A solid state rechargeable zinc-air / iodine hybrid battery based on a polymer electrolyte

Abstract

The application belongs to the field of energy storage devices, and discloses a solid-state rechargeable zinc-air / iodine hybrid battery based on a polymer electrolyte, wherein the polymer electrolyte comprises a hydrogel electrolyte with a double network structure and an alkaline electrolyte; the polymer system is a polymer framework of a polyacrylamide gel electrolyte, sodium alginate is crosslinked with zinc ions to form an ionic crosslinking network, and iodine ions are added as an electrolyte additive; the composition and detailed structure of the polymer electrolyte are improved, sodium alginate is introduced into the polyacrylamide hydrogel to obtain a polyacrylamide / sodium alginate composite gel with a double network structure, and an alkaline electrolyte containing iodine ions is introduced to obtain a polymer electrolyte with high ionic conductivity, excellent water retention performance, and improved mechanical properties and other characteristics. The corresponding solid-state rechargeable zinc-air / iodine hybrid battery further constructed has the characteristics of long cycle time and high energy efficiency.

Description

Technical Field

[0001] This invention belongs to the field of energy storage devices, and more specifically, relates to a solid-state rechargeable zinc-air / iodine hybrid battery based on a polymer electrolyte. Background Technology

[0002] Rapid societal development has led to a surge in energy demand, necessitating the development of efficient energy storage devices to meet this growing need. Lithium-ion batteries, with their high cycle life and energy efficiency, have captured a dominant market share; however, low energy density, high cost, and safety concerns hinder their further development. In contrast, metal-air batteries, such as zinc-air batteries, offer higher energy density, better environmental friendliness, and lower cost, making them a highly promising energy storage device. Zinc-air batteries consist of a zinc anode, an air cathode, and an electrolyte. The electrolyte, connecting the anode and cathode, determines ion transport and interfacial chemistry, thus influencing the battery's electrochemical performance. However, traditional liquid electrolytes often suffer from leakage and evaporation issues, and their rigid structure and large size make zinc-air batteries unsuitable for other applications (such as wearable devices). Therefore, polymer electrolytes based on substrates such as polyvinyl alcohol, polyacrylic acid, and polyacrylamide have been gradually developed and successfully applied in flexible zinc-air batteries. However, the semi-open system of zinc-air batteries still causes water loss in the polymer electrolyte, reducing ionic conductivity; furthermore, zinc dendrite growth is unavoidable. Therefore, achieving a long cycle life for solid-state rechargeable batteries is a significant challenge.

[0003] Chinese patent CN113937304 A discloses a flexible neutral zinc-air battery and its preparation method. Although it also discloses that the neutral electrolyte can avoid corrosion and carbonization, it still suffers from problems such as low hydroxide concentration and low ionic conductivity. Chinese patent CN113258172A discloses a solid electrolyte suitable for room-temperature all-solid-state zinc-air batteries and its preparation method. Although it also discloses that the solid electrolyte is composed of a plastic crystal small molecule matrix, anhydrous zinc salt, and inert inorganic nanofillers, exhibiting good electrochemical stability and thermal reversibility, it still suffers from low ionic conductivity (only 10). -4 The S / cm ratio limits its application in zinc-air batteries.

[0004] Chinese patent CN108539330A discloses an all-solid-state zinc-air battery and its gel electrolyte. Although it also discloses that the gel electrolyte includes an organic gel support polyacrylamide, an alkaline aqueous solution, and an anodic corrosion inhibitor, and that it has good chemical compatibility with the alkaline electrolyte and good repeatability, the assembled zinc-air battery still has the problem of poor performance.

[0005] In summary, alkaline hydrogel electrolytes are currently a research hotspot in zinc-air batteries. They can not only improve ionic conductivity and water retention to a certain extent, but also enhance the cycle stability of solid-state batteries assembled using them. Furthermore, the development of high-performance alkaline hydrogel electrolytes and their corresponding solid-state batteries is of great significance. Summary of the Invention

[0006] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a solid-state rechargeable zinc-air / iodine hybrid battery based on a polymer electrolyte. This is achieved by improving the composition and detailed structure of the polymer electrolyte, introducing sodium alginate into a polyacrylamide hydrogel to obtain a polyacrylamide / sodium alginate composite gel with a dual-network structure, and simultaneously introducing an alkaline electrolyte containing iodide ions (such as KI). The resulting polymer electrolyte exhibits high ionic conductivity, excellent water retention, and improved mechanical properties. The corresponding solid-state rechargeable zinc-air / iodine hybrid battery further develops features long cycle time and high energy efficiency.

[0007] To achieve the above objectives, according to one aspect of the present invention, a polymer electrolyte is provided, characterized in that the polymer electrolyte comprises a hydrogel electrolyte having a dual-network structure and an alkaline electrolyte containing zinc ions contained within the hydrogel electrolyte; wherein the polymer system corresponding to the hydrogel electrolyte having the dual-network structure uses polyacrylamide as the polymer backbone of the gel electrolyte, and also contains sodium alginate, which crosslinks with zinc ions to form an ionic crosslinking network, thereby constructing the dual-network structure; furthermore, the alkaline electrolyte also contains iodide ions.

[0008] As a further preferred embodiment of the present invention, the polyacrylamide is obtained by adding acrylamide monomer, crosslinking agent and initiator to water, stirring thoroughly and then heating to react;

[0009] Preferably, the crosslinking agent is any one of polyethylene glycol diacrylate and N,N-methylenebisacrylamide;

[0010] The initiator is either potassium persulfate or ammonium persulfate;

[0011] The mass ratio of the acrylamide monomer to the water is (10-20%):1; the mass ratio of the crosslinking agent to the acrylamide monomer is (0.02-0.1%):1; the mass ratio of the initiator to the acrylamide monomer is (0.2-1%):1.

[0012] More preferably, the heating is performed after the fully stirred reaction system is injected into the mold.

[0013] As a further preferred embodiment of the present invention, the mass of sodium alginate in the polymer electrolyte is 10-20% of the mass of acrylamide monomer in the polymer electrolyte.

[0014] As a further preferred embodiment of the present invention, the solute of the alkaline electrolyte simultaneously includes potassium hydroxide (KOH), zinc acetate (Zn(Ac)2), and iodide ions; and the concentration of potassium hydroxide in the alkaline electrolyte is 4-6 mol / L, the concentration of zinc acetate is 0.2-0.4 mol / L, and the concentration of iodide ions is 0.5-2 mol / L.

[0015] As a further preferred embodiment of the present invention, the iodide ions in the solute of the alkaline electrolyte are derived from either potassium iodide (KI) or sodium iodide (NaI).

[0016] According to another aspect of the present invention, the present invention provides a method for preparing a polymer electrolyte, characterized by comprising the following steps:

[0017] (1) Mix acrylamide monomer, crosslinking agent and initiator with water and stir until homogeneous to obtain a mixed solution;

[0018] (2) Add sodium alginate to the mixed solution obtained in step (1) and continue stirring until the mixture is homogeneous; then, sonicate the resulting solution to remove air bubbles and obtain the precursor liquid system.

[0019] (3) The precursor liquid system obtained in step (2) is heated to thermally initiate the polymerization reaction of the monomers and obtain a polyacrylamide / sodium alginate composite hydrogel with a dual network structure.

[0020] Preferably, the heating is performed after the precursor liquid system is injected into the mold and sealed, and then heated.

[0021] (4) Immerse the polyacrylamide / sodium alginate composite hydrogel obtained in step (3) in an alkaline electrolyte to obtain a polymer gel electrolyte.

[0022] As a further preferred embodiment of the present invention, in step (1), the mass ratio of the acrylamide monomer to the water is (10-20%):1; the mass ratio of the crosslinking agent to the acrylamide monomer is (0.02-0.1%):1; and the mass ratio of the initiator to the acrylamide monomer is (0.2-1%):1.

[0023] The mass ratio of sodium alginate in step (2) to acrylamide monomer in step (1) is (10-20%): 1.

[0024] As a further preferred embodiment of the present invention, the stirring time in step (1) is 0.5 to 1 h; the stirring time in step (2) is 1 to 1.5 h, and the ultrasonic treatment time is 15 to 30 min; in step (3), the reaction temperature of the polymerization reaction is 50 to 60 °C, and the reaction time is 10 to 12 h; in step (4), the soaking time in the alkaline electrolyte is 10 to 12 h.

[0025] According to another aspect of the invention, the present invention provides the application of the above-described polymer electrolyte as a solid electrolyte in a solid-state rechargeable zinc-air / iodine hybrid battery.

[0026] According to another aspect of the present invention, a solid-state rechargeable zinc-air / iodine hybrid battery is provided, comprising a zinc sheet negative electrode, a solid electrolyte, and a positive electrode arranged sequentially, characterized in that the solid electrolyte is the aforementioned polymer electrolyte; the positive electrode is a catalyst-supported nickel foam positive electrode containing a gas diffusion layer, wherein the catalyst is prepared from a solution of platinum carbon, ruthenium dioxide, isopropanol, and perfluorosulfonic acid type polymer; the gas diffusion layer is obtained by uniformly mixing PTFE solution, acetylene black, and carbon black; and the gas diffusion layer is adhered to the nickel foam by roll pressing.

[0027] Preferably, the ratio of the amounts of platinum carbon, ruthenium dioxide, isopropanol, and perfluorosulfonic acid polymer solution used to constitute the catalyst is 2-2.5 mg: 2-2.5 mg: 0.4-0.5 mL: 0.008-0.01 mL;

[0028] For the positive electrode, the total loading of platinum-carbon and ruthenium dioxide is 0.8–1 mg cm⁻¹. -2 ;

[0029] For the gas diffusion layer, the ratio of PTFE solution, acetylene black, and carbon black is 3-4g: 0.3-0.4g: 1.1-1.2g.

[0030] Compared with existing technologies, the technical solution conceived in this invention, by using polyacrylamide as the polymer backbone of the gel electrolyte and introducing sodium alginate to form an ionic cross-linking network with zinc ions, creates a dual-network structure that increases the mechanical properties and ionic conductivity of the polymer electrolyte. Simultaneously, the use of iodide ions as an electrolyte additive further enhances the ionic conductivity. Furthermore, iodide ions can suppress zinc dendrites and promote cathode reaction kinetics. Therefore, the synergistic effect of sodium alginate and iodide ions jointly improves the electrochemical performance of the zinc-air / iodine hybrid battery assembled using this polymer electrolyte.

[0031] This invention constructs a hydrogel electrolyte with a dual-network structure, using polyacrylamide as the polymer backbone and sodium alginate to construct the dual-network structure. Iodine ions are introduced into the entire system as an electrolyte additive. The polymer electrolyte obtained by this invention exhibits high ionic conductivity (up to 82 mS / cm in the examples below). -1 It exhibits excellent water retention properties (in the examples below, the hydrogel loses only 17% of its water after 20 hours) and improved mechanical properties (in the examples below, at 13 kPa, 600%). Furthermore, the prepared polymer electrolyte can be further placed between a zinc sheet electrode and a catalyst-supported nickel foam electrode containing a gas diffusion layer to assemble a zinc-air / iodine hybrid battery. This battery maintains high cycle stability even under sealed conditions (unlike existing zinc-air batteries, which often require open conditions; in the examples below, the zinc-air / iodine hybrid battery obtained based on this invention exhibits high cycle stability even under sealed conditions and at 1 mA cm⁻¹). -2 It can cycle for up to 110 hours while maintaining an energy efficiency of up to 80%, providing a new direction for the development of high-performance energy conversion and storage devices.

[0032] Specifically, the present invention can achieve the following beneficial effects:

[0033] 1. This invention introduces sodium alginate and iodide ions. Sodium alginate forms an ionic cross-linked network by cross-linking with zinc ions, which can then be used to construct a dual-network structure with covalently cross-linked polyacrylamide, improving the poor mechanical properties of a single polyacrylamide network. Furthermore, iodide ions, as an electrolyte additive, work synergistically with sodium alginate to jointly enhance the water retention and ionic conductivity of the gel electrolyte.

[0034] 2. The electrolyte additive iodide ions introduced in this invention change the hydration structure of zinc ions, thereby inhibiting the growth of zinc dendrites and ensuring good contact between the electrolyte and the anode interface.

[0035] 3. This invention proposes a novel concept for zinc-air / iodine hybrid batteries, providing a direction for the development of high-performance energy storage devices. Since the conversion of iodide ions / iodate ions replaces the traditional oxygen reduction / oxygen evolution reaction, performance tests were conducted on a sealed battery for the first time. The results showed significantly improved cycle performance (up to 110 hours in the examples below) and extremely high energy efficiency (up to 80% in the examples below). This is mainly attributed to the avoidance of water loss issues inherent in the semi-open system of traditional zinc-air batteries under sealed conditions.

[0036] 4. The present invention obtains a polymer electrolyte by sequentially mixing different components of the polymer electrolyte and then thermally polymerizing them. This method is simple to operate, has mild conditions, and uses inexpensive materials.

[0037] In summary, this invention yields a dual-network structure gel electrolyte with excellent ionic conductivity and water retention, characterized by high ionic conductivity, excellent water retention, and improved mechanical properties. Furthermore, this polymer electrolyte can be used to construct a novel solid-state rechargeable zinc-air / iodine hybrid battery, which exhibits long cycle time and high energy efficiency. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the preparation process and structure of the polymer electrolyte in Example 1 of the present invention.

[0039] Figure 2 This is a scanning electron microscope image of the polymer electrolyte of Example 1 of the present invention.

[0040] Figure 3 The stress-strain curves are for the polymer electrolytes of Example 1 and Comparative Examples 1 and 2 of this invention.

[0041] Figure 4 The diagram shows the ionic conductivity of the polymer electrolytes in Example 1 and Comparative Examples 1 and 2 of this invention.

[0042] Figure 5 The diagram shows the water retention performance of the polymer electrolytes in Example 1 and Comparative Examples 1 and 2 of this invention.

[0043] Figure 6 This is a scanning electron microscope (SEM) image of the zinc anode of the solid-state battery assembled with the polymer electrolyte of Comparative Example 1 of the present invention after 18 hours of cycling.

[0044] Figure 7 This is a scanning electron microscope (SEM) image of the zinc anode of the zinc-air / iodine hybrid battery assembled with polymer electrolyte according to Example 1 of the present invention after 18 hours of cycling.

[0045] Figure 8 To test the solid-state batteries using the polymer electrolytes of Examples 1 and 1 and 2 of this invention in a sealed environment and at 1 mA cm⁻¹ -2 The constant current discharge diagram below.

[0046] Figure 9 To test the solid-state batteries using the polymer electrolytes of Examples 1 and 1 and 2 of this invention in a sealed environment and at 1 mA cm⁻¹ -2 The following is a cyclic stability plot. For the legend shown in the figure, black corresponds to "polyacrylamide / sodium alginate / potassium iodide", dark gray corresponds to "polyacrylamide / sodium alginate", and light gray corresponds to polyacrylamide.

[0047] Figure 10 Solid-state batteries using the polymer electrolytes of Comparative Examples 2 and 3 of this invention operate at 1 mA cm⁻¹.-2 The following is a graph showing the cyclic stability of the circuit. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0049] Example 1:

[0050] A method for preparing a solid-state rechargeable zinc-air / iodine hybrid battery based on a polymer electrolyte, comprising the following steps:

[0051] (1) Preparation of polymer electrolytes:

[0052] S1. Add 5g of acrylamide monomer, 0.03g of potassium persulfate initiator, and 0.003g of N,N'-methylenebisacrylamide (MBAA) crosslinking agent to 40mL of water in sequence, and stir for 30min to mix evenly.

[0053] S2, add 0.8g of sodium alginate to the above solution, stir for 1 hour, and then use ultrasound to remove bubbles.

[0054] S3, the above mixed solution is transferred to a plastic petri dish with a depth of about 1 cm, sealed and placed in an oven at 60°C for 10 h to polymerize, thus obtaining a polymer gel.

[0055] S4. The prepared polymer gel was immersed in a 6M KOH / 0.2M Zn(Ac)2 / 1M KI electrolyte for 12 hours to obtain a polymer gel electrolyte with high ionic conductivity. The corresponding polymer gel electrolyte is denoted as "polyacrylamide / sodium alginate / potassium iodide".

[0056] (2) Preparation of platinum carbon and ruthenium dioxide catalyst: Weigh 2.5 mg each of platinum carbon and ruthenium dioxide, add 0.49 mL of isopropanol and 0.01 mL of perfluorosulfonic acid polymer solution, and sonicate for 30 min to obtain platinum carbon and ruthenium dioxide catalyst ink.

[0057] (3) Fabrication of diffusion electrode:

[0058] 4g of 10% PTFE solution, 0.4g of acetylene black, and 1.2g of carbon black were mixed evenly to obtain a slurry. Then, the obtained slurry was adhered to nickel foam using a roller press to prepare the diffusion electrode for the battery. The platinum-carbon and ruthenium dioxide catalyst ink prepared in step (2) was drop-coated onto the surface of the diffusion electrode as the positive electrode. The catalyst loading was 1mg cm⁻¹.-2 .

[0059] (4) Solid-state battery assembly:

[0060] The solid-state battery of this invention has a sandwich structure with layers, and is assembled by stacking. First, the surface of the zinc sheet is sanded to remove the surface oxide layer, which is then used as the negative electrode. Then, the zinc negative electrode, polymer electrolyte, and foamed nickel positive electrode containing a gas diffusion layer and loaded with a catalyst are stacked and fixed in place with flexible tape.

[0061] Example 2:

[0062] This embodiment is basically the same as the polymer electrolyte in Example 1 in terms of composition and preparation method. The difference is that in the first step (corresponding to step S1) of the preparation process of the polymer gel in this embodiment, the amount of water added is 30 mL. The polymer gel electrolyte is then obtained.

[0063] Example 3:

[0064] This embodiment is basically the same as the polymer electrolyte in Example 1 in terms of composition and preparation method. The difference is that in the first step (corresponding to step S1) of the preparation process of the polymer gel in this embodiment, the amount of water added is 50 mL. The polymer gel electrolyte is then obtained.

[0065] Example 4:

[0066] The components and preparation method of the polymer electrolyte in this embodiment are basically the same as those in Example 1. The difference is that in the last step of the preparation process (corresponding to step S4), the polymer gel in this embodiment is soaked in 4M KOH / 0.2M Zn(Ac)2 / 1M KI electrolyte for 12 hours to obtain polymer gel electrolyte.

[0067] Example 5:

[0068] The components and preparation method of the polymer electrolyte in this embodiment are basically the same as those in Example 1. The difference is that in the last step of the preparation process (corresponding to step S4), the polymer gel in this embodiment is soaked in 6M KOH / 0.4M Zn(Ac)2 / 1M KI electrolyte for 12 hours to obtain polymer gel electrolyte.

[0069] Comparative Example 1:

[0070] The composition and preparation method of the polymer electrolyte in this comparative example are basically the same as those in Example 1. The difference is that the polymer gel in this comparative example is soaked in 6M KOH / 0.2M Zn(Ac)2 electrolyte for 12 hours in the last step of the preparation process (corresponding to step S4) to obtain the polymer gel electrolyte.

[0071] The resulting polymer gel electrolyte is denoted as "polyacrylamide / sodium alginate".

[0072] Comparative Example 2:

[0073] The composition and preparation method of the polymer electrolyte in this comparative example are basically the same as those in Comparative Example 1. The difference is that sodium alginate is not added to the polymer gel electrolyte in this comparative example (i.e., step S2 is omitted).

[0074] The resulting polymer gel electrolyte is denoted as "polyacrylamide".

[0075] Comparative Example 3:

[0076] The composition and preparation method of the polymer electrolyte in this comparative example are basically the same as those in Comparative Example 2. The difference is that the polymer gel in this comparative example is immersed in a 6M KOH / 0.2M Zn(Ac)2 / 1M KI electrolyte for 12 hours in the last step of the preparation process (corresponding to step S4) to obtain the polymer gel electrolyte.

[0077] The resulting polymer gel electrolyte is denoted as "polyacrylamide / potassium iodide".

[0078] Performance testing:

[0079] Figure 1 This is a schematic diagram of the preparation process and structure of the polymer electrolyte in Example 1. In this polymer electrolyte, the covalently cross-linked polyacrylamide network and the sodium alginate network formed by zinc ion cross-linking form a double network structure through physical entanglement, and a large amount of electrolyte is fixed inside the gel by the polymer network.

[0080] Figure 2 This is a scanning electron microscope (SEM) image of the polymer electrolyte of Example 1. It can be seen that Example 1 has a porous structure, which facilitates electrolyte absorption and promotes ion transport, thereby increasing ionic conductivity.

[0081] Figure 3 , Figure 4 and Figure 5 These are the stress-strain curves, ionic conductivity at room temperature and pressure, and water retention performance diagrams of the polymer electrolytes in Example 1 and Comparative Examples 1 and 2. Figure 3 As can be seen, the mechanical properties of Example 1 and Comparative Example 1 are similar (600%, 13 kPa), both superior to Comparative Example 2 (420%, 3 kPa). This means that the addition of sodium alginate improves the mechanical properties of polyacrylamide, while the introduction of KI does not affect its mechanical properties; Figure 4 and Figure 5 As can be seen, Example 1 has the highest ionic conductivity (82 mS / cm). -1It exhibits optimal water retention properties (water loss of the hydrogel was only 17% after 20 hours). This demonstrates that sodium alginate and potassium iodide synergistically improve the ionic conductivity and water retention of polyacrylamide.

[0082] Figure 6 and Figure 7 This is a scanning electron microscope (SEM) image of the zinc anode of the solid-state battery assembled with the polymer electrolytes of Comparative Example 1 and Example 1 after 18 hours of cycling. Figure 6 It can be observed that a large number of dendrites appeared on the zinc surface after cycling in Comparative Example 1; Figure 7 It can be observed that no obvious dendrites were formed on the zinc surface after the cycle in Example 1, proving that the addition of potassium iodide can effectively inhibit dendrite formation.

[0083] Figure 8 and Figure 9 Solid-state batteries using polymer electrolytes from Examples 1 and Comparative Examples 1 and 2 were tested in a sealed environment at 1 mA / cm². -2 The constant current discharge and cycle stability diagrams are shown below. It can be seen that at 1 mA cm⁻¹... -2 In Example 1, the discharge voltage remained almost constant over 40 hours, significantly higher than that of Comparative Example 1 (2 hours) and Comparative Example 2 (8 hours). In particular, Example 1 showed a discharge voltage of 1 mA cm⁻¹. -2 It can cycle for up to 110 hours and achieves an energy efficiency of 80%. This demonstrates that the polymer electrolyte prepared in this invention can improve the electrochemical performance of solid-state batteries.

[0084] Figure 10 Solid-state batteries using the polymer electrolytes of Comparative Examples 2 and 3 of this invention operate at 1 mA cm⁻¹. -2 The following is a plot of the cycle stability. Figure 10 As can be seen, the cycle times of Comparative Example 2 and Comparative Example 3 are almost the same, namely 14 hours. This indicates that without the use of sodium alginate, the addition of iodine ions alone has almost no impact on the cycle stability of the battery. This indirectly confirms the synergistic effect of sodium alginate and iodine ions, and that both sodium alginate and iodine ions are indispensable.

[0085] In addition, both Example 2 and Example 3 showed good cycle performance (although not as good as Example 1, meaning that Example 1 was the best).

[0086] Example 4 also achieved good ionic conductivity and cycling performance (although not as good as Example 1, that is, Example 1 had the best ionic conductivity and cycling performance).

[0087] Example 5 also achieved good cycle performance (although not as good as Example 1, that is, Example 1 has the best cycle performance).

[0088] The above embodiments are merely examples. For instance, in addition to using KI to provide iodine ions, iodine ions can also come from iodides such as NaI.

[0089] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polymer electrolyte, characterized in that, The polymer electrolyte comprises a hydrogel electrolyte with a dual-network structure and an alkaline electrolyte containing zinc ions contained within the hydrogel electrolyte. The polymer system corresponding to the hydrogel electrolyte with the dual-network structure uses polyacrylamide as the polymer backbone of the gel electrolyte and also contains sodium alginate. The sodium alginate crosslinks with zinc ions to form an ionic crosslinking network, thereby constructing the dual-network structure. The solutes in the alkaline electrolyte include potassium hydroxide, zinc acetate, and iodide ions. The mass of sodium alginate in the polymer electrolyte is 10% to 20% of the mass of acrylamide monomer in the polymer electrolyte. The polymer electrolyte is prepared by a method comprising the following steps: (1) Mix acrylamide monomer, crosslinking agent and initiator with water and stir until homogeneous to obtain a mixed solution; (2) Add sodium alginate to the mixed solution obtained in step (1) and continue stirring until the mixture is homogeneous; then, sonicate the resulting solution to remove air bubbles and obtain the precursor solution system. (3) The precursor liquid system obtained in step (2) is heated to thermally initiate the polymerization reaction of the monomers and obtain a polyacrylamide / sodium alginate composite hydrogel with a dual network structure. (4) The polyacrylamide / sodium alginate composite hydrogel obtained in step (3) is immersed in an alkaline electrolyte to obtain a polymer gel electrolyte; wherein the solute of the alkaline electrolyte includes potassium hydroxide, zinc acetate and iodide ions.

2. The polymer electrolyte as described in claim 1, characterized in that, The polyacrylamide is obtained by adding acrylamide monomer, crosslinking agent and initiator to water, stirring thoroughly and then heating to react.

3. The polymer electrolyte as described in claim 2, characterized in that, The crosslinking agent is any one of polyethylene glycol diacrylate and N,N-methylenebisacrylamide; The initiator is either potassium persulfate or ammonium persulfate; The mass ratio of the acrylamide monomer to the water is (0.1~0.2):1; the mass ratio of the crosslinking agent to the acrylamide monomer is (0.0002~0.001):1; and the mass ratio of the initiator to the acrylamide monomer is (0.002~0.01):

1.

4. The polymer electrolyte according to claim 3, characterized in that, The heating is performed after the fully stirred reaction system is injected into the mold.

5. The polymer electrolyte as described in claim 1, characterized in that, In the alkaline electrolyte, the concentration of potassium hydroxide is 4~6 mol / L, the concentration of zinc acetate is 0.2~0.4 mol / L, and the concentration of iodide ions is 0.5~2 mol / L.

6. The polymer electrolyte as described in claim 5, characterized in that, The iodide ions in the solute of the alkaline electrolyte come from either potassium iodide (KI) or sodium iodide (NaI).

7. A method for preparing a polymer electrolyte, characterized in that, Includes the following steps: (1) Mix acrylamide monomer, crosslinking agent and initiator with water and stir until homogeneous to obtain a mixed solution; (2) Add sodium alginate to the mixed solution obtained in step (1) and continue stirring until the mixture is homogeneous; then, sonicate the resulting solution to remove air bubbles and obtain the precursor solution system. (3) The precursor liquid system obtained in step (2) is heated to thermally initiate the polymerization reaction of the monomers and obtain a polyacrylamide / sodium alginate composite hydrogel with a dual network structure. (4) The polyacrylamide / sodium alginate composite hydrogel obtained in step (3) is immersed in an alkaline electrolyte to obtain a polymer gel electrolyte; wherein the solute of the alkaline electrolyte includes potassium hydroxide, zinc acetate and iodide ions. The mass ratio of sodium alginate in step (2) to acrylamide monomer in step (1) is (0.1~0.2):

1.

8. The preparation method according to claim 7, characterized in that, In step (3), the heating is performed by injecting the precursor liquid system into the mold, sealing it, and then heating it.

9. The preparation method according to claim 7, characterized in that, In step (1), the mass ratio of the acrylamide monomer to the water is (0.1~0.2):1; the mass ratio of the crosslinking agent to the acrylamide monomer is (0.0002~0.001):1; and the mass ratio of the initiator to the acrylamide monomer is (0.002~0.01):

1.

10. The preparation method according to claim 7, characterized in that, The stirring time in step (1) is 0.5~1h; the stirring time in step (2) is 1~1.5h, and the ultrasonic treatment time is 15~30min; in step (3), the reaction temperature of the polymerization reaction is 50~60℃, and the reaction time is 10~12h; in step (4), the soaking time in the alkaline electrolyte is 10~12h.

11. The application of the polymer electrolyte as described in any one of claims 1-6 as a solid electrolyte in a solid-state rechargeable zinc-air / iodine hybrid battery.

12. A solid-state rechargeable zinc-air / iodine hybrid battery, comprising a zinc sheet negative electrode, a solid electrolyte, and a positive electrode arranged sequentially, characterized in that, The solid electrolyte is a polymer electrolyte as described in any one of claims 1-6; the positive electrode is a catalyst-supported nickel foam positive electrode containing a gas diffusion layer, wherein the catalyst is prepared from a solution of platinum carbon, ruthenium dioxide, isopropanol and perfluorosulfonic acid type polymer; the gas diffusion layer is obtained by uniformly mixing PTFE solution, acetylene black and carbon black; and the gas diffusion layer is adhered to the nickel foam by roll pressing.

13. The solid-state rechargeable zinc-air / iodine hybrid battery as described in claim 12, characterized in that, The ratio of the amounts of platinum on carbon, ruthenium dioxide, isopropanol, and perfluorosulfonic acid polymer solution used to constitute the catalyst is 2~2.5 mg: 2~2.5 mg: 0.4~0.5 mL: 0.008~0.01 mL; For the positive electrode, the total loading of platinum-carbon and ruthenium dioxide is 0.8~1 mg cm⁻¹. -2 ; For the gas diffusion layer, the ratio of PTFE solution, acetylene black, and carbon black is 3~4g: 0.3~0.4g: 1.1~1.2g.

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