Zinc-iodine flow battery electrolyte, application thereof and zinc-iodine flow battery

Abstract

The invention discloses a neutral zinc-iodine flow battery electrolyte composition based on two-electron reaction and application thereof, and belongs to the field of flow batteries. Zinc salt, iodized salt, acetate, a specific amine compound and a supporting electrolyte are adopted as main active components of the electrolyte. According to the amine compound used in the electrolyte, an active substance iodine on the positive electrode side of the battery can be subjected to a two-electron transfer reaction, so that a reversible oxidation-reduction reaction from-1 valence iodine to + 1 valence iodine is realized. Compared with the original irreversible multi-electron transfer reaction, the two-electron transfer reaction has higher reversibility, two reversible charging and discharging platforms can exist, the energy efficiency of the battery can be remarkably improved, and the application of the zinc-iodine flow battery based on the multi-electron transfer reaction is facilitated.

Description

Technical Field

[0001] This application relates to a zinc-iodine flow battery electrolyte and its application in zinc-iodine flow batteries, belonging to the field of flow batteries. Background Technology

[0002] As fossil fuels are gradually depleted, renewable energy is playing an increasingly important role in energy utilization. However, renewable energy sources such as wind and solar power are highly volatile due to weather conditions and difficult to effectively connect to the grid. To address this issue, energy storage technology can be used to smooth peak and valley loads, enabling renewable energy to be smoothly and stably output into the grid. Among various energy storage technologies, flow batteries offer advantages such as high safety, long cycle life, and flexible design, making them suitable for large-scale renewable energy utilization. Among different flow battery energy storage technologies, zinc-iodine flow batteries offer advantages such as high safety, high battery voltage, good battery kinetics, and abundant sources, making them a promising flow battery system. However, zinc-iodine flow batteries still have some problems that prevent their large-scale application. The high cost of iodine and low utilization rate per unit of iodine are the main obstacles to their application. Currently, traditional zinc-iodine flow batteries generally only utilize the electron transfer reaction from iodide ions to iodine triple negatives, corresponding to the transfer of 2 / 3 of an iodine atom. In reality, iodine has a wide range of valence states, including -1, 0, +1, +3, and +5. Utilizing iodine in higher valence states would effectively increase the number of electrons transferred per iodine atom, thereby improving the battery's energy density and iodine utilization, and reducing the cost of zinc-iodine batteries. However, in aqueous solution, the transformation of iodine at valence 0 to higher valence states generates irreversible iodate ions. Iodate ions exhibit very high polarization during direct discharge, resulting in the formation of only a portion of iodide ions, which then react with iodate ions to form elemental iodine, which is then used for discharge. This results in a single discharge plateau with a large potential difference between the charge and discharge plateaus, leading to low energy efficiency in zinc-iodine flow batteries, which is highly detrimental to their application in energy storage scenarios. Therefore, improving iodine utilization and the reversibility of iodine in multi-electron transfer reactions are crucial technical challenges for the successful application of zinc-iodine flow batteries. Summary of the Invention

[0003] To address the above technical problems, this invention aims to provide a neutral zinc-iodine flow battery electrolyte with reversible two-electron reaction and its application in flow batteries.

[0004] This invention employs iodide salts, acetates, and amine compounds as reactants on the positive electrode side of the electrolyte. The amine compounds selected in this invention can undergo a reversible two-electron transfer reaction with iodide ions, effectively increasing the number of electrons transferred per iodine atom. During charging, iodide ions are first electrochemically oxidized to elemental iodine, achieving a one-electron transfer from -1 to 0 valence. Then, the 0-valence iodine is further electrochemically oxidized and reacts with the amine compounds to form iodoamine compounds, achieving a one-electron transfer from 0 to +1 valence. During the conversion from amine compounds to iodoamine compounds, a proton is released; therefore, acetate is needed to bind this proton to form acetic acid, effectively buffering the pH of the solution. During discharging, the +1-valence iodoamine compounds are first electrochemically reduced to elemental iodine, achieving a one-electron transfer from +1 to 0 valence. Then, the 0-valence iodine is further electrochemically reduced to iodide ions, achieving a one-electron transfer from 0 to -1 valence. The entire process involves two steps and two-electron transfers, with excellent reversibility. The selected amine compounds react with the +1 valence iodine intermediate to form iodoamine compounds, which exhibit high stability. This stability is attributed to the electron-withdrawing groups adjacent to the amine compounds, which effectively bind electrons to the nitrogen atom, allowing the iodine to form a stable Ni covalent bond. Using zinc as the negative electrode, a neutral zinc-iodine flow battery can be constructed. Due to the reversible two-electron transfer reaction of iodine on the positive electrode side, the zinc-iodine flow battery exhibits two reversible charge-discharge plateaus during charging and discharging. The battery capacity is doubled compared to zinc-iodine flow batteries with only single-electron transfer, and the higher voltage further enhances the energy density. Compared to irreversible multi-electron zinc-iodine flow batteries, this reaction offers greater reversibility, effectively improving the energy efficiency of multi-electron zinc-iodine flow batteries.

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

[0006] In a first aspect, the present invention provides a zinc-iodine flow battery electrolyte, wherein the electrolyte contains iodide ions, zinc ions, acetate ions, amine compounds, and a supporting electrolyte.

[0007] Furthermore, the iodide ions in the electrolyte are provided by adding iodized salts, which are one or more of sodium iodide, potassium iodide, ammonium iodide, magnesium iodide, and calcium iodide, preferably sodium iodide.

[0008] The iodide ion concentration was 0.01-7 mol / L. -1 Preferably 0.4-4 mol L -1 .

[0009] Furthermore, the zinc ions in the electrolyte are provided by an added zinc salt, which is one or more of zinc acetate, zinc sulfate, zinc iodide, zinc chloride, zinc nitrate, and zinc perchlorate, preferably zinc acetate. Zinc acetate can be used as either a zinc salt or an acetate.

[0010] The zinc salt concentration was 0.1-4 mol / L. -1 Preferably 1-2 mol L -1 Zinc salts primarily serve as the anode active material to match the cathode, and are not the main innovation of this invention. The main innovation of this invention lies in the two-electron transfer reaction between iodine and amine compounds on the cathode side.

[0011] Furthermore, the acetate ions in the electrolyte are provided by added acetate, which is one or more of sodium acetate, potassium acetate, zinc acetate, magnesium acetate, and ammonium acetate, preferably sodium acetate.

[0012] The acetate concentration is 0.1-3 mol / L. -1 Preferably 0.5-3 mol L -1 Acetate is used as a pH buffer solution to absorb and release protons during charging and discharging.

[0013] Furthermore, the amine compound in the electrode solution is one or more of succinimide, sodium aminosulfonate, potassium aminosulfonate, 5,5-dimethylhydantoin, and thioamide, preferably succinimide.

[0014] The concentration of amine compounds was 0.5-6 mol / L. -1 Preferably 1-4 mol L -1 Amine compounds are mainly used to stabilize the +1 valence charging products of iodine on the positive electrode side, forming stable and reversible iodoamine compounds.

[0015] Furthermore, the supporting electrolyte in the electrolyte is one or more of sodium sulfate, ammonium sulfate, sodium chloride, potassium chloride, sodium nitrate, and potassium nitrate. Sodium sulfate is preferred. The supporting electrolyte is mainly selected from commonly used substances with high conductivity to balance ions during charging and discharging.

[0016] According to another aspect of this application, the application of the above-mentioned flow battery electrolyte is provided, which is used in a zinc-iodine flow battery.

[0017] The zinc-iodine flow battery includes a metal end plate, a current collector, a flow frame, activated carbon felt or graphite felt as electrodes, a separator for separating the positive and negative electrodes, and a rubber gasket for sealing. The cavity between the positive current collector and the separator is filled with positive graphite felt or carbon felt and positive electrolyte, and the cavity between the negative current collector and the separator is filled with negative graphite felt or carbon felt and negative electrolyte. The electrolyte is circulated between the cavity and the storage tank by a magnetic centrifugal pump or a peristaltic pump. The positive electrolyte may not circulate and is sealed in the cavity, thus serving as a single-flow battery.

[0018] Specifically, the metal end plate can be selected from any one of aluminum alloy plate, stainless steel plate and other acid corrosion resistant metal plates, preferably stainless steel plate; the current collector can be selected from any one of graphite plate and titanium plate, and the positive current collector is preferably titanium plate; the diaphragm can be selected from any one of perfluorosulfonic acid membrane, porous polyolefin membrane, sulfonated polyether ether ketone membrane, polybenzimidazole membrane, preferably perfluorosulfonic acid membrane.

[0019] The electrolyte used in this neutral zinc-iodine flow battery comprises iodine salts, zinc salts, amine compounds, and a supporting electrolyte. The zinc-iodine flow battery system using this electrolyte can achieve reversible two-electron transfer reactions and has two reversible charge-discharge plateaus.

[0020] The amine compounds used in the electrolyte can rapidly react with the +1 valent iodine intermediate generated during the charging process of the iodine salt on the positive electrode side to form iodoamine compounds, creating stable charging products and enabling reversible discharge. The zinc-iodine flow battery, composed of zinc salt on the negative electrode side, achieves a reversible two-step two-electron transfer reaction. Its capacity is higher than that of traditional zinc-iodine flow batteries with single-electron transfer reactions, and its energy efficiency is higher than that of previous zinc-iodine flow batteries with multi-electron transfer reactions. It offers advantages such as low cost and high energy density, making it suitable for large-scale and distributed energy storage.

[0021] The amine compounds used in the electrolyte enable the iodine active material on the positive electrode side of the battery to undergo a two-electron transfer reaction, achieving a reversible redox reaction from -1 valence iodine to +1 valence iodine. Compared to the previously irreversible multi-electron transfer reaction, this two-electron transfer reaction has higher reversibility, allowing for two reversible charge-discharge plateaus, which can significantly improve the energy efficiency of the battery and is beneficial for the application of zinc-iodine flow batteries based on multi-electron transfer reactions.

[0022] The beneficial effects that this application can produce include:

[0023] The electrolyte provided in this application can be used as an electrolyte in zinc-iodine flow batteries and is suitable for low-cost flow battery systems for large-scale energy storage and distributed energy storage.

[0024] 1) The electrolyte for the flow battery provided in this application utilizes a two-electron transfer reaction between amine compounds and iodine. Compared to traditional zinc-iodine flow batteries, the number of electrons transferred per iodine atom increases from 2 / 3 to 2. Using 2 mol L... -1 The sodium iodide zinc-iodine flow battery can achieve 106.5 Ah / L. -1 The discharge capacity.

[0025] 2) The zinc-iodine flow battery based on the electrolyte of this application exhibits high energy efficiency. Compared to zinc-iodine flow batteries utilizing the irreversible multi-electron transfer reaction of iodate, this reaction has higher reversibility and can have an independent high discharge plateau. The battery's energy efficiency in charge-discharge cycles can reach 81%, which is 11% higher than the 70% energy efficiency of zinc-iodine flow batteries utilizing the multi-electron transfer reaction of iodate.

[0026] 3) The zinc-iodine flow battery based on the electrolyte of this application has a long cycle life. Due to the highly reversible two-electron transfer reaction between iodine and amine compounds, the flow battery can achieve a long cycle life of over 300 cycles.

[0027] 4) The electrolyte components used in this application have the advantage of low cost. In addition to iodine, the selected zinc salts, acetates, amine compounds and supporting electrolytes are all common chemical raw materials, which can be used to prepare this zinc-iodine flow battery electrolyte at a low cost, thereby making the zinc-iodine flow battery using this electrolyte have a low operating cost.

[0028] 5) The electrolyte used in this application has the advantage of high safety. First, the electrolyte in this application is prepared in an aqueous solution, which can effectively avoid the flammability risk present in organic electrolytes. Second, the zinc salt, iodine salt, acetate, amine compounds, and supporting electrolyte in the electrolyte of this application are all almost non-volatile and environmentally friendly compounds, and the pH of the solution is close to neutral, eliminating the risk of acid and alkali corrosion. The zinc-iodine flow battery using this electrolyte has the characteristic of high safety. Attached Figure Description

[0029] Figure 1 The graph shows the charge-discharge curves of the batteries in Example 1 and Comparative Example 1. The dashed line in the graph represents the charge-discharge curve of Comparative Example 1, and the solid line represents the charge-discharge curve of Example 1.

[0030] Figure 2 The graph shows the charge and discharge curves for Example 7. The solid line represents the charging process, and the dashed line represents the discharging process.

[0031] Figure 3 This is a battery efficiency graph for long-cycle charge and discharge of the battery in Example 1. Detailed Implementation

[0032] The following embodiments are further illustrations of this application, but not limitations on its scope. Unless otherwise specified, the materials used in the embodiments and comparative examples of this application were all purchased commercially. Battery performance testing was performed using a Newway charge-discharge instrument.

[0033] Example 1

[0034] Assemble a flow battery:

[0035] The positive and negative electrode electrolytes have the same composition, and the volume of each electrolyte is 60 mL. Both electrolytes contain 0.5 mol / L... -1 Sodium iodide, 1 mol L -1 Zinc acetate, 0.5 mol L -1 Sodium sulfate, 1.0 mol L -1 An aqueous solution of succinimide. Zinc acetate is used both as a zinc salt and as an acetate salt to reduce the cost of material addition and to lower electrolyte viscosity.

[0036] Assembly of a single battery:

[0037] The structure of a single cell includes an end plate and a graphite plate as a current collector, with a length × width of 6 × 8 cm. 2 The system consists of carbon felt as the positive and negative electrodes, Nafion membrane as the perfluorosulfonic acid diaphragm, flow frame, gaskets, end plates, positive and negative electrode electrolyte storage tanks, pumps, and pipelines.

[0038] The structure of a single cell includes, in sequence, an end plate, a silicone pad, a current collector, a silicone pad, an annular liquid flow frame with the positive electrode placed in a central through hole, a silicone pad, a diaphragm, a silicone pad, an annular liquid flow frame with the negative electrode placed in a central through hole, a silicone pad, and an end plate; the electrolyte in the positive and negative electrolyte storage tanks flows through pipelines via pumps through the electrode chambers in the annular liquid flow frame of the positive electrode and the electrode chambers in the annular liquid flow frame of the negative electrode, respectively, and returns to the positive and negative electrolyte storage tanks.

[0039] Battery test:

[0040] A constant current charge-discharge mode was adopted, with an electrolyte flow rate of 60 mL / min. -1 The charging and discharging current density is 20 mA cm⁻¹ -2 The charging cutoff voltage is 2.0V, and the discharging cutoff voltage is 0.1V. Coulombic efficiency (CE), voltage efficiency (VE), and energy efficiency (EE) are the average values ​​obtained from the tests.

[0041] The other examples and comparative examples assembled flow batteries differed from Example 1 only in electrolyte composition; all other aspects were the same. Examples 1-3 and Examples 5-11 were mainly examples of neutral zinc-iodine flow batteries based on succinimide as an amine compound. Examples 4 and Comparative Examples 7-9 were comparisons of neutral zinc-iodine flow batteries with the addition of other amine compounds. Comparative Examples 1-6 were comparisons of batteries lacking a certain component compared to Example 1. See Table 1 for details.

[0042] Table 1. Battery composition and performance of different embodiments and comparative examples.

[0043]

[0044]

[0045]

[0046]

[0047] As can be seen from the battery performance data of Examples 1-7, the coulombic efficiency, voltage efficiency and energy efficiency of the neutral zinc-iodine flow battery with an electrolyte composed of iodine salt, zinc salt, acetate, amine compound and supporting electrolyte can be maintained at a relatively high level, indicating that the zinc-iodine flow battery based on this two-electron transfer reaction has high reversibility and stability.

[0048] As can be seen from Examples 1 and 2, the different metal cations in iodized salts cause certain differences in battery voltage efficiency. This is mainly due to the different hydration structures and migration kinetics of the different metal cations. The iodide ions in iodized salts play a major role, serving as the active material on the positive electrode side.

[0049] As can be seen from Examples 1 and 3, changing the type of zinc salt leads to a certain degree of change in voltage efficiency. This is mainly because the anions of different zinc salts affect the conductivity of the electrolyte to some extent. The strength of the binding force between anions and cations also affects the ion migration rate of cations, thus leading to changes in polarization.

[0050] As can be seen from Examples 1, 4, 5, 6, and 7, the selected amine compounds can achieve a reversible two-electron transfer reaction. The difference lies in the varying binding forces between different amine compounds and +1 valence iodine, resulting in differences in the stability of the generated iodoamine compounds. This difference leads to variations in the length of the high discharge plateau. The preferred succinimide has the highest discharge plateau, meaning that the generated iodosuccinimide has the highest stability; therefore, succinimide is the preferred amine compound.

[0051] As can be seen from Examples 1 and 8, different acetates can lead to certain differences in battery efficiency. This is mainly because different metal cations in acetates can change the ion ratio in the solution to a certain extent, resulting in different ion diffusion intensities.

[0052] As can be seen from Examples 1 and 9, different supporting electrolytes lead to certain differences in battery efficiency. This is mainly because the supporting electrolyte acts as an ion conductor. Using different supporting electrolytes will result in differences in ionic conductivity, thus leading to certain differences in battery voltage efficiency and energy efficiency.

[0053] As can be seen from Examples 1 and 10, increasing the concentration of iodide ions can increase the capacity of the zinc-iodine flow battery, while the voltage efficiency of the battery will decrease to some extent due to the increase in solution viscosity. Because this reaction is characterized by a two-electron transfer reaction, 0.5 mol L... -1 The iodide ion can have 26.8 Ah L. -1 The theoretical capacity, while 2 mol L -1 The iodide ion can achieve 107.2 Ah L -1 It has the theoretical capacity and the advantage of high specific capacity.

[0054] As can be seen from Examples 1 and 11, although a low iodine ion concentration can still achieve reversible charge-discharge of a neutral zinc-iodine battery and has high battery efficiency, its capacity will also be reduced accordingly, which is not conducive to achieving a high energy density neutral zinc-iodine battery. Conversely, a high iodine ion concentration will lead to excessively high electrolyte viscosity due to limited battery solubility. Therefore, the preferred iodine salt concentration is 0.4-4 mol / L. -1 .

[0055] As can be seen from Examples 1 and 12, although a relatively low zinc acetate concentration can still achieve the two-electron transfer reaction, the excessive protons generated on the positive electrode side cannot be effectively buffered due to the pH buffering effect of acetic acid. This leads to protons crossing to the negative electrode side, causing some corrosion of the zinc on the negative electrode side. Furthermore, a relatively low zinc ion concentration also results in poorer zinc deposition / stripping kinetics, leading to a certain decrease in the coulombic efficiency of the battery compared to Example 1. Excessive zinc salt or acetate concentrations are also limited by the battery's solubility; therefore, a zinc salt concentration of 1-2 mol / L is preferred. -1 The preferred acetate concentration is 0.5-3 mol / L. -1 .

[0056] As can be seen from Examples 1, 13, 14, and 15, both excessively high and excessively low succinimid concentrations reduce the energy efficiency of the battery. A decrease in succinimid concentration leads to a certain degree of reduction in battery voltage efficiency. This is mainly because succinimid is key to achieving a stable +1 valence iodine intermediate, and the reaction between succinimid and iodine competes with the formation of iodate. A lower succinimid concentration results in a larger proportion of the competing reaction for iodate, thus causing an irreversible decrease in voltage efficiency. Excessive succinimid also makes the dissolution of other battery components more difficult; therefore, the preferred concentration of the amine compound is 1-4 mol / L. -1 It can maintain a suitable electrolyte conductivity without sacrificing the product stability of the battery.

[0057] As can be seen from Examples 1 and 16, a lower concentration of the supporting electrolyte leads to a certain degree of decrease in the battery's voltage efficiency. This is mainly because the supporting electrolyte plays a role in ion transport; insufficient ion transport results in increased concentration polarization, thus reducing the battery's voltage efficiency. However, adding too much supporting electrolyte will also reduce the solubility of the active material. Therefore, the preferred supporting electrolyte concentration is 0.3-2 mol / L. -1 .

[0058] A comparison of Example 1 with Comparative Examples 1 and 2 shows that iodine salt and zinc salt are indispensable in this neutral zinc-iodine battery. The lack of iodine salt leads to an oxygen evolution reaction on the positive electrode side, and since amine compounds themselves have no redox activity, the battery's voltage efficiency and coulombic efficiency are extremely low. The lack of zinc salt leads to a hydrogen evolution reaction on the negative electrode side, resulting in irreversible charge-discharge.

[0059] A comparison of Example 1 with Comparative Examples 3 and 4 reveals two outcomes due to the lack of specific amine compounds. First, if charge-discharge is performed according to the capacity of a two-electron transfer reaction (Comparative Example 3), the lack of amine compounds results in the irreversible formation of an iodate ion for the second electron, leading to a single discharge plateau and very low voltage efficiency. Second, if charge-discharge is performed according to a single-electron transfer reaction (Comparative Example 4), although the battery efficiency is even higher than that of the two-electron transfer reaction battery with added amine compounds, its capacity is only half that of the two-electron transfer reaction, failing to achieve high iodine utilization and high energy density.

[0060] As can be seen from Example 1 and Comparative Example 5, the lack of acetate leads to a significant decrease in the coulombic efficiency of the battery. This is mainly because the multi-electron transfer reaction on the positive electrode side is a proton-coupled electron transfer reaction, which generates a large number of protons during charging. Without the absorption of acetate ions, these protons will cross over to the negative electrode and react with the zinc deposited on the negative electrode to generate hydrogen gas, thus reducing the coulombic efficiency of the battery.

[0061] As can be seen from Example 1 and Comparative Example 6, the lack of a supporting electrolyte leads to a decrease in battery voltage efficiency. This is mainly because the supporting electrolyte provides conductive ions; the lack of a supporting electrolyte results in a higher conductivity of the solution, increasing concentration polarization during charging and discharging, which reduces battery voltage efficiency.

[0062] A comparison of Example 1 with Comparative Examples 7, 8, 9, and 10 shows that zinc-iodine batteries with added non-selected electron-donating amine compounds exhibit lower voltage efficiency. This is mainly because the amino groups of these non-selected amine compounds are connected to electron-donating groups such as methyl or methylene groups at the ortho position, which cannot react with the +1 valence iodine intermediate to form stable iodoamine compounds. Therefore, the reaction is essentially an irreversible reaction to form iodate, resulting in a similarly low voltage efficiency as batteries without added amine compounds.

[0063] A comparison of Example 1 with Comparative Examples 11, 12, and 13 reveals that zinc-iodine batteries with added non-selected electron-withdrawing groups exhibit low voltage efficiency. This is primarily because the electron-withdrawing capabilities of these amine compounds are either too low to effectively combine with the +1 valence iodine intermediate to form stable iodoamine compounds, or the electron-withdrawing capabilities are too strong, directly ionizing hydrogen ions to form fully ionized anions, also failing to effectively form stable iodoamine compounds, resulting in low voltage efficiency similar to that without the addition of amine compounds. Therefore, it is necessary to add selected amine compounds with suitable electron-withdrawing groups, capable of combining with +1 valence iodine to form stable iodoamine compounds with stable Ni covalent bonds, in order to achieve a reversible two-electron transfer reaction and exhibit high voltage efficiency in the battery.

[0064] A comparison of Example 1 and Comparative Example 14 shows that the zinc-iodine battery with the addition of N-methylsuccinimidyl amine compounds exhibits low voltage efficiency. This is mainly because the methyl group in N-methylsuccinimidyl amine replaces the hydrogen atom on the amino group. The covalent bond between the methyl group and the nitrogen atom is very strong and cannot dissociate, resulting in the absence of a site for iodine to combine with the nitrogen atom on the amino group to form a Ni covalent bond. Therefore, an effective iodoamine compound cannot be formed. Although it has an electron-withdrawing group structure similar to succinimidyl amine, the substitution of the methyl group still leads to a low voltage efficiency in the battery.

[0065] Figure 1 The figures show the charge-discharge curves of the batteries in Example 1 and Comparative Example 3. As can be seen from the figures, Comparative Example 1, due to the absence of amine compounds, although the battery could be further charged to the capacity of the two-electron transfer reaction, only had one plateau during discharge, resulting in an energy efficiency of only 70.2%. In contrast, the neutral zinc-iodine flow battery with added amine compounds exhibited two reversible charge-discharge plateaus, and its voltage efficiency was increased to 81.2%.

[0066] Figure 2 This is the charge-discharge curve for Example 7. As can be seen from the graph, by adjusting the electrolyte, adding 2 mol / L... -1 iodide ions and 2 mol L -1 The zinc-iodine flow cell with succinimide can achieve 4 mol L -1 The electron transfer reaction is efficient, and the cell has a high coulombic efficiency, achieving 106.5 Ah L / 1000 rpm. -1 It has a high discharge capacity and the advantage of high specific capacity.

[0067] Figure 3 This is a long-cycle diagram of Example 1. As can be seen from the diagram, the neutral zinc-iodine flow battery using the electrolyte prepared according to this invention can stably cycle for over 300 cycles with virtually no efficiency degradation. This is mainly due to the highly reversible two-electron transfer reaction between iodine and succinimide, and the resulting iodosuccinimide exhibits high stability, providing good support for the battery's long-cycle operation.

[0068] Based on the above analysis, the electrolyte composition of this application enables reversible operation of a neutral zinc-iodine flow battery based on a two-electron transfer reaction. It has the advantages of high specific capacity, high efficiency, and high iodine utilization rate, and is suitable for large-scale energy storage and distributed energy storage.

[0069] Furthermore, the above descriptions are merely several embodiments and corresponding comparative examples of this application, and are not intended to limit this application in any way. Although preferred embodiments have been shown above, they are not intended to limit this application. Any modifications or alterations made by those skilled in the art using the above-displayed technical content without departing from the scope of the technical solution of this application are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A zinc-iodine flow battery electrolyte, characterized in that, The electrolyte contains iodide ions, zinc ions, acetate ions, amine compounds, and supporting electrolytes.

2. The zinc-iodine flow battery electrolyte according to claim 1, characterized in that: The iodide ions in the electrolyte are provided by added iodized salts, which are one or more of sodium iodide, potassium iodide, ammonium iodide, magnesium iodide, and calcium iodide.

3. The zinc-iodine flow battery electrolyte according to claim 1, characterized in that: The zinc ions in the electrolyte are provided by adding zinc salts, which are one or more of zinc acetate, zinc sulfate, zinc iodide, zinc chloride, zinc nitrate, and zinc perchlorate.

4. The zinc-iodine flow battery electrolyte according to claim 1, characterized in that: The acetate ions in the electrolyte are provided by added acetate, which is one or more of sodium acetate, potassium acetate, zinc acetate, magnesium acetate, and ammonium acetate.

5. The zinc-iodine flow battery electrolyte according to claim 1, characterized in that: The amine compound in the electrolyte is one or more of succinimide, sodium aminosulfonate, potassium aminosulfonate, 5,5-dimethylhydantoin, and thioamide.

6. The zinc-iodine flow battery electrolyte according to claim 1, characterized in that: The supporting electrolyte in the electrolyte is one or more of sodium sulfate, ammonium sulfate, sodium chloride, potassium chloride, sodium nitrate, and potassium nitrate.

7. The zinc-iodine flow battery electrolyte according to claim 1, characterized in that: The electrolyte is an aqueous solution; The concentration of iodized salt is 0.01-7 mol / L. -1 Preferably 0.4-4 mol L -1 ; The zinc salt concentration is 0.1-4 mol / L. -1 Preferably 1-2 mol L -1 ; The acetate concentration is 0.1-3 mol / L. -1 Preferably 0.5-3 mol L -1 ; The concentration of amine compounds is 0.5-6 mol / L. -1 Preferably 1-4 mol L -1 ; Supported electrolyte concentrations: 0.1-3 mol / L -1 Preferably 0.3-2 mol L -1 .

8. The application of the zinc-iodine flow battery electrolyte according to any one of claims 1-7 as an electrolyte in a zinc-iodine flow battery.

9. A zinc-iodine flow battery, characterized in that, The flow battery includes a positive electrode, a negative electrode, and a separator for separating the positive and negative electrodes. The positive electrode is placed in the positive electrode side cavity, and the negative electrode is placed in the negative electrode side cavity. The positive and negative electrode side cavities are respectively filled or flow through one or more electrolytes including any one of claims 1-7.

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