Hydrated eutectic electrolyte and preparation method and application thereof

Abstract

The invention discloses a hydrated eutectic electrolyte and a preparation method and application thereof, and belongs to the technical field of batteries. The invention provides a mixed ligand hydration eutectic electrolyte strategy based on thermodynamic-dynamic balance. According to the strategy, through functional synergy of acetamide (Ace) and 1, 3-dioxolane (Dol), integrated regulation and control of an electrolyte liquid phase microenvironment and interface chemistry are achieved, so that side reactions are remarkably inhibited, and the electrochemical performance is comprehensively improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to a hydrated eutectic electrolyte, its preparation method, and its application. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The core challenge facing aqueous zinc batteries in practical applications stems from the inherent problems of their electrolyte system. Currently, aqueous electrolytes struggle to achieve an effective balance between thermodynamic stability and rapid reaction kinetics. Thermodynamically, zinc electrodes cannot remain stable in an aqueous environment, remaining in a metastable state, which leads to spontaneous dissolution, accompanied by hydrogen evolution side reactions and the formation of a surface passivation layer. This directly results in a decrease in battery coulombic efficiency and a sharp reduction in cycle life. Kinetically, problems such as high ion migration resistance and slow interfacial charge transfer cause uneven distribution of zinc ions when deposited on the electrode surface, easily forming zinc dendrites and electrochemically deactivated "dead zinc," thus irreversibly consuming the active material.

[0004] Existing electrolyte optimization schemes often fall into a dilemma: for example, measures to enhance thermodynamic stability, such as increasing salt concentration, often reduce ionic conductivity; while measures to improve kinetic performance, such as reducing viscosity, may exacerbate interfacial thermodynamic instability. This mutual constraint between performance indicators makes it impossible for conventional electrolyte designs to simultaneously achieve the reversibility of the zinc anode reaction and interfacial stability, seriously hindering the technological industrialization of aqueous zinc batteries. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a hydrated eutectic electrolyte, its preparation method, and its application. This invention provides a weakly solvated hydrated eutectic electrolyte with high interfacial stability, which effectively suppresses hydrogen evolution side reactions and dendrite problems caused by insufficient interfacial stability in traditional electrolytes. Furthermore, it improves bulk and interfacial kinetic properties through an entropy increase strategy, possessing significant scientific and application value. The preparation method is simple, easy to operate, environmentally friendly, and uses readily available raw materials, making it suitable for industrial applications.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a hydrated eutectic electrolyte, the electrolyte comprising a zinc salt, a two-component mixed eutectic ligand molecule, and water; The two-component mixed eutectic ligand molecule is a mixture of two of the following: urea, acetamide, N-methylacetamide, nicotinamide, difluorobenzene, 1,3-dioxolane, sulfolane, and tetrahydrofuran.

[0008] Secondly, the present invention provides a method for preparing the above-mentioned hydrated eutectic electrolyte, comprising the following steps: The zinc salt, the two-component mixed eutectic ligand molecules, and water are mixed and stirred to obtain the product.

[0009] Thirdly, the present invention provides the application of the above-mentioned hydrated eutectic electrolyte or the hydrated eutectic electrolyte prepared by the above preparation method in the preparation of batteries, preferably in the application of aqueous zinc-ion batteries.

[0010] Fourthly, the present invention provides a zinc-ion battery, comprising an electrolyte, wherein the electrolyte is a hydrated eutectic electrolyte as described above.

[0011] One or more of the above technical solutions have the following advantages or beneficial effects: (1) This invention provides a hydrated eutectic electrolyte comprising a zinc salt, a two-component mixed eutectic ligand molecule, and water; the two-component mixed eutectic ligand molecule is a two-component mixture of urea, acetamide, N-methylacetamide, nicotinamide, difluorobenzene, 1,3-dioxolane, sulfolane, and tetrahydrofuran. Therefore, this invention provides a "two-component synergistic" design concept, aiming to optimize kinetic behavior while maintaining thermodynamic stability through a functionally complementary molecular combination, thus opening a new path for the construction of next-generation high-performance aqueous zinc battery electrolytes.

[0012] (2) This invention proposes a mixed-ligand hydrated eutectic electrolyte strategy based on thermodynamic-kinetic equilibrium. This strategy achieves integrated regulation of the electrolyte phase microenvironment and interfacial chemistry through the functional synergy of acetamide (Ace) and 1,3-dioxolane (Dol), thereby significantly suppressing side reactions and comprehensively improving electrochemical performance. Specifically, Ace molecules preferentially occupy the electrode interface due to their strong adsorption tendency, effectively blocking direct contact between water molecules and the zinc anode by adjusting the double-layer structure, fundamentally enhancing interfacial thermodynamic stability and significantly suppressing hydrogen evolution and corrosion. Simultaneously, the appropriate introduction of Dol molecules can reconstruct the hydrogen bond network in the electrolyte, not only significantly reducing system viscosity and increasing ionic conductivity, but also participating in the regulation of Zn. 2+ The primary solvation sheath structure promotes the formation of anions (OTf). -The electrolyte enters the inner coordination ring, thereby optimizing desolvation kinetics and improving interfacial ion transport efficiency. More importantly, this anion-involved solvation structure can preferentially reduce at the electrode interface, inducing the formation of a uniform and stable anion-derived organic-inorganic hybrid SEI layer. This SEI layer further consolidates the interfacial thermodynamic stability, providing long-lasting dynamic protection for the zinc anode. This spatial synergistic design from bulk phase to interface successfully achieves an efficient balance between the thermodynamic stability of the zinc anode, interfacial charge transfer kinetics, and bulk ion transport performance, enabling the battery to maintain long-term cycle stability even under high current conditions. The Zn / / PANI full cell assembled based on this electrolyte exhibits excellent rate performance and cycle durability. This study, through the synergistic regulation of bulk solvation structure and interfacial chemistry, overcomes the inherent design limitation of traditional aqueous zinc batteries where thermodynamic stability and kinetic enhancement are difficult to achieve simultaneously, providing a new design idea and theoretical paradigm for the development of high-efficiency, long-life aqueous zinc batteries.

[0013] (3) The present invention has successfully found a high-performance, long-term stable hydrated eutectic electrolyte to improve the problems of high viscosity and low ionic conductivity of traditional hydrated eutectic electrolytes. It can effectively improve the cycle performance, rate performance and safety performance of zinc batteries, while improving the safety of the electrolyte. Attached Figure Description

[0014] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0015] Figure 1 The relevant test diagrams for the electrolyte are shown below; (a) salt-ligand-water ternary phase diagram, (b) conductivity and viscosity of different electrolytes, (c) rate performance test of different electrolytes, and (d) polarization voltage of different electrolytes at different current densities. Figure 2 Impedance plots and corresponding Arrhenius curves of Zn / / Zn batteries with different electrolytes at different temperatures are shown; (a) impedance plots of a Zn / / Zn symmetrical battery with PA electrolyte at different temperatures, (b) impedance plots of a Zn / / Zn symmetrical battery with HA2D1 electrolyte at different temperatures, and (c) impedance plots of a Zn / / Zn symmetrical battery with HA2D1 electrolyte at different temperatures. 1.5 D 1.5 Impedance plots of Zn / / Zn symmetric cells with different electrolytes at different temperatures, (d) Impedance plots of Zn / / Zn symmetric cells with HA1D2 electrolyte at different temperatures, (e) Impedance plots of Zn / / Zn symmetric cells with PD electrolyte at different temperatures, (f) Arrhenius curves of activation energy of Zn / / Zn symmetric cells based on different electrolytes. Figure 3Impedance diagrams and DRT curves of Zn / / Zn batteries with different electrolytes at different amplitude voltages are shown. Among them, (a) impedance diagram of Zn / / Zn symmetrical battery with PA electrolyte at 1-20mV amplitude voltage, (b) impedance diagram of Zn / / Zn symmetrical battery with HA2D1 electrolyte at 1-20mV amplitude voltage, (c) impedance diagram of Zn / / Zn symmetrical battery with PD electrolyte at 1-20mV amplitude voltage, (d) DRT curves of PA, HA2D1 and PD electrolytes at 1mV amplitude voltage, (e) DRT curves of PA, HA2D1 and PD electrolytes at 10mV amplitude voltage, and (f) DRT curves of PA, HA2D1 and PD electrolytes at 20mV amplitude voltage. Figure 4 Infrared spectra of different electrolytes; where (a) C=O, (b) CO, (c) -SO3 groups; Figure 5 The binding energies are coordination number, binding energy of different zinc ion solvation structures, and binding energy of the main solvation structures in different electrolytes; among which, (a) in different hydrated eutectic electrolyte systems, Zn 2+ Surrounding water molecules, OTf - Coordination number (CN) of anions and different ligand molecules, (b) different Zn 2+ Binding energy of solvated structures, (c) binding energy of major solvated structures in PA, HA2D1 and PD electrolytes; Figure 6 For different electrolytes surrounding Zn 2+ The radial distribution function (solid line) and coordination number (dashed line) curves; Figure 7 To study the SEI layer on the zinc anode surface using PA, HA2D1, and PD electrolytes under different argon ion (Ar) conditions. + The F 1s XPS spectral region corresponding to the sputtering depth; Figure 8 The SEI layer on the zinc substrate surface in PA, HA2D1 and PD electrolytes under different argon ion (Ar) concentrations was compared. + O1s XPS spectral region at sputtering depth; Figure 9 Data for adsorption energy, interfacial impedance, and polarization voltage; where, (a) Zn 2+ (a) Adsorption energies on Zn anode and ZnF2 respectively; (b) Interfacial impedance of cells with different SEI layers; (c) Enlarged view of (b); (d) Polarization voltage of cells with different SEI layers. Figure 10The table shows the FTIR peak patterns and the ratio of free water to clustered water in different electrolytes; where (a) is the FTIR peak pattern (OH stretching vibration region) of different electrolytes, (b) is the ratio of free water in different electrolytes, and (c) is the ratio of clustered water in different electrolytes. Figure 11 The results show the adsorption energy, differential capacitance curves, LUMO and HOMO, and contact angle measurements; among them, (a) adsorption energy of H2O, Ace, and Dol on the Zn(002) crystal plane, (b) differential capacitance curves of Zn / / Ti half-cell in different electrolytes, (c) LUMO and HOMO of H2O, Ace, and Dol, and (d) contact angle measurements of droplets from different electrolytes on the zinc metal surface. Figure 12 XRD patterns, chronoamperometry curves of zinc deposition, linear sweep voltammetry curves, and coulombic efficiency are shown. Specifically, (a) XRD patterns (5°–80°) of the zinc anode after 50 cycles in PA, HA2D1, and PD electrolytes; (b) chronoamperometry curves of zinc deposition at a -200 mV overpotential; and (c) XRD patterns of different electrolytes at a scan rate of 0.5 mV s⁻¹. -1 Linear sweep current-voltage curves at time (d) Coulombic efficiency of zinc deposition / stripping in Zn / / Cu cells under “pre-deposition” mode; Figure 13 SEM images and in-situ optical micrographs are provided; among them, (a) a typical SEM image of the zinc anode after 50 cycles of a Zn / / Zn battery based on PA, HA2D1, and PD electrolytes, and (b) an SEM image of the zinc anode after 50 cycles of a Zn / / Zn battery based on PA, HA2D1, and PD electrolytes at 2 mA cm⁻¹. -2 In-situ optical micrographs of the zinc deposition process at current density; Figure 14 For constant current cycling performance; among them, (a) Zn / / Zn batteries using PA, HA2D1 and PD electrolytes at 1 mA cm⁻¹ -2 1mAh cm -2 Constant current cycling performance under the following conditions; (a) Zn / / Zn battery using PA, HA2D1 and PD electrolytes at 5 mA cm⁻¹ -2 1mAh cm -2 Constant current cycling performance under certain conditions. Detailed Implementation

[0016] Hydrated eutectic electrolytes (HEEs) have attracted much attention due to their environmental friendliness and sustainability. Traditional systems often employ strong Lewis basic ligands (such as acetamide and urea), which preferentially compete with water molecules for Zn. 2+The solvation sheath enhances the thermodynamic stability of the desolvation process and strengthens local protection through interfacial adsorption. However, its strong coordination ability and dense hydrogen bond network also lead to high electrolyte viscosity and limited ionic conductivity, severely restricting bulk ion migration. Simultaneously, the overly stable solvation structure slows down desolvation kinetics, and anions struggle to participate in coordination, preventing the formation of a robust and ion-conducting solid electrolyte interface (SEI) at the electrode interface. Therefore, traditional single-ligand hydrated eutectic systems struggle to balance thermodynamic stability and kinetic efficiency because a single component cannot simultaneously meet multiple, even conflicting, functional requirements. To overcome this limitation, the "dual-component synergistic" design concept has emerged, aiming to optimize kinetic behavior while maintaining thermodynamic stability through functionally complementary molecular combinations, opening a new path for the construction of next-generation high-performance aqueous zinc battery electrolytes.

[0017] Traditional single-ligand hydrated eutectic systems struggle to balance thermodynamic stability and kinetic efficiency because a single component cannot simultaneously meet multiple, or even conflicting, functional requirements. Therefore, this invention provides a weakly solvated hydrated eutectic electrolyte with high interfacial stability. This electrolyte effectively suppresses hydrogen evolution side reactions and dendrite formation caused by insufficient interfacial stability in traditional electrolytes. Furthermore, it improves bulk and interfacial kinetic performance through an entropy increase strategy. The preparation method is simple, easy to operate, environmentally friendly, and uses readily available raw materials, making it suitable for industrial applications.

[0018] In addition, it should be noted that, compared with other existing batteries (such as lithium batteries or aluminum batteries), the technical problem to be solved by this invention is to focus on the side reactions of aqueous zinc batteries.

[0019] Specifically, compared to other existing batteries (such as lithium batteries or aluminum batteries), aqueous zinc batteries face unique challenges: ① Dendrite growth: Zinc readily forms dendrites during deposition, which can pierce the separator and cause a short circuit (this is a problem that also exists in lithium batteries, but the mechanism is slightly different, and lithium dendrites are more reactive).

[0020] ② Hydrogen evolution reaction (HER): In an aqueous environment, the deposition / deposition potential of zinc is often close to the decomposition voltage of water, leading to hydrogen evolution, which causes a decrease in coulombic efficiency and battery swelling (this is a problem unique to aqueous batteries; organic systems of lithium / aluminum batteries do not have this problem).

[0021] ③Side reactions / passivation: The zinc negative electrode is prone to corrosion in aqueous solution, generating byproducts such as basic zinc sulfate or zinc oxide, which leads to battery failure.

[0022] Therefore, the core starting point of this invention is to solve the inherent problems of aqueous zinc batteries, which either do not exist in non-aqueous lithium batteries or are not the main problem in non-aqueous lithium batteries or aluminum batteries.

[0023] In addition, the uniqueness of the synergistic effect of the components should be emphasized in this invention.

[0024] Reconstructing the solvation structure induces the anion-derived SEI layer while simultaneously improving conductivity (distinguishing it from traditional aqueous electrolytes and organic systems): Phenomenon: Acetamide and 1,3-dioxolane, acting as eutectic ligands, can enter Zn 2+ The solvation of the sheath layer promotes OTf - Anions also participate in coordination, thereby partially substituting with Zn. 2+ Tightly bound water molecules. This structural change not only optimizes the solvation configuration but also promotes the derivation of anions at the electrode interface to form an SEI layer, achieving effective protection of the zinc anode. Furthermore, the introduction of 1,3-dioxolane can reduce the strength of hydrogen bond interactions in the bulk electrolyte, increase the hydrogen bond exchange rate, and thus further improve the electrolyte conductivity.

[0025] Effects: This water-poor solvation structure fundamentally reduces hydrolysis and hydrogen evolution side reactions that accompany zinc ion deposition. Simultaneously, the addition of ligands with lower hydrogen bonding forces helps improve the overall conductivity of the electrolyte.

[0026] In contrast to lithium batteries, which utilize a purely organic system devoid of water, this invention addresses the issue of water binding. One ligand molecule competes with water for coordination, suppressing water-related side reactions; simultaneously, another molecule effectively reduces electrolyte viscosity, thereby increasing Zn content. 2+ The migration speed is improved, and ion migration kinetics are optimized. This improved kinetics allows the battery to maintain stable cycling even at higher current densities, further suppressing side reactions. Therefore, this invention differs fundamentally from lithium-ion battery systems in its technical approach.

[0027] In one typical embodiment, the present invention provides a hydrated eutectic electrolyte, the electrolyte comprising a zinc salt, a two-component mixed eutectic ligand molecule, and water; The two-component mixed eutectic ligand molecule is a mixture of two of the following: urea, acetamide, N-methylacetamide, nicotinamide, difluorobenzene, 1,3-dioxolane, sulfolane, and tetrahydrofuran.

[0028] In one or more embodiments, the zinc salt is one or more of ZnCl2, Zn(ClO4)2, ZnSO4, Zn(OTf)2, and Zn(BF4)2, preferably zinc trifluoromethanesulfonate (Zn(OTf2)).

[0029] The two-component mixed eutectic ligand molecule includes eutectic ligand molecule 1 and eutectic ligand molecule 2.

[0030] Cocrystal ligand 1 and cocrystal ligand 2 can be selected from urea, acetamide, N-methylacetamide, nicotinamide, difluorobenzene, 1,3-dioxolane, sulfolane, and tetrahydrofuran. However, cocrystal ligand 1 and cocrystal ligand 2 are different molecular compounds.

[0031] Preferably, the co-crystal ligand molecule 1 is acetamide (Ace), and the co-crystal ligand molecule 2 is 1,3-dioxolane (Dol). The synergistic effect of the two was verified in the examples.

[0032] In one or more embodiments, the molar ratio of zinc salt, eutectic ligand 1 (acetamide), eutectic ligand 2 (1,3-dioxolane), and water in the hydrated eutectic electrolyte is (0.5~1.5):(0.5~3):(0.5~3):(1.5~2.5), preferably 1:(1~2):(1~2):2, more preferably 1:(1.5~2):(1~1.2):2, and most preferably 1:2:1:2.

[0033] In a typical embodiment, the present invention provides a method for preparing the above-mentioned hydrated eutectic electrolyte, comprising the following steps: The zinc salt, the two-component mixed eutectic ligand molecules, and water are mixed and stirred to obtain the product.

[0034] Further, stir for 5-10 minutes until there is no obvious precipitate in the reagent bottle.

[0035] In a typical embodiment, the present invention provides the application of the above-described hydrated eutectic electrolyte or the hydrated eutectic electrolyte prepared by the above preparation method in the preparation of batteries, preferably in aqueous zinc-ion batteries.

[0036] In a typical embodiment, the present invention provides an aqueous zinc-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is a hydrated eutectic electrolyte as described above. Further, the negative electrode may be made of zinc metal foil; the positive electrode may be made of one or more of sodium vanadate, polyaniline, manganese dioxide, ammonium vanadate, and vanadium pentoxide; and the separator may be made of glass fiber.

[0037] In this invention, unless otherwise specified, all other test materials and instruments are conventional test materials in the field and can be purchased through commercial channels.

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0039] Example 1 1. Weigh out 0.3635 g (1 mmol) of zinc trifluoromethanesulfonate (Zn(OTf)2), 0.1772 g (3 mmol) of acetamide (Ace), 0 g (0 mmol) of 1,3-dioxolane (Dol), and 0.0360 g (2 mmol) of deionized water (H2O) at room temperature. The ratio of this formula is Zn(OTf)2:Ace:Dol:H2O = 1:3:0:2.

[0040] 2. Place the weighed substances into a reagent bottle and stir for 5-10 minutes until there is no obvious precipitate in the reagent bottle.

[0041] Example 2 1. Weigh out 0.3635 g (1 mmol) of zinc trifluoromethanesulfonate (Zn(OTf)2), 0.118 g (2 mmol) of acetamide (Ace), 0.074 g (1 mmol) of 1,3-dioxolane (Dol), and 0.0360 g (2 mmol) of deionized water (H2O) at room temperature. The ratio of this formula is Zn(OTf)2:Ace:Dol:H2O = 1:2:1:2.

[0042] 2. Place the weighed substances into a reagent bottle and stir for 5-10 minutes until there is no obvious precipitate in the reagent bottle.

[0043] Example 3 1. Weigh out 0.3635 g (1 mmol) of zinc trifluoromethanesulfonate (Zn(OTf)2), 0.0886 g (1.5 mmol) of acetamide (Ace), 0.1111 g (1.5 mmol) of 1,3-dioxolane (Dol), and 0.0360 g (2 mmol) of deionized water (H2O) at room temperature. The ratio of this formula is Zn(OTf)2:Ace:Dol:H2O = 1:1.5:1.5:2.

[0044] 2. Place the weighed substances into a reagent bottle and stir for 5-10 minutes until there is no obvious precipitate in the reagent bottle.

[0045] Example 4 1. Weigh out 0.3635 g (1 mmol) of zinc trifluoromethanesulfonate (Zn(OTf)2), 0.0591 g (1 mmol) of acetamide (Ace), 0.1482 g (2 mmol) of 1,3-dioxolane (Dol), and 0.0360 g (2 mmol) of deionized water (H2O) at room temperature. The ratio of this formula is Zn(OTf)2:Ace:Dol:H2O = 1:1:2:2.

[0046] 2. Place the weighed substances into a reagent bottle and stir for 5-10 minutes until there is no obvious precipitate in the reagent bottle.

[0047] Example 5 1. Weigh out 0.3635 g (1 mmol) of zinc trifluoromethanesulfonate (Zn(OTf)2), 0 g (0 mmol) of acetamide (Ace), 0.2222 g (3 mmol) of 1,3-dioxolane (Dol), and 0.0360 g (2 mmol) of deionized water (H2O) at room temperature. The ratio of this formula is Zn(OTf)2:Ace:Dol:H2O = 1:0:3:2.

[0048] 2. Place the weighed substances into a reagent bottle and stir for 5-10 minutes until there is no obvious precipitate in the reagent bottle.

[0049] from Figure 1 (b) It can be seen that the electrolytes constructed from two-component eutectic ligands (Examples 2–4) have higher conductivity compared to the single-component electrolyte containing only Ace (Example 1). Further from... Figure 2 As shown in (f), the desolvation energy diagram reveals that, compared to the single-component Ace electrolyte (Example 1) and Dol electrolyte (Example 5), the electrolyte constructed from the two-component mixed eutectic ligand molecules (Examples 2–4) exhibits a lower desolvation energy, which is beneficial for promoting Zn production. 2+ The desolvation process at the electrode interface. These results indicate that the electrolyte constructed using a two-component mixed ligand exhibits a good synergistic effect.

[0050] Zn / / Zn battery assembly method: Both the positive and negative electrodes are zinc sheets, the separator is a glass fiber separator, and the electrolyte is the hydrated eutectic electrolyte prepared in Examples 1-5, with a dosage of 100 μL.

[0051] Figure 1 (a) Ternary phase diagrams of salt-ligand-water obtained from tests on the electrolytes prepared in Examples 1, 2, 3, 4, and 5. (b) Conductivity and viscosity of different electrolytes. (c) Rate performance tests of different electrolytes. (d) Polarization voltages of different electrolytes at different current densities.

[0052] Figure 1 Electrolyte testing methods: (1) Ternary phase diagram testing: Under the condition of fixed molar ratio of zinc salt: eutectic ligand molecules, the water content under different conditions was tested. (2) The conductivity of the electrolyte was measured using a conductivity meter. (3) The variable current rate performance of Zn / / Zn symmetrical cells assembled with different electrolytes was tested using a blue electric system. (4) The polarization voltage was extracted from the data obtained from the rate test.

[0053] from Figure 1 It can be seen that: Figure 1 As shown in (a), with the increase of the proportion of Dol in the mixed ligands, the minimum water content required for complete dissolution of zinc salts first decreases and then increases, with a clear turning point at a specific ratio. This phenomenon indicates that the introduction of an appropriate amount of Dol can effectively reconstruct the original eutectic network structure and promote the formation of a novel composite solvation system with a lower eutectic point.

[0054] To clearly distinguish electrolyte systems composed of different ligands, electrolytes with a single Ace ligand are named PA, electrolytes with a single Dol ligand are named PD, and electrolytes with mixed ligands (Zn(OTf)2:Ace:Dol:H2O=1:x:y:2, where x+y=3) are uniformly labeled HA. x D y The ionic conductivity test results are as follows: Figure 1 (b) shows that as the Dol ratio increases, the conductivity of the electrolyte system gradually increases, while the viscosity decreases accordingly, indicating that the introduction of Dol effectively improves the bulk transport performance of the electrolyte. However, the Zn / / Zn symmetric cells assembled based on these electrolytes showed poor rate performance in tests. Figure 1 (c) exhibits non-monotonic polarization behavior, indicating that the increase in bulk conductivity is not the sole factor determining the overall battery kinetics. Further statistical analysis of polarization voltages under different formulations ( Figure 1 (d) It was found that the polarization voltage of the battery was minimized when the molar ratio of Ace to Dol was 2:1 (i.e., the HA₂D₁ system). This result suggests that, in addition to bulk ion transport, Zn at the electrode / electrolyte interface... 2+ Desolvation is also a key kinetic link affecting battery polarization behavior. Optimizing ligand composition can synergistically regulate bulk transport and interfacial reactions, thereby achieving more efficient electrochemical performance.

[0055] Figure 2 Zn / / Zn batteries were prepared for Examples 1-5, and then impedance tests were performed on them using an electrochemical workstation, and desolvation energy was obtained after post-processing.

[0056] from Figure 2 It can be seen that the Zn / / Zn battery assembled with the hydrated eutectic electrolyte prepared in Example 2 has the smallest desolvation energy barrier. This indicates that using the battery assembled in Example 2 can help improve the kinetic performance at the interface.

[0057] Figure 3 Impedance tests were performed on Zn / / Zn batteries assembled in Examples 1, 2, and 5 at different amplitude voltages on an electrochemical workstation, and DRT plots for different electrolytes were obtained through post-processing. Figure 3It can be seen that in the DRT diagram obtained by decoupling through impedance spectroscopy, the peak of the interfacial desolvation process represented by Example 2 appears for the shortest time, while the same peak in Example 5 appears for the longest time. This indicates that the desolvation rate of Example 2 is faster, while the desolvation rate of Example 5 is slower.

[0058] Figure 4 The infrared spectra of CO, C=O, and -SO3 obtained by FTIR testing in Examples 1-5 are shown. Figure 4 It can be seen that during Examples 1 to 5, C=O underwent a red shift, CO underwent a blue shift, and -SO3 also underwent a blue shift. This indicates that increasing the Dol content weakens the effect of Ace on Zn. 2+ Coordination with Dol and OTf - For Zn 2+ Coordination.

[0059] Figure 5 In the simulation calculations, Zn in (a) Examples 1-5 is obtained. 2+ Surrounding water molecules, OTf - Coordination number (CN) of anions and different ligand molecules. (b) Different Zn 2+ Binding energy of the solvated structure. (c) Binding energy of the main solvated structures in Examples 1, 2, and 5. From Figure 5 It can be seen that: simulation calculations show that as the Dol content increases, OTf - anion-paired Zn 2+ The coordination number also increases. [Zn(H2O)5Dol] 2+ Relative to [Zn(H2O)5Ace] 2+ The solvation energy is smaller. The larger solvation energy of Example 5 compared to the main solvation structures in Examples 1 and 2 indicates that increasing the Dol content promotes OTf. - For Zn 2+ The coordination of the Dol molecule is mainly due to the weak solvation energy of the Dol molecule relative to the Ace molecule. This results in different solvation structures in the final examples. As a result, the desolvation energy barrier in Example 5 is larger, while that in Example 2 is smaller, indicating that Example 2 is easier to desolvate, while Example 5 is more difficult to desolvate.

[0060] Figure 6 The radial distribution functions of Examples 1-5 obtained through simulation calculations are as follows: Figure 5 The coordination number of a is obtained by post-processing this graph.

[0061] Figure 7 The SEI layer on the zinc anode surface of Examples 1, 2, and 5 was applied under different argon ion (Ar) conditions. +The F 1s XPS spectral region corresponding to the sputtering depth. From Figure 7 It can be seen that the ZnF2 content is highest in the SEI layer of application example 5 as the Dol content increases. This indicates that increasing the Dol content promotes OTf. - Increased decomposition at the zinc anode interface leads to an increased content of ZnF2.

[0062] Figure 8 The different argon ion (Ar) levels in the SEI layer on the zinc substrate surface in Examples 1, 2, and 5. + The O1s XPS spectral region at the sputtering depth. From Figure 8 Quantitative analysis of the O 1s spectrum at a depth of 5 nm in the zinc anode showed that the relative ZnO content in Example 2 was only 34%, significantly lower than that in Example 1 (45%) and Example 5 (41%). This indicates that Example 2 can more effectively suppress the formation of ZnO-like byproducts during cycling, thereby mitigating electrode structure degradation caused by dendrite growth. The lower ZnO content also reflects more uniform zinc deposition and better control of interfacial side reactions in this system, thus contributing to improved reversibility and cycle life of the zinc anode.

[0063] exist Figure 9 middle, Figure 9 (a) Zn 2+ The adsorption energies on the Zn anode and ZnF2, respectively. Figure 9 (b) to (c) are the interfacial impedances measured after cycling with the base electrolyte (1M Zn(OTf)2) in Examples 1, 2, and 5, with the SEI layer removed and the cells reassembled. (d) are the polarization voltages measured after cycling with the base electrolyte (1M Zn(OTf)2) in Examples 1, 2, and 5, with the SEI layer removed and the cells reassembled. Figure 9 It can be known that: Zn 2+ The adsorption energy on ZnF2 is greater than that on Zn. In Example 5, the interfacial impedance was lowest after cycling and the SEI layer was removed and the cell was reassembled. The electrolyte with added eutectic ligand molecules showed less polarization after cycling compared to the electrolyte without them. This indicates that ZnF2 is more suitable for adsorbing Zn... 2+ Greater adsorption promotes Zn 2+ Migration on ZnF2. The battery assembled in Example 5, which has the highest ZnF2 content, has the lowest measured impedance and also exhibits less polarization after cycling.

[0064] Figure 10 (a) FTIR peak profiles (OH stretching vibration region) for Examples 1-5. (b) Ratio of free water to (c) clustered water. From Figure 10It can be seen that with the increase of Dol content, the FTIR peak fitting results show a decrease in free water content and an increase in clustered water content. This indicates that in the bulk electrolyte, an increase in Dol content is more conducive to breaking water activity and forming a greater proportion of hydrogen bonds with water.

[0065] Figure 11 (a) Adsorption energies of H₂O, Ace, and Dol on the Zn(002) crystal plane. (b) Differential capacitance curves of the Zn / / Ti half-cell in different embodiments. (c) LUMO and HOMO of H₂O, Ace, and Dol. (d) Contact angle measurements of droplets on the zinc metal surface in different embodiments. Figure 11 It can be seen that Ace has the highest adsorption energy with the Zn anode, and its differential capacitance is also the lowest. Ace has the narrowest HOMO-LUMO band gap compared to other molecules. The droplet in Example 1, with the highest Ace content, has the largest contact angle on the zinc metal, while the droplet in Example 5, with the highest Dol content, has the smallest contact angle on the zinc metal. This indicates that Ace is thermodynamically more likely to undergo strong adsorption on the electrode surface, thus preferentially occupying interfacial active sites. Ace molecules can effectively embed into the inner layer of the electric double layer structure, displacing and replacing water molecules originally adsorbed on the electrode surface, thereby improving the thermodynamic stability of the interface and suppressing water-related side reactions. Furthermore, Ace molecules exhibit higher electronic activity, making them more likely to participate in interfacial charge exchange processes, consistent with their strong adsorption capacity and interfacial reaction tendency. Although Ace shows significant advantages when considering adsorption alone, contact angle tests reveal that increasing the Dol content significantly improves the wettability of the electrolyte.

[0066] Figure 12 In Examples 1, 2, and 5, (a) XRD patterns of the zinc anode after 50 cycles (5°–80°). (b) Chronocurrent curves of zinc deposition at an overpotential of -200 mV. (c) Scan rate at 0.5 mV s. -1 Linear sweep voltammograms at different times. (d) Coulombic efficiency of zinc deposition / stripping in Zn / / Cu cells under "pre-deposition" mode. From Figure 10 It can be seen that, compared to other embodiments, the battery in Example 2 produces fewer byproducts during operation. Simultaneously, the battery reaches a current-stabilized state in a shorter time. Furthermore, the electrolyte system of Example 2 exhibits a larger hydrogen evolution overpotential. Ultimately, these advantages work together to achieve a higher coulombic efficiency in Example 2. This indicates that Example 2 is more effective than other embodiments in suppressing hydrogen evolution side reactions and dendrite formation.

[0067] Figure 13(a) Typical SEM images of the zinc anode after 50 cycles of Zn / / Zn batteries in Examples 1, 2, and 5. (b) Images of the zinc anode in Examples 1, 2, and 5 at 2 mA cm⁻¹. -2 In-situ optical micrographs of the zinc deposition process at current density. From Figure 13 SEM analysis revealed that the zinc anode surface deposited in Example 2 exhibited a significantly flat and uniform morphology (dense structures were visible at both the 5 μm and 2 μm scales), indicating that Example 2 facilitated uniform deposition with three-dimensional expansion. In contrast, the zinc anode surfaces in Examples 1 and 5 showed a distinctly vertically oriented deposition structure after cycling. This oriented growth is prone to evolving into dendrites over time, increasing the risk of membrane puncture and severely impacting battery safety and cycle life. In-situ optical microscopy results also indicated that the faster interfacial kinetics of Example 2 contributed to the Zn... 2+ Uniform diffusion and orderly deposition are achieved at the electrode / electrolyte interface, thereby effectively suppressing dendrite nucleation and growth, providing a key morphological basis for improving the cycle stability of zinc anodes.

[0068] Figure 14 In the examples 1, 2, and 5, Zn / / Zn batteries were assembled at (a) 1 mA cm -2 1mAh cm -2 and (b) 5mA cm -2 1mAh cm -2 Long-cycle testing was performed at current density. From Figure 11 It can be seen that, compared with other embodiments, the battery in Example 2 has less polarization and a longer cycle life. This indicates that, due to the series of characterization tests shown in the preceding series, Example 2 can effectively suppress the generation of battery side reactions, thus demonstrating a longer cycle life and greater durability in long-cycle tests.

[0069] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A hydrated eutectic electrolyte, characterized in that, The electrolyte comprises zinc salt, a two-component mixed eutectic ligand molecule, and water; The two-component mixed eutectic ligand molecule is any two of the following two-component mixtures: urea, acetamide, N-methylacetamide, nicotinamide, difluorobenzene, 1,3-dioxolane, sulfolane, and tetrahydrofuran.

2. The hydrated eutectic electrolyte according to claim 1, characterized in that, The zinc salt is one or more of ZnCl2, Zn(ClO4)2, ZnSO4, Zn(OTf)2, and Zn(BF4)2.

3. The hydrated eutectic electrolyte according to claim 1, characterized in that, The two-component mixed eutectic ligand molecule includes eutectic ligand molecule 1 and eutectic ligand molecule 2; In the hydrated eutectic electrolyte, the molar ratio of zinc salt, eutectic ligand 1, eutectic ligand 2, and water is (0.5~1.5):(0.5~3):(0.5~3):(1.5~2.5).

4. The hydrated eutectic electrolyte according to claim 3, characterized in that, In the hydrated eutectic electrolyte, the molar ratio of zinc salt, eutectic ligand 1, eutectic ligand 2, and water is (0.8~1.2):(1~2):(1~2):(1.8~2.2).

5. The hydrated eutectic electrolyte according to claim 3, characterized in that, When the co-crystal ligand 1 is acetamide and the co-crystal ligand 2 is 1,3-dioxolane, the molar ratio of co-crystal ligand 1 to co-crystal ligand 2 is (1.5~2):(1~1.5), preferably (1.8~2):(1~1.2).

6. A method for preparing the hydrated eutectic electrolyte according to any one of claims 1 to 5, characterized in that, Includes the following steps: The zinc salt, the two-component mixed eutectic ligand molecules, and water are mixed and stirred to obtain the product.

7. The preparation method according to claim 6, characterized in that, Stir for 5-10 minutes.

8. The application of the hydrated eutectic electrolyte according to any one of claims 1 to 5 or the hydrated eutectic electrolyte prepared by the preparation method according to claim 6 or 7 in the preparation of batteries.

9. The application according to claim 8, characterized in that, The battery is an aqueous zinc-ion battery.

10. A zinc-ion battery, characterized in that, Includes an electrolyte, wherein the electrolyte is the hydrated eutectic electrolyte according to any one of claims 1 to 5 or the hydrated eutectic electrolyte prepared by the preparation method according to claim 6 or 7.

Images