A VS4 / C composite material, its preparation method and application

Abstract

The application discloses a VS4 / C composite material, a preparation method and application thereof, and belongs to the technical field of electrochemical energy storage. The VS4 / C composite material has a morphology of an octopus-like shape and is composed of core particles and whiskers; the core particles are stacked by nanosheets with a certain direction and have a spherical shape as a whole; the lattice of the whiskers rotates in the layer direction and extends in a highly twisted continuous spiral shape. The application is applied to a water-based zinc ion battery and solves the problem that the existing VS4 and conductive carbon are compounded or form a coating structure to enhance the electronic transmission and buffer the huge volume change caused by Zn 2+ The mode of embedding / detaching of the existing VS4 / C composite material does not fully consider the problem of slow ion transmission kinetics, has low high-rate capacity and poor long cycle stability, and the VS4 / C composite material provided by the application has a curved lattice, a large exposure ratio of (011) crystal surface, a high specific surface area and uniformly distributed carbon.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage technology, and particularly relates to a VS4 / C composite material, its preparation method and application. Background Technology

[0002] With the continuous development of economy and technology, human demand for energy is increasing day by day, and renewable energy has great development prospects in the future. At present, rechargeable batteries are receiving widespread attention as a new generation of energy storage devices. Among them, zinc-ion batteries are regarded as a very promising candidate due to the unparalleled advantages of zinc anodes. These advantages include: high theoretical capacity (820mAh g / g). -1 Zn has the following properties: low redox potential (-0.76 V, relative to the standard hydrogen electrode), high conductivity, and non-toxicity. However, in ZIBs, Zn... 2+ The large radius of hydrated ions hinders their rapid insertion / extraction from cathode materials, and cathode materials also suffer from low capacity and poor cycle life, limiting the further development of zinc-ion batteries. Therefore, developing suitable cathode materials for zinc-ion batteries to obtain zinc-ion batteries with superior electrochemical performance remains a challenge.

[0003] Among existing cathode materials, VS4 has a one-dimensional chain structure with a chain spacing of up to [missing information]. It also contains high levels of sulfur (S2). 2- The VS4 group has shown great potential in metal ion storage. However, in practical applications, the electrochemical performance of VS4 is still limited by its unsatisfactory specific capacity and poor cycling stability. Therefore, it is urgent to enhance the ion and electron transport kinetics of VS4 to further improve its electrochemical performance in zinc-ion batteries. Most existing solutions involve combining VS4 with conductive carbon or forming a coating structure to enhance electron transport and buffer the ion transport and electron transport of zinc-ion batteries. 2+ The huge volume changes caused by insertion / extraction. For example, the 2nm thick carbon layer-coated VS4 composite structure disclosed in Chinese patent CN115744983A, the VS4@C hollow mesoporous nanospheres disclosed in Chinese patent CN119191261A, and the VS4 / rGO composite structure disclosed in Chinese patent CN113130863A.

[0004] However, the materials disclosed in the aforementioned patents did not fully consider the problem of slow ion transport dynamics in their structural design, resulting in low high-rate capacity and poor long-cycle stability. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is the existing method of combining VS4 with conductive carbon or forming a coating structure to enhance electron transport and buffer Zn. 2+The large volume change caused by insertion / extraction does not fully take into account the problem of slow ion transport kinetics, resulting in low high-rate capacity and poor long-cycle stability. This paper proposes a VS4 / C composite material with lattice bending, a large exposure ratio of (011) crystal planes, high specific surface area and uniform carbon distribution, its preparation method and application.

[0006] To solve the aforementioned technical problem, the technical solution adopted by the present invention is as follows:

[0007] This invention provides a VS4 / C composite material with an octopus-like morphology, composed of core particles and whiskers; the core particles are composed of stacked nanosheets with a certain orientation, and the whole is spherical; the lattice of the whiskers rotates along the in-layer direction and extends in a highly twisted continuous spiral shape.

[0008] Preferably, the carbon component in the VS4 / C composite material has an amorphous structure, is uniformly distributed throughout the structure, and accounts for 1-20% by mass.

[0009] Preferably, the diameter of the core particle is 100-900 nm; the length of the whisker is 100-500 nm, and the radial dimension along the core particle is 20-100 nm.

[0010] Another aspect of the present invention provides a method for preparing the VS4 / C composite material according to any of the above-described technical solutions, including VO x / C preparation steps, the VO x The preparation steps of / C include: dispersing vanadium source and carbon source in solvent, mixing thoroughly, and then carrying out a solvothermal reaction at 100-200℃ for 6-48 hours. After the reaction, solid-liquid separation, washing, and drying are performed to obtain VO with a hollow structure. x / C material.

[0011] Preferably, the VO x / C material has a multi-layered hollow spherical structure with a diameter of 200-1500nm and 1-4 hollow layers. Each shell is composed of stacked nanoparticles and is uniformly coated with an amorphous carbon layer of 1-5nm thickness.

[0012] Preferably, it further includes a vulcanization step, the vulcanization step comprising: vulcanizing the VO x The C material and sulfur source were mixed and dispersed in a solvent. After thorough mixing, a secondary solvothermal reaction was carried out at 80-200℃ for 3-48 hours. After the reaction, solid-liquid separation, washing, and drying were performed to obtain VS. x / C vulcanization precursor.

[0013] Preferably, it further includes a calcination step, the calcination step comprising: [the following steps are described in the original text, but are not directly related to the previous sentence] xThe VS4 / C vulcanization precursor was calcined to obtain the VS4 / C composite material.

[0014] The calcination temperature is 200-650℃, the calcination atmosphere is nitrogen, argon, argon-hydrogen mixture or vacuum, the heating rate is 1-10℃ / min, and the calcination time is 1-12h.

[0015] Preferably, the vanadium source is one or more of sodium orthovanadate, ammonium metavanadate, vanadium acetylacetonate, and vanadium oxysulfate; the carbon source is one or more of citric acid, glucose, sucrose, and dopamine hydrochloride; and the sulfur source is one or more of vanadium oxysulfate, hydrogen sulfide, sodium thiosulfate, and thioacetamide.

[0016] The molar ratio of the vanadium source to the carbon source is 1:0.1-10; the molar ratio of the vanadium source to the sulfur source is 1:0.1-20.

[0017] The solvent is one or more of deionized water, ethanol, and ethylene glycol.

[0018] Preferably, the VO x The solvothermal reaction temperature in the / C preparation step is 100-200℃, and the reaction time is 2-48h; the secondary solvothermal reaction temperature in the vulcanization step is 100-200℃, and the reaction time is 2-48h.

[0019] The present invention also provides the application of the VS4 / C composite material described in any of the above technical solutions as a positive electrode material in aqueous zinc-ion batteries.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] This invention provides a VS4 / C composite material in which the whiskers rotate along the a-axis (in-layer direction), causing the (011) crystal plane to bend and the crystal plane to be fully exposed. There are a large number of defects such as dislocations and vacancies in the adjacent bent lattice regions. When used as a positive electrode of zinc-ion batteries, due to its special nanostructure, large exposure ratio of (011) crystal plane, high surface area and uniformly distributed carbon, it provides abundant adsorption sites and ion migration channels, achieving excellent rate capability and cycle stability at high current density.

[0022] Another aspect of the present invention provides a method for preparing VS4 / C composite materials, firstly by using VO x / C preparation steps yield VO with a hollow structure x / C materials provide a foundation for obtaining VS4 / C composites with unique torsional nanostructures exhibiting lattice bending, if VO xSince the VS4 / C material does not have a hollow structure, whiskers cannot be grown or there is no lattice bending phenomenon. In addition, by limiting the vulcanization steps, especially the amount of sulfur source and the secondary solvothermal reaction, the anions are fully exchanged, thereby obtaining the octopus-like structure of the VS4 / C composite material. Attached Figure Description

[0023] Figure 1 This is a SEM image of the VS4 / C composite material provided in Example 1 of the present invention;

[0024] Figure 2 This is a TEM image of the VS4 / C composite material provided in Example 1 of the present invention;

[0025] Figure 3 The zinc storage rate performance diagram of the VS4 / C composite material provided in Example 1 of this invention as a positive electrode material is shown.

[0026] Figure 4 The VS4 / C composite material provided in Example 1 of this invention is used as a positive electrode material in 3Ag -1 The following is a diagram of zinc storage cycle performance;

[0027] Figure 5 The zinc storage rate performance diagram of the VS4 / C composite material as a positive electrode material provided in Comparative Example 1 of this invention is shown.

[0028] Figure 6 The image shows the VS4 / C composite material used as the cathode material provided in Comparative Example 3 of this invention;

[0029] Figure 7 The graph shows the zinc storage rate performance of the VS4 / C composite material provided in Comparative Example 3 of this invention as a positive electrode material. Detailed Implementation

[0030] The technical solutions in specific embodiments of the present invention will be described in detail and completely below. Obviously, the described embodiments are only some specific implementations of the overall technical solution of the present invention, and not all implementations. Based on the overall concept of the present invention, all other embodiments obtained by those skilled in the art fall within the protection scope of the present invention.

[0031] This invention provides a VS4 / C composite material with an octopus-like morphology, composed of core particles and whiskers; the core particles are composed of stacked nanosheets with a certain orientation, and the whole is spherical; the lattice of the whiskers rotates along the in-layer direction and extends in a highly twisted continuous spiral shape.

[0032] The aforementioned VS4 / C composite material is composed of core particles and whiskers, forming an octopus-like structure. The whiskers rotate along the a-axis (intra-layer direction) (unlike the existing Eshelby torsion along the c-axis (inter-layer direction) driven by helical dislocations), resulting in the bending of the (011) crystal plane, which is fully exposed. There are a large number of defects such as dislocations and vacancies in the adjacent bent lattice regions. When used as a positive electrode for zinc-ion batteries, its special nanostructure, large exposure ratio of the (011) crystal plane, high surface area, and uniformly distributed carbon provide abundant adsorption sites and ion migration channels, achieving excellent rate capability and cycle stability at high current densities.

[0033] This invention achieves torsional nanostructures and lattice bending, which may also lead to changes in the surface and space charge, spontaneous polarization, etc. of the material, thereby endowing the material with special properties in electrical, optical and thermal properties.

[0034] In a preferred embodiment, the carbon component in the VS4 / C composite material exhibits an amorphous structure, uniformly distributed throughout the structure, with a mass percentage of 1-20%. This technical solution limits the distribution of the carbon component in the composite material because the carbon source and vanadium source of this invention are combined in dissolved ionic form. Therefore, the carbon component can be uniformly distributed during subsequent hydrothermal and calcination processes, which helps ensure uniform electron transport throughout the structure and alleviates the volumetric strain of each small particle. This invention further limits the mass percentage of the carbon component in the composite material because, since the carbon component does not contribute substantially to lithium storage, too much will lead to a decrease in the zinc storage volumetric density and energy density of the material; too little will hinder electron transport, affecting high-rate performance. In addition, too little will also lead to insufficient and uneven coating of each small particle, and the effect of alleviating the volume effect will be insignificant. It is understood that the mass percentage of the carbon component in the composite material can also be any value within the range of 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%.

[0035] In a preferred embodiment, the diameter of the core particle is 100-900 nm; the length of the whisker is 100-500 nm, and the radial dimension along the core particle is 20-100 nm. This VS4 / C composite material structure fully exposes the desired crystal planes capable of zinc ion insertion / extraction.

[0036] It is understood that the diameter of the core particle can be any value within the range of 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, etc.; the length of the whisker can be any value within the range of 200nm, 300nm, 400nm, etc.; and the size of the whisker along the radial direction of the core particle can be any value within the range of 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, etc.

[0037] Another aspect of the present invention provides a method for preparing the VS4 / C composite material according to any of the above-described technical solutions, including VO x / C preparation steps, the VO x The preparation steps of / C include: dispersing vanadium source and carbon source in solvent, mixing thoroughly, and then carrying out a solvothermal reaction at 100-200℃ for 6-48 hours. After the reaction, solid-liquid separation, washing, and drying are performed to obtain VO with a hollow structure. x / C material. It is understandable that VO x The temperature of the solvothermal reaction in the / C preparation step can be any value within the range of 120℃, 140℃, 160℃, 180℃, and the reaction time can be any value within the range of 10h, 20h, 30h, 40h, and 10h.

[0038] It should be noted that VO with a hollow structure was prepared. x The / C material is key to the VS4 / C composite material with a unique torsional nanostructure exhibiting lattice bending, which is the technical solution of this invention. If VO x / C materials do not have a hollow structure, therefore whiskers cannot grow or lattice bending occurs. The aforementioned VO x In the / C preparation step, it is necessary to ensure the full combination of carbon source and vanadium source, as well as the hydrothermal time. This is because: the carbon source plays a partial role in inducing the formation; the hydrothermal time affects the degree of atomic diffusion, thereby affecting the formation of hollow structure.

[0039] In a preferred embodiment, the VO x / C material has a multi-layered hollow spherical structure with a diameter of 200-1500nm and 1-4 hollow layers. Each shell is composed of stacked nanoparticles and is uniformly coated with an amorphous carbon layer of 1-5nm thickness.

[0040] Understandably, VO xThe diameter of the / C material can be any value within the range of 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, 1100nm, 1200nm, 1300nm, 1400nm; the number of hollow layers can be any value within the range of 2 or 3; and the thickness of the amorphous carbon layer can be any value within the range of 2nm, 3nm, 4nm.

[0041] In a preferred embodiment, the method further includes a vulcanization step, the vulcanization step comprising: vulcanizing the VO x The C material and sulfur source were mixed and dispersed in a solvent. After thorough mixing, a secondary solvothermal reaction was carried out at 80-200℃ for 3-48 hours. After the reaction, solid-liquid separation, washing, and drying were performed to obtain VS. x / C Sulfurization precursor. In the above-mentioned sulfidation step, if the amount of sulfur source is insufficient or the secondary solvothermal reaction time is insufficient, it will lead to incomplete anion exchange, making it difficult to obtain an octopus-like structure. In a preferred embodiment, the molar ratio of the vanadium source to the sulfur source is 1:0.1-20.

[0042] Understandably, the temperature in the vulcanization step can be any value within the range of 100℃, 120℃, 140℃, 160℃, 180℃, and the reaction time can be any value within the range of 10h, 20h, 30h, 40h, and the molar ratio of vanadium source to sulfur source can be any ratio within the range of 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, and the range of 1:19.

[0043] In a preferred embodiment, the method further includes a calcination step, the calcination step comprising: [the following steps are described in the original text, but are not directly related to the previous sentence: "to VS..."] x The VS4 / C vulcanization precursor is calcined to obtain the VS4 / C composite material. The calcination temperature is 200-650℃, the calcination atmosphere is nitrogen, argon, argon-hydrogen mixture or vacuum, the heating rate is 1-10℃ / min, and the calcination time is 1-12h. It is understood that the calcination temperature can also be any value within the range of 300℃, 400℃, 500℃, 600℃, and the heating rate can also be any value within the range of 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, and so on.

[0044] In a preferred embodiment, the vanadium source is one or more of sodium orthovanadate, ammonium metavanadate, vanadium acetylacetonate, and vanadium oxysulfate; the carbon source is one or more of citric acid, glucose, sucrose, and dopamine hydrochloride; the sulfur source is one or more of vanadium oxysulfate, hydrogen sulfide, sodium thiosulfate, and thioacetamide; the molar ratio of the vanadium source to the carbon source is 1:0.1-10; and the solvent is one or more of deionized water, ethanol, and ethylene glycol.

[0045] The above technical solution limits the molar ratio of vanadium source to carbon source in order to control the overall amount of carbon source used. It is understood that the molar ratio of vanadium source to carbon source can also be 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9 and any value within the range thereof.

[0046] In a preferred embodiment, the VO x The solvothermal reaction temperature in the / C preparation step is 100-200℃, and the reaction time is 2-48h; the secondary solvothermal reaction temperature in the vulcanization step is 100-200℃, and the reaction time is 2-48h.

[0047] This invention also provides the application of the VS4 / C composite material described in any of the above technical solutions as a cathode material in an aqueous zinc-ion battery. This zinc-ion battery exhibits high rate performance, high specific capacity, and excellent cycle stability.

[0048] To provide a clearer and more detailed description of the VS4 / C composite material, its preparation method, and its applications provided in the embodiments of the present invention, the following description will be based on specific embodiments.

[0049] Example 1

[0050] VO x Preparation steps of / C: Weigh 80 mg of vanadium acetylacetonate and dissolve it in 40 ml of ethanol, and stir at room temperature for 30 min; weigh 160 mg of dopamine hydrochloride and dissolve it in 40 ml of distilled water, and stir at room temperature for 30 min; then mix the two solutions and stir vigorously for 1 h; finally, transfer the solution to the liner of a 100 ml hydrothermal reactor, heat it to 180 °C at a heating rate of 5 °C / min and carry out a solvothermal reaction for 24 h. After the reaction, perform solid-liquid separation, wash, and dry to prepare VO with a hollow structure. x / C material;

[0051] Vulcanization step: Weigh 28mg of VO xMaterial C and 432 mg of thioacetamide were dissolved in 40 ml of ethanol and stirred vigorously at room temperature for 30 min. The solution was then transferred to the liner of a 100 ml hydrothermal reactor and reacted at 180 °C for 24 h. After the reaction, solid-liquid separation was performed. The mixture was filtered three times with ethanol and then dried in a forced-air oven at 80 °C for 12 h to obtain VS. x / C vulcanization precursor;

[0052] Calcination step: After the above precursor is fully ground, it is placed in a muffle furnace and heated to 400°C at a heating rate of 5°C / min and calcined for 2 hours to finally obtain the VS4 / C electrode material of this embodiment.

[0053] Structural characterization and performance test results:

[0054] like Figure 1 , 2 As shown, the VS4 / C electrode material prepared in Example 1 exhibits a novel octopus-like morphology with highly twisted whiskers of nanometer size;

[0055] Test results show that, Figure 3 , 4 As shown, the vanadium sulfide-based electrode material of this embodiment has excellent zinc storage performance at room temperature: at room temperature, it has a specific capacity of 290 mAh / g (100 mA / g current density) and a specific capacity of 100 mAh / g (3 A / g current density), and the capacity retention rate is close to 100% after 300 cycles.

[0056] Example 2

[0057] VO x Preparation steps of / C: Weigh 85 mg of ammonium metavanadate and dissolve it in 40 ml of ethanol, and stir at room temperature for 30 min; weigh 160 mg of dopamine hydrochloride and dissolve it in 40 ml of distilled water, and stir at room temperature for 30 min; then mix the two solutions and stir vigorously for 1 h; finally, transfer the solution to the liner of a 100 ml hydrothermal reactor, heat it to 200 °C at a heating rate of 5 °C / min and carry out a solvothermal reaction for 6 h. After the reaction, perform solid-liquid separation, wash, and dry to prepare VO with a hollow structure. x / C material;

[0058] Vulcanization step: Weigh 28mg VO x Material C and 432 mg of thioacetamide were dissolved in 40 ml of ethanol and stirred vigorously at room temperature for 30 min. The solution was then transferred to the liner of a 100 ml hydrothermal reactor and reacted at 80 °C for 48 h. After the reaction, solid-liquid separation was performed. The mixture was filtered three times with ethanol and then dried in a forced-air oven at 80 °C for 12 h to obtain VS. x / C vulcanization precursor;

[0059] Calcination step: After the above precursor is fully ground, it is placed in a muffle furnace and heated to 300°C at a heating rate of 5°C / min and calcined for 2 hours to finally obtain the VS4 / C electrode material of this embodiment.

[0060] Structural characterization and performance test results:

[0061] The prepared VS4 / C electrode material exhibits spherical morphology and particle size similar to those of Example 1;

[0062] Test results show that the specific capacity, rate capability, and cycle stability of the VS4 / C electrode material obtained in this embodiment are close to those of Example 1.

[0063] Example 3

[0064] VO x Preparation steps of / C: Weigh 160 mg of vanadium acetylacetonate and dissolve it in 40 ml of ethanol, and stir at room temperature for 30 min; weigh 160 mg of dopamine hydrochloride and dissolve it in 40 ml of distilled water, and stir at room temperature for 30 min; then mix the two solutions and stir vigorously for 1 h; finally, transfer the solution to the liner of a 100 ml hydrothermal reactor, heat it to 100 °C at a heating rate of 5 °C / min and carry out a solvothermal reaction for 48 h. After the reaction, perform solid-liquid separation, wash, and dry to prepare VO with a hollow structure. x / C material;

[0065] Vulcanization step: Weigh 28mg of VO x Material C and 714 mg of thioacetamide were dissolved in 40 ml of ethanol and stirred vigorously at room temperature for 30 min. The solution was then transferred to the liner of a 100 ml hydrothermal reactor and reacted at 200 °C for 3 h. After the reaction, solid-liquid separation was performed. The mixture was filtered three times with ethanol and then dried in a forced-air oven at 80 °C for 12 h to obtain VS. x / C vulcanization precursor;

[0066] Calcination step: After the above precursor is fully ground, it is placed in a muffle furnace and heated to 300°C at a heating rate of 5°C / min and calcined for 2 hours to finally obtain the VS4 / C electrode material of this embodiment.

[0067] Structural characterization and performance test results:

[0068] The prepared VS4 / C electrode material exhibits spherical morphology and particle size similar to those of Example 1;

[0069] Test results show that the specific capacity, rate capability, and cycle stability of the VS4 / C electrode material obtained in this embodiment are close to those of Example 1.

[0070] Comparative Example 1

[0071] Same as Example 1, except that VO x In the / C preparation step, the temperature was increased to 180℃ at a heating rate of 5℃ / min and a solvothermal reaction was carried out for 3 hours. After the reaction, solid-liquid separation, washing, and drying were performed to obtain VO with a solid structure. x / C material.

[0072] Structural characterization and performance test results:

[0073] The prepared VS4 / C electrode material exhibits a solid spherical morphology with a small number of lamellar structures on the surface, but no twisted whiskers have grown. This is because, due to VO x In the / C preparation step, the reaction is insufficient, vanadium ion diffusion is inadequate, and ion transport is slow, resulting in a solid structure that cannot achieve the desired morphology and poor zinc storage ratio performance.

[0074] Test results show that, Figure 5 As shown, the high-rate specific capacity of the VS4 / C electrode material obtained in this embodiment is not as good as that in Example 1.

[0075] Comparative Example 2

[0076] Same as Example 1, except that VO x In the / C preparation step, the temperature was increased to 80℃ at a heating rate of 5℃ / min and a solvothermal reaction was carried out for 24 hours. After the reaction, solid-liquid separation, washing, and drying were performed to obtain VO with a solid structure. x / C material.

[0077] Structural characterization and performance test results:

[0078] The prepared VS4 / C electrode material exhibits a solid spherical morphology with a small number of lamellar structures on the surface, but no twisted whiskers have grown.

[0079] Test results show that at a current density of 100 mA / g, the zinc storage capacity is less than 120 mAh / g, and at a high current density of 1000 mA / g, the zinc storage capacity is less than 50 mAh / g.

[0080] Comparative Example 3

[0081] Same as Example 1, except that the reaction was carried out at 180°C for 2 hours. After the reaction, solid-liquid separation was performed, and the mixture was filtered three times with ethanol and then dried in a forced-air oven at 80°C for 12 hours to obtain VS. x / C vulcanization precursor.

[0082] Structural characterization and performance test results:

[0083] The prepared VS4 / C electrode material exhibits an internally hollow structure, but its surface is composed of interwoven thin sheets forming a spherical morphology. It does not show the growth of core particles formed by stacked nanosheets with a specific orientation, nor twisted whiskers. Figure 6 As shown. The reason is that the vulcanization process is too short, and sufficient anion exchange does not occur.

[0084] Test results show that, Figure 7 As shown, at a current density of 100 mA / g, the zinc storage capacity is close to 100 mAh / g, and at a high current density of 1000 mA / g, the zinc storage capacity is close to 50 mAh / g, with the overall rate performance significantly lower than that of Example 1. This is because incomplete sulfidation prevents the complete formation of the lamellar structure of the core particles and the extension of twisted whiskers, resulting in insufficient exposure of the zinc ion insertion and extraction crystal faces. This leads to slow ion transport kinetics and a lower rate capacity.

[0085] Comparative Example 4

[0086] Same as Example 1, except that the reaction was carried out at 60°C for 24 hours. After the reaction, solid-liquid separation was performed, and the mixture was filtered three times with ethanol and then dried in a forced-air oven at 80°C for 12 hours to obtain VS. x / C vulcanization precursor.

[0087] Structural characterization and performance test results:

[0088] It has a similar morphology to Comparative Example 3.

[0089] The test results showed similarities to those of Comparative Example 3.

Claims

1. A VS4 / C composite material, characterized in that, The morphology is octopus-like, composed of core particles and whiskers; the core particles are composed of stacked nanosheets with a certain orientation, and the whole is spherical; the lattice of the whiskers rotates along the in-layer direction and extends in a highly twisted continuous spiral shape.

2. The VS4 / C composite material according to claim 1, characterized in that, The carbon component in the VS4 / C composite material exhibits an amorphous structure, is uniformly distributed throughout the entire structure, and accounts for 1-20% of the mass.

3. The VS4 / C composite material according to claim 1, characterized in that, The diameter of the core particle is 100-900 nm; the length of the whisker is 100-500 nm, and the radial dimension along the core particle is 20-100 nm.

4. The method for preparing the VS4 / C composite material according to any one of claims 1-3, characterized in that, Including VO x / C preparation steps, the VO x The preparation steps of / C include: dispersing vanadium source and carbon source in solvent, mixing thoroughly, and then carrying out a solvothermal reaction at 100-200℃ for 6-48 h. After the reaction, solid-liquid separation, washing, and drying are performed to obtain VO with a hollow structure. x / C material; It also includes a vulcanization step, which includes: vulcanizing the VO x The / C material and sulfur source were mixed and dispersed in a solvent. After thorough mixing, a secondary solvothermal reaction was carried out at 80-200℃ for 3-48 h. After the reaction, solid-liquid separation, washing, and drying were performed to obtain VS. x / C vulcanization precursor; It also includes a calcination step, which includes: calcining the VS x The VS4 / C vulcanization precursor was calcined to obtain the VS4 / C composite material.

5. The method for preparing the VS4 / C composite material according to claim 4, characterized in that, The VO x / C material has a multi-layered hollow spherical structure with a diameter of 200-1500 nm and 1-4 hollow layers. Each shell is composed of stacked nanoparticles and is uniformly coated with an amorphous carbon layer of 1-5 nm thickness.

6. The method for preparing the VS4 / C composite material according to claim 4, characterized in that, The calcination temperature is 200-650℃, the calcination atmosphere is nitrogen, argon, argon-hydrogen mixture or vacuum, the heating rate is 1-10℃ / min, and the calcination time is 1-12 h.

7. The method for preparing the VS4 / C composite material according to claim 4, characterized in that, The vanadium source is one or more of sodium orthovanadate, ammonium metavanadate, vanadium acetylacetonate, and vanadium oxysulfate; the carbon source is one or more of citric acid, glucose, sucrose, and dopamine hydrochloride; and the sulfur source is one or more of vanadium oxysulfate, hydrogen sulfide, sodium thiosulfate, and thioacetamide. The molar ratio of the vanadium source to the carbon source is 1:0.1-10; the molar ratio of the vanadium source to the sulfur source is 1:0.1-20. The solvent is one or more of deionized water, ethanol, and ethylene glycol.

8. The application of the VS4 / C composite material according to any one of claims 1-3 as a positive electrode material in an aqueous zinc-ion battery.

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