Magnesium battery cycle stability enhancing material and applications thereof

Abstract

This invention discloses a magnesium battery cycle stability enhancement material, which is obtained by dissolving an appropriate amount of vanadium source and surfactant in a mixed solution of isopropanol and diethylene glycol, followed by solvothermal reaction and calcination. This method offers high production efficiency, large production volume, fast preparation time, low cost, and excellent reproducibility, avoiding the problem of traditional sheet-like V2O5 agglomeration. Using coral-like V2O5 nanomaterials as the cathode material for magnesium batteries, its open three-dimensional porous structure not only increases ion attachment sites but also provides multiple pathways for electron transfer. Furthermore, the exposed (110) crystal planes reduce interfacial side reactions between the electrode and electrolyte surfaces, reduce the formation of passivation films on the electrode surface, thereby accelerating the redox reaction of the battery. It exhibits very high capacity storage and good rate performance, making it an excellent cathode material for magnesium batteries.

Description

Technical Field

[0001] This invention belongs to the field of novel energy storage technology, specifically relating to a magnesium battery cycle stability enhancement material (specifically referring to a coral-like V2O5-based magnesium battery cathode material), its preparation method, and its application in magnesium batteries. Background Technology

[0002] In recent years, with the continuous exploration and development of clean and renewable energy (solar, wind, tidal, etc.), high-efficiency energy storage systems have attracted the attention of researchers. V₂O₅, due to its excellent performance, is widely used in various types of batteries, such as lithium-ion batteries and lead-acid batteries. As a positive electrode material in batteries, V₂O₅ possesses high specific capacity and superior cycle performance, showing broad application prospects in improving battery performance and lifespan. As a transition metal oxide, V₂O₅ is abundant, low-cost, and safe. Compared to other electrode materials, V₂O₅ boasts a specific capacity as high as 300 mAh / g, several times that of many other materials. Furthermore, during cycle testing at room temperature, V₂O₅ retains over 85% of its capacity.

[0003] V₂O₅ has been widely used in various novel battery fields in recent years, especially zinc-ion batteries, demonstrating excellent ion storage capabilities and exhibiting remarkable capacity and rate performance. Due to the diversity of V₂O₅ preparation methods, various morphologies have been developed, such as urchin-like, windmill-like, and fibrous spinnated forms. These morphologies optimize the electrochemical performance of batteries to some extent, and some even promote redox reactions through exposed active sites.

[0004] However, the low ion diffusion coefficient, low conductivity, and structural instability caused by repeated ion insertion / extraction of V2O5 cathode materials limit their application in metal-ion batteries. To address these issues, researchers have conducted a series of studies using modification methods such as morphology control, crystal structure modification, chemical pre-insertion, and composite with other materials. For example, Chinese invention patent CN118825249A discloses an amorphous carbon-coated three-dimensional porous cellular VO2 / V2O5 composite material, providing multiple active sites while being coated with carbon on the outer layer. The three-dimensional conductive network formed by their cross-linking effectively improves the ionic and electronic conductivity of the electrode system. CN118598186A discloses a V2O5 / H... x V₂O₅ composite cathode material, through proton insertion, expands the Zn content. 2+ The diffusion pathway weakens Zn 2+ The interaction with the V2O5 lattice improves the rate performance of aqueous zinc-ion batteries.

[0005] Among all research methods, improving the morphology of V₂O₅ is the simplest and most convenient way to enhance the electrochemical performance of batteries. By microscopically controlling the morphology during the preparation process, its ability to absorb metal ions is enhanced. Currently, researchers have improved the morphology through methods such as electrospinning, chemical vapor deposition, and hydrothermal treatment. However, V₂O₅ still suffers from drawbacks such as poor conductivity and structural instability, and sometimes even severe accumulation leading to structural collapse.

[0006] Therefore, developing a structurally stable and cost-effective preparation method remains a key area of ​​future research. Based on this, this application was developed. Summary of the Invention

[0007] To address the problems existing in traditional preparation methods, this invention proposes a method for preparing a magnesium battery cycle stability enhancement material. This method uses V₂O₅ nanomaterials prepared by a solvothermal method as the cathode material for magnesium batteries. These nanomaterials possess a highly porous structure and ion transport channels, with a three-dimensional size of only about 5 μm. This solves the problem of V₂O₅ nanosheet stacking and agglomeration in traditional preparation processes, effectively improving the surface activity state, exposing more active sites, and providing multiple short channel paths for rapid electron transfer, thus exhibiting excellent cycle stability.

[0008] The present invention also provides the above-mentioned magnesium battery cycle stability enhancement material and its application in magnesium batteries.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A method for preparing a magnesium battery cycle stability enhancement material includes the following steps:

[0011] 1) Dissolve an appropriate amount of vanadium source and surfactant in a mixed solution of isopropanol and diethylene glycol to obtain a colored solution A;

[0012] 2) Place solution A in a hydrothermal reactor and react it at 180~200 ℃ for 18~24 h; the filling ratio of the hydrothermal reactor is 60~70%;

[0013] 3) After hydrothermal reaction, the precursor powder material is obtained by washing and drying.

[0014] 4) After heating the precursor powder material to 400~500℃ and holding it for 1~5h, it is cooled to obtain a coral-like V2O5-based magnesium battery cathode material with exposed (110) crystal planes. Its diameter is 2~10 μm, its thickness is 5~10 nm, and its width is 30~100 nm.

[0015] Specifically, the vanadium source mentioned in step 1) is NH4VO3 and / or commercial V2O5 powder. The surfactant mentioned in step 1) is one or more of citric acid monohydrate (C6H8O7·H2O), polyvinylpyrrolidone (PVP), hexadecyltrimethylammonium bromide (CTAB), etc.

[0016] Furthermore, the mass ratio of the vanadium source and the surfactant mentioned in step 1) is 1:2~4.

[0017] Furthermore, in step 1), the volume ratio of isopropanol to diethylene glycol is 1:0.5~2. In step 1), a water bath at 100±15℃ can be used for heating and magnetic stirring until completely dissolved, and the magnetic stirring time is 1~1.5 h.

[0018] Furthermore, the hydrothermal temperature mentioned in step 2) is 180~200 ℃. Repeated experiments have proven that under this condition, V2O5 has the highest purity, the largest yield, the most stable structure, and the best morphology, making it the optimal process condition.

[0019] Specifically, in step 3), the precipitate is washed with ethanol 3 to 5 times, and then freeze-dried using freeze-drying technology. The precipitate is frozen in a refrigerator for 8 to 12 hours and then freeze-dried at −55±10 °C for 10 to 24 hours.

[0020] Furthermore, in step 4), the temperature is increased to the heating temperature in a muffle furnace at a heating rate of 5~10 °C / min.

[0021] This invention provides a magnesium battery cycle stability enhancement material (coral-like V2O5-based magnesium battery cathode material) prepared by the above method.

[0022] This invention also provides the application of the above-mentioned magnesium battery cycle stability enhancement material (coral-like V2O5-based magnesium battery cathode material) in magnesium batteries.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention utilizes a solvothermal method to prepare V2O5 nanomaterials as the cathode material for magnesium batteries. These nanomaterials possess a highly porous structure and ion transport channels, with a three-dimensional size of only about 5 μm. This solves the problem of V2O5 nanosheet stacking and agglomeration in traditional preparation processes, effectively improving surface activity, exposing more active sites, and providing multiple short pathways for rapid electron transfer, while simultaneously achieving efficient ion insertion / extraction. Furthermore, the exposed (110) crystal planes reduce interfacial side reactions between the electrode and electrolyte surfaces, significantly reducing the yield of the surface passivation film, thereby greatly increasing its storage capacity and exhibiting excellent cycle stability. In addition, this invention features a short preparation process, high production efficiency, high yield, large production volume, high product purity, fast preparation time, low cost, and good reproducibility, avoiding the problem of traditional sheet-like V2O5 stacking and agglomeration.

[0025] This invention employs coral-like V₂O₅ nanomaterials as the cathode material for magnesium batteries. Its open three-dimensional porous structure not only increases ion attachment sites but also provides multiple pathways for electron transfer. Furthermore, the exposed (110) crystal planes reduce interfacial side reactions between the electrode and electrolyte surfaces, and decrease the formation of passivation films on the electrode surface, thereby accelerating the redox reaction of the battery. It exhibits very high capacity storage and excellent rate performance, making it an excellent cathode material for magnesium batteries. Attached Figure Description

[0026] Figure 1 These are SEM images of the coral-like V2O5 nanomaterials prepared in Examples 1(a), 2(b), 3(c), and 4(d) of this invention.

[0027] Figure 2 This is a cross-sectional SEM image of the coral-like V2O5 obtained in Example 1 of this invention exposed under fracture conditions;

[0028] Figure 3 These are optical electron microscope images of precursors of different colors before calcination in Examples 1(a), 2(b), 3(c), and 4(d) of the present invention;

[0029] Figure 4 These are the X-ray diffraction patterns of the coral-like V2O5 nanomaterials obtained after calcination in Examples 1-4 of this invention.

[0030] Figure 5 The coral-like V₂O₅ nanomaterials prepared in Examples 1-4 of this invention are 50 mA g −1 Cyclic curves for the first 100 cycles at current density;

[0031] Figure 6 This is a rate performance graph of different current densities after 20 cycles of activation in Example 1 of the present invention. Detailed Implementation

[0032] 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.

[0033] In the following examples, all raw materials used are commercially available products that can be directly purchased or prepared using conventional techniques in the art. Room temperature refers to 25±5℃.

[0034] Example 1

[0035] 1) Dissolve 0.4 g of NH4VO3 and 1.2 g of CTAB in 60 mL of a mixed solution of isopropanol and diethylene glycol (volume ratio of isopropanol to diethylene glycol is 1:1), heat in a water bath to 100 °C, and stir magnetically for 1 h until completely dissolved to obtain a gray-blue solution.

[0036] 2) Place the solution in a hydrothermal reactor at a hydrothermal temperature of 200 ℃ for 24 h, with a filling ratio of 60%;

[0037] 3) After the reaction was completed, the precipitate was centrifuged and washed three times with ethanol. Then it was frozen in a refrigerator for 12 hours and freeze-dried in a freezer at −55 °C and a vacuum of 1 Pa for 24 hours to obtain a dark purple precursor powder material.

[0038] 4) The precursor material was heated in a muffle furnace at 5 °C for 1 min. −1 The temperature was increased to 400 °C at a heating rate of 0.5, and then kept in air for 2 h before being cooled to room temperature in the furnace to obtain orange-yellow coral-like V2O5 with an average diameter of 5 μm.

[0039] Example 2

[0040] 1) Dissolve 0.4 g of NH4VO3 and 1.2 g of PVP in 60 mL of a mixed solution of isopropanol and diethylene glycol (volume ratio of isopropanol to diethylene glycol is 1:1), heat in a water bath to 100 °C, and stir magnetically for 1 h until completely dissolved to obtain a grayish-brown solution.

[0041] 2) Place the solution in a hydrothermal reactor at a hydrothermal temperature of 200 ℃ for 24 h, with a filling ratio of 60%;

[0042] 3) After the reaction was completed, the precipitate was centrifuged and washed three times with ethanol. Then it was placed in a refrigerator and frozen for 12 hours. It was then freeze-dried in a freezer at −55 °C and a vacuum of 1 Pa for 24 hours to obtain a light purple precursor powder material.

[0043] 4) The precursor material was heated in a muffle furnace at 5 °C for 1 min. −1The temperature was increased to 400 °C at a heating rate of 0.5, and then kept in air for 2 h before being cooled to room temperature in the furnace to obtain orange-yellow coral-like V2O5 with an average diameter of 5 μm.

[0044] Example 3

[0045] 1) Dissolve 0.4 g of commercial V2O5 powder and 1.2 g of C6H8O7·H2O in 60 mL of a mixed solution of isopropanol and diethylene glycol (volume ratio of isopropanol to diethylene glycol is 1:1), heat in a water bath to 100 °C, and stir magnetically for 1 h until completely dissolved to obtain a dark blue solution.

[0046] 2) Place the solution in a hydrothermal reactor at a hydrothermal temperature of 200 ℃ for 24 h, with a filling ratio of 60%;

[0047] 3) After the reaction was completed, the precipitate was centrifuged and washed three times with ethanol. Then it was placed in a refrigerator and frozen for 12 hours. It was then freeze-dried in a freezer at −55 °C and a vacuum of 1 Pa for 24 hours to obtain a dark gray precursor powder material.

[0048] 4) The precursor material was heated in a muffle furnace at 5 °C for 1 min. −1 Heated to 400 °C at a heating rate of 0.5, held in air for 2 h, and then cooled to room temperature in the furnace to obtain orange-yellow coral-like V2O5 with an average diameter of 4 μm.

[0049] Example 4

[0050] 1) Dissolve 0.4 g of NH4VO3 and 1.2 g of C6H8O7·H2O in 60 mL of a mixed solution of isopropanol and diethylene glycol (volume ratio of isopropanol to diethylene glycol is 1:1), heat in a water bath to 100 °C, and stir magnetically for 1 h until completely dissolved to obtain an orange-yellow solution.

[0051] 2) Place the solution in a hydrothermal reactor at a hydrothermal temperature of 200 ℃ for 24 h, with a filling ratio of 60%;

[0052] 3) After the reaction was completed, the precipitate was centrifuged and washed three times with ethanol. Then it was placed in a refrigerator and frozen for 12 hours. It was then freeze-dried in a freezer at −55 °C and a vacuum of 1 Pa for 24 hours to obtain a light purple precursor powder material.

[0053] 4) The precursor material was heated in a muffle furnace at 5 °C for 1 min. −1 The temperature was increased to 400 °C at a heating rate of 0.5, and then kept in air for 2 h before being cooled to room temperature in the furnace to obtain orange-yellow coral-like V2O5 with an average diameter of 5 μm.

[0054] Figure 1 The figures show a comparison of scanned images from Examples 1-4 of this invention. As can be seen from the figures: Example 1 yielded an average yield of 483 mg of V₂O₅ nanomaterials with an average diameter of 5 μm; Example 2 yielded an average yield of 285 mg of coral-like V₂O₅ nanomaterials with an average diameter of 5 μm; Example 3 yielded an average yield of 278 mg of coral-like V₂O₅ nanomaterials with an average diameter of 4 μm; and Example 4 yielded an average yield of 250 mg of coral-like V₂O₅ nanomaterials with an average diameter of 5 μm. The stable coral-like V₂O₅ structure effectively improves the surface activity state, exposes more active sites, and provides multiple short channel paths for rapid electron transfer, achieving efficient ion insertion / extraction.

[0055] Figure 2 The image shows a scanned cross-section of a broken coral-like V₂O₅ structure from Example 1. As can be seen from the image, it is composed of many branches with a uniform morphology, radiating outwards from the center. A small hollow sphere exists at the center, a structure that more easily accommodates ions, enabling rapid charge transport.

[0056] Figure 3 The images shown are optical electron microscope (OSM) images of the precursor powders in Examples 1-4 before calcination. The results show that Example 1 is dark purple, Example 2 is light purple, Example 3 is dark gray, and Example 4 is the lightest in color, but still shows a purple hue.

[0057] Figure 4 The images show the XRD patterns after calcination of Examples 1-4. Example 1 exhibits the highest peak intensity and best crystallinity, while also exposing a specific (110) crystal plane. Example 2 exposes the (001) crystal plane, with slightly weaker crystallinity. Examples 3 and 4 also show the strongest (110) crystal planes, but Example 4 has slightly weaker crystallinity. Exposing more (110) crystal planes indicates more active sites, minimal passivation film formation, and minimal impact from interfacial side reactions between the electrode and electrolyte surfaces, which is beneficial to the electrochemical performance of the battery.

[0058] To verify that the above method can obtain coral-like V2O5 nanomaterials with excellent performance, the coral-like V2O5 nanomaterial sample obtained in Example 1 was prepared as the positive electrode material of a magnesium battery, with magnesium foil as the negative electrode, and assembled into a 2032 coin cell. Its electrochemical performance was tested in the voltage range of 0.1 ~ 1.9 V.

[0059] The manufacturing process of the battery electrode is as follows: The above-mentioned coral-like V2O5 nanomaterials, conductive carbon black, and binder PVDF are uniformly mixed at a mass ratio of 7:2:1, and the organic solvent N-methylpyrrolidone 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.

[0060] The electrolyte preparation process is as follows: First, add 6 ml of anhydrous tetrahydrofuran (THF≥99.9%) to beaker 1, weigh 0.534 g of anhydrous AlCl3, add it to the beaker, and stir continuously. Then, add 4 ml of 2 mol / L phenyl magnesium chloride solution to beaker 2. Next, use a dropper to add the liquid from beaker 2 dropwise to beaker 1, and continue stirring for 16 hours to obtain an APC solution. Weigh 0.4239 g of LiCl and measure 5 ml of THF into a beaker. After stirring until completely dissolved, add 5 ml of the prepared APC solution dropwise, mix, and stir for 12 hours to obtain a mixed electrolyte.

[0061] Figure 5 The figures shown are from Examples 1-4 at 50 mA g. −1 Charge-discharge cycle curves at current density. Results show that after 100 cycles, the capacity of Example 1 remained at 102.4 mAh g⁻¹. −1 It has the highest capacity retention rate.

[0062] Figure 6 The graph shows the rate performance of Example 1 and commercial V2O5 after 20 cycles of activation at different current densities. The results show that at 500 mA g −1 Even at high current densities, Example 1 still maintains 78.9 mAh g⁻¹. −1 Its capacity is much higher than that of commercial V2O5, demonstrating its excellent rate performance.

[0063] In summary, compared with existing technologies, the preparation method of this invention is efficient and rapid. The prepared V2O5 product has a super-porous structure and ion transport channels, solving the problem of V2O5 nanosheet stacking and agglomeration in traditional preparation processes. This effectively improves the surface activity state, exposes more active sites, and provides multiple and short channel paths for rapid electron transfer, while achieving efficient ion insertion and extraction. In addition, the exposed (110) crystal plane can reduce interfacial side reactions between the electrode and electrolyte surfaces, resulting in a significant reduction in the yield of the surface passivation film. As a cathode material for magnesium batteries, its storage capacity is greatly improved, and it exhibits excellent cycle stability.

Claims

1. A method for preparing a magnesium battery cycle stability enhancement material, characterized in that, Includes the following steps: 1) Dissolve an appropriate amount of vanadium source and surfactant in a mixed solution of isopropanol and diethylene glycol to obtain solution A; 2) React solution A hydrothermally at 180~200 ℃ for 18~24 h; 3) After hydrothermal reaction, the precursor powder material is obtained by washing and drying. 4) Heat the precursor powder material to 400~500℃ and hold for 2 hours, then cool to obtain the product; The vanadium source mentioned in step 1) is NH4VO3 and / or commercial V2O5 powder; The surfactant mentioned in step 1) is one or more of citric acid monohydrate, polyvinylpyrrolidone, and hexadecyltrimethylammonium bromide; The prepared material is coral-like V2O5 with an average diameter of 5 μm; The coral-like V₂O₅ was used as the positive electrode material for a magnesium battery, and magnesium foil was used as the negative electrode. These were assembled into a 2032-type coin cell and tested at 50 mA g⁻¹. -1 After 100 charge-discharge cycles at the current density, the capacity remained at 102.4 mAh g⁻¹. -1 ;at 500 mA g -1 Even at high current densities, it can still maintain 78.9 mAh g⁻¹. -1 The capacity.

2. The preparation method according to claim 1, characterized in that, The mass ratio of vanadium source to surfactant in step 1) is 1:2~4.

3. The preparation method according to claim 1, characterized in that, In step 1), the volume ratio of isopropanol to diethylene glycol is 1:0.5~2.

4. The preparation method according to claim 1, characterized in that, In step 1), heat the mixture in a water bath at 100±15 ℃ and stir magnetically until completely dissolved. The stirring time is 1~1.5 h.

5. The preparation method according to claim 1, characterized in that, In step 3), the precipitate is washed with ethanol 3 to 5 times, then frozen in a refrigerator for 8 to 12 hours, and then freeze-dried at -55±10 ℃ for 10 to 24 hours.

6. The preparation method according to claim 1, characterized in that, In step 4), the temperature is increased to the heating temperature in a muffle furnace at a heating rate of 5~10 °C / min.

7. A magnesium battery cycle stability enhancement material prepared by any one of the methods described in claims 1 to 6.

8. The application of the magnesium battery cycle stability enhancement material according to claim 7 in magnesium batteries.

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