Preparation method and application of a material of spherical cobalt tungstate wrapped by nickel cobaltate composite carbon nanotubes

Abstract

This invention discloses a method and application for preparing nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material using microwave hydrothermal processing, belonging to the technical field of supercapacitor electrode materials. The method includes the following steps: S1, dissolving cobalt tungstate and nickel cobalt oxide composite carbon nanotubes in deionized water, and drying the resulting mixed solution using microwave hydrothermal processing to obtain a precursor powder; S2, thoroughly grinding the precursor powder obtained in step S1 and then pyrolyzing it in a tube furnace to obtain the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material. This invention features a simple process, low cost, and suitability for mass production. It exhibits good capacitance and cycle performance under alkaline conditions, meeting the requirements for the commercial large-scale production and application of capacitors for energy storage.

Description

Technical Field

[0001] This invention relates to a method for preparing and applying a nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material, belonging to the technical field of capacitor electrode materials. Background Technology

[0002] The origins of materials science can be traced back to ancient humans' use of materials, such as the discovery and application of metals, ceramics, and composite materials. With the advancement of the Industrial Revolution, especially since the 20th century, materials science has gradually developed into an independent discipline. Materials used in new energy sources, such as solar cells, hydrogen storage materials, lithium-ion batteries, and supercapacitors, all support the utilization of renewable energy. Due to the non-renewable nature and limited reserves of fossil fuels, the supply-demand gap continues to widen, leading to increasingly tense competition for energy resources. On the other hand, greenhouse gases produced by the combustion of fossil fuels are causing increasingly severe damage to the global climate. According to statistics from the International Energy Agency, the transportation industry accounts for 25% of global carbon emissions, making it the second largest carbon-emitting sector globally, highlighting the growing urgency of pollution control. Therefore, finding alternatives to oil and developing and utilizing new green energy sources has become imperative. Consequently, there is also a greater demand for energy storage devices.

[0003] Supercapacitors (also known as electrochemical capacitors) are a new type of power storage device that has emerged in recent years. They are a novel energy storage device that falls between traditional capacitors and rechargeable batteries, with capacities ranging from hundreds to thousands of farads. Compared to traditional capacitors, they offer larger capacity, higher energy density, a wider operating temperature range, and extremely long cycle life; while compared to batteries, they have higher power density and are environmentally friendly. However, the low energy density of supercapacitors limits their large-scale application. Therefore, developing high-energy-density supercapacitors as a power source for practical devices is of great significance.

[0004] Cobalt and nickel-based oxides, with their advantages of high theoretical specific capacitance and good stability, are widely used in fields such as electricity, magnetism, catalysis, energy storage and conversion, and are gradually becoming one of the hot materials for capacitors. However, due to the self-aggregation of particles during the preparation process, the active sites of cobalt and nickel-based oxides are often reduced, making it difficult to achieve their theoretical capacity. Moreover, their inherent low conductivity reduces rate performance and cycle performance, making it difficult to achieve the ideal performance of supercapacitor materials. In addition, existing preparation methods are complex and cannot meet the needs of large-scale commercial production and application of capacitor electrode materials. Summary of the Invention

[0005] To address the issues raised in existing technologies where cobalt and nickel-based oxides often suffer from reduced active sites due to particle aggregation during preparation, hindering the achievement of their theoretical capacities, and where low conductivity reduces rate and cycle performance, thus failing to meet the ideal performance requirements of supercapacitor electrode materials, this invention provides a method for preparing and applying a microwave hydrothermal method for using nickel cobalt oxide composite carbon nanotubes to encapsulate spherical cobalt tungstate materials. Improving the electrochemical storage capacity of electrodes and thus increasing their specific capacity through microstructure design, conductivity optimization, and composite structure construction are excellent solutions to these problems.

[0006] To achieve the above objectives, the technical means employed in this invention are as follows: The first aspect of this invention provides a method for preparing spherical cobalt tungstate material encapsulated in nickel cobalt oxide composite carbon nanotubes, the method comprising the following steps: S1. Dissolve cobalt tungstate and nickel cobaltate of composite carbon nanotubes in deionized water, and dry the resulting mixed solution by microwave hydrothermal treatment to obtain precursor powder. S2. After thoroughly grinding the precursor powder obtained in step S1, place it in a tube furnace for pyrolysis to obtain the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material.

[0007] In the above technical solution, further, in step S1, the method for preparing the nickel cobalt oxide composite carbon nanotube includes the following steps: (1) Dissolve CoCl2·6H2O, Ni(NO3)26H2O, ammonium fluoride, urea and carbon nanotubes in deionized water to obtain a mixed solution; (2) Transfer the mixed solution to a microwave hydrothermal synthesizer and react at a temperature of 100~240°C for 1~3 h; (3) After centrifugation, washing and drying, it is then subjected to an air atmosphere at 2~10°C for min. -1 The temperature was increased to 250-600°C and held for 1-4 hours. After natural cooling, nickel cobalt oxide composite carbon nanotubes were obtained.

[0008] In the above technical solution, further, in step (1), the molar ratio of CoCl2·6H2O and Ni(NO3)26H2O is 2:1.

[0009] In the above technical solution, further, in step S1, the mass ratio of the cobalt tungstate to nickel cobalt oxide composite carbon nanotube is 1:1 to 1:4.

[0010] In the above technical solution, further, in step S1, the microwave hydrothermal time is 40~80 minutes.

[0011] In the above technical solution, further, in step S1, the temperature of the microwave hydrothermal system is 120~160℃, and the microwave power is 700~900W.

[0012] In the above technical solution, further, in step S1, the drying temperature is 50~70℃.

[0013] In the above technical solution, further, in step S2, the pyrolysis conditions are: the protective gas is nitrogen, the temperature is raised from room temperature to 250~350℃, held for 1~3 hours, and then cooled to room temperature with the furnace.

[0014] In the above technical solution, further, in step S2, the heating rate of the pyrolysis is 4~6℃ / min.

[0015] Another aspect of the present invention provides the application of the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared by the above preparation method in a supercapacitor, wherein the material is used as an electrode material of the supercapacitor.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared by the method of the present invention reduces the self-aggregation of particles. This is attributed to the synergistic effect of the spatial steric hindrance effect of the three-dimensional conductive network of carbon nanotubes, the synchronous nucleation mechanism induced by microwave bulk uniform heating, and the particle migration restriction and system surface energy reduction caused by the anchoring effect of the heterogeneous interface between the multi-component components.

[0017] 2. The nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared by the method of the present invention has a carbon nanotube structure. Its hollow tube structure can shorten the mass transfer distance, realize rapid electron transfer, and has excellent conductivity. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 The image shows a scanning electron microscope image of the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared in Example 2. The scale bar is 200 nm for a and 100 nm for b. Figure 2 The CV curves of the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared in Examples 2 and 4-6 are shown at different scan rates. Figure 3 The GCD curves of nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate materials prepared in Examples 2 and 4-6 are shown below under different current densities. Figure 4 The cycling performance curve of the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared in Example 2 is shown. Figure 5 CV curves of the composite materials prepared in comparative examples 1-4; Figure 6 GCD curves of the composite materials prepared in comparative examples 1-4; Figure 7 The image shows a SEM image of the composite material prepared in Comparative Example 1. Detailed Implementation

[0020] To clearly express the purpose and specific implementation methods of this invention, the technical solutions in the embodiments of this invention will be clearly and completely described below. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0021] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0022] Example 1 A microwave hydrothermal method for preparing nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material comprises the following steps: (1) Weigh 0.2 mM CoCl2·6H2O, 0.1 mM Ni(NO3)2·6H2O, 0.6 mM NH4F and 0.3 mM CH4N2O and dissolve them in deionized water. Add 0.2 g of carbon nanotubes and place the mixture in a microwave hydrothermal synthesizer. React at 160°C for 1 h. After centrifugation, washing and drying, place the mixture in a crucible and transfer it to a tube furnace. In an air atmosphere, heat the mixture at 5°C for 1 min. -1 The temperature was increased to 400°C and held for 2 hours. After natural cooling, the mixture was ground to obtain brownish-green composite carbon nanotube nickel cobalt oxide powder. (2) Add 0.4g of cobalt tungstate powder and 0.8g of nickel cobaltate powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and put the resulting mixed solution into a microwave hydrothermal reactor and heat it to 120℃ at 900W power for 1h. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After grinding the precursor powder obtained in step (3) thoroughly, place it in a tube furnace. During pyrolysis, nitrogen gas is introduced as a protective gas. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and kept at that temperature for 2 hours. Then, the furnace is cooled to room temperature to obtain black powder, namely nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material. Place the black powder in an agate mortar and grind it finely for later use.

[0023] Example 2 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 0.8g of nickel cobalt oxide powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and put the resulting mixed solution into a microwave hydrothermal reactor and heat it to 140℃ at 900W power for 1h. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After grinding the precursor powder obtained in step (3) thoroughly, place it in a tube furnace. During pyrolysis, nitrogen gas is introduced as a protective gas. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and kept at that temperature for 2 hours. Then, the furnace is cooled to room temperature to obtain black powder, namely nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material. Place the black powder in an agate mortar and grind it finely for later use.

[0024] Example 3 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 0.8g of nickel cobalt oxide powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and put the resulting mixed solution into a microwave hydrothermal reactor and heat it to 160℃ at 900W power for 1h. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After grinding the precursor powder obtained in step (3) thoroughly, place it in a tube furnace. During pyrolysis, nitrogen gas is introduced as a protective gas. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and kept at that temperature for 2 hours. Then, the furnace is cooled to room temperature to obtain black powder, namely nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material. Place the black powder in an agate mortar and grind it finely for later use.

[0025] Example 4 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 0.4g of nickel cobalt oxide powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and put the resulting mixed solution into a microwave hydrothermal reactor and heat it to 140℃ at 900W power for 1h. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After grinding the precursor powder obtained in step (3) thoroughly, place it in a tube furnace. During pyrolysis, nitrogen gas is introduced as a protective gas. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and kept at that temperature for 2 hours. Then, the furnace is cooled to room temperature to obtain black powder, namely nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material. Place the black powder in an agate mortar and grind it finely for later use.

[0026] Example 5 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 1.2g of nickel cobalt oxide powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and put the resulting mixed solution into a microwave hydrothermal reactor and heat it to 140℃ at 900W power for 1h. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After grinding the precursor powder obtained in step (3) thoroughly, place it in a tube furnace. During pyrolysis, nitrogen gas is introduced as a protective gas. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and kept at that temperature for 2 hours. Then, the furnace is cooled to room temperature to obtain black powder, namely nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material. Place the black powder in an agate mortar and grind it finely for later use.

[0027] Example 6 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 1.6g of nickel cobalt oxide powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and put the resulting mixed solution into a microwave hydrothermal reactor and heat it to 140℃ at 900W power for 1h. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After grinding the precursor powder obtained in step (3) thoroughly, place it in a tube furnace. During pyrolysis, nitrogen gas is introduced as a protective gas. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and kept at that temperature for 2 hours. Then, the furnace is cooled to room temperature to obtain black powder, namely nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material. Place the black powder in an agate mortar and grind it finely for later use.

[0028] Comparative Example 1 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 0.8g of nickel cobaltate powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and then place the resulting mixed solution into an ultrasonic cleaner for ultrasonic vibration for 30 min. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After fully grinding the precursor powder obtained in step (3), place it in a tube furnace, and purge it with nitrogen as a protective gas during pyrolysis. The temperature is raised from room temperature to 300°C at a rate of 5°C / min, and kept at that temperature for 2 hours. Then, the temperature is cooled to room temperature with the furnace to obtain the composite material.

[0029] Comparative Example 2 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 0.4g of nickel cobaltate powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and then place the resulting mixed solution into an ultrasonic cleaner for ultrasonic vibration for 30 min. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After the precursor powder obtained in step (3) is fully ground, it is placed in a tube furnace. Nitrogen gas is introduced as a protective gas during pyrolysis. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and held for 2 hours. Then the furnace is cooled to room temperature to obtain the composite material.

[0030] Comparative Example 3 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 1.2g of nickel cobaltate powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and then place the resulting mixed solution into an ultrasonic cleaner for ultrasonic vibration for 30 min. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After the precursor powder obtained in step (3) is fully ground, it is placed in a tube furnace. Nitrogen gas is introduced as a protective gas during pyrolysis. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and held for 2 hours. Then the furnace is cooled to room temperature to obtain the composite material.

[0031] Comparative Example 4 (1) The nickel cobalt oxide composite carbon nanotubes were prepared using the same method as in Example 1; (2) Add 0.4g of cobalt tungstate powder and 1.6g of nickel cobaltate powder of composite carbon nanotubes to 100mL of deionized water, stir evenly, and then place the resulting mixed solution into an ultrasonic cleaner for ultrasonic vibration for 30 min. (3) After cooling the suspension obtained in step (2) to room temperature, centrifuge and wash it, and then place it in a vacuum drying oven at 60°C for 12 hours to obtain precursor powder; (4) After the precursor powder obtained in step (3) is fully ground, it is placed in a tube furnace. Nitrogen gas is introduced as a protective gas during pyrolysis. The temperature is raised from room temperature to 300°C at a rate of 5°C / min and held for 2 hours. Then the furnace is cooled to room temperature to obtain the composite material.

[0032] Test Example 1 0.04 g of the sample prepared in Example 2 was weighed and mechanically mixed with conductive additive (acetylene black) and binder (polyvinylidene fluoride PVDF) at a mass ratio of 8:1:1. A slurry was prepared using N-methylpyrrolidone (NMP) as a solvent, then coated onto nickel foam and dried in a vacuum drying oven at 60°C for 12 h. Using mercury / mercury oxide (Hg / HgO) as the reference electrode, a platinum mesh electrode as the counter electrode, and 6 mol / L KOH solution as the electrolyte, tests were conducted at room temperature using a VMP3 (Princeton Company) electrochemical workstation with a suitable potential window selected.

[0033] Figure 1 This is a scanning electron microscope image of the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared in Example 2 of the present invention. The image shows a large number of carbon nanotubes wrapped around nanorod-like structures, forming a composite structure together with the nanospheres. The nanospheres are cobalt tungstate (CoWO4), and the nanorod-like structures are nickel cobalt oxide (NiCo2O4). The nickel cobalt oxide (NiCo2O4 / CNT) structure, composed of numerous carbon nanotubes wrapped around nanorod-like structures, uniformly encapsulates the starfruit-like CoWO4.

[0034] Figure 2The figures show the CV curves of nickel cobaltate composite carbon nanotube-encapsulated spherical cobalt tungstate materials prepared in Examples 2 and 4-6 of this invention at different scan rates; the horizontal axis represents potential (V) vs. SCE), and the vertical axis represents current density (A·g). -1 )). Figure 3 The figures show the GCD curves of the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared in Examples 2 and 4-6 of this invention under different current densities; the horizontal axis represents time (s) and the vertical axis represents potential (Poteneial (V) vs. SCE). Figure 4 The graphs show the cycling performance curves of the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate materials prepared in Examples 2 and 4-6 of this invention; the horizontal axis represents the number of charge-discharge cycles, and the vertical axis represents the percentage of retained capacitance. It can be seen that all samples exhibit obvious redox peaks, but the redox potentials show variations. This may be related to the presence of Co in the material. 2+ With Co 3+ Derived from NiCo2O4 and CoWO4, when the ratio of the two materials is different, the contact ratio with the electrolyte changes, leading to Co... 2+ With Co 3+ The dominant process in the redox reaction also changes. Among all samples, the sample in Example 2 has the largest area of ​​integration on its CV curve, which is related to... Figure 3 The results are consistent with the GCD curves. Calculations using the formula show that at a current density of 1 A g... -1 At that time, the specific capacity of the sample was 3440.6 F g. -1 .

[0035] Figure 5 and Figure 6 For Comparative Examples 1-4, the CV and GCD curves of composite materials prepared by mechanically mixing cobalt tungstate powder (CoWO4) and nickel cobalt oxide powder of composite carbon nanotubes were obtained according to the mass ratios corresponding to Examples 2 and 4-6. It can be seen that the mechanically mixed material exhibits poor electrochemical performance; at maximum capacity (mass ratio 1:2), the sample at a current density of 1 A g... -1 At that time, the specific capacity was only 781.9 F g. -1 This indicates that microwave hydrothermal is crucial.

[0036] Figure 7 The image shows the SEM image of Comparative Example 1. As can be seen from the image, under the action of mechanical mixing, the connection between CoWO4 and NiCo2O4 / CNT is only a mechanical stacking at the microscopic level and does not form an encapsulation. The interface bonding is relatively loose.

[0037] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material, characterized in that, The method includes the following steps: S1. Dissolve cobalt tungstate and nickel cobaltate of composite carbon nanotubes in deionized water, and dry the resulting mixed solution by microwave hydrothermal treatment to obtain precursor powder. S2. After thoroughly grinding the precursor powder obtained in step S1, place it in a tube furnace for pyrolysis to obtain the nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material.

2. The preparation method according to claim 1, characterized in that, In step S1, the method for preparing the nickel cobalt oxide composite carbon nanotube includes the following steps: (1) Dissolve CoCl2·6H2O, Ni(NO3)26H2O, ammonium fluoride, urea and carbon nanotubes in deionized water to obtain a mixed solution; (2) Transfer the mixed solution to a microwave hydrothermal synthesizer and react at a temperature of 100~240°C for 1~3 h; (3) After centrifugation, washing and drying, heat it to 250-600°C at a heating rate of 2-10°C min -1 in air atmosphere, and keep it for 1-4 h, and obtain the composite carbon nanotube nickel cobaltate after natural cooling.

3. The preparation method according to claim 2, characterized in that, In step (1), the molar ratio of CoCl2·6H2O and Ni(NO3)26H2O is 2:

1.

4. The preparation method according to claim 1, characterized in that, In step S1, the mass ratio of the cobalt tungstate to nickel cobalt oxide composite carbon nanotubes is 1:1 to 1:

4.

5. The preparation method according to claim 1, characterized in that, In step S1, the microwave hydrothermal time is 40-80 minutes.

6. The preparation method according to claim 1, characterized in that, In step S1, the temperature of the microwave hydrothermal system is 120~160℃, and the microwave power is 700~900W.

7. The preparation method according to claim 1, characterized in that, In step S1, the drying temperature is 50~70℃.

8. The preparation method according to claim 1, characterized in that, In step S2, the pyrolysis conditions are as follows: the protective gas is nitrogen, the temperature is raised from room temperature to 250~350℃, held for 1~3 hours, and then cooled to room temperature with the furnace.

9. The preparation method according to claim 8, characterized in that, In step S2, the heating rate of the pyrolysis is 4~6℃ / min.

10. The application of a nickel cobalt oxide composite carbon nanotube-encapsulated spherical cobalt tungstate material prepared by the preparation method according to any one of claims 1-9 in a supercapacitor, characterized in that, The material is used as the electrode material for a supercapacitor.

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