Eutectic solvent electrolyte for zinc-iodine battery as well as preparation method and application of eutectic solvent electrolyte

Abstract

The invention discloses a deep eutectic solvent electrolyte for a zinc-iodine battery as well as a preparation method and application of the deep eutectic solvent electrolyte. The electrolyte comprises a deep eutectic solvent and zinc iodide; wherein the eutectic solvent comprises a hydrogen bond acceptor which is selected from choline chloride; the invention discloses a low-eutectic solvent, which comprises the following components in percentage by mass: 1-50 percent of low-eutectic solvent, 1-50 percent of hydrogen bond donor and 1-50 percent of deionized water. According to the technical scheme provided by the invention, the problems of Zn dendritic crystal, iodine shuttling and the like caused by the aqueous zinc-iodine battery electrolyte are well solved, and the zinc-iodine battery containing the electrolyte has the characteristics of high battery capacity, high coulombic efficiency, long cycle life and the like.

Description

Technical Field

[0001] The present invention relates to the fields of new electrochemical cells and new energy batteries. More specifically, it relates to a deep eutectic solvent electrolyte for zinc-iodine batteries, its preparation method and application. Background Art

[0002] Aqueous zinc-ion secondary batteries have the advantages of high safety performance, low raw material cost, and environmental friendliness. They are considered to be strong competitors for the next generation of new energy batteries and an important way to serve the "dual carbon" strategy and achieve "new energy + energy storage". However, the low voltage window of aqueous electrolytes, as well as the side reactions such as passivation, corrosion, and hydrogen evolution during the deposition and stripping of zinc, and the dendrite growth caused by uneven zinc deposition, lead to battery capacity attenuation, low coulombic efficiency, and limited lifespan.

[0003] In addition, the current cathode materials for such batteries mainly include manganese-based materials, vanadium-based materials, Prussian blue analogs, organic compounds, etc. They still have certain deficiencies in terms of cost, capacity, stability, and energy density. Using the redox process of halogen elements such as iodine to achieve energy storage and release is another feasible way. Due to its wide source, low cost, environmental friendliness, etc., and being a multi-electron transfer reaction with a highly reversible redox process, relatively high specific capacity and energy density, it has been widely studied as a cathode material for aqueous zinc-ion batteries in recent years. For electrolytes with high water content, they have a high solubility for iodides, and the active substance iodine will quickly be lost from the cathode, resulting in a series of problems such as poor cycle stability and inferior rate performance. Based on this, seeking a suitable anhydrous or low-water-content electrolyte for the preparation of zinc-iodine batteries has become an important research direction.

[0004] In recent years, a new type of "green solvent" - deep eutectic solvents (DESs), which are two-component or three-component eutectic mixtures composed of a certain stoichiometric ratio of hydrogen bond acceptors, such as quaternary ammonium salts, and hydrogen bond donors, such as amides, carboxylic acids, and polyols, etc. Their melting points are significantly lower than those of the pure substances of each component. Due to their characteristics such as cheap and easily available raw materials, simple preparation, stable physical and chemical properties, adjustable structural properties, good conductivity, non-volatile, non-flammable, and biodegradable, they have received extensive attention from scholars in the field of electrochemistry. However, due to the relatively high viscosity of deep eutectic solvents themselves, the resistance to ion movement is too large, which is not conducive to the transport of active ions in them, thus limiting their application scope. Summary of the Invention

[0005] Based on the above facts, the object of the present invention is to provide a deep eutectic solvent electrolyte for zinc-iodine batteries, a preparation method and an application thereof, so as to solve at least the problems of Zn dendrites and iodine shuttling caused by the electrolyte of aqueous zinc-iodine batteries. The zinc-iodine battery containing this electrolyte has characteristics such as high battery capacity, high Coulombic efficiency, good stability and long cycle life.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] On the one hand, the present invention provides a deep eutectic solvent electrolyte for zinc-iodine batteries, and the electrolyte contains a deep eutectic solvent and zinc iodide; wherein,

[0008] The deep eutectic solvent contains:

[0009] A hydrogen bond acceptor, selected from choline chloride;

[0010] A hydrogen bond donor, and

[0011] Deionized water, wherein, in the deep eutectic solvent, the mass percentage content of deionized water is 1-50 wt%.

[0012] In the present invention, it is found through research that choline chloride is particularly suitable for the electrolyte of zinc-iodine batteries, making the electrolyte have appropriate viscosity and good ion transport rate.

[0013] Further, in the deep eutectic solvent, the mass percentage content of deionized water is 1-15 wt%. At this time, after the obtained deep eutectic solvent electrolyte is used in a zinc-iodine battery, the obtained zinc-iodine battery has higher battery capacity and Coulombic efficiency, and also has a longer cycle life. In some specific examples, the mass percentage content of deionized water in the deep eutectic solvent includes but is not limited to 1-10 wt%, 1-5 wt%, 1-2 wt%, 1-8 wt%, 2-10 wt%, 2-5 wt%, 5-10 wt%, 5-8 wt%, 2 wt%, 5 wt%, 10 wt%, etc., and more preferably 1-8 wt%. At this time, the above-mentioned effects are better.

[0014] Further, the hydrogen bond donor is selected from one of urea, acetamide, N-methylacetamide, N,N-diethylacetamide, ethylenediamine, N-ethylethylenediamine, N,N-diethylethylenediamine and isopropylamine.

[0015] Further, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:5 to 5:1. In some examples, the molar ratio of the hydrogen bond acceptor to the hydrogen bond donor includes but is not limited to 1:0.5 to 1:5, 1:1 to 1:5, 1:2 to 1:5, 1:0.5 to 1:2, 1:1 to 1:2, 1:1.5 to 1:2, 1:2, etc. Preferably, it is 1:1 to 1:2, more preferably 1:1.5 to 1:2, and most preferably 1:2. At this time, it can well ensure that the obtained eutectic solvent is a liquid-phase solvent; at the same time, it makes the electrolyte have appropriate viscosity, good ion transport rate, and long cycle stability.

[0016] If the concentration of zinc iodide is too low, there is not enough active substance for the reaction, resulting in a low energy density of the battery; if it is too high (high-concentration salt system), it will affect the ionic conductivity, thereby affecting the rate performance of the battery and increasing the cost. Further, in the electrolyte, the content of zinc iodide is 0.1 mol / L to 0.5 mol / L. In some specific examples, in the electrolyte, the content of zinc iodide includes but is not limited to 0.2 mol / L to 0.5 mol / L, 0.2 mol / L to 0.4 mol / L, 0.1 mol / L to 0.2 mol / L, 0.4 mol / L to 0.5 mol / L, 0.2 mol / L, 0.4 mol / L, etc.

[0017] On the other hand, the present invention provides a method for preparing the eutectic solvent electrolyte as described above, and the preparation method includes the following steps:

[0018] Dissolve solid zinc iodide into the eutectic solvent to obtain the eutectic solvent electrolyte.

[0019] Further, the preparation of the eutectic solvent includes the following steps:

[0020] After mixing the hydrogen bond acceptor and the hydrogen bond donor, add deionized water, and after heating and stirring evenly, obtain the eutectic solvent.

[0021] Further, the temperature of the heating and stirring is 50 to 120 °C, and the time is 10 min to 2 h. In some preferred examples, the temperature of the heating and stirring is 60 to 80 °C, and the time is 20 min to 40 min.

[0022] Further, the method of dissolving solid zinc iodide into the eutectic solvent can be achieved by heating and stirring. The temperature of the heating and stirring is 50 to 120 °C, and the time is 10 min to 2 h. In some preferred examples, the temperature of the heating and stirring is 60 to 80 °C, and the time is 20 min to 40 min.

[0023] On the other hand, the present invention provides a zinc-iodine battery, and the zinc-iodine battery contains the eutectic solvent electrolyte as described above.

[0024] Furthermore, the zinc-iodine battery is a button battery.

[0025] It can be understood that in the zinc-iodine battery, a positive electrode battery case and a negative electrode battery case buckled with the positive electrode battery case are included; wherein, a shrapnel, a gasket, a zinc negative electrode, a separator, the above-mentioned eutectic solvent electrolyte, and a positive electrode current collector are sequentially arranged in the positive electrode motor case.

[0026] Furthermore, the zinc negative electrode is selected from at least one of zinc foil, zinc plate, zinc sheet, zinc powder, electrogalvanized zinc, foam zinc, zinc alloy or zinc elemental material.

[0027] Furthermore, the separator is selected from at least one of ordinary filter paper, aqueous filter paper or glass fiber filter paper;

[0028] The positive electrode current collector is at least one of carbon cloth, carbon paper or carbon felt

[0029] On the other hand, the present invention provides an application of the above-mentioned eutectic solvent electrolyte in the preparation of a zinc-iodine battery.

[0030] The beneficial effects of the present invention are as follows:

[0031] The eutectic solvent electrolyte for zinc-iodine battery provided by the present invention has multifunctional characteristics of alleviating dendrite growth, inhibiting corrosion, hydrogen evolution and other side reactions, and significantly improves the cycle life and Coulomb efficiency of rechargeable secondary zinc batteries at high current densities. In addition, the eutectic solvent electrolyte is a non-flammable substance and has higher safety compared with organic electrolytes / ionic liquid electrolytes. Furthermore, in the eutectic solvent electrolyte, by adding a small amount of deionized water to the eutectic solvent, on the one hand, the viscosity of the synthesized eutectic solvent is reduced, and the transmission resistance of zinc ions is reduced; on the other hand, the lower water content is beneficial to reducing the loss of iodine in the positive electrode reaction, so that the whole system operates stably.

[0032] In the preparation of the eutectic solvent electrolyte provided by the present invention, the raw materials are widely sourced, the cost is low, the preparation method has simple processes, a short cycle and is environmentally friendly, and it is easy to mass-produce.

[0033] The present invention can realize the charge and discharge reactions of the positive and negative electrodes only with the synthesized eutectic solvent electrolyte. The raw material cost is low, and the battery assembly steps are simple, and it is expected to be industrialized. Description of the Drawings

[0034] The following further details the specific embodiments of the present invention with reference to the drawings.

[0035] Figure 1 Shows the GVD curves of the zinc-iodine battery assembled in Example 1 of the present invention at the 100th, 200th, and 300th cycles.

[0036] Figure 2 Show the scanning electron microscope images of the Zn surface after the zinc-iodine battery assembled in Example 1 of the present invention has been cycled 50 times.

[0037] Figure 3 Show the optical photograph of the Zn negative electrode sheet after the zinc-iodine battery assembled in Example 1 of the present invention has been cycled 50 times.

[0038] Figure 4 Show the GVD curve graphs of the zinc-iodine battery assembled in Example 2 of the present invention at the 100th, 200th, and 300th cycles.

[0039] Figure 5 Show the optical photograph of the etched Zn negative electrode sheet after the zinc-iodine battery assembled in Example 2 of the present invention has been cycled 50 times.

[0040] Figure 6 Show the scanning electron microscope images of the Zn surface after the zinc-iodine battery assembled in Comparative Example 1 of the present invention has been cycled 50 times.

[0041] Figure 7 Show the optical photograph of the Zn negative electrode sheet after the zinc-iodine battery assembled in Comparative Example 1 of the present invention has been cycled 50 times.

[0042] Figure 8 Show the GVD curve graphs of the zinc-iodine battery assembled in Comparative Example 2 of the present invention at the 10th, 20th, and 50th cycles.

[0043] Figure 9 Show the scanning electron microscope images of the Zn surface after the zinc-iodine battery assembled in Comparative Example 2 of the present invention has been cycled 50 times.

[0044] Figure 10 Show the optical photograph of the Zn negative electrode sheet after the zinc-iodine battery assembled in Comparative Example 2 of the present invention has been cycled 50 times.

[0045] Figure 11 Show the GVD curve graphs of the zinc-iodine battery assembled in Comparative Example 3 of the present invention at the 10th, 20th, and 50th cycles. Detailed implementation manners

[0046] To illustrate the present invention more clearly, the present invention will be further described below in conjunction with preferred embodiments and the accompanying drawings. Similar components in the drawings are denoted by the same reference numerals. Those skilled in the art should understand that the content specifically described below is illustrative rather than restrictive, and should not be used to limit the protection scope of the present invention.

[0047] Example 1

[0048] A preparation method of a deep eutectic solvent electrolyte for a zinc-iodine battery, comprising the following steps:

[0049] Weigh choline chloride and urea solids with a molar ratio of 1:2, add deionized water with a mass fraction of 5% (where the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids and deionized water), heat at 80 °C for 30 min, after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the eutectic solvent electrolyte.

[0050] The preparation of the zinc-iodine battery includes the following steps:

[0051] In the positive electrode case of the battery, add a shrapnel, a gasket, a zinc sheet, ordinary filter paper, 70 μL of the above-mentioned eutectic solvent electrolyte, carbon cloth in sequence, and then fasten the negative electrode case to assemble a button battery for electrochemical performance testing.

[0052] The GVD curves of the zinc-iodine battery at the 100th, 200th, and 300th cycles are as Figure 1 shown. It can be seen from the figure that the discharge capacity of the zinc-iodine battery is 0.108 mAh and the Coulomb efficiency is 95%.

[0053] After the zinc-iodine battery is cycled 50 times, the scanning electron microscope image of the Zn surface is as Figure 2 shown. It can be seen from this figure that the surface of the Zn negative electrode is flat and there is no obvious corrosion.

[0054] After the zinc-iodine battery is cycled 50 times, the optical photo of the Zn negative electrode sheet is as Figure 3 shown. It can be seen from this figure that the Zn sheet after cycling still has metallic luster and no corrosion.

[0055] Example 2

[0056] A preparation method of a eutectic solvent electrolyte for a zinc-iodine battery includes the following steps:

[0057] Weigh choline chloride and urea solids with a molar ratio of 1:2, add deionized water with a mass fraction of 10% (where the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids and deionized water), heat at 80 °C for 30 min, after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the eutectic solvent electrolyte.

[0058] The preparation of the zinc-iodine battery includes the following steps:

[0059] In the positive electrode case of the battery, add a shrapnel, a gasket, a zinc sheet, ordinary filter paper, 70 μL of the above-mentioned eutectic solvent electrolyte, carbon cloth in sequence, and then fasten the negative electrode case to assemble a button battery for electrochemical performance testing.

[0060] The GVD curves of the zinc-iodine battery at the 100th, 200th, and 300th cycles are as follows Figure 4 shown. It can be seen from the figure that the discharge capacity of the zinc-iodine battery is 0.102 mAh and the Coulombic efficiency is 91%.

[0061] After the zinc-iodine battery is cycled 50 times, the optical photograph of the Zn negative electrode sheet is as follows Figure 5 shown. It can be seen from this figure that most of the Zn sheets after cycling retain metallic luster and are slightly corroded.

[0062] Example 3

[0063] A preparation method of a deep eutectic solvent electrolyte for a zinc-iodine battery includes the following steps:

[0064] Weigh choline chloride and urea solids with a molar ratio of 1:2, add deionized water with a mass fraction of 2% (where the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids, and deionized water), heat at 80 °C for 30 min, and after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the deep eutectic solvent electrolyte.

[0065] The preparation of a zinc-iodine battery includes the following steps:

[0066] Add a shrapnel, a gasket, a zinc sheet, a common filter paper, 70 μL of the above deep eutectic solvent electrolyte, a carbon cloth into the battery positive electrode case in sequence, and then buckle the negative electrode battery case to assemble a button battery for electrochemical performance testing.

[0067] After the zinc-iodine battery is cycled 300 times, the discharge capacity is 0.109 mAh and the Coulombic efficiency is 97%.

[0068] After the zinc-iodine battery is cycled 50 times, the Zn sheet still has metallic luster and no corrosion.

[0069] Example 4

[0070] A preparation method of a deep eutectic solvent electrolyte for a zinc-iodine battery includes the following steps:

[0071] Weigh choline chloride and urea solids with a molar ratio of 1:2, add deionized water with a mass fraction of 5% (where the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids, and deionized water), heat at 80 °C for 30 min, and after mixing evenly, add potassium iodide solid to make its concentration 0.5 mol / L, and then heat and stir at 80 °C for 30 min to obtain the deep eutectic solvent electrolyte.

[0072] The preparation of a zinc-iodine battery includes the following steps:

[0073] In the positive electrode shell of the battery, a shrapnel, a gasket, a zinc sheet, ordinary filter paper, 70 μL of the above-mentioned eutectic solvent electrolyte, carbon cloth are added in sequence, and then the negative electrode battery shell is buckled to assemble a button battery, and the electrochemical performance is tested.

[0074] After the zinc-iodine battery is cycled 300 times, the discharge capacity is 0.112 mAh and the Coulomb efficiency is 90%.

[0075] After the zinc-iodine battery is cycled 50 times, the Zn sheet still has a metallic luster and no corrosion.

[0076] Example 5

[0077] A preparation method of a eutectic solvent electrolyte for a zinc-iodine battery includes the following steps:

[0078] Weigh choline chloride and acetamide solids with a molar ratio of 1:2, add deionized water with a mass fraction of 5% (wherein, the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids and deionized water), heat at 80 °C for 30 min, after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the eutectic solvent electrolyte.

[0079] The preparation of the zinc-iodine battery includes the following steps:

[0080] In the positive electrode shell of the battery, a shrapnel, a gasket, a zinc sheet, ordinary filter paper, 70 μL of the above-mentioned eutectic solvent electrolyte, carbon cloth are added in sequence, and then the negative electrode battery shell is buckled to assemble a button battery, and the electrochemical performance is tested.

[0081] After the zinc-iodine battery is cycled 300 times, the discharge capacity is 0.106 mAh and the Coulomb efficiency is 94%.

[0082] After the zinc-iodine battery is cycled 50 times, the Zn sheet still has a metallic luster and no corrosion.

[0083] Example 6

[0084] A preparation method of a eutectic solvent electrolyte for a zinc-iodine battery includes the following steps:

[0085] Weigh choline chloride and N-methylacetamide solids with a molar ratio of 1:2, add deionized water with a mass fraction of 5% (wherein, the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids and deionized water), heat at 80 °C for 30 min, after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the eutectic solvent electrolyte.

[0086] Preparation of zinc-iodine battery, comprising the following steps:

[0087] In the positive electrode case of the battery, a shrapnel, a gasket, a zinc sheet, a common filter paper, 70 μL of the above-mentioned eutectic solvent electrolyte, a carbon cloth are sequentially added, and then the negative electrode case is buckled to assemble a button battery for electrochemical performance testing.

[0088] After the zinc-iodine battery is cycled 300 times, the discharge capacity is 0.108 mAh and the Coulomb efficiency is 94%.

[0089] After the zinc-iodine battery is cycled 50 times, the Zn sheet still has a metallic luster and no corrosion.

[0090] Example 7

[0091] A preparation method of a eutectic solvent electrolyte for a zinc-iodine battery, comprising the following steps:

[0092] Weigh choline chloride and urea solids with a molar ratio of 1:1, add deionized water with a mass fraction of 5% (wherein, the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids and deionized water), heat at 80 °C for 30 min, after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the eutectic solvent electrolyte.

[0093] Preparation of zinc-iodine battery, comprising the following steps:

[0094] In the positive electrode case of the battery, a shrapnel, a gasket, a zinc sheet, a common filter paper, 70 μL of the above-mentioned eutectic solvent electrolyte, a carbon cloth are sequentially added, and then the negative electrode case is buckled to assemble a button battery for electrochemical performance testing.

[0095] After the zinc-iodine battery is cycled 300 times, the discharge capacity is 0.099 mAh and the Coulomb efficiency is 92%.

[0096] After the zinc-iodine battery is cycled 50 times, most of the Zn sheet after cycling retains a metallic luster and has slight corrosion.

[0097] Comparative Example 1

[0098] A preparation method of a eutectic solvent electrolyte for a zinc-iodine battery, comprising the following steps:

[0099] Weigh choline chloride and urea solids with a molar ratio of 1:2, add deionized water with a mass fraction of 20% (wherein, the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids and deionized water), heat at 80 °C for 20 min, after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the eutectic solvent electrolyte.

[0100] Preparation of the zinc-iodine battery includes the following steps:

[0101] In the positive electrode case of the battery, a shrapnel, a gasket, a zinc sheet, a common filter paper, 70 μL of the above-mentioned deep eutectic solvent electrolyte, a carbon cloth are sequentially added, and then the negative electrode case is buckled to assemble a button battery, and the electrochemical performance is tested.

[0102] After the zinc-iodine battery is cycled 50 times, the scanning electron microscope image of the Zn surface is as Figure 6 shown. It can be seen from Figure 6 that the surface of the Zn negative electrode is uneven and is corroded to a certain extent.

[0103] After the zinc-iodine battery is cycled 50 times, the optical photograph of the Zn negative electrode sheet is as Figure 7 shown. It can be seen from Figure 7 that the Zn sheet becomes darker after cycling, has no metallic luster, and is severely corroded.

[0104] Comparative Example 2

[0105] A preparation method of a deep eutectic solvent electrolyte for a zinc-iodine battery includes the following steps:

[0106] Weigh choline chloride and urea solids with a molar ratio of 1:2, add deionized water with a mass fraction of 50% (wherein, the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids and deionized water), heat at 80 °C for 10 min, after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the deep eutectic solvent electrolyte.

[0107] Preparation of the zinc-iodine battery includes the following steps:

[0108] In the positive electrode case of the battery, a shrapnel, a gasket, a zinc sheet, a common filter paper, 70 μL of the above-mentioned deep eutectic solvent electrolyte, a carbon cloth are sequentially added, and then the negative electrode case is buckled to assemble a button battery, and the electrochemical performance is tested.

[0109] The GVD curve diagrams of the zinc-iodine battery at the 10th, 20th, and 50th cycles are as Figure 8 shown. It can be known from this figure that the discharge capacity of the zinc-iodine battery is 0.059 mAh and the Coulomb efficiency is 52%.

[0110] After the zinc-iodine battery is cycled 50 times, the scanning electron microscope image of the Zn surface is as Figure 9 shown. It can be seen from this figure that there are obvious protrusions on the surface of the Zn negative electrode and it is severely corroded.

[0111] After the zinc-iodine battery is cycled 50 times, the optical photograph of the Zn negative electrode sheet is as Figure 10As shown. It can be seen from this figure that after cycling, the Zn sheet becomes dark, without metallic luster, and there is also yellow iodine shuttling to the surface of the negative electrode, and a serious corrosion forms a passivation layer.

[0112] Comparative Example 3

[0113] Preparation of an aqueous zinc-ion battery:

[0114] In the positive electrode case of the battery, a shrapnel, a gasket, a zinc sheet, ordinary filter paper, an electrolyte of an aqueous ZnI2 solution with a concentration of 0.2 mol / L, carbon cloth are sequentially added, and then the negative electrode case is buckled to assemble a button battery for electrochemical performance testing.

[0115] The GVD curves of the zinc-iodine battery at the 10th, 20th, and 50th cycles are as Figure 11 shown. It can be seen from this figure that the discharge capacity of the zinc-iodine battery is 0.042 mAh, and the Coulomb efficiency is 37%.

[0116] Comparative Example 4

[0117] A preparation method of an electrolyte for a zinc-iodine battery, comprising the following steps:

[0118] Weigh choline chloride and urea solids with a molar ratio of 1:10, add deionized water with a mass fraction of 5% (wherein, the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, urea solids and deionized water), heat at 80 °C for 10 min, after mixing evenly, add potassium iodide solid to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the electrolyte.

[0119] Preparation of a zinc-iodine battery, comprising the following steps:

[0120] In the positive electrode case of the battery, a shrapnel, a gasket, a zinc sheet, ordinary filter paper, 70 μL of the above electrolyte, carbon cloth are sequentially added, and then the negative electrode case is buckled to assemble a button battery for electrochemical performance testing.

[0121] Due to the too high viscosity of the electrolyte system, which affects the ionic conductivity, the battery cannot be charged and discharged cyclically.

[0122] Comparative Example 5

[0123] A preparation method of an electrolyte for a zinc-iodine battery, comprising the following steps:

[0124] Weigh choline chloride and ethylene glycol at a molar ratio of 1:2, add deionized water with a mass fraction of 5% (where the mass fraction of deionized water is the content of deionized water relative to the total mass of choline chloride, ethylene glycol, and deionized water), heat at 80 °C for 10 min, mix evenly, add solid potassium iodide to make its concentration 0.2 mol / L, and then heat and stir at 80 °C for 30 min to obtain the electrolyte solution.

[0125] The preparation of the zinc-iodine battery includes the following steps:

[0126] In the positive electrode case of the battery, add a shrapnel, a gasket, a zinc sheet, ordinary filter paper, 70 μL of the above-mentioned eutectic solvent electrolyte, carbon cloth in sequence, and then buckle the negative electrode case to assemble a button battery for electrochemical performance testing.

[0127] Since the addition of ethylene glycol will dissolve the iodine generated at the positive electrode, the battery of this system cannot be charged and discharged cyclically and is not suitable for the zinc-iodine battery system.

[0128] Comparative Example 6

[0129] Repeat Example 1, with the difference that choline chloride is replaced by tetraethylammonium chloride and the other conditions remain unchanged. The viscosity of the obtained eutectic solvent is too high and it is not suitable for further preparation of the electrolyte solution.

[0130] Obviously, the above-mentioned embodiments of the present invention are only examples for clearly explaining the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or variations can be made based on the above description. It is impossible to list all the implementation manners here. All obvious changes or variations derived from the technical solutions of the present invention still fall within the protection scope of the present invention.

Claims

1. A deep eutectic solvent electrolyte for a zinc-iodine battery, characterized in that, The electrolyte contains a deep eutectic solvent and zinc iodide; wherein, The deep eutectic solvent contains: A hydrogen bond acceptor selected from choline chloride; A hydrogen bond donor, and Deionized water, wherein the mass percentage content of deionized water in the deep eutectic solvent is 1-50 wt%.

2. The eutectic solvent electrolyte according to claim 1, wherein The hydrogen bond donor is selected from one of urea, acetamide, N-methylacetamide, N,N-diethylacetamide, ethylenediamine, N-ethylethylenediamine, N,N-diethylethylenediamine, and isopropylamine.

3. The eutectic solvent electrolyte according to claim 1, wherein The molar ratio of the hydrogen bond acceptor to the hydrogen bond donor is 1:5 to 5:

1.

4. The eutectic solvent electrolyte according to claim 1, wherein In the electrolyte, the content of zinc iodide is 0.1 mol / L to 0.5 mol / L.

5. The preparation method of the eutectic solvent electrolyte according to any one of claims 1-4, characterized in that, It includes the following steps: Dissolve solid zinc iodide into the deep eutectic solvent to obtain the deep eutectic solvent electrolyte.

6. The preparation method according to claim 5, wherein The preparation of the deep eutectic solvent includes the following steps: After mixing the hydrogen bond acceptor and the hydrogen bond donor, add deionized water, and after heating and stirring evenly, obtain the deep eutectic solvent.

7. The preparation method according to claim 6, characterized in that, The temperature of the heating and stirring is 50-120 °C, and the time is 10 min-2 h.

8. A zinc-iodine battery, characterized in that, The zinc-iodine battery contains the deep eutectic solvent electrolyte according to any one of claims 1-4.

9. The zinc-iodine battery according to claim 8, wherein, The zinc-iodine battery is a button battery.

10. Use of the deep eutectic solvent electrolyte according to any one of claims 1-4 in the preparation of a zinc-iodine battery.

Images