Electrode material and preparation method thereof, battery and energy storage system

Abstract

An electrode material and a preparation method thereof, a battery and an energy storage system, wherein the electrode material comprises a shell, the shell comprises tungsten sulfide having sulfur vacancies, the shell encloses a cavity, and the chemical formula of the tungsten sulfide is WS 2‑x , wherein 0<x<2. The electrode material provided by the present invention solves the problem of few electrochemical active sites and poor reaction kinetics of tungsten sulfide.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to an electrode material and a preparation method thereof, a battery and an energy storage system. Background Art

[0002] Tungsten sulfide (WS2) is a layered transition metal sulfide with high theoretical specific capacity and conductivity, and has broad application prospects in fields such as electrochemical energy storage and catalysis. However, most existing tungsten sulfide is in the form of fine crystals or powders, belonging to the hexagonal system with a layered structure. When used as an electrode, this type of tungsten sulfide faces the problems of few electrochemically active sites and poor reaction kinetics. Therefore, how to improve the physical and chemical properties of tungsten sulfide by improving its material structure has become a key issue. Summary of the Invention

[0003] The purpose of the present invention is to provide an electrode material and a preparation method thereof, a battery and an energy storage system to solve the problems of few electrochemical active sites and poor reaction kinetics of tungsten sulfide.

[0004] To achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0005] In a first aspect, the present invention provides an electrode material, comprising a shell, wherein the shell comprises tungsten sulfide having sulfur vacancies, the shell enclosing a cavity, and the chemical formula of the tungsten sulfide is WS 2-x , where 0<x<2.

[0006] In one embodiment, the shell includes an inner shell layer and an outer shell layer, the inner shell layer encloses the cavity, and the outer shell layer is arranged on the periphery of the inner shell layer.

[0007] In one embodiment, there is a gap between the inner shell layer and the outer shell layer.

[0008] In one embodiment, the thickness of the inner shell layer is 10 nm to 30 nm.

[0009] In one embodiment, the outer shell layer has a thickness of 10 nm to 30 nm.

[0010] In one embodiment, the gap distance between the inner shell layer and the outer shell layer is 20 nm to 30 nm.

[0011] In one embodiment, the shell includes multiple layers of stacked nanosheets, and the nanosheets are tungsten sulfide having sulfur vacancies.

[0012] In one embodiment, the thickness of the multilayer nanosheet is 2 nm to 10 nm.

[0013] In one embodiment, the interplanar spacing between two adjacent nanosheets is 0.6 nm to 0.7 nm.

[0014] In one embodiment, the electrode material is in the form of one or more of a hollow sphere, a hollow rod, and a hollow line.

[0015] In one embodiment, the specific surface area of ​​the electrode material is 100m 2 / g~150m 2 / g.

[0016] In one embodiment, the electrode material is in the shape of a hollow sphere, and the particle size D50 of the electrode material is 600 nm to 800 nm.

[0017] In a second aspect, the present invention provides a method for preparing an electrode material, comprising: sintering a hollow structure of tungsten oxide and thiourea together to react a portion of the tungsten oxide to form tungsten sulfide; placing the sintered composite structure of the tungsten sulfide and the tungsten oxide in an etching solution, and removing the tungsten oxide in the composite structure using the etching solution to obtain the electrode material; the electrode material includes a shell, the shell includes tungsten sulfide having sulfur vacancies, the shell encloses a cavity, and the chemical formula of the tungsten sulfide is WS 2-x , where 0<x<2.

[0018] In one embodiment, the method for preparing the hollow structured tungsten oxide comprises: dispersing a template material and a tungsten source in a solvent so that the tungsten source coats the surface of the template material; sintering the template material coated with the tungsten source, removing the template material and converting the tungsten source into the tungsten oxide.

[0019] In one embodiment, the template material includes one or more of polystyrene, polymethyl methacrylate, and carbon nanotubes.

[0020] In a third aspect, the present invention provides a battery, comprising the electrode material as described in any one of the first aspects.

[0021] In a fourth aspect, the present invention provides an energy storage system, characterized in that the energy storage system includes the battery as described in the third aspect.

[0022] The electrode material provided by the present invention is a hollow nanostructure, and the electrode material includes a shell of tungsten sulfide having sulfur vacancies. The material has the following advantages: in the electrode material, the hollow structure of tungsten sulfide can improve electrochemical performance and stability. Specifically, the advantages include: 1) Increased specific surface area. Since the electrode material has a hollow structure, it has a larger specific surface area than the existing solid electrode material, which not only provides more active sites for electrochemical reactions, but also enhances the contact area between the electrode material and the electrolyte, thereby increasing the capacity of the electrode material; 2) Improved rate performance. Since the shell thickness of the electrode material is relatively thin, the diffusion distance of electrons and ions can be shortened, thereby improving the rate performance of the electrode material; 3) Adaptation to volume changes. During the charge and discharge process, the hollow structure of tungsten sulfide and sulfur vacancies are beneficial to reducing the volume change and stress / strain during repeated charge and discharge, thereby enhancing the structural stability of the electrode material; 4) Promote the electrochemical reaction kinetics and reaction activity in the battery. The establishment of sulfur vacancies increases the reaction active sites on the material, significantly reduces the diffusion energy barrier of metal carriers, improves the diffusion kinetics of metal carriers, and thus improves the charge and discharge efficiency of the battery; 5) Improved electrical conductivity. Sulfur vacancies can improve the conductivity of the material, thereby improving the transmission efficiency of electrons and ions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 is a schematic diagram of the cross-sectional structure of an electrode material according to an embodiment;

[0025] Figure 2 is a flow chart of a method for preparing an electrode material according to an embodiment;

[0026] Figure 3 The present invention is a flow chart of a method for preparing hollow-structured tungsten oxide according to an embodiment;

[0027] Figure 4 is a transmission electron microscope image of the WO3 hollow nanospheres prepared after step 1) in Example 1;

[0028] Figure 5 The WS rich in sulfur vacancies prepared after step 6) in Example 1 2-x Transmission electron microscopy images of hollow microspheres;

[0029] Figure 6The WS rich in sulfur vacancies prepared after step 6) in Example 1 2-x Near-edge X-ray absorption spectroscopy of hollow microspheres;

[0030] Figure 7 The sulfur vacancy-rich WS prepared in Example 7 2-x XRD diffraction test pattern of hollow microspheres;

[0031] Figure 8 The sulfur vacancy-rich WS prepared in Example 7 2-x X-ray photoelectron spectroscopy of S element in hollow microspheres;

[0032] Figure 9 The WS rich in sulfur vacancies prepared in Example 7 2-x Electron paramagnetic resonance spectrum of S element in hollow microspheres.

[0033] Explanation of reference numerals: 10 - shell, 11 - inner shell layer, 12 - outer shell layer, 20 - cavity, 30 - gap. DETAILED DESCRIPTION

[0034] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] The following embodiments of the present invention are described in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0037] The present invention provides an electrode material, please refer to Figure 1 The main material of the electrode material is tungsten sulfide with sulfur vacancies, and the electrode material is a hollow nanostructure. The electrode material includes a shell 10, which includes tungsten sulfide with sulfur vacancies. The shell 10 encloses a cavity 20. The chemical formula of tungsten sulfide is WS 2-x , where 0<x<2.

[0038] Specifically, the electrode material can be in one or more of the following shapes: hollow spheres, hollow rods, and hollow lines. The shape of the housing 10 that can be directly observed under an electron microscope corresponds to the shape of the electrode material. The housing 10 is made of tungsten sulfide, which has sulfur vacancies.

[0039] Alternatively, the cavity 20 enclosed by the shell 10 can be prepared using a template method. For example, in a specific embodiment, a template material such as PS (polystyrene) microspheres, PMMA (polymethyl methacrylate) microspheres, or carbon nanotubes can be provided in advance. Tungsten sulfide is then formed on the outer surface of the template material to form the shell 10. The template material is then removed to obtain the hollow electrode material.

[0040] Furthermore, the tungsten sulfide provided by the present invention has sulfur vacancies, that is, defects caused by the absence of sulfur atoms in the tungsten sulfide, so that the chemical formula of the tungsten sulfide is WS 2-x , where 0<x<2, represents the average content of sulfur vacancies in the lattice. In X-ray absorption spectra, WS 2-x The diffraction peak absorption coefficient ratio is smaller than that of the conventional mixture of tungsten oxide and tungsten sulfide (such as Figure 6 As shown), this is because WS 2-x It is obtained by removing oxygen from a mixture of tungsten oxide and tungsten sulfide, so WS 2-x The diffraction peak absorption coefficient is relatively weak.

[0041] Among electrode materials, hollow tungsten sulfide can improve electrochemical performance and stability. Specifically, the advantages include: 1) Increased specific surface area. Since the electrode material is hollow, it has a larger specific surface area than existing solid electrode materials. This not only provides more active sites for electrochemical reactions, but also enhances the contact area between the electrode material and the electrolyte, thereby increasing the capacity of the electrode material; 2) Improved rate performance. Since the shell thickness of the electrode material is relatively thin, it can shorten the diffusion distance of electrons and ions, thereby improving the rate performance of the electrode material; 3) Adaptation to volume changes. During the charge and discharge process, the hollow structure of tungsten sulfide helps to reduce volume changes and stress / strain during repeated charge and discharge, thereby enhancing the structural stability of the electrode material.

[0042] Furthermore, the tungsten sulfide provided by the present invention is different from existing tungsten sulfide in that it has a relatively large number of sulfur vacancies. Sulfur vacancies refer to vacancy defects formed in the tungsten sulfide crystal structure due to the absence of sulfur atoms.

[0043] Among electrode materials, tungsten sulfide with sulfur vacancies has the following advantages: 1) Promoting the electrochemical reaction kinetics and reaction activity within the battery. The establishment of sulfur vacancies increases the reaction active sites on the material, significantly reduces the diffusion energy barrier of metal carriers, and improves the diffusion kinetics of metal carriers, thereby improving the charge and discharge efficiency of the battery; 2) Improving electrical conductivity. Sulfur vacancies can improve the conductivity of the material, thereby improving the transmission efficiency of electrons and ions; 3) Improving the capacity of the electrode material. Sulfur vacancies can provide more active sites for electrochemical reactions, thereby improving the capacity of the electrode material.

[0044] In one embodiment, the housing 10 includes an inner shell layer 11 and an outer shell layer 12 . The inner shell layer 11 encloses the cavity 20 , and the outer shell layer 12 is disposed on the periphery of the inner shell layer 11 .

[0045] Specifically, the electrode material can have a double-shell structure, where the shell 10 comprises two layers: an inner shell 11 and an outer shell 12. The inner shell 11 encloses the cavity 20, and the outer shell 12 covers the outer periphery of the inner shell 11. Furthermore, both the inner shell 11 and the outer shell 12 are made of tungsten sulfide with sulfur vacancies.

[0046] By setting the shell 10 of the electrode material to be two layers, the specific surface area of ​​the electrode material can be further increased. Compared with the existing solid material, the double-layer hollow structure has a larger specific surface area, which not only enhances the contact between the electrode material and the electrolyte, but also provides more active sites for electrochemical reactions, thereby improving the capacity of the electrode material.

[0047] In one embodiment, a gap 30 is provided between the inner shell 11 and the outer shell 12. Specifically, the gap 30 between the inner shell 11 and the outer shell 12 of the hollow tungsten sulfide structure serves as a channel for material transport. This design allows electrons or ions to smoothly enter the microsphere, contact and react with the catalytic sites on the inner shell 11, and simultaneously allows the products to effectively diffuse out of the microsphere.

[0048] In one embodiment, the thickness of the inner shell layer 11 is 10 nm to 30 nm. Optionally, the thickness of the inner shell layer 11 can be 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, or 30 nm.

[0049] In one embodiment, the outer shell layer 12 has a thickness of 10 nm to 30 nm. Alternatively, the outer shell layer 12 may have a thickness of 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, 26 nm, 28 nm, or 30 nm. The outer shell layer 12 and the inner shell layer 11 may have the same or different thicknesses.

[0050] Meeting the thickness of the inner shell layer 11 and the outer shell layer 12 within the above range can ensure the structural stability of the inner and outer shell layers and avoid reducing the electron transmission performance and mechanical properties; at the same time, it can effectively shorten the diffusion distance of electrons / ions, achieve rapid electrochemical reactions, and improve the rate performance of the electrode material.

[0051] In one embodiment, the gap distance between the inner shell layer 11 and the outer shell layer 12 is 20 nm to 30 nm. Optionally, the gap distance between the inner shell layer 11 and the outer shell layer 12 can be 20 nm, 21 nm, 22 nm, 23 nm, 24 nm, 25 nm, 26 nm, 27 nm, 28 nm, 29 nm, or 30 nm. Satisfying the gap distance between the inner shell layer 11 and the outer shell layer 12 is within the above range can ensure the structural stability of the shell and avoid reducing the electron transport performance and mechanical properties. Moreover, based on the sulfur vacancies and the expanded interlayer spacing, it can significantly reduce the diffusion energy barrier of metal cations, improve the diffusion kinetics of metal cations, and further enhance the performance of the electrode material.

[0052] In one embodiment, the shell 10 includes multiple stacked nanosheets, each of which is tungsten sulfide with sulfur vacancies. Specifically, the inner shell 11 and the outer shell 12 can each be formed by stacking multiple nanosheets, each of which is tungsten sulfide with sulfur vacancies. Tungsten sulfide nanosheets can be compared to multilayer graphene. Therefore, in an electrode material, a nanosheet can be the smallest structural unit of the electrode material. Optionally, the number of nanosheets in the inner shell 11 and the outer shell 12 is not limited, and the number of nanosheets in the inner shell 11 and the outer shell 12 can be different.

[0053] The shell 10 composed of multiple layered tungsten sulfide nanosheets has the following advantages: 1) excellent electrical conductivity. The layered nanosheets form a two-dimensional structure with conductivity similar to that of graphene and high electron transfer efficiency; 2) high structural stability. In the layered tungsten sulfide crystal structure, the SWS layer is strongly chemically bonded, which makes it have good stability, ensuring that tungsten sulfide can maintain its performance unchanged in harsh environments such as high temperature and high pressure; 3) the thickness of the shell 10 can be adjusted. The layers of the layered tungsten sulfide are bonded to each other by weak van der Waals forces, and the layers are easily peeled off. The thickness and number of the layers can be easily adjusted, thereby achieving precise control of its performance.

[0054] In one embodiment, the thickness of the multilayer nanosheet is 2 nm to 10 nm. Optionally, the thickness of the nanosheet can be 2 nm, 3.5 nm, 4.8 nm, 6.0 nm, 7.3 nm, 8.0 nm, 8.8 nm, 9.4 nm, or 10 nm. It should be noted that in specific embodiments, the nanosheet is a stacked product of multiple monolithic sheets, so the thickness of the nanosheet is the sum of the thicknesses of the multilayer monolithic sheets. A nanosheet thickness within the above range can ensure the structural stability of the shell and prevent the shell from being too thick or too thin.

[0055] In one embodiment, the interplanar spacing between two adjacent nanosheets is 0.6 nm to 0.7 nm. Optionally, the interplanar spacing between two adjacent nanosheets can be 0.6 nm, 0.61 nm, 0.62 nm, 0.63 nm, 0.64 nm, 0.65 nm, 0.66 nm, 0.67 nm, 0.68 nm, 0.69 nm, or 0.7 nm. Satisfying that the interplanar spacing between two nanosheets is within the above range can ensure the structural stability of the shell and avoid degrading the electron transport performance and mechanical properties.

[0056] In one embodiment, the specific surface area of ​​the electrode material is 100m 2 / g~150m 2 / g. Optionally, the specific surface area of ​​the electrode material can be 100m 2 / g, 115m 2 / g, 120m 2 / g, 125m 2 / g, 130m 2 / g, 135m 2 / g, 140m 2 / g, 145m 2 / g, 150m 2 / g. Satisfying the specific surface area of ​​the electrode material within the above range can ensure sufficient contact between the material and the electrolyte, thereby improving the electrochemical reaction rate.

[0057] In one embodiment, the electrode material is in the form of a hollow sphere, and the particle size D50 of the electrode material is 600 nm to 800 nm. Optionally, the particle size D50 of the electrode material can be 600 nm, 620 nm, 640 nm, 600 nm, 660 nm, 680 nm, 700 nm, 720 nm, 740 nm, 760 nm, 780 nm, or 800 nm. Satisfying the particle size of the electrode material within the above range can reduce the difficulty of material preparation and improve the electrochemical performance of the material.

[0058] In one embodiment, the present invention also provides a method for preparing an electrode material, please refer to Figure 2 , including the following steps:

[0059] In step S10, the hollow structured tungsten oxide and thiourea are sintered together to allow a portion of the tungsten oxide to react to form tungsten sulfide.

[0060] In step S20 , the sintered composite structure of tungsten sulfide and tungsten oxide is placed in an etching solution, and the tungsten oxide in the composite structure is removed by the etching solution to obtain an electrode material.

[0061] The electrode material includes a shell, which includes tungsten sulfide with sulfur vacancies. The shell encloses a cavity, and the chemical formula of tungsten sulfide is WS 2-x , where 0<x<2.

[0062] Specifically, in step S10, the hollow structure of tungsten oxide and thiourea are subjected to a high temperature reaction, specifically comprising: placing the hollow structure of tungsten oxide (WO3) and thiourea at a certain mass ratio at both ends of a porcelain boat, and covering them with aluminum foil to construct a relatively closed reaction system; then, placing the aluminum foil-covered porcelain boat in a tube furnace, passing a protective gas, and sintering at a preset heating rate, temperature, and time to obtain a composite structure of tungsten oxide and sulfide. It should be explained that the oxidized nano-hollow microspheres described in the present invention are the hollow structure of tungsten oxide mentioned above.

[0063] Optionally, the mass ratio of the hollow tungsten oxide to the thiourea is 1:(0.5-16). Optionally, the mass ratio of the hollow tungsten oxide to the thiourea is 1:8.

[0064] Optionally, the preset heating rate is 1°C / min to 15°C / min, the reaction temperature is 300°C to 600°C, and the holding time is 0.5h to 6h.

[0065] It's important to note that the sulfur sources used in the prior art for preparing tungsten sulfide are mostly sulfur powder or thioacetamide. Because sulfur powder has a strong reducing property under high temperature conditions, the layered structure of the tungsten sulfide in the reaction product grows larger, which is not conducive to the construction of nanostructures. Thioacetamide, on the other hand, is difficult to control the degree of sulfurization of the sample due to the high temperature and high pressure conditions. Furthermore, the solvent thermal reaction byproduct has a foul odor, which is highly polluting to the environment.

[0066] Thiourea is used as the sulfur source in this invention because the high-temperature decomposition of thiourea in the tubular furnace produces a weakly reducing gas, which slows the sulfurization reaction of the metal oxide under high-temperature conditions. This also results in smaller and more active nanocrystals in the reaction product. Furthermore, during the sulfurization reaction, the porcelain boat and aluminum foil form a closed reaction system, allowing for precise control of the sulfurization degree by precisely controlling the ratio of thiourea to tungsten oxide. Furthermore, the reaction byproducts pass through an exhaust gas treatment device, preventing environmental pollution.

[0067] Furthermore, in step S20, the composite structure of sintered tungsten sulfide and tungsten oxide is placed in an etching solution, and the etching solution is used to remove the tungsten oxide in the composite structure, specifically including: dispersing the sintered product in the etching solution, stirring the reaction at a preset temperature so that the etching solution reacts with the remaining tungsten oxide, thereby removing the tungsten oxide; then, centrifuging, washing, and drying to collect a black powder sample, which is the electrode material.

[0068] Optionally, the etching solution may be an alkaline solution, such as sodium hydroxide solution or ammonia water. The alkali content in the etching solution may be 0.5 mol to 6 mol.

[0069] Optionally, the sintered product is dispersed in an etching solution by ultrasonic dispersion for 0.25 to 1 hour, the reaction temperature is 25 to 60° C., and the stirring speed is 300 to 800 r / min for 2 to 4 hours.

[0070] Optionally, after removing tungsten oxide, the sample can be left to stand for 6 to 12 hours before centrifugation, and then centrifuged in a centrifuge at a speed of 6000 to 12000 r / min for 3 to 7 minutes; the centrifuged sample is washed alternately with deionized water and anhydrous ethanol three times.

[0071] Optionally, the sample collected by centrifugation is placed in a vacuum drying oven and dried at a temperature of 40° C. to 80° C. for 12 hours, and then a black powder sample is collected.

[0072] In the present invention, after the sulfurization process is completed, the remaining tungsten oxide is removed by chemical etching, and while obtaining pure phase tungsten sulfide, more active edge sulfur vacancies are introduced, avoiding the complex process and harsh reaction conditions required for the introduction of sulfur vacancies. Moreover, during the sulfurization process of tungsten oxide, a rich tungsten oxide / tungsten sulfide two-phase interface is formed on its surface. When the tungsten oxide is selectively removed by chemical etching, the interface of the tungsten sulfide is exposed, forming more sulfur vacancies and edge active sites on the surface of the tungsten sulfide nanostructure, thereby exhibiting higher reactivity. In addition, the removal of tungsten oxide causes the reaction product tungsten sulfide to exhibit a unique hollow structure. The original single-layer tungsten oxide hollow microspheres are etched to form unique metal sulfide hollow microspheres with a double-layer structure. Moreover, when the interface is exposed, a large number of sulfur vacancies are formed.

[0073] In one embodiment, the preparation method of hollow structure tungsten oxide is as follows: Figure 3 , including the following steps:

[0074] Step S01 : dispersing a template material and a tungsten source in a solvent so that the tungsten source covers the surface of the template material.

[0075] Step S02 , sintering the template material coated with the tungsten source, removing the template material and converting the tungsten source into tungsten oxide.

[0076] Specifically, in step S01 , the template material and the tungsten source are dispersed in a solvent, specifically including: dispersing the template material in an ethanol / water solution, and hydrolyzing the tungsten source to coat the surface of the template material.

[0077] Optionally, the template material may be PS (polystyrene) microspheres, PMMA (polymethyl methacrylate) microspheres, carbon nanotubes, etc. The tungsten source may be tungsten hexachloride.

[0078] Optionally, the calcination temperature for removing the template material is 400° C. to 700° C., and the calcination time is 3 hours.

[0079] The preparation method of the electrode material provided by the present invention has the following advantages: 1) thiourea is used as a sulfur source, and its high-temperature decomposition product exhibits low reducibility, so the sulfurized product has a smaller grain size and higher reaction activity; 2) due to the sulfurization reaction, a rich metal oxide / metal sulfide interface is formed on the surface of the metal oxide nanoparticles. After the metal oxide is selectively removed by the etching reaction, abundant sulfur vacancies and edge active sites are formed at the original interface, thereby improving its electrochemical reaction kinetics and reaction activity; 3) the double-layer hollow nanospheres formed by etching not only have a more novel structure, but also have better structural stability.

[0080] Furthermore, the preparation method of the electrode material provided by the present invention first controls the sulfurization reaction process during the synthesis of metallic tungsten sulfide, and then selectively removes the remaining tungsten oxide by chemical etching, thereby obtaining pure-phase tungsten sulfide while introducing sulfur vacancies. This avoids the complex process and harsh reaction conditions required by previous methods for introducing sulfur vacancies. In addition, this method can also achieve the regulation of the hollow microsphere structure. The hollow microsphere structure of the single-layer tungsten oxide precursor is subjected to sulfurization etching treatment to evolve into tungsten sulfide with a double-layer hollow microsphere structure. The prepared tungsten sulfide hollow microspheres exhibit excellent performance in electrochemical lithium storage applications.

[0081] In one embodiment, the present invention further provides a battery, which includes the electrode material provided in the above embodiment.

[0082] In one embodiment, the present invention further provides an energy storage system, which includes the battery provided in the above embodiment.

[0083] The technical solution of the present invention is described in detail below through specific embodiments.

[0084] Example 1

[0085] This embodiment provides an electrode material having a hollow nano-microsphere structure. The electrode material includes a shell, which encloses a cavity; the shell includes an inner shell layer and an outer shell layer, and the inner shell layer and the outer shell layer are both made of WS rich in sulfur vacancies. 2-x The thickness of the inner shell is 20 nm, the thickness of the outer shell is 20 nm, and the gap between the inner shell and the outer shell is 25 nm. The inner shell and the outer shell are both made of WS. 2-x The nanosheets are stacked, and the (002) interplanar spacing in the nanosheets is about 0.70nm; the specific surface area of ​​the electrode material is 110m 2 / g, and the particle size D50 of the electrode material is 0.7μm.

[0086] The preparation method of the electrode material provided in this embodiment is as follows:

[0087] 1) Polystyrene (PS) microspheres were prepared as templates. Tungsten hexachloride was used as a tungsten source in an ethanol / water solution, which was hydrolyzed and coated onto the surface of the PS microspheres. The template was then removed by high-temperature calcination to synthesize WO3 hollow nanospheres. The calcination temperature was controlled at 500°C and maintained for 2 hours.

[0088] 2) According to the mass ratio of 1:8, weigh the corresponding mass of WO3 hollow nanospheres and thiourea and place them on both ends of the porcelain boat, and then seal the porcelain boat with aluminum foil.

[0089] 3) Transfer the aluminum foil-sealed porcelain boat to a position inside the quartz tube of a tubular furnace near the thermocouple. Under an argon atmosphere, heat the boat to 500°C at a rate of 10°C / min and hold the temperature for 4 h.

[0090] 4) After the tube furnace has cooled, collect the dark gray powder sample and add it to a 3 mol NaOH solution. Ultrasonicate for a period of time to ensure uniform dispersion of the sample. Then, stir the sample in a 50°C water bath at a stirring speed of 600 rpm for 4 h.

[0091] 5) The suspension after the reaction was transferred to a centrifuge tube, allowed to stand for 12 hours, collected by centrifugation, and washed three times alternately with anhydrous ethanol and deionized water.

[0092] 6) The washed sample was placed in a vacuum drying oven and vacuum dried at 40° C. for 12 h, and then a powder sample was collected to obtain the electrode material.

[0093] in, Figure 4 3 is a transmission electron microscope image of the WO3 hollow nanospheres prepared after step 1) in Example 1. Figure 5 The WS rich in sulfur vacancies prepared after step 6) in Example 1 2-x Transmission electron microscopy image of hollow microspheres. Figure 6The WS rich in sulfur vacancies prepared after step 6) in Example 1 2-x Near-edge X-ray absorption spectra of hollow microspheres.

[0094] from Figure 4 and Figure 5 It can be seen that after being treated with the method provided by the present invention, the original WO3 single-layer hollow structure evolves into a tungsten sulfide double-layer hollow microsphere. Figure 6 It can be seen that the peak intensity of the K-edge X-ray near-edge absorption spectrum of sulfur element in the sample decreases after etching with NaOH solution, which indicates that the tungsten sulfide double-layer hollow microsphere sample formed by the chemical etching process contains abundant sulfur vacancies.

[0095] Example 2

[0096] This embodiment provides an electrode material having a hollow nano-microsphere structure. The electrode material includes a shell, which encloses a cavity; the shell includes an inner shell layer and an outer shell layer, and the inner shell layer and the outer shell layer are both made of WS rich in sulfur vacancies. 2-x The thickness of the inner shell is 10 nm, the thickness of the outer shell is 10 nm, and the gap between the inner shell and the outer shell is 25 nm. The inner shell and the outer shell are both stacked by WS2 nanosheets, and the (002) crystal plane spacing in the nanosheets is about 0.70 nm. The specific surface area of ​​the electrode material is 110 m 2 / g, and the particle size D50 of the electrode material is 0.7μm.

[0097] The preparation method of the electrode material provided in this embodiment 2 is the same as that in embodiment 1.

[0098] Example 3

[0099] This embodiment provides an electrode material having a hollow nano-microsphere structure. The electrode material includes a shell, which encloses a cavity; the shell includes an inner shell layer and an outer shell layer, and the inner shell layer and the outer shell layer are both made of WS rich in sulfur vacancies. 2-x The thickness of the inner shell is 20 nm, the thickness of the outer shell is 20 nm, and the gap between the inner shell and the outer shell is 20 nm. The inner shell and the outer shell are both stacked by WS2 nanosheets, and the (002) crystal plane spacing in the nanosheets is about 0.70 nm. The specific surface area of ​​the electrode material is 110 m 2 / g, and the particle size D50 of the electrode material is 0.7μm.

[0100] The preparation method of the electrode material provided in this embodiment 3 is the same as that in embodiment 1.

[0101] Example 4

[0102] This embodiment provides an electrode material having a hollow nano-microsphere structure. The electrode material includes a shell, which encloses a cavity; the shell includes an inner shell layer and an outer shell layer, and the inner shell layer and the outer shell layer are both made of WS rich in sulfur vacancies. 2-x The thickness of the inner shell is 20 nm, the thickness of the outer shell is 20 nm, and the gap between the inner shell and the outer shell is 25 nm. The inner shell and the outer shell are both stacked by WS2 nanosheets, and the (002) crystal plane spacing in the nanosheets is about 0.62 nm. The specific surface area of ​​the electrode material is 110 m 2 / g, and the particle size D50 of the electrode material is 0.7μm.

[0103] The preparation method of the electrode material provided in this embodiment 4 is the same as that in embodiment 1.

[0104] Example 5

[0105] This embodiment provides an electrode material having a hollow nano-microsphere structure. The electrode material includes a shell, which encloses a cavity; the shell includes an inner shell layer and an outer shell layer, and the inner shell layer and the outer shell layer are both made of WS rich in sulfur vacancies. 2-x The thickness of the inner shell is 20 nm, the thickness of the outer shell is 20 nm, and the gap between the inner shell and the outer shell is 25 nm. The inner shell and the outer shell are both stacked by WS2 nanosheets, and the (002) crystal plane spacing in the nanosheets is about 0.70 nm. The specific surface area of ​​the electrode material is 150 m 2 / g, and the particle size D50 of the electrode material is 0.7μm.

[0106] The preparation method of the electrode material provided in this embodiment 5 is the same as that in embodiment 1.

[0107] Example 6

[0108] This embodiment provides an electrode material having a hollow nano-microsphere structure. The electrode material includes a shell, which encloses a cavity; the shell includes an inner shell layer and an outer shell layer, and the inner shell layer and the outer shell layer are both made of WS rich in sulfur vacancies. 2-x The thickness of the inner shell layer is 20 nm, the thickness of the outer shell layer is 20 nm, and the spacing between the inner shell layer and the outer shell layer is 25 nm. The inner shell layer and the outer shell layer are both stacked by WS2 nanosheets, and the (002) crystal plane spacing in the nanosheets is about 0.70 nm. The specific surface area of ​​the electrode material is 110 m 2 / g, and the particle size D50 of the electrode material is 0.8μm.

[0109] The preparation method of the electrode material provided in this Example 6 is the same as that in Example 1.

[0110] Example 7

[0111] This embodiment provides an electrode material having a hollow nano-microsphere structure. The electrode material includes a shell, which encloses a cavity; the shell includes an inner shell layer and an outer shell layer, and the inner shell layer and the outer shell layer are both made of WS rich in sulfur vacancies. 2-x The thickness of the inner shell is 20 nm, the thickness of the outer shell is 20 nm, and the gap between the inner shell and the outer shell is 25 nm. The inner shell and the outer shell are both stacked by WS2 nanosheets, and the (002) crystal plane spacing in the nanosheets is about 0.70 nm. The specific surface area of ​​the electrode material is 110 m 2 / g, and the particle size D50 of the electrode material is 0.7μm.

[0112] The method for preparing the electrode material provided in this embodiment 7 differs from that in embodiment 1 in that the NaOH solution is replaced with NH 3 ·H 2 O.

[0113] in, Figure 7 The WS rich in sulfur vacancies prepared in Example 7 2-x XRD diffraction test pattern of hollow microspheres. Figure 8 The WS rich in sulfur vacancies prepared in Example 7 2-x X-ray photoelectron spectroscopy of S element in hollow microspheres. Figure 9 The WS rich in sulfur vacancies prepared in Example 7 2-x Electron paramagnetic resonance spectrum of S element in hollow microspheres.

[0114] from Figure 7 It can be seen from the figure that the sample phase is tungsten sulfide; moreover, the diffraction peak intensity corresponding to the (002) crystal plane in the test spectrum is weak and shifts to a lower angle, which indicates that the sample contains defects. Figure 8 and Figure 9 It can be seen from the figure that the leftward shift of the S element peak position in the sample's X-ray photoelectron spectrum and the peak in the electron paramagnetic resonance spectrum both indicate the presence of sulfur vacancies in the sample.

[0115] Comparative Example 1

[0116] This comparative example provides an electrode material. The electrode material is common tungsten sulfide sold on the market and does not contain sulfur vacancies. The tungsten sulfide is a hexagonal material with a layered structure.

[0117] Comparative Example 2

[0118] This comparative example provides an electrode material having a hollow nanosphere structure. The electrode material includes a shell that encloses a cavity; the shell includes an inner shell layer and an outer shell layer, both of which are made of tungsten sulfide and do not contain sulfur vacancies.

[0119] The preparation method of the electrode material provided in this embodiment is as follows:

[0120] 1) Polystyrene (PS) microspheres were prepared as templates. Tungsten hexachloride was used as a tungsten source in an ethanol / water solution, which was hydrolyzed and coated onto the surface of the PS microspheres. The template was then removed by high-temperature calcination to synthesize WO3 hollow nanospheres. The calcination temperature was controlled at 500°C and maintained for 2 hours. The WO3 hollow nanospheres were obtained after cooling.

[0121] 2) Weighing the corresponding mass of WO3 hollow nanospheres and sulfur powder in a mass ratio of 1:8 and sintering them in a tube furnace to obtain tungsten sulfide without sulfur vacancies.

[0122] Comparative Example 3

[0123] This comparative example provides an electrode material, which is a solid nanosphere structure made of WS rich in sulfur vacancies. 2-x .

[0124] The preparation method of the electrode material provided in this embodiment is as follows:

[0125] 1) According to the mass ratio of 1:8, weigh the corresponding mass of WO3 nanospheres and thiourea and place them on both ends of the porcelain boat, and then seal the boat with aluminum foil.

[0126] 2) Transfer the aluminum foil-sealed porcelain boat to a position inside the quartz tube of a tubular furnace near the thermocouple. Under an argon atmosphere, heat the boat to 500°C at a rate of 10°C / min and hold the temperature for 4 h.

[0127] 3) After the tube furnace has cooled, collect the dark gray powder sample and add it to a 3 mol NaOH solution. Ultrasonicate for a period of time to ensure uniform dispersion of the sample. Then, stir the sample in a 50°C water bath at a stirring speed of 600 rpm for 4 h.

[0128] 4) The suspension after the reaction was transferred to a centrifuge tube, allowed to stand for 12 hours, collected by centrifugation, and washed three times alternately with anhydrous ethanol and deionized water.

[0129] 5) The washed sample was placed in a vacuum drying oven and vacuum dried at 40° C. for 12 h, and then a powder sample was collected to obtain the electrode material.

[0130] It should be noted that the electrode material testing methods in the above Examples 1 and 7 are as follows:

[0131] The scanning electron microscope (SEM) images of the samples in the present invention were taken using a Zeiss Supra-55 field emission scanning electron microscope at an accelerating voltage of 10 kV. The particle size D50 of the electrode material can be obtained through SEM testing.

[0132] Transmission electron microscopy (TEM) images were taken using a JEOL JEM-2100F field emission transmission electron microscope at an accelerating voltage of 200 kV. TEM measurements reveal the thickness of the inner and outer shells of the electrode material, as well as the gap between them. High-resolution transmission electron microscopy (HRTEM) images were analyzed using Digital Micrograph software to determine the (002) interplanar spacing in the nanosheets.

[0133] Powder X-ray diffraction (XRD) was measured by a Panalytical X'Pert PRO MPD diffractometer under the test conditions of 40 kV and 40 mA. TEM testing confirmed that the electrode material contained abundant sulfur vacancies.

[0134] The specific surface area test is performed using the Quantachrome AUTOSORB IQ fully automatic specific surface and porosity analyzer, which measures the BET specific surface area of ​​the material by measuring the amount of nitrogen adsorbed on the solid surface.

[0135] According to GB / T 41949-2022, the particle size of the material was tested using a Mastersizer 3000 laser particle size distribution analyzer.

[0136] The electrode materials provided in Examples 1-7 and Comparative Examples 1-3 were assembled into button-type CR2032 lithium batteries according to the following methods:

[0137] Positive electrode: lithium sheet.

[0138] Negative electrode: Mix the electrode material, Ketjen black and polyvinylidene fluoride in a ratio of 7:2:1, then add a certain amount of N-methylpyrrolidone and continue grinding until a uniform slurry is obtained; the slurry is evenly coated on the copper foil current collector, first placed in a 60°C oven to dry, then transferred to a 120°C oven to dry for 12 hours, and finally used a slicer to cut to obtain an electrode disc with a diameter of 12nm.

[0139] Electrolyte: LiPF6 / (EC+DMC) was used as the electrolyte.

[0140] Lithium battery assembly: Completed in a glove box filled with argon (the concentration of H2O and O2 does not exceed 0.1ppm).

[0141] The lithium batteries assembled in the above examples and comparative examples were subjected to electrochemical performance tests under the following test conditions:

[0142] Constant current charge and discharge test: performed on a BlueDian multi-channel battery test system, with a test voltage range of 0.01V to 3V and a test temperature of 25°C.

[0143] The test results are shown in Table 1 below:

[0144] Table 1. Test results of Examples and Comparative Examples

[0145]

[0146] From the test results of the examples and comparative examples, it can be seen that the sulfur-vacancy-rich WS provided by the present invention 2-x The electrode material has excellent electrochemical properties. The first-cycle discharge capacity, first-cycle coulombic efficiency and capacity retention rate after 200 cycles are all higher than those of the control example. The presence of sulfur vacancies can effectively reduce the energy barrier for lithium ion diffusion, thereby improving the kinetics of the tungsten sulfide lithium storage process.

[0147] The above-mentioned implementation cases only describe the preferred implementation methods of the present invention and do not limit the scope of the invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering technicians in this field should fall within the scope of protection determined by the claims of the present invention.

[0148] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" is based on the orientation or positional relationship described in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0149] The above disclosure is only a preferred embodiment of the present invention, and certainly cannot be used to limit the scope of the rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. An electrode material, characterized in that The shell comprises a tungsten sulfide having a sulfur vacancy, the shell enclosing a cavity, and the chemical formula of the tungsten sulfide is WS 2-x , where 0<x<2; The shell includes an inner shell layer and an outer shell layer. The inner shell layer encloses the cavity, and the outer shell layer is arranged on the outer periphery of the inner shell layer. A gap is provided between the inner shell layer and the outer shell layer.

2. The electrode material according to claim 1, characterized in that The thickness of the inner shell layer is 10 nm to 30 nm; and / or The thickness of the outer shell layer is 10 nm to 30 nm; and / or The gap distance between the inner shell layer and the outer shell layer is 20 nm to 30 nm.

3. The electrode material according to claim 1, characterized in that The shell includes multiple stacked nanosheets, and the nanosheets are tungsten sulfide with sulfur vacancies.

4. The electrode material according to claim 3, characterized in that The thickness of the nanosheet is 2 nm to 10 nm; and / or The interplanar spacing between two adjacent nanosheets is 0.6 nm to 0.7 nm.

5. The electrode material according to claim 1, characterized in that The specific surface area of ​​the electrode material is 100 m 2 / g~150 m 2 / g; and / or The electrode material is in the shape of a hollow sphere, and the particle size D50 of the electrode material is 600nm~800nm.

6. A method for preparing an electrode material, characterized in that: include: sintering the hollow tungsten oxide and thiourea together to react a portion of the tungsten oxide to form tungsten sulfide; placing the sintered composite structure of the tungsten sulfide and the tungsten oxide in an etching solution, and removing the tungsten oxide in the composite structure using the etching solution to obtain the electrode material; The electrode material includes a shell, the shell includes tungsten sulfide with sulfur vacancies, the shell encloses a cavity, and the chemical formula of the tungsten sulfide is WS 2-x , where 0<x<2.

7. The method for preparing the electrode material according to claim 6, wherein: The method for preparing the hollow structured tungsten oxide comprises: Dispersing the template material and the tungsten source in a solvent so that the tungsten source covers the surface of the template material; The template material coated with the tungsten source is sintered, and the template material is removed to convert the tungsten source into the tungsten oxide.

8. The method for preparing the electrode material according to claim 7, wherein: The template material includes one or more of polystyrene, polymethyl methacrylate, and carbon nanotubes.

9. A battery, characterized in that: The battery comprises the electrode material according to any one of claims 1 to 5.

10. An energy storage system, characterized in that: The energy storage system comprises the battery according to claim 9.

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