A gel electrolyte and its preparation method, and a zinc-bromine micro battery and its preparation method.

Abstract

This invention provides a gel electrolyte and its preparation method, as well as a zinc-bromine micro-battery and its preparation method, belonging to the technical field of aqueous static zinc-bromine batteries. A gel electrolyte is obtained by immersing a dry gel in an electrolyte solution, wherein the electrolyte contains electrochemically active bromide and zinc ions, with a zinc ion concentration of 5–12.5 mol / L. The zinc-bromine micro-battery is then assembled using the gel electrolyte. The gel electrolyte does not require the addition of additional complexing agents or antifreeze agents, making the preparation method simple. The zinc-bromine micro-battery can serve as a power supply device for flexible or microelectronic devices, significantly broadening the application scenarios and prospects of zinc-bromine batteries, and providing stable power even under varying temperature conditions. The zinc-bromine micro-battery can cycle more than 5000 times at room temperature, with a specific capacity of 184 μAh·cm⁻¹. －2 It can cycle more than 500 times at a temperature of -60°C with a capacity retention of 98%.

Description

Technical Field

[0001] This invention relates to the field of aqueous static zinc-bromine battery technology, and particularly to a gel electrolyte and its preparation method, and a zinc-bromine micro battery and its preparation method. Background Technology

[0002] With the emergence of miniaturized electronic devices such as micro supercapacitors, microrobots, and wearable sensors, the application potential of micro energy storage devices is increasing. Therefore, high-performance, easily manufactured micro batteries have been extensively studied. Zinc-ion batteries, due to their high theoretical capacity, abundant reserves, and safety and efficiency, have become a promising energy storage system for large-scale energy storage. Among them, zinc-bromine micro batteries possess high energy density, fast reaction kinetics, and high output voltage. However, the capacity loss of zinc-bromine micro batteries under low-temperature conditions is a problem that urgently needs to be solved. During the charging and discharging process of zinc-bromine batteries, the cathode charging product Br2 reacts with Br in the electrolyte... - Formation of polybrominated compounds (Br) n - (n≥3). The shuttle effect of soluble polybrominates directly leads to a decrease in coulombic efficiency and a shortened cycle life. The current mainstream solution is to limit polybrominates through complexing agents to avoid cross-diffusion of active materials. This method significantly increases internal resistance and cost, making it unsuitable for manufacturing batteries that operate at low temperatures. On the other hand, current reported research mainly employs the strategy of adding organic antifreeze agents to lower the high freezing point of aqueous electrolytes. However, the introduced polar organic antifreeze agents cause polybrominates to dissolve. This leads to cross-diffusion of active materials, thereby reducing the coulombic efficiency and cycle life of the battery. In addition, adding antifreeze agents reduces electrolyte utilization and affects the kinetics of electrochemical reactions. These methods cannot simultaneously solve the problems encountered by zinc-bromine batteries operating at low temperatures, thus making it difficult to meet the practical application requirements of zinc-bromine batteries. Summary of the Invention

[0003] The purpose of this invention is to provide a gel electrolyte and its preparation method, and a zinc-bromine micro battery and its preparation method, so as to solve the problems of low coulombic efficiency, short cycle life and high capacity loss under low temperature conditions in the prior art of zinc-bromine micro batteries.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0005] This invention provides a method for preparing a gel electrolyte, comprising the following steps: immersing a dry gel in an electrolyte to obtain a gel electrolyte;

[0006] The electrolyte contains bromide ions and zinc ions, with the zinc ion concentration ranging from 5 to 12.5 mol / L.

[0007] Preferably, the concentration of bromide ions is 10–25 mol / L.

[0008] Preferably, the dry gel is a polyacrylamide dry gel or a sodium carboxymethyl cellulose dry gel.

[0009] Preferably, the impregnation continues until saturation is achieved.

[0010] Preferably, the preparation method of the polyacrylamide dry gel is as follows: acrylamide monomer, ammonium persulfate and N,N'-methylenebisacrylamide are polymerized in water, and then allowed to stand and dry to obtain polyacrylamide dry gel.

[0011] Preferably, the sodium carboxymethyl cellulose dry gel is prepared by mixing sodium carboxymethyl cellulose and water at 40-70°C for 0.5-3 hours, allowing it to stand, and then drying it to obtain sodium carboxymethyl cellulose dry gel.

[0012] The present invention also provides a gel electrolyte prepared by the above-described method for preparing gel electrolyte.

[0013] The present invention also provides a zinc-bromine micro battery, which includes a flexible substrate, a positive electrode, a negative electrode and the gel electrolyte described above.

[0014] The present invention also provides a method for preparing the zinc-bromine micro battery described above, comprising the following steps: attaching the positive electrode and the negative electrode to a flexible substrate respectively, then covering the positive electrode and the negative electrode with a gel electrolyte, and finally encapsulating to obtain the zinc-bromine micro battery.

[0015] Preferably, the areas of the positive and negative electrodes are independently 0.1–5 cm². 2 The thickness of the gel electrolyte is 2-5 mm.

[0016] The beneficial effects of this invention are:

[0017] (1) This invention utilizes the influence of zinc and bromide ions on the hydrogen bond structure under a strong electric field and the unique solvation reconstruction effect in aqueous electrolytes to disrupt the hydrogen bonds between water molecules in the aqueous electrolyte. By adjusting the concentration, the hydrogen bonds and interionic interactions are balanced, resulting in a gel electrolyte with an extremely low freezing point and a zinc-bromine microbattery with high ionic conductivity.

[0018] (2) This invention achieves the complexation effect of polybrominated compounds by regulating the concentration of cations in a strong electric field, thereby suppressing the shuttle effect of polybrominated compounds, suppressing the diffusion of positive electrode charging products, and thus effectively improving the stability of zinc-bromine micro batteries.

[0019] (3) No additional complexing agents and antifreeze agents are needed in gel electrolytes. The preparation method is simple and greatly improves the electrolyte utilization rate, safety and practicality of zinc-bromine micro batteries.

[0020] (4) The zinc-bromine micro battery of the present invention can be used as a power supply device for flexible or micro electronic devices, significantly expanding the operating temperature range of the zinc-bromine micro battery, and can provide stable power supply under varying temperature conditions.

[0021] (5) The gel electrolyte of the present invention has an ionic conductivity as high as 62.5 mS·cm at room temperature. －1 At -20℃, the ionic conductivity can reach as high as 10.1 mS·cm. －1 At -40℃, the ionic conductivity can reach as high as 4.1 mS·cm. －1 At -60℃, the ionic conductivity can reach as high as 0.8 mS·cm. －1 .

[0022] (6) The zinc-bromine micro-battery of the present invention can be cycled more than 5000 times at room temperature, with a specific capacity of 184 μAh·cm. －2 It can cycle more than 500 times at a temperature of -60°C with a capacity retention of 98%. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the zinc-bromine micro battery of the present invention;

[0024] Figure 2 The graph shows the charge-discharge cycle performance of the zinc-bromine micro battery in Example 1 under normal temperature conditions.

[0025] Figure 3 The rate performance diagram of the zinc-bromine micro battery in Example 1 is shown.

[0026] Figure 4 The temperature-dependent performance diagram of the zinc-bromine microcell in Example 1 is shown.

[0027] Figure 5 The graph shows the charge-discharge cycle performance of the zinc-bromine micro battery in Example 1 at a temperature of -60°C.

[0028] Figure 6 A photograph of the zinc-bromine micro battery of the present invention powering an electronic watch in a bent state;

[0029] Figure 7 The graph shows the charge-discharge cycle performance of the zinc-bromine micro battery in Example 2 under normal temperature conditions.

[0030] Figure 8 The temperature performance diagram of the zinc-bromine microcell in Example 2 is shown.

[0031] Figure 9The graph shows the charge-discharge cycle performance of the zinc-bromine micro battery in Example 3 under normal temperature conditions.

[0032] Figure 10 The temperature-dependent performance diagram of the zinc-bromine microcell in Example 3 is shown.

[0033] Figure 11 The temperature-dependent performance of the zinc-bromine microcell in Comparative Example 1 is shown in the graph.

[0034] Figure 12 The graph shows the temperature-dependent performance of the zinc-bromine microcell in Comparative Example 2.

[0035] Figure 13 The graph shows the temperature-dependent performance of the zinc-bromine microcell in Comparative Example 3. Detailed Implementation

[0036] This invention provides a method for preparing a gel electrolyte, comprising the following steps: immersing a dry gel in an electrolyte to obtain a gel electrolyte;

[0037] The electrolyte contains bromide ions and zinc ions, wherein the concentration of zinc ions is 5–12.5 mol / L.

[0038] In this invention, the concentration of zinc ions is preferably 7.5–12.5 mol / L.

[0039] In this invention, the concentration of bromide ions is 10-25 mol / L, preferably 15-25 mol / L.

[0040] In this invention, the dry gel is a polyacrylamide dry gel or a sodium carboxymethyl cellulose dry gel.

[0041] In this invention, the impregnation continues until saturation is achieved.

[0042] In this invention, the preparation method of the polyacrylamide dry gel is as follows: acrylamide monomer, ammonium persulfate, and N,N'-methylenebisacrylamide are added to water and mixed at 40-70°C for 0.2-1 h, then kept at 40-70°C for 8-16 h, and then allowed to stand and dry to obtain polyacrylamide dry gel. The polymerization process is preferably carried out by mixing at 50-65°C for 0.3-0.7 h and then keeping at 50-65°C for 10-14 h; more preferably, by mixing at 58-62°C for 0.5 h and then keeping at 58-62°C for 11-12.5 h.

[0043] In this invention, the mass ratio of the acrylamide monomer, ammonium persulfate, N,N'-methylenebisacrylamide, and water is 1500-3000:6-15:0.5-2.5:10000-20000.

[0044] In this invention, the preparation method of the sodium carboxymethyl cellulose dry gel is as follows: sodium carboxymethyl cellulose powder and water are mixed at 40-70°C for 0.5-3 hours, preferably at 60°C for 1.5 hours, and then allowed to stand and dry to obtain sodium carboxymethyl cellulose dry gel.

[0045] In this invention, the mass ratio of sodium carboxymethyl cellulose to water is 1:200 to 1:400.

[0046] In this invention, the electrolyte is impregnated with a dry gel, and the gel, as a carrier of the electrolyte, can achieve the bending and other effects of flexible batteries.

[0047] The present invention also provides a gel electrolyte prepared by the above-described method for preparing gel electrolyte.

[0048] The present invention also provides a zinc-bromine micro battery, which includes a flexible substrate, a positive electrode, a negative electrode and the gel electrolyte described above.

[0049] In this invention, the flexible substrate is made of polyvinyl alcohol, polyethylene terephthalate, polyimide or polyethylene naphthalate, preferably polyethylene terephthalate.

[0050] In this invention, the positive electrode material includes titanium foil, stainless steel foil, carbon nanotube paper or carbon cloth, preferably carbon nanotube paper.

[0051] In this invention, the negative electrode material includes zinc foil, titanium foil, stainless steel foil, carbon nanotube paper or carbon cloth, preferably carbon nanotube paper.

[0052] The present invention also provides a method for preparing the zinc-bromine micro battery described above, comprising the following steps: attaching the positive electrode and the negative electrode to a flexible substrate respectively, then covering the positive electrode and the negative electrode with a gel electrolyte, and finally encapsulating to obtain the zinc-bromine micro battery.

[0053] In this invention, the areas of the positive and negative electrodes are independently 0.1–5 cm². 2 Preferably 0.1–3 cm 2 More preferably 0.2–2 cm 2 The thickness of the gel electrolyte is 2-5 mm, preferably 3-4 mm.

[0054] In this invention, the area of ​​the gel electrolyte is greater than the sum of the areas of the positive and negative electrodes.

[0055] In this invention, the encapsulation is preferably performed using polyimide tape.

[0056] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] 2.9 g of acrylamide monomer, 14.3 mg of ammonium persulfate, 1.8 mg of N,N'-methylenebisacrylamide, and 20 mL of deionized water were mixed and stirred at 60 °C for 0.5 h. The mixture was then kept at this temperature and allowed to stand for 12 h to obtain a polyacrylamide hydrogel. Finally, the polyacrylamide hydrogel was dried at 60 °C for 12 h to obtain a polyacrylamide dry gel.

[0059] Zinc bromide was dissolved in deionized water to obtain an electrolyte (with a zinc ion concentration of 7.5 mol / L and a bromide ion concentration of 15 mol / L). Polyacrylamide dry gel was then immersed in the electrolyte for 3 days until saturation was achieved. The gel was then removed to obtain the electrolyte.

[0060] Carbon nanotube paper was placed in a laser printer and cut into the desired shape, ensuring that the positive and negative electrodes had the same area, with an electrode area of ​​0.2 cm². 2 The positive and negative electrodes are separately attached to a flexible polyethylene terephthalate substrate. Then, a gel electrolyte (3 mm thick) is placed over the positive and negative electrodes, ensuring that the area of ​​the gel electrolyte is larger than the sum of the areas of the positive and negative electrodes. Finally, the substrate is encapsulated with polyimide tape to obtain a zinc-bromine micro battery.

[0061] from Figure 2 As can be seen, the zinc-bromine micro-battery in this embodiment can undergo more than 5000 cycles at room temperature, with a capacity of 184 μAh·cm⁻¹. －2 .from Figure 3 As can be seen, the zinc-bromine micro battery in this embodiment operates at a capacity of 1–20 mAh·cm⁻¹. －2 Discharge at current density with a capacity retention of 94%. Figure 4 It can be seen that the zinc-bromine micro-battery in this embodiment exhibits no capacity loss at a temperature of -60°C. From... Figure 5 As can be seen, the zinc-bromine micro battery in this embodiment can undergo more than 500 cycles at a temperature of -60°C with a capacity retention rate of 98%.

[0062] Example 2

[0063] The difference from Example 1 is that the concentration of zinc ions in the electrolyte is 10 mol / L and the concentration of bromide ions is 20 mol / L, while all other conditions are the same.

[0064] from Figure 7 As can be seen, the zinc-bromine micro-battery in this embodiment can undergo more than 3000 cycles at room temperature, with a capacity of 183.1 μAh·cm⁻¹. －2 .from Figure 8It can be seen that the zinc-bromine micro battery in this embodiment has only a small capacity loss at a temperature of -60°C.

[0065] Example 3

[0066] The difference from Example 1 is that the concentration of zinc ions in the electrolyte is 12.5 mol / L and the concentration of bromide ions is 25 mol / L, while all other conditions are the same.

[0067] from Figure 9 As can be seen, the zinc-bromine micro-battery in this embodiment can undergo more than 3000 cycles at room temperature, achieving a capacity of 182.6 μAh·cm⁻¹. －2 .from Figure 10 It can be seen that the zinc-bromine micro battery in this embodiment has only a small capacity loss at a temperature of -60°C.

[0068] Comparative Example 1

[0069] The difference from Example 1 is that the concentration of zinc ions in the electrolyte is 15 mol / L and the concentration of bromide ions is 30 mol / L, while all other conditions are the same.

[0070] from Figure 11 It can be seen that the zinc-bromine micro battery prepared in Comparative Example 1 has poor anti-freezing performance. When the temperature drops to -60℃, the capacity decreases and the capacity retention rate is only 69%.

[0071] Comparative Example 2

[0072] The difference from Example 1 is that the concentration of zinc ions in the electrolyte is 2.5 mol / L and the concentration of bromide ions is 5 mol / L, while all other conditions are the same.

[0073] from Figure 12 It can be seen that the zinc-bromine micro battery prepared in Comparative Example 2 has poor anti-freezing performance. Its capacity decreases significantly when the temperature drops to -60℃, and it fails below -50℃.

[0074] Comparative Example 3

[0075] The difference from Example 1 is that the concentration of zinc ions in the electrolyte is 10 mol / L, the concentration of chloride ions is 15 mol / L, and the concentration of bromide ions is 5 mol / L, while all other conditions are the same.

[0076] from Figure 13 It can be seen that the zinc-bromine micro battery prepared in Comparative Example 3 has poor anti-freezing performance, with a capacity retention rate of 82%, and the discharge capacity decreases as the number of cycles increases.

[0077] Figure 6The photo shows a zinc-bromine microcell powering an electronic watch in a bent state, illustrating its flexibility and bendability, making it suitable for use in flexible devices.

[0078] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A zinc-bromine micro battery, characterized in that, The zinc-bromine microbattery comprises a flexible substrate, a positive electrode, a negative electrode, and a gel electrolyte. The preparation method of the gel electrolyte includes the following steps: immersing a dry gel in an electrolyte to obtain the gel electrolyte; the electrolyte contains bromide ions and zinc ions, with a zinc ion concentration of 7.5 mol / L and a bromide ion concentration of 15 mol / L. The dry gel is a polyacrylamide dry gel or a sodium carboxymethyl cellulose dry gel.

2. The zinc-bromine micro battery according to claim 1, characterized in that, The impregnation continues until saturation is achieved.

3. The zinc-bromine micro battery according to claim 2, characterized in that, The preparation method of the polyacrylamide dry gel is as follows: acrylamide monomer, ammonium persulfate and N,N'-methylenebisacrylamide are polymerized in water, and then allowed to stand and dry to obtain polyacrylamide dry gel.

4. The zinc-bromine micro battery according to claim 3, characterized in that, The method for preparing the sodium carboxymethyl cellulose dry gel is as follows: sodium carboxymethyl cellulose and water are mixed, allowed to stand, and then dried to obtain sodium carboxymethyl cellulose dry gel.

5. The method for preparing the zinc-bromine micro battery according to any one of claims 1 to 4, characterized in that, The process includes the following steps: attaching the positive and negative electrodes to a flexible substrate, then covering the positive and negative electrodes with a gel electrolyte, and finally encapsulating them to obtain a zinc-bromine micro battery.

6. The method for preparing the zinc-bromine micro battery according to claim 5, characterized in that, The areas of the positive and negative electrodes are independently 0.1–5 cm². 2 The thickness of the gel electrolyte is 2-5 mm.

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