Aqueous zinc-iodine batteries based on four-electron conversion reactions, their electrolytes, and positive electrodes.

Abstract

This invention provides an aqueous zinc-iodine battery based on a four-electron conversion reaction, along with its electrolyte and positive electrode. The zinc-iodine battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte. The electrolyte used in this invention is prepared by adding an iodine source to a Zn(OTF)₂ electrolyte and then sonicating it at room temperature. The OTF is SO₃CF₃. The positive electrode is prepared from an indium-based metal-organic framework In(dobpdc), where dobpdc is 4,4'-dihydroxy-3,3'-biphenyl dicarboxylic acid. During operation, the zinc-iodine battery electrolyte excites four electrons (I₂, I₃, I₂, I₃, I₃, I₄) to form an iodine source. ‑ / I2 / I + The conversion reaction involves the positive electrode material reacting with I through redox active carbonyl and hydroxyl groups. + Coordination reactions occur and Zn is involved through the In metal center. 2+ An alloying reaction occurs to provide additional capacity. The zinc-iodine battery constructed in this invention achieves I0 through the synergistic effect of the electrolyte and electrode. + The activation, stabilization, and reversibility of cations enable them to possess ultra-high specific capacity and high energy density.

Description

Technical Field

[0001] This invention belongs to the field of energy storage device technology, specifically relating to an aqueous zinc-iodine battery based on a four-electron conversion reaction, its electrolyte, and its positive electrode. Background Technology

[0002] Driven by the national strategic goal of "peak carbon and carbon neutrality," there is an urgent need to develop sustainable and efficient energy storage technologies and devices to meet human needs. Developing safe, high-energy-density aqueous batteries is currently one of the research hotspots in the field of energy storage devices. Among various aqueous batteries, rechargeable zinc-iodine batteries have the advantages of multiple electron transfers and abundant valence states, showing broad prospects for large-scale energy storage. However, traditional zinc-iodine batteries rely solely on I0... − The I₂ (0.54 V vs. standard hydrogen electrode, SHE) single-electron conversion reaction results in an output voltage plateau below 1.2 V, with a theoretical capacity of only 211 mAh g⁻¹. −1 This does not truly leverage the high energy density advantage of zinc-iodine batteries. Furthermore, the iodine conversion reaction is accompanied by polyiodide ions (I3). − and I5 − The formation of polyiodine ions (such as those in zinc-iodine batteries) allows these polyiodine ions to easily cross the membrane and react with the zinc anode, resulting in a "shuttle effect" and thus low coulombic efficiency. Therefore, developing multivalent iodine conversion reactions with higher reaction potentials is key to achieving high specific energy in zinc-iodine batteries.

[0003] Researchers have recently successfully activated high-potential I2 / I2 / I2 batteries in their research on metal-iodine batteries. + The conversion reaction (redox potential of 0.99 V vs. SHE) is based on I₂ / I₂. + The additional electron transport mechanism of the conversion can double the theoretical capacity of zinc-iodine batteries, and the increased operating voltage further elevates the maximum energy density to ultra-high levels. However, I + Cations in aqueous electrolytes generally face the problem of being difficult to stabilize and reversibly convert, typically leading to low cycle life and coulombic efficiency. To date, in aqueous zinc-iodine battery systems, only the ZnCl2 electrolyte modulation method has been able to achieve Io... − / I2 / I + The activation and transformation. For example, the invention entitled "An Aqueous Zinc-Iodine Battery Based on a Four-Electron Conversion Reaction and Its Electrolyte" (Chinese Invention Patent, Application No. 202010392522.6) proposes a solvation structure regulation method based on the ZnCl2 electrolyte system, which activates the I2 / I ... + The reversible reaction resulted in a novel zinc-iodine battery exhibiting a significant capacity improvement (594 mAh g⁻¹). −1vs. 211 mAh g −1 ) and high energy density (750 Whkg) −1 In 2022, Professor Zhi Chunyi's research group reported a method to regulate the Cl content in commercial electrolytes. − Ion content activation-stabilization I − / I2 / I + Transformation reaction methods, studies have shown that besides Cl − For high potential I2 / I + The activation effect of the conversion reaction is achieved by the special nanostructure of the Ti3C2I2 electrode, which confines active iodine within the MXene layers, effectively suppressing the polyiodine shuttle effect and enabling reversible multivalent transitions in iodine-ion conversion batteries (Two-Electron Redox Chemistry Enabled High-Performance Iodide Ion Conversion Battery, Angew. Chem. Int. Ed. 2022, 61,e202113576). In addition, regarding I... + Feasible activation schemes are rarely reported, which greatly limits the development of zinc-iodine batteries. Therefore, in order to fully utilize the capacity and energy density advantages of zinc-iodine batteries, activation-stabilization I... − / I2 / I + Efficient methods for transformation reactions urgently need to be developed. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and aims to provide an aqueous zinc-iodine battery based on a four-electron conversion reaction, as well as its electrolyte and positive electrode.

[0005] This invention provides a zinc-iodine battery electrolyte for an aqueous zinc-iodine battery based on a four-electron conversion reaction, characterized by the following: the zinc-iodine battery electrolyte is prepared by adding an iodine source to a Zn(OTF)2 electrolyte and then sonicating it at room temperature, wherein the OTF is SO3CF3, and the iodine source is one or more of 2-iodoterephthalic acid, 1-methyl-3-propylimidazolium iodide, tris(4-iodophenyl)amine, 1,2-diiodobenzene, and (iodomethyl)triphenylphosphonium iodide.

[0006] The zinc-iodine battery electrolyte of the aqueous zinc-iodine battery based on the four-electron conversion reaction provided by the present invention may also have the following characteristic: wherein the ultrasonic duration during ultrasonication is 0.5h.

[0007] The zinc-iodine battery electrolyte of the aqueous zinc-iodine battery based on the four-electron conversion reaction provided by the present invention may also have the following characteristics: wherein the total molar concentration of zinc ions and iodine ions in the zinc-iodine battery electrolyte is 4M~9M, and the molar ratio of zinc ions to iodine ions is 1M~3M:3M~6M.

[0008] This invention also provides a positive electrode material for an aqueous zinc-iodine battery based on a four-electron conversion reaction, characterized in that the positive electrode material is an indium-based metal-organic framework In(dobpdc), wherein dobpdc is 4,4'-dihydroxy-3,3'-biphenyl dicarboxylic acid.

[0009] The preparation method of indium-based metal-organic framework In(dobpdc) is as follows: NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, InSO4 and deionized water are weighed in sequence according to the mass ratio of 1:1.2~5:10~20:10~3. First, NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, InSO4 and deionized water are mixed evenly and transferred to a high-pressure reactor. The reactor is placed in an oven at 80℃~160℃ and reacted for 12h~24h. After filtration and washing with ethanol, the reactor is dried under vacuum at 80℃ for 12h to obtain indium-based metal-organic framework In(dobpdc).

[0010] This invention also provides a zinc-iodine battery positive electrode for an aqueous zinc-iodine battery based on a four-electron conversion reaction, characterized in that the zinc-iodine battery positive electrode is prepared from the above-mentioned positive electrode material, and the preparation method of the zinc-iodine battery positive electrode is as follows:

[0011] Weigh out the positive electrode material, carbon black and polytetrafluoroethylene, add N-methylpyrrolidone and grind evenly to obtain a slurry. Then coat the slurry evenly on the titanium foil current collector and dry it to obtain the positive electrode of the zinc-iodine battery.

[0012] This invention also provides an aqueous zinc-iodine battery based on a four-electron conversion reaction, characterized by comprising: a positive electrode, a negative electrode, a separator, and an electrolyte.

[0013] The electrolyte is the zinc-iodine battery electrolyte described above, and the positive electrode is the positive electrode of the zinc-iodine battery. During operation, the zinc-iodine battery electrolyte excites four electrons (I). − / I2 / I + The conversion reaction involves the positive electrode material reacting with I through redox active carbonyl and hydroxyl groups. + Coordination reactions occur and Zn is involved through the In metal center. 2+ An alloying reaction occurs.

[0014] The role and effect of invention

[0015] According to the present invention, an aqueous zinc-iodine battery based on a four-electron conversion reaction, its electrolyte, and positive electrode are disclosed. Firstly, the present invention activates the four-electron I-SO3CF3 by adding an organic iodine source to the Zn(OTF)2 electrolyte to form an interhalogen compound I-SO3CF3. − / I2 / I + The present invention provides a Zn conversion reaction. 2+ I − A novel electrolyte system with joint regulation is developed, which selects a special iodine source to replace traditional elemental iodine, and combines it with I₂ generated at high potential through halogen bonding. + The formation of sulfonate iodine compounds can stably excite four-electron I − / I2 / I + Transformation reaction.

[0016] Furthermore, in order to achieve I in this invention + The reversible transformation involves using indium-based metal-organic frameworks (In(dobpdc)) as the cathode material. In(dobpdc) can interact with I through redox active carbonyl and carboxyl groups. + A coordination reaction occurs, subsequently utilizing the In metal center with Zn. 2+ Alloying occurs to provide additional capacity. Therefore, thanks to the novel coordination and alloying reaction mechanisms of this invention, the device can be endowed with ultra-high specific capacity and high energy density. This allows the aqueous zinc-iodine battery assembled according to this invention to overcome the bottlenecks of existing energy storage mechanisms. The discharge capacity of the zinc-iodine battery assembled according to this invention can reach 962 mAh g⁻¹. −1 Furthermore, the energy density of zinc-iodine batteries can reach 1131 Wh / kg. −1 .

[0017] In addition, the main raw materials used in this invention are widely available, inexpensive and environmentally friendly. The entire electrolyte preparation process is carried out at room temperature and pressure, and is simple to operate, safe and pollution-free. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the working mechanism of the zinc-iodine battery of the present invention;

[0019] Figure 2 This is a scanning electron microscope image of the positive electrode material prepared in Embodiment 1 of the present invention;

[0020] Figure 3 This is a scanning electron microscope image of the positive electrode material prepared in Example 2 of the present invention;

[0021] Figure 4 This is an electrochemical performance diagram of the zinc-iodine battery assembled in Example 3 of the present invention using MPII-Zn(OTF)2 as the electrolyte;

[0022] Figure 5 This is an electrochemical performance diagram of the zinc-iodine battery assembled in Comparative Example 1 of the present invention using Zn(OTF)2 as the electrolyte;

[0023] Figure 6 This is an electrochemical performance diagram of the zinc-iodine battery assembled in Comparative Example 1 of the present invention using I2-Zn(OTF)2 as the electrolyte;

[0024] Figure 7 This is an electrochemical performance diagram of the zinc-iodine battery assembled using KI-Zn(OTF)2 as the electrolyte in Comparative Example 1 of the present invention. Detailed Implementation

[0025] The present invention provides an aqueous zinc-iodine battery based on a four-electron conversion reaction, comprising: a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is a zinc-iodine battery electrolyte of an aqueous zinc-iodine battery based on a four-electron conversion reaction, and the positive electrode is the positive electrode of an aqueous zinc-iodine battery based on a four-electron conversion reaction.

[0026] The zinc-iodine battery electrolyte of the present invention is prepared by adding an iodine source to a Zn(OTF)2 electrolyte and then sonicating it at room temperature. The OTF is SO3CF3.

[0027] The iodine source is one or more of 2-iodoterephthalic acid, 1-methyl-3-propylimidazolium iodide (MPII), tris(4-iodophenyl)amine, 1,2-diiodobenzene, and (iodomethyl)triphenylphosphonium iodide, and the ultrasound duration is 0.5 h.

[0028] The total molar concentration of zinc ions and iodine ions in the electrolyte of zinc-iodine batteries is 4M~9M, and the molar ratio of zinc ions to iodine ions is 1M~3M:3M~6M.

[0029] This invention involves adding an iodine source to Zn(SO3CF3)2 (OTF) − =CF3SO3 − In the electrolyte, an interhalogen compound I-OTF is formed, activating four-electron I... − / I2 / I + Transformation reaction.

[0030] The zinc-iodine battery positive electrode of the present invention is prepared from the positive electrode material In(dobpdc), and the preparation method of the zinc-iodine battery positive electrode is as follows:

[0031] Weigh out the positive electrode material, carbon black, and polytetrafluoroethylene, add N-methylpyrrolidone, and grind uniformly to obtain a slurry. Then, uniformly coat the slurry onto a titanium foil current collector and dry it to obtain the positive electrode of a zinc-iodine battery. The positive electrode material is an indium-based metal-organic framework In(dobpdc), where dobpdc is 4,4'-dihydroxy-3,3'-biphenyl dicarboxylic acid.

[0032] The preparation method of indium-based metal-organic framework In(dobpdc) is as follows: NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, InSO4 and deionized water are weighed in sequence according to the mass ratio of 1:1.2~5:10~20:10~3. First, NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, InSO4 and deionized water are mixed evenly and transferred to a high-pressure reactor. The reactor is placed in an oven at 80℃~160℃ and reacted for 12h~24h. After filtration and washing with ethanol, the reactor is dried under vacuum at 80℃ for 12h to obtain indium-based metal-organic framework In(dobpdc).

[0033] In this invention, the cathode material In(dobpdc) is further reacted with I through redox active carbonyl and hydroxyl groups. + A coordination reaction occurs, subsequently utilizing the In metal center with Zn. 2+ Alloying occurs to provide additional capacity, giving the device ultra-high specific capacity and high energy density.

[0034] Figure 1 This is a schematic diagram of the working mechanism of the zinc-iodine battery of the present invention.

[0035] like Figure 1 As shown, this invention proposes an OTF. − Initiation of Electrolyte-Electrode Activation-Stabilization Synergistic I − / I2 / I + The four-electron switching mechanism. Ig absorbed from the electrolyte. − First, it is oxidized to I. 0 Then generate I(OTF), I − / I2 / I + The pathway is activated. In the subsequent electrochemical reaction, two reversible chemical reactions occur sequentially in In(dobpdc): I + Coordination with the carbonyl / hydroxyl groups of organic ligands and Zn 2+ Alloying with In centers. The entire conversion reaction can be represented as:

[0036] 2I – -2 e – → I2

[0037] I2 + 2OTF − → I(OTF) + 2 e–

[0038] In2L + 4I + +4 e – ↔ 2In + I⁴L (L = dobpdc 4– )

[0039] In + xZn 2+ + 2x e – ↔ Zn 2x In (0 ≤ x ≤ 4)

[0040] To make the technical means, creative features, objectives and effects of the present invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate an aqueous zinc-iodine battery based on a four-electron conversion reaction, its electrolyte and positive electrode.

[0041] <Example 1>

[0042] In this embodiment, the cathode material is an indium-based metal-organic framework In(dobpdc), where dobpdc is 4,4'-dihydroxy-3,3'-biphenyl dicarboxylic acid. The preparation method of the indium-based metal-organic framework In(dobpdc) in this embodiment is as follows:

[0043] NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, and InSO4 were weighed in sequence at a mass ratio of 1:3.21:20 and dissolved in 20 mL of deionized water. NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, InSO4, and deionized water were mixed evenly and transferred to a high-pressure reactor. The reactor was placed in an oven at 120 °C and reacted for 12 h. After filtration and washing with ethanol, the mixture was dried under vacuum at 80 °C for 12 h to obtain the indium-based metal-organic framework In(dobpdc).

[0044] Figure 2 This is a scanning electron microscope image of the indium-based metal-organic framework In(dobpdc) prepared in Example 1 of the present invention.

[0045] like Figure 2 As shown, the indium-based metal-organic framework In(dobpdc) prepared in this embodiment...

[0046] Scanning electron microscope (SEM) images show that the material is composed of nanoflower-like sheets.

[0047] <Example 2>

[0048] In this embodiment, the cathode material is an indium-based metal-organic framework In(dobpdc), where dobpdc is 4,4'-dihydroxy-3,3'-biphenyl dicarboxylic acid. The preparation method of the indium-based metal-organic framework In(dobpdc) in this embodiment is as follows:

[0049] NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, and InSO4 were weighed in sequence according to a mass ratio of 1:2.28:17 and dissolved in 20 mL of deionized water. NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, InSO4, and deionized water were mixed evenly and transferred to a high-pressure reactor. The reactor was placed in an oven at 160 °C and reacted for 24 h. After filtration and washing with ethanol, the reactor was dried under vacuum at 80 °C for 12 h to obtain the indium-based metal-organic framework In(dobpdc).

[0050] Figure 3 This is a scanning electron microscope image of the positive electrode material prepared in Example 2 of the present invention.

[0051] like Figure 3 As shown, the indium-based metal-organic framework In(dobpdc) prepared in Example 2

[0052] It is a uniform, smooth, porous, polyhedral nanomaterial with a diameter of approximately 10 μm.

[0053] <Example 3>

[0054] In this embodiment, the zinc-iodine battery is first assembled, which includes a positive electrode, a negative electrode, a separator, and an electrolyte.

[0055] In this embodiment, MPII-Zn(OTF)2 was prepared using 1-methyl-3-propylimidazolium iodide (MPII) as the iodine source and used as the electrolyte for assembly.

[0056] The positive electrode used for assembly was prepared using the positive electrode material prepared in Example 1. The preparation process of the positive electrode is as follows: Indium-based metal-organic framework In (dobpdc), carbon black and polytetrafluoroethylene obtained in Example 1 were weighed in a mass ratio of 7:2:1. N-methylpyrrolidine was added to the mortar and the mixture was ground evenly for 30 min. Then, the slurry was evenly coated onto a titanium foil current collector with a diameter of about 1.2 cm using a blade. The slurry was then placed in an 80 ℃ vacuum oven and dried for 12 h to obtain the electrode sheet to be assembled.

[0057] A CR2032 type button cell battery casing was selected, with the prepared electrode sheet as the positive electrode and a zinc sheet (purity ≥99.00%) as the negative electrode. A GE-Whatman glass fiber separator was used, and 3 M Zn(CF3SO3)2 containing 1 M MPII (1-methyl-3-propylimidazolium iodide; C7H) was employed. 13Using IN2, 99%; Meryer as the electrolyte, a zinc-iodine battery was assembled and its electrochemical performance was tested.

[0058] Electrochemical performance testing included testing the device's energy storage performance using a CHI660E electrochemical workstation. Cycle and rate performance tests were performed on a LAND CT2001A battery testing system. The voltage window was 0.1–1.8 V. All electrochemical performance tests in this embodiment were performed at room temperature.

[0059] Figure 4 This is an electrochemical performance diagram of the zinc-iodine battery assembled in Example 3 of the present invention using MPII-Zn(OTF)2 as the electrolyte. Figure 4 a is the CV curve, Figure 4 b is the cycle performance graph.

[0060] like Figure 4 As shown, the CV curve of the zinc-iodine battery tested with MPII-Zn(OTF)2 electrolyte showed an additional redox pair at 1.67 / 1.60 V. Figure 4 a), with I2 / I + The redox pairs are consistent. The two distinct discharge plateaus at 1.20 V and 1.67 V represent I0, respectively. − / I 0 and I 0 / I + The conversion is completely different from the CV redox peaks of the I2-Zn(OTF)2 electrolyte. Figure 4 a). A zinc-iodine battery with an In(dobpdc) cathode, tested with MPII-Zn(OTF)2 electrolyte, achieved a 962 mAh g⁻¹. −1 The record-breaking discharge capacity far exceeds 211 mAh g. −1 With a theoretical capacity, a coulombic efficiency exceeding 99%, and an energy density reaching a new level of 1131 Wh / kg, the energy density achieves a new high. −1 ( Figure 4 b).

[0061] Comparative Example 1

[0062] In this comparative example, the zinc-iodine battery was first assembled. Except for replacing the electrolyte with pure 3 M Zn(CF3SO3)2, the other battery assembly materials and preparation process were the same as in Example 3. After battery assembly, the electrolyte was tested at 1 A g. −1 Cyclic performance and CV curves were tested at the specified current density.

[0063] Figure 5 This is an electrochemical performance diagram of the zinc-iodine battery assembled using Zn(OTF)2 as the electrolyte in Comparative Example 1 of the present invention. Figure 5a is the CV curve, Figure 5 b is the cycle performance graph.

[0064] like Figure 5 As shown, in contrast, the CV curve of the In(dobpdc) cathode in pure Zn(CF3SO3)2 electrolyte without the addition of an iodine source is as follows: Figure 5 a. Because it contains no iodine during charging, there is no obvious redox peak, and the discharge capacity is only 58 mAh g. −1 ( Figure 5 b).

[0065] <Comparative Example 2>

[0066] In this comparative example, the zinc-iodine battery was first assembled. Except for replacing the electrolyte with a 2 M I2-3 M Zn(CF3SO3)2 electrolyte, the other battery assembly materials and preparation process were the same as in Example 3. After battery assembly, the electrolyte was tested at 1 A g. −1 Cyclic performance and CV curves were tested at the specified current density.

[0067] Figure 6 This is an electrochemical performance diagram of the zinc-iodine battery assembled in Comparative Example 1 of the present invention using I2-Zn(OTF)2 as the electrolyte. Figure 6 a is the CV curve, Figure 6 b is the cycle performance graph.

[0068] like Figure 6 As shown, the CV curves of the I2-Zn(CF3SO3)2 electrolyte exhibit two pairs of sharp redox peaks at 1.38 / 1.20 V and 0.76 / 0.43 V, respectively. Figure 6 a), corresponding to I2 / I3 − The conversion. Furthermore, the discharge capacity of the In(dobpdc) cathode is 104 mAh g. −1 (Theoretical capacity is 211 mAh g) −1 Coulomb efficiency is as low as 71% ( Figure 6 b). The low capacity and coulombic efficiency can be attributed to soluble polyiodide (I3). − The severe shuttle effect leads to irreversible loss of active quality.

[0069] Comparative Example 3

[0070] In this comparative example, the zinc-iodine battery was first assembled. Except for replacing the electrolyte with a 3M KI-3M Zn(CF3SO3)2 electrolyte, the other battery assembly materials and preparation process were the same as in Example 3. After battery assembly, the electrolyte was tested at 1 A g. −1 Cyclic performance and CV curves were tested at the specified current density.

[0071] Figure 7 This is an electrochemical performance diagram of the zinc-iodine battery assembled using KI-Zn(OTF)2 as the electrolyte in Comparative Example 1 of the present invention. Figure 7 a is the CV curve, Figure 7 b is the cycle performance graph.

[0072] like Figure 7 As shown, when testing the electrochemical performance of the zinc-iodine battery constructed using KI-Zn(OTF)2, the capacity can reach 580 mAh g. −1 However, the coulomb efficiency is as low as 80%, and the capacity decays rapidly after 80 cycles.

[0073] The role and effect of the embodiments

[0074] As can be seen from Examples 1 and 2, the present invention can successfully prepare indium-based metal-organic frameworks In(dobpdc) for use as cathode materials.

[0075] As can be seen from Example 3 and Comparative Examples 1-3, the zinc-iodine battery constructed in this invention achieves I0 under the synergistic effect of electrolyte and electrode. + The activation, stabilization, and reversibility of cations enable a 962 mAh g⁻¹. −1 The discharge capacity is 1131 Wh kg. −1 The zinc-iodine battery exhibits excellent electrochemical performance with high energy density and a coulombic efficiency exceeding 99%. Therefore, only zinc-iodine batteries assembled using the zinc-iodine battery electrolyte prepared in this invention and the zinc-iodine battery cathode can achieve excellent electrochemical performance.

[0076] In this embodiment, an organic iodine source is added to the Zn(OTF)2 electrolyte to form an interhalogen compound I-SO3CF3, which activates the four-electron I- − / I2 / I + The conversion reaction, in this embodiment, provides a Zn 2+ I − A novel electrolyte system with joint regulation is developed, which selects a special iodine source to replace traditional elemental iodine, and combines it with I₂ generated at high potential through halogen bonding. + The formation of sulfonate iodine compounds can stably excite four-electron I − / I2 / I + Transformation reaction.

[0077] Furthermore, in this embodiment, in order to achieve I + The reversible transformation involves using indium-based metal-organic frameworks (In(dobpdc)) as the cathode material. In(dobpdc) can interact with I through redox active carbonyl and carboxyl groups. +A coordination reaction occurs, subsequently utilizing the In metal center with Zn. 2+ Alloying occurs to provide additional capacity. Therefore, thanks to the novel coordination and alloying reaction mechanisms of this embodiment, the device can be endowed with ultra-high specific capacity and high energy density.

[0078] In addition, the main raw materials used in this embodiment are widely available, inexpensive and environmentally friendly. The entire electrolyte preparation process is carried out at room temperature and pressure, which is simple to operate and safe and pollution-free.

[0079] The above embodiments are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

Claims

1. A zinc-iodine battery electrolyte for an aqueous zinc-iodine battery based on a four-electron conversion reaction, characterized in that: The zinc-iodine battery electrolyte is prepared by adding an iodine source to a Zn(OTF)2 electrolyte and then sonicating it at room temperature. The OTF is SO3CF3, and the iodine source is one or more of 2-iodoterephthalic acid, 1-methyl-3-propylimidazolium iodide, tris(4-iodophenyl)amine, 1,2-diiodobenzene, and (iodomethyl)triphenylphosphonium iodide.

2. The zinc-iodine battery electrolyte of the aqueous zinc-iodine battery based on a four-electron conversion reaction according to claim 1, characterized in that: in, The ultrasound duration during the procedure is 0.5 hours.

3. The zinc-iodine battery electrolyte of the aqueous zinc-iodine battery based on a four-electron conversion reaction according to claim 1, characterized in that: in, The total molar concentration of zinc ions and iodine ions in the zinc-iodine battery electrolyte is 4M~9M, and the molar ratio of zinc ions to iodine ions is 1M~3M:3M~6M.

4. An aqueous zinc-iodine battery based on a four-electron conversion reaction, characterized in that, include: Positive electrode, negative electrode, separator, and electrolyte. The electrolyte is the zinc-iodine battery electrolyte according to any one of claims 1 to 3, and the positive electrode is prepared from a positive electrode material. During operation, the zinc-iodine battery electrolyte excites four electrons I − / I2 / I + In the conversion reaction, the positive electrode material further reacts with I through redox active carbonyl and hydroxyl groups. + Coordination reactions occur and Zn is involved through the In metal center. 2+ An alloying reaction occurs.

5. The aqueous zinc-iodine battery based on a four-electron conversion reaction according to claim 4, characterized in that: The cathode material is an indium-based metal-organic framework, In(dobpdc). Wherein, dobpdc is 4,4'-dihydroxy-3,3'-biphenyl dicarboxylic acid. The preparation method of the indium-based metal-organic framework In(dobpdc) is as follows: NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, InSO4 and deionized water are weighed in sequence according to the mass ratio of 1:1.2~5:10~20:10~3. NaOH, 4,4'-biphenyl-3,3'-dicarboxylic acid, InSO4 and deionized water are mixed evenly and transferred to a high-pressure reactor. The reactor is placed in an oven at 80℃~160℃ and reacted for 12h~24h. After filtration and washing with ethanol, the reactor is vacuum dried at 80℃ for 12h to obtain the indium-based metal-organic framework In(dobpdc).

6. The aqueous zinc-iodine battery based on a four-electron conversion reaction according to claim 4, characterized in that: The method for preparing the positive electrode is as follows: Weigh the positive electrode material, carbon black, and polytetrafluoroethylene, add N-methylpyrrolidine, and grind them evenly to obtain a slurry. Then, coat the slurry evenly onto a titanium foil current collector and dry it to obtain the positive electrode.

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