Vanadium oxide-based aqueous zinc ion battery, performance optimization method and positive electrode material

Abstract

The application belongs to the technical field of nanometer material preparation, and discloses a vanadium oxide-based aqueous zinc ion battery, a performance optimization method and a positive electrode material. The VO2 powder is treated by using a specific method, small molecule coupled VO2 (M-VO2) is obtained on the basis of pure VO2, and is used as a positive electrode material of the aqueous zinc ion battery, so that the cycle stability and specific capacity of the VO2 as the positive electrode material of the aqueous zinc ion battery are better. The cycle stability and specific capacity of the VO2-based aqueous zinc ion battery are successfully improved, and the development of the aqueous zinc ion battery is greatly influenced. The method is relatively simple, only needs to add one step in the preparation process, does not need complex equipment and large power consumption, and has simple and controllable process, low requirement on operators, low cost, and easy industrial production. The cycle stability of the VO2 treated by the small molecule as the positive electrode material of the aqueous zinc ion battery is greatly improved compared with that of the pure VO2.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nanomaterial preparation and application in new energy storage devices, and particularly relates to a vanadium oxide-based aqueous zinc ion battery, a performance optimization method and a positive electrode material, especially a vanadium oxide-based aqueous zinc ion battery with improved cycle stability and mass specific capacity performance. BACKGROUND

[0002] Lithium ion batteries have always occupied a very high market share in the past few decades due to their excellent energy density and cycle stability, and aqueous zinc ion batteries have gradually become a promising candidate due to their excellent theoretical capacity and high safety. Similar to other ion batteries, the main factor restricting the performance of zinc ion batteries is the positive electrode material. The most advanced zinc ion batteries in recent years are concentrated in VO2 or V2O5-based materials. Vanadium-based materials have excellent electrochemical activity and are suitable for zinc ion intercalation and deintercalation, so as to achieve high capacity and energy density.

[0003] At present, vanadium oxide is mostly used as the cathode material of the aqueous zinc ion secondary battery. The structure of this material is unstable, and the ion intercalation and deintercalation capacity is limited. Irreversible phase change may occur in multiple cycle tests, which ultimately leads to low energy density of the battery, poor cycle life and other shortcomings. Therefore, it is of great research value and application prospect to develop a VO2 with improved VO2 structure stability, electrical conductivity and strong zinc ion storage capacity.

[0004] Through the above analysis, the problems and defects of the prior art are that there are three methods commonly used to improve the performance of vanadium-based zinc ion batteries in the reports. First, metal ions are pre-intercalated or doped between the VO2 layers. This method can increase and stabilize the interlayer spacing of the crystal material, thereby ensuring that Zn 2+ There is enough space for intercalation and deintercalation during the charging and discharging of the battery, which ultimately improves the stability. However, this method cannot control the doping degree during the material preparation process, and the process parameters are difficult to explore. The second method is to composite VO2 with carbon nanotubes, graphene oxide and the like. This method can improve the electrical conductivity and ion transport capacity of the composite material, and can improve the electrochemical performance. However, these carbon materials are expensive, the preparation process is complex, and the energy and heat consumption is large. The third method is in-situ phase transformation self-conversion, that is, the electrode material gradually undergoes phase transformation during electrochemical charging and discharging, and finally forms another compound to act as an electrode material. However, the degree and process of phase transformation in this method are often uncontrollable.

[0005] The significance of solving the above problems and defects is that according to the three methods of improving the performance of the battery described above, the above problems can be solved to control the battery cost, reduce the energy consumption, meet the development trend of the new energy field, and easily realize the industrial production of new technologies and new processes. The vanadium oxide-based aqueous zinc ion battery, performance optimization method and positive electrode material provided by the application have obvious battery performance improvement effect, simple preparation process, very low raw material cost, easy mass production, and according to the comparison of different methods in the literature, the process and the result of the application are very excellent. SUMMARY

[0006] In view of the problems or defects of the prior art, the purpose of the application is to provide a vanadium oxide-based aqueous zinc ion battery, a performance optimization method and a positive electrode material. The M-VO2 prepared by the method of the application has a near-amorphous structure with high electrical conductivity, which is very beneficial to the insertion and extraction of zinc ions during the charging and discharging process, and exhibits better electrochemical performance than VO2. Moreover, the preparation method is simple and easy to realize industrial production, and the performance improvement is very significant.

[0007] In order to achieve the above purpose of the application, the technical scheme adopted by the application is as follows: a performance optimization method of a VO2-based aqueous zinc ion battery, specifically comprising the following steps:

[0008] 1. VO2 is prepared by using a hydrothermal method, that is, a precursor solution is obtained by using V2O5 and oxalic acid;

[0009] 2. Hydrothermal reaction is carried out, the precursor solution is transferred into a polytetrafluoroethylene liner and sealed in a stainless steel kettle, and the kettle is placed in a drying box;

[0010] 3. Small molecules are used to treat VO2, and the treatment steps are to mix a specific amount of small molecule powder with the VO2 suspension obtained by hydrothermal method, heat and stir for several minutes;

[0011] 4. Filtration, using a filtration device to filter the suspension into powder, drying in a nitrogen environment to obtain M-VO2 as the positive electrode material of the aqueous zinc ion battery;

[0012] 5. Preparation of electrode, the dried powder is mixed with a dispersing liquid in a certain proportion, uniformly coated on a current collector, dried in a drying box, and ready for use;

[0013] 6. Packaging and testing, preparing 2M ZnSO4 or 3M Zn(CF3SO3)2 as electrolyte, zinc foil as negative electrode, M-VO2 as positive electrode, and testing the charge-discharge curve and cycle performance respectively.

[0014] Furthermore, the precursor solution is prepared by mixing V2O5 and oxalic acid in a molar ratio of 1:9 to 9:1 in 10 to 500 mL of deionized water and stirring for 10 to 200 minutes to obtain a precursor solution for standby use;

[0015] Furthermore, the hydrothermal reaction is carried out in a drying oven at 100-200° C. for 12-90 hours;

[0016] Further, the precursor solution is transferred into a polytetrafluoroethylene liner, and 10% to 90% of the volume of the precursor solution is added into the polytetrafluoroethylene liner;

[0017] The small molecule is a benzene ring, five-membered or six-membered heterocyclic small molecule with an R substituent, such as one or more of tyrosine, maleic anhydride, sucrose, ascorbic acid, phenylpropionic acid, N,N-dimethylbenzamide, sodium benzoate, sodium ascorbate, and phenylglycine.

[0018] -R can be one or more of =O, -OH, -SH, ≡CN, -NH2, -CONH2.

[0019] Furthermore, the specific mass of small molecule powder is added in an amount of 0.1 to 1 g per 100 ml of suspension;

[0020] The heating and stirring conditions are as follows: the small molecule powder is mixed with the VO2 suspension, and placed in a constant temperature water bath at 30 to 90° C. under the protection of an inert gas, and heated and stirred for 0.5 to 8 hours.

[0021] Furthermore, the dispersion is a liquid prepared by using deionized water and ethanol in a volume ratio of 4:1 as solvents and acetylene black and PTFE emulsion as solutes, and the concentration of acetylene black and PTFE is 5 mg / ml.

[0022] Furthermore, the current collector is one of foam nickel, stainless steel mesh, and carbon cloth, and is a disc with a diameter of 1.2 cm.

[0023] Another object of the present invention is to provide a positive electrode material M-VO2 for improving the performance of aqueous zinc ion batteries, which is prepared using the performance optimization method of VO2-based aqueous zinc ion batteries.

[0024] Another object of the present invention is to provide an aqueous zinc ion battery prepared using the positive electrode material M-VO2.

[0025] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows:

[0026] The present invention provides a method for optimizing the performance of VO2-based aqueous zinc-ion batteries. This method is relatively simple, requiring only an additional step in the preparation process, eliminating the need for complex equipment and high power consumption. The process is simple and controllable, with low operator requirements and low costs, making it easy to implement industrial production. Using VO2 treated with small molecules as the positive electrode material for aqueous zinc-ion batteries significantly improves the cycle stability compared to pure VO2, and significantly increases the specific mass capacity at various current densities, bringing profound implications for the development of aqueous zinc-ion batteries.

[0027] The M-VO2 cathode prepared by the present invention is used in aqueous zinc ion battery devices. The electrochemical performance test shows that the cycle stability is as follows: Figure 7 As shown, after 3000 cycles of charge and discharge, 77% of the initial capacity is retained. The rate performance is shown in Figure 8 As shown, both showed that M-VO2 had significantly improved stability compared to pure VO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a flow chart of a method for optimizing the performance of a VO2-based aqueous zinc-ion battery according to an embodiment of the present invention.

[0029] Figure 2 Actual photos of VO2 and M-VO2 electrode material powders prepared in Examples 1 and 2 of the present invention;

[0030] Figure 3 This is a photo of the M-VO2 electrode prepared in Example 2 of the present invention;

[0031] Figure 4 This is a scanning electron microscope photograph of the VO2 electrode material powder prepared in Example 1 of the present invention;

[0032] Figure 5 This is a scanning electron microscope photograph of the M-VO2 electrode material powder prepared in Example 2 of the present invention;

[0033] Figure 6 XRD patterns of the VO2 and M-VO2 electrode material powders prepared in Examples 1 and 2 of the present invention, including a standard peak card for VO2;

[0034] Figure 7 The VO2 and M-VO2 electrode materials prepared in Examples 1 and 2 of the present invention are used as aqueous zinc ion batteries at 10Ag -1 Comparison chart of performance test after 3000 cycles at current density;

[0035] Figure 8 Comparison of the performance of aqueous zinc-ion batteries using VO2 and M-VO2 electrode materials prepared in Examples 1 and 2 of the present invention at different current densities;

[0036] Figure 9 XPS spectrum of oxygen element of VO2 and M-VO2 electrode material powder prepared for the embodiment 4 of the present application;

[0037] Figure 10 XPS spectrum of vanadium element of VO2 and M-VO2 electrode material powder prepared for the embodiment 4 of the present application;

[0038] Figure 11 Non-in-situ XRD spectrum of VO2 and M-VO2 electrode prepared for the embodiment 4 of the present application after cycling. DETAILED DESCRIPTION

[0039] The present application will be described in detail below with reference to the drawings and embodiments, and the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0040] As shown in the formula (I), the performance optimization method of the VO2-based aqueous zinc ion battery provided by the embodiment of the present application comprises: Figure 1

[0041] S101, using V2O5 and oxalic acid as precursors, using polytetrafluoroethylene as the inner container of the hydrothermal reaction pressure device, and using a hydrothermal method to prepare VO2.

[0042] S102, mixing a small molecule powder M with the VO2 suspension for treatment, and heating, stirring and drying to obtain treated M-VO2.

[0043] S103, using a stainless steel mesh as a current collector, a zinc sheet as a negative electrode, glass fiber as a separator, and ZnSO4 or Zn(CF3SO3)2 as an electrolyte, and packaging into a button cell.

[0044] In step S101, the precursor is obtained by adding V2O5 and oxalic acid in a molar ratio of 1:9 to 9:1 into 10 to 500 mL of deionized water and stirring for 10 to 200 minutes.

[0045] In step S101, the hydrothermal method is to add 10% to 90% of the precursor solution by volume into the polytetrafluoroethylene inner container, and the hydrothermal time and temperature are one of 12 to 90 hours and 100 to 200°C.

[0046] In step S102, the small molecule is a benzene ring, a five-membered or six-membered heterocyclic small molecule with R substituents, such as one or more of histidine, butenedioic anhydride, sucrose, ascorbic acid, phenylalanine, N,N'-dimethylbenzamide, sodium benzoate, sodium ascorbate, and phenylglycine. ​

[0047] -R can be one or more of =O, -OH, -SH, ≡CN, -NH2, -CONH2.

[0048] In step S102, the mass of the small molecule powder is 0.1-1 g per 100 ml of suspension.

[0049] In step S102, the mixing treatment steps are as follows: mixing the small molecule powder with the VO2 suspension, placing it in a constant temperature water bath at 30 to 90°C under the protection of an inert gas, heating and stirring for 0.5 to 8 hours.

[0050] The present invention also provides a prepared positive electrode material M-VO2 for improving the performance of aqueous zinc ion batteries.

[0051] The present invention also provides a prepared positive electrode material M-VO2 for use in aqueous zinc-ion batteries to improve the performance of VO2-based aqueous zinc-ion batteries, including cycle stability and mass specific capacity.

[0052] The present invention will be further described below with reference to specific embodiments.

[0053] Example 1

[0054] This case is about preparing pure VO2 and using it as the positive electrode of aqueous zinc-ion batteries.

[0055] (1) Preparation of precursor solution

[0056] Weigh 1 mmol of anhydrous oxalic acid and place it in a 100 ml beaker. Add 35 ml of deionized water to the beaker and stir magnetically until the oxalic acid is completely dissolved. Then weigh 6 mmol of V2O5 and transfer it to the beaker. Stir magnetically at room temperature until it dissolves.

[0057] (2) Hydrothermal reaction

[0058] The precursor solution was transferred into a 100 ml polytetrafluoroethylene liner and sealed in a stainless steel Teflon autoclave. The autoclave was then placed in a 120°C drying oven for hydrothermal reaction for 18 h. After the reaction was completed, the solution was cooled to room temperature to obtain a VO2 suspension for later use.

[0059] (3) Filter and dry

[0060] The VO2 suspension was filtered out using a suction device and washed three times with deionized water and ethanol respectively. The filter paper and the powder were transferred to a tube furnace at 120°C with nitrogen and dried for 48 hours. The VO2 powder was taken out and set aside.

[0061] (4) Preparation of electrodes

[0062] First, prepare the dispersion: take 10ml of deionized water and 40ml of anhydrous ethanol, transfer them to a 100ml beaker, weigh 250mg of acetylene black and 417mg of PTFE emulsion (60wt%) and add them to the beaker respectively. After vigorous shaking, put it in an ultrasonic machine for 12h for later use; take 2mg of VO2 powder and mix it with 50μl of dispersion and grind it thoroughly to form an electrode slurry. Then, coat the slurry on the current collector and finally put it in a drying oven at 120℃ for 12h for later use;

[0063] (5) Packaging test

[0064] Prepare 2M ZnSO4 or 3M Zn(CF3SO3)2 as the electrolyte, zinc foil as the negative electrode, and the electrode obtained in step 4 as the positive electrode, and test the charge-discharge curves and cycle performance respectively.

[0065] The actual photo of the VO2 powder, a positive electrode material for aqueous zinc ion batteries, obtained in this embodiment is shown in FIG. Figure 2 The actual photo of the electrode prepared from VO2 powder is shown in Figure 3 As shown, the scanning electron microscope photo of VO2 powder is as follows Figure 4 As shown in Figure 2, these nanosheets are in the shape of flowers, which shows an increased specific surface area and is more conducive to the redox reaction between the cathode material and the ions in the electrolyte. Figure 6 As shown, it matches the VO2 standard card.

[0066] The VO2 positive electrode prepared in this embodiment is used for aqueous zinc ion battery devices. After electrochemical performance testing, the cycle stability obtained is as follows: Figure 7 As shown, after 3000 cycles of charge and discharge, 51% of the initial capacity is retained. The rate performance is as follows Figure 8 As shown, both exhibit poor stability of VO2 and low gravimetric capacity.

[0067] Example 2

[0068] This case is the preparation of small molecule-treated VO2 (M-VO2) and its use as the positive electrode of aqueous zinc-ion batteries.

[0069] (1) Preparation of precursor solution

[0070] Weigh 1 mmol of anhydrous oxalic acid and place it in a 100 ml beaker. Add 35 ml of deionized water to the beaker and stir magnetically until the oxalic acid is completely dissolved. Then weigh 6 mmol of V2O5 and transfer it to the beaker. Stir magnetically at room temperature until it dissolves.

[0071] (2) Hydrothermal reaction

[0072] The precursor solution was transferred into a 100 ml polytetrafluoroethylene liner and sealed in a stainless steel Teflon autoclave. The autoclave was then placed in a 120°C drying oven for hydrothermal reaction for 18 h. After the reaction was completed, the solution was cooled to room temperature to obtain a VO2 suspension for later use.

[0073] (3) Using small molecules to treat VO2

[0074] Transfer the VO2 suspension obtained in step 2 into a three-necked flask, weigh 0.1 g of tyrosine and mix thoroughly. Then, place the three-necked flask in a 90°C water bath and heat with magnetic stirring. Add nitrogen gas at a constant rate through one of the three-necked flask openings. After reacting for several hours, cool and set aside.

[0075] (4) Filter and dry

[0076] The product obtained in step 3 was filtered to remove the liquid using a suction filtration device, and washed with deionized water and ethanol three times respectively. The filter paper and the powder were transferred to a tube furnace at 120°C and passed through nitrogen to dry for 12 hours. The M-VO2 powder was taken out and set aside.

[0077] (5) Preparation of electrodes

[0078] First, prepare the dispersion: take 10ml of deionized water and 40ml of anhydrous ethanol, transfer them to a 100ml beaker, weigh 250mg of acetylene black and 417mg of PTFE emulsion (60wt%) and add them to the beaker respectively. After vigorous shaking, put it in an ultrasonic machine for 12h for later use; take 2mg of VO2 powder and mix it with 50μl of dispersion and grind it thoroughly to form an electrode slurry. Then, coat the slurry on the current collector and finally put it in a drying oven at 120℃ for 12h for later use;

[0079] (6) Packaging test

[0080] Prepare 2M ZnSO4 or 3M Zn(CF3SO3)2 as the electrolyte, zinc foil as the negative electrode, and the electrode obtained in step 5 as the positive electrode, and test the charge and discharge curves and cycle performance respectively.

[0081] The actual photo of the positive electrode material M-VO2 powder for aqueous zinc ion batteries obtained in this example is as follows Figure 2 As shown, the scanning electron microscope image of M-VO2 powder is as follows Figure 5 As shown in Figure 2, these nanosheets exhibit an increased specific surface area, which is more conducive to the redox reaction between the cathode material and the ions in the electrolyte. The X-ray diffraction peaks of M-VO2 powder are as follows: Figure 6 As shown, there is a peak shift compared to the VO2 standard card.

[0082] The M-VO2 cathode prepared in this embodiment is used for aqueous zinc ion battery devices. The electrochemical performance test shows that the cycle stability is as follows: Figure 7 As shown, after 3000 cycles of charge and discharge, 77% of the initial capacity is retained. The rate performance is shown in Figure 8 As shown, both showed that M-VO2 had significantly improved stability compared to pure VO2.

[0083] Example 3

[0084] A method for optimizing the performance of a VO2-based aqueous zinc ion battery, the method specifically comprising the following steps:

[0085] 1. VO2 is prepared by hydrothermal method, i.e., a precursor solution is obtained by using V2O5 and oxalic acid;

[0086] 2. Carry out hydrothermal reaction, transfer the precursor solution into a polytetrafluoroethylene liner and seal it in a stainless steel kettle, and place it in a drying oven;

[0087] 3. Treating VO2 with small molecules involves mixing a specific mass of small molecule powder with a hydrothermally obtained VO2 suspension, heating and stirring for several minutes.

[0088] 4. Filter the suspension into powder using a filtration device, and dry it under a nitrogen environment to obtain the M-VO2 positive electrode material for aqueous zinc ion batteries of the present invention;

[0089] 5. Prepare the electrode by mixing the dried powder with the dispersion in proportion, evenly coating it on the current collector, and drying it in a drying oven for later use;

[0090] 6. For packaging test, prepare 2M ZnSO4 or 3M Zn(CF3SO3)2 as electrolyte, zinc foil as negative electrode, and M-VO2 as positive electrode, and test the charge-discharge curve and cycle performance respectively.

[0091] The precursor solution is prepared by mixing V2O5 and oxalic acid in a molar ratio of 1:9 to 9:1 in 10 to 500 mL of deionized water and stirring for 10 to 200 minutes to obtain a precursor solution for later use;

[0092] The hydrothermal reaction is carried out in a drying oven at 100-200° C. for 12-90 hours.

[0093] The precursor solution is transferred into a polytetrafluoroethylene liner, and 10% to 90% of the volume of the precursor solution is added into the polytetrafluoroethylene liner;

[0094] The small molecule is a benzene ring, five-membered or six-membered heterocyclic small molecule with an R substituent, such as one or more of tyrosine, maleic anhydride, sucrose, ascorbic acid, phenylpropionic acid, N,N-dimethylbenzamide, sodium benzoate, sodium ascorbate, and phenylglycine.

[0095] -R can be one or more of =O, -OH, -SH, ≡CN, -NH2, -CONH2.

[0096] The specific mass of small molecule powder is added in an amount of 0.1 to 1 g per 100 ml of suspension;

[0097] The heating and stirring conditions are as follows: the small molecule powder is mixed with the VO2 suspension, and placed in a constant temperature water bath at 30 to 90° C. under the protection of an inert gas, and heated and stirred for 0.5 to 8 hours.

[0098] The dispersion is a liquid prepared by using deionized water and ethanol in a volume ratio of 4:1 as solvents and acetylene black and PTFE emulsion as solutes. The concentration of acetylene black and PTFE is 5 mg / ml.

[0099] The current collector is one of foam nickel, stainless steel mesh, and carbon cloth, and is a disc with a diameter of 1.2 cm.

[0100] Example 4

[0101] This case is the preparation of small molecule-treated VO2 (M-VO2) and its use as the positive electrode of aqueous zinc-ion batteries.

[0102] (1) Preparation of precursor solution

[0103] Weigh 1 mmol of anhydrous oxalic acid and place it in a 100 ml beaker. Add 35 ml of deionized water to the beaker and stir magnetically until the oxalic acid is completely dissolved. Then weigh 6 mmol of V2O5 and transfer it to the beaker. Stir magnetically at room temperature until dissolved. Add 1 g of tyrosine and dissolve it.

[0104] (2) Hydrothermal reaction

[0105] The precursor solution was transferred into a 100 ml polytetrafluoroethylene liner and sealed in a stainless steel Teflon autoclave. The autoclave was then placed in a 120°C drying oven for hydrothermal reaction for 18 h. After the reaction was completed, the solution was cooled to room temperature to obtain a VO2 suspension for later use.

[0106] (3) Filter and dry

[0107] The product obtained in step 2 was filtered out of the liquid using a suction filtration device, and washed with deionized water and ethanol three times respectively. The filter paper and the powder were transferred to a tube furnace at 120°C and passed through nitrogen to dry for 12 hours. The M-VO2 powder was taken out and set aside.

[0108] (4) Preparation of electrodes

[0109] First, prepare the dispersion: take 10ml of deionized water and 40ml of anhydrous ethanol, transfer them to a 100ml beaker, weigh 250mg of acetylene black and 417mg of PTFE emulsion (60wt%) and add them to the beaker respectively. After vigorous shaking, put it in an ultrasonic machine for 12h for later use; take 2mg of VO2 powder and mix it with 50μl of dispersion and grind it thoroughly to form an electrode slurry. Then, coat the slurry on the current collector and finally put it in a drying oven at 120℃ for 12h for later use;

[0110] (5) Packaging test

[0111] Prepare 2M ZnSO4 or 3M Zn(CF3SO3)2 as the electrolyte, zinc foil as the negative electrode, and the electrode obtained in step 4 as the positive electrode, and test the charge-discharge curves and cycle performance respectively.

[0112] The actual photo of the positive electrode material M-VO2 powder for aqueous zinc ion batteries obtained in this example is as follows Figure 2 As shown, the scanning electron microscope image of M-VO2 powder is as follows Figure 5 As shown in Figure 2, these nanosheets exhibit an increased specific surface area, which is more conducive to the redox reaction between the cathode material and the ions in the electrolyte. The X-ray diffraction peaks of M-VO2 powder are as follows: Figure 6 As shown, there is a peak shift compared to the VO2 standard card.

[0113] The M-VO2 cathode prepared in this embodiment is used for aqueous zinc ion battery devices. The electrochemical performance test shows that the cycle stability is as follows: Figure 7 As shown, after 3000 cycles of charge and discharge, 77% of the initial capacity is retained. The rate performance is shown in Figure 8 As shown, both showed that M-VO2 had significantly improved stability compared to pure VO2.

[0114] Example 5

[0115] Demonstration of a method for optimizing the performance of a VO2-based aqueous zinc-ion battery, the method specifically comprising the following steps:

[0116] 1. Use XRD to perform X-ray diffraction analysis on pure VO2 and M-VO2 to obtain the XRD diffraction patterns of the two, such as Figure 6 As shown in the figure, the diffraction peak intensity indicates that M-VO2 is less crystalline than pure VO2, exhibiting a near-amorphous structure. Compared to pure VO2, the main peak of M-VO2 is shifted to the right by 0.1-0.4 degrees. As reported in the literature, electrode materials with weak crystallinity often outperform those with strong crystallinity.

[0117] 2. Use XPS to analyze the valence state of O element in pure VO2 and M-VO2, and obtain the XPS spectra of the two, such as Figure 9 As shown. Oxygen vacancies O d It can be seen from the area ratio that the oxygen vacancies in M-VO2 account for a high proportion, that is, oxygen vacancies can be introduced into VO2 after small molecule treatment, which can make the material show a strong Zn 2+ adsorption capacity, thereby optimizing the electrochemical performance of the device.

[0118] 3. Use XPS to analyze the valence state of V element in pure VO2 and M-VO2, and obtain the XPS spectra of the two, such as Figure 10 As shown in the figure, after being treated with small molecules, V 3+ According to previous reports, the emergence of mixed valence states can significantly improve the electrochemical performance of materials.

[0119] 4. Figure 7 The two batteries were disassembled after the intermediate cycle, and the two different electrodes were rinsed in deionized water and anhydrous ethanol, respectively, and then dried for XRD characterization.

[0120] 5. Use XRD to perform non-in-situ X-ray diffraction analysis on pure VO2 and M-VO2, and obtain the XRD diffraction patterns of the two after recycling, such as Figure 11 As shown in the figure, the standard peak card for by-products is included. The peak intensity shows that after the charge and discharge cycles of VO2 treated with small molecules, the accumulation of by-products is significantly reduced, ultimately achieving excellent cycling stability.

[0121] This invention primarily utilizes a specific method to treat VO2 powder, producing small-molecule coupled VO2 (M-VO2) from pure VO2 for use as a cathode material in aqueous zinc-ion batteries. The resulting material exhibits cycle stability and specific capacity superior to VO2 as a cathode material for aqueous zinc-ion batteries. The method is as follows: ① VO2 is prepared using a hydrothermal method, whereby V2O5 and oxalic acid in a molar ratio of 1:9 to 9:1 are added to 10 to 500 mL of deionized water and stirred for 10 to 200 minutes to obtain a precursor solution, which is then hydrothermally heated. ② The prepared VO2 is treated with small-molecule powder by mixing a specific mass of small-molecule powder with a hydrothermally obtained VO2 suspension, heating at 10 to 90°C and stirring for several minutes. ③ The suspension is filtered to a powder using a suction filtration device and then dried under a nitrogen atmosphere. This invention successfully improves the cycle stability and specific capacity of VO2-based aqueous zinc-ion batteries, significantly impacting the development of aqueous zinc-ion batteries.

[0122] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for optimizing the performance of a VO2-based aqueous zinc ion battery, characterized in that: The performance optimization method of the VO2-based aqueous zinc ion battery comprises: VO2 was prepared by hydrothermal method using V2O5 and oxalic acid as precursors and polytetrafluoroethylene as the inner liner of hydrothermal reaction pressure device; Then, the small molecule powder M is mixed with the VO2 suspension, and the treated M-VO2 is obtained after heating, stirring and drying; The battery is packaged into a button cell with stainless steel mesh as the current collector, zinc sheet as the negative electrode, glass fiber as the separator, and ZnSO4 or Zn(CF3SO3)2 as the electrolyte. The precursor is prepared by adding V2O5 and oxalic acid in a molar ratio of 1:9 to 9:1 to 10 to 500 mL of deionized water and stirring for 10 to 200 minutes to obtain a precursor solution; The hydrothermal method is to add 10% to 90% of the volume of the precursor solution into the polytetrafluoroethylene liner, and the hydrothermal time and temperature are 12 to 90 hours and 100 to 200 degrees Celsius; The small molecule is a benzene ring, a five-membered or six-membered heterocyclic small molecule having an R substituent, including one or more of tyrosine, maleic anhydride, sucrose, ascorbic acid, phenylpropionic acid, N,N'-dimethylbenzamide, sodium benzoate, sodium ascorbate, and phenylglycine; -R includes one or more of =O, -OH, -SH, ≡CN, -NH2, -CONH2; The mixing process comprises the following steps: mixing the small molecule powder with the VO2 suspension, placing the mixture in a constant temperature water bath at 30 to 90° C. under inert gas protection, heating and stirring for 0.5 to 8 hours; The performance optimization method of the VO2-based aqueous zinc ion battery further specifically includes: VO2 was prepared using a hydrothermal method, where a precursor solution was obtained using V2O5 and oxalic acid; After hydrothermal reaction, the precursor solution was transferred into a polytetrafluoroethylene liner and sealed in a stainless steel kettle, which was then placed in a drying oven; Using small molecules to treat VO2, the treatment steps are to mix a specific mass of small molecule powder with a hydrothermally obtained VO2 suspension, heating and stirring for several minutes; Filtering the suspension into powder using a filtration device, and drying under a nitrogen environment to obtain the M-VO2 as a positive electrode material for an aqueous zinc ion battery; Prepare the electrode by mixing the dried powder with the dispersion in proportion, evenly coating it on the current collector, and drying it in a drying oven for later use; For packaging test, 2M ZnSO4 or 3M Zn(CF3SO3)2 was prepared as the electrolyte, zinc foil as the negative electrode, and M-VO2 as the positive electrode, and the charge-discharge curves and cycle performance were tested respectively.

2. The method for optimizing the performance of a VO2-based aqueous zinc ion battery according to claim 1, wherein: The mass of the small molecule powder is 0.1 to 1 g per 100 ml of suspension.

3. The performance optimization method of a VO2-based aqueous zinc ion battery according to claim 1, wherein: In the electrode preparation, the dispersion is a liquid prepared using deionized water and ethanol in a volume ratio of 4:1 as solvents, acetylene black and PTFE emulsion as solutes, and the concentration of acetylene black and PTFE is 5 mg / ml; the current collector is one of foam nickel, stainless steel mesh, and carbon cloth, and is a circular piece with a diameter of 1.2 cm.

4. A positive electrode material M-VO2 for improving the performance of an aqueous zinc ion battery, prepared by the performance optimization method of a VO2-based aqueous zinc ion battery according to any one of claims 1 to 3.

5. An aqueous zinc ion battery prepared using the positive electrode material M-VO2 according to claim 4.

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