A solid-state zinc-air battery double-network structure conductive hydrogel electrolyte and a preparation method thereof

Abstract

The application provides a solid-state zinc-air battery double-network structure conductive hydrogel electrolyte and a preparation method thereof, and solves the problems of insufficient mechanical properties, poor water retention, low ionic conductivity and poor cycle stability of the gel electrolyte used in the current solid-state zinc-air battery. The gel electrolyte with excellent mechanical properties, excellent ionic conductivity and high water retention capacity is prepared by a thermal polymerization method. The hydrogen bond between sulfonated starch and acrylamide is utilized to form a double-network structure with stronger supporting performance, so that the mechanical properties of the gel electrolyte are improved, and more ion transmission channels are provided, and the ionic conductivity is improved; the sulfonate groups in the sulfonated starch enhance the interface stability between the gel and the electrode, and the cycle stability is improved; the hydroxyl groups of the starch and the carboxyl groups of the sodium citrate serve as hydrophilic groups to improve the water retention capacity of the gel electrolyte.

Description

Technical Field

[0001] This invention belongs to the field of solid-state zinc-air battery technology, specifically relating to a conductive hydrogel electrolyte with a dual-network structure for solid-state zinc-air batteries and its preparation method. Background Technology

[0002] Research and development of batteries with high energy density and high safety and stability has become a top priority.

[0003] Among various metal-based batteries, zinc-air batteries stand out due to their theoretical energy density of up to 1080 Wh·kg⁻¹. -1 Solid-state zinc-air batteries, with their superior safety and readily available raw materials, have become a research hotspot. Traditional zinc-air batteries use a 6M KOH solution as the electrolyte, which suffers from problems such as easy electrolyte leakage, low storage efficiency, and poor safety. Therefore, solid-state zinc-air batteries have attracted much attention due to their advantages such as foldability, high safety, and resistance to electrolyte leakage. However, the key issues currently limiting the further development of solid-state zinc-air batteries mainly lie in the insufficient mechanical properties, poor water retention, low ionic conductivity, and poor cycle stability of gel electrolytes.

[0004] Therefore, the present invention provides a solid zinc-air battery dual-network structure conductive hydrogel electrolyte and its preparation method. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of the gel electrolytes currently used in solid-state zinc-air batteries, such as insufficient mechanical properties, poor water retention, low ionic conductivity, and poor cycle stability, and to provide a conductive hydrogel electrolyte with a dual-network structure for solid-state zinc-air batteries and its preparation method.

[0006] To achieve the above objectives, the technical solution provided by this invention is:

[0007] A method for preparing a solid zinc-air battery dual-network structure conductive hydrogel electrolyte, characterized by comprising the following steps:

[0008] 1) In an inert atmosphere, sulfonated starch is dissolved in deionized water, heated and stirred until completely gelatinized. Then potassium persulfate (KPS) is added and stirred until homogeneous to form solution A. The operation in an inert atmosphere is mainly to prevent the sulfonated starch from being oxidized and decomposed in the air, and to maintain the stability of the moisture content in the system, because heating will cause moisture to evaporate, and the protection of an inert gas (such as nitrogen) can reduce the loss. Potassium persulfate, as an initiator, releases free radicals due to its strong oxidizing properties, promotes the polymerization reaction, and cross-links or polymerizes with the components in the sulfonated starch under the action of free radicals, thereby enhancing the stability of the structure.

[0009] Acrylamide, sodium citrate, and N,N-methylenebisacrylamide (MBA) were added to deionized water and stirred until completely dissolved to form solution B. N,N-methylenebisacrylamide, as a crosslinking agent, contains acrylamide groups that can crosslink with other acrylamide monomers to form a three-dimensional network structure. The network structure reduces the fluidity of the gel, maintains a certain shape, and thus increases the mechanical strength of the gel. It also has good water retention and is not easily swelled by absorbing water.

[0010] The mass ratio of sulfonated starch to acrylamide is 1.5-3:2-5.

[0011] 2) In an inert atmosphere, slowly add solution A prepared in step 1) to solution B, and degas to form solution C;

[0012] 3) Pour the solution C obtained in step 2) into a mold, heat it to polymerize, and obtain a hydrogel;

[0013] 4) The hydrogel obtained in step 3) is placed in an alkali / zinc salt composite system for ion exchange to obtain a solid zinc-air battery dual-network structure conductive hydrogel electrolyte.

[0014] Further, in step 1), the mass ratio of sulfonated starch to deionized water is 1.5-3:15-20, and the conditions for complete gelatinization of sulfonated starch are: heating temperature of 40-60℃, stirring speed of 300-500r / min, and gelatinization time of 0.5-1.5h.

[0015] Further, in step 1), the mass ratio of acrylamide, sodium citrate, N,N-methylenebisacrylamide, and deionized water is 2-5:0.3-1:2-5:5-15;

[0016] The specific conditions for completely dissolving acrylamide, sodium citrate, and N,N-methylenebisacrylamide are: stirring speed of 200-600 r / min and dissolution time of 10 min-30 min.

[0017] Furthermore, in step 2), the degassing method is ultrasonic degassing, and the ultrasonic time is 15-60 minutes.

[0018] Further, in step 3), the heating temperature is 60-80℃, the polymerization time is 1.5-3h, and the height of the mold is 0.2-0.5cm.

[0019] Further, in step 4), the alkali / zinc salt composite system is composed of alkali, zinc salt and water, and the molar concentration of alkali is 4-8 mol / L and the molar concentration of zinc salt is 0.2-0.6 mol / L;

[0020] The ion exchange time is 22-26 hours.

[0021] Further, in step 4), the alkali is potassium hydroxide; the zinc salt is zinc acetate or zinc chloride.

[0022] Meanwhile, the present invention provides a solid zinc-air battery with a dual-network structure conductive hydrogel electrolyte obtained by the above preparation method, and a solid zinc-air battery using the dual-network structure conductive hydrogel electrolyte. The battery is composed of an air cathode, a conductive hydrogel electrolyte and a zinc anode from top to bottom, and the air cathode is composed of a current collector and a catalyst layer from top to bottom. The current collector is commercially available nickel foam, commercial carbon cloth or commercial carbon paper.

[0023] The principle of this invention:

[0024] This invention utilizes a thermal polymerization method to prepare a gel electrolyte with excellent mechanical properties, superior ionic conductivity, and high water retention capacity. The invention leverages the hydrogen bonds between sulfonated starch and acrylamide to form a more robust dual-network structure, thereby enhancing the mechanical properties of the gel electrolyte and providing more ion transport channels, thus improving ionic conductivity. The sulfonate groups in the sulfonated starch enhance the interfacial stability between the gel and the electrode, improving cycle stability. The hydroxyl groups of starch and the carboxyl groups of sodium citrate, acting as hydrophilic groups, improve the water retention capacity of the gel electrolyte.

[0025] Advantages of this invention:

[0026] 1. The sulfonated starch introduced in this invention has sulfonic acid groups and a large number of hydroxyl groups. The presence of sulfonic acid groups enhances the interfacial stability between the gel electrolyte and the electrode, improving the cycle stability of the battery. Hydroxyl groups, as hydrophilic groups, have good hydrophilicity and water retention capacity, which can improve the electrolyte retention rate and the ionic conductivity of the gel. Simultaneously, its unique dual-network structure improves the mechanical properties of the gel electrolyte (the gel stress can reach 280 kPa and the strain can reach 2010%).

[0027] 2. This invention introduces sodium citrate as an additive, in which a large number of carboxyl groups act as hydrophilic groups, greatly enhancing the water retention capacity of the gel electrolyte.

[0028] 3. The dual-network structure gel electrolyte of the solid zinc-air battery of the present invention is a solid electrolyte, which overcomes the problems of rigid structure and easy leakage of electrolyte in traditional batteries. Moreover, the preparation method is simple, the raw materials are widely available and the cost is low, and it is suitable for industrial production of gel electrolytes and solid zinc-air batteries.

[0029] 4. The gel-assembled zinc-air battery preparation method proposed in this invention is simple, inexpensive, safe and environmentally friendly, and is of great significance to the development of zinc-air batteries.

[0030] 5. The conductive hydrogel electrolyte with a dual-network structure prepared by this invention, which has good mechanical properties, excellent ion transport capacity, and strong water retention capacity, is of great significance for the development of zinc-air batteries and the improvement of energy utilization efficiency, replacing traditional electrolytes. Attached Figure Description

[0031] Figure 1 The tensile stress-strain curve of the conductive hydrogel electrolyte with a dual-network structure prepared in Example 1.

[0032] Figure 2 The 252h water retention capacity curve of the conductive hydrogel electrolyte with a dual network structure prepared in Example 1.

[0033] Figure 3 The discharge polarization-power density curves of a solid zinc-air battery assembled with a dual-network structure conductive hydrogel electrolyte prepared in Example 1.

[0034] Figure 4 The specific capacity curve of a solid zinc-air battery assembled with a dual-network structure conductive hydrogel electrolyte prepared in Example 1.

[0035] Figure 5 Cyclic charge-discharge test curves of a solid zinc-air battery assembled with a dual-network structure conductive hydrogel electrolyte prepared in Example 1. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0037] A method for preparing a solid zinc-air battery dual-network structure conductive hydrogel electrolyte includes the following steps:

[0038] 1) Under a nitrogen atmosphere, sulfonated starch is dissolved in deionized water, heated and stirred until completely gelatinized, then potassium persulfate (KPS) is added and stirred until homogeneous to form solution A; wherein, the mass ratio of sulfonated starch to deionized water is 1.5-3:15-20, and the conditions for complete gelatinization of sulfonated starch are: heating temperature of 40-60℃, stirring speed of 300-500 r / min, and gelatinization time of 0.5-1.5 h;

[0039] Acrylamide, sodium citrate, and N,N-methylenebisacrylamide (MBA) were added to deionized water and stirred until completely dissolved to form solution B. The mass ratio of acrylamide, sodium citrate, N,N-methylenebisacrylamide, and deionized water was 2-5:0.3-1:2-5:5-15. The specific conditions for completely dissolving acrylamide, sodium citrate, and N,N-methylenebisacrylamide were: stirring speed of 200-600 r / min and dissolution time of 10-30 min.

[0040] The mass ratio of sulfonated starch to acrylamide is 1.5-3:2-5.

[0041] 2) In a nitrogen atmosphere, slowly add solution A prepared in step 1) to solution B to degas and form solution C; wherein, the degassing method is ultrasonic degassing, and the ultrasonic time is 15-60 min;

[0042] 3) Pour the solution C obtained in step 2) into a mold and heat it to polymerize, thereby obtaining a hydrogel; wherein the heating temperature is 60-80℃ and the polymerization time is 1.5-3h; the height of the mold is 0.2-0.5cm.

[0043] 4) The hydrogel obtained in step 3) is placed in an alkali / zinc salt composite system for ion exchange for 22-26 hours to obtain a solid zinc-air battery dual-network structure conductive hydrogel electrolyte; wherein, the alkali / zinc salt composite system is composed of alkali, zinc salt and water, and the alkali is potassium hydroxide with a molar concentration of 4-8 mol / L, and the zinc salt is zinc acetate or zinc chloride with a molar concentration of 0.2-0.6 mol / L.

[0044] In addition, a solid zinc-air battery with a dual-network structure conductive hydrogel electrolyte is provided. The battery consists of an air cathode, the aforementioned dual-network structure conductive hydrogel electrolyte, and a zinc anode, from top to bottom. The air cathode consists of a current collector and a catalyst layer from top to bottom. The current collector is commercially available nickel foam, commercially available carbon cloth, or commercially available carbon paper.

[0045] The following are specific examples:

[0046] Example 1

[0047] A method for preparing a solid zinc-air battery dual-network structure conductive hydrogel electrolyte includes the following steps:

[0048] 1) Stir 2.0g of sulfonated starch in 12mL of deionized water at 400r / min for 1h until the starch is completely gelatinized under N2 atmosphere at 40℃. Then add 0.2g of potassium persulfate and continue stirring for 0.5h to form solution A.

[0049] Dissolve 2.8g acrylamide, 0.5g sodium citrate hydrate and 2.8mg MBA in 7mL of deionized water to form solution B. Stir at 500r / min for 20min.

[0050] 2) Under a nitrogen atmosphere, solution A is gradually added dropwise to solution B, and the mixture is sonicated for 30 minutes to remove bubbles, thus forming solution C;

[0051] 3) Pour solution C into a glass mold with a height of 0.5 cm and polymerize at 70 °C for 2 h to obtain a hydrogel;

[0052] 4) The hydrogel was immersed in 50 ml of water containing 6 mol / L potassium hydroxide and 0.2 mol / L zinc acetate electrolyte solution for ion exchange for 24 h to obtain a solid zinc-air battery dual-network structure conductive hydrogel electrolyte with high ionic conductivity.

[0053] To test the performance of the conductive hydrogel electrolyte prepared according to this invention, a typical "sandwich" structure was used to assemble the zinc-air battery under test. The top layer was an air cathode loaded with a catalyst, the middle layer was the double-network structure conductive hydrogel electrolyte of this invention, and the bottom layer was a zinc sheet. The air cathode was carbon cloth loaded with a catalyst, wherein the catalyst was commercially available Pt / C, and the catalyst loading was 2.5 mg·cm³. -2 The zinc sheet is 0.6cm thick and is polished before use; the double-network structure conductive hydrogel electrolyte layer is 3mm thick.

[0054] The test results are as follows:

[0055] like Figure 1 As shown, the conductive hydrogel with a dual-network structure exhibits a tensile strain of up to 2010% and a fracture strength of 280 kPa.

[0056] like Figure 2 As shown, the conductive hydrogel with dual network structure has excellent electrolyte retention ability. After 252 hours of testing, the retention rate is still around 90%.

[0057] like Figure 3 As shown, the discharge polarization-power density curve of the solid-state zinc-air battery assembled in the embodiment exhibits a high power density (5.4 mW cm⁻¹). -2 ).

[0058] like Figure 4 As shown, the specific capacity of the solid-state zinc-air battery assembled in the embodiment can reach 895 mAh g at room temperature. Zn -1 .

[0059] Figure 5 The cycling stability of the battery assembled in the embodiment is demonstrated, which can be stably cycled for 205 hours at room temperature, which greatly proves the application potential of the solid zinc-air battery dual-network structure conductive hydrogel electrolyte of the present invention.

[0060] Example 2

[0061] A method for preparing a solid zinc-air battery dual-network structure conductive hydrogel electrolyte includes the following steps:

[0062] 1) Place 1.5g of sulfonated starch in 20mL of deionized water at 300r / min for 0.5h under N2 atmosphere at 50℃ until the starch is completely gelatinized. Then add 0.15g of potassium persulfate and continue stirring for 0.5h to form solution A.

[0063] Dissolve 2g acrylamide, 0.4g sodium citrate hydrate and 2mg MBA in 5mL of deionized water to form solution B. Stir at 200r / min for 30min.

[0064] 2) Under a nitrogen atmosphere, solution A is gradually added dropwise to solution B, and the mixture is sonicated for 15 minutes to remove bubbles, thus forming solution C;

[0065] 3) Pour solution C into a glass mold with a height of 0.5 cm and polymerize at 60 °C for 1.5 h to obtain a hydrogel;

[0066] 4) The hydrogel was immersed in 50 ml of water containing 4 mol / L potassium hydroxide and 0.4 mol / L zinc acetate electrolyte solution for ion exchange for 22 h to obtain a solid zinc-air battery dual-network structure conductive hydrogel electrolyte with high ionic conductivity.

[0067] Example 3

[0068] A method for preparing a solid zinc-air battery dual-network structure conductive hydrogel electrolyte includes the following steps:

[0069] 1) Stir 3g of sulfonated starch in 15mL of deionized water at 500r / min for 1.5h at 40℃ and N2 atmosphere until the starch is completely gelatinized. Then add 0.3g of potassium persulfate and continue stirring for 0.5h to form solution A.

[0070] Dissolve 5g acrylamide, 0.9g sodium citrate hydrate and 5mg MBA in 14mL of deionized water to form solution B. Stir at 600r / min for 10min.

[0071] 2) Under a nitrogen atmosphere, solution A is gradually added dropwise to solution B, and the mixture is sonicated for 60 minutes to remove bubbles, thus forming solution C;

[0072] 3) Pour solution C into a glass mold with a height of 0.5 cm and polymerize at 80 °C for 3 h to obtain a hydrogel;

[0073] 4) The hydrogel was immersed in 100 ml of water containing 8 mol / L potassium hydroxide and 0.6 mol / L zinc acetate electrolyte solution for ion exchange for 26 h to obtain a solid zinc-air battery dual-network structure conductive hydrogel electrolyte with high ionic conductivity.

[0074] In summary, the dual-network structure conductive hydrogel electrolyte prepared by this invention has excellent mechanical properties, excellent ionic conductivity, high water retention capacity, and stable cycling performance, making it suitable for industrial production of gel electrolytes and solid-state zinc-air batteries.

[0075] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A method for preparing a solid zinc-air battery dual-network structure conductive hydrogel electrolyte, characterized in that, Includes the following steps: 1) In an inert atmosphere, sulfonated starch is dissolved in deionized water, heated and stirred until completely gelatinized, then potassium persulfate is added and stirred until homogeneous to form solution A; Add acrylamide, sodium citrate, and N,N-methylenebisacrylamide to deionized water and stir until completely dissolved to form solution B; The mass ratio of sulfonated starch to acrylamide is 1.5-3:2-5. 2) In an inert atmosphere, slowly add solution A prepared in step 1) to solution B, and degas to form solution C; 3) Pour the solution C obtained in step 2) into a mold, heat it to polymerize, and obtain a hydrogel; 4) The hydrogel obtained in step 3) is placed in an alkali / zinc salt composite system for ion exchange to obtain a solid zinc-air battery dual-network structure conductive hydrogel electrolyte.

2. The method for preparing the solid zinc-air battery dual-network structure conductive hydrogel electrolyte according to claim 1, characterized in that: In step 1), the mass ratio of sulfonated starch to deionized water is 1.5-3:15-20, and the conditions for complete gelatinization of sulfonated starch are: heating temperature of 40-60℃, stirring speed of 300-500r / min, and gelatinization time of 0.5-1.5h.

3. The method for preparing the solid zinc-air battery dual-network structure conductive hydrogel electrolyte according to claim 1 or 2, characterized in that: In step 1), the mass ratio of acrylamide, sodium citrate, N,N-methylenebisacrylamide, and deionized water is 2-5:0.3-1:2-5:5-15; The specific conditions for completely dissolving acrylamide, sodium citrate, and N,N-methylenebisacrylamide are: stirring speed of 200-600 r / min and dissolution time of 10 min-30 min.

4. The method for preparing the solid zinc-air battery dual-network structure conductive hydrogel electrolyte according to claim 3, characterized in that: In step 2), the degassing method is ultrasonic degassing, and the ultrasonic time is 15-60 minutes.

5. The method for preparing the solid zinc-air battery dual-network structure conductive hydrogel electrolyte according to claim 4, characterized in that: In step 3), the heating temperature is 60-80℃ and the polymerization time is 1.5-3h.

6. The method for preparing the solid zinc-air battery dual-network structure conductive hydrogel electrolyte according to claim 5, characterized in that: In step 4), the alkali / zinc salt composite system is composed of alkali, zinc salt and water, and the molar concentration of alkali is 4-8 mol / L and the molar concentration of zinc salt is 0.2-0.6 mol / L. The ion exchange time is 22-26 hours.

7. The method for preparing the solid zinc-air battery dual-network structure conductive hydrogel electrolyte according to claim 6, characterized in that: In step 4), the alkali is potassium hydroxide; the zinc salt is zinc acetate or zinc chloride.

8. A conductive hydrogel electrolyte with a dual-network structure for solid zinc-air batteries, characterized in that: It is prepared by any of the methods described in claims 1-7.

9. A solid-state zinc-air battery, characterized in that: From top to bottom, it consists of an air cathode, a conductive hydrogel electrolyte, and a zinc anode, and the air cathode consists of a current collector and a catalyst layer from top to bottom. The conductive hydrogel electrolyte is prepared by any one of the methods described in claims 1-7.

10. The solid-state zinc-air battery according to claim 9, characterized in that: The current collector is commercially available nickel foam, commercially available carbon cloth, or commercially available carbon paper.

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