Vanadium-based oxide positive electrode material for aqueous zinc ion battery and preparation method thereof

Abstract

The application discloses a vanadium-based oxide positive electrode material for a water-based zinc ion battery and a preparation method thereof. 13 or V6O 13 / VO2 composite positive electrode material, and the preparation method comprises the following steps: S1, adding acetic acid into a light yellow ammonium metavanadate solution, stirring, adjusting the pH value to 2-4, and obtaining a dark yellow solution; S2, placing the dark yellow solution obtained in the step S1 into a polytetrafluoroethylene reaction kettle for high-temperature reaction, and obtaining a green solid after cooling; S3, performing suction filtration and washing on the green solid obtained in the step S2 until the pH value is 6-6.5, and performing freeze-drying until the weight is constant, so as to obtain a precursor; and S4, grinding the precursor into a powder, and sintering and heat-preserving under an argon atmosphere, so as to obtain the vanadium-based oxide positive electrode material for the water-based zinc ion battery. The vanadium-based oxide positive electrode material for the water-based zinc ion battery has a variety of valence states, excellent rate performance and good cycle performance, and the preparation method is simple, low in cost, high in yield and easy to control.

Description

Technical Field

[0001] The present invention relates to the technical field of positive electrode materials for aqueous zinc ion batteries, and in particular to a vanadium-based oxide positive electrode material for aqueous zinc ion batteries and a preparation method thereof. The vanadium-based oxide is hexavanadium trioxide (V6O 13 ) or vanadium trioxide / vanadium dioxide (V6O 13 / VO2) composite materials. Background Art

[0002] Among various energy storage devices, aqueous zinc-ion batteries (AZIBs) have shown their excellent competitiveness. The zinc anode used in AZIBs has several advantages, such as 820 mAh g -1 Ultra-high theoretical capacity, 5851 mAh mL -1 The extremely high energy density and low standard potential (-0.762 V vs. standard hydrogen electrode) of AZIB are the main features of AZIB. However, the shortage of cathode materials has posed a challenge to the development of AZIB. Therefore, researchers are working on developing cathode materials with excellent performance, including transition metal oxides, Prussian blue analogs (PBA) and conductive polymers. Among them, vanadium-based oxides have the advantages of high theoretical capacity, diverse valence states and high electrochemical activity, and have been widely used as cathode materials for AZIB. However, the relationship between vanadium-based oxides and Zn 2+ There are strong electrostatic interactions between them, resulting in poor electrical conductivity. The solubility of vanadium leads to inherent problems such as potential decay and structural collapse, which hinder the further development of vanadium-based oxides in AZIBs. By regulating the valence distribution of vanadium-based oxides, vanadium-based oxides can be optimized according to different application scenarios and needs, thereby meeting higher performance requirements. Therefore, exploring the regulation of the valence distribution of vanadium-based oxides is an important topic in the research of vanadium-based oxides. To this end, the present invention proposes a vanadium trioxide (V6O3) for aqueous zinc ion batteries. 13 ) Positive electrode materials and V6O 13 The preparation method of vanadium / VO2 composite materials utilizes the multivalent nature of vanadium ions to produce multiple reversible redox reactions during the charge and discharge process of AZIB, which helps to improve the energy density, rate performance, and cycle performance of AZIB. Summary of the Invention

[0003] The present invention aims to provide a vanadium-based oxide positive electrode material for aqueous zinc ion batteries and a preparation method thereof, wherein the vanadium-based oxide comprises hexavanadium trioxide (V6O 13 ) or V6O 13 / VO2 composite positive electrode material. The purpose of the present invention is achieved through the following technical solutions:

[0004] In a first aspect, the present application provides a preparation method of a vanadium-based oxide positive electrode material for aqueous zinc ion batteries, the vanadium-based oxide being V6O 13 or V6O 13 / VO2 composite positive electrode material, the preparation method comprising the following steps:

[0005] S1, adding acetic acid to the light yellow ammonium metavanadate solution and mixing, adjusting the pH to 2-4 to obtain a dark yellow solution;

[0006] S2, transferring the dark yellow solution obtained in step S1 into a polytetrafluoroethylene reaction kettle for high-temperature reaction, and obtaining a green solid after cooling;

[0007] S3, performing suction filtration and washing on the green solid obtained in step S2 until the pH value is 6-6.5 (washing the impurities in the green solid obtained in step S2 with acid), and freeze-drying to constant weight to obtain a precursor;

[0008] S4, grinding the precursor into a powder, (placing it in a porcelain boat and transferring it to a tube furnace) and sintering and holding at a temperature of 300-450°C under an argon atmosphere to obtain a V6O 13 or V6O 13 / VO2 composite positive electrode material.

[0009] As some specific embodiments of the present application, in step S4, when the sintering and holding temperature is ≥300°C and <375°C, the obtained product is a V6O 13 positive electrode material;

[0010] and / or, when the sintering and holding temperature is ≥375°C and ≤450°C, the obtained product is a V6O 13 / VO2 composite positive electrode material.

[0011] As some specific embodiments of the present application, in step S1, the concentration of the ammonium metavanadate solution is 0.02-0.04 mol / L.

[0012] As some specific embodiments of the present application, in step S1, the preparation method of the ammonium metavanadate solution is: dissolving ammonium metavanadate in water, stirring at 20-40°C for 30-60 min until the solution is light yellow, thereby obtaining the ammonium metavanadate solution.

[0013] As some specific embodiments of the present application, in step S1, the volume ratio of acetic acid to ammonium metavanadate solution is 1:5-10. Stable acetic acid is used to adjust the pH value of the solution to 2-4, so that uniform nanorod-shaped products of the present application can be formed.

[0014] As some specific embodiments of the present invention, in step S1, the mixing and stirring temperature is 20°C to 40°C and the time is 30 to 60 minutes.

[0015] As some specific embodiments of the present invention, in step S2, the temperature of the high temperature reaction is 160° C. to 200° C. and the time is 8 to 12 h.

[0016] As some specific embodiments of the present invention, in step S4, during sintering, the temperature is heated from 20°C to 40°C to 300°C to 450°C, with a heating rate of 2°C / min to 5°C / min.

[0017] As some specific embodiments of the present invention, in step S4, when the heat preservation is performed, the heat preservation temperature is 300° C. to 450° C., and the heat preservation time is 3 to 4 hours.

[0018] As some specific embodiments of the present invention, the method for preparing the vanadium-based oxide positive electrode material specifically includes the following steps:

[0019] (1) Weigh 1 mmol of ammonium metavanadate and dissolve it in 40 mL of water. Stir at room temperature for 30 minutes until the solution turns light yellow.

[0020] (2) 5 mL of acetic acid was added to the light yellow solution obtained in step (1), the pH was adjusted to 2-4, and stirred at room temperature for 40 minutes to obtain a dark yellow solution;

[0021] (3) The dark yellow solution obtained in step (2) was transferred to a 50 mL polytetrafluoroethylene reactor, and then the reactor was placed in an oven at 180 °C for 12 h; after the reactor was cooled to room temperature, a green solid sample was obtained, which was then filtered and washed until the pH value of the sample was greater than 6.5, and then freeze-dried to constant weight to obtain a precursor;

[0022] (4) The precursor obtained in step (3) was ground into powder, and then transferred to a tube furnace, heated from room temperature to 350 °C under argon atmosphere at a heating rate of 5 °C / min, and kept at 350 °C for 3 hours to obtain V6O 13 or V6O 13 / VO2 composite positive electrode material.

[0023] In a second aspect, the present invention provides a vanadium-based oxide positive electrode material for aqueous zinc ion batteries, wherein the vanadium-based oxide is V6O 13 or V6O 13 / VO2 composite material, which is prepared by any of the methods described above.

[0024] Wu et al. (Journal of Alloys and Compounds 926 (2022) 166773) prepared V6O by hydrothermal reaction with vanadium pentoxide followed by aging. 13 As the positive electrode material of AZIB, the morphology is nanosheets, with the -1 At a high current density of 300 mA hg -1 The extremely high capacity at 0.3 A g -1 It maintains 421mA hg in 100 cycles -1 capacity, with a high capacity retention rate of 95%.

[0025] Selvam et al. (ACS Appl. Mater. Interfaces 2023, 15, 30350−30359) prepared V6O by hydrothermal reaction of ammonium metavanadate with thiourea (which has reducing properties) followed by argon annealing. 13 As the positive electrode material of AZIB, the morphology is layered nanosheets. -1 The specific capacity is 394 mAh g -1 At 2 A g -1 Under the current density cycle, its capacity retention rate is about 94% after 100 cycles, and the Coulombic efficiency is about 96%.

[0026] VO prepared by Xie et al. (ACS Appl. Mater. Interfaces 2024, 16, 8679−8687) x (V2O5 / V3O7 / V6O 13 Composite material) as AZIB positive electrode material, the morphology is irregular nanosheets, and its rate performance is 3A g -1 There are 111.9mAh g -1 , the cycle performance is 2A g -1 After 800 cycles, there is 142.4 mAh g -1 capacity.

[0027] The V6O of the present invention 13 and V6O 13 The morphology of the / VO2 composite cathode material is nanorod-shaped, and as the cathode of AZIB, it has better rate performance and better cycle performance; the V6O 13 and V6O 13 / VO2 in the rate performance test 5A g -1 The current density is 348.90 mAh g -1 and 168.48mAh g -1The battery capacity of the present invention is V6O 13 and V6O 13 / VO2 at 10A g -1 (High current density) cycle test of V6O 13 The material still has a specific capacity of 190 mAhg after 2000 cycles -1 And with 100% coulombic efficiency; and V6O 13 The peak discharge capacity of the / VO2 composite cathode material is 311.96 mAh g -1 Moreover, the capacity retention rate is close to 100% after 2000 cycles, so this application can adapt to a higher current density and a greater number of cycles.

[0028] The prior art CN111646460B uses citric acid, oxalic acid, etc. as reducing agents and reacts them with ammonium metavanadate. Ammonium metavanadate or vanadium pentoxide reacts with citric acid to form a vanadium citrate intermediate. In this process, the original vanadium ions are reduced to lower-valent vanadium ions. The acetic acid used in the present invention is more inclined to act as a buffer, reacting with ammonium metavanadate to form acetate and vanadate, thereby generating low-valent vanadium ions. The synthesis method used is the hydrothermal method. Most of the vanadium oxides synthesized by the hydrothermal method have layered or flaky structures. The V6O synthesized in the present invention is more inclined to act as a buffer, reacting with ammonium metavanadate to form acetate and vanadate, thereby generating low-valent vanadium ions. 13 and V6O 13 / VO2 composite material is a nanorod structure, and the prepared V6O 13 The crystallinity of the materials is not the same. In addition, the V6O prepared by the patented method 13 The material needs to be composited with graphene oxide to improve the electrochemical performance; and the V6O prepared by the present invention 13 and V6O 13 As a cathode material for aqueous zinc-ion batteries, VO2 inherently possesses excellent electrochemical properties, eliminating the need for composite graphene oxide, thus saving costs and enabling the preparation of high-performance cathode materials for aqueous zinc-ion batteries. The present invention introduces oxygen vacancies through argon annealing. While the method of the patented invention can also introduce oxygen vacancies, the oxygen vacancies therein and in the present invention occupy different areas, resulting in performance differences between the two.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1) The method of the present invention has simple preparation process, low cost, high yield, and easy control of preparation conditions;

[0031] 2) V6O prepared by the present invention 13 and V6O 13 / V2O5 composite cathode materials have valence diversity and have excellent rate performance and good cycle performance as cathode materials for aqueous zinc-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0033] Figure 1 V6O prepared in Example 1 13 SEM images of cathode materials;

[0034] Figure 2 V6O prepared in Example 2 13 SEM images of / VO2 composite cathode materials;

[0035] Figure 3 V6O prepared in Example 1 13 XRD pattern of the cathode material;

[0036] Figure 4 V6O prepared in Example 2 13 XRD pattern of / VO2 composite cathode material;

[0037] Figure 5 XRD pattern of the V2O5 / VO2 composite cathode material prepared in Comparative Example 2;

[0038] Figure 6 V6O prepared in Examples 1 and 2 13 Cathode materials and V6O 13 / VO2 composite cathode material rate performance diagram;

[0039] Figure 7 V6O prepared in Examples 1 and 2 13 Cathode materials and V6O 13 / VO2 composite cathode material cycle performance diagram;

[0040] Figure 8 This is a rate performance diagram of the New-AVO cathode material prepared in Comparative Example 1;

[0041] Figure 9 This is a cycling performance test diagram of the New-AVO cathode material prepared in Comparative Example 1;

[0042] Figure 10 This is a rate performance diagram of the V2O5 / VO2 composite cathode material prepared in Comparative Example 2;

[0043] Figure 11 This is a test diagram of the cycle performance of the V2O5 / VO2 composite cathode material prepared in Comparative Example 2;

[0044] Figure 12 This is a photo of the green precipitate obtained in the solution when preparing the precursor in Example 1 and Example 2;

[0045] Figure 13 This is a photo of the blue-black precipitate obtained in the solution when preparing the precursor in Comparative Example 1. DETAILED DESCRIPTION

[0046] The present invention will be further described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0047] Example 1

[0048] (1) Weigh 1 mmol of ammonium metavanadate and dissolve it in 40 mL of water. Stir at room temperature for 30 minutes until the solution turns light yellow.

[0049] (2) 5 mL of acetic acid was added to the light yellow solution obtained in step (1) and stirred at room temperature for 40 minutes to obtain a dark yellow solution.

[0050] (3) The dark yellow solution obtained in step (2) was transferred to a 50 mL polytetrafluoroethylene reactor, and then the reactor was placed in an oven at 180 °C for 12 h. After the reactor was cooled to room temperature, a green solid sample (such as Figure 12 The precursor was then filtered and washed until the pH value of the sample was greater than 6.5, and then freeze-dried to a constant weight to obtain a precursor.

[0051] (4) The precursor obtained in step (3) was ground into powder, and then transferred to a tube furnace, heated from room temperature to 350 °C under argon atmosphere at a heating rate of 5 °C / min, and kept at 350 °C for 3 hours to obtain V6O 13 positive electrode material.

[0052] Example 2

[0053] (1) Weigh 1 mmol of ammonium metavanadate and dissolve it in 40 mL of water. Stir at room temperature for 30 minutes until the solution turns light yellow.

[0054] (2) 5 mL of acetic acid was added to the light yellow solution obtained in step (1) and stirred at room temperature for 40 minutes to obtain a dark yellow solution.

[0055] (3) The dark yellow solution obtained in step (2) was transferred to a 50 mL polytetrafluoroethylene reactor, and the reactor was placed in an oven at 180°C for 12 h. After the reactor cooled to room temperature, a green solid sample was obtained. The sample was then filtered and washed until the pH value was greater than 6.5, and then freeze-dried to constant weight to obtain the precursor.

[0056] (4) The precursor obtained in step (3) was ground into powder, and then transferred to a tube furnace, heated from room temperature to 450 °C under argon atmosphere at a heating rate of 5 °C / min, and kept at 450 °C for 3 hours to obtain V6O 13 / VO2 composite positive electrode material.

[0057] Electrochemical performance test: V6O prepared in Example 1 13 Positive electrode material and V6O prepared in Example 2 13 The VO2 / VO2 composite cathode material was mixed as the active material, conductive carbon black (Super P) as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder in a mass ratio of 7:2:1. After being uniformly ground, the mixture was transferred to a small bottle and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added. After stirring at room temperature for 8 hours, the mixture was evenly coated on a stainless steel foil. After vacuum drying at 80°C for 12 hours, the mixture was cut into circular electrode sheets with a diameter of 12 mm. The cut electrode sheets were used as the working electrode, metallic zinc as the counter electrode, a glass fiber membrane (GF / D) as the separator, and 2.0 mol / L zinc sulfate as the electrolyte. CR2025 button cells were assembled in air. The constant current charge and discharge performance of the battery was tested using a BTS-5V / 20mA charge and discharge tester from Shenzhen Xinwei Company, with a charge and discharge voltage range of 0.2–1.6 V. The current density of the rate performance test was 0.5 A g -1 , 1 A g -1 、2A g -1 、3A g -1 , 5 A g -1 、10A g -1 . When testing the cycle performance, select 5 A g -1 or 10 A g -1 The current density was cycled up to 2000 times.

[0058] like Figure 1 As shown, the V6O prepared in Example 1 13 SEM image of the positive electrode material. As can be seen from the figure, the V6O prepared in Example 1 13 The positive electrode materials are all composed of aggregated nanorods.

[0059] like Figure 2 As shown, the V6O prepared in Example 2 13 SEM image of the V6O / VO2 composite cathode material. 13 / VO2 composite cathode materials are all composed of agglomerates of thinner and longer nanorods.

[0060] like Figure 3As shown, the V6O prepared in Example 1 13 XRD spectrum of the positive electrode material. It can be seen from the figure that the main phase of the material prepared by the present invention is V6O 13 , and can correspond to the standard atlas.

[0061] like Figure 4 As shown, the V6O prepared in Example 2 13 XRD spectrum of / VO2 composite positive electrode material. It can be seen from the figure that the main phase of the material prepared by the present invention is V6O 13 and VO2, and can correspond to the standard graph.

[0062] like Figure 6 As shown, the V6O prepared in Example 1 13 Positive electrode material and V6O prepared in Example 2 13 / VO2 composite cathode materials at different current densities (0.5, 1, 2, 3, 5, 10 A g -1 As can be seen from the figure, the V6O prepared in Example 1 13 The positive electrode material has very good rate performance, among which, at 0.5 A g -1 , 1 A g -1 , 2 A g -1 , 3 A g -1 , 5 A g -1 and 10 A g -1 The charge / discharge specific capacity at the current density is 427.2 mAh g -1 / 419.74 mAh g -1 、398.65 mAh g -1 / 395.95 mAh g -1 、377.77 mAh g -1 / 376.6 mAh g -1 、365.76 mAh g -1 / 364.92mAh g -1 、348.90 mAh g -1 / 348.47 mAh g -1 and 315.28 mAh g -1 / 315.0 mAh g -1 ; V6O prepared in Example 2 13 / VO2 composite cathode material also has good rate performance, among which, at 0.5 A g -1 , 1 A g -1 , 2 A g -1 , 3 A g -1 , 5 A g-1 and 10 A g -1 The charge / discharge specific capacity at the current density is 279.67 mAh g -1 / 272.84 mAh g -1 , 240.68 mAh g -1 / 238.85 mAh g -1 , 206.62 mAh g -1 / 205.62 mAh g -1 、190.51 mAh g -1 / 189.76 mAh g -1 、168.89 mAh g -1 / 168.48 mAh g -1 and 136.95 mAh g -1 / 136.67 mAh g -1 Therefore, the V6O of the present invention 13 Cathode materials and V6O 13 / VO2 composite cathode material has good charge and discharge reversibility, that is, excellent coulombic efficiency.

[0063] like Figure 7 As shown, the V6O prepared in Example 1 13 Positive electrode material and V6O prepared in Example 2 13 / VO2 composite cathode material at 10A g -1 The cycle performance curve of the V6O prepared in Example 1 is shown in the figure after 2000 cycles. 13 The positive electrode material has a high initial discharge capacity (291.65 mAh g -1 ) and good cycle stability; V6O prepared in Example 2 13 The peak discharge capacity of the / VO2 composite cathode material is 311.96 mAh g -1 And the capacity retention rate after 2000 cycles is close to 100%; therefore, the V6O 13 Cathode materials and V6O 13 / VO2 composite cathode material has good cycle performance.

[0064] Comparative Example 1

[0065] (1) Weigh 2.74 mmol of ammonium metavanadate and dissolve it in 40 mL of water. Stir at room temperature for 30 minutes until the solution turns light yellow.

[0066] (2) Weigh 4.6 mmol of citric acid and add it to the light yellow solution obtained in step (1). Stir at room temperature for 40 minutes to obtain a dark yellow solution.

[0067] (3) The dark yellow solution obtained in step (2) was transferred to a 50 mL polytetrafluoroethylene reactor, and then the reactor was placed in an oven at 180 ° C for 12 h. After the reactor was cooled to room temperature, a blue-black precipitate (such as Figure 13 The precursor was then filtered and washed until the pH value of the sample was greater than 6.5, and then freeze-dried to a constant weight to obtain a precursor.

[0068] (4) The precursor obtained in step (3) was ground into powder, and then transferred to a tube furnace. It was heated from room temperature to 350 °C under an argon atmosphere at a heating rate of 5 °C / min and kept at 350 °C for 3 hours. Finally, the product was obtained and named New-AVO positive electrode material.

[0069] Figure 8 and Figure 9 The figure shows the rate performance and cycle performance test of the material as the positive electrode material of aqueous zinc ion battery. It can be seen that compared with the V6O prepared by the present invention, 13 Cathode materials and V6O 13 / VO2 composite positive electrode material, the performance of this material is significantly poor, the charge / discharge specific capacity is low, and it has no research value.

[0070] Comparative Example 2

[0071] (1) Weigh 1 mmol of ammonium metavanadate and dissolve it in 40 mL of water. Stir at room temperature for 30 minutes until the solution turns light yellow.

[0072] (2) 5 mL of acetic acid was added to the light yellow solution obtained in step (1) and stirred at room temperature for 40 minutes to obtain a dark yellow solution.

[0073] (3) The dark yellow solution obtained in step (2) was transferred to a 50 mL polytetrafluoroethylene reactor, and the reactor was placed in an oven at 180°C for 48 h. After the reactor cooled to room temperature, a green solid sample was obtained. The sample was then filtered and washed until the pH value was greater than 6.5, and then freeze-dried to constant weight to obtain the precursor.

[0074] (4) The precursor obtained in step (3) was ground into powder, and then transferred to a tube furnace, heated from room temperature to 350 °C under an argon atmosphere at a heating rate of 5 °C / min, and kept at 350 °C for 12 hours to obtain a V2O5 / VO2 composite positive electrode material.

[0075] like Figure 5 The figure shows the XRD pattern of the V2O5 / VO2 composite cathode material prepared in Comparative Example 2. As can be seen from the figure, the main phases of the material prepared in Comparative Example 2 are V2O5 and VO2, and they correspond to the standard pattern.

[0076] Figure 10 and Figure 11 respectively are the rate performance and cycle performance test figures of the material as a positive electrode material of a water-based zinc ion battery, it can be seen that compared with the prepared V6O 13 positive electrode material and V6O 13 / VO2 composite positive electrode material, the material has low charge / discharge specific capacity and poor performance.

[0077] The specific embodiments of the present application are described above. It should be understood that the present application is not limited to the specific embodiments described above, and various modifications or changes can be made by those skilled in the art within the scope of the claims, which does not affect the essential content of the present application.

Claims

1. A method for preparing a vanadium-based oxide positive electrode material for an aqueous zinc ion battery, characterized in that: The vanadium-based oxide is a nanorod-shaped V6O 13 / VO2 composite positive electrode material, the preparation method thereof comprises the following steps: S1. Add acetic acid to the light yellow ammonium metavanadate solution, mix and stir, and adjust the pH to 2-4 to obtain a dark yellow solution; S2. Transfer the dark yellow solution obtained in step S1 to a polytetrafluoroethylene reactor for high-temperature reaction at a temperature of 160° C. to 200° C. for 8 to 12 h, and obtain a green solid after cooling; S3. Filter and wash the green solid obtained in step S2 to a pH of 6-6.5, and freeze-dry to a constant weight to obtain a precursor; S4, grind the precursor into powder, sinter and keep warm at 300℃~450℃ in argon atmosphere for 3~4 hours to obtain nanorod-shaped V6O 13 / VO2 composite positive electrode material.

2. The preparation method according to claim 1, characterized in that In step S4, when the sintering and holding temperature is ≥375°C and ≤450°C, the obtained product is nanorod-shaped V6O 13 / VO2 composite positive electrode material.

3. The preparation method according to claim 1, characterized in that In step S1, the concentration of the ammonium metavanadate solution is 0.02-0.04 mol / L.

4. The preparation method according to claim 1 or 3, characterized in that The preparation method of the ammonium metavanadate solution comprises: dissolving ammonium metavanadate in water, and stirring at 20° C. to 40° C. for 30 to 60 minutes until the solution turns light yellow, thereby obtaining the ammonium metavanadate solution.

5. The preparation method according to claim 1, characterized in that In step S1, the volume ratio of the acetic acid to the ammonium metavanadate solution is 1:5-10.

6. The preparation method according to claim 1, characterized in that In step S1, the mixing and stirring is performed at a temperature of 20° C. to 40° C. for 30 to 60 minutes.

7. The preparation method according to claim 1, characterized in that In step S4, during sintering, the temperature is heated from 20°C to 40°C to 300°C to 450°C at a heating rate of 2°C / min to 5°C / min.

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