A one-step method for preparing double-doped vanadium dioxide electrode material and its application

Abstract

A one-step method for preparing a dual-doped vanadium dioxide electrode material and its application, which relates to a method for preparing an electrode material and its application. The purpose of the present invention is to solve the problem that the existing carbon material used as an electrode material for a supercapacitor has low capacitance and the current dual-defect modified electrode material is mostly realized by a multi-step method. Method: 1. Add V2O5, H2C2O4 and triethanolamine to deionized water; 2. Add anhydrous ethanol and H2O2 solution; 3. Hydrothermal reaction, and obtain the dual-doped vanadium dioxide electrode material in one step. The dual-doped vanadium dioxide electrode material is used as a positive electrode material for a supercapacitor. The dual-doped vanadium dioxide electrode material prepared by the present invention has excellent capacitance performance. When the current density is 1A / g, the specific capacitance of the electrode material in a 1mol / L Na2SO4 aqueous electrolyte can reach 182F / g.

Description

Technical Field

[0001] The invention relates to a method for preparing an electrode material and application thereof. Background Art

[0002] At present, most of the energy supply systems for automobiles, power generation and other applications still rely mainly on the combustion of traditional fossil fuels, such as coal, oil, and natural gas. However, with the growing population and the gradual consumption of fossil energy, energy crisis and environmental pollution are two major problems facing mankind in the 21st century, and have even threatened the sustainable development of mankind. Therefore, the development of green, environmentally friendly and efficient new energy and the development of large-scale energy storage and conversion technologies that match them are considered to be one of the effective ways to solve the above problems. At present, energy storage is mainly divided into electrochemical energy storage, physical energy storage, and fuel energy storage, etc. Among them, electrochemical energy storage mainly includes two categories: alkali metal ion batteries and supercapacitors. Among them, supercapacitors have attracted people's attention due to their high power density, long cycle stability, wide working range, and fast charging and discharging speed. According to the working characteristics of supercapacitors, they are widely used in smart grids, electronic devices, hybrid vehicles and other fields. Although the field of supercapacitors has made significant progress and achieved many good research results, in order to meet the greater demand for energy storage, there are still many problems and challenges in this field that need to be solved. At present, the electrode materials used in commercial supercapacitors are mainly activated carbon materials with high specific surface area. Carbon materials have the advantages of stable structure and long cycle period. However, carbon materials have a very low specific capacitance because they store energy via a double-layer mechanism. Summary of the invention

[0003] The purpose of the present invention is to solve the problems of low capacitance of existing carbon materials used as electrode materials for supercapacitors and the fact that double-defect modified electrode materials are currently mostly achieved by a multi-step process, and to provide a one-step method for preparing a double-doped vanadium dioxide electrode material and its application.

[0004] A one-step method for preparing a dual-doped vanadium dioxide electrode material is completed by the following steps:

[0005] 1. Add V2O5, H2C2O4 and triethanolamine into deionized water, and then stir and react under heating conditions to obtain a mixed solution I;

[0006] 2. Add anhydrous ethanol and 30% H2O2 solution by mass to the mixed solution I, stir, and obtain a mixed solution II;

[0007] 3. Transfer the mixed solution II to a reactor with a polytetrafluoroethylene liner, seal the reactor and place it in a blast oven for hydrothermal reaction at 180°C to 185°C. After the reaction is completed, cool it naturally to room temperature to obtain a reaction product. Wash the reaction product and then vacuum dry it to obtain a black powder, which is the dual-doped vanadium dioxide electrode material.

[0008] The double-doped vanadium dioxide electrode material is used as the positive electrode material of the supercapacitor.

[0009] Principles and advantages of the present invention:

[0010] 1. The present invention prepares a vanadium dioxide electrode material with double defects (oxygen vacancies and nitrogen doping) (a method for double-doped vanadium dioxide electrode material) by a simple one-step hydrothermal method, and explores its application in the positive electrode of supercapacitors; in the prior art, defect modification is usually achieved by a multi-step method, such as hydrothermal combined with high-temperature annealing, hydrothermal combined with plasma treatment, the experimental scheme is complicated, and high temperature sometimes affects the crystal structure of the material itself; the present invention introduces triethanolamine organic liquid as a complexing agent, and successfully prepares a double-defect VO2 electrode material with oxygen vacancies and nitrogen doping by a one-step hydrothermal method; the presence of vacancies can increase the active sites of the electrode material, and nitrogen doping can improve the conductivity of the electrode material, which is beneficial to the embedding and extraction of sodium ions in the electrolyte, so the double-defect VO2 has excellent diffusion kinetics, high specific capacity and good rate performance;

[0011] 2. The double-doped vanadium dioxide electrode material (N-VO 2-δ ) were tested for their electrochemical properties. The results of cyclic voltammetry and constant current charge and discharge tests showed that: N-VO 2-δ The invention has excellent capacitance performance. When the current density is 1A / g, the specific capacitance of the electrode material in 1mol / L Na2SO4 aqueous electrolyte can reach 182F / g; when the current density increases to 5A / g, the specific capacity of 100F / g can still be maintained; after a single electrode is cycled 8000 times, there is still 81.7% of the initial capacitance value; the above electrochemical performance test results show that the double-doped vanadium dioxide electrode material prepared by the invention has a long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The scanning electron microscope image shows that a is the N-VO prepared in Example 1. 2-δ Scanning electron microscope image at 10k magnification, b is N-VO prepared in Example 1 2-δ Scanning electron microscope image at 80k magnification;

[0013] Figure 2 N-VO prepared in Example 1 2-δSEM mapping of

[0014] Figure 3 N-VO prepared in Example 1 2-δ XRD pattern of

[0015] Figure 4 N-VO prepared in Example 1 2-δ XPS spectra of O1s and N1s in the sample;

[0016] Figure 5 N-VO prepared in Example 1 2-δ Cyclic voltammetry curves measured at different scan rates in the voltage range of -0.1 to 0.5 V;

[0017] Figure 6 N-VO prepared in Example 1 2-δ Constant current charge and discharge curves measured at different current densities in the voltage range of -0.1 to 0.5 V;

[0018] Figure 7 N-VO prepared in Example 1 2-δ Cyclic performance curve of the first 8000 cycles at a charge and discharge current density of 5A / g;

[0019] Figure 8 VO2 prepared in the comparative example and N-VO prepared in Example 1 2-δ Comparison of constant current charge and discharge curves at a current density of 1A / g;

[0020] Fig. 9 This is the effect of the amount of triethanolamine added on the electrochemical performance. DETAILED DESCRIPTION

[0021] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0022] Specific implementation method 1: This implementation method is a one-step method for preparing a dual-doped vanadium dioxide electrode material, which is completed by the following steps:

[0023] 1. Add V2O5, H2C2O4 and triethanolamine into deionized water, and then stir and react under heating conditions to obtain a mixed solution I;

[0024] 2. Add anhydrous ethanol and 30% H2O2 solution by mass to the mixed solution I, stir, and obtain a mixed solution II;

[0025] 3. Transfer the mixed solution II to a reactor with a polytetrafluoroethylene liner, seal the reactor and place it in a blast oven for hydrothermal reaction at 180°C to 185°C. After the reaction is completed, cool it naturally to room temperature to obtain a reaction product. Wash the reaction product and then vacuum dry it to obtain a black powder, which is the dual-doped vanadium dioxide electrode material.

[0026] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that the volume ratio of the amount of V2O5 in step 1 to deionized water is (1 mmol to 2 mmol): 30 mL. The other steps are the same as those in specific implementation method 1.

[0027] Specific implementation method 3: This implementation method is different from specific implementation method 1 or 2 in that the volume ratio of the amount of H2C2O4 and deionized water in step 1 is (4mmol-6mmol):30mL. The other steps are the same as those in specific implementation method 1 or 2.

[0028] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the volume ratio of triethanolamine to deionized water in step 1 is (0.5-5):30. The other steps are the same as those of specific embodiments 1 to 3.

[0029] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: in step 1, the reaction is stirred at 70° C. to 80° C. for 20 min to 40 min. The other steps are the same as those of specific embodiments 1 to 4.

[0030] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the volume ratio of the mixed solution I to anhydrous ethanol in step 2 is 1:1. The other steps are the same as those of specific embodiments 1 to 5.

[0031] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that the volume ratio of the mixed solution I described in step 2 to the 30% H2O2 solution is 30:(1 mL to 2 mL). The other steps are the same as those of specific embodiments 1 to 6.

[0032] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the stirring time in step 2 is 5 to 10 minutes, and the hydrothermal reaction time in step 3 is 10 to 12 hours. The other steps are the same as those in specific embodiments 1 to 7.

[0033] Specific embodiment 9: This embodiment differs from specific embodiments 1 to 8 in that: in step 3, the reaction product is first washed 3 to 5 times with anhydrous ethanol, and then washed 3 to 5 times with deionized water; the vacuum drying temperature in step 3 is 60°C, and the vacuum drying time is 10h to 12h. The other steps are the same as those of specific embodiments 1 to 8.

[0034] Specific implementation method ten: In this implementation method, the double-doped vanadium dioxide electrode material is used as the positive electrode material of the supercapacitor.

[0035] The following examples are used to verify the beneficial effects of the present invention:

[0036] Example 1: A one-step method for preparing a dual-doped vanadium dioxide electrode material, characterized in that the method is specifically completed according to the following steps:

[0037] 1. Add 1.5mmolV2O5, 5mmolH2C2O4 and 1mL triethanolamine into 30mL deionized water, and then stir and react at 75℃ for 30min to obtain mixed solution I;

[0038] 2. Add 30 mL of anhydrous ethanol and 1.5 mL of 30% H2O2 solution to the mixed solution I and stir for 5 min to obtain a mixed solution II.

[0039] 3. Transfer the mixed solution II to a reactor with a polytetrafluoroethylene liner, seal the reactor and place it in a blast oven for hydrothermal reaction at 180°C for 12 hours. After the reaction is completed, cool it naturally to room temperature to obtain a reaction product. First, wash the reaction product with anhydrous ethanol for 3 times, and then wash the reaction product with deionized water for 3 times. Finally, vacuum dry it at 60°C for 12 hours to obtain a black powder, which is the dual-doped vanadium dioxide electrode material (N-VO 2-δ ).

[0040] Figure 1 The scanning electron microscope image shows that a is the N-VO prepared in Example 1. 2-δ Scanning electron microscope image at 10k magnification, b is N-VO prepared in Example 1 2-δ Scanning electron microscope image at 80k magnification;

[0041] from Figure 1 It can be seen that the N-VO prepared in Example 1 2-δ It has a spherical structure, and the surface is composed of many tiny nanoparticles; the size of the sphere is about 1μm.

[0042] Figure 2 N-VO prepared in Example 1 2-δ SEM mapping of the

[0043] from Figure 2 It can be seen that: V, O, N elements are evenly distributed in the electrode material; at the same time, the presence of nitrogen also shows that the prepared electrode material contains nitrogen atoms, thus proving the successful doping of N.

[0044] Figure 3 N-VO prepared in Example 1 2-δ XRD pattern of

[0045] from Figure 3 As can be seen in: N-VO after the introduction of defects 2-δ The standard crystal structure of vanadium dioxide can still be maintained without introducing other impurity peaks, that is, the introduction of defects does not destroy the structure of the electrode material.

[0046] Figure 4 N-VO prepared in Example 1 2-δ XPS spectra of O1s and N1s in the sample;

[0047] from Figure 4 In the left figure, we can see that N-VO 2-δ There are more oxygen vacancies in Figure 4 The existence of VNO bonds in the right figure is sufficient to prove that the one-step hydrothermal method successfully introduced two defects, namely oxygen vacancies and nitrogen doping.

[0048] Figure 5 N-VO prepared in Example 1 2-δ Cyclic voltammetry curves measured at different scan rates in the voltage range of -0.1 to 0.5 V;

[0049] Figure 5 The scanning speed from inside to outside is 10mVs respectively -1 , 20mVs -1 、30mVs -1 , 40mVs -1 , 50mVs -1 、70mVs -1 and 100mVs -1 ;from Figure 5 No obvious redox peaks were observed in the curve, and the upper and lower peaks were approximately symmetrical, indicating that the capacitor had good reversibility. When the scan rate increased from 5mV / s to 100mV / s, the cyclic voltammetry curve profile did not change significantly, indicating that N-VO 2-δ Has very good capacitance performance.

[0050] Figure 6 N-VO prepared in Example 1 2-δ Constant current charge and discharge curves measured at different current densities in the voltage range of -0.1 to 0.5 V;

[0051] from Figure 6 It can be seen that the curve has no obvious charge and discharge voltage platform, which further proves that N-VO 2-δ No redox reaction occurs during energy storage, which is consistent with the CV test results. 2-δ Energy storage mainly relies on the insertion / extraction of ions, which mainly manifests as pseudocapacitive behavior.

[0052] Figure 7 N-VO prepared in Example 1 2-δ Cyclic performance curve of the first 8000 cycles at a charge and discharge current density of 5A / g;

[0053] from Figure 7 It can be seen that after 8000 repeated charge and discharge, the electrode material can still maintain 81.7% of the initial capacitance value, indicating that the double-defect electrode material has very excellent cycle performance.

[0054] Comparative Example: VO2 was prepared according to the following steps:

[0055] 1. Add 1.5mmol V2O5 and 5mmol H2C2O4 into 30mL deionized water, and then stir and react at 75℃ for 30min to obtain mixed solution I;

[0056] 2. Add 30 mL of anhydrous ethanol and 1.5 mL of 30% H2O2 solution to the mixed solution I and stir for 5 min to obtain a mixed solution II.

[0057] 3. Transfer the mixed solution II to a reactor with a polytetrafluoroethylene liner, seal the reactor and place it in a forced air oven for hydrothermal reaction at 180°C for 12 hours. After the reaction is completed, naturally cool it to room temperature to obtain a reaction product. First, wash the reaction product with anhydrous ethanol for 3 times, then wash the reaction product with deionized water for 3 times. Finally, vacuum dry it at 60°C for 12 hours to obtain VO2.

[0058] Figure 8 VO2 prepared in the comparative example and N-VO prepared in Example 1 2-δ Comparison of constant current charge and discharge curves at a current density of 1A / g;

[0059] from Figure 8 It can be seen that: N-VO 2-δ The discharge time of N-VO2 is longer than that of pure VO2, indicating that 2-δ Has a higher discharge specific capacity.

[0060] Example 2: This example is different from Example 1 in that in step 1, 1.5 mmol V2O5, 5 mmol H2C2O4 and 0.5 mL triethanolamine are added to 30 mL deionized water, and then stirred at 75°C for 30 min to obtain a mixed solution I. The other steps and parameters are the same as those in Example 1.

[0061] Example 3: This example is different from Example 1 in that in step 1, 1.5 mmol V2O5, 5 mmol H2C2O4 and 3 mL triethanolamine are added to 30 mL deionized water, and then stirred at 75°C for 30 min to obtain a mixed solution I. The other steps and parameters are the same as those in Example 1.

[0062] Example 4: This example is different from Example 1 in that in step 1, 1.5 mmol V2O5, 5 mmol H2C2O4 and 5 mL triethanolamine are added to 30 mL deionized water, and then stirred at 75°C for 30 min to obtain a mixed solution I. The other steps and parameters are the same as those in Example 1.

[0063] Fig. 9 This is the effect of the amount of triethanolamine added on the electrochemical performance;

[0064] from Fig. 9 It can be seen that when the amount of triethanolamine added is 1 mL (Example 1), the CV closed area of ​​the prepared electrode material reaches the maximum value, so 1 mL is the optimal ratio.

Claims

1. A one-step method for preparing a dual-doped vanadium dioxide electrode material, characterized in that The method is specifically completed in the following steps:

1. Add V2O5, H2C2O4 and triethanolamine into deionized water, and then stir and react under heating conditions to obtain a mixed solution I; 2. Add anhydrous ethanol and 30% H2O2 solution by mass to the mixed solution I, stir, and obtain a mixed solution II; 3. Transfer the mixed solution II to a reactor with a polytetrafluoroethylene liner, seal the reactor and place it in a blast oven for hydrothermal reaction at 180°C to 185°C. After the reaction is completed, cool it naturally to room temperature to obtain a reaction product. Wash the reaction product and then vacuum dry it to obtain a black powder, which is the dual-doped vanadium dioxide electrode material.

2. The method for preparing a dual-doped vanadium dioxide electrode material in one step according to claim 1, characterized in that The volume ratio of the amount of V2O5 described in step 1 to deionized water is (1mmol~2mmol):30mL.

3. The method for preparing a dual-doped vanadium dioxide electrode material in one step according to claim 1, characterized in that The volume ratio of the amount of H2C2O4 described in step 1 to deionized water is (4mmol~6mmol):30mL.

4. The method for preparing a dual-doped vanadium dioxide electrode material in one step according to claim 1, characterized in that The volume ratio of the triethanolamine described in step 1 to the deionized water is (0.5-5):

30.

5. The method for preparing a dual-doped vanadium dioxide electrode material in one step according to claim 1, characterized in that In step 1, the reaction is stirred at 70° C. to 80° C. for 20 min to 40 min.

6. The method for preparing a dual-doped vanadium dioxide electrode material in one step according to claim 1, characterized in that The volume ratio of the mixed solution I described in step 2 to anhydrous ethanol is 1:

1.

7. The method for preparing a dual-doped vanadium dioxide electrode material in one step according to claim 1, characterized in that The volume ratio of the mixed solution I described in step 2 to the H2O2 solution with a mass fraction of 30% is 30:(1mL~2mL).

8. The method for preparing a dual-doped vanadium dioxide electrode material in one step according to claim 1, characterized in that The stirring time in step 2 is 5 min to 10 min; the hydrothermal reaction time in step 3 is 10 h to 12 h.

9. The method for preparing a dual-doped vanadium dioxide electrode material in one step according to claim 1, characterized in that In step three, the reaction product is firstly washed with anhydrous ethanol for 3 to 5 times, and then washed with deionized water for 3 to 5 times; the vacuum drying temperature in step three is 60° C., and the vacuum drying time is 10 h to 12 h.

10. Application of the double-doped vanadium dioxide electrode material prepared by the method according to claim 1, characterized in that The double-doped vanadium dioxide electrode material is used as the positive electrode material of the supercapacitor.

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