Carbon fiber packaged VSTe-CFs composite material as well as preparation method and application thereof

Abstract

The invention discloses a carbon fiber packaged VSTe-CFs composite material as well as a preparation method and application thereof, and belongs to the technical field of sodium ion batteries. According to the carbon fiber packaged VSTe (at) CFs composite material, VS2 nanosheets are packaged in PVP through electrostatic spinning, agglomeration of the VS2 nanosheets is inhibited, the PVP is carbonized into carbon nanofibers through calcination, a conductive network is formed, electron conduction is enhanced, and volume change is buffered; te is doped to form a V-Te bond which is easier to break compared with V-S, so that the conductivity and interlayer spacing are improved, and sodium ion diffusion is facilitated; the composite material still keeps excellent stability after 1000 cycles under the current density of 1A. G <-1 >, and shows good electrochemical performance.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a carbon fiber encapsulated VSTe@CFs composite material, its preparation method, and its application. Background Technology

[0002] In the field of sodium-ion batteries, the performance of the anode material directly determines the battery's energy density, cycle life, and rate capability. Layered transition metal sulfides (VS2) have become a research hotspot for anodes due to their suitable sodium intercalation / deintercalation potential, high theoretical specific capacity, and unique layered structure, and are candidate materials with great industrialization potential.

[0003] Currently, VS2-based anode materials face the following core technical bottlenecks: First, the high surface energy of the nanosheets leads to easy aggregation during preparation and charge / discharge, resulting in insufficient exposure of active sites and reduced actual specific capacity. Second, poor intrinsic conductivity means that electron transport cannot keep up with the sodium insertion / extraction rate at high currents, resulting in poor rate performance. Third, repeated sodium insertion / extraction during charge / discharge causes severe volume expansion, leading to material breakage, electrode collapse, and short cycle life. Fourth, the high VS bond energy and narrow interlayer distance result in high sodium diffusion resistance and slow electrochemical reaction kinetics. To address these technical problems, existing technologies have attempted carbon coating or single-element doping modification, but these still have the following limitations: carbon coating only alleviates expansion and improves conductivity, but cannot suppress initial aggregation or improve VS bond and sodium diffusion issues; single doping only fine-tunes the crystal structure, making it difficult to simultaneously solve the problems of conductivity and expansion, and thus failing to achieve a breakthrough in overall performance.

[0004] Therefore, developing a modification scheme that can simultaneously address the issues of VS2 aggregation, conductivity, volume stability, and reaction kinetics is a key requirement for the industrialization of sodium-ion batteries. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a carbon fiber encapsulated VSTe@CFs composite material, its preparation method and application, to solve technical problems such as VS2 agglomeration, conductivity, volume stability and reaction kinetics.

[0006] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for preparing carbon fiber-encapsulated VSTe@CFs composite material, comprising the following steps: S1. Add ammonium metavanadate (NH4VO3), thioacetamide (TAA) and ammonia to water, stir to obtain precursor solution A, subject precursor solution A to hydrothermal treatment, wash and dry to obtain VS2. S2. Add polyvinylpyrrolidone (PVP) to N,N-dimethylformamide (DMF), stir, and then add VS2 to obtain precursor solution B; S3. Spinning the precursor solution B yields organic nanofibers VS2@CFS. S4. Add Te powder to organic nanofibers VS2@CFS and then calcine to obtain carbon fiber encapsulated VSTe@CFs composite material.

[0007] In one embodiment, in S1, the ratio of NH4VO3, TAA, ammonia and water is 0.234g:1.127g~1.352g:1mL~2mL:30mL.

[0008] In one embodiment, in S1, the temperature of the hydrothermal treatment is 160 °C, and the hydrothermal treatment time is 6 to 8 hours.

[0009] In one embodiment, in S2, the ratio of PVP, DMF and VS2 is 1g to 1.2g: 10g: 0.805g to 1.035g.

[0010] In one embodiment, in S3, the injection flow rate of the spinning process is 282 µm·min. -1 The voltage is 15 kV and the receiving distance is 15 cm.

[0011] In one embodiment, in step S4, the amount of Te powder used is 2.042–5.104 g; the calcination temperature is 800°C, the calcination time is 5 h, and the heating rate is 5°C·min. -1 .

[0012] In another aspect, the present invention provides a carbon fiber encapsulated VSTe@CFs composite material, which is prepared by the aforementioned method for preparing carbon fiber encapsulated VSTe@CFs composite material. The carbon fiber encapsulated VSTe@CFs composite material includes carbon fibers, with the carbon fibers serving as a skeleton to encapsulate VSTe in a nanoflower-like structure.

[0013] In one embodiment, at 1A·g -1 At high current densities, the carbon fiber-encapsulated VSTe@CFs composite material achieves a cycle life of 1000 cycles.

[0014] The present invention also provides an application of carbon fiber-encapsulated VSTe@CFs composite material prepared by the above-mentioned method for preparing carbon fiber-encapsulated VSTe@CFs composite material as a negative electrode material in sodium-ion batteries.

[0015] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing carbon fiber-encapsulated VSTe@CFs composite material. VS2 nanosheets are uniformly encapsulated in PVP via electrospinning, effectively mitigating the aggregation of VS2 nanosheets. Furthermore, the PVP is carbonized into carbon nanofibers under high-temperature calcination, constructing an interconnected conductive network. This not only facilitates electron transport, thereby improving the conductivity of the anode material, but also effectively alleviates volume expansion caused by charging and discharging, improving the cycle stability of the anode material. Finally, the V-Te bands formed by Te atom doping are more prone to breakage during the conversion reaction than VS bands. On the one hand, this provides the anode material with higher electronic conductivity and an extended interlayer distance; on the other hand, it results in higher reactivity. Simultaneously, the expanded interlayer distance helps reduce sodium ion diffusion resistance, promoting the electrochemical kinetics of sodium-ion batteries.

[0016] This invention also provides a method for preparing carbon fiber-encapsulated VSTe@CFs composite materials. The carbon fiber-encapsulated VSTe@CFs composite material is prepared by uniformly encapsulating VS2 nanosheets within carbon nanofibers through structural design and elemental regulation. This not only effectively improves the electronic conductivity of the VS2 material but also provides a flexible supporting framework during charge and discharge, buffering the volume changes caused by sodium ion insertion and extraction. Thanks to this unique structural advantage, the carbon fiber-encapsulated VSTe@CFs composite material exhibits excellent electrochemical performance as a negative electrode material for sodium-ion batteries, even at 1 A·g... -1 Even at high current densities, the cycle life can still reach 1000 cycles, demonstrating extremely high cycle stability. Attached Figure Description

[0017] Figure 1 The graphs show the specific capacity and coulombic efficiency of the carbon fiber-encapsulated VSTe@CFs composites prepared in Examples 1-8. Figure 2 SEM images of VS2 and the carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2, where: a - SEM image of VS2; b - SEM image of the carbon fiber-encapsulated VSTe@CFs composite material; Figure 3 XRD patterns of VS2, carbon fiber-encapsulated VS2 composite material, and carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2; Figure 4 XPS images of the carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2, where: a-V2p spectrum; b-C1s spectrum; c-S2p spectrum; d-Te3d spectrum; Figure 5The VS2, carbon fiber-encapsulated VS2 composite material, and carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2 were used as anodes in sodium-ion batteries at 0.1 Ag. -1 Cyclic performance diagram after 100 cycles at current density; Figure 6 The carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2 was used as the anode of a sodium-ion battery at 1 A·g -1 Cyclic performance diagram after 1000 cycles at current density; Figure 7 Impedance spectra of the VS2 and carbon fiber-encapsulated VSTe@CFs composite materials prepared in Example 2. Detailed Implementation

[0018] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0019] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0020] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0021] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0022] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0023] To address the shortcomings of existing technologies, this invention discloses a carbon fiber-encapsulated VSTe@CFs composite material, its preparation method, and its applications. The preparation method first involves electrospinning VS2 nanosheets uniformly encapsulating them within PVP to effectively alleviate VS2 nanosheet aggregation. Then, high-temperature calcination carbonizes the PVP into carbon nanofibers, constructing an interconnected conductive network. This network not only facilitates electron transport, improving the conductivity of the anode material, but also provides a flexible support framework, effectively mitigating the volume expansion caused by sodium ion insertion / extraction during charging and discharging, thereby improving the cycle stability of the anode material. Simultaneously, the doping of Te atoms makes the V-Te formed in the material more prone to breakage than VS during the conversion reaction, providing higher electronic conductivity for the anode material and expanding the interlayer distance, which helps reduce sodium ion diffusion resistance and further promotes the electrochemical kinetics of sodium-ion batteries. Ultimately, this composite material exhibits excellent electrochemical performance as a sodium-ion battery anode material, even at 1 A·g -1 Even at high current densities, the cycle life can still reach 1000 cycles, demonstrating extremely high cycle stability.

[0024] Specifically, the present invention provides a method for preparing a carbon fiber encapsulated VSTe@CFs composite material, comprising the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.127–1.352 g of thioacetamide (TAA), and 1–2 mL of ammonia water and add them to 30 mL of deionized water. Stir at 500 r / min for 30 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160 °C for 6–8 h, then allow it to cool naturally to room temperature. Wash it alternately with deionized water and anhydrous ethanol 3 times each, and dry it at 65 °C for 24 h to obtain VS2. S2. Weigh 1-1.2g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir for 30min at 500r / min. Add 0.805-1.035g of VS2 obtained in step S1 and continue stirring for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 2.042–5.104 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min.-1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0025] In the carbon fiber-encapsulated VSTe@CFs composite material prepared by the above method, carbon fiber acts as a skeleton to encapsulate VSTe in a nanoflower-like structure.

[0026] The carbon fiber-encapsulated VSTe@CFs composite material prepared by the above method was applied to the anode material of sodium-ion batteries.

[0027] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0028] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0029] The preparation method and characterization in the following examples are based on... Figures 1-7 Unless otherwise specified, all methods are conventional; unless otherwise specified, the materials used in the following examples are all new materials purchased from the market.

[0030] Example 1: A method for preparing carbon fiber encapsulated VSTe@CFs composite material includes the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.127 g of thioacetamide (TAA) and 2 mL of ammonia water and add them sequentially to 30 mL of deionized water. Stir at 500 r / min for 90 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160 °C for 6 h, then cool naturally to room temperature, wash with deionized water and anhydrous ethanol alternately 6 times each, and dry at 60 °C for 12 h to obtain VS2. S2. Weigh 1g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir at 500r / min for 12h. Add 0.805g of VS2 obtained in step S1 and continue stirring at the above speed for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 2.042 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min. -1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0031] The carbon fiber-encapsulated VSTe@CFs composite material prepared by the above method was applied to the anode material of sodium-ion batteries.

[0032] Example 2: A method for preparing carbon fiber encapsulated VSTe@CFs composite material includes the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.352 g of thioacetamide (TAA) and 2 mL of ammonia water and add them sequentially to 30 mL of deionized water. Stir at 500 r / min for 90 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160℃ for 6 h, then cool naturally to room temperature, wash with deionized water and anhydrous ethanol alternately 6 times each, and dry at 60℃ for 12 h to obtain VS2. S2. Weigh 1g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir at 500r / min for 12h. Add 0.805g of VS2 obtained in step S1 and continue stirring at the above speed for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 2.042 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min. -1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0033] Example 3: A method for preparing carbon fiber encapsulated VSTe@CFs composite material includes the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.127 g of thioacetamide (TAA) and 1 mL of ammonia water and add them sequentially to 30 mL of deionized water. Stir at 500 r / min for 90 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160 °C for 6 h, then cool naturally to room temperature, wash with deionized water and anhydrous ethanol alternately 6 times each, and dry at 60 °C for 12 h to obtain VS2. S2. Weigh 1g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir at 500r / min for 12h. Add 0.805g of VS2 obtained in step S1 and continue stirring at the above speed for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 2.042 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min. -1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0034] Example 4: A method for preparing carbon fiber encapsulated VSTe@CFs composite material includes the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.127 g of thioacetamide (TAA) and 2 mL of ammonia water and add them sequentially to 30 mL of deionized water. Stir at 500 r / min for 90 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160 °C for 8 h, then cool naturally to room temperature, wash with deionized water and anhydrous ethanol alternately 6 times each, and dry at 60 °C for 12 h to obtain VS2. S2. Weigh 1g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir at 500r / min for 12h. Add 0.805g of VS2 obtained in step S1 and continue stirring at the above speed for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 2.042 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min. -1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0035] Example 5: A method for preparing carbon fiber encapsulated VSTe@CFs composite material includes the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.127 g of thioacetamide (TAA) and 2 mL of ammonia water and add them sequentially to 30 mL of deionized water. Stir at 500 r / min for 30 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160℃ for 6 h, then cool naturally to room temperature, wash with deionized water and anhydrous ethanol alternately 6 times each, and dry at 60℃ for 12 h to obtain VS2. S2. Weigh 1g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir at 500r / min for 12h. Add 0.805g of VS2 obtained in step S1 and continue stirring at the above speed for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 2.042 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min. -1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0036] Example 6: A method for preparing carbon fiber encapsulated VSTe@CFs composite material includes the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.127 g of thioacetamide (TAA) and 1 mL of ammonia water and add them sequentially to 30 mL of deionized water. Stir at 500 r / min for 90 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160 °C for 6 h, then cool naturally to room temperature, wash with deionized water and anhydrous ethanol alternately 6 times each, and dry at 60 °C for 12 h to obtain VS2. S2. Weigh 1g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir at 500r / min for 30min. Add 0.805g of VS2 obtained in step S1 and continue stirring at the above speed for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 5.104 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min. -1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0037] Example 7: A method for preparing carbon fiber encapsulated VSTe@CFs composite material includes the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.127 g of thioacetamide (TAA) and 2 mL of ammonia water and add them sequentially to 30 mL of deionized water. Stir at 500 r / min for 90 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160 °C for 6 h, then cool naturally to room temperature, wash with deionized water and anhydrous ethanol alternately 6 times each, and dry at 60 °C for 1 h to obtain VS2. S2. Weigh 1g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir at 500r / min for 30min. Add 1.305g of VS2 obtained in step S1 and continue stirring at the above speed for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 5.104 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min. -1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0038] Example 8: A method for preparing carbon fiber encapsulated VSTe@CFs composite material includes the following steps: S1. Weigh 0.234 g of ammonium metavanadate (NH4VO3), 1.127 g of thioacetamide (TAA) and 2 mL of ammonia water and add them sequentially to 30 mL of deionized water. Stir at 500 r / min for 90 min to obtain precursor solution A. Perform hydrothermal treatment on the obtained precursor solution A at 160 °C for 6 h, then cool naturally to room temperature, wash with deionized water and anhydrous ethanol three times each, and dry at 65 °C for 24 h to obtain VS2. S2. Weigh 1.2g of polyvinylpyrrolidone (PVP) and add it to 10g of N,N-dimethylformamide (DMF). Stir at 500r / min for 30min. Add 1.305g of VS2 obtained in step S1 and continue stirring at the above speed for 2h to obtain precursor solution B. S3. The precursor solution B obtained in step S2 is treated by electrospinning, wherein the injection flow rate for spinning is 282 µm·min. -1 The voltage was 15KV, the receiving distance was 15cm, and the product was collected using a stainless steel disk to obtain organic nanofibers VS2@CFs. S4. Weigh 5.104 g of Te powder and add it to the organic nanofibers VS2@CFs obtained in step S3. Calcinate the nanofibers at 800 °C for 5 h under an Ar atmosphere with a flow rate of 300 mL and a heating rate of 5 °C / min. -1 After being naturally cooled to room temperature, carbon fiber-encapsulated VSTe@CFs composite material was obtained.

[0039] Obviously, the above comparative examples and embodiments are only a part of the comparative examples and embodiments of the present invention, and they, along with the comparative examples and embodiments referenced based on such examples, are all within the scope of protection of this invention.

[0040] The carbon fiber-encapsulated VSTe@CFs composite material prepared by the above method is applied as a negative electrode material for sodium-ion batteries. The specific assembly and application process is as follows: Preparation of negative electrode sheet: 0.8g of carbon fiber encapsulated VSTe@CFs composite material, 0.1g of polyvinylidene fluoride and 0.1g of acetylene black prepared in the example were mixed into a uniform slurry, coated on copper foil, dried at 60°C for 12h, and then cut into negative electrode sheets with a diameter of 10mm for experimental batteries by a cutting machine.

[0041] Preparation of positive electrode: 0.8g of sodium vanadium phosphate, 0.1g of polyvinylidene fluoride and 0.1g of acetylene black were mixed into a uniform slurry, coated on aluminum foil, dried at 60℃ for 12h, and then cut into positive electrode sheets with a diameter of 12mm for experimental batteries using a cutting machine.

[0042] Battery assembly: A carbon fiber-encapsulated VSTe@CFs composite material was used as the negative electrode; sodium vanadium phosphate was used as the positive electrode; the electrolyte was a 1M NaPF6 solution of methyl ethyl carbonate, dimethyl carbonate, and ethylene carbonate mixed in a 1:1:1 volume ratio; the separator was a glass fiber separator GF / D1823-090; the battery assembly sequence was as follows: negative electrode shell, negative electrode sheet, separator, positive electrode sheet, gasket, spring sheet, positive electrode shell, assembled into a coin cell in a glove box filled with an inert atmosphere. Charge-discharge cycle testing was performed on this coin cell: the charge-discharge cutoff voltage was 0.01V, and the charge-discharge current was 0.1A·g. -1 .

[0043] The following tests were conducted on the battery materials assembled from the carbon fiber-encapsulated VSTe@CFs composite material prepared in the examples: The specific capacity and coulombic efficiency test results of the carbon fiber-encapsulated VSTe@CFs composite materials prepared in Examples 1-8 are as follows: Figure 1 As shown, Example 2 exhibits the best overall performance, with a specific capacity consistently maintained at 350.5 mAh·g. -1 Between these parameters, the coulombic efficiency reached 99.87%. Meanwhile, a comparison of the test results of different embodiments shows that appropriate control of the amount of thioacetamide (TAA), ammonia concentration, hydrothermal time, tellurium powder addition, and drying conditions has a key impact on improving capacity and efficiency.

[0044] Figure 2 SEM image of the carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2. From... Figure 2 As can be seen, VS2 prepared by hydrothermal method exhibits a uniform nanoflower-like structure with a large specific surface area and abundant active sites, which is beneficial to improving the electrochemical performance of the material. Figure 2 As shown in b, after high-temperature annealing and tellurization treatment, VS2 is transformed into VSTe. The VSTe nanoflower-like structure is tightly wrapped and uniformly distributed within the carbon fiber skeleton, and the carbon fiber structure remains intact. This encapsulation relationship ensures the good structural stability of the VSTe@CFs composite material.

[0045] Figure 3 The XRD curves of the carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2 are shown in the figure. As can be seen from the figure, the characteristic peaks of VS2 and the carbon fiber-encapsulated VS2 composite material at 2θ of 15.7°, 34.9°, and 35.2° are consistent with the three strong peaks in the VS2 (PDF#29-1381) standard card, indicating that VS2 was successfully prepared via a hydrothermal method, and that the phase composition of the VS2 prepared by the hydrothermal method remained unchanged after electrospinning. The carbon fiber-encapsulated VSTe@CFs composite material exhibits characteristic peaks at 2θ of 44.7°, 45.3°, and 55.7° consistent with the VSTe@CFs (PDF#73-2026) standard card, indicating that the carbon fiber-encapsulated VSTe@CFs composite material was successfully prepared via a high-temperature tellurization reaction.

[0046] Figure 4 The XPS spectrum of the carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2 is shown. As can be seen from the figure, the sample is composed of four elements: V, S, C, and Te. The XPS spectrum of V2p is shown below. Figure 4 As shown in figure a, the four peaks correspond to V respectively. 3+ V-Te, VC and V 2+The corresponding binding energies are 531.5 eV, 511.4 eV, 516.2 eV and 522.8 eV, which are the four characteristic peaks of V, further proving the existence of V-Te bonds in carbon fiber encapsulated VSTe@CFs composites. Figure 4 b is the S 2p spectrum showing two peaks, corresponding to SB0 (163.4 eV) and ST-1 (166.7 eV). Figure 4 c is the fine spectrum of C ls, and the absorption peaks at 292.7 eV and 284.2 eV can be fitted to CS bonds and CC bonds, respectively. Figure 4 d is the fine spectrum of Te 3d, which shows two peaks, corresponding to Te-O (583.7 eV) and Te-V (572.3 eV).

[0047] Figure 5 The carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2 was used as the anode of a sodium-ion battery at 0.1 A·g -1 Cycling performance graph after 100 cycles. As can be seen from the graph, the carbon fiber-encapsulated VSTe@CFs composite material exhibits excellent cycling stability, maintaining 350.5 mAh·g after 100 charge-discharge cycles. -1 Its high discharge specific capacity is far higher than that of pure VS2 (72.8 mAh·g). -1 ) and carbon fiber encapsulated VS2 composite material (244.2 mAh·g) -1 This performance improvement is mainly attributed to the effective coating structure of carbon fiber on VS2 particles, which effectively inhibits particle agglomeration and significantly alleviates the volume expansion problem during charge and discharge, thereby improving the structural stability and cycle life of the electrode.

[0048] Figure 6 The carbon fiber-encapsulated VSTe@CFs composite material prepared in Example 2 was used as the anode of a sodium-ion battery at 1 A·g -1 The cycling performance graph shows the results after 1000 charge-discharge cycles. As can be seen from the graph, the reversible specific capacity of the carbon fiber-encapsulated VSTe@CFs composite material remains at 245.3 mAh·g after 1000 charge-discharge cycles. -1 Coulomb efficiency is also relatively stable, with fluctuations ranging from 96.1% to 100%.

[0049] Figure 7Impedance spectra of carbon fiber-encapsulated VSTe@CFs composites prepared for VS2 and Example 2 are shown. As can be seen from the figures, the charge transport resistance of the carbon fiber-encapsulated VSTe@CFs composite is significantly reduced to only 55.4 Ω, exhibiting superior electron transport capability compared to 100.0 Ω of pure VS2. This is mainly due to the introduction of carbon nanotubes, which effectively improves the conductivity and electron / ion transport efficiency of the material. Furthermore, the doping of Te atoms facilitates the formation of more easily broken V–Te bonds during the reaction, providing higher electronic conductivity compared to V–S bonds and expanding the interlayer spacing, thereby further accelerating the sodium ion insertion / extraction kinetics and promoting the overall improvement of electrochemical performance.

[0050] This invention belongs to the field of sodium-ion battery technology, specifically referring to a carbon fiber encapsulated VSTe@CFs composite material, its preparation method, and its application. The carbon fiber encapsulated VSTe@CFs composite material involves encapsulating VS2 nanosheets within PVP via electrospinning to inhibit agglomeration, followed by calcination to carbonize the PVP into carbon nanofibers, forming a conductive network that enhances electron conduction and buffers volume changes. Te doping forms V-Te bonds, which are more easily broken than VS, improving conductivity and interlayer spacing, thus facilitating sodium ion diffusion. This composite material exhibits high conductivity at 1 A·g⁻¹. -1 It maintains excellent stability after 1000 cycles at current density, demonstrating good electrochemical performance.

[0051] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing carbon fiber encapsulated VSTe@CFs composite material, characterized in that, Includes the following steps: S1. Add ammonium metavanadate, thioacetamide and ammonia to water and stir to obtain precursor solution A. Perform hydrothermal treatment on precursor solution A, wash and dry to obtain VS2. S2. Add polyvinylpyrrolidone to N,N-dimethylformamide, stir, and then add VS2 to obtain precursor solution B; S3. Spinning the precursor solution B yields organic nanofibers VS2@CFS. S4. Add Te powder to organic nanofibers VS2@CFS and then calcine to obtain carbon fiber encapsulated VSTe@CFs composite material.

2. The method for preparing a carbon fiber encapsulated VSTe@CFs composite material according to claim 1, characterized in that, In S1, the ratio of ammonium metavanadate, thioacetamide, ammonia, and water is 0.234g:1.127g~1.352g:1mL~2mL:30mL.

3. The method for preparing a carbon fiber encapsulated VSTe@CFs composite material according to claim 1, characterized in that, In S1, the temperature of the hydrothermal treatment is 160 ℃, and the time of the hydrothermal treatment is 6 to 8 h.

4. The method for preparing a carbon fiber encapsulated VSTe@CFs composite material according to claim 1, characterized in that, In S2, the ratio of polyvinylpyrrolidone, N,N-dimethylformamide and VS2 is 1g~1.2g:10g:0.805g~1.035g.

5. The method for preparing a carbon fiber encapsulated VSTe@CFs composite material according to claim 1, characterized in that, In S3, the injection flow rate of the spinning process is 282 µm·min. -1 The voltage is 15 kV and the receiving distance is 15 cm.

6. The method for preparing a carbon fiber encapsulated VSTe@CFs composite material according to claim 1, characterized in that, In S4, the amount of Te powder used is 2.042–5.104 g; the calcination temperature is 800℃, the calcination time is 5 h, and the heating rate is 5℃·min. -1 .

7. A carbon fiber-encapsulated VSTe@CFs composite material, characterized in that, The composite material was prepared using the method described in any one of claims 1-6 for encapsulating carbon fiber VSTe@CFs.

8. The carbon fiber encapsulated VSTe@CFs composite material according to claim 7, characterized in that, The carbon fiber encapsulated VSTe@CFs composite material includes carbon fibers, with the carbon fibers acting as a skeleton to encapsulate VSTe in a nanoflower-like structure.

9. The carbon fiber encapsulated VSTe@CFs composite material according to claim 7, characterized in that, In 1A·g -1 At high current densities, the carbon fiber-encapsulated VSTe@CFs composite material achieves a cycle life of 1000 cycles.

10. The application of a carbon fiber-encapsulated VSTe@CFs composite material prepared by the preparation method of any one of claims 1-6 as a negative electrode material in a sodium-ion battery.

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