Preparation method of hydrogel electrolyte membrane and zinc-air battery

Abstract

The invention provides a preparation method of a hydrogel film containing a stable bipyridine functional group. The preparation method comprises the following steps: firstly, ball-milling a covalent organic framework (COFs) containing a bipyridine functional group, and then ultrasonically dispersing the covalent organic framework in a sodium acrylate solution; adding ammonium persulfate serving as an initiator and N, N '-methylene bisacrylamide serving as a cross-linking agent, and uniformly stirring; pouring the mixed solution into a mold, polymerizing at a certain temperature, and drying; and finally, soaking the prepared dry membrane in an electrolyte aqueous solution to obtain the hydrogel electrolyte membrane. The ultrasonic treatment and stirring process needs to be carried out at low temperature, and meanwhile, argon needs to be introduced to remove oxygen in the solution. The hydrogel film can promote migration and deposition of zinc metal and can assist in reducing overpotential of oxygen evolution and oxygen reduction reaction catalyzed by the transition metal-nitrogen-carbon material, so that the voltage difference of the whole aqueous zinc battery in the constant-current charging and discharging process is reduced, and the energy utilization efficiency and stability are improved.

Description

Technical Field

[0001] The present invention focuses on the preparation of polymer hydrogel membranes and gel electrolytes, and is mainly used in the field of green energy storage devices represented by rechargeable aqueous zinc-based batteries. Background Art

[0002] In the key field of energy storage and conversion, zinc-ion batteries and zinc-air batteries have become electrochemical energy storage systems with great development potential due to their outstanding advantages such as low cost, high safety and large theoretical specific capacity, attracting widespread attention from scientific researchers and the industry. However, in actual application scenarios, both types of batteries encounter the problem of large charge and discharge voltage difference. Normally, the charge and discharge voltage difference of zinc-ion batteries is 0.3~0.5 V, and the charge and discharge voltage difference of zinc-air batteries is even as high as 0.8~1.2 V. Such a large charge and discharge voltage difference reduces the energy efficiency of the battery. During the charge and discharge process, about 20~40% of the energy is lost in the form of heat energy, which seriously restricts the actual application value and promotion process of the battery.

[0003] As a key component in batteries, gel electrolyte plays an important role in battery performance. It combines the high ionic conductivity of liquid electrolytes with the good mechanical properties and safety of solid electrolytes. It can effectively inhibit the leakage of electrolytes and enhance the stability and reliability of batteries. In zinc-ion batteries and zinc-air batteries, gel electrolytes help improve the ion transport process and provide a good ion conduction environment for electrolyte reactions.

[0004] Studies have found that the functional groups of gel electrolytes have a significant impact on battery performance. By optimizing the functional groups of gel electrolytes, the stability of electrolyte materials during the charge and discharge process can be significantly increased. For example, certain specific functional groups can form more stable chemical bonds or interactions with the surface of electrolyte materials, reduce structural changes and dissolution of electrolytes during charge and discharge, and thus improve the cycle stability of electrolytes. At the same time, suitable functional groups can also have a positive effect on the migration and deposition process of zinc ions, and promote the reversibility of zinc metal during charge and discharge. It can guide zinc ions to deposit evenly on the electrolyte surface, effectively inhibit the growth of zinc dendrites, reduce the risk of short circuits caused by zinc dendrites, extend the service life of the battery, and improve the overall performance of the battery.

[0005] At present, the research on reducing the charge and discharge voltage difference of zinc-ion batteries and zinc-air batteries is mostly focused on the optimization of electrolyte materials and the improvement of electrolytes. However, the existing technology still has many shortcomings in solving this problem. For example, traditional electrolyte materials have poor structural stability during the charge and discharge process, which leads to slow electrolyte reaction kinetics, thereby increasing voltage polarization. In terms of electrolytes, although the common aqueous solution system has high ionic conductivity, there are problems such as zinc dendrite growth and hydrogen evolution side reactions, which will also cause the charge and discharge voltage difference to increase. Taking zinc-air batteries as an example, the energy utilization efficiency of liquid and quasi-solid (using gel electrolyte) zinc-air batteries is generally less than 60%, and a small number can reach 65%. Summary of the invention

[0006] In view of this, the research and development of new electrolytes that can effectively reduce the charge and discharge voltage difference is of vital importance to improving the performance of zinc-ion batteries and zinc-air batteries and promoting their widespread application in large-scale energy storage, electric vehicles and other fields.

[0007] A method for preparing a hydrogel electrolyte membrane for reducing the charge-discharge voltage difference, the preparation comprising the following steps: (1) Preparation of sodium acrylate mixed solution containing covalent organic frameworks (COFs): First, dry-grind COFs solid using a high-speed ball mill (without adding solvent, the diameter of the spherical agate beads in the ball mill is 0.8~1.2 cm), the ball milling time is 4~8 h, and the COFs after ball milling are collected. Next, a certain mass of ball-milled COFs is added to the sodium acrylate solution, ultrasonically dispersed at a power of 100~400 W for 0.5~1 h, and then vigorously stirred to form a dispersion. The ultrasonic and stirring processes are both carried out in a cold water bath environment and in an argon protective atmosphere. The COFs described here are a type of COFs containing bipyridyl functional groups, the mass ratio of sodium acrylate to dry COFs solid powder is 1:0.0005~0.002; the sodium acrylate solution is an aqueous solution, and its concentration is 0.2~1.0 g·mL⁻¹.

[0008] (2) Adding initiator and crosslinker: Add a certain amount of initiator ammonium persulfate and crosslinker N,N'-methylenebisacrylamide to the above dispersion, and continue stirring for 0.5~1 h in a cold water bath under argon protection. The concentration of ammonium persulfate in the mixed solution is 0.2~0.3 mg·mL⁻¹, and the concentration of crosslinker N,N'-methylenebisacrylamide in the mixed solution is 0.05~0.15 mg·mL⁻¹.

[0009] (3) Polymerization and drying: Pour the above-mentioned mixed solution into a mold, place it in a vacuum oven, keep it warm at 60-80 °C for polymerization, and bake it for 2-4 h to obtain a sodium polyacrylate hydrogel dry film containing COFs. During the polymerization process, the mold needs to be sealed to prevent water evaporation; during the drying process, the mold needs to be opened to allow the water to evaporate completely. The entire polymerization and drying process needs to maintain a vacuum state (air pressure less than 10 Pa).

[0010] (4) Preparation of hydrogel electrolyte membrane: The prepared dry membrane is immersed in an aqueous electrolyte solution. After a certain period of time, a sodium polyacrylate hydrogel electrolyte membrane containing COFs can be obtained. The electrolyte solution includes a 5-8 M alkaline electrolyte with potassium hydroxide, sodium hydroxide, and lithium hydroxide as the main components, and a 1-3 M neutral electrolyte with zinc sulfate, zinc chloride, and ammonium chloride as the main components. The immersion temperature of the dry membrane in the electrolyte ranges from room temperature to 80°C (the electrolyte needs to be sealed at high temperatures to prevent a large amount of water from evaporating), and the immersion time is 1-4 days.

[0011] The core feature of the present invention is the introduction of COFs containing bipyridyl functional groups, and the uniformity of the gel electrolyte and the uniform distribution of COFs therein are ensured through processes such as ball milling, ultrasound, strong stirring, cold water bath and argon protection. Subsequent examples show that when applied to zinc-air batteries, (1) the gel electrolyte with COFs containing bipyridyl functional groups performs better than the gel electrolyte with other COFs, and the corresponding battery energy utilization rate is higher (over 70%); (2) the overall effect of the gel electrolyte with COFs is better than that of PANa (pure sodium polyacrylate) electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 . Cyclic charge-discharge curves of zinc-air batteries assembled with pure PANa gel.

[0013] Figure 2 . Schematic diagram of the monomer structures of six COFs.

[0014] Figure 3 . XRD patterns of six COFs, (a) XRD of COF(a), (b) XRD of COF(b), (c) XRD of COF(c) and COF(d), (d) XRD of COF(e) and COF(f).

[0015] Figure 4 . Comparison of the cyclic charge and discharge curves of zinc-air batteries assembled with gels containing different contents of COF.

[0016] Figure 5. (a) Comparison of the cycle charge and discharge curves of zinc-air batteries assembled with different COF types added to gel Figure 1 ; (b) Enlarged image of the cyclic charge and discharge curve of the zinc-air battery assembled with PANa-COF (d) gel.

[0017] Figure 6 . (a) Comparison of the cycle charge and discharge curves of zinc-air batteries assembled with different COF types added to gel Figure 2 ; (b) Enlarged image of the cyclic charge and discharge curve of the zinc-air battery assembled with PANa-COF (d) gel. DETAILED DESCRIPTION

[0018] Characterization conditions The gel prepared in the embodiment of the present invention is used to assemble a flexible zinc-air battery, and its composition structure is as follows: a zinc plate is selected as the anode; 2 mg of Co-NC catalyst (reference: Chemical Engineering Journal, 2021,404, 127112.) is loaded on a homemade hydrophobic conductive current collector (i.e., nickel foam coated with carbon powder), and the drop coating area of ​​the Co-NC catalyst is 1 cm 2 , which serves as the air cathode. The cathode and anode are located on both sides of the hydrogel electrolyte to form a sandwich structure, and the outermost layer of the battery is wrapped with a breathable tape. It should be noted that only the battery corresponding to Figure 6 uses commercial carbon cloth (instead of the homemade hydrophobic conductive current collector) as the hydrophobic conductive current collector.

[0019] Synthesis of COF(a): 42 mg of Tp and 32.4 mg of p-phenylenediamine were placed in an ampoule tube, 1 mL of 1,3,5-trimethylbenzene and 1 mL of 1,4-dioxane were added, and ultrasonic dispersion was performed for 10 min. Then 400 μL of 6M acetic acid was added and ultrasonic dispersion was continued for 10 min. The ampoule tube was then subjected to three freeze-vacuum-thaw cycles and flame-sealed after completion. The sealed ampoule tube was placed in an oven at 120°C for three days, and the obtained product was washed with organic solvents such as N,N-dimethylacetamide, dichloromethane, and tetrahydrofuran. The product was then placed in an oven at 70°C and dried for 24 h.

[0020] Synthesis of COF(b): 42 mg of Tp and 56.4 mg of o-sulfonic p-phenylenediamine were placed in an ampoule tube, 1.6 mL of n-butanol and 1.5 mL of o-dichlorobenzene were added, ultrasonic dispersion was performed for 10 min, and then 500 μL of 6M acetic acid was added and ultrasonic dispersion was continued for 10 min. The ampoule tube was then subjected to three freeze-vacuum-thaw cycles and flame-sealed after completion. The sealed ampoule tube was placed in a 120°C oven for three days, and the obtained product was washed with organic solvents such as N,N-dimethylacetamide, dichloromethane, and tetrahydrofuran. The product was then placed in a 70°C oven and dried for 24 h.

[0021] Synthesis method of COF(c): 42 mg of Tp and 32.7 mg of 2,5-diaminopyridine were placed in an ampoule tube, 3 mL of 1,3,5-trimethylbenzene and 3 mL of 1,4-dioxane were added, ultrasonic dispersion was performed for 10 min, and then 600 μL of 6M acetic acid was added and ultrasonic dispersion was continued for 10 min. The ampoule tube was then subjected to three freeze-vacuum-thaw cycles and flame-sealed after completion. The sealed ampoule tube was placed in an oven at 120°C for three days, and the obtained product was washed with organic solvents such as N,N-dimethylacetamide, dichloromethane, and tetrahydrofuran. The product was then placed in an oven at 70°C and dried for 24 h.

[0022] Synthesis method of COF(d): 42 mg of Tp and 47 mg of 2,2,5,5-diaminobipyridine were placed in an ampoule tube, 4.5 ml of N,N-dimethylacetamide and 15 ml of o-dichlorobenzene were added, ultrasonic dispersion was performed for 10 min, and then 600 μL of 6M acetic acid was added and ultrasonic dispersion was continued for 10 min. The ampoule tube was then subjected to three freeze-vacuum-thaw cycles and flame-sealed after completion. The sealed ampoule tube was placed in a 120°C oven for three days, and the obtained product was washed with organic solvents such as N,N-dimethylacetamide, dichloromethane, and tetrahydrofuran. The product was then placed in a 70°C oven and dried for 24 h.

[0023] Synthesis method of COF(e): 42 mg of Tp and 81.6 mg of 3,3-diamino-[1,1-biphenyl]-4,4-dicarboxylic acid were placed in an ampoule tube, 1.5 mL of 1,3,5-trimethylbenzene and 0.5 mL of 1,4-dioxane were added, ultrasonic dispersion was performed for 10 minutes, and then 200 μL of 6 M acetic acid was added and ultrasonication was continued for 10 minutes. The ampoule tube was then subjected to three freeze-vacuum-thaw cycles and flame-sealed after completion. The sealed ampoule tube was placed in a 120°C oven for three days, and the obtained product was washed with organic solvents such as N,N-dimethylacetamide, dichloromethane, and tetrahydrofuran. The product was then placed in an oven at 70 degrees Celsius and dried for 24 hours.

[0024] Synthesis method of COF(f): 42 mg Tp, 27.6 mg benzidine and 40.8 mg 4,4-diaminobiphenyl-2,2-dicarboxylic acid were dispersed in 2 mL o-dichlorobenzene and 2 mL n-butanol solution, respectively, and ultrasonically dispersed for 10 min, followed by the addition of 200 μL 6 M acetic acid and continued ultrasonication for 10 min. The ampoule tube was then subjected to three freeze-vacuum-thaw cycles and flame-sealed after completion. The sealed ampoule tube was placed in a 120°C oven for three days, and the obtained product was washed with organic solvents such as N,N-dimethylacetamide, dichloromethane, and tetrahydrofuran. The product was then placed in a 70°C oven and dried for 24 h.

[0025] Example 1 First, 4 g of sodium hydroxide was dissolved in 13 mL of deionized water (18.25 MΩ·cm). After the solution was completely dissolved, it was allowed to stand and cool to room temperature. Then, in an ice bath environment, argon was continuously introduced to create a protective atmosphere, and 7.5 mL of acrylic acid was slowly added to the sodium hydroxide aqueous solution. After the addition was completed, stirring was continued for 30 min. Subsequently, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide (ice bath and argon protection) were added to the solution. After the addition was completed, stirring was continued for more than 40 min. After completing the above steps, the mixed solution was poured into a suitable container and placed in a vacuum oven. First, cover the lid and perform the polymerization reaction at 70 °C for 2 h. After the polymerization reaction was completed, open the lid of the oven and dry it. Both polymerization and drying were carried out in a vacuum environment with an air pressure of less than 10 Pa. Finally, the prepared dry glue was taken out and placed in a 6 M KOH and 0.2 M Zn (Ac) 2 The immersion time should be more than 1 day, until the dry gel is completely swollen. At this time, take it out to get PANa electrolyte.

[0026] Figure 1 This is the constant current charge and discharge curve of the flexible zinc-air battery assembled with gel electrolyte prepared in Example 1. As can be seen from the figure, the battery can -2 The effective working time under constant current charge and discharge is about 55 h, the discharge voltage is 1.0 V, the charge voltage is 2.0 V, the charge and discharge voltage difference is ~1.0 V, and the energy utilization (efficiency) is about 50% (1.0 V / 2.0 V).

[0027] Example 2 First, 4 g of sodium hydroxide was dissolved in 13 mL of deionized water (18.25 MΩ·cm). After the solution was completely dissolved, it was allowed to stand and cool to room temperature. Then, in an ice bath environment, argon was continuously introduced to create a protective atmosphere, and 7.5 mL of acrylic acid was slowly added to the sodium hydroxide aqueous solution. After the addition was completed, stirring was continued for 30 min. Subsequently, 15 mg of ball-milled COF(a) was added to the above solution under the conditions of ice bath and argon protection. The solution was ultrasonically treated for more than 30 min in an ice bath and argon protection environment using an ultrasonic device with a power of 100 W to promote the uniform dispersion of COF (a) in the solution. After the ultrasonic treatment, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added to the solution in sequence under continuous stirring, still in an ice bath and argon protection environment. The addition process should be operated carefully to ensure that the reagents are slowly and evenly integrated into the solution. After the addition was completed, stirring was continued for more than 40 min. After completing the above steps, pour the mixed solution into a suitable container and place it in a vacuum oven. Cover the lid first and perform the polymerization reaction at 70 °C for 2 h. After the polymerization reaction is completed, open the lid of the oven and dry it. It should be noted that the entire polymerization and drying process is carried out in a vacuum environment, and the air pressure in the oven must always be kept below 10 Pa. Finally, take out the prepared dry glue and place it in a 6 M KOH and 0.2 M Zn (Ac) 2 The immersion time should be more than 1 day, until the dry gel is completely swollen. At this point, take it out to obtain the PANa-COF(a) electrolyte.

[0028] Figure 2 shows the schematic diagram of the monomer structure of six COFs. Among them, the Tp monomer reacts with another monomer of COF (a) through an amine-aldehyde condensation reaction to generate COF (a). Figure 3 (a) presents the XRD spectrum of COF (a), which clearly shows that COF (a) forms a crystalline framework structure.

[0029] Figure 4 The constant current charge-discharge curve of the PANa-COF(a) gel electrolyte assembled flexible zinc-air battery prepared in Example 2 is shown. As can be seen from the figure, the battery can work effectively for about 36 h (cycle life), the discharge voltage is 1.27 V, the charge voltage is 2.0 V, the charge-discharge voltage difference is ~0.73 V, and the energy utilization rate (efficiency) is about 64% (1.27V / 2.0 V).

[0030] Example 3 First, 4 g of sodium hydroxide was dissolved in 13 mL of deionized water (18.25 MΩ·cm). After the solution was completely dissolved, it was allowed to stand and cool to room temperature. Then, in an ice bath environment, argon was continuously introduced to create a protective atmosphere, and 7.5 mL of acrylic acid was slowly added to the sodium hydroxide aqueous solution. After the addition was completed, stirring was continued for 30 min. Subsequently, 10 mg of ball-milled COF(a) was added to the above solution under the conditions of ice bath and argon protection. The solution was ultrasonically treated for more than 30 min in an ice bath and argon protection environment using an ultrasonic device with a power of 100 W to promote the uniform dispersion of COF (a) in the solution. After the ultrasonic treatment, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added to the solution in sequence under continuous stirring, still in an ice bath and argon protection environment. The addition process should be operated carefully to ensure that the reagents are slowly and evenly integrated into the solution. After the addition was completed, stirring was continued for more than 40 min. After completing the above steps, pour the mixed solution into a suitable container and place it in a vacuum oven. Cover the lid first and perform the polymerization reaction at 70 °C for 2 h. After the polymerization reaction is completed, open the lid of the oven and dry it. It should be noted that the entire polymerization and drying process is carried out in a vacuum environment, and the air pressure in the oven must always be kept below 10 Pa. Finally, take out the prepared dry glue and place it in a 6 M KOH and 0.2 M Zn (Ac) 2 The immersion time should be more than 1 day, until the dry gel is completely swollen. At this point, take it out to obtain the PANa-COF(a)-2 electrolyte.

[0031] Figure 2 shows the schematic diagram of the monomer structure of six COFs. Among them, the Tp monomer reacts with another monomer of COF (a) through an amine-aldehyde condensation reaction to generate COF (a). Figure 3 (a) presents the XRD spectrum of COF (a), which clearly shows that COF (a) forms a crystalline framework structure.

[0032] Figure 4 The constant current charge-discharge curves of the flexible zinc-air battery assembled with the PANa-COF(a)-2 gel electrolyte prepared in Example 3 are shown. As can be seen from the figure, the PANa-COF(a)-2 gel electrolyte is better than PANa-COF(a)-1, the battery can work effectively for about 54 h (cycle life), the discharge voltage is 1.29 V, the charge voltage is 1.84 V, the charge-discharge voltage difference is ~0.55 V, and the energy utilization rate (efficiency) is about 70% (1.29 V / 1.84 V).

[0033] Example 4 First, 4 g of sodium hydroxide was dissolved in 13 mL of deionized water (18.25 MΩ·cm). After the solution was completely dissolved, it was allowed to stand and cool to room temperature. Then, in an ice bath environment, argon was continuously introduced to create a protective atmosphere, and 7.5 mL of acrylic acid was slowly added to the sodium hydroxide aqueous solution. After the addition was completed, stirring was continued for 30 min. Subsequently, 10 mg of ball-milled COF(b) was added to the above solution under the conditions of ice bath and argon protection. The solution was ultrasonically treated for more than 30 min in an ice bath and argon protection environment using an ultrasonic device with a power of 100 W to promote the uniform dispersion of COF (b) in the solution. After the ultrasonic treatment, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added to the solution in sequence under continuous stirring, still in an ice bath and argon protection environment. The addition process should be operated carefully to ensure that the reagents are slowly and evenly integrated into the solution. After the addition was completed, stirring was continued for more than 40 min. After completing the above steps, pour the mixed solution into a suitable container and place it in a vacuum oven. Cover the lid first and perform the polymerization reaction at 70 °C for 2 h. After the polymerization reaction is completed, open the lid of the oven and dry it. It should be noted that the entire polymerization and drying process is carried out in a vacuum environment, and the air pressure in the oven must always be kept below 10 Pa. Finally, take out the prepared dry glue and place it in a 6 M KOH and 0.2 M Zn (Ac) 2 The immersion time should be more than 1 day, until the dry gel is completely swollen. At this point, take it out to obtain the PANa-COF (b) electrolyte.

[0034] Example 5 First, 4 g of sodium hydroxide was dissolved in 13 mL of deionized water (18.25 MΩ·cm). After the solution was completely dissolved, it was allowed to stand and cool to room temperature. Then, in an ice bath environment, argon was continuously introduced to create a protective atmosphere, and 7.5 mL of acrylic acid was slowly added to the sodium hydroxide aqueous solution. After the addition was completed, stirring was continued for 30 min. Subsequently, 10 mg of ball-milled COF(c) was added to the above solution under the conditions of ice bath and argon protection. The solution was ultrasonically treated for more than 30 min in an ice bath and argon protection environment using an ultrasonic device with a power of 100 W to promote the uniform dispersion of COF (c) in the solution. After the ultrasonic treatment, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added to the solution in sequence under continuous stirring, still in an ice bath and argon protection environment. The addition process should be operated carefully to ensure that the reagents are slowly and evenly integrated into the solution. After the addition was completed, stirring was continued for more than 40 min. After completing the above steps, pour the mixed solution into a suitable container and place it in a vacuum oven. Cover the lid first and perform the polymerization reaction at 70 °C for 2 h. After the polymerization reaction is completed, open the lid of the oven and dry it. It should be noted that the entire polymerization and drying process is carried out in a vacuum environment, and the air pressure in the oven must always be kept below 10 Pa. Finally, take out the prepared dry glue and place it in a 6 M KOH and 0.2 M Zn (Ac) 2 The immersion time should be more than 1 day, until the dry gel is completely swollen. At this point, take it out to obtain the PANa-COF(c) electrolyte.

[0035] Example 6 First, 4 g of sodium hydroxide was dissolved in 13 mL of deionized water (18.25 MΩ·cm). After the solution was completely dissolved, it was allowed to stand and cool to room temperature. Then, in an ice bath environment, argon was continuously introduced to create a protective atmosphere, and 7.5 mL of acrylic acid was slowly added to the sodium hydroxide aqueous solution. After the addition was completed, stirring was continued for 30 min. Subsequently, 10 mg of ball-milled COF(d) was added to the above solution under the conditions of ice bath and argon protection. The solution was ultrasonically treated for more than 30 min in an ice bath and argon protection environment using an ultrasonic device with a power of 100 W to promote the uniform dispersion of COF (d) in the solution. After the ultrasonic treatment, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added to the solution in sequence under continuous stirring, still in an ice bath and argon protection environment. The addition process should be operated carefully to ensure that the reagents are slowly and evenly integrated into the solution. After the addition is completed, stirring is continued for more than 40 min. After completing the above steps, pour the mixed solution into a suitable container and place it in a vacuum oven. Cover the lid first and perform the polymerization reaction at 70 °C for 2 h. After the polymerization reaction is completed, open the lid of the oven and dry it. It should be noted that the entire polymerization and drying process is carried out in a vacuum environment, and the air pressure in the oven must always be kept below 10 Pa. Finally, take out the prepared dry glue and place it in a 6 M KOH and 0.2 M Zn (Ac) 2 The immersion time should be more than 1 day, until the dry gel is completely swollen. At this point, take it out to obtain the PANa-COF(d) electrolyte.

[0036] Example 7 First, 4 g of sodium hydroxide was dissolved in 13 mL of deionized water (18.25 MΩ·cm). After the solution was completely dissolved, it was allowed to stand and cool to room temperature. Then, in an ice bath environment, argon was continuously introduced to create a protective atmosphere, and 7.5 mL of acrylic acid was slowly added to the sodium hydroxide aqueous solution. After the addition was completed, stirring was continued for 30 min. Subsequently, 10 mg of ball-milled COF(e) was added to the above solution under the conditions of ice bath and argon protection. The solution was ultrasonically treated for more than 30 min in an ice bath and argon protection environment using an ultrasonic device with a power of 100 W to promote the uniform dispersion of COF (e) in the solution. After the ultrasonic treatment was completed, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added to the solution in sequence under continuous stirring, still in an ice bath and argon protection environment. The addition process should be operated carefully to ensure that the reagents are slowly and evenly integrated into the solution. After the addition was completed, stirring was continued for more than 40 min. After completing the above steps, pour the mixed solution into a suitable container and place it in a vacuum oven. Cover the lid first and perform the polymerization reaction at 70 °C for 2 h. After the polymerization reaction is completed, open the lid of the oven and dry it. It should be noted that the entire polymerization and drying process is carried out in a vacuum environment, and the air pressure in the oven must always be kept below 10 Pa. Finally, take out the prepared dry glue and place it in a 6 M KOH and 0.2 M Zn (Ac) 2 The immersion time should be more than 1 day, until the dry gel is completely swollen. At this point, take it out to obtain the PANa-COF(e) electrolyte.

[0037] Example 8 First, 4 g of sodium hydroxide was dissolved in 13 mL of deionized water (18.25 MΩ·cm). After the solution was completely dissolved, it was allowed to stand and cool to room temperature. Then, in an ice bath environment, argon was continuously introduced to create a protective atmosphere, and 7.5 mL of acrylic acid was slowly added to the sodium hydroxide aqueous solution. After the addition was completed, stirring was continued for 30 min. Subsequently, 10 mg of ball-milled COF(f) was added to the above solution under the conditions of ice bath and argon protection. The solution was ultrasonically treated for more than 30 min in an ice bath and argon protection environment using an ultrasonic device with a power of 100 W to promote the uniform dispersion of COF (f) in the solution. After the ultrasonic treatment, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added to the solution in sequence under continuous stirring, still in an ice bath and argon protection environment. The addition process should be operated carefully to ensure that the reagents are slowly and evenly integrated into the solution. After the addition was completed, stirring was continued for more than 40 min. After completing the above steps, pour the mixed solution into a suitable container and place it in a vacuum oven. Cover the lid first and perform the polymerization reaction at 70 °C for 2 h. After the polymerization reaction is completed, open the lid of the oven and dry it. It should be noted that the entire polymerization and drying process is carried out in a vacuum environment, and the air pressure in the oven must always be kept below 10 Pa. Finally, take out the prepared dry glue and place it in a 6 M KOH and 0.2 M Zn (Ac) 2 The immersion time should be more than 1 day, until the dry gel is completely swollen. At this point, take it out to obtain the PANa-COF(f) electrolyte.

[0038] Figure 2 shows the schematic diagram of the monomer structure of six COFs. Among them, Tp monomer and another monomer of COF (b), COF (c), COF (d), COF (e) and COF (f) can generate corresponding COFs through amine-aldehyde condensation reaction. Figure 3 (b) shows the XRD spectrum of COF (b), Figure 3 (c) shows the XRD spectrum of COF (c) and COF (d), and Figure 3 (d) shows the XRD spectrum of COF (e) and COF (f). The spectrum clearly shows that these COFs form a crystalline framework structure.

[0039] Figure 5The constant current charge-discharge curves of flexible zinc-air batteries assembled with gel electrolytes added to all COFs are shown. The air electrode current collector is a homemade carbon-nickel foam. As can be seen from the figure, the PANa-COF(d) gel electrolyte is better than other PANa-COFs. The battery can work effectively for about 85 h (cycle life), with a discharge voltage of 1.30 V, a charge voltage of 1.83 V, a charge-discharge voltage difference of ~0.53 V, and an energy utilization rate (efficiency) of about 71% (1.30 V / 1.83 V).

[0040] Figure 6 The constant current charge-discharge curves of the flexible zinc-air battery assembled with gel electrolytes added to all COFs are shown. The air electrode current collector is a commercial hydrophobic carbon cloth. As can be seen from the figure, the PANa-COF(d) gel electrolyte with bipyridine functional groups is still better than the PANa-COFs with other functional groups. The battery can work effectively for about 76 h (cycle life), with a discharge voltage of 1.25 V, a charge voltage of 1.93 V, a charge-discharge voltage difference of ~0.68 V, and an energy utilization rate (efficiency) of about 65% (1.25 V / 1.93 V).

Claims

1. A method for preparing a hydrogel electrolyte membrane, characterized in that: The steps include: S1. First, add the covalent organic framework COFs into the sodium acrylate solution, and ultrasonically stir to obtain a COFs dispersion; S2. Add a certain amount of initiator ammonium persulfate and crosslinking agent N,N'-methylenebisacrylamide to the above dispersion, and continue stirring under argon protection until uniform; S3. The mixture is poured into a mold, polymerized and dried in a vacuum oven to obtain a sodium polyacrylate hydrogel dry film containing COFs; S4. Soak the prepared dry film in an aqueous electrolyte solution, and after a certain period of time, a sodium polyacrylate hydrogel electrolyte membrane containing COFs is obtained.

2. The method for preparing a hydrogel electrolyte membrane according to claim 1, characterized in that: The COFs described in S1 are covalent organic framework materials obtained by condensation reaction of Tp monomer and one or more amino-substituted aromatic hydrocarbons or heterocyclic aromatic hydrocarbons.

3. The method for preparing a hydrogel electrolyte membrane according to claim 2, characterized in that: The amino-substituted aromatic hydrocarbons include p-phenylenediamine (C6H8N), o-sulfonic p-phenylenediamine C6H8N2O3S, 3,3-diamino-[1,1-biphenyl]-4,4-dicarboxylic acid C 14 H 12 N2O4, 4,4-diaminobiphenyl-2,2-dicarboxylic acid C 14 H 12 Any one of N2O4; The heterocyclic aromatic hydrocarbons include p-aminopyridine C5H7N3, 2,2,5,5-diaminobipyridine C 10 H 10 Any one of N4.

4. The method for preparing a hydrogel electrolyte membrane according to claim 3, characterized in that: The mass ratio of sodium acrylate to COFs is 1:0.0005~0.002; the sodium acrylate solution is an aqueous solution, and the concentration of sodium acrylate is 0.2~1.0 g·mL -1 .

5. The method for preparing a hydrogel electrolyte membrane according to claim 1, characterized in that: The COFs sodium acrylate dispersion in S1 was ultrasonically dispersed at a power of 100-400 W for 0.5-1 h.

6. The method for preparing a hydrogel electrolyte membrane according to claim 1, wherein: The concentration of the initiator ammonium persulfate in the mixed solution in S2 is 0.2~0.3 mg / mL, the concentration of the cross-linking agent N,N'-methylenebisacrylamide in the mixed solution is 0.05~0.15 mg / mL, the mass ratio of the cross-linking agent to the initiator is 1:2~3, and the stirring time after adding the initiator and the cross-linking agent to S2 is continued for 0.5~1 h.

7. The method for preparing a hydrogel electrolyte membrane according to claim 1, characterized in that: The vacuum oven temperature described in S3 is 60~80℃, the polymerization drying time is 2~4 h, the mold is sealed during the polymerization process to prevent water evaporation, and is opened during the drying process to allow water to evaporate. The vacuum is maintained at less than 10 Pa during the polymerization and drying processes.

8. The method for preparing a hydrogel electrolyte membrane according to claim 1, characterized in that: The electrolyte solution described in S4 includes an alkaline electrolyte with potassium hydroxide, sodium hydroxide, and lithium hydroxide as main components, and a neutral electrolyte with zinc sulfate, zinc chloride, and ammonium chloride as main components; the dry film is immersed in the electrolyte for 1 to 4 days.

9. The method for preparing a hydrogel electrolyte membrane according to claim 1, characterized in that: The concentration of the alkaline electrolyte is 5-8 M; the concentration of the neutral electrolyte is 1-3 M.

10. A zinc-air battery, characterized in that A hydrogel electrolyte membrane prepared by the method according to any one of claims 1 to 9.

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