Preparation method of vanadium pentoxide-based magnesium battery positive electrode material

Abstract

The application discloses a vanadium pentoxide-based magnesium battery positive electrode material and a preparation method thereof. The application obtains flower-spherical vanadium pentoxide through a hydrothermal reaction of an ammonium metavanadate and a mixed solution of reactants and subsequent calcination; the method has high production efficiency, is convenient to produce, has short preparation time, is low in cost and has good repeatability. The flower-spherical vanadium pentoxide nanomaterial is used as a magnesium battery positive electrode material, more surface active sites can be exposed, ion transmission channels are increased, the problem of stacking and agglomeration of vanadium pentoxide nanosheets in a cycle process is solved, the exposed (001) crystal face reduces the interface side reaction of an electrode and an electrolyte surface, the storage capacity of vanadium pentoxide is greatly improved, the vanadium pentoxide has good cycle stability and is an excellent magnesium battery positive electrode material.

Description

A method for preparing a vanadium pentoxide-based magnesium battery cathode material Technical Field

[0001] This invention belongs to the field of novel energy storage, specifically relating to the preparation of a flower-shaped vanadium pentoxide nanomaterial with exposed specific crystal faces and its application in magnesium batteries. Background Technology

[0002] With the continuous growth of the global population and the accelerating pace of industrialization, the energy shortage problem has become increasingly prominent, prompting people to constantly explore the feasibility of new energy sources. Vanadium pentoxide, as a semiconductor material, possesses advantages such as abundant reserves, low development costs, and good safety performance. It is a transition metal oxide with unique optical and electrochemical properties. In recent years, it has played a very important role in the research of cathode materials in various battery fields, such as lithium batteries, zinc batteries, and sodium batteries, exhibiting excellent capacity and rate performance. Unsurprisingly, in recent years, vanadium pentoxide has also entered the research field of magnesium battery cathode materials in various forms (such as layered, honeycomb, and fibrous structures).

[0003] In addition to possessing the basic properties of vanadium pentoxide, nano-sized vanadium pentoxide offers a larger surface area, providing more atomic reaction contact sites. This facilitates the contact reaction between the electrode and electrolyte in electrode materials, significantly improving reaction efficiency. Furthermore, nano-sized vanadium pentoxide can shorten the distances for electron transport and ion diffusion, and plays a good regulatory role in ion insertion / extraction, making vanadium pentoxide stand out among various transition metal oxide electrode materials.

[0004] Currently, people have made extensive progress in preparing one-dimensional and multi-dimensional vanadium pentoxide nanomaterials through hydrothermal methods, chemical solid-state methods, electrospinning methods, sol-gel methods, etc. For example, CN108847483A discloses a method for rapid and large-scale preparation of vanadium pentoxide nanosheets with high purity and good crystallinity, which are used as active materials and catalysts for batteries and exhibit excellent performance. CN102502825A discloses an orthorhombic vanadium pentoxide nanostructure with a myricetite-like shape, which is applied in the field of nano-optoelectronics.

[0005] Among various preparation methods, the simplest is to synthesize vanadium pentoxide through hydrothermal methods. However, the previously reported vanadium pentoxide nanomaterials inevitably suffer from structural instability, poor conductivity, and nanosheet stacking. During multiple charge-discharge cycles, vanadium pentoxide undergoes multiple phase transitions and structural collapses, reducing cycle stability. Therefore, developing a simple, economical, and efficient method for preparing vanadium pentoxide nanomaterials still faces severe challenges. Summary of the Invention

[0006] To address the problems existing in the prior art, this invention proposes a flower-shaped vanadium pentoxide-based magnesium battery cathode material with exposed specific crystal planes and its preparation method. Using flower-shaped vanadium pentoxide nanosheets prepared by a hydrothermal method as the cathode material for magnesium batteries effectively improves the structure and controls its morphology. This not only exposes more surface active sites but also increases ion transport channels, achieving effective ion insertion / extraction, while simultaneously solving the problem of vanadium pentoxide nanosheet stacking and agglomeration during cycling. Furthermore, the exposed (001) crystal planes can reduce interfacial side reactions between the electrode and electrolyte surfaces. Using this material as a cathode material for magnesium-ion batteries significantly improves the storage capacity of vanadium pentoxide and exhibits excellent cycle stability. In addition, the process is simple, efficient, low-cost, and yields products with high purity and high production volume.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a vanadium pentoxide-based magnesium battery cathode material, comprising the following steps:

[0008] (1) Dissolve ammonium metavanadate (NH4VO3) and reactants in deionized water, heat in a water bath and stir magnetically until completely dissolved to obtain a clear pale yellow reactant solution;

[0009] (2) Place the reactant solution in a hydrothermal reactor to carry out the hydrothermal reaction;

[0010] (3) The solution after hydrothermal reaction is washed with deionized water 3 to 5 times, and the precipitate is freeze-dried to obtain blue-green precursor material;

[0011] (4) The precursor material is heated to 400~500 ℃ in a muffle furnace at a heating rate of 5-10 ℃ / min, held for 5-10 h and then cooled to room temperature in the furnace to obtain orange-yellow flower-shaped vanadium pentoxide.

[0012] In step (1), the mass ratio of ammonium metavanadate to reactants is 30-50:1.

[0013] The reactants in step (1) are any one of polyvinyl ether (Brij58), hydrogen peroxide, sodium citrate, and oxalic acid.

[0014] In step (1), the temperature of the magnetic stirring water bath is 60-80 ℃, and the stirring time is 1~1.5 h.

[0015] The hydrothermal temperature in step (2) is 180-200 ℃, the heat preservation time is 10-12 h, and the filling ratio is 60-70%.

[0016] The freezing time in step (3) is 8 to 12 hours, and the freeze-drying time is 10 to 24 hours.

[0017] The flower-shaped vanadium pentoxide has a diameter of 50-150 μm, a thickness of 50-200 nm, and a width of 200-5000 nm.

[0018] The beneficial effects of this invention are: the preparation method of this invention is efficient and fast, the prepared vanadium pentoxide product effectively improves the structure and controls its morphological characteristics, not only can more surface active sites be exposed, but also the ion transport channels are increased. At the same time, it solves the problem of vanadium pentoxide nanosheet stacking and agglomeration during cycling. The stable (001) crystal plane reduces the interfacial side reactions between the electrode and the electrolyte surface, thereby greatly improving the storage capacity of vanadium pentoxide and having good cycling stability. It is an excellent cathode material for magnesium batteries. Attached Figure Description

[0019] Figure 1 is a SEM image of the flower-shaped vanadium pentoxide nanomaterials prepared in Examples 1-4 of this invention.

[0020] Figure 2 shows the low-resolution and high-resolution SEM images of the flower-shaped vanadium pentoxide nanomaterials prepared in Example 1 of this invention.

[0021] Figure 3 shows the X-ray diffraction patterns of the flower-shaped vanadium pentoxide nanomaterials obtained before and after calcination in Example 1 of this invention.

[0022] Figure 4 is the X-ray diffraction pattern of the flower-shaped vanadium pentoxide nanomaterials obtained after calcination in Examples 1-4 of this invention.

[0023] Figure 5 shows 10 mA g of the flower-shaped vanadium pentoxide nanomaterials prepared in Examples 1-4 of this invention. −1 The first 100 cycles under current density. Detailed Implementation

[0024] The following are specific embodiments of the present invention, and the technical solutions of the present invention will be further described in conjunction with the accompanying drawings, but the scope of protection of the present invention is not limited thereto.

[0025] Example 1

[0026] 1) Dissolve 1.2 g of NH4VO3 and 0.04 g of Brij58 in 80 mL of deionized water, heat in a water bath to 60 °C, and stir magnetically for 1 h until completely dissolved to obtain a clear pale yellow solution.

[0027] 2) Place the solution in a hydrothermal reactor at a hydrothermal temperature of 180 ℃ and maintain the temperature for 10 h, with a filling ratio of 60%;

[0028] 3) After the reaction was completed, the solution was washed three times with deionized water, then frozen in a refrigerator for 12 hours, and freeze-dried at −55 °C and a vacuum of 1 Pa for 24 hours to obtain the blue-green precursor powder material (NH4VO). 10 );

[0029] 4) The precursor material was heated in a muffle furnace at 5 °C for 1 min. −1 Heating to 500 °C at a heating rate of 0.5%, holding in air for 5 h, and then cooling to room temperature with the furnace yielded orange-yellow flower-shaped vanadium pentoxide with an average diameter of 120 μm.

[0030] Example 2

[0031] 1) Dissolve 1.2 g of NH4VO3 and 0.04 g of hydrogen peroxide in 80 mL of deionized water, heat in a water bath to 60 °C, and stir magnetically for 1 h until completely dissolved to obtain a clear, pale yellow solution.

[0032] 2) Place the solution in a hydrothermal reactor at a hydrothermal temperature of 180 ℃ and maintain the temperature for 10 h, with a filling ratio of 60%;

[0033] 3) After the reaction was completed, the solution was washed three times with deionized water, then frozen in a refrigerator for 12 h, and freeze-dried at −55 °C and a vacuum of 1 Pa for 24 h to obtain the blue-green precursor powder material (NH4VO). 10 );

[0034] 4) The precursor material is heated in a muffle furnace at 5°C for 5 min. −1 The vanadium pentoxide was heated to 500°C at a heating rate of [missing information], held in air for 5 hours, and then cooled to room temperature in the furnace to obtain orange-yellow flower-shaped vanadium pentoxide. The average diameter of the obtained flower-shaped vanadium pentoxide was 80 μm.

[0035] Example 3

[0036] 1) Dissolve 1.2 g of NH4VO3 and 0.04 g of sodium citrate in 80 mL of deionized water, heat in a water bath to 60 °C, and stir magnetically for 1 h until completely dissolved to obtain a clear pale yellow solution.

[0037] 2) Place the solution in a hydrothermal reactor at a hydrothermal temperature of 180 ℃ and maintain the temperature for 10 hours. The filling ratio is 60%.

[0038] 3) After the reaction was completed, the solution was washed three times with deionized water, then frozen in a refrigerator for 12 h, and freeze-dried at −55 °C and a vacuum of 1 Pa for 24 h to obtain the blue-green precursor powder material (NH4VO). 10 );

[0039] 4) The precursor material was heated in a muffle furnace at 5 °C for 1 min. −1 Heating to 500 °C at a heating rate of 0.5%, holding in air for 5 h, and then cooling to room temperature with the furnace yielded orange-yellow flower-shaped vanadium pentoxide with an average diameter of 60 μm.

[0040] Example 4

[0041] 1) Dissolve 1.2 g of NH4VO3 and 0.04 g of oxalic acid in 80 mL of deionized water, heat in a water bath to 60 °C, and stir magnetically for 1 h until completely dissolved to obtain a clear pale yellow solution.

[0042] 2) Place the solution in a hydrothermal reactor at a hydrothermal temperature of 180 ℃ and maintain the temperature for 10 h, with a filling ratio of 60%;

[0043] 3) After the reaction was completed, the solution was washed three times with deionized water, then frozen in a refrigerator for 12 hours, and freeze-dried at −55 °C and a vacuum of 1 Pa for 24 hours to obtain the blue-green precursor powder material (NH4VO). 10 );

[0044] 4) The precursor material was heated in a muffle furnace at 5 °C for 1 min. −1 Heating to 500 °C at a heating rate of 0.5%, holding in air for 5 h, and then cooling to room temperature with the furnace yielded orange-yellow flower-shaped vanadium pentoxide with an average diameter of 50 μm.

[0045] The flower-shaped vanadium pentoxide nanomaterial samples obtained in Examples 1-4 were prepared as positive electrode materials for magnesium batteries, with magnesium foil as the negative electrode. They were assembled into 2032 coin cells, and their electrochemical performance was tested in the voltage range of 0.1 to 2 V.

[0046] The manufacturing process of the battery electrode is as follows: The above-mentioned flower-shaped vanadium pentoxide nanomaterial, conductive carbon black, and binder PVDF are uniformly mixed at a mass ratio of 7:2:1, and the organic solvent NMP is added to obtain the positive electrode slurry. The positive electrode slurry is coated on copper foil, and the coating thickness is controlled to be 50 μm. After drying, rolling and stamping, the magnesium battery positive electrode is obtained.

[0047] The electrolyte preparation process is as follows: APC solution is synthesized using 4 mL of phenyl magnesium chloride, 6 mL of tetrahydrofuran, and 0.534 g of anhydrous AlCl. Then, LiCl solution is prepared using 10 mL of tetrahydrofuran and 0.439 g of LiCl. The APC:LiCl solution is prepared in a 1:1 ratio to form the electrolyte.

[0048] Figure 1 shows a comparison of scanned images of Examples 1-4 of the present invention. Figure 1a shows the flower-shaped vanadium pentoxide nanomaterials prepared in Example 1, with an average yield of 120 mg and an average flower diameter of 100 μm; Figure 1b shows the flower-shaped vanadium pentoxide nanomaterials prepared in Example 2, with an average yield of 80 mg and an average flower diameter of 80 μm; Figure 1c shows the flower-shaped vanadium pentoxide nanomaterials prepared in Example 3, with an average yield of 60 mg and an average flower diameter of 60 μm; Figure 1d shows the flower-shaped vanadium pentoxide nanomaterials prepared in Example 4, with an average yield of 60 mg and an average flower diameter of 50 μm. The flower-shaped structure not only exposes more surface active sites but also increases ion transport channels, achieving effective ion insertion / extraction, while simultaneously solving the problem of vanadium pentoxide nanosheet stacking and aggregation during cycling.

[0049] Figure 2 shows the scan patterns of Example 1 at low resolution (Figure 2a) and high resolution (Figure 2b). At low resolution, it can be observed that the nanospheres are uniformly distributed on the conductive adhesive, with uniform morphology. The vanadium pentoxide nanosheets forming the nanospheres are uniformly dispersed from the center outwards, and the structure is stable. At high resolution, it can be observed that some nanoparticles are also directionally grown in situ on the nanosheets, which is beneficial to the diffusion and transport of ions.

[0050] Figure 3 shows the XRD patterns of Example 1 before calcination (Figure 3a) and after calcination (Figure 3b). It can be seen from the figure that the substance before calcination is ammonium vanadate, and the substance after calcination is vanadium pentoxide, which we obtained.

[0051] Figure 4 shows the XRD patterns of Examples 1-4 after calcination. Comparing the peak intensities of the (001) crystal planes of Examples 1-3 with their respective (101) crystal planes, it was calculated that Example 4 had the largest proportion, followed by Example 1. Furthermore, Example 1 was able to maintain its flower-shaped structure very stably. Examples 1-4 exposed more (001) crystal planes, thus possessing more active sites. The stable (001) crystal planes also reduce interfacial side reactions between the electrode and electrolyte surfaces, which is beneficial to the electrochemical performance of the battery.

[0052] Figure 5 shows the results of Examples 1-4 at 10 mA g. −1 The charge-discharge cycle curves at current density show that after 100 cycles, the capacity of Example 1 remained at 37.5 mAh g⁻¹. −1 It exhibits good stability.

Claims

1. A method for preparing a vanadium pentoxide-based magnesium battery cathode material, characterized in that, The steps are as follows: (1) Dissolve ammonium metavanadate and reactants in deionized water. The mass ratio of ammonium metavanadate to reactants is 30-50:

1. Heat in a water bath and stir magnetically until completely dissolved to obtain a reactant solution. The reactants are any one of polyethylene ether, hydrogen peroxide, sodium citrate, and oxalic acid. (2) Place the reactant solution in a hydrothermal reactor and carry out a hydrothermal reaction. The hydrothermal temperature is 180-200 ℃, and the temperature is maintained for 10-12 h. The filling ratio is 60-70%. (3) Wash the solution after the hydrothermal reaction with deionized water 3-5 times. Freeze-dry the precipitate to obtain the precursor material. (4) Heat the precursor material in a muffle furnace at a heating rate of 5-10 ℃ / min to 500 ℃. After maintaining the temperature for 5-10 h, cool it to room temperature with the furnace to obtain flower-shaped vanadium pentoxide. The diameter of the flower-shaped vanadium pentoxide is 50-150 mm. μm, thickness 50 ~ 200 nm, width 200 ~ 5000 nm.

2. The preparation method according to claim 1, characterized in that: In step (1), the temperature of the magnetic stirring water bath is 60-80 ℃, and the stirring time is 1~1.5 h.

3. The preparation method according to claim 1, characterized in that: The freezing time in step (3) is 8 to 12 hours, and the freeze-drying time is 10 to 24 hours.

4. The application of the flower-shaped vanadium pentoxide prepared by any one of claims 1-3 in the cathode material of magnesium batteries.

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