WO2021228001A1 - 一种基于四电子转换反应的水系锌碘电池及其电解液 - Google Patents

一种基于四电子转换反应的水系锌碘电池及其电解液 Download PDF

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WO2021228001A1
WO2021228001A1 PCT/CN2021/092488 CN2021092488W WO2021228001A1 WO 2021228001 A1 WO2021228001 A1 WO 2021228001A1 CN 2021092488 W CN2021092488 W CN 2021092488W WO 2021228001 A1 WO2021228001 A1 WO 2021228001A1
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zinc
electrolyte
water
iodine
electron conversion
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French (fr)
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梁宵
邹一平
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湖南大学
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0002—Aqueous electrolytes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the invention belongs to the field of energy storage devices and specifically relates to a four-electron conversion reaction aqueous zinc-iodine battery and a preparation method of its electrolyte.
  • organic electrolytes lithium/sodium/potassium ion batteries, etc.
  • lithium ion batteries LIBs
  • the key to the high energy density of lithium-ion batteries-the high cost of positive ternary materials, the storage and mining limitations of negative lithium, and the inherent toxicity and flammability of traditional organic solvents in the electrolyte have forced people to continue Looking for a new energy storage system that balances performance, safety and cost.
  • the corresponding aqueous electrochemical system has the advantages of high safety and low cost.
  • Zinc has a high overpotential for hydrogen evolution and is the metal with the lowest electrode potential that can stably exist in aqueous solutions (0.76V vs. SHE).
  • the insertion of high-valent ions in the positive electrode further enhances the battery's energy.
  • the metal zinc is abundant in the earth's crust (180 million tons), and the mining cost is low.
  • high-power, high-safety and low-cost water-based zinc-ion batteries are ideal energy storage systems in the future.
  • the current mainstream water-based zinc-ion battery cathodes are mainly based on the intercalation/extraction of Zn 2+ in layered structural materials. Such zinc intercalation materials face structural damage during charging and discharging, difficulties in ion intercalation/extraction, and complex preparation processes. This led to the further development of zinc-ion batteries.
  • the average discharge voltage of the battery is 1.22V, and the specific capacity is close to the theoretical capacity of iodine (209mAh g -1 vs. 211mAh g -1 ), which can cycle more than 1000 times at a rate of 5C.
  • zinc iodide secondary battery positive electrode coverage based only on stage I - / conversion between 2 I, as compared to the capacity and the energy performance of zinc ion battery without significant advantage.
  • a first object of the present invention is to provide an aqueous zinc iodide electrolyte cell realizing high capacity four-electron conversion reaction, aims to provide a new adaptable I - / The electrolyte of the water-based zinc-iodine battery with the four-electron conversion reaction mechanism of I 2 /I +.
  • the second object of the present invention is to provide a new I - / I 2 / I + aqueous zinc iodide electronic switching four battery reaction mechanism.
  • An aqueous zinc-iodine battery electrolyte based on four-electron conversion iodine-based electrochemical reaction which is an aqueous solution containing Zn 2+ and I + stabilizers (four-electron mechanism stimulators).
  • the I + stabilizer is an anion or a nucleophilic water-soluble solvent that can form an electron transfer compound with I + during charging and discharging.
  • the total molar concentration of Zn 2+ and I + stabilizers is not less than 5 M.
  • the present invention provides a new electrolyte, which is jointly controlled by the innovation of Zn 2+, I + ion concentration and stabilizer, can be changed charge and discharge reaction mechanism, can stimulate I - / I 2 / I the four-electron reaction + conversion mechanism, can be avoided and the new four-electron conversion mechanism of the hydrolysis reaction of I +, I + to improve stability and improve the I - / I 2 / I + four-electron conversion reactivity.
  • Electrolyte according to the present invention enables the I - / I 2 / I + four electronic converter mechanism of the reaction, and thanks to the new reaction mechanism, the energy storage mechanisms may be beyond the current performance bottlenecks, significantly improving battery The electrochemical performance.
  • Electrolyte according to the present invention which Zn 2+, Cl - specific combination and the concentration control is to avoid hydrolysis of I +, I + to improve stability, to achieve the I - / I 2 / I + four-electron conversion reaction mechanism , And the key to improving electrochemical performance.
  • the Zn 2+ is provided by ionization of a water-soluble zinc ion source with a solubility in water of not less than 100 g/L at room temperature.
  • the zinc ion source is zinc chloride, zinc nitrate, zinc sulfate, zinc acetate, zinc bistrifluoromethanesulfonimide (Zn(TFSI) 2 ), zinc trifluoromethanesulfonate (Zn( OTf) 2 ) At least one of its hydrates.
  • the anion in the I + stabilizer is Cl- and/or CN-.
  • the nucleophilic water-soluble compound in the I + stabilizer is at least one of tetrahydrofuran, pyridine, amine, ester, and ether.
  • the water-soluble source of chloride ions is at room temperature solubility in water of not less than 100 g / L of water-soluble salts ; More preferably, at least one of zinc chloride, lithium chloride, sodium chloride, potassium chloride, tetraethylammonium chloride (TEAC), and ammonium chloride.
  • TEAC tetraethylammonium chloride
  • the CN- is provided by a water-soluble cyano compound capable of ionizing CN- in water; preferably, the water-soluble cyanide ion source is a water-soluble salt with a solubility in water of not less than 100 g/L at room temperature; More preferably, at least one of sodium cyanide, potassium cyanide, and a nitrile compound.
  • the I + stabilizer is Cl-.
  • Cl- at the stated concentration is used as the stimulator of the four-electron conversion reaction mechanism, which can reduce the I + to form Interhalogen compound, and control the water activity of the water system to inhibit the I + Hydrolysis improves the stability of I+ , improves the four-electron reaction activity, and helps to improve electrochemical performance.
  • the research of the present invention found that in the electrolyte, under the ionic system of the Zn 2+ and I + stabilizers, the concentration of ions and the relationship between the ions can be further regulated, which helps to further improve the I + in the water system. system stability, improving I - / I 2 / I + conversion of a four-electron reaction, improving the performance of zinc-iodine electrochemical cell under the new mechanism.
  • the total molar concentration of Zn 2+ and I + stabilizers is not less than 10 M, and less than or equal to the total molar concentration of the saturated solution; more preferably, it is 15-90 M.
  • the molar ratio of I + stabilizer/zinc ion is greater than or equal to 1; preferably greater than or equal to 2; further preferably, the molar ratio is 2 to 3:1.
  • the concentration of Zn 2+ is not less than 5M, and is less than or equal to the zinc ion concentration of the saturated solution; preferably 5-30M; more preferably 10-20M.
  • the molar concentration of I + stabilizer is not less than 10M, and is less than or equal to the zinc ion concentration of the saturated solution; preferably, it is 10-60M.
  • the electrolyte of the present invention in addition to containing zinc ions and I + stabilizers, it is also allowed to contain other anions introduced to provide zinc ions other than I + stabilizers, such as sulfate ions, acetate ions, and nitrate ions. Ion, trifluoromethanesulfonate ion, etc.
  • the cations can also provide other cations other than zinc ions introduced by providing I + stabilizer anions, such as sodium ions, potassium ions, lithium ions, ammonium ions, quaternary ammonium ions and other cations. There are no special requirements for the content of other anions and cations, as long as they meet the stoichiometric ratio of zinc ions or I + stabilizer anions.
  • an organic solvent is further added, and the organic solvent is an organic solvent that is miscible with water and does not participate in the charge-discharge reaction.
  • the research of the present invention found that the further addition of organic solvent helps to further reduce the viscosity of the high-concentration electrolyte and improve the conductivity of the solution; and participates in the solvation of metal cations to increase the activity of I + stabilizer anions (such as Cl-); improve I + stability, in favor of the I - / I 2 / I + four-electron conversion reaction mechanism effectively help to improve the performance of zinc-iodine electrochemical cell of the new mechanism.
  • the organic solvent is at least one of acetonitrile and ether solvents; more preferably, acetonitrile (ACN), ethylene glycol dimethyl ether (DME), dioxolane (DOL), tetrahydrofuran (THF) , At least one of 1,4-dioxane (DX); most preferably acetonitrile.
  • ACN acetonitrile
  • DME ethylene glycol dimethyl ether
  • DOL dioxolane
  • THF tetrahydrofuran
  • DX 1,4-dioxane
  • the molar ratio of organic solvent to water in the electrolyte is 0.1-0.5.
  • the electrolyte is an aqueous solution containing at least Zn 2+ and Cl-, wherein the molar ratio of Cl-/Zn 2+ is greater than or equal to 2; and the concentration of Zn 2+ is greater than or equal to 5M; preferably 10 ⁇ 20M.
  • the aqueous high-concentration salt electrolyte contains zinc chloride, lithium chloride, organic solvent additives and water; the molar ratio of each component is 10 ⁇ 31:0-20:0-20:55.6; further preferably The molar ratio is 15-20: 15-20: 5-10: 55.6.
  • the organic solvent additive is ACN.
  • the present invention also provides an aqueous zinc-iodine battery based on a four-electron conversion reaction, which includes a positive electrode, a negative electrode, a separator separating the positive electrode and the negative electrode; and the electrolyte solution of the positive electrode, the negative electrode, and the separator; I - / I 2 / I + reversible electrochemical reaction.
  • the present invention provides a new basis of I - / I 2 / I + reversible electrochemical reaction mechanisms iodine aqueous zinc batteries, and battery found in this new mechanism can overcome the bottleneck of the conventional mechanism, may exhibit more Excellent capacity, current density and cycle stability.
  • the electrolyte is the electrolyte of the present invention.
  • the electrolyte of the present invention can effectively stabilize I+, thereby realizing the four-electron reaction mechanism, and further improving the performance of the prepared aqueous zinc-iodine battery.
  • the positive electrode is a negative iodine porous material; it includes a porous material and a simple substance of iodine carried in it.
  • the porous material is one or more of porous activated carbon, mesoporous carbon, carbon fiber cloth, MOFs, graphene, and graphene oxide.
  • the iodine content is 20-50% (mass fraction).
  • the preparation method of the negative iodine porous material is, for example, adding elemental iodine and porous material into a sample bottle containing deionized water, heating to 40-60°C until the porous material completely adsorbs iodine, and then adding the obtained iodine-carbon composite suspension to 4000 Centrifuge at -6000 rpm, discard the supernatant and heat it in an oven at 60-80°C for 6-12h.
  • the positive electrode cell operation occurs when I - / I 2 / I + reversible electrochemical reaction, the reversible electrochemical reaction products and intermediates are adsorbed on the electrode surface, the reaction process without forming polyiodide.
  • the negative electrode is a zinc elemental negative electrode; for example, a zinc foil.
  • the negative electrode undergoes a zinc deposition/dissolution reaction; its negative electrode reaction is as follows.
  • the separator is a kind of glass fiber/qualitative filter paper.
  • the present invention first provides an implementation of I - / I 2 / four-electron mechanism of zinc iodide battery I + reversible electrochemical reaction, and further proposed a new mechanism for the adaptation of I + electrolysis can be stably liquid.
  • I + stabilizer as Cl- as an example, it innovatively selects Cl- which is more soluble in water as the electrolyte. They can provide Cl - needed to stabilize I + in the aqueous solution and form a halogen interaction with it. Interhalogen compound.
  • a higher concentration of chloride can reduce the activity of water in the solution, thereby inhibiting the hydrolysis of I +.
  • (1) of the present invention first in the industry to put forward a new I - / I 2 / I + zinc iodide aqueous battery of a four-electron conversion mechanism of the reaction; and found that this new mechanism of cell having an aqueous zinc iodide better The electrochemical performance; for example, has a better capacity and current density.
  • Research shows that the battery prepared realized I - / I 2 / I + four-electron reaction, as compared to conventional zinc iodide than doubling the battery capacity, high rate capability and cycle life are improved.
  • the present invention also provides an aqueous zinc-iodine battery electrolyte that can form the new four-electron conversion reaction mechanism, which can change the reaction mechanism through the joint control of Zn 2+ , I + stabilizer and concentration. generated based on I - / I 2 / four-electron mechanism of zinc iodide battery + I reversible electrochemical reaction, and can effectively avoid hydrolysis of I +, which improve stability, in addition, can improve the I - / I 2 / I + The reversible electrochemical reaction activity and reduction of zinc dendrite formation can overcome the performance bottleneck of existing conventional zinc-iodine batteries and significantly improve electrochemical performance.
  • the electrolytic solution in said organic solvent further compatibility, helps to further improve the I - / I 2 / I + reactivity of four electrons contribute to the further improvement of the new mechanism The electrochemical performance of the battery.
  • Figure 1 is a graph showing the charge and discharge curves of a zinc-iodine battery assembled with the electrolyte of Example 1 (ZnCl2:LiCl:ACN:H2O, 19:19:8:55.6) at a current density of 400 mA g -1.
  • Figure 2 is a graph showing the charge and discharge curves of a zinc-iodine battery assembled with electrolyte of Comparative Example 1 (1m ZnSO 4 ) at a current density of 400 mA g -1.
  • Example 3 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Example 1-1 (10m ZnCl 2 ) at a current density of 400 mA g -1.
  • Example 4 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Example 1-2 (1M ZnSO 4 + 10M LiCl) at a current density of 400 mA g -1.
  • Figure 5 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Example 1-3 (1M Zn(TFSI) 2 + 10M LiCl) at a current density of 400 mA g -1.
  • Figure 6 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Example 1-4 (20M ZnCl 2 + 3M KCl) at a current density of 400 mA g -1.
  • Fig. 7 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Example 1-5 (20M ZnCl 2 + 3M TEAC) at a current density of 400 mA g -1.
  • Fig. 8 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Example 1-6 ((15M ZnCl 2 + 15M LiCl) at a current density of 400 mA g -1.
  • Figure 9 is a graph showing the charge and discharge curves of a zinc-iodine battery assembled from the electrolyte of Examples 1-7 (ZnCl 2 :LiCl:ACN:H2O, 30:19:8:55.6) at a current density of 400 mA g -1.
  • Fig. 10 is a graph showing the charge and discharge curves of a zinc-iodine battery assembled with the electrolyte of Examples 1-8 (ZnCl 2 :LiCl:ACN:H2O, 30:19:8:55.6) at a current density of 400 mA g -1.
  • 11 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Examples 1-9 (ZnCl 2 :LiCl:ACN:H 2 O, 19:19:5:55.6) at a current density of 400 mA g -1.
  • Fig. 12 is a graph showing the charge and discharge curves of a zinc-iodine battery assembled with the electrolyte of Examples 1-10 (ZnCl 2 :LiCl:THF:H 2 O, 19:19:8:55.6) at a current density of 400 mA g -1.
  • Fig. 13 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Example 1-11 (ZnCl 2 :LiCl:DME:H 2 O, 10:10:8:55.6) at a current density of 400 mA g -1.
  • Figure 14 is a graph showing the charge and discharge curves of a zinc-iodine battery assembled with electrolyte of Comparative Example 1-1 (ZnTFSI:LiTFSI:H 2 O, 1:20:55.6) at a current density of 400 mA g -1.
  • Figure 15 is a graph showing the charge and discharge curves of the zinc-iodine battery assembled with the electrolyte of Example 1-12 (10m ZnCl 2 + 0.8m pyridine) at a current density of 400 mA g -1.
  • Figure 16 is a cyclic voltammetry curve of the zinc-iodine battery assembled in Example 1 and Comparative Example 1, and Example 1-1 at a sweep rate of 0.5 mV s -1.
  • Figure 17 is a high-rate (2000mA g -1 ) cycle performance graph of the zinc-iodine battery assembled in Example 1.
  • Example 18 is a voltage-time graph of the Zn
  • Example 19 is an SEM image of the Zn
  • FIG. 21 shows the charge-discharge curve and the corresponding in-situ Raman spectrum of the assembled in-situ battery in Comparative Example 3.
  • the electrolyte is an aqueous solution prepared with ZnCl 2 :LiCl:ACN:H 2 O in a substance ratio of 19:19:8:55.6 (the molar concentration of ZnCl 2 is 19M; the molar concentration of LiCl is 19M; the molar concentration of ACN is 8M).
  • Figure 1 shows the charge and discharge curve at 400mA g -1 current density.
  • the first lap discharge capacity is 594mAh g -1 ; the 100 discharge capacity is 572mAh g-1; the coulombic efficiency is 98.5%; the discharge platform is 1.65, 1.15V.
  • Example 2 shows the charge and discharge curve at 400mA g -1 current density.
  • the first lap discharge capacity is 308mAh g -1 ; the 100 discharge capacity is 277mAh g-1; the coulombic efficiency is 83.2%; and the discharge platform is 1.2V.
  • Example 2 Compared with Example 1, the difference is that the electrolyte is a pure zinc chloride aqueous solution: 10M ZnCl 2 ; the rest of the steps are the same; the charge and discharge curve at a current density of 400 mA g -1 is shown in FIG. 3.
  • the first lap discharge capacity is 466mAh g -1 ; the 100 discharge capacity is 373mAh g-1; the coulombic efficiency is 69.4%; the discharge platform is 1.7, 1.2V.
  • Example 1 Compared with Example 1, the difference is that the electrolyte is a 1M ZnSO4 + 10M LiCl aqueous solution (changing the Zn source).
  • Figure 4 shows the charge and discharge curve at 400mA g -1 current density.
  • the first lap discharge capacity is 439mAh g -1 ; the 100 discharge capacity is 311mAh g-1; the coulombic efficiency is 96.1%; the discharge platform is 1.65, 1.2V.
  • Example 1 Compared with Example 1, the difference is that the electrolyte is 1M Zn(TFSI)2 + 10M LiCl aqueous solution (changing the Zn source); the rest of the steps are the same.
  • Figure 5 shows the charge and discharge curve at 400mA g -1 current density.
  • the first lap discharge capacity is 423mAh g -1 ; the 100 discharge capacity is 292mAh g-1; the coulombic efficiency is 90.5%; the discharge platform is 1.65, 1.2V.
  • Example 1 Compared with Example 1, the difference is that the electrolyte is a 20M ZnCl2 + 3M KCl aqueous solution (change the Cl source). The rest of the steps are the same.
  • Figure 6 shows the charge and discharge curve at 400mA g -1 current density.
  • the first lap discharge capacity is 535mAh g -1 ; the 100 discharge capacity is 409mAh g-1; the coulombic efficiency is 93.4%; the discharge platform is 1.65, 1.15V.
  • Example 1 Compared with Example 1, the difference is that the electrolyte is a 20M ZnCl2 + 3M TEAC (tetraethylammonium chloride) aqueous solution (with the Cl source changed); the rest of the steps are the same.
  • Figure 7 shows the charge-discharge curve at 400mA g -1 current density.
  • the first lap discharge capacity is 548mAh g -1 ; the 100 discharge capacity is 399mAh g-1; the Coulomb efficiency is 87.7%; the discharge platform is 1.65, 1.15V.
  • the electrolyte is a saturated solution of ZnCl2 and LiCl (molar ratio 1:1) without adding any organic additives, and the actual concentration is an aqueous solution of 15M ZnCl2 + 15M LiCl.
  • Figure 8 shows the charge and discharge curve at 400mA g -1 current density.
  • the first lap discharge capacity is 524mAh g -1 ; the 100 discharge capacity is 442mAh g-1; the coulombic efficiency is 84.2%; the discharge platform is 1.65, 1.15V.
  • the electrolyte is an aqueous solution prepared with a substance ratio of 30:19:8:55.6 ZnCl2:LiCl:ACN:H2O.
  • Figure 9 shows the charge and discharge curve at 400mA g -1 current density. (Change the optimal system Zn source concentration); the first lap discharge capacity is 470mAh g -1 ; the 100 discharge capacity is 346mAh g-1; the coulombic efficiency is 99.2%; the discharge platform is 1.65, 1.05V.
  • the electrolyte is an aqueous solution prepared with a substance ratio of 19:5:8:55.6 ZnCl2:LiCl:ACN:H2O.
  • Figure 10 shows the charge and discharge curve at 400mA g -1 current density. (Change the optimal system Li source concentration); the first lap discharge capacity is 522mAh g -1 ; the 100 discharge capacity is 387mAh g-1; the coulombic efficiency is 83.3%; the discharge platform is 1.65, 1.15V.
  • Example 1 The difference compared with Example 1 is that the electrolyte is an aqueous solution prepared with a substance ratio of 19:19:5:55.6 ZnCl2:LiCl:ACN:H2O.
  • Figure 11 shows the charge and discharge curve at 400mA g -1 current density. (Change the concentration of organic additives in the optimal system); the first lap discharge capacity is 537mAh g -1 ; the 100 discharge capacity is 420mAh g-1; the coulombic efficiency is 98.8%; the discharge platform is 1.65, 1.15V.
  • the electrolyte is an aqueous solution prepared with a substance ratio of 19:19:8:55.6 ZnCl2:LiCl:THF:H2O.
  • Figure 12 shows the charge and discharge curve at 400mA g -1 current density. (Change the source of organic additives in the optimal system); the first lap discharge capacity is 515mAh g -1 ; the 100 discharge capacity is 396mAh g-1; the coulomb efficiency is 86.6%; the discharge platform is 1.65, 1.15V.
  • Example 1 The difference compared with Example 1 is that the electrolyte is an aqueous solution prepared with a substance ratio of 10:10:8:55.6 ZnCl2:LiCl:DME:H2O.
  • Figure 13 shows the charge and discharge curve at 400mA g -1 current density. (Change the optimal system to add organic additive source, the solubility of zinc salt and lithium salt in DME cannot be prepared at the same concentration); the first-lap discharge capacity is 474mAh g -1 ; the 100 discharge capacity is 367mAh g-1; the coulombic efficiency is 82.4% ; Discharge platform 1.65, 1.15V.
  • the electrolyte is an aqueous solution prepared with a substance ratio of 1:20:55.6 ZnTFSI:LiTFSI:H2O.
  • Figure 14 shows the charge and discharge curve at 400mA g -1 current density. (The case where the high concentration salt does not contain Cl-).
  • the first lap discharge capacity is 295mAh g -1 ; the 100 discharge capacity is 266mAh g-1; the coulombic efficiency is 98.9%; and the discharge platform is 1.2V.
  • Example 1-1 Compared with Example 1-1, the difference is that the electrolyte is an aqueous solution of 10m ZnCl 2 + 0.8m Pyridine, and the charge and discharge curve at a current density of 400 mA g -1 is shown in FIG. 15.
  • the first lap discharge capacity is 515mAh g -1 ; the 100 discharge capacity is 435mAh g-1; the coulombic efficiency is 92.7%; the discharge platform is 1.65, 1.15V.
  • Figure 1-15 is the charge and discharge curve of the assembled battery between 0.6-1.8V. It can be seen from the figure that under the condition of conventional water-based zinc-iodine battery electrolyte and zinc-based high-concentration salt without Cl (Comparative Example 1 and Comparative Example 1-1), only a low discharge voltage plateau (on behalf of I - / I 2 conversion). When a solution containing Cl - (Examples 1-1 to 1-11), two platforms are discharge occurs, representing conversion / I + a I- / I 2 and I 2.
  • the high-voltage discharge platform of the low-Cl-concentration electrolyte system (Examples 1-2 and 1-3): the ratio of the low-voltage discharge platform is significantly smaller than that of the high-Cl-concentration electrolyte system (Examples 1-4 to 1- 11), indicating that the concentration of Cl- plays a key role in the stability of I+.
  • Changing the concentration of zinc salt (embodiment 1-7), lithium salt (embodiment 1-8), and organic solvent (embodiment 1-9) of the optimal system will reduce the battery performance.
  • Example 1 Only in Example 1, the high-order and low-order voltage platforms of the battery are obvious and close in proportion, the coulombic efficiency is high, and the discharge capacity reaches 594 mAh g -1 , which represents the realization of fully reversible four-electron conversion under this system. (See Table 1 for specific electrochemical performance).
  • Figure 16 shows the cyclic voltammetry curves of the batteries assembled in Example 1, Comparative Example 1, and Example 1-1, with a scanning speed of 0.5 mV s -1 , and there are 2 pairs of redox peaks in both Example 1-1 and Example 1. In Comparative Example 1, only the redox peak appeared at low potential.
  • FIG 17 is a high rate cycling performance (2000mA g -1) Example 1 battery, under condition that the magnification after 6000 cycles, the battery capacity is still able to achieve more than 420mAh g -1.
  • a clean zinc sheet was used as the working battery and counter electrode, the Swagelok battery was assembled in the following electrolyte, and then the zinc deposition test experiment was carried out. SEM was taken after electrode treatment after cycling.
  • Figure 18 shows the electrochemical performance of the assembled Zn
  • Figure 19 is the SEM image of the zinc sheet of the assembled Zn
  • the electrode surface of Example 2 is smoother than that of Comparative Example 2, and the surface of Comparative Example 2 has obvious dendrite formation.
  • the positive electrode slurry was dropped on the glassy carbon electrode and dried and then assembled in the following electrolyte for in-situ battery assembly.
  • the counter electrode was a platinum wire and the reference electrode was an Ag/AgCl electrode.
  • the assembled battery undergoes in-situ Raman testing.
  • Figure 20 shows the charge and discharge curves of Example 3 and the corresponding in-situ Raman spectra. As the charging depth increases, a signal peak gradually appears near 200cm -1 , corresponding to the stretching vibration of I-Cl. The intensity of the signal peak reaches the maximum when the charge is cut off, and then the signal gradually weakens and eventually disappears during the discharge process, corresponding to I + / The conversion of I 2 ends.
  • Figure 21 shows the charge and discharge curves of Comparative Example 3 and the corresponding in-situ Raman spectra. It can be seen that during the entire charge and discharge process, there is no I-Cl stretching vibration signal. Combined with the electrochemical characterization described above, it can be concluded that under this system, only the I-/I 2 conversion is reversible.

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Abstract

一种四电子转化的碘基电化学反应水系锌碘电池和可实现所述四电子转化的电解液，该电解液为含有Zn 2+、I +稳定剂的水系溶液；Zn 2+、I +稳定剂的总摩尔浓度不低于5M；此外，所述的电解液还选择性包含有机溶剂。该锌碘电池基于全新的转化机制，可以突破现有锌碘电池性能瓶颈，有效改善电化学性能。

Description

一种基于四电子转换反应的水系锌碘电池及其电解液 技术领域
本发明属于储能器件领域 具体涉及一种四电子转换反应的水系锌碘电池及其电解液的制备方法。
 背景技术
现阶段的储能体系中，有机系电解液（锂/钠/钾离子电池等）具有足够宽的电化学窗口，从而理论上能够达到较高的能量密度。其中，锂离子电池（LIBs）因其能量密度高和循环寿命长的优势，自1990年问世以来已经大规模应用于消费电子产品和新能源汽车。然而，锂离子电池高能量密度的关键—正极三元材料的成本居高不下，以及负极锂的储量和开采限制，加上电解液存在传统有机溶剂固有的毒性，可燃性等问题，迫使人们继续寻找性能，安全和成本兼顾的新型储能系统。与之对应的水系电化学体系，其具有高安全性和低成本的优势，虽然其电化学窗口只有1.23V，但离子电导率相较于有机体系更大，从而拥有更大的功率密度，故而在大规模储能领域具有更强的竞争力。目前的二次水系电池依据嵌入离子分类的话，主要有水系锂离子电池（其他一价阳离子：Na +, K +, H +, NH4 +）以及水系锌离子电池。其中碱金属水系电池现阶段存在着诸多问题，如充放电伴随着严重副反应，电极材料易水解，电化学稳定窗口较窄等，这些缺陷限制了水系电池进一步发展。而锌具备较高的析氢过电位，是能够在水系溶液中稳定存在的电极电位最低的金属（0.76V vs. SHE）。此外，正极高价离子的嵌入使得电池能量进一步提升，加上金属锌在地壳中储量丰富（18000万吨），开采成本低。综上所述，高功率，高安全性以及低成本的水系锌离子电池是未来理想的储能体系。但是目前主流的水系锌离子电池正极主要基于Zn 2+在层状结构材料的嵌入/脱出，这类嵌锌材料面临充放电过程中结构破坏、离子嵌入/脱出困难、制备工艺复杂等问题，限制了锌离子电池的进一步发展。
近年来，锌-卤素电池也成为锌离子电池的另一大研究方向。审阅卤素一族，氟元素电极电位过低，水溶液中离子导电性较差；氯常温下为气态，并且电极电位高于水的分解电位；溴常温下为液体，电极电位为1.066V（vs. SHE），因其独特的物态（元素中唯二的常温下液体元素），人们早在100年前就已经提出了锌溴液流电池的概念，但由于未能有效抑制Br -穿梭而鲜有应用于二次电池；而对于元素碘而言，1）碘的还原电位为0.54V（vs. SHE）与锌匹配起来能够达到1.2V以上的电压；2）单质碘常温下为固体，且在水溶液中溶解度很低；3）单质碘的理论容量达到211mAh g -1，理论能量密度超过250Wh kg -1。因此，卤素中碘元素成为了理想电极材料的选择。1984年，人们首次提出了Zn/ZnI 2二次电池，但受限于正极碘载体性能，穿梭效应产生的自放电和严重的锌枝晶生长问题未能商业化（Yamamoto T, Hishinuma M, Yamamoto A. Zn∣ ZnI 2∣ iodine secondary battery using iodine-nylon-6 adduct as positive electrode, and its charge-discharge performance[J]. Inorganica chimica acta, 1984, 86(2): L47-L49.）。2017西北太平洋国家实验室的刘军等人报道的水系锌碘二次电池，将I 2负载在活性碳纤维布上（ACF），尽管放电过程形成水溶性的I 3 -，但微孔碳的吸附作用有效地抑制了碘物种穿梭效应引起的自放电，因此避免了使用昂贵的离子交换膜。该电池的平均放电电压为1.22V，比容量接近碘的理论容量（209mAh g -1 vs. 211mAh g -1）5C倍率下能够循环1000次以上。但现阶段报道的锌碘二次电池正极只是基于I -/I 2之间的转换，在容量以及能量性能和锌离子电池相比没有显著的优势。
技术问题
针对锌碘电池容量以及能量密度不理想的问题，本发明第一目的在于，提供一种实现高容量四电子转换反应的水系锌碘电池电解液，旨在提供一种可适配全新I -/I 2/I +的四电子转换反应机制的水系锌碘电池的电解液。
本发明第二目的在于，提供一种全新的I -/I 2/I +的四电子转换反应机制的水系锌碘电池。
为解决现有锌碘二次电池正极均是基于I -/I 2转换机制，电化学性能不理想的问题，本发明在行业内首次提出一种基于I -/I 2/I +的四电子转换反应机制的水系锌碘电池，然而，为了在行业内首次实现该全新放电机制，成功获得高电化学性能的锌碘二次电池，需要妥善解决该全新机制下的I +的在水系溶液体系下的水解、稳定性以及反应活性等问题。
技术解决方案
一种基于四电子转化的碘基电化学反应的水系锌碘电池电解液，其为含有Zn 2+、I +稳定剂（四电子机制激发剂）的水系溶液。
所述的I +稳定剂为能在充、放电过程中与I +生成电子转移化合物的的阴离子或者亲核水溶性溶剂。
所述的电解液中，Zn 2+、I +稳定剂的总摩尔浓度不低于5 M。
本发明提供了一种全新的电解液，其创新地通过所述的Zn 2+、I +稳定剂以及离子浓度的联合控制，能够改变充、放电反应机制，可以激发I -/I 2/I +的四电子转换反应机制，且能够避免该全新四电子转换反应机制I +的水解，改善I +的稳定性，并且改善I -/I 2/I +的四电子转换反应活性。本发明所述的电解液能够实现所述的I -/I 2/I +的四电子转换反应机制，且得益于该全新的反应机制，可突破现有储能机制性能瓶颈，显著改善电池的电化学性能。
本发明所述的电解液，其Zn 2+、Cl -的联合以及浓度的特殊控制是避免I+水解、改善I+稳定性、实现所述的I -/I 2/I +的四电子转换反应机制、并改善电化学性能的关键。
所述的Zn 2+由在常温下水中溶解度不低于100 g/L的水溶性锌离子源电离提供。
作为优选，所述的锌离子源为氯化锌、硝酸锌、硫酸锌、醋酸锌、双三氟甲磺酰亚胺锌（Zn(TFSI) 2）、三氟甲基磺酸锌（Zn(OTf) 2）及其水合物中的至少一种。
所述的I +稳定剂中的阴离子为Cl-和/或CN-。
所述的I +稳定剂中的亲核水溶性化合物为四氢呋喃、吡啶、胺、酯、醚中的至少一种。
所述的Cl-由能在水中电离出Cl -的水溶性氯离子源电离提供；优选地，所述的水溶性氯离子源为在常温下水中溶解度不低于100 g/L的水溶性盐；进一步优选为氯化锌、氯化锂、氯化钠、氯化钾、四乙基氯化铵（TEAC）、氯化铵中的至少一种。
所述的CN-由能在水中电离出CN-的水溶性氰基化合物提供；优选地，所述的水溶性氰离子源为在常温下水中溶解度不低于100 g/L的水溶性盐；进一步优选氰化钠、氰化钾、腈类化合物中的至少一种。
进一步优选，所述的I +稳定剂为Cl-。
本发明中，采用所述浓度下的Cl-作为四电子转换反应机制激发剂，其能够下的I +形成卤素互化物（Interhalogen compound），并控制水系体系的水的活度，抑制I +的水解，改善I +的稳定性，改善所述的四电子反应活性，有助于改善电化学性能。
本发明研究发现，所述的电解液中，在所述的Zn 2+、I +稳定剂的离子体系下，进一步调控离子的浓度以及离子之间的关系，有助于进一步改善I +在水系体系下的稳定性，改善I -/I 2/I +的四电子转换反应，改善该全新机制下的锌碘电池的电化学性能。
Zn 2+、I +稳定剂的总摩尔浓度不低于10 M，小于或等于饱和溶液的总摩尔量；进一步优选为15~90M。
优选地，所述的电解液中，I +稳定剂/锌离子的摩尔比大于等于1；优选大于等于2；进一步优选的摩尔比为2~3:1。
作为优选，所述的电解液中，Zn 2+的浓度不低于5M，小于或等于饱和溶液的锌离子浓度；优选为5~30M；更进一步优选为10~20M。
本发明中，所述的电解液中，I +稳定剂的摩尔浓度不低于10M，小于或等于饱和溶液的锌离子浓度；优选为10~60M。
本发明所述的电解液中，除了含有锌离子以及I +稳定剂外，还允许含有提供锌离子而引入的除I +稳定剂以外的其他阴离子，例如硫酸根离子、醋酸根离子、硝酸根离子、三氟甲磺酸根离子等。此外，所述的阳离子，还允许提供I +稳定剂阴离子而引入的除锌离子以外的其他阳离子，例如，钠离子、钾离子、锂离子、铵根离子、季铵根离子等其他阳离子。其他阴离子以及阳离子的含量没有特别要求，符合提供锌离子或I +稳定剂阴离子化学计量比即可。
本发明所述的电解液中，还添加有有机溶剂，所述的有机溶剂为能与水互溶、且不参与充放电反应的有机溶剂。本发明研究发现，进一步添加有机溶剂，有助于进一步降低高浓度电解液的粘度，改善溶液导电性；且参与金属阳离子溶剂化，提高I +稳定剂阴离子（如Cl-）活度；改善I +的稳定性，有利于所述的I -/I 2/I +的四电子转换反应机制有效进行，有助于改善该全新机制的锌碘电池的电化学性能。
作为优选，所述的有机溶剂为乙腈、醚类溶剂中的至少一种；进一步优选为乙腈（ACN）、乙二醇二甲醚（DME）、二氧戊烷（DOL）、四氢呋喃（THF）、1,4-二氧六环（DX）中的至少一种；最优选为乙腈。
本发明中，所述电解液中，有机溶剂与水的摩尔比为0.1~0.5。
作为优选，所述的电解液为至少包含有Zn 2+、Cl-的水溶液，其中，Cl-/Zn 2+的摩尔比大于或等于2；且Zn 2+的浓度大于等于5M；优选为10~20M。
进一步优选，所述的水系高浓盐电解液包含氯化锌、氯化锂、有机溶剂添加剂和水；各成分的摩尔比为10~31：0-20：0-20：55.6；进一步优选的摩尔比为15~20：15~20：5~10：55.6。所述的有机溶剂添加剂为ACN。
本发明还提供了一种基于四电子转换反应的水系锌碘电池，其包括正极、负极、将正极和负极分隔的隔膜；以及浸泡正极、负极、隔膜的电解液；其中，在工作时正极发生I -/I 2/I +的可逆电化学反应。
本发明提供了一种全新的基于I -/I 2/I +的可逆电化学反应机制的水系锌碘电池，且发现该全新机制下的电池可以突破现有机制的性能瓶颈，可以表现出更优的容量、电流密度以及循环稳定性。
所述的I +稳定剂为Cl-时，所述的I -/I 2/I +的可逆电化学反应式为。
2 I - ↔ I 2 + 2 e-   Eo = 0.53 V vs. SHE。
I 2 + 2 Cl- ↔ 2 ICl + 2 e-  Eo = 1.07 V vs. SHE。
本发明所述的水系锌碘电池，所述的电解液为本发明所述的电解液。本发明所述的电解液，可以有效稳定I+，从而实现所述的四电子反应机制，进而改善制得的所述的水性锌碘电池的性能。
所述的正极为负碘多孔材料；其包括多孔材料以及负载在其中的碘单质。
所述的多孔材料为多孔活性碳、介孔碳、碳纤维布、MOFs、石墨烯、氧化石墨烯的一种或几种。
所述的负碘多孔材料中，碘含量为20-50%（质量分数）。
负碘多孔材料的制备方法例如为；将单质碘与多孔材料加入含有去离子水的样品瓶中，加热至40-60℃待多孔材料完全吸附碘，然后将所得碘碳复合物悬浊液4000-6000转离心，弃置上清液后在60-80℃烘箱中热处理6-12h后即得。
电池工作时正极发生I -/I 2/I +的可逆电化学反应，该可逆电化学反应产物以及中间体均吸附在电极表面，反应过程中无多碘化物形成。
优选地，所述的水系锌碘电池，所述的负极为锌单质负极；例如为锌箔。负极发生锌的沉积/溶解反应；其负极反应如下。
Zn 2+ + 2 e- ↔ Zn   Eo = -0.76 V vs. SHE。
作为优选，隔膜为玻璃纤维/定性滤纸的一种。
本发明首创性地提供了一种实现I -/I 2/I +的可逆电化学反应的四电子锌碘电池机制，且进一步提出了一种适配所述全新机制的能够稳定I +的电解液。以所述的I +稳定剂为Cl-为例，其创新地选取了在水中溶解度较大的Cl-作为电解质，它们在水溶液中能够提供稳定I +所需的Cl -并与之形成卤素互化物（Interhalogen compound），此外，较高浓度的氯化物能够降低溶液中水的活度，从而抑制I +的水解。此外，进一步优选添加有机溶剂，且有助于进一步协同改善I +，改善所述全新机制下的水系锌碘电池的性能。
有益效果
（1）本发明在行业内首创性地提出了一种全新的I -/I 2/I +的四电子转换反应机制的水系锌碘电池；且发现该全新机制的水系锌碘电池具有更优的电化学性能；例如，具有更优的容量以及电流密度。研究表明，所制备的电池实现了I -/I 2/I +的四电子反应，相较于传统锌碘电池比容量提高了一倍，高倍率性能和循环寿命都得到改善。
（2）：本发明还提供了一种可形成所述全新四电子转换反应机制的水系锌碘电池电解液，其通过Zn 2+、I +稳定剂以及浓度的联合控制，能够改变反应机制，产生基于I -/I 2/I +的可逆电化学反应的四电子锌碘电池机制，并能够有效避免I +的水解、改善其稳定性，此外，还能够有效改善I -/I 2/I +的可逆电化学反应活性以及降低锌枝晶形成，能够克服现有常规锌碘电池性能瓶颈，显著改善电化学性能。
（3）本发明中，在所述的电解液中进一步配伍所述的有机溶剂，有助于进一步改善I -/I 2/I +的四电子反应活性，有助于进一步改善该全新机制下的电池的电化学性能。
附图说明
图1为实施例1（ZnCl2:LiCl:ACN:H2O, 19:19:8:55.6）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图2为对比例1（1m ZnSO 4）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图3为实施例1-1（10m ZnCl 2）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图4为实施例1-2（1M ZnSO 4 + 10M LiCl）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图5为实施例1-3（1M Zn(TFSI) 2 + 10M LiCl）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图6为实施例1-4（20M ZnCl 2 + 3M KCl）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图7为实施例1-5（20M ZnCl 2 + 3M TEAC）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图8为实施例1-6（（15M ZnCl 2 + 15M LiCl）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图9为实施例1-7（ZnCl 2:LiCl:ACN:H2O, 30:19:8:55.6）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图10为实施例1-8（ZnCl 2:LiCl:ACN:H2O, 30:19:8:55.6）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图11为实施例1-9（ZnCl 2:LiCl:ACN:H 2O, 19:19:5:55.6）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图12为实施例1-10（ZnCl 2:LiCl:THF:H 2O, 19:19:8:55.6）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图13为实施例1-11（ZnCl 2:LiCl:DME:H 2O, 10:10:8:55.6）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图14为对比例1-1（ZnTFSI:LiTFSI:H 2O, 1:20:55.6）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图15为实施例1-12（10m ZnCl 2 + 0.8m pyridine）的电解液组装的锌碘电池在400mA g -1电流密度下的充放电曲线图。
图16为实施例1和对比例1、实施例1-1组装的锌碘电池在0.5mV s -1扫速下的循环伏安曲线图。
图17为实施例1组装的锌碘电池的高倍率（2000mA g -1）循环性能图。
图18为实施例2和对比例2组装的Zn||Zn对称电池的电压-时间图，沉积/溶解电流密度为1mA cm -2，沉积/溶解时间为10min。
图19为实施例2和对比例2组装的Zn||Zn对称电池的SEM图。
图20为实施例3组装的原位电池的充放电曲线和对应的原位拉曼光谱图。
图21为对比例3组装的原位电池的充放电曲线和对应的原位拉曼光谱图。
 本发明的实施方式
实施例 1。
将300mg 高比表面积活性碳与100mg单质碘加入20ml去离子水中混合，密封后加热至60℃保持12h，然后将该悬浊液5000转离心，弃置上清液，下层混合物在60℃烘箱中热处理12h后得到碘-活性碳复合物作为活性物质。将活性物质、Super P、CMC按8:1:1质量比混合加水研磨成浆料并涂在钛箔上，60℃干燥后得到正极极片。负极为干净的锌片。电解液为ZnCl 2:LiCl:ACN:H 2O按19:19:8:55.6物质的量比配制的水溶液（ZnCl 2摩尔浓度为19M；LiCl摩尔浓度为19M；ACN摩尔浓度为8M）。组装成Swagelok电池。在400mA g -1电流密度下的充放电曲线图见图1。首圈放电容量为594mAh g -1；100放电容量为572mAh g-1；库伦效率为98.5%；放电平台1.65,1.15V。
对比例 1。
和实施例1相比区别在于，电解液为常规水系锌碘电池电解液：1M ZnSO 4；其余步骤相同。在400mA g -1电流密度下的充放电曲线图见图2。首圈放电容量为308mAh g -1；100放电容量为277mAh g-1；库伦效率为83.2%；放电平台1.2V。
实施例 1-1。
和实施例1相比区别在于，电解液为纯氯化锌水溶液：10M ZnCl 2；其余步骤相同；在400mA g -1电流密度下的充放电曲线图见图3。首圈放电容量为466mAh g -1；100放电容量为373mAh g-1；库伦效率为69.4%；放电平台1.7,1.2V。
实施例 1-2。
和实施例1相比区别在于，电解液为1M ZnSO4 + 10M LiCl水溶液（改变Zn源）。在400mA g -1电流密度下的充放电曲线图见图4。首圈放电容量为439mAh g -1；100放电容量为311mAh g-1；库伦效率为96.1%；放电平台1.65,1.2V。
实施例 1-3。
和实施例1相比区别在于，电解液为1M Zn(TFSI)2 + 10M LiCl水溶液（改变Zn源）；其余步骤相同。在400mA g -1电流密度下的充放电曲线图见图5。首圈放电容量为423mAh g -1；100放电容量为292mAh g-1；库伦效率为90.5%；放电平台1.65,1.2V。
实施例 1-4。
和实施例1相比区别在于，电解液为20M ZnCl2 + 3M KCl水溶液（改变Cl源）。其余步骤相同。在400mA g -1电流密度下的充放电曲线图见图6。首圈放电容量为535mAh g -1；100放电容量为409mAh g-1；库伦效率为93.4%；放电平台1.65,1.15V。
实施例 1-5。
和实施例1相比区别在于，电解液为20M ZnCl2 + 3M TEAC（四乙基氯化铵）水溶液（改变Cl源）；其余步骤相同。在400mA g -1电流密度下的充放电曲线图见图7。首圈放电容量为548mAh g -1；100放电容量为399mAh g-1；库伦效率为87.7%；放电平台1.65,1.15V。
实施例 1-6。
和实施例1相比区别在于，电解液为不添加任何有机添加剂的ZnCl2和LiCl（摩尔比1:1）饱和溶液，实际浓度为15M ZnCl2 + 15M LiCl的水溶液。在400mA g -1电流密度下的充放电曲线图见图8。首圈放电容量为524mAh g -1；100放电容量为442mAh g-1；库伦效率为84.2%；放电平台1.65,1.15V。
实施例 1-7。
和实施例1相比区别在于，电解液为ZnCl2:LiCl:ACN:H2O按30:19:8:55.6物质的量比配制的水溶液。在400mA g -1电流密度下的充放电曲线图见图9。（改变最佳体系Zn源浓度）；首圈放电容量为470mAh g -1；100放电容量为346mAh g-1；库伦效率为99.2%；放电平台1.65,1.05V。
实施例 1-8。
和实施例1相比区别在于，电解液为ZnCl2:LiCl:ACN:H2O按19:5:8:55.6物质的量比配制的水溶液。在400mA g -1电流密度下的充放电曲线图见图10。（改变最佳体系Li源浓度）；首圈放电容量为522mAh g -1；100放电容量为387mAh g-1；库伦效率为83.3%；放电平台1.65,1.15V。
实施例 1-9。
和实施例1相比区别在于，电解液为ZnCl2:LiCl:ACN:H2O按19:19:5:55.6物质的量比配制的水溶液。在400mA g -1电流密度下的充放电曲线图见图11。（改变最佳体系有机添加剂浓度）；首圈放电容量为537mAh g -1；100放电容量为420mAh g-1；库伦效率为98.8%；放电平台1.65,1.15V。
实施例 1-10。
和实施例1相比区别在于，电解液为ZnCl2:LiCl:THF:H2O按19:19:8:55.6物质的量比配制的水溶液。在400mA g -1电流密度下的充放电曲线图见图12。（改变最佳体系有机添加剂源）；首圈放电容量为515mAh g -1；100放电容量为396mAh g-1；库伦效率为86.6%；放电平台1.65,1.15V。
实施例 1-11。
和实施例1相比区别在于，电解液为ZnCl2:LiCl:DME:H2O按10:10:8:55.6物质的量比配制的水溶液。在400mA g -1电流密度下的充放电曲线图见图13。（改变最佳体系添有机加剂源，锌盐锂盐在DME溶解度原因，无法配制同样浓度）；首圈放电容量为474mAh g -1；100放电容量为367mAh g-1；库伦效率为82.4%；放电平台1.65,1.15V。
对比例 1-1。
和实施例1相比区别在于，电解液为ZnTFSI:LiTFSI:H2O按1:20:55.6物质的量比配制的水溶液。在400mA g -1电流密度下的充放电曲线图见图14。（高浓度盐不含Cl-的案例）。首圈放电容量为295mAh g -1；100放电容量为266mAh g-1；库伦效率为98.9%；放电平台1.2V。
实施例 1-12。
和实施例1-1相比区别在于，电解液为10m ZnCl 2 + 0.8m Pyridine的水溶液，在400mA g -1电流密度下的充放电曲线图见图15。首圈放电容量为515mAh g -1；100放电容量为435mAh g-1；库伦效率为92.7%；放电平台1.65,1.15V。
图1-15为所组装电池在0.6-1.8V之间的充放电曲线，由图可知，在常规水系锌碘电池电解液以及锌系不含Cl的高浓盐条件下（对比例1和对比例1-1），放电只有一个低电压平台（代表I -/I 2转化）。而当溶液含有Cl -时（实施例1-1至1-11），充放电均出现2个平台，分别代表I-/I 2和I 2/I +的转化。其中，低Cl-浓度电解液体系（实施例1-2和1-3）的高电压放电平台：低电压放电平台的比值明显小于高Cl-浓度电解液体系（实施例1-4至1-11），说明Cl-浓度对I+的稳定起到关键作用。改变最佳体系的锌盐（实施例1-7）、锂盐（实施例1-8）、有机溶剂（实施例1-9）的浓度，电池性能均降低。只有在实施例1中，电池高阶和低阶电压平台明显且比例接近，库伦效率高，放电容量达到了594mAh g -1，代表着该体系下完全可逆的四电子转化的实现。（具体电化学性能见表1）。
Figure 307515dest_path_image001
。
表1。
图16为实施例1、对比例1以及实施例1-1所组装电池的循环伏安曲线，扫描速度0.5mV s -1，实施例1-1和实施例1均出现2对氧化还原峰，而对比例1只在低电位下出现氧化还原峰。
图17为实施例1电池的高倍率循环性能（2000mA g -1），在该倍率条件下，循环6000次后，电池容量仍能够达到420mAh g -1以上。
实施例 2。
以干净的锌片作为工作电池和对电极，在如下电解液进行Swagelok电池组装，随后进行锌沉积测试实验。循环后的电极处理后拍摄SEM。
电解液：与实施例1一致。
对比例 2。
电解液：与对比例1一致。
其余步骤与实施例2相同。
图18为所组装的Zn||Zn对称电池的电化学性能，可以看出，实施例2锌的沉积/溶解极化要小于对比例2，且实施例2循环1000h以上电池仍未短路，对比例2只能循环400h左右。
图19为所组装的Zn||Zn对称电池循环10h后锌片的SEM图，实施例2电极表面比对比例2要更光滑，且对比例2表面有明显枝晶生成。
实施例 3。
将正极浆料滴在玻碳电极上烘干后在如下电解液中进行原位电池组装，对电极为铂丝，参比电极为Ag/AgCl电极。组装后的电池进行原位拉曼测试。
电解液：与实施例1一致。
对比例 3。
电解液：与对比例1一致。
其余步骤与实施例3相同。
图20为实施例3的充放电曲线和对应的原位拉曼光谱。随着充电深度增加，在200cm -1附近逐渐出现信号峰，对应I-Cl的伸缩振动，该信号峰在充电截止时强度达到最大，随后放电过程中信号逐渐减弱并最终消失，对应I +/I 2的转换结束。
图21为对比例3的充放电曲线和对应的原位拉曼光谱。可以看出，在整个充放电过程中，没有I-Cl的伸缩振动信号，结合前文的电化学表征可以得出，在该体系下，只有I-/I 2的转换是可逆的。

Claims (10)

  1. 一种基于四电子转换反应的水系锌碘电池的电解液，其特征在于，其为含有Zn 2+、I +稳定剂的水系溶液；
    所述的I +稳定剂为能在充、放电过程中与I +生成电子转移化合物的的阴离子或者亲核水溶性溶剂；
    所述的电解液中，Zn 2+、I +稳定剂的总摩尔浓度不低于5 M。
  2. 如权利要求1所述的基于四电子转换反应的水系锌碘电池的电解液，其特征在于，所述的Zn 2+由在常温下水中溶解度不低于100 g/L的水溶性锌离子源电离提供；
    优选地，所述的水溶性锌离子源为氯化锌、硝酸锌、硫酸锌、醋酸锌、双三氟甲磺酰亚胺锌（Zn(TFSI) 2）、三氟甲基磺酸锌（Zn(OTf) 2）及其水合物中的至少一种。
  3. 如权利要求1所述的基于四电子转换反应的水系锌碘电池的电解液，其特征在于，所述的I +稳定剂中的阴离子为Cl-和/或CN-；
    所述的I +稳定剂中的亲核水溶性溶剂为四氢呋喃、吡啶、胺、醚、酯中的至少一种；
    进一步优选，所述的I +稳定剂为Cl-；
    所述的Cl-由能在水中电离出Cl -的水溶性氯离子源电离提供；优选地，所述的水溶性氯离子源为在常温下水中溶解度不低于100 g/L的水溶性盐；进一步优选为氯化锌、氯化锂、氯化钠、氯化钾、四乙基氯化铵（TEAC）、氯化铵中的至少一种。
    所述的CN-由能在水中电离出CN-的水溶性氰基化合物提供；优选地，所述的水溶性氰离子源为在常温下水中溶解度不低于100 g/L的水溶性盐；进一步优选氰化钠、氰化钾、腈类化合物中的至少一种。
  4. 如权利要求1所述的基于四电子转换反应的水系锌碘电池的电解液，其特征在于，所述的电解液中，Zn 2+、I +稳定剂的总摩尔浓度不低于10 M；进一步优选为15~90M；
    优选地，所述的电解液中，I +稳定剂/锌离子的摩尔比大于等于1；优选大于等于2；进一步优选的摩尔比为2~3:1；
    进一步优选，电解液中，Zn 2+的浓度不低于5M；优选为5~30M；更进一步优选为10~20M；
    优选地，所述的电解液中，I +稳定剂的摩尔浓度不低于10M；进一步优选为10~60M。
  5. 如权利要求1~4任一项所述的基于四电子转换反应的水系锌碘电池的电解液，其特征在于，电解液中，还添加有有机溶剂，所述的有机溶剂为能与水互溶、且不参与充放电反应的有机溶剂；
    优选地，所述的有机溶剂为乙腈（ACN）、乙二醇二甲醚（DME）、二氧戊烷（DOL）、四氢呋喃（THF）、1,4-二氧六环（DX）中的至少一种。
  6. 如权利要求5所述的基于四电子转换反应的水系锌碘电池的电解液，其特征在于，所述电解液中，有机溶剂与水的摩尔比为0.1~0.5。
  7. 一种基于四电子转换反应的水系锌碘电池，其包括正极、负极、将正极和负极分隔的隔膜；以及浸泡正极、负极、隔膜的电解液；其特征在于，在工作时正极发生I -/I 2/I +的可逆电化学反应。
  8. 如权利要求7所述的基于四电子转换反应的水系锌碘电池，其特征在于，其正极反应的反应式为：
    电池工作时正极发生如下反应：
    2 I - ↔ I 2 + 2 e-   Eo = 0.53 V vs. SHE
    I 2 + 2 Cl- ↔ 2 ICl + 2 e-  Eo = 1.07 V vs. SHE。
  9. 如权利要求7或8所述的基于四电子转换反应的水系锌碘电池，其特征在于，所述的电解液为权利要求1~6任一项所述的电解液。
  10. 如权利要求7~9任一项所述的基于四电子转换反应的水系锌碘电池，其特征在于，所述的正极为负碘多孔材料；其包括多孔材料以及负载在其中的碘单质；
    优选地，所述的多孔材料为多孔活性碳、介孔碳、碳纤维布、MOFs、石墨烯、氧化石墨烯的一种或几种；
    优选地，所述的负碘多孔材料中，碘含量为20-50%（质量分数）；
    优选地，所述的负极为锌单质负极；
    优选地，隔膜为玻璃纤维/定性滤纸的一种。
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