Preparation method for in-situ polymerization of sodium polyacrylate hydrogel containing covalent organic framework material

Abstract

The invention provides a preparation method for in-situ polymerization of sodium polyacrylate hydrogel containing a covalent organic framework material. The preparation method comprises the following steps: firstly, dissolving a cross-linking agent N, N '-methylene bisacrylamide in acrylic acid, and neutralizing by using a sodium hydroxide solution to obtain a sodium acrylate solution; dissolving potassium hydroxide and zinc acetate in water, then pouring into a sodium acrylate solution, and uniformly stirring and mixing; adding a covalent organic framework material TpPa (SO3H), and uniformly stirring and dispersing; and finally, adding an initiator ammonium persulfate, pouring the solution into a mold, and standing to wait for gel polymerization, thereby obtaining the hydrogel electrolyte.

Description

Technical Field

[0001] The invention relates to the preparation of a polymer hydrogel film and a gel electrolyte, and is applied to the field of green energy storage devices represented by rechargeable metal-based batteries. Background Art

[0002] With the rapid development of society, zinc-based batteries have become a promising choice for advanced energy storage devices due to their high energy density, safety, environmental friendliness, and cost-effectiveness. Among them, flexible zinc-based batteries, including flexible zinc-air batteries (FAZABs), have the advantages of high flexibility, wearability, safety, and low risk of electrolyte leakage, and have great potential in wearable and implantable electronic devices. For batteries, as an ionic conductor connecting the anode and the cathode, the electrolyte system determines the mass transfer and interfacial chemistry of the entire charging and discharging process, and is crucial to the overall performance of ZABs (e.g., energy density, rechargeability, and operating voltage).

[0003] GPE consists of two parts, namely polymer matrix and electrolyte, which combines the advantages of liquid and solid electrolytes. Compared with liquid electrolytes, gel electrolytes (GPEs) give ZABs the characteristics of portability, flexibility, and wearability. And it plays an important role in preventing electrolyte leakage, stabilizing the three-phase interface, and inhibiting zinc dendrites. However, the use of GPEs in FAZABs has the following problems: (a) Compared with liquid electrolytes, polymer electrolytes exhibit lower ionic conductivity. (b) The semi-open structure of the battery accelerates the loss of water in GPEs, resulting in battery failure. (c) During the battery cycle, the interface between the zinc anode and the electrolyte is unstable, and dendrites are easily generated. Therefore, it is necessary to improve GPEs to improve the conductivity, mechanical stability, and alkali resistance of the polymer to increase the service life of the battery. Among them, covalent organic framework (COF) materials are introduced into GPE. The modified groups on COF, such as sulfonic acid groups and carboxyl groups, can form hydrogen bonds with polymer chains to improve the water retention and mechanical properties of GPE. The sulfonic acid groups can induce uniform deposition of zinc, which has great potential in optimizing GPE. Summary of the invention

[0004] Based on the above problems, the present invention introduces COF materials into the in-situ polymerization process of sodium polyacrylate. The modified groups on COF can form hydrogen bonds with the sodium polyacrylate molecular chain and water molecules, and the obtained gel electrolyte has high ionic conductivity and electrolyte retention capacity; at the same time, the modified sulfonic acid groups can induce uniform zinc deposition, inhibit zinc plate corrosion and dendrite generation; it is intended to be applied to rechargeable flexible zinc-air batteries, provide a stable and uniform electrode / electrolyte interface for the zinc anode, and achieve a long cycle life of the zinc-air battery.

[0005] In view of this, the present invention provides a method for preparing a sodium polyacrylate hydrogel containing a covalent organic framework material by in-situ polymerization, wherein the preparation method comprises the following steps: Step 1: Preparation of sodium acrylate solution: First, dissolve sodium hydroxide in water and N,N'-methylenebisacrylamide in acrylic acid, and stir them separately to obtain a uniformly dispersed solution. The purpose of this step is to make sodium hydroxide and N,N'-methylenebisacrylamide uniformly dispersed in water and acrylic acid solution, respectively, so as to facilitate the subsequent uniform mixing of the two solutions. Slowly add the sodium hydroxide solution dropwise to the acrylic acid solution containing N,N'-methylenebisacrylamide and continue stirring to obtain a neutralized sodium acrylate solution; In some implementations, the concentration of the sodium hydroxide is 5-10 mol / L, the concentration of the crosslinking agent N,N'-methylenebisacrylamide in the acrylic acid solution is 30-40 mg / mL, and the molar ratio of sodium hydroxide to acrylic acid is 1:1.0-1.10.

[0006] The temperature of the magnetic stirring of the sodium acrylate solution is 0-10°C.

[0007] This is to obtain a neutralized sodium acrylate solution. The cold water bath, strong magnetic stirring, and slow dripping of sodium hydroxide solution are to avoid the explosion of acrylic acid caused by the large amount of heat released by the neutralization reaction.

[0008] Step 2: Preparation of a potassium hydroxide / zinc salt / sodium acrylate mixed solution: Dissolve potassium hydroxide and zinc acetate in water, and stir them magnetically to obtain a uniform dispersion. Then, add the prepared sodium acrylate solution to the potassium hydroxide / zinc acetate solution, and stir to disperse them uniformly.

[0009] In some implementations, the concentration of potassium hydroxide is 5-8 mol / L, and the concentration of zinc salt is 0.1-0.5 mol / L.

[0010] The zinc salt includes any one of zinc acetate, zinc sulfate, zinc chloride, zinc oxalate and zinc nitrate.

[0011] Step 3: Preparation of sodium acrylate mixed solution containing covalent organic framework material: Add COF material to the prepared sodium acrylate solution and stir to disperse evenly. The purpose of this step is to mix the mixed solution and COF material evenly.

[0012] The covalent organic framework material (COF material) is selected from any one of TpPa(SO3H), TpPa(COOH), TpBD(SO3H)2, and TpBD(COOH)2.

[0013] In some implementations, the concentration of the covalent organic framework material in the solution is 0.12-0.36 mg / mL.

[0014] Step 4: Preparation of sodium polyacrylate hydrogel containing covalent organic framework materials: Add a certain amount of initiator ammonium persulfate to the above solution, then pour the solution into the mold and wait for gel polymerization. After the third step, sodium acrylate, crosslinker, potassium hydroxide, zinc acetate, and COF materials are evenly dispersed. In this case, adding an initiator can help form a more uniform structure.

[0015] In some embodiments, the concentration of the initiator ammonium persulfate in the mixed solution is 1-2 mg / mL, and the standing time is 10-20 min.

[0016] The initiator ammonium persulfate causes the free radical polymerization of the sodium acrylate monomer to form a sodium acrylate chain. The sodium acrylate chain further reacts with the N,N'-methylenebisacrylamide crosslinker to form a sodium polyacrylate polymer. At the same time, the carboxylic acid groups on the sodium acrylate chain form hydrogen bonds with water molecules and N and O on the surface of COF to form a crosslinked polymer. The power density of the battery assembled using the technical solution of the present application is 200 mWcm -2 Above; further preferably up to 230 mWcm -2 More than; further preferably up to 200 mWcm -2 The cycle life of the battery is 50 h or more, preferably 80 h or more, preferably 100 h or more, and preferably 120 h or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Schematic diagram of the structures of the six COF materials used.

[0018] Figure 2 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 1 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled from the sample in Example 1 are measured at 1 mA cm -2 The constant current charge-discharge curves at 1 mAcm -2 Constant current charge and discharge curve.

[0019] Figure 3 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 2 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled from the sample in Example 2 are measured at 1 mA cm-2 The constant current charge-discharge curves at 1 mAcm -2 Constant current charge and discharge curve.

[0020] Figure 4 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 3 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled from the sample in Example 3 are measured at 1 mA cm -2 The constant current charge-discharge curves at 1 mAcm -2 Constant current charge and discharge curve.

[0021] Figure 5 The open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled with the sample prepared in Example 4 are measured at 1 mA cm -2 The constant current charge-discharge curves at 1 mA cm -2 Constant current charge and discharge curve.

[0022] Figure 6 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 5 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled from the sample in Example 5 are measured at 1 mA cm -2 The constant current charge-discharge curves at 1 mAcm -2 Constant current charge and discharge curve.

[0023] Figure 7 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 6 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled from the sample in Example 6 are measured at 1 mA cm -2 The constant current charge-discharge curves at 1 mAcm -2 Constant current charge and discharge curve.

[0024] Figure 8 The open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled with the sample prepared in Example 7 are measured at 1 mA cm -2 The constant current charge-discharge curves at 1 mA cm -2 Constant current charge and discharge curve. DETAILED DESCRIPTION

[0025] Characterization conditions In the embodiment of the present invention, the electrochemical impedance spectroscopy (EIS) was measured by Shanghai Chenhua workstation, and the test method was as follows: a certain thickness ( T ) hydrogel was cut into 1 cm wide ( W ) , length 1 cm ( L ) strip, with the upper and lower planes in contact with the copper foil. Then the stainless steel electrode clamp is clamped on the copper foil for testing, and the frequency range is 0.01 ~10 6 HZ. According to ionic conductivity σ = T / A * R ( T represents the thickness of the gel), A is the cross-sectional area of ​​the polymer gel electrolyte ( A = L * W , the cross-sectional area is the product of the length and width of the gel). R The ionic conductivity of the gel can be calculated from the resistance of the polymer gel electrolyte.

[0026] The composition structure of the flexible zinc-air battery assembled by the gel prepared in the embodiment of the present invention is: a zinc plate is used as an anode, 3.5 mg of carbon black, 3.5 mg of carbon nanotubes and 3.5 mg of CoN4 material are loaded on 1 cm 2 The carbon cloth is used as the air cathode, the cathode and anode are sandwiched on both sides 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.

[0027] The open circuit voltage and discharge polarization curve of the flexible zinc-air battery prepared in the embodiment of the present invention were measured by Shanghai Chenhua workstation, and the rate and charge-discharge cycle curve were measured by the battery on the blue power test system.

[0028] Example 1 First, dissolve 60 mg of the cross-linking agent N,N'-methylenebisacrylamide in 1.8 ml of acrylic acid, neutralize with 3.75 mL of 10 mol / L sodium hydroxide, and stir for 10 min to obtain a sodium acrylate solution. Dissolve 8.6 g of potassium hydroxide and 1.12 g of zinc acetate in 20 mL of water, then pour in the sodium acrylate solution and stir for 10 min to mix evenly. Finally, add 40 mg of initiator ammonium persulfate. After completion, pour the solution into the mold and let it stand for 10 to 20 min to wait for gel polymerization to obtain a hydrogel electrolyte.

[0029] Figure 2 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 1 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled in Example 1 are measured at 1 mA cm -2 The constant current charge-discharge curve at 270 mS cm-1 can be calculated from Figure (a). -1 The electrolyte was used to assemble a zinc-air battery. Figure (b) shows the rate of the prepared battery. Figure (c) shows that the open circuit voltage is 1.43 V. Figure (d) shows that the power density of the battery is 139 mW cm -2 , from Figure (e), the cycle life of the battery is 72 h.

[0030] Example 2 First, dissolve 60 mg of the cross-linking agent N,N'-methylenebisacrylamide in 1.8 ml of acrylic acid, neutralize it with 3.75 mL of 10 mol / L sodium hydroxide, and stir for 10 min to obtain a sodium acrylate solution. Dissolve 8.6 g of potassium hydroxide and 1.12 g of zinc acetate in 20 mL of water, then pour in the sodium acrylate solution and stir for 10 min to mix evenly. Add 6 mg of TpPa and stir for 10 min to disperse evenly. Finally, add 40 mg of initiator ammonium persulfate. After completion, pour the solution into the mold and let it stand for 10 to 20 min to wait for gel polymerization to obtain a hydrogel electrolyte.

[0031] Figure 1 Schematic diagrams of the structures of the six COF materials used are shown, where Figure (a) is a schematic diagram of the structure of TpPa.

[0032] Figure 3 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 2 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled in Example 2 are measured at 1 mA cm -2 The constant current charge-discharge curve at . From Figure (a), it can be calculated that the ionic conductivity of the gel electrolyte is 307 mS cm -1The electrolyte was used to assemble a zinc-air battery. Figure (b) shows the rate of the prepared battery. Figure (c) shows that the open circuit voltage is 1.44 V. Figure (d) shows that the power density of the battery is 180 mW cm -2 , from Figure (e), we can see that the cycle life of the battery is 76 h.

[0033] Example 3 First, dissolve 60 mg of the cross-linking agent N,N'-methylenebisacrylamide in 1.8 ml of acrylic acid, neutralize with 3.75 mL of 10 mol / L sodium hydroxide, and stir for 10 min to obtain a sodium acrylate solution. Dissolve 8.6 g of potassium hydroxide and 1.12 g of zinc acetate in 20 mL of water, then pour in the sodium acrylate solution and stir for 10 min to mix evenly. Add 6 mg of TpPa(SO3H) and stir for 10 min to disperse evenly. Finally, add 40 mg of initiator ammonium persulfate. After completion, pour the solution into the mold and let it stand for 10 to 20 min to wait for gel polymerization to obtain a hydrogel electrolyte.

[0034] Figure 1 Schematic diagrams of the structures of the six COF materials used are shown, among which Figure (b) is a schematic diagram of the structure of TpPa(SO3H).

[0035] Figure 4 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 3 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled in Example 4 are measured at 1 mA cm -2 The constant current charge-discharge curve at . From Figure (a), it can be calculated that the ionic conductivity of the gel electrolyte is 346 mS cm -1 The electrolyte was used to assemble a zinc-air battery. Figure (b) shows the rate of the prepared battery. Figure (c) shows that the open circuit voltage is 1.5 V. Figure (d) shows that the power density of the battery is 255 mWcm -2 , from Figure (e), we can see that the cycle life of the battery is 120 h.

[0036] Example 4 First, dissolve 60 mg of the cross-linking agent N,N'-methylenebisacrylamide in 1.8 ml of acrylic acid, neutralize it with 3.75 mL of 10 mol / L sodium hydroxide, and stir for 10 min to obtain a sodium acrylate solution. Dissolve 8.6 g of potassium hydroxide and 1.12 g of zinc acetate in 20 mL of water, then pour in the sodium acrylate solution and stir for 10 min to mix evenly. Add 6 mg of TpPa(COOH) and stir for 10 min to disperse evenly. Finally, add 40 mg of initiator ammonium persulfate. After completion, pour the solution into the mold and let it stand for 10 to 20 min to wait for gel polymerization to obtain a hydrogel electrolyte.

[0037] Figure 1 Schematic diagrams of the structures of the six COF materials used are shown, among which Figure (e) is a schematic diagram of the structure of TpPa(COOH).

[0038] Figure 5 The open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled with the sample prepared in Example 4 are measured at 1 mA cm -2 The constant current charge-discharge curves of the prepared battery are shown in Figure (a). The open circuit voltage of the prepared battery is 1.42 V. Figure (b) shows the rate of the prepared battery. Figure (c) shows the power density of the battery is 232 mW cm -2 , from Figure (d), we can see that the cycle life of the battery is 51 h.

[0039] Example 5 First, dissolve 60 mg of the cross-linking agent N,N'-methylenebisacrylamide in 1.8 ml of acrylic acid, neutralize with 3.75 mL of 10 mol / L sodium hydroxide, and stir for 10 min to obtain a sodium acrylate solution. Dissolve 8.6 g of potassium hydroxide and 1.12 g of zinc acetate in 20 mL of water, then pour in the sodium acrylate solution and stir for 10 min to mix evenly. Add 6 mg of TpBD and stir for 10 min to disperse evenly. Finally, add 40 mg of initiator ammonium persulfate. After completion, pour the solution into the mold and let it stand for 10 to 20 min to wait for gel polymerization to obtain a hydrogel electrolyte.

[0040] Figure 1 Schematic diagrams of the structures of the six COF materials used are shown, among which Figure (b) is a schematic diagram of the structure of TpBD.

[0041] Figure 6 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 5 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled in Example 3 are measured at 1 mA cm -2The constant current charge-discharge curve at . From Figure (a), it can be calculated that the ionic conductivity of the gel electrolyte is 325 mS cm -1 The electrolyte was used to assemble a zinc-air battery. Figure (b) shows the rate of the prepared battery. Figure (c) shows that the open circuit voltage is 1.45 V. Figure (d) shows that the power density of the battery is 195 mWcm -2 , from Figure (e), we can see that the cycle life of the battery is 87 h.

[0042] Example 6 First, dissolve 60 mg of the cross-linking agent N,N'-methylenebisacrylamide in 1.8 ml of acrylic acid, neutralize with 3.75 mL of 10 mol / L sodium hydroxide, and stir for 10 min to obtain a sodium acrylate solution. Dissolve 8.6 g of potassium hydroxide and 1.12 g of zinc acetate in 20 mL of water, then pour in the sodium acrylate solution and stir for 10 min to mix evenly. Add 6 mg of TpBD(SO3H)2 and stir for 10 min to disperse evenly. Finally, add 40 mg of initiator ammonium persulfate. After completion, pour the solution into the mold and let it stand for 10 to 20 min to wait for gel polymerization to obtain a hydrogel electrolyte.

[0043] Figure 1 Schematic diagrams of the structures of the six COF materials used are shown, among which Figure (b) is a schematic diagram of the structure of TpBD(SO3H)2.

[0044] Figure 7 The electrochemical impedance spectroscopy (EIS) of the sample prepared in Example 6 and the open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled in Example 5 are measured at 1 mA cm -2 The constant current charge-discharge curve at . From Figure (a), it can be calculated that the ionic conductivity of the gel electrolyte is 325 mS cm -1 The electrolyte was used to assemble a zinc-air battery. Figure (b) shows the rate of the prepared battery. Figure (c) shows that the open circuit voltage is 1.47 V. Figure (d) shows that the power density of the battery is 220 mWcm -2 , from Figure (e), we can see that the cycle life of the battery is 95 h.

[0045] Example 7 First, dissolve 60 mg of the cross-linking agent N,N'-methylenebisacrylamide in 1.8 ml of acrylic acid, neutralize with 3.75 mL of 10 mol / L sodium hydroxide, and stir for 10 min to obtain a sodium acrylate solution. Dissolve 8.6 g of potassium hydroxide and 1.12 g of zinc acetate in 20 mL of water, then pour in the sodium acrylate solution and stir for 10 min to mix evenly. Add 6 mg of TpBD(COOH)2 and stir for 10 min to disperse evenly. Finally, add 40 mg of initiator ammonium persulfate. After completion, pour the solution into the mold and let it stand for 10 to 20 min to wait for gel polymerization to obtain a hydrogel electrolyte.

[0046] Figure 1 The schematic diagrams of the structures of the six COF materials used are shown, among which Figure (f) is the schematic diagram of the structure of TpBD(COOH)2 Figure 8 The open circuit voltage, rate, discharge polarization curve and corresponding power density of the flexible air battery assembled with the sample prepared in Example 7 are measured at 1 mA cm -2 The constant current charge-discharge curves of the prepared battery are shown in Figure (a). The open circuit voltage of the prepared battery is 1.44 V. Figure (b) shows the rate of the prepared battery. Figure (c) shows the power density of the battery is 248 mW cm -2 , as shown in Figure (d), the cycle life of the battery is 93 h.

Claims

1. A method for preparing a sodium polyacrylate hydrogel containing a covalent organic framework material by in situ polymerization, characterized in that: The steps include: Zinc salt and sodium hydroxide solution are added to the sodium acrylate solution, and the mixture is stirred and dispersed evenly; then the covalent organic framework material is added, and after stirring evenly, an initiator is added, and the mixture is introduced into a mold for gel polymerization, thereby obtaining an in-situ polymerized sodium polyacrylate hydrogel containing the covalent organic framework material.

2. The method for preparing the in-situ polymerized sodium polyacrylate hydrogel containing a covalent organic framework material according to claim 1, characterized in that: The sodium acrylate solution is prepared by dropping a sodium hydroxide solution into an acrylic acid solution containing N,N'-methylenebisacrylamide and continuing to stir to obtain a neutralized sodium acrylate solution.

3. The method for preparing the in-situ polymerized sodium polyacrylate hydrogel containing a covalent organic framework material according to claim 2, characterized in that: The concentration of the sodium hydroxide is 5-10 mol / L, the concentration of the cross-linking agent N,N'-methylenebisacrylamide in the acrylic acid solution is 30-40 mg / mL, and the molar ratio of the sodium hydroxide to the acrylic acid is 1:1.0-1.

10.

4. The method for preparing the in-situ polymerized sodium polyacrylate hydrogel containing a covalent organic framework material according to claim 1, characterized in that: The zinc salt includes any one of zinc acetate, zinc sulfate, zinc chloride, zinc oxalate and zinc nitrate.

5. The method for preparing the in-situ polymerized sodium polyacrylate hydrogel containing a covalent organic framework material according to claim 1, characterized in that: The concentration of potassium hydroxide is 5-8 mol / L, and the concentration of zinc acetate is 0.1-0.5 mol / L.

6. The method for preparing the in-situ polymerized sodium polyacrylate hydrogel containing a covalent organic framework material according to claim 1, characterized in that: The covalent organic framework material is selected from any one of TpPa(SO3H), TpPa(COOH), TpBD(SO3H)2, and TpBD(COOH)2.

7. The method for preparing the sodium polyacrylate hydrogel containing a covalent organic framework material by in-situ polymerization according to claim 1, characterized in that: The concentration of the covalent organic framework material was 0.12~0.36 mg / mL.

8. The method for preparing the in-situ polymerized sodium polyacrylate hydrogel containing a covalent organic framework material according to claim 1, characterized in that: The concentration of the initiator ammonium persulfate in the mixed solution is 1-2 mg / mL, and the polymerization time is 10-20 min.

9. A gel electrolyte, characterized in that: The method comprises adopting the method described in any one of claims 1 to 8 to prepare an in-situ polymerized sodium polyacrylate hydrogel containing a covalent organic framework material.

10. A rechargeable flexible zinc-air battery, characterized in that: The invention comprises the gel electrolyte as claimed in claim 9.

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