Aqueous zinc-iodine battery low-temperature electrolyte, preparation method and application thereof

Abstract

The application discloses a water-based zinc-iodine battery low-temperature electrolyte and a preparation method and application thereof, relates to the technical field of zinc-iodine batteries, and the water-based zinc-iodine battery low-temperature electrolyte is an aqueous solution containing an additive and a zinc salt; the molar concentration of the additive in the water-based zinc-iodine battery low-temperature electrolyte is 0.2M-0.8M; the additive is selected from at least one of guanidine salt and ammonium salt; the additive reduces the freezing point by destroying the hydrogen bond between water molecules in the electrolyte, and inhibits the iodine shuttle at the positive electrode interface and stabilizes I during the charging and discharging process + The intermediate. The working temperature range of the water-based zinc-iodine battery assembled by the water-based zinc-iodine battery low-temperature electrolyte is-60℃-25℃.

Description

Technical Field

[0001] This invention relates to the field of zinc-iodine battery technology, and more specifically, to an aqueous zinc-iodine battery low-temperature electrolyte, its preparation method, and its application. Background Technology

[0002] Aqueous zinc-iodine batteries (AZIBs) are promising candidates for large-scale energy storage due to their low cost, high safety, and environmental friendliness. Based on I... - / I 0 / I + Four-electron redox reactions of AZIBs provide up to 422 mAh g. -1 Its theoretical specific capacity far exceeds that of traditional two-electron reactions (211 mAh g). -1 This system demonstrates great potential for achieving high energy density and is suitable for renewable energy storage. However, its practical application, especially in extreme low-temperature environments such as polar regions, high altitudes, or the deep sea, faces severe challenges. Key issues include: firstly, aqueous electrolytes are prone to freezing at low temperatures, and ice crystal formation disrupts ion transport channels, leading to a sharp decrease in ionic conductivity and limiting the battery's operating temperature range; secondly, the highly reactive I4 in the four-electron reaction... + The intermediates are easily hydrolyzed, and the soluble polyiodides generated during charge and discharge lead to a shuttle effect. This not only reduces the utilization rate of active materials and coulombic efficiency, but also exacerbates zinc dendrite growth and negative electrode side reactions, resulting in a rapid degradation of cycle stability.

[0003] Therefore, it is necessary to develop a product that combines excellent antifreeze properties, effectively inhibits polyiodide shuttle, and stabilizes I. + The electrolyte of the intermediate is crucial for advancing the practical application of four-electron AZIBs, especially in widening the operating temperature range and enhancing low-temperature performance.

[0004] Existing electrolyte engineering strategies, such as introducing organic cosolvents (e.g., ethylene glycol) to dilute the water molecule network, designing ultra-high concentration "salt-in-water" electrolytes to reduce free water content, constructing hydrogel electrolytes to restrict water molecule migration, or adding specific functional salts (e.g., perchlorate, nitrate), whose anions act as hydrogen bond acceptors to competitively disrupt the water-water hydrogen bond network, significantly lowering the electrolyte's freezing point. These strategies primarily focus on the interaction between anions and water molecules. While effectively addressing the problem of low-temperature ion transport, current research often struggles to simultaneously optimize cathode interface chemistry, particularly how to accelerate the slow redox kinetics of iodine species and achieve I-240 in an aqueous environment. + Efficient stabilization of intermediates remains a key bottleneck. For example, despite being rich in Cl... - High-concentration halide electrolytes can stabilize I through the formation of I-Cl coordination. +However, high concentrations of free halide ions often cause severe pitting corrosion in the zinc anode, impairing battery cycle life. Therefore, it is crucial to develop novel electrolyte systems that synergistically enhance freeze resistance, optimize cathode reaction kinetics, and maintain anode-friendly properties. Summary of the Invention

[0005] The purpose of this invention is to overcome the aforementioned deficiencies in the existing technology and provide an aqueous zinc-iodine battery low-temperature electrolyte, its preparation method, and its application. By adding specific types and concentrations of additives to the aqueous electrolyte, a highly reversible four-electron conversion aqueous low-temperature zinc-iodine battery electrolyte is obtained. This allows for simultaneous control of the bulk electrolyte structure and interfacial chemistry, achieving high reversibility of the four-electron reaction and low-temperature adaptability. The core of this invention lies in the fact that the cations in the additives effectively disrupt the hydrogen bond network of water molecules through strong ion-dipole interactions, significantly reducing the electrolyte's freezing point. Simultaneously, at the positive electrode interface, the cations exhibit unique coordination chemistry capabilities, not only anchoring polyiodides through strong binding energies to suppress the shuttle effect but also synergistically forming stable complexes with anions to effectively stabilize highly reactive I-1+. + The intermediate activates a highly reversible four-electron Ig - / I 0 / I + The redox reaction enables the preparation of high-capacity, long-life four-electron conversion aqueous low-temperature zinc-iodine batteries, which have broad application prospects in the low-temperature electrolyte industry of zinc-iodine batteries.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A low-temperature electrolyte for an aqueous zinc-iodine battery is provided, wherein the aqueous zinc-iodine battery low-temperature electrolyte is an aqueous solution containing additives and zinc salts; the molar concentration of the additives in the aqueous zinc-iodine battery low-temperature electrolyte is 0.2M~0.8M; the additives are selected from at least one of guanidine salts and ammonium salts; the operating temperature range of the aqueous zinc-iodine battery assembled with the aqueous zinc-iodine battery low-temperature electrolyte is -60℃~25℃.

[0007] Optionally, the guanidine salt is selected from at least one of guanidine hydrochloride, guanidine nitrate, guanidine carbonate, guanidine acetate, methyl guanidine hydrochloride, dimethyl guanidine hydrochloride, and isopropyl guanidine hydrochloride.

[0008] Optionally, the ammonium salt is selected from at least one of ammonium chloride and ammonium bromide.

[0009] Optionally, the additive is preferably guanidine hydrochloride and / or ammonium chloride.

[0010] Optionally, the molar concentration of the additive in the aqueous zinc-iodine battery low-temperature electrolyte can be 0.2M, 0.3M, 0.4M, 0.5M, 0.6M, 0.7M, 0.8M, or any value within a range of any two values.

[0011] Optionally, the zinc salt is selected from at least one of zinc sulfate, zinc trifluoromethanesulfonate, zinc tetrafluoroborate, zinc acetate, zinc nitrate, zinc bis(trifluoromethanesulfonyl)imide, and zinc perchlorate.

[0012] Optionally, in the aqueous zinc-iodine battery low-temperature electrolyte, the molar concentration of the zinc salt is 0.5M~5M.

[0013] Optionally, in the aqueous zinc-iodine battery low-temperature electrolyte, the molar concentration of the zinc salt can be 0.5M, 1M, 2M, 2.3M, 2.5M, 2.8M, 3M, 4M, 5M, or any value within a range of any two values.

[0014] Optionally, in the aqueous zinc-iodine battery low-temperature electrolyte, the molar concentration of the zinc salt is 2M~3M; the molar concentration of the additive is 0.4M~0.6M; preferably, in the aqueous zinc-iodine battery low-temperature electrolyte, the molar concentration of the zinc salt is 2.5M~3M; the molar concentration of the additive is 0.4M~0.5M.

[0015] Optionally, the molar concentration ratio of the additive to the zinc salt is 1:6. More preferably, in the aqueous zinc-iodine battery low-temperature electrolyte, the molar concentration of the zinc salt is 3M; and the molar concentration of the additive is 0.5M. The preferred concentrations of zinc salt and additive in the electrolyte allow for better synergy, further improving the overall performance of the aqueous zinc-iodine battery low-temperature electrolyte, and also reducing zinc deposition overpotential and iodine cathode polarization.

[0016] The present invention also discloses a method for preparing the aqueous zinc-iodine battery low-temperature electrolyte as described above, comprising: mixing additives, zinc salts and water to obtain the aqueous zinc-iodine battery low-temperature electrolyte.

[0017] Optionally, the mixing temperature is 25°C.

[0018] This invention provides a simple electrolyte preparation method, avoiding complex processes such as high temperature and vacuum, thus reducing production costs. The preparation process spontaneously forms an electrode interface control layer, requiring no additional steps and making it well-suited for industrial mass production. The raw materials used in the above-described method for preparing low-temperature electrolytes for aqueous zinc-iodine batteries are all commercially available, and the equipment and processes used are well-known to those skilled in the art.

[0019] This invention also discloses a method for improving the low-temperature performance of aqueous zinc-iodine batteries, using the aqueous zinc-iodine battery low-temperature electrolyte as described above, or the aqueous zinc-iodine battery low-temperature electrolyte prepared by the method described above, as the aqueous zinc-iodine battery electrolyte; the additive lowers the freezing point by disrupting the hydrogen bonds between water molecules in the electrolyte, and during charging and discharging, inhibits polyiodide shuttle at the positive electrode interface and stabilizes I in the anions of the electrolyte.+ An intermediate to enable the aqueous zinc-iodine battery assembled from the aqueous zinc-iodine battery low-temperature electrolyte to operate in a temperature range of -60℃ to 25℃.

[0020] The present invention also discloses the application of the aqueous zinc-iodine battery low-temperature electrolyte as described above, or the aqueous zinc-iodine battery low-temperature electrolyte prepared by the preparation method described above, in a four-electron conversion aqueous low-temperature zinc-iodine battery, wherein the operating temperature range of the four-electron conversion aqueous low-temperature zinc-iodine battery is -60℃ to 25℃.

[0021] The present invention also discloses a four-electron reversible conversion aqueous low-temperature zinc-iodine battery, comprising the aqueous zinc-iodine battery low-temperature electrolyte as described above, or the aqueous zinc-iodine battery low-temperature electrolyte prepared by the preparation method described above; the operating temperature range of the aqueous low-temperature zinc-iodine battery is -60℃ to 25℃.

[0022] This invention can directionally regulate the deposition kinetics of zinc anode and iodine cathode, promoting uniform zinc ion deposition and suppressing side reactions during charging, and inhibiting polyiodide shuttle and I during discharging. + Hydrolysis enables reversible four-electron conversion, giving the battery better low-temperature performance and has broad application prospects in the zinc-iodine battery low-temperature electrolyte industry.

[0023] This invention introduces a specific multifunctional electrolyte additive. Its cations disrupt the inherent hydrogen bond network of water molecules in the bulk electrolyte through strong ion-dipole interactions, significantly lowering the electrolyte's freezing point and laying the foundation for low-temperature operation. Simultaneously, at the positive electrode interface, the cations exhibit unique coordination chemistry capabilities. On one hand, they effectively suppress the shuttle effect through strong coordination and anchoring with polyiodides; on the other hand, they synergistically construct a stable coordination network with anions, greatly stabilizing highly reactive I-. + Intermediate, inhibiting its hydrolysis side reactions, significantly enhancing I - / I 0 / I + The kinetics and reversibility of four-electron redox reactions are explored. The type and content of additives are crucial to the battery's cycle performance. The specific additives used in this invention promote uniform zinc ion deposition, suppress side reactions, and achieve highly reversible four-electron conversion, enabling stable cycling of Zn-I2 pouch batteries under low-temperature conditions. This invention shows broad application prospects in the low-temperature electrolyte industry for zinc-iodine batteries.

[0024] Implementing the embodiments of the present invention will have the following beneficial effects: This invention introduces specific types and concentrations of additives into zinc-iodine batteries to synergistically regulate the kinetics of zinc anode deposition and iodine cathode reaction at low temperatures. As typical strongly ionizing cations, the dispersed positive charge distribution of guanidino and / or ammonium cations, along with the -NH2 group which can act as hydrogen bond acceptors, can coordinate with the negative dipole end of water molecules through strong ion-dipole interactions. This competitively seizes the binding sites originally used to build water-water hydrogen bonds, systematically disrupting the original tetrahedral hydrogen bond network of water molecules, thereby lowering the freezing point. Simultaneously, it alters the original solvation structure, promoting zinc ion migration and thus uniform deposition. Furthermore, the strong coordination of guanidino and / or ammonium cations immobilizes polyiodides, suppressing the shuttle effect, while simultaneously forming stable complexes with anions to anchor highly reactive I-. + This species thus accelerates the four-electron reaction kinetics, achieving four-electron I under low-temperature conditions. - / I 0 / I + Improved redox reversibility. The method of this invention is low-cost, simple to operate, and ensures the safety of the pharmaceutical ingredients.

[0025] This invention achieves rapid and reversible four-electron conversion at low temperatures. Tests show that the full cell has a discharge specific capacity of 220~280 mAh g⁻¹ at -60℃. -1 The results show that the zinc-iodine soft-pack battery maintains a discharge specific capacity of 50 mAh to 100 mAh at -60℃, with a capacity retention of 33% to 50% at room temperature. Simultaneously, the zinc-iodine four-electron soft-pack battery can cycle 1100 times at -40℃ with a coulombic efficiency as high as 99.8%. This indicates that the additives suppress polyiodide shuttle and self-discharge at low temperatures, achieving four-electron I... - / I 0 / I + Improved redox reversibility. This electrolyte preparation process is simple and low-cost, utilizing anion-stabilized I₂. + It also inhibits hydrolysis, and the cations break the hydrogen bonds of water molecules, thus providing a green and safe solution for low-temperature, high-specific-energy water system energy storage. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 The graph shows the number of cycles of Zn / / I2 versus the discharge specific capacity of Example 1 and Comparative Example 1 at different temperatures.

[0028] Figure 2 This is a comparison chart of the CV curves of Embodiment 1 and Comparative Example 1 of the present invention.

[0029] Figure 3 This is a graph showing the number of Zn / / I2 cycles versus discharge specific capacity at different temperatures for Embodiment 2 and Comparative Example 2 of the present invention.

[0030] Figure 4 This is a comparison chart of the Tafel slopes of Embodiment 2 and Comparative Example 2 of the present invention.

[0031] Figure 5 This is a graph showing the cycle number and discharge capacity of a Zn / / I2 soft-pack battery at different temperatures according to Embodiment 1 of the present invention.

[0032] Figure 6 This is a graph showing the cycle number and discharge capacity of a Zn / / I2 soft-pack battery at -40℃ in Embodiment 2 of the present invention.

[0033] Figure 7 This is the two-dimensional LF-NMR T1-T2 relaxation spectrum of Example 2 of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0035] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this invention.

[0036] Unless otherwise specified, the techniques or conditions described in the embodiments of this invention shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Devices, instruments, reagents, etc., without specified manufacturers, are all conventional products that can be purchased through legitimate channels. All experimental reagents and raw materials involved are commercially available products, and all reagents are analytical grade products.

[0037] Example 1 The low-temperature electrolyte for the aqueous zinc-iodine battery in this embodiment is an aqueous solution containing ammonium chloride with a molar concentration of 0.5M and zinc perchlorate with a molar concentration of 3M.

[0038] The method for preparing the aqueous zinc-iodine battery low-temperature electrolyte in this embodiment includes: mixing ammonium chloride, zinc perchlorate and water to obtain the aqueous zinc-iodine battery low-temperature electrolyte (ZnClO4 / NH4Cl).

[0039] Comparative Example 1 The only difference between this comparative example and Example 1 is that ammonium chloride is not added. The electrolyte in this comparative example is an aqueous solution containing zinc perchlorate at a molar concentration of 3M (ZnClO4 / H2O).

[0040] Example 2 The low-temperature electrolyte for the aqueous zinc-iodine battery in this embodiment is an aqueous solution containing guanidine hydrochloride with a molar concentration of 0.5M and zinc perchlorate with a molar concentration of 3M.

[0041] The aqueous zinc-iodine battery low-temperature electrolyte (ZnClO4 / GuHCl) of this embodiment was prepared according to the preparation method of Example 1.

[0042] Comparative Example 2 The only difference between this comparative example and Example 2 is that the electrolyte in this comparative example is an aqueous solution (ZnClO4 / NaCl) containing sodium chloride with a molar concentration of 0.5M and zinc perchlorate with a molar concentration of 3M.

[0043] Test case The electrolytes from Example 1 and Comparative Example 1 were assembled into full cells, and their cycle performance was tested at different temperatures (25°C, -20°C, -40°C, -60°C) with a current density of 1 C. The cycle number-discharge specific capacity curves are shown below. Figure 1 As shown, Example 1 has a discharge specific capacity of 350 mAh g at room temperature. -1 This is significantly higher than that of Comparative Example 1, and the discharge specific capacity is 300 mAh g at -20 ℃, -40 ℃, and -60 ℃. -1 250 mAh g -1 220 mAh g -1 . Figure 2 The CV curves of Example 1 and Comparative Example 1 are shown in the comparison graph. It can be seen that Example 1 exhibits a clear dual redox characteristic, with a significant I at 1.2 / 1.4 V. - / I 0 The conversion, and the significantly enhanced I0 / I at 1.6 / 1.8 V. + Transformation. It can be inferred that ammonium chloride can suppress side reactions and increase the four-electron I at low temperatures. / I0 / I + Redox reversibility releases more capacity, significantly improving the battery's low-temperature performance.

[0044] The electrolytes from Example 2 and Comparative Example 2 were assembled into full cells, and their cycle performance was tested at different temperatures (25°C, -20°C, -40°C, -60°C) with a current density of 1 C. The cycle number-discharge specific capacity curves are shown below. Figure 3 As shown, Example 2 has a discharge specific capacity of 400 mAh g at room temperature. -1 This is significantly higher than that of Comparative Example 2, and the discharge specific capacity is 350 mAh g at -20℃, -40℃, and -60℃. -1 300 mAh g -1 280 mAh g -1 . Figure 4 This is a comparison of the Tafel slopes of Example 2 and Comparative Example 2. Example 2 maintains a relatively low η value even at -60 °C, indicating that the introduction of guanidine hydrochloride effectively promotes and maintains I0 / I under low-temperature conditions. + Redox kinetics.

[0045] Example 1 was configured with a positive electrode loading of 4 mg / cm³. 2 A pouch cell battery measuring 8 cm × 8 cm was subjected to cycle performance tests at different temperatures. Its cycle count-discharge capacity curve is shown below. Figure 5 As shown, in Example 1, the discharge capacity is approximately 150 mAh at 2C and 25°C. As the temperature gradually decreases to -60°C, the pouch cell still maintains a discharge capacity of 50 mAh, with a room temperature capacity retention rate of 33%.

[0046] Example 2 was configured with a positive electrode loading of 4 mg / cm³. 2 A soft-pack battery with a size of 8 cm × 8 cm. For example... Figure 6 As shown, it operates stably for 1100 cycles at -40℃ with an average coulombic efficiency of 99.8% and maintains a discharge capacity of 150 mAh.

[0047] Two-dimensional low-field nuclear magnetic resonance (LF-NMR) spectra from Example 2 were used to probe the relaxation dynamics and mobility of water molecules in the electrolyte. Figure 7 As shown, the proportion of fixed and bound water in the H2O / GuHCl electrolyte significantly increased after incorporation of GuHCl. Simultaneously, the T2 distribution shifted towards shorter relaxation times, indicating accelerated spin-spin relaxation and reduced molecular mobility. This enhanced interaction between GuHCl and water molecules restricts the dynamic rearrangement of water, thereby effectively lowering the electrolyte's freezing point.

[0048] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A water-based zinc-iodine battery low-temperature electrolyte, characterized in that, The aqueous zinc-iodine battery low-temperature electrolyte is an aqueous solution containing additives and zinc salts; The molar concentration of the additive in the low-temperature electrolyte of the aqueous zinc-iodine battery is 0.2M~0.8M; The additive is selected from at least one of guanidine salts and ammonium salts; The operating temperature range of the aqueous zinc-iodine battery assembled with the aqueous zinc-iodine battery low-temperature electrolyte is -60℃ to 25℃.

2. The aqueous zinc-iodine battery low-temperature electrolyte according to claim 1, characterized in that, The zinc salt is selected from at least one of zinc sulfate, zinc trifluoromethanesulfonate, zinc tetrafluoroborate, zinc acetate, zinc nitrate, zinc bis(trifluoromethanesulfonyl)imide, and zinc perchlorate; The guanidine salt is selected from at least one of guanidine hydrochloride, guanidine nitrate, guanidine carbonate, guanidine acetate, methyl guanidine hydrochloride, dimethyl guanidine hydrochloride, and isopropyl guanidine hydrochloride; The ammonium salt is selected from at least one of ammonium chloride and ammonium bromide.

3. The aqueous zinc-iodine battery low-temperature electrolyte according to claim 1, characterized in that, In the aqueous zinc-iodine battery low-temperature electrolyte, the molar concentration of the zinc salt is 0.5M~5M.

4. The aqueous zinc-iodine battery low-temperature electrolyte according to claim 1, characterized in that, In the aqueous zinc-iodine battery low-temperature electrolyte, the molar concentration of the zinc salt is 2M~3M; the molar concentration of the additive is 0.4M~0.6M.

5. The aqueous zinc-iodine battery low-temperature electrolyte according to claim 1, characterized in that, The molar ratio of the additive to the zinc salt is 1:

6.

6. A method for preparing a low-temperature electrolyte for an aqueous zinc-iodine battery as described in any one of claims 1-5, characterized in that, include: The additives, zinc salts, and water are mixed to obtain the aqueous zinc-iodine battery low-temperature electrolyte.

7. A method for improving the low-temperature performance of aqueous zinc-iodine batteries, characterized in that, The aqueous zinc-iodine battery low-temperature electrolyte as described in any one of claims 1-5, or the aqueous zinc-iodine battery low-temperature electrolyte prepared by the preparation method as described in claim 6, is used as the aqueous zinc-iodine battery electrolyte. The additive lowers the freezing point by disrupting the hydrogen bonds between water molecules in the electrolyte, and during charging and discharging, it inhibits polyiodide shuttle at the positive electrode interface and stabilizes I in the anions of the electrolyte. + An intermediate to enable the aqueous zinc-iodine battery assembled from the aqueous zinc-iodine battery low-temperature electrolyte to operate in a temperature range of -60℃ to 25℃.

8. The application of an aqueous zinc-iodine battery low-temperature electrolyte as described in any one of claims 1-5, or an aqueous zinc-iodine battery low-temperature electrolyte prepared by the preparation method as described in claim 6, in a four-electron conversion aqueous low-temperature zinc-iodine battery, characterized in that, The operating temperature range of the four-electron conversion aqueous low-temperature zinc-iodine battery is -60℃ to 25℃.

9. A four-electron reversible conversion aqueous low-temperature zinc-iodine battery, characterized in that, Includes the aqueous zinc-iodine battery low-temperature electrolyte as described in any one of claims 1-5, or the aqueous zinc-iodine battery low-temperature electrolyte prepared by the preparation method described in claim 6; The operating temperature range of the aqueous low-temperature zinc-iodine battery is -60℃ to 25℃.

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