Choline chloride-lactic acid deep eutectic solvent modified aqueous zinc ion battery electrolyte, preparation method and application thereof

Abstract

This invention discloses a choline chloride-lactic acid eutectic modified aqueous zinc-ion battery electrolyte, its preparation method, and its application. Using zinc sulfate aqueous solution as a base, a choline chloride-lactic acid eutectic solvent is introduced to synergistically regulate the solvation structure of zinc ions. Lactic acid preferentially disrupts the hydration shell of choline cations, promoting the synergistic insertion of choline cations into Zn. 2+ The first solvation layer reconstructs the water-depleted solvation shell, disrupting the hydrogen bond network in the water and significantly reducing the free water content at the interface. This electrolyte can construct an organic / inorganic composite SEI film on the zinc anode surface, inducing uniform zinc deposition along the (002) crystal plane, suppressing zinc dendrite formation, hydrogen evolution, and corrosion side reactions, and improving zinc ion transport number and coulombic efficiency. Both the symmetric cell and the phenazine full cell exhibit ultra-long cycle life and excellent rate performance. The preparation process of this invention is simple, the raw materials are inexpensive, and the safety is high, making it suitable for large-scale energy storage aqueous zinc-ion batteries.

Description

Technical Field

[0001] This invention relates to the field of aqueous zinc-ion battery electrolyte technology, specifically disclosing an aqueous electrolyte that achieves triple synergistic modification by relying on a choline chloride-lactic acid eutectic solvent to "reconstruct the hydrogen bond network, regulate zinc ion solvation, and construct a stable interface film in situ", which can be used to prepare long-cycle, highly reversible aqueous zinc energy storage batteries. Background Technology

[0002] Aqueous zinc-ion batteries are widely recognized as a new type of green energy storage battery with great industrialization potential due to their outstanding advantages, including high theoretical capacity of metallic zinc anodes, abundant zinc reserves in the Earth's crust, non-flammable electrolytes, no need for anhydrous and oxygen-free preparation environments, low production and usage costs, and environmental friendliness. However, the traditional single zinc sulfate aqueous electrolyte system contains a large number of active free water molecules, which can cause a series of unavoidable anode failure problems during battery charging and discharging: First, the zinc ion-rich solvation layer has high desolvation resistance, and the zinc ion deposition process is prone to local current concentration, inducing continuous growth of zinc dendrites. Sharp dendrites can easily pierce the separator, causing internal short circuits and posing safety hazards. Second, a large amount of free water in the electrolyte undergoes hydrogen evolution side reactions on the anode surface, continuously consuming electrolyte and producing hydrogen gas, causing battery bulging and a continuous decline in coulombic efficiency. Third, water reacts with the zinc anode to produce insulating byproducts such as basic zinc sulfate, which accumulate on the electrode surface, blocking ion transport channels, leading to a continuous increase in interfacial impedance, rapid capacity decay, and a significant reduction in cycle life.

[0003] To address the aforementioned shortcomings, existing technologies mainly employ three modification schemes: high-concentration zinc salt electrolytes, single organic and inorganic additives, and zinc anode surface coatings. However, all of these have significant drawbacks: high-concentration zinc salt electrolytes exhibit a substantial increase in viscosity, a decrease in ionic conductivity, and a significant increase in raw material costs, and are prone to salt crystal precipitation at low temperatures; single additives have limited functions, only weakly inhibiting dendrite formation or hydrogen evolution, and cannot simultaneously regulate solvation structure and molecular hydrogen bonds; the electrode coating process is complex, increasing battery manufacturing steps, and the coating is prone to peeling and failure during long-term cycling.

[0004] In recent years, eutectic solvents (DES) have been used for electrolyte modification. This invention aims to provide a choline chloride-lactic acid eutectic solvent modified aqueous zinc-ion battery electrolyte, its preparation method, and its application, addressing the shortcomings of traditional aqueous electrolytes such as zinc dendrite formation, hydrogen evolution side reactions, low-temperature freezing, and poor interfacial stability. This invention uses zinc sulfate aqueous solution as a base and introduces a 1:1 molar ratio choline chloride-lactic acid eutectic solvent for synergistic modification. Lactic acid can disrupt the outer hydrated shell of choline cations, releasing free choline cations, and lactate ions synergistically intercalate with choline cations into Zn. 2+The first solvation shell reconstructs the water-deficient solvation structure, significantly reducing the free water activity of the electrolyte and inhibiting the hydrogen evolution reaction; at the same time, the two work together to generate an organic outer layer and an inorganic inner layer composite SEI film in situ on the zinc anode surface, inducing zinc to be uniformly deposited along the low surface energy (002) crystal plane, inhibiting the formation of dendrites and corrosion byproducts. Summary of the Invention

[0005] The purpose of this invention is to provide a choline chloride-lactic acid eutectic solvent modified aqueous zinc-ion battery electrolyte, its preparation method and application, to solve the problems of traditional aqueous electrolytes such as zinc dendrite formation, hydrogen evolution side reaction, and poor interface stability.

[0006] This invention uses zinc sulfate aqueous solution as a base and introduces a 1:1 molar ratio choline chloride-lactic acid eutectic solvent for synergistic modification. Lactic acid can destroy the outer hydration shell of choline cations, releasing free choline cations, and lactate ions and choline cations synergistically intercalate into Zn. 2+ The first solvation shell reconstructs the water-deficient solvation structure, significantly reducing the free water activity of the electrolyte and inhibiting the hydrogen evolution reaction; at the same time, the two work together to generate an organic outer layer and an inorganic inner layer composite SEI film in situ on the zinc anode surface, inducing zinc to be uniformly deposited along the low surface energy (002) crystal plane, inhibiting the formation of dendrites and corrosion byproducts.

[0007] Preferably, the volume ratio of the eutectic solvent to deionized water is 1:20.

[0008] Compared with existing technologies, this invention has the following advantages: Triple synergistic modification: simultaneous hydrogen bond reconstruction, zinc ion solvation regulation, and anode interface film construction using a eutectic solvent, resulting in multiple inhibitions of zinc anode failure; simple and mild preparation process, inexpensive and readily available raw materials, no need for high temperature and high pressure, and low threshold for large-scale production; environmentally friendly: aqueous system, non-toxic and harmless; excellent performance: improved cycle life and significant dendrite suppression effect. Attached Figure Description

[0009] Figure 1 The XRD pattern of the zinc sheet after immersing it in the electrolyte for 10 days is shown in the low eutectic solvent electrolyte and the basic zinc sulfate electrolyte prepared in Example 1.

[0010] Figure 2 The XRD pattern of an aqueous zinc-ion battery after 100 hours of testing with the low eutectic solvent electrolyte and the basic zinc sulfate electrolyte prepared in Example 1.

[0011] Figure 3 Scanning electron microscope image of an aqueous zinc-ion battery prepared using the low eutectic solvent electrolyte and the basic zinc sulfate electrolyte of Example 1 after 100 hours of cycling.

[0012] Figure 4The graph shows the results of chronoamperometry testing of an aqueous zinc-ion battery made with the low eutectic solvent electrolyte and the basic zinc sulfate electrolyte prepared in Example 1.

[0013] Figure 5 Impedance diagrams of aqueous zinc-ion batteries prepared using the low eutectic solvent electrolyte and the basic zinc sulfate electrolyte in Examples 1-3.

[0014] Figure 6 Example 1 shows the long-cycle results of an aqueous zinc-zinc symmetric battery using the prepared low-eutectic solvent electrolyte and the basic electrolyte zinc sulfate, with a current density of 1 mA·cm⁻¹. -2 .

[0015] Figure 7 Example 1 shows the long-cycle results of an aqueous zinc-copper half-cell battery prepared using the low-eutectic solvent electrolyte and the basic electrolyte zinc sulfate, with a current density of 1 mA·cm⁻¹. -2 .

[0016] Figure 8 Example 1 shows a comparison of the capacity stability of phenazine full cells prepared with the low eutectic solvent electrolyte and the basic electrolyte zinc sulfate, with a current density of 15 A / g. Detailed Implementation

[0017] The electrolyte preparation method of this invention includes: mixing choline chloride and lactic acid in a molar ratio of 1:1 and stirring at a constant temperature of 60°C for 0.5 h to obtain a eutectic solvent; mixing the eutectic solvent with deionized water in a certain proportion, and then adding zinc sulfate and stirring until completely dissolved to obtain the target electrolyte. The final concentration of zinc sulfate is controlled at 2 mol / L.

[0018] In this invention, unless otherwise specified, all raw material components are commercially available products well known to those skilled in the art.

[0019] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the protection scope of this invention. Example

[0020] Mix 1 mL of choline chloride-lactic acid eutectic solvent with 20 mL of deionized water, add 11.502 g of zinc sulfate heptahydrate, stir at room temperature for 40 min, and control the concentration of zinc salt to 2 mol / L to obtain 5 DEE electrolyte.

[0021] The choline chloride-lactic acid eutectic solvent electrolyte was prepared according to the method in Example 1, and the preparation conditions are shown in Table 1. Table 1. Preparation conditions of Examples 2-3 Example 1 11.502g 1ml 20mL 5 DEE Example 2 11.502g 0.2ml 20mL 2 DEE Example 3 11.502g 2ml 20mL 10 DEE

[0022] Literature "YF Wang, LN Song, Y. Wang, JY Wu, WB Tu, and JJXu, "Synergistic Regulation ofHydrogen Bonds and Electrocrystallization for Enhanced Aqueous Zinc Batteries,” Advanced EnergyMaterials 14 (2024):2401896.”

[0023] Literature "F. Liu, Y. Zhang, G. Li, et al., "Hydrated Eutectic ElectrolytePromotes the Preferential Growth of Zn (0 0 2) Plane and Suppresses SideReaction for High-stability ZincAnodes,” Chemical Engineering Journal 493(2024):152526.”

[0024] Document "V. Aupama, J. Sangsawang, W. Kao-ian, S. Wannapaiboon, J.Pimoei, Y. Warunyoo, M. Opchoei, Z. Tehrani, S. Margadonna, S. Kheawhom,Electrochim. Acta 2024, 506, 145059."

[0025] Figure 1 The XRD pattern of zinc sheet immersed in a low-eutectic solvent electrolyte is shown in Example 1. Figure 1 It can be seen that the low eutectic solvent electrolyte prepared after soaking for 10 days has no byproducts and has good corrosion resistance.

[0026] Figure 2The XRD pattern of an aqueous zinc-ion battery using the low eutectic solvent electrolyte prepared in Example 1 after 100 hours of use is shown in the figure. Figure 2 It can be seen that no byproduct peaks appeared, and they were preferentially deposited on the 002 crystal plane. This phenomenon indicates that the low eutectic solvent electrolyte can effectively suppress the occurrence of side reactions, showing good stability and suppression performance.

[0027] Figure 3 Scanning electron microscope image of an aqueous zinc-ion battery prepared with the eutectic solvent electrolyte of Example 1 after 100 hours of cycling. Figure 3 It can be seen that after 100 hours of cycling test, the zinc anode surface was smooth after adding the low eutectic solvent electrolyte, which successfully suppressed the formation of by-products and showed excellent stability.

[0028] Figure 4 The results of chronoamperometry tests were performed on an aqueous zinc-ion battery and a basic electrolyte zinc-ion battery using the low eutectic solvent electrolyte prepared in Example 1. Figure 4 It can be seen that for the zinc electrode, there is a continuous increase in current from the initial current to the final current within 400s, while the current of the aqueous zinc-ion battery made with the eutectic solvent electrolyte only gradually stabilizes from the initial current in a very short time. This indicates that the aqueous zinc-ion battery made with the eutectic solvent electrolyte undergoes rapid 3D diffusion, the process is diffusion-controlled, effectively suppressing side reactions such as hydrogen evolution, and resulting in more uniform zinc ion deposition.

[0029] Figure 5 The graph shows the results of cycle resistance tests for aqueous zinc-ion batteries and basic electrolyte zinc-ion batteries prepared with different proportions of the low eutectic solvent electrolytes in Examples 1-3. Figure 5 It can be seen that aqueous zinc-ion batteries based on low eutectic solvent electrolytes exhibit lower charge transfer resistance, which is superior to zinc-ion batteries based on basic electrolytes.

[0030] Aqueous zinc-ion batteries made with a low-eutectic solvent electrolyte obtained through experiments and zinc-ion batteries made with a basic electrolyte were subjected to performance tests in a blue battery system. The test results are as follows: Figures 6-8 As shown.

[0031] Figure 6 The graph shows the long-cycle results of an aqueous zinc-ion battery prepared with the low eutectic solvent electrolyte of Example 1. Figure 6 It can be seen that when the proportion of the eutectic solvent electrolyte is 5 DEE, the cycle life of the battery is significantly extended, the electrochemical performance is greatly improved, and it exhibits superior overall performance.

[0032] Figure 7 This is a long-cycle result diagram of an aqueous zinc-ion zinc-copper half-cell prepared using the low eutectic solvent electrolyte, as shown in Example 1. Figure 7 It can be seen that the zinc-copper battery using a low eutectic solvent electrolyte exhibits excellent coulombic efficiency, with an efficiency of up to 99.78%, which is significantly better than the 99.39% efficiency of the basic electrolyte battery.

[0033] Figure 8 This is a comparison chart of the capacity stability of zinc-phenazine full cells prepared with the low eutectic solvent electrolyte of Example 1 and full cells prepared with the basic electrolyte. Figure 8 It can be seen that the full cell using the low eutectic solvent electrolyte exhibits excellent capacity stability, with a capacity retention rate of up to 75.7%, which is significantly better than the capacity of the battery using ordinary electrolyte.

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An aqueous zinc-ion battery electrolyte, characterized in that, Using zinc sulfate aqueous solution as a base, a eutectic solvent of choline chloride and lactic acid was introduced.

2. The aqueous zinc-ion battery electrolyte according to claim 1, characterized in that, The eutectic solvent is prepared by mixing choline chloride and lactic acid in a molar ratio of 1:1; the volume ratio of the eutectic solvent to deionized water is 0.1:20 to 5:

20.

3. The aqueous zinc-ion battery electrolyte according to claim 2, characterized in that, The optimal volume ratio of the eutectic solvent to deionized water is 1:20, and the final concentration of zinc sulfate is 2 mol / L.

4. The aqueous zinc-ion battery electrolyte according to claim 1, characterized in that, The zinc salt in the aqueous zinc salt solution is selected from at least one of zinc sulfate, zinc trifluoromethanesulfonate, zinc perchlorate, and zinc acetate.

5. The aqueous zinc-ion battery electrolyte according to claim 4, characterized in that, The final concentration of zinc sulfate selected is 2 mol / L.

6. The method for preparing the aqueous zinc-ion battery electrolyte according to any one of claims 1 to 5, characterized in that, It includes the following steps: (1) Choline chloride and lactic acid were mixed in a molar ratio of 1:1 and stirred at 60°C for 0.5 h to obtain a choline chloride-lactic acid eutectic solvent; (2) Mix the obtained eutectic solvent with deionized water in proportion, then add zinc sulfate and stir until completely dissolved. Stir at room temperature for 20-60 min until the system is homogeneous and transparent to obtain the aqueous zinc-ion battery electrolyte.

7. An aqueous zinc-ion battery, characterized in that, It comprises a positive electrode, a metallic zinc negative electrode, and the aqueous zinc-ion battery electrolyte as described in any one of claims 1 to 5.

8. The aqueous zinc-ion battery according to claim 7, characterized in that, The battery is a zinc-zinc symmetrical battery, a zinc-copper half-cell, or a zinc-ion full cell; the positive electrode material of the full cell is any one of phenazine, manganese oxide, vanadium oxide, or Prussian blue analogues.

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