An electrolyte that can be used for four-electron conversion reaction of aqueous zinc-iodine battery

Abstract

This invention belongs to the field of electrochemical battery technology, specifically relating to an electrolyte that can be used in the four-electron conversion reaction of an aqueous zinc-iodine battery. The electrolyte comprises a zinc salt, deionized water, an organic solvent, and an organic halide salt. This invention utilizes pyridine cations to pretreat the charge distribution of tribromide ions, reducing polyiodide shuttle, and under high voltage, through reaction with I... + Strong interaction, excites and stabilizes I 0 / I + Redox couples, realizing I ‑ / I 0 / I + The reversible four-electron conversion reaction enhances battery capacity. On the zinc anode side, the activity of water is weakened by an organic solvent, while pyridine cations preferentially adsorb onto its surface, suppressing competitive water adsorption, inhibiting zinc dendrite formation and hydrogen evolution side reactions, thus protecting the zinc metal anode. This simultaneously achieves activation of the four-electron reaction at the cathode and protection of the anode interface. Consequently, the zinc-iodine battery achieves excellent rate performance, outstanding cycle stability, and high reversible capacity.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical battery technology, specifically relating to an electrolyte that can be used in the four-electron conversion reaction of aqueous zinc-iodine batteries. Background Technology

[0002] With the ongoing global energy structure transformation, large-scale energy storage technology has become a key support for achieving a high proportion of renewable energy grid integration. Among various electrochemical energy storage systems, lithium-ion batteries dominate, but their resource constraints, cost pressures, and safety risks are becoming increasingly prominent. In contrast, aqueous batteries exhibit enormous application potential due to their inherent safety, low cost, and environmental friendliness. Among these, aqueous zinc-ion batteries are widely considered strong contenders for next-generation large-scale energy storage technology due to the high theoretical capacity, low redox potential, and abundant reserves of zinc in the Earth's crust. However, current mainstream aqueous zinc-ion battery cathode materials, such as manganese-based or vanadium-based oxides, generally suffer from limited capacity, low voltage platforms, or poor structural stability, making it difficult to break through the overall energy density barrier and limiting their practical application prospects.

[0003] To overcome these limitations, researchers have turned their attention to halogen-based cathode materials with high theoretical capacity, particularly iodine cathodes. Iodine possesses multi-electron conversion properties, which are based on I... - / I 0 The theoretical capacity of the two-electron reaction can reach 211 mAh g. -1 Furthermore, when matched with a zinc negative electrode, it can achieve an operating voltage exceeding 1.2V. Early concepts of zinc-iodine secondary batteries can be traced back to the 1980s, but they were limited by poor positive electrode carrier performance and the presence of polyiodide ions (such as Iodide). 3- The severe self-discharge caused by the dissolution shuttle of iodine species and the growth of zinc dendrites have prevented its commercialization. In recent years, by loading iodine into porous carbon materials, the shuttle of iodine species can be suppressed to some extent through physical confinement. For example, research reported by the Pacific Northwest National Laboratory has achieved iodine-based... - / I 0 The alternative is a zinc-iodine battery with a longer cycle life. Nevertheless, this traditional two-electron reaction mechanism has not shown a significant advantage over zinc-ion batteries in terms of capacity and energy density, and its performance bottlenecks urgently need to be overcome.

[0004] Theoretically, the oxidation state of iodine can change from -1 to +1. If this could be achieved... - / I 0 / I + If the conversion is completely reversible, i.e., a four-electron reaction, then its theoretical capacity can be doubled to 422 mAh g. -1 Energy density is expected to exceed 400 Wh / kg -1This would greatly enhance the competitiveness of zinc-iodine batteries. However, realizing this four-electron reaction mechanism faces enormous challenges. The core issue lies in the high cost of I4. + It is extremely unstable in aqueous electrolytes, readily undergoing hydrolysis, and its reaction kinetics are slow. In existing technologies, to activate and stabilize I... + This typically employs a strategy using ultra-high concentration halide ion electrolytes, such as those with a concentration of not less than 5 mol / L. -1 Even as high as 30 mol L -1 A mixed solution of zinc salts such as ZnCl2 and chloride salts. High concentration of Cl... - Can be used with I + Formation of interhalogen compounds such as ICl, thereby stabilizing I + At the same time, a high-salt environment can reduce water activity and inhibit I... + Hydrolysis.

[0005] While the above strategy confirms the possibility of a four-electron reaction, its side effects are extremely significant. First, the ultra-high concentration leads to a sharp increase in electrolyte viscosity and a decrease in ionic conductivity, significantly hindering reaction kinetics and impairing rate performance. Second, high concentrations of free halide ions (such as Cl-) - , Br - This solution is highly corrosive to zinc anodes, causing severe pitting corrosion, accelerating anode failure, and potentially accompanied by side reactions such as hydrogen evolution. Finally, the high salt content also increases electrolyte costs, hindering practical applications. Currently, there is still a lack of an integrated solution that can synergistically address systemic issues such as the excitation and stabilization of four-electron reactions on the positive electrode side, the suppression of polyiodide shuttles, and the corrosion and dendrite suppression on the negative electrode side.

[0006] Therefore, it is necessary to develop a novel electrolyte system that can effectively excite and stabilize I under moderate or low concentration conditions. - / I 0 / I + The four-electron reaction, which can effectively protect the zinc anode interface while suppressing the shuttle effect of polyiodides, is crucial for promoting the practical application of high-energy-density, long-life aqueous zinc-iodine batteries. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, this invention provides an electrolyte suitable for the four-electron conversion reaction in aqueous zinc-iodine batteries. This invention pretreats the charge distribution of tribromide ions by adding an organic halide salt containing a nitrogen-containing heterocyclic cation to the electrolyte, utilizing the introduced pyridine cation to capture elemental iodine on the positive electrode surface, forming a stable -I₂Br₃ solid-phase interhalogen compound. This effectively suppresses the formation of polyiodides, thus mitigating polyiodide shuttle. Under high voltage, through interaction with I₂Br₃... + The strong interaction between them excites and stabilizes I0 / I + Redox couples, thereby achieving I-based - / I 0 / I + The reversible four-electron conversion reaction improves battery capacity. On the zinc anode side, while the activity of water is weakened by an organic solvent, pyridine cations preferentially adsorb onto its surface, inhibiting competitive water adsorption, thereby suppressing zinc dendrite formation and hydrogen evolution side reactions, effectively protecting the zinc metal anode. The electrolyte system constructed in this invention simultaneously achieves the activation of the positive electrode four-electron reaction and the protection of the anode interface, effectively enhancing the reversibility of the iodine positive electrode four-electron reaction and mitigating capacity loss caused by polyiodide shuttle, thus achieving a zinc-iodine battery with excellent rate performance, outstanding cycle stability, and high reversible capacity.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The first aspect of the present invention provides an electrolyte that can be used in the four-electron conversion reaction of an aqueous zinc-iodine battery, the electrolyte comprising zinc salt, deionized water, organic solvent and organic halide salt.

[0010] Further, the zinc salt is at least one selected from zinc sulfate, zinc perchlorate, zinc tetrafluoroborate, zinc trifluoromethanesulfonate, and zinc acetate, and the concentration of the zinc salt is 0.5~3 mol L. -1 .

[0011] Furthermore, the zinc salt is zinc perchlorate.

[0012] Furthermore, the concentration of the zinc salt is 2 mol L. -1 .

[0013] Furthermore, the organic halide salt is a nitrogen-containing heterocyclic cation, pyridinium tribromide, and the concentration of the organic halide salt is 0.01~1 mol L. -1 .

[0014] Furthermore, the concentration of the organic halide salt is 0.05~0.2 mol L. -1 .

[0015] Furthermore, the concentration of the organic halide salt is 0.1 mol L. -1 .

[0016] Further, the organic solvent is at least one selected from acetonitrile, dimethyl sulfoxide, dimethyl sulfone, dimethylacetamide, and N,N-dimethylformamide.

[0017] Furthermore, the organic solvent is acetonitrile, and the volume ratio of deionized water to acetonitrile is (1~4):1.

[0018] Furthermore, the volume ratio of deionized water to acetonitrile is 2:1.

[0019] A second aspect of the present invention provides a method for preparing the above-mentioned electrolyte, comprising the following steps:

[0020] (1) After mixing deionized water and organic solvent, stir at room temperature to obtain a mixed solvent; add zinc salt to the mixed solvent and stir at room temperature to obtain a zinc salt solution;

[0021] (2) Add organic halide salts to zinc salt solution and stir at room temperature to prepare electrolyte containing organic halide salts.

[0022] A third aspect of the present invention provides a four-electron iodine conversion type zinc-iodine battery, the battery comprising a positive electrode, a negative electrode, a separator, and the aforementioned electrolyte, wherein during operation, the positive electrode generates Io... - / I 0 / I + A reversible electrochemical reaction. The electrolyte utilizes introduced pyridine cations to pretreat the charge distribution of tribromide ions, allowing them to capture elemental iodine on the positive electrode surface, forming a stable -I₂Br₃ solid-phase interhalogen compound. This effectively suppresses the formation of polyiodides, thus mitigating the polyiodide shuttle effect. When charged to 1.35V (vs. Zn) 2+ When the concentration of pyridinium tribromide is above 1 / Zn, it reacts with I... + They combine to form -BrI type organohalogen intercalary compounds, thereby stabilizing I. + Activate and stabilize I 0 / I + A reversible redox reaction.

[0023] Furthermore, the positive electrode is a carbon-based porous material loaded with iodine, wherein the carbon-based porous material is at least one of activated carbon, mesoporous carbon, carbon cloth, graphene, and graphene oxide; and the mass fraction of iodine in the composite material is 20-60%.

[0024] Furthermore, the mass fraction of the iodine in the composite material is 40%.

[0025] Furthermore, the negative electrode is any one of zinc foil, zinc powder coated electrode, or electrodeposited zinc layer.

[0026] Furthermore, the diaphragm is any one of a glass fiber diaphragm, a cellulose diaphragm, or a polypropylene porous diaphragm.

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] This invention provides an electrolyte suitable for the four-electron conversion reaction in aqueous zinc-iodine batteries. The electrolyte comprises a zinc salt, deionized water, an organic solvent, and an organic halide salt. This invention utilizes pyridine cations to pretreat the charge distribution of tribromide ions, reducing polyiodide shuttle, and under high voltage, through reaction with I... + Strong interaction, excites and stabilizes I 0 / I + Redox couples, realizing I - / I 0 / I + The reversible four-electron conversion reaction enhances battery capacity. On the zinc anode side, the activity of water is weakened by an organic solvent, while pyridine cations preferentially adsorb onto its surface, suppressing competitive water adsorption, inhibiting zinc dendrite formation and hydrogen evolution side reactions, thus protecting the zinc metal anode. This simultaneously achieves activation of the four-electron reaction at the cathode and protection of the anode interface. Consequently, the zinc-iodine battery achieves excellent rate performance, outstanding cycle stability, and high reversible capacity.

[0029] Specifically, the present invention has the following advantages:

[0030] (1) This invention introduces the organic halide salt pyridinium tribromide for the first time, and uses an additional organic solvent to enhance the charge distribution pretreatment of tribromide ions, enabling it to capture elemental iodine on the positive electrode surface and form a stable -I₂Br₃ solid-phase interhalogen compound, thereby effectively suppressing the formation of polyiodides and mitigating the shuttle effect. More importantly, it can react with I₂ under high voltage. + Strong interactions occur, further forming -BrI type organohalogen compounds, thereby exciting and stabilizing I. + / I 0 Redox couples, ultimately realizing I - / I 0 / I + The reversible four-electron conversion reaction doubles the capacity of zinc-iodine batteries (140mAh g). -1 vs. 280mAh g -1 ).

[0031] (2) The electrolyte proposed in this invention, which can be used for the four-electron conversion reaction of aqueous zinc-iodine batteries, can not only weaken the activity of bulk water through organic solvents, but its pyridine cations can also preferentially adsorb onto the electrode surface to competitively inhibit the adsorption of interfacial water and regulate the zinc ion flux, thereby effectively inhibiting zinc dendrite growth and hydrogen evolution side reaction, enabling the zinc metal anode and zinc-iodine battery to achieve rapid, uniform and dense zinc deposition behavior, and ultimately enabling the battery to obtain ultra-high coulombic efficiency (99.96%) and ultra-long cycle life (3500 hours).

[0032] (3) The electrolyte system constructed in this invention, based on the above-mentioned positive and negative electrode synergistic effect, simultaneously realizes the activation of the reversible four-electron reaction of the positive electrode and the efficient protection of the electrolyte-electrode interface of the negative electrode, effectively enhances the reversibility of the four-electron reaction of the iodine positive electrode and alleviates the capacity loss caused by polyiodide shuttle, thereby realizing a zinc-iodine battery with excellent rate performance, excellent cycle stability (16,600 cycles) and high reversible capacity. Attached Figure Description

[0033] Figure 1 The image shows the Tafel curves of the zinc metal anodes in Example 1 and Comparative Example 1.

[0034] Figure 2 This is a scanning electron microscope image of the zinc metal anode in Example 1 after cycling.

[0035] Figure 3 This is a scanning electron microscope image of the zinc metal anode in Comparative Example 1 after cycling.

[0036] Figure 4 The graph shows the rate cycling curves of the symmetric cells prepared in Example 1 and Comparative Example 1.

[0037] Figure 5 The graph shows the rate electrochemical performance of the zinc-iodine batteries prepared in Example 1 and Comparative Example 1 at different currents.

[0038] Figure 6 The zinc-iodine batteries prepared in Example 1 and Comparative Example 2 were used at a current density of 0.2 A g. -1 The following is a graph showing the cyclic performance.

[0039] Figure 7 The zinc-iodine battery prepared in Example 1 was tested at a current density of 0.2 A g. -1 Voltage-to-capacity curves below

[0040] Figure 8 The zinc-iodine battery prepared in Comparative Example 1 was tested at a current density of 0.2 A g. -1 Voltage-to-capacity curves below

[0041] Figure 9 The zinc-iodine battery prepared in Example 1 was tested at a current density of 1 A g. -1 The following is a long-cycle performance graph. Detailed Implementation

[0042] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0043] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0044] Example 1

[0045] This embodiment provides a method for preparing an electrolyte suitable for the four-electron conversion reaction in aqueous zinc-iodine batteries and a method for assembling the battery. The detailed steps of this method are as follows:

[0046] (1) Mix deionized water and acetonitrile in a volume ratio of 2:1, stir at room temperature, and the mixed solvent can be obtained after the mixture is stirred evenly.

[0047] (2) Take 20 mL of the mixed solvent from step (1), add 14.89 g of zinc perchlorate to it, stir at room temperature until it is homogeneous, and you will get 2 mol L. -1 Zinc perchlorate electrolyte.

[0048] (3) Take 20 mL of zinc perchlorate electrolyte from step (2), add 0.64 g of pyridinium tribromide to it, stir at room temperature, and after stirring evenly, you can get the electrolyte of Example 1 that can be used for the four-electron conversion reaction of aqueous zinc-iodine battery.

[0049] (4) At room temperature, the supercapacitor activated carbon-encapsulated iodine composite material (I@AC) (iodine accounts for 40% of the composite material mass), conductive additive (Super P) and sodium carboxymethyl cellulose binder (CMC aqueous solution) in a mass ratio of 8:1:1 are ground and mixed thoroughly to form a slurry, which is then coated onto the carbon cloth current collector and dried overnight at 60 °C to obtain the I@AC electrode.

[0050] (5) After coupling the electrolyte from step (3) together with two zinc metal and glass fiber separators into a 2032 button cell, the symmetrical cell of Example 1 can be obtained.

[0051] (6) The electrolyte from step (3), with the I@AC electrode as the positive electrode, is placed together with a zinc metal and glass fiber separator into a 2032 button cell for coupling, and the zinc-iodine battery of Example 1 is obtained.

[0052] Figure 9 The zinc-iodine battery prepared in Example 1 was tested at a current density of 1 A g. -1 The following is a graph showing the long-cycle performance of the zinc-iodine battery. In Example 1, the zinc-iodine battery maintained a capacity of 158 mAh g after 16,600 cycles. -1 This demonstrates that the zinc-iodine battery in Example 1 has high reversible capacity and ultra-long cycle life.

[0053] Example 2

[0054] This embodiment provides a method for preparing an electrolyte for the four-electron conversion reaction in an aqueous zinc-iodine battery and a method for assembling the battery. The main differences between this method and Example 1 are as follows:

[0055] In step (3), 1.28 g of pyridinium tribromide is added to 20 mL of 2 mol L⁻¹ solution. -1 In zinc perchlorate electrolyte, an electrolyte suitable for the four-electron conversion reaction in aqueous zinc-iodine batteries is obtained.

[0056] The remaining steps and experimental parameters are the same as in Example 1.

[0057] Example 3

[0058] This embodiment provides a method for preparing an electrolyte for the four-electron conversion reaction in an aqueous zinc-iodine battery and a method for assembling the battery. The main differences between this method and Example 1 are as follows:

[0059] In step (3), 1.92 g of pyridinium tribromide is added to 20 mL of 2 mol L⁻¹ solution. -1 In zinc perchlorate electrolyte, an electrolyte suitable for the four-electron conversion reaction in aqueous zinc-iodine batteries is obtained.

[0060] The remaining steps and experimental parameters are the same as in Example 1.

[0061] Example 4

[0062] This embodiment provides a method for preparing an electrolyte for the four-electron conversion reaction in an aqueous zinc-iodine battery and a method for assembling the battery. The main differences between this method and Example 1 are as follows:

[0063] In step (2), 14.54 g of zinc trifluoromethanesulfonate is added to 20 mL of a mixed solvent of deionized water and acetonitrile in a volume ratio of 2:1 to obtain an electrolyte that can be used for the four-electron conversion reaction of an aqueous zinc-iodine battery.

[0064] The remaining steps and experimental parameters are the same as in Example 1.

[0065] Comparative Example 1

[0066] This comparative example provides a method for preparing an electrolyte suitable for the four-electron conversion reaction in aqueous zinc-iodine batteries and a method for assembling the battery. The detailed steps of this method are as follows:

[0067] (1) Mix deionized water and acetonitrile in a volume ratio of 2:1, stir at room temperature, and the mixed solvent can be obtained after the mixture is stirred evenly.

[0068] (2) Take 20 mL of the mixed solvent from step (1), add 14.89 g of zinc perchlorate to it, stir at room temperature until it is homogeneous, and you will get 2 mol L. -1 Zinc perchlorate electrolyte.

[0069] (3) Take 20 mL of zinc perchlorate electrolyte from step (2), add 0.62 g of sodium bromide to it, stir at room temperature, and after it is stirred evenly, you can get the electrolyte of Comparative Example 1 that can be used for the four-electron conversion reaction of aqueous zinc-iodine battery.

[0070] (4) At room temperature, the supercapacitor activated carbon-encapsulated iodine composite material (I@AC) (iodine accounts for 40% of the composite material mass), conductive additive (Super P) and sodium carboxymethyl cellulose binder (CMC aqueous solution) in a mass ratio of 8:1:1 are ground and mixed thoroughly to form a slurry, which is then coated onto the carbon cloth current collector and dried overnight at 60 °C to obtain the I@AC electrode.

[0071] (5) After coupling the electrolyte from step (3) together with two zinc metal and glass fiber separators into a 2032 button cell, the symmetrical cell of Comparative Example 1 can be obtained.

[0072] (6) The electrolyte from step (3), with the I@AC electrode as the positive electrode, is placed together with a zinc metal and glass fiber separator into a 2032 button cell for coupling, and the zinc-iodine battery of Comparative Example 1 can be obtained.

[0073] Figure 1 The zinc metal anode in Example 1 and Comparative Example 1 has a scan rate of 1 mV / s in a three-electrode system. -1 The Tafel curve at that time. From Figure 1 As can be seen from the data, the corrosion potential of Example 1 is significantly higher than that of Comparative Example 1, and its corresponding corrosion current is also lower. This indicates that the zinc metal anode in Example 1 is less prone to corrosion, and even if corrosion does occur, its rate is significantly slower than that in Comparative Example 1, proving that the zinc metal anode in Example 1 has excellent corrosion resistance.

[0074] Figure 2 and Figure 3 The images are scanning electron microscope (SEM) images of the zinc metal anodes from Example 1 and Comparative Example 1 after 50 cycles. It can be observed that the zinc metal anode in Comparative Example 1 has a large amount of unevenly distributed "dead zinc" on its surface after cycling. In contrast, the zinc metal anode in Example 1 remains smooth and dense after cycling, demonstrating that the zinc deposition process in Example 1 is more uniform.

[0075] Figure 4These are rate cycling curves of the symmetrical cells prepared in Example 1 and Comparative Example 1. Figure 4 As shown, when the zinc metal anode is cycled in Comparative Example 1, the polarization of the battery rapidly becomes disordered with increasing current density, reaching a peak at 2 mAcm. -2 It fails rapidly. However, as shown in Example 1, the zinc metal anode operates stably at every current density, up to a maximum of 40 mA cm⁻¹. -2 It is worth noting that when the current drops back to 1 mA cm⁻¹ -2 In Example 1, the zinc metal still exhibited normal zinc ion deposition / dissolution behavior, while in Comparative Example 1, a battery short circuit occurred. These findings indicate that the zinc metal anode in Example 1 possesses excellent ion transport capabilities, ensuring a uniform zinc ion concentration distribution at high rates, thereby achieving highly stable deposition / stripping behavior.

[0076] Figure 5 These are rate electrochemical performance graphs of the zinc-iodine batteries prepared in Example 1 and Comparative Example 1 at different currents. Figure 5 It can be seen that the rate capability of Example 1 is far superior to that of Comparative Example 1 at 0.2, 0.5, 1, 2, and 5 Ag. -1 At the given current densities, the battery capacities were 302, 283, 252, 224, and 184 mAh g, respectively. -1 .

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing an electrolyte and assembling a battery that can be used in aqueous zinc-iodine batteries. The main differences between this method and Comparative Example 1 are as follows:

[0079] No NaBr additive is added in step (3). The electrolyte is a 2 mol L solution of deionized water and acetonitrile in a volume ratio of 2:1. -1 Zinc perchlorate electrolyte.

[0080] Figure 6 The zinc-iodine batteries prepared in Example 1 and Comparative Example 2 operate at a current density of 0.2 A g. -1 The following is a graph showing the cycle performance. Figure 6 It can be seen that the capacity of the zinc-iodine battery in Comparative Example 2 is 170 mAh g. -1 In contrast, the zinc-iodine battery in Example 1 has a capacity of 280 mAh g. -1 The battery capacity was significantly improved. In Comparative Example 2, after 850 cycles, the capacity decreased to 133 mAh g. -1The capacity retention rate was 78%, indicating that excessive iodine loss occurred during the reversible cycling process, generating a large number of byproducts and leading to severe capacity loss under long-term cycling. In contrast, the zinc-iodine battery in Example 1 maintained a capacity of 240 mAh g⁻¹ after 850 cycles. -1 The capacity retention rate was 86%, which indicates that the zinc-iodine battery in Example 1 has excellent cycle stability and high reversible capacity.

[0081] Figure 7 and Figure 8 The zinc-iodine batteries prepared in Example 1 and Comparative Example 2 operate at a current density of 0.2 A g. -1 The voltage-to-capacity curves are shown below. It can be observed that the voltage-to-capacity curves of the zinc-iodine battery in Comparative Example 2 differ significantly between the 1st and 200th cycles. This indicates that iodine undergoes a side reaction during the reversible cycling process, generating a large number of byproducts, leading to a gradual loss of capacity during cycling. In contrast, the voltage-to-capacity curves of the zinc-iodine battery in Example 1 remain essentially consistent between the 1st and 200th cycles, further demonstrating that the zinc-iodine battery in Example 1 exhibits excellent cycle stability and high reversible capacity.

[0082] Comparative Example 3

[0083] This comparative example provides a method for preparing an electrolyte and assembling a battery that can be used in aqueous zinc-iodine batteries. The main differences between this method and Comparative Example 1 are as follows:

[0084] Acetonitrile is not added in step (1), NaBr additive is not added in step (3), and the electrolyte is 2 mol L of deionized water as the solvent. -1 Zinc perchlorate electrolyte.

[0085] The zinc-iodine batteries prepared in Examples 1-4 and Comparative Examples 1-3 were tested at a current density of 1 A g. -1 Electrochemical tests were performed, and the results are shown in Table 1.

[0086] Table 1

[0087] <![CDATA[Discharge capacity after 850 cycles (mAh g -1 )]]> Average Coulomb efficiency (%) Cycle life (number of cycles) Example 1 225 97.4 16600 Example 2 208 94.6 8936 Example 3 185 91.8 3648 Example 4 154 93.8 5640 Comparative Example 1 168 74.3 2734 Comparative Example 2 169 79.3 3570 Comparative Example 3 150 74.2 1356

[0088] Table 1 shows that the cycle life and average coulombic efficiency of Examples 1-4 all exceed those of Comparative Examples 1-3, and the battery capacity of Examples 1-4 all exceed that of Comparative Example 3. This indicates that adding acetonitrile as a mixed solvent can improve cycle stability, with Example 1 exhibiting the best electrochemical performance, demonstrating the most significant improvement effect. The discharge capacity of Examples 1-3 after 850 cycles is higher than that of Comparative Examples 1-3, indicating that the addition of pyridinium tribromide can more stably activate the four-electron conversion reaction of iodine, significantly improving battery capacity. Simultaneously, the average coulombic efficiency of Examples 1-4 is higher than that of Comparative Example 1, indicating that pyridinium tribromide has superior charge-discharge reversibility compared to single bromide ions. All these results collectively demonstrate that the zinc-iodine battery in Example 1 possesses excellent cycle stability and high reversible capacity.

[0089] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. An electrolyte suitable for the four-electron conversion reaction in aqueous zinc-iodine batteries, characterized in that, The electrolyte comprises zinc salt, deionized water, organic solvent, and organic halide salt; the concentration of the zinc salt is 0.5~3 mol L. -1 The organic halide salt is a nitrogen-containing heterocyclic cation, pyridinium tribromide, and the concentration of the organic halide salt is 0.01~1 mol L. -1 .

2. The electrolyte according to claim 1, which can be used in the four-electron conversion reaction of an aqueous zinc-iodine battery, is characterized in that, The zinc salt is at least one of zinc sulfate, zinc perchlorate, zinc tetrafluoroborate, zinc trifluoromethanesulfonate, and zinc acetate.

3. The electrolyte according to claim 1, which can be used in the four-electron conversion reaction of an aqueous zinc-iodine battery, is characterized in that, The organic solvent is at least one selected from acetonitrile, dimethyl sulfoxide, dimethyl sulfone, dimethylacetamide, and N,N-dimethylformamide.

4. The electrolyte according to claim 3, which can be used in the four-electron conversion reaction of an aqueous zinc-iodine battery, is characterized in that, The organic solvent is acetonitrile, and the volume ratio of deionized water to acetonitrile is (1~4):

1.

5. A method for preparing an electrolyte as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) After mixing deionized water and organic solvent, stir at room temperature to obtain a mixed solvent; add zinc salt to the mixed solvent and stir at room temperature to obtain a zinc salt solution; (2) Add organic halide salts to zinc salt solution and stir at room temperature to prepare electrolyte containing organic halide salts.

6. A four-electron iodine conversion type zinc-iodine battery, characterized in that, The battery includes a positive electrode, a negative electrode, a separator, and an electrolyte as described in any one of claims 1-4. During operation, the positive electrode generates Ig. - / I 0 / I + Reversible electrochemical reactions.

7. A four-electron iodine conversion zinc-iodine battery according to claim 6, characterized in that, The positive electrode is a carbon-based porous material loaded with iodine, wherein the carbon-based porous material is at least one of activated carbon, mesoporous carbon, carbon cloth, graphene, and graphene oxide; and the mass fraction of iodine in the composite material is 20-60%.

8. A four-electron iodine conversion zinc-iodine battery according to claim 6, characterized in that, The negative electrode is any one of a zinc foil electrode, a zinc powder coated electrode, or an electrodeposited zinc layer.

9. A four-electron iodine conversion zinc-iodine battery according to claim 6, characterized in that, The diaphragm is any one of glass fiber diaphragm, cellulose diaphragm, or polypropylene porous diaphragm.

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