Preparation Method and Application of a Carbon Nanofiber-Supported WSe2 / Dy-WO3 Heterojunction Electrode Material

Abstract

The present invention relates to a preparation method and application of a carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction electrode material. In this method, a polymer containing W and Dy bimetallic salts is used as a spinning solution, and carbon fiber-supported Dy-WO3 is obtained by electrospinning-high temperature calcination method. Then, the Dy-WO3 is selenized by chemical vapor deposition (CVD) method, and a WSe2 / Dy-WO3 heterojunction interface is constructed by the amount of Se reaction and the carrier gas components. The carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction material obtained in the present invention is used as a positive electrode, which solves the technical problems of high cost and low energy density of electrode materials in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage, and particularly relates to a flexible tungsten diselenide / dysprosium-tungsten oxide (WSe2 / Dy-WO3) heterostructure electrode material for supercapacitors, a preparation method thereof, and an application thereof. Background Art

[0002] The overexploitation and utilization of traditional fossil fuels have led to the depletion of resources, thus highlighting the urgent need for sustainable and renewable energy storage solutions. In this context, supercapacitors (SCs) have become promising candidates to meet the growing demand for high-efficiency energy storage devices due to their high power density and fast charge-discharge capabilities. However, the relatively low energy density and limited cycle life of SCs are still the main obstacles to large-scale applications. In recent years, flexible asymmetric supercapacitors (ASCs) assembled by combining pseudocapacitive and electric double-layer capacitive electrode materials have both the advantages of flexibility, portability, and high performance, and have shown great application potential in fields such as wearable electronic devices and flexible displays. In these application scenarios, not only is it required that the energy storage device has good electrochemical performance, but it also needs to be able to adapt to different mechanical deformations such as bending and folding without affecting its performance. Therefore, from the perspective of material design and preparation, rationally designing and preparing Faraday-type positive electrode materials is crucial for improving the energy density and cycle life of flexible ASCs, providing an important way to solve the current energy challenges.

[0003] In recent years, in view of the comprehensive consideration of material performance and cost, many studies have focused on exploring low-cost transition metal materials as substitutes for precious metals. Transition metals such as Fe, Co, Mo, Mn, and W have become key candidate materials in this field due to their excellent pseudocapacitive behavior. Among them, W-based compounds have shown outstanding performance in the field of pseudocapacitive materials, with good photoelectric response and high conductivity. For example, WO3, WS2, WSe2, etc. have emerged in the field of electrochemical energy storage due to the advantages of their polycrystalline structure properties. In the existing invention patents, Chinese invention patent CN202410907274.2 discloses a WO3 / g-C3N4@WS2 ternary photocatalyst, a preparation method thereof, and an application thereof. By constructing a heterojunction, the electron transfer ability is enhanced, the recombination rate of electron-hole pairs is reduced, and its transient photocurrent increases by about 18.18%, and the specific surface area is 100.77 m 2 g -1, the degradation efficiency of Rhodamine B reaches 97.9% under visible light in 15 min. This technology focuses on photocatalytic degradation based on the excellent optoelectronic response of W-based materials, rather than the energy storage field (such as SCs). The performance of the materials in terms of pseudocapacitance mechanism, conductivity, and cycle stability has not been fully verified. Therefore, it is necessary to develop a technology that converts multiphase W-based materials from photocatalysis to the energy storage field, combines the pseudocapacitance and double-layer capacitance mechanisms, and designs electrode materials with both high energy density and long cycle life to fill the gaps in existing technologies. Chinese invention patent CN106206071A discloses a WO3·H2O / PbO2 composite electrode with high specific capacitance, its preparation method and application. WO3·H2O and PbO2 cooperate to endow the composite electrode with good pseudocapacitance characteristics. During the charge and discharge process, charges are stored and released through redox reactions. The WO3·H2O / PbO2 electrode can reach a maximum specific capacitance of 445 F g -1 at a scanning rate of 2 mV s -1 . However, although this technology WO3·H2O / PbO2 shows excellent performance in specific capacitance, its PbO2 is toxic, does not meet the environmental protection requirements of green energy materials, and has high subsequent recycling and treatment costs. In addition, the shortcomings of the synthesis method and cycle life are difficult to meet the adaptability requirements of flexible SCs for mechanical deformations such as bending and folding. Therefore, designing electrode materials for SCs with environmental protection, low cost, and excellent mechanical flexibility to fill the gaps in environmentally friendly flexible energy storage technologies is an urgent problem to be solved currently. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method and application of a carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction electrode material in view of the limitations in current technologies. This method uses a polymer containing W and Dy double metal salts as the spinning solution, and obtains carbon fiber-supported Dy-WO3 by electrospinning-high temperature calcination method. Then, the Dy-WO3 is selenized by chemical vapor deposition (CVD). During the CVD process, only when the appropriate Se reaction amount and carrier gas components (H2 / Ar(5% + 95%), 80 sccm) reach the equilibrium point can a WSe2 / Dy-WO3 heterojunction interface be constructed, realizing electron redistribution and improving the electrochemistry reaction kinetics. In addition, the carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction material is used as the positive electrode, while pure PCNFs are prepared as the negative electrode, and TEAOH-KOH / PVA is used as the gel electrolyte to assemble a flexible ASC.

[0005] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] A preparation method of a carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction electrode material, the method comprising the following steps:

[0007] Step 1: Preparation of Dy-WO3 flexible material

[0008] (1)Preparation of spinning solution: PAN and AMT were added to the mixed solvent, stirred at room temperature for 2 - 4 h until dissolved, then Dy(NO3)3·6H2O was added and stirred at room temperature for 20 - 30 h, followed by ultrasonic treatment for 20 - 40 min to obtain a pale yellow transparent spinning solution;

[0009] Among them, 0.05 - 0.3 g of PAN, 1.0 - 5.0 g of AMT and 0.01 - 0.05 g of Dy(NO3)3·6H2O were added to every 10 g of the mixed solvent; the solvent in the mixed solution consisted of PVP and DMF, and the mass ratio of the two was 1:9;

[0010] (2)Electrospinning: The above spinning solution was loaded into a syringe for electrospinning, and a three-dimensional dynamic receiving device was used for fiber collection, with the amplitude adjustment range of 5 - 15 mm. Thus, a Dy(NO3)3-AMT / PAN-PVP polymer thin film accumulated on the aluminum foil was obtained, and then the thin film was placed in a vacuum oven at 50 - 70 °C for 6 - 8 h;

[0011] Among them, the electrospinning conditions were: receiving distance 18 - 22 cm, adjustable voltage of 13 - 17 kV, fluid pushing speed of 0.3 - 0.7 mL h -1 , roller rotation speed of 70 - 80 r min -1 ; the ambient temperature was maintained at 25 ± 3 °C, and the humidity was controlled at 40 ± 5 %rh;

[0012] (3)Heat treatment: The film treated in the oven was placed in the center of a tube furnace, and the material obtained in the previous step was heated to 200 - 300 °C at a heating rate of 1 - 3 °C min -1 for pre-oxidation in an air atmosphere for 0.5 - 1.5 h; after the pre-oxidation was completed, Ar gas was introduced as a protective gas, and it was continuously heated to 500 - 700 °C at the same heating rate and maintained for 1 - 3 h to finally obtain the Dy-WO3 flexible material;

[0013] Step 2: Preparation of WSe2 / Dy-WO3 material:

[0014] (1)Material placement: First, Dy-WO3 was placed in a quartz porcelain boat and placed downstream of the CVD tube; second, Se powder (m2) was loaded into a ceramic crucible, placed flat in another porcelain boat, placed upstream of the CVD tube, and the distance from Dy-WO3 was 28 - 32 cm;

[0015] Among them, the mass ratio of Dy-WO3 to Se powder was = 1:0.50 - 1.00;

[0016] (2) Reaction process: In H2 / Ar (5%+95%) atmosphere, maintain a constant flow rate of 60~100 sccm and a temperature of 8~12℃ min -1 The downstream temperature zone was rapidly raised to 700-900 °C at a heating rate, while the upstream temperature zone was maintained at 350-450 °C, and the reaction was continued for 90-150 min. After the reaction, the material was cooled in an Ar atmosphere to finally obtain WSe2 / Dy-WO3 supported by carbon nanofibers.

[0017] Application of the carbon nanofiber-loaded WSe2 / Dy-WO3 heterojunction electrode material prepared by the method as a positive electrode material in flexible SCs;

[0018] The specific steps include:

[0019] (1) Preparation of WSe2 / Dy-WO3 electrode

[0020] The WSe2 / Dy-WO3 flexible electrode material was sandwiched between two sheets of nickel foam (1×1 cm 2 ) and prepare the electrode sheet at a pressure of 5 to 20 MPa;

[0021] The thickness of the WSe2 / Dy-WO3 flexible electrode material is 0.1-0.4 mm;

[0022] (2) Preparation of TEAOH-KOH / PVA gel electrolyte

[0023] Add polyvinyl alcohol to the mixed solution to dissolve, then add KOH, and stir at 80-100°C for 4-6 hours; then, pour the obtained liquid gel into a mold, and freeze at -20°C for 8-12 hours to obtain a solid TEAOH-KOH / PVA gel electrolyte;

[0024] Among them, 2-3 g of polyvinyl alcohol and 1-5 g of KOH are added to every 20-30 g of the mixed solution; the composition of the mixed solution is TEAOH and deionized water; the mass ratio of the two is 3:5;

[0025] (3) Assembling ASC of PCNFs / / WSe2 / Dy-WO3

[0026] With WSe2 / Dy-WO3 as the positive electrode, PCNFs as the negative electrode, and TEAOH-KOH / PVA as the gel electrolyte, button-type ASCs and flexible solid-state soft packages were assembled.

[0027] The essential features of the present invention are:

[0028] In the current technology, there is a scheme for preparing in-situ Ce-doped WO3 carbon nanofibers (Ce / WO3-CNFs) by electrospinning and calcination techniques. The introduction of Ce enhances the electrolyte permeability and electron transport efficiency by expanding the lattice spacing of WO3 (XRD shows that the interplanar spacing of the (002) plane increases from 0.382 nm to 0.401 nm). The specific capacitance of Ce / WO3-CNFs reaches 407 F g -1 (-0.5 A g -1 ), which is superior to that of undoped WO3-CNFs (322 F g -1 ). However, due to the polycrystalline structure and multiple oxidation states of WO3, simply through simple high-temperature treatment and rare-earth Ce modification, the advantages of WO3 in SCs have not been fully exploited.

[0029] In the present invention, a simple and feasible electrospinning combined with CVD two-step method is used to construct a built-in electric field of WSe2 / Dy-WO3 that induces the redistribution of interfacial charges, forming a stacking or splicing of metal-like materials with different energy level structures and electronic configurations on the heterojunction interface, inducing the redistribution and transfer of charges at the interface. WSe2 / Dy-WO3 promotes electron redistribution and improves the electrochemistry reaction kinetics due to its advantages of being 'anchored' to the one-dimensional nanobulk structure and the interfacial electric field having the ability to regulate the electronic structure. Among them, each step cooperates with each other to achieve the specific structure and performance of the material. During the preparation of the Dy-WO3 flexible material, PVP, PAN, AMT, and Dy(NO3)3·6H2O are mixed and then formed into a film by electrospinning. The electrospinning parameters affect the morphology and structure of the film. The pre-oxidation and calcination processes change the chemical composition and crystal structure of the material, making it form a Dy-WO3 flexible material with specific properties. When preparing the WSe2 / Dy-WO3 material, using different temperature zones and gas atmospheres in the CVD tube, Dy-WO3 reacts with Se powder. Different mass ratios will result in different proportions of each component in the material, thereby affecting the microstructure and performance of the material, providing material selection with different characteristics for subsequent applications in energy storage and other fields.

[0030] The beneficial effects of the present invention are as follows:

[0031] The present invention constructs a WSe2 / Dy-WO3 nanofiber heterostructure by electrospinning combined with CVD method, and at the same time gives full play to the similar electronegativity characteristics of O element and Se element to regulate the electron migration behavior and improve the electrochemistry reaction kinetics.

[0032] When the current density of the WSe2 / Dy-WO3 electrode is 0.5 A g -1 , the specific capacitance is 679.23 F g -1 , which is superior to that of Dy-WO3 (557.28 F g -1)、L WSe / Dy-WO3(611.22 F g -1 ) and H WSe / Dy-WO3(583.22 F g -1 ). Based on WSe2 / Dy-WO3 as the positive electrode and PCNFs as the negative electrode, button-type ASCs and flexible solid-state soft packs were assembled respectively. This ASC has a high energy density (when the power density is 362.54 W kg -1 , its energy density reaches 46.33 Wh kg -1 ). Compared with the WO3 nano-petal-like structure with a similar'marigold' surface morphology grown on a stainless-steel substrate by solution chemistry method reported in the Journal of Colloid And Interface Science in 2024. At a scanning rate of 5 mV s -1 , the specific capacitance is 271.67±9.37 F g -1 , and the energy density of the assembled solid-state SCs device is only 6.26±0.21 Wh kg -1 when the power density is 131.53±4.41 W kg -1 . Using Dy-WO3 / PCNFs as the positive electrode and CNFs as the negative electrode, the energy density of the assembled ASC is only 29.8 Wh kg -1 when the power density is 363.48 W kg-1. Therefore, the present invention uses electrospinning combined with in-situ CVD technology to prepare carbon nanofibers loaded with WSe2 / Dy-WO3 heterojunction with high electrochemical performance, which solves the technical problems of high cost of electrode materials and low energy density in the prior art. Description of the Drawings

[0033] Figure 1 SEM image of the electrospun Dy(NO3)3-AMT / PAN-PVP polymer film obtained in Example 1.

[0034] Figure 2 SEM image of the heat-treated Dy-WO3 flexible material obtained in Example 1.

[0035] Figure 3 SEM image of the WSe2 / Dy-WO3 flexible material obtained by gas-phase deposition selenization treatment in Example 3.

[0036] Figure 4 XRD of Dy-WO3 and WSe2 / Dy-WO3 obtained in Examples 1 and 3.

[0037] Figure 5 TEM of WSe2 / Dy-WO3 obtained in Example 3; among them, Figure 5(a) TEM of WSe2 / Dy-WO3 supported on carbon nanofibers, Figure 5 (b, c) HR-TEM of WSe2 / Dy-WO3, showing the (002) crystal plane of WSe2 and the (002) crystal plane of WO3. Among them, the lattice spacings corresponding to the (002) crystal plane of WSe2 and the (002) crystal plane of WO3 are 0.68 nm and 0.38 nm, respectively. It is worth noting that WSe2 / Dy-WO3 shows an obvious lattice interface.

[0038] Figure 6 Electrochemical performance diagrams of Dy-WO3, L WSe / Dy-WO3, WSe2 / Dy-WO3, and H WSe / Dy-WO3 obtained in Examples 1, 2, 3, and 4.

[0039] Figure 7 Energy density diagram of the ASC assembled with PCNFs / / WSe2 / Dy-WO3 obtained in Example 3.

[0040] Figure 8 A 3.6 V LED lamp lit by a button-type ASC assembled with three series-connected PCNFs / / WSe2 / Dy-WO3.

[0041] Figure 9 Schematic diagram of a solid-state ASC soft package assembled with PCNFs / / WSe2 / Dy-WO3.

[0042] Figure 10 TEAOH-KOH / PVA solid gel obtained in Example 3. Specific implementation manners

[0043] Example 1:

[0044] A preparation method of a Dy-WO3 electrode material supported on carbon nanofibers, the method comprising the following steps:

[0045] (1) Preparation of Dy(NO3)3-AMT / PAN-PVP polymer fiber membrane

[0046] Solution preparation: Dissolve 1.0 g of polyvinylpyrrolidone (PVP) and 0.1 g of polyacrylonitrile (PAN) in 9 g of N,N-dimethylformamide (DMF), stir for 3 h until completely dissolved, then add 2 g of ammonium metatungstate (AMT) and 0.02 g of dysprosium nitrate hexahydrate (Dy(NO3)3·6H2O), stir at room temperature for 24 h, and then ultrasonicate for 30 min to obtain a pale yellow transparent spinning solution.

[0047] Electrospinning: The above-mentioned spinning solution was loaded into a 10 ml plastic syringe for electrospinning (electrospinning equipment: Nafiber BS-200). A three-dimensional dynamic receiving device was used for fiber collection. The electrospinning conditions were set as a receiving distance of 20 cm, a voltage of 15 kV, a pushing speed of 0.5 mL h -1 , a spinning amplitude of 10 mm, and a roller rotation speed of 70 r min -1 ; The ambient temperature was maintained at 25 ± 3 °C, and the humidity was controlled at 40 ± 5 %rh; Thus, a Dy(NO3)3-AMT / PAN-PVP polymer film accumulated on the aluminum foil was obtained. The film was placed in a vacuum oven at 60 °C for 6 h.

[0048] (2) Preparation of Dy-WO3 flexible material

[0049] Heat treatment: The film treated in the oven was placed in the center of a tube furnace and heated to 250 °C at a heating rate of 2 °C min -1 and pre-oxidized in an air atmosphere for 1 h. After the pre-oxidation was completed, Ar gas was introduced as a protective gas, and it was continuously heated to 600 °C at the same heating rate and held for 2 h. Finally, a Dy-WO3 flexible material was obtained. At a current density of 0.5 A g -1 , the specific capacitance of the Dy-WO3 electrode was 557.28 F g -1 . The Dy-WO3 obtained in Example 1 was used as a blank experiment to explore the Seization process in CVD.

[0050] Electrochemical testing instrument: Electrochemical workstation - CHI660E - Shanghai Chenhua Instrument Co., Ltd.

[0051] Three-electrode electrochemical performance testing method: The electrochemical performance of the electrode was evaluated in a 4 M KOH electrolyte. First, cyclic voltammetry (CV) was tested to determine the CV test voltage window (0~0.6 V), and the test scanning speed range was changed to 0.05, 0.03, 0.02, 0.01, 0.005, 0.002 V s -1 , and 2 cycles were tested at each scanning speed; The galvanostatic charge-discharge GCD curve was used to determine the test voltage window (0~0.5 V), and the test current density was changed to 0.5, 0.8, 1, 3, 5, 8, 10 A g -1 , and the charge-discharge was carried out 2 times at each current density; The electrochemical impedance spectroscopy (EIS) test frequency range was 0.01~10 5 Hz. At a certain open-circuit voltage, the sine AC amplitude current was 0.05 V.

[0052] Example 2:

[0053] A preparation method of a carbon nanofiber-supported L WSe / Dy-WO3 electrode material, the method comprising the following steps:

[0054] Step 1: Preparation of the Dy-WO3 flexible material, the steps being the same as in Example 1;

[0055] Step 2: Preparation of the L WSe / Dy-WO3 material

[0056] Material placement: First, put Dy-WO3 (m1) into a quartz porcelain boat and place it downstream in the CVD tube; second, load Se powder (m2) into a ceramic crucible, place it flat in another porcelain boat, place it upstream in the CVD tube, and the distance from Dy-WO3 is 32 cm. The mass ratio of Dy-WO3 to Se powder is m1:m2 = 1:0.50.

[0057] Reaction process: In an H2 / Ar (volume ratio 5% + 95%) atmosphere, maintain a constant flow rate of 100 sccm, and rapidly raise the temperature of the downstream temperature zone to 800 °C at a heating rate of 10 °C min -1 while keeping the upstream temperature zone at 400 °C and reacting for 90 min. After the reaction is completed, the material is cooled in an Ar gas atmosphere to obtain the L WSe / Dy-WO3 electrode material. At a current density of 0.5 A g -1 the specific capacitance is 583.22 F g -1 .

[0058] Example 3:

[0059] A preparation method of a carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction, the method comprising the following steps:

[0060] Step 1: Preparation of the Dy-WO3 flexible material, the steps being the same as in Example 1;

[0061] Step 2: Preparation of the carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction

[0062] Material placement: First, put Dy-WO3 (m1) into a quartz porcelain boat and place it downstream in the CVD tube; second, load Se powder (m2) into a ceramic crucible, place it flat in another porcelain boat, place it upstream in the CVD tube, and the distance from Dy-WO3 is 30 cm. The mass ratio of Dy-WO3 to Se powder is m1:m2 = 1:0.75.

[0063] Reaction process: In an H2 / Ar (5% + 95%) atmosphere, maintain a constant flow rate of 80 sccm, and at a rate of 10 °C min -1The downstream temperature zone was quickly raised to 800 °C at a heating rate of 1.5 °C, while the upstream temperature zone was kept at 400 °C for 120 min. After the reaction, the material was cooled in an Ar atmosphere to obtain a carbon nanofiber-loaded WSe2 / Dy-WO3 heterojunction material. -1 The specific capacitance is 679.23 F g -1 .

[0064] Embodiment 4:

[0065] A method for preparing a carbon nanofiber-loaded HWSe / Dy-WO3 electrode material, the method comprising the following steps:

[0066] Step 1: Preparation of Dy-WO3 flexible material, the steps are the same as those in Example 1;

[0067] Step 2: Preparation of H WSe / Dy-WO3 materials

[0068] Material placement: First, Dy-WO3 (m1) was placed in a quartz porcelain boat and placed downstream of the CVD tube. Second, Se powder (m2) was loaded into a ceramic crucible and placed flat in another porcelain boat, which was placed upstream of the CVD tube with a distance of 28 cm from Dy-WO3. The mass ratio of Dy-WO3 and Se powder was m1:m2=1:1.00.

[0069] Reaction process: In H2 / Ar (5%+95%) atmosphere, maintain a constant flow rate of 60 sccm and heat at 10 ℃ min -1 The downstream temperature zone was quickly raised to 800 °C at a heating rate of 1.5 °C, while the upstream temperature zone was kept at 400 °C for 150 min. After the reaction, the material was cooled in an Ar atmosphere to obtain H WSe / Dy-WO3 electrode material. -1 The specific capacitance is 611.22 F g -1 .

[0070] The carbon nanofiber-loaded WSe2 / Dy-WO3 electrode material with the best electrochemical performance obtained in Example 3 was used as the positive electrode to assemble SCs:

[0071] (1) Preparation of WSe2 / Dy-WO3 electrode sheet

[0072] A 0.2 mm thick WSe2 / Dy-WO3 flexible electrode material (0.5 mg) was sandwiched between two sheets of nickel foam (1×1 cm 2) and prepared the electrode sheets under 10 MPa pressure (benchtop powder tablet press FYC-25). The electrochemical performance of the three-electrode system was investigated in 4 M KOH electrolyte, with WSe2 / Dy-WO3, platinum mesh and Hg / HgO electrodes as working electrode, counter electrode and reference electrode, respectively. The CV, GCD and EIS were tested and recorded on an electrochemical workstation (CHI760E). The specific capacitance (C, F·g -1 ) is calculated as follows:

[0073]

[0074] Where C (F g -1 ) is the specific capacity of the electrode, I is the discharge current, Δt is the discharge time, ΔV is the potential window during the GCD process, and m is the mass of the active material.

[0075] (2) Preparation of negative electrode PCNFs materials and electrode sheets

[0076] Solution preparation: 0.6 g PVP and 0.4 g PAN were dissolved in 9 g DMF and stirred for 24 h until completely dissolved to obtain a colorless and transparent spinning solution.

[0077] The electrospinning conditions were set in accordance with the preparation process of Dy(NO3)3-AMT / PAN-PVP polymer film in Example 1 above, and a PAN-PVP polymer film was obtained.

[0078] The heat treatment conditions were consistent with the preparation process of Dy-WO3 material in Example 1 above, and PCNFs were obtained as negative electrode materials. -1 The specific capacitance is 161 F g -1 .

[0079] The PCNFs material was sandwiched between two sheets of nickel foam (1×1 cm 2 ) and prepare the negative electrode sheet under a pressure of 10 MPa.

[0080] (3) Preparation of TEAOH-KOH / PVA gel electrolyte

[0081] 2.5 g PVA was added to a mixture containing 9 g TEAOH and 15 g deionized water, heated and stirred at 90 °C until dissolved, and then 3 g KOH was added. The heating was continued for 4 to 6 hours, at which time the solution was yellow and clear. Subsequently, the liquid gel was poured into a mold, frozen at -20 °C for 8 to 12 hours, and taken out to obtain a solid TEAOH-KOH / PVA gel electrolyte.

[0082] (4) An ASC was assembled with the WSe2 / Dy-WO3 electrode as the positive electrode and PCNFs as the negative electrode. The mass calculation formulas for the two electrodes are as follows:

[0083]

[0084] Among them, is the mass of the active material in the positive electrode, is the mass of the active material in the negative electrode. and are the specific capacitances of the positive and negative electrodes. and are the potential ranges of the positive and negative electrodes respectively. After balancing the charge capacity, the mass ratio of the positive electrode to the negative electrode working electrode materials was controlled at 2.83.

[0085] (5) Two-electrode system test: First, CV was used to determine the voltage window for CV testing. The test scanning speed range was 0.05, 0.03, 0.02, 0.01, 0.005 V s -1 , and 2 cycles were tested at each scanning speed; for the galvanostatic charge-discharge GCD curve, the test voltage window was determined, and the current density was 0.5, 0.8, 1, 3, 5, 8, 10 A g -1 , and charge and discharge were performed 2 times at each current density.

[0086] The energy density (E) and power density (P) of the ACS were calculated by the following methods:

[0087]

[0088]

[0089] (6) Assembly of the PCNFs / / WSe2 / Dy-WO3 ASC

[0090] Using WSe2 / Dy-WO3 as the positive electrode, PCNFs as the negative electrode, and TEAOH-KOH / PVA as the gel electrolyte, a button-type ASC and a flexible solid-state soft package were assembled. Introducing TEAOH into the electrolyte can strengthen the hydrogen bond interaction and has a water retention function, thus extending the service life of the SCs.

[0091] In summary, based on the structural characteristics of WO3 with a polycrystalline morphology, the present invention regulates the crystal structure of WO3 by introducing rare earth elements, thereby improving its reaction activity in the electrochemical process. Among numerous rare earth elements, Dy has the structural characteristics of having a large number of outer electron orbital numbers and a relatively large number of unpaired electrons in the 4f orbitals, which can provide a more efficient electron conduction path, thus increasing the storage capacity of Dy-WO3. While deeply exploring the excellent performance of WO3 in the field of pseudocapacitive materials, researchers noticed that from the perspective of element synergy, non-metallic elements such as S, Se, P, etc. often induce physicochemical property changes when combined with transition metal compounds. By further modifying the precursor, the electronic structure of the material can be effectively regulated to prepare a composite electrode with more excellent electrochemical performance. Therefore, introducing non-metallic elements to form chemical bonding with metal atoms, this process forms a stacking or splicing of metalloid materials with different energy level structures and electron configurations on the heterojunction interface. Therefore, in view of the photoelectric response characteristics of WO3 and the similarity and gradation of chemical properties among elements in the same group, we will select Se element, which is in the same main group as O element and has a relatively strong electronegativity, to further modify Dy-WO3, and construct a WSe2 / Dy-WO3 heterojunction for flexible electrode materials with excellent performance. The WSe2 / Dy-WO3 electrode has the largest specific capacitance of 679.23 F g -1 at a current density of 0.5 A g -1 , which is better than that of the Dy-WO3 electrode (557.28 F g -1 ), the L WSe / Dy-WO3 electrode (583.22 F g -1 ) and the H WSe / Dy-WO3 electrode (611.22 F g -1 ).

[0092] Matters not covered by the present invention are well-known technologies.

Claims

1. A preparation method of a carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction electrode material, characterized in that, The method includes the following steps: Step 1: Preparation of Dy-WO3 flexible material (1) Preparation of spinning solution: PAN and AMT are added to a mixed solvent, stirred at room temperature for 2 - 4 h until dissolved, then Dy(NO3)3·6H2O is added and stirred at room temperature for 20 - 30 h, followed by ultrasonic treatment for 20 - 40 min to obtain a pale yellow transparent spinning solution; Among them, 0.05 - 0.3 g of PAN, 1.0 - 5.0 g of AMT and 0.01 - 0.05 g of Dy(NO3)3·6H2O are added to every 10 g of the mixed solvent; the solvent in the mixed solution consists of PVP and DMF, and the mass ratio of the two is 1:9; (2) Electrospinning: The above spinning solution is loaded into a syringe for electrospinning to obtain a Dy(NO3)3-AMT / PAN-PVP polymer film accumulated on an aluminum foil, and then the film is placed in a vacuum oven at 50 - 70 °C for 6 - 8 h; Among them, the electrospinning conditions are as follows: the receiving distance is 18 - 22 cm, the voltage is an adjustable voltage of 13 - 17 kV, the fluid pushing speed is 0.3 - 0.7 mL h -1 , the roller rotation speed is 70 - 80 r min -1 ; the environmental temperature is maintained at 25 ± 3 °C, and the humidity is controlled at 40 ± 5 %rh; (3) Heat treatment: Heat the substance obtained in the previous step at a heating rate of 1 - 3 °C / min -1 to 200 - 300 °C, and keep it for 0.5 - 1.5 h in an air atmosphere for pre-oxidation; after the pre-oxidation is completed, introduce Ar gas as the protective gas, continue to heat it to 500 - 700 °C at the same heating rate and keep it for 1 - 3 h to finally obtain the Dy-WO3 flexible material; Step 2: Preparation of WSe2 / Dy-WO3 material: (1) Placement of materials: First, Dy-WO3 is placed in a quartz porcelain boat and placed downstream of the CVD tube; second, Se powder is loaded into a ceramic crucible, placed flat in another porcelain boat, placed upstream of the CVD tube, and the distance from Dy-WO3 is 28 - 32 cm; Among them, the mass ratio of Dy-WO3 to Se powder is = 1:0.50 - 1.00; (2) Reaction process: Under an H2 / Ar (5% + 95%) atmosphere, maintaining a constant flow rate of 60 - 100 sccm, the downstream temperature zone was raised to 700 - 900 °C at a heating rate of 8 - 12 °C min -1 -1, while the upstream temperature zone was maintained at 350 - 450 °C, and the reaction continued for 90 - 150 min; after the reaction ended, it was cooled in an Ar gas atmosphere, and finally, WSe2 / Dy-WO3 supported on carbon nanofibers was obtained; In the electrospinning in Step 1, a three-dimensional dynamic receiving device is used for fiber collection, and the amplitude adjustment range is 5 - 15 mm.

2. Application of the carbon nanofiber-supported WSe2 / Dy-WO3 heterojunction electrode material prepared by the method according to claim 1, characterized in that, It is used as a positive electrode material in flexible SCs.

3. The application according to claim 2, characterized in that it includes The following steps: (1) Preparation of WSe2 / Dy-WO3 electrode: The WSe2 / Dy-WO3 flexible electrode material is sandwiched between two pieces of nickel foam and an electrode sheet is prepared under a pressure of 5 - 20 MPa; The thickness of the WSe2 / Dy-WO3 flexible electrode material is 0.1 - 0.4 mm; (2) Preparation of TEAOH-KOH / PVA gel electrolyte: Polyvinyl alcohol is added to a mixed solution to dissolve, and then KOH is added, and stirred at 80 - 100 °C for 4 - 6 hours; subsequently, the obtained liquid gel is poured into a mold and frozen at -20 °C for 8 - 12 hours to obtain a solid TEAOH-KOH / PVA gel electrolyte; Among them, 2 - 3 g of polyvinyl alcohol and 1 - 5 g of KOH are added to every 20 - 30 g of the mixed solution; the mixed solution consists of TEAOH and deionized water; the mass ratio of the two is 3:5; (3) Assembly of PCNFs / / WSe2 / Dy-WO3 ASC Using WSe2 / Dy-WO3 as the positive electrode, PCNFs as the negative electrode, and TEAOH-KOH / PVA as the gel electrolyte, a button-type ASC and a flexible solid-state soft package are assembled.

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