An interface-enhanced PVA / MOF composite gel electrolyte, its preparation method, and its application in an aqueous zinc battery.

Abstract

This invention discloses an interface-enhanced PVA / MOF composite gel electrolyte, its preparation method, and an aqueous zinc battery. The preparation method is based on the Hofmeister effect, employing salt ion induction to achieve in-situ crosslinking of PVA and in-situ crystallization of UiO-66-NH2, constructing a strong molecular-level bonding interface between PVA and MOF. This effectively solves the technical bottlenecks of poor interfacial compatibility and poor MOF dispersion in traditional composite electrolytes, and significantly optimizes Zn. 2+ The transport and deposition kinetics of zinc anodes were investigated. The prepared electrolyte not only effectively suppressed side reactions such as dendrite growth, hydrogen evolution, and corrosion in zinc anodes, significantly improving the cycle stability of zinc anodes, but also featured a mild and highly controllable preparation process with no high-temperature side reactions. When applied to aqueous zinc batteries, the cycle life of the batteries was significantly improved, demonstrating promising prospects for large-scale production and industrial application.

Description

Technical Field

[0001] This invention relates to an interface-enhanced PVA / MOF composite gel electrolyte, its preparation method, and an aqueous zinc battery, belonging to the field of aqueous zinc battery electrolyte technology. Background Technology

[0002] Aqueous zinc batteries have become a research hotspot in the energy storage field due to their high safety, low cost, environmental friendliness, and high theoretical capacity. However, the zinc anode is prone to Zn oxidation during charge-discharge cycles. 2+ Uneven deposition, hydrogen evolution, corrosion, and other side reactions lead to dendrite formation, causing short circuits and resulting in reduced coulombic efficiency and significantly shortened cycle life. Polyvinyl alcohol (PVA)-based gel electrolytes are preferred materials for aqueous zinc batteries due to their excellent film-forming properties, flexibility, and ion conductivity. Metal-organic framework (MOF) materials such as UiO-66-NH2 possess high specific surface area, regular zinc-loving channels, and excellent Zn content. 2+ Due to its affinity, Zn can be combined with PVA to prepare PVA / MOF composite electrolytes, which can enhance the mechanical properties of PVA and further optimize Zn. 2+ Diffusion / deposition stabilizes the zinc anode.

[0003] However, traditional PVA / MOF composite electrolytes suffer from severe interfacial compatibility issues: on the one hand, MOF precursors are prone to aggregation and are difficult to disperse uniformly in the PVA matrix; on the other hand, the interaction between PVA and MOF is merely a simple physical mixture, resulting in poor structural stability of the composite and making it difficult to construct continuous and ordered Zn. 2+ Ion channels limit the effect of composite electrolytes on improving the stability of zinc anodes. Furthermore, the fixed reaction parameters in the preparation of traditional PVA / MOF composite electrolytes lack controllability and are difficult to adapt to the battery performance requirements of different application scenarios. Therefore, developing a method for preparing PVA / MOF composite gel electrolytes that can enhance the interfacial compatibility between PVA and MOF and achieve multi-parameter controllability has become crucial for solving the zinc anode problem in aqueous zinc batteries. Summary of the Invention

[0004] The purpose of this invention is to provide an interface-enhanced PVA / MOF composite gel electrolyte, its preparation method, and an aqueous zinc battery. Based on the Hofmeister effect, salt ion induction is used to achieve in-situ crosslinking of PVA and in-situ crystallization of UiO-66-NH2, constructing a strong molecular-level bonding interface between PVA and MOF. This effectively solves the technical bottlenecks of poor interfacial compatibility and poor MOF dispersion in traditional composite electrolytes, and significantly optimizes Zn. 2+The transport and deposition kinetics of zinc anodes were investigated. The prepared electrolyte not only effectively suppressed side reactions such as dendrite growth, hydrogen evolution, and corrosion in zinc anodes, significantly improving the cycle stability of zinc anodes, but also featured a mild and highly controllable preparation process with no high-temperature side reactions. When applied to aqueous zinc batteries, the cycle life of the batteries was significantly improved, demonstrating promising prospects for large-scale production and industrial application.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A PVA / MOF composite gel electrolyte with in-situ interface reinforcement includes a PVA matrix; the PVA matrix is ​​in-situ crosslinked to form a crosslinked network with confined space by salting out, and UiO-66-NH2 crystallizes in-situ within the confined space of the crosslinked network; there is a molecular-level binding interface between UiO-66-NH2 and the PVA matrix.

[0007] The above-mentioned method for preparing PVA / MOF composite gel electrolyte involves using Zr... 4+ A carboxylic acid stable complex solution and a homogeneous suspension of NH2-BDC are dispersed in a PVA solution to form a homogeneous PVA-MOF precursor solution. Then, under heating and stirring, a salt solution is added dropwise to the homogeneous PVA-MOF precursor solution and kept at the temperature to obtain a composite gel precursor, which can be obtained by freeze-thaw after cooling.

[0008] The ion used in the salt solution is SO42-. 2- Ac - Cl - NO3 - I - One or more of alginate and citrate, and Zn 2+ Na + K + One or more of them.

[0009] Preferably, the PVA solution is prepared as follows: water and DMSO are mixed at a volume ratio of (3-5):(4-6), PVA is added, and the mixture is stirred at 80-85°C until the PVA is completely dissolved; the PVA concentration in the solution is 5-15 wt.%.

[0010] Zr 4+ The method for preparing a stable complex solution of carboxylic acid is as follows: ZrCl4 and carboxylic acid are mixed at a ratio of 1g:(6-8)mL;

[0011] The preparation method of the homogeneous suspension of NH2-BDC is as follows: NH2-BDC is dispersed in a solvent obtained by mixing water and DMSO in a volume ratio of (3-5):(4-6); the concentration of NH2-BDC in the solution is 0.1-0.2 g / mL;

[0012] The molar ratio of ZrCl4 to NH2-BDC in the solution used was 1:(0.8-1.2).

[0013] Preferably, the degree of polymerization of PVA is 1750±50, and the degree of alcoholysis is ≥98%; the carboxylic acid is one or more of acetic acid, formic acid, and citric acid.

[0014] Preferably, the heating and stirring conditions are 85-95℃, 200-500r / min, and holding for 2-6h.

[0015] Preferably, the concentration of the salt solution is 0.05-0.5 mol / L, the dropping rate is 0.05-1 mL / min, and the volume ratio of the salt solution to the homogeneous liquid of the PVA-MOF precursor is 1:(1.5-2.5).

[0016] Preferably, the freeze-thaw conditions are: freezing at -25~-15℃ for 10-14 hours, thawing at room temperature for ≥2 hours; and 1-3 freeze-thaw cycles.

[0017] An aqueous zinc battery includes a positive electrode, a negative electrode, a separator, and the aforementioned PVA / MOF composite gel electrolyte.

[0018] Preferably, the positive electrode is composed of positive electrode active material, conductive agent and binder in a mass ratio of 60-99:0.5-20:0.5-20; the positive electrode active material is one or more of manganese dioxide, Prussian blue analogue, vanadium-based compound, and zinc iron phosphate; the negative electrode is a zinc sheet, zinc foil or zinc-plated electrode.

[0019] The beneficial effects of this invention are as follows:

[0020] (1) Relying on the Hofmeister effect, PVA in-situ crosslinking is achieved. This PVA in-situ crosslinking network can exert a confinement effect, increase the local concentration of MOF precursor, promote its in-situ nucleation, and finally achieve a strong molecular-level binding interface between PVA in-situ crosslinking and MOF in-situ crystallization, thereby strengthening the system stability of the composite structure and fundamentally solving the technical pain points of easy MOF aggregation and poor compatibility between PVA and MOF interface.

[0021] (2) By setting multi-dimensional controllable reaction parameters, such as salt ion parameters (type, concentration, dropping rate), reaction temperature, reaction time, etc., composite gel electrolytes with different structures and properties can be prepared to meet the needs of large-scale production and diversified applications.

[0022] (3) Applying composite gel electrolytes to aqueous zinc batteries can effectively suppress side reactions such as zinc anode dendrite growth, hydrogen evolution, and corrosion, thus optimizing Zn. 2+ Diffusion / deposition kinetics significantly improve battery cycle life;

[0023] (4) The preparation process is mild, and the reaction temperature is controlled at 80~95℃ throughout the process, avoiding side reactions such as PVA esterification and degradation. It is simple to operate, the parameters are controllable, and the repeatability is high. All raw materials used are conventional commercial products, which are inexpensive and do not require complex equipment, making them suitable for large-scale production. Attached Figure Description

[0024] Figure 1 EIS curves of zinc / zinc symmetric cells assembled with gel electrolytes prepared in Comparative Examples 1, 2 and 4;

[0025] Figure 2 Stress-strain curves of the gel electrolytes prepared in Comparative Examples 1, 2 and 4;

[0026] Figure 3 Scanning electron microscope images of the gel electrolytes prepared in Comparative Examples 1, 2 and 4;

[0027] Figure 4 Tafel curves of zinc / zinc symmetric cells assembled with gel electrolytes prepared in Comparative Examples 1, 2 and 4;

[0028] Figure 5 The gel electrolytes prepared for Comparative Examples 1, 2, and 4 were used to assemble zinc / zinc symmetric cells at 5 mA / cm². -2 1mAh cm -2 The constant current charge-discharge curve. Detailed Implementation

[0029] The raw materials used in the following examples are all commercially available conventional products, including:

[0030] PVA (1750±50, degree of alcoholysis ≥98%), dimethyl sulfoxide (DMSO), ZrCl4, acetic acid, formic acid, citric acid, 2-aminoterephthalic acid (NH2-BDC), zinc sulfate (ZnSO4·7H2O), zinc acetate, sodium sulfate, sodium acetate, etc.; positive electrode active materials: manganese dioxide, Prussian blue analogues, vanadium-based compounds; conductive agents: carbon black, acetylene black, carbon nanotubes, graphene; binders: polytetrafluoroethylene, polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose.

[0031] Example 1

[0032] A method for preparing an interface-enhanced PVA / MOF composite gel electrolyte, the specific steps of which are as follows:

[0033] Step 1: Measure 4 mL of deionized water and 5.4 mL of DMSO (volume ratio 4:5.4), mix well, transfer to a 50 mL three-necked flask, add 1 g of PVA powder with a degree of polymerization of 1750±50 and a degree of alcoholysis ≥98%, heat and stir at 80 °C until the PVA is completely dissolved.

[0034] Weigh 0.7g of ZrCl4 into a 10mL beaker, add 5.4mL of acetic acid, and stir magnetically until completely dissolved, forming a transparent, pale yellow ZrCl4 solution. 4+ - Acetic acid-stabilized complex solution; take 0.54 g NH2-BDC (NH2-BDC and Zr 4+ Place the mixture (molar ratio 1:1) into another 10mL beaker, add 5mL of water / DMSO (volume ratio 4:5.4) mixed solvent, sonicate for 10min, and magnetically stir for 20min to form a homogeneous suspension.

[0035] Step 2: At 85℃, first... 4+ The acetic acid complex solution was slowly added dropwise to the PVA clear solution at a rate of 1 mL / min, and the mixture was stirred for 10 min until the system was homogeneous. Then, the NH2-BDC homogeneous suspension was added dropwise at a rate of 1 mL / min, and the mixture was stirred at a constant temperature for 30 min to form a PVA-MOF precursor homogeneous system.

[0036] Step 3: Maintain a constant temperature of 90℃ and stir at 400r / min. Add 10mL of 0.2mol / L zinc sulfate solution dropwise into the precursor system at a flow rate of 0.4mL / min. After the addition is complete, continue stirring at a constant temperature of 90℃ for 3h to obtain a semi-transparent milky PVA / UiO-66-NH2 composite gel precursor.

[0037] Step 4: Inject the gel precursor into a polytetrafluoroethylene mold, allow it to cool naturally to room temperature, freeze at -20℃ for 12 hours, thaw at room temperature for 3 hours, and repeat the freeze-thaw cycle twice to obtain an interface-strengthened PVA / MOF composite gel electrolyte.

[0038] Example 2

[0039] Step 1: exactly the same as step 1 in Example 1.

[0040] Step 2: exactly the same as step 2 in Example 1.

[0041] Step 3: Maintain a constant temperature of 85℃ and stir at 400r / min. Add 10mL of 0.2mol / L zinc sulfate solution dropwise into the precursor system at a flow rate of 0.4mL / min. After the addition is complete, continue stirring at 85℃ for 3h to obtain a semi-transparent, milky PVA / UiO-66-NH2 composite gel precursor.

[0042] Step 4: exactly the same as step 4 in Example 1.

[0043] Example 3

[0044] Step 1: exactly the same as step 1 in Example 1.

[0045] Step 2: exactly the same as step 2 in Example 1.

[0046] Step 3: Maintain a constant temperature of 95℃ and stir at 400r / min. Add 10mL of 0.2mol / L zinc sulfate solution dropwise into the precursor system at a flow rate of 0.4mL / min. After the addition is complete, continue stirring at a constant temperature of 95℃ for 3h to obtain a semi-transparent milky PVA / UiO-66-NH2 composite gel precursor.

[0047] Step 4: exactly the same as step 4 in Example 1.

[0048] Example 4

[0049] Step 1: exactly the same as step 1 in Example 1.

[0050] Step 2: exactly the same as step 2 in Example 1.

[0051] Step 3: Maintain a constant temperature of 90℃ and stir at 400r / min. Add 10mL of 0.1mol / L zinc sulfate solution dropwise into the precursor system at a flow rate of 0.2mL / min. After the addition is complete, continue stirring at a constant temperature of 90℃ for 3h to obtain a semi-transparent milky PVA / UiO-66-NH2 composite gel precursor.

[0052] Step 4: exactly the same as step 4 in Example 1.

[0053] Example 5

[0054] Step 1: exactly the same as step 1 in Example 1.

[0055] Step 2: exactly the same as step 2 in Example 1.

[0056] Step 3: Maintain a constant temperature of 90℃ and stir at 400r / min. Add 10mL of 0.1mol / L zinc sulfate solution dropwise into the precursor system at a flow rate of 0.05mL / min. After the addition is complete, continue stirring at a constant temperature of 90℃ for 2h to obtain a semi-transparent milky PVA / UiO-66-NH2 composite gel precursor.

[0057] Step 4: exactly the same as step 4 in Example 1.

[0058] Comparative Example 1

[0059] This comparative example uses pure PVA gel electrolyte. Except for the absence of ZrCl4 and NH2-BDC, the preparation steps are completely consistent with those in Example 1.

[0060] Comparative Example 2

[0061] This comparative example is a physically mixed PVA / UiO-66-NH2 composite gel electrolyte. The pre-prepared UiO-66-NH2 crystals were directly added to a PVA (water / DMSO) solution, stirred and dispersed at 90°C, and then crosslinked with 0.2 mol / L zinc sulfate solution. The post-treatment was the same as in Example 1, and the amounts of other raw materials were the same as in Example 1.

[0062] Assembly of aqueous zinc batteries.

[0063] Manganese dioxide (positive electrode active material), acetylene black (conductive agent), and PVDF (binder) were mixed in a mass ratio of 7:2:1. An appropriate amount of N-methylpyrrolidone (NMP) solvent was added, and the mixture was ground to form a uniform and viscous electrode slurry. The slurry was coated onto a carbon cloth current collector, dried, and then cut into circular positive electrode sheets for later use.

[0064] Using a zinc sheet as the negative electrode and the gel electrolyte prepared above as the electrolyte, an aqueous zinc battery was assembled according to the conventional button cell assembly sequence, resulting in zinc / manganese dioxide full cells using the gel electrolytes of Examples 1-5 and Comparative Examples 1-2, as well as corresponding zinc / zinc symmetrical cells (the positive electrode was replaced with a zinc sheet of the same specification).

[0065] Performance testing and results analysis.

[0066] Conductivity was tested using the AC impedance method, and the results are as follows: Figure 1 As shown in Table 1.

[0067] Table 1. Conductivity test results of electrolytes in Examples 1-5 and Comparative Examples 1-2

[0068]

[0069] Depend on Figure 1 As shown in Table 1, the in-situ strategy for constructing the PVA / MOF composite electrolyte helps improve the conductivity of the gel electrolyte. This is mainly because the in-situ synthesis strategy enhances the bonding strength of the PVA / MOF composite interface and improves the dispersibility of the MOF, thus constructing a highly efficient ion transport channel. With increasing synthesis temperature, the conductivity initially increases and then decreases. This is because at too low a temperature, the crystallinity of UiO-66-NH2 is poor; at too high a temperature, the PVA network is damaged. Lower salt ion concentration and slower dropping rate contribute to a more uniform and complete reaction, resulting in a stable PVA / MOF composite electrolyte and thus improving ion diffusion efficiency. Example 4 exhibits the optimal reaction temperature, ion concentration, and dropping rate, resulting in a conductivity of 7.1 × 10⁻⁶.-3 S cm -1 The high conductivity, compared to 2.0 × 10⁻⁶ in Comparative Example 1. -3 S cm -1 And 4.6 × 10⁻⁶ in Comparative Example 2 -3 S cm -1 There has been a significant improvement.

[0070] Stress-strain tests were performed on the gel electrolyte, and the results are as follows: Figure 2 As shown.

[0071] In Comparative Example 2, UiO-66-NH2 was introduced into PVA in situ, increasing the maximum stress of the PVA in Comparative Example 1 from 2.16 MPa to 3.44 MPa and the maximum strain from 179.8% to 314.5%. However, due to poor PVA / MOF interfacial compatibility and uneven MOF dispersion in Comparative Example 2, the MOF's effect on improving the mechanical properties of PVA was limited. In contrast, Example 4 employed an in-situ strategy to enhance the PVA / MOF interfacial compatibility, significantly increasing the maximum stress and strain of the composite electrolyte to 4.44 MPa and 862.24%, respectively, effectively improving the electrolyte's mechanical properties.

[0072] Scanning electron microscopy was performed on the gel electrolyte, and the results are as follows: Figure 3 As shown.

[0073] In Comparative Example 2, due to the lack of an effective interface control strategy, the MOF, with its high surface energy, experienced intermolecular aggregation, forming visible agglomerates with insufficient dispersion uniformity. In contrast, in Example 4, the solution exhibited a uniform and transparent single-phase state, with no obvious particle agglomerates observed. This demonstrates that the proposed solution effectively improved the interfacial compatibility between the MOF and the substrate medium, fundamentally suppressing particle agglomeration.

[0074] Assemble zinc / zinc symmetric cells and perform Tafel curve testing. The results are as follows: Figure 4 As shown in Table 2.

[0075] Table 2. Corrosion current density test results of zinc / zinc symmetric cells in Examples 1-5 and Comparative Examples 1-2.

[0076]

[0077] From Table 2 and Figure 4As can be seen, after introducing MOF, the corrosion current density of Comparative Example 2 decreased significantly from 0.3704 to 0.2192. This is because MOF can act as an interface modifier and physical barrier layer, constructing a stable interface film on the zinc anode surface, while reducing the free water content of the system, effectively inhibiting zinc corrosion and hydrogen evolution side reactions, thus reducing the corrosion current density. After synthesizing PVA / MOF using an in-situ strategy, the sufficient dispersion of MOF further reduced the corrosion current density. With increasing synthesis temperature, the corrosion current density first decreased and then increased, because excessively low temperatures are not conducive to UiO-66-NH2 crystallization; excessively high temperatures easily damage the PVA structure. Lower salt ion concentration and dropping rate help ensure the reaction proceeds fully, thereby improving the stability of PVA / MOF and inhibiting electrode corrosion. Example 4 exhibited the lowest corrosion current density of 0.2023, significantly lower than 0.3704 in Comparative Example 1 and 0.2192 in Comparative Example 2.

[0078] A constant current charge-discharge test was performed on a zinc / zinc symmetric battery under the following conditions: current density 5 mA*cm². -2 Capacity 1mAh*cm -2 The result is as follows Figure 5 As shown in Table 3.

[0079] Table 3. Electrochemical performance test results of zinc / zinc symmetric batteries in Examples 1-5 and Comparative Examples 1-2.

[0080]

[0081] Depend on Figure 5 As shown in Table 3, there are significant differences in the cycling stability of zinc symmetric batteries with different gel electrolytes: the zinc symmetric battery using the gel electrolyte in Comparative Example 1 experienced a rapid increase in polarization voltage and a short circuit after 530 h of cycling; the zinc symmetric battery in Comparative Example 2 showed improved cycling stability, but still experienced a sudden increase in polarization voltage and a short circuit after 850 h; the zinc symmetric battery using the gel electrolyte in Example 4 had a significantly extended cycle life, and could cycle stably for more than 1100 h. The above results fully demonstrate that the PVA / MOF composite gel electrolyte constructed by in-situ crystallization of UiO-66-NH2 and in-situ crosslinking of PVA can effectively suppress zinc dendrite growth, thereby significantly improving the cycling stability of zinc symmetric batteries. The core reasons can be simplified to two points: (1) The in-situ strategy can achieve in-situ strengthening of the composite interface, improving the uniformity and stability of the composite electrolyte. (2) PVA and MOF synergistically construct ordered ion channels, improve ionic conductivity and promote uniform ion diffusion, effectively suppress zinc dendrites and various side reactions, and improve cycling stability.

[0082] The electrochemical performance of the zinc / manganese dioxide full cell was tested, and the results are shown in Table 4.

[0083] Table 4. Electrochemical performance test results of zinc / manganese dioxide full cells in Examples 1-5 and Comparative Examples 1-2

[0084]

[0085] As shown in Table 4, Example 4 exhibits the best cycle life of the zinc / manganese dioxide full cell. After 100 cycles, the capacity retention rate is as high as 90.4%, which is significantly improved compared with Comparative Example 1 (68.5%) and Comparative Example 2 (72.4%).

[0086] In summary, the interface-enhanced PVA / MOF composite gel electrolyte prepared by in-situ crosslinking of PVA and in-situ crystallization of UiO-66-NH2 solves the technical problems of poor interfacial compatibility and easy aggregation of MOF in traditional PVA / MOF composite electrolytes. It significantly improves the ion transport performance and structural stability of the electrolyte, thereby improving the stability of the zinc anode, improving the cycle life, coulombic efficiency and overall electrochemical performance of the battery. Moreover, the preparation process is simple, the conditions are mild, the parameters are controllable and the cost is low, making it suitable for large-scale production and application.

Claims

1. A PVA / MOF composite gel electrolyte with in-situ interface reinforcement, characterized in that, It includes a PVA matrix; the PVA matrix is ​​cross-linked in situ through salting-out to form a cross-linked network with a confined space, and UiO-66-NH2 crystallizes in situ within the confined space of the cross-linked network; there is a molecular-level bonding interface between UiO-66-NH2 and the PVA matrix.

2. The preparation method of the PVA / MOF composite gel electrolyte according to claim 1, characterized in that, It is Zr 4+ A carboxylic acid stable complex solution and a homogeneous suspension of NH2-BDC are dispersed in a PVA solution to form a homogeneous PVA-MOF precursor solution. Then, under heating and stirring, a salt solution is added dropwise to the homogeneous PVA-MOF precursor solution and kept at the temperature to obtain a composite gel precursor, which can be obtained by freeze-thaw after cooling. The ion used in the salt solution is SO42-. 2- Ac - Cl - NO3 - I - One or more of alginate and citrate, and Zn 2+ Na + K + One or more of them.

3. The preparation method according to claim 2, characterized in that, The method for preparing the PVA solution is as follows: Mix water and DMSO at a volume ratio of (3-5):(4-6), add PVA, and stir at 80-85℃ until the PVA is completely dissolved; the PVA concentration in the solution is 5-15 wt.%. Zr 4+ The method for preparing a stable carboxylic acid complex solution is as follows: ZrCl4 and carboxylic acid are mixed at a ratio of 1g:(6-8)mL; the method for preparing a homogeneous suspension of NH2-BDC is as follows: NH2-BDC is dispersed in a solvent obtained by mixing water and DMSO at a volume ratio of (3-5):(4-6); the concentration of NH2-BDC in the solution is 0.1-0.2g / mL; The molar ratio of ZrCl4 to NH2-BDC in the solution used was 1:(0.8-1.2).

4. The preparation method according to claim 3, characterized in that, The degree of polymerization of PVA is 1750±50, and the degree of alcoholysis is ≥98%; the carboxylic acid is one or more of acetic acid, formic acid, and citric acid.

5. The preparation method according to claim 2, characterized in that, The heating and stirring conditions are 85-95℃, 200-500r / min, and holding for 2-6h.

6. The preparation method according to claim 2, characterized in that, The concentration of the salt solution is 0.05-0.5 mol / L, the dropping rate is 0.05-1 mL / min, and the volume ratio of the salt solution to the homogeneous liquid of the PVA-MOF precursor is 1:(1.5-2.5).

7. The preparation method according to claim 2, characterized in that, The freeze-thaw conditions are: freezing at -25~-15℃ for 10-14 hours, thawing at room temperature for ≥2 hours; and 1-3 freeze-thaw cycles.

8. An aqueous zinc battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and the PVA / MOF composite gel electrolyte as described in claim 1.

9. The aqueous zinc battery according to claim 8, characterized in that, The positive electrode sheet is composed of positive electrode active material, conductive agent and binder in a mass ratio of 60-99:0.5-20:0.5-20; the positive electrode active material is one or more of manganese dioxide, Prussian blue analogue, vanadium-based compound, and zinc iron phosphate. The negative electrode is a zinc sheet, zinc foil, or zinc-plated electrode.

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