used as the anode of the battery, the electrode sheet prepared in the previous step was used as the cathode, and Celgard 2400 was used as the diaphragm. A CR-2025 button cell was assembled in a glove box filled with Ar. The electrolyte was composed of ethylene glycol diethyl ether (DME) and 1,3-dioxolane (DOL) (the volume ratio of the two was 1:1) / 1.0 mol·L -1 Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 0.2 mol·L -1 It is prepared from a mixed solvent of LiNO3.

[0180] Electrochemical performance test

[0181] According to the above method, the M prepared in Examples 1 to 29 were respectively x Co 3-x S4 is made into corresponding M x Co 3-x S4-S composite material, reuse M x Co 3-x The S4-S composite material was prepared into the corresponding lithium-sulfur battery positive electrode material and assembled into a battery. The lithium-sulfur battery of the comparative example was tested on the Xinwei BTS-5V3A battery testing system produced by Shenzhen Xinwei Electronics Co., Ltd. with a charge and discharge voltage range of 1.7 to 2.8 V and maintained at 25°C. The test results are listed in Table 1.

[0182] Table 1

[0183]

[0184]

[0185] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0186] Due to M x Co 3-x S4 is a sulfide material with a spinel structure. Its delocalized electronic structure gives it high ionic and electronic conductivity. x Co 3-x S4 has a high specific surface area (more active sites). x Co 3-x S4 is used for S loading. On the one hand, a large amount of S enters the cavity inside the hollow porous nanocube through the pores on the surface of the hollow porous nanocube, and a part of S is also adsorbed on the surface of the hollow porous nanocube, thereby greatly improving M x Co3-x The sulfur fixation effect of S4 yields M containing more S x Co 3-x The S4-S composite, on the other hand, can alleviate the volume expansion caused by charge and discharge; meanwhile, the strongly polar M x Co 3-x S4 is beneficial to its combination with polysulfide ions to form TM-S covalent bonds. The TM-S covalent bond has a strong binding energy and electron transfer ability, which is conducive to the effective chemical adsorption and conversion of polysulfides. Then, the dual metals (M and Co) with multiple valences play a synergistic role in the catalytic conversion of polysulfides, greatly alleviating the shuttle effect of polysulfide ions, thereby improving the theoretical capacity of the lithium-sulfur battery cathode material and improving the rate performance and cycle performance of the lithium-sulfur battery.

[0187] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bimetallic sulfide, characterized in that, The chemical formula of the bimetallic sulfide is M x Co 3-x S4, where M is selected from any one of Ni, Cu, Mn, V, Fe, Zn, and Mo. The morphology of the bimetallic sulfide is a hollow porous nanocube structure, where 0.5 ≤ x ≤ 1.5; The pore diameter of the bimetallic sulfide is 2 to 6 nm, and the specific surface area of the bimetallic sulfide is 25 to 40 m 2 / g; The edge length of the porous nanocube is 450 - 550 nm; The preparation method of the bimetallic sulfide includes: Step S1, etching the M x Co 3-x [Co(CN)6]2 precursor with an acid solution to obtain hollow M x Co 3-x [Co(CN)6]2; Step S2, subject the hollow M x Co 3-x [Co(CN)6]2 to calcination to obtain the bimetallic sulfide, and the calcination is carried out in a gas containing H2S.

2. The preparation method of the bimetallic sulfide according to claim 1, characterized in that, The preparation method includes: Step S1, etching the M x Co 3-x [Co(CN)6]2 precursor with an acid solution to obtain hollow M x Co 3-x [Co(CN)6]2; Step S2, subjecting the hollow M x Co 3-x [Co(CN)6]2 to calcination to obtain the bimetallic sulfide, wherein the calcination is carried out in a gas containing H2S.

3. The preparation method according to claim 2, wherein The gas containing H2S is a mixed gas including H2S and N2 or a mixed gas including H2S and an inert gas.

4. The preparation method according to claim 2, characterized in that, The process of the etching treatment includes: Mix the acid solution, surfactant, and the M x Co 3-x [Co(CN)6]2 precursor and then perform the etching treatment. The hydrogen ion concentration in the acid solution is 1 to 5 mol / L.

5. The preparation method according to claim 4, characterized in that, The surfactant is selected from polyvinylpyrrolidone or cetyltrimethylammonium bromide.

6. The preparation method according to claim 4, wherein, The acid solution is selected from any one or more of hydrochloric acid, aqueous nitric acid solution, and aqueous sulfuric acid solution.

7. The preparation method according to claim 4, characterized in that, The described M x Co 3-x The mass ratio of the [Co(CN)6]2 precursor to the surfactant is 1:5 to 1:

7.

8. The preparation method according to claim 4, characterized in that, The temperature of the etching treatment is 140 - 200 °C.

9. The preparation method according to claim 2, wherein In terms of hydrogen ions, the M x Co 3-x [Co(CN)6]2 precursor and the acid solution have a molar ratio of 1:2×10 4 ~1:10×10 4 .

10. The preparation method according to claim 2, characterized in that, The H2S and the hollow M x Co 3-x The molar ratio of [Co(CN)6]2 is 4:1 to 8:

1.

11. The preparation method according to claim 3, characterized in that, The volume fraction of H2S in the mixed gas is 5 - 15%.

12. The preparation method according to claim 3, wherein, The process of the calcination includes: Heat the hollow M x Co 3-x [Co(CN)6]2 in the mixed gas to 350 - 400 °C at a rate of 2 - 5 °C / min to obtain a calcined intermediate, and the calcination time is 3 - 5 h; Cooling the calcination intermediate in the mixed gas at a rate of 2 - 5 °C / min to 20 - 25 °C to obtain the bimetallic sulfide.

13. A kind of M x Co 3-x S4-S complex, characterized in that In the M x Co 3-x S4-S complex, the mass ratio of M x Co 3-x S4 to S is 1:4 to 5, and the M x Co 3-x S4 is the M x Co 3-x S4 recited in claim 1.

14. The preparation method of the M described in claim 13 x Co 3-x for the S4-S complex, characterized in that The preparation method includes: Mix M x Co 3-x with the S4 suspension and the S8 solution to obtain a mixture; Adjust the pH value of the mixture to 6-7, then stir, wash and dry to obtain the M. x Co 3-x S4-S complex, and the stirring time is 8-10 h.

15. The preparation method according to claim 14, wherein, The said M x Co 3-x The solid content of the CoS4 suspension is 0.25 to 0.3 mg / mL.

16. The preparation method according to claim 15, characterized in that, The S8 solution is obtained by dissolving S8 in an aqueous sulfide solution.

17. The preparation method according to claim 16, wherein, The mass ratio of the S8 to the sulfide is 1:12.5 - 15.

18. The preparation method according to claim 16, characterized in that, The concentration of the aqueous sulfide solution is 1.6 - 1.8 mol / L.

19. The preparation method according to claim 16, characterized in that, The aqueous sulfide solution is selected from any one or more of aqueous sodium sulfide solution, aqueous potassium sulfide solution, and aqueous ammonium sulfide solution.

20. A lithium-sulfur cathode material, the lithium-sulfur cathode material comprising a sulfur-containing composite, characterized in that, The sulfur-containing complex is M as described in claim 13 x Co 3-x S4-S complex 21. A lithium-sulfur battery, the lithium-sulfur battery comprising a positive electrode and a negative electrode, characterized in that, The positive electrode is the lithium-sulfur positive electrode material described in claim 20.

Images