Vanadium tetrasulfide nanosheet embedded nitrogen-sulfur co-doped carbon fiber composite material as well as preparation method and application thereof
By preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composites, the problems of insufficient energy density and cycle stability of lithium-ion batteries were solved, achieving high discharge specific capacity, good rate performance and excellent cycle stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-30
- Publication Date
- 2026-03-31
AI Technical Summary
Existing lithium-ion batteries suffer from insufficient energy density and cycle stability. Metal sulfides also experience volume changes and dissolution during lithiation, which affect their electrochemical performance.
Vanadium tetrasulfide nanosheets were prepared by electrospinning and embedded in nitrogen-sulfur co-doped carbon fiber composites. Through pre-oxidation and high-temperature vulcanization, a three-dimensional conductive framework was formed. The nanosheets were vertically anchored to the inner wall of the carbon fibers, and the carbon fibers were cross-linked to form a continuous electron/ion dual transport channel.
It improves the discharge specific capacity, rate performance, and cycle stability of lithium-ion batteries, reduces charge transfer impedance, suppresses volume expansion during charging and discharging, and extends cycle life.
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Figure CN121769052A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery anode material preparation technology, and particularly relates to a vanadium tetrasulfide nanosheet embedded in nitrogen-sulfur co-doped carbon fiber composite material, its preparation method, and its application in lithium-ion batteries. Background Technology
[0002] With the increasing demand for green energy, high-efficiency energy storage devices have attracted significant attention. Among them, lithium-ion batteries, which combine environmental friendliness and long cycle life, have become the most widely researched energy storage system. Although lithium-ion batteries are already used in electric vehicles, their energy density currently limits their application range, preventing them from competing with vehicles powered by internal combustion engines. Therefore, designing and developing new, safe, and low-cost electrode materials with higher energy density, better cycle stability, and stronger mechanical stability to achieve high-performance batteries is now imperative.
[0003] Metal sulfides possess remarkable advantages such as easily controllable morphology and high theoretical specific capacity, and have attracted much attention due to their great potential applications in various energy devices (fuel cells, lithium / sodium-ion batteries, and supercapacitors). Specifically, compared with their corresponding oxides, metal sulfides exhibit better electrical conductivity and lower thermal effects. Furthermore, compared with oxide materials, sulfide materials often demonstrate greater electrochemical reversibility during charge / discharge reactions. Among these, Zhou et al. successfully prepared a hierarchical structure composed of ultrathin vanadium disulfide nanosheets for lithium-ion battery anodes, exhibiting a high specific capacity of up to 1000 mAh g⁻¹. -1 The reversible capacity and excellent rate performance were demonstrated. Li et al. prepared a three-dimensional vanadium tetrasulfide / reduced graphene composite material for lithium-ion battery anodes, exhibiting a high reversible capacity of up to 1044 mAh g⁻¹. -1 The specific capacity is high. However, metal sulfides still face many challenges in practical applications. For example, during continuous lithiation, drastic volume changes and shuttle effects (dissolution of polysulfides in organic electrolytes) lead to unsatisfactory electrochemical performance. Summary of the Invention
[0004] To address the shortcomings of existing technologies, the first objective of this invention is to provide a vanadium tetrasulfide nanosheet embedded in a nitrogen-sulfur co-doped carbon fiber composite material.
[0005] The second objective of this invention is to provide a method for preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite materials. This preparation method is simple and easy to implement, operates under mild conditions, is low in cost, and the morphology of the obtained product is easily controllable, showing strong application prospects.
[0006] A third objective of this invention is to provide the application of the aforementioned vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite materials in lithium-ion batteries. The resulting lithium-ion battery exhibits high discharge specific capacity, good rate performance, and excellent cycle stability.
[0007] A vanadium tetrasulfide nanosheet embedded in a nitrogen-sulfur co-doped carbon fiber composite material is disclosed. The composite material consists of vanadium tetrasulfide nanosheets and carbon fibers. The nanosheets are coated with a carbon layer and embedded in the carbon fibers. The carbon fibers are doped with nitrogen and sulfur and have a diameter of 300 nm to 2 μm. Preferably, the diameter of the carbon fibers is 400 to 800 nm. As a further preferred embodiment, the diameter of the carbon fibers is 500 nm.
[0008] A method for preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material includes the following steps: Vanadium acetylacetonate and sulfur powder were dispersed in an N,N-dimethylformamide (DMF) solution containing polyacrylonitrile (PAN) and polypyrrole (PPy). After being heated and stirred at a constant temperature for a certain period of time, a homogeneous mixture was formed. The resulting homogeneous mixture was then electrospun to obtain a vanadium-containing precursor fiber film. The obtained precursor fibers were placed in a muffle furnace for pre-oxidation for a certain period of time. The obtained precursor fiber film was then subjected to high-temperature vulcanization calcination under a protective atmosphere to obtain vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material.
[0009] A method for preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite materials, wherein the average molecular weight of PAN in the PAN-containing DMF solution is one of 50,000, 85,000, and 150,000, and the ratio of PPy to PAN is 1g:10-20g. Preferably, the average molecular weight of PAN is 150,000, and the ratio of PPy to PAN is 1g:15g. The solid-liquid ratio of PAN to DMF is 1g:7-25mL, the stirring time is 2-4h at room temperature, and the stirring speed is 250-650r / min. More preferably, the solid-liquid ratio of PAN to DMF is 1g:10-20mL, the stirring time is 3h at room temperature, and the stirring speed is 400r / min. Even more preferably, the solid-liquid ratio of PAN to DMF is 1g:15mL, the stirring time is 3h at room temperature, and the stirring speed is 400r / min.
[0010] A method for preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite materials, wherein the molar ratio of vanadium acetylacetonate to sulfur powder is 1:2~10, dissolved in a DMF solution containing PAN / PPy, and heated and stirred at a temperature of 30~60℃, a stirring speed of 250~650 r / min, and a stirring time of 6~24 h. Preferably, the molar ratio of vanadium acetylacetonate to sulfur powder is 1:3~7, dissolved in a DMF solution containing PAN and PPy, and heated and stirred at a temperature of 45℃, a stirring speed of 450 r / min, and a stirring time of 12 h. More preferably, the molar ratio of vanadium acetylacetonate to sulfur powder is 1:5, dissolved in a DMF solution containing PAN and PPy, and heated and stirred at a temperature of 45℃, a stirring speed of 450 r / min, and a stirring time of 12 h.
[0011] A method for preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite materials, wherein the electrospinning voltage is 5-15 kV, the receiving distance is 10-20 cm, the feed speed is 6-12 μL / min, and the inner diameter of the stainless steel needle is one of 1.45, 1.25, 1.12, 0.90, 0.70, 0.60, 0.51, 0.41, and 0.33 mm. Preferably, the electrospinning voltage is 8-12 kV, the receiving distance is 15 cm, the feed speed is 8-10 μL / min, and the inner diameter of the stainless steel needle is one of 0.90, 0.70, 0.60, 0.51, and 0.41 mm. More preferably, the electrospinning voltage is 9.5 kV, the receiving distance is 15 cm, the feed speed is 9 μL / min, and the inner diameter of the stainless steel needle is 0.60 mm.
[0012] A method for preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite materials, wherein the pre-oxidation treatment temperature is 150~350℃, the heating rate is 1~10℃ / min, and the holding time is 0.5~6h. Preferably, the pre-oxidation treatment temperature is 200~300℃, the heating rate is 2℃ / min, and the holding time is 1h. More preferably, the pre-oxidation treatment temperature is 250℃, the heating rate is 2℃ / min, and the holding time is 1h.
[0013] A method for preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite materials, wherein the inert atmosphere of the high-temperature calcination and vulcanization treatment is argon or nitrogen, the temperature is 500~1000℃, the heating rate is 1~10℃ / min, the holding time is 1~8 h, and the mass ratio of fiber to sulfur powder after pre-oxidation treatment is 1:2~10. Preferably, the inert atmosphere of the high-temperature calcination and vulcanization treatment is argon, the temperature is 700~800℃, the heating rate is 4~6℃ / min, the holding time is 3 h, and the mass ratio of fiber to sulfur powder after pre-oxidation treatment is 1:4~6. More preferably, the inert atmosphere of the high-temperature calcination and vulcanization treatment is argon, the temperature is 750℃, the heating rate is 5℃ / min, the holding time is 3 h, and the mass ratio of fiber to sulfur powder after pre-oxidation treatment is 1:5.
[0014] An application of vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material: using vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material as a negative electrode material for lithium-ion batteries.
[0015] The principles and advantages of this invention: This invention, based on electrospinning, utilizes readily available and inexpensive polyacrylonitrile (PAI) and polypyrrole (PPD) as the carbon-nitrogen dual source and sublimed sulfur as the sulfur source. Through a two-step heat treatment process of "pre-oxidation-high-temperature vulcanization," the vanadium precursor is converted in situ into vanadium tetrasulfide nanosheets, while simultaneously, PAN fibers are converted into nitrogen-sulfur co-doped carbon fibers, ultimately obtaining a three-dimensional network structure of "vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fibers." The addition of PPD further modulates the microstructure of the nitrogen-sulfur co-doped carbon fibers, promoting the precipitation of vanadium tetrasulfide nanosheets. The resulting composite material exhibits uniform fiber diameter (≈500 nm), with the vanadium tetrasulfide nanosheets vertically anchored to the inner wall of the carbon fibers and cross-linked to form continuous electron / ion dual transport channels.
[0016] The product synthesized in this invention has uniform particle size and a unique structure. Vanadium tetrasulfide nanosheets are embedded in nitrogen-sulfur co-doped carbon fiber composite material. The vanadium tetrasulfide nanosheets are vertically anchored in situ to the carbon fibers, and the carbon fibers are cross-linked to form a three-dimensional conductive framework, which helps to reduce charge transfer impedance. The nitrogen and sulfur co-doping of the carbon fibers introduces abundant defects and active sites, which contribute additional reversible lithium storage capacity. The nanosheets are embedded in situ by the carbon walls, which effectively suppresses the volume expansion during the charge and discharge process, which helps to enhance the specific capacity and cycle stability of lithium-ion batteries.
[0017] Compared with traditional bulk materials or isolated nanoparticles, the "nanosheet embedded carbon fiber" structure in this invention has the following advantages: (1) The nanosheet-level thickness shortens the lithium-ion diffusion path and increases the material's specific surface area, allowing for full contact with the electrolyte and improving the utilization rate of active sites; (2) The cross-linking of carbon fibers forms a continuous conductive network, shortening the electron path, increasing the diffusion rate, and making it easier to reversibly insert and remove from the material, thus improving rate performance; (3) The carbon shell binding combined with the fiber confinement synergistic effect effectively avoids problems such as fusion between nanosheets and boundary side reactions, improving the cycling stability of the material, delaying capacity decay, and extending cycle life; (4) One-step sulfurization completes the generation of vanadium tetrasulfide crystal phase and the construction of carbon defects. The process is simple, the conditions are mild, and no additional templates or toxic reducing agents are required.
[0018] The present invention provides a method for preparing vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material, which has controllable morphology, low cost, and is environmentally friendly. It can be directly used as a negative electrode for lithium-ion batteries and has strong application prospects. Attached Figure Description
[0019] Figure 1 This is the XRD pattern of vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material in Example 1.
[0020] Figure 2 This is a scanning electron microscope image of vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material in Example 1.
[0021] Figure 3 This is a cycle performance diagram of the vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material used as the negative electrode of a lithium-ion battery in Example 1.
[0022] Figure 4 This is a rate performance diagram of the vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material used as the negative electrode of a lithium-ion battery in Example 1.
[0023] Figure 5 This is a cycle performance diagram of vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material in Example 2, used as the negative electrode of a lithium-ion battery.
[0024] Figure 6 This is a rate performance diagram of the vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material used as the negative electrode of a lithium-ion battery in Example 2.
[0025] Figure 7 This is a rate performance diagram of the vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composite material used as the negative electrode of a lithium-ion battery in Example 3.
[0026] Figure 8 This is the XRD pattern of the material in Comparative Example 1.
[0027] Figure 9 This is the XRD pattern of the material in Comparative Example 2.
[0028] Figure 10 This is a scanning electron microscope image of the material in Comparative Example 3. Detailed Implementation
[0029] The following examples are intended to further illustrate the present invention, but not to limit it. Example
[0030] 1 g of polyacrylonitrile (PAN, average molecular weight 150,000) was dissolved in 15 mL of N,N-dimethylformamide (DMF), and 0.075 g of polypyrrole (PPy) solid powder was added. The mixture was stirred vigorously for 3 h to form a transparent solution. Then, 3 mmol of acetylacetonate vanadyl oxyacetate (C) was added to the above solution. 10 H 14 O5V) and 15 mmol of sulfur powder (S) were heated and stirred at 45 °C for 12 h to form a dark green solution. The resulting homogeneous viscous solution was then loaded into a 20 mL plastic syringe equipped with a 20-gauge stainless steel needle (0.6 mm inner diameter, 0.9 mm outer diameter). An aluminum foil was wrapped around a roller as a receiver, with the syringe needle 15 cm away from the roller, and electrospinning was performed at a rate of 9 μL / min. To ensure continuous nanofibers, a high voltage of 9.5 kV was applied between the needle and the aluminum foil. After electrospinning, the resulting precursor fibers were pre-oxidized (cured) in a muffle furnace at 250 °C for 1 h (heating rate 2 °C / min). Finally, 0.1 g of the pre-oxidized fibers and 0.5 g of sublimed sulfur were placed in two separate ceramic boats and calcined at 750 °C for 3 h under an argon atmosphere (heating rate 5 °C / min) to obtain vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composites. The obtained XRD results are as follows Figure 1 As shown in the figure, the obtained image is completely consistent with the spectrum of the monoclinic V3S4 phase (space group ). C 2 / m (12), crystal parameters are a =12.638 Å, b =3.294 Å, c =5.878 Å). A distinct diffraction peak is observed near 22°, which can be attributed to the (002) crystal plane of graphitic carbon. The microstructure of the composite material was observed by SEM, such as... Figure 2 As shown, many nanosheets appear uniformly on the surface of carbon nanofibers, which is due to the precipitation of V3S4 from the interior of the carbon fibers during the vulcanization process.
[0031] The prepared vanadium tetrasulfide nanosheets were embedded in nitrogen-sulfur co-doped carbon fiber composite material. A slurry was prepared by uniformly mixing 80 wt.% active material, 10 wt.% SuperP, and 10 wt.% CMC, and uniformly coating it onto copper foil. After vacuum drying, the slurry was assembled into coin cells for electrochemical performance testing. The cycle performance and rate performance results are as follows: Figure 3 and Figure 4 As shown in the figure, the cycle performance test voltage range is 0.01–3 V. At a current density of 0.1 A / g, the initial discharge specific capacity is 1209 mAh / g, the initial charge specific capacity is 955.9 mAh / g, and the initial efficiency is 79.1%. After 100 cycles, it still maintains a reversible specific capacity of 873.2 mAh / g, demonstrating good capacity retention. The rate performance test voltage range is 0.01–3 V. At a current density of 3 A / g, it still has a specific capacity of 515.3 mAh / g, demonstrating good rate performance. Example
[0032] 1 g of polyacrylonitrile (PAN, average molecular weight 150,000) was dissolved in 15 mL of N,N-dimethylformamide (DMF), and 0.05 g of polypyrrole (PPy) solid powder was added and stirred vigorously for 3 h to form a transparent solution. Then, 3 mmol of acetylacetonate vanadyl oxyacetate (C) was added to the above solution. 10 H 14 O5V) and 15 mmol of sulfur powder (S) were heated and stirred at 45 °C for 12 h to form a dark green solution. The resulting homogeneous viscous solution was then loaded into a 20 mL plastic syringe equipped with a 20-gauge stainless steel needle (0.6 mm inner diameter, 0.9 mm outer diameter). An aluminum foil was wrapped around a roller as a receiver, and the syringe needle was kept 15 cm away from the roller. Electrospinning was performed at a rate of 9 μL / min. To ensure continuous nanofibers, a high voltage of 9.5 kV was applied between the needle and the aluminum foil. After electrospinning, the resulting precursor fibers were pre-oxidized (cured) in a muffle furnace at 250 °C for 1 h (heating rate 2 °C / min). Finally, 0.1 g of the pre-oxidized fibers and 0.5 g of sublimed sulfur were placed in two separate ceramic boats and calcined at 800 °C for 3 h under an argon atmosphere (heating rate 5 °C / min) to obtain vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composites. Cyclic performance and rate performance, such as Figure 5As shown in Figure 6, the cycle performance test voltage range is 0.01–3 V. At a current density of 0.1 A / g, the initial discharge specific capacity is 1171.5 mAh / g, the initial charge specific capacity is 879.7 mAh / g, and the initial efficiency is 75.1%. After 100 cycles, only a reversible specific capacity of 238.3 mAh / g is maintained. The rate performance test voltage range is 0.01–3 V, and at a current density of 3 A / g, a specific capacity of 366.7 mAh / g is still maintained. Example
[0033] 2 g of polyacrylonitrile (PAN, average molecular weight 150,000) was dissolved in 15 mL of N,N-dimethylformamide (DMF), and 0.2 g of polypyrrole (PPy) solid powder was added and stirred vigorously for 3 h to form a transparent solution. Then, 2 mmol of acetylacetonate vanadyl oxyacetate (C) was added to the above solution. 10 H 14 O5V) and 15 mmol of sulfur powder (S) were heated and stirred at 45 °C for 12 h to form a dark green solution. The resulting homogeneous viscous solution was then loaded into a 20 mL plastic syringe equipped with a 21-gauge stainless steel needle (0.51 mm inner diameter, 0.81 mm outer diameter). An aluminum foil was wrapped around a roller as a receiver, with the syringe needle held 15 cm away from the roller, and electrospinning was performed at a feed rate of 8 μL / min. To ensure continuous nanofibers, a high voltage of 10 kV was applied between the needle and the aluminum foil. After electrospinning, the resulting precursor fibers were pre-oxidized (cured) in a muffle furnace at 200 °C for 1 h (heating rate 2 °C / min). Finally, 0.1 g of the pre-oxidized fibers and 0.6 g of sublimed sulfur were respectively loaded into two separate ceramic boats and calcined at 700 °C for 3 h under an argon atmosphere (heating rate 5 °C / min) to obtain vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composites. Rate performance is as follows: Figure 7 As shown, the test voltage range is 0.01 to 3 V, and the specific capacity is still 171.2 mAh / g at a current density of 3 A / g.
[0034] Comparative Example 1 1.8 g of polyacrylonitrile (PAN, average molecular weight 150,000) was dissolved in 15 mL of N,N-dimethylformamide (DMF), and 0.18 g of polypyrrole (PPy) solid powder was added and stirred vigorously for 3 h to form a transparent solution. Then, 3 mmol of vanadium acetylacetonate (C) was added to the above solution. 10 H 14O5V) and 6 mmol of sulfur powder (S) were heated and stirred at 45 °C for 12 h to form a dark green solution. The resulting homogeneous viscous solution was then loaded into a 20 mL plastic syringe equipped with a 20-gauge stainless steel needle (0.6 mm inner diameter, 0.9 mm outer diameter). An aluminum foil was wrapped around a roller as a receiver, and the syringe needle was kept 15 cm away from the roller. Electrospinning was performed at a feed rate of 9 μL / min. To ensure continuous nanofibers, a high voltage of 9.5 kV was applied between the needle and the aluminum foil. After electrospinning, the resulting precursor fibers were pre-oxidized (cured) in a muffle furnace at 250 °C for 1 h (heating rate 2 °C / min). Finally, 0.2 g of the pre-oxidized fibers and 0.5 g of sublimed sulfur were respectively loaded into two separate ceramic boats and calcined at 500 °C for 3 h under an argon atmosphere (heating rate 5 °C / min) to obtain vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composites. The obtained XRD pattern is shown below. Figure 8 As shown, the crystallinity is weak, and only strong diffraction peaks were detected at 34.7°, 44.4°, 45.2° and 54.5°.
[0035] Comparative Example 2 1 g of polyacrylonitrile (PAN, average molecular weight 85000) was dissolved in 25 mL of N,N-dimethylformamide (DMF), and 0.05 g of polypyrrole (PPy) solid powder was added and stirred vigorously for 3 h to form a transparent solution. Then, 3 mmol of acetylacetonate vanadyl oxyacetate (C) was added to the above solution. 10 H 14 O5V) and 6 mmol of sulfur powder (S) were heated and stirred at 45 °C for 12 h to form a dark green solution. The resulting homogeneous viscous solution was then loaded into a 20 mL plastic syringe equipped with a 20-gauge stainless steel needle (0.6 mm inner diameter, 0.9 mm outer diameter). An aluminum foil was wrapped around a roller as a receiver, with the syringe needle held 15 cm away from the roller, and electrospinning was performed at a feed rate of 9 μL / min. To ensure continuous nanofibers, a high voltage of 8.5 kV was applied between the needle and the aluminum foil. After electrospinning, the resulting precursor fibers were pre-oxidized (cured) in a muffle furnace at 250 °C for 1 h (heating rate 2 °C / min). Finally, 0.2 g of the pre-oxidized fibers and 0.4 g of sublimed sulfur were respectively loaded into two separate ceramic boats and calcined at 900 °C for 3 h under an argon atmosphere (heating rate 5 °C / min) to obtain vanadium tetrasulfide nanosheets embedded in nitrogen-sulfur co-doped carbon fiber composites. The XRD pattern of the material is shown below. Figure 9 As shown in the figure, the V3S4 phase is almost undetectable in the prepared material.
[0036] Comparative Example 3 1 g of polyacrylonitrile (PAN, average molecular weight 85000) was dissolved in 20 mL of N,N-dimethylformamide (DMF), and 0.05 g of polypyrrole (PPy) solid powder was added and stirred vigorously for 3 h to form a transparent solution. Then, 3 mmol of acetylacetonate vanadyl oxyacetate (C) was added to the above solution. 10 H 14 O5V) and 8 mmol of sulfur powder (S) were heated and stirred at 45 °C for 12 h to form a dark green solution. The resulting homogeneous viscous solution was then loaded into a 20 mL plastic syringe equipped with a 20-gauge stainless steel needle (0.6 mm inner diameter, 0.9 mm outer diameter). An aluminum foil was wrapped around a roller as a receiver, with the syringe needle held 15 cm away from the roller, and electrospinning was performed at a feed rate of 9 μL / min. To ensure continuous nanofibers, a high voltage of 10 kV was applied between the needle and the aluminum foil. After electrospinning, the resulting precursor fibers were pre-oxidized (cured) in a muffle furnace at 250 °C for 1 h (heating rate 2 °C / min). Finally, 0.2 g of the pre-oxidized fibers and 0.7 g of sublimed sulfur were respectively loaded into two separate ceramic boats and calcined at 700 °C for 4 h under an argon atmosphere (heating rate 5 °C / min). The resulting scan image is shown below. Figure 10 As shown in the figure, the obtained material structure exhibits numerous nanoribbon-like structures on the surface of carbon nanofibers with a diameter of approximately 500 nm.
[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A kind of trivanadium tetrasulfide nanosheet is embedded in nitrogen-sulfur co-doped carbon fiber composite material, it is characterized by: The composite material is composed of trivanadium tetrasulfide nanosheets and carbon fibers, the nanosheets are coated with a carbon layer on the surface and embedded in the carbon fibers, and the carbon fibers are nitrogen and sulfur co-doped carbon fibers. 2.The trivanadium tetrasulfide nanosheet embedded in nitrogen and sulfur co-doped carbon fiber composite material according to claim 1, characterized in that: The diameters of the nitrogen and sulfur elements are 300 nm to 2 μm.
3. A method for preparing a trivanadium tetrasulfide nanosheet embedded in a nitrogen and sulfur co-doped carbon fiber composite material according to any one of claims 1-2, characterized by the following steps: The vanadyl acetylacetonate and sulfur powder are dispersed in a N, N-dimethylformamide solution containing polyacrylonitrile and polypyrrole, and after constant temperature heating and stirring for a certain time, a uniform mixture is formed; then the obtained uniform mixture is subjected to electrospinning to obtain a vanadium-containing precursor fiber film; the obtained vanadium-containing precursor fiber film is placed in a muffle furnace for pre-oxidation for a certain time, and then the obtained vanadium-containing precursor fiber film is subjected to high-temperature sulfurization calcination treatment in a protective atmosphere, thereby obtaining the trivanadium tetrasulfide nanosheet embedded in the nitrogen and sulfur co-doped carbon fiber composite material.
4. The preparation method of the trivanadium tetrasulfide nanosheet embedded in nitrogen-sulfur co-doped carbon fiber composite material according to claim 3, characterized in that: The average molecular weight of the polyacrylonitrile is one of 50,000, 85,000 and 150,000; the ratio of the polyacrylonitrile to the polypyrrole is 1 g: 10-20 g; and the solid-liquid ratio of the polyacrylonitrile to the N, N-dimethylformamide solution is 1 g: 7-25 mL, the stirring time at room temperature is 2-4 h, and the stirring speed is 250-650 r / min.
5. The preparation method of claim 3, wherein the preparation method of the trivanadium tetrasulfide nanosheet embedded in nitrogen-sulfur co-doped carbon fiber composite material is characterized by: The molar ratio of the vanadyl acetylacetonate to the sulfur powder is 1:2-10, and the mixture is heated and stirred in the N, N-dimethylformamide solution containing the polyacrylonitrile and the polypyrrole, the temperature is 30-60 °C, the stirring speed is 250-650 r / min, and the stirring time is 6-24 h.
6. The method of claim 3, wherein: The voltage of the electrospinning is 5-15 kV, the receiving distance is 10-20 cm, the advancing speed is 6-12 μL / min, and the inner diameter of the stainless steel needle is one of 1.45, 1.25, 1.12, 0.90, 0.70, 0.60, 0.51, 0.41 and 0.33 mm.
7. The method of claim 3, wherein: The pre-oxidation treatment temperature is 150-350 °C, the heating rate is 1-10 °C / min, and the holding time is 0.5-6 h.
8. The method of claim 3, wherein: The inert atmosphere for the high-temperature calcination sulfurization treatment is argon or nitrogen, the temperature is 500-1000 °C, the heating rate is 1-10 °C / min, the holding time is 1-8 h, and the mass ratio of the fiber after the pre-oxidation treatment to the sulfur powder is 1:2-10.
9. The application of the vanadium tetrasulfide nanosheet intercalated nitrogen and sulfur co-doped carbon fiber composite material according to any one of claims 1-2 or the vanadium tetrasulfide nanosheet intercalated nitrogen and sulfur co-doped carbon fiber composite material prepared by the preparation method according to any one of claims 3-8, characterized in that: It is used as a negative electrode material for lithium ion batteries.