A method for preparing a polyacrylate hydrogel film

Abstract

The application provides a preparation method of a polyacrylate hydrogel film. Carbon nitride is uniformly dispersed in deionized water, nitrogen is used as a protective atmosphere, a neutralized sodium acrylate solution is added, and mixing is uniform; a certain amount of initiator ammonium persulfate and crosslinking agent N,N'-methylene bisacrylamide are added, and stirring is uniform; the above mixture is poured into a mold, polymerization is carried out at a certain temperature, and baking is performed; finally, the above prepared dry film is soaked in an electrolyte aqueous solution at room temperature to obtain a hydrogel electrolyte film. The carbon nitride used in the application is prepared by baking melamine, and a small amount of boric acid, oxalic acid or cyanuric acid is doped in the baking process to introduce a hydrophilic functional group into the carbon nitride to improve the dispersibility of the carbon nitride in water. The gel electrolyte film has a strong water retention capacity, a high ionic conductivity, can inhibit the uneven deposition and dendrite formation of zinc, and realizes the long cycle life of a zinc-air battery.

Description

Technical Field

[0001] This invention relates to the preparation of polymer hydrogel membranes and gel electrolytes, and is applied to the field of green energy storage devices, represented by rechargeable metal-based batteries. Background Technology

[0002] In recent years, portable and wearable electronic devices with flexibility and scalability have attracted increasing attention. Portable and wearable devices have a wide range of applications, including flexible mobile phones, humanoid electronic skin, and smart bracelets. Therefore, there is an urgent need to develop flexible and scalable power systems, such as batteries and supercapacitors. Among these energy devices, rechargeable metal-air batteries have relatively high capacity, making them more suitable for long-term power supply to wearable devices. Flexible rechargeable zinc-air batteries are a relatively mature technology with a theoretical energy density of up to 1086 Wh / Kg, five times that of current lithium-ion batteries. At the same time, flexible zinc-air batteries have good flexibility and weavability, making them very suitable for application in portable and wearable devices. Furthermore, this battery has the advantages of low cost and environmental friendliness, which provides broad prospects for low-cost mass production.

[0003] In flexible rechargeable zinc-air batteries, the polymer gel electrolyte (GPE) is a crucial component, serving as a bridge between the cathode and anode and determining the battery's performance and lifespan. Currently, the most reported GPE is obtained by polymers absorbing large amounts of high-concentration KOH solution to form a gel. The addition of KOH significantly improves the electrolyte's ionic conductivity, thereby enhancing the overall battery performance. However, in a strongly alkaline environment, the dissolution and deposition of the zinc anode are not entirely reversible. The semi-open structure allows for easy loss of water from the electrolyte, which in turn affects the dissolved Zn(OH)₄. 2- Supersaturation ultimately leads to the formation of Zn dendrites. Especially at high current densities, the non-uniform electric field distribution easily induces ion concentration and charge deposition on the zinc electrode, thereby promoting dendrite growth. Excessive dendrite growth can cause a short circuit between the cathode and anode, leading to battery failure. It has been reported that dense and vertically aligned zinc electrodeposition can be achieved through an artificial interface formed by dynamic adsorption in a simple colloidal electrolyte containing stony carbon nitride (g-C3N4) nanosheets, thus inhibiting zinc dendrite formation.

[0004] Based on the above research, this invention will use a hydrothermal method to prepare a polyacrylate hydrogel membrane, and obtain a gel electrolyte membrane through electrolyte permeation. The carbon nitride used in this invention is produced by calcining melamine; however, the carbon nitride obtained by this method has poor dispersibility in water. To improve its hydrophilicity, a small amount of boric acid, oxalic acid, or cyanuric acid will be added during the calcination process to introduce hydrophilic functional groups into the carbon nitride, thereby improving its dispersibility in water. The gel electrolyte membrane prepared by this invention is expected to have strong water retention capacity, high ionic conductivity, and the ability to inhibit uneven zinc deposition and dendrite formation, thus achieving a long cycle life for zinc-air batteries. Summary of the Invention

[0005] In view of this, the present invention provides a method for preparing a polyacrylate hydrogel membrane, the preparation of which includes the following steps:

[0006] A method for preparing a polyacrylate hydrogel membrane, the specific preparation method being as follows:

[0007] S1. Preparation of sodium acrylate mixture containing carbon nitride: First, a certain mass of C3N4 solid is placed in deionized water and ultrasonically dispersed to obtain a dispersion. Then, sodium hydroxide is dissolved in deionized water and slowly added dropwise to acrylic acid under cold water bath and strong magnetic stirring conditions. Stirring is continued to obtain a neutralized acrylic acid solution. Under nitrogen protection, the sodium acrylate solution is slowly added dropwise to the carbon nitride dispersion and stirred evenly.

[0008] S2. Add a certain amount of initiator ammonium persulfate and crosslinking agent N,N'-methylenebisacrylamide to the above solution, and continue stirring under nitrogen protection until homogeneous;

[0009] S3. Preparation of sodium polyacrylate hydrogel dry film containing carbon nitride: Pour the above mixture into a mold, polymerize at a certain temperature and dry to obtain sodium polyacrylate hydrogel dry film containing carbon nitride.

[0010] S4. Preparation of sodium polyacrylate hydrogel electrolyte membrane containing carbon nitride: The prepared dry membrane is immersed in an electrolyte aqueous solution, and after a certain period of time, a sodium polyacrylate hydrogel electrolyte membrane containing carbon nitride is obtained.

[0011] In S1, the concentration of the carbon nitride dispersion is 0.2~0.6 mg / L, the concentration of the sodium hydroxide solution is 5~10 mol / L, the molar ratio of sodium hydroxide to acrylic acid is 1:1~1.1, and the volume ratio of acrylic acid to carbon nitride dispersion is 1:1.5~2.

[0012] The carbon nitride described in S1 is ultrasonically dispersed at a power of 300~600 W for 2~6 h.

[0013] In step S1, if C3N4 solid is replaced with polyethylene oxide, then the concentration of the polyethylene oxide dispersion is 0.02~0.04 g / mL, the concentration of the sodium hydroxide solution is 5~10 mol / L, the molar ratio of sodium hydroxide to acrylic acid is 1:1~1.1, and the mass ratio of acrylic acid to polyethylene oxide is 1:0.04~0.08.

[0014] If the sodium hydroxide solution is replaced with a potassium hydroxide solution, a sodium polyacrylate hydrogel electrolyte membrane is finally obtained.

[0015] The concentration of the initiator ammonium persulfate in the mixture described in S2 is 0.5~2.5 mg / mL, the concentration of the crosslinking agent N,N'-methylenebisacrylamide in the mixture is 0.1~0.5 mg / mL, and the mass ratio of the crosslinking agent to the initiator is 1:4-5.

[0016] The solution in S2 is stirred for 0.5-1 h before adding the initiator and crosslinking agent, and stirred for another 0.5-1 h after adding the initiator and crosslinking agent; the vacuum oven temperature in S3 is 60-80℃, and the polymerization drying time is 6-12 h.

[0017] The electrolyte solution in S4 includes an alkaline electrolyte with potassium hydroxide, sodium hydroxide, and lithium hydroxide as the main components, and a neutral electrolyte with zinc sulfate, zinc chloride, and ammonium chloride as the main components, or other small molecule aqueous solutions or ionic liquids; the dry film is soaked in the electrolyte for 6 to 24 hours.

[0018] The concentration of the alkaline electrolyte is 5-8M; the concentration of the neutral electrolyte is 1-3M.

[0019] In another technical solution of the present invention, a sodium polyacrylate hydrogel membrane containing carbon nitride and a polyacrylate / polyoxyethylene hydrogel membrane are prepared by the method described in the present invention.

[0020] Regarding the steps of the sodium polyacrylate hydrogel membrane containing carbon nitride in the technical solution of this application, the first step is the preparation of the polyacrylic acid mixture containing the carbon nitride dispersion: First, a certain mass of C3N4 solid is placed in deionized water, and a dispersion is obtained by strong ultrasonication using a cell disruptor; in this process, the carbon nitride is obtained by calcining melamine. To improve the dispersibility of carbon nitride in water, this invention introduces hydrophilic functional groups by doping a small amount of boric acid, oxalic acid, or cyanuric acid during the melamine calcination process. Strong ultrasonication of the carbon nitride dispersion using a cell disruptor can make its dispersion more uniform; then, sodium hydroxide is dissolved... In deionized water, sodium hydroxide solution is slowly added dropwise to acrylic acid under cold water bath and strong magnetic stirring. Stirring continues to obtain a neutralized acrylic acid solution. Sodium acrylate solution is then slowly added dropwise to carbon nitride dispersion under nitrogen protection and stirred evenly. Slowly adding sodium hydroxide solution dropwise to acrylic acid under cold water bath and strong magnetic stirring can effectively prevent acrylic acid from bursting due to the large amount of heat released during the neutralization reaction. After obtaining neutralized sodium acrylate, it is mixed with carbon nitride dispersion to avoid the carbon nitride dispersion from polymerizing and settling due to a sudden change in pH. The role of nitrogen protection is to remove oxygen from the mixture and prevent sodium acrylate from being oxidized and polymerized.

[0021] Meanwhile, in the first step of the technical solution of this invention, the preparation of the polyethylene oxide / acrylate mixture: First, a certain amount of polyethylene oxide is dissolved in deionized water and stirred with a strong magnetic force at a certain temperature to obtain a uniform solution; the purpose is to uniformly disperse the polyethylene oxide in the deionized water, so as to facilitate its uniform mixing with the sodium (potassium) acrylate solution later; then, sodium hydroxide (or potassium hydroxide) is dissolved in deionized water and slowly added dropwise to the acrylic acid under the conditions of cold water bath and strong magnetic stirring, and stirring is continued to obtain a sodium (potassium) acrylate solution. This is to obtain a neutralized sodium (potassium) acrylate solution, so as to avoid the precipitation of polyethylene oxide due to the change of pH value when mixing with the polyethylene oxide dispersion. The cold water bath, strong magnetic stirring, and slow dropwise addition of sodium (potassium) hydroxide solution are to avoid the explosive polymerization of acrylic acid caused by the large amount of heat released by the neutralization reaction; finally, at room temperature and under nitrogen protection, the sodium (potassium) acrylate solution is slowly added dropwise to the cooled polyethylene oxide dispersion, and the mixture is stirred with a strong magnetic force for 30 minutes to obtain a uniform mixture. The sodium (potassium) acrylate solution is added slowly to facilitate uniform mixing. The room temperature and cooling of the polyethylene oxide dispersion are to prevent premature polymerization of the sodium (potassium) acrylate monomers due to high temperature. The purpose of introducing nitrogen gas is to remove oxygen from the mixture and prevent the sodium (potassium) acrylate from being oxidized.

[0022] In the second step of the technical solution of this application, a certain mass of initiator ammonium persulfate and crosslinking agent N,N'-methylenebisacrylamide are added to the mixture and stirred until homogeneous. In this step, the amount of initiator and crosslinking agent is extremely important. Too much initiator and crosslinking agent will result in a hydrogel dry film that cannot form a solid mass after absorbing the electrolyte, instead appearing as scattered particles. Too little initiator and crosslinking agent will result in a hydrogel dry film with poor electrolyte absorption capacity, failing to form a quasi-solid electrolyte membrane.

[0023] Regarding the third step of the technical solution of this application, the polymerization and drying of the mixture: the sodium acrylate mixture containing carbon nitride is poured into a mold, polymerized and dried in a vacuum oven. During this process, the bottom of the selected mold must be flat, and the mold must also be placed level in the oven. Uneven liquid levels in the mold will cause uneven polymerization of the hydrogel, resulting in an uneven gel surface after soaking in the electrolyte. To prevent the sodium acrylate from being oxidized by oxygen in the air during polymerization, the polymerization must be carried out in a vacuum oven.

[0024] In the fourth step of the technical solution of this application, after the hydrogel dry film is dried and cooled, a certain volume of electrolyte is poured into the mold, and after soaking for a certain period of time, a sodium polyacrylate hydrogel electrolyte membrane containing carbon nitride is obtained. The purpose of this step is to absorb the electrolyte to form a gel electrolyte. The bottom area of ​​the mold and the volume of electrolyte absorbed directly affect the thickness and conductivity of the gel. By optimizing both, gels with high conductivity and various thicknesses can be obtained. Attached Figure Description

[0025] Figure 1 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0026] Figure 2 The electrochemical impedance spectroscopy (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0027] Figure 3The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 3 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0028] Figure 4 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 4 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0029] Figure 5 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 5 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0030] Figure 6 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 6 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0031] Figure 7 A digital photograph of the sample prepared in Example 1.

[0032] Figure 8 This is a digital photograph of the sample prepared in Example 2.

[0033] Figure 9 The image shows a scanning electron microscope (SEM) image of the sample prepared in Example 3 after freeze-drying.

[0034] Figure 10The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured at 5 mA / cm² for the sample prepared in Example 7. 2 Constant current charge-discharge curves at current density. Where a is the electrochemical impedance spectroscopy (EIS), b is the electrolyte retention capacity over seven days, and c is the constant current charge-discharge curve of the flexible zinc-air battery at 5 mA / cm².

[0035] Figure 11 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 8 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery at 5 mA / cm² are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0036] Figure 12 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 9 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0037] Figure 13 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 10 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0038] Figure 14 The electrochemical impedance spectroscopy (EIS) and electrolyte retention capacity were measured for the sample prepared in Example 11. Where a represents the electrochemical impedance spectroscopy (EIS) and b represents the electrolyte retention capacity over seven days.

[0039] Figure 15 The electrochemical impedance spectroscopy (EIS) and electrolyte retention capacity were measured for the sample prepared in Example 12. Where a represents the electrochemical impedance spectroscopy (EIS) and b represents the electrolyte retention capacity over seven days.

[0040] Figure 16The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 13 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0041] Figure 17 The electrochemical impedance spectroscopy (EIS) and electrolyte retention capacity of the sample prepared in Example 14 are shown. Where a is the electrochemical impedance spectroscopy (EIS) and b is the electrolyte retention capacity over seven days.

[0042] Figure 18 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 15 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves of the flexible zinc-air battery are shown. Where a represents the electrochemical impedance spectroscopy (EIS), b represents the electrolyte retention capacity over seven days, and c represents the constant current charge-discharge curves of the flexible zinc-air battery at a current density of 5 mA / cm². 2 The constant current charge-discharge curve at that time.

[0043] Figure 19 A digital photograph of the sample prepared in Example 7.

[0044] Figure 20 This is a digital photograph of the sample prepared in Example 12.

[0045] Figure 21 The image shown is a scanning electron microscope image of the sample prepared in Example 12.

[0046] Figure 22 The image shown is a scanning electron microscope image of the sample prepared in Example 15. Detailed Implementation

[0047] Characterization conditions

[0048] The electrochemical impedance spectroscopy (EIS) of the sample prepared in this embodiment of the invention was measured by the Shanghai Chenhua workstation. The testing method was as follows: a hydrogel of a certain thickness (T) was cut into strips 2.5 cm wide (W) and 7 cm long. Both ends were wrapped with copper foil, leaving a 5 cm (L) length of exposed gel between the copper foil. A stainless steel electrode clamp was then placed on the copper foil for testing, with a frequency range of 0.01 Hz to 10 Hz. 6HZ. The resistance (R) of the gel is inferred from the actual axial intercept of the EIS curve. The ionic conductivity of the gel can be calculated using the formula σ = L / A*R (where L represents the distance between the stainless steel electrodes (i.e., the length of the exposed gel between the copper foils), A is the cross-sectional area of ​​the polymer gel electrolyte (A = T*W, where the cross-sectional area is the product of the gel thickness and width), and R is the resistance of the polymer gel electrolyte).

[0049] The electrolyte retention capacity test method in this embodiment of the invention is as follows: take a piece of gel of the same mass prepared by various embodiments, put them together and expose them to the air, and measure their mass retention rate over seven days.

[0050] The flexible zinc-air battery assembled from gels prepared in this embodiment of the invention has the following structure: a zinc plate as the anode, and 2 mg of Co-NC material loaded at a 1 cm⁻¹ layer. 2 The battery uses carbon cloth as an air cathode, with the cathode and anode sandwiched on either side of the electrolyte to form a sandwich structure. One side of the cathode is covered with a current collector, and the outermost layer of the battery is wrapped with breathable tape. The battery was tested on the Blue Electric testing system and the current was measured at 5 mA / cm². 2 The charge / discharge cycle curve is obtained.

[0051] The dry film prepared in the embodiments of the present invention absorbs a certain mass of deionized water to obtain a hydrogel film, which is then freeze-dried and scanned electron microscope (SEM) images are obtained using an Inspect F50 scanning electron microscope (FEI America).

[0052] Example 1

[0053] Preparation of carbon nitride (C3N4): 2 g of melamine was placed in a crucible and placed in a muffle furnace and calcined at 550℃ for 4 h to obtain primary carbon nitride material; 0.2 g of primary carbon nitride and 1 g of anhydrous glucose were placed in a ball mill jar and ball-milled for 3 h to obtain mixed powder; the mixed powder was then dispersed in 60 mL of deionized water and sonicated for 2 h to make it uniformly dispersed; the dispersion was then centrifuged and the upper clear liquid was taken; the upper clear liquid was filtered to obtain carbon nitride powder; and then it was placed in a freeze desiccant and dried for 48 h to obtain the final carbon nitride (C3N4) material.

[0054] 7.5 mg of carbon nitride (C3N4) powder was poured into 15 mL of deionized water and sonicated vigorously for 2 h using a cell disruptor to obtain a uniformly distributed carbon nitride dispersion. Then, 10 mL of 10 mol / L sodium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a homogeneous solution. Sodium acrylate solution was then slowly added dropwise to the carbon nitride (C3N4) dispersion at room temperature under nitrogen protection and stirred magnetically for 30 min to obtain a homogeneous mixture. 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were then added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry membrane was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0055] Figure 1 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 263 mS / cm. Figure (b) shows that the electrolyte retains 85.8% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of 46 hours. Figure 7 A digital photograph of the sample prepared in Example 1.

[0056] Example 2

[0057] Preparation of boric acid-doped carbon nitride (C3N4): 2g of melamine and 0.5g of boric acid were mixed evenly and placed in a crucible and placed in a muffle furnace. The mixture was calcined at 550℃ for 4 h to obtain primary boric acid-doped carbon nitride material. 0.2g of primary boric acid-doped carbon nitride and 1g of anhydrous glucose were placed in a ball mill and ball-milled for 3 h to obtain a mixed powder. The mixed powder was then dispersed in 60 mL of deionized water and sonicated for 2 h to ensure uniform dispersion. The dispersion was then centrifuged and the supernatant was collected. The supernatant was filtered to obtain carbon nitride powder, which was then dried in a freeze-drying agent for 48 h to obtain the final boric acid-doped carbon nitride (C3N4) material.

[0058] 7.5 mg of boric acid-doped carbon nitride (C3N4) powder was poured into 15 mL of deionized water and subjected to strong sonication for 2 h using a cell disruptor to obtain a uniformly distributed carbon nitride dispersion. Then, 10 mL of 10 mol / L sodium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a homogeneous solution. At room temperature and under nitrogen protection, sodium acrylate solution was slowly added dropwise to the carbon nitride (C3N4) dispersion, and the mixture was stirred magnetically for 30 min to obtain a homogeneous mixture. Then, 6 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry membrane was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain the hydrogel electrolyte membrane.

[0059] Figure 2 The electrochemical impedance spectroscopy (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 238 mS / cm. Figure (b) shows that the electrolyte retains 80% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of 55 hours. Figure 8 This is a digital photograph of the sample prepared in Example 2. Figure 9 The image shows a scanning electron microscope (SEM) image of the sample prepared in Example 2. As can be seen from the image, the hydrogel membrane has a porous structure.

[0060] Example 3

[0061] The preparation method and steps were the same as in Example 2, except that oxalic acid was added during the preparation of carbon nitride (C3N4). Specifically, 2g of melamine and 0.5g of oxalic acid were mixed evenly, placed in a crucible, and calcined at 550°C for 4 hours to obtain primary oxalic acid-doped carbon nitride material. Finally, boric acid-doped carbon nitride (C3N4) material was obtained. Other steps were the same as in Example 1, resulting in the preparation of a hydrogel electrolyte membrane.

[0062] Figure 3 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 3 at a current density of 5 mA / cm². 2The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 312 mS / cm. Figure (b) shows that the electrolyte retains 83.6% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of 46 hours.

[0063] Example 4

[0064] The preparation method and steps were the same as in Example 2, except that cyanuric acid was added during the preparation of carbon nitride (C3N4). Specifically, 2g of melamine and 0.5g of cyanuric acid were mixed evenly, placed in a crucible, and calcined at 550°C for 4 hours to obtain primary cyanuric acid-doped carbon nitride material. Finally, cyanuric acid-doped carbon nitride (C3N4) material was obtained. Other steps were the same as in Example 1, resulting in the preparation of a hydrogel electrolyte membrane.

[0065] Figure 4 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 4 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 250 mS / cm. Figure (b) shows that the electrolyte retains 80% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of 41 hours.

[0066] Example 5

[0067] The preparation method and steps are the same as in Example 2, except that the amount of carbon nitride doped with boric acid is 5 mg during the preparation of the hydrogel electrolyte membrane, thus obtaining the hydrogel electrolyte membrane.

[0068] Figure 5 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 5 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 238 mS / cm. Figure (b) shows that the electrolyte retains 81.5% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of up to 30 hours.

[0069] Example 6

[0070] The preparation method and steps are the same as in Example 2, except that the amount of carbon nitride doped with boric acid is 10 mg during the preparation of the hydrogel electrolyte membrane, thus obtaining the hydrogel electrolyte membrane.

[0071] Figure 6 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 6 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 222 mS / cm. Figure (b) shows that the electrolyte retains 83.7% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of 27 h.

[0072] Example 7

[0073] First, 0.5 g of polyethylene glycol with a molecular weight of 20,000 was poured into 15 mL of deionized water and stirred magnetically for 6 h in a constant temperature water bath at 70 °C to obtain a uniform dispersion. Then, 10 mL of 10 mol / L sodium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a uniform solution. At room temperature, under nitrogen protection, sodium acrylate solution was slowly added dropwise to the polyethylene oxide dispersion and stirred magnetically for 30 min to obtain a uniform mixture. Then, 60 mg of ammonium persulfate and 12 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry film was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0074] Figure 10 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 7 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 381 mS / cm. Figure (b) shows that the electrolyte retains 75.4% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of 155 h. Figure 19 An optical photograph of the sample prepared in Example 7.

[0075] Example 8

[0076] First, 0.5 g of polyethylene oxide with a molecular weight of 100,000 was poured into 15 mL of deionized water and stirred magnetically for 6 h in a constant temperature water bath at 70 °C to obtain a uniform dispersion. Then, 10 mL of 10 mol / L sodium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a uniform solution. At room temperature, under nitrogen protection, sodium acrylate solution was slowly added dropwise to the polyethylene oxide dispersion and stirred magnetically for 30 min to obtain a uniform mixture. Then, 60 mg of ammonium persulfate and 12 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry film was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0077] Figure 11 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 8 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 356 mS / cm. Figure (b) shows that the electrolyte retains 70.1% of its initial mass within seven days. Figure (c) shows that the cycle life of the zinc-air battery assembled with this electrolyte is 56 h.

[0078] Example 9

[0079] First, 0.5 g of polyethylene oxide with a molecular weight of 600,000 was poured into 15 mL of deionized water and stirred magnetically for 6 h in a constant temperature water bath at 70 °C to obtain a uniform dispersion. Then, 10 mL of 10 mol / L sodium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a uniform solution. At room temperature, under nitrogen protection, sodium acrylate solution was slowly added dropwise to the polyethylene oxide dispersion and stirred magnetically for 30 min to obtain a uniform mixture. Then, 60 mg of ammonium persulfate and 12 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry film was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0080] Figure 12The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 9 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 326 mS / cm. Figure (b) shows that the electrolyte retains 75.7% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of 165 h. Figure 11 An optical photograph of the sample prepared in Example 3. Figure 12 The image shows a scanning electron microscope (SEM) image of the sample prepared in Example 3. As can be seen from the image, the gel has a large number of micropores.

[0081] Example 10

[0082] First, 0.25 g of polyethylene oxide with a molecular weight of 2,000,000 was poured into 30 mL of deionized water and stirred magnetically for 6 h in a constant temperature water bath at 70 °C to obtain a uniform dispersion. Then, 10 mL of 10 mol / L sodium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a uniform solution. At room temperature, under nitrogen protection, sodium acrylate solution was slowly added dropwise to the polyethylene oxide dispersion and stirred magnetically for 30 min to obtain a uniform mixture. Then, 60 mg of ammonium persulfate and 12 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry film was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0083] Figure 13 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 10 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 234 mS / cm. Figure (b) shows that the electrolyte retains 71.2% of its initial mass within seven days. Figure (c) shows that the zinc-air battery assembled with this electrolyte has a cycle life of 76 hours.

[0084] Example 11

[0085] First, 0.5 g of polyethylene glycol with a molecular weight of 20,000 was poured into 15 mL of deionized water and stirred magnetically for 6 h in a constant temperature water bath at 70 °C to obtain a uniform dispersion. Then, 10 mL of 10 mol / L potassium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a uniform solution. At room temperature, under nitrogen protection, potassium acrylate solution was slowly added dropwise to the polyethylene oxide dispersion and stirred magnetically for 30 min to obtain a uniform mixture. Then, 60 mg of ammonium persulfate and 12 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry film was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0086] Figure 14 The electrochemical impedance spectroscopy (EIS) and electrolyte retention capacity of the sample prepared in Example 11 were measured. Figure (a) shows that the ionic conductivity of the gel electrolyte is 345 mS / cm. Figure (b) shows that the electrolyte retains 74.2% of its initial mass within seven days.

[0087] Example 12

[0088] First, 0.5 g of polyethylene oxide with a molecular weight of 100,000 was poured into 15 mL of deionized water and stirred magnetically for 6 h in a constant temperature water bath at 70 °C to obtain a uniform dispersion. Then, 10 mL of 10 mol / L potassium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a uniform solution. At room temperature, under nitrogen protection, sodium potassium acrylate solution was slowly added dropwise to the polyethylene oxide dispersion and stirred magnetically for 30 min to obtain a uniform mixture. Then, 60 mg of ammonium persulfate and 12 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry film was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0089] Figure 15The electrochemical impedance spectroscopy (EIS) and electrolyte retention capacity of the sample prepared in Example 12 are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 370 mS / cm. Figure (b) shows that the electrolyte retains 70.8% of its initial mass within seven days.

[0090] Example 13

[0091] First, 0.5 g of polyethylene oxide with a molecular weight of 600,000 was poured into 15 mL of deionized water and stirred magnetically for 6 h in a constant temperature water bath at 70 °C to obtain a uniform dispersion. Then, 10 mL of 10 mol / L potassium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a uniform solution. At room temperature, under nitrogen protection, potassium acrylate solution was slowly added dropwise to the polyethylene oxide dispersion and stirred magnetically for 30 min to obtain a uniform mixture. Then, 60 mg of ammonium persulfate and 12 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry film was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0092] Figure 16 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 13 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 290 mS / cm. Figure (b) shows that the electrolyte retains 72.1% of its initial mass within seven days. Figure (c) shows that the cycle life of the zinc-air battery assembled with this electrolyte is 65 h.

[0093] Example 14

[0094] First, 0.25 g of polyethylene oxide with a molecular weight of 2,000,000 was poured into 30 mL of deionized water and stirred magnetically for 6 h in a constant temperature water bath at 70 °C to obtain a uniform dispersion. Then, 10 mL of 10 mol / L potassium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After the addition was complete, the mixture was stirred for 30 min to form a uniform solution. At room temperature, under nitrogen protection, potassium acrylate solution was slowly added dropwise to the polyethylene oxide dispersion and stirred magnetically for 30 min to obtain a uniform mixture. Then, 60 mg of ammonium persulfate and 12 mg of N,N'-methylenebisacrylamide were added, and the mixture was stirred for another 30 min under nitrogen protection. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry film was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain a hydrogel electrolyte membrane.

[0095] Figure 17 The electrochemical impedance spectroscopy (EIS) and electrolyte retention capacity of the sample prepared in Example 14 were measured. Figure (a) shows that the ionic conductivity of the gel electrolyte is 357 mS / cm. Figure (b) shows that the electrolyte retains 73% of its initial mass after seven days.

[0096] Example 15

[0097] 10 mL of 10 mol / L potassium hydroxide solution was slowly added dropwise to 7.2 mL of acrylic acid under strong magnetic stirring in a cold water bath. After stirring under strong magnetic stirring for 30 min in a nitrogen atmosphere, 9 mg of ammonium persulfate and 3 mg of N,N'-methylenebisacrylamide were added, and stirring was continued for another 30 min. The mixture was then poured into a glass mold, covered, and polymerized in a vacuum oven at 70 °C for 2 h. After removing the lid, the mixture was dried for another 6 h until completely dry. Finally, the resulting dry membrane was immersed in a mixed solution of 6 M KOH + 2 M Zn(OAC)2 for 24 h to obtain the hydrogel electrolyte membrane.

[0098] Figure 18 The electrochemical impedance (EIS), electrolyte retention capacity, and the assembled flexible zinc-air battery were measured for the sample prepared in Example 15 at a current density of 5 mA / cm². 2 The constant current charge-discharge curves are shown in Figure (a). The ionic conductivity of the gel electrolyte is calculated to be 333 mS / cm. Figure (b) shows that the electrolyte retains 69% of its initial mass within seven days. Figure (c) shows that the cycle life of the zinc-air battery assembled with this electrolyte is 56 h. Figure 22The image shows a scanning electron microscope (SEM) image of the sample prepared in Example 15. As can be seen from the image, the gel has a large number of micropores.

Claims

1. A method for preparing a polyacrylate hydrogel membrane, characterized in that, The specific preparation method is as follows: S1. Preparation of sodium acrylate mixture containing carbon nitride: First, a certain mass of C3N4 solid is placed in deionized water. The concentration of carbon nitride dispersion is 0.2~0.6 mg / L. Carbon nitride is ultrasonically dispersed at a power of 300~600 W for 2~6 h. The dispersion is obtained by ultrasonication. Then, sodium hydroxide is dissolved in deionized water and slowly added dropwise to acrylic acid under cold water bath and strong magnetic stirring. Stirring is continued to obtain a neutralized sodium acrylate solution. Under nitrogen protection, the sodium acrylate solution is slowly added dropwise to the carbon nitride dispersion and stirred evenly. S2. Add a certain amount of initiator ammonium persulfate and crosslinking agent N,N'-methylenebisacrylamide to the sodium acrylate mixture containing carbon nitride, and continue stirring under nitrogen protection until homogeneous; S3. Preparation of sodium polyacrylate hydrogel dry film containing carbon nitride: Pour the mixture obtained in step S2 into a mold, polymerize it at a certain temperature and dry it to obtain sodium polyacrylate hydrogel dry film. S4. Preparation of sodium polyacrylate hydrogel electrolyte membrane containing carbon nitride: The prepared dry membrane is immersed in an electrolyte aqueous solution, and after a certain period of time, the sodium polyacrylate hydrogel electrolyte membrane is obtained.

2. The method for preparing a polyacrylate hydrogel membrane according to claim 1, characterized in that, The concentration of sodium hydroxide in S1 is 5~10 mol / L, the molar ratio of sodium hydroxide to acrylic acid is 1:1~1.1, and the volume ratio of acrylic acid to carbon nitride dispersion is 1:1.5~2.

3. The method for preparing a polyacrylate hydrogel membrane according to claim 1, characterized in that, If sodium hydroxide is replaced with potassium hydroxide, a potassium polyacrylate hydrogel electrolyte membrane is finally obtained.

4. The method for preparing a polyacrylate hydrogel membrane according to any one of claims 1-3, characterized in that, The concentration of the initiator ammonium persulfate in the mixture described in S2 is 0.5~2.5 mg / mL, the concentration of the crosslinking agent N,N'-methylenebisacrylamide in the mixture is 0.1~0.5 mg / mL, and the mass ratio of the crosslinking agent to the initiator is 1:4-5.

5. The method for preparing a polyacrylate hydrogel membrane according to claim 4, characterized in that, The solution in S2 is stirred for 0.5 to 1 h before adding the initiator and crosslinking agent, and stirred for another 0.5 to 1 h after adding the initiator and crosslinking agent; the temperature in S3 is 60 to 80 °C, and the polymerization drying time is 6 to 12 h.

6. The method for preparing a polyacrylate hydrogel membrane according to claim 5, characterized in that, The electrolyte aqueous solution described in S4 includes an alkaline electrolyte with potassium hydroxide, sodium hydroxide, and lithium hydroxide as the main components, and a neutral electrolyte with zinc sulfate, zinc chloride, and ammonium chloride as the main components; the dry film is soaked in the electrolyte for 6 to 24 hours.

7. The method for preparing a polyacrylate hydrogel membrane according to claim 6, characterized in that, The concentration of the alkaline electrolyte is 5-8M; the concentration of the neutral electrolyte is 1-3M.

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