Three-dimensional porous carbon encapsulated V2O5 carbon fiber electrode constructed by in-situ growth and preparation method and application thereof

Abstract

The invention discloses a three-dimensional porous carbon encapsulated V2O5 carbon fiber electrode constructed by in-situ growth and a preparation method and application thereof, belongs to the technical field of aluminum ion battery positive electrode materials, and aims to solve the problems that the intercalation and deintercalation dynamics of AlCl4 in a polyacrylonitrile (Pan)-based carbon fiber is blocked due to disordered graphite structure, and the performance of the Pan-based carbon fiber is influenced. And the material cannot be used as an effective electrode material to be applied to an aluminum ion battery system. According to the preparation method, an in-situ growth technology is adopted, a three-dimensional porous carbon substrate is grown on the surface of carbon fiber, then an orthorhombic system vanadium pentoxide (V2O5) nano material which has high theoretical specific capacity and can realize large-current charging and discharging is packaged in the three-dimensional porous carbon substrate, and the V2O5-based carbon fiber electrode is prepared. According to the electrode, the electrostatic interaction between Al < 3 + > ions and crystal lattices is effectively relieved, the structural advantages of the carbon fibers and the energy storage performance of V2O5 are fully combined, the energy storage effect of the aluminum ion battery is remarkably improved, and a new effective scheme is provided for development of aluminum ion battery electrode materials.

Description

Technical Field

[0001] This invention belongs to the field of aluminum-ion battery cathode materials, specifically a carbon fiber electrode for in-situ growth of three-dimensional porous carbon-encapsulated V2O5, its preparation method, and its application. Background Technology

[0002] Against the backdrop of energy transition and surging demand for energy storage, aluminum-ion batteries have become a key research and development direction in the energy storage field due to their high theoretical capacity, readily available raw materials, low cost, and excellent safety performance. The key to improving their performance lies in breakthroughs in cathode materials. Carbon fiber, with its high specific surface area, excellent conductivity, and mechanical stability, is considered an ideal electrode material. Among them, polyacrylonitrile (Pan)-based carbon fiber, due to its mature manufacturing process and controllable cost, is widely used in the field of composite materials and theoretically has the potential to become an electrode for aluminum-ion batteries. However, the smooth, inert surface and disordered graphite structure of carbon fiber hinder the insertion and extraction kinetics of the key charge carrier AlCl4⁻ within the carbon fiber during battery charging and discharging.

[0003] To address this challenge, this invention proposes a composite electrode fabrication technique and selects in-situ growth technology. This technique can significantly enhance the interfacial bonding between the matrix and the active material by forming chemically bonded active substances on the carbon fiber surface, while ensuring the continuity of the microstructure. It effectively avoids the problems of easy detachment of active substances and high interfacial resistance in traditional physical mixing methods, providing a feasible path to improve the performance of carbon fiber-based composite electrodes.

[0004] In the field of positive electrode active materials for aluminum-ion batteries, orthorhombic vanadium pentoxide (V₂O₅) has become a highly promising active component due to its high theoretical specific capacity and adaptability to high-current charge and discharge requirements. However, V₂O₅ itself suffers from poor electronic conductivity, and its layered structure is easily damaged by Al during charge and discharge. 3+ The problem of collapse during embedding / de-embedding makes it difficult to meet the high-performance requirements of batteries when used alone.

[0005] Therefore, this invention prepares a composite structure through in-situ growth, growing a three-dimensional porous carbon matrix on carbon fibers, and then encapsulating V2O5 nanomaterials within the three-dimensional porous carbon matrix. V2O5 serves as the active material for the electrode, facilitating the charge-discharge process of ion insertion and extraction. The porous carbon material provides a three-dimensional continuous conductive network on the carbon fiber surface. This network effectively compensates for the conductivity defects caused by the disordered graphite structure of Pan-based carbon fibers, connecting isolated conductive sites into interconnected conductive channels. Simultaneously, the three-dimensional porous structure helps achieve uniform dispersion of V2O5, preventing particle agglomeration, maximizing the exposure of active sites, and improving the utilization rate of the active material. Summary of the Invention

[0006] The purpose of this invention is to provide a carbon fiber electrode for in-situ growth of three-dimensional porous carbon-encapsulated V2O5, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for in-situ growth of carbon fiber electrodes for constructing three-dimensional porous carbon-encapsulated V2O5, comprising the following specific steps: S1. Place the carbon fiber in a Soxhlet extraction apparatus, add organic solvent for reflux treatment, then rinse the carbon fiber with deionized water and dry it; S2. Add starch and KOH to deionized water, stir and mix, then transfer the mixed solution to an oven for heat preservation to form a sol-gel solution; S3. The carbon fibers treated in step S1 are immersed in the sol-gel solution, removed and dried, and then placed in a tube furnace under a nitrogen atmosphere, heated to the target temperature and kept at that temperature, then washed and dried to obtain 3D mesh porous carbon matrix coated flexible carbon fibers. S4. Add triisopropoxyvanadium oxide to isopropanol, stir and mix to obtain a mixed solution. Immerse the 3D mesh porous carbon matrix coated flexible carbon fiber prepared in step S3 into the mixed solution, heat and react. After the reaction is completed, wash the sample, dry it, and anneal the dried sample in air to obtain the carbon fiber electrode of three-dimensional porous carbon encapsulated V2O5.

[0008] Furthermore, in step S1, the reflux treatment time is 24-48 hours, the deionized water rinsing time is 6-12 hours, and the drying temperature is 60-80℃. Further, in step S2, the mass ratio of starch to KOH is (1~4):(1~4), the mass-volume ratio of starch to deionized water is (1~4)g:(10~40)mL, the oven temperature is 50~70℃, and the holding time is 20~30 hours. Further, in step S3, during soaking, the temperature of the sol-gel solution is 75~85℃, and the soaking time is 1~6 hours; the drying temperature after removal is 70~90℃, and the drying time is 20~30 hours; the target temperature of the tube furnace is 550~650℃, the heating rate is 2~5℃・min⁻¹, and the holding time is 1~3 hours; the drying temperature after cleaning is 70~90℃, and the drying time is 20~30 hours. Further, in step S4, the volume ratio of triisopropoxyvanadium oxide to isopropanol is (0.05~0.15):(35~45), the stirring time is 25~35 minutes, the reaction temperature is 170~190℃, and the reaction time is 10~15 hours; the air annealing temperature is 300~350℃, and the annealing time is 1~3 hours; the drying time is 20~24 hours.

[0009] The carbon fiber electrode with three-dimensional porous carbon encapsulation of V2O5 was prepared by the above method.

[0010] The above-mentioned three-dimensional porous carbon-encapsulated V2O5 carbon fiber electrode is used in aluminum-ion batteries.

[0011] Furthermore, a carbon fiber electrode encapsulating V2O5 in a three-dimensional porous carbon environment is used as the positive electrode, and a molybdenum sheet is used as the positive electrode tab. The molybdenum sheet is attached to the carbon fiber electrode encapsulating V2O5 in a three-dimensional porous carbon environment using conductive silver paste. An aluminum mesh is used as the negative electrode material, with tabs reserved. A glass fiber diaphragm is used as the separator. An aluminum-plastic film is used as the outer shell of the energy storage composite material. The electrodes are stacked in the order of positive electrode-separator-negative electrode, encapsulated in the aluminum-plastic film, and filled with electrolyte in a glove box. After standing for 20-30 hours, the product is obtained.

[0012] The beneficial effects of this invention are as follows: 1. The problem of low charge and discharge capacity of Pan-based carbon fiber electrodes has been effectively solved, and high-performance carbon fiber-based electrode materials have been prepared.

[0013] 2. Synergistic enhancement of V2O5 electrochemical performance, balancing high capacity and long lifetime. The three-dimensional porous carbon matrix provides uniform loading sites for V2O5 nanomaterials, effectively preventing V2O5 particle aggregation, maximizing the exposure of active sites, and fully leveraging its high theoretical specific capacity. At the same time, the three-dimensional porous carbon can act as a "spatial confinement" mechanism, effectively mitigating the volume change of V2O5 during ion insertion and extraction, and enhancing stability.

[0014] 3. The preparation process is simple. Three-dimensional porous carbon-encapsulated V2O5 carbon fiber electrodes are constructed by in-situ growth. The in-situ growth method can enhance the interaction between the active material and the carbon fiber substrate, avoid the shedding of the active material during cycling, and avoid the presence of inactive materials in traditional coating processes. It can significantly improve the capacity and performance of the battery and has broad application prospects. Attached Figure Description

[0015] Figure 1 In the image: (a) is a SEM image of 3DC-CF (×1400); (b) is a SEM image of V2O5 / 3DC-CF (×6500). Figure 2 In the image: (a) XRD pattern of CF and 3DC-CF; (b) XRD pattern of V2O5 / 3DC-CF; (c) Raman spectroscopy of CF and 3DC-CF; (d) XPS full spectrum of 3DC-CF and V2O5 / 3DC-CF; (e) V2p XPS of V2O5 / 3DC-CF; (f) V2p XPS of 3DC-CF. Figure 3 In the middle: (a) is the charge-discharge curve of CF(T800 6K) / / GF / / Al pouch cell; (b) is the charge-discharge curve of V2O5 / 3DC-CF / / / / GF / / Al pouch cell; (c) is the long-cycle curve of V2O5 / 3DC-CF / / / / GF / / Al pouch cell. Detailed Implementation

[0016] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited thereto.

[0017] A method for in-situ growing and constructing a carbon fiber electrode encapsulating three-dimensional porous carbon V2O5 includes the following steps: (1) Pretreatment of carbon fiber: First, T800 (6K) carbon fiber was placed in a Soxhlet extraction apparatus and refluxed for 48 hours with acetone as a solvent to remove surface adhesives and contaminants. Then, the carbon fiber was repeatedly rinsed with deionized water for 6 hours to remove the acetone solution on the surface. Finally, it was dried in a vacuum oven at 60°C for 24 hours.

[0018] (2) In a beaker (50 mL), mix 10 g starch and 10 g KOH in 80 mL deionized water while stirring vigorously at 600 rpm; (3) Transfer the mixed solution to an oven and keep it at 60°C for 24 hours to form a sol-gel solution; (4) Soak a 10cm*10cm piece of carbon cloth in a sol-gel solution at 80℃ for 12 hours, then take it out and dry it at 80℃ for 24 hours; (5) Under a nitrogen atmosphere at 600℃ (2~5℃ min) -1 Heating in a tube furnace at a heating rate of 600℃ for 2 hours; (6) Then wash with 1 mol / L dilute HCl and distilled water in sequence, and clean with ultrasound (ultrasound frequency: 40KHz, ultrasound power: 300W) for 30 minutes to remove loosely attached carbon material. (7) The sample was dried in a vacuum oven at 80°C for 24 hours to obtain a 3D mesh porous carbon matrix coated flexible carbon fiber (3DC CF). (8) Add 100 μL of triisopropoxyvanadium oxide to 40 mL of isopropanol (IPA) and stir for 30 minutes while stirring vigorously at 500 rpm. (9) Transfer the mixed solution and a piece of prepared 3DC CF to an autoclave, place the autoclave in an oven, and keep it at 180°C for 13 hours; (10) Wash the sample with deionized water and ethanol in sequence to remove residual ionic species, and then dry it in a vacuum drying oven at 60°C for 24 hours; (11) The dried sample was further annealed in air at 320°C for 2 hours to obtain a three-dimensional porous carbon-encapsulated V2O5 carbon fiber electrode, denoted as V2O5 / 3DC-CF.

[0019] (12) Battery preparation: Cut 4cm × 4cm V2O5 / 3DC-CF as aluminum ion structure energy storage electrode material; cut "L"-shaped molybdenum sheet as positive electrode tab; cut 5cm × 5cm aluminum mesh as negative electrode material, while reserving the tab; cut 6cm × 6cm Whatman separator; cut 8cm × 8cm aluminum-plastic film as the outer shell of energy storage composite material. Use conductive silver paste to attach the molybdenum tab to V2O5 / 3DC-CF as positive electrode material, and put the above materials into a 60℃ oven for complete drying.

[0020] (13) Stack the electrodes in the order of positive electrode-separator-negative electrode, encapsulate them in an aluminum-plastic film, and fill the glove box with 1 mL of electrolyte (AlCl3 / [EMIm]Cl ionic liquid electrolyte, with a molar ratio of AlCl3 to [EMIm]Cl = 1.3:1). After standing for 24 h, perform electrochemical performance testing.

[0021] First, this application describes the growth of a three-dimensional porous carbon layer on carbon fibers (T800 6K) using an impregnation method. Then, V₂O₅ nanoparticles were successfully encapsulated within the three-dimensional porous carbon layer using a hydrothermal method. These two layers were named 3DC-CF and V₂O₅ / 3DC-CF, respectively. SEM images show... Figure 1 This application successfully constructed a three-dimensional porous carbon layer, with V2O5 nanoparticles uniformly distributed in the middle of the three-dimensional porous carbon layer, consistent with the expected results. Next, this application demonstrated the successful preparation of the material through microstructure characterization. Figure 2 Image a depicts the X-ray diffraction (XRD) patterns of pure carbon fiber and carbon fiber after the growth of a porous carbon layer. The image shows a broad diffraction peak at 2θ≈27° pointing towards the (002) plane of the graphitic carbon (carbon fiber). After growing a three-dimensional porous carbon layer on the carbon fiber, the crystallinity of the material significantly decreases. Figure 2The Raman spectroscopy results for C show that the ID / IG ratio increased after the growth of the three-dimensional porous carbon layer, indicating the successful introduction of a three-dimensional porous carbon layer, and that it is porous and disordered carbon. The porous properties require further quantitative analysis using BET spectroscopy. Figure 2 The XRD results in section b show that orthorhombic V2O5 was successfully introduced into V2O5 / 3DC-CF, corresponding to the diffraction peak positions in the PDF card. Next, XPS results further confirm the successful introduction of V2O5 material, with V in a mixed state of tetravalent and pentavalent oxidation states. Figure 2 (d, e, f). The above characterization demonstrates that this application successfully grew three-dimensional porous carbon on carbon fibers and successfully introduced the active material V2O5, proving the successful preparation of the material.

[0022] Next, electrochemical performance tests were conducted. Pure carbon fiber (T800 6K) showed virtually no capacity when used as the positive electrode in an aluminum-ion battery, meaning that pure carbon fiber (T800 6K) could not perform ion insertion / extraction. Figure 3 (a). After modification, V2O5 nanoparticles serve as the active material, and the three-dimensional porous carbon layer serves as the conductive network and charge shielding layer. When V2O5 / 3DC-CF material is used as the positive electrode material for aluminum-ion batteries, the specific capacity can reach 171.45 mAh / g at a current density of 500 mAh / g, significantly improving the energy storage capacity of carbon fiber-based materials. Figure 3 (b). Furthermore, after 200 cycles, the electrode maintains a capacity retention of 44% and a coulombic efficiency close to 100%. Figure 3 (c)

[0023] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the specific implementation of the present invention and not to limit it. Those skilled in the art should understand that any equivalent substitutions or obvious modifications made to the implementation of the present invention without changing its performance or use, without departing from the spirit of the present invention, should be covered within the scope of protection claimed by the present invention.

Claims

1. A method for in-situ growth of carbon fiber electrodes containing three-dimensional porous carbon-encapsulated V2O5, characterized in that, The specific steps are as follows: S1. Place the carbon fiber in a Soxhlet extraction apparatus, add organic solvent for reflux treatment, then rinse the carbon fiber with deionized water and dry it; S2. Add starch and KOH to deionized water, stir and mix, then transfer the mixed solution to an oven for heat preservation to form a sol-gel solution; S3. The carbon fibers treated in step S1 are immersed in the sol-gel solution, removed and dried, and then placed in a tube furnace under a nitrogen atmosphere, heated to the target temperature and kept at that temperature, then washed and dried to obtain 3D mesh porous carbon matrix coated flexible carbon fibers. S4. Add triisopropoxyvanadium oxide to isopropanol, stir and mix to obtain a mixed solution. Immerse the 3D mesh porous carbon matrix coated flexible carbon fiber prepared in step S3 into the mixed solution, heat and react. After the reaction is completed, wash the sample, dry it, and anneal the dried sample in air to obtain the carbon fiber electrode of three-dimensional porous carbon encapsulated V2O5.

2. The method according to claim 1, characterized in that, In step S1, the reflux treatment time is 24-48 hours, the deionized water rinsing time is 6-12 hours, and the drying temperature is 60-80℃.

3. The method according to claim 1, characterized in that, In step S2, the mass ratio of starch to KOH is (1~4):(1~4), the mass-volume ratio of starch to deionized water is (1~4)g:(10~40)mL, the oven temperature is 50~70℃, and the holding time is 20~30 hours.

4. The method according to claim 1, characterized in that, In step S3, during soaking, the temperature of the sol-gel solution is 75~85℃, and the soaking time is 1~6 hours; after removal, the drying temperature is 70~90℃, and the drying time is 20~30 hours; the target temperature of the tube furnace is 550~650℃, the heating rate is 2~5℃・min⁻¹, and the holding time is 1~3 hours; after cleaning, the drying temperature is 70~90℃, and the drying time is 20~30 hours.

5. The method according to claim 1, characterized in that, In step S4, the volume ratio of triisopropoxyvanadium oxide to isopropanol is (0.05~0.15):(35~45), the stirring time is 25~35 minutes, the reaction temperature is 170~190℃, and the reaction time is 10~15 hours; the air annealing temperature is 300~350℃, and the annealing time is 1~3 hours; the drying time is 20~24 hours.

6. The carbon fiber electrode of three-dimensional porous carbon encapsulated V2O5 prepared by the method of any one of claims 1 to 5.

7. The application of the carbon fiber electrode with three-dimensional porous carbon encapsulated V2O5 as described in claim 6 in aluminum-ion batteries.

8. The application according to claim 7, characterized in that, A carbon fiber electrode encapsulating V2O5 in a three-dimensional porous carbon layer is used as the positive electrode, and a molybdenum sheet is used as the positive electrode tab. The molybdenum sheet is attached to the carbon fiber electrode encapsulating V2O5 in a three-dimensional porous carbon layer with conductive silver paste. An aluminum mesh is used as the negative electrode material, and tabs are reserved. A glass fiber membrane is used as the separator. An aluminum-plastic film is used as the outer shell of the energy storage composite material. The electrodes are stacked in the order of positive electrode-separator-negative electrode, encapsulated in the aluminum-plastic film, and filled with electrolyte in a glove box. After standing for 20-30 hours, the product is obtained.

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