Preparation method and application of composite zinc negative electrode with high discharge depth

Abstract

This invention provides a method for preparing and applying a composite zinc anode with high depth of discharge, relating to the power industry. The method includes: using zinc salt and dimethylimidazole as raw materials, modifying them through in-situ aniline polymerization, and calcining to obtain a zinc-supported substrate material; compounding the zinc-supported substrate material with a conductive agent and a binder to form a slurry, coating and drying it to obtain a zinc-supported substrate electrode sheet; and electrodepositing metallic zinc onto the zinc-supported substrate electrode sheet to obtain a composite zinc anode suitable for weakly acidic zinc-ion battery systems. The composite zinc anode prepared by this invention achieves a cycle life of 500 hours under a high depth of discharge of 50%; when the composite zinc anode and a polyaniline cathode are combined to form a full cell, the cycle life reaches 10Ag. ‑1 The material was stably cycled 1000 times under the specified test conditions. This invention also provides a method for synthesizing zinc anode-supported substrate materials with different nitrogen element doping ratios (pyrrole nitrogen, pyridine nitrogen), which is simple and can effectively control the doping ratio of different nitrogen elements.

Description

Technical Field

[0001] This invention relates to the field of the power industry, and in particular to a method for preparing and applying a composite zinc anode with high depth of discharge. Background Technology

[0002] With societal development, the demand for new energy sources that can replace traditional fossil fuels is increasing, making the development of green energy technologies imperative to meet this ever-growing energy demand. In the storage and conversion of new energy sources, novel high-safety energy storage batteries, represented by aqueous zinc-ion batteries, have become a key research focus. Aqueous zinc-ion batteries mainly consist of four parts: a positive electrode, a negative electrode, an electrolyte, and a separator. Currently, the negative electrode material for aqueous zinc-ion batteries is primarily made of metallic zinc sheets or zinc powder. Although assembling batteries using metallic zinc sheets or zinc powder is simple, their poor electrochemical reversibility and cycle life still fail to meet the demands of practical applications.

[0003] On the other hand, zinc sheets or powder suffer from low depth of discharge during use, leading to a reduction in the actual usable capacity and energy conversion efficiency of the battery. Therefore, developing novel zinc anodes with high depth of discharge and long cycle life is of great significance for further advancing aqueous zinc-ion batteries. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing a composite zinc anode with high depth of discharge, and also provides applications for the obtained composite zinc anode, solving the problems of low cycle life and low depth of discharge in zinc sheet or zinc powder anodes. To achieve the above objectives, this invention provides the following technical solution:

[0005] The first aspect of this invention aims to provide a method for preparing a composite zinc anode with high depth of discharge, comprising the following steps:

[0006] 1) The zinc salt and dimethylimidazole were reacted in methanol solvent. After removing the methanol solvent and drying, a white precursor was obtained.

[0007] 2) The white precursor obtained in step 1), aniline, and ammonium persulfate were reacted in an ice-water bath for 2 hours, and then dried to obtain a yellowish-brown product;

[0008] 3) The yellowish-brown product obtained in step 2) is calcined under an inert gas atmosphere to obtain the calcined product;

[0009] 4) Wash the calcined material obtained in step 3) three times with water and dry it to obtain the zinc-supported substrate material;

[0010] 5) The zinc-loaded substrate material obtained in step 4) is mixed with a conductive agent and a binder to form a slurry, which is then uniformly coated onto a copper foil and subsequently vacuum dried to obtain a zinc-loaded substrate material electrode sheet.

[0011] 6) A 15 mAh cm⁻¹ electrodeposition is performed uniformly on the zinc-loaded substrate material electrode obtained in step 5). -2 Metallic zinc is used to obtain a composite zinc anode.

[0012] Preferably, in step 1), the zinc salt and dimethylimidazole have masses of 2.975 g and 3.284 g, respectively.

[0013] Preferably, the zinc salt is zinc nitrate hexahydrate.

[0014] Preferably, the reaction conditions in step 1) include: stirring for 15 minutes and then letting stand for 12 hours.

[0015] Preferably, in step 2), the volume of the white precursor, the volume of aniline, and the amount of ammonium persulfate are 200 mg, 75 μL, and 211 mg, respectively.

[0016] Preferably, the calcination conditions in step 3) are: a temperature of 700°C and a time of 2 hours;

[0017] The inert gas includes argon.

[0018] Preferably, in step 5), the conductive agent and the binder are Ketjen Black and PVDF, respectively. The mass ratio of the zinc-supported substrate material to the conductive agent and binder is 8:1:1; the homogenizing solvent is NMP.

[0019] Preferably, the electrodeposition process of metallic zinc in step 6) specifically involves: using a zinc-loaded substrate material as the negative electrode, a zinc metal sheet as the positive electrode, 2M ZnSO4 as the electrolyte, and a constant current (1 mA cm⁻¹). 2 After discharging for 15 hours, a composite zinc anode was obtained.

[0020] Furthermore, in step 2) of this invention, the amount of aniline added was adjusted to 0 μL, 75 μL, and 300 μL. Subsequently, zinc anode substrate materials with different nitrogen element configurations (pyrrole nitrogen and pyridine nitrogen) were obtained by calcination under the same experimental conditions as in steps 3-4).

[0021] The second objective of this invention is to provide an application of a long-cycle-life aqueous zinc-ion battery composed of a composite zinc anode and a polyaniline cathode material prepared by the preparation method described above.

[0022] Beneficial effects:

[0023] 1. Long cycle life: The composite zinc anode prepared in this invention can achieve a cycle life of 1 mA cm⁻¹. -21mAh cm -2 Stable cycling for 750 hours under test conditions; can operate at 1mA cm -2 7.5mAh cm -2 It can be stably cycled for 500 hours under test conditions.

[0024] 2. High discharge depth: The composite zinc anode prepared by this invention can achieve a discharge depth of 50% and can be stably cycled for 500 hours under these conditions;

[0025] 3. High charge and discharge efficiency: The composite zinc anode prepared by this invention has a charge and discharge efficiency of up to 99.5% during the cycling process of a symmetrical battery, which greatly improves the energy conversion efficiency;

[0026] 3. Suppressing zinc dendrite formation: The composite zinc anode prepared by this invention can effectively suppress the formation of zinc dendrites during cycling, reducing the risk of battery short circuit;

[0027] 4. Suppressing hydrogen evolution side reactions: The composite zinc anode prepared by this invention can effectively suppress hydrogen evolution side reactions during cycling, reducing the risk of battery bulging;

[0028] 5. High practicality: The preparation process of this invention does not have harsh conditions, uses inexpensive non-precious metal materials, and is low in cost and easy to promote.

[0029] 6. Convenient structural control: The doping ratio of pyrrole nitrogen and pyridine nitrogen can be effectively controlled by adjusting the amount of aniline added, forming zinc anode support substrate materials with different chemical environments.

[0030] This invention utilizes ZIF-8 as a precursor to prepare a zinc-supported substrate material through in-situ aniline polymerization with adjusted nitrogen doping ratio. Different nitrogen configurations (pyrrole nitrogen, pyridine nitrogen) doped in the zinc-supported substrate material can be prepared by a simple method of controlling the amount of aniline added. A composite zinc anode is then prepared by electrodepositing metallic zinc on a preferred zinc-supported substrate material. This synthesis method is practical and innovative, achieving a composite zinc anode with high discharge depth through an innovative method of directional control of metallic zinc deposition on the supported substrate. The composite zinc anode obtained by this invention exhibits a long cycle life (750 hours) at a high discharge depth (50%), significantly exceeding that of traditional zinc sheet anodes (50 hours). The composite zinc anode obtained by this invention also exhibits high charge-discharge efficiency, increasing the charge-discharge efficiency to 99.5% during symmetrical battery cycling, resulting in a substantial improvement in energy conversion efficiency. Furthermore, the composite zinc anode obtained by this invention significantly reduces the risk of battery short circuits and bulging by suppressing zinc dendrite formation and hydrogen evolution side reactions, further enhancing battery safety. Under conditions of using a weakly acidic electrolyte and a polyaniline cathode, the full cell can achieve a charge of 10Ag. -1 The current density is stable for 1000 cycles, showing good application prospects. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the embodiments will be briefly described below.

[0032] Figure 1 This is a scanning electron microscope image of the zinc-loaded substrate material obtained in Example 1 of this invention;

[0033] Figure 2 This is a test diagram of the symmetrical battery in Example 3 of the present invention, charged and discharged at a constant current with a discharge depth of 10%.

[0034] Figure 3 This is a test diagram of the symmetrical battery of Comparative Example 1 in this invention, charged and discharged at a constant current with a discharge depth of 10%.

[0035] Figure 4 This is a test diagram of the symmetrical battery in Example 3 of the present invention, charged and discharged at a constant current with a discharge depth of 50%.

[0036] Figure 5 This is a test diagram of the symmetrical battery of Comparative Example 1 in this invention, charged and discharged at constant current with 50% depth of discharge.

[0037] Figure 6 This is a scanning electron microscope image of the composite zinc anode material in Example 4 of this invention;

[0038] Figure 7 This is a scanning electron microscope image of zinc metal deposited on copper foil in Comparative Example 2 of this invention.

[0039] Figure 8 This is a constant current charge-discharge test diagram of a full cell formed by combining a composite zinc anode and a polyaniline cathode in Example 1 of this invention.

[0040] Figure 9 The X-ray absorption spectrum test results and structure fitting results are for zinc anode loaded substrate materials with different nitrogen element (pyrrole nitrogen, pyridine nitrogen) doping ratios in Example 5 of this invention. Detailed Implementation

[0041] This invention provides a method for preparing a composite zinc anode, comprising the following steps:

[0042] 1) The zinc salt and dimethylimidazole were reacted in methanol solvent. After removing the methanol solvent and drying, a white precursor was obtained.

[0043] 2) The white precursor obtained in step 1), aniline, and ammonium persulfate were reacted in an ice-water bath for 2 hours, and then dried to obtain a yellowish-brown product;

[0044] 3) The yellowish-brown product obtained in step 2) is calcined under an inert gas atmosphere to obtain the calcined product;

[0045] 4) Wash the calcined product obtained in step 3) three times with water and dry it to obtain a black product;

[0046] 5) The black product obtained in step 4) is mixed with a conductive agent and a binder to form a slurry, which is then uniformly coated onto a copper foil and subsequently vacuum dried to obtain a zinc-loaded substrate material electrode sheet.

[0047] 6) A 15 mAh cm⁻¹ electrodeposition is performed uniformly on the zinc-loaded substrate material electrode obtained in step 5). -2 Metallic zinc is used to obtain a composite zinc anode.

[0048] In this invention, zinc salt and dimethylimidazole are reacted in methanol solvent, and after removing the methanol solvent and drying, a white precursor is obtained.

[0049] In this invention, the zinc salt preferably comprises zinc nitrate hexahydrate. In this invention, the preferred masses of the zinc salt and dimethylimidazole are 2.975 g and 3.284 g, respectively. In this invention, the preferred reaction conditions include stirring for 15 min followed by standing for 12 h. In this invention, the zinc salt is preferably dissolved in methanol to obtain a zinc nitrate methanol solution; the dimethylimidazole is dissolved in methanol to obtain a dimethylimidazole methanol solution, and then the dimethylimidazole methanol solution is slowly poured into the zinc nitrate methanol solution. In this invention, magnetic stirring is preferably used. After removing the methanol reagent, the product is preferably washed by centrifugation with methanol. The preferred centrifugation speed is 5000 rpm, the preferred centrifugation time is 5 min, and the preferred number of centrifugations is 4-5 times. In this invention, the preferred drying conditions include a temperature of 80°C and a time of 12 h.

[0050] In this invention, a white precursor, aniline, and ammonium persulfate are reacted in water, and the product is dried to obtain a yellowish-brown product.

[0051] In this invention, the preferred ratios of the mass of the white precursor to the volume of aniline and the mass of ammonium persulfate are 200 mg:75 μl:221 mg, respectively. Preferably, the white precursor is ultrasonically dispersed in water to obtain a uniform colloidal dispersion; the aniline is dissolved in 6 mL of water to obtain an aqueous aniline solution; the ammonium persulfate is dissolved in 6 mL of water to obtain an aqueous ammonium persulfate solution; the aqueous aniline solution is added dropwise to the dispersion, followed by the addition of the aqueous ammonium persulfate solution dropwise. Preferably, the reaction is carried out in an ice-water bath. Preferably, the reaction is carried out under stirring, with a preferred stirring speed of 500 rpm and a preferred stirring time of 2 hours. Preferably, the reaction product is filtered, washed three times with water, and dried. Preferably, the drying conditions include a temperature of 80°C and a time of 8 hours.

[0052] The present invention calcines the obtained yellowish-brown product under inert gas protection to obtain a black calcined product.

[0053] In this invention, the calcination conditions preferably include: a temperature of 700°C and a time of 2 hours. In this invention, the inert gas preferably includes argon. In this invention, the heating rate during calcination is preferably 5°C / min, and the temperature is maintained at 700°C for 2 hours.

[0054] This invention involves compounding a zinc-supported substrate material with a conductive agent and a binder to prepare an electrode slurry, which is then coated onto a copper foil. The conductive agent used is Ketjen Black, and the binder is PVDF. The mass ratio of the zinc-supported substrate material, conductive agent, and binder is 8:1:1. The specific preparation process of the electrode slurry is as follows: the black calcined product, conductive agent, and binder powder are ground evenly in a mortar, then 1 mL of NMP is added dropwise, and grinding continues until a slurry is formed. The slurry is transferred to a clean copper foil and coated onto an electrode sheet with a thickness of 20 μm using a doctor blade. The evenly coated electrode sheet is then vacuum dried. In this invention, the preferred drying conditions include a temperature of 110°C and a time of 12 hours.

[0055] This invention involves stamping dried electrode sheets into circular electrode sheets with a diameter of 10 mm, then using the circular electrode sheet as the positive electrode and the zinc sheet as the negative electrode, with a constant current of 1 mA cm⁻¹. -2 A composite zinc anode was obtained by discharging for 15 hours. In this invention, the zinc sheet is a circular sheet with a thickness of 0.1 mm and a diameter of 16 mm.

[0056] This invention combines two prepared composite zinc anodes into a symmetrical battery and performs constant current charge-discharge tests; this invention also combines a prepared composite zinc anode with a polyaniline cathode into a full battery and performs full battery charge-discharge tests.

[0057] This invention can effectively control the doping ratio of pyrrole nitrogen and pyridine nitrogen by adjusting the amount of aniline added, thereby forming zinc anode support substrate materials with different zinc-loving sites.

[0058] To further illustrate the present invention, the following detailed description is provided in conjunction with embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0059] Example 1 – Preparation of Zinc-Supported Substrate Material

[0060] First, measure 100 mL of methanol into a beaker, weigh 2.975 g of zinc nitrate hexahydrate and add it to the methanol, stirring until completely dissolved. Then, measure another 100 mL of methanol into another beaker, weigh 3.284 g of dimethylimidazole and add it to the methanol, stirring until completely dissolved. Next, slowly pour the dimethylimidazole methanol solution into the methanol solution containing dissolved zinc nitrate hexahydrate, stirring for 15 minutes until the solution becomes milky white and turbid. Remove the magnetic stir bar and let it stand for 12 hours. After standing, pour off as much of the supernatant as possible, shake well, and pour into a centrifuge tube. Centrifuge at 5000 rpm for 3 minutes, then repeat the centrifugation process 4-5 times with methanol until the liquid is colorless. Transfer the white viscous substance after centrifugation to a forced-air drying oven and dry at 80°C for 12 hours to obtain the white precursor.

[0061] Weigh 200 mg of a white precursor and ultrasonically disperse it in 100 mL of deionized water, then transfer it to an ice bath. Dissolve 75 μL of aniline in 6 mL of deionized water, and weigh 211 mg of ammonium persulfate in 6 mL of deionized water. First, add the aniline solution dropwise to the white precursor dispersion, stirring for 2 minutes. Then, add the ammonium persulfate solution dropwise, maintaining the ice bath condition while stirring for 2 hours. Pour the reacted solution into a centrifuge tube and centrifuge at 6000 rpm for 6 minutes. Repeat the centrifugation process 4-5 times with deionized water until the liquid is colorless. Transfer the brown viscous substance after centrifugation to a vacuum oven and dry it at 80°C for 12 hours to obtain a yellowish-brown powder.

[0062] The obtained yellowish-brown powder was transferred to a porcelain boat and placed in a tube furnace. It was calcined at 700℃ under an argon atmosphere for 2 hours to obtain a black calcined product. This product was then ground to obtain a black powder. The black powder was washed three times with distilled water by centrifugation. The centrifuged product was transferred to a vacuum oven and dried at 80℃ for 8 hours to obtain a zinc-supported substrate material. The scanning electron microscope image of the obtained zinc-supported substrate material is shown below. Figure 1 As shown.

[0063] Example 2 – Preparation of Composite Zinc Anode

[0064] Weigh 80 mg of zinc-supported substrate material, 10 mg of Ketjen Black, and 10 mg of PVDF into an agate mortar and grind the solids until homogeneous. Add 1 mL of NMP solvent and grind for 10 minutes to form a uniform black slurry. Place a 0.01 mm thick copper foil on a flat surface and clean the rough surface with ethanol. After the ethanol dries, transfer the black slurry onto the copper foil and spread it evenly to a thickness of 20 μm using a special coating tool. Then, transfer the copper foil covered with the black slurry to a forced-air oven and bake at 80°C for 20 minutes, followed by vacuum drying at 80°C for 12 hours. Finally, use a stamping machine to press the dried copper foil into a positive electrode sheet with a diameter of 10 mm for later use.

[0065] Prepare a 0.1mm thick zinc foil, and polish it evenly with 2000-grit sandpaper for 5 minutes, followed by ultrasonic cleaning to remove surface contaminants. Use a stamping machine to press the polished zinc foil into a 16mm diameter negative electrode sheet. Prepare a hydrophilic glass fiber membrane, and use a stamping machine to press it into a 19mm diameter membrane. Prepare a microporous organic filter membrane, and use a stamping machine to press it into a 16mm diameter disc. Finally, prepare 10ml of 2M ZnSO4 as the electrolyte.

[0066] Assemble the battery using CR2025 button cell components. The specific implementation method is as follows: Place the negative electrode shell on a table, with the polished zinc foil negative electrode plate facing upwards, and then cover it with a glass fiber separator. Next, evenly drop 160 μl of 2M ZnSO4 electrolyte onto the separator, and then cover it with a microporous organic filter membrane. Place the positive electrode plate, with the side covered by the black substrate material facing down, onto the microporous organic filter membrane, and then place a gasket to press it firmly. Finally, place the spring contact and positive electrode shell in sequence, and use a button cell pressing mold to press and shape it. After assembly, use a multimeter to check that the voltage is between 0.9 and 1.2V, indicating that the battery assembly is successful.

[0067] The assembled battery was left to stand for 2 hours, then discharged for 15 hours using a Newway battery tester at a current of 0.785mA. During this period, a total of 15mAh cm⁻¹ was discharged. -2 Metallic zinc is deposited on the positive electrode. Then, the discharged battery is disassembled using battery disassembly equipment, the positive electrode is carefully removed, and the microporous organic filter membrane covering its surface is peeled off to obtain the composite zinc negative electrode.

[0068] Example 3 – Test of a Symmetrical Composite Zinc Anode Cell

[0069] Two prepared composite zinc negative electrodes were used to assemble a symmetrical battery using CR2025 coin cells. The specific method was as follows: The negative electrode shell was placed on a table, with the zinc-loaded side of the composite zinc negative electrode facing upwards, and then covered with a glass fiber separator. 160 μl of 2M ZnSO4 electrolyte was then evenly added to the separator. The zinc-loaded side of the composite zinc negative electrode was placed downwards on the separator, and a gasket was placed in place to press it firmly. Finally, the spring contact and positive electrode shell were placed in sequence, and the coin cell pressing mold was used to press and shape it. After assembly, the voltage was checked with a multimeter and found to be within ±0.005V, indicating that the symmetrical battery assembly was successful.

[0070] Two assembled symmetrical batteries were left to stand for 2 hours, followed by charge / discharge tests using a Newway battery tester. One battery's charge / discharge current was set to 0.785mA, the single charge / discharge time was 1 hour, and the single charge / discharge capacity was set to 1mAh cm⁻¹. -2 The cycle count is set to 500 cycles. The other battery's charge / discharge current is set to 0.785mA, the single charge / discharge time is 7.5 hours, and the single charge / discharge capacity is set to 7.5mAh cm⁻¹. -2 The cycle count was set to 500 cycles. The test results are shown in the figure, with a 1mAh cm⁻¹... -2 The battery cycle life reaches 500 hours when charged and discharged at its capacity; with a 7.5mAh cm⁻¹ capacity. -2 The battery cycle life reaches 750 hours under charge-discharge conditions. It is worth noting that the total capacity of the composite zinc anode is determined by the electrodeposited metallic zinc, which is 15 mAh cm⁻¹. -2 Therefore, the two symmetrical batteries achieved discharge depths of 10% and 50% respectively during cycling, which greatly exceeded the discharge depth of ordinary zinc foil anodes, proving that composite zinc anodes still have the advantage of long cycle life at high discharge depths. Figure 2 The diagram shows a constant current charge-discharge test of the symmetrical battery in this embodiment at 10% depth of discharge. Figure 4 The diagram shows a constant current charge-discharge test of the symmetrical battery in this embodiment at 50% depth of discharge.

[0071] Example 4 – Microstructure Characterization of Composite Zinc Anode

[0072] A prepared composite zinc anode was placed in a vacuum drying oven and dried at 80℃ for 12 hours. The dried electrode was then attached to the scanning electron microscope (SEM) stage using conductive adhesive, followed by SEM characterization. The results are as follows: Figure 6As shown, the metallic zinc deposited on the surface of the composite zinc anode exhibits a tight planar arrangement with a regular hexagonal structure. This test result demonstrates that the zinc-loaded substrate material induces uniform electrodeposition of metallic zinc while significantly suppressing zinc dendrite formation, thus contributing to the long cycle life of the composite zinc anode.

[0073] Example 5 – Preparation and structural characterization of zinc anode substrate materials doped with nitrogen elements (pyrrole nitrogen, pyridine nitrogen) of different configurations.

[0074] Using the white precursor prepared in Example 1, 0 μL, 75 μL, and 300 μL of aniline were added, respectively, and the same reaction conditions as in Example 1 were used to prepare nitrogen-doped zinc anode substrates with different configurations (pyrrole nitrogen and pyridine nitrogen). The three zinc anode substrates were named ZP-0, ZP-1, and ZP-2 according to the different amounts of aniline added (0 μL, 75 μL, and 300 μL). The fine structures of ZP-0, ZP-1, and ZP-2 were analyzed using a benchtop X-ray absorption spectrometer and fitted using Artemis software. The results are shown below. Figure 9 As shown, in ZP-0, ZP-1, and ZP-2, the nitrogen elements coordinated to Zn are composed of different proportions of pyrrolic nitrogen and pyridine nitrogen. In ZP-0, all nitrogen elements coordinated to Zn are pyridine nitrogen; in ZP-1, the ratio of pyrrolic nitrogen to pyridine nitrogen is 1:3; and in ZP-2, the ratio is pyrrolic nitrogen to pyridine nitrogen is 3:1. These test results demonstrate that different configurations of nitrogen-doped (pyrrolic nitrogen, pyridine nitrogen) zinc anode substrate materials can be prepared by simply adjusting the amount of aniline added.

[0075] Comparative Example 1 – Zinc Foil Negative Electrode Symmetrical Cell Test

[0076] Two polished zinc foil negative electrodes, each 16mm in diameter, were used to assemble a symmetrical battery using CR2025 coin cells. The specific method was as follows: Place the negative electrode shell on a table, with the polished side of the zinc foil negative electrode facing upwards, and then cover it with a glass fiber separator. Next, evenly drop 160μl of 2M ZnSO4 electrolyte onto the separator. Then, place the polished side of the zinc foil negative electrode downwards onto the separator, and place a gasket to press it firmly. Finally, place the spring contact and positive electrode shell in sequence, and press it into shape using a coin cell pressing mold. After assembly, use a multimeter to check that the voltage is within ±0.005V, indicating that the symmetrical battery assembly is successful.

[0077] Two assembled symmetrical batteries were left to stand for 2 hours, followed by charge / discharge tests using a Newway battery tester. One battery's charge / discharge current was set to 0.785mA, the single charge / discharge time was 1 hour, and the single charge / discharge capacity was set to 1mAh cm⁻¹. -2The cycle count is set to 500 cycles. The other battery's charge / discharge current is set to 0.785mA, the single charge / discharge time is 7.5 hours, and the single charge / discharge capacity is set to 7.5mAh cm⁻¹. -2 The number of cycles was set to 500. The test results are as follows: Figure 3 and Figure 5 As shown, with 1mAh cm -2 The battery cycle life under charge / discharge conditions is 45 hours; at a capacity of 7.5mAh cm⁻¹ -2 The battery achieved a cycle life of 80 hours under charge-discharge conditions. Comparative Example 1 demonstrates that the composite zinc anode significantly improves cycle life and depth of discharge.

[0078] Comparative Example 2 – Characterization of the microstructure of electrodeposited metallic zinc on copper foil surface

[0079] Assemble the battery using CR2025 button cell components. The specific implementation method is as follows: Place the negative electrode shell on a table, with the polished zinc foil negative electrode plate facing upwards inside, and then cover it with a glass fiber separator. Next, evenly drop 160 μl of 2M ZnSO4 electrolyte onto the separator, and then cover it with a microporous organic filter membrane. Place a 10mm diameter copper foil, rough side down, on the microporous organic filter membrane, and then place a gasket to press it firmly. Finally, place the spring contact and positive electrode shell in sequence, and use a button cell pressing mold to press and shape it. After assembly, use a multimeter to check that the voltage is between 0.9 and 1.2V, indicating that the battery assembly is good.

[0080] The assembled battery was left to stand for 2 hours, then discharged for 15 hours using a Newway battery tester at a current of 0.785mA. During this period, a total of 15mAh cm⁻¹ was discharged. -2 Metallic zinc was deposited on the copper foil positive electrode. The discharged battery was then disassembled using battery disassembly equipment. The positive electrode was carefully removed, and the microporous organic filter membrane covering its surface was peeled off, yielding a 5mAh electrodeposited layer. -2 Copper foil containing zinc.

[0081] Take a piece of electrodeposited material with a capacity of 5 mAh cm⁻¹ -2 Copper foil containing metallic zinc was placed in a vacuum drying oven and dried at 80°C for 12 hours. The dried electrode was then attached to the scanning electron microscope (SEM) stage using conductive adhesive, followed by SEM characterization. Results are as follows: Figure 7 As shown, the zinc deposited on the copper foil surface exhibits a severe dendritic morphology, with sharp edges piercing the separator, which could potentially cause a short circuit in the battery.

[0082] Application Example 1 – A full cell composed of a composite zinc anode and a polyaniline cathode

[0083] Polyaniline cathodes possess high reversibility and a simple preparation method. Combining them with composite zinc anodes to form a full cell effectively demonstrates the application value of composite zinc anodes. The preparation method of the polyaniline cathode is as follows: Dissolve 520 mg of 3-aminobenzenesulfonic acid in 30 ml of 1 M HClO4 solution, then add 274 μl of aniline and stir until homogeneous to prepare the electrolyte. Cut conductive carbon paper into 2*2 cm pieces. 2 A square sheet was used as the working electrode, held in place by a titanium electrode holder; a graphite rod electrode was used as the counter electrode; and a silver / silver chloride reference electrode was used to form a three-electrode electrolytic cell. A constant current of 0.8 mA was applied using an Autolab electrochemical workstation and maintained for 2 hours. During this time, aniline polymerized and deposited on the carbon paper surface under the influence of the electric field to form a polyaniline positive electrode. After the experiment, the electrolyte on the surface of the polyaniline positive electrode was rinsed off with distilled water, and then it was placed in a vacuum drying oven at 80°C for 12 hours. The polyaniline positive electrode was then stamped into a 16 mm diameter sheet for later use. Each polyaniline positive electrode sheet contained approximately 0.3 mg of polyaniline.

[0084] Assemble a full battery using CR2025 button cell components. The specific implementation method is as follows: Place the negative electrode shell on a table, with the zinc composite negative electrode (zinc deposited side up) placed inside, and then cover it with a glass fiber separator. Next, evenly drop 160 μl of 2M ZnSO4 electrolyte onto the separator. Place the polyaniline positive electrode sheet on the separator, and then press it in place with a gasket. Finally, place the spring contact and positive electrode shell in sequence, and press it into shape using a button cell clamping mold. After assembly, use a multimeter to check that the voltage is between 0.9 and 1.2V, indicating that the battery assembly is successful.

[0085] The assembled battery was left to stand for 2 hours, and then charged and discharged using a Xinwei battery tester at a current of 3mA. Considering that the positive electrode active material is 0.3mg, the battery charge and discharge current density is 10A / g. The charge and discharge test results are as follows. Figure 8 As shown, after 1000 charge-discharge cycles, the full battery still retains 82% of its capacity, which proves that the composite zinc anode has excellent cycle stability in the full battery and has ideal practical value.

[0086] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a composite zinc anode with high depth of discharge, characterized in that, Includes the following steps: 1) The zinc salt and dimethylimidazole were reacted in methanol solvent. After removing the methanol solvent and drying, a white precursor was obtained. 2) The white precursor obtained in step 1), aniline, and ammonium persulfate were reacted in an ice-water bath for 2 hours, and then dried to obtain a yellowish-brown product; 3) The yellowish-brown product obtained in step 2) is calcined under an inert gas atmosphere to obtain the calcined product; 4) Wash the calcined material obtained in step 3) three times with water and dry it to obtain the zinc-supported substrate material; 5) The zinc-loaded substrate material obtained in step 4) is mixed with a conductive agent and a binder to form a slurry, which is then uniformly coated onto a copper foil and subsequently vacuum dried to obtain a zinc-loaded substrate material electrode sheet. 6) The zinc anode substrate material obtained in step 5) is uniformly electrodeposited at a depth of 15 mAh cm⁻¹. -2 Metallic zinc is used to obtain a composite zinc anode.

2. The preparation method according to claim 1, characterized in that, Step 1) The zinc salt is zinc nitrate hexahydrate, with a dosage of 2.975g, and the dimethylimidazole dosage is 3.284g.

3. The preparation method according to claim 1, characterized in that, In step 2), the amounts of white precursor, aniline, and ammonium persulfate were 200 mg, 75 μL, and 211 mg, respectively.

4. The preparation method according to claim 1, characterized in that, Step 3) The calcination conditions are: calcination at 700℃ for 2 hours under argon inert gas protection.

5. The preparation method according to claim 1, characterized in that, In step 5), the conductive agent is Ketjen Black, the binder is PVDF, the mass ratio of zinc-supported substrate material to conductive agent and binder is 8:1:1, and the homogenizing solvent is NMP.

6. The preparation method according to claim 1, characterized in that, The electrodeposition process of metallic zinc in step 6) specifically involves using a zinc-supported substrate material as the positive electrode, a zinc metal sheet as the negative electrode, 2M ZnSO4 as the electrolyte, and a current of 1 mA cm⁻¹. -2 A composite zinc anode was obtained by constant current discharge for 15 hours.

7. According to the preparation method of claim 1, in step 2), by controlling three different amounts of aniline added, three zinc-supported substrate materials with different nitrogen configurations are obtained, and the three amounts of aniline added are 0 μL, 75 μL, and 300 μL, respectively, and the nitrogen element is selected from pyrrole nitrogen or pyridine nitrogen.

8. The composite zinc anode obtained by the preparation method according to any one of claims 1-7 is combined with a polyaniline cathode material to form a weakly acidic zinc-ion battery for energy storage and conversion.

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