Eutectic-based electrolytes for rechargeable zinc batteries

Abstract

An electrolyte for an electrochemical device is disclosed. The electrolyte can include a triethylamine halide and a zinc salt, where the triethylamine halide and zinc salt are a eutectic electrolyte mixture. The electrolyte can include where the triethylamine halide is a chloride or a hydrochloride. The zinc salt can include a sulfate, a tetrafluoroborate, or where the zinc salt is hydrated. The eutectic electrolyte mixture may include triethylamine hydrochloride and a zinc sulfate hydrate. The eutectic electrolyte mixture may include triethylamine hydrochloride and zinc trifluoromethane sulfonic acid (Zn(CF3SO3)2). The eutectic electrolyte mixture may include a zinc tetrafluoroborate, a zinc perchlorate, a zinc acetate, a zinc bis(trifluoromethylsulfonyl)imide, or a combination thereof.

Description

Eutectic-Based Electrolytes for Rechargeable Zinc BatteriesREFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 605,760, filed on December 4, 2023, which is hereby incorporated by reference in its entirety.STATEMENT OF GOVERNMENT INTEREST

[0002] This invention was made with government support under Grant Number 2119688 awarded by the National Science Foundation. The government has certain rights in the invention.TECHNICAL FIELD

[0003] The present teachings relate generally to energy storage devices and, more particularly, to eutectic-based electrolytes for use in rechargeable batteries.BACKGROUND

[0004] Rechargeable batteries are important in ongoing technological developments, providing portable and sustainable energy solutions for a multitude of applications ranging from electric vehicles to grid storage to remote power solutions. Among the components of rechargeable batteries, electrolyte compositions can represent an important rechargeable battery feature as the electrolyte composition can impact performance, safety, and efficiency. Electrolyte compositions are the conductive medium facilitating ion transport between the cathode and anode within a battery or electrochemical device, impacting the performance attributes of a battery. Traditional liquid electrolytes, while widely employed, possess inherent limitations such as flammability, volatility, and sensitivity to high temperatures, thereby introducing potential safety concerns while limiting their application in technologies demanding higher levels of performance.

[0005] For such energy storage or conversion systems, recent attention has been focused on eutectic-based electrolytes. Eutectic mixtures are characterized by lower melting points and desirable electrochemical properties as compared to conventional electrolytes. Eutectic-based electrolytes can improve the energy density, cycle life, and safety of energy storage devices. Eutectic-based electrolytes also provide lower volatility, reduced flammability, and improved thermal stability.

[0006] Therefore, it is desirable to fabricate rechargeable batteries or energy storage devices using improved materials including eutectic-based electrolytes.SUMMARY

[0007] The following presents a simplified summary in order to provide a basic understanding of some aspects of one or more embodiments of the present teachings. This summary is not an extensive overview, nor is it intended to identify key or critical elements of the present teachings, nor to delineate the scope of the disclosure. Rather, its primary purpose is merely to present one or more concepts in simplified form as a prelude to the detailed description presented later.

[0008] An electrolyte for an electrochemical device is disclosed. The electrolyte also a triethylamine hydrohalide or a triethylammonium halide, and a zinc salt, and where the triethylamine hydrohalide or the triethylammonium halide and the zinc salt include a eutectic electrolyte mixture. Implementations of the electrolyte for an electrochemical device include where the electrolyte includes triethylamine hydrochloride. The triethylamine hydrohalide is selected from the group may include of triethylamine hydrofluoride, triethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydroiodide, triethylamine hydroastatide, or a combination thereof. The electrolyte may include triethylammonium halide. The triethylammonium halide is selected from the group may include of triethylammonium fluoride, triethylammonium chloride, triethylammonium bromide, triethylammonium iodide, and triethylammonium astatide, or a combination thereof. The zinc salt may include a hydrated form of the zinc salt. The zinc salt is selected from the group may include of zinc tetrafluoroborate, zinc acetate, zinc chloride, zinc bis(trifluoromethane)sulfonimide, zinc nitrate, zinc perchlorate, and zinc trifluoromethanesulfonate. The eutectic electrolyte mixture may include zinc sulfate heptahydrate and triethylamine hydrochloride, zinc trifluoromethanesulfonate and triethylamine hydrochloride, zinc tetrafluoroborate hydrate and triethylamine hydrochloride, or zinc bis(trifluoromethane)sulfonimide and triethylamine hydrochloride. The electrolyte may include an additional metal salt, such as zinc, magnesium, calcium, iron, aluminum, lithium, sodium, or a combination thereof. A molar ratio of the triethylamine hydrohalide or the triethylammonium halide and the zinc salt is from about 1 : 0. 1 to about 1: 10.

[0009] An electrochemical device is disclosed. The electrochemical device includes a cathode, an anode, and an electrolyte disposed to facilitating ion transport between the cathode and the anode, which may include a triethylamine hydrohalide or a triethylammonium halide and a zinc salt, and where the triethylamine hydrohalide or the triethylammonium halide and zinc salt form a eutectic electrolyte mixture. Implementations of the electrochemical device include where the cathode can include conversion-type materials, intercalation-type materials,doping-type materials, or a combination thereof. The cathode may include manganese oxide, vanadium oxide, graphite, graphene, polyaniline, carbon nanotubes, or a combination thereof. The anode may include zinc. The electrolyte may include triethylamine hydrochloride and is selected from the group may include of triethylamine hydrofluoride, triethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydroiodide, triethylamine hydroastatide, or a combination thereof. The electrolyte may include triethylammonium halide and is selected from the group may include of triethylammonium fluoride, triethylammonium chloride, triethylammonium bromide, triethylammonium iodide, and triethylammonium astatide, or a combination thereof. A molar ratio of the triethylamine hydrohalide or the triethylammonium halide and the zinc salt is from about 1 :0.1 to about 1: 10.

[0010] An electrolyte for an electrochemical device is disclosed. The electrolyte includes a triethylamine hydrohalide or a triethylammonium halide, and a zinc salt. The electrolyte also includes an additional metal salt where the triethylamine hydrohalide or the triethylammonium halide and the metal salt form a eutectic electrolyte mixture. The additional metal salt can include zinc, magnesium, calcium, iron, aluminum, lithium, sodium, or a combination thereof.

[0011] The features, functions, and advantages that have been discussed can be achieved independently in various implementations or can be combined in yet other implementations further details of which can be seen with reference to the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present teachings and together with the description, serve to explain the principles of the disclosure. In the figures:

[0013] FIG. 1 depicts a plot of a representative electrochemical impedance spectra recorded for the eutectics formed between [Et3NH]Cl-ZnSO4.7H2O in the frequency range of 1MHz to 100 mHz, in accordance with the present disclosure.

[0014] FIG. 2 depicts a series of typical chronoamperometric plots obtained for SS|[Et3NH]Cl-ZnSC>4.7H2O|SS cell, measured at a constant potential of 10 mV, in accordance with the present disclosure.

[0015] FIG. 3 is a plot demonstrating linear sweep voltammetry recorded on SS 316 substrate to decipher the potential stability window of 1:0.43 mole% of [Et3NH]Cl:ZnSC>4.7H2O eutectic electrolyte, in accordance with the present disclosure.

[0016] FIGS. 4A - 4C depict plots showing measurements of cyclic voltammetry recorded on a Zn / [Et3NH]Cl:ZnSC>4.7H2O / SS 316 plate in the voltage range of -0.5-1.5 V at the slew rate of 0.5 mV.s1, in accordance with the present disclosure.

[0017] FIGS. 5 A and 5B depict a plot demonstrating galvanostatic charge-discharge plating followed by stripping at 0.1 mA / cm2 on a Cu substrate, and a scanning electron microscope (SEM) image of successful Zn deposits, respectively, in accordance with the present disclosure.

[0018] FIGS. 6A and 6B depict a plot demonstrating galvanostatic charge-discharge stripping followed by plating at 0.1 mA / cm2 on a Cu substrate, and a scanning electron microscope (SEM) image of successful Zn deposits, respectively, in accordance with the present disclosure.

[0019] FIGS . 7A and 7B depict plots of XRD patterns recorded for the samples shown in FIG. 5B and FIG. 6B, respectively, in accordance with the present disclosure.

[0020] FIG. 8 is a plot depicting galvanostatic plating and stripping in a Zn||Zn symmetric cell using 1:0.43 mole% of [EtsNHJCFZnSO^FEO under different current densities, as noted in the plot, in accordance with the present disclosure.

[0021] FIG. 9 is a plot depicting galvanostatic plating / stripping in a Zn||Zn symmetric cell in 1 :0.43 mole% of [EtsNHJCFZnSO^FEO at a current density of 0.1 mA. cm2and the cyclability of the cell achieved for >3000 hours, in accordance with the present disclosure.

[0022] FIGS. 10A - 10C are plots depicting representative cyclic voltammetric profdes of electrochemical devices using electrodes made from Zn-Graphene Nanoplatelets (FIG. 10A), Zn-V20s (FIG. 10B), and Zn-PANI / CNTs (FIG. 10C), respectively, with 1:0.43 mole% of [Et3NH]Cl:ZnSO4.7H2O electrolyte, in accordance with the present disclosure.

[0023] FIGS. 11A and 1 IB are plots depicting galvanostatic charge-discharge profdes of Zn||PANI / CNTs in 1:0.43 mole% of [Et3NH]Cl:ZnSO4.7H2O, and cell performance recorded at 50 mA / g, respectively, in accordance with the present disclosure.

[0024] FIGS. 12A and 12B are plots depicting galvanostatic charge-discharge profde of Zn||V2C>5 in [Et3NH]Cl:ZnSO4.7H2O and cell performance recorded at 50 mA / g, respectively, in accordance with the present disclosure.

[0025] FIG. 13 is a plot depicting representative electrochemical impedance spectra recorded for the eutectic mixtures formed between [Et3NH]Cl-Zn(CF3SO3)2 in the frequency range of 1MHz to 100 mHz, in accordance with the present disclosure.

[0026] FIGS. 14A-14D depict cyclic voltammetry plots recorded on a Zn / [EtsNHJCl- Zn(CF3SO3)2 / SS 316 plate in the voltage range of -0.5-1.5 V at the slew rate of 0.5 mV.s'1, for molar ratios of 1:0.303, 1:0.34, 1:0.38, and 1:0.42, respectively, in accordance with eh present disclosure.

[0027] FIG. 15 depicts a plot showing linear sweep voltammetry recorded on SS 316 substrate to decipher the potential stability window of 1 :0.34 mole% of [ EtsNH ]C1- ZniCFsSOsh eutectic electrolyte composition, in accordance with the present disclosure.

[0028] FIGS. 16A and 16B depict a data plot associated with a galvanostatic chargedischarge plating followed by stripping at 0. 1 mA / cm2 on Cu substrate, and a scanning electron microscope (SEM) image of successful Zn deposits during the experiments, respectively, in accordance with the present disclosure.

[0029] FIGS. 17A-17C are data plots depicting a galvanostatic charge-discharge stripping followed by plating at 0. 1 mA / cm2 on Cu substrate, a scanning electron microscope (SEM) image of successful Zn deposits, and a plot showing XRD patterns from the examples shown in FIG. 16B and 17B, respectively, in accordance with the present disclosure.

[0030] FIGS. 18A-18C are plots depicting a representative cyclic voltammetric profde of Zn-PANI / CNTs cell in 1:0.34 mole% of [EtsNHJCFZ^CFsSOs , a galvanostatic chargedischarge profde of Zn||PANI / CNTs in 1:0.34 mole% of [Et3NH]Cl:Zn(CF3SO3)2 and cell performance recorded at 50 mA / g, and cycling performance of a galvanostatic chargedischarge profde of Zn||PANI / CNTs in 1:0.34 mole% of [Et3NH]Cl:Zn(CF3SO3)2, respectively, in accordance with the present disclosure.

[0031] FIGS. 19 and 19B are data plots showing representative cyclic voltammetric profdes of Zn-V20s in 1 :0.34 mole% of [Et3NH]Cl:Zn(CF3SC>3)2 recorded at different scan rates, and plots of the peak current measured versus the square root of the scan rate for the Zn-A^CE cell, respectively, in accordance with the present disclosure.

[0032] FIGS. 20A and 20B are data plots showing the galvanostatic charge-discharge profde of Zn||V2O5in 1:0.3 mole% of [EtsNHJCkZnlCFsSCEE and cell performance recorded at 50 mA / g, respectively, in accordance with the present disclosure.

[0033] It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding of the present teachings rather than to maintain strict structural accuracy, detail, and scale.DETAILED DESCRIPTION

[0034] Reference will now be made in detail to exemplary embodiments of the present teachings, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same, similar, or like parts.

[0035] The present disclosure provides the use of electrolyte compositions including eutectic-based electrolytes to exploit the properties of eutectic -based electrolytes and toovercome the limitations of conventional liquid electrolytes. Eutectic mixtures are formed by combining two or more components to yield a mixture with a lower melting point than the individual constituents, offering advantages such as wider electrochemical stability windows and improved compatibility with electrode materials as compared to conventional electrodes. A eutectic system or eutectic mixture provides a homogeneous mixture where the lowest possible melting point of all the mixing ratios of the constituents or ingredients is referred to as the eutectic temperature. These properties make eutectic-based electrolytes particularly attractive for use in high-performance rechargeable batteries. In the included examples, the deep eutectic point of a specific composition widens the liquid range significantly, enhancing ionic conductivity and ion transport capability. This characteristic enables batteries to performs exceptionally well even under extreme conditions.

[0036] Eutectic compositions also provide additional tunability for tailoring electrolyte properties to meet specific application requirements. This flexibility enables the design of electrolytes that can provide enhanced energy storage or energy conversion performance with added environmental sustainability.

[0037] Common energy storage devices include certain components necessary for their operation. Batteries, for example, typically consist of two main electrodes, the anode, and the cathode, which participate in the electrochemical reactions that occur within the battery or battery cell during charging and discharging cycles. An anode is the electrode where oxidation or a loss of electrons takes place during discharge. Anode materials include graphite, zinc, and various forms of carbon can be used. Cathodes are the electrode where reduction, or a gain of electrons occurs during discharge. Cathode materials are usually dependent upon the battery type. In examples of lithium-ion batteries, cathodes can contain lithium transition metal oxides such as, but not limited to lithium cobalt oxide (LiCoCT). lithium manganese oxide (LiM^CE), or lithium iron phosphate (LiFePO4). Lead-acid battery examples can include cathodes including lead compounds such as lead dioxide (PbO2). while nickel-metal hydride (NiMH) batteries, can include nickel oxyhydroxide compounds as exemplary cathode materials.

[0038] An electrochemical device, in a general sense, can include devices that utilize electrochemical processes to convert electrical energy into chemical energy or vice versa. These devices often involve the movement of electrons and ions between electrodes and electrolytes. Electrochemical devices can be employed in applications, such as but not limited to energy storage (batteries), energy conversion (fuel cells), and environmental processes (CO2 capture devices).

[0039] An electrochemical cell or device, such as a battery includes an electrolyte, or a conductive medium that serves to facilitate the movement of ions between the anode and cathode. Electrolytes can be liquid, solid, or gel-based, depending on the battery technology.Liquid electrolytes can include those used in lithium-ion batteries, where the liquid electrolytes can be or include lithium salts dissolved in organic solvents, such as but not limited to lithium hexafluorophosphate (LiPFe). Solid Electrolytes such as those used in solid- state batteries can employ materials like lithium garnet, also referred to as LiyLasZ Oi 2 or LLZO.

[0040] A separator of an electrochemical cell or battery physically separates the anode and cathode to prevent short circuits while allowing the flow of ions. Separators can further separate different cells or sections of a cell that may include materials in different phases. Common separator materials include microporous polymer membranes, polyethylene, and polypropylene. Other battery or electrochemical cell components can include current collectors for the electrodes, which aid in the efficient flow of electrons to and from an external circuit, such as those made from high conductivity metals like copper or aluminum. Batteries or electrochemical cells can also incorporate enclosures, terminals, and other additives to enhance performance, such as stabilizing agents, flame retardants, or conductive salts.

[0041] Common components in CO2 capture devices include absorbent materials, used in solvent-based CO2 capture systems, used to selectively capture CO2. Common absorbents include amines or other chemical compounds with high CO2 affinity. Also used in CO2 capture devices are adsorbent materials, which include porous materials like activated carbon or metal-organic frameworks, used to physically adsorb CO2 molecules. A reactor is a vessel or system in which the CO2 capture process takes place and can contain the absorbent or adsorbent material while providing the necessary conditions for CO2 capture. CO2 capture devices can also include a regeneration system for the purpose of releasing any captured CO2 to prepare the material for a subsequent capture cycle. This regeneration step typically involves changing conditions such as temperature or pressure.

[0042] Other examples of electrochemical cells or devices include fuel cells, electrolyzers, and sensors. Fuel cells are electrochemical devices that convert chemical energy directly into electrical energy. Electrolyzers utilize electrical energy to drive a non-spontaneous chemical reaction, such as the splitting of water into hydrogen and oxygen. Fuel cells and electrolyzers include anodes, cathodes, and electrolytes, and their respective arrangements and specific components are known to those skilled in the art. Sensors, such as glucose sensors or gas sensors, use electrochemical principles, such as the electrical response of a chemical reaction to detect and quantify the presence of specific substances.

[0043] Electrochemical devices of the present disclosure can include aqueous based eutectic electrolyte mixtures that provide air-stable electrolytes that can be operated at high voltage charge and discharge conditions at high current densities. Potential combinations of electrolytes for the application of rechargeable zinc -based energy storage or conversiondevices, can use triethylamine -hydrochloride or triethylamine -chloride as well. Exemplary zinc -based eutectic electrolytes include mixtures of triethylamine hydrochloride ([Et3NH]Cl) and various salts, such as [Et3NH]Cl and zinc sulfate ZnSCE xFEO, [Et3NH]Cl and zinc tetrafluoroborate Zn(BF4)3xFEO, [Et3NH]Cl and zinc perchlorate Zn(ClC>4)2 xFEO, [Et3NH]Cl and zinc acetate Zn(CH3CC>2)2 xFEO, [Et3NH]Cl and zinc trifluoromethane sulfonic acid Zn(CF3SO3)2, [Et3NH]Cl and zinc bis(trifluoromethylsulfonyl)imide Zn[(CF3SO2)2N]2 or combinations thereof. In the examples described herein, x>0 for the hydrated salts, and the eutectics are applied for the energy storage / conversion with or without additional zinc-based salts as supporting electrolyte. The zinc -based eutectic electrolyte show homogenous mixtures when combined. Other ingredients including a zinc salt or mixture of multiple zinc salts, including chlorides or other halide salts, such as a triethylamine halide including fluoride, chloride, bromide, iodide, or astatide, as well as combinations thereof can be used in the eutectic electrolyte mixtures. Other examples of eutectic electrolyte mixtures include zinc nitrate (Zn(NO3)2.xH2O), zinc chloride (ZnCF.xFEO) or mixtures including triethylamine hydrochloride ([Et3NH]Cl), triethylamine hydrofluoride ([Et3NH]F), triethylamine hydrobromide ([Et3NH]Br), triethylamine hydroiodide ([Et3NH]I) or combinations thereof.

[0044] Exemplary electrolytes of the present disclosure can include a triethylamine hydrohalide or alternatively, a triethylammonium halide, and a zinc salt, and where the triethylamine hydrohalide or the triethylammonium halide and the zinc salt combine to form a eutectic electrolyte mixture. When the electrolyte includes triethylamine hydrohalide, it can be selected from the group including triethylamine hydrofluoride, triethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydroiodide, triethylamine hydroastatide, or a combination thereof. Additional examples, similar to triethylamine hydrohalide, can include compositions having a structure of [RIR2R3N]HX where Ri, R2, R3= CnFEn+i where n >0.The electrolyte may include triethylammonium halide, where the triethylammonium halide is selected from the group of triethylammonium fluoride, triethylammonium chloride, triethylammonium bromide, triethylammonium iodide, and triethylammonium astatide, or a combination thereof. Additional examples, similar to triethylammonium halide can include compositions having a structure denoted by [RIR2R3R4N]+X_where Ri, R2, R3, R4 = H, CnEfcn+i where n>0. The zinc salt may include a hydrated, or alternatively a non-hydrated form of the zinc salt. The zinc salt can be or include zinc tetrafluoroborate, zinc acetate, zinc chloride, zinc bis(trifluoromethane)sulfonimide, zinc nitrate, zinc perchlorate, zinc trifluoromethane sulfonate, or a combination thereof. In examples, the eutectic electrolyte mixture may include zinc sulfate heptahydrate and triethylamine hydrochloride, zinc trifluoromethane sulfonate and triethylamine hydrochloride, zinc tetrafluoroborate hydrate and triethylamine hydrochloride, or zincbis(trifluoromethane)sulfonimide and triethylamine hydrochloride. The electrolyte may include an additional metal salt, to form a ternary eutectic mixture, and include metals such as zinc, magnesium, calcium, iron, aluminum, lithium, sodium, potassium, calcium, manganese, or a combination thereof. A molar ratio of the triethylamine hydrohalide or the triethylammonium halide and the zinc salt is from about 1:0.1 to about 1: 10. In further examples of the electrolyte composition, the triethylamine halide can include either a chloride or a hydrochloride.

[0045] The electrochemical device includes an electrolyte that allows the ions to diffuse from one electrode to another electrode. The electrolyte can be in non-aqueous form or aqueous form or combination thereof. The electrolyte may be considered eutectic which is the combination of two or more compounds leading to attain liquid phase at room temperature and allow it to retain liquid phase at extremely low-temperatures, such as those described herein. The eutectic electrolyte may include additional components such as triethylamine hydrohalide or triethylammonium halide where triethylamine hydrohalide may include triethylamine hydrofluoride, triethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydroiodide, triethylamine hydroastitide, or combinations thereof, or triethylammonium halides including triethylammonium fluoride, triethylammonium chloride, triethylammonium bromide, triethylammonium iodide, triethylammonium astitide.

[0046] The eutectic electrolyte can include zinc salt where the zinc salt can be hydrated or non-hydrated salt or include a combination thereof. The zinc salt may be composed of a zinc cation and various anions such as but not limited to sulfate, nitrate, chloride, perchlorate, acetate, tetrafluoroborate, trifluoromethanesulfonate, bis(triethylamine)sulfonimide, bis(trifluoromethane)sulfonimide, or combinations thereof. The electrolyte may be a nonaqueous system. The zinc salt comprising zinc cation and various anions may also include the water in the electrolyte leading to hydrated electrolyte or aqueous electrolyte compositions.

[0047] While small amounts of the zinc salts in electrolyte compositions of the present disclosure contribute to improved battery performance, suitable molar ratios can include a ratio of the triethylamine hydrohalide or the triethylammonium halide to the zinc salt of from about 1:0.1 to about 1: 10, or 1:2, or 1:4, or 1:7, or from about 1:0.25 to about 1:0.6. It should be noted that these ranges or effective ratios can be dependent on the specific zinc salt anion utilized in the electrolyte composition. In examples, the eutectic electrolyte mixture has an ionic conductivity of from about 0. 1 mScm-1to about 10 mScm1, or from about 0.2 mScm1to about 0.8 mScm1. These conductivity values of the eutectic electrolyte mixture or composition are also dependent upon the specific components.

[0048] In further examples of electrochemical devices as disclosed herein, there is a separator present in the electrochemical device as well. The electrochemical device comprises an anode, a cathode, electrolyte and the separator which separates the anode and cathode. Aseparator can be defined as a material or structure positioned between the electrodes of an electrochemical cell, designed to allow the transfer of ionic species while preventing direct physical contact between the electrodes. The separator can be made from porous, non-porous, or composite materials, and may include polymers, ceramics, or other materials with suitable ionic permeability and chemical stability in the operating environment of the cell.

[0049] Examples of the present disclosure include an electrochemical device which includes a cathode, an anode, and an electrolyte disposed to facilitating ion transport between the cathode and the anode, which may include a triethylamine hydrohalide or a triethylammonium halide and a zinc salt, and where the triethylamine hydrohalide or the triethylammonium halide and zinc salt form a eutectic electrolyte mixture. In examples, the cathode may include insertion type cathode such as manganese oxide, intercalation type cathode such as vanadium oxide, graphite or graphene, doping type of cathode polyaniline composite with carbon nanotube, or a combination thereof. The device can include an anode (electrode) composed of zinc in pure form or in an alloy form comprising zinc, and the electrode can be in any form such as plate or powder or combination thereof. The zinc anode can be in its pure form or mechanically or chemically or electrochemically coated with any other metals or metal oxides or vice-versa. Alloys of zinc can also include magnesium, aluminum, iron, or combinations thereof.

[0050] FIG. 1 depicts a plot of a representative electrochemical impedance spectra recorded for the eutectics formed between | EhNH ICI-ZnSCf.VtEO in the frequency range of 1MHz to 100 mHz, in accordance with the present disclosure. The measurements shown in FIG. 1 include compositions as noted in the plot, as well as the ionic conductivity measurements listed in Table 1 below.Table 1: Ionic conductivity measured for different molar ratio containing [Et3NH]Cl-ZnSO4.7H2O eutectic electrolyte compositions

[0051] FIG. 2 depicts a series of typical chronoamperometric plots obtained for SS|[Et3NH]Cl-ZnSC>4.7H2O|SS cell, measured at a constant potential of 10 mV, in accordance with the present disclosure. As shown, the measured ionic transport number for all compositions of eutectic electrolytes is 0.95. Desirable ionic transport numbers of >0.9 are beneficial for usage within batteries or other electrochemical devices.

[0052] FIG. 3 is a plot demonstrating linear sweep voltammetry recorded on SS 316 substrate to decipher the potential stability window of 1:0.43 mole% of [Et3NH]Cl:ZnSO4.7H2O eutectic electrolyte, in accordance with the present disclosure. Cyclic voltammetry (CV) is an electrochemical technique that measures the current response of an electrochemical cell to a potential sweep applied at a constant rate. To generate a CV profile, the potential is cyclically varied between two electrodes and the resulting current is recorded. In the context of battery or energy storage device performance, a cyclic voltammetry profile can demonstrate insights into electrochemical reactions occurring within the battery. Peaks in the profile are related to specific electrochemical processes, such as the charging and discharging of the battery. The position, shape, and intensity of these peaks can provide additional information related to reaction kinetics, redox reactions, and electrode stability. While details about the energy storage capacity, charge / discharge efficiency, and overall electrochemical behavior of a battery can be discerned from cyclic voltammetry measurements, anomalies or changes in the peaks may indicate issues such as electrode degradation, electrolyte instability, or other factors affecting battery performance. The linear sweep voltammetry data recorded on SS 316 substrate to decipher the potential stability window of 1 :0.43 mole% of [EtsNHJCFZnSCETFEO eutectic electrolyte shows that the electrolyte demonstrates an excellent oxidative stability of -2.48V vs. Zn / Zn+2.

[0053] FIGS. 4A - 4C depict plots showing measurements of cyclic voltammetry recorded on a Zn / [Et3NH]Cl:ZnSO4.7H2O / SS 316 plate in the voltage range of -0.5-1.5 V at the slew rate of 0.5 mV.s1. The data depicts the Zn stripping and plating, of FIGS 4A, 4B, and 4C corresponding to the compositions of [Et3NH]Cl:ZnSO4.7H2O having 1:0.4, 1:0.43 and 1:0.48 mole%, respectively.

[0054] FIGS. 5 A and 5B depict a plot demonstrating galvanostatic charge-discharge plating followed by stripping at 0.1 mA / cm2on a Cu substrate, and a scanning electron microscope (SEM) image of successful Zn deposits, respectively, in accordance with the present disclosure.

[0055] FIGS. 6A and 6B depict a plot demonstrating galvanostatic charge-discharge stripping followed by plating at 0.1 mA / cm2on a Cu substrate, and a scanning electron microscope (SEM) image of successful Zn deposits, respectively, in accordance with the present disclosure.

[0056] FIGS. 7A and 7B depict plots of XRD patterns recorded for the samples shown in FIG. 5B and FIG. 6B, respectively, in accordance with the present disclosure. The measurements of the samples confirm the successful Zinc deposition on the copper substrate.

[0057] FIG. 8 is a plot depicting galvanostatic plating and stripping in a Zn||Zn symmetric cell using 1 :0.43 mole% of [EtsNHICFZnSChTFbO under different current densities, as noted in the plot, in accordance with the present disclosure. This plot demonstrates the symmetrical Zn cell sustains for >400 hours under different current densities ranging from 0. 1-0.4 mA / cm2, demonstrating stable performance and potential for sustained, long-term use in energy applications.

[0058] FIG. 9 is a plot depicting galvanostatic plating / stripping in a Zn||Zn symmetric cell in 1:0.43 mole% of [EtsNHICFZnSChTFbO at a current density of 0.1 mA. cm2and the cyclability of the cell achieved for >3000 hours, in accordance with the present disclosure.

[0059] FIGS. 10A - 10C are plots depicting representative cyclic voltammetric profdes of electrochemical devices using electrodes made from Zn-Graphene Nanoplatelets (FIG. 10A), Zn-X O (FIG. 10B), and Zn-PANI / CNTs (FIG. 10C), respectively, with 1:0.43 mole% of [Et3NH]Cl:ZnSO4.7H2O electrolyte, in accordance with the present disclosure. These plots and the included data demonstrate successful de- / intercalation or de- / doping of ions at the active electrode site. Electrodes made of zinc-graphene nanoplatelets (NP), zinc- polyaniline / carbon nanotubes (Zn-PANI / CNTs), and zinc-vanadium oxide (Zn-A^CE) are exemplary but can also be made, in alternate examples, from materials such as other carbonbased materials, conductive polymers, or intercalation-type cathode materials, such as vanadium oxide-based materials. In other examples, zinc can be paired with other cathode materials, such as doping-type materials, for example, conductive polymers, conversion-type cathode materials such as manganese oxides, carbon-based materials, and metal oxides or sulfides in pristine or composite form that undergo the de - / intercalation, de- / doping and / or conversion mechanism at the cathode site.

[0060] FIGS. 11A and 1 IB are plots depicting galvanostatic charge -discharge profiles of Zn||PANI / CNTs in 1:0.43 mole% of [EtsNHICFZnSChTFEO, and cell performance recorded at 50 mA / g, respectively, in accordance with the present disclosure. The cell shows a high discharge capacity of 100 mAh / g for first cycle and delivers 50 mAh / g after 100 cycles.

[0061] FIGS. 12A and 12B are plots depicting galvanostatic charge-discharge profile of Zn||V2C>5 in [Et3NH]Cl:ZnSO4.7H2O and cell performance recorded at 50 mA / g, respectively, in accordance with the present disclosure. A high discharge capacity of -600 mAh / g was obtained for the 1:0.33 mole% whereas -1200 mAh / g discharge capacity was retained for 1:0.43 mole%. After 450 cycles, a discharge capacity of -60 mAh / g was retained, as shown in cycle performance data shown in FIG. 12B.

[0062] Advantages of the Et3NH]Cl:ZnSC>4.7H2O eutectic electrolyte composition used in electrochemical devices can include or provide devices having elevated open circuit potential, of from about 1.1 V to about 1.2V, extended operational voltage windows of from about 2.45 V as compared to materials using Zn / Zn+2. The eutectic electrolyte compositions further offer robust liquid range maintenance, that can show superior performance as compared to hydrogen evolution reaction in alternate electrochemical devices. The eutectic electrolyte compositions of the present disclosure also provide the capability of operating in all-climate conditions, across a range of operating temperatures. Without being bound by any particular theory, it is theorized that a suitable operating range should be -20 °C to 100 °C, or alternatively from -30 °C to 120 °C.

[0063] These eutectic electrolyte compositions can be paired with various choices of cathodes, such as graphene, V2O5, and PANI / CNTs, as well as other cathodes or electrodes known to those skilled in the art, while operating at an ultra-high capacity of >1200 mAh / g, which is shown for at least Zn||V2C>5 in 1:0.43 mole% of [EtsNHJCTZnSChTEhO. Other benefits of electrochemical devices using the eutectic electrolyte compositions described herein include the ability of fabricating the cells or devices in an open atmosphere and providing cyclability of the resulting cell of >500 cycles.

[0064] Additional data has been compiled for various eutectic mixtures of electrolyte compositions including [EtsNEQCl and ZniCRSCEE. Triethylamine hydrochloride, also referred to as TEA, was mixed with zinc trifluoromethanesulfonic acid, ZniCRSCfE. to form eutectic mixtures for electrolytes for electrochemical devices.

[0065] FIG. 13 is a plot depicting representative electrochemical impedance spectra recorded for the eutectic mixtures formed between | EhNH ICd-ZnfC sSOsE in the frequency range of 1MHz to 100 mHz, in accordance with the present disclosure. The measurements shown in FIG. 13 include compositions as noted in the plot, as well as the ionic conductivity measurements listed in Table 2 below for similar compositions. A notable result for ionic conductivity of -0.73 mS.cnr1was measured for the composition having 1:0.34 mole percentage of [EtsNHJCl-Z^CFsSOs .Table 2: Ionic conductivity measured for the different molar ratio containing [Et3NH]Cl-ZnSO4.7H2O eutectic electrolyte.

[0066] FIGS. 14A-14D depict cyclic voltammetry plots recorded on a Zn / | Et,NH | Cl- ZnlGFsSOs / SS 316 plate in the voltage range of -0.5-1.5 V at the slew rate of 0.5 mV.s1, for molar ratios of 1:0.303, 1:0.34, 1:0.38, and 1:0.42, respectively, in accordance with eh present disclosure. The data in FIGS. 14A, 14B, 14C, and 14D depicts the successful Zn stripping and plating during the cyclic voltammetry measurements.

[0067] FIG. 15 depicts a plot showing linear sweep voltammetry recorded on SS 316 substrate to decipher the potential stability window of 1 :0.34 mole% of [ EtsNH ]C1- Zn(CF3SO3)2 eutectic electrolyte composition, in accordance with the present disclosure. The electrolyte demonstrates an oxidative stability of -2.2V vs. Zn / Zn+2.

[0068] FIGS. 16A and 16B depict a data plot associated with a galvanostatic chargedischarge plating followed by stripping at 0. 1 mA / cm2 on Cu substrate, and a scanning electron microscope (SEM) image of successful Zn deposits during the experiments, respectively, in accordance with the present disclosure.

[0069] FIGS. 17A-17C are data plots depicting a galvanostatic charge -discharge stripping followed by plating at 0. 1 mA / cm2 on Cu substrate, a scanning electron microscope (SEM) image of successful Zn deposits, and a plot showing XRD patterns from the examples shown in FIG. 16B and 17B, respectively, in accordance with the present disclosure. The x-ray diffraction (XRD) pattern measurements of Zn deposits recorded for the examples shown in FIG. 16B and 17B confirm the successful Zinc deposits on Cu substrate during measurement and operation with the exemplary eutectic electrolyte mixtures.

[0070] FIGS. 18A-18C are plots depicting a representative cyclic voltammetric profile of Zn-PANI / CNTs cell in 1:0.34 mole% of [Et3NH]Cl:Zn(CF3SO3)2, a galvanostatic chargedischarge profile of Zn||PANI / CNTs in 1:0.34 mole% of [Et3NH]Cl:Zn(CF3SC>3)2 and cell performance recorded at 50 mA / g, and cycling performance of a galvanostatic chargedischarge profile of Zn||PANI / CNTs in 1:0.34 mole% of [Et3NH]Cl:Zn(CF3SO3)2, respectively, in accordance with the present disclosure. The cyclic voltammetric profile of Zn-PANI / CNTs cell in 1:0.34 mole% of [Et3NH]Cl:Zn(CF3SO3)2 demonstrates successful de- / doping of ions at the active electrode site.

[0071] FIGS. 19 and 19B are data plots showing representative cyclic voltammetric profiles of Zn-X O in 1 :0.34 mole% of [Et3NH]Cl:Zn(CF3SC>3)2 recorded at different scan rates, and plots of the peak current measured versus the square root of the scan rate for the Zn-X O cell, respectively, in accordance with the present disclosure.

[0072] FIGS. 20A and 20B are data plots showing the galvanostatic charge-discharge profile of Zn||V2O5in 1:0.3 mole% of [Et3NH]Cl:Zn(CF3SC>3)2 and cell performance recorded at 50 mA / g, respectively, in accordance with the present disclosure. A high discharge capacity of~250 mAh / g was obtained for the 1:0.3 mole% and ~100 Coulombic efficiency retained for >90 cycles with <0.1% capacity fade.

[0073] Advantages of the | Et; H ICTZniCTNO;,)? eutectic electrolyte mixture include an elevated open circuit potential or approximately 1. 1 V to 1 ,2V, an extended operational voltage window of about -2.2V as compared to Zn / Zn+2, a robust environmental range of liquid maintenance, for example, where the TiiqUid (effective temperature range of the eutectic liquid mixture is from about -60 °C to about 150 °C, providing potential to operate at all climate conditions, and enhanced efficiency at ultra-high currents. In exemplary electrochemical cells, these electrolyte mixtures can be paired with various choices of cathodes, such as, but not limited to graphene, V2O5, and PANI / CNTs, resulting in an ultra- high capacity of >250 mAh / g as determined in at least a cell having Zn||V2C>5 in 1:0.34 mole% of [Et3NH]Cl:Zn(CF3SO3)2. These cells further exhibited -100% Coulombic retention and <0.1% capacity fade observed with non-dendritic growth and uniform metal plating of metal, which can provide the prevention of short circuits while sustaining ultra-high current during operation.

[0074] While the present teachings have been illustrated with respect to one or more implementations, alterations and / or modifications may be made to the illustrated examples without departing from the spirit and scope of the appended claims. For example, it may be appreciated that while the process is described as a series of acts or events, the present teachings are not limited by the ordering of such acts or events. Some acts may occur in different orders and / or concurrently with other acts or events apart from those described herein. Also, not all process stages may be required to implement a methodology in accordance with one or more aspects or embodiments of the present teachings. It may be appreciated that structural objects and / or processing stages may be added, or existing structural objects and / or processing stages may be removed or modified. Further, one or more of the acts depicted herein may be carried out in one or more separate acts and / or phases. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” The term “at least one of’ is used to mean one or more of the listed items may be selected. Further, in the discussion and claims herein, the term “on” used with respect to two materials, one “on” the other, means at least some contact between the materials, while “over” means the materials are in proximity, but possibly with one or more additional intervening materials such that contact is possible but not required. Neither “on” nor “over” implies any directionality as used herein. The term “conformal” describes a coating material in which angles of the underlying material are preserved by the conformal material. The term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of theprocess or structure to the illustrated embodiment. The terms “couple,” “coupled,” “connect,” “connection,” “connected,” “in connection with,” and “connecting” refer to “in direct connection with” or “in connection with via one or more intermediate elements or members.” Finally, the terms “exemplary” or “illustrative” indicate the description is used as an example, rather than implying that it is an ideal. Other embodiments of the present teachings may be apparent to those skilled in the art from consideration of the specification and practice of the disclosure herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the present teachings being indicated by the following claims.

Claims

WHAT IS CLAIMED IS:

1. An electrolyte for an electrochemical device, comprising: a triethylamine hydrohalide or a triethylammonium halide; and a zinc salt; and wherein: the triethylamine hydrohalide or the triethylammonium halide and the zinc salt comprise a eutectic electrolyte mixture.

2. The electrolyte for an electrochemical device of claim 1, wherein the electrolyte comprises triethylamine hydrochloride.

3. The electrolyte for an electrochemical device of claim 2, wherein the triethylamine hydrohalide is selected from the group consisting of triethylamine hydrofluoride, triethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydroiodide, triethylamine hydroastatide, or a combination thereof.

4. The electrolyte for an electrochemical device of claim 1, wherein the electrolyte comprises triethylammonium halide.

5. The electrolyte for an electrochemical device of claim 4, wherein the triethylammonium halide is selected from the group consisting of triethylammonium fluoride, triethylammonium chloride, triethylammonium bromide, triethylammonium iodide, and triethylammonium astatide, or a combination thereof.

6. The electrolyte for an electrochemical device of claim 1, wherein the zinc salt comprises a hydrated form of the zinc salt.

7. The electrolyte for an electrochemical device of claim 1, wherein the zinc salt is selected from the group consisting of zinc sulfate, zinc tetrafluoroborate, zinc acetate, zinc chloride, zinc bis(trifluoromethane)sulfonimide, zinc nitrate, zinc perchlorate, and zinc trifluoromethanesulfonate.

8. The electrolyte for an electrochemical device of claim 1, wherein the eutectic electrolyte mixture comprises zinc sulfate heptahydrate and triethylamine hydrochloride, zinctrifluoromethane sulfonate and triethylamine hydrochloride, zinc tetrafluoroborate hydrate and triethylamine hydrochloride, or zinc bis(trifluoromethane)sulfonimide and triethylamine hydrochloride.

9. The electrolyte of an electrochemical device of claim 1, further comprising an additional metal salt.

10. The electrolyte of an electrochemical device of claim 9, wherein the additional metal salt comprises zinc, magnesium, calcium, iron, aluminum, lithium, sodium, potassium, calcium, manganese, or a combination thereof.

11. The electrolyte for an electrochemical device of claim 1, wherein a molar ratio of the triethylamine hydrohalide or the triethylammonium halide and the zinc salt is from about 1 :0.1 to about 1: 10.

12. An electrochemical device, comprising: a cathode; an anode; and an electrolyte disposed to facilitating ion transport between the cathode and the anode, comprising a triethylamine hydrohalide or a triethylammonium halide and a zinc salt, and wherein the triethylamine hydrohalide or the triethylammonium halide and zinc salt comprise a eutectic electrolyte mixture.

13. The electrochemical device of claim 12, wherein the cathode comprises conversion-type materials, intercalation-type materials, doping-type materials, or a combination thereof.

14. The electrochemical device of claim 12, wherein the cathode comprises manganese oxide, vanadium oxide, graphite, graphene, polyaniline, carbon nanotubes, or a combination thereof.

15. The electrochemical device of claim 12, wherein the anode comprises zinc.

16. The electrochemical device of claim 12, wherein the electrolyte comprises triethylamine hydrochloride and is selected from the group consisting of triethylamine hydrofluoride, triethylamine hydrochloride, triethylamine hydrobromide, triethylamine hydroiodide, triethylamine hydroastatide, or a combination thereof.

17. The electrochemical device of claim 12, wherein the electrolyte comprises triethylammonium halide and is selected from the group consisting of triethylammonium fluoride, triethylammonium chloride, triethylammonium bromide, triethylammonium iodide, and triethylammonium astatide, or a combination thereof.

18. The electrochemical device of claim 12, wherein a molar ratio of the triethylamine hydrohalide or the triethylammonium halide and the zinc salt is from about 1 :0.1 to about 1: 10.

19. An electrolyte for an electrochemical device, comprising: a triethylamine hydrohalide or a triethylammonium halide; and a zinc salt; an additional metal salt; and wherein: the triethylamine hydrohalide or the triethylammonium halide and the metal salt comprise a eutectic electrolyte mixture.

20. The electrolyte for an electrochemical device of claim 19, wherein the additional metal salt comprises zinc, magnesium, calcium, iron, aluminum, lithium, sodium, or a combination thereof.

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