Biphase electrolyte, application thereof and zinc-iodine battery

Abstract

The invention provides a two-phase electrolyte, application thereof and a zinc-iodine battery, and belongs to the technical field of electrolytes. The double-phase electrolyte provided by the invention comprises an ionic liquid phase and a water phase which are arranged in a contact manner, the ionic liquid phase is a mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propyl imidazolium iodide, and the ionic liquid phase is a mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propyl imidazolium iodide; the water phase is a zinc sulfate water solution; the concentration of the zinc sulfate aqueous solution is 1-2.5 mol / L. The ionic liquid in the biphase electrolyte and the polyiodide have strong interaction, migration of the polyiodide is limited, and the stability of the polyiodide is effectively improved. The result of the embodiment shows that the double-phase electrolyte provided by the invention can stabilize the polyiodide in the ionic liquid phase of the positive electrode side, and meanwhile, the iodine can still be kept stable under the condition of 90 DEG C.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytes, and in particular to a two-phase electrolyte and application thereof and a zinc-iodine battery. Background Art

[0002] As the energy crisis and environmental pollution problems facing the world gradually intensify, countries have stepped up their efforts in the research and development and application of sustainable clean energy. Building an efficient energy storage system is a key supporting technology for realizing the large-scale utilization of clean energy; large-scale energy storage systems can effectively balance the uncertainty of renewable energy, alleviate energy volatility and intermittency, improve the reliability and stability of the power system, and achieve efficient utilization of electric energy. Although lithium-ion battery technology dominates the current market, its application in large-scale energy storage systems is still subject to certain restrictions. The zinc-iodine battery constructed with iodine and its compounds as the positive electrode, zinc metal as the negative electrode, and aqueous solvents as the electrolyte has gradually demonstrated its unique advantages. The discharge platform is high and relatively flat, so it shows a higher energy density.

[0003] However, zinc-iodine batteries still face great challenges in actual use. First, during the oxidation process of iodine, the polyiodide generated will dissolve in the aqueous electrolyte, thereby passing through the diaphragm, corroding the negative electrode, and reducing the cycle life. Second, iodine will sublime under conditions above 50°C, making zinc-iodine batteries unable to adapt to high-temperature use environments.

[0004] In order to solve the problem of polyiodide diffusion, researchers have proposed many solutions, among which the design of the electrode / electrolyte interface is an important strategy. Usually, the interface design scheme relies on the coating of special materials to adsorb polyiodides and suppress the shuttle effect. However, the adsorption process using special materials is usually irreversible. After multiple cycles, it will lead to the loss of active iodine and the decrease of interface adsorption capacity. Its stability of polyiodides still cannot meet the needs of practical applications. Summary of the invention

[0005] The purpose of the present invention is to provide a biphasic electrolyte and its application and a zinc-iodine battery. The biphasic electrolyte provided by the present invention can stabilize polyiodides and avoid the problems of iodine loss and adsorption capacity limitation caused by the use of adsorption materials, and can make the zinc-iodine battery adapt to high temperature environments.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a two-phase electrolyte, comprising an ionic liquid phase and an aqueous phase arranged in contact;

[0008] The ionic liquid phase is a mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide;

[0009] The aqueous phase is an aqueous solution of zinc sulfate;

[0010] The concentration of the zinc sulfate aqueous solution is 1-2.5 mol / L.

[0011] Preferably, the concentration of the zinc sulfate aqueous solution is 1.8-2.2 mol / L.

[0012] Preferably, the volume ratio of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide in the ionic liquid phase is (0.5-2):1.

[0013] Preferably, the volume ratio of the ionic liquid phase to the aqueous phase is 1:(1-10).

[0014] The present invention also provides the use of the biphasic electrolyte described in the above technical solution in a zinc-iodine battery, wherein the ionic liquid phase in the biphasic electrolyte is arranged on the positive electrode side of the zinc-iodine battery, and the water phase is arranged on the negative electrode side of the zinc-iodine battery.

[0015] The present invention also provides a zinc-iodine battery, comprising the biphasic electrolyte described in the above technical solution, and a positive electrode, a diaphragm and a negative electrode arranged in contact with each other from top to bottom;

[0016] The ionic liquid phase in the two-phase electrolyte is arranged on the positive electrode side, and the water phase in the two-phase electrolyte is adsorbed in the diaphragm.

[0017] Preferably, the positive electrode is an adsorption material, and the ionic liquid phase in the two-phase electrolyte is adsorbed in the positive electrode.

[0018] Preferably, the positive electrode comprises a porous carrier and a conductive agent and a binder loaded on the porous carrier, and the total loading amount of the conductive agent and the binder is 10 to 20 mg / cm 2 .

[0019] Preferably, the adsorption amount of the ionic liquid phase in the positive electrode is 10 to 30 μL.

[0020] Preferably, the diaphragm is a glass fiber diaphragm.

[0021] The invention provides a two-phase electrolyte, comprising an ionic liquid phase and an aqueous phase arranged in contact; the ionic liquid phase is a mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide; the aqueous phase is a zinc sulfate aqueous solution; the concentration of the zinc sulfate aqueous solution is 1.5-2.5 mol / L. The imidazolium cations in the ionic liquid phase of the dual-phase electrolyte of the present invention can generate electrostatic interaction with polyiodides. When in use, the ionic liquid phase is arranged on the positive electrode side to achieve fixation of the polyiodides generated at the positive electrode, while avoiding the problems of iodine loss and decreased adsorption force of the adsorption material in chemical adsorption; at the same time, the solvation between the ionic liquid phase and iodine can prevent the polyiodide molecules from escaping to the gas phase, making it stable under high temperature conditions; the phase interface formed by the ionic liquid phase of a specific composition and the zinc sulfate aqueous solution phase has polarity differences and tension gradients on both sides, which can hinder the polyiodides from shuttling and transferring to the aqueous phase. When in use, the aqueous phase is arranged at the negative electrode to avoid the polyiodides from corroding the negative electrode of the battery; by controlling the concentration of the zinc sulfate aqueous solution, it is avoided that the concentration of the zinc sulfate aqueous solution is too high to increase the chance of ion contact, so that sulfate is precipitated when the ionic liquid phase contacts the aqueous phase, deteriorating the battery performance, and it is also avoided that the zinc sulfate aqueous solution concentration is too low to cause the dual-phase electrolyte to be unable to be normally stratified, thereby further improving the performance of the dual-phase electrolyte. The results of the examples show that the dual-phase electrolyte provided by the present invention can stabilize polyiodides in the ionic liquid phase and can keep iodine stable at 90°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a macroscopic photograph of the electrolyte of Comparative Example 1;

[0023] Figure 2 This is a macroscopic photograph of the electrolyte of Comparative Example 2;

[0024] Figure 3 The macroscopic photographs of different iodine contents added to the ionic liquid phase of the dual-phase electrolyte of Example 1;

[0025] Figure 4 The UV-vis spectra of the ionic liquid phase in the dual-phase electrolyte of Example 1 with different iodine contents;

[0026] Figure 5 The cycle performance diagrams of the zinc-iodine batteries of Example 3 and Comparative Example 4 at different temperatures;

[0027] Figure 6 The macroscopic photographs are of heating after adding iodine to the ionic liquid phase in the dual-phase electrolyte of Example 1 and the electrolyte of Comparative Example 3;

[0028] Figure 7The UV-vis spectra of the ionic liquid phase in the dual-phase electrolyte of Example 1 and the electrolyte of Comparative Example 3 after adding iodine and heating at 60° C.

[0029] Figure 8 The UV-vis spectra of the ionic liquid phase in the dual-phase electrolyte of Example 1 and the electrolyte of Comparative Example 3 after adding iodine and heating at 75° C.

[0030] Fig. 9 The UV-vis spectra are obtained by adding iodine to the ionic liquid phase in the dual-phase electrolyte of Example 1 and the electrolyte of Comparative Example 3 and then heating at 90°C. DETAILED DESCRIPTION

[0031] The present invention provides a two-phase electrolyte, comprising an ionic liquid phase and an aqueous phase arranged in contact;

[0032] The ionic liquid phase is a mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide;

[0033] The aqueous phase is an aqueous solution of zinc sulfate;

[0034] The concentration of the zinc sulfate aqueous solution is 1-2.5 mol / L.

[0035] The biphasic electrolyte provided by the present invention comprises an ionic liquid phase, wherein the ionic liquid phase is a mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide.

[0036] As an embodiment of the present invention, the volume ratio of the mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide in the ionic liquid phase can be (0.5-2):1, or (0.8-1.5):1, or (1-1.2):1. In the present invention, by limiting the composition of the ionic liquid phase, it is ensured that it has enough iodine source to participate in the reaction, and at the same time, the stratification of the ionic liquid phase and the aqueous phase is ensured, so as to achieve the stability of the polyiodide.

[0037] The two-phase electrolyte provided by the present invention also includes an aqueous phase arranged in contact with the ionic liquid, and the aqueous phase is a zinc sulfate aqueous solution.

[0038] As an embodiment of the present invention, the concentration of the zinc sulfate aqueous solution is 1 to 2.5 mol / L, preferably 1.5 to 2.2 mol / L, and more preferably 2 to 2.1 mol / L. In the present invention, by limiting the concentration of the zinc sulfate aqueous solution, the stratification between the ionic liquid phase and the aqueous phase can be ensured, and the polyiodide can be further fixed to prevent the polyiodide from shuttling into the aqueous phase to corrode the negative electrode material.

[0039] As an embodiment of the present invention, the volume ratio of the ionic liquid phase to the aqueous phase can be 1:(1-10), or 1:(2-8), or 1:(5-6). In the present invention, by limiting the dosage ratio of the ionic liquid phase to the aqueous phase, the stratification between the two phases and the restriction of the shuttling of polyiodides are further ensured.

[0040] The dual-phase electrolyte provided by the present invention can stabilize the polyiodides, fix them in the ionic liquid phase, avoid their shuttling, ensure the full reaction of the polyiodides, and avoid their corrosion to the negative electrode material.

[0041] The present invention also provides the use of the biphasic electrolyte described in the above technical solution in a zinc-iodine battery.

[0042] As an embodiment of the present invention, the ionic liquid phase in the biphasic electrolyte can be arranged on the positive electrode side of the zinc-iodine battery, and the aqueous phase can be arranged on the negative electrode side of the zinc-iodine battery. In the present invention, by limiting the positions of the two phases in the biphasic electrolyte, the polyiodide is fixed and its shuttling in the electrolyte is inhibited.

[0043] The present invention also provides a zinc-iodine battery, comprising the biphasic electrolyte described in the above technical solution, and a positive electrode, a diaphragm and a negative electrode which are contacted with each other in sequence from top to bottom.

[0044] As an embodiment of the present invention, the positive electrode can be an adsorption material, and the ionic liquid phase in the two-phase electrolyte can be adsorbed in the positive electrode; the adsorption amount of the ionic liquid phase in the positive electrode can be 10 to 30 μL, or 12 to 25 μL, or 15 to 20 μL. In an embodiment of the present invention, the positive electrode can be a high-load activated carbon. In the present invention, by limiting the type of positive electrode material and the loading method of the ionic liquid phase, the combination of the positive electrode material and the ionic liquid phase is effectively improved, so that the iodine-containing compound in the ionic liquid phase can fully react, and the polyiodide is fixed in the positive electrode material, further improving the stability of the polyiodide.

[0045] As an embodiment of the present invention, the positive electrode may include a porous carrier and a conductive agent and a binder loaded on the porous carrier; the porous carrier may be activated carbon; the conductive agent and the binder may be carbon black materials; the binder may be polytetrafluoroethylene; the total loading amount of the conductive agent and the binder may be 10 to 20 mg / cm 2 , or 12-18 mg / cm 2 , can also be 15-16 mg / cm 2In the present invention, by limiting the composition of the positive electrode material, the conductivity of the positive electrode material can be effectively improved, and the binding effect of polytetrafluoroethylene can be used to further fix the polyiodide.

[0046] As an embodiment of the present invention, the positive electrode may be obtained by mixing a porous carrier and an active material, grinding the mixed material, and then rolling the mixed material.

[0047] The present invention has no special limitation on the grinding and rolling operations, and the grinding and rolling operations commonly used by those skilled in the art can be adopted.

[0048] As an embodiment of the present invention, the separator can be a glass fiber separator; the water phase in the two-phase electrolyte can be loaded on the separator; the loading amount of the water phase in the separator can be 50-100 μL, 60-90 μL, or 70-80 μL. In the present invention, by limiting the type of separator and the loading amount of the water phase in the two-phase electrolyte, the stratification of the ionic liquid phase and the water phase is further improved, the separator is used to limit the migration of polyiodide, and it is further stabilized on the positive electrode side.

[0049] As an embodiment of the present invention, the negative electrode may be metal zinc.

[0050] The zinc-iodine battery provided by the present invention arranges the ionic liquid phase in the biphasic electrolyte on the positive electrode side and the aqueous phase on the negative electrode side, utilizes the ionic liquid to fix the polyiodides and the two-phase interface to restrict the migration of the polyiodides, thereby effectively improving the stability of the polyiodides and thus improving the performance of the zinc-iodine battery.

[0051] In order to further illustrate the present invention, the biphasic electrolyte and its application and the zinc-iodine battery provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] A two-phase electrolyte, comprising an ionic liquid phase and an aqueous phase arranged in contact;

[0054] The ionic liquid phase is a mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide; wherein the volume ratio of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate to 1-methyl-3-propylimidazolium iodide is 1.5:1;

[0055] The aqueous phase is an aqueous solution of zinc sulfate;

[0056] The concentration of the zinc sulfate aqueous solution is 2 mol / L.

[0057] Example 2

[0058] A two-phase electrolyte, wherein the water phase in the two-phase electrolyte is a zinc sulfate aqueous solution with a concentration of 1 mol / L, and the rest is the same as in Example 1.

[0059] Example 3

[0060] A zinc-iodine battery is composed of the biphasic electrolyte of Example 1, and high-loaded activated carbon, a glass fiber separator and zinc that are sequentially arranged in contact from top to bottom;

[0061] The high-loaded activated carbon is activated carbon and carbon black material and polytetrafluoroethylene loaded on the activated carbon; wherein the total loading amount of the carbon black material and the polytetrafluoroethylene is 10 mg;

[0062] The preparation method of high-load activated carbon is as follows: activated carbon, carbon black material and polytetrafluoroethylene are mixed in a mass ratio of 8:1:1, and then ground and rolled to obtain high-load activated carbon;

[0063] The ionic liquid phase in the dual-phase electrolyte of Example 1 was added dropwise to the high-loaded activated carbon, and the electrolyte was used as the positive electrode after absorption; wherein the loading amount of the ionic liquid phase was 20 μL;

[0064] The water phase in the dual-phase electrolyte of Example 1 was added dropwise to a glass fiber separator to obtain a separator; wherein the loading amount of the water phase was 100 μL.

[0065] Comparative Example 1

[0066] 1 mol / L 1-ethyl-3-methylimidazolium trifluoromethanesulfonate was mixed with 1 mol / L, 2 mol / L, and 3 mol / L aqueous zinc sulfate solutions at a volume ratio of 1:1. The state after mixing was as follows: Figure 1 shown.

[0067] from Figure 1 It can be seen that when the concentration of zinc sulfate aqueous solution is 3 mol / L, sulfate precipitation will occur in the electrolyte, affecting the use of electrolysis and the operation of the battery.

[0068] Comparative Example 2

[0069] 1 mol / L 1-ethyl-3-methylimidazolium trifluoromethanesulfonate was mixed with 1 mol / L Zn(NO 3 ) 2 、Zn(ClO 4 ) 2 、Zn(OTf) 2 、ZnSO 4 The aqueous solutions are mixed in a volume ratio of 1:1, and the state after mixing is as follows Figure 2 shown.

[0070] from Figure 2It can be seen that the only solute in the water phase is ZnSO 4 It can form a stratified solution with the ionic liquid phase, and the volume ratio of the upper and lower layers is 64:36; while other zinc salts form a uniform mixed solution with the ionic liquid.

[0071] Comparative Example 3

[0072] One electrolyte is a mixed solution of zinc sulfate and potassium iodide, wherein the concentration of zinc sulfate is 1 mol / L and the concentration of potassium iodide is 0.5 mol / L.

[0073] Comparative Example 4

[0074] The only difference between Comparative Example 4 and Example 3 is that the potassium iodide solution in the electrolyte of Comparative Example 3 is added dropwise to the high-loaded activated carbon, and the rest is the same as Example 3.

[0075] Test Example 1

[0076] 10 mg, 25 mg and 50 mg of iodine were added to the ionic liquid phase of the biphasic electrolyte of Example 1, respectively, and recorded as ILM-10, ILM-25 and ILM-50, and then mixed with the water phase. The results are as follows: Figure 3 shown.

[0077] from Figure 3 As can be seen from the figure, as the iodine content increases, the color of the ionic liquid phase gradually darkens, while the water phase remains transparent, indicating that after iodine is added to the biphasic electrolyte of Example 1, iodine reacts with iodide ions in the ionic liquid phase to generate I 3- The formed polyiodides are stably present in the ionic liquid phase, indicating that the dual-phase electrolyte of Example 1 can stabilize the polyiodides in the ionic liquid phase and effectively avoid the migration of the polyiodides.

[0078] The UV-vis spectra of ILM-10, ILM-25 and ILM-50 were detected by Perkinelmer lambda1050+ UV spectrometer. Figure 4 As shown. Figure 4 It can be seen that the positions of 280nm and 380nm are I 3 - The ultraviolet absorption peak of the ionic liquid phase contains a large amount of I 3 - , while there is almost no water phase, proving that a large amount of I 3 - are confined in the ionic liquid phase, which further illustrates that the dual-phase electrolyte of Example 1 can effectively avoid the migration of polyiodides.

[0079] Test Example 2

[0080] The zinc-iodine battery of Example 3 was charged at 1 mA / cm 2 The results obtained are as follows: Figure 5 As shown, wherein BP-IL represents the zinc-iodine battery of Example 3, and SP-AQ represents the battery of Comparative Example 4;

[0081] The surface capacity of the zinc-iodine battery at 25°C is 1.28 mA·h / cm 2 ;

[0082] The surface capacity of the zinc-iodine battery at 60°C is 1.44 mA·h / cm 2 ;

[0083] The surface capacity of the zinc-iodine battery at 75°C is 1.52 mA·h / cm 2 ;

[0084] The surface capacity of zinc-iodine battery at 90℃ is 1.61mA·h / cm 2 .

[0085] Comparative test example 1

[0086] 50 mg of iodine was added to the electrolyte consisting of zinc sulfate solution and potassium iodide solution in Comparative Example 3, denoted as H 2 O-50;

[0087] ILM-50 and H in Test Example 1 2 O-50 was placed on a heating table at 75°C. Figure 6 As shown. Figure 6 It can be seen that H 2 Obvious purple smoke appeared in O-50, indicating that iodine formed iodine vapor at this temperature, while no change occurred in ILM-50. This shows that the dual-phase electrolyte provided by the present invention can effectively improve the stability of iodine under high temperature conditions.

[0088] The UV spectra of ILM-50 and H were analyzed by PerkinElmer lambda1050+. 2 O-50 was tested at 60℃, 75℃ and 90℃, and the UV-vis spectra were as follows: Figures 7 to 9 As shown. Figures 7 to 9 It can be seen that the concentration of polyiodides in the mixed ionic liquid does not change with increasing temperature, while the concentration of polyiodides in the aqueous phase decreases with increasing temperature, further illustrating that the dual-phase electrolyte provided by the present invention can effectively improve the stability of iodine under high temperature conditions.

[0089] Comparative test example 2

[0090] The zinc-iodine battery of Comparative Example 4 was charged at 1 mA / cm 2The results are shown in Figure 2. Figure 5 As shown;

[0091] The surface capacity of the zinc-iodine battery at 25°C is 1.35 mA·h / cm 2 ;

[0092] The surface capacity of the zinc-iodine battery at 60°C is 1.44 mA·h / cm 2 ;

[0093] At 75°C and 90°C, the surface capacity of zinc-iodine batteries decays rapidly and cannot be cycled stably.

[0094] from Figure 5 It can be seen that the biphasic electrolyte provided by the present invention can maintain the stability of polyiodides, so that the zinc-iodine battery can be used normally at high temperatures.

[0095] In summary, the biphasic electrolyte provided by the present invention can stabilize polyiodides and keep them stable under high temperature conditions.

[0096] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A two-phase electrolyte, characterized in that: including an ionic liquid phase and an aqueous phase in a contact arrangement; The ionic liquid phase is a mixed ionic liquid of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide; The aqueous phase is an aqueous solution of zinc sulfate; The concentration of the zinc sulfate aqueous solution is 1-2.5 mol / L.

2. The two-phase electrolyte according to claim 1, characterized in that The concentration of the zinc sulfate aqueous solution is 1.8-2.2 mol / L.

3. The two-phase electrolyte according to claim 1, characterized in that: The volume ratio of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate and 1-methyl-3-propylimidazolium iodide in the ionic liquid phase is (0.5-2):

1.

4. The two-phase electrolyte according to any one of claims 1 to 3, characterized in that: The volume ratio of the ionic liquid phase to the water phase is 1:(1-10).

5. Use of the biphasic electrolyte according to any one of claims 1 to 4 in a zinc-iodine battery, characterized in that: The ionic liquid phase in the dual-phase electrolyte is arranged on the positive electrode side of the zinc-iodine battery, and the water phase is arranged on the negative electrode side of the zinc-iodine battery.

6. A zinc-iodine battery, comprising the biphasic electrolyte according to any one of claims 1 to 4, and a positive electrode, a separator and a negative electrode arranged in contact with each other from top to bottom; The ionic liquid phase in the two-phase electrolyte is arranged on the positive electrode side, and the water phase in the two-phase electrolyte is adsorbed in the diaphragm.

7. The zinc-iodine battery according to claim 6, characterized in that: The positive electrode is an adsorption material, and the ionic liquid phase in the two-phase electrolyte is adsorbed in the positive electrode.

8. The zinc-iodine battery according to claim 7, characterized in that: The positive electrode comprises a porous carrier and a conductive agent and a binder loaded on the porous carrier; the total loading amount of the conductive agent and the binder is 10 to 20 mg / cm 2 .

9. The zinc-iodine battery according to claim 8, characterized in that: The adsorption amount of the ionic liquid phase in the positive electrode is 10 to 30 μL.

10. The zinc-iodine battery according to claim 6, characterized in that: The diaphragm is a glass fiber diaphragm.

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