Method for preparing aqueous zinc ion battery positive electrode material and detecting charge reaction of aqueous zinc ion battery positive electrode material in metal ion battery

Abstract

The invention discloses preparation of an aqueous zinc ion battery positive electrode material and a detection method of charge reaction of the aqueous zinc ion battery positive electrode material in a metal ion battery, and belongs to the technical field of batteries. The invention provides the preparation method of the vanadium-based positive electrode material, which is simple in process and low in cost. The preparation method of the positive electrode material comprises the following steps: grinding vanadium pentoxide powder; performing ultrasonic treatment with deionized water, adding inorganic salt, sealing, performing water bath heating reaction, and performing centrifugal washing; and then drying or freeze-drying to finally obtain the batched and high-performance positive electrode material. In 8000 times of charging and discharging, the positive electrode material provided by the invention has excellent cycling stability, and the capacity retention rate is as high as 93%. In addition, an in-situ alternating-current impedance technology is used for rapidly detecting the charge transfer process in the battery, and complex and expensive in-situ X-ray diffraction and transmission electron microscope technologies are avoided. The vanadium pentoxide activation process is accurately controlled through the water bath, the process is simple, the cost is low, and the method has good batch production potential and application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and specifically relates to a method for preparing a cathode material for an aqueous zinc-ion battery and detecting internal charge reactions in a metal-ion battery. Background Art

[0002] With the continuous pursuit of sustainable and environmentally friendly technologies, the development of safe, economical, and efficient energy storage systems has become a global research focus. Although lithium-ion batteries have achieved remarkable success in fields such as portable electronic devices and electric vehicles, their defects in terms of limited resources, high manufacturing costs, safety hazards, and energy density make it difficult to meet large-scale energy storage requirements. In particular, the uneven distribution of lithium resources and the use of flammable organic electrolytes further prompt researchers to explore more sustainable and economical alternative solutions. As an emerging energy storage system, aqueous zinc-ion batteries have attracted much attention due to their excellent safety and low cost. First, zinc is a metal with abundant reserves and environmental friendliness, having a high theoretical capacity (820 mAh g -1 ) and a low redox potential (-0.78 V vs. standard hydrogen electrode), making it an ideal anode material for batteries. Second, aqueous zinc-ion batteries use aqueous electrolytes, which not only reduce costs but also significantly improve safety, avoiding the flammability risk of organic electrolytes. However, despite the great theoretical advantages of aqueous zinc-ion batteries, the selection of cathode materials and the improvement of their electrochemical performance remain key issues to be urgently solved.

[0003] Vanadium-based materials often have multiple valence states and open framework structures and have been proven to have good zinc storage capacity. Among them, vanadium pentoxide has a typical orthorhombic layered structure, which can conveniently realize the insertion and extraction processes of zinc ions and also has the advantage of low price. However, in practical applications, directly using vanadium pentoxide as an electrode material has problems such as a decrease in battery cycle life and insufficient discharge capacity. Therefore, modifying it through structural design, doping, or introducing a carbon substrate is an effective means. Wang et al. (Adv. Funct. Mater., 33, 2023, 2213127) obtained the Li@MnVO material based on a dual-ion sequence insertion strategy and achieved a long-term discharge capacity of 5000 times at an ultra-high current density of 10 Ag -1 . Liang et al. (J. Energy Chem., 59, 2021, 126 - 133) introduced a highly flexible composite membrane composed of a CNTs membrane and commercial vanadium pentoxide, which had a capacity of 356.6 mAh g -1 at a current density of 0.4 Ag -1with a high discharge specific capacity. Tang and his team (Electrochim. Acta, 475, 2024, 143641) designed a core-shell structured vanadium pentoxide, which still had a capacity retention rate of 91.4% after 5000 cycles at a current density of 3Ag -1 Current density. Although these strategies have significantly improved the electrochemical performance of commercial vanadium pentoxide, their design is difficult, the preparation process is cumbersome, and the cost is expensive, which is not suitable for large-scale processing. In addition, the understanding of the electrochemical behavior and structural changes of the cathode material during charge and discharge is not sufficient. Traditional physical characterization techniques, such as in-situ scanning electron microscopy, in-situ X-ray diffraction, and transmission electron microscopy, although providing information, are complex to operate and may damage the battery. Under actual working conditions, the detection method of internal charge reactions in the battery has also become a bottleneck problem in this field of research. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a vanadium-based cathode material with a simple process and low production cost and a rapid detection technology for the charge transfer process in metal ion batteries. To achieve the above invention purpose, the present invention uses a conventional water bath technology to accurately control the synthesis temperature, reaction time, and raw material concentration, and mass-produces a high-performance vanadium-based cathode material, and uses in-situ electrochemical impedance technology to accurately judge the internal charge reaction process of the battery. By real-time monitoring the changes of key parameters such as interfacial charge transfer impedance and diffusion impedance under the working state of the battery, the present invention not only has important application value in aqueous zinc-ion batteries, but also in other metal ion battery systems such as lithium-ion batteries, sodium-ion batteries, and magnesium-ion batteries, especially suitable for studying the interfacial kinetic behavior and reaction mechanism of electrolytes / electrodes.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The purpose of the present invention is to provide a method for preparing a cathode material for an aqueous zinc-ion battery, comprising the following steps:

[0007] Step 1, grinding vanadium pentoxide powder;

[0008] Step 2, then adding it to deionized water, ultrasonically treating it, adding inorganic salts, sealing it, heating it in a water bath to react, and centrifuging and washing;

[0009] Step 3, then drying or freeze-drying to finally obtain a mass-produced, high-performance vanadium-based cathode material. Finally, assemble the cathode, anode, separator, and electrolyte into a button cell for testing, and obtain the charge transfer path of the positive active material during charge and discharge through in-situ electrochemical impedance technology.

[0010] The grinding of the invention is to better promote the dissolution and recrystallization process in the water bath process; the ultrasonic treatment is to promote the dispersion of vanadium pentoxide in advance and reduce its interface binding energy; and the preactivated vanadium-based material is obtained by heating in the water bath.

[0011] It is further defined that in step 1, the grinding time is 30 min to 60 min. The grinding can be performed using an agate mortar.

[0012] It is further defined that in step 2, the ultrasonic treatment time is 5 minutes to 60 minutes, the ultrasonic temperature is controlled at 5°C to 10°C, and the ultrasonic frequency is controlled at 30KHz to 50KHz; if the ultrasonic time is too long, it will cause serious cracks in the material structure, especially in the process of temperature rising. During the ultrasonic process, ice cubes are added to the water to cool it down so as to control the temperature.

[0013] It is further defined that in step 2, the inorganic salt is sodium chloride or potassium sulfate.

[0014] It is further defined that in step 2, the centrifugation process is maintained at 4000-8000 rpm for 30-60 minutes to obtain a precipitate, and the precipitate is washed with deionized water and anhydrous ethanol multiple times in sequence.

[0015] It is further defined that in step 2, the reaction is heated in a water bath at 25°C to 95°C for 12h to 72h.

[0016] It is further defined that in step 3, the drying is performed at 60° C. to 90° C. for 12 hours to 48 hours, and a blast dryer can be used for drying.

[0017] It is further defined that in step 3, freeze drying is performed at -45°C to -80°C for 12 hours to 48 hours. A freeze dryer can be used for drying.

[0018] The present invention provides a positive electrode material for an aqueous zinc ion battery prepared by any of the above methods.

[0019] The method for detecting the charge reaction of the positive electrode material in the metal ion battery of the present invention comprises the following steps:

[0020] Step 1: Grind the positive electrode material and add it into nitrogen methyl pyrrolidone together with acetylene black and polyvinylidene fluoride, disperse it evenly, stir it at room temperature for 8 hours, then transfer it to Ti foil, dry it in a vacuum environment at 80°C for 12 hours, cut it into 12mm positive electrode sheets, and then assemble it into button batteries with zinc foil, separator and 2mol / L zinc sulfate electrolyte at room temperature;

[0021] Step 2: Perform an in-situ AC impedance spectrum test on the battery with a test voltage between 0.3-1.6V.

[0022] Further limit that the mass ratio of the positive electrode material, acetylene black and polyvinylidene fluoride is 7:2:1.

[0023] Further limit that before the in-situ alternating current impedance spectroscopy test, a charge-discharge process is carried out on the battery, and then the battery is charged at a constant voltage under open-circuit voltage until its voltage reaches the maximum value of 1.6V and remains stable at this voltage for 15 minutes. During the test, an alternating current impedance spectroscopy test is carried out every time a 50mV voltage step is performed. The test amplitude is 5mV, and the frequency range is 0.01-10 5 Hz. The voltage changes from 1.6V to 0.3V, and the reverse charge gradually increases from 0.3V to 1.6V. After remaining stable for 15 minutes at each voltage stage, an in-situ alternating current impedance spectroscopy test is carried out.

[0024] In the present invention, the in-situ electrochemical impedance technique uses a button cell to perform an alternating current impedance test at different voltage platforms (such as for the V 2 O 5 ||Zn full cell is 0.3-1.6V, and for the MoS 2 ||Na full cell is 0-3V). Before the test, it is necessary to carry out a complete charge-discharge process on the full cell to ensure that the inside of the battery is in a unified state. Then, the first test is carried out on the battery in the open-circuit voltage state, and after continuing to charge to the highest voltage that the full cell can reach, the second test is carried out. And so on, an alternating current impedance test is carried out every 10-100mV voltage interval. All test amplitudes are 3-10mV, and the frequency range is 0.01-10 5 Hz. Finally, several alternating current impedance curves are obtained, and the charge transfer path of the positive electrode active material during the charge-discharge process can be distinguished without fitting.

[0025] In the present invention, the water bath reaction is a heating technique that uses water as a heat transfer medium; it is simple and safe to operate and does not require special high-temperature protection equipment; the temperature uniformity is good. Water has good heat conduction performance and can form a relatively uniform temperature field throughout the water bath tank; for the present invention, the water bath process can ensure that the temperature of vanadium pentoxide is consistent during the treatment process, which is beneficial to improving the repeatability and stability of the experiment; during the water bath process, with the heat input, a dissolution-recrystallization process occurs for vanadium pentoxide, which can drive the crystal to undergo thermal expansion, thereby increasing the lattice spacing of the crystal and being beneficial to improving the electrochemical performance of the electrode material. In addition, during the dissolution and recrystallization process of vanadium pentoxide, by introducing a salt solution, metal cations can be embedded between the [V-O] main structures and the lattice spacing can also be increased.

[0026] The in-situ electrochemical impedance testing technology of the present invention is a technology for real-time monitoring of the dynamic changes in an electrochemical system. By applying a small-amplitude alternating voltage signal to an electrode and measuring the response current, the impedance information of the electrode system can be obtained to judge the charge transfer process inside the battery. For the present invention, the in-situ electrochemical impedance testing technology is used for the first time to detect the charge transfer process of vanadium pentoxide and its composite with metal cations after water bath treatment. The process of zinc storage is realized for non-destructive and real-time monitoring, and the intercalation and de-intercalation states of zinc ions at different voltage stages are accurately distinguished.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The raw materials used in the present invention are water, vanadium pentoxide, and some inorganic salts or organic salts, which are widely sourced and inexpensive;

[0029] The activation process of vanadium pentoxide in the present invention is accurately controlled by water bath, with a simple process, low cost, and the potential for batch production, and has good industrial application prospects;

[0030] Both the pre-activated vanadium pentoxide and the vanadium-based composite material intercalated with metal cations in the present invention have larger interlayer spacings, which is beneficial to improving the electrochemical performance; during 8,000 continuous charge and discharge processes, the positive electrode material of the present invention exhibits excellent cycle stability, with a capacity retention rate as high as 93%, and the Coulomb efficiency always remains above 99%.

[0031] The present invention uses in-situ alternating impedance technology to quickly detect the charge transfer process inside the battery, avoiding complex and expensive in-situ X-ray diffraction and transmission electron microscopy technologies. The in-situ electrochemical impedance technology of the present invention can explore the internal reaction process of the battery without disassembling the battery, and has the advantages of being faster and more convenient than in-situ XRD. It not only has important application value in aqueous ion batteries, but also in other metal ion battery systems such as lithium-ion batteries, sodium-ion batteries, and magnesium-ion batteries, especially suitable for studying the electrolyte / electrode interface kinetic behavior and reaction mechanism.

[0032] In order to further understand the features and technical content of the present invention, please refer to the following detailed description and drawings of the present invention. However, the attached drawings are only for reference and illustration purposes and are not used to limit the present invention. Description of the Drawings

[0033] Figure 1 is the XRD pattern of the pretreated vanadium pentoxide and commercial vanadium pentoxide in Comparative Example 1 of the method of the present invention;

[0034] Figure 2 is the SEM morphology diagram of the pretreated vanadium pentoxide and commercial vanadium pentoxide in Comparative Example 1 of the method of the present invention;

[0035] Figure 3 It is the long - cycle performance graph of the pre - treated vanadium pentoxide and the commercial vanadium pentoxide electrode in Comparative Example 1 of the method of the present invention;

[0036] Figure 4 It is the in - situ AC impedance spectrum of the full cell assembled with the pre - treated vanadium pentoxide and the commercial vanadium pentoxide electrode in Comparative Example 1 of the method of the present invention;

[0037] Figure 5 It is the XRD pattern of the sodium - intercalated hydrated sodium vanadate material prepared by introducing sodium chloride in Example 1 of the method of the present invention;

[0038] Figure 6 It is the thermogravimetric analysis graph of the hydrated sodium vanadate material in Example 1 of the method of the present invention;

[0039] Figure 7 It is the SEM morphology graph of Na 2 V 6 O 16 ·2.74H 2 O prepared in Example 1 of the method of the present invention;

[0040] Figure 8 It is the long - cycle performance graph of the Na 2 V 6 O 16 ·2.74H 2 O electrode prepared in Example 1 of the method of the present invention;

[0041] Figure 9 It is the in - situ AC impedance spectrum of the full cell assembled with the Na 2 V 6 O 16 ·2.74H 2 O electrode prepared in Example 1 of the method of the present invention. Detailed implementation manners

[0042] The present invention will be described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, and at the same time do not limit the present invention in any form. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can be made. These all fall within the protection scope of the present invention.

[0043] Example 1: The preparation method of the positive electrode material of the aqueous zinc - ion battery in this example is carried out according to the following steps:

[0044] Add 1 g of vanadium pentoxide to 60 mL of deionized water, and ultrasonically disperse it for 30 min at a temperature controlled at 5 °C to 10 °C and an ultrasonic frequency of 40 KHz. Add 14 g of sodium chloride, transfer it to a magnetic stirrer, and then seal the container with a sealing film. In a water bath environment at 65 °C, continuously stir for 12 h at a rotation speed of 600 rpm, let it stand for 2 h, filter the supernatant, wash it multiple times with deionized water, and then wash it 3 times with ethanol. Finally, dry the sample in a blast drying oven at 65 °C for 12 h; finally, a hydrated sodium vanadate material intercalated with sodium ions is obtained.

[0045] Grind the hydrated sodium vanadate material intercalated with sodium ions obtained in this example, and weigh the hydrated sodium vanadate material, acetylene black, and polyvinylidene fluoride according to a mass ratio of 7:2:1 and add them to a weighing bottle. Add N-methylpyrrolidone solvent to disperse them evenly, stir at room temperature for 8 h, transfer the slurry to a Ti foil, and dry it in a vacuum environment at 80 °C for 12 h. Cut it into a positive electrode sheet with a size of 12 mm. Subsequently, assemble it into a button battery with a zinc foil, a separator, and a 2 mol / L zinc sulfate electrolyte at room temperature.

[0046] Perform in-situ alternating current impedance spectroscopy testing on the battery, and the test voltage is between 0.3 - 1.6 V. Before the test starts, the battery needs to undergo a charge-discharge process to ensure that the entire battery is in a stable state. Then, perform constant voltage charging on the battery at open circuit voltage until its voltage reaches the maximum value of 1.6 V and remains stable at this voltage for 15 minutes. During this period, every time a 50 mV voltage step is performed, an alternating current impedance spectroscopy test is carried out. The test amplitude is 5 mV, and the frequency range is 0.01 - 10 5 Hz. The voltage changes from 1.6 V to 0.3 V, and the reverse charging gradually increases from 0.3 V to 1.6 V. After maintaining stability for 15 minutes at each voltage stage, the in-situ alternating current impedance spectroscopy test can be carried out.

[0047] Comparative Example 1:

[0048] (1) Add 1 g of vanadium pentoxide to 60 mL of deionized water, ultrasonically disperse it for 30 min at a temperature controlled at 5 °C to 10 °C and an ultrasonic frequency of 50 KHz, then seal the container with a sealing film and transfer it to a water bath environment at 65 °C. Continuously stir for 48 h at a rotation speed of 600 rpm, let it stand for 2 h, filter the supernatant, wash it multiple times with deionized water, and then wash it 3 times with ethanol. Finally, dry the sample in a freeze dryer at -70 °C for 12 h;

[0049] (2) Grind the dried pretreated vanadium pentoxide, and weigh the pretreated vanadium pentoxide, acetylene black, and polyvinylidene fluoride according to a mass ratio of 7:2:1 and add them to a weighing bottle. Add N-methylpyrrolidone solvent to disperse evenly, stir at room temperature for 8 h, transfer the slurry to a Ti foil, and dry it in a vacuum environment at 80 °C for 12 h. Cut it into a positive electrode sheet with a size of 12 mm. Subsequently, assemble it into a button cell with a zinc foil, a separator, and a 2 mol / L zinc sulfate electrolyte at room temperature.

[0050] (3) Perform in-situ alternating current impedance spectroscopy testing on the battery, and the test voltage is between 0.3 - 1.6 V. Before the test starts, the battery needs to undergo a charge-discharge process to ensure that the entire battery is in a stable state. Then, perform constant voltage charging on the battery under open circuit voltage until its voltage reaches the maximum value of 1.6 V and remains stable at this voltage for 15 minutes. During this period, for every 50 mV voltage step, an alternating current impedance spectroscopy test is performed, the test amplitude is 5 mV, and the frequency range is 0.01 - 10 5 Hz. The voltage changes from 1.6 V to 0.3 V, and the reverse charging gradually increases from 0.3 V to 1.6 V. After remaining stable for 15 minutes at each voltage stage, the in-situ alternating current impedance spectroscopy test can be performed.

[0051] Example 2:

[0052] Repeat Comparative Example 1, with the difference that the water bath temperature is controlled at 25 °C, mainly to test whether room temperature can cause the dissolution and recrystallization process of vanadium pentoxide. Other steps and parameters are the same as those in Comparative Example 1.

[0053] Example 3:

[0054] Repeat Comparative Example 1, with the difference that the water bath temperature is controlled at 95 °C. Other steps and parameters are the same as those in Comparative Example 1.

[0055] Example 4:

[0056] Repeat Comparative Example 1, with the difference that the stirring time is 24 h. Other steps and parameters are the same as those in Comparative Example 1.

[0057] Example 5:

[0058] Repeat Comparative Example 1, with the difference that the stirring time is 72 h. Other steps and parameters are the same as those in Comparative Example 1.

[0059] As Figure 1As shown, the XRD patterns of the pretreated vanadium pentoxide prepared in Comparative Example 1 and commercial vanadium pentoxide show that both materials can be indexed from the standard card PDF#41-1426. However, the highest diffraction peak (001) crystal plane of the pretreated vanadium pentoxide is significantly shifted to a lower angle, indicating an increase in the lattice spacing during the water bath treatment.

[0060] As Figure 2 shown, the SEM morphology of the pretreated vanadium pentoxide prepared in Comparative Example 1 shows a clearer and smaller layered structure, while the SEM morphology of commercial vanadium pentoxide is a stacked nanosheet layer structure, forming a massive aggregate with a radial size exceeding 10 μm and a transverse size of about 6 μm.

[0061] As Figure 3 shown, the long-term cycling performance of the electrodes of the pretreated vanadium pentoxide prepared in Comparative Example 1 and commercial vanadium pentoxide. At a current density of 2 Ag -1 , the initial discharge capacity of the pretreated vanadium pentoxide shows relatively high performance, indicating its good Zn 2+ storage capacity in the electrochemical reaction. As the number of cycles increases to 5000, the final discharge capacity of the pretreated vanadium pentoxide is still significantly better than that of the untreated vanadium pentoxide, reflecting the effectiveness of the water bath treatment in improving the reactivity of the electrode material.

[0062] As Figure 4 shown, in-situ AC impedance spectroscopy tests of all-solid-state batteries assembled with the electrodes of the pretreated vanadium pentoxide prepared in Comparative Example 1 and commercial vanadium pentoxide. As the voltage gradually decreases from the initial 1.6 V, the charge transfer resistance value shows a gradually increasing trend, indicating that Zn 2+ is rapidly embedded into the electrode material. However, due to the large size of Zn 2+ , the reaction kinetics of this process is relatively slow. Until the discharge approaches 0.7 V, the charge transfer resistance value begins to show a downward trend, indicating that the embedding process reaches a peak at this stage. As the discharge process continues, smaller protons begin to be embedded, further increasing the reaction kinetics of the electrode. At this time, the charge transfer resistance value shows an upward trend near the plateau voltage of 0.5 V, reflecting the process of simultaneous embedding of Zn 2+ and protons. Due to the mutual restraint between the two, the increase in the charge transfer resistance value is relatively slow, but the overall reaction kinetics of the electrode is improved. During the charging process, the charge transfer resistance value starts to increase from 0.3 V in the initial stage and reaches a maximum near 0.6 V, indicating that Zn 2+ is extracted. When the voltage reaches 0.7 V, the charge transfer resistance value continues to decrease, demonstrating the rapid extraction process of Zn 2+ .

[0063] As Figure 5 shown, for the XRD pattern of the sodium-ion intercalated sodium vanadate hydrate material prepared in Example 1 by introducing sodium chloride, it can be seen that the synthesized sample has obvious diffraction peaks at 7.3°, 11.2°, 23.9°, 25.9°, 28.4°, 39.7°, 44.6°, 50.7°, 59.6° and 66.4°. These peaks respectively correspond to the (100), (001), (-301), (110), (111), (-303), (-403), (204), (612) and (-323) crystal planes of Na 2 V 6 O 16 ·nH 2 O (standard card PDF#16 - 0601), indicating that the sample has good crystallinity.

[0064] As Figure 6 shown, for the thermogravimetric analysis of the sodium vanadate hydrate material prepared in Example 1, during the process of heating the sample to 450 °C, the total mass loss is 7.51%. Therefore, it is deduced that the sample contains 2.74 crystal water molecules, and finally its chemical formula is determined to be Na 2 V 6 O 16 ·2.74H 2 O.

[0065] As Figure 7 shown, the SEM morphology of Na 2 V 6 O 16 ·2.74H 2 O prepared in Example 1 shows a nanowire shape, with a diameter of about 40 - 60 nm. It is significantly different from the pretreated vanadium pentoxide without introducing a salt solution, proving that the introduction of metal cations has led to a complete change in both the phase and structure.

[0066] As Figure 8 shown, for the long-term cycling performance of the Na 2 V 6 O 16 ·2.74H 2 O electrode in Example 1, at the initial stage of the test, the charge released by the Na 2 V 6 O 16 ·2.74H 2 O electrode gradually increases, indicating that the activation process between the electrode and the electrolyte is ongoing. During the continuous 8000 charge-discharge cycles, the electrode exhibits excellent cycling stability, with a capacity retention rate as high as 93%, and the Coulomb efficiency always remains above 99%.

[0067] AsFigure 9 As shown, the in-situ AC impedance spectrum test of the full cell assembled with the Na 2 V 6 O 16 ·2.74H 2 O electrode prepared in Example 1. When the voltage gradually decreases from the initial 1.6 V, the charge transfer resistance value shows a gradually increasing trend, indicating that Zn 2+ is rapidly embedded into the electrode material. However, due to the relatively large size of Zn 2+ , the reaction kinetics of this process is relatively slow. When discharging to about 1.05 V, the charge transfer resistance begins to decrease, and this change indicates that the embedding rate reaches a peak at this time. As discharging continues, small-sized protons begin to be embedded into the electrode, thus further enhancing the reaction kinetics of the electrode. Near 0.8 V, the charge transfer resistance value rises again, reflecting the process of co-embedding of Zn 2+ and protons. Although there is mutual restraint between the two, resulting in a relatively slow increase in the charge transfer resistance value, the reaction kinetics of the overall electrode is improved. This stage lasts until about 0.4 V, and the charge transfer resistance value gradually decreases, indicating that the Na 2 V 6 O 16 ·2.74H 2 O electrode has transformed into another stable phase, which significantly improves the efficiency of the charge transfer process. During the continued charging of the full cell, at the initial stage when the voltage is 0.3 V, the charge transfer resistance begins to increase and reaches a maximum value near 0.55 V. This indicates that although some Zn 2+ has been deintercalated, the rate of phase transformation still lags behind the charge transfer process. When the voltage is increased to 0.6 V, the phase begins to stabilize, and the charge transfer resistance value gradually decreases until the voltage plateau at 0.85 V. Subsequently, the charge transfer resistance value continues to decrease, demonstrating the rapid deintercalation process of Zn 2+ .

[0068] The specific embodiments of the present invention have been described above. It should be noted that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a positive electrode material for an aqueous zinc ion battery, characterized in that: The following steps are involved: Step 1, grinding vanadium pentoxide powder; Step 2, then add deionized water, add inorganic salt after ultrasonic treatment, seal, heat in a water bath for reaction, and centrifuge for washing; Step 3: drying or freeze-drying to obtain the positive electrode material.

2. The method according to claim 1, characterized in that: The grinding time is 30min to 60min.

3. The method according to claim 1, characterized in that: Ultrasound for 5min to 60min at 5℃~10℃, 30KHz~50KHz; the inorganic salt is sodium chloride or potassium sulfate.

4. The method according to claim 1, characterized in that: Heat the reaction in a water bath at 25°C to 95°C for 12h to 72h.

5. The method according to claim 1, characterized in that: Dry at 60℃~90℃.

6. The method according to claim 1, characterized in that: Freeze-dry at -45℃~-80℃.

7. A positive electrode material for an aqueous zinc ion battery prepared by the method of any one of claims 1 to 6.

8. A method for detecting the charge reaction of a positive electrode material prepared by the method of any one of claims 1 to 6 in a metal ion battery, comprising the following steps: Step 1: Grind the positive electrode material and add it into nitrogen methyl pyrrolidone together with acetylene black and polyvinylidene fluoride, disperse it evenly, stir it at room temperature for 8 hours, then transfer it to Ti foil, dry it in a vacuum environment at 80°C for 12 hours, cut it into 12mm positive electrode sheets, and then assemble it into button batteries with zinc foil, separator and 2mol / L zinc sulfate electrolyte at room temperature; Step 2: Perform an in-situ AC impedance spectrum test on the battery with a test voltage between 0.3V and 1.6V.

9. The detection method according to claim 8, characterized in that: The mass ratio of the positive electrode material, acetylene black and polyvinylidene fluoride is 7:2:

1.

10. The detection method according to claim 8, characterized in that: Before the test begins, the battery is charged and discharged once, and then the battery is charged at a constant voltage under open circuit voltage until its voltage reaches a maximum value of 1.6V and remains stable at this voltage for 15 minutes. During the test, an AC impedance spectrum test is performed every time a 50mV voltage step is performed, with a test amplitude of 5mV and a frequency range of 0.01Hz to 10 5 Hz, the voltage range is reduced from 1.6V to 0.3V, while the reverse charge is gradually increased from 0.3V to 1.6V. After each voltage stage is kept stable for 15 minutes, in-situ AC impedance spectrum test is performed.

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