Low-temperature-resistant zinc-based flow battery electrolyte and application

Abstract

The invention discloses a zinc-based flow battery electrolyte and application thereof, and belongs to the technical field of electrochemical energy storage. The electrolyte is an aqueous solution containing a zinc salt and an additive, and the additive comprises a calcium salt and a magnesium salt; the additive also comprises one or more of lithium salt, sodium salt and strontium salt. Wherein Ca < 2 + > and Mg < 2 + > can strongly interact with water molecules, and a hydrogen bond network in the electrolyte is effectively weakened, so that the freezing point is remarkably reduced; and a small amount of other added metal cations generate a synergistic effect with Ca < 2 + > and Mg < 2 + >, so that the electrolyte still keeps excellent electrochemical properties such as high ionic conductivity and the like while obtaining an ultra-low freezing point. On the basis, the electrolyte successfully realizes stable circulation of the zinc-iodine flow battery in an extremely low-temperature environment. The electrolyte is low in cost, safe and environment-friendly, and a reliable technical scheme is provided for widening the application scene of the zinc-based flow battery to the extreme low-temperature field.

Description

Technical Field

[0001] This application relates to the field of electrochemical energy storage technology, specifically to a low-temperature resistant zinc-based flow battery electrolyte and its application. Background Technology

[0002] With the increasing scarcity of fossil fuels and the growing environmental problems associated with their use, the development and utilization of renewable energy sources such as solar and wind power are becoming increasingly important. However, the inherent intermittent and fluctuating nature of these renewable energy generation methods poses a challenge to the stable operation of the power grid when they are connected to the grid on a large scale, which has become a key obstacle restricting their efficient utilization and widespread development.

[0003] To address these challenges, energy storage technologies, particularly electrochemical energy storage technologies, are considered an effective means to enhance the grid's capacity to absorb renewable energy and ensure system stability and efficiency. Electrochemical energy storage technology is gradually becoming one of the key technologies supporting the clean energy transition and achieving a sustainable energy system. Among various electrochemical batteries suitable for large-scale stationary energy storage, redox flow batteries have attracted widespread attention due to their moderate cost, high modularity, independent design of capacity and power, and flexible operation control.

[0004] Aqueous zinc-based flow batteries are highly competitive in large-scale energy storage systems due to their significant advantages in high energy density and low cost. However, the performance of this battery system at low temperatures exhibits significant defects, severely restricting its practical application over a wide temperature range. Specifically, at low temperatures, aqueous electrolytes experience kinetic deterioration phenomena such as hindered ion migration, increased charge transfer impedance, and solvation structure imbalance. Simultaneously, the zinc anode is prone to uncontrolled dendrite growth and intensified interfacial side reactions, leading to metal corrosion passivation and rapid capacity decay. When the temperature approaches the electrolyte's freezing point, phase transition crystallization occurs within the system. This not only physically blocks ion transport channels but also causes electrode / electrolyte interface delamination due to volume expansion, ultimately resulting in battery failure. Under the combined effect of these factors, the capacity retention rate of traditional aqueous zinc-based flow batteries at low temperatures is generally less than 30% of the theoretical value, greatly limiting its industrialization process.

[0005] Currently, modification schemes for low-temperature zinc-based electrolytes mainly include constructing "salt-encapsulated" electrolytes using high-concentration salts, introducing organic solvents to form organic-water mixed electrolytes, or adding functional antifreeze agents. These methods aim to lower the electrolyte's freezing point and inhibit zinc dendrite growth, thereby maintaining efficient and stable zinc ion transport and reversible deposition at low temperatures. However, existing technologies still have the following drawbacks: high-concentration salt systems are costly and have high viscosity, and their ionic conductivity remains limited at low temperatures; organic components in organic-water mixed electrolytes are volatile and flammable, and may reduce ionic conductivity and the reversibility of zinc deposition; while antifreeze additives can lower the freezing point to some extent, their effect on inhibiting zinc dendrites and side reactions is limited, making it difficult to fundamentally improve the overall stability of the electrolyte at low temperatures. Furthermore, most of these strategies come at the cost of sacrificing the battery's energy density, power density, or cycle life.

[0006] Therefore, existing technologies still lack an aqueous zinc-based flow battery electrolyte solution that can simultaneously achieve anti-freezing properties, dendrite suppression, and interface stability at low temperatures without significantly increasing costs or sacrificing overall battery performance. This invention aims to develop a low-temperature resistant electrolyte system based on low-cost metal chloride additives, achieving excellent low-temperature antifreeze properties at low additive concentrations and effectively maintaining efficient and stable zinc ion transport and reversible deposition behavior in low-temperature environments. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-temperature resistant electrolyte suitable for zinc-based flow batteries. This electrolyte can effectively improve the electrochemical performance of zinc-based flow batteries in low-temperature environments and ensure their stable cycling.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A zinc-based flow battery electrolyte, wherein the electrolyte is an aqueous solution comprising zinc salt and additives, wherein the additives include calcium salt and magnesium salt; the additives further include one or more of lithium salt, sodium salt, and strontium salt.

[0009] Furthermore, the additives include: calcium salts, magnesium salts, lithium salts, sodium salts, and strontium salts.

[0010] Furthermore, the zinc salt is zinc chloride, the lithium salt is lithium chloride, the sodium salt is sodium chloride, the calcium salt is calcium chloride, the magnesium salt is magnesium chloride, and the strontium salt is strontium chloride.

[0011] Furthermore, the concentration of zinc chloride in the electrolyte is 0.15-0.9 mol / L.

[0012] Furthermore, in the electrolyte, the concentration of calcium chloride is 0.33-2.2 mol / L and the concentration of magnesium chloride is 0.4-2.11 mol / L.

[0013] Furthermore, in the electrolyte, the concentration of lithium chloride is 0.01-0.75 mol / L, the concentration of sodium chloride is 0.01-0.41 mol / L, and the concentration of strontium chloride is 0.01-0.15 mol / L.

[0014] Another object of the present invention is to provide the application of the above-mentioned electrolyte in zinc-based flow batteries.

[0015] Furthermore, the zinc-based flow battery is a zinc-iodine flow battery.

[0016] Furthermore, the zinc-based flow battery includes a carbon felt positive electrode, a Nafion membrane, and a carbon felt negative electrode.

[0017] Furthermore, the zinc-based flow battery operates at a temperature below -20°C.

[0018] The advantages of this invention over the prior art are as follows: (1) Excellent low-temperature performance: By using a specific ratio of lithium salt, sodium salt, calcium salt, magnesium salt, strontium salt and zinc salt to construct a multi-element aqueous high-entropy electrolyte system, the hydrogen bond network between water molecules is effectively destroyed, the freezing point of the electrolyte is greatly reduced, and it can still maintain a stable liquid state under ultra-low temperature conditions of -30 ℃ to -50 ℃, which significantly improves the low-temperature adaptability of the battery.

[0019] (2) High ionic conductivity: The multi-salt blended electrolyte system provides abundant charge carriers. Even at low temperatures, the electrolyte can still maintain high ionic conductivity, effectively reducing the battery internal resistance and charge / discharge polarization, and improving the battery's electrochemical performance at low temperatures.

[0020] (3) Environmentally friendly and cost-controllable: The electrolyte is composed of water and inorganic salts, which fundamentally avoids the environmental risks and high costs of organic solvents, making it safe and reliable. Zinc-iodine flow batteries based on this electrolyte can still stably perform charge-discharge cycles at extreme low temperatures of -30 ℃ to -50 ℃, demonstrating excellent low-temperature adaptability and cycle characteristics, providing an effective technical solution for energy storage applications in cold regions. Attached Figure Description

[0021] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below. For those skilled in the art, other related drawings can be obtained from the above drawings without any creative effort.

[0022] Figure 1 This is a diagram illustrating the coulombic efficiency test protocol for zinc-copper button batteries at -50 °C in this application. Figure 2This is a performance diagram of the zinc-based flow battery operating at room temperature in Example 1 of this application; Figure 3 This is a performance diagram of the zinc-based flow battery operating at room temperature in Example 2 of this application; Figure 4 This is a performance diagram of the zinc-based flow battery operating at room temperature in Example 3 of this application; Figure 5 This is a performance diagram of the zinc-based flow battery operating at room temperature in Example 4 of this application; Figure 6 This is a performance diagram of the zinc-based flow battery operating at room temperature in Comparative Example 4 of this application; Figure 7 This is a performance diagram of the zinc-based flow battery operating at room temperature in Comparative Example 5 of this application; Figure 8 This is a performance diagram of the zinc-based flow battery operating at room temperature in Comparative Example 1 of this application; Figure 9 This is a performance diagram of the zinc-based flow battery operating at -30 °C in Example 1 of this application; Figure 10 This is a performance diagram of the zinc-based flow battery operating at -30 °C in Example 2 of this application; Figure 11 This is a performance diagram of the zinc-based flow battery operating at -50 °C in Example 1 of this application; Figure 12 This is a performance diagram of the zinc-based flow battery operating at -50 °C in Example 2 of this application; Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. It should be particularly noted that the following embodiments are only for illustrating this application and do not limit the scope of this application. Similarly, the following embodiments are only some embodiments of this application and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0023] Unless otherwise specified, the experimental methods involved in the embodiments of this invention are all conventional methods; the materials, reagents, instruments, equipment, etc. used are all commercially available unless otherwise specified.

[0024] In the table, " / " indicates battery failure at -50 ℃.

[0025] This application provides a zinc-based flow battery electrolyte, which is an aqueous solution comprising zinc salt and additives. The additives include calcium salt and magnesium salt, and further include one or more of lithium salt, sodium salt, and strontium salt.

[0026] In this application, Zn 2+ As the energy carrier and reaction center of zinc-based flow batteries, it is crucial for realizing electrochemical energy storage; Ca 2+ Mg 2+ It can interact strongly with water molecules, effectively weakening the hydrogen bond network, thereby significantly lowering the freezing point of the electrolyte; while the trace amount of added Li + Na + and Sr 2+ Used to maintain interfacial reaction stability and cycle stability, and with Ca 2+ Mg 2+ This produces a synergistic effect, enabling the electrolyte to simultaneously possess both a low freezing point and high electrochemical performance.

[0027] In an optional embodiment, the zinc salt is zinc chloride, the lithium salt is lithium chloride, the sodium salt is sodium chloride, the calcium salt is calcium chloride, the magnesium salt is magnesium chloride, and the strontium salt is strontium chloride.

[0028] In this application embodiment, Cl is selected. - As an anion in the electrolyte, chloride salts are chosen based on their multiple beneficial effects: Firstly, Cl... - The chloride salts, possessing high charge density, are highly effective in disrupting the hydrogen bond network between water molecules and lowering the freezing point. Secondly, the chloride salts corresponding to the selected cations generally exhibit high solubility, greatly facilitating the design and precise control of electrolyte composition. Finally, the low cost of chloride raw materials is a crucial advantage that cannot be ignored for the commercial application of large-scale energy storage devices.

[0029] Furthermore, the concentrations of each component in the electrolyte are as follows: The concentration of zinc chloride is 0.15-0.9 mol / L, specifically 0.154 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8624 mol / L, and 0.9 mol / L.

[0030] The concentration of calcium chloride is 0.33-2.2 mol / L, preferably 1.9-2.2 mol / L; specific concentrations are 0.33 mol / L, 0.4 mol / L, 0.53 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8624 mol / L, 0.95 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.85 mol / L, 1.917 mol / L, and 2.183 mol / L.

[0031] The concentration of magnesium chloride is 0.4-2.11 mol / L, with a preferred concentration of 0.4-0.85 mol / L; specific concentrations are 0.4 mol / L, 0.516 mol / L, 0.6 mol / L, 0.7 mol / L, 0.853 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1797 mol / L, 1.2534 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.93 mol / L, 2.0 mol / L, and 2.11 mol / L.

[0032] The concentration of lithium chloride is 0.01-0.75 mol / L, preferably 0.01-0.2 mol / L; specific concentrations are 0.01 mol / L, 0.02 mol / L, 0.0315 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L, 0.126 mol / L, 0.13 mol / L, 0.14 mol / L, 0.1575 mol / L, 0.16 mol / L, 0.17 mol / L, 0.18 mol / L, 0.19 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, etc. mol / L, 0.4 mol / L, 0.45 mol / L, 0.5 mol / L, 0.5355 mol / L, 0.6 mol / L, 0.65 mol / L, 0.7 mol / L, 0.75 mol / L.

[0033] The concentration of sodium chloride is 0.01-0.41 mol / L, preferably 0.01-0.1 mol / L; specific concentrations are 0.01 mol / L, 0.0128 mol / L, 0.02 mol / L, 0.0385 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.1283 mol / L, 0.14 mol / L, 0.16 mol / L, 0.18 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, 0.35 mol / L, and 0.41 mol / L.

[0034] The concentration of strontium chloride is 0.01-0.35 mol / L, specifically 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L, 0.12 mol / L, 0.13 mol / L, 0.14 mol / L, 0.15 mol / L, 0.16 mol / L, 0.17 mol / L, 0.18 mol / L, 0.19 mol / L, 0.2 mol / L, 0.25 mol / L, 0.3 mol / L, and 0.35 mol / L.

[0035] This application also provides an application of the above-described electrolyte in a zinc-based flow battery.

[0036] Furthermore, the zinc-based flow battery is a zinc-iodine flow battery.

[0037] Furthermore, the zinc-based flow battery consists of a carbon felt positive electrode, a Nafion membrane, and a carbon felt negative electrode.

[0038] Furthermore, the zinc-based flow battery operates at a temperature below -20°C.

[0039] Example 1 A mixed electrolyte consisting of 0.4 mol / L zinc chloride, 0.853 mol / L magnesium chloride, 0.0315 mol / L lithium chloride, 1.917 mol / L calcium chloride, 0.07 mol / L strontium chloride, and 0.0385 mol / L sodium chloride was prepared and subjected to low-temperature freeze resistance tests. A zinc-copper asymmetric battery was assembled and subjected to low-temperature tests, and a zinc-iodine flow battery was assembled and tested.

[0040] Low-temperature antifreeze properties evaluation: After the electrolyte preparation is completed, it is placed in a -50 ℃ low-temperature incubator for 24 h and the results are observed.

[0041] To characterize the low-temperature resistance of the electrolyte prepared above, a zinc-copper asymmetric battery was used. The negative electrode material was zinc foil, the positive electrode material was copper foil, the separator was a glass fiber separator, and the current density was 0.5 mAh cm⁻¹. -2 Pre-deposition capacity 1 mAh cm⁻¹ -2 Cyclic capacity 0.5 mAh cm⁻¹ -2 The cutoff voltage is 0.4 V.

[0042] The battery is a flow battery with circulating electrolytes on both the positive and negative electrode sides. The negative electrode electrolyte is the low-temperature resistant electrolyte described in this invention, while the positive electrode electrolyte is the electrolyte of this invention with 1 M potassium iodide added as an active material. Both the positive and negative electrodes are made of 2 cm * 2 cm carbon felt, and the separator is a Nafion 212 membrane. The tested current density at -30 ℃ and -50 ℃ is 20 mA cm⁻². -2 The test current density at room temperature was 40 mA cm⁻¹ -2 .

[0043] Example 2 A mixed electrolyte of 0.4 mol / L zinc chloride, 0.516 mol / L magnesium chloride, 0.1575 mol / L lithium chloride, 2.183 mol / L calcium chloride, 0.11 mol / L strontium chloride and 0.01 mol / L sodium chloride was prepared and subjected to low-temperature antifreeze test. A zinc-copper asymmetric battery was assembled and subjected to low-temperature test. A zinc-iodine flow battery was assembled and tested.

[0044] The low-temperature performance test of the prepared electrolyte is the same as that of the electrolyte in Example 1, and will not be repeated here. The only difference is that the electrolyte prepared in Example 2 is used for the test.

[0045] Example 3 A mixed electrolyte consisting of 0.154 mol / L zinc chloride, 1.1797 mol / L magnesium chloride, 0.126 mol / L lithium chloride, 1.85 mol / L calcium chloride, 0.02 mol / L strontium chloride, and 0.1283 mol / L sodium chloride was prepared and subjected to low-temperature antifreeze tests. A zinc-copper asymmetric battery was assembled and subjected to low-temperature tests, and a zinc-iodine flow battery was assembled and subjected to room-temperature tests.

[0046] The low-temperature performance test of the prepared electrolyte is the same as that of the electrolyte in Example 1. The test of the zinc-iodine flow battery at room temperature is also the same as that of the electrolyte in Example 1, and will not be repeated here. The only difference is that the electrolyte prepared in Example 3 is used for the test.

[0047] Example 4 A mixed electrolyte of 0.8624 mol / L zinc chloride, 1.2534 mol / L magnesium chloride, 0.5355 mol / L lithium chloride, 0.95 mol / L calcium chloride, 0.35 mol / L strontium chloride and 0.0128 mol / L sodium chloride was prepared and subjected to low-temperature antifreeze test. A zinc-copper asymmetric battery was assembled and subjected to low-temperature test, and a zinc-iodine flow battery was assembled and subjected to room-temperature test.

[0048] The low-temperature performance test of the prepared electrolyte is the same as that of the electrolyte in Example 1. The test of the zinc-iodine flow battery at room temperature is also the same as that of the electrolyte in Example 1, and will not be repeated here. The only difference is that the electrolyte prepared in Example 4 is used for the test.

[0049] Example 5 A mixed electrolyte consisting of 0.4 mol / L zinc chloride, 1.93 mol / L magnesium chloride, 0.5 mol / L lithium chloride, 0.53 mol / L calcium chloride, and 0.06 mol / L strontium chloride was prepared and subjected to low-temperature freeze resistance testing. A zinc-copper asymmetric battery was then assembled and subjected to low-temperature testing.

[0050] The low-temperature antifreeze test of the prepared electrolyte and the low-temperature test of the zinc-copper asymmetric battery are the same as the relevant test procedures of the electrolyte in Example 1, and will not be repeated here. The only difference is that the electrolyte prepared in Example 5 is used for the test.

[0051] Comparative Example 1 A 0.4 mol / L zinc chloride electrolyte was prepared and subjected to a low-temperature freeze resistance test. The zinc-iodine flow cell was tested at room temperature.

[0052] The low-temperature freeze resistance test of the prepared electrolyte and the test of the zinc-iodine flow battery at room temperature are the same as the relevant test procedures of the electrolyte in Example 1, and will not be repeated here. The only difference is that the electrolyte prepared in Comparative Example 1 is used for the test.

[0053] Comparative Example 2 A mixed electrolyte of 0.4 mol / L zinc chloride and 3 mol / L calcium chloride was prepared and subjected to low-temperature freeze resistance test. A zinc-copper asymmetric battery was then assembled and subjected to low-temperature test.

[0054] The low-temperature antifreeze test of the prepared electrolyte and the low-temperature test of the zinc-copper asymmetric battery are the same as the relevant test procedures of the electrolyte in Example 1, and will not be repeated here. The only difference is that the electrolyte prepared in Comparative Example 2 is used for the test.

[0055] Comparative Example 3 A mixed electrolyte of 0.4 mol / L zinc chloride and 3 mol / L magnesium chloride was prepared and subjected to low-temperature freeze resistance test. A zinc-copper asymmetric cell was then assembled and subjected to low-temperature test.

[0056] The low-temperature antifreeze test of the prepared electrolyte and the low-temperature test of the zinc-copper asymmetric battery are the same as the relevant test procedures of the electrolyte in Example 1, and will not be repeated here. The only difference is that the electrolyte prepared in Comparative Example 3 is used for the test.

[0057] Comparative Example 4 A mixed electrolyte of 0.4 mol / L zinc chloride, 0.853 mol / L magnesium chloride, and 1.917 mol / L calcium chloride was prepared and subjected to low-temperature antifreeze tests. A zinc-copper asymmetric cell was assembled and subjected to low-temperature tests, and a zinc-iodine flow cell was assembled and subjected to room-temperature tests.

[0058] The low-temperature antifreeze test of the prepared electrolyte was conducted. The low-temperature test of the zinc-copper asymmetric battery was conducted in the same manner as the electrolyte in Example 1. The room-temperature test of the zinc-iodine flow battery was also conducted in the same manner as the electrolyte in Example 1. The details will not be repeated here. The only difference is that the electrolyte prepared in Comparative Example 4 was used for the test.

[0059] Comparative Example 5 A mixed electrolyte consisting of 0.4 mol / L zinc chloride, 0.516 mol / L magnesium chloride, and 2.183 mol / L calcium chloride was prepared. Low-temperature freeze resistance tests were conducted, a zinc-copper asymmetric cell was assembled for low-temperature testing, and a zinc-iodine flow cell was tested at room temperature.

[0060] The low-temperature antifreeze test of the prepared electrolyte was conducted. The low-temperature test of the zinc-copper asymmetric battery was conducted in the same manner as the relevant test of the electrolyte in Example 1. The room-temperature test of the zinc-iodine flow battery was also conducted in the same manner as the relevant test of the electrolyte in Example 1. The details will not be repeated here. The only difference is that the electrolyte prepared in Comparative Example 5 was used for the test.

[0061] Figure 1 This is the protocol diagram for the coulombic efficiency test of zinc-copper button batteries at -50 °C in this application. Figure 1 The procedure shown was used to measure the coulombic efficiency of the zinc-copper asymmetric batteries at -50 °C for Examples 1-5 and Comparative Examples 1-5. The electrolyte states of the electrolytes in the low-temperature antifreeze test and the coulombic efficiency of the zinc-copper button batteries at -50 °C are summarized in Table 1 below.

[0062] Table 1. Summary of electrolyte states and coulombic efficiency of zinc-copper button batteries at -50 °C in low-temperature freeze resistance test.

[0063] Analyzing the results in Table 1, in Comparative Example 1, the electrolyte contained only 0.4 mol / L zinc chloride and no other components. It solidified at -50 °C, indicating that zinc chloride alone does not possess low-temperature resistance. In Comparative Examples 2 and 3, the electrolytes remained liquid at -50 °C, indicating that Ca... 2+ With Mg 2+Both can effectively disrupt the hydrogen bonds between water molecules, significantly lower the freezing point, and endow the electrolyte with low-temperature antifreeze properties. Further comparison of electrochemical performance revealed that the coulombic efficiency of Comparative Example 2 was better than that of Comparative Example 3, indicating that the introduction of magnesium ions has an inhibitory effect on the improvement of coulombic efficiency, while the addition of calcium ions has a better effect on improving coulombic efficiency.

[0064] Further analysis of the results in Table 1 shows that, compared with Comparative Examples 4-5, Examples 1-2 of the present invention added at least one of lithium salt, strontium salt, or sodium salt in small amounts. The introduction of these additive ions improves battery performance through the following synergistic mechanisms: In the bulk electrolyte, they enrich the solvation structure of zinc ions, reduce the formation of ion clusters, thereby promoting ion mass transfer and achieving rapid ion transport, which is directly reflected in the improvement of coulombic efficiency; at the electrode interface, they can participate in adsorption and jointly construct a stable composite interface layer, effectively guiding zinc to achieve uniform deposition, thereby significantly improving the cycle stability of the battery.

[0065] Figure 8 The average coulombic efficiency of Comparative Example 1 under room temperature cycling conditions was 97%, and the average energy efficiency was 70%. Figure 2 and Figure 3 Examples 1 and 2 demonstrate an average coulombic efficiency of 99% and an average energy efficiency of over 85% during room temperature cycling, indicating significant improvements in battery reversibility and kinetics.

[0066] Figure 6 and Figure 7 The battery cycle performance of Comparative Examples 4 and 5 at room temperature is shown. Since both examples' electrolytes contain only different proportions of ZnCl2, MgCl2, and CaCl2, and lack Li, the cycling performance is different. + Na + and Sr 2+ Its coulombic efficiency and energy efficiency both show a relatively rapid decline. Figure 2 and Figure 3 A comparison of the results of Examples 1 and 2 shows that adding Li... + Na + and Sr 2+ It can significantly improve the stability of the electrolyte, thereby effectively enhancing the cycle performance of zinc-iodine flow batteries.

[0067] Figure 9 and Figure 10 The cycle performance of the batteries in Examples 1 and 2 at -30 °C is shown respectively, with an average coulombic efficiency of 99% and an average energy efficiency of nearly 80%.

[0068] Figure 11 and Figure 12The performance of Examples 1 and 2 at -50 °C shows that the average coulombic efficiency remains unchanged compared to -30 °C, while the energy efficiency only decreases slightly. The zinc-iodine flow batteries of Examples 1 and 2 can operate stably under low-temperature conditions, exhibiting high reversibility and superior electrodynamic characteristics.

[0069] This invention provides an electrolyte for zinc-based flow batteries. The electrolyte is an aqueous solution comprising zinc salts and additives, wherein the additives include calcium salts and magnesium salts; the additives further include one or more of lithium salts, sodium salts, and strontium salts. This electrolyte is obtained by introducing Ca... 2+ and Mg 2+ It interacts strongly with water molecules, effectively disrupting the hydrogen bond network and significantly lowering the freezing point; simultaneously, Li... + Na + 、Sr 2+ isocations and Ca 2+ Mg 2++ This produces a synergistic effect, achieving an ultra-low freezing point while maintaining excellent electrochemical properties such as high ionic conductivity. Cl is selected. - As an anion, its high charge density not only enhances the effects of breaking hydrogen bonds and lowering the freezing point, but the selected chloride salt also possesses high solubility, facilitating component ratio control, and has low raw material costs, making it suitable for large-scale energy storage applications. Experimental results show that this electrolyte can achieve stable long-cycle operation of zinc-iodine flow batteries under extreme low-temperature conditions. The electrolyte of this invention has advantages such as low cost, high safety, and environmental friendliness, providing a reliable technical solution for expanding the application of zinc-based flow batteries in low-temperature environments.

[0070] It should be noted that the low-temperature resistant zinc-based flow battery electrolyte of the present invention, in addition to the zinc-iodine flow battery mentioned in this patent, can also be applied to zinc-based batteries with other zinc as the negative electrode active material, and can serve as an extension of the low-temperature resistant zinc-based electrolyte in extremely cold environments.

[0071] The specific embodiments of the present invention have been described above. It should be understood that the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A zinc-based flow battery electrolyte, characterized in that, The electrolyte is an aqueous solution comprising a zinc salt and an additive, the additive comprising a calcium salt, a magnesium salt; The additive further comprises one or more of a lithium salt, a sodium salt, and a strontium salt.

2. The electrolyte according to claim 1, characterized in that, The additive comprises a calcium salt, a magnesium salt, a lithium salt, a sodium salt, and a strontium salt.

3. The electrolyte according to claim 2, characterized in that, The zinc salt is zinc chloride, the lithium salt is lithium chloride, the sodium salt is sodium chloride, the calcium salt is calcium chloride, the magnesium salt is magnesium chloride, and the strontium salt is strontium chloride.

4. The electrolyte according to claim 3, characterized in that, In the electrolyte, the concentration of zinc chloride is 0.15-0.9 mol / L.

5. The electrolyte of claim 3, wherein In the electrolyte, the concentration of calcium chloride is 0.33-2.2 mol / L, and the concentration of magnesium chloride is 0.4-2.11 mol / L.

6. The electrolyte of claim 3, wherein, In the electrolyte, the concentration of lithium chloride is 0.01-0.75 mol / L, the concentration of sodium chloride is 0.01-0.41 mol / L, and the concentration of strontium chloride is 0.01-0.15 mol / L.

7. Use of the electrolyte according to any one of claims 1-6 in a zinc-based flow battery.

8. Use according to claim 7, characterized in that, The zinc-based flow battery is a zinc-iodine flow battery.

9. Use according to claim 8, characterized in that, The zinc-based flow battery comprises a carbon felt positive electrode, a Nafion separator, and a carbon felt negative electrode.

10. Use according to claim 7, characterized in that, The working temperature of the zinc-based flow battery is lower than -20℃.

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